A system for selective removal of certain components from plasma drawn from a patient comprises an extracorporeal blood circulation circuit and a cannula. The extracorporeal blood circulation circuit has an uptake line for transporting blood from the patient, a plasma separator, and a return line connected to the plasma separator for transporting selectively depleted blood from the plasma separator to the patient. The plasma separator is connected to the uptake line for receiving the blood, selectively removing plasma components (e.g., heparin) by separating plasma from whole blood and interfacing such plasma with an adsorption substrate, recombining depleted plasma, and reinfusing selectively depleted blood into the return line for transport to the patient. The cannula has an uptake conduit with an intake end and an exit end, and a return conduit, connected to the uptake conduit, with an outflow end and an entry end. The exit end is connected to the uptake line of the bypass circuit and the entry end is connected to the return line of the bypass circuit. Structure at the outflow end of the return conduit alters the direction of flow and directs selectively depleted blood being returned to the patient into the right atrium of the patient's heart when the intake end of the uptake conduit is disposed within the patient's inferior vena cava. An alternative cannula with washers may be inserted into a venous return cannula whereby recirculation and pooling of the selectively depleted blood is prevented.

During most cardiopulmonary bypass surgery procedures, the patient is administered heparin for anticoagulation. Subsequent to the cardiopulmonary bypass surgery, it becomes necessary to reverse the anticoagulation state. Typically, protamine sulfate is administered to reverse the heparin-induced anticoagulation. Heretofore, there has been no viable alternative to the administration of protamine for heparin reversal short of allowing the patient to metabolize and eliminate the heparin.
Administering protamine has raised concerns in the medical community because several types of adverse reactions to protamine in the presence of heparin have occurred. Adverse reactions that have been documented include systemic and pulmonary edema, fatal anaphylaxis, thrombocytopenia and altered platelet function, complement activation, and postoperative heparin rebound. It has been estimated that anywhere from 3,500 to over 70,000 open heart patients each year are affected by adverse reactions upon administration of protamine in the United States alone. Despite efforts to circumvent potential problems, patients that become hypertensive because of the administration of protamine are still being encountered. As a consequence, there is some anticipation that more fragile, aging and diabetic patients are at greater risk of adverse effects.
Research seems to indicate that the formation of the insoluble protamine-heparin complex is key to initiating many of the adverse hemodynamic responses. Such responses are not seen in the administration of protamine alone prior to any heparinization. Consequently, there is some pressure to solve the heparin removal problem by avoiding the use of protamine.
Although there are developments that may reduce the need for the administration of heparin as an anticoagulant for extracorporeal procedures, the need for achieving anticoagulation in the surgical field continues. Hence, the need to counteract the anticoagulant effect of heparin will remain.
An additional concern is that any device or method used to reverse the heparin must not compromise the cardiopulmonary bypass circuit or the patient. Avoidance of additional incisions or operative procedures is paramount for the well-being of the patient and would minimize the possibility of complications.
Hence, it would be a significant advance in the art if reversal of heparin could be accomplished using a cannula that can be inserted rapidly into the same incision or even the same venous return cannula used for the cardiopulmonary bypass circuit during the surgery, and can be removed rapidly to permit reintroduction of the cardiopulmonary bypass circuit used during the surgery if the surgeon believes such is necessary. It would be a further advance if a system utilizing the cannula and a plasma separator could be used as a high flow extracorporeal blood circulation circuit to remove selectively certain non-cellular blood components.

Cannula apparatus and system for heparin removal from blood


Techniques are provided for performing internal measurement of heart sounds to estimate patient cardiac function in terms of stroke volume, cardiac output, or a maximum rate of change of aortic pressure with time (max dP/dt). Control parameters of the medical device are then automatically adjusted so as to optimize overall cardiac function or to provide for ventricular resynchronization therapy. In one example, heart sound signals are derived from acceleration signals received from an accelerometer. The heart sound signals are analyzed to identify S1 and S2 heart sounds as well as ejection period and isovolumic interval (ISOV). Proxies for max dP/dt, stroke volume and cardiac output are then derived from the S1 and S2 heart sounds, the ejection period and the ISOV. Alternative techniques, not requiring detection of ISOV, are employed for use if the patient has heart value regurgitation.

Cardiac function is a measure of the overall effectiveness of the cardiac system of a patient and is typically represented in terms of, one or more of, stroke volume, cardiac output, end-diastolic volume, end-systolic volume, ejection fraction or cardiac output index. Stroke volume is the amount of blood ejected from the left ventricle during systole. Cardiac output is the volume of blood pumped by the left ventricle per minute (or stroke volume times the heart rate). End-diastolic volume is the volume of blood in the chamber at the end of the diastolic phase, when the chamber is at its fullest. End-systolic volume is the volume of blood in the chamber at the end of the systolic phase, when the chamber contains the least volume. Ejection fraction is percentage of the end-diastolic volume ejected by the ventricle per beat. Cardiac index is the volume of blood ejected per minute normalized to the body surface area of the patient. Other factors representative of cardiac function include the contractility of the left ventricle or the maximum rate of change of pressure with time (i.e. max dP/dt).
Overall cardiac function should be carefully monitored in patients with pacemakers or ICDs, particularly patients suffering from heart failure. Heart failure is one of the most widespread and devastating cardiac afflictions, currently affecting approximately 15 million people worldwide, including over 5 million in the United States. In the U.S., approximately 450,000 new patients are diagnosed with heart failure each year and the majority die within five years of diagnosis. One factor that contributes to heart failure is asynchronous activation of the ventricles such that the mechanical contraction is not coordinated effectively thus compromising cardiac function. As a result, the pumping ability of the heart is diminished and the patient experiences shortness of breath, fatigue, swelling, and other debilitating symptoms. The weakened heart is also susceptible to potentially lethal ventricular tachyarrhythmias. A decrease in cardiac function can result in a progression of heart failure. In many cases, pacing control parameters of the pacemaker or ICD can be adjusted to help improve cardiac function and reduce the degree of heart failure effectively reducing symptoms and improving the quality of life.
In view of the importance of maintaining adequate cardiac function, it would be desirable to provide improved techniques for use with pacemakers or ICDs for monitoring cardiac function and for automatically adjusting pacing parameters to optimize cardiac function and reduce the degree of heart failure. It is to this end that aspects of the invention are generally directed.
One particularly promising technique for reducing the risk of heart failure is "ventricular resynchronization therapy", which seeks to normalize asynchronous cardiac electrical activation and the resultant asynchronous contractions by delivering synchronized pacing stimulus to both ventricles using pacemakers or ICDs equipped with biventricular pacing capability. The stimulus is synchronized so as to help to improve overall cardiac function. This may have the additional beneficial effect of reducing the susceptibility to life-threatening tachyarrhythmias. With conventional resynchronization therapy, an external Doppler-echocardiography system may be used to noninvasively assess cardiac function. It can also be used to assess the effectiveness of any programming changes on overall cardiac function.
Then, biventricular pacing control parameters of the pacemaker or ICD are adjusted by a physician using an external programmer in an attempt to synchronize the ventricles and to optimize patient cardiac function. For example, the physician may adjust the interventricular delay, which specifies the time delay between pacing pulses delivered to the right and left ventricles, in an attempt to maximize stroke volume. To assess the effectiveness of any programming change, Doppler-echocardiography, impedance cardiography or some other independent measure of cardiac function is utilized.
However, this evaluation and programming requires an office visit and is therefore a timely and expensive process. It also restricts the evaluation to a resting state, commonly with the patient in a supine position. As such, the system is not necessarily optimized for activity, for the upright position, for other times of day since there may also be a circadian rhythm to cardiac function. It is known that heart rate and blood pressure have a diurnal variation. In a study by Chew and colleagues (See: "Overnight Heart Rate And Cardiac Function In Patients With Dual Chamber Pacemakers", Chew, et al., PACE 1996; 19: 822–828), cardiac function was shown to have a diurnal or circadian variation. Moreover, when relying on any external hemodynamic monitoring system, the control parameters of the pacemaker or ICD cannot be automatically adjusted to respond to on-going changes in patient cardiac function. Accordingly, it would be desirable to provide a technique to assess cardiac function using the implanted cardiac stimulation device. In this manner, cardiac function can be automatically evaluated and mono or biventricular pacing control parameters adjusted in a closed loop system so as to permit optimal ventricular resynchronization therapy when the patient is upright as well as supine, at various times of the day and during various activities. It is to this end that further aspects of the invention are directed.
In particular, it would be desirable to provide a technique for assessing cardiac function using heart sounds detected internally by a pacemaker or ICD. Briefly, a first (S1) heart sound (HS) is associated with closure of the mitral valve but as the valve leaflets are tissue thin, other mechanical factors associated with the closure of the valve are believed to account for the audible sounds. These include the oscillation of blood in the ventricular chambers, vibration of the chamber walls, abrupt tensing of the chordae tendinae supporting the mitral valve leaflets and tensing of the mitral valve itself. A second (S2) heart sound is associated with closure of the aortic and pulmonic valves. Commonly, two distinct components of the second sound are audible with the aortic component preceding the pulmonic component in a normal heart. The cause of the sound is not the valve leaflets coming together. Rather, it is due to the sudden deceleration of backward blood flow after ventricular contraction has ended and stretching of the aortic and pulmonic walls by the attempted backward flow of blood. Normally, the aortic component precedes the pulmonic component. The two components may move further apart during inspiration and closer together during exhalation. When there is a delayed activation of the left ventricle as may occur with an intraventricular conduction abnormality such as left bundle branch block, the aortic component may follow the pulmonic component with S2 becoming single during inspiration and widely split during exhalation. Correlating with overall cardiac function are heart sounds in the absence of primary valve abnormalities. The intensity of S1 may vary with the AV delay as well as with the vigor of contraction. The timing of S2 may also vary with contractility and the relative coordination or lack of coordination of cardiac contraction.
To implement internal detection of heart sounds using a pacemaker or ICD, acceleration signals detected by an on-board accelerometer can be processed to derive heart sound signals. One exemplary technique for deriving heart sounds using an accelerometer of an implanted device is discussed in U.S. Pat. No. 5,935,081 to Kadhiresan. More specifically, in the technique of Kadhiresan, the accelerometer signal is filtered using a band-pass filter to derive heart sounds. However, high frequency heart noises due to rapid turbulent flow are not detected. Moreover, the heart sounds appears to be derived only for diagnostic purposes, i.e. heart sound data is merely transmitted to an external device for subsequent review. Although the filter-based technique of Kadhiresan may be effective for recording certain types of heart sound data for diagnostic purposes, it does not provide for the on-board evaluation of overall cardiac function or for the automatic adjustment of pacing control parameters to permit ventricular resynchronization therapy. Moreover, by filtering out noises associated with turbulent flow, the technique does not permit detection of heart murmurs and the like, which can be important in determination of appropriate therapy.
Another exemplary technique for deriving heart sounds using an accelerometer is discussed in U.S. Pat. No. 5,836,987 to Baumann et al. Although the technique of Baumann et al. provides for automatic adjustment of certain pacing parameters (such as AV intervals) based on heart sound signals, it does not appear to provide for ventricular resynchronization therapy. Also, although Baumann et al. discuss the adjustment of certain pacing parameters so as to optimize cardiac performance, the technique does not appear to provide any capability for actually evaluating overall cardiac output in terms of, e.g., stroke volume, cardiac output, or max dP/dt. Hence, overall cardiac function is not actually tracked and optimization of pacing parameters based on overall cardiac function is not achieved.
Accordingly, it would be desirable provide improved techniques for use with implantable devices that permit the detection of heart sounds and heart murmurs, that provide for evaluation of overall cardiac function particularly in terms of stroke volume, cardiac output, or max dP/dt, and that permit optimization of pacing control parameters to maximize overall cardiac output and not just individual heart sound parameters. Additional aspects of the invention are directed to those ends.

