Chemical natures and distributions of metal impurities in multicrystalline silicon materials

We present a comprehensive summary of our observations of metal‐rich particles in multicrystalline silicon (mc‐Si) solar cell materials from multiple vendors, including directionally‐solidified ingot‐grown, sheet, and ribbon, as well as multicrystalline float zone materials contaminated during growth. In each material, the elemental nature, chemical states, and distributions of metal‐rich particles are assessed by synchrotron‐based analytical x‐ray microprobe techniques. Certain universal physical principles appear to govern the behavior of metals in nearly all materials: (a) Two types of metal‐rich particles can be observed (metal silicide nanoprecipitates and metal‐rich inclusions up to tens of microns in size, frequently oxidized), (b) spatial distributions of individual elements strongly depend on their solubility and diffusivity, and (c) strong interactions exist between metals and certain types of structural defects. Differences in the distribution and elemental nature of metal contamination between different mc‐Si materials can largely be explained by variations in crystal growth parameters, structural defect types, and contamination sources. Copyright © 2006 John Wiley & Sons, Ltd.     

Sulbactam/ampicillin in comparison with cefuroxime for infections of the lower respiratory tract. Results of a prospective, randomized comparative study

Gallbladder removal using laparoscopic techniques has rapidly been adopted by surgeons around the world. Questions have been raised concerning laparoscopic cholecystectomy, including the safety of the operation, its implications for management of common bile duct stones, and the means by which surgeons should be trained. In the present series, 424 patients were referred to a single surgeon for cholecystectomy during a 22-month period. A traditional open cholecystectomy was performed in 9 patients (2.1%) because of presumed contraindications to laparoscopic cholecystectomy. Laparoscopic cholecystectomy was attempted in the remaining 415 patients (97.9%). On the basis of preoperative investigations, 19 patients (4.6%) underwent endoscopic retrograde cholangiopancreatography. Endoscopic sphincterotomy and stone extraction were performed in the 13 patients (3.1%) demonstrating choledocholithiasis. Laparoscopic cholecystectomy was converted to an open operation in 8 patients (1.9%) owing to dense adhesions, obscure anatomy, or cholangiographic abnormalities. Laparoscopic cholecystectomy was successfully performed in 407 patients (96%) in 95 +/- 2 minutes (mean +/- SEM). Surgical trainees were involved in all operations and performed 68% of the procedures under supervision. Cystic duct cholangiograms were obtained selectively in 129 patients (30.4%). Intraoperative complications occurred in 3 patients, including 1 patient with a minor injury to the common bile duct (0.2%). There was no perioperative mortality, and major complications occurred in 6 patients (1.4%). Minor complications were seen in 12 others (2.8%), and one patient required reoperation for a trocar injury to the jejunum. Prolonged follow-up has revealed one case of asymptomatic retained common bile duct stones (0.2%). Laparoscopic cholecystectomy can therefore be performed in more than 95% of patients with no mortality and minimal morbidity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Switched-capacitor track-and-hold amplifier with low sensitivity to op-amp imperfections

This paper describes a high-precision switched-capacitor (SC) track-and-hold amplifier (THA) stage. It uses a novel continuous-time correlated double sampling (CDS) scheme to desensitize the operation to amplifier imperfections. Unlike earlier predictive-CDS THAs, the circuit does not need a sample-and-held input signal for its operation. During the tracking period, an auxiliary continuous-time signal path is established, which predicts the output voltage during the holding period. This allows accurate operation even for low amplifier gains and large offsets over a wide input frequency range. Extensive simulations were performed to compare the performance of the proposed THA with earlier circuits utilizing CDS. The results verify that its operation is far more robust than that of any previously described THA.     

A procedure for rupture-free preparation of confluently grown monolayer cells for scanning electron microscopy

Monolayers of PtK-1 and HeLa cells grown on glass or plastic supports are extremely susceptible to lacerations, e.g., splits and cracks caused mainly by shrinkage when prepared for scanning electron microscopy (SEM). We find that a four-step fixation procedure including glutaraldehyde, OsO₄, tannic acid, and uranylacetate application, in combination with critical point drying, drastically reduces these structural damages. In addition, the conductivity of the specimens is enhanced, so that they can be investigated without gold coating. Transmission electron microscopy (TEM) investigation of perpendicular sections in the area of lacerations provides evidence that the subcortical cytoskeletal elements are of crucial importance in maintaining cell membrane stability during the preparations. Our relatively quick and simple procedure results in an improved structural appearance of the cells.     

