Stimulating rays are linearly irradiated onto an area of a stimulable phosphor sheet, and light emitted by the sheet is detected with a CCD line sensor comprising photoelectric converting sections arrayed along the linear area of the sheet exposed to the linear stimulating rays. Accumulated electric charges obtained from each set of n number of the photoelectric converting sections adjacent to one another are read together. The accumulated electric charges, which have thus been read together from the set of the photoelectric converting sections, are taken as an image signal component corresponding to one pixel. The value of n is set in accordance with image recording information and/or diagnostic information.

1. Field of the Invention
This invention relates to a radiation image read-out method and apparatus, wherein stimulating rays are irradiated to a stimulable phosphor sheet, on which a radiation image has been stored, and light, which is emitted by the stimulable phosphor sheet when the stimulable phosphor sheet is exposed to the stimulating rays, is photoelectrically detected, an image signal representing the radiation image being thereby obtained. This invention particularly relates to a radiation image read-out method and apparatus, wherein a pixel density of a read-out image is capable of being altered.
2. Description of the Related Art
Radiation image recording and reproducing systems utilizing a stimulable phosphor sheet, which comprises a substrate and a layer of a stimulable phosphor overlaid on the substrate, have heretofore been widely used in practice.
With the radiation image recording and reproducing systems, a stimulable phosphor sheet is exposed to radiation carrying image information of an object, such as a human body, and a radiation image of the object is thereby recorded on the stimulable phosphor sheet. Thereafter, stimulating rays, such as a laser beam, are caused to scan the stimulable phosphor sheet in two-dimensional directions. The stimulating rays cause an exposed area of the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted from the exposed area of the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal by photoelectric read-out means.
The image signal, which has been obtained from the radiation image recording and reproducing systems described above, is then subjected to image processing, such as gradation processing and processing in the frequency domain, such that a visible radiation image, which has good image quality and can serve as an effective tool in, particularly, the efficient and accurate diagnosis of an illness, can be obtained. The image signal having been obtained from the image processing is utilized for reproducing a visible image for diagnosis, or the like, on film or displaying a visible image for diagnosis, or the like, on a cathode ray tube (CRT) display device. In cases where the stimulable phosphor sheet, from which the image signal has been detected, is then exposed to erasing light, and energy remaining on the stimulable phosphor sheet is thereby released, the erased stimulable phosphor sheet is capable of being used again for the recording of a radiation image.
Also, a novel radiation image recording and reproducing system aiming at enhancement of a detection quantum efficiency in the formation of the radiation image, i.e., a radiation absorptivity, alight emission efficiency, an emitted light pickup efficiency, and the like, wherein a novel type of stimulable phosphor sheet is utilized, has been proposed in, for example, Japanese Patent Application No. 11(1999)-372978. With the novel type of the stimulable phosphor sheet utilized in the proposed radiation image recording and reproducing system, the radiation absorbing functions and the energy storing functions of the conventional stimulable phosphor sheet are separated from each other.
The novel type of the stimulable phosphor sheet utilized in the proposed radiation image recording and reproducing system contains a layer of a stimulable phosphor for energy storage, which is capable of absorbing light having wavelengths falling within an ultraviolet to visible region and thereby storing energy of the light having wavelengths falling within the ultraviolet to visible region, and which is capable of being stimulated by light having wavelengths falling within a visible to infrared region and thereby radiating out the stored energy as emitted light.
The novel type of the stimulable phosphor sheet should preferably take on the form combined with a layer of a phosphor for radiation absorption, which is capable of absorbing radiation and being caused to emit light having wavelengths falling within an ultraviolet to visible region. In such cases, energy from the light having wavelengths falling within the ultraviolet to visible region, which light is emitted from the layer of the phosphor for radiation absorption when the layer of the phosphor for radiation absorption is exposed to the radiation carrying image information of an object, (the amount of the energy corresponding to the radiation image information) is stored on the layer of the stimulable phosphor for energy storage. When the stimulable phosphor sheet, on which the radiation image has thus been stored, is scanned with the stimulating rays, the light carrying the radiation image information is emitted from the layer of the stimulable phosphor for energy storage.
The novel type of the stimulable phosphor sheet need not necessarily be provided with the layer of the phosphor for radiation absorption. In such cases, the novel type of the stimulable phosphor sheet is utilized in combination with a fluorescent screen, which is provided with the layer of the phosphor for radiation absorption capable of absorbing radiation and being caused to emit the light having wavelengths falling within the ultraviolet to visible region.
Specifically, in such cases, the fluorescent screen is kept in close contact with the novel type of the stimulable phosphor sheet, and the radiation carrying the image information of the object is irradiated to the fluorescent screen. As a result, the light having wavelengths falling within the ultraviolet to visible region is emitted from the layer of the phosphor for radiation absorption of the fluorescent screen. Also, energy from the light emitted from the phosphor for radiation absorption (the amount of the energy corresponding to the radiation image information) is stored on the layer of the stimulable phosphor for energy storage of the stimulable phosphor sheet. When the stimulable phosphor sheet, on which the radiation image has thus been stored, is scanned with the stimulating rays, the light carrying the radiation image information is emitted from the layer of the stimulable phosphor for energy storage.
Novel radiation image read-out apparatuses for use in the radiation image recording and reproducing systems described above have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 60(1985)-111568, 60(1985)-236354, and 1(1989)-101540. In the proposed radiation image read-out apparatuses, from the point of view of keeping the emitted light detection time short, reducing the size of the apparatus, and keeping the cost low, a line sensor comprising a charge coupled device (CCD) image sensor, or the like, is utilized as the photoelectric read-out means.
Basically, the radiation image read-out apparatuses of such types comprise:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a CCD line sensor, which comprises a plurality of photoelectric conversion devices arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
iii) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in a direction (a sub-scanning direction) intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays (a main scanning direction).
The stimulating ray irradiating means for linearly irradiating the stimulating rays onto the stimulable phosphor sheet in the manner described above may be constituted so as to produce fan beam-like stimulating rays. Alternatively, the stimulating ray irradiating means may be constituted so as to deflect a thin beam and to cause the deflected thin beam to linearly scan the stimulable phosphor sheet.
In cases where the radiation image is to be reproduced from the image signal, which has been obtained with the radiation image read-out apparatuses described above, it is desired that a pixel density of the reproduced image be capable of being altered in accordance with the portion of the object, the image of which was recorded, a region of interest, or the like. For example, in cases where the radiation image is an image of the chest of a human body, or the like, the pixel density of the reproduced image may be comparatively low. In cases where the radiation image is an image of bone structures, an image having a comparatively high pixel density is ordinarily required for making a diagnosis.
Heretofore, in order for the requirement for the pixel density transform to be satisfied, the pixel density of the reproduced radiation image has been altered by subjecting an analog image signal, which has been obtained with the radiation image read-out apparatuses, to analog-to-digital conversion to yield a digital image signal, and thereafter subjecting the digital image signal to pixel density transform processing.
However, in such cases, it is necessary to utilize an expensive frame memory for temporarily storing the digital image signal representing one radiation image. Therefore, the problems occur in that the cost of the radiation image read-out apparatuses cannot be kept low.
The primary object of the present invention is to provide a radiation image read-out method, wherein a pixel density of a read-out image is capable of being transformed and which is capable of being carried out with a low-cost radiation image read-out apparatus.
Another object of the present invention is to provide an apparatus for carrying out the radiation image read-out method.
The present invention provides a first radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, with stimulating ray irradiating means, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted by the stimulable phosphor sheet, with a CCD line sensor comprising a plurality of photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, the received light being subjected to photoelectric conversion performed by the CCD line sensor, and
iii) moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in a sub-scanning direction intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, wherein the improvement comprises the steps of:
a) reading accumulated electric charges of the CCD line sensor, which accumulated electric charges are obtained from each set of n number of the photoelectric converting sections adjacent to one another in the array direction of the plurality of the photoelectric converting sections, where 2xe2x89xa6n, together such that the value of n is capable of being altered, the accumulated electric charges, which have thus been read together from the set of the photoelectric converting sections, being taken as an image signal component corresponding to one pixel, and
b) setting the value of n in accordance with image recording information and/or diagnostic information.
The processing for reading the accumulated electric charges together is referred to as the binning processing. The binning processing is a technique wherein, instead of the accumulated electric charge being taken out from one of the photoelectric converting sections, which are formed in the CCD line sensor, the accumulated electric charges at the plurality of the photoelectric converting sections are taken out together.
The term xe2x80x9cimage recording informationxe2x80x9d as used herein means the information giving specifics about an image recording operation, e.g., image recording conditions, such as a tube voltage of a radiation source, a tube current of the radiation source, and time over which radiation is irradiated, and conditions, such as the size of the stimulable phosphor sheet and the kind of the stimulable phosphor sheet. The term xe2x80x9cdiagnostic informationxe2x80x9d as used herein means the information concerning diagnosis utilizing the radiation image, e.g., the purpose of diagnosis, such as primary screening or close examination, and a region of interest.
