DC to 2.5 Gb/s×4 p-i-n/HBT optical receiver array with lowcrosstalk

A multichannel optical receiver with an In_0.53Ga_0.47As p-i-n photodetector array and a monolithic transimpedance amplifier array fabricated in AlGaAs/GaAs HBT (heterojunction bipolar transistor) technology were demonstrated. Both flip-chip rear-illuminated and wire-bonded front-illuminated detector configurations were implemented. The transimpedance was 65 dBΩ, and the 3-dB bandwidth was measured to be 2.3 GHz. By using series feedback, the transimpedance gain of each cell was matched to within 0.5 dB, and the entire array operated from a single 5-V supply. A low interchannel crosstalk of less than -40 dB was measured up to a data rate of 2 Gb/s     

Attempting guards in parallel: A data flow approach to execute generalized guarded commands

Earlier approaches to execute generalized alternative/repetitive commands of Communicating Sequential Processes (CSP) attempt the selection of guards in a sequential order. Also, these implementations are based on either shared memory or message passing multiprocessor systems. In contrast, we propose an implementation of generalized guarded commands using the data-driven model of computation. A significant feature of our implementation is that it attempts the selection of the guards of a process in parallel. We prove that our implementation is faithful to the semantics of the generalized guarded commands. Further, we have simulated the implementation using discrete-event simulation and measured various performance parameters. The measured parameters are helpful in establishing the fairness of our implementation and its superiority, in terms of efficiency and the parallelism exploited, over other implementations. The simulation study is also helpful in identifying various issues that affect the performance of our implementation. Based on this study, we have proposed an adaptive algorithm which dynamically tunes the extent of parallelism in the implementation to achieve an optimum level of performance.The first author's work was supported by a MICRONET, Network Centers of Excellence, research grant. Support for the second author is from the NSERC (Canada) Grant. The last author's work was supported by grants from NSERC (Canada) and FCAR (Quebec).     

Single-walled carbon nanotube induces oxidative stress and activates nuclear transcription factor-kappaB in human keratinocytes

Carbon nanotubes are now becoming an important material for use in day to day life because of their unique physical properties. The toxicological impact of these materials has not yet been studied in detail, thereby limiting their use. In the present study, the toxicity of single-walled carbon nanotubes (SWCNT) was assessed in human keratinocyte cells. The results show increased oxidative stress and inhibition of cell proliferation in response to treatment of keratinocytes with SWCNT particles. In addition, the signaling mechanism in keratinocytes upon exposure to SWCNT particles was investigated. Results from the study suggest that SWCNT particles activate NF-kappaB in a dose-dependent manner in human keratinocytes. Further, the mechanism of activation of NF-kappaB was due to the activation of stress-related kinases by SWCNT particles in keratinocytes. In conclusion, these studies show the mechanism of toxicity induced by SWCNT particles.     

A Unified Framework for Instruction Scheduling and Mapping for Function Units with Structural Hazards

Software pipelining methods based on an ILP (integer linear programming) framework have been successfully applied to derive rate-optimal schedules under resource constraints. However, like many other previous works on software pipelining, ILP-based work has focused on resource constraints of simple function units, e.g., “clean pipelines”—pipelines without structural hazards. The problem for architectures beyond such clean pipelines remains open. One challenge is how to represent such resource constraints for unclean pipelines, i.e., pipelined function units, but having structural hazards.In this paper, we propose a method to constructrate-optimalsoftware pipelined schedules for pipelined architectures with structural hazards. A distinct feature of this work is that it provides a unified ILP framework for two challenging and interrelated aspects of software pipelining—the scheduling of instructions at particular times and the mapping of those instructions to specific function units. Solving both of these aspects is essential to finding schedules which will work both on VLIW machines which map instructions to fixed function units and on dynamic out-of-order superscalars. We propose two ILP formulations to solve the integrated scheduling and mapping problem. Both adopt principles of graph coloring in an ILP framework, and one usesforbidden latenciesin an elegant extension of classical hardware pipeline control theory.We have run experiments on four variations of our proposed formulations. As input we used a set of 415 “unique” loops taken from several benchmark suites, and we targeted an architecture whose function units contain many structural hazards. All four of our variations did well, with the best finding a rate-optimal schedule for 65% of the loops. This compares favorably with a leading heuristic, Huff'sSlack Scheduling—the ILP approaches found a schedule with smaller initiation interval for over 50% of the loops, with a mean improvement of almost 30%. Finally, we have found that reusing pipeline stages—and thus adding hazards—results in only a 10% drop in performance, while permitting significant savings in area.     

