Quaternary n-Al0.08In0.08Ga0.84N/p-Si-based solar cell

Quaternary n-type Al_0.08In_0.08Ga_0.84N grown on p-Si using molecular beam epitaxy technique was fabricated as a pn-junction and an anti-reflection coating (ARC) of solar cells. The structural properties and surface morphology of the solar cells were investigated using scanning electron and atomic force microscopy. Optical reflectance was obtained using an optical reflectometery system (Filmetric F20-VIS). Current–voltage characteristics were examined under 100 mW cm^?2 illumination conditions. Quaternary n-type Al_0.08In_0.08Ga_0.84N coating was found to be an excellent ARC against incident light compared with other ARCs. This material also exhibited good light trapping over a wide wavelength spectrum, which produced highly efficient solar cells. The unique and strong polarization, as well as the piezoelectric effect, of the quaternary-nitrides was employed to reduce surface recombination velocities and enhance the solar cell performance. A solar cell with reasonable conversion efficiency of 9.74% was obtained when the n-Al_0.08In_0.08Ga_0.84N/p-Si was employed.     

Charge transfer complexes of some anilides with nitrobenzene derivatives as pi-electron acceptors

The charge transfer complexes formed between some anilides and pi-electron acceptors [picric acid, 2,4-dinitrophenol, 3,5-dinitrobenzoic aicd, 3,5-dinitrosalicylic acid and m-dinitrobenzene] are synthesized and characterized. Spectral characteristics and stability of the complexes are investigated and discussed in terms of donor molecular structure, pi-acceptor electron affinity, and solvent polarity. It is deduced that the complexes are mainly of the n-pi* and pi-pi* type where the ground state wave function can be described primarily by the non-bonding structure. The optimum conditions favouring the formation of the coloured complexes are extensively studied for the microdetermina-tion of anilides derivatives in pharmaceutical drugs using nitrobenzene as acceptor; the molecular structure was found to be 1:1 (D:A). Beer's law is obeyed up to 23.0, 18.60 and 16.0 micrograms ml-1 for p(OH), p-(OCH3), and p-N(CH3)2, respectively.     

Spectrophotometric microdetermination of phenylephrine hydrochloride in pure and in pharmaceutical formulations using haematoxylin

A simple, rapid, selective and sensitive method for the micro amount determination of phenylephrine hydrochloride either in pure form (raw material) or in pharmaceutical formulations is described. The method is based on the development of violet colour charge transfer complex with haematoxylin in alkaline medium with 10 min after heating at 65 °C. The wavelength and maximum absorption range was found in the range from 640 to 620 nm. Molar absorptivity and Sandell sensitivity were found to be 2.38 × 10⁴ L mol^− 1 cm^− 1 and 8.6 ng cm^− 2 respectively. A linear correlation was found between absorbance (at the λ_max) and concentration. The resulting colour is stable for more than 10 h. Results of the analyses of pure drug and dosage forms by the proposed method are in good agreement with those of the official BP 1998 procedure.     

Dielectric relaxation spectroscopy of heteronuclear cobalt(II)-copper(II) complex of 1-phenyl-3-methyl-5-pyrazolone

A bright green CoCu(PMP)(OH)2(H2O)2 complex was synthesized. Its structure was elucidated and characterized by different spectroscopic techniques. Both cobalt and copper atoms attain tetrahedral geometry. The complex was investigated by the dielectric relaxation spectroscopy. The dielectric parameters are discussed in terms of temperature and frequency changes. The conductivity of the complex decreased as the temperature increased in the temperature range 30-100 degrees C, while above this temperature range stepwise increase in the conductivity was observed.     

On the Number of Trace-One Elements in Polynomial Bases for \mathbb{F}_{2^n}

This paper investigates the number of trace-one elements in a polynomial basis for . A polynomial basis with a small number of trace-one elements is desirable because it results in an efficient and low cost implementation of the trace function. We focus on the case where the reduction polynomial is a trinomial or a pentanomial, in which case field multiplication can also be efficiently implemented. Communicated by: P. Wild     

Sound absorption by wood in relation to anatomical and mechanical properties

The results of basic research on sound absorption by transverse and longitudinal sections of four Egyptian woods are presented. The amount of sound absorption was determined by laboratory experiments with wood samples in a standing wave apparatus. The specific gravity, maximum crushing strength and hardness of tested samples were also determined in order to study the relationship between wood absorption of sound and its mechanical properties. Cross-sections of the wood samples were also microscopically tested. The results are discussed in terms of two basic mechanisms of sound absorption—the flow resistance and mechanical hysterisis. The results show that sound absorption measurements have potential both as a non-destructive test and for the evaluation of the mechanical properties of woods.     

Two novel long-chain alkanoic acid esters of lupeol from alecrim-propolis

Two new long-chain alkanoic acid esters of lupeol were isolated together with known triterpenoids, alpha-amyrin, beta-amyrin, cycloartenol, lanosta-7,24-diene-3beta-ol and lupeol from Alecrim-propolis collected in Brazil. The structures were characterized by spectroscopic means.     

Statistical analysis of HDPE fatigue lifetime

Fatigue lifetime of HDPE structures such as pipes is recognized to show a large scatter. This study aims to compare different statistical methods and distributions, in order to give convenient modeling of tensile and fatigue test results of commercially available polyethylene compression molded sheets. The median rank, the maximum likelihood and the Kolmogorov-Smirnov fitting are compared for the estimation of Weibull parameters. The choice of the best distribution to fit fatigue lifetime is discussed on the basis of the goodness-of-fit results. It is found that whether the three-parameter distributions of Weibull and lognormal types are suitable for lifetime prediction, the two-parameter Weibull is more conservative for probabilistic fatigue design.     

Colorimetric Estimation of Melatonin in Pharmaceutical Formulations

 Three simple and sensitive colorimetric methods (A–C) for the determination of melatonin in bulk samples and in pharmaceutical formulations are described. They are based on the formation of coloured species by reaction of ninhydrin with the drug (method A, λ_max 397 nm) by oxidation of the indol moiety in melatonin with potassium persulphate (method B, λ_max 450 nm) or by reduction of osmium (VIII) (method C, λ_max 516 nm). Regression analysis of Beer-Lambert plots showed good correlations in concentration ranges between 0.8–14.2, 70.0–140.0 and 2.0–40.0 μg/mL for methods A, B and C, respectively. The molar absorptivity, Sandell sensitivity and detection limit were calculated. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing melatonin. The relative standard deviations were ≤ 0.95% with recoveries 99.0–101.33%. Received October 20, 1999. Revision February 10, 1999.     

Application of Secondary Amines in the Synthesis of Some New Spiro Heterocyclic Compounds

1-Anilinocycloalkanecarbonitriles 1a–c were prepared and reacted with active methylene reagents to give compounds 5a–c through 10a–c and reacted with different other reagents such as benzaldehyde, ethyl aminoacetate, ethyl mercaptoacetate, or hydrazine carbothioamide, which afforded the desired spiro heterocycles compounds 11a–c through 14a–c.