The image recording information and the diagnostic information are capable of being acquired with, for example, a technique wherein the information is automatically acquired from a radiation image recording apparatus, or the like, a technique wherein the information is inputted from an identification (ID) information input device, or the like, and a technique wherein the information is transferred from an image display terminal of a medical doctor for instructing the purpose of diagnosis to a radiographic engineer.
As will be understood from the specification, it should be noted that the term xe2x80x9cmoving a stimulable phosphor sheet with respect to stimulating ray irradiating means and a CCD line sensorxe2x80x9d as used herein means movement of the stimulable phosphor sheet relative to the stimulating ray irradiating means and the CCD line sensor, and embraces the cases wherein the stimulable phosphor sheet is moved while the stimulating ray irradiating means and the CCD line sensor are kept stationary, the cases wherein the stimulating ray irradiating means and the CCD line sensor are moved while the stimulable phosphor sheet is kept stationary, and the cases wherein both the stimulable phosphor sheet and the stimulating ray irradiating means and the CCD line sensor are moved. In cases where the stimulating ray irradiating means and the CCD line sensor are moved, they should be moved together with each other.
The first radiation image read-out method in accordance with the present invention may be modified such that the method further comprises the steps of:
performing addition processing on each set of image signal components having been obtained, each of which image signal components corresponds to one of m number of read-out lines standing side by side with respect to the sub-scanning direction, where 2xe2x89xa6m, and which image signal components are adjacent to one another in the sub-scanning direction, such that the value of m is capable of being altered, a sum of the set of the image signal components, which sum has been obtained from the addition processing, being taken as one of image signal components corresponding to one line, and
setting the value of m in accordance with the image recording information and/or the diagnostic information.
Also, the first radiation image read-out method in accordance with the present invention may be modified such that the method further comprises the steps of:
altering a sub-scanning speed of the movement in the sub-scanning direction, and
setting the sub-scanning speed in accordance with the image recording information and/or the diagnostic information.
The present invention also provides a second radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, with stimulating ray irradiating means, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted by the stimulable phosphor sheet, with a CCD line sensor comprising a plurality of photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays and along a sub-scanning direction intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, the received light being subjected to photoelectric conversion performed by the CCD line sensor, and
iii) moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in the sub-scanning direction intersecting with the length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
wherein the improvement comprises the steps of:
a) reading accumulated electric charges of the CCD line sensor, which accumulated electric charges are obtained from each set of n number of the photoelectric converting sections adjacent to one another in the array direction of the plurality of the photoelectric converting sections along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, where 2xe2x89xa6n, and m number of the photoelectric converting sections adjacent to one another in the sub-scanning direction, where 2xe2x89xa6m, together such that the value of n is capable of being altered, the accumulated electric charges, which have thus been read together from the set of the photoelectric converting sections, being taken as an image signal component corresponding to one pixel, and
b) setting the value of n and the value of m in accordance with image recording information and/or diagnostic information.
Specifically, in the second radiation image read-out method in accordance with the present invention, the binning processing is performed with respect to both the length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays (i.e, the main scanning direction) and the sub-scanning direction intersecting with the main scanning direction.
The present invention further provides a third radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, with stimulating ray irradiating means, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted by the stimulable phosphor sheet, with a CCD line sensor comprising a plurality of photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, the received light being subjected to photoelectric conversion performed by the CCD line sensor, and
iii) moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in a sub-scanning direction intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
wherein the improvement comprises the steps of:
a) performing addition processing on each set of output signal components having been obtained from the CCD line sensor, each of which output signal components corresponds to one of m number of read-outlines standing side by side with respect to the sub-scanning direction, where 2xe2x89xa6m, and which output signal components are adjacent to one another in the sub-scanning direction, such that the value of m is capable of being altered, a sum of the set of the output signal components, which sum has been obtained from the addition processing, being taken as one of image signal components corresponding to one line, and
b) setting the value of m in accordance with image recording information and/or diagnostic information.
The present invention still further provides a fourth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, with stimulating ray irradiating means, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted by the stimulable phosphor sheet, with a CCD line sensor comprising a plurality of photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, the received light being subjected to photoelectric conversion performed by the CCD line sensor, and
iii) moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in a sub-scanning direction intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
wherein the improvement comprises the steps of:
a) altering a sub-scanning speed of the movement in the sub-scanning direction, and
b) setting the sub-scanning speed in accordance with image recording information and/or diagnostic information.
The present invention also provides an apparatus for carrying out the first radiation image read-out method in accordance with the present invention. Specifically, the present invention also provides a first radiation image read-out apparatus, comprising:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a CCD line sensor comprising a plurality of photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
iii) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in a sub-scanning direction intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
wherein the improvement comprises the provision of:
a) reading means for reading accumulated electric charges of the CCD line sensor, which accumulated electric charges are obtained from each set of n number of the photoelectric converting sections adjacent to one another in the array direction of the plurality of the photoelectric converting sections, where 2xe2x89xa6n, together such that the value of n is capable of being altered, and taking the accumulated electric charges, which have thus been read together from the set of the photoelectric converting sections, as an image signal component corresponding to one pixel, and
b) control means for setting the value of n in accordance with image recording information and/or diagnostic information.
The first radiation image read-out apparatus in accordance with the present invention may be modified such that the apparatus further comprises:
signal addition processing means for performing addition processing on each set of image signal components having been obtained from the reading means, each of which image signal components corresponds to one of m number of read-out lines standing side by side with respect to the sub-scanning direction, where 2xe2x89xa6m, and which image signal components are adjacent to one another in the sub-scanning direction, such that the value of m is capable of being altered, and taking a sum of the set of the image signal components, which sum has been obtained from the addition processing, as one of image signal components corresponding to one line, and
control means for setting the value of m in accordance with the image recording information and/or the diagnostic information.
Also, the first radiation image read-out apparatus in accordance with the present invention may be modified such that the apparatus further comprises:
means for altering a sub-scanning speed of the movement in the sub-scanning direction, which movement is performed by the sub-scanning means, and
control means for setting the sub-scanning speed in accordance with the image recording information and/or the diagnostic information.
The present invention further provides an apparatus for carrying out the second radiation image read-out method in accordance with the present invention. Specifically, the present invention further provides a second radiation image read-out apparatus, comprising:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a CCD line sensor comprising a plurality of photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays and along a sub-scanning direction intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
iii) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in the sub-scanning direction intersecting with the length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
wherein the improvement comprises the provision of:
a) reading means for reading accumulated electric charges of the CCD line sensor, which accumulated electric charges are obtained from each set of n number of the photoelectric converting sections adjacent to one another in the array direction of the plurality of the photoelectric converting sections along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, where 2xe2x89xa6n, and m number of the photoelectric converting sections adjacent to one another in the sub-scanning direction, where 2xe2x89xa6m, together such that the value of n is capable of being altered, and taking the accumulated electric charges, which have thus been read together from the set of the photoelectric converting sections, as an image signal component corresponding to one pixel, and
b) control means for setting the value of n and the value of m in accordance with image recording information and/or diagnostic information.
The present invention still further provides an apparatus for carrying out the third radiation image read-out method in accordance with the present invention. Specifically, the present invention still further provides a third radiation image read-out apparatus, comprising:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a CCD line sensor comprising a plurality of photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
iii) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in a sub-scanning direction intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
wherein the improvement comprises the provision of:
a) signal addition processing means for performing addition processing on each set of output signal components having been obtained from the CCD line sensor, each of which output signal components corresponds to one of m number of read-out lines standing side by side with respect to the sub-scanning direction, where 2xe2x89xa6m, and which output signal components are adjacent to one another in the sub-scanning direction, such that the value of m is capable of being altered, and taking a sum of the set of the output signal components, which sum has been obtained from the addition processing, as one of image signal components corresponding to one line, and
b) control means for setting the value of m in accordance with image recording information and/or diagnostic information.
The present invention also provides an apparatus for carrying out the fourth radiation image read-out method in accordance with the present invention. Specifically, the present invention also provides a fourth radiation image read-out apparatus, comprising:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a CCD line sensor comprising a plurality of photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
iii) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the CCD line sensor and in a sub-scanning direction intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
wherein the improvement comprises the provision of:
a) means for altering a sub-scanning speed of the movement in the sub-scanning direction, which movement is performed by the sub-scanning means, and
b) control means for setting the sub-scanning speed in accordance with image recording information and/or diagnostic information.
With the first radiation image read-out method and apparatus in accordance with the present invention, the binning processing is performed, wherein the accumulated electric charges of the CCD line sensor, which accumulated electric charges are obtained from each set of n number of the photoelectric converting sections adjacent to one another in the array direction of the plurality of the photoelectric converting sections, where 2xe2x89xa6n, are read together such that the value of n is capable of being altered. Also, the accumulated electric charges, which have thus been read together from the set of the photoelectric converting sections, are taken as an image signal component corresponding to one pixel. Therefore, the pixel density in the main scanning direction is capable of being altered arbitrarily. Specifically, for example, the accumulated electric charges of the CCD line sensor, which accumulated electric charges are obtained from each set of two photoelectric converting sections adjacent to each other in the array direction of the plurality of the photoelectric converting sections (in this case, n=2), may be read together. Also, the accumulated electric charges, which have thus been read together from each set of the two photoelectric converting sections, may be taken as an image signal component corresponding to one pixel. In such cases, the pixel density in the main scanning direction is capable of being altered to one half of the pixel density occurring when the binning processing is not performed.
Further, with the first radiation image read-out method and apparatus in accordance with the present invention, the value of n, i.e. the number of the photoelectric converting sections subjected to the binning processing with respect to the main scanning direction, is set in accordance with the image recording information and/or the diagnostic information. Therefore, the pixel density in the main scanning direction is capable of being set automatically at a value appropriate for the image recording information and/or the diagnostic information without complicated operations being required.
The first radiation image read-out method and apparatus in accordance with the present invention may be modified such that the addition processing is performed on each set of the image signal components having been obtained from the binning processing described above, each of which image signal components corresponds to one of m number of read-out lines standing side by side with respect to the sub-scanning direction, where 2xe2x89xa6m, and which image signal components are adjacent to one another in the sub-scanning direction, such that the value of m is capable of being altered, the sum of the set of the image signal components, which sum has been obtained from the addition processing, being taken as one of image signal components corresponding to one line; and the value of m is set in accordance with the image recording information and/or the diagnostic information. With the modification of the first radiation image read-out method and apparatus in accordance with the present invention, besides the pixel density in the main scanning direction being capable of being altered in the manner described above, the pixel density in the sub-scanning direction is also capable of being altered arbitrarily. Specifically, for example, the addition processing may be performed on each set of the image signal components having been obtained from the binning processing described above, each of which image signal components corresponds to one of two read-out lines standing side by side with respect to the sub-scanning direction (in this case, m=2), and which image signal components are adjacent to each other in the sub-scanning direction. Also, the sum of each set of the image signal components, which sum has been obtained from the addition processing, may be taken as one of the image signal components corresponding to one line. In such cases, the pixel density in the sub-scanning direction is capable of being altered to one half of the pixel density occurring when the addition processing is not performed.
Further, with the aforesaid modification of the first radiation image read-out method and apparatus in accordance with the present invention, the value of m, i.e. the number of the read-out lines subjected to the addition processing, is set in accordance with the image recording information and/or the diagnostic information. Therefore, the pixel density in the sub-scanning direction is capable of being set automatically at a value appropriate for the image recording information and/or the diagnostic information without complicated operations being required.
Also, the first radiation image read-out method and apparatus in accordance with the present invention may be modified such that the sub-scanning speed of the movement in the sub-scanning direction is altered, and the sub-scanning speed is set in accordance with the image recording information and/or the diagnostic information. In such cases, besides the pixel density in the main scanning direction being capable of being altered in the manner described above, the pixel density in the sub-scanning direction is also capable of being altered arbitrarily by the alteration of the sub-scanning speed. Specifically, for example, in cases where the sub-scanning speed is altered to two times as high as the original sub-scanning speed, the pixel density in the sub-scanning direction is capable of being altered to one half of the pixel density occurring when the sub-scanning speed is set at the original sub-scanning speed. Also, since the sub-scanning speed is set in accordance with the image recording information and/or the diagnostic information, the pixel density in the sub-scanning direction is capable of being set automatically at a value appropriate for the image recording information and/or the diagnostic information without complicated operations being required.
With the second radiation image read-out method and apparatus in accordance with the present invention, the binning processing with respect to the main scanning direction is performed in the same manner as that in the first radiation image read-out method and apparatus in accordance with the present invention. Therefore, the pixel density in the main scanning direction is capable of being altered arbitrarily.
Also, with the second radiation image read-out method and apparatus in accordance with the present invention, as the CCD line sensor, the CCD line sensor comprising the plurality of the photoelectric converting sections, which are arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays and along the sub-scanning direction, is employed. Further, the binning processing is performed with respect to both the main scanning direction and the sub-scanning direction. Therefore, the number of stages for reading the accumulated electric charges is capable of being kept small. Accordingly, noise is capable of being reduced, and the reading speed is capable of being kept high.
Further, with the second radiation image read-out method and apparatus in accordance with the present invention, the value of n, i.e. the number of the photoelectric converting sections subjected to the binning processing with respect to the main scanning direction, is set in accordance with the image recording information and/or the diagnostic information. Therefore, the pixel density in the main scanning direction is capable of being set automatically at a value appropriate for the image recording information and/or the diagnostic information without complicated operations being required.
Furthermore, with the second radiation image read-out method and apparatus in accordance with the present invention, the value of m, i.e. the number of the photoelectric converting sections subjected to the binning processing with respect to the sub-scanning direction, is set in accordance with the image recording information and/or the diagnostic information. Therefore, the reading speed, or the like, is capable of being set automatically at a value appropriate for the image recording information and/or the diagnostic information without complicated operations being required.
With the third radiation image read-out method and apparatus in accordance with the present invention, the addition processing is performed on each set of output signal components having been obtained from the CCD line sensor, each of which output signal components corresponds to one of m number of read-out lines standing side by side with respect to the sub-scanning direction, where 2xe2x89xa6m, and which output signal components are adjacent to one another in the sub-scanning direction. Also, the sum of each set of the output signal components, which sum has been obtained from the addition processing, is taken as one of the image signal components corresponding to one line. Therefore, the pixel density in the sub-scanning direction is capable of being altered arbitrarily. Specifically, for example, the addition processing may be performed on each set of the output signal components having been obtained from the CCD line sensor, each of which output signal components corresponds to one of two read-out lines standing side by side with respect to the sub-scanning direction (in this case, m=2), and which output signal components are adjacent to each other in the sub-scanning direction. Also, the sum of each set of the output signal components, which sum has been obtained from the addition processing, may be taken as one of the image signal components corresponding to one line. In such cases, the pixel density in the sub-scanning direction is capable of being altered to one half of the pixel density occurring when the addition processing is not performed.
Further, with the third radiation image read-out method and apparatus in accordance with the present invention, the value of m, i.e. the number of the read-out lines subjected to the addition processing, is set in accordance with the image recording information and/or the diagnostic information. Therefore, the pixel density in the sub-scanning direction is capable of being set automatically at a value appropriate for the image recording information and/or the diagnostic information without complicated operations being required.
With the fourth radiation image read-out method and apparatus in accordance with the present invention, the sub-scanning speed of the movement in the sub-scanning direction is altered. By the alteration of the sub-scanning speed, the pixel density in the sub-scanning direction is capable of being altered arbitrarily. Specifically, for example, in cases where the sub-scanning speed is altered to two times as high as the original sub-scanning speed, the pixel density in the sub-scanning direction is capable of being altered to one half of the pixel density occurring when the sub-scanning speed is set at the original sub-scanning speed.
Also, with the fourth radiation image read-out method and apparatus in accordance with the present invention, the sub-scanning speed is set in accordance with the image recording information and/or the diagnostic information. Therefore, the pixel density in the sub-scanning direction is capable of being set automatically at a value appropriate for the image recording information and/or the diagnostic information without complicated operations being required.
Further, with the first, second, third, and fourth radiation image read-out methods in accordance with the present invention and the first, second, third, and fourth radiation image read-out apparatuses in accordance with the present invention, the pixel density is altered at the stage at which an analog image signal is formed. Therefore, an expensive frame memory for temporarily storing a digital image signal representing one radiation image need not be utilized. Accordingly, the cost of the radiation image read-out apparatuses is capable of being kept low.

