An improved process and apparatus for measuring performance characteristics of microwave power components. The invention involves the use of a rotating phase reference technique to improve measurement. The process and apparatus result in fast, accurate, reproducible determination of the desired properties. In addition, the apparatus of the present invention is lightweight, compact, and portable.

The present invention relates to an improved system for measuring selected performance characteristics of electronic components. In one preferred embodiment, the present invention comprises a method and apparatus for evaluating selected performance criteria of microwave power components, and in particular, microwave transmitter and receiver components. The present invention comprises improvements that individually or in combination increase the accuracy, reproducibility, and speed of these determinations, in a system that is lightweight, portable, and low cost, relative to prior known devices.
Microwave components have long been critical features of radar systems, electronic devices, and other systems. Errors in the parameters of microwave components translate directly into decreased accuracy and precision of the equipment, systems, and processes in which they are employed. There has long been a need to improve the accuracy, reliability, repeatability, and correlation of signal-to-noise ratio (xe2x80x9cSNRxe2x80x9d) measurements of microwave power transmitter and receiver components. Prior to the present invention, a relatively high degree of variability existed between test sites, as well as between test sets at the same test site. Improvement in the accuracy of the performance characteristics of microwave components contributes directly to improved accuracy and precision in the systems in which they are used. Prior approaches have not adequately met this need. In response to this need, a self-calibrating measurement technique having improved speed, accuracy, repeatability, and portability of the present invention has been developed.
Many microwave transmitters have stringent requirements on their output signal-to-noise ratio (xe2x80x9cSNRxe2x80x9d). For example, in a pulsed radar system, the transmitter SNR can limit the ability of the radar to detect and/or track weak targets against a background of echoes from the earth""s surface (clutter). The techniques commonly used prior to the present invention to measure transmitter and microwave tube SNR can have errors of xc2x11.5 dB. As a result, there has been poor agreement among SNR measurements made at the component factory, transmitter manufacturer, system integrator, and end user. This lack of agreement causes disputes over product acceptance, results in rejection of components meeting specification and acceptance of components failing to meet specification, creates unnecessary product returns, and generates wasteful requests to retest components. Moreover, the prior known methods for determining the performance characteristics of microwave power components, and in particular SNR, were: cumbersome; time consuming; expensive; and involved the use of large, heavy, bulky, and expensive equipment to carry out the analysis.
Prior to the present invention, microwave components have been tested in a test setup of the type depicted in the right-hand portion of FIG. 1. The right-hand portion of FIG. 1 depicts a test set up used for evaluating a component under test, in this example, a microwave power tube (or transmitter). A radio frequency (rf) drive signal was supplied to the component. The rf output from the component under test was applied to a vector demodulator circuit which, converted it into in-phase (I) and quadrature (Q) video signals. The rf drive signal to the component was also used as the reference (local oscillator) input to the demodulator as shown in FIG. 1. The signals were then digitalized and filtered. In the test setup depicted in FIG. 1, a Tektronix RTD-710A digitizer, sampling at 50 Msa/sec, was used to convert the I and Q video signals into 10-bit digital format. Analog 5 MHZ 6-pole Bessel filters at the inputs of the digitizer channels were used to define the bandwidth in which the tube noise is measured, i.e. xc2x15 MHZ about the carrier. For pulsed radar tubes, the digitized data was captured in a 2-microsecond window located near the middle of the pulse. The raw data was then transferred to a general purpose digital computer. Application software compensated the data for pulse-to-pulse variations caused by the modulator, and computed the average intrapulse SNR referenced to a 1 MHZ bandwidth. This conventional technique, however, took substantial amounts of time per measurement and resulted in SNR measurements with an error of xc2x11.5 dB.
The inventor observed that accuracy of prior known methods was limited by vector demodulator errors, which could be removed by lengthy calibration procedures. Specifically, there are both linear and non-linear error sources in the measurement of microwave power components.
Linear Distortion: An ideal vector demodulator (VDM) generates a unit circle centered at the origin on the IQ plane. The I and Q video output voltages are defined by the equations:
xe2x80x83I=kA cos xcex8
Q=kA sin xcex8
where
A=rf signal voltage
k=mixer conversion loss
xcex8=phase angle of rf signal with respect to the LO
Plotting I and Q data from a real vector demodulator generated an elliptical locus displaced from the origin as shown in FIG. 2. The inventor observed that this linear distortion resulted from three error sources:
DC Offsetxe2x80x94Imbalances in the mixer diodes and transformers create low level dc outputs in the I and Q channels when the local oscillator signal is applied. This causes displacement of the center of the locus from the origin. These offsets are a function of the measurement frequency and, if not compensated, cause a few tenths of a dB error.
I/Q Channel Gain Imbalancexe2x80x94This difference in gain between I and Q channels changes the locus into an ellipse with its principal axes parallel to the I and Q axes. Factors which contribute to gain imbalance include variations in:
rf power split into the I and Q channel mixers;
VSWR of the mixer rf ports;
mixer conversion loss;
insertion loss of video filters;
digitizer channel gains;
The first three items were considered by the present inventor to be dominant, and varied as a function of the test frequency.
Quadrature Errorxe2x80x94Quadrature error causes the principal axes of the elliptical locus to tilt relative to the I/Q axes and results from the I and Q channel phases differing from 90 degrees. Differential phase errors are caused by:
The rf power splitters used to supply RF and LO to the I and Q mixers;
Rf line lengths; and
Mixer VSWRs.
These errors are also functions of the test frequency. These three linear distortions were determined by the inventor to be the major causes of SNR measurement inaccuracy.
The distorted I and Q voltages take the form:       I    =                  kA                          (                      1            -                          C              2                                )                                  xe2x80x83                                  cos                                (                          θ              -                              D                2                                      )                              +              B                          xe2x80x83                        cos                          xe2x80x83                        E                  Q    =                  kA                          (                      1            +                          C              2                                )                                  xe2x80x83                                  sin                                (                          θ              +                              D                2                                      )                              +              B                          xe2x80x83                        sin                          xe2x80x83                        E
where             xe2x80x83                  C      =              gain imbalance;                  D    =          quadrature error            B    =          dc offset amplitude            E    =          dc offset phase relative to the I axis                          C        dB            =              2                          log                                (                                          1                +                                  (                                      C                    2                                    )                                                            1                -                                  (                                      C                    2                                    )                                                      )                                          xe2x80x83
FIG. 3 illustrates the linear distortion in a typical vector demodulator. A gain imbalance of xc2x11 dB and a phase error of xc2x16 degrees are typical values. These errors are attributed to mixer Voltage Standing Wave Ratios (xe2x80x9cVSWRsxe2x80x9d), which can be in the range 3.0:1. In addition, this vector demodulator (VDM) shows a bias in the phase of about xe2x88x928 degrees. This is attributed to a small differential error (c. 0.05 inches) in the rf line lengths feeding the I/Q mixers. The dc offset for this VDM is on the order of 1%, and is a small error source.
Non-Linear Distortionxe2x80x94Prior to the present invention, the LO to signal ratio typically was not tightly controlled. The inventor observed that non-linear distortion generated in the demodulator could be made negligible by maintaining the signal amplitude 15 dB below the LO reference level. The LO/signal ratio was typically only 8 dB, where considerable amplitude compression was readily observable.
The calibration procedure of prior known methods typically required considerable time (3-5 seconds or longer) and entailed relatively large errors (xc2x12dB). The procedure of the present invention speeds the assessment and removes these errors by implementing a local oscillator (LO) offset frequency technique, and digital signal processing of the video data. Specifically, the invention employs a Rotating Phase Reference (xe2x80x9cRPRxe2x80x9d) technique to improve accuracy. The invention may also use digital filters to create a precise noise bandwidth, and to significantly reduce the noise floor of the measurement. The technique of the present invention is suitable for use in both Government and commercial applications. The improved accuracy of the present invention results in far better agreement between tube vendors, equipment integrators, and the final customer, leading to lower costs by increasing equipment acceptance.
Others, prior to the present invention, have sought to develop methods of real-time measurement of signal-to-noise ratio. None, however, employ the RPR technique of the present invention.
One method for determining signal-to-noise ratio is described in Glomb, U.S. Pat. No. 3,101,446 for Signal-to-Noise Ratio Indicator (Aug. 20, 1963). Glomb discloses a signal-to-noise ratio indicator for a communication system that employs a combination of a low frequency sine wave and out of band noise.
Another patent issued to Taylor, U.S. Pat. No. 3,287,646 for Signal-To-Noise Ratio Meter (Oct. 28, 1963), discloses a meter for the direct measurement of the signal-to-noise ratio of a modulated continuous wave that has noise level superimposed on it. Taylor""s method involves mixing the incoming (noisy) signal with a different frequency oscillation and performing a series of limiting and filtering steps.
Newman, U.S. Pat. No. 3,743,932 for Clipped Correlation to Signal-to-Noise Ratio Meter (Jul. 3, 1973), discloses a circuit for converting the output of a clipper correlator to signal-to-noise ratio in a signal from a sonar array.
Hammett, U.S. Pat. No. 3,825,835 for Signal-to Noise Ratio Measurement (Jul. 23, 1974), discloses a system and apparatus for the measurement of signal-to-noise ratio in electrical signals. Hammett notes that the two prior methods known at that time for measurement of signal-to-noise ratio are complex and/or extremely bulky. Col. 1, at 11. 43-50. Although Hammett discloses what he describes as a xe2x80x9cportablexe2x80x9d system, that system employs cathode-ray oscilloscope equipment that is considerably more complex, bulky, costly, and heavy than the apparatus of the present invention.
Campbell, U.S. Pat. No. 4,004,230 for Critical Parameter Receiver Tester (Jan. 18, 1977), discloses test equipment on which a modulated signal is injected into a receiver under test. The output is fed directly to a first power measuring device, then through a digital filter, to a second measuring device. The two measured quantities are then fed to a divider circuit which provides an indication of the signal-to-noise ratio.
Tenten, U.S. Pat. No. 4,172,263 for Methods and Apparatus for Measuring Signal-to Noise Ratio (Oct. 23, 1979), discloses a method and apparatus for measuring signal-to-noise ratio in video waveforms, based upon tangential noise measurement principles.
Wong, U.S. Pat. No. 5,386,495 for Method and Apparatus for Determining the Signal Quality of a Digital Signal (Jan. 31, 1995), discloses a receiver for receiving and decoding a carrier signal. The carrier signal is modulated with a digital signal. The receiver signal is demodulated and converted into digital format. A digital signal processor is then used to calculate the signal-to-noise ratio.
Mueller, U.S. Pat. No. 5,465,412 for Apparatus and Method for Determining a Point in Time for Detecting a Sampled Signal in a Receiver (Nov. 7, 1995), discloses a system adapted for mobile communications systems.
None of the prior known methods and devices achieves the rapid, high resolution measurement of signal-to-noise ratio of the present invention. Moreover, none of them has been able to improve substantially the accuracy of prior measurement methods through a light weight, portable measurement device or system. The present invention overcomes many of the drawbacks of prior methods and greatly improves the accuracy, ease, and precision of measurement, its reproducibility, and results in greater reliability of the systems in which the components are used. Specifically, the technique of the present invention results in an accuracy of better than about 0.1 dB, in contrast to errors of xc2x11.5 dB, typical in prior techniques. The repeatability of the measurement of signal-to-noise ratio depends primarily on the number of independent noise samples taken. The present invention facilitates the rapid measurement of parameters and, hence, the measurement of a larger number of samples, improving accuracy. In addition, the apparatus of the present invention is faster, smaller, less expensive, and more robust and light weight than prior apparatus and methods.
