This invention is a multiple-frequency signal generator apparatus and method primarily for simulating a cell site interference environment for electromagnetic communications systems. The generator can produce a plurality of frequencies having a frequency-spacing of d cycles per second. The invention comprises a single frequency multiplier, at least three oscillators and two mixers for providing a multitude of frequencies closely spaced about a carrier frequency. The simple design and components avoid complexity and save costs.

Mobile telephone cellular communications systems divide geographic areas into cells, each cell being served by a cell site having a transmitter and receiver.
When a user in a car (the "mobile unit") desires to make a call, the mobile telephone unit scans the set-up channels, selects the strongest and locks on for a certain time. Each cell site is assigned a different set-up channel, so locking on to the strongest usually means selecting the nearest cell site.
A call request sent from the mobile unit is received by a cell site which typically selects a directive antenna for the communications channel. At the same time, the cell site also sends a request for a voice channel to the Mobile Telephone Switching Office (MTSO) via a high-speed data link. The MTSO selects an appropriate voice channel for the call and the cell site links the channel with the directive antenna to the mobile unit. The MTSO also connects the wire-line party through the telephone company central office.
A call from a land-line party to a mobile unit goes first to the telephone company central office which recognizes that the number is for a mobile unit and forwards the call to the MTSO. The MTSO sends a paging message to certain cell sites based on the mobile unit number and a search algorithm. Each cell site transmits the page on its own set-up channel. The mobile unit recognizes its own identification on a strong set-up channel, locks onto it, and responds to the cell site instruction to tune to an assigned voice channel.
Communications with mobile units passing from one cell to another are maintained by handoff schemes whereby cell sites transfer the communications between each other.
A core concept of cellular mobile communications systems is the reuse of frequency channels in order to increase the efficiency of use of a limited allocated spectrum. In a frequency reuse system, users in different geographic locations (different cells) simultaneously use the same frequency channel. This increases the spectrum use efficiency, but also may produce serious interference problems. Interference due to the common use of the same channel is called cochannel interference.
The minimum distance between cells using the same channel depends on factors such as the number of cochannel cells in the vicinity, the terrain, antenna heights, and transmission power at each cell site. To maximize spectrum utilization efficiency, it is necessary to minimize the distance between cells using the same channel while maintaining a sufficiently low level of cochannel interference. A comprehensive discussion of minimum distance and cochannel interference can be found in Mobile Cellular Telecommunications Systems, Chapter 2, (McGraw-Hill 1989) by William C. Y. Lee.
It is a difficult undertaking to accurately determine the areas of serious cochannel interference in a mobile communications system. A first test, simply described, involves transmitting on one channel at night while the mobile unit travels in one of the cochannel cells. A field-strength recorder in the mobile unit monitors changes in signal compared with the condition of no cochannel transmission. The test must be repeated as the mobile unit travels in every cochannel cell. A channel scanning receiver in the mobile unit records the signal level on the no-cochannel condition on one channel, the interference level on another channel, and a third non-utilized channel. By comparing the signal levels in the channels, the sufficiency of coverage may be estimated and the areas of cochannel interference spotted.
A second test involves, in a first approach, simultaneously using mobile units travelling in each cochannel cell and monitoring the signal levels. Since it is difficult to use multiple mobile units simultaneously, an alternative approach is to use a single moving mobile unit in one of the cochannel cells at a time and to record the signal strength at every other cochannel cell site. By determining the highest and lowest average signal strengths, the carrier-to-interference ratio received at a particular cell may be estimated. For details of these tests, see Mobile Cellular Telecommunications Svstems, Chapter 6, (McGraw-Hill 1989) by William C. Y. Lee.
Real-time cochannel interference measurements at the mobile transceivers are difficult to achieve in practice. Simply stated, this is because the sampling delay time must be sufficiently small such that both the amplitudes of the signal and the interference have not changed appreciably in the interim. A description of this problem can be found on pages 183-184 of Lee's book supra.
The determination of cochannel interference in practice is clearly difficult and the estimation of cochannel interference is crucial to the design of cellular mobile communications systems. Thus, it would be a significant advance in the art to have a frequency generator which can generate a realistic sequence of frequencies to simulate cochannel interference in a mobile communications system.
There are also other kinds of interference in mobile communications system, termed "noncochannel interference." "Adjacent-channel interference" includes next-channel (the channel next to the operation channel) and neighboring-channel (more than one channel away for the operating channel) interference. Next-channel interference must originate at other cell sites. This is because any channel combiner at the cell site must combine the selected channels. Therefore, next-channel interference will arrive at the mobile unit from other cell sites if the system is not designed properly. Also, a mobile unit initiating a call on a control channel in a cell may cause interference with the next control channel at another cell site.
Neighboring-channel interference typically results when all the channels are simultaneously transmitting at one cell site. Avoidance of interference problems requires a sufficient amount of band isolation between channels.
Further, there is a type of adjacent-channel interference that is unique to mobile communications systems. Since many mobile units are in motion simultaneously, their relative positions change with time. Some mobile units are close to the cell site and some are not. The close-in mobile units have strong signals which cause adjacent-channel interference. This type of interference is called near-end/far-end interference. There also can be interference between different mobile communications systems. That is, if a mobile unit in one system is closer to a cell site of another system while a call is initiated through the first system, then adjacent channel interference may be produced.
Finally, because some UHF television channels overlap cellular mobile channels, there may be UHF TV signal interference with mobile cellular signals. There may also be interference from long-distance telephone communications.
The communications environment itself contains naturally occurring non-linear junctions (such as buildings and other structures) which act upon transmitted signals to generate cross-products or intermodulation products between simultaneously transmitted signals. These products generate signals having frequencies the same or nearly the same as those carrying desired information and can thus be sources of interference.
Operable designs of mobile communications systems must consider the various kinds of interference described above. Many methods and devices to reduce interference are discussed in Mobile Cellular Telecommunications Svstems, Chapter 7, (McGraw-Hill 1989) by William C. Y. Lee. The choice of an optimum system design requires knowledge of the effects of interference. This knowledge can be gained by field testing through reproduction of the interference environment or by computer simulation. Computer simulation has the disadvantage that it does not allow a physical test of all the equipment and personnel. Thus, the best test of a mobile communications system is a subjective voice-quality monitoring for a given carrier-to-noise ratio. Therefore, there is a distinct need for an interference simulating device to subjectively test the voice quality of mobile communications systems and to rapidly and accurately identify which of a multitude of frequencies are causing the interference.
Prior art interference frequency generators include U.S. Pat. No. 4,317,214 to Attinello which injects interference signals into a receiver to simulate environmental interference effects. The types of interference injected include white noise, pseudo-random pulses, sawtooth or comb signals and other types of signal distortion.
U.S. Pat. No. 3,806,809 to Firman discloses a frequency generator simulating intermodulation interference. The generator produces, mixes, and non-linearly amplifies harmonic and beat frequencies of the carrier signal to produce a spectrally-expanded composite signal. This composite signal can then be analyzed for the main interference component affecting the carrier signal.
The prior art described above can not, however, produce frequencies with spacing of less than 150 Khz from a single multiplier. Such close frequency spacing is necessary to adequately and realistically simulate the signal transmissions from mobile communication cell sites.

Frequency signal generator apparatus and method for simulating interference in mobile communication systems


A retainer strip for a window flashing used to weatherproof the installation of a window comprises a window grip leg for holding the retainer strip in a kerf in the window frame, and a flashing grip leg adapted to be mounted parallel to the side of the window frame for retaining the flashing in the space between the window grip leg and the side of the window frame.

When windows are installed in buildings, such as residential dwellings, they are installed in window openings. Replacement windows, as opposed to new residential windows, are usually installed in existing window openings. After the replacement window is installed, prepainted aluminum flashing is used to cover the gap between the new window and the existing siding, brick, or other exterior wall surface of the window opening.
One of the problems with the installation of replacement windows is that the cover or flashing for the opening or gap between the new window frame and the existing building wall needs to be secured or fixed in place, and in a manner which will prevent wind or moisture from entering the building. Further, the flashing must be attached in an aesthetically pleasing manner. Typical means for fastening the window flashing includes nailing, bending, and gluing the flashing in place. Nailing is often difficult because the wood surrounding the window opening may be old and rotten. Another method commonly used is merely caulking the flashing all the way around the perimeter of the window for a wind and water-tight joint. This old method of caulking can degrade after a period of weathering, resulting in air and water leaks into the building. It would be extremely desirable to provide an improved means for retaining the window flashing, particularly if such a method resulted in an easier installation method than methods heretofore employed.


A valve seal for a rotary valve assembly for use in internal combustion engines having rotary intake valves and rotary exhaust valves which have a spherical peripheral surface, the valve seal being of two-piece construction surrounding the intake or exhaust port and having an upper surface designed to contact the peripheral surface of the rotary valve, the two-piece construction defining a channel whereby compressed gases exert additional pressure on the seal enhancing the sealing contact between the seal and the valve.