System and method for monitoring cardiac function via cardiac sounds using an implantable cardiac stimulation device


An amplifier circuit includes a first transistor having a control terminal that receives a first amplifier input, a first terminal, and a second terminal. A second transistor includes a control terminal that receives a second amplifier input, a first terminal, and a second terminal that communicates with the second terminal of the first transistor. A differential transimpedance amplifier includes a first input that communicates with the first terminal of the first transistor, a second input that communicates with the first terminal of the second transistor, a first output, and a second output. A differential output amplifier includes a first input that communicates with the first output of the differential transimpedance amplifier, a second input that communicates with the second output of the differential transimpedance amplifier, a first output, and a second output.

One method for increasing bandwidth of an operational amplifier (opamp) is to use a low-gain, high-bandwidth amplifier as an input amplifier preceding a regular opamp, which forms a composite opamp. For example, one suitable composite opamp is described in "A Pipelined 13-bit, 250-ks/s, 5-V Analog-to-Digital Converter," Sehat Sutardja and Paul Gray, IEEE Journal of Solid-State Circuits (1988), which is hereby incorporated by reference in its entirety. The low-gain input amplifier of the composite opamp may be implemented using a gm*R or gm/gm configuration. That is, the input amplifier uses a resistor or a transistor as a load. This input amplifier, however, has a limited gain bandwidth product.
Referring now to FIGS. 1 and 2, a composite opamp 10 includes a transistor 14 having a gate coupled to an input voltage Vin. One terminal of the transistor 14 is coupled to a current source 18. A second terminal of the transistor 14 is coupled to a resistive load or resistor 16 and to a gate of a transistor 20. The resistor 16 and a first terminal of the transistor 20 are biased by a voltage source Vdd. A second terminal of the transistor 20, which acts as a follower, is coupled to an opamp 30. In FIG. 2, the resistor 16 may be replaced by an active load or a transistor 38 such as a diode-connected transistor.


A compact disk player/changer for compact disks fits within the standard half-height disk drive form factor for computer peripherals. A disk, either a 5-1/4-inch or 31/2 inch in size, is inserted through an aperture and supported, at opposite contact points on its edge, between laterally movable left and right-side disk guides. The disk's left side is frictionally engaged by a belt revolved on the left-side disk guide. The disk's right side rolls along a fixed wall on the right-side disk guide. The belt slides along a rigid wall of the left-side disk guide that prevents bowing from pressure exerted by the disk's edge. A motor that drives the revolving belt is fixedly mounted on a chassis. An extensible transmission transmits rotational force from the motor to a timing pulley to propel the belt on the laterally movable left-side disk guide. The extensible transmission consists of gear train on a pair of hinged members to provide a thin profile. The use of the extensible transmission reduces the movable weight, reducing the power and bearing load of the movement mechanism. In addition, the clearance required for a moving drive motor is avoided.

Drive mechanisms used for revolving the belts in prior drives employ a motor connected to the support system for the drive belt. For example, Japanese utility model 60-106250 and Japanese utility model 61-24851, show 1such systems. In the prior art disk players, a pair of endless tractor drive belts transfer a disk between an eject position and a playback position. In these devices, the drive belts are held taut on either side of and parallel to a disk transfer path. A disk inserted between the belts is frictionally engaged by the drive belts at opposite points on its edge and pulled along when the drive belt is revolved. The distance separating the stretched regions of the belts must be roughly equal to the diameter of a disk so that the disk may be inserted between the belts and carried along when the belts are revolved. To avoid interfering with the rotation of the disk when it is played back, the drive belts are separated by distance greater than the disk diameter so as to clear the disk completely.
In the prior art devices, since the belt moves, the motor must move with it. This requires clearance space for a large motor, undesirably limiting the compactness that can be achieved in the disk player. In addition, since the motor must be moved with the drive belt, the drive belt support and movement mechanism must be capable of bearing a greater weight load.

Disk transferring device that employs an extensible transmission to transmit rotational forces to a revolving belt causing movement of the disk


Designed to determine a number of frames of data for acquisition from video data on the basis of image quality setting data that allows image quality to be set for an image output by an image output device; and to acquire from the video data the determined number of frames of data, and synthesize the acquired number of frames of data to generate image data representing tones of an image by means of a multitude of pixels. Since image data can be generated by synthesizing frames of data in a number appropriate to the image quality of the output image, the process of generating image data representing a still image can be performed efficiently, and a still image derived efficiently.

1. Field of the Invention
The present invention relates to a technique of generating image data from information consisting of multiple frames.
2. Description of the Related Art
Generation of image data representing a still image from video data representing video shot with a digital video camera or the like, and printing out of still images based on such image data, is known in the prior art. Video data is composed of data for a plurality of frames representing images by means of tone data for a multitude of pixels, on a pixel by pixel basis; image data that represents a still image by means of tone representation with a multitude of pixels is created by acquiring and synthesizing data for a predetermined number of frames selected from the video data.
Since video shot with a digital video camera is often shaky due to camera shake, vertical and horizontal deviation among images represented by multiple frames of data is detected in pixel units, superimposing the image over a standard image, and translating it (i.e. subjecting to parallel movement) by Nx pixels in the horizontal direction and Ny pixels in the vertical direction (where Nx and Ny are positive integers) in order to minimize vertical and horizontal deviation.
Japanese Patent Laid-Open No. H11-164264 teaches a process for resolution conversion from a standard resolution image into a high resolution image, by providing high-resolution image memory, detecting motion of the image, and infilling the pixels of the high resolution image a plurality of standard resolution image pixels translated according to motion of the image. As disclosed in section 0089 of this cited publication, the process of infilling each pixel of the image is repeated until a determination is made that a scene change has occurred, or that input of distorted images (standard resolution images) has been completed.
The prior art has drawbacks such as the following.
The former technique has the drawback of requiring extended processing time, due to generation of more image data than is necessary for the required image quality, resulting from the fixed number of frames of data synthesized.
The latter technique has the drawback also has the drawback of requiring extended processing time, since frame information continues to be synthesized until determination is made that a scene change has occurred or that input of frame information has been completed, thus also generating more image data than necessary for the required image quality.

Image generating device, image generating method, and image generating program


A method for treating cullet before use as a raw material in a glass manufacturing process is disclosed. The method includes providing a bed of cullet; passing hot gases through the bed, the quantity and temperature of gases being sufficient to pyrolyze odor creating impurities within the bed of cullet; entraining volatile products of pyrolysis into gases leaving the moving bed; heating the gases leaving the bed to oxidize odor creating impurities; and discharging the gases to the atmosphere. The apparatus includes a housing containing a moving bed of cullet; a source of hot gases which permits the gases to pass through the moving bed of cullet to pyrolyze odor creating impurities within the cullet and entrain volatile products of pyrolysis into gases leaving the moving bed; and an incinerator to remove odor creating impurities from gases leaving the moving bed.

