InP-HBT chip-set for 40-Gb/s fiber optical communication systemsoperational at 3 V

A chip set for a 40 Gb/s fiber optical communication system has been designed and fabricated. On-wafer measurements have been performed to verify circuit operations. As far as available measurement capabilities show, all circuits are functionally fulfilling specifications for 10 Gb/s operation at less than or equal to 3 V supply voltage. During the design phase especially the influence of interconnects on signal integrity was investigated and the results were implemented for automatic extraction. All the circuits were operational after the first processing round. No redesign was necessary     

Electron spin resonance of impurities in magnetic insulators

It is possible to observe and very useful to study the electron spin resonance of impurities in paramagnetic hosts. Among the interesting phenomena observable and measurable in these studies are: (a) symmetric and antisymmetric exchange interactions between the impurities and the hosts determined from the indirect superhyperfine interactions, pseudo-Zeeman interactions and pseudo crystal field effects, (b) the Jahn-Teller induced random strains effects resulting in the magnetic field dependence of the fine structure linewidths, and (c) the nature of the dynamical interactions of the hosts manifested in the lifetime broadenings of the impurity spectra.     

Planar waveguide model for calculating microstrip components

A planar waveguide model with a frequency-dependent effective relative permittivity and a frequency-dependent effective width is developed for the open microstrip line. The validity of this waveguide model is shown by experimental results from measurements with a resonator and a sliding-load technique.     

Optical detectors on GaSe and InSe layered crystals

Fast uncooled GaSe and InSe detectors that can record ultrashort (10^?12–10^?9 s) laser pulses in the visual and near-IR ranges are developed. The quick response of the detectors is due to rapid recombination channels with a high capture cross section present in the crystals.     

Visualization of different pathways of DNA release from interpolyelectrolyte complex

The release of double-stranded DNA from its interpolyelectrolyte complex with positively charged poly(allylamine hydrochloride) via exchange reaction with added polyanion, poly(sodium styrenesulfonate), is directly observed by fluorescence microscopy. It is shown that the pathways of DNA release depend essentially on the amount of added low-molecular-weight salt. At low salt content, the DNA release proceeds via the formation of an intermediate "beads-on-string" structure, whereas at high salt content the release goes directly from globule to coil states without any intermediate structures. The reasons for different character of DNA release are discussed.     

Separation,pre-concentration and determination of trace amounts of lead(II) ions in environmental samples using two functionalised nanoporous silica gels containing a dipyridyl sub-unit

In this study, two functionalised nanoporous silica gels containing dipyridyl sub-unit (SiL1 and SiL2) as selective solid-phase extraction materials for separation, pre-concentration and determination of trace levels of Pb(II) ions by inductively coupled plasma optical emission spectroscopy (ICP-OES) was investigated. The experimental parameters including pH, amounts and type of sorbent, sample volume, eluent type and interfering ions on the recovery of the target analytes were investigated, and the optimal experimental conditions were established. Under the optimised operating conditions with the SiL2 as sorbent, an enrichment factor of 300 was obtained. The detection limit based on three times standard deviations of the blanks was 150 ng L^–1. The proposed method was applied to the determination of lead in natural and wastewater samples with satisfactory results (recoveries greater than 96.5%, RSDs lower than 5.0%).     

脂肪胺水溶液吸收CO2的热力学参数的密度泛函理论研究

采用密度泛函理论研究CO₂在脂肪胺水溶液热力学参数．研究的脂肪胺包括烷基胺、链烷醇胺、二胺以及氨基酰胺．在B3LYP/6-311+ G(d,p)水平计算脂肪胺在CO₂气相中的振动频率．通过连续介质模型在HF/6-31G(d)水平计算了溶剂几何优化的标准自由能,评价了CO₂吸收到脂肪胺水溶液过程有关的两个重要参数：酸解离常数和标准焓变二者之间大致呈线性关系．随着胺碱度的提高,CO₂吸收过程释放的热量增加,则胺再生所需的能量增加．     

Description of phenomenological process during thermal formation of an epoxy system in presence of metal nanoparticles using advanced kinetics analysis

The curing process of diglycidyl ether of bisphenol A (DGEBA)–isophoronediamine (IPDA) system filled with different contents of Fe nanoparticles (nano-Fe) has been investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy analysis in order to understand the effect of nano-Fe. These studies revealed that high percentage of the nanofiller, i.e. 10 %, results in improved epoxy matrix as evidenced by increasing in the reaction heat and conversion degree. Kinetics of DGEBA/IPDA/10 % nano-Fe cure was studied by calorimetry measurements at isothermal mode. Isothermal kinetic parameters, including k ₁, k ₂, m, and n were determined and it was shown that the reaction kinetics could be expressed well by dα/dt = (k ₁ + k ₂ α ^m)(1?α)ⁿ which called Kamal model. The results also showed that the diffusion control does not occur. The excellent fitting Kamal model with experimental data at the end of the isothermal cure process could be mentioned as evidences here. The dispersion of 10 % nano-Fe into epoxy matrix was analyzed by atomic force microscopy observations.     

Determination of lewisite metabolite 2-chlorovinylarsonous acid in urine by use of dispersive derivatization liquid-liquid microextraction followed by gas chromatography–mass spectrometry

The purpose of this study was to develop a sensitive and simple method, based on dispersive derivatization liquid-liquid microextraction–gas chromatography–mass spectrometry (DDLLME–GC–MS) in scanning and selected-ion-monitoring (SIM) modes, for detection of 2-chlorovinylarsonous acid (CVAA) as a hydrolysis product and urinary metabolite of lewisite in urine samples. Chloroform (65 μL), methanol (500 μL), and ethanedithiol (10 μL) were used as extraction solvent, dispersive solvent, and derivatizing reagent, respectively. Critical conditions of the proposed method were optimized. The nucleophilic reactions of dithiol and monothiol compounds with CVAA were also studied using a competitive method. In view of the high affinity of trivalent arsenic for sulfhydryl groups, the interaction between CVAA and bis(2-chlorovinyl)arsonous acid (BCVAA) and free cysteine (Cys) was also investigated using liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS). The interference of Cys, present in human urine, with the detection of CVAA was evaluated using dithiol and monothiol chemicals as derivatization agents. The developed method provided a preconcentration factor of 250, and limits of detection of 0.015 and 0.30 μg L^?1 in SIM and scanning modes, respectively. The calibration curves were linear over the concentration range of 1–400 μg L^?1 in full-scan mode. The relative standard deviation (RSD) values were calculated to be 5.5 and 3.2 % at concentrations of 20 and 100 μg L^?1, respectively. Collision-induced dissociation studies of the major electron-impact (EI) ions were performed to confirm the proposed fragment structure of CVAA-dithiols derivatives. Results indicated that the developed method for analysis of CVAA is suitable not only for verification of human exposure to lewisite, but also for quantification of CVAA in urine samples.