A Critique and an Appraisal of VLSI Models of Computation

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / N00014-79-C-0424National Science Foundation / MCS-81-0555

On the Chemical Origin of the Gap Bowing in (GaAs)1−xGe2x Alloys: A Combined DFT–QSGW Study

Motivated by the research and analysis of new materials for photovoltaics and by the possibility of tailoring their optical properties for improved solar energy conversion, we have focused our attention on the (GaAs)1−xGe2x series of alloys. We have investigated the structural properties of some (GaAs)1−xGe2x compounds within the local-density approximation to density-functional theory, and their optical properties within the Quasiparticle Self-consistent GW approximation. The QSGW results confirm the experimental evidence of asymmetric bandgap bowing. It is explained in terms of violations of the octet rule, as well as in terms of the order–disorder phase transition

Dilute magnetic semiconductor of ZnCoSe thin films: Structural, optical, and magnetic characteristics

A series of Zn1−xCoxSe (x = 0, 0.025, 0.050, 0.075, and 0.100) films using were evaporated (thickness of 1 μm) using electron beam gun. The effect of Co doping on the structural, optical, and magnetic properties has been investigated. X‐ray diffraction studies confirm formation of zinc blend structure for all Zn1−xCoxSe films. The crystallite size increases and the lattice strain decreases with the increase in Co content. The elemental constituents were characterized by energy dispersive X‐ray. Optical studies showed an increase in refractive index and a decrease in energy gap with the increase in the cobalt doping. The dispersion of the refractive index has been analyzed in terms of the Wemple‐DiDomenico single oscillator model. The oscillator parameters including the single oscillator energy (Eo), the dispersion energy (Ed), and the static refractive index (n0) were estimated. Magnetization measurements via vibrating sample magnetometer showed a hysteresis loop and confirmed room‐temperature ferromagnetism in Co‐doped ZnSe films

Analytical modelling and analysis of thermal behavior for series resistance of solar cell

In this paper, the analysis of the nonlinear and complex modelling of a solar cell is addressed, to study its thermal behaviour. From literature it is well known that the output power of a solar cell monotonically decreases with the temperature; here, we investigate the specific expression based on derivation of current and power to simplify the equation model. Thus, applying the specific expression of the series resistance, we analyze the relation characteristics between the power and the temperature. Moreover, we aim to present a method to determine the specific theoretical expression of the series resistance with combination of parallel parasitic resistances. The analytical model equation is tested and compared with experimental results to add validity to the model

Phenotyping of N-acetyltransferase type 2 and xanthine oxidase with caffeine: when should urine samples be collected?

OBJECTIVES: Individual activities of N-acetyltransferase 2 (NAT2) and of xanthine oxidase (XO) can be assessed using ratios of urinary caffeine metabolites. We investigated how ratios changed over time and which urine collection interval would be the best for NAT2 and XO activity assessments. METHODS: On two occasions separated by 14 days, 16 healthy male Caucasians collected urine before and 0-2, 2-4, 4-6, 6-8, 8-12, 12-16 and 16-24 h after a dose of 150 mg caffeine given in the framework of a phenotyping cocktail study. The metabolites 5-acetylamino-6-formylamino-3-methyluracil (AFMU), 5-acetylamino-6-amino-3-methyluracil (AAMU), 1-methylxanthine (1X), and 1-methylurate (1U) were quantified with LC-MS/MS. The molar ratio (AFMU + AAMU)/(1X + 1U + AFMU + AAMU) was used as a NAT2 metric, while the ratio 1U/(1X + 1U) served as XO metric. RESULTS: The NAT2 ratios were stable in the intervals 4-24 h after caffeine dosing. Mean intra-individual coefficients of variation were 11-23% starting 4 h post-dose, while inter-individual variability reached 37-75%. The XO ratios increased gradually by 14% from the 2-4 to the 16-24 h interval. The mean intra- and inter-individual coefficients of variation of XO activity were 3-18 and 7-10% respectively. No significant differences between study occasions were observed. CONCLUSIONS: Any sampling interval at least 4 h after caffeine dosing is suitable for NAT2 and XO activity assessments. XO activities can only be compared between volunteers and studies if the same urine collection schedule has been respected. The low intraindividual variability allows for sample sizes of 16 and 6 participants in crossover interaction studies of NAT2 and XO activity respectively