The present invention is the result of several years"" development work. In a 1994 paper, entitled High Accuracy Signal/Noise Measurement of Microwave Power Amplifiers (the xe2x80x9c1994 paperxe2x80x9d), by the inventor, Alexander MacMullen, of Technology Service Corporation, and Steve Hillenberg, NSWC, Crane Division, the inventor""s contact at the U.S. Navy""s Crane Laboratory, the authors disclose many of the problems involved in improving the accuracy of measurements of the properties of microwave power components and outline a general conceptual path toward a solution. Papers describing the work were presented at the 1994 Microwave Power Tube Conference, the IEEE/MTTS Automatic RF Techniques Group (xe2x80x9cARFTGxe2x80x9d), and were published in NASA Technical Briefs, and elsewhere. That 1994 paper, as well as each of the IEEE/MTTS, ARFTG, and NASA papers, are hereby incorporated by reference, as if fully set forth herein. Although the 1994 paper describes, in general terms, the basic RPR concept involved in the system of the present invention to achieve an accuracy of better than 0.1 dB, it does not disclose the system, apparatus, or process of the present invention.
The 1994 paper discloses that an analysis of the demodulator circuit was performed to see how the major error sources could be eliminated or reduced. It was determined that the vector demodulator components were already of the highest quality commercially available and, therefore, it was impractical to improve their characteristics without tedious and time-consuming tuning, matching, and adjustment. Very high-level mixers were selected for the demodulator. These units, Anaren model 76127, were operated with an LO level of +18 dBm. The third order intercept point was above +24 dBm. With a signal level of +3 dBm, non-linear distortion products were reported to have been negligible.
The measurement procedure employed in the 1994 paper used a hardware configuration of the type shown in FIG. 1. In contrast to the prior technique, in which the rf drive signal was supplied to both the test component and as the local oscillator input to the vector demodulator, the LO reference signal was offset in frequency from the rf signal by a small amount, and data was collected over a time base T=N/xcex94f, where xcex94f=LO frequency offset and N is an integer. The data values were uniformly distributed over all values of xcex8 and any cyclic errors could be removed by averaging.
As an example, a pulsed S-band crossed-field amplifier tube was operated at a prf of 2000 Hz. The frequency offset was adjusted to 20 Hz. Data was collected over a time base of 0.05 seconds, or 100 pulses. Each pulse had an incremental phase of 3.60 degrees. Over the total data base, the accumulated phase was 360 degrees.
The digitized I and Q data were transferred to the computer where the mean values in each pulse window were calculated. The data were normalized to remove pulse-to-pulse variations which may have been generated by the pulse modulator. The variances of the normalized data were computed and summed to yield the total noise power in each pulse. Results from all pulses were averaged. Finally, the signal-to-noise ratio was computed for the entire group of pulses in the data base. The errors caused by linear distortion were removed because the average of sinusoidal functions over N cycles is zero.
Based upon this technique, the 1994 paper reports improved accuracy of SNR measurements on microwave tubes and transmitters of about 0.1 dB rms, compared to xc2x11.5 dB in previous known procedures. Nonetheless, the disclosure of the 1994 Paper retained a number of the drawbacks of prior techniques. Although the technique disclosed in the 1994 Paper was more accurate than prior known techniques, the process remained slow, on the average of 3 to 5 seconds per measurement. The instrumentation used was large, heavy, bulky, and expensive, industrial grade equipment. The system was not portable. Two microwave signal generators, operating at slightly offset frequencies, produced the Rotating Phase Reference (RPR). This had two distinct disadvantages: (1) the second microwave synthesizer was costly, and (2) the phase noise of the two synthesizers was cumulative, creating a high measurement noise floor. The only performance parameter evaluated in the 1994 paper was SNR. The number of measured phases was substantial. None of the details of the process, algorithms, or software employed were disclosed.
The inventor has made significant improvements in various elements and components of the work described in the 1994 Paper. The present invention represents a significant advance over prior know methods of signal-to-noise ratio measurement. High accuracy has been retained. Many of the functions have been converted from hardware- to software-based systems. The number of phases at which data are collected has been reduced. The present invention uses standard, off the shelf, readily available components, is more lightweight, and is easily portable. In addition, the present invention offers the significant improvements in the speed of measurement of signal-to-noise ratio. This improvement was made possible by two innovations: (1) the rapid transfer of data between components of the testing system; and (2) employing a special purpose, high speed, digital processor rather than a general purpose digital computer. The inventor has made additional improvements to speed up the processing of the raw data acquired during the RPR measurement and provide operators with an SNR vs. frequency display in two seconds. This represents an increase in speed of about 3000:1 relative to prior known techniques and several times the speeds reported in the 1994 paper.
The present invention is useful to accurately and rapidly measure and display SNR (and its related parameters, moving target indication (MTI) and clutter attenuation (CA), and other fundamental parameters of microwave components such as insertion phase, gain, and time delay.
It is therefore an object of the present invention to provide a process and apparatus to improve the accuracy of SNR measurements on microwave components, including but not limited to tubes, transmitters, and other electronic components.
Another object of the present invention is to improve the accuracy of SNR measurements to approximately xc2x10.1 dB, or better.
An object of the invention is to reduce the time required to make accurate signal-to-noise ratio measurements in less than 3 to 5 seconds.
A further object of the present invention is reduce errors in SNR measurement by employing a reference LO shifted in phase from the signal to the demodulator.
Yet, a further object of the present invention is the use of a Rotating Phase Reference (RPR) technique to improve the accuracy of determination of performance parameters of electronic components.
An additional object of the present invention is to improve the reproducibility of measurement of selected performance characteristics of microwave power components.
Yet another object of the present invention is to decrease the time required to measure selected performance characteristics, while maintaining a high degree of accuracy.
Another object of the present invention is to provide a system for the measurement of selected performance characteristics of microwave power components that is portable and light weight.
A further object of the present invention is to employ a Rotating Phase Reference (RPR) technique to improve the accuracy and speed of the measurement of selected performance characteristics of microwave power components.
An additional object of the present invention is to improve the accuracy and repeatability of measurement by automating data collection.
Yet another object of the present invention is to improve the accuracy of determination of performance parameters of electronic components by automating the processing of the collected data.
A further object of the present invention to provide a standard measurement technique and apparatus for the determination of selected performance characteristics of microwave power components.
Another object of the present invention is to provide a rugged measurement system that is portable.
Yet another object of the invention is to provide a measurement system that is light weight.
A further object of the present invention is to improve the accuracy of phase, gain, signal to noise, time delay measurements, and system stability.
Another object of the present invention is to provide a system for determining performance parameters of electronic components that weighs less than about 120 pounds.
An additional object of the present invention is to provide a system for determining performance parameters of electronic components that weights less than about 50 pounds.
A further object of the present invention is to provide a system for determining performance parameters of electronic components having a package that is smaller than about 3,000 cubic inches.
An additional object of the present invention is to provide a system that employs improved accuracy based upon an increased number of measurements at a reduced number of phases.
Additional objects and advantages of the invention are set forth, in part, in the description which follows and, in part, will be obvious from the description or may be learned by practice of the invention. The objects and advantages of the invention will be realized in detail by means of the instrumentalities and combinations particularly pointed out in the appended claims.
As illustrated in the accompanying diagrams and disclosed in the accompanying claims, the invention is a method for the measurement of selected fundamental performance parameters of test unit, comprising:
a. generating a first reference signal;
b. generating a second reference signal, that is rotated in phase relative to said first reference signal;
c. Supplying said first reference signal to the test unit;
d. Supplying the output of the test unit to vector demodulator means;
e. Supplying said second reference signal to vector demodulator means;
f. Generating a signal from vector modulator means;
g. Processing said signal from said vector demodulator means to determine the selected fundamental performance parameters of the test unit.
In another embodiment, the present invention is an apparatus for the measurement of fundamental parameters of a test unit, comprising:
a. first signal generator means, for generating a first signal having first phase;
b. phase shifter means, cooperating with said first signal generator means, for rotating the phase of said first signal to produce a second signal having a second phase, wherein said second signal is shifted in phase relative to said first signal;
c. test unit input means, for supplying said first signal to said test unit input means,
d. demodulator means, for accepting an rf signal from the test unit,
e. means for supplying said second signal to said demodulator means,
f. data processing means for computing the fundamental parameter of the test unit from the output of said digitizer.
The invention is a PC-based test instrument that performs high accuracy, quantitative measurements of microwave components over the 2 to 18 Ghz frequency band. Used with a conventional synthesizer that sweeps over user-specified frequencies, the MCA analyzes the CW or pulse output from the device under test and generate the following measures: Signal-to-Noise Ratio; Insertion Gain; and Insertion Phase. The invention includes the MCA, a GPIB compatible synthesizer, a power divider, and the device under test (DUT). The MCA controls the synthesizer sweep using gain and frequency parameters defined by the operator. The power divider provides the RF stimulus to the DUT and a reference signal for the MCA.
The invention measures the output Signal-to-Noise Ratio (SNR), insertion gain and phase of the DUT under continuous wave (CW) or pulsed conditions. For pulsed waveforms, the invention synchronizes its measurements to an externally supplied trigger. For CW waveforms, the invention generates its own internal 1 KHz trigger. The MCA operates at discrete frequencies over any portion of the 2-8 GHz band. Once enabled by the operator, the invention automatically scans the programmed frequencies, collects and processes data for each frequency, and displays results on the invention""s display. The display connects the individual measurement points with a line for clarity and then repeats the measurement process until stopped by the operator. This allows the user to make adjustments to the DUT and immediately observe the results.
The invention sends frequency information to a digitally controlled frequency synthesizer via the IEEE-488 bus. Software drivers for Hewlett Packard Models 8672A and 836x series synthesizers are supplied. The number of frequencies and the frequency steps chosen must be compatible with the particular synthesizer used. The invention also controls the amplitude of the synthesizer output. It is recommended that the synthesizer amplitude be set to at least +13 dBm. This will return the nominal reference input amplitude of +10 dBm after a 3 dB loss in the passive power splitter.
The invention comprises a commercial off-the-shelf (COTS) personal computer (PC) and TSC-designed electronic modules housed in a rugged aluminum, portable chassis. The host processor is a Pentium III with a 15.1-inch, high brightness, active matrix TFT. The integral keyboard/pointing device is sealed and water-resistant. A plug-in IEEE-488, GPIB controller is used to control the external synthesizer.
In addition to the COTS components, the chassis houses two, TSC-designed plug-in circuit boardsxe2x80x94a RF Module and a Digital Signal Processor (DSP). These modules include phase shifter and vector demodulator circuits, two 12-bit, 50 MHZ analog to digital converters, and a high-performance DSP that implements rotating phase reference (RPR) algorithms to generate the outputs.
Once enabled by the operator, the invention automatically steps through the specified frequencies and graphically displays the results on its display screen in a matter of seconds. Numerical results can be saved to disk for further review and analysis or can be viewed on the screen at any time.
The invention""s graphical user interface was developed using LabVIEW for Windows. It provides familiar-looking, virtual instrument panel that includes indicators and controls that are manipulated using the keyboard and/or pointing device (mouse).
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and constitute a part of the specification, illustrate certain embodiments of the invention, and together with the detailed description, serve to explain the principles of the present invention.

