High-gain SiGe transimpedance amplifier array for a 12/spl times/10 Gb/s parallel optical-fiber link

A transimpedance amplifier array for 12 parallel optical-fiber channels each operating at 10 Gb/s is presented, which is used in the receiver of short-distance links. It stands out for the following features: high gain (transimpedance 25 k/spl Omega/ in the limiting mode), high input sensitivity and wide input dynamic range (input current swing from 20 to 240 /spl mu/A/sub p-p/), constant output voltage swing (differential 0.5 V/sub p-p/ at 50 /spl Omega/ load), and low power consumption (1.4 W) at a single supply voltage (5 V). Each channel has its own offset-current control circuit. To the best of the authors' knowledge, the total throughput of 12/spl times/10 Gb/s=120 Gb/s is the highest value reported for a single-chip amplifier array. The target specifications have been achieved with the first technological run without needing any redesign. This fact demonstrates that the inherent severe crosstalk problems of such high-gain amplifier arrays can reliably be solved by applying adequate decoupling measures and simulation tools.     

A Trend to the Production of Calcium Hydroxide and Precipitated Calcium Carbonate with Defined Properties

In this paper, production of precipitated calcium carbonate (PCC) with required particle size and morphological structure, along with its dependence on technological parameters and the properties of Ca(OH)₂, is discussed. The effect of the reaction environment on the kinetics of CaO hydration and the formation of crystals in water suspension was established. A remarkable difference in the system's restoration ability after stirring was observed. The hydration process is initially controlled by a kinetic mechanism, followed by a diffusion‐controlled process. The dissolution speed of lime hydrated to suspension is eight times higher than that of lime hydrated to powder. Particles of hydrated lime appeared in various forms.     

Structure-based discovery of allosteric modulators of two related class B G-protein-coupled receptors

Despite the availability of X-ray crystal structure data for several members of the G-protein-coupled receptor (GPCR) superfamily, structure-based discovery of GPCR ligands has been exclusively restricted to class A (rhodopsin-like) receptors. Herein we report the identification, by a docking-based virtual screening approach, of noncompetitive ligands for two related class B (secretin-like) GPCRs: the glucagon receptor (GLR) and the glucagon-like peptide 1 receptor (GLP-1R). Starting from a knowledge-based three-dimensional model of the GLR, a database of 1.9 million commercially available drug-like compounds was screened for chemical similarity to existing GLR noncompetitive antagonists and docked to the transmembrane cavity of the GLR; 23 compounds were then selected based on protein-ligand interaction fingerprints, and were then purchased and evaluated for in vitro binding to GLR and modulation of glucagon-induced cAMP release. Two of the 23 compounds inhibited the effect of glucagon in a dose-dependent manner, with one inhibitor exhibiting the same potency as L-168 049, a reference noncompetitive GLR antagonist, in a whole-cell-based functional assay. Interestingly, one virtual hit that was inactive at the GLR was shown to bind to GLP-1R and potentiate the response to the endogenous GLP-1 ligand.     

Elaboration of Ultra‐High Molecular Weight Polyethylene/Carbon Nanotubes Electrospun Composite Fibers

Micron‐sized fibers of UHMWPE reinforced with CNT were fabricated by the electrospinning process. Conditions for a metastable mutual solution of UHMWPE and CNTs were found at elevated temperature. These solutions were used for electrospining using a device having controlled temperature and gaseous environment around the electrospun liquid jet. The fabricated micron‐sized fibers exhibited the reinforcing CNTs as self‐organized nano‐ropes embedded within them. A post‐spinning drawing process enhanced the mechanical properties of the composite fibers to the level of 6.6 GPa strength and elongation at break of 6%. The CNT nano‐ropes form spontaneously in the liquid jet during electrospinning, and provide the reinforcement framework which is amenable for post‐drawing of the fibers for subsequent utilization as composite nanofibers. The experimental results exhibit the highest strength value reported to date for electrospun fibers.

     

Comparison of Mass Transfer Efficiency and Energy Consumption in Static Mixers

The aim of this study was to compare the pressure drop (Δp) generated by a static mixer with sieve plates in two-phase downflow (water as a continuous phase), and the mass transfer efficiency (k_La, a) with the performance of other static mixers (Sulzer, Kenics, Karman, etc.). The relationships for Δp, k_La and interfacial area (a) calculation depending on liquid and gas phase velocities and geometry of the plates (sieves) in this static mixer are presented. k_La was found to be strictly proportional to the power consumption (P/V) and its values were quite close to those obtained in Sulzer & Kenics mixers with an 8-element mesh. Enhancement factors for oxygen absorption in the sodium sulphite solution and for ozone absorption in Lake Ülemiste water were calculated and the plausible values of the interfacial area (a) were estimated.     

SiGe driver circuit with high output amplitude operating up to 23Gb/s

A high-speed driver circuit is presented with special regard to layout aspects. The IC, which was fabricated in an advanced SiGe bipolar technology, was developed for driving external modulators in a 20 Gb/s fiber-optic time division multiplex transmission system but can also be used as an output stage of multipurpose pulse generators. Measurements on mounted chips show clear eye diagrams up to 23 Gb/s data rate and high single-ended and differential output swings of 3.5 and 7 V_p-p , respectively, at 50 Ω external load. To the best of the authors' knowledge, this is the highest voltage swing reported so far for a silicon-based driver circuit at comparable operating speed     

Ultrasonically induced degradation of microcystin-LR and -RR: identification of products, effect of pH, formation and destruction of peroxides

Microcystins (MCs) are a family of toxic peptides produced by a number of cyanobacteria commonly found in lakes, water reservoirs, and recreational facilities. The increased eutrophication of freshwater supplies has led to an increase in the incidence of cyanobacterial harmful algal blooms and concerns over the public health implications of these toxins in the water supply. Conventional water treatment methods are ineffective at removing low concentrations of cyanotoxins, hence specialized treatment is usually recommended for treatment of contaminated water. In this study, the products of ultrasonically induced degradation of microcystin-LR (MC-LR) and microcystin-RR (MC-RR) were analyzed by LC-MS to elucidate the probable pathways of degradation of these toxins. Results indicate preliminary products of sonolysis of MCs are due to the hydroxyl radical attack on the benzene ring and diene of the Adda peptide residue and cleavage of the Mdha-Ala peptide bond. The effect of pH on the toxin degradation was evaluated since the pH of the solution changes upon ultrasonic irradiation and varies with the water quality of treatable waters. The initial rate of MC-LR degradation is greater at acidic pH and coincides with the change in hydrophobic character of MC-LR as a function of pH. Hydrogen and organic peroxides are formed during ultrasonic irradiation, but can be eliminated by adding Fe(II). The addition of Fe(II) also accelerates the degradation of MC-LR, presumably by promoting the formation of hydroxyl radicals via conversion of ultrasonically produced H2O2. These findings suggest that sonolysis can effectively degrade MCs in drinking water.