Radiation image read-out method and apparatus


Digital circuits and methods for designing digital circuits are presented. More particularly, the present invention relates to error correction circuits and methods in communications and other systems. In the present invention, a novel K-nested layered look-ahead method and its corresponding architecture, which combine K-trellis steps into one trellis step (where K is the encoder constraint length), are proposed for implementing low-latency high-throughput rate Viterbi decoder circuits. The main idea of the present invention involves combining K-trellis steps as a pipeline structure and then combining the resulting look-ahead branch metrics as a tree structure in a layered manner to decrease the ACS precomputation latency of look-ahead Viterbi decoder circuits. The proposed method guarantees parallel paths between any two trellis states in the look-ahead trellises and distributes the add-compare-select (ACS) computations to all trellis layers. It leads to regular and simple architecture for the Viterbi decoding algorithm. The look-ahead ACS computation latency of the proposed method increases logarithmically with respect to the look-ahead step (M) divided by the encoder constraint length (K) as opposed to linearly as in prior work. The main advantage of this invention is that it has the least latency among all known look-ahead Viterbi decoder circuits for a given level of parallelism.

A convolutional code has been widely used in many communication systems as a forward error correction (FEC) method. The Viterbi decoding algorithm is optimum for decoding of the received data, which is transmitted after convolutional encoding.
The decoding speed of the Viterbi decoding algorithm is limited by the iteration bound because the add-compare-select (ACS) recursion in the Viterbi decoding algorithm contains feedback loops. A look-ahead technique, which combines several trellis steps into one trellis step in time sequence, has been used for breaking the iteration bound of the Viterbi decoding algorithm. In the look-ahead technique, the combined branch metrics can be computed outside of the ACS recursion (referred as ACS precomputation). This allows the ACS loop to be pipelined or computed in parallel. Thereby, the decoding throughput rate can be increased. This is an advantage of the look-ahead technique. The look-ahead step (M) for a given throughput rate is obtained as the desired throughput rate divided by the ACS recursion clock rate since the overall decoding speed is limited by the allowed maximum frequency of the ACS recursion clock. Therefore, large number of look-ahead steps or high parallelism factor is needed to implement high-throughput rate Viterbi decoding.
In this invention, the ACS computation without the addition of the previous state metrics (or path metrics or accumulated branch metrics) is referred as the ACS precomputation to distinguish it from the ACS recursion, which adds the previous state metrics to the look-ahead branch metrics used for state update operation inside the feedback loop.
The main drawback of the traditional M-step look-ahead technique is that it leads to long latency for look-ahead ACS precomputation, especially when very large number of look-ahead steps is required. When the ACS precomputation unit is implemented as a pipeline structure, the ACS precomputation latency of the traditional M-step look-ahead method increases linearly with respect to the look-ahead step.
In this invention, an alternate approach is considered where the method of combining trellis steps is changed such that the inherent decoding latency can be. It combines K-trellis (where K is the encoder constraint length) steps into one trellis-step and then combines resulting sub-trellises in a layered manner (refereed as K-nested layered look-ahead, LLA). In this approach, the ACS precomputation latency can be significantly decased for high order look-ahead cases as long as the level of parallelism, M, is a multiple of the encoder constraint length, K.
The practical use of this invention is extremely important for implementation of high speed, i.e., 5 or 10 Gb/s, serializer-deserializer (SERDES), where the latency constraint is critical. The SERDES can be used in 10 Gb/s fiber channel synchronous optical network (SONET) or 10 Gb/s Ethernet local area network (LAN), etc. The low-latency Viterbi detector based on this invention may also be used in high density optical or magnetic storage y such as digital video disk (DVD) and hard disk drive (HDD) systems.

Low-latency architectures for high-throughput Viterbi decoders


The invention relates to devices and methods for hybridization assisted sequencing of biomolecule analytes in nanopores, nano-channels and micro-channels. An alternating current signal may be employed to achieve a significantly improved signal-to-noise ratio, thereby enhancing system performance.

A number of different approaches for sequencing nucleic acids exist. The traditional methods are the dideoxy-chain termination method described by Sanger et al., Proc Natl. Acad. Sci. USA, (1977) 74: 5463-67 and the chemical degradation method described by Maxam et al., Proc. Natl. Acad. Sci. USA, (1977) 74: 560-564. Of these two methods, the Sanger procedure has been the most widely used. The original Sanger method relied on radioactive labeling of the reaction products and separation of the reaction products by slab gel electrophoresis.
Both the Sanger and Maxam methods are time- and labor-intensive. The start of the Human Genome Project was the impetus for the development of improved, automated systems to perform Sanger sequencing. As a result, detection of fluorescence has replaced autoradiography and capillary electrophoresis has replaced the ultrathin slab gels originally used to separate reaction products. Automated sequencers have been developed and are capable of processing large numbers of samples without operator intervention.
The completion of the Human Genome Project has refocused the need for new technologies that are capable of rapidly and inexpensively determining the sequence of human and other genomes. There is has been much discussion in recent years about personalized medicine. The vision of personalized medicine involves every individual having his or her complete genome sequenced at high accuracy and using this information to guide clinical care, specifically for risk stratification of patients and pharmacogenomics.
In recent years, a number of technological advances have been developed enabling a great reduction in the cost of sequencing and substantially increasing the amount of sequence data produced. Most sequencing methods currently available utilize optical detection for the determination of the DNA sequence. The most prevalent sequencing methods are referred to as sequencing by synthesis (SBS).
Typical embodiments of SBS consist of the stepwise synthesis of a strand of DNA that is complementary to a template sequence from the target genome to be sequenced. The SBS methods can be divided into those that are performed in batch mode and those that are performed in real-time. The batch mode processes rely on the stepwise synthesis of the new DNA strand with the limitation that the synthesis is only allowed to proceed for one nucleotide position, for one nucleotide type, or for the combination of one nucleotide position and one nucleotide type. The incorporation of the nucleotide occurs in parallel for large numbers of templates. Detection is achieved using a variety of methods.
Embodiments of the batch mode utilizing a single nucleotide type are used by Roche for pyrosequencing with the 454 platform. The Roche technology (see, e.g., Margulies et al. (2005) Nature, 437:376-380; U.S. Pat. Nos. 6,274,320; 6,258,568; 6,210,891) utilizes pyrosequencing. The method depends on several enzymes and cofactors to produce luminescence when a nucleotide is incorporated. A single nucleotide species is introduced into a large number of small reaction vessels each containing multiple copies of a single template. The incorporation of the nucleotide is accompanied by light emission. When the reaction has run to completion, the reagents are washed from the reaction volumes and a next nucleotide and its required reagents are washed into the reactions. Each template is thus extended in an iterative fashion, one nucleotide at a time. Multiple incorporations of the same nucleotide require the quantitative determination of the amount of light emitted. Homopolymer tracts in templates may be difficult to accurately sequence as the incremental amount of light emitted for each subsequent position in the homopolymer becomes small compared to the total amount emitted.
In a second embodiment of the SBS method, platforms by Helicos (see, e.g., Quake et al Proc. Nat. Acad. Sci. USA (2003) 100: 3960-3964; U.S. Pat. Nos. 6,818,395; 6,911,345; 7,297,518; 7,462,449 and 7,501,245), Illumina (see, e.g., Bennett et al. Pharmacogenomics (2005) 6:373-382), and Intelligent Bio-Systems (see, e.g., Ju et al. Proc. Nat. Acad. Sci. USA (2006) 103:19635-19640) allow only the incorporation of a single nucleotide at each step. Template strands are attached to a solid support and a primer sequence is annealed. A polymerase is used to extend the primer to make a complement to the template. The nucleotides are derivatized such that after the incorporation of a single nucleotide, the growing strand is incapable of further extension. The nucleotides are further derivatized to make them fluorescent. In the Helicos technology, the four nucleotides are labeled with the same fluorescent tag. This requires that each nucleotide type be added separately. In contrast, the Illumina and Intelligent Bio-Systems technologies utilize four different fluorescent tags so that a mixture of all four derivatized nucleotides may be added at the same time. For both technologies, the incorporation of a nucleotide is accompanied by the appearance of fluorescence in the growing strand. In the case of Illumina, the wavelength of the fluorescence emission indicates the identity of the newly incorporated nucleotide. In the Helicos technology, only a single nucleotide type is added at each cycle. Thus, the appearance of fluorescence at a position on the solid support indicates the incorporation of the added nucleotide for that template. Templates that do not incorporate the nucleotide present in the reaction remain dark.
Following the observation of any incorporated fluorescence, the blocking groups and fluorescent tags are removed prior to the next cycle. Multiple cycles result in the acquisition of sequence data for many templates in a single run. The instrumentation typical for these technologies is said to allow for the automated acquisition of sequence information for hundreds of thousands to millions of templates in parallel.
SBS methods may also be performed in real-time. In this embodiment, polymerase is used to incorporate fluorescently labeled nucleotides and the fluorescence is observed during DNA strand synthesis. The four nucleotides are labeled with different fluorescent tags. The fluorescent tags are attached to the terminal phosphate of the nucleotide triphosphate. During incorporation of the nucleotide into the growing strand the fluorophore is released to solution and the growing strand remains non-fluorescent. The identity of the incorporated strand is determined while the nucleotide resides in the active site of the enzyme and before the cleaved diphosphate is released to bulk solution.
The fluorescence of the incorporated nucleotide typically is measured in a background fluorescence from a much larger concentration of unincorporated nucleotide. Pacific Biosciences (see, e.g., U.S. Pat. Nos. 7,170,050; 7,302,146; 7,315,019; 7,476,503; and 7,476,504) identifies the incorporated nucleotide based on the residence time in the polymerase active site. Fluorescence emission from the active site for an appropriate time indicates incorporation and the emission wavelength determines the identity of the incorporated nucleotide. Polymerase is attached to the bottom of zero-mode waveguides. Zero-mode waveguides are reaction cells whose dimensions limit the passage of light from the excitation sources. Thus, only fluorescent tags close to the bottom surface of the reaction volume are excited.
Visigen identifies the incorporated nucleotide through Fluorescent Resonant Energy Transfer (FRET) between an acceptor in the polymerase active site and a fluorescent tag on the nucleotide (see, e.g., U.S. Pat. Nos. 7,211,414 and 7,329,492). Only nucleotides held in the active site of the polymerase show fluorescence. Incorporation is identified by the residence time of the fluorescence in the active site and the nucleotide identity is determined by the emission wavelength.
Other recently developed methods to sequence DNA rely on hybridization and ligation. Both the SOLiD and Complete Genomics technologies rely on the combination of hybridization and ligation. The SOLiD system (Life Technologies) immobilizes short template strands via an adapter. A primer and a pool of labeled oligonucleotides containing two fixed positions and six degenerate positions is hybridized to the template. The primer hybridizes to the adaptor. Each pool consists of 16,384 different sequences. Four fluorescent dyes are used to label the oligonucleotides in a pool in a fashion that creates four subsets from the sixteen combinations at the two fixed positions. Thus, each fluorescent tag is associated with four of the sixteen possible combinations. Following hybridization, a ligase is added and any probes in the pool that hybridized contiguously with the primer are ligated to the primer. The fluorescence of the hybridized and ligated product is determined. The fluorescence defines which subset of sequences hybridized to the template and ligated to the primer. The terminal three bases and the associated fluorescent tag are cleaved from the hybridized and ligated oligonucleotide. Subsequent rounds of another round of hybridization, ligation, and cleavage are performed. In this first series of reactions, each cycle identifies a subset for the pair of nucleotides in the template that is 5 nucleotides downstream from subset of pairs that were identified in the last cycle. After several cycles, the primer, and the oligonucleotides that have been ligated to it, is washed off the template
The entire procedure is repeated starting with a primer that is one nucleotide shorter than the original primer, then with primers that are two, three, and four nucleotides shorter than the original primer. These subsequent rounds shift the frame of interrogation so that the bases that make-up the template strand can be identified from the union between the two subsets of reaction that overlapped at that position.
Complete Genomics technology utilizes a similar hybridization and ligation method (see, e.g., US Patent Application Publication Nos. 20080234136; 20090005252; 20090011943; and 20090176652). In the Complete Genomics technology, a primer is hybridized to an adaptor that is attached to the end of the template. A series of pools of oligonucleotides is constructed. In each pool, the nucleotide at a single position is identified by using four-color fluorescence. The remaining positions are degenerate. The first pool is hybridized to the template. Oligonucleotides that hybridize adjacent to the primer are subsequently ligated. After washing excess oligonucleotides away, the fluorescence of the ligated oligonucleotide identifies the nucleotide at the defined position in that pool. The ligated primer and oligonucleotide are washed off the template and the process is repeated with the next pool of oligonucleotides that probe the next position down from the primer.
The SBS and hybridization-ligation methods generate short pieces or reads of DNA sequence. While the short reads can be used to re-sequence human genomes, they are not favorable for the de novo assembly of human genomes. With the recent realization that human genomes contain large numbers of inversions, translocations, duplications, and indels (e.g., mutations that include both insertions, deletions, and the combination thereof), the quality of human genome data from short reads is even more suspect. Genetic rearrangements are even more prevalent in cancer.
While embodiments of the short read technologies that incorporate paired-end reads have been proposed and the length of the sequence data from these technologies has increased incrementally over the last two years, it is clear that longer read technologies are necessary for the accurate assembly of human genome data.
In addition to the undesirable nature of short reads, all of the DNA sequencing methods described above employ optical detection. The throughput of optical methods limits the ultimate performance characteristics of any of these sequencing technologies. Optical methods are capable of identifying single molecules. However, the time required to observe and accurately identify events is typically too slow to meet the need for higher throughput. While the current generation of sequencing technologies has lowered the cost of sequencing by orders of magnitude in comparison to the methods used to sequence the first human genomes, the methods remain too slow, costly, and inaccurate for routine analysis of human genomes.
A need therefore exists for efficient methods and devices capable of rapid and accurate nucleic acid sequencing for de novo assembly of human genomes. It is desirable to have long read lengths and to use as little nucleic acid template as possible. Moreover, single-molecule optical detection of DNA has limitations with respect to sensitivity and speed.
Thus, there remains a need for improved methods and devices for the analysis of biopolymers, including methods and devices for mapping and sequencing such biopolymers.

