Effects of alkali halides on the thermal decompositions of poly(methyl methacrylate) and poly(2-hydroxy ethyl methacrylate)

The effects of alkali halides on the nonoxidative thermal degradations of poly(methyl methacrylate) and poly(2-hydroxy ethyl methacrylate) are described. The magnitudes of the effects of various alkali halides on polymer thermal degradation were found to depend on the salt and the polymer. Mass spectrometric analysis of volatiles evolved during polymer degradation detected alkyl halides formed by reactions between the salts and polymers. Compared to poly(methyl methacrylate), more alkyl halide was evolved from samples containing alkali halides and poly(2-hydroxy ethyl methacrylate). To varying degrees, salts also catalyzed ester decomposition reactions for this polymer. Infrared spectroscopic analysis results showed that carboxylate salts, carbonate, and carbon monoxide were formed by heating polymer/salt mixtures. © 1996 John Wiley & Sons, Inc.     

Bio-electrohydrolysis as a pretreatment strategy to catabolize complex food waste in closed circuitry: Function of electron flux to enhance acidogenic biohydrogen production

A novel bio-electrohydrolysis system (BEH) based on self-inducing electrogenic activity was designed as a pretreatment device to enhance biohydrogen (H₂) production efficiency of food waste. Experimental strategy involved two-stage integrated/hybrid operation with hydrolysis in initial stage followed by acidogenic fermentation for H₂ production in second stage. After pre-treatment, catabolized food waste from control (anaerobic) and BEH (closed circuit mode of operation) system was used as substrate in a separate bioreactor to evaluate H₂ production in dark-fermentation process. Pretreated-waste from BEH showed higher H₂ production (29.12 ml/h; 24th h) than control (26.75 ml/h; 16th h). Higher cumulative H₂ production and maximum substrate degradation were also noticed with BEH-pretreated substrate (CHP, 0.91 l; COD, 52.42%) than control (CHP, 0.68 l; COD, 43.68%). Under closed circuitry, anode served as an alternative electron acceptor promoting biotransformation of complex organics to simpler molecules through catabolism.     

Geochemistry of thermal springs around Lake Abhe,Western Djibouti

The Republic of Djibouti, occupying an area of 23,180 km², falls within the arid zone of East Africa and is located above the ‘Horn of Africa’, adjacent to the Red Sea. This country has several thermal springs and fumaroles distributed over three regions – Lake Assal, Lake Hanle and Lake Abhe. The most characteristic feature of Lake Abhe is the presence of several linear chains of travertine chimneys. The thermal waters are typical of the Na-Cl type near neutral waters rich in CO₂. These waters show an oxygen shift, indicating reservoir temperatures>200°C. The chemical signature of the thermal springs and the geology of the Lake Abhe region are very similar to the Tendaho geothermal area of Ethiopia. The geology, temperature gradient and its proximity to Damah Ale volcano make the Lake Abhe region a potential site for geothermal power development.     

High-gain mode-adapted semiconductor optical amplifier with12.4-dBm saturation output power at 1550 nm

A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB ± 1.3 dB and a saturation output power of 12.4 dBm ± 0.4 dBm are typical at a bias of 500 mA for λ = 1550 nm. Polarization sensitivity at 1550 nm was measured to be 1.1 dB ± 0.4 dB and the transverse electric (TE) polarization state noise figure (NF) was determined to be 7.0 dB ± 0.5 dB. The coupling loss was 1.3 dB ± 0.1 dB per facet. This SOA, with a 1.3-nm filter, was used as an optical preamplifier in a 10-Gb/s return-to-zero (RZ) system testbed with a pseudorandom binary sequence (PRBS) of 2³¹ -1. A 14.5-dB improvement in receiver sensitivity was observed at a bit error rate (BER) of 10^-11     

Impact of filtering on RZ-DPSK reception

We discuss the influence of optical and electrical filtering on the performance of beat-noise limited balanced and single-ended direct detection of return-to-zero differential phase-shift keying (DPSK). Our simulations, supported by 40-Gb/s measurements, show that balanced DPSK detection outperforms both its single-ended equivalent and ON-OFF keying by /spl sim/2.7 dB, with higher gains at narrower optical filter bandwidths.     