Applicant has pending applications, Ser. Nos. 270,027 409,037 and 422,053 directed to the design of a spherical rotary valve assembly for an internal combustion engine of the piston and cylinder type which are incorporated herein by reference. The prior applications are directed towards the spherical rotary valve assembly having the rotary intake valve and rotary exhaust valve mounted on single or dual shafts having single or dual ports to operate at one-half or one-quarter speed of the engine's revolutions per minute. The prior application discloses a lubricating system for the spherical rotary valve assembly and seals positioned in the spherical rotary valve assembly in contact with the rotary intake valve and rotary exhaust valve. The advantages of Applicant's invention and the background thereof are set forth in the prior application.
This present application is directed towards an improved seal for use with the rotary intake valve and rotary exhaust valve which provides for an improved gas tight seal during the introduction of the fuel/air mixture and the evacuation of the spent gases. The design of this improved seal is such that it provides for an improved seal by utilizing the compression and expansion of the fuel/air mixture in the cylinder to effectuate a gas tight seal with the rotary intake valve and rotary exhaust valve during the compression stroke.


A dispenser cathode including a dispenser body formed of a metal matrix and an emission surface formed of emission material impregnated into the dispenser body metal matrix. The metal matrix is a porous sintered metal matrix containing at least one metal frown a first group (W, Mo, Cr) and at least one metal of a second group (Fe, Co, Ni, Ru, Rh, Pd, Re, Os, Ir, Pt) and chromium oxide. The chromium oxide and the metals from the two groups are provided as a powder mixture to form the matrix. The emission material includes at least two alkaline earth metal oxides such as CaO, BaO and at least one oxide of a metal of group IIIa or IIIb of the Periodic Table. The oxide of a metal group is Al.sub.2 O.sub.3.

Dispenser oath are also called matrix cathodes or reserve cathodes. They consist, in general, of a dispenser body, also called a metal matrix, which is pressed or sintered from a metal powder and is impregnated with the actual emission material. Metals such as tangsten and molybdenum can be considered for use as the metal powder for the dispenser body. The use of mixtures of such metal powders has been known as well. Pressing the dispenser body into a cavity of a cathode sleeve has been known from German Offenlegungsschrift No. DE-OS 20,48,224. For example, building up the dispenser body in layers has been known from German Offenlegungsschrift No. DE-OS 41,14,856. The porous matrix body can be impregnated with an emission material, which consists of, e.g., BaO-CaO-Al.sub.2 O.sub.3, by impregnation, melting in or the like.
It was found, in general, that so-called mixed-metal matrix cathodes (MM cathodes), i.e., cathodes whose dispenser bodies are pressed and sintered from a metal powder mixture, have improved dimensional stability and better current stability. The dispenser bodies of mixed-metal matrix cathodes consist, in general, of metals of a first group, such as tungsten, chromium or molybdenum, and metals of a second group, such as iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pal), rhenium (Re), osmium (Os), iridium (It), and platinum (Pt).
Adding tungsten or tungsten oxide to the emission material has also been known from German Patent No. DE-PS 30,17,429.
It has also been known that the emission capacity of the cathodes can be improved by adding scandium compounds to the cathode body or to the emission material. However, the long-term properties of these so-called "Scandat cathodes" are not yet satisfactory.

Dispenser cathode with porous sintered compacted metal dispenser body containing chromium oxide


There is provided a display device: a display unit including a plurality of scan electrodes arranged to extend in parallel to each other along a first direction, a plurality of data electrodes arranged to extend in parallel to each other along a second direction crossing the scan electrodes, and a plurality of pixels, each pixel at which a pair of the scan electrode and the data electrode cross each other, each pixel having a light emitting layer and a dielectric layer interposed between the scan electrode and the data electrode from a direction vertical to a face; and an erasing pulse supplying unit operable to supply attenuation voltage pulse, to the light emitting layer of each pixel, which starts at a voltage not more than an emission starting voltage at which the light emitting layer starts emission and in which polarity is alternately reversed between positive and negative.

Recently, there are large expectations for EL elements in the field of a flat-type display device. An EL element is characterized as to have a self-luminous property, a high level of visibility, a wide viewing angle, a fast response and the like. EL elements currently developed include an inorganic EL element using an inorganic material as a light emitting material and an organic EL element using an organic material as a light emitting material.
In an inorganic EL element in which an inorganic phosphor such as zinc sulfide is used as a light emitting material, electrons accelerated in a high electric field of 106V/cm collision-excites the light emitting center of the phosphor, and when they are relieved, light is emitted. Inorganic EL elements includes a dispersion EL element having such a structure that phosphor powder is dispersed in polymeric organic materials and electrodes are provided on top and bottom, and a thin-film EL element having two dielectric layers between a pair of electrodes and a thin film light emitting layer interposed between the dielectric layers. A dispersion EL element is easily manufactured, but the brightness is low and the service life is short, so it has been used only for limited purposes. On the other hand, as for a thin film EL element, an element having a dual insulating structure proposed by Inoguchi et al. in 1974 (see, for example, Japanese Patent Laid-open Publication No. 52-33491) shows high brightness and a long service life, which has been used practically for an in-car display or the like.
Here, a typical configuration of the thin film EL element will be explained by using FIG. 12. FIG. 12 is a sectional view vertical to a light emitting face of a thin film EL element 60. The EL element 60 has such a configuration that a transparent electrode 62, a first dielectric layer 63, a light emitting layer 64, a second dielectric layer 65, and a counter electrode 66 are laminated in this order on a transparent substrate 61. By applying alternating voltage between the transparent electrode 62 and the counter electrode 66, light is emitted from the light emitting layer 64. The first dielectric layer 63 and the second dielectric layer 65 interposing the light emitting layer 64 have a function of limiting current flowing through the light emitting layer 64, are capable of suppressing dielectric breakdown of the EL element 60, and act so as to obtain stable light emitting characteristics. Light emitted from the light emitting layer 64 is taken out from the transparent electrode 62 side.
Further, a display device may be configured by aligning a plurality of EL elements two-dimensionally in such a manner that the transparent electrode 62 is shared by a plurality of EL elements in the same row, and the counter electrode 65 is shared by a plurality of EL elements in the same row. In such a case, one transparent electrode extends in a row direction, and a plurality of transparent electrodes, parallel to each other, and a plurality of counter electrodes are stripe patterned so as to be made orthogonal to each other, and by applying a voltage to specific pixels selected by a matrix, it is possible to obtain a passive matrix driving type display device which performs any pattern display.
A basic driving method of a display device using the above-described EL element is realized such that transparent electrodes of the EL elements are used as data electrodes and counter electrodes are used as scan electrodes, and modulation voltage corresponding to display data determining whether to emit light or not is applied to the data electrodes while writing voltage is applied to the scan electrodes in a linear order. In this driving method, a superposed effect or an offset effect of writing voltage and modulation voltage is generated at parts where the scan electrodes and the data electrodes cross to each other (hereinafter referred to as pixels for short) in the EL element. The EL element has a voltage-brightness characteristic as shown in FIG. 13, and as an emission starting voltage Vth (hereinafter Vth indicates a positive real number), a high voltage as much as about 200V is required generally. In each pixel, when a voltage of not less than the emission starting voltage Vth is applied, light is emitted, and when a voltage of not more than the emission starting voltage Vth is applied, a state where light is not emitted is shown, whereby a desired display is obtained as a whole.
In a display device using such thin film EL elements, as a driving method for realizing gradation display of each pixel, there is known a voltage modulation method in which control is performed with voltage pulse amplitude applied to EL elements (see, for example, Japanese Patent Laid-open Publication No. 63-15590) or a pulse width modulation method in which control is performed with a pulse width (see, for example, Japanese Patent Laid-open Publication No. 01-307797). Among them, the voltage modulation method is capable of realizing a medium brightness by applying amplitude of modulation voltage applied to data electrodes in a multistage manner, but has a problem that gradation control accuracy is extremely low due to precipitous property and nonlinearity of voltage-brightness characteristics and hysteresis characteristics. On the other hand, the pulse width modulation method is capable of realizing a medium brightness by controlling the pulse width of modulation voltage applied to the data electrode in a multistage manner theoretically, but when driving pulse in a rectangle waveform is applied to the EL element, current contributing to light emission rises with a precipitous peak immediately after a rise of the voltage, and then shows a behavior of being attenuated rapidly as the same as charge current to the capacitor. The period in which the current flows is a short period of several μ seconds, and even though the pulse width is extended after the current is attenuated, current will not flow any more, so a brightness difference corresponding to the pulse width cannot be obtained. In order to obtain a sufficient gradation display by controlling the pulse width, it is required to control a multistage pulse width within the period of several μ seconds during which the current flows. However, if the pulse width varies slightly due to the response velocity of a driving circuit or the control accuracy of the pulse width or the like, the brightness largely changes. Therefore, gradation control by the pulse width modulation method is not suitable for EL elements.
Consideration will be given for the reason why the current contributing to light emission in an EL element rises with a precipitous peak immediately after a rise of voltage and then behaves to be attenuated rapidly as described above. One reason may be a fact that the EL element is a capacitive element. That is, the EL element has such a structure that the light emitting layer 64 is interposed between the dielectric layers 63 and 65, so it may be seen as a capacitive element from a viewpoint of equivalent circuit. In this case, when voltage pulse not less than an emission starting voltage is applied to the light emitting layer 64, the resistance of the light emitting layer 64 falls rapidly and electrons pass through the light emitting layer 64 in the high electric field to thereby excite the light emitting center, and then they reach the interface with the dielectric layer 65 and are retained. In this way, after light emitting operation is carried out, polarization charges remain in the light emitting layer. Hereinafter, this polarization charges are referred to as "first polarization charges" for short, and the potential difference caused inside the light emitting layer by the first polarization charges is referred to as a "first polarization voltage" for short. With the first polarization charges, a potential difference acting in a reverse direction to the outside voltage is caused inside the light emitting layer 64, whereby an effective voltage acted on the light emitting layer 64 becomes smaller than the emission starting voltage Vth due to an offset with the outside applied voltage, so current will not flow any more. Therefore, when voltage pulse is applied to an EL element, current contributing to light emission rises with a precipitous peak immediately after a rise of voltage, and then is attenuated rapidly.
This phenomenon will be explained in more detail by using FIG. 14, in which the horizontal axis shows the applied voltage V and the vertical axis shows the first polarization charges P. When voltage is not applied to an EL element and the first polarization charges do not exist in the light emitting layer, it is in a state of position A (polarization amount 0) in the Figure. Then, when a driving voltage Vr (voltage higher than emission starting voltage) in a pulse shape is applied so as to cause the EL element to emit light, it is transferred to a state of position B (polarization amount Pb) in the Figure as the applied voltage V rises, and then, even when the applied voltage V becomes 0, it is transferred not to a state of the first position A (polarization amount 0) but to a state of position C (polarization amount Pc). Namely, the first polarization charges remain in the light emitting layer even though voltage is not applied. This is considered as being based on a fact that when a voltage not less than the emission starting voltage is applied to the light emitting layer, electrons discharged from the proximity of the interface of one dielectric layer pass through the light emitting layer and reach the interface of the other dielectric layer, and are captured in a deep trap near the interface. Between the captured electrons and positive spatial charges in the light emitting layer, a steady electric field is formed and maintained. Then, when the polarity of the applied voltage between electrodes are reversed and a driving voltage −Vr in a pulse shape like the above-described one is applied, it is transferred from a state of position C (polarity amount Pc) via a state of position D (polarity amount 0) along the oblique line of negative voltage application to a state of position E (polarization amount Pe). Then, when the applied voltage becomes 0, it is transferred to a state of position F. In the state of position F, negative first polarization charges (polarization amount Pf) remain.
As described above, if a state where the first polarization charges remain in the light emitting layer continues, the first polarization voltage caused by the first polarization charges will be applied to the inside of the light emitting layer. Then, when light is emitted next time, the first polarization voltage is superposed with the outside applied voltage and applied to the light emitting layer. Therefore, although a voltage not more than the emission starting voltage Vth, providing operation of not emitting light, is applied, an effective voltage exceeding the emission starting voltage Vth is applied to the light emitting layer due to the first polarization voltage, which may cause false light emission.
Conventionally, in order to prevent such a false light emission at the time of next light emission, there has been proposed a method in which after a writing voltage is applied to each field, a polarization correction voltage of reversed polarization with respect to that of the writing voltage is applied so as to erase the first polarization charges (see, for example, Japanese Patent Laid-open Publication No. 03-69990). FIG. 15 is a time chart of a voltage applied to a light emitting layer of each pixel, showing an exemplary driving method for applying a polarization correction voltage. In a writing period 71, selective light emission is performed for each scan line, and then in a polarization erasing period 72, a polarization correction voltage of reverse polarity with respect to that of the writing voltage is applied. Further, C11 and C12 in FIG. 15 show pixels of different scan electrodes. In the Figure, an outside voltage applied to a pixel is shown by a continuous line, and the first polarization voltage caused by the remaining first polarization charges in the light emitting layer is shown by a broken line. In this conventional example, after a voltage not less than the emission starting voltage Vth is applied as a writing voltage in a linear order so as to perform light emission displaying, a polarization correction voltage near the emission starting voltage Vth is applied to all pixels. By applying the writing voltage, each pixel emits light, and then the first polarization voltage of reverse polarity with respect to that of the writing voltage is caused by the first polarization charges in the light emitting layer due to the first polarization charges remain in the light emitting layer. Then, when the polarization correction voltage is applied, a voltage in which the first polarization voltage and the polarization correction voltage are superposed is applied to the light emitting layer, and when the value of this voltage becomes the emission starting voltage Vth or more, the pixel emits light. After the emission, the first polarization voltage of reverse polarity with respect to that of the polarization correction voltage is applied to the light emitting layer, but the polarization correction voltage is so set as to be smaller than the first polarization voltage after the writing voltage is applied.
On the other hand, a conventional thin film EL element as shown in FIG. 12 does not have brightness sufficient for a high definition display such as a television, in general. Here, the relationship between an outside voltage applied to an EL element and a voltage allocated to a light emitting layer will be explained. Assuming that an outside voltage applied to an EL element is V′, the relative dielectric constant of a dielectric layer is εi, the film thickness is di, the relative dielectric constant of a light emitting layer is εp, and the film thickness is dp, the voltage V allocated to the light emitting layer is given by the following equation (1).V=εi·dp/(εi·dp+εp·di)·V′  (1)
As obvious from the equation (1), in order to allocate a voltage effectively to a light emitting layer, it is desirable to make it to be a thin film by using a material having a large relative dielectric constant of a dielectric layer. For improving brightness of an EL element, Japanese Patent Publication No. 07-44072, for example, proposes an El element in which an insulating ceramic substrate is used as a substrate and one dielectric layer constituting a dual insulating structure is a thick film dielectric layer. In the thick film dielectric layer, fine particles of a dielectric material having the perovskite structure such as BaTiO3, SrTiO3, PbTiO3, CaTiO3, Sr(Zr, Ti)O3, Pb(Zr, Ti)O3 are dispersed in an organic polymer matrix and made into paste, and then deposited by using a printing method, and then processed by heat treatment at high temperature whereby a large relative dielectric constant is realized. In general, a ferroelectric having the perovskite structure has large relative dielectric constant, which is preferable for making an EL element to have high brightness.


