A 0.9 V 92 dB Double-Sampled Switched-RC Delta-Sigma Audio ADC

A 0.9 V third-order double-sampled delta-sigma audio ADC is presented. A new method using a combination of a switched-RC technique and a floating switched-capacitor double-sampling configuration enabled low-voltage operation without clock boosting or bootstrapping. A three-level quantizer with simple dynamic element matching was used to improve linearity. The prototype IC implemented in a 0.13 CMOS process achieves 92 dB DR, 91 dB SNR and 89 dB SNDR in a 24 kHz audio signal bandwidth, while consuming 1.5 mW from a 0.9 V supply. The prototype operates from 0.65 V to 1.5 V supply with minimal performance degradation.     

Stem cells in prostatic epithelia

The normal prostate is, structurally and functionally, a highly complex glandular tissue in which populations of epithelial and stromal cells interact, one with the other, and are under a constant state of proliferation, differentiation, elimination and selective secondary replenishment so that functional integrity of the tissue is maintained. The ability of normal prostatic tissue to maintain its structure and function is dependent upon retention of cells, generally regarded as 'stem cells', which are able to respond by proliferation and selective differentiation within a wide range of phenotypic alternatives. With respect to cells in the epithelial compartment, replenishment is possible at several levels from within distinct pathways of normal cellular differentiation. It is now appreciated that fully differentiated prostatic epithelial cells retain a far greater degree of phenotypic 'plasticity' than was earlier apparent from morphological examination of the intact tissue. This inherent plasticity, coupled with the ability of the intact tissue to respond to diverse environmental (particularly humoral) stimuli by regenerating a wide and divergent spectrum of functional prostatic epithelial phenotypes is its strength--but also its weakness. Disturbance and distortion of the homeostatic regulatory mechanisms, whether physical or humoral, which control the normal sequence of epithelial proliferation, differentiation and elimination exposes these cells, particularly multipotent 'stem cells', to an increased probability of genetic change, thus resulting in either transient, or permanent, neoplastic transformation.     

Genetic control of immunity to Heligmosomoides polygyrus: presentation of promiscuous antigens to parasite-specific T cell hybridomas

The role of MHC class II in the presentation of Heligmosomoides polygyrus antigens has been investigated, using a number of T cell hybridomas produced in A and E positive and negative mice. By using fixed and irradiated antigen presenting cells (APC), further evidence has emerged, to support earlier data, that there can be differential processing requirements during the presentation of H. polygyrus antigens by A and E molecules. In concordance with these earlier observations, this work provides further evidence than individual T cells can respond to antigen when presented by more than one MHC molecule. Previously, this evidence has been restricted to individual MHC molecules of the same haplotype, but these data show that H. polygyrus produces antigens which can be presented by both syngeneic and allogeneic MHC molecules. These antigens do not appear to be synonymous with the previously described H. polygyrus superantigen, as presentation is restricted to specific MHC haplotypes. It is proposed that H. polygyrus may produce these antigenic molecules as part of its strategy to manipulate the host immune system.     

Isothermal interphase diffusion with consecutive reactions

For multi-step heterogeneous consecutive reactions affected entirely by interphase diffusion under isothermal condition, the equations for the effectiveness factors, the surface concentrations and the point yields were derived in terms of the Damkoehler numbers or the measurables from the mass balances set up on the assumption that the mass-transfer rate balances the surface-reaction rate at steady state. From the analyses of the equations derived, the effectiveness factors for the intermediate steps and the surface concentrations of intermediates were understood to be enhanced by the measurables inclusive of the concentrations and the mass-transfer coefficients. Then the effect of the concentrations was concluded to be most significant. The effects of these measurables to the effectiveness factors and the surface concentrations were qualitatively discussed for simple consecutive reactions and also for additive consecutive reactions. Especially, as for two-step additive consecutive reactions, the effects of measurables η Da and the concentrations to the effectiveness factors were examined with graphical presentations. Finally, the brief discussion of the dependency of the Damkoehler number upon reaction time and the effect of the Renolds number and diffusivity to the extent of the mass-transfer resistance were presented.     

自动化服务器对客户端访问的实现

用一个实例说明如何用Delphi来实现服务器对客户的访问。     

In situ polymerization and characterization of polyester‐based polyurethane/nano‐silica composites

Polyester‐based polyurethane/nano‐silica composites were obtained via in situ polymerization and investigated by Fourier‐transform infrared spectroscopy (FTIR), or FTIR coupled with attenuated total reflectance (FTIR‐ATR), Transmission electron microscopy (TEM), atomic force microscopy (AFM), an Instron testing machine, dynamic mechanical analysis (DMA) and ultraviolet‐visible spectrophotometry (UV‐vis). FTIR analysis showed that in situ polymerization provoked some chemical reactions between polyester molecules and nano‐silica particles. FTIR‐ATR, TEM and AFM analyses showed that both surface and interface contained nano‐silica particles. Instron testing and DMA data showed that introducing nano‐silica particles into polyurethane enhanced the hardness, glass temperature and adhesion strength of polyurethane to the substrate, but also increased the resin viscosity. UV‐vis spectrophotometry showed that nano‐silica obtained by the fumed method did not shield UV radiation in polyurethane films. Copyright © 2003 Society of Chemical Industry     

Foundations'' impact on policy making: results from a pilot study

Thirty-two consecutive patients with haematological disorders, in need of a permanent central venous catheter (CVC) were randomly allocated to have their CVC bandages (Tegaderm) changed once (OAW, n = 20) or twice (TAW, n = 19) a week. The two randomization arms were balanced in respect of age, sex, and underlying disease. The exit site of the CVC was inspected daily through the transparent bandage and erythema was noted. If severe erythema occurred, daily wet gauze dressings were applied. Samples for bacterial cultures were taken from the exit site of the CVC at every change of bandages. There was no difference in complications leading to removal of the CVC between the two groups (7/20 OAW vs. 7/19 TAW) or in CVC survival-time (P = 0.4). However, the OAW group had more positive CVC tip cultures (OAW 11/14 vs. TAW 2/9; P < 0.05) and a tendency to: (i) more extra dressings (P = 0.08); (ii) more cultures from the exit skin site showing high numbers of colony forming units (P = 0.07); (iii) shorter time to first exit site infection (P = 0.09); and (iv) more Gram-positive septicaemias (P = 0.08). Both clinical and bacteriological data in this study indicate that changing transparent polyurethane CVC bandages twice a week is superior to once a week.