Apparatus and methods for analysis of biomolecules using high frequency alternating current excitation


A piezoelectric laminate including a base and a first piezoelectric layer formed above the base and including potassium sodium niobate. The first piezoelectric layer is shown by a compositional formula (KaNa1-a)xNbO3, “a” and “x” in the compositional formula being respectively 0.1<a<1 and 1≦x≦1.2.

The present invention relates to a piezoelectric laminate including a potassium sodium niobate layer, and a surface acoustic wave device, a thin-film piezoelectric resonator, and a piezoelectric actuator including the piezoelectric laminate.
A demand for a surface acoustic wave device has rapidly increased along with a remarkable development in the communication field represented by mobile communication such as a portable telephone. The development of the surface acoustic wave device has been trending toward a reduction in size and an increase in efficiency and frequency. This requires a higher electromechanical coupling factor (coefficient) (k2), more stable temperature properties, and a higher surface acoustic wave propagation velocity.
A surface acoustic wave device has been mainly used which has a structure in which interdigital transducers are formed on a piezoelectric single crystal. As typical examples of the piezoelectric single crystal, a rock crystal, lithium niobate (LiNbO3), lithium tantalate (LiTaO3), and the like can be given. For example, LiNbO3 with a high electromechanical coupling factor is used for an RF filter for which an increase in band and a decrease in loss in the passband are required. A rock crystal with a small temperature coefficient of frequency is used for an IF filter for which stable temperature properties are required in a narrow band. LiTaO3 with an electromechanical coupling factor and a temperature coefficient of frequency between those of LiNbO3 and a rock crystal plays an intermediate role between LiNbO3 and a rock crystal. In recent years, a cut angle of a potassium niobate (KNbO3) single crystal showing a high electromechanical coupling factor has been found. A KNbO3 single crystal plate is disclosed in JP-A-10-65488.
In a surface acoustic wave device using a piezoelectric single crystal base, properties such as the electromechanical coupling factor, temperature coefficient, and speed of sound are specific to the material and determined by the cut angle and the propagation direction. For example, a 0°Y-X KNbO3 single crystal base has an excellent electromechanical coupling factor, but does not show zero temperature properties at or near room temperature, differing from a 45° to 75° rotated Y-X KNbO3 single crystal base.

Piezoelectric laminate, surface acoustic wave device, thin-film piezoelectric resonator, and piezoelectric actuator


Crosstalk interference induced by the adjacent pairs is one of the major performance limiting factors of DSL systems. As there is a rapid increase in the deployment of DSL services worldwide, the need to provide information about noise related parameters to the operators and the service providers is of utmost importance. Satisfying such a need enables operators to anticipate the line capacity and understand the noise level characteristics of the loop environment. Specifically, crosstalk and more particularly upstream near end crosstalk (NEXT) in the presence of narrowband interference can be classified to isolate the particular service type causing the upstream NEXT. The identification of the service type of the upstream NEXT would enable operators to address the disturber.