1. Field of the Invention
The present invention lies in the art of glass manufacture. More particularly, the invention concerns the processing of cullet which is fed to a glass melting furnace along with other raw materials. In particular, the invention is directed to a method and apparatus which removes odor and pollutants when preparing cullet for use in an electrostatic bed filter.
2. Description of the Prior Art
Glass manufacture involves the mixing of various batch ingredients, generally including silica sand, dry powders, granular oxides, carbonates, and other raw materials (depending on the desired glass type) and heating them to a temperature of about 1500.degree. C. where they become molten and acquire a homogeneous nature. Substantial quantities of heat are required for the melting process, generally supplied by combustion of fossil fuels. Because of the relatively poor heat transfer from the hot combustion gases to the pool of molten glass, exhaust gas temperatures from the process are usually quite high in spite of various types of heat recovery equipment employed. As well, pollutants of various types are emitted from the melting process along with the exhaust gases.
Cullet, that is, broken pieces of glass, is added to the other batch ingredients and charged to the melting furnace. A certain minimum proportion of the total batch is required to be cullet in order to provide proper melting characteristics, generally in the range of 10-20% by weight. Cullet normally used for this purpose is generated within the glass factory, either from product breakage during the manufacturing process, or from dumping of molten glass during product changes.
Recent emphasis on waste recycling has resulted in the collection of large quantities of what is called ecological cullet. This is generally glass bottles returned to recycling centers. With proper processing such as sorting by color, removing foreign substances and crushing to smaller sized pieces, ecological cullet can be made suitable for remelting into new glass. Currently there are a number of glass factories set up with glass melting furnaces where some 80-90% of the batch feed material is ecological cullet.
When used in these quantities, the possibility of preheating cullet with waste exhaust gases from the furnace becomes economically attractive and equipment for such purpose is commercially available. See, Zippe, "Economics of Cullet Preheating", Glass International June 1992.
One such type of equipment potentially useful in this role is an electrostatic granular bed filter. Electrostatic granular bed filters employ a bed of electrically charged granules. Exhaust gases containing particulate pollution are electrostatically charged and contacted with the granular bed. The electrostatically charged particles in the exhaust gases are attracted to and retained on the electrically charged granular bed.
U.S. Pat. No. 4,338,112, incorporated herein by reference, discloses methods for utilizing electrostatic granular bed filter technology for air pollution reduction from glass furnaces. However, this patent provides no teaching of a workable system for replacing the granules in the electrostatic granular bed filter with cullet.
The simple substitution of cullet for the widely used silica-based granules in an electrostatic granular bed filter results in several operational problems which render the system ineffective and inoperative. First, cullet is generally wet either from washing in the waste recycling process or from storage in open outside locations. Wet granules in an electrostatic granular bed filter would present an electrical short circuit and prevent the application of substantial voltages to the bed.
Second, the heat transfer resulting from direct contact of the hot exhaust gases and the cullet is quite good. As a result, the exhaust gases are very effectively cooled by the cold cullet as it is first contacted by the gases. Continued heat transfer cools the gases to below their acid dew point temperature, at which point an acid mist would be former which would in turn result in excessive equipment corrosion.
Third, as cullet is handled mechanically, the glass is subject to breakage and formation of substantial quantities of fine glass dust. When exhaust gases are passed through the cullet in the electrostatic granular bed filter, this glass dust would become entrained in the gases and exit the filter as dust emissions.
U.S. Pat. No. 5,342,427, incorporated herein by reference, discloses an apparatus and methods for simultaneously preheating cullet and removing pollutants from glass furnace gases. Raw moist cullet having fine glass dust material and often impurities adhered to its surface is heated by furnace gases which remove the moisture and the impurities by entrainment. The dry, clean cullet is then electrically charged and used to filter the exhaust gases which have been electrostatically charged.
It is especially attractive to utilize this process in cases where the glass manufacturing process is receiving large amounts of cullet from recycling efforts in the community. This recycled cullet is often contaminated with a wide range of materials such as organic residues in bottles, paper, and other non-glass waste materials mistakenly deposited into recycled containers.
In the case where raw cullet used in the process is contaminated with these materials, it has been found that the process described in U.S. Pat. No. 5,342,427 produces objectionable odors which are discharged to the atmosphere. Apparently, when the organic residues and other contaminates are heated, the contaminates are sometimes volatilized and discharged to the atmosphere. Hence, there remains a need in the art for a method and apparatus which removes odor caused by volatilization of these pollutants when preparing cullet for use in an electrostatic bed filter.

Method which removes odor and pollutants when preparing cullet for use in an electrostatic bed filter


A power down circuit for a memory device is provided that includes a burn-in voltage detector to generate a burn-in voltage detecting signal to control a power down signal when a burn-in voltage reaches a predetermined level. The power down circuit enhances a burn-in function by operating the memory cells and peripheral circuits for a relatively long time at a high level voltage when a burn-in is performed on the memory device with an auto power down function. Thus, the memory device reliability is also enhanced. The memory device includes a power down timer for generating a power down signal to control an input/output operation of a memory cell in response to a plurality of address transition detecting signals, a plurality of data input detecting signals, a chip select detecting signal, a write mode detecting signal and the burn-in voltage detecting signal.

1. Field of the Invention
The present invention relates to a memory device, and in particular, to a power down circuit for a memory device.
2. Background of the Related Art
Burn-in mode is performed on a memory device to eliminate premature failures after fabricating a substrate and packaging the memory device regardless of an auto power down function. In the burn-in mode, a high voltage is applied to operate memory cells and neighboring circuits, and thereby, a vulnerable memory device can be eliminated.
In a static random access memory device (SRAM), a direct current (DC) voltage keeps flowing through power source supplying elements during a read cycle and a write cycle in a burn-in mode as well as in a normal mode, which results in a high power consumption in the SRAM. However, reducing power consumption in the SRAM is desirable.
U.S. Pat. No. 4,962,487 (issued: Oct. 9, 1990) discloses a method for reducing power consumption during a write cycle, which was proposed to satisfy the demand for lower SRAM power consumption. In U.S. Pat. No. 4,962,487, the cycle for performing an actual write operation is not determined using a write cycle determined by an external control signal, but by a cycle during which a pulse signal generator generates an arbitrary pulse signal. Therefore, when an actual write cycle is finished, the mode is converted into a power down mode even during a write cycle according to the pulse signal generator.
U.S. Pat. No. 4,947,379 (issued: Aug. 7, 1990) discloses data output circuits connected to word lines and bit lines that are disabled after a word line enabling pulse signal and a sense amplifier enabling pulse signal are finished. Thereby, power consumption during the read cycle can be reduced.
FIG. 1 is a block diagram showing a related art power down circuit. As shown in FIG. 1, a power down timer 15 receives a plurality of address transition detecting signal (.0.ATD1 . . . .0.ATDk) from an address transition detector 5, a chip select detecting signal (.0.CSD) and a write mode detecting signal (.0.WTD) from a chip select/write mode detector 13 and a plurality of data input detecting signals (.0.DTD1 . . . .0.DTDn) from a data transition detector 33, to generate a power down signal (.0.PD) having an arbitrary pulse width.
FIG. 2 is a circuit diagram showing the power down timer 15. As shown in FIG. 2, the power down timer 15 receives the address transition detecting signals (.0.ATD1 . . . .0.ATDk), the data input detecting signals (.0.DTD1 . . . .0.DTDn), the chip select detecting signal (.0.CSD) and the write mode detecting signal (.0.WTD), respectively, through NOR gates 42,44,46. A NAND gate 48 receives the output signals from the NOR gates 42,44,46. An output signal from the NAND gate 48 is inputted to a pulse extending circuit 50, from which the power down signal (.0.PD) is generated in response to any transition among the detecting signals.
As shown in FIG. 1, the power down signal (.0.PD) controls a data input circuit 29 and is inputted to a plurality of NOR gates (NOR1 . . . NORn) to enable a plurality of word lines (WL1 . . . WLn). The power down signal (.0.PD) is also inputted to a NOR gate 17 to enable a write switching signal (.0.SWE) for connecting the data input circuit 29 to a pair of data lines (DL,DLB). The power down signal is also inputted to a NOR gate 31 to generate a sense amplifier enabling signal (.0.SAE).
With reference to the timing waveform diagrams shown in FIG. 3, the read and write operations of the circuit in FIG. 1 will now be described. During a write cycle, a chip select signal (.0.CSB) and a write enabling signal (WEB) are maintained low level, as shown in FIGS. 3A and 3C. In addition, an output enabling signal (OEB) is maintained high level as shown in FIG. 3D.
First, when a write cycle starts, the chip select detecting signal (CSD) is outputted as a high pulse signal as shown in FIG. 3F in response to a level transition of the chip select signal (.0.CSB). Further, the address transition detecting signals (.0.ATDi:i=1 . . . k) are outputted as a high pulse signal as shown in FIG. 3H in response to a transition of address bits (Ai:i=1 . . . k) as shown in FIG. 3B.
The write mode detecting signal (.0.WTD) is outputted as a high pulse signal, as shown in FIG. 3G, in response to a transition to a low level of the write enabling signal (WEB). The data detecting signals (.0.DTDi:i=1 . . . n) are outputted as a high pulse signal shown in FIG. 3I, in response to a transition of an input data bit. Accordingly, the power down signal (.0.PD) shown in FIG. 3J is generated from the power down timer 15 in accordance with a logical state of the above-mentioned detecting signals (.0.CSD, .0.WTD, .0.ATDi and .0.DTDi).
While the power down signal (.0.PD) is maintained low level with a predetermined pulse width by the pulse extending circuit 50, the selected word lines (WLi:i=1 . . . n) are enabled. Then, when the power down signal (.0.PD) becomes a high level, the enabling operation for the word line (WLi) is finished. Accordingly, the data input circuit 29 is disabled and the write switching signal (.0.SWE) becomes low level as shown in FIG. 3N. As a result, current is inhibited from flowing from the data input circuit 29 to the memory cells.
During the read cycle, the chip select signal (.0.CSB), the write enabling signal (WEB) and the output enabling signal (OEB) are maintained low, high and low levels, respectively, as shown in FIGS. 3A, 3C and 3D. In accordance with the power down signal (PD) maintained low level as shown in FIG. 3J, the sense amplifier enabling signal (.0.SAE) is outputted as a high pulse signal as shown in FIG. 3O during the cycle of the predetermined pulse width of the power down signal (PD). Then, the selected word line (WLi) and the sense amplifier 35 are disabled after a latching operation by the data output buffer 37 when the power down signal (PD) is transited to be high level. That is, the circuit in FIG. 1 disables a word line in a burn-in mode after a data writing into the memory cells is performed during the write cycle and disables the word line and the sense amplifier after a data reading from the memory cells is performed during the read cycle. Thereby, the current path is cut off, which reduces the power consumption.
However, the related art power down circuit has various disadvantages. When a burn-in is performed to eliminate premature failures irrespective of a power down function after the memory device is packaged or a wafer is produced, a high voltage is applied to a memory cell as shown in FIG. 4 and to peripheral circuits for the operation thereof, thereby to prevent a vulnerability in a semiconductor device. In particular, the burn-in eliminates defects in a gate oxide of a transistor. However, in related art memory devices having an auto power down function, burning-in proceeds only during a relatively short period when powering-down does not occur. Thus, a burn-in effect influences only part of the memory cells and peripheral circuits, and as a whole, the burn-in effect is reduced.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.

