Gain-clamping in two-stage L-band EDFA using an unwanted backward ase from second stage

A gain clamping technique for the long wavelength band erbium-doped fiber amplifier (L-band EDFA) is presented. It uses two circulators and a broad band fiber Bragg grating to route wasted backward C-band ASE from the second stage and launch it back into the input end of the first stage of a two-stage amplifier. The two-stage L-band EDFA has shown a small signal gain improvement of 5.7 dB compared to a single-stage amplifier with a slight noise figure degradation. By utilizing the wasted backward ASE, a L-band gain-clamped EDFA with high gain can be realized. Compared to the unclamped case, this gain-clamping technique is effective in reducing the total gain variation as small as 0.3 dB.     

Electrical properties of plasticized chitosan-lithium imide with oleic acid-based polymer electrolytes for lithium rechargeable batteries

Solid polymer electrolytes (SPEs) were prepared and their electrochemical characteristics were characterized. The composition of SPEs containing chitosan, lithium trifluoromethane sulfonimide (LiN(CF₃SO₂)₂) and oleic acid (OA) was optimized employing ac impedance measurements at various temperatures. The electrical conductivity of the SPEs with OA shows the highest value and the presence of OA does not change the structure of the polymer. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Synthesis,Characterization, and in vitro Cytotoxicity of Gold(I) Complexes of 2‐(Diphenylphosphanyl)ethylamine and Dithiocarbamates

Gold(I) complexes of 2‐(diphenylphosphanyl)ethylamine or (2‐aminoethyl)diphenylphosphine (AEP), and dithiocaarbamates (R₂NCS₂) were prepared by the reaction of these ligands with (CH₃)₂S‐AuCl in dichloromethane. The synthesized complexes [Au(AEP)Cl] ( 1 ), [Au(AEP)₂]Cl ( 2 ), and [Au₂(R₂NCS₂)₂]_n (R₂ = dimethyl ( 3 ), diethyl ( 4 ), and dibenzyl ( 5 )) were characterized by elemental analysis, IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The complexes were evaluated for anticancer activity against three cancer cells, A549 (human lung carcinoma), HCT15 (human colon cancer), and MCF7 (human breast cancer) cell lines. Three of the five tested complexes showed significant in vitro cytotoxicity and for A549, the inhibition effect of three compounds is greater than cisplatin.     

Nanocatalysts for Solar Water Splitting and a Perspective on Hydrogen Economy

In this review article, nanocatalysts for solar hydrogen production are the focus of discussion as they can contribute to the development of sustainable hydrogen production in order to meet future energy demands. Achieving this task is subject of scientific aspirations in the field of photo‐ and photoelectrocatalysis for solar water splitting where systems of single catalysts or tandem configurations are being investigated. In search of a suitable catalyst, a number of crucial parameters are laid out which need to be considered for material design, in particular for nanostructured materials that provide exceptional physical and chemical properties in comparison to their bulk counterparts. Apart from synthetic approaches for nanocatalysts, key parameters and properties of nanostructured photocatalysts such as light absorption, charge carrier generation, charge transport, separation and recombination, and other events that affect nanoscale catalysts are discussed. To provide a deeper understanding of these key parameters and properties, their contribution towards existing catalyst systems is evaluated for photo‐ and photoelectrocatalytic solar hydrogen evolution. Finally, an insight into hydrogen production processes is given, stressing the current development of sustainable hydrogen sources and presenting a perspective towards a hydrogen‐based economy.     

On the Convergence of Bernstein-Stancu Polynomials in the Variation Seminorm

This article studies the variation detracting property and rate of approximation of the Bernstein-Stancu polynomials in the space of functions of bounded variation with respect to the variation seminorm. Moreover, we will present Voronovskaya-type theorems for Bernstein-Stancu polynomials B_{n, α, β}f and for the first derivative of these polynomials. Finally we include some graphical examples.     