A sensor holding apparatus for facilitating dental imaging, in accordance with one embodiment of the present invention, comprises a handle, an elongated shaft, and a sensor holder. The holder includes a coupling component configured to removably attach to a portal end of the shaft. The shaft comprises a cross-section adapted to receive a user's bite, the cross-section having a substantially polygonal perimeter to aid manipulation of the sensor inside the patient's mouth. The sensor holder further comprises a substantially flat body having a substantially flat surface adapted for removably attaching a sensor to the sensor holder. Furthermore, the substantially flat surface of the body of the sensor holder may comprise at least one edge that is adapted for removably attaching the sensor to the sensor holder by a pressure, or the sensor holder may be configured to receive an adhesive for removably attaching the sensor to the sensor holder.

Dental radiographs are x-rays used by medical professionals to ascertain detailed images of a patient's mouth so as to better identify dental disease. These radiographs are taken utilizing x-ray units, which include an x-ray tube or cone adjacent to an x-ray sensing device, and which is parallel to the area of interest in the oral cavity. The x-ray is directed perpendicular to the area and to the sensing device. X-ray sensing devices typically include x-ray film, digital sensors, phosphor plates and other related technologies that would be known by a person of ordinary skill in the art. These sensing devices are in a flat and commonly rectangular or elongated configuration, and can be placed into the oral cavity.
The x-ray sensing devices may be placed in the oral cavity in different ways to view various perspectives, orientations, and locations. For instance, a periapical placement displays the anterior or posterior tooth or teeth; included in the image is the tip of the root. Alternatively, a bitewing placement displays the central area around which the top and bottom set of teeth make contact with one another, additionally showing the crown of the imaged tooth. These placements can then be subdivided into right and left as well as maxillary and mandibular. Additionally, sensors may be placed such that images are taken in a vertical or horizontal direction depending on the desired depth or width of the desired field of view.
Recently, advancements in dentistry have shifted the focus from using x-ray film to digital sensors due in part to a decrease in the amount of x-rays (i.e. radiation) these sensors require the patient to be exposed to, as well as their convenient compatibility with electronic devices such as computers. The emergence of digital sensor devices has prompted creation of a respective field known as digital dental radiography.
Traditional holding mechanisms for x-ray film could be designed to clamp or pinch the thin x-ray film to keep it in place. However, this method cannot be utilized in digital sensors, which are thicker due to their imbedded technology. Moreover, digital sensors are more fragile and expensive and therefore must be handled very carefully. Makers of sensor holders adjusted for this change in a number of different ways. Many methods utilize a large biteplate as well as a ring and rod mechanism, wherein the rod is inserted perpendicular to the sensor holder and a ring slides through the holder, whereby the x-ray cone is properly aligned. Let biteplate be construed as part of a phosphor plate, film or digital x-ray sensor holder or sensor wherein a patient bites down on it in order to properly orient the plate, film, or sensor. While this design may be utilized when taking x-rays for routine examination, it is cumbersome to use during root canal procedures or other procedures involving obstructions within or surrounding the oral cavity.
In such cases, a device that employs a typical biteplate is not useful in such circumstances because the patient is not able to bite down on the biteplate due to the extreme pain in the tooth or due to the obstructions necessitated by many procedures, some of which include dental clamps, rubber dams, or files. This problem is further compounded by the ongoing concern that the operating field may become contaminated.
A rubber dam comprises a flexible sheet of latex or silicone and is a mandatory component of many procedures including root canals. The rubber dam creates a sterile environment within the tooth being treated by preventing bacteria and other contaminants from entering the patient's tooth from within the oral cavity. It also protects the oral cavity and the patient's airway by preventing medicaments as well as other materials used during the procedure from entering. A rubber dam is secured in a proper position around the tooth by placing it over a clamp and around the tooth. During root canal procedures, it is necessary to manipulate the rubber dam to take multiple radiographs to acquire appropriate measurements of the width and depth of the infected or aggravated areas which need cleaning and reshaping. To accomplish this, the sensor or film device has to be placed between the oral cavity and the underside of the rubber dam adjacent to the tooth being treated. When traditional sensor holders are utilized to achieve this, the rubber dam and adjacent parts need to be removed. Removal of the rubber dam allows for the introduction of foreign material, for instance bacteria, to enter the patient's tooth, potentially causing leakage and contamination of the field. In addition, it is quite difficult to fit the entire sensor holder on the underside of the rubber dam.
The biteplate portion of a typical sensor holder compounds the difficulties of properly placing the holder in the correct orientation and location because the clamp as well as the files rest in the occlusal field, also referred to as the biting surface of the tooth, which prevents the patient from biting down. Furthermore, the biteplate itself is a hindrance to acquiring useful radiographs because it prevents the patient from pushing the sensor into the vestibule to obtain a deep root image. Once the holder is finally placed under the dam, the alignment ring portion still needs to be slid into place for use by the x-ray cone. This has the adverse effect of agitating patients with the number and size of items in their mouth. Subjects commonly gag, have tongue thrusts, and misalign the imaging system, or compromise the operating field.
To prevent the issues discussed above, there is a need in the art for a sensor holding apparatus that can operate without a biteplate and which allows for compact, convenient sensor placement in the oral cavity with a variety of sensor shapes and dimensions so as to mitigate the problems associated with taking radiographs during dental surgeries. It is to these ends that the present invention has been developed.

