Current status and future prospects for the PVMaT project

The goals of the Photovoltaic Manufacturing Technology project (PVMaT) are to help the US PV industry improve photovoltaic manufacturing processes and accelerate cost reductions for PV components and systems. PVMaT is in its ninth year of implementation, and subcontracts with industry have been completed from four solicitations for R&D on manufacturing process problems. We are in the second year of subcontracts for a fifth PVMaT solicitation.Based on the latest (1998) data from ten PVMaT industrial participants, the average direct manufacturing cost for these producers has been reduced by 29% – from $4.08 to $2.91 per peak watt since 1992 – and there has also been a more than five-fold increase in manufacturing capacity – from 13.1 to 73.3 MW. We believe R&D on manufacturing processes contributes significantly to expeditious reductions in PV manufacturing costs, and we identify areas for future R&D.     

Allan variances and spectral densities for DC voltage measurements with polarity reversals

Using a polarity reversal technique, precise dc voltage measurements were made with both digital and analog voltmeters. The results were analyzed by calculating Allan variances and spectral densities for polarity-reversed measurements and comparing them with similar analyses of unreversed or unipolar measurements of the same processes. The Allan variances and spectra for the two measurement methods were found to agree quite well, particularly for sampling times corresponding to the 1/f noise regime for the measurement of Zener-diode voltages. The results show that polarity reversals do not affect 1/f noise of the Zeners. In polarity-reversed measurements, a rectangular voltage waveform is presented to the detector. Since this waveform can be synthesized by ac waveforms, the results also demonstrate that ac detection does not remove 1/f noise in the voltage source being measured. We also estimated the spectral density and Allan variance of some thermal (Johnson) noise processes and found that the results agree with the Nyquist expression to within 4%. This provides direct validation of our measurement and analysis methods.     

Two-fold efficiency increase by selective excitation of ions for consecutive activation by ion-electron reactions and vibrational excitation in tandem fourier transform ion cyclotron resonance mass spectrometry

A new technique called selective excitation of ions for consecutive activation (SEICA) is proposed for obtaining complementary fragmentation mass spectra from the same precursor ion population. SEICA utilizes precursor ions remaining intact after electron capture dissociation or another ion-electron reaction for efficient MS/MS based on a vibrational excitation (VE) technique, such as infrared multiphoton dissociation. SEICA uses the ability of ion-trapping instruments to detect product ions while retaining inside the trap intact precursor ions, making the latter available for consecutive activation by a VE technique. The possibility of practical implementation of SEICA by software-only modification of a commercial instrument is demonstrated. A 2-fold increase in the efficiency is achieved for both "single-scan" and "multiple-scan" experiments. This improvement can be particularly important for high-sensitivity applications in, for example, proteomics, where limited ECD efficiency poses an obstacle for broad implementation of this technique.     

Evaluation of optical properties of decorative coatings by spectroscopic ellipsometry

Some of the hard coatings (e.g. TiN, TiCN, TiCN, TiAlCN) occur in different colours. Using goniospectroscopy in the visible wavelength range colours are deduced by measuring the spectral reflectance factor R_λ. This factor depends on both the samples and the white reference as well as on the geometry of illumination and measurement. It is very difficult or even impossible to distinguish colours according to their origin and to relate them to bulk material composition, thin film coatings and interference layers by means of goniospectroscopy as unpolarized light is used. By using polarized light in spectroscopic ellipsometry these difficulties could be overcome as there is no reference to white and the geometric influences of illumination and measurement are negligible, but on the contrary the visual impression is not correctly described. From the measurement of the relative amplitude ratio tan Ψ and the relative phase shift cos Δ it is possible to calculate either the parallel and normal components R_p and R_s of the reflectivity R or the complex refractive index N = n + ik as well as the dielectric function = ₁ + i₂ which are strongly related to the electronic structure of the material used. It is shown that in this way it is possible to describe optical properties more physically, to separate interference effects and to detect changes in stoichiometry.     