Auto power down circuit for a semiconductor memory device


A belt drive controller for controlling each belt stopping position with high accuracy during intermittent movement of a belt. This belt drive controller controls driving of a belt to intermittently move a belt wrapped around a plurality of supporting rollers including a driven roller and a drive roller. This controller detects a rotation angular displacement or a rotation angular velocity of two supporting rollers having mutually different diameters, and controls driving of the drive roller based on the detected rotation data so that the position of the belt in the direction of movement becomes a predetermined target position.

1. Field of the Invention
The present invention relates to a belt drive controller for controlling the driving of a belt so as to intermittently move an endless belt wrapped around a plurality of supporting rotating bodies, and an image forming apparatus of an ink jet recording type and so forth provided therewith.
2. Description of the Background Art
A known example of this type of image forming apparatus is an ink jet recording type of image forming apparatus which forms an image on a recording material by intermittently moving a recording material transport member to repeatedly advance the recording material in steps when forming an image on a recording material supported and transported on a recording material transport member comprising an endless belt.
In this type of image forming apparatus, a conveyor belt (recording material transport member) may be used as a recording material transport mechanism. In this type of recording material transport mechanism, a code wheel (encoder disk) is installed on supporting rollers (supporting rotating bodies) on which the conveyor belt is wrapped around, and a code on the code wheel is read with an encoder. The conveyor belt is moved intermittently based on the output of the encoder, and driving is controlled so that the recording material stops at each target stopping position. As a result of carrying out this type of driving control, since the accuracy of each stopping position during intermittent transport of the recording material can be improved, the accuracy of the impact position of the ink droplets on the recording material can be improved, there by making it possible to enhance image quality. An image forming apparatus employing this type of driving control method is described in, for example, Japanese Patent Application Laid-open No. 2001-248822. The image forming apparatus described in this publication transports a recording material in a secondary scanning direction by arranging a transport roller and a discharge roller on the upstream side and down stream side of a platen. A code wheel is installed on the transport roller shaft, a code on the code wheel is read with an encoder, and the transport roller and conveyor belt are moved intermittently based on the encoder output.
In addition, Japanese Patent Application Laid-open No. 2005-115398 describes a method for controlling driving of an endless belt provided in a so-called electrophotographic type of image forming apparatus. This driving control method controls driving by detecting the rotation angular displacement or rotation angular velocity of a driven supporting rotating body among a plurality of supporting rotating bodies around which a belt is wrapped, and suppresses fluctuations in the movement velocity of the belt caused by periodical fluctuations in thickness in the circumferential direction of the belt based on the detection result so that the belt moves at a constant movement velocity.
Ink jet recording types of image recording apparatuses have recently come to use pigment-based ink instead of dye-based ink so as to improve ink light resistance and deterioration over time, resulting in a trend in which ink viscosity is increasing. Although bleeding on to the recording material has decreased considerably as a result of increasing the viscosity of the ink, poor accuracy resulting from shifts in the impact position of the ink droplets on the recording material is readily apparent visually in the form white lines, black lines and banding. This deterioration in image quality has a particularly large effect on the accuracy of each belt stopping position during intermittent movement by the conveyor belt which supports and transports the recording material in the direction of secondary scanning (direction of transport of the recording material) in particular. Consequently, controlling each belt stopping position during intermittent movement of the conveyor belt to attain even higher accuracy has become an important technical issue. However, conventional methods for controlling driving as described in the above-mentioned Japanese Patent Application Laid-open No. 2001-248822 had the problem of being unable to control each belt stopping position during intermittent movement of the conveyor belt with sufficiently high accuracy so as to be able to adequately suppress deterioration of image quality in the form of white lines, black lines and banding.
A first cause of being unable to control each belt stopping position with sufficiently high accuracy during intermittent movement of the conveyor belt is fluctuation during belt driving in the distance from the roller surface to the belt pitch line, namely the pitch line distance (PLD), at the portion of the belt wound around the drive roller (driving supporting rotating body). More specifically, the movement velocity of a belt is typically determined by the PLD. This PLD is equivalent to the distance between the center of the belt in the direction of thickness and the belt inner surface, namely the roller surface, in the case of a single-layer belt made of a uniform material and the absolute value of belt flexibility of the inside and outside of the belt being nearly equal. Thus, since the relationship between PLD and belt thickness is nearly constant in the case of such a single-layer belt, the movement velocity of the belt can be determined according to the amount of unevenness in belt thickness. However, as a result of different mutual flexibility between hard layers and soft layers in a belt composed of a plurality of layers, the distance from a position shifted from the center of the belt in the direction of thickness and the roller surface becomes the PLD.
If PLD fluctuates in the portion of the belt wound around the drive roller during belt driving, the belt movement velocity increases when a portion of the belt having a large PLD is wound around the drive roller, while conversely the belt movement velocity decreases when a portion of the belt having a small PLD is wound around the drive roller. As a result, the belt movement distance becomes longer when a portion of the belt having a large PLD is wound around the drive roller, while conversely the belt movement distance becomes shorter when a portion of the belt having a small PLD is wound around the drive roller. Consequently, if fluctuations in the PLD occur in a portion of the belt wound around the drive roller during belt driving, even if the drive roller rotates by the same rotation angle, the distance over which the belt moves as a result of that rotation changes. As a result, even if the drive roller is rotated by the same rotation angle during each movement of the conveyor belt during intermittent transport of the recording material, each distance by which the recording material is transported ends up being different. For this reason, the belt stopping position during intermittent movement of the conveyor belt ends up shifting from the target position, and each belt stopping position cannot be controlled accurately during intermittent movement of the conveyor belt.
In addition, a second cause of being unable to accurately control each belt stopping position during intermittent movement of the conveyor belt is detection error attributable to the encoder or other detection means. In the case of detecting a single rotation angular displacement or rotation angular velocity of a supporting roller around which a conveyor belt is wrapped, and controlling driving based on that detection result, an error occurs between the belt movement distance obtained from the detection result and the actual belt movement distance due to eccentricity of the supporting roller and the assembly accuracy of the detection means with respect to that supporting roller. If driving is controlled based on a detection result which contains this type of error, the belt stopping position during intermittent movement of the conveyor belt ends up shifting from the target position, thereby preventing accurate control of each belt stopping position during intermittent movement of the conveyor belt.
In addition, a third cause of being unable to accurately control each belt stopping position during intermittent movement of the conveyor belt is a change in the diameter of a supporting roller attributable to temperature changes, wear over time and so on. If the diameter of a supporting roller changes, even if the supporting roller rotates by the same rotation angle, the belt movement distance at that time differs. As a result, if the diameter of the drive roller changes, for example, even if that drive roller is rotated by the same rotation angle, the distance the belt is driven due to that rotation changes. As a result, even if the drive roller is rotated by the same rotation angle during each movement of the conveyor belt during intermittent transport of the recording material, the distance the recording material is transported ends up differing each time, thereby preventing accurate control of each belt stopping position during intermittent movement of the conveyor belt. In addition, if the diameter of a driven roller provided with detection means changes, a result is obtained which is different from the distance the belt has actually moved even in the case of a detection result for the same rotation angle, thereby resulting in detection error. Accordingly, if driving is controlled based on a detection result which contains this type of error, the belt stopping positions during intermittent movement of the conveyor belt end up shifting from the target position, and each belt stopping position during intermittent movement of the conveyor belt cannot be accurately controlled.
Furthermore, the above-mentioned problems of the prior art are not limited to driving control which intermittently moves a belt used as a recording material transport member which supports and transports a recording material, but also can similarly occur for all types of driving control of a belt which is moved intermittently.
Technologies relating to the present invention are also disclosed in, for example, Japanese Patent No. 3,564,953, Japanese Patent No. 3,658,262, Japanese Patent Application Laid-open No. H08-282009 and Japanese Patent Application Laid-open No. 2000-330353.

Belt drive controller and image forming apparatus provided with same


Long distance country codes that are used by a group of users are updated by automatically sending an electronic message to the group of users that includes at least one new or changed long distance country code, in response to automatically obtaining a listing of long distance country codes from an International Telecommunication Union (ITU) website. More specifically, a listing of long distance country codes is automatically obtained from the ITU website. The listing of long distance country codes that is obtained from the ITU website is automatically compared to preexisting long distance country codes that are used by the group of users, to identify at least one new or changed long distance country code. An electronic message, such as an email message, is automatically sent to the group of users that includes the at least one new or changed long distance country code that was identified.

