A monolithic 5 Gb/s p-i-n/HBT integrated photoreceiver circuit realized from chemical beam epitaxial material

The authors report on a high performance monolithic photoreceiver fabricated from chemical beam epitaxy (CBE) grown InP/InGaAs heterostructures, incorporating a p-i-n photodetector followed by a transimpedance preamplifier circuit configured from heterojunction bipolar transistors (HBTs). The optoelectronic integrated circuit (OEIC) was fabricated on a semi-insulating Fe-doped InP substrate. Microwave on-wafer measurements of the frequency response of the transistors yielded unity current gain cutoff frequencies of 32 GHz and maximum oscillation frequencies of 28 GHz for collector currents between 2 and 5 mA. The photoreceiver was operated up to 5 Gb/s, at which bit rate a sensitivity of -18.8 dBm was measured at a wavelength of 1.5 mu m. The results demonstrate that the CBE growth technique is suitable for high performance HBT-based OEICs.<>     

Optimization of hybrid laser–TIG welding of 316LN stainless steel using genetic algorithm

Determination of optimum hybrid laser–TIG welding process variables for achieving the maximum depth of penetration (DOP) in type 316LN stainless steel has been carried out using a genetic algorithm (GA). Nd:YAG pulsed laser and the TIG heat source were coupled at the weld pool to carry out hybrid welding. Design of experiments approach was used to generate the experimental design matrix. Bead-on-plate welds were carried out based on the design matrix. The input variables considered were laser power, pulse frequency, pulse duration, and TIG current. The response variable considered was the DOP. Multiple-regression model was developed correlating the process variables with the DOP using the generated data. The regression model was used for evaluating the objective function in GA. GA-based model was developed and it produced a set of solutions. Tournament and roulette wheel selection methods were used during the execution of GA. It was found that both the selection methods identified similar welding process parameters for achieving the maximum DOP. Excellent agreement was observed between the target DOP and the DOP values obtained in the validation experiments during hybrid laser–TIG welding.     

Enhancement of biological hydrogen production using green alga Chlorococcum minutum

It is estimated that the fossil fuel reserves are going to deplete continuously due to extensive usage. In order to cope with this crisis, it is necessary to increase the efforts towards production of biofuels such as biological hydrogen (H₂). It is well-known fact that the biological hydrogen is a clean and ideal energy and liberates high amount of energy per unit mass. Several groups are working for the large scale production of H₂ chemically and also using photosynthetic organisms, but output is not satisfactory. The best way to achieve enhancement of H₂ is through altering the photosynthetic process by applying various stress conditions or by natural selection. In the process of selection, Chlorococcum minutum was found with improved H₂ output when compared to model green alga Chlamydomonas reinhardtii in a massively parallel and competitive high-throughput screen of different green algae. Both the species belongs to class chlorophyceae of green algae and live in fresh water conditions. In extent various light, pH and temperature conditions were applied and achieved the enhancement of H₂ production in this species under in vitro settings. Augmented hydrogenase activity was found in Chlorococcum minutum when compared to model alga and this may be one of the reason behind improved H₂ output. Hence this species may be considered as one of the best species with respect to H₂ production and also this work may be useful for future renewable energy research.     

Evidences for diabetes and insulin mimetic activity of medicinal plants: Present status and future prospects

Diabetes mellitus (DM) is a considerable systemic metabolic disorder to exhibit various metabolic and cardiovascular disorders, mainly hyperglycemia. The global projected estimate of diabetes in 2030 will be about 439 million adults, out of which 300 million expected are of type-2 diabetes mellitus (T2DM). The present knowledge revealed responsible factors, occurrence and mechanism of these factors involved in the DM diseases. Hence, the aim of this review is to address and summarize the causes, plant resources, importance, present status and future programmes for diabetes control. The present review answers the contemporary present questions raised in the scientific field on DM. Two major problems are explained in detail about the autoimmune attack or dysfunction of β-cell and insulin resistance involved for Type 1 and Type 2 DM, respectively. Though there are various approaches to reduce the ill effects of diabetes and its secondary complications, many preferred herbal formulations due to lesser side effects and low cost. For this reason still it is getting increased attention in searching antidiabetic medicinal plants for hot research and to develop targeted medicine. Recurrence of islet autoimmunity lesson from pancreatic islet cell transplantation to cure T1D was outlined. With these highlights, the review summarizes the current knowledge on diabetes occurrence, factors (environmental and genetics), and types (I, II, gestation, and secondary DM), antidiabetic plants, sources for insulin mimetic plant principle compounds and their target mechanism with current and future trusted research areas for controlling of DM.     

RZ-DPSK transmission using a 42.7-Gb/s integrated balanced optical front end with record sensitivity

We have demonstrated a record sensitivity of -37.0 dBm (38 photons/bit) for a BER of 10/sup -9/ at 42.7-Gb/s using an integrated balanced optical front end. Results were obtained using optical preamplification of RZ-DPSK modulation and an external delay-interferometer. The OSNR requirement was measured to be 16.9 dB in a 0.1-nm bandwidth. The impact of polarization-mode dispersion (PMD) and chromatic dispersion on the optical front end performance has been measured. Performance for enhanced forward error correction has been projected based on 10/sup -3/ BER performance.     

Demonstration of enhanced performance of an InP/InGaAsheterojunction phototransistor with a base terminal

The optical gain and the small-signal frequency response of an InP/InGaAs heterojunction phototransistor (HPT) with a base terminal are investigated in detail for the first time. When operated under an optimally chosen external base current, the optical gain is enhanced more than five times over that of the same device operated as a two-terminal device, over a 17-dB range of input optical power. The small-signal 3-dB bandwidth of the three-terminal device is enhanced 15 times over that of the two-terminal device over the same range of input optical power. For a pseudorandom NRZ bit stream at 100 Mb/s, a clear eye opening is observed at an incident optical power of -33 dBm (500 nW)     

A parallel polygon-clipping algorithm

We describe a new parallel polygonclipping algorithm based on a novel technique that allows a processor to compute output vertices independently of the results of the other processors. The basis for the method is a collision-free labeling scheme to compute the labels of the vertices of the output polygon. This labeling scheme depends only on the id of the vertices of the output polygon. This labeling scheme depends only on the id of the vertex in the input polygon. This procedure allows us to defer the synchronization between processors to the final stages of the algorithm, reduces the amount of overhead due to fine-grain synchronization, and helps makes the algorithm efficient.