System for measurement of selected performance characteristics of microwave components


According to this invention, a semiconductor device includes a plurality of MOS transistors arranged in a matrix form, common wiring lines connected to MOS transistors of the same row or the same column, diodes each having one end connected to a corresponding one of the common wiring lines of each row or column, and a voltage applying circuit for controlling the potential of other terminal of each of the diodes and simultaneously applying a predetermined voltage to all the common wiring lines or arbitrary common wiring lines having the number larger than the number of wiring lines selected during a normal operation.

1. Field of the Invention
The present invention relates to a semiconductor device and, more particularly, to a semiconductor device having a stress testing device for applying a voltage stress, e.g., when defect screening is performed in a wafer state.
2. Description of the Related Art
When semiconductor devices are to be shipped, in order to obtain the reliability of the semiconductor devices, screening for exposing potential defects of the devices and for removing defective devices is generally performed to prevent the non-defective devices from degradation and from being defective. As a method of performing the screening, a burn-in method capable of simultaneously achieving electric field acceleration and temperature acceleration is often used. According to this burn-in method, when devices are operated at a voltage higher than a rated voltage and a temperature higher than a rated temperature, since a stress received in an initial failure period or more under rated conditions acts on the devices for a short time, devices which may cause an initial operative failure are screened in advance before the devices are shipped. Therefore, the devices which may cause an initial operative failure can be efficiently removed, and the reliability of the products can be increased.
When defective DRAMs (Dynamic Random Access Memories) are to be screened, a method of scanning word lines in an order of addresses and sequentially accessing the word lines is conventionally used. In this case, when a transfer gate transistor (cell transistor) of a memory cell having a gate connected to a word line is considered, a voltage stress is applied to the transistor in a frequency lower than that of a transistor of a peripheral circuit. For example, when a DRAM having a memory capacity of 4 Mbits is exemplified, only 4 word lines of the 4069 word lines of the DRAM are selected in one cycle, and a test for a cell transistor is completed in 1024 cycles. For this reason, the gate of the cell transistor receives a voltage stress for a 1/1024 period of the transistor of the peripheral circuit. Therefore, since a substantial period of applying a maximum electric field to the gate is short, a long time is required for screening defects.
In a DRAM used in recent years, a half (Vcc/2) of a power supply potential Vcc is generally applied to the electrode of a capacitor of a memory cell. For this reason, even when a thin film is used as the insulating film of the capacitor, since an electric field applied to the film is decreased, the reliability of the DRAM is rarely degraded. In contrast to this, since the gate oxide film of a memory cell transistor receives a potential (e.g., about 1.5.times.Vcc) boosted during selection of the cell transistor, even when the oxide film having a large thickness is used, an intensive electric field is applied to the oxide film. As a result, the reliability of the memory cell transistor is often degraded. When defective DRAMs are to be screened, especially, a cell transistor having the gate receiving a boosted potential is positively subjected to screening.
As described above, a memory cell transistor which is to be positively screened receives a voltage stress in a low frequency. In order to solve this problem, a semiconductor memory as disclosed in Published Unexamined Japanese Patent Application (Kokai) No. 3-35491 T. FURUYAMA includes a voltage stress is simultaneously applied to all word lines or word lines having a number equal to or larger than the number of word lines selected during a normal operation, thereby increasing the efficiency of applying a stress to a cell transistor.
According to this proposal, when screening of DRAMs set in a wafer state is performed using a prober and a probe card, defects are set at a level such that all defective cell transistors in each chip region are sufficiently screened, and all bit defects as major defects of a 1-M DRAM or a 4-M DRAM can be screened at a high speed. Therefore, efficiency of defect screening can be considerably increased.
The number of inputs required for a voltage stress test is preferably decreased, and it is preferable that a voltage stress can be simultaneously applied to MOS transistors of the same row (or column) in a semiconductor device having a plurality of MOS transistors arranged in a matrix form. The semiconductor device is not limited to a semiconductor memory.


A data management computing system for tracking data protection compliance of a plurality of entities using a data management (“DM”) server is provided. The DM server includes at least one processor programmed to: (i) receive, from a requesting entity, a personally identifying information (“PII”) consent request for access to a requested PII set of a user, (ii) determine at least one PII item associated with a reason code, (iii) compare the at least one PII item to the requested PII set, (iv) generate a consent recommendation, (v) transmit the consent recommendation to the user, (vi) receive a response indicating user consent, (vii) transmit, to the requesting entity, a notification indicating the user consent for the requesting entity to retrieve the at least one PII item from a third-party PII storage entity, and (viii) update a user profile to track the requesting entity with the at least one PII item.

The present application relates generally to managing the propagation of personally identifying information ("PII"), and more specifically, to a system and method for tracking data protection compliance of entities that use PII.
Data breaches, security incidents, and the sale of customer data to third party buyers are some of the reasons that many individuals are becoming increasingly wary of entities (e.g., companies and organization) that access their personal data. Most individuals maintain PII sharing relationships with a number of entities, such as an employer, one or more financial institutions, and service providers (e.g., utility company, internet company). Often times, individuals are not fully aware of each PII item that is stored by these entities. Further, many individuals are not aware of each activity (e.g., marketing, advertising) for which their PII is being used. Thus, there exists a lack of transparency between many PII-using entities and individuals when it comes to how PII is being handled and used. Often, this makes it increasingly difficult for an individual to trust entities with their PII.
Further, instead of blindly consenting to every PII item requested, many individuals want to be able to make informed decisions when it comes to sharing their PII. Also, even after providing consent, those concerned with unnecessarily oversharing personal data and/or data privacy concerns may want to be able to actively control how long their PII items are accessed and stored by these entities. Accordingly, it is desirable to have a system that enables users to directly manage and control the PII items that are shared with entities by allowing users to not only track the PII items accessed by specific entities, but also to provide informed consent as well as withdrawal of consent.

Systems and methods for tracking data protection compliance of entities that use personally identifying information (PII)


Methods of shuffling nucleic acids to acquire or enhance mycotoxin detoxification activity, libraries of shuffled mycotoxin detoxification nucleic acids, transgenic cells, plants and DNA shuffling mixtures are provided.