Telecommunications systems, methods and computer program products are widely used for worldwide communications of voice, multimedia and/or data. As is well known to those having skill in the art, long distance country codes are used in international direct dialing. The long distance country codes are also referred to in the telecommunications industry as assigned country codes, IDDD codes or simply as country codes. For example, the United States is assigned country code 1, France is assigned country code 33 and Japan is assigned country code 81. These country codes are assigned by the International Telecommunication Union (ITU).
The long distance country codes are used within a telecommunications provider that operates a plurality of telecommunications switches to provision the switches. In particular, a telecommunications provider may include a Complex Translations Group (CTG), often referred to as a Translations Group, which includes technicians who are responsible for programming country codes, area codes, local switch codes and/or other codes in the switches. This process is referred to as provisioning the switches. If an improper long distance country code is provisioned in the switch, it may result in improper routing of a call. Other telecommunications system users also may use the long distance country codes for direct dialing of long distance calls, either manually or in connection with speed dialing or automatic dialing devices.
As is also well known to those having skill in the art, country codes may change. These changes may occur when a new country code is added or a country code is changed. The CTG within a telecommunications company often finds out about a new or changed country code as a result of a customer trouble report, when a customer attempted to dial an international long distance number and was routed to the wrong number or could not connect. In other instances, an email may be received from another member of the CTG staff, or another member of the telecommunications provider who learns about the new or changed country code. This may be contrasted from changes in area codes, wherein the telecommunications provider typically initiates the change in an area code, and therefore has advance notice of the change in an area code. The switch can then be provisioned with the new area code at the appropriate time, to reduce or eliminate dialing or routing errors.

Methods, systems and computer program products for automatically updating long distance country codes

BellSouth Intellectual Property Corporation


Displacement measuring apparatus for measuring the displacement and movement of an object includes a sensor having an operative surface and circuitry for producing an electrical output signal whose value is dependent upon the area of the operative surface covered by an electrical/magnetic field producing member. The apparatus also includes an elongate, flexible band capable of producing an electric/magnetic field, where the band is attached at one end to the sensor to roll over and cover or unroll from over and uncover the operative surface as the object whose displacement is to be measured is moved. The value of the electrical output signal produced by the circuitry is thus dependent upon the area of the operative surface covered by the band and thus by the position and movement of the object.

This invention relates in general to apparatus for sensing displacement or position of an object, and in particular to apparatus which utilizes a flexible moveable band or other moveable element to convert a physical measure of displacement and position of an object into an electrical signal representing such measure.
In the operation of various mechanical and electro-mechanical systems, it is necessary to monitor the position and displacement of either some element of the system or some object which is not part of the system. For example, in robotic systems (a technology whose use is dramatically increasing) it is almost always necessary to monitor and control the movement and position of various component parts of the systems, such as an arm, fingers or other grasping elements, etc. Such monitoring and control yields the dexterity and precision required for a robotic system to carry out its functions.
Prior art mechanisms for sensing position and displacement have most often utilized a direct connection between the article or object whose position or displacement was to be monitored, and some type of gauge, needle or other visual indicator. Movement of the article or object would thus cause a corresponding movement of the gauge or needle. As expected, such mechanisms have typically been large and cumbersome and have lacked precision in carrying out the monitoring function. Further, since some type of sliding action of some part of the measuring mechanism typically was involved, friction was present which, of course, resulted in wear.
Although electronic apparatus for measuring position and displacement has come into greater use in recent years and has at least partially solved the bulkiness and imprecision problems of the prior art mechanisms, such apparatus has been complicated in design and, as a result of such complication, generally lacking in reliability. Also, the contact friction and attendant wear generally remained.


A method for dithering image data is provided. The method is suitable for representing A-bit grayscale values with a B-bit resolution, where A and B are positive integers and A>B. The main steps of the method include calculating 2A target grayscale values with decimals within an interval from 0 to (2B−1)*2A−B, and then representing the target grayscale values with the decimals through 2-dimensional dithering or 3-dimensional dithering.

1. Field of the Invention
The present invention relates to a method for dithering image data. More particularly, the present invention relates to a method for dithering image data capable of completely representing source signal grayscale values.
2. Description of Related Art
It is a common problem in the display of digital images that the grayscale resolution of a display device is less than the grayscale resolution of an output device. For example, the output device is a personal computer with an 8-bit resolution, while the display device is a thin film transistor liquid crystal display panel (TFT LCD panel) with a 6-bit resolution. At this time, the simplest method is to delete two least significant bits (LSB) of the signal grayscale value output from the personal computer, so as to turn the 8-bit grayscale value to a 6-bit grayscale value. However, the color levels of the displayed images are sacrificed if this method is adopted.
Accordingly, a method for increasing the color levels is developed, which performs dithering on the signal grayscale values of the output device. The method utilizes the feature that human eyes automatically average the grayscale values in a small region when viewing from distance to enable the average values to have more color levels. There are two common dithering methods: one of the methods includes the spatial dithering or also referred to as 2-dimensional dithering, and the other method includes the spatial dithering plus temporal dithering or also referred to as 3-dimensional dithering.
The 2-dimensional dithering process is performed in a unit of a pixel block of a fixed size. Table 1 is a table of correspondence between input blocks and output blocks according to the conventional 2-dimensional dithering method, in which the pixel block with a size of 4*2 is used. In the input block section, only two LSBs of the signal grayscale values, i.e., the bits deleted before being transmitted to the display device, are listed. In the output block section, 0 denotes that the signal grayscale value of this pixel needs a non-carry operation, and 1 denotes that the signal grayscale value of this pixel needs a carry operation.
TABLE 1Table of Correspondence of Conventional 2-Dimensional DitheringInput BlocksOutput Blocks(Two LSBs)(Carry)000000000000000000000000010101011000010101010010101010100000101010101111111111110111111111111101
The non-carry operation is performed to set the two LSBs of the signal grayscale value to 0, and the carry operation is performed to set the two LSBs of the signal grayscale value to 0 and then add 4 to the result. For example, Table 2 shows the output blocks of the signal grayscale values from 8 (1000 in binary) to 11 (1011 in binary) obtained in accordance with the rules of Table 1. As for the values from 8-11, the result of the carry operation is 12, and the result of the non-carry operation is 8.
TABLE 2Examples of Conventional 2-Dimensional DitheringInput BlocksOutput Blocks(Decimal)(Decimal)88888888888888889999128889999881281010101088881010101012121212111111118121212111111111212812
It is known from Table 2 that the average values of four output blocks equal to the signal grayscale values of the respective corresponding input blocks, while Table 2 only uses two numerals 8 and 12 to represent 4 different color levels. The two LSBs of 8 and 12 are both 0, which is applicable to the 6-bit resolution.
In another aspect, the 3-dimensional dithering process is performed in a unit of the pixel block of a fixed size in several continuous frames. Table 3 is a table of correspondence between input blocks and output blocks according to the conventional 3-dimensional dithering method, in which the pixel block with the size of 4*2 in four continuous frames is used. Similarly, only two LSBs of the signal grayscale values are listed in the input block section in Table 3. After an input block is found, the fields under the input block are the corresponding output blocks in four continuous frames, wherein 0 denotes that the signal grayscale value of this pixel needs the non-carry operation, and 1 denotes that the signal grayscale value of this pixel needs the carry operation. According to the rules of Table 3, the overall average value of all pixels in the four continuous frames equals to the input signal grayscale value.
TABLE 3Table of Correspondence of Conventional 3-Dimensional DitheringInput Blocks (LSB)00000000010101011010101011111111000000000101010110101010111111111st Frame0000100000000111(Carry)00000010111111012nd Frame0000000111111110(Carry)00000100000010113rd Frame0000001000001101(Carry)00001000111101114th Frame0000010011111011(Carry)0000000100001110
However, the conventional dithering methods are disadvantageous in that not all signal grayscale values are represented. For example, in the above examples, the display device has a 6-bit resolution only, so the maximum value is 63, and after being multiplied by 4, only 252 signal grayscale values can be represented in maximum. However, the three primary colors red, green, and blue can be combined to represent 2563=16,777,216 color originally, while only 2533=16,194,277 is represented after the dithering, thus losing about 3.5% of the color levels.


A method of preparing glass fiber strands is shown wherein the glass fibers as they are drawn from the glass fiber forming bushing are wound in a unique way. The fibers are drawn from the bushings using high speed, low energy drawing devices such as capstans and godets. They are then passed to high speed, low energy flyers for distribution onto the surface of light weight, low energy, slowing rotating mandrels. All the winding equipment and the attenuation devices are light in weight requiring very low horsepower motors compared to the high horsepower, high energy devices of the current state of the art. The flyers are shown driven by conventional motors or by a compressed air system. Collection of the strand takes place on the ends of the elongated mandrels shown and create a novel doughnut shaped forming package of fiber glass with properly distributed strands thereon suitable for unwinding.

In the manufacture of glass fiber strands as practiced today the emphasis is on increased productivity for each fiber forming position located on the forehearths of the furnaces used to process the raw glass making ingredients into molten glass. The glass, once molten, flows from the forehearth of the furnace through the fiber forming bushings which produce multiple streams of glass from a multiplicity of holes of precise dimension. These streams of molten glass solidify as they leave the bushing are gathered together to form strands after usually having a size or binder applied to them and are then collected on a paper or plastic tube which is rotated at high speed on the surface of a winding machine. The paper tube with the collected glass is slipped off of the winder when it is stopped upon completion of a package forming cycle.
The winder used to form the glass fiber packages are used both to wind the glass strands thereon and to impart the attenuation forces to the molten glass streams that are forming glass fibers as they emerge from the bushings. In a modern fiber glass manufacturing facility these winders operate at speeds that result in strands being collected at 12,000 to 20,000 feet per minute (3,658 to 6096 meters per minutes). In addition to operating at high speed, the winders are increasing in size and weight. The net result of the necessity to achieve high rates of production from the winding of the glass is that the costs of the winding equipment now represents a substantial capital investment in an industry that is already burdened with high capital costs for furnaces and the platinum alloys used to fabricate the bushings that produce the fibers.
Typical of the winders that are used to collect glass fiber strands in forming are those shown in U.S. Pat. Nos. 3,151,963, 3,041,663, and 3,547362. These winders are positioned below a forming bushing and after the strands are formed are rotated at high speeds to collect the product. The high collection speeds employed impart considerable tension to the strands that are collected which wrinkles the forming tubes used on the winder to collect the strands. High speeds also cause broken filaments, and more importantly, cause quality defects with inconsistent strands being poduced in the same package.
For these and other reasons a need exists to provide a method of winding strands of glass fibers that is less expensive than the high technology winders now employed but that will duplicate their productivity and minimize their product quality shortcomings. The instant invention satisfactorily meets that need.