1. Field of the Invention
The invention relates to digital subscriber line (xDSL) communications and more particularly to identifying crosstalk in an xDSL system.
2. Background Information
Crosstalk in a communications system is the undesired effect or interference in a channel or circuit caused by another circuit or channel. Crosstalk interference by the adjacent pairs is one of the major performance limiting factors of xDSL systems.
FIG. 1 illustrates a typical communications system such as an xDSL system. Central office equipment (CO) 102 communicates to at least one consumer premises equipment (CPE) 104 (and in this example CPE 106 as well). Data transmitted towards the CPE shown by lines 108 and 112 is referred to as downstream. Data transmitted towards the CO shown by lines 110 and 114 is referred to as upstream. For a given line, crosstalk typically occurs when the interfering disturber is in close proximity to the line, which most likely occurs near either the CO or the CPE, because that is where there is a likelihood of aggregating lines.
FIG. 2 illustrates the various types of crosstalk typically experienced in a communications system. For simplicity, two CO's and two CPE's are shown. CO 202 is in communications with CPE 204 and CO 206 is in communications with CPE 208. For the sake of example, the crosstalk from CO 206 and CPE 208 to either CO 202 or CPE 204 is described. The term "far-end" refers to when the interference is away from the receiving side and the term "near-end" refers to when the interference is close to the receiving side. For example, interference shown by arrow 212 illustrates noise generated by CO 206 coupled into the downstream communications and received by CPE 204. The term "victim" is applied to the line or the circuit being examined for crosstalk, and the term "disturber" is applied to the source of the crosstalk. Since the noise is generated away from the receiving side, this is referred to as downstream far-end crosstalk (FEXT). Likewise, interference shown by arrow 214 illustrates upstream near-end crosstalk (NEXT). Interference shown by arrow 216 illustrates upstream FEXT, and interference shown by arrow 218 illustrates downstream NEXT.
In xDSL communications, the communications bands are divided channels known as bins or tones. For example, the asymmetric digital subscriber line (ADSL) bins are 4.3125 kHz wide. Typically, the upstream communications uses fewer bins (for example, 26 bins spanning from 25.875 kHz to 138 kHz) making them more susceptible to interference.
Furthermore, FEXT, in general, is typically less severe than NEXT as it gets attenuated by the loop. In ADSL, the available lower bandwidth for the upstream channel might be severely affected by the low frequency components of NEXT generated by sources such as single line high rate digital subscriber line (SHDSL). Also, the number of NEXT sources or potential disturbers at the CO side is higher due to large density mix of services at the CO. Further, self-NEXT can become the dominant NEXT disturber at long distances because other services do not extend so far. Therefore, upstream NEXT crosstalk is the most crucial interference to address for ADSL systems
In the past, the identification of noise and interference required loop qualification and line testing that had to be performed by deploying technicians to both ends of a connection and having them take measurements in a coordinated manner using special test equipment. Recently, xDSL standards such as ADSL2, ADSL2+, or very high speed digital subscriber line 2 (VDSL2) have recognized that xDSL modems are capable of transmitting and processing the necessary test signals, and of controlling the collection and exchange of these measurements from one end of the connection, typically the CO end. Within these standards, the capability is referred to as Dual Ended Line Testing (DELT).
A DELT session can be requested by either the CO or the CPE, and is often requested as part of the discovery phase of the initialization procedure. The difficulty is that the results, such as Quiet Line Noise (QLN) measurements, from the DELT session provide raw measurements, but such measurements in raw form do not provide meaningful information to a service provider. One approach applied in the past is to find a maximum correlation with a "basis or a representative set" of measured crosstalk coupling functions. This basis is supposed to be representative of the crosstalk disturber. However, such an approach does not consider the fact that the basis set is shaped by the effects of the front-end, such as filter effects. Also, in a real world situation, in addition to the crosstalk disturber (which is a wideband disturber), a narrowband disturber may generate radio frequency interference (RFI) which can arise from radio transmissions such as amplitude modulations (AM) radio transmitters and amateur radio transmitters like HAM radios and operate at frequencies that fall into the frequency bands of xDSL. This situation is not accounted for by the correlation approach just described. Accordingly, various needs exist in the industry to address the aforementioned deficiencies and inadequacies.

Crosstalk recognition in presence of radio frequency interference


The present application is generally directed to methods for identifying immunogens from organisms and pathogens, and in particular for identifying immunogens which when administered as vaccines elicit a cellular and/or humoral immune response. The present application is also directed to pneumococcal T-cell immunogens, and vaccine compositions comprising one or a combination of pneumococcal immunogens and methods for treating or preventing pneumococcal infections using the vaccines thereof. The present invention also encompasses use of the pneumococcal immunogens for diagnostic purposes to identify a subject with a pneumococcal infection.

Almost one million children in the developing world die of pneumococcal infections each year. Despite the effectiveness of the conjugate pneumococcal vaccines, problems with this approach remain including the expense of production and delivery, and resulting serotype replacement as demonstrated in several clinical trials and epidemiologic studies. One positive effect of the current capsular-based vaccines has been evident in the patient population that is not being vaccinated: herd immunity plays an impressive role in the current vaccine strategy. For each case of pneumococcal disease prevented in children, about three cases of pneumococcal disease are prevented in adults by herd immunity. In this context at least, prevention of pneumococcal colonization is a main goal of protein-based vaccine approaches, because blocking colonization will block disease.
Alternative pneumococcal vaccines that elicit serotype-independent immunity, and that maybe more readily available to economically emerging countries are needed urgently. New antigens that can address this need would be very attractive. Additionally, current methods to identify immunogens focus on techniques that do not fully optimize the extraction or identification of the full antigen repertoire. This is true in the case of pneumococcus as well as other pathogens. A method that can identify a new set of antigens has potential to be impactful for the development of vaccines for a wide set of pathogens, including pneumococcus.

Immunogens and methods for discovery and screening thereof


A battery connector including an electrical connector including a plurality of terminals, each mechanically and electrically connectable with a battery, the terminals being in electrical communication with each other and mechanically connected to each other with a joint member that permits flexing the batteries with respect to one another.

A typical prior art flashlight 10 is shown in FIG. 1. The flashlight 10 typically includes a rigid tubular battery housing 12, in which one or more batteries 14 are disposed. One of the batteries 14 electrically connects to a light bulb assembly 16 or any other consumer of the energy supplied from the battery, which may have screw threads for screwing on to housing 12. (It is noted that a flashlight is just one example. Other examples include the battery connecting to a small motor, toy and the like.) An end cap 18 may also have screw threads for screwing on to the opposite end of housing 12. End cap 18 may be in electrical communication with one of the batteries 14 by means of a spring 20 or other resilient connection designed to compensate for any tolerances. A switch 22 selectively closes the circuit between the batteries 14 and the light bulb assembly 16.
One of the drawbacks of such prior art such as flashlights is their rigidity. The more the batteries or the longer they are, the more inconvenient and bulky the appliance such as a flashlight becomes to carry on one's person or to store or to use.
Various attempts have been made in the past to make flexible flashlights. The prior art flexible flashlights typically include a rigid battery housing connected by some flexible connection to the light bulb assembly. However, such prior art flexible flashlights still comprise a rigid battery housing and therefore do not adequately solve the abovementioned problem.


Methods for the manufacture of assemblies which included brazed components and in which nickel/chromium-based filler metals are used wherein the manufactured assemblies are characterized by low leaching rates of nickel in water and water-based fluids, are disclosed. More specifically, there are disclosed methods for the manufacture of a heat exchanger or other assembly which method includes a brazing step, as well as a post-brazing conditioning step for treating the heat exchanger or other assembly. The manufactured heat exchangers and other assemblies are particularly useful in the handling of materials intended for human consumption such as water, beverages or food as the manufactured heat exchangers or other assemblies are characterized by reduced leaching rates of nickel into fluids passed through the heat exchanger. Brazing compositions useful in such manufactured assemblies are also described.