This patent is subject to a terminal disclaimer.

Sensor holding apparatus for facilitating dental imaging


The moulding tool is a near-net-shape negative mould for shaping a ceramic green body for the lens. The mould has a shaping surface, which is described by the following equation B:

The present invention relates to a moulding tool for moulding a ceramic green body in the production of at least one optical lens made of an opto-ceramic. The invention furthermore addresses a process for producing the lenses mentioned before. Also, the invention is directed to the use of a moulding tool for producing opto-ceramic lenses.
Transparent ceramics suited as materials for lenses are hereinafter referred to as opto-ceramics. Such materials have very convenient properties (refractive indices, dispersions) and contribute to an improvement of optical imaging systems. In special cases new imaging concepts are only possible with such new optical material options. Especially the possibilities of more compact construction of for example digital cameras or improved of simplified colour corrections (chromatical or apochromatical) or mentioned here.
The lenses that can be produced with the moulding tool according to the invention and by making use of the new and advantageous process claimed herein consist of opto-ceramics. Such materials are defined afterwards. The term "consist of" in the sense of this invention does not exclude the presence of remaining binders or other additives present in the final lens besides the single phase, poly crystalline material (see below). Such compounds may be present depending on what concise process was used for producing the respective lens.
An opto-ceramic is substantially a single phase, poly crystalline material based on oxides and having high transparency. Opto-ceramics are hence a subdivision of ceramics. Lenses made of opto-ceramics are therefore in certain applications preferred over conventional lenses made of glass. A prerequisite for the successful placement on the market is the supply of sufficient amounts of high quality lenses with good reproducibility at acceptable prices. The prices are geared to the prices of conventional lenses of glass.
A further aspect in providing cost-effective lenses from opto-ceramics is that these lenses should not only comprise a refractive function but also function reflectively, transmittively and diffractively.
Additionally, mechanical properties like for example supporting areas, adjoining the lens circularly on the sides and thereby allowing positioning of the lens in the carrier, are often needed next to the optical functions. Even more complex mould recesses that are placed onto a local part of the lens might be needed in order to make integration into an optical system possible (monolithic optical elements).
Today lenses made from opto-ceramics are usually produced as follows. First the powders of the basic material (mostly oxides) are produced (first step: powder production). The powders used are often of high purity and in the nanometre scale as far as their sizes are concerned. Then the powders are conditioned (second step: powder conditioning). This step comprises milling of the powders, homogenizing the powder mixture and drying the batch. This step is followed by the third step which is the moulding step, where a green body is formed, already determining the final shape of the lens, and if necessary certain additives are added that depend on the moulding method to be applied.
Afterwards the green body is—if necessary—dried and/or debindered (if necessary: fourth step: drying and/or debindering). In the fifth step, sintering, the grains that are in loose contact to each other after moulding and—if necessary—drying and/or debindering form fixed contacts by mass transfer and/or diffusion. Simultaneously an increase in grain size is achieved and open porosity is removed from the body. In the subsequent sixth step of hot isostatic pressing (HIP) the closed porosity within the grain boundaries is pressed out of the sintered body. The thus obtained body can if necessary be further processed in a further step (seventh step: thermic post-processing), a post-processing step in form of further annealing steps and/or profiles, in order to remove the oxygen vacancies or graphite impurities produced by the HIP process or reduce the intergranulary fine porosity.
Preferably lenses from the following opto-ceramics are produced by using the above-mentioned production process:                a) cubic garnets of the generic stoichiometry(1−m){(M1)3+z3(M2)5−z3O12}m{A}wherein z3 has a value in the range of from −1 to +1, m has a value of from near zero to less than 0.05, preferably less than 0.03 and further preferred near zero or equal to zero.
M1 is selected from Y, La, Gd, Lu, Yb, Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm or a mixture of one or more of these elements, wherein the active lanthanides Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm are either present within the opto-ceramic in amounts of together up to 100 wtppm or at least 15 mol % relating to the amount of these oxides;
M2 is selected from one or more of the elements of the group III or IIIa of the periodic table of elements, preferably from Al, Ga, In, Sc or a mixture of two or more of these elements;
A is one or more of additional components, especially selected from SiO2, Na2O, MgO, CaO or TiO2.                b) zirconium oxide, preferably cubically stabilized zirconia, of the generic formula(1−m){z1[ZrO2]z2[HfO2](1−z1−z2)[X2O3]}m[A] or(1−m){z1[ZrO2]z2[HfO2](1−z1−z2)[MO]}m[A]wherein z1+z2 is less than or equal to 0.92 and preferably smaller or equal to 0.90, wherein z1 and z2 are more than or equal to zero, m is less than 0.10 and preferably less than 0.06, further preferred less than 0.03 and most preferred m is zero;
X is selected from Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or a mixture of one or more of these elements, preferably selected from Y, Yb and Lu or a mixture of two or all three of these elements and particularly preferred X is Y. M is selected from Ca and Mg;
and
A is one or more components, especially selected from SiO2, Na2O, MgO, CaO, or TiO2.                c) cubic sesquioxides like Y2O3, Lu2O3, Yb2O3, In2O3, Sc2O3 and/or isotype cubic mixed crystal phases of the above oxides with other oxides like Gd2O3, La2O3, ZrO2, HfO2 etc.        d) Mg—Al-spinels of the approximate formula MgAl2O4 and        e) Al-Oxinitrides of the generic formulaAl23−1/3XO27+XN5−X, wherein 0.429<X<2, for example Al23O27N5         f) perovskites
It can be taken from the above explanation of the production process for lenses made from opto-ceramics that the third step of moulding is decisive for the final form of the lens, because the shape obtained within this process step is not changed considerably during subsequent process steps. The subsequent steps merely cause contraction and shrinkage of the green body obtained by the moulding step.
Furthermore, the moulding method used and, hence, also the applied mould decisively determine the later properties of the opto-ceramic as far as optical properties are concerned, as the moulding step decisively influences the conduct of subsequent sintering and/or drying/debindering.
As moulding method different methods are used that differ mainly by their moisture content. Casting (25-40% moisture) comprises the methods of slip casting, vacuum pressure casting, pressure slip casting or electrophoresis as well as centrifugal slip casting.
The term plastic moulding (15-25% moisture) means the methods of extrusion, squeezing, turning and free forming.
The methods of wet pressing, dry pressing, pounding and compacting by vibration belong to the pressing techniques (0-15% moisture). As further methods that are not classified according to the moisture content of the moulded material the moulding methods of hot casting (also referred to as low pressure die casting) or die casting can be used.
It is known from the prior art that lenses made of transparent ceramics can be obtained by moulding by pressing. For example, DE 101 95 586 T1 describes the production of special opto-ceramics with perovskite structure. Therein (see from page 15) " . . . the ceramic powder material is processed with a binder to a predetermined shape such that a ceramic green compact is obtained . . . ". In a subsequent burning step the green compact is preferably embedded in specific powder. The processing of the ceramic powder material to a predetermined geometry is done using a binder. According to exemplary embodiment 7 moulding is done especially by pressing at 2000 kg/cm2 (196 MPa) in order to obtain a pane-shaped green compact with a diameter of 30 mm and a thickness of 1.8 mm.
EP 1 701 179 A1 discloses the use of cubic garnets for optical elements in microlithography in wavelength region<200 nm. Particularly, this document discloses the production of mono-crystals. Moulding tools or processes are not mentioned.
Further US 2004/0159984 A1 describes the production of transparent Y2O3 ceramics by moulding methods like slip casting or die casting. The document mentions the production of complex geometries, however, without specifying the shape of the moulding tool in detail. Especially, the production of components with curved surfaces is not mentioned.
The process of slip casting for the production of transparent ceramics for laser applications based on pane-shaped specimen is described by Ueda ('Scalable Ceramic Lasers for IFE Driver'. Institute for Laser Science, Univ. of Electro-Communications, Japan-US Workshop ILE/Osaka, Mar. 13, 2003).
The processes described in the prior art are not suited for the cost-effective production of transparent ceramic lenses having superior optical qualities mad. In order to achieve the desired optical effects, lenses comprise definitely curved surfaces.
According to "Optical System Design" by Robert E. Fischer, ISBN 0071314916-2 the mathematical description of lens surfaces is achieved by the following equation:
                    y        =                                            c                                                                                x                2                                                    1              +                                                1                  -                                                            (                                              k                        +                        1                                            )                                                                                c                      2                                                                                x                      2                                                                                +                                    a              1                                                  x              2                                +                                    a              2                                                  x              4                                +                                    a              3                                                  x              6                                +                                    a              4                                                  x              8                                +          …                                    (                  Equation                                                              A                )
Wherein y is the location on the optical axis, k is the conic constant, x is the perpendicular distance from the optical axis, c=1/R and R is the radius of the curve and a1, a2, a3, a4, . . . are the coefficients of the aspheric term.
Spherical lenses are distinguished from aspherical lenses as follows:
k=0 and a1, a2, a3 . . . =0 spherical lens
k≠0 aspherical lens,
wherein the curves can be distinguished as follows:
                k<−1 hyperboloid surface        k=−1 paraboloidal surface        −1<k<0 ellipsoid surface        k>0 flattened spherical
These lens surfaces are according to the prior art obtained by extensive chemical milling, grinding and polishing processes from a bulk semi-finished part. The processing of these simply shaped bulk semi-finished parts is time consuming and cost-intensive. This is especially true, because many opto-ceramic systems, like for example the group of sesquioxides (Y2O3, Yb2O3, Sc2O3, Lu2O3) and/or mixed crystals of these, garnets (for example YAG Yttrium-Aluminum-Garnet), AlON (Aluminum Oxinitride), Al2O3, perovskites, spinels, cubically stabilized zirconium oxide or hafnium oxide, are very hard materials. Especially the chemical milling and grinding processes for the production of shapes with recesses are thus very cost-intensive.