A color image forming device has an image forming cartridge including a cartridge frame that receives a plurality of image forming units. A movable fixing part supports at least one of the shafts of a plurality of photosensitive bodies disposed in the image forming units so that the shaft is rotatably fixed. The shafts of the other photosensitive bodies are movable and rotatable when the plurality of image forming units are received in the cartridge frame. A mounting frame receives the image forming cartridge, and has a shaft receiving part formed at a position corresponding to the ends of the shafts of the photosensitive bodies. The color image forming device accurately fixes the position of the shafts of the photosensitive bodies when the image forming cartridge is assembled in the mounting frame, thereby producing a high quality image reliably.

1. Field of the Invention
The present invention relates to an electrophotographic image forming device such as a printer, copier, and facsimile machine. More particularly, the present invention relates to a tandem color image forming apparatus to transfer toner images formed respectively on a plurality of photosensitive bodies by a plurality of corresponding image forming units, onto an intermediate transfer unit or printing medium.
2. Description of the Related Art
A conventional electrophotographic tandem color image forming device is provided with a plurality of image forming units disposed in parallel, a plurality of photosensitive bodies, each being disposed in the corresponding image forming units and forming toner images representing yellow, magenta, cyan and black colors, respectively, and a transfer unit such as a transfer belt or a transfer drum to sequentially transfer the toner images formed on the photosensitive bodies onto a recording medium such as a sheet of printing paper. Additionally, conventional electrophotographic tandem color image forming devices include a fusing unit to fuse and fix the toner images transferred onto the recording medium with heat and pressure.
Other conventional tandem color image forming devices further include an intermediate transfer unit disposed between the photosensitive bodies and the transfer unit. In this case, the toner images formed on the photosensitive bodies are not directly transferred to the recording medium, but are first transferred as a first transfer image onto the intermediate transfer unit and then retransferred from the intermediate transfer unit onto the recording medium.
The conventional tandem color image forming devices that have the plurality of photosensitive bodies therein for forming images by simultaneously revolving the plurality of photosensitive bodies have an advantage in that they can obtain color images very quickly, as compared with other color image forming devices that have only a single photosensitive body therein for forming images by revolving the single photosensitive body several times. Since construction is complicated with use of a plurality of photosensitive bodies and image forming units, it is important that the tandem color image forming device be constructed to be easily assembled, maintained and repaired.
FIGS. 1 and 2 show a tandem image forming device having a mounting frame for easily assembling, maintaining, and repairing. The tandem image forming device is disclosed in Japanese patent No. 2002-108049, the entire contents of which are incorporated herein by reference.
The color image forming device 1 comprises a paper feeding unit 21 to feed sheets of printing paper P stacked in a paper cassette 20, four image forming units 10Y, 10M, 10C and 10K to form toner images of four colors, i.e., yellow, magenta, cyan, and black disposed vertically in parallel, and an intermediate transfer unit 7 having a belt-shaped intermediate transfer element 70 (FIG. 5) rotatably supported on a plurality of rollers 71, 72, 73 and 74 (FIG. 5) at a left side of photosensitive bodies 1Y, 1M, 1C, and 1K disposed respectively in the image forming units 10Y, 10M, 10C and 10K. The color imaging forming device 1 further comprises a mounting frame 8 to install the image forming units 10Y, 10M, 10C and 10K and the intermediate transfer unit 7 therein, a transfer unit 5A to retransfer the toner images transferred on the intermediate transfer element 70 of the intermediate transfer unit 7 from the photosensitive bodies lY, 1M, 1C, and 1K, onto a sheet of printing paper, and a fusing unit 24 to fuse and fix the toner images transferred onto the sheet of printing paper with heat and pressure.
Each of the image forming units 10Y, 10M, 10C and 10K are provided with photosensitive body assemblies 11Y, 11M, 11C and 11K (FIG. 5) having photosensitive bodies 1Y, 1M, 1C and 1K, charging units 2Y, 2M, 2C and 2K and cleaning units 6Y, 6M, 6C and 6K, laser scanning units 3Y, 3M, 3C and 3K (see FIG. 2), and developing units 4Y, 4M, 4C and 4K, which are formed in the proximity of the circumferences of the photosensitive bodies 1Y, 1M, 1C and 1K.
The intermediate transfer unit 7 has primary transfer parts 5Y, 5M, 5C, and 5K pressing the photosensitive bodies 1Y, 1M, 1C, 1K at a predetermined pressure with the intermediate transfer element 70 interposed therebetween.
As shown in FIGS. 1–4, the mounting frame 8 is formed of a casing 81 constructed to be guided and projected forward along left and right supporting rails 82L and 82R of main body 1A, to install the image forming units 10Y, 10M, 10C and 10K and the intermediate transfer unit 7 into the main body 1A.
The casing 81 is provided with an upper cover member 83 to cover an upper portion of the photosensitive body assembly 11Y, and a lower cover member 84 to protect the intermediate transfer element 70 in mounting and dismounting of the intermediate transfer unit 7, and preferably to act as an upper guide of a paper conveying path (at the same time).
Vertical grooves 86 and horizontal grooves 85 are formed at inner surfaces of front and rear walls of the casing 81 to guide positioning pins 75 (FIG. 3) formed at both sides of the intermediate transfer unit 7 to install the intermediate transfer unit 7.
The casing 81 is provided with supports 87Y, 87M, 87C and 87K (FIG. 5) to support the photosensitive body assemblies 11Y, 11M, 11C and 11K including the photosensitive bodies 1Y, 1M, 1C and 1K, the charging units 2Y, 2M, 2C and 2K and the cleaning units 6Y, 6M, 6C and 6K in corresponding assembling positions, respectively. Supporting sliders 88Y, 88M, 88C and 88K (FIG. 3) receive and support the developing units 4Y, 4M, 4C and 4K in corresponding assembling positions, respectively.
Accordingly, in disassembling of the intermediate transfer unit 7 and the image forming units 10Y, 10M, 10C and 10K for maintenance and repair, the mounting frame 8 is guided and projected forward along the left and the right supporting rails 82L and 82R in the main body 1A, as shown in FIG. 1.
Subsequently, the intermediate transfer unit 7 is moved away from the photosensitive body assemblies and then lifted upwardly, as shown in FIG. 5. Durign the lifting procedure, the positioning pins 75 of the intermediate transfer unit 7 are guided along the horizontal grooves 85 and then vertically along the vertical grooves 86, so that the intermediate transfer unit 7 can be easily pulled out.
After pulling out the intermediate transfer unit 7, the photosensitive body assemblies 11Y, 11M, 11C and 11K and the developing units 4Y, 4M, 4C and 4K are moved and then pulled out in the directions shown by the arrows in FIG. 5 from the supports 87Y, 87M, 87C and 87K and the supporting sliders 88Y, 88M, 88C and 88K, respectively.
The procedure for assembling the intermediate transfer unit 7 and the image forming units 10Y, 10M, 10C and 10K into the mounting frame 8 is performed in the opposite order of disassembling them as described above.
The conventional tandem color image forming device 1 as described above has a mounting frame 8 that can easily assemble and disassemble the intermediate transfer unit 7 and the image forming units 10Y, 10M, 10C and 10K. To accurately mount the photosensitive body assemblies 11Y, 11M, 11C and 11K, however, and the developing units 4Y, 4M, 4C and 4K of the image forming units 10Y, 10M, 10C and 10K in position in the mounting frame 8, they should be fabricated to have dimensions that accurately coincide with those of the supports 87Y, 87M, 87C and 87K and the supporting sliders 88Y, 88M, 88C and 88K of the mounting frame 8, respectively.
Fabricating the dimensions in both side components to accurately coincide with one another as described above can complicate the design of the fabricating mold, and can induce assembling errors when assembling both of the side components.
Furthermore, in the conventional tandem color image forming device 1, the photosensitive body assemblies 11Y, 11M, 11C and 11K and the developing units 4Y, 4M, 4C and 4K should be exactly and individually mounted on assembling positions in the mounting frame 8. This is difficult to achieve, and causes assembling efficiency to decrease and increases assembling time, thereby lowering manufacturing productivity.


Disclosed are cell membrane-derived nanovesicles, a method of preparing the nanovesicles, and a pharmaceutical composition and a diagnostic kit using the nanovesicles. The cell membrane-derived nanovesicles may prevent potential adverse effects because intracellular materials (e.g., genetic materials and cytosolic proteins) unnecessary for delivering therapeutic or diagnostic substances are removed from the nanovesicles. In addition, as the nanovesicles may be targeted to specific cells or tissues, therapeutic or diagnostic substances may be predominantly delivered to the targeted cells or tissues, while delivery of the substances may be inhibited. Therefore, the nanovesicles may alleviate suffering and inconvenience of patients by reducing adverse effects of therapeutic substances and by improving efficacy of the substances. In addition, the cell membrane-derived nanovesicles loaded with therapeutic or diagnostic substances and a method of preparing the nanovesicles may be used in vitro or in vivo for therapeutic or diagnostic purposes, or for experimental use.