Performance of MLSE Receiver in a Dispersion-Managed Multispan Experiment at 10.7 Gb/s Under Nonlinear Transmission

We report the first comparison of the performance of a maximum likelihood sequence estimation (MLSE) receiver with that of a standard threshold receiver in a dispersion-managed eight-span transmission experiment at 10.7 Gb/s in the presence of fiber nonlinearities. We find a loss of performance advantage of the MLSE receiver for compensating fiber chromatic dispersion under highly nonlinear transmission conditions     

Determination of Alkyl‐Donor Promiscuity of Tyrosine‐O‐Prenyltransferase SirD from Leptosphaeria maculans

Natural product prenyltransferases are known to display relaxed acceptor substrate specificity. Although recent studies with a small set of unnatural alkyl donors have revealed that prenyltransferases are flexible with regard to their alkyl donors, the scope of their alkyl donor specificity remains poorly understood. Towards this goal, we report the synthesis of 20 unnatural alkyl pyrophosphate donors and an assessment of the reactions of these synthetic unnatural alkyl pyrophosphate analogues catalyzed by tyrosine O‐prenyltransferase SirD. This study demonstrates that SirD can utilize 16 out of 21 alkyl pyrophosphate analogues (including the natural donor) in catalyzing mostly O‐alkylation of l ‐tyrosine. This study reveals the broad alkyl donor specificity of SirD and opens the door for the interrogation of the alkyl donor specificity of other prenyltransferases for potential utility as biocatalysts for differential alkylation applications.     

Design of low noise pHEMT amplifier for mobile satellite receiver using ANN technique

On May 26, 2011 Mitsubishi Electric Corporation released its GaN HEMT power amplifier for C-band satellite communication, which offers a power-added efficiency (PAE) of 67%. Frequency and bias dependence of scattering parameters of microwave transistors can be successfully modeled by artificial neural networks (ANN). Dependence of angle of a scattering parameter may result in inappropriate modeling accuracy in the vicinity of the frequency, when sharp changes occur. In this paper we are discussing pre-processing of the training data in order to make modeling accuracy better. The proposed approach is illustrated by a suitable example. By doing so we are proposing to design an onboard low noise Amplifier for Mobile Satellite Receiver.     

ANN modeling for design of a matched low noise pHEMT amplifier for mobile application

For high quality performance, future efficient wireless communication systems require a Broadband Amplifier in the frequency range under consideration. When such an amplifier is plugged into the measuring path it would enable the system to perceive even the weakest of signals. To achieve this, a new Scattering-parameter model that is valid for a wide frequency range has been developed for microwave analysis of a pseudomorphic high electron mobility transistors (pHEMT). The developed neural network model is used for designing a pHEMT power amplifier. The calculated S-parameters, gain and minimum noise figure from the artificial neural networks (ANN) model are the parameters used to design the low noise pHEMT power amplifier. The various gains so obtained from the S-parameters have been plotted with the frequency and it was found to yield a close fit to the simulated model. Neural network training has been done using Levenberg-Marqaurdt back propagation algorithm implemented in ANN toolbox of MATLAB software. All the results have been compared with the experimental data that showed a close agreement and validated our model. The calculated S-parameters, gain and minimum noise figure from the ANN model are the parameters used to design a stabilized and matched LNA.     

An improved synthesis of lysosomal activated mustard prodrug for tumor-specific activation and its cytotoxic evaluation

Cyclophosphamide, an alkylating agent widely used as anticancer agent, biotransformed in vivo to unstable phosphoramidic mustard and acrolein, where the latter metabolite has been found responsible for hemorrhagic cystitis and renal toxicity. Being one of the most popular strategies to avoid these deleterious effects, prodrug design has been attempted, which can, in addition, enable selective drug targeting. Our efforts to design, synthesize and evaluate the enzymatically activated prodrug phosphorodiamidic mustard as potential candidate for selective chemotherapy in antibody-directed enzyme prodrug therapy or prodrug monotherapy strategies are described. We propose an improved synthesis of prodrug 14, consisting of a galactose moiety, a spacer and a cytotoxic drug and its cytotoxicity has been investigated. The prodrug 14 has been found to be nontoxic (in vitro) which could be a valuable candidate for further development.