从PCI总线-12V电源获得3.3V电压

通用的多电源总线,如ＶＭＥ、ＶＸＩ和ＰＣＩ总线,都可提供功率有限的３．３Ｖ、５Ｖ和±１２Ｖ（或±２４Ｖ）电源,如果在这些系统中添加设备（如插卡等）,则需要额外的３．３Ｖ或５Ｖ电源,这个电源通常由负载较轻的－１２Ｖ电源提供。图１电路,将－１２Ｖ电压升压到１５．３Ｖ（相对于－１２Ｖ电压）,从而得到３．３Ｖ的电源电压,输出电流可达３００ｍＡ。Ｑ２将３．３Ｖ电压转换成适当的电压（－１０．７５Ｖ）反馈给ＩＣ１的ＦＢ引脚,ＰＷＭ升压控制器可提供１Ｗ的输出功率,转换效率为８３％。整个电路大约占６．２５ｃｍ２的…     

Characterization of the invariant reaction involving the L, η, γ and σ phases in the Ti–Al–Nb system

Ti–Al–Nb alloys have shown promising properties for high-temperature applications. Although the phase diagram has been well researched, several controversies exist over the high-temperature phase equilibria. Among them, the invariant reaction involving the L, γ, σ, η phases, which has been classified as either class 1 (eutectic reaction) or class 2 (transition reaction), has not been well developed. To address this invariant reaction, two alloys that cross through the invariant plane during solidification were investigated. Differential thermal analysis in conjunction with detailed microstructural analysis of the as-cast as well as heat-treated samples determined the invariant reaction to be a ternary eutectic reaction. The results of this study indicate that a large energy barrier is associated with nucleation of the σ phase from the liquid. Additionally, extension of the γ phase field is shown to extend further into the Nb-rich corner of the ternary system at elevated temperatures.     

Abelès method revisited

The Abelès method is a classical method for determining the refractive index of dielectric thin films. In this paper we examine the main features of the method in a formal manner, using closed-form equations, and we show that the method is ambiguous in certain yet unreported situations.     

Sarcoplasmic Protein Profile from Drip Loss in Relation to Pork Quality

The aim of this research was to correlate the sarcoplasmic protein profile of the natural drip loss of muscle with the technological and sensory quality of pork meat. Material for analysis was taken from 14 PenArLan pigs. Simple analysis of relationships between the test protein and meat quality traits showed that they adopt a range of from –0.58 to 0.72. It has been shown that the significance of glycolysis expressed as level of glycogen and lactic acid may be 86% (coefficient of correlations, C_R = 0.93), explained by the amount of certain enzymes. The higher relation has been obtained between studied enzymes and value of pH₂₄, L^* and b^* parameters of raw meat (98%; C_R = 0.99). By contrast, L^* and a^* parameters, sour flavor, and tenderness of grilled meat in 79% can be explained based on the content of the enolase, glyceraldehyde‐3‐phosphate dehydrogenase, and phosphoglycerate mutase (C_R = 0.89). The results of the multiple regression showed that amount of lactic acid was related to the quantity of the 3 enzymes: phosphofructokinase, AMP deaminase, phosphorylase b/phosphorylase b kinase (r = 0.88).     

Sensitization to doxorubicin resistance in breast cancer cell lines by tamoxifen and megestrol acetate

Acquired drug resistance is a major factor in the failure of doxorubicin-based chemotherapy in breast cancer. We determined the ability of megestrol acetate and/or tamoxifen to reverse doxorubicin drug resistance in a doxorubicin-resistant breast cancer line (the human MCF-7/ADR). The cytotoxicity of doxorubicin, megestrol acetate, and/or tamoxifen was determined in the sensitive and resistant cell lines utilizing the sulphorhodamine B assay. Tamoxifen alone produced an IC50 (concentration resulting in 50% inhibition of control growth) of 10.6 microM, whereas megestrol acetate alone resulted in an IC50 of 48.7 microM in the MCF-7/ADR cell line. The IC50 of doxorubicin in MCF-7/ADR was 1.9 microM. Neither megestrol acetate alone nor tamoxifen alone at 1 or 5 microM altered the IC50 of doxorubicin. However, the combination of tamoxifen (1 or 5 microM) and megestrol acetate (1 or 5 microM) synergistically sensitized MCF-7/ADR cells. Additionally, megestrol acetate and tamoxifen inhibited iodoarylazidoprazosin binding to P-glycoprotein, and, in their presence, there was an increased doxorubicin accumulation in the MCF-7/ADR cells. Furthermore, the combination of tamoxifen and megestrol acetate had much less effect on the cytotoxicity of doxorubicin in MCF-7 wild-type cells. Clinically achievable concentrations of tamoxifen and megestrol acetate can largely sensitize MCF-7/ADR to doxorubicin. The combination of these three drugs in a clinical trial may be informative.     

Optical characteristics of the compound PLZT

We present a summary of measured characteristics of lanthanum-doped lead zirconium titanate (PLZT) compound in its mechanical housing. It is expected that the PLZT device will be used as the main component in an ultrafast electro-optic switch. We have performed several experiments to measure and calculate the following characteristics: optical power transmission, thermodynamic effects, switching speed, and dc drift phenomenon.     