When a drug is administered to an individual for disease treatment, a drug delivery system (DDS) that controls the delivery and release of the administered drug into cells, tissues, and organs for optimal efficacy is important. The drug delivery system is used to maintain adequate blood concentrations of a drug to achieve the maximum therapeutic effect. When the drug delivery system is applied, advantages such as maximizing the efficacy and stability of a drug, prolonging the residence time of a drug, increasing the bioavailability of a drug, and minimizing the side effects of a drug can be achieved. Thus, the drug delivery system is a medical technique required to efficiently deliver a drug to specific body parts and is considered as important as medicine itself. Since the early 1960s, drug delivery systems have been developed in the forms of injection and infusion, in the form of suppositories, for nasal and oral administration, and for administration via the skin or the lungs. In recent years, various drug delivery systems (DDSs), such as absorption-promoting and controlled DDSs (oral, transdermal, mucosal), sustained DDSs (injections, oral, transdermal), targeted DDSs (oral, injections, etc.), and artificial intelligence (intelligent) DDSs (on-demand type), have been developed and applied differently according to patients and purpose of use.
Among DDSs, liposomes have been widely studied as a drug delivery system since liposomes were first used in the 1960s. Liposomes are artificial membranes similar to cell membranes made of various phospholipids, and can be seen as colloidal semi-solid dispersants with a nanoscale particle size. Liposomal preparations have low toxicity and are highly applicable because the size, charge, membrane composition, and membrane permeability of the liposomal preparations may be controlled according to prescription. Recently, stealth liposomes prepared by conjugating liposomes with a polymer such as polyethylene glycol (PEG) have been developed. The stealth liposomes increase the circulatory half-life of drugs by preventing drug-containing liposomes from being easily removed from the blood. Using this method, DOXIL that delivers doxorubicin, an anti-cancer agent, has been commercialized. However, since liposomes and stealth liposomes lack the ability to recognize specific types of cells, the liposomes and stealth liposomes may not be used for the purpose of delivering drugs to specific types of cells or tissues. To enable liposomes to bind to specific targets, liposomes conjugated with antibodies specific to a single target have been developed, but none have been commercialized after passing clinical trials.
Therefore, a delivery system using natural cell membranes instead of liposomes made of artificially synthesized lipids is being developed. Since cell-derived delivery systems utilize the natural targeting systems of the cells, unlike conventional delivery systems such as liposomes, targeting may be easily induced. As a representative example, studies on drug delivery using extracellular vesicles which are naturally secreted from cells are underway. In addition, studies have been reported on loading various drugs, such as anticancer drugs, into nanovesicles (microvesicles) artificially prepared from nucleated mammalian cells and delivering the nanovesicles to cancer tissues.
In addition to substances required for their targeting, however, the extracellular vesicles and the nanovesicles artificially prepared from cells include intracellular components, such as cytosolic proteins and genetic materials (DNA and RNA), which are unnecessary for targeting. The components unnecessary for their targeting have a potential to lower the efficiency of drug loading or to induce side effects when administered into the body, and thus development of systems that are lacking their intraluminal components is essential.

Cell membrane-derived nanovesicles and use thereof


A sintered compact contains cubic sialon, β-sialon, and at least one of a first component and a second component. The first component is at least one element selected from the group consisting of iron, cobalt, nickel, and group 4 elements, group 5 elements, and group 6 elements of the periodic table. The second component is at least one compound containing at least one element selected from the group consisting of group 4 elements, group 5 elements, and group 6 elements and at least one element selected from the group consisting of carbon, nitrogen, and boron.

1. Field of the Invention
The present invention relates to sintered compacts, cutting tools formed using sintered compacts, and methods for manufacturing sintered compacts, and more particularly to sintered compacts containing cubic boron nitride, cutting tools formed using such sintered compacts, and methods for manufacturing such sintered compacts.
2. Description of the Related Art
Sialon (also written as "SiAlON") is silicon nitride having aluminum and oxygen dissolved therein and takes two types of crystal forms, namely, α-type and β-type, which belong to the hexagonal system (hereinafter referred to as "α-sialon" and "β-sialon"). Sintered compacts containing sialon have been studied as a cutting tool material for their low reactivity with workpieces.
For example, Japanese Patent No. 2849055 discloses a sialon-based sintered compact based on α-sialon and/or β-sialon, with the balance including a composite oxide of a rare earth element, a group 4 element, and at least one of group 2, 6, 7, and 8 elements.
Japanese Unexamined Patent Application Publication No. 2005-212048 discloses a ceramic containing Si3N4 or sialon particles bound together with a metal and/or an alloy in an amorphous phase.
The above sialon ceramics have low reactivity with workpieces, although they have a lower hardness than cubic boron nitride and exhibit insufficient wear resistance when used as a cutting tool material.
In view of hardness and reactivity with workpieces, therefore, there is a need for a sintered compact that can be used as a cutting tool material to form a cutting tool having both superior wear resistance and superior fracture resistance.

Sintered compact, cutting tool formed using sintered compact, and method for manufacturing sintered compact


A power take off device for an automatic transmission for taking off auxiliary power has a power take off switch which turns on the power take off device. The automatic transmission includes a torque converter and a lock-up clutch. The torque converter is connected to the power take off device when the power take off switch is turned on. The automatic transmission includes a lock-up control valve operating the lock-up clutch and a 1-2 shift valve for changing gear speed from a first stage to a second stage. The 1-2 shift valve supplies line pressure to the lock-up control valve when the shift lever is in the neutral position or the parking position and cuts off line pressure supplied to the lock-up control valve when the 1-2 shift valve is in the first stage.

In general, passenger cars which employ an automatic transmission of the hydraulic type have a torque converter on board. On the other hand, special motor vehicles used for specific purposes, such as a dump trucks or fire engines, employ a power take off device with the transmission system for supplying auxiliary power for functions other than moving the vehicle.
A conventional power take off device for an automatic transmission has been proposed in Japanese Patent Publication No. 6(1994)-74848. This publication discloses a lock-up control device that locks up the transmission when a power take off device is turned on while a shift lever position is in the P (parking) position or the N (neutral) position. Accordingly, it is possible to effectively use the engine power.
However, in this device, in situations where the solenoid valve or the lock-up control valve does not operate because of a valve sticking while the transmission is locked up, the lock-up condition is kept on even if the power take off switch is turned off. In the above situation, when the shift lever is moved from the P (parking) position to the D (drive) position for running the vehicle, the transmission changes the gears from the neutral stage to the first stage. The engine may stop because of the large shock to the engine that is caused by the lock-up condition of the transmission.

Power take off device for an automatic transmission


Method and apparatus for developing high range resolution radar target profiles. An outgoing radar waveform is encoded with coefficients corresponding to a wavelet transformation and then transmitted in the direction of a radar target. Incoming waveforms, including return waveforms reflected from the radar target, are decoded using an inverse wavelet transform to produce a high range resolution profile of the target. In an exemplary embodiment, the outgoing waveform is phase-shifted to create finite-duration waveform pulses, each pulse having a phase-state pattern corresponding to a set of coefficients in a transposed wavelet transform matrix. Phase-state duration is adjusted to achieve a desired range resolution.

The present invention relates to radar systems, and more particularly, to the development of high resolution range (HRR) radar target profiles.
Many present day radar systems combine frequency-stepped transmit waveforms with Fourier-type receiver decoding in order to develop HRR target profiles. In other words, transmit waveform pulses of incrementally increasing frequency are sent out in the direction of a target, and reflected return signals are received and then Fourier-transformed to produce coefficients indicating individual target scatters. The resolution of the resulting target profiles is inversely proportional to the frequency range, or Agile Bandwidth, of the discrete frequency-stepped pulses. In conventional non-FFT radar systems, resolution is proportional to pulse width, and because very short pulses can be difficult to generate, FFT HRR systems are superior to conventional non-FFT systems in certain contexts.
The Fourier-based systems are premised on the fact that the frequency-stepping process is equivalent to encoding an inverse-Fourier transform on the outgoing transmit signal. Such systems are described in, for example, "Generation of High Resolution Radar Range Profiles and Range Profile Auto-Correlation Functions Using Stepped-Frequency Pulse Trains" (Project Report No. ESD-TR-84-046), by T. H. Einstein, Massachusetts Institute of Technology, Lincoln Laboratory, Lexington, Mass., Oct. 18, 1994. While Fourier-based HRR systems do provide advantages over traditional coarse-range systems as noted above, the Fourier transform process is computationally intensive, requiring on the order of Nlog.sub.2 N complex multiply-and-accumulate operations for an N-point transform. As a result, Fourier-based systems are limited in terms of speed, and therefore in terms of radar range resolution, and may be unsuitable in modern applications requiring high speed and accuracy. Thus, there is a need for a radar system in which HRR profiles can be generated more quickly and with finer resolution as compared to known systems.


Carbon nanotube (CNT) films, patterns and biochips and methods of making the same are provided. Such a biochip comprises a bio-receptor attached by means of an exposed chemical functional group on a surface of a high density CNT film or pattern produced by repeated lamination of CNTs on a substrate with exposed amine groups. Various types of CNT-biochips may be fabricated by bonding of bio-receptors to a CNT pattern (or film) containing exposed carboxyl groups or modified by various chemical functional groups. Further, the CNT-biochip may be used to measure an electrical or electrochemical signal using both conductor and semiconductor properties of the CNT, thereby not needing labeling. Upon fluorescent measurement of DNA hybridization using such a CNT-DNA chip it is possible to show more distinct signals useful for genotyping, mutation detection, pathogen identification and the like.