Pursuant to 37 C.F.R. 1.71(e), Applicants note that a portion of this disclosure contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
This invention pertains to the shuffling of nucleic acids to achieve or enhance mycotoxin detoxification, especially in plants.
xe2x80x9cMycotoxinsxe2x80x9d generically refer to a number of toxic molecules produced by fungal species, such as polyketides (including aflatoxins, demethylsterigmatocystin, O-methylsterigmatocystin etc.), fumonisins, alperisins (e.g., A1, A2, B1, B2), sphingofungins (A, B, C and D), trichothecenes, fumifungins, and the like. Polyketides are a large structurally diverse class of secondary metabolites synthesized by bacteria, fungi, and plants and are formed by a polyketide synthase (PKS) through the sequential condensation of small carboxylic acids. Katz and Donandio (1993) Annu Rev. Microbiool. 47:875-912; Brown et al. (1996) PNAS 93:14873-14877; Silva et al. (1996) J. Biol Chem. 271: 13600-608.
Aflatoxin B1, is the principal member of the aflatoxin (AF) family of polyketide mycotoxins produced by Aspergillus parasiticus, Aspergillus flavus and Aspergillus nomius. Aflatoxin B1 is the most potent mycotoxin known to man. For example, AF was characterized as the causative agent for the death of more than a hundred thousand poultry in England that had ingested AF-contaminated peanut meal. This discovery led to legislation regulating the trade of AF-contaminated agricultural commodities.
Sterigniatocystin (ST) is a related polyketide mycotoxin, which is produced by several members of the Aspergillus. ST is the second to last intermediate in the biosynthesis of AF. Kelkar et al. (1997) J. Biol Chem. 272: 1589-94. Various Aspergillus species that produce AF and ST are known to be pathogenic to corn, grains and nuts and are known to produce these mycotoxins during the growth of the crops and during storage, leading to the introduction of AF and ST into primary food stuffs. AF and ST are acutely toxic and carcinogenic and are a serious concern from human and animal health perspective. Busby and Wogan (1985) in Chemical Carcinogens (Searle ed., 1985) pp 945-1136, American Chemical Society, Washington D.C.
Trichothecenes are another family of sesquiterpenoid mycotoxins produced by Fusarium species and other molds that are known plant pathogens. These compounds are potent inhibitors of protein synthesis in eukaryotes (Kimura et al. (1998) J. Biol Chem. 273: 1654-1661) and reportedly bind to the 60S ribosomal subunits to prevent polypeptide chain initiation or elongation. Trichothecenes are also an important group of mycotoxins that cause serious problems of food pollution. They have been implicated in incidents of mycotoxicosis including vomiting, dermatitis and hemorrhagic septicemia in humans and livestock, resulting in loss of productivity and even death. Lastly, fumonisins (F) are another structurally distinct class of mycotoxins produced by several Fusarium species that is involved in food poisoning and toxic effects. Scott (1993) International Journal of Food Microbiology 18:257-270 and the references therein provide a review of the Fuminosins.
Thus, the contamination of corn, grains and nuts with various types of mycotoxins produced by pathogenic species such as Aspergillus and Fusarium is a major health and food pollution problem, as well as causing reduction in crop yields by being toxic to infected plants. These mycotoxins survive food processing, which adds to the problem. It is well known that ST and AF induce liver cancer and are linked to a specific mutation in a tumor suppressor gene. Brown et al. (1996) PNAS 93: 14873-14877. Natural aflatoxins and other mycotoxins like ST do not pose a major health threat per se; however, renal and hepatic oxidative detoxification of these compounds in contaminated foods by cytochrome P450 enzymes yields an epoxide which is cytotoxic.
For example, AFB1 is converted to its 15,16-exo-epoxide, which is a highly toxic mutagen. Silva et al. (1996), supra and references therein. It has been shown that this epoxide targets guanine residues and selectively alkylates the N-7 position of this purine in double-stranded DNA. Depurination of the alkylated base has been correlated to bladder cancer in laboratory mice, teratogenic effects in chicken embryos and liver cancer in humans. A direct correlation between DNA damage and human cancer has been established and is related to the mutational hot spots of p53, an important tumor suppressor gene. Approximately 50% of all cancers have associated altered p53 sequences.
Trading of AF-contaminated agricultural commodities is tightly regulated at both national and international levels. Compliance to these regulations causes the loss of millions of dollars in agricultural produce in US each year. Trade sanctions and health effects on mycotoxin contaminated grains add significantly to the losses (Brown et al. (1996) PNAS 93: 14873-14877).
Accordingly, it is highly desirable to transform various mycotoxins produced by fungal pathogens in various crops into inactive compounds with respect to plant, human and animal toxicity. This would alleviate important food pollution problems, as well as cost associated with complying with detecting AF-contamination in various crop commodities and destroying them. Surprisingly, the present invention provides for the detoxification of mycotoxis by transformation of the mycotoxins into non-toxic compounds. This detoxification is particularly useful in crops, thereby solving each of the problems outlined above, as well as providing a variety of other features which will be apparent upon review.
In the present invention, DNA shuffling is used to generate new or improved mycotoxin detoxification genes. These mycotoxin detoxification genes are used to provide enzymes which degrade mycotoxins, in agricultural and industrial processes. These new and/or improved genes have surprisingly superior properties as compared to naturally occurring mycotoxin detoxification genes.
In the methods for obtaining mycotoxin resistant genes, a plurality of parental forms (homologs) of a selected nucleic acid are recombined. The selected nucleic acid is derived either from one or more parental nucleic acid(s) which encodes an enzyme which degrades or modifies a mycotoxin, or a fragment thereof, or from a parental nucleic acid which does not encode mycotoxin detoxification, but which is a substrate for DNA shuffling to develop monooxygenase activity. The plurality of forms of the selected nucleic acid differ from each other in at least one (and typically two or more) nucleotides, and, upon recombination, provide a library of recombinant mycotoxin detoxification nucleic acids. The library can be an in vitro set of molecules, or present in cells, phage or the like. The library is screened to identify at least one recombinant mycotoxin detoxification nucleic acid that exhibits distinct or improved mycotoxin detoxification activity (typically in an encoded polypeptide) compared to the parental nucleic acid or nucleic acids.
In selecting for mycotoxin detoxification activity, a candidate shuffled DNA can be tested for encoded mycotoxin detoxification activity in essentially any process. Common processes that can be screened include screening for inactivation or modification of an aflatoxin, inactivation or modification of a sterigmatocystin, inactivation or modification of a trichothecene, and inactivation or modification of a fumonisin. Similarly, instead of, or in addition to, testing for an increase in mycotoxin detoxification activity, it is also desirable to screen for shuffled nucleic acids which produce higher levels of a mycotoxin detoxification nucleic acid or enhanced or reduced recombinant mycotoxin detoxification polypeptide expression, or increased stability encoded by the recombinant mycotoxin resistant nucleic acid.
A variety of screening methods can be used to screen a library, depending on the mycotoxin detoxification activity for which the library is selected. By way of example, the library to be screened can be present in a population of cells. The library is selected by growing the cells in or on a medium comprising the mycotoxin to be degraded and selecting for a detected physical difference between, e.g., oxidized or reduced forms of the mycotoxin and the non-oxidized or reduced form of the mycotoxin, either in the cell, or the extracellular medium. Alternately, survival of library cells on a medium which includes a mycotoxin can be used to screen the library.
Iterative selection for mycotoxin detoxification nucleic acids is also a feature of the invention. In these methods, a selected nucleic acid identified as encoding mycotoxin detoxification activity can be shuffled, either with the parental nucleic acids, or with other nucleic acids (e.g., mutated forms of the selected nucleic acid) to produce a second shuffled library. The second shuffled library is then selected for one or more form of mycotoxin detoxification activity, which can be the same or different than the mycotoxin detoxification activity previously selected.
This process can be iteratively repeated as many times as desired, until a nucleic acid with optimized or desired mycotoxin detoxification properties is obtained. If desired, any nucleic acid identified by any of the methods herein can be cloned and, optionally, expressed. Because of the need to reduce mycoxin pollution/contamination of foods, it is desirable to express mycotoxin detoxification nucleic acids in, e.g., plants, thereby reducing the occurrence of mycotoxins in the plants. Furthermore, mycotoxin detoxification in plants also adds to the vigor of the plants.
The invention also provides methods of increasing mycotoxin detoxification activity by whole genome shuffling. In these methods, a plurality of genomic nucleic acids are shuffled in a cell (in whole cell shuffling, entire genomes are shuffled, rather than specific sequences, although xe2x80x9cspikingxe2x80x9d of selected nucleic acids can be used to bias shuffling outcomes). The resulting shuffled nucleic acids are selected for one or more mycotoxin detoxification traits. The genomic nucleic acids can be from a species or strain different from the cell in which activity is desired. Similarly, the shuffling reaction can be performed in cells using genomic DNA from the same or different species, or strains. Strains or enzymes exhibiting enhanced activity can be identified.
The distinct or improved activity encoded by a nucleic acid identified after shuffling can encode one or more of a variety of properties, including, e.g., inactivation or modification of a polyketide, an aflatoxin, inactivation or modification of a sterigmatocystin, inactivation or modification of a trichothecene, inactivation or modification of a fumonisin, an increased ability to chemically modify a mycotoxin, an increase in the range of mycotoxin substrates which the distinct or improved nucleic acid operates on, an increased expression level of a polypeptide encoded by the nucleic acid, a decrease in susceptibility of a polypeptide encoded by the nucleic acid to protease cleavage, a decrease in susceptibility of a polypeptide encoded by the nucleic acid to high or low pH levels, a decrease in susceptibility of the protein encoded by the nucleic acid to high or low temperatures, and a decrease in toxicity to a host cell of a polypeptide encoded by the selected nucleic acid.
The selected nucleic acids to be shuffled can be from any of a variety of sources, including synthetic or cloned DNAs. Exemplar targets for recombination include: nucleic acids encoding a monooxygenase, a P450, trichothecene-3-O-acetyltransferase, a 3-O-Methyltransferase, a glutathione S-transferase, an epoxide hydrolase, an isomerase, a macrolide-O-acytyltransferase, a 3-O-acytyltransferase, and a cis-diol producing monooxygenase which is specific for furan. Typically, shuffled nucleic acids are cloned into expression vectors to achieve desired expression levels.
One feature of the invention is the production of libraries and shuffling mixtures for use in the methods as set forth above. For example, a phage display library comprising shuffled forms of a nucleic acid is provided. Similarly, a shuffling mixture comprising at least three homologous DNAs, each of which is derived from a nucleic acid encoding a polypeptide or polypeptide fragment, is provided. These polypeptides can be, for example, any of those noted herein.
Isolated nucleic acids identified by selection of the libraries in the methods above are also a feature of the invention, as are kits comprising any of: mycotoxin detoxification nucleic acid libraries, shuffled mycotoxin detoxification nucleic acids, instructional materials for practicing any of the methods herein, containers for holding other kit components, and the like.
Not Applicable.
Unless clearly indicated to the contrary, the following definitions supplement definitions of terms known in the art.
A xe2x80x9crecombinant monooxygenase nucleic acidxe2x80x9d is a recombinant nucleic acid encoding a protein or RNA which confers monooxygenase activity to a cell when the nucleic acid is expressed in the cell.
A xe2x80x9crecombinantxe2x80x9d nucleic acid is a nucleic acid produced by recombination between two or more nucleic acids, or any nucleic acid made by an in vitro or artificial process. The term xe2x80x9crecombinantxe2x80x9d when used with reference to a cell indicates that the cell comprises (and optionally replicates) a heterologous nucleic acid, or expresses a peptide or protein encoded by a heterologous nucleic acid. Recombinant cells can contain genes that are not found within the native (non-recombinant) form of the cell. Recombinant cells can also contain genes found in the native form of the cell where the genes are modified and re-introduced into the cell by artificial means. The term also encompasses cells that contain a nucleic acid endogenous to the cell that has been artificially modified without removing the nucleic acid from the cell; such modifications include those obtained by gene replacement, site-specific mutation, and related techniques.
A xe2x80x9crecombinant mycotoxin detoxification nucleic acidxe2x80x9d is a recombinant nucleic acid encoding a protein or RNA which confers mycotoxin detoxification or degradation activity to a cell when the nucleic acid is expressed in the cell (and, most typically, translated into a polypeptide).
A xe2x80x9cplurality of formsxe2x80x9d of a selected nucleic acid refers to a plurality of homologs of the nucleic acid. The homologs can be from naturally occurring homologs (e.g., two or more homologous genes) or by artificial synthesis of one or more nucleic acids having related sequences, or by modification of one or more nucleic acid to produce related nucleic acids. Nucleic acids are homologous when they are derived, naturally or artificially, from a common ancestor sequence. During natural evolution, this occurs when two or more descendent sequences diverge from a parent sequence over time, i.e., due to mutation and natural selection. Under artificial conditions, divergence occurs, e.g., in one of two ways. First, a given sequence can be artificially recombined with another sequence, as occurs, e.g., during typical cloning, to produce a descendent nucleic acid. Alternatively, a nucleic acid can be synthesized de novo, by synthesizing a nucleic acid which varies in sequence from a given parental nucleic acid sequence.