Moulding tool for moulding a ceramic green body and use of said moulding tool

Abstract: y                                                                          1                    =                                                    cz                2                                            1                +                                                      1                    -                                                                  (                                                  k                          +                          1                                                )                                                                                c                        2                                                                                z                        2                                                                                +                                          a                1                                                          z                2                                      +                                          a                2                                                          z                4                                      +                                          a                3                                                          z                6                                      +                                          a                4                                                          z                8                                      +            …                                                            ,                            (        B        )            y1 gives a position on an optical axis; x designates a perpendicular distance from the optical axis to the surface; k, c, and a1, a2, a3, a4, . . . are constants describing a surface of the lens to be moulded and z=|x|+b, wherein b is a constant with a value greater than 0 and less than 0.3 mm, which is a measure of a deviation of the shaping surface from the surface of the lens.


Provided is a method of controlling driving, based on sensing information, the method being performed, for example, by a device included in an object and including: obtaining sensing information; determining a sensing blind zone in a sensing zone based on the sensing information; generating a control signal based on the sensing blind zone; and controlling driving of the object using the control signal.

1. Field
The disclosure relates to a method, device, and system for controlling driving using sensing information.
2. Description of Related Art
Recently, due to convergence of information communication technologies and car industries, cars have rapidly become smart. Accordingly, a car has evolved from a simple mechanism to a smart car, and in particular, driving control technology using at least one sensor of a car is highlighted as a core technology of smart cars. Various sensors are mounted in a smart car, and the smart car obtains, using the sensors, various types of sensing information to provide convenience and safety to a user, and controls driving or assists with driving control using the sensing information.
However, not all information in a sensing-target zone can be obtained by the sensors mounted in the smart car. For example, in the case where a certain zone is obstructed by a building or another car, the sensors mounted in the smart car may not be able to detect or identify objects in the obstructed zone. Thus, there may be an increased risk of accident due to a zone that is not detectable by the sensors.
Accordingly, there is demand for a method of decreasing uncertainty and risk even in a zone from which a sensor cannot obtain information.

Method and device for controlling driving based on sensing information


This invention is to provide a process for producing a glycoprotein comprising a mammalian type sugar chain, characterized in that the process comprises introducing an α-1,2-mannosidase gene into a methylotrophic yeast having a mutation of a sugar chain biosynthesizing enzyme gene, so that the α-1,2-mannosidase gene is expressed under the control of a potent promoter in the yeast; culturing in a medium the methylotrophic yeast cells with a heterologous gene transferred thereinto; and obtaining the glycoprotein comprising a mammalian type sugar chain from the culture. Using the newly created methylotrophic yeast having a sugar chain mutation, a neutral sugar chain identical with a high mannose type sugar chain produced by mammalian cells such as human cells, or a glycoprotein comprising such a neutral sugar chain, can be produced in a large amount at a high purity. By introducing a mammalian type sugar chain biosynthesizing gene into the above-described mutant, a mammalian type sugar chain, such as a hybrid or complex, or a protein comprising a mammalian type sugar chain can be efficiently produced.

Yeast has been intensively studied as a host for production of foreign genes since establishment of yeast transformation systems. The use of a yeast for production of foreign proteins involves advantages in that molecular-genetic manipulation and culture of yeasts are as easy as those of prokaryotic organisms, and that yeasts bear eukaryotic type functions to allow post-translational modifications of proteins such as glycosylation. However, since production of proteins using Saccharomyces cerevisiae is low with exception of some successes, protein production systems using yeasts other than Saccharomyces cerevisiae have been developed, including systems using, for example, Shizosaccharomyces pombe, Kluyveromyces lactis, methylotrophic yeasts, or the like.
A methylotrophic yeast (or methanol-utilizing yeast), which can grow on methanol as a single carbon source, has been developed as a host for production of foreign proteins (K. Wolf (ed.) "Non Conventional Yeasts in Biotechnology" (1996)). This is because methods of culturing yeasts have been established in industrial scale and because the yeast has a potent promoter controlled by methanol. At that time when a methylotrophic yeast was discovered, the use thereof as SCP (Single Cell Protein) was studied and, as a result, a high-density culture technique at a dry cell weight of 100 g/L or more was established in an inexpensive culture medium, which contains minerals, trace elements, biotin, and carbon sources.
Researches on elucidation of a C1 compound-metabolic pathway, as well as on application of C1 compounds, revealed that a group of enzymes required for the methanol metabolism was strictly regulated by carbon sources. The methanol metabolism in a methanol-utilizing yeast generates formaldehyde and hydrogen peroxide from methanol and oxygen by alcohol oxidase in the first reaction. The generated hydrogen peroxide is decomposed into water and oxygen by catalase, while formaldehyde is oxidized to carbon dioxide by actions of formaldehyde dehydrogenase, S-formylglutathione hydrolase, and alcohol oxidase, and NADH generated during the oxidation is utilized as an energy source of the cell. At the same time, formaldehyde is condensed with xylulose-5-phosphate by dihydroxyacetone synthase, then converted into glyceraldehyde-3-phosphate and dihydroxyacetone, which subsequently enter the pentose phosphate pathway and serve as cell components.
Alcohol oxidase, dihydroxyacetone synthase, and formate dehydrogenase are not detected in the cell when it is cultured in the presence of glucose, but they are induced in the cell cultured in methanol, so that the amount of them is dozens of percentage of the total inner cell protein. Since the production of these enzymes is controlled at a transcription level, inducible expression of a foreign gene of interest is enabled under the regulation of promoters of the genes which encode the enzymes. The foreign gene expression system using a promoter for a methanol metabolizing enzyme gene has been estimated so highly among yeast expression systems due to its efficient production, with an example in which the expression amount of a foreign gene was dozens of percentage of the total protein in cell or several g/L culture medium in secretion.
To date, four types of the transformation and foreign gene expression systems have been established in the methylotrophic yeasts: Candida boidinii, Hansenula polymorpha, Pichia pastoris and Pichia methanolica. Differences are recognized among the expression systems in terms of codon usage, expression regulation, and integration of expression plasmid, which provide characteristics of each expression system.
In the meantime, it is known that naturally occurring proteins are classified into two types, i.e., the one being a simple protein comprising amino acids alone, the other being a complex protein comprising sugar chains, lipids, phosphates or the like attached thereto, and that most of cytokines are glycoproteins. Recently, besides conventional analyses with lectin, new analyses using HPLC, NMR or FAB-MAS have been developed in analyzing sugar chain structures, by which new sugar chain structures of a glycoprotein have been found successively. On the other hand, studies on functional analysis of sugar chains lead to elucidation of the fact that the sugar chain plays an important role in lots of bio-mechanisms, such as intercellular recognition, molecular recognition, keeping of protein structures, contribution to protein activity, in vivo clearance, secretion, localization, etc.
For example, it has been revealed that erythropoietin (EPO), tissue plasminogen activator (TPA) or the like did not exhibit its inherent bioactivity when the sugar chains are removed (Akira Kobata, Tanpakushitsu-Kakusan-Koso, 36, 775-788 (1991)). Importance of sugar chains has been pointed out in erythropoietin, which was the first glycoprotein medicament in history produced by transgenic animal cells as the host. Specifically, the sugar chains of erythropoietin act in inhibitory manner against binding to receptor, whereas they have a decisive contribution to keeping of active structures and to improvement in in vivo pharmacokinetics, and are totally essential for expression of the pharmacological activity (Takeuchi and Kobata, Glycobiology, 1, 337-346 (1991)). Furthermore, high correlation between the structure, type and number of branches (i.e., the number of branches formed by GlcNAc attached to Man3GlcNAc2) of sugar chains and the pharmacological effect of erthropoietin has been found (Takeuchi et al., Proc. Natl. Acad. Sci. USA, 86, 7819-7822 (1989)). It was reported that a main cause of this phenomenon was that erythropoietin with immature branch structure is prone to occur its rapid clearance from the kidney, resulting in a shorter retention time in the body (Misaizu et al., Blood, 86, 4097-4104 (1995)). Another similar example is observed in serum glycoproteins including fetuin. That is, it was found that when removal of sialic acid at the end of a sugar chain leads to exposure of galactose, the galactose is recognized by lectin on the surface of liver cells, whereby the serum glycoprotein disappears promptly from the blood (Ashwell and Harford, Annu. Rev. Biochem., 51, 531-554 (1982); Morell et al., J. Biol. Chem., 243, 155-159 (1968)).
Glycoprotein sugar chains are largely classified into Asn-linked (N-linked), mucin type, O-GlcNAc type, GPI-anchored type, and proteoglycan type (Makoto Takeuchi, Glycobiology Series 5, Glycotechnology; edited by Akira Kibata and Senichiro Hakomori, Katsutaka Nagai, Kodansha Scientific, 191-208 (1994)), each of which has an intrinsic biosynthesis pathway and serves for individual physiological functions. Of them, for the biosynthesis pathway of Asn-linked sugar chains, there are many findings and detailed analyses.
Biosynthesis of Asn-linked sugar chains starts with synthesis of a precursor comprising N-acetylglucosamine, mannose and glucose on a lipid carrier intermediate, which precursor is converted to a specific sequence (Asn-X-Ser or -Thr) of a glycoprotein in the endoplasmic reticulum (ER). It is then subjected to processing (i.e., cleavage of glucose and specific mannose residues) to synthesize an M8 high-mannose type sugar chain comprising eight mannose residues and two N-acetylglucosamine residues (Man8GlcNAc2). The protein including high mannose type sugar chains is transported to the Golgi apparatus which undergoes a variety of modifications significantly different between yeast and mammal (Gemmill, T. R., Trimble, R. B., Biochim. Biophys. Acta., 1426, 227 (1999)).
In mammalian cells, in many cases, α-mannosidase I (α-1,2-mannosidase), an exomannosidase which cleaves an α-1,2-mannoside linkage, acts on high mannose type sugar chains to cut off several mannose residues. The sugar chain (Man5-8GlcNAc2) generated in this process is a sugar chain referred to as a high mannose type. N-acetylglucosaminyl transferase (GnT) I acts on an M5 high mannose type sugar chain (Man5GlcNAc2) from which three mannose residues have been cut off, to transfer one N-acetylglucosamine residue to the sugar chain, resulting in formation of a sugar chain comprising GlcNAcMan5GlcNAc2. The thus formed sugar chain is referred to as a hybrid type. Further, when α-mannosidase II and GnT II act, the sugar chain structure GlcNAc2Man3GlcNAc2, referred to as a complex type, is formed. Thereafter, a variety of mammalian type sugar chains are formed through the action of a group of ten-odd glycosyltransferase enzymes, by which addition of N-acetylglucosamine, galactose, sialic acid, etc. occurs (FIG. 1).
Accordingly, the mammalian type sugar chain as defined in this application means an N-linked (or Asn-linked) sugar chain present in mammals, which is generated in the sugar chain biosynthesis process of mammals. Specifically, they include an M8 high mannose type sugar chain represented by Man8GlcNAc2; an M5, M6 or M7 high mannose type sugar chain represented by Man5GlcNAc2, Man6GlcNAc2 or Man7GlcNAc2, respectively, generated from Man8GlcNAc by action of α-mannosidase I; a hybrid type sugar chain represented by GlcNAcMan5GlcNAc2 generated from Man5GlcNAc2 by action of GlcNAc transferase-I (GnT-I); a double-stranded complex type sugar chain represented by GlcNAc2Man3GlcNAc2 generated from GlcNAcMan5GlcNAc2 by action of α-mannosidase-I and GlcNAc transferase-II (GnT-II); and a double-stranded complex type sugar chain represented by Gal2GlcNAc2Man3GlcNAc2 generated from GlcNAc2Man3GlcNAc2 by action of galactosyl transferase (GalT).
In mammals, any of high mannose type, hybrid type and complex type sugar chains can be found. In one case, sugar chains to be attached are different depending on a protein, or in another, different types of sugar chains are attached within a protein. These sugar chains exhibit important functions, such as biosynthesis of glycoproteins, sorting within a cell, concealment of antigenicity, in vivo stability, organ-targeting properties, and the like, depending on the type or class of sugar chains attached to a glycoprotein (Tamao Endo, Tosa Kogaku (Sugar chain engineering), Sangyo Chosakai, 64-72 (1992)).
On the other hand, in yeast a mannan-type sugar chain (outer sugar chain) is produced, in which several to 100 or more mannose residues are attached to M8 high mannose type sugar chain. For example, the biosynthesis of outer sugar chains in Saccharomyces cerevisiae known as baker's yeast or laboratory yeast is considered to proceed along a pathway as shown in FIG. 2 (Ballou et al., Proc. Natl. Acad. Sci. USA, 87, 3368-3372 (1990)). That is, a reaction for initiating elongation begins in which a mannose is first attached to M8 high mannose type sugar chain through α-1,6 linkage (FIG. 2, Reaction I, B). The enzyme performing this reaction is clarified as a protein encoded by OCH1 gene (Nakayama et al., EMBO J., 11, 2511-2519 (1992)). Further, sequential elongation of mannose by α-1,6-linkage reaction (FIG. 2, II), forms a poly α-1,6-mannose linkage being the backbone of an outer sugar chain (FIG. 2, E). The α-1,6-mannose linkage sometimes contains a branch of α-1,2-linked mannose (FIG. 2: C, F, H), and additionally, α-1,3-linked mannose is attached to the end of the branched α-1,2-linked mannose chain (FIG. 2: D, G, H, I). The addition of the α-1,3-linked mannose is caused by a MNN1 gene product (Nakanishi-Shindo et al., J. Biol. Chem., 268, 26338-26345 (1993)). Formation of an acidic sugar chain, in which mannose-1-phosphate has been attached to high mannose type sugar chain moieties and outer chain moieties, is known as well (FIG. 2, *; a possible phosphorylation site corresponding to * in the above formula (I)). This reaction was found to be caused by a protein encoded by MNN6 gene (Wang et al., J. Biol. Chem., 272, 18117-18124 (1997)). Further, a gene (MNN4) coding for a protein positively regulating the transfer reaction was clarified (Odani et al., Glycobiology, 6, 805-810 (1996); Odani et al., FEBS Letters, 420, 186-190 (1997)).
Production of substances using microorganisms including yeast has some advantages as mentioned above, such as low production costs and utilizing culture technology developed as fermentation engineering, as compared with the production of substances using animal cells. There is a problem, however, that microorganisms cannot attach sugar chains with the same structure as human glycoprotein. Specifically, glycoproteins from cells of an animal including human have a variety of mucin type sugar chains in addition to three kinds of Asn-linked sugar chains, i.e., complex type, hybrid type and high mannose type as shown in FIG. 1, while the Asn-linked sugar chain whose attachment is observed even in baker's yeast (Saccharomyces cerevisiae), is only a high mannose type, and a mucin type is attached only to a sugar chain mainly composed of mannose.
Such sugar chains of yeast may produce a heterogeneous protein product resulting in difficulties in purification of the protein or in reduction of specific activity (Bekkers et al., Biochim. Biophys. Acta, 1089, 345-351 (1991)). Furthermore, since the structure of the sugar chains significantly differ, glycoproteins produced by yeast may not have the same detectable biological activity as those of the mammalian origin, or have strong immunogenicity to a mammal, etc. Thus, yeast is unsuitable as a host for producing useful glycoproteins from mammalian origin, and in general microorganisms are not suitable for DNA recombinant production of a glycoprotein, such as erythropoietin as described above, in which sugar chain has an important function. Indeed, for production of erythropoietin, Chinese hamster ovary (CHO) cells are used.
Thus, it is expected that the sugar chain of a glycoprotein not only has a complicated structure but also plays an important role in expression of biological activity. However, since the correlation of the structure of sugar chain with biological activity is not necessarily clear, development of the technology, which enables to freely modify or control the structure (the type of sugar, a linking position, chain length, etc.) of a sugar chain attached to a protein moiety, is needed. When developing a glycoprotein especially as medicament, the structure and function analyses of the glycoprotein become important. Under these circumstances, the development of yeast, which can produce a glycoprotein with biological activity equivalent to that of the mammalian origin, i.e., a glycoprotein comprising a mammalian type sugar chain, is desired by the academic society and the industrial world.