1. Field of the Invention
The present invention relates to a biochip comprising a bio-receptor chemically or physicochemically attached to a high density carbon nanotube (CNT) film or pattern having chemical functional groups exposed, in which the bio-receptor is capable of binding to a target biomaterial, and a method for preparing the same.
2. Background of the Related Art
Carbon nanotube (CNT) is an allotrope of carbon, which consists of carbons exists abundantly on the earth. They are tubular materials where a carbon atom is connected to other carbons in the form of a hexagonal honeycomb structure. Their diameter is about size of nanometer ( 1/109 meter). CNT is known to have excellent mechanical properties, electrical selectivity, field emission properties and highly efficient hydrogen storage properties and be new and almost defect-free of all the existing materials.
Because of their properties of excellent structural rigidity, chemical stability, ability to act as ideal one-dimensional (1D) "quantum wires" with either semiconducting or metallic behaviors and a large aspect ratio, CNT exhibits a broad range of potential applications as a basic material of flat panel displays, transistors, energy reservoirs, etc., and as various sensors with nanosize (Dai, H., Acc. Chem. Res., 35:1035-1044, 2002).
In order to apply such properties more diversely, the purified single-walled CNT has been cut into short nanotube pieces using an acid. The cut CNT pieces have mainly —COOH chemical functional groups at a part of ends and sidewall of the open tube. The properties of the CNT have been modified by chemical binding of various materials using these chemical functional groups. Further, there have been reported that the functional group of CNT was substituted for —SH group by chemical manipulation and patterned on a gold surface (Nan, X. et al., J. Colloid Interface Sci., 245:311-8, 2002) and that CNT was immobilized on substrate using the electrostatic method (Rouse, J. H. et al., Nano Lett., 3:59-62, 2003). However, the former has disadvantages of the low CNT surface density and the weak bonding, and the latter also has a fatal disadvantage that the patterning method for selective immobilization on the surface cannot be applied. Therefore, there is an urgent demand for developing a new type surface immobilizing method with high density.
Recently, researches are being conducted to detect reactions both protein-protein and protein-ligand by means of electrochemical changes of CNT after immobilization of a biomaterial (Dai, H. et al., ACC. Chem. Res., 35:1035-44, 2002; Sotiropoulou, S. et al., Anal. Bioanal. Chem., 375:103-5, 2003; Erlanger, B. F. et al., Nano Lett., 1:465-7, 2001; Azamian, B. R. et al., JACS, 124:12664-5, 2002). A representative example of a protein-ligand reaction is an avidin-biotin reaction. Star et al. formed a channel on a substrate, which had been treated with a polymer, using CNT and measured the binding activity of streptoavidin by means of an electrochemical method (Star, A. et al., Nano Lett., 3:459-63, 2003).
The reasons that CNT attracts public attention as a biochip are as followings: Firstly, it needs no labeling; secondly, it has high sensitivity to signal change; and thirdly, it is capable of reacting in an aqueous solution without deterioration of a protein. The combination of a new nanomaterial and a biological system will create important fusion technologies in respective fields of disease diagnosis (hereditary diseases), proteomics and nanobiotechnology.
In order to develop a rapider and cheaper biochip, many researches have been conducted on technologies of DNA hybridization detection. Various labeling technologies for detecting DNA hybridization have been developed. An effective surface treatment capable of increasing hybridization efficiency and simultaneously, removing the background from non-specific binding is required to detect the DNA hybridization effectively using the DNA chip. Many researches have been conducted to prepare a surface-treated DNA chip platform (Rogers, Y. et al., Anal. Biochem., 266:23-30, 1999; Hu, J. et al., Nuc. Acid. Res., 29:106-10, 2001). Also, various methods for detecting DNA hybridization were developed, which include the scanometric method, the calorimetric method, a method using nanoparticle, a method using electrochemistry, and etc. (Taton, T. A. et al., Science, 289:1757-60, 2000; Alexandre, I. et al., Anal. Biochem., 295:1-8, 2001; Cai, H. et al., Analyst., 127:803-8, 2002; Cai, H. et al., Anal. Bioanal. Chem., 375:287-93, 2003).
Besides many applications with CNT in the bioengineering field have been recently being appeared. It is being suggested that the applicability of CNT to biochips, such as glucose biosensors, detecting protein, detecting a certain DNA sequence and the like (Sotiropoulou, S. et al., Anal. Bioanal. Chem., 375:103-5, 2003; Chen, R. J. et al., Proc. Natl. Acad. Sci. USA, 100:4984-9, 2003; Cai, H. et al., Anal. Bioanal. Chem., 375:287-93, 2003). Screening bio-molecules from multilayer based on CNT can increase the amount of immobilized bio-substances, such as DNAs and detecting sensitivity to the bio-substances, since the CNT has wide surface area and high electric conductivity.
At the present time, the most universal method for detecting the result of the reaction in a biochip is to use conventional fluorescent materials and isotopes (Toriba, A. et al., Biomed. Chromatogr., 17:126-32, 2003; Syrzycka, M. et al., Anal. Chim. Acta, 484:1-14, 2003; Grow, A. E. et al., J. Microbio. Meth., 53:221-33, 2003). However, as novel methods to easily and precisely measure an electrical or electrochemical signal are attempted, there are increased demands for CNT as a new material.
The methods comprising preparing a high density CNT multiplayer, attaching DNA thereon and detecting complementary DNA are useful in genotyping, mutation detection, pathogen identification and the like. It has been reported that PNA (peptide nucleic acid: DNA mimic) is regio-specifically fixed on a single walled CNT and the complementary binding to probe DNA is detected (Williams, K. A. et al., Nature, 420:761, 2001). Also, there has been an example, in which an oligonucleotide was fixed on a CNT array by a electrochemical method and DNA was detected by guanine oxidation (Li, J. et al., Nano Lett., 3:597-602, 2003). However, these methods do not apply CNT to fabrication and development of biochips.
Recently, a high capacity biomolecule detection sensor using CNT was disclosed (WO 03/016901 A1). This patent relates to a multi-channel type biochip produced by arranging a plurality of CNTs on a substrate using a chemical linker and attaching various types of receptors. However, it has a disadvantage of relative weakness to environmental changes.
Therefore, the present inventors have found a method for producing a CNT-biochip by repeated laminating CNT on a substrate having exposed amine groups by chemical bonding to form a high density CNT film or pattern having exposed chemical functional groups and chemically binding a bio-receptor to the CNT film or pattern, or treating the CNT surface with a chemical to prevent the non-specific binding by physical adsorption and chemically binding the bio-receptor to the treated surface, and completed the present invention.

Method for fabricating a biochip using the high density carbon nanotube film or pattern


A resistive structure formed on an integrated circuit substrate is disclosed. The structure includes a plurality of resistive elements serially connected. Each resistive element comprises a forward biased semiconductor junction and a reverse biased semiconductor junction. The resistive value of each resistive element can be varied with a preferred range being from about 500 megohms to about 5 gigaohms. In fabrication, the multiple resistive elements are electrically and physically simultaneously formed and are connected in series to obtain higher resistive values. The disclosed resistive structure allows very high resistances to be obtained using very little planar surface area.

1. The Field of the Invention
This invention relates to integrated circuit structures. More particularly, the present invention relates to resistive structures and methods for forming same on integrated circuits.
2. The Prior Art
One of the most common elements in electrical circuit design is a resistor. Nearly all circuit designs require the inclusion of one or more resistive elements. In the case of discrete electrical components, the resistor is generally the easiest and least expensive component to manufacture when compared to capacitors, inductors, and active components. In the case of integrated circuit elements, however, resistors are often difficult to manufacture. In particular, resistors having high resistive values are difficult to incorporate as part of an integrated circuit.
In general, the resistance value exhibited by a resistor is determined by the cross sectional area of the resistive material and the length of the resistive material. As the length of the resistive material increases, and the resistivity and the cross sectional area of the resistive material remain constant, the total resistance will increase.
In the case of integrated circuits, the amount of planar surface area available for forming resistive elements is limited. For example, as the size of circuit elements decreases, and the density at which those circuit elements are packed onto each die, the area which can be devoted to resistive elements decreases.
In particular, in the case of Static Random Access Memory (SRAM) integrated circuits it is necessary to include load resistors or resistive elements (generally two) in each memory cell. As integrated circuit technology has progressed, the four or six transistors comprising each SRAM cell have greatly decreased in size.
Nevertheless, even though the transistors in the SRAM cell have decreased in size, the resistive value of the load resistive elements must not decrease, and preferably should increase. It will be appreciated that as the number of cells on each integrated circuit increases, it is desirable to increase the resistance of each load resistive element to keep the total current consumed by the integrated circuit from increasing.
In order to increase the resistance of the structures functioning as load resistive elements, one approach in the art has been to reduce the cross sectional area, i.e., the thickness, of the material, generally polysilicon, forming the resistive structure. As the thickness of the resistive structure is decreased, a resulting increase in the total resistive value of the structure occurs.
Disadvantageously, as the thickness of resistive structure decreases, the occurrence of defects introduced during the manufacturing process and other failures increases dramatically. Thus, as the thickness of the structure decreases to increase its total resistive value to desirable levels, the number of failures increases to unacceptable levels. As the size of other integrated circuit components continues to decrease, the problems encountered with increasing the resistive value possessed by the resistive elements included on integrated circuits will continue to be a problem in the art.
In view of the foregoing, it would be an advance in the art to provide an integrated circuit resistive structure which provides a high resistance value in a small planar area and which does not require additional processing steps. It would also be an advance in the art to provide an integrated circuit resistive structure which can provide increased resistance values while decreasing the planar surface area required by the structure and which can be reliably manufactured and operated.

Resistive structure for integrated circuits