High performance dual-MAC DSP architecture

The convergence of voice and video in next-generation wireless applications requires a processor that can efficiently implement a broad range of advanced third generation (3G) wireless algorithms. The micro signal architecture (MSA) core is a dual-MAC modified Harvard architecture that has been designed to have good performance on both voice and video algorithms. In addition, some of the best features and simplicity of microcontrollers has been incorporated into the MSA core. This article presents an overview of the MSA architecture, key engineering issues and their solutions, and details associated with the first implementation of the core. The utility of the MSA architecture for practical 3G wireless applications is illustrated with several application examples and performance benchmarks for typical DSP and image/video kernels. The DSP features of the MSA core include: two 16-bit single-cycle throughput multipliers, two 40-bit split data ALUs, and hardware support for on-the-fly saturation and clipping; two 32-bit pointer ALUs with support for circular and bit-reversed addressing; two separate data ports to a unified 4 GB memory space, a parallel port for instructions, and two loop counters that allow nested zero overhead looping     

Combining PARAFAC analysis of HPLC-PDA profiles and structural characterization using HPLC-PDA-SPE-NMR-MS experiments: commercial preparations of St. John's Wort

Herbal preparations represent very complex mixtures, potentially containing multiple pharmacologically active entities. Methods for global characterization of the composition of such mixtures are therefore of pertinent interest. In this work, chemometric analysis of high-performance liquid chromatography with photodiode-array detection (HPLC-PDA) data from extracts of commercial preparations of Hypericum perforatum (St. John's wort) that originate from several continents is described. The spectral HPLC profiles were aligned in the elution mode using correlation optimized warping in order to remove peak misalignment caused by retention time shifts due to matrix effects. Furthermore, the warping was assisted by HPLC-PDA-SPE-NMR-MS (SPE = solid-phase extraction) experiments that yielded 1H NMR and 13C NMR data (from 1H-detected heteronuclear correlations), as well as ESI-MS and HRMS data, which enabled the identification of all major mixture constituents. The preprocessed HPLC-PDA data were subjected to parallel factor analysis (PARAFAC), a chemometric method that is a generalization of principal component analysis (PCA) to multi-way data arrays. PCA of the peak areas obtained from the PARAFAC analysis was used to facilitate sample comparison and allowed straightforward interpretation of constituents responsible for the differences in composition between individual preparations. In addition, loadings from the PARAFAC analysis provided pure elution profiles and pure UV spectra even for coeluting peaks, thus enabling the identification of chromatographically unresolved components. In conclusion, PARAFAC analysis of the readily accessible HPLC-PDA data provides the means for unsupervised and unbiased assessment of the composition of herbal preparations, of interest for assessment of their pharmacological activity and clinical efficacy.     

Pituitary adenylate cyclase activating peptides relax human pulmonary arteries by opening of KATP and KCa channels

BACKGROUND: Pituitary adenylate cyclase activating peptides (PACAPs) are potent endothelium independent dilators of human coronary arteries; however, their effects on human pulmonary arteries are unknown. METHODS: The vasorelaxant effects of PACAP27 on human pulmonary segmental arteries were studied and the specific potassium (K+) channel regulatory mechanisms in the vasorelaxant effects were tested by means of isometric contraction experiments. RESULTS: PACAP27 produced dose dependent relaxations of 10 microM rings preconstricted with prostaglandin F2 alpha (PGF2 alpha) with half maximal relaxation (IC50) at 17 nM. Pretreatment of the vessels with the ATP sensitive K+ (KATP) channel blocker glibenclamide (1 microM) or with the Ca2+ activated K+ (KCa) channel blocker iberiotoxin (100 nM) inhibited the PACAP27 induced relaxation. CONCLUSIONS: These results provide evidence that PACAPs are potent vasodilators of human pulmonary arteries and that this relaxation might be mediated by opening of KATP and KCa channels.     

Effect of valproate on the pharmacokinetics and pharmacodynamics of lorazepam

The pharmacokinetic-pharmacodynamic interaction between valproate and lorazepam was evaluated in this randomized, double-blind, placebo-controlled crossover study. Sixteen healthy male volunteers enrolled in the study to receive either divalproex sodium (500 mg every 12 hours) or matching placebo for 12 days in the first period, and then to receive the other regimen for an identical second 12-day period. In both periods, lorazepam (1 mg every 12 hours) was administered on days 6 through 9 and on the morning of day 10. Concomitant administration of divalproex sodium with lorazepam resulted in an 8%, 20%, and 31% increase in steady-state maximum plasma concentration, area under the concentration-time curve, and trough plasma concentrations of lorazepam, respectively. The apparent clearance of lorazepam through the formation of lorazepam glucuronide was reduced by 31% during coadministration of divalproex sodium. Pharmacokinetic properties of valproate did not change significantly in the ten available participants during coadministration of lorazepam. Sedation scales revealed no statistically significant differences in sedation between the two regimens. It is concluded that valproate increases plasma concentrations and reduces clearance of lorazepam, most likely by impairing hepatic glucuronidation, and that coadministration of lorazepam does not affect the steady-state pharmacokinetic properties of valproate.