A Low-Power Wide-Linear-Range Transconductance Amplifier

The linear range of approximately ±75mV of traditional subthreshold transconductance amplifiers istoo small for certain applications—for example, for filtersin electronic cochleas, where it is desirable to handle loudsounds without distortion and to have a large dynamic range.We describe a transconductance amplifier designed for low-power(< 1 µW) subthreshold operation with a wideinput linear range. We obtain wide linear range by widening thetanh, or decreasing the ratio of transconductance to bias current,by a combination of four techniques. First, the well terminalsof the input differential-pair transistors are used as the amplifierinputs. Then, feedback techniques known as source degeneration(a common technique) and gate degeneration (a new technique)provide further improvements. Finally, a novel bump-linearizationtechnique extends the linear range even further. We present signal-flowdiagrams for speedy analysis of such circuit techniques. Ourtransconductance reduction is achieved in a compact 13-transistorcircuit without degrading other characteristics such as dc-inputoperating range. In a standard 2 µm process,we were able to obtain a linear range of ±1.7V.Using our wide-linear-range amplifier and a capacitor, we constructa follower–integrator with an experimental dynamic rangeof 65 dB. We show that, if the amplifier's noise is predominantlythermal, then an increase in its linear range increases thefollower–integrator'sdynamic range. If the amplifier's noise is predominantly 1/f,then an increase in its linear range has no effect on thefollower–integrator'sdynamic range. To preserve follower–integrator bandwidth,power consumption increases proportionately with an increasein the amplifier's linear range. We also present data for changesin the subthreshold exponential parameter with current leveland with gate-to-bulk voltage that should be of interest to alllow-power designers. We have described the use of our amplifierin a silicon cochlea [1, 2].     

The role of optimism in social network development, coping, and psychological adjustment during a life transition.

The authors investigated the extent to which social support and coping account for the association between greater optimism and better adjustment to stressful life events. College students of both genders completed measures of perceived stress, depression, friendship network size, and perceived social support at the beginning and end of their 1st semester of college. Coping was assessed at the end of the 1st semester. Greater optimism, assessed at the beginning of the 1st semester of college, was prospectively associated with smaller increases in stress and depression and greater increases in perceived social support (but not in friendship network size) over the course of the 1st semester of college. Mediational analyses were consistent with a model in which increases in social support and greater use of positive reinterpretation and growth contributed to the superior adjustment that optimists experienced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pseudo-characteristic method of lines solution of first-order hyperbolic equation systems

First-order hyperbolic partial differential equations are difficult to solve numerically because of their ability to transmit steep waves. It is well known that the method of characteristics is the natural method for such equations, as it precisely follows wave interactions. However, a characteristic solution is expensive, as it requires repeated solution of non-linear algebraic equations. This gives considerable motivation to the development of fixed grid numerical schemes.Unfortunately any attempt to use a finite fixed grid generates spurious numerical oscillation and dispersion, which must be minimized by artificial damping or directional differentiation. For sets of hyperbolic equations, the appropriate assignment of damping or direction is difficult to determine, as variables are coupled in non-linear form. However, a clear definition of directionality is given in the characteristic form of the equations, and may be used to develop a pseudo characteristic fixed grid statement of the equations, which is readily solved by the method of lines, is simple to implement, and produces stable accurate solutions.Applications are illustrated for the solution of equations describing shallow water flow, and compressible gaseous flow.     

Growth and properties of high-quality very-thin SOS films

The increased emphasis on submicron geometry CMOS/SOS devices has created a need for high quality silicon-on-sapphire films with thicknesses of the order of 0.1 to 0.2 μm. To date the only viable way of producing high quality SOS films with these thicknesses has been through the application of recrystallization and regrowth techniques. The need for as-grown, high-quality, very-thin SOS films has prompted a study of film quality vs growth rate for films with thicknesses in the 0.1 to 0.2 μm range as a possible way of producing thin high-quality SOS films. It has been found that film quality increased as the growth rate increased. It was possible to produce films as thin as 0.1 μm with mobilities nearly as high as 1 μm films, if the film growth rate was higher than 4 μm/ min.     

A class library for implementing, testing, and debugging concurrent programs

We describe the Modern Multithreading (MM) class library. MM is a class library consisting of thread and synchronization classes that provide significant support for testing and debugging multithreaded programs. The synchronization classes implement commonly used synchronization objects such as semaphores, monitors, and asynchronous and synchronous message passing channels, for programs that run on a single computer or on a distributed system. MM uses controlled executions to provide program tracing and replay and to support a number of implementation-based and specification-based testing techniques, including non-deterministic and deterministic testing and several forms of reachability testing. MM is portable and easy to use, and has been implemented in Java and C++, with C++ versions for the POSIX Pthreads library and for the Windows Win32 API.     