In order to produce a mammalian type sugar chain using yeast, it is important to prepare a mutant having the sugar chain biosynthesis system, which does not comprise a reaction as mentioned above of attaching a lot of mannose residues to modify the glycoprotein sugar chain as seen particularly in yeast; in which no outer sugar chains are attached; and the synthesis of sugar chains generates M5 high mannose type sugar chain. Subsequently, M8 high mannose type sugar chain, a precursor for this mammalian type sugar chain, might be produced by introducing biosynthetic genes for the mammalian type sugar chain into the mutant yeast.
To obtain a glycoprotein lacking outer sugar chains, use of a mutant strain deficient in enzymes for producing outer sugar chains in yeast, particularly a mutant of Saccharomyces cerevisiae, has been studied so far. Methods to obtain such a deficient mutant strain include obtaining a gene mutant by chemicals, ultraviolet irradiation or natural mutation, or obtaining it by artificial disruption of a target gene.
As to the former methods, there are many reports thereon. For example, mnn2 mutant is defective in the step of branching which causes α-1,2 linkage from the α-1,6 backbone of an outer sugar chain, and mnn1 mutant is defective in the step of producing α-1,3-linked mannose at the end of the branch. However, these mutants do not have defects in α-1,6 mannose linkage as the backbone of outer sugar chains and so they produce a long outer sugar chain in length. Mutants like mnn7, 8, 9, 10 mutants have been isolated as mutants having only about 4 to 15 molecules of the α- 1,6 mannose linkage. In these mutants, the outer sugar chains are merely shortened, but the elongation of high mannose type sugar chains does not stop (Ballou et al., J. Biol. Chem., 255, 5986-5991 (1980); Ballou et al., J. Biol. Chem., 264, 11857-11864 (1989)). Defects in the addition of outer sugar chains are also observed in, for example, secretion mutants such as sec18 in which the transportation of a protein from endoplasmic reticulum to Golgi apparatus is temperature-sensitive. However, in a sec mutant, since the secretion of a protein itself is inhibited at a high temperature, the sec mutant is not suitable for secretion and production of glycoproteins.
Accordingly, since these mutants cannot completely biosynthesize the high mannose type sugar chain of interest, they are considered unsuitable as host yeast for producing a mammalian type sugar chain.
On the other hand, as to the latter, the deficient mutant strain in which a plurality of target genes have been disrupted can be established by development of genetic engineering techniques in recent years. Specifically, through in vitro operation, a target gene DNA on plasmid is first fragmentated or partially deleted, and an adequate selectable marker DNA is inserted at the fragmented or deleted site to prepare a construct in which the selectable marker is sandwiched between upstream and downstream regions of the target gene. Subsequently, the linear DNA having this structure is transferred into a yeast cell to cause two homologous recombinations at portions homologous between both ends of the introduced fragment and the target gene on chromosome, thereby substituting the target gene with a DNA construct in which the selectable marker has been sandwiched (Rothstein, Methods Enzymol., 101, 202-211 (1983)).
Molecular cloning of a yeast strain deficient in outer sugar chain has already been described by Jigami et al. in Japanese Patent Publication (Kokai) No. 6-277086A (1994) and No. 9-266792A (1997). Jigami et al. succeeded in cloning of the S. cerevisiae OCH1 gene (which expresses α-1,6-mannosyl transferase), the OCH1 enzyme being assumed to be a key enzyme for elongation of the α-1,6 linked mannose. The glycoprotein of the OCH1 gene knockout mutant (Δoch1) had three types of attached sugar chains, i.e., Man8GlcNAc2, Man9GlcNAc2 and Man10GlcNAc2. Of them, the Man8GlcNAc2 chain had the same structure (i.e., the structure shown in FIG. 2A) as the ER core sugar chain which was common between S. cerevisiae and mammalian cell, while the Man9GlcNAc2 and Man10GlcNAc2 chains had a structure where α-1,3-linked mannose was attached to this ER core sugar chain [Nakanish-Shindo, Y., Nakayama, K., Tanaka, A., Toda, Y. and Jigami, Y., (1994), J. Biol. Chem.]. Furthermore, a S. cerevisiae host which can attach only the Man8GlcNAc2 chain having the same structure as the ER core sugar chain, which structure is common between S. cerevisiae and mammalian cell, was successfully produced by preparing a Δoch1mnn1 dual mutant and inhibiting the α-1,3-linked mannose transfer at the end. It is supposed that this Δoch1mnn1 double mutant serves as a host useful in case where the mammalian glycoprotein, which has a high mannose type sugar chain, is produced by DNA recombinant technology [Yoshifumi Jigami (1994) Tanpakushitsu-Kakusan-Koso, 39, 657].
It was found, however, that sugar chains of the glycoprotein produced by the double mutant (Δoch1mnn1) described in Japanese Patent Publication (Kokai) No. 6-277086 (1994) comprised acidic sugar chains containing a phosphate residue. This acidic sugar chain has a structure which is not present in sugar chains of mammals including human, and it is likely to be recognized as a foreign substance in mammal, thereby exhibiting antigenicity (Ballou, Methods Enzymol., 185, 440-470 (1990)). Hence, a quadruple mutant (as described in Japanese Patent Publication (Kokai) No. 9-266792A (1997)) was constructed in which the functions of a gene for positively regulating the transfer of mannose-1-phosphate (MNN4) and of a mannose transferase gene for performing the elongation reaction for an O-linked sugar chain (KRE2) have been disrupted. It was revealed that the sugar chain of a glycoprotein produced by the yeast strain described therein had the M8 high mannose type sugar chain of interest. It was further found that a strain in which Aspergillus saitoi-derived α-1,2-mannosidase gene is transferred to a yeast cell where a gene involved in the particular sugar chain biosynthesis system of yeast has been disrupted, had a high mannose type sugar chain (Man5-8GlcNAc2) in which one to several mannose residues were cleaved (Chiba et al., J. Biol. Chem., 273, 26298-26304 (1998)). Furthermore, they attempted production of a mammalian type glycoprotein in yeast by transfer of a gene involved in the mammalian sugar chain biosynthesis system into this prepared strain (PCT/JP 00/05474). However, despite that an α-1,2-mannosidase gene was expressed using a promoter for glyceraldehyde-3-phosphate dehydrogenase gene which is considered to be the highest in the expression amount as a constitutive expression promoter according to the disclosure, the conversion efficiency to Man5GlcNAc2 by carboxypeptidaseY (CPY) in the cell wall-derived mannoprotein is as low as 10-30% and so it is hard to say that its application to various glycoproteins is sufficiently prospective, although the rate of conversion to a high mannose type sugar chain (Man5GlcNAc2) was almost 100% in FGF as a foreign protein.
Separately, Schwientek et al. reported on the expression of the activity of human β-1,4-galactosyl transferase gene in S. cerevisiae in 1994 [Schwientek, T. and Ernst, J. F., Gene, 145, 299 (1994)]. Similarly, Krezdrn et al. achieved the expression of the activity of human β-1,4-galactosyl transferase gene and α-2,6-sialyl transferase in S. cerevisiae [Krezdrn, C. H. et al., Eur.J.Biochem.220, 809 (1994)].
However, when these findings are tried to be applied to other yeast, various problems anise. First of all, it is known that yeasts themselves have various sugar chain structures (K. Wolf et al., Nonconventional Yeasts in Biotechnology (1995) ).
For example, a divided yeast Schizosaccharomyces pombe contains galactose. Kluyveromyces lactis has GlcNAc. Both the methylotrophic yeast Pichia pastoris and the pathogenic yeast Candida albicans have been confirmed to contain β-mannoside linkage. Even yeasts having xylose and rhamnose as sugar chain components exist (Biochim. et Biophy. Acta, 1426, 1999, 227-237).
In fact, no yeasts capable of producing mammalian type sugar chains have been obtained except Saccharomyces cerevisiae as reported by Jigami et al. Also, although use of a methylotrophic yeast as the host for producing a foreign protein was exemplified in Japanese Patent Publication (Kokai) No. 9-3097A (1997), substantially no other example has been given.
In Japanese Patent Publication (Kokai) No. 9-3097A (1997), a homologue of Pichia pastoris OCH1 gene and a Pichia pastoris mutant strain in which the OCH1 gene was knockout were prepared, to obtain from them a modified methylotrophic yeast strain whose ability to extend a sugar chain was inhibited as compared with natural methylotrophic yeast strain. This publication, however, provides only information on SDS-PAGE of the produced glycoprotein, and no such support as structural analysis data. That is, it did not actually identify the activity but only pointed out about possibility of being α-1,6-mannosyl transferase. In fact, although HOC1 gene (GenBank accession number; U62942), which is an OCH1 gene homologue, exists also in Saccharomyces cerevisiae, the activity and function thereof are unknown at present.
Moreover, in the same publication a sugar chain having β-mannoside linkage in P. pastoris was identified, but it did not describe about the structure of the chain in any way. Indeed, structural analysis of the sugar chain was neither performed nor identified the produced sugar chain. So, it was not demonstrated whether or not the obtained gene is actually the OCH1 gene, and whether or not the sugar chain of the knockout strain was a mammalian type. Accordingly, one cannot safely say that the technique disclosed in Japanese Patent Publication (Kokai) No. 9-3097A (1997) produces a mammalian type sugar chain bearing glycoprotein and is sufficient as the production system that can be adapted for production of medicaments.
There is also a study using a filamentous fungus Trichoderma reesei by Maras et al. as an attempt to produce a mammalian type sugar chain using a microorganism other than yeast (U.S. Pat. No. 5,834,251). The disclosed method comprises making α-1,2-mannosidase and GnT-I to act on filamentous fungus and yeast to synthesize a hybrid type sugar chain (i.e., GN1Man5 sugar chain).
Filamentous fungi inherently express α-1,2-mannosidase, and consequently it is believed that little sugar chain modification occurs as compared with the case of yeast. On the other hand, since yeast attaches a particular outer sugar chain, all sugar chains are not obtained as Man5 by the procedure in which only α-1,2-mannosidase is introduced. In fact, produced in Saccharomyces cerevisiae as disclosed in this patent publication was a mixture of Man5 as the final product with sugar chains of Man6 or more as partial decomposition products, which mixture is produce by action of the outer sugar chain synthesizing gene OCH1, as described by Jigami or Chiba et al. (supra). It would accordingly be hard to say that the mammalian type sugar chain was produced in S. cerevisiae, and so this purpose cannot be attained without disrupting a sugar chain biosynthesizing gene of yeast. Maras et al. did not mention the gene disruption in the sugar chain biosynthesis system inherent to yeast at all, so obviously this technique could not be applied to yeasts (Pichia pastoris, Hansenula polymorpha, Kluyveromyces lactis, Saccharomyces cerevisiae, Yarrowia lipolytica). Moreover, Maras et al. refers to RNaseB as a heterologous expression protein in the Examples, but RNaseB has originally a high mannose type sugar chain of Man5 or Man6. Many of the sugar chains of the animal cell origin are complex type sugar chains having complicated structures, and many of glycoproteins such as cytokines expected to be applied to medicaments etc. have complex type sugar chains. In fact, it is known that the sugar chain structure changes greatly depending on kinds of foreign glycoproteins expressed (Method in Molecular Biologylogy, 103, 95-105 (1998)). Therefore, it is considered inappropriate to use as an example RNaseB which is a glycoprotein originally having a high mannose type sugar chain, in the application to glycoproteins having complex type sugar chains.
Furthermore, filamentous fungi are commonly used for the production of industrial enzymes, food enzymes, etc., and the transformation system is established, and production of enzymes by DNA recombinant technology has also been conducted. Nevertheless, there are the following disadvantages:    1) Since the protease activity is very strong, proteins produced are prone to receive limited proteolysis.    2) Since the fungi produce many proteins secreted outside the cell, they are unsuitable for the production of proteinous medicaments where homogeneity would be required.
Ogataea minuta as defined in the present invention is a strain once referred to as Pichia minuta or Hansenulla minuta, and was named Ogataea minuta by Ogata et al. (Biosci. Biotecnol. Biochem., 58, 1245-1257 (1994)). Ogataea minuta produces significant amounts of alcohol oxidase, dihydroxyacetone synthase and the formate dehydrogenase within the cell as in other methylotrophic yeasts, but nothing was known about the genes relating to these methanol utilization enzyme nor about sugar chain structures of this yeast.
Under the above-mentioned circumstances, the object of the present invention is to solve the above-described problems in production of glycoproteins in yeast, and to provide a process for mass production of non-antigenic mammalian type sugar chains and glycoproteins containing the sugar chains using a methylotrophic yeast wherein the sugar chain structures are identical to those of sugar chains as produced in human and other mammalian cells.