When there is no explicit knowledge about the ancestry of two nucleic acids, homology is typically inferred by sequence comparison between two sequences. Where two nucleic acid sequences show sequence similarity it is inferred that the two nucleic acids share a common ancestor. The precise level of sequence similarity required to establish homology varies in the art depending on a variety of factors. For purposes of this disclosure, two sequences are considered homologous where they share sufficient sequence identity to allow direct recombination to occur between two nucleic acid molecules (as opposed to recombination using oligonucleotide intermediates, which does not require sequence similarity to acheive recombination). Typically, nucleic acids require regions of close similarity spaced roughly the same distance apart to permit recombination to occur. The recombination can be in vitro or in vivo.
The terms xe2x80x9cidenticalxe2x80x9d or percent xe2x80x9cidentity,xe2x80x9d in the context of two or more nucleic acid or polypeptide sequences, refer to two or more sequences or subsequences that are the same or have a specified percentage of amino acid residues or nucleotides that are the same, when compared and aligned for maximum correspondence, as measured using one of the sequence comparison algorithms described below (or other algorithms available to persons of skill) or by visual inspection.
The phrase xe2x80x9csubstantially identical,xe2x80x9d in the context of two nucleic acids or polypeptides (e.g., DNAs encoding a monooxygenase, or the amino acid sequence of the monooxygenase) refers to two or more sequences or subsequences that have at least about 60%, preferably 80%, most preferably 90-95% nucleotide or amino acid residue identity, when compared and aligned for maximum correspondence, as measured using one of the following sequence comparison algorithms or by visual inspection. Such xe2x80x9csubstantially identicalxe2x80x9d sequences are typically considered to be homologous. Preferably, the xe2x80x9csubstantial identityxe2x80x9d exists over a region of the sequences that is at least about 50 residues in length, more preferably over a region of at least about 100 residues, and most preferably the sequences are substantially identical over at least about 150 residues, or over the full length of the two sequences to be compared.
For sequence comparison and homology determination, typically one sequence acts as a reference sequence to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are input into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percent sequence identity for the test sequence(s) relative to the reference sequence, based on the designated program parameters.
Optimal alignment of sequences for comparison can be conducted, e.g., by the local homology algorithm of Smith and Waterman, Adv. Appl. Math. 2:482 (1981), by the homology alignment algorithm of Needleman and Wunsch, J. Mol. Biol. 48:443 (1970), by the search for similarity method of Pearson and Lipman, Proc. Nat""l. Acad. Sci. USA 85:2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by visual inspection (see generally, Ausubel et al., infra).
One example of algorithm that is suitable for determining percent sequence identity and sequence similarity is the BLAST algorithm, which is described in Altschul et al., J. Mol. Biol. 215:403-410 (1990). Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/). This algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length W in the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul et al., supra). These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are then extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always  greater than 0) and N (penalty score for mismatching residues; always  less than 0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. The BLAST algorithm parameters W, T, and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a wordlength (W) of 11, an expectation (E) of 10, a cutoff of 100, M=5, N=xe2x88x924, and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults a wordlength (W) of 3, an expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff and Henikoff (1989) Proc. Natl. Acad. Sci. USA 89:10915).
In addition to calculating percent sequence identity, the BLAST algorithm also performs a statistical analysis of the similarity between two sequences (see, e.g., Karlin and Altschul (1993) Proc. Nat""l. Acad. Sci. USA 90:5873-5787). One measure of similarity provided by the BLAST algorithm is the smallest sum probability (P(N)), which provides an indication of the probability by which a match between two nucleotide or amino acid sequences would occur by chance. For example, a nucleic acid is considered similar to a reference sequence if the smallest sum probability in a comparison of the test nucleic acid to the reference nucleic acid is less than about 0.1, more preferably less than about 0.01, and most preferably less than about 0.001.
Another indication that two nucleic acid sequences are substantially identical/homologous is that the two molecules hybridize to each other under stringent conditions. The phrase xe2x80x9chybridizing specifically to,xe2x80x9d refers to the binding, duplexing, or hybridizing of a molecule only to a particular nucleotide sequence under stringent conditions, including when that sequence is present in a complex mixture (e.g., total cellular) DNA or RNA. xe2x80x9cBind(s) substantiallyxe2x80x9d refers to complementary hybridization between a probe nucleic acid and a target nucleic acid and embraces minor mismatches that can be accommodated by reducing the stringency of the hybridization media to achieve the desired detection of the target polynucleotide sequence.
xe2x80x9cStringent hybridization conditionsxe2x80x9d and xe2x80x9cstringent hybridization wash conditionsxe2x80x9d in the context of nucleic acid hybridization experiments such as Southern and northern hybridizations are sequence dependent, and are different under different environmental parameters. Longer sequences hybridize specifically at higher temperatures. An extensive guide to the hybridization of nucleic acids is found in Tijssen (1993) Laboratory Techniques in Biochemistry and Molecular Biologyxe2x80x94Hybridization with Nucleic Acid Probes part I chapter 2 xe2x80x9cOverview of principles of hybridization and the strategy of nucleic acid probe assays,xe2x80x9d Elsevier, N.Y. Generally, highly stringent hybridization and wash conditions are selected to be about 5xc2x0 C. lower than the thermal melting point (Tm) for the specific sequence at a defined ionic strength and pH. Typically, under xe2x80x9cstringent conditionsxe2x80x9d a probe will hybridize to its target subsequence, but no to unrelated sequences.
The Tm is the temperature (under defined ionic strength and pH) at which 50% of the target sequence hybridizes to a perfectly matched probe. Very stringent conditions are selected to be equal to the Tm for a particular probe. An example of stringent hybridization conditions for hybridization of complementary nucleic acids which have more than 100 complementary residues on a filter in a Southern or northern blot is 50% formamide with 1 mg of heparin at 42xc2x0 C., with the hybridization being carried out overnight. An example of highly stringent wash conditions is 0.15M NaCl at 72xc2x0 C. for about 15 minutes. An example of stringent wash conditions is a 0.2xc3x97SSC wash at 65xc2x0 C. for 15 minutes (see, Sambrook, infra., for a description of SSC buffer). Often, a high stringency wash is preceded by a low stringency wash to remove background probe signal. An example medium stringency wash for a duplex of, e.g., more than 100 nucleotides, is 1xc3x97SSC at 45xc2x0 C. for 15 minutes. An example low stringency wash for a duplex of, e.g., more than 100 nucleotides, is 4-6xc3x97SSC at 40xc2x0 C. for 15 minutes. For short probes (e.g., about 10 to 50 nucleotides), stringent conditions typically involve salt concentrations of less than about 1.0 M Na ion, typically about 0.01 to 1.0 M Na ion concentration (or other salts) at pH 7.0 to 8.3, and the temperature is typically at least about 30xc2x0 C. Stringent conditions can also be achieved with the addition of destabilizing agents such as formamide. In general, a signal to noise ratio of 2xc3x97 (or higher) than that observed for an unrelated probe in the particular hybridization assay indicates detection of a specific hybridization.
A further indication that two nucleic acid sequences or polypeptides are substantially identical/homologous is that the polypeptide encoded by the first nucleic acid is immunologically cross reactive with, or specifically binds to, the polypeptide encoded by the second nucleic acid. Thus, a polypeptide is typically substantially identical to a second polypeptide, for example, where the two peptides differ only by conservative substitutions.
xe2x80x9cConservatively modified variationsxe2x80x9d of a particular polynucleotide sequence refers to those polynucleotides that encode identical or essentially identical amino acid sequences, or where the polynucleotide does not encode an amino acid sequence, to essentially identical sequences. Because of the degeneracy of the genetic code, a large number of functionally identical nucleic acids encode any given polypeptide. For instance, the codons CGU, CGC, CGA, CGG, AGA, and AGG all encode the amino acid arginine. Thus, at every position where an arginine is specified by a codon, the codon can be altered to any of the corresponding codons described without altering the encoded polypeptide. Such nucleic acid variations are xe2x80x9csilent variations,xe2x80x9d which are one species of xe2x80x9cconservatively modified variations.xe2x80x9d Every polynucleotide sequence described herein which encodes a polypeptide also describes every possible silent variation, except where otherwise noted. One of skill will recognize that each codon in a nucleic acid (except AUG, which is ordinarily the only codon for methionine) can be modified to yield a functionally identical molecule by standard techniques. Accordingly, each xe2x80x9csilent variationxe2x80x9d of a nucleic acid which encodes a polypeptide is implicit in each described sequence.
Furthermore, one of skill will recognize that individual substitutions, deletions or additions which alter, add or delete a single amino acid or a small percentage of amino acids (typically less than 5%, more typically less than 1%) in an encoded sequence are xe2x80x9cconservatively modified variationsxe2x80x9d where the alterations result in the substitution of an amino acid with a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art. The following five groups each contain amino acids that are conservative substitutions for one another: Aliphatic: Glycine (G), Alanine (A), Valine (V), Leucine (L), Isoleucine (I); Aromatic: Phenylalanine (F), Tyrosine (Y), Tryptophan (W); Sulfur-containing: Methionine (M), Cysteine (C); Basic: Arginine (R), Lysine (K), Histidine (H); Acidic: Aspartic acid (D), Glutamic acid (E), Asparagine (N), Glutamine (Q). See also, Creighton (1984) Proteins, W. H. Freeman and Company.
In addition, individual substitutions, deletions or additions which alter, add or delete a single amino acid or a small percentage of amino acids in an encoded sequence are also xe2x80x9cconservatively modified variations.xe2x80x9d Sequences that differ by conservative variations are generally homologous.
A xe2x80x9csubsequencexe2x80x9d refers to a sequence of nucleic acids or amino acids that comprise a part of a longer sequence of nucleic acids or amino acids (e.g., polypeptide) respectively.
The term xe2x80x9cgenexe2x80x9d is used broadly to refer to any segment of DNA associated with expression of a given RNA or protein. Thus, genes include regions encoding expressed RNAs (which typically include polypeptide coding sequences) and, often, the regulatory sequences required for their expression. Genes can be obtained from a variety of sources, including cloning from a source of interest or synthesizing from known or predicted sequence information, and may include sequences designed to have desired parameters.
The term xe2x80x9cisolatedxe2x80x9d, when applied to a nucleic acid or protein, denotes that the nucleic acid or protein is essentially free of other cellular components with which it is associated in the natural state.
The term xe2x80x9cnucleic acidxe2x80x9d refers to deoxyribonucleotides or ribonucleotides and polymers thereof in either single- or double-stranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides which have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g. degenerate codon substitutions) and complementary sequences and as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues (Batzer et al. (1991) Nucleic Acid Res. 19: 5081; Ohtsuka et al. (1985) J. Biol. Chem. 260: 2605-2608; Cassol et al. (1992); Rossolini et al. (1994) Mol. Cell. Probes 8: 91-98). The term nucleic acid is generic to the terms xe2x80x9cgenexe2x80x9d, xe2x80x9cDNA,xe2x80x9d xe2x80x9ccDNAxe2x80x9d, xe2x80x9coligonucleotide,xe2x80x9d xe2x80x9cRNA,xe2x80x9d xe2x80x9cmRNA,xe2x80x9d and the like.
xe2x80x9cNucleic acid derived from a genexe2x80x9d refers to a nucleic acid for whose synthesis the gene, or a subsequence thereof, has ultimately served as a template. Thus, an mRNA, a cDNA reverse transcribed from an mRNA, an RNA transcribed from that cDNA, a DNA amplified from the cDNA, an RNA transcribed from the amplified DNA, etc., are all derived from the gene and detection of such derived products is indicative of the presence and/or abundance of the original gene and/or gene transcript in a sample.
A nucleic acid is xe2x80x9coperably linkedxe2x80x9d when it is placed into a functional relationship with another nucleic acid sequence. For instance, a promoter or enhancer is operably linked to a coding sequence if it increases the transcription of the coding sequence.
A xe2x80x9crecombinant expression cassettexe2x80x9d or simply an xe2x80x9cexpression cassettexe2x80x9d is a nucleic acid construct, generated recombinantly or synthetically, with nucleic acid elements that are capable of effecting expression of a structural gene in hosts compatible with such sequences. Expression cassettes include at least promoters and optionally, transcription termination signals. Typically, the recombinant expression cassette includes a nucleic acid to be transcribed (e.g., a nucleic acid encoding a desired polypeptide), and a promoter. Additional factors necessary or helpful in effecting expression may also be used as described herein. For example, an expression cassette can also include nucleotide sequences that encode a signal sequence that directs secretion of an expressed protein from the host cell. Transcription termination signals, enhancers, and other nucleic acid sequences that influence gene expression, can also be included in an expression cassette.