The invention is generally a method for the manufacture of assemblies which included brazed metal components, wherein the manufactured assemblies are characterized by low leaching rates of nickel into a fluid contacting the brazed metal components.
The invention is particularly directed to methods for the manufacture of assemblies which included brazed metal components, such as heat exchangers as well wherein the manufactured assemblies are characterized by low leaching rates of nickel into fluids subsequently passing therethrough. These methods providing reduced nickel leaching rates are particularly useful for the production of various manufactured assemblies. These methods are particularly advantageous in the manufacture of heat exchangers and food processing equipment, including water treatment equipment, as well as other devices where low nickel leaching rates into a treated fluid would be desired.
Brazing is a process for joining parts, often of dissimilar compositions, to each other. Typically, a brazing filler metal having a melting point lower than that of the parts to be joined together is interposed between the parts to form an assembly. This assembly of the parts to be brazed and the filler metal is then heated to a temperature sufficient to melt the filler metal but generally lower than the melting point of the parts. Upon cooling, ideally a strong, void-free joint is formed.
Brazing in widely used in the manufacture of various assemblies, which themselves may be finished articles which may be used or sold, or which assemblies may be components of such articles. One class of products produced by brazing processes are heat exchangers and food processing apparatuses. These may take a wide variety of configurations. For examples, heat exchangers such as xe2x80x9cshell-and-tubexe2x80x9d types, xe2x80x9cplate/platexe2x80x9d and xe2x80x9cplate/finxe2x80x9d type heat exchangers are most usually encountered. In the first configuration, a larger diameter housing typically referred to as a xe2x80x9cshellxe2x80x9d encompasses one or more small diameter tubes or pipes. According to this configuration, a first fluid (i.e., liquid, gas) passes through, the shell and about the exterior of the tubes while simultaneously, a second fluid (liquid, gas) passes through the interior of the tubes. While no physical contact is permitted between the first and second fluids, heat transfer occurs across the walls of the tubes. In plate/plate and plate/fin type heat exchangers, again a physical member, namely one or more plates separate a first fluid from a second fluid while heat transfer occurs across the plate. In these types of heat exchanger (as well as in other assemblies), metals are most commonly used due to their high strength and good heat transfer characteristics. Typically, the individual parts which are used to make up these type of heat exchangers are joined by brazing. Thus, it is imperative that joints exhibit high strength, and be resistant to any potential detrimental effects which might result from contact with one or both of the fluids.
One field of use wherein heat exchangers find utility are in the processing of materials which were ultimately used for human ingestion and consumption. These include foodstuffs as well as fluids such as water and beverages, juices, etc. Materials of construction used for heat exchangers to be used in such applications are of critical importance in that not only do they need to provide excellent operative characteristics with regard to heat transfer, but also at the same time these materials need to be compatible with the fluids being treated. One particular concern is to ensure that undesired leaching of any elemental or molecular components of the materials of construction used to produce the heat exchanger do not elute into the fluids. If they do, then it is imperative that any leaching of any such undesired materials be minimized. Frequently, local governmental or regulatory authorities have established maximum amounts of materials, such as metal ions, which may be permitted to leach per unit volume (liter, gallon) into fluids passing therethrough. Ideally, the materials of construction, including brazing filler metals, are optimized so to meet or preferably not to exceed such governmental regulations.
To minimize this undesired technical effect, the materials of construction for heat exchangers, particularly those used for foodstuffs, need to be very carefully selected. Stainless steels are very commonly encountered for they exhibit desirable properties including low leaching rates into fluids or gases, and generally good corrosion resistance. However, the brazing manufacturing process carried out at high temperatures may also affect stainless steels leaching adversely. Previously, elemental copper was used as a brazing filler metal as such featured low leaching of nickel into fluids, especially water However, the corrosion resistance of heat exchangers whose components were brazed using a copper based brazing filler metal is poor. Typically these heat exchangers required frequent replacement, which incurs cost not only for new heat exchanger assemblies, but also the costs associated with the labor and replacement of such failed heat exchanger assemblies. To improve corrosion resistance it was recently found that brazing filler metals with compositions based primarily on nickel and chromium (xe2x80x9cNi/Crxe2x80x9d) can be used to join stainless steel parts used in such assemblies. Unfortunately, it was also found that when such Ni/Cr-based brazing filler metals are used, often an undesirable high amount of nickel was leached into water or other fluids flowing through these assemblies. As such Ni/Cr-based brazing, filler metals include a significant proportion of nickel, they are believed to be the source of the undesired nickel found to leach into fluids. Thus, such Ni/Cr-based brazing filler metals are usually avoided from use in applications wherein the amount of nickel leaching into a fluid is a concern, as is the case wherein materials are ultimately to be used for human ingestion or consumption. Additionally, governmental regulations in some countries have sometime imposed strict limitations in the amount of nickel which may be leached into said fluids. Accordingly, it is to one or more of these technical needs that the present invention is directed.
In a first aspect, the present invention provides methods for the manufacture of assemblies especially those which include parts made of stainless steels wherein these assemblies include parts joined using nickel/chromium-based brazing filler metals, wherein the manufactured assemblies ale characterized by low leaching rates of nickel.
In a second aspect, the present invention relates to a method for the manufacture of a heat exchanger or other manufactured assembly which method includes a brazing step, as well as a post-brazing conditioning step for treating the heat exchanger. The manufactured heat exchangers are characterized by reduced leaching rates of nickel into fluids passed through the heat exchanger.
In a third aspect of the invention, there are provided manufactured assemblies which comprise parts joined by nickel/chromium-based brazing filler metals, wherein the assemblies are characterized bid reduced nickel leaching rates.
Further aspects and features of the invention will become more apparent from the following description.
As noted, the present invention provides methods for the manufacture of assemblies which included brazed metal components, wherein the manufactured assemblies are characterized by low leaching rates of nickel in the manufactured assembly.
As is understood in the art, in any brazing process, the brazing filler metal must have a melting point that will be sufficiently high to provide strength to meet service requirements of the metal parts brazed together. However, the melting point must not be so high as to make the brazing operation difficult. Further the filler material must be compatible both chemically and metallurgically, with the materials being brazed.
The nickel/chromium-based brazing filler metals particularly useful in the methods and assemblies according to the present invention are metal alloys which can be produced in various forms, including but not limited to powders, foils, ribbons and wires according to well known techniques. Methods commonly used to fabricate alloys in powder form include gas or water atomization as well as mechanical pulverization. Alloys of the present invention are most preferably formed into ductile foils, ribbons or wire by a rapid solidification process. Such rapid solidification processes are processes whereby a melt of molten material is solidified by quenching the melt by rapidly cooling al a rate of at least about 103xc2x0 C./sec although higher rates are known and more commonly used. Among the variety of rapid solidification processes available today, the most preferred process employs a rapidly rotating chill wheel onto which a molten alloy is cast. Such a process is per se, known to the art.
Ideally, the nickel/chromium-based brazing filler metals used according to the present invention is in the form of a ductile foil which can be readily handled. When in the form of a ductile foil form the nickel/chromium-based brazing filler metals may also be formed into complex shapes in order to fit contours in metal parts used in the assembly of manufactured assemblies. Formation into complex shapes can occur by bending or stamping the ductile foil. Further, ideally, the brazing foil should be essentially homogeneous in its compositions, that is to say that it contains no binders, such as organic binders which would provide the potential for void formation or the deposition of contaminating residues during brazing.
Rapidly solidified products produced from homogeneous melts of the alloys are usually homogeneous in the solid state. The products may be glassy or crystalline depending upon the alloy compositions and processing parameters. In addition, products at least 50% glassy usually exhibit sufficient ductility to enable foil, ribbon and wire forms of the alloys to be bent to a radius as small as ten times their thickness without fracture. Preferably, the nickel/chromium-based brazing filler metals of the present invention are metal alloys which are formed by rapidly solidifying a melt of the metal alloy at quenching rates of at least about 105xc2x0 C./sec. Such quenching rates produce alloys which are at least about 50% glassy and, as a result, are sufficiently ductile so as to enable them to be stamped into complex shapes. More preferably, the alloys of the present invention are at least about 80% glassy, and most preferably substantially glassy (i.e., at least 90% glassy) because substantially glassy alloys exhibit the highest degree of ductility.
The alloys useful in the present invention are particularly suited as brazing filler metals for the methods described herein. Most preferably, the alloys are produced in foil form and are useful regardless of whether the foil is glassy or microcrystalline. The foils of the present invention typically are between about 0.0007 inches and about 0.004 inches (about 18 to 100 micrometers) thick. In many instances, the foil thickness corresponds to the desired spacing between parts to be brazed.
The brazing filler metals of the present invention are particularly useful for the joining of metal parts, and in particularly stainless steel parts. Stainless steels are most frequently used in processing of fluids including foodstuffs such as juices or other beverages, such as water which are ultimately intended for human consumption. Exemplary grade of such stainless steels includes: steel S31603 according to UNS Classifications as well as the 316L stainless steel which is described as typically containing approximately 0.03% wt. carbon, 2.00% wt. manganese, 1.0% wt. silicon, 16 to 18% wt. chromium, 10 to 14% wt. nickel, 2 to 3% wt. molybdenum, 0.1% wt. nitrogen and iron as the balance to 100% wt. It is of course contemplated that other materials which may benefit from the inventive teaching can also be used in accordance with the invention described herein and enjoy the benefit of reduced nickel leaching rates. By way of non-limiting (example these include other grades of stainless steel, as well as other corrosion resistant alloys such as those including nickel or chromium.