Developing highly reliable software

To build dependable software for safety-related applications in nuclear power plants, we developed a few qualified software components and used them in all the systems. Most of the safety-critical systems are real-time systems that require a guaranteed response time. These systems need real-time supervisory software to control task execution according to well-defined priority requirements. This led us to develop a highly reliable real-time executive called X-RTE     

Optimized Model Based Controller with Model Plant Mismatch for NMP Mitigation in Boost Converter

In this paper, an optimized Genetic Algorithm (GA) based internal model controller-proportional integral derivative (IMC-PID) controller has been designed for the control variable to output variable transfer function of dc-dc boost converter to mitigate the effect of non-minimum phase (NMP) behavior due to the presence of a right-half plane zero (RHPZ). This RHPZ limits the dynamic performance of the converter and leads to internal instability. The IMC PID is a streamlined counterpart of the standard feedback controller and easily achieves optimal set point and load change performance with a single filter tuning parameter λ. Also, this paper addresses the influences of the model-based controller with model plant mismatch on the closed-loop control. The conventional IMC PID design is realized as an optimization problem with a resilient controller being determined through a genetic algorithm. Computed results suggested that GA–IMC PID coheres to the optimum designs with a fast convergence rate and outperforms conventional IMC PID controllers.     

Noninvasive beam-wave spectrometric instrumentation for measuring dielectric constant at microwave frequencies

From the characteristics of the reflected Gaussian beam-wave for oblique incidence, measured with a spectrometer arrangement, the dielectric properties of a selectively exposed region of a dielectric slab are ascertained at microwave frequencies. For this purpose, a focused (Gaussian) microwave beam is launched from a suitable applicator to irradiate obliquely a selected protion of the test dielectric and the complex reflection coefficient is measured and analyzed. Further, the magnitude of the angular shift involved in the direction of the reflected beam is also used to calculate the dielectric constant. Application of this method to noninvasive measurements of dielectric properties of selective partial-bodies of commercial dielectrics and biological substances is discussed.     

Electrosynthesis of ferrate in a batch reactor at neutral conditions for drinking water applications

We report on the electrochemical generation of ferrate species in a batch reactor at neutral conditions (pH ～7) using boron‐doped diamond (BDD) electrodes and Fe (III) salts for applications in drinking water treatment. The impact of several relevant variables, including current density (5–55 mA cm^?2), pH (5–8), and type and concentration of the dissolved iron salts on the production of ferrates were examined. In addition, linear sweep voltammetry (LSV) studies were conducted using buffered electrolytes with and without the presence of iron (III) to decouple the parasitic oxygen evolution reaction. The LSV measurements in the presence of iron (III) and with a neutral electrolyte exhibit oxidation peaks centered ～2.0 V (versus SHE), indicating the production of ferrates at this pH. The rate of ferrate generation is not strongly affected by the pH condition (≤ 20 %); however, current density and the source of iron were found to have a higher impact on the production rate of ferrates. The efficacy of the process was higher using FeCl₃ instead of other sources of iron such as Fe₂O₃ and FeO(OH). The batch reactor results were successfully interpreted by a simple model that considered the kinetics of the ferrate generation and degradation reactions.

     

Analysis of stress responsive genes induced by single-walled carbon nanotubes in BJ Foreskin cells

Nanotechnology is finding its use as a potential technology in consumer products, defense, electronics, and medical applications by exploiting the properties of nanomaterials. Single-walled carbon nanotubes are novel forms of these nanomaterials with potential for large applications. However, the toxicity studies on this material are not explored in detail and therefore limiting its use. It has been earlier reported that single-walled carbon nanotubes induces oxidative stress and also dictates activation of specific signaling pathway in keratinocytes. The present study explores the effect of single-walled carbon nanotubes on stress genes in human BJ Foreskin cells. The results show induction of oxidative stress in BJ Foreskin cells by single-walled carbon nanotubes and increase in stress responsive genes. The genes included inducible genes like HMOX1, HMOX2, and Cyp1B1. In addition we validated increase for four genes by SWCNT, namely ATM, CCNC, DNAJB4, and GADD45A by RT-PCR. Moreover results of the altered stress related genes have been discussed and that partially explains some of the toxic responses induced by single-walled carbon nanotubes.