DNA shuffling to produce nucleic acids for mycotoxin detoxification


A short-body miniature DIN connector consists of a dielectric body defining an inverted T-shaped locking slot, a horizontal and vertical ridge on a right and left face. A number of contacts each has a first fitting portion having an interference fit with the body defining a corresponding contact passage extending through the body, and a second fitting portion having an interference fit with the body defining a corresponding locating groove located at a bottom of a rear face of the body. A shielding shell covers the body and has an upper wall defining an inverted-T shaped locking tab bent into the locking slot to have an interference fit with the body and two flaps extending downwards from two sides thereof. The shielding shell further has a right and left wall each defining a vertical and horizontal projection engaging the horizontal and vertical ridges, and an upper fin engaging with a corresponding flap, whereby a rebound of the right and left walls to move away from the dielectric body can be prevented.

1. Field of the Invention
The invention relates to a miniature DIN connector, particularly to a miniature DIN connector of a short body type which has a thickness of 8.0 mm, while a long body type has a thickness of 12.8 mm.
2. The Prior Art
Miniature DIN connectors have been used as a connector for connecting a periphery device to a computer, for example an external keyboard to a laptop computer. The following documents relate to some prior art miniature DIN connectors: Taiwan Patent Application Nos. 77208107, 78204790, 80104898, 80208342, 80211820, 82111200, 82201874, and 84201441 and U.S. Pat. Nos. 4,637,669, 4,842,554, 4,842,555, 4,908,335, 4,995,819, 5,017,158 and 5,186,633.
To save the space that the miniature DIN connectors would occupy, short-body miniature DIN connectors have been developed which have a thickness of 8 mm to replace long-body miniature DIN connectors which have a thickness of 12.8 mm.
However, the conventional short-body miniature DIN connectors are found to have the disadvantages as set forth below.
Firstly, since each of the short-body miniature DIN connectors has a dielectric body with a short thickness, the area available for connecting the dielectric body with an electromagnetic shielding shell is greatly limited. This brings about that to securely connect the dielectric body and the shielding shell needs a very complicated assembling operation.
Secondly, the contacts thereof each has a complicated structure, which brings about that to manufacture the contacts and to assemble the contacts with the dielectric body are difficult and troublesome.
Therefore, an objective of the invention is to provide a short-body miniature DIN connector with a shielding shell and a dielectric body which can be easily and securely connected with each other by a simple assembling operation.
Another objective of the invention is to provide a short-body miniature DIN connector with contacts which have a simple structure so that they can be easily formed; furthermore, the contacts can be easily and securely mounted to the dielectric body.


A memory controller and a semiconductor device comprising the same are provided. The semiconductor device comprises a memory block comprising a plurality of memory banks and a memory controller. The memory controller outputs an auto refresh command and memory bank information indicating a memory bank that is to be auto refreshed in an auto refresh mode. Thus, only the selected memory bank performs an auto refresh operation in the auto refresh mode while reducing current consumption in the semiconductor device.

1. Technical Field
The present invention relates to a semiconductor device, and more particularly, to a memory controller capable of outputting an auto refresh command and bank information in an auto refresh mode and a semiconductor device comprising the same.
2. Discussion of the Related Art
As wireless applications are developed for portable devices, there is a need for processing large amounts of data in such devices. This results in an increased use of dynamic random access memory (DRAM) memory cells in portable devices.
In order to preserve data in a DRAM, a refresh operation is performed in a memory cell of the DRAM. Refresh operations, however, consume excess current and drain battery power in portable devices employing DRAMs. Thus, the DRAM memory cells are not commonly used in portable devices that use batteries such as mobile phones, personal digital assistants (PDAs), etc.
Methods for reducing the amount of current consumed during refresh operations have been studied in order to increase the lifetime of batteries in portable devices. However, when refresh operations employing such methods are performed in semiconductor devices having memory banks and/or cells, currents are unnecessarily consumed because each memory cell in the semiconductor device conducts the refresh operations.

Memory controller and semiconductor comprising the same


An electron emission device includes: a semiconductor layer; a porous semiconductor; and a thin-film metal electrode which are layered in turn. The electrode faces a vacuum space. The porous semiconductor layer has at least two or more of porosity-changed layers which have porosities which are different from each other in the thickness direction. The electron emission device emits electrons when an electric field is applied between the semiconductor layer and the thin-film metal electrode. An insulator layer made of a material selected from silicon oxide or silicon nitride may be formed between the porous semiconductor layer and the thin-film metal electrode. Si skeletons of the porous semiconductor layer are oxidized or nitrided.

1. Field of the Invention
The present invention relates to an electron emission device and particularly to a porous semiconductor electron emission device.
2. Description of the Related Art
In field electron emission display apparatuses, an FED (Field Emission Display) is known as a planar emission display device equipped with an array of cold-cathode electron emission source which does not require cathode heating. There also exists attentions to planar electron sources such as an electron emission device with a metal-insulator-metal (MIM) structure and to an electron emission device using a porous semiconductor such as silicon (Si) with a homogeneous porosity.
As shown in FIG. 1, the electron emission device using a porous semiconductor layer comprises a porous semiconductor layer 13 and a thin-film metal electrode 15 which are formed in turn on a silicon layer 12 provided with an ohmic electrode 11 at the back side.
The porous semiconductor electron emission device can be regarded as a diode of which the thin-film metal electrode 15 at its surface is connected to a positive potential Vps and the back i.e., ohmic electrode 11 is connected to a ground potential. When the voltage Vps is applied between the ohmic electrode 11 and the thin-film metal electrode 15 to supply electrons into the semiconductor layer 12 of semiconductor Si, a diode current Ips flows. Since the porous semiconductor layer 13 has a high resistance, most of the applied electric field is applied to the porous semiconductor layer 13. The electrons travel inside the porous semiconductor layer 13 toward the thin-film metal electrode 15. Some of the electrons that reach near the thin-film metal electrode 15 tunnel through the thin-film metal electrode 15, due to the strong electric field, to be discharged out into the vacuum space 4. The electrons e (emission current Iem) discharged from the thin-film metal electrode 15 by the tunnel effect are accelerated by a high voltage Vc, which is applied to an opposing collector electrode (transparent electrode) 2, and is collected at the collector electrode 2. If a fluorescent substance is coated on the collector electrode 2, corresponding visible light is emitted.
To fabricate a color display panel using the porous semiconductor electron emission device, the collector electrodes 2 capturing emitted electrons are grouped per three for R, G and B color signals corresponding to Red, Green and Blue emitting portions. Thus, fluorescent material layers 3R, 3G and 3B corresponding to R, G and B emissions are formed on the corresponding collector electrodes 2 onto which the electrons caused by the tunnel effect are impinged after the travel in the vacuum space 4.
However, there are problems as follows:
(1) When the diode current Ips is in an over-current, the electron emission efficiency .eta. (emission current Iem/diode current Ips) decreases; PA1 (2) The surface of the porous semiconductor layer is considerably rough, and its contact to thin-film metal electrode prepared later becomes defective, so that the electron emission becomes unstable in the element. PA1 (3) Since the thermal conductivity of the porous semiconductor layer of Si is low in comparison with that of the original silicon, heat destruction of the element tends to occur. PA1 a semiconductor layer for supplying electrons; PA1 a porous semiconductor layer formed on the semiconductor layer; and PA1 a thin-film metal electrode which is formed on the porous semiconductor layer and faces a vacuum space; wherein the porous semiconductor layer has at least two or more of porosity-changed layers which have porosities which are different from each other in the thickness direction, whereby the electron emission device emits electrons when an electric field is applied between the semiconductor layer and the thin-film metal electrode. PA1 a semiconductor layer for supplying electrons; PA1 a porous semiconductor layer formed on the semiconductor layer; PA1 an insulator layer formed on the porous semiconductor layer and made of a material selected from silicon oxide or silicon nitride; and PA1 a thin-film metal electrode which is formed on the insulator layer and faces a vacuum space; whereby the electron emission device emits electrons when an electric field is applied between the semiconductor layer and the thin-film metal electrode. PA1 a semiconductor layer for supplying electrons; PA1 a porous semiconductor layer formed on the semiconductor layer; and PA1 a thin-film metal electrode which is formed on the porous semiconductor layer and faces a vacuum space; wherein skeletons of the porous semiconductor layer are oxidized or nitrided, whereby the electron emission device emits electrons when an electric field is applied between the semiconductor layer and the thin-film metal electrode.
On the other hand, the porous silicon layer is formed by anodization to a silicon film in a mixed solution of hydroflouric acid and ethyl alcohol.
By heating the porous silicon layer at a high temperature in a vacuum after the anodization thereof, hydrogen terminuses existing adjacent to the surface of the porous silicon layer are removed, and then dangling bonds are terminated with atoms of oxygen or nitrogen through some processes such as heating or plasma-processing in oxygen gas or nitrogen gas, so that the porous silicon layer becomes stable.
However, even by use of the above termination method, there is a difficulty to control the thickness of the portion terminated with oxygen and nitrogen in the porous silicon layer. Optimization of terminus processing conditions is because it is hard. Therefore, since the porous silicon portion terminated with oxygen and nitrogen is an important condition for electroluminescence (EL) and photoluminescence (PL), any uniform stable EL and PL light-emissions are not yet obtained from the porous semiconductor electron emission device.