While nickel/chromium-based brazing filler metals useful according to the invention are believed to encompass most known Ni- and Ni/Cr-based alloys which are commonly used in brazing of stainless steel parts, compositions which are particularly useful as the nickel/chromium-based brazing filler metals useful in the methods and manufactured articles according to the invention include metal alloy compositions which may be represented by the formula:
NiaCobCrcBdSieFefMogWhX
where the subscripts xe2x80x9caxe2x80x9d, xe2x80x9cbxe2x80x9d, xe2x80x9ccxe2x80x9d, xe2x80x9cdxe2x80x9d, xe2x80x9cexe2x80x9d, xe2x80x9cfxe2x80x9d, xe2x80x9cgxe2x80x9d, and xe2x80x9chxe2x80x9d are all in weight percent and wherein, xe2x80x9cbxe2x80x9d is between about 0 and 75, xe2x80x9ccxe2x80x9d is between 0 and about 25, xe2x80x9cdxe2x80x9d is between 0 and about 4, xe2x80x9cexe2x80x9d is between 0 and about 11, xe2x80x9cfxe2x80x9d is between 0 and about 10, xe2x80x9cgxe2x80x9d is between 0 and about 5, xe2x80x9cixe2x80x9d is between 0 and about 5. xe2x80x9cXxe2x80x9d represents other elements, including impurities which may be present to about 1 weight percent, and xe2x80x9caxe2x80x9d is the balance to the total amount to 100. Preferably these nickel/chromium-based brazing filler metals consist essentially of the elements recited above. It is to be understood that the term xe2x80x9cnickel/chromium-based brazing filler metalsxe2x80x9d encompasses alloys wherein chromium is absent, but as chromium is typically present the use of this term is retained.
Preferably, the nickel/chromium-based brazing filler metals are based on an alloy which is in a metastable structural state having at least 50 percent glassy structure, more preferably having at least 75% glassy structure, and most preferably having at least 90% glassy structure. Such alloys are also frequently referred to in the art as xe2x80x9camorphous metal alloys.xe2x80x9d Further examples of nickel/chromium-based brazing filler metals based on alloys which may be used as brazing filler metals described herein and which are presently commercially available include: those referred to according to ANSI classification A5.8 (per the American Welding Society) as filler metals BNi-1, BNi-1a, BNi-2, BNi-5, BNi-7, BNi-9, BNi-10, BNi-11, and BCo-1 as well as sub-categories of each. Examples of preferred Ni- and Ni/Cr-based alloys useful as the nickel/chromium-based brazing filler metals which having chemical compositions as described above and which are presently commercially available include: BNi-2, BNi-5a, and BNi-5b compositions according to the above mentioned ANSI/A5.8 Classification. Ideally, the nickel/chromium-based brazing filler metals used according to the present invention are in ductile foil form which can be readily handled and when necessary, shaped to fit contours or shaped into necessary complex shapes. Further ideally, the nickel/chromium-based brazing filler metals are brazing foils essentially homogeneous in its composition, that is to say that it contains no binders, such as organic binders which would provide the potential for void formation or the deposition of contaminating residues during brazing.
In a preferred aspect of the invention there is provided a method for the manufacture of heat exchangers and other apparatuses which are ultimately used for the processing of materials for human ingestion or human consumption which method includes a brazing step, as well as a post-brazing conditioning step for treating the heat exchanger or other apparatus. These manufactured heat exchangers and other apparatuses are characterized by reduced leaching rates of nickel into fluids passed therethrough.
According to this method there is a provided a method for the manufacture of a heat exchanger or other assembly which includes brazed parts which includes the steps of:
(a) juxtaposing parts to define one or more joints therebetween;
(b) supplying to the one or more joints a nickel/chromium brazing filler metal;
(c) heating the juxtaposed parts and the brazing filler metal under appropriate conditions in order to cause the melting of the brazing filler metal;
(d) cooling the melted brazing filler metal to produce a brazed joint;
(e) subsequently, conditioning the brazed parts by exposing it to an elevated temperature, preferably at a temperature of from about 150xc2x0 C. to about 600xc2x0 C., but preferably between about 150xc2x0 C. to about 400xc2x0 C. in an oxygen-containing atmosphere, preferably air, for a sufficient time to substantially reduce the amount of nickel leaching into water or other fluids contacting the brazed joints of the brazed assembly.
In a preferred embodiment of the method described above, as the nickel/chromium-based brazing filler metals (in which cobalt may be absent) there is provided a brazing filler metal having a composition represented by the formula:
NiaCobCrcBdSieFefMogWyX
where the subscripts xe2x80x9caxe2x80x9d, xe2x80x9cbxe2x80x9d, xe2x80x9ccxe2x80x9d, xe2x80x9cdxe2x80x9d, xe2x80x9cexe2x80x9d, xe2x80x9cfxe2x80x9d, xe2x80x9cgxe2x80x9d, and xe2x80x9chxe2x80x9d are all in weight percent and wherein, xe2x80x9cbxe2x80x9d is between about 0 and 75, xe2x80x9ccxe2x80x9d is between 0 and about 25, xe2x80x9cdxe2x80x9d is between 0 and about 4, xe2x80x9cexe2x80x9d is between 0 and about 11, xe2x80x9cfxe2x80x9d is between 0 and about 10, xe2x80x9cgxe2x80x9d is between 0 and about 5, xe2x80x9chxe2x80x9d is between 0 and about 5, xe2x80x9cXxe2x80x9d represents other elements, including impurities which may be present to about 1 weight percent, and xe2x80x9caxe2x80x9d is the balance to the total amount to 100.
Preferably in the process described above heating of the juxtaposed parts to cause the brazing of the parts occurs in a closed oven in the presence of a protective gas such as argon or nitrogen. Alternately, heating may occur in a closed oven under vacuum conditions as well and in certain instances is preferred. These brazing conditions are typically used in industry to achieve a high joint strength and integrity when using Ni/Cr-based filler metals containing oxygen-active elements such as boron, silicon, and phosphorus. During this heating stage of the brazing cycle the parts and joint surfaces which are present under vacuum conditions or are under a protective atmosphere acquire only an insufficiently thin layer of chromium oxide. Such a chromium oxide layer has however been found wholly deficient in protecting against leaching of nickel from the brazed joint into a fluid passing through an assembly. The present inventor has overcome this deficiency in the prior art by his post-brazing step wherein an assembly, such as a heat exchanger or other device is maintained in an oxygen-containing atmosphere, such as air, at an elevated temperature for a sufficient time in order to provide for the satisfactory buildup of a surface oxide layer, believed to be predominantly composed of chromium oxide on the brazed parts and joints of the assembly. With respect to this post-brazing conditioning step, the brazed assembly is exposing it to a temperature of from about 150xc2x0 C. to about 600xc2x0 C. under an oxygen-containing atmosphere, preferably air, for a sufficient time to sufficiently oxidize the brazed joint of the assembly. While it will be understood that the optimal treatment conditions depend upon the type and size of the assembly, being treated, the optimal treatment conditions for a particular assembly may be determined by routine experimentation, such as by varying the time and temperature of the exposure to the elevated temperature. Surprisingly, the present inventor has found that better results are typically expected when the brazed assemblies are exposed to lower temperatures, preferably between about 150xc2x0 C.-400xc2x0 C., in the oxygen-containing atmosphere. This was in contravention to the normal expectation that higher temperatures would provide more effective and perhaps shorten the exposure time of the brazed joints to elevated temperatures.
Manufactured assemblies, and especially heat exchangers manufactured according to the methods described herein are characterized by reduced leaching rates of nickel into water-based fluids passed therethrough. With respect to the reduction of nickel leaching, which is attained by the practice of the post-brazing conditioning step it is to be understood that the degree of reduction may vary. While it is to be understood that any reduction in nickel leaching, particularly into a liquid such as water is to be considered to fall within the scope of the present invention, a reduction on the order of at least 50%, preferably at least about 70% and most preferably a reduction of at least about 85% is attained. Such percentages are based upon a comparison of the nickel leaching rates under identical test conditions of trio identical heat exchangers (or other manufactured assembly) which have been similarly manufactured, but wherein only one is manufactured in a process which includes the post-brazing conditioning step described herein.
The present inventor has unexpectedly found that the post-brazing conditioning step has overcome many of the technical problems which to date have plagued the art. More particularly the heat exchangers and other assemblies according to the present invention surprisingly elute (xe2x80x9cleach xe2x80x9d) a substantially reduced amount of nickel into water-based fluids passing therethrough as compared to the same heat exchangers wherein the final post-brazing conditioning step has been omitted. This is surprising due to the fact that as the brazing filler metals described herein typically include a substantial amount of nickel in their compositions and, therefore, a significant leaching of nickel would be expected. However, it has been found that the post-brazing conditioning step substantially reduces this effect. Prior to the present invention, it has been nearly impossible to attain in stainless steel heat exchangers brazed using nickel/chromium-based alloys of the type described herein which had nickel leaching rates comparable to the nickel leaching rates of like stainless steel heat exchangers which included brazed joints wherein a copper brazing filler metal was used.
Additionally, the heat exchangers and other assemblies produced according to the process described herein are believed to exhibit greatly increased resistance corrosion which in turn provides a substantially longer expected service life of the assembly. This is particularly relevant as a longer service life reduces the risk of failure, as well as reduces the expected frequency of replacement or maintenance of such heat exchangers and other assemblies.
Significant fields of application wherein the inventive heat exchangers and other assemblies manufactured according to them methods described herein include the cooling of drinking water or other beverages. Of course the methods described herein can be used in manufacture of other devices or articles useful both within the technical area related to in food and beverage processing, as well as outside of this technical area.
It will of course be understood that the utility of the present invention is not limited to the manufacture of heat exchangers but also finds use in any application wherein it is desired to reduce the amount of nickel which may leach from two or more brazed metal parts. More generally then invention also relates to process for joining two or more metal parts, particularly two or more stainless steel parts, which process comprises the steps of:
(a) placing brazing filler metal between the parts to form an assembly, the brazing filler metal having a melting temperature less than that of any of the parts;
(b) heating, the assembly to at least the melting temperature of the brazing filler metal such as
(c) cooling the assembly; and subsequently,
(d) subsequently, conditioning the brazed parts by exposing it to an elevated temperature, preferably at a temperature of from about 150xc2x0-600xc2x0 C., but preferably between about 150xc2x0-400xc2x0 C. in an oxygen-containing atmosphere, especially air, for a sufficient time to substantially reduce the amount of nickel leaching into water or other fluids contacting the brazed joints of the brazed assembly.

Heat exchanger manufacturing methods and brazing filler metal compositions useful therein, characterized by low nickel leaching rates