Methylotrophic yeast producing mammalian type sugar chain

National Institute of Advanced Industrial Science & Technology


There disclosed a boiler compound which comprises as the effective components thereof: (A) metabisulfurous acid or metabisulfites; (B) aliphatic dicarboxylic acids or salts thereof represented by the general formula: EQU M.sup.1 OOC--(CH.sub.2).sub.n --COOM.sup.,. wherein M.sup.1 and M.sup.2 are each a hydrogen atom, a sodium atom, a potassium atom or an ammonium group and n is an integer of 1 to 10; and optionally (C) a water-soluble polymer for scale inhibitor. The boiler compound is safe for human health, has excellent stability, can be used as a liquid formulation having anticorrosion activity (activity of eliminating oxygen) or both of anticorrosion activity and antiscale activity and exhibits enhanced anticorrosion activity by increasing concentration of sulfite ion which is an oxygen scavenger.

1. Field of the Invention
The present invention relates to a novel composition for the treatment of boiler water and to a method of treating boiler water. More particularly, it relates to a boiler water treatment composition human health, has excellent stability, can be used as a liquid formulation having anticorrosion activity (activity of eliminating oxygen) or both of anticorrosion activity and antiscale activity and exhibits enhanced anticorrosion activity by increasing concentration of sulfite ion which is an oxygen scavenger.
2. Description of the Prior Art
Various kinds of oxygen scavengers for example hydrazine and sodium sulfite, have heretofore been used for prevention of corrosion in boilers. However, hydrazine has a drawback that it has a safety issue for human health. Sodium sulfite has drawbacks that its concentration in a solution tank is decreased by reaction with dissolved oxygen because of excessively large rate of reaction with oxygen and corrosion is not effectively inhibited or may even be accelerated because of the resultant insufficient addition and that a large amount of a solution of the compound has to be added to a boiler because the amount of the compound dissolved into the solution is limited when the compound is dissolved together with an alkali agent, such as sodium hydroxide and the like, or a polymer to form a liquid composite and this situation causes problems such as alkali corrosion and carrying-over because of excessive addition of the compound or the alkali agent. There is also known a method in which an agent containing an organic polybasic acid having two or more carboxyl groups is used for treatment of boiling water in a boiler in combination with sulfite (Japanese Patent Application Laid-Open No. 1992-232285). However, this method has the same drawbacks as those described above caused by using the sulfite.
Boiler water treatment compositions containing organic oxygen scavengers have been used to replace the aforementioned agents. However, these compounds have a drawback that measurement of residual concentration of the oxygen scavenger is difficult and the amount of addition of the composition is not easily adjusted in such a manner that concentration of the scavenger compound is always kept at the optimum value.


A full color liquid crystal driver which includes a line memory for dividing an input video signal for each horizontal scan period into n groups and expanding each divided signal to n folds, n amplifiers for amplifying the output signals of the line memory to be voltages necessary to drive a liquid crystal display element, and n signal output circuits. Given that the number of horizontal pixels of the liquid crystal display element is x and the horizontal scan period is t, the necessary operation frequency for the amplifiers and signal output circuits becomes 1/(n(t/x)), which is lower by 1/n than the operation frequency necessary for the amplifiers and signal output circuits of prior art. In the case where the number of horizontal pixels is significantly increased in a conventional active matrix type liquid crystal display element, providing full color display requires very-fast amplifiers and very-fast signal output circuits for applying a voltage to the liquid crystal display element. The present invention can still use amplifiers and signal output circuits both functioning at the normal speed to easily drive a liquid crystal display element having a vast number of horizontal scan period.

The present invention relates to a full color liquid crystal driver, and, more particularly, to a full color liquid crystal driver which drives an active matrix type liquid crystal element.
FIG. 1 is an equivalent circuit diagram illustrating a full color liquid crystal display (hereinafter referred to as "LCD") of an active matrix type (see NEC, Technical Report Vol. 41 No. 5/1988). Liquid crystal pixels 21 are arranged in a matrix form, each pixels 21 connected to an amorphous silicon TFT (Thin Film Transistor) 22. Connected to those liquid crystal pixels 21 and TFTs 22 are a signal supplying circuit 23 and a scan circuit 24. In this active matrix type LCD, at the time the signal of each pixel 21 is selected, the scan circuit 24 turns the TFT 22 corresponding to that pixel 21 on to write a signal voltage in the pixel 21. During the other time, the scan circuit 24 turns that TFT 22 off to prevent the crosstalk between the adjoining pixels while holding the signal voltage in that pixel 21. In this driving system, only a signal voltage is always applied to the liquid crystal pixels, thus ensuring high-quality display.
FIG. 2 presents a block diagram illustrating a conventional full color liquid crystal driver that drives this active matrix type liquid crystal display element.
When an analog video signal in a horizontal scan period t is input from a video signal input terminal 5, an amplifier 2 amplifies this video signal to be a voltage necessary to drive a liquid crystal display (LCD) element 4 which consists of x horizontal pixels. Thus the amplifier 2 has an operation frequency of 1/(t/x). A signal output circuit 3 has a sample/hold circuit, which samples the output signal of the amplifier 2 in accordance with the individual horizontal pixels of the LCD element 4, and an output buffer, and outputs a signal at an operation frequency of 1/(t/x). This signal output circuit 3 divides the received video signal into x signals which are equal in number to the horizontal pixels of the LCD element 4 and outputs the divided signals to the LCD element 4.
According to this conventional full color liquid crystal driver, however, to provide full color display (analog display) when the number of horizontal pixels of the LCD element is increased, the frequency response of the analog amplifier 2 should be improved. In other words, the driver needs to operate at a significantly high speed, thus requiring that the amplifier 2 and the signal output circuit 3 function very fast. Due to the limited operation frequency of the amplifier 2 and the signal output circuit 3, typically used, the conventional driver has a difficulty in driving an LCD element that has a vast amount of pixels. If the amplifier 2 and signal output circuit 3 are designed to have an improved operation frequency in order to drive an LCD element having a number of horizontal pixels, their manufacturing costs become considerably high, resulting in a prominent cost increase of the driver.