Coaggregation of κ‐Casein and β‐Lactoglobulin Produces Morphologically Distinct Amyloid Fibrils

The unfolding, misfolding, and aggregation of proteins lead to a variety of structural species. One form is the amyloid fibril, a highly aligned, stable, nanofibrillar structure composed of β‐sheets running perpendicular to the fibril axis. β‐Lactoglobulin (β‐Lg) and κ‐casein (κ‐CN) are two milk proteins that not only individually form amyloid fibrillar aggregates, but can also coaggregate under environmental stress conditions such as elevated temperature. The aggregation between β‐Lg and κ‐CN is proposed to proceed via disulfide bond formation leading to amorphous aggregates, although the exact mechanism is not known. Herein, using a range of biophysical techniques, it is shown that β‐Lg and κ‐CN coaggregate to form morphologically distinct co‐amyloid fibrillar structures, a phenomenon previously limited to protein isoforms from different species or different peptide sequences from an individual protein. A new mechanism of aggregation is proposed whereby β‐Lg and κ‐CN not only form disulfide‐linked aggregates, but also amyloid fibrillar coaggregates. The coaggregation of two structurally unrelated proteins into cofibrils suggests that the mechanism can be a generic feature of protein aggregation as long as the prerequisites for sequence similarity are met.     

Dispositional optimism and recovery from coronary artery bypass surgery: The beneficial effects on physical and psychological well-being.

The effect of dispositional optimism on recovery from coronary artery bypass surgery was examined in a group of 51 middle-aged men. Patients provided information at three points in time—(a) on the day before surgery, (b) 6–8 days postoperatively, and (c) 6 months postoperatively. Information was obtained relating to the patient's rate of physical recovery, mood, and postsurgical quality of life. Information was also gathered regarding the manner in which the patients attempted to cope with the stress of the surgery and its aftermath. As expected, dispositional optimism proved to be an important predictor of coping efforts and of surgical outcomes. More specifically, dispositional optimism (as assessed prior to surgery) correlated positively with manifestations of problem-focused coping and negatively with the use of denial. Dispositional optimism was also associated with a faster rate of physical recovery during the period of hospitalization and with a faster rate of return to normal life activities subsequent to discharge. Finally, there was a strong positive association between level of optimism and postsurgical quality of life at 6 months. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The 1982 International Geoscience And Remote Sensing Symposium: A Summary

IGARSS'82 (the International Geoscience and Remote Sensing Symposium) was held from June 1-4, 1982 at the University of Munich, Munich, West Germany. A comprehensive technical program was presented with many excellent papers on the utility of remote sensing techniques for geoscientific research, major international remote sensing programs, and missions in the planning stage, new generation remote sensor systems, and recent advances in data processing and image classification techniques. Sponsored by the IEEE Geoscience and Remote Sensing Society as an annual symposium, IGARSS is an important international forum for the dissemination and discussion of research results and planning activities in the important fields of geoscience and remote sensing.     

Results of human factors testing in a novel Hemodialysis system designed for ease of patient use

Introduction Home hemodialysis has not been widely adopted despite superior outcomes relative to conventional in‐center hemodialysis. Patients receiving home hemodialysis experience high rates of technique failure owing to machine complexity, training burden, and the inability to master treatments independently. Methods We conducted human factors testing on 15 health care professionals (HCPs) and 15 patients upon release of the defined training program on the Tablo? Hemodialysis System. Each participant completed one training and one testing session conducted in a simulated clinical environment. Training sessions lasted <3 hours for HCPs and <4 hours for patients, with an hour break between sessions for knowledge decay. During the testing session, we recorded participant behavior and data according to standard performance and safety‐based criteria. Findings Of 15 HCPs, 10 were registered nurses and five patient care technicians, with a broad range of dialysis work experience and no limitations other than visual correction. Of 15 patients (average age 48 years), 13 reported no limitations and two reported modest limitations—partial deafness and blindness in one eye, respectively. The average error rate was 4.4 per session for HCPs and 2.9 per session for patients out of a total possible 1,710 opportunities for errors. Despite having received minimal training, neither HCPs nor patients committed safety‐related errors that required mitigation; rather, we noted only minor errors and operational difficulties. Discussion The Tablo? Hemodialysis System is easy to use, and may help to enable self‐care and home hemodialysis in settings heretofore associated with high rates of technique failure.     

The Impact of Educational Background on the Effectiveness of Requirements Inspections: An Empirical Study

While the inspection of various software artifacts increases the quality of the end product, the effectiveness of an inspection depends largely on the individual inspectors involved. To address that issue, a large-scale controlled inspection experiment with over 70 professionals was conducted at Microsoft Corporation that focused on the relationship between an inspector's background and their effectiveness during a requirements inspection. The results of the study showed that inspectors with university degrees in majors not related to computer science found significantly more defects than those with degrees in computer science majors. We also observed that level of education (Masters, PhD), prior industrial experience or other job related experiences did not significantly impact the effectiveness of an inspector. The only other type of experience that had a significant impact on effectiveness was experience in writing requirements, i.e. professionals with prior experience writing requirements found statistically significant more defects than their counterparts.