Electron emission device and display device using the same


A ceria-zirconia-based composite oxide oxygen storage material with a fast oxygen storage rate having an OSC ability enabling fast response to changes in exhaust gas which does not greatly fluctuate in composition, but varies at a fast rate near the stoichiometric air-fuel ratio, an exhaust gas purification catalyst, and a honeycomb structure for exhaust gas purification are provided. A ceria-zirconia-based composite oxide oxygen storage material, which oxygen storage material has a molar ratio of cerium and zirconium, by cerium/(cerium+zirconium), of 0.33 to 0.90, has an ion conductivity measured by an AC impedance method of 1×10−5S/cm or more at 400° C., and contains metal ions M of one or more types of rare earth elements selected from Sm3+, Eu3+, Pr3+, Gd3+, and Dy3+ with a coordination number of over 7.0 in an amount of 0.5 mol % to 15 mol % with respect to the total amount of cations.

In the past, as the method for removing harmful substances from the exhaust gas of automobiles such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOX), three-way catalysts having precious metals (for example, Pt, Rh, Pd, Ir, Ru, etc.) as catalytic ingredients have been used. In three-way catalysts, the CO and HC are oxidized and the nitrogen oxides (NOX) are reduced simultaneously to purify the exhaust gas.
In a three-way catalyst used for purifying the exhaust gas of a gasoline engine, to enhance the action of the precious metal, it is preferable to keep the ratio of the fuel and air (air-fuel ratio) constant (at the stoichiometric air-fuel ratio). However, the air-fuel ratio greatly changes in accordance with acceleration, deceleration, low speed running, high speed running, and other driving conditions. For this reason, feedback control using an oxygen sensor has been employed to try to keep the air-fuel ratio A/F (air/fuel), which fluctuates depending on the engine operating conditions, constant. However, the A/F fluctuates along with time along with the feedback time, so with just engine control, it has been difficult to hold the exhaust gas composition at the stoichiometric air-fuel ratio or the vicinity of the same.
For this reason, it is necessary to finely adjust the composition at the catalyst side so as to store oxygen when the concentration of oxygen in the exhaust gas is high and to release oxygen when the concentration of oxygen in the exhaust gas is low. Ceria (cerium oxide CeO2) has an oxygen storage capacity (below, sometimes simply referred to as "OSC"), so is being widely used as an oxygen storage material (co-catalyst) for adjusting the oxygen partial pressure of catalysts for purifying automotive exhaust gas. This utilizes the redox reaction of Ce3+/Ce4+. Ceria is generally used in the form of a ceria-zirconia-based composite oxide in which it forms a solid solution with zirconia (zirconium oxide ZrO2) so as to enhance its property.
The ceria-zirconia-based composite oxide is generally mixed with alumina in a ratio of several percent or several tens of percent in a state where Pt, Pd, Rh, or another catalyst precious metal is supported. This mixture is coated on the surface of a honeycomb support in a wash-coat layer of a thickness of ten or so μm to several hundreds of μm (for example, 10 to 600 μm). The ceria-zirconia-based composite oxide functions as a co-catalyst assisting the action of the catalyst precious metal.
The catalyst wash-coated at the inside of the honeycomb support purifies the exhaust gas by contact with it as the gas circulates. The total length of the honeycomb support is a short one of 10 cm to about 30 cm. The time for purifying the exhaust gas is extremely short. To complete the purification in this short time, it is necessary to complete the adjustment of the oxygen partial pressure by the ceria-zirconia in an extremely short time of millisecond units.
PTL 1 has as its object to increase the specific surface area of a ceria-zirconia-based oxide and proposes a metal acetyl acetonate-surface-modified ceria-zirconia-based hydrated oxide comprised of a ceria-zirconia-based hydrated oxide with a surface modified by at least one type of acetyl acetonate selected from the group comprising La, Pr, Nd, Sm, Gd, and Y. PTL 2 proposes a zirconia-based porous body maintaining its pore size and pore volume even after treatment at a high temperature. The object of this is to keep the particle surfaces large and prevent sintering of the supported precious metal particles and to enable oxygen to be smoothly moved even after the ceria-zirconia-based composite oxide through which the oxygen moves is exposed to high temperature exhaust gas.
PTL 3 discloses development focused in the OSC amount. This is for enabling adjustment of the composition of the exhaust gas even if the composition greatly deviates from the stoichiometric air-fuel ratio or continues for a long time.
PTL 4 proposes focusing on the oxygen release rate up to 60 seconds after start of reduction. PTL 5 proposes ceria-zirconia with a large OSC amount and large release rate by combining a fluorite type structure ceria-zirconia with ceria-zirconia having a pyrochlore structure. These development efforts focusing on the rate of oxygen release from ceria-zirconia-based oxides aim at smoother movement of oxygen from the ceria-zirconia-based composite oxide particles and improved purification performance.

Ceria-zirconia-based composite oxide oxygen storage material, exhaust gas cleaning catalyst, and honeycomb structure for exhaust gas cleaning


A new plant variety of Loropetalum chinese var. rubrum named ‘Sato's Dwarf Red’, having a low growing, compact habit and red foliage throughout the year.

The present invention relates to a new and distinct variety of Loropetalum chinense var. rubrum and was developed in a controlled breeding program in Angyo Kichi Zo, Saitama Prefecture, Japan by the originator Mr. Noboru Sato. The varietal denomination of the new variety is 'Sato's Dwarf Red'.
The genus Loropetalum is included in the family Hamamelidaceae that comprises about 15 genera of shrubs and trees growing in the northern hemisphere. Loropetalum comprises one species of evergreen shrub or small tree, which possesses desirable ornamental characteristics. Loropetalum was first introduced to Europe as an ornamental plant in the 1880s, and is believed to have been cultivated in North America since the early 1930s.
Loropetalum chinense is a native of China, and was first discovered in 1928 in Hunan province. It was rediscovered in the late 1980s and subsequently introduced to the United States. Loropetalum chinense generally has alternate, ovate leaves to 6 cm. long and 3 cm. wide. The plant is evergreen or partly evergreen depending on winter temperature. Leaf color ranges from light to dark burgundy, occasionally green, depending on light intensity, cultural conditions and cultivar. Shoots are slender, brown, and densely pubescent, pit is solid. Leaves are generally densely pubescent overall.
Flowers of Loropetalum chinense are perfect, four strap like, about 2 cm. long, and about 0.3 cm. wide petals. Three to six flowers are together in each leaf axil. Pedicel and calyx have a white pubescence. Flower color is pinkish to reddish purple depending on the cultivar. Flowering is heaviest in early spring.

Plant variety of Loropetalum chinense var. rubrum named ‘Sato's Dwarf Red’


An electrical measurement device is described with an acquisition unit that is configured to receive an input signal, a post-processing unit, and a visualization unit. The acquisition unit comprises an acquisition trigger unit and an acquisition memory, the acquisition memory being configured to acquire sampled output data and to store the sampled output data by control of the acquisition trigger unit. The post-processing unit comprises a measurement unit that is configured to process at least parts of the sampled output data and to generate processed sampled output data. The post-processing unit further comprises a measurement trigger unit that is configured to evaluate the processed sampled output data in view of a measurement trigger condition, the measurement trigger unit being configured to output a measurement trigger event if the measurement trigger condition is met. The measurement trigger unit is further configured to control the visualization unit. Moreover, a method for operating an electrical measurement device is described.

Known electrical measurement devices, in particular known digital oscilloscopes, comprise an acquisition unit with an acquisition trigger unit and an acquisition memory. Input data is acquired by the acquisition unit in view of an acquisition trigger condition. The acquired data can then be stored in the acquisition memory. Moreover, the acquired data can be visualized on a graphic display, on which a user can observe a curve of measured values corresponding to the input data acquired.
If the measured values change in a certain way over the time, it would be desirable for the user to be able to see the input signal which has caused that change.

Electrical measurement device and method