Three-dimensional optical-transfer-function analysis of fiber-optical two-photon fluorescence microscopy

The three-dimensional optical transfer function is derived for analyzing the imaging performance in fiber-optical two-photon fluorescence microscopy. Two types of fiber-optical geometry are considered: The first involves a single-mode fiber for delivering a laser beam for illumination, and the second is based on the use of a single-mode fiber coupler for both illumination delivery and signal collection. It is found that in the former case the transverse and axial cutoff spatial frequencies of the three-dimensional optical transfer function are the same as those in conventional two-photon fluorescence microscopy without the use of a pinhole.However, the transverse and axial cutoff spatial frequencies in the latter case are 1.7 times as large as those in the former case. Accordingly, this feature leads to an enhanced optical sectioning effect when a fiber coupler is used, which is consistent with our recent experimental observation.     

The effects of combined antifolates on inhibition of growth of murine leukemia cells cultured in vitro

PURPOSE: Long-term patency of cryopreserved vascular grafts is determined by maintained cellular and tissue viability, which implies preservation of various biochemical, smooth muscle, and endothelial functions. Therefore, it was investigated whether the presence of fetal calf serum (FCS) in the cryomedium improves the postthaw contractile and endothelial function of human arteries. METHODS: Rings from human mesenteric (HMA) and left circumflex coronary arteries (HCA) obtained from organ donors were randomized into three groups and studied either unfrozen or after storage for 3 to 6 weeks at -196 degrees C while suspended in Krebs-Henseleit solution without or with 20% FCS as the vehicles and 1.8 mol/L dimethyl sulfoxide and 0.1 mol/L sucrose as cryoprotecting agents. The samples were slowly frozen to -70 degrees C and then stored in liquid nitrogen. Before use, the tissues were thawed within 3 minutes in a 40 degrees C water bath. RESULTS: After thawing the sensitivity to various agonists and maximal responses to the endothelium-independent relaxing agent sodium nitroprusside were unchanged. However, after cryopreservation of HMA was performed without and with FCS, maximal contractile responses to noradrenaline were significantly reduced to 10.1 +/- 0.7 gm and 9.9 +/- 0.9 gm compared with 13.3 +/- 0.6 gm in unfrozen HMA (mean +/- SEM, n = 15). After cryopreservation of HCA was performed without and with FCS, maximal contractile responses to prostaglandin F2 alpha (6.9 +/- 0.4 gm in unfrozen HCA) were significantly reduced to 4.3 +/- 0.3 gm and 3.8 +/- 0.2 gm (mean +/- SEM, n = 6). In both types of arteries cryopreservation also attenuated significantly the endothelium-dependent relaxant responses to bradykinin during U46619 (10 nmol/L)-induced tone. In HMA the maximal bradykinin-induced relaxation (85% +/- 4%) was significantly diminished to 29% +/- 7% and 38% +/- 9% after cryopreservation without and with FCS (mean +/- SEM, n = 6). In HCA maximal bradykinin-induced relaxation (88% +/- 4%) was significantly diminished to 26% +/- 10% and 36% +/- 11% after cryopreservation without and with FCS (mean +/- SEM, n = 6). This result was reflected by a marked endothelial denudation in all groups of cryopreserved arteries. Neither functional nor morphologic preservation of the endothelial cell lining was significantly improved by FCS supplementation of the cryomedium. CONCLUSIONS: Cryopreservation diminished contractile and endothelium-dependent relaxant responses of human arteries. The presence of FCS in the cryomedium did not modify these changes.     

Detecting reduced bone mineral density from dental radiographs using statistical shape models.

We describe a novel method of estimating reduced bone mineral density (BMD) from dental panoramic tomograms (DPTs), which show the entire mandible. Careful expert width measurement of the inferior mandibular cortex has been shown to be predictive of BMD in hip and spine osteopenia and osteoporosis. We have implemented a method of automatic measurement of the width by active shape model search, using as training data 132 DPTs of female subjects whose BMD has been established by dual-energy X-ray absorptiometry. We demonstrate that widths measured after fully automatic search are significantly correlated with BMD, and exhibit less variability than manual measurements made by different experts. The correlation is highest towards the lateral region of the mandible, in a position different from that previously employed for manual width measurement. An receiver-operator characterstic (ROC) analysis for identifying osteopenia (T < -1: BMD more than one standard deviation below that of young healthy females) gives an area under curve (AUC) value of 0.64. Using a minimal interaction to initiate active shape model (ASM) search, the measurement can be made at the optimum region of the mandible, resulting in an AUC value of 0.71. Using an independent test set, AUC for detection of osteoporosis (T < -2.5) is 0.81.     

Guest Editors' Introduction: Global Software Development: How Far Have We Come?

Global software development efforts have increased in recent years, and such development seems to have become a business necessity for various reasons, including cost, availability of resources, and the need to locate development closer to customers. However, there's still much to learn about global software development before the discipline becomes mature. This special issue aims to assess the gap between the state of the art and the state of the practice. It presents five articles that cover various aspects of global software development, including knowledge management strategies, distributed software development, requirements engineering, distributed requirements, and managing offshore collaboration. A Point/Counterpoint department discusses whether global software development is indeed a business necessity.This article is part of a special issue on Global Software Development.