Immobilization of collared peccaries (Tayassu tajacu) and feral hogs (Sus scrofa) with Telazol and xylazine

Quantitative [125I]protein G-based immunohistochemistry was used to map the distribution of beta1 thyroid hormone receptor (TRbeta1) in normal and thyroidectomized adult rat brain, using a previously characterized polyclonal antibody. The distribution of TRbeta1-like immunoreactivity in normal brain was largely but not perfectly concordant with previous accounts of TRbeta1 mRNA distribution in rat brain. Thyroidectomy resulted in increased immunolabeling in most brain regions (mean increase: 14%, range: -4% to +25%), with statistically significant effects being observed in 9 of the 36 brain regions examined. Brain regions showing the most pronounced effects included the habenular nucleus (+22%), the oriens layer of the hippocampal CA3 region (+24%), and the lateral geniculate nucleus of the thalamus (+23%). These results demonstrate that the TRbeta1 protein in brain is capable of plastic changes in response to adult-onset alterations in TH levels. The observed pattern of brain regional receptor changes following thyroidectomy may provide clues for functional effects of thyroid function alterations in adults.     

Mode selection schemes for unicasting device‐to‐device communications supported by network coding

Device‐to‐device (D2D) communication in a cellular spectrum increases the spectral and energy efficiency of local communication sessions, while also taking advantage of accessing licensed spectrum and higher transmit power levels than when using unlicensed bands. To realize the potential benefits of D2D communications, appropriate mode selection algorithms that select between the cellular and D2D communication modes must be designed. On the other hand, physical‐layer network coding (NWC) at a cellular base station—which can be used without D2D capability—can also improve the spectral efficiency of a cellular network that carries local traffic. In this paper, we ask whether cellular networks should support D2D communications, physical‐layer NWC, or both. To this end, we study the performance of mode selection algorithms that can be used in cellular networks that use physical‐layer NWC and support D2D communications. We find that the joint application of D2D communication and NWC scheme yields additional gains compared with a network that implements only one of these schemes, provided that the network implements proper mode selection and resource allocation algorithms. We propose 2 mode selection schemes that aim to achieve high signal‐to‐interference‐plus‐noise ratio and spectral efficiency, respectively, and take into account the NWC and D2D capabilities of the network.     

A wide-band high-accuracy incremental ADC

In this paper, a high resolution and wideband incremental ADC with extended counting is described and analyzed. The modulator introduced inter-stage gain to reduce the quantization noise without adding any hardware. Also, a gain scaling technique was used to decrease the power consumption by reducing the integrators’ output swing. First, the 2nd order incremental ΔΣ ADC and 11-bit SAR ADC were measured separately. Second, the incremental ΔΣ ADC with extended counting was tested. It achieved a 91.6 dB dynamic range and 77.8 dB SNDR in the 0–1.25 MHz signal band. The total power consumption is 53.5 mW with dual power supplies (analog 3.3 V, digital 1.8 V).     

The colour of monolithic zirconia restorations determined by spectrophotometric examination

ABSTRACT

Objective: The aim of this in vitro study is to examine the optical effects of monolithic zirconia of different translucency and thickness, combined with substrates of different colours. Materials and methods: Zirconia specimens of two colours (A2P1, WHITE) were used for the study, three try-in pastes (Variolink Esthetic); substrates were prepared from nine types of materials (six VITA SIMULATE, three metals). Measurements were carried out at the Faculty of Atomic Physics of the Technical University of Budapest with the state-of-the-art PerkinElmer® Lambda 1050 spectrophotometer. Results: The colouring of zirconia has a major effect on dE values resulting in different colour perceptibility and acceptability. Try-in pastes, however, have no significant effects overall. Conclusion: Applying coloured zirconia is highly eligible for preparing aesthetic crowns as their substrate-covering effect makes it possible to reproduce the desired colour. Uncoloured zirconia nonetheless is unaffected by the substrate material, especially above a certain layer thickness.