Sol–gel synthesis and characterization of Li<Subscript>2</Subscript>CO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite solid electrolytes

Composite solid electrolytes in the system (1???x)Li₂CO₃–xAl₂O₃, with x?=?0.0–0.5 (mole), were synthesized by a sol–gel method. The synthesis carried out at low temperature resulted in voluminous and fluffy products. The obtained materials were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy/energy-dispersive X-ray, Fourier transform infrared spectroscopy and AC impedance spectroscopy. Structural analysis of the samples showed an amorphous feature of Li₂CO₃ and traces of α-LiAlO₂, γ-LiAlO₂ and LiAl₅O₈. The prepared composite samples possess high ionic conductivities at 130–180 °C on account of the presence of lithium aluminates as well as the formation of a high concentration of an amorphous phase of Li₂CO₃ via this sol–gel preparative technique.     

Influence of Composition of Nickel-Iron Nanoparticles for Abiotic CO2 Conversion to Early Prebiotic Organics

Abiotic synthesis of formate and short hydrocarbons takes place in serpentinizing vents where some members of vent microbial communities live on abiotic formate as their main carbon source. To better understand the catalytic properties of Ni−Fe minerals that naturally exist in hydrothermal vents, we have investigated the ability of synthetic Ni−Fe based nanoparticular solids to catalyze the H₂-dependent reduction of CO₂, the first step required for the beginning of pre-biotic chemistry. Mono and bimetallic Ni−Fe nanoparticles with varied Ni-to-Fe ratios transform CO₂ and H₂ into intermediates and products of the acetyl-coenzyme A pathway—formate, acetate, and pyruvate—in mM range under mild hydrothermal conditions. Furthermore, Ni−Fe catalysts converted CO₂ to similar products without molecular H₂ by using water as a hydrogen source. Both CO₂ chemisorption analysis and post-reaction characterization of materials indicate that Ni and Fe metals play complementary roles for CO₂ fixation.     

Heterogeneous Membrane and Coated Wire Type Electrode with Chitosan as Ionophore in the Potentiometric Determination of Glutamate: Comparative Study

This study reports on two types of glutamate sensors based on chitosan, i) heterogeneous membrane and ii) coated wire (CWE). The linearity ranges are: i) membrane, 1.0×10^?5 to 1.0×10^?1 M and ii) CWE, 1.0×10^?5 to 1.0×10^?3 M. The LODs, and pH ranges are i) membrane, 5.0×10^?6 M and 4–8 and ii) CWE, 1.0×10^?5 M and 3–5, respectively. The presence of ionic species normally found in foodstuffs did not interfere in both electrodes. Interference in CWE was minimized by prior dilution of the sample. The CWE was further investigated for on‐line analysis. The material for proposed electrodes was cheaper and environmental friendly. Hence, they were suggested as alternative tools for the analysis of glutamate.     

Development of Prototype Wireless Transmission Measurement for Glucose in Subcutaneous and Brain Striatum

Monitoring of glucose in subcutaneous and brain striatum have been extensively studied in the past. While biocompatibility was one of the limitations, others included the messy measuring equipments preclude monitoring in a complex environment. This study tried to establish an amperometric measurement of glucose in pre‐ and post‐insulin‐administration on diabetic and hyperglycemia rats via wireless. The results have indicated that the wireless sensing kit used was capable of monitoring glucose in both subcutaneous and brain. The physiological data have also shown a new insight on the fabrication of implantable glucose sensors.     

Principles of Water Electrolysis and Recent Progress in Cobalt-, Nickel-, and Iron-Based Oxides for the Oxygen Evolution Reaction

Water electrolysis that results in green hydrogen is the key process towards a circular economy. The supply of sustainable electricity and availability of oxygen evolution reaction (OER) electrocatalysts are the main bottlenecks of the process for large-scale production of green hydrogen. A broad range of OER electrocatalysts have been explored to decrease the overpotential and boost the kinetics of this sluggish half-reaction. Co-, Ni-, and Fe-based catalysts have been considered to be potential candidates to replace noble metals due to their tunable 3d electron configuration and spin state, versatility in terms of crystal and electronic structures, as well as abundance in nature. This Review provides some basic principles of water electrolysis, key aspects of OER, and significant criteria for the development of the catalysts. It provides also some insights on recent advances of Co-, Ni-, and Fe-based oxides and a brief perspective on green hydrogen production and the challenges of water electrolysis.