用MDBT分析纳米Zn及其合金

应用高能球磨机械合金化方法制备纳米Zn及Zn—Al合金体材料，采用拉伸实验和MDBT实验对这些材料的样品的机械性能进行测量分析．结果表明：球磨3～5h获得的Zn-0．6％Al含金具有很好的塑性．室温下球磨3h所得的纯Zn比液氮温度下球磨3h加室温球磨6h所得的纯Zn具有更好的塑性．     

Frequency Stabilization of a Ho:Tm:YLF Laser to Absorption Lines of Carbon Dioxide

A single-frequency Ho:Tm:YLF laser, operating at an eye-safe wavelength of 2 mum, has been developed with tuning characteristics optimized for spectroscopy of absorption features. The laser frequency was stabilized to three different absorption lines of carbon dioxide by a wavelength modulation technique. Long-term frequency drift has been eliminated from the laser, and shorter-term jitter has been reduced to within 13.5 MHz of the absorption line center. This stabilized laser is an ideal injection seed source for a differential absorption lidar system for measurement of atmospheric gases.     

Measurement of ultrasonic pressure by heterodyne interferometry with a fiber-tip sensor

A fiber-optic measurement system is described that allows ultrasound to be detected in fluids. It is based on a heterodyne interferometer, and the sensing element consists of a metal-coated fiber tip. The heterodyne technique permits direct acquisition of the sound pressure. The required ac photodetection is carried out with wide bandwidth, and the system provides high temporal and spatial resolution. For optimum performance the system parameters are matched to the sound-wave properties of the current application with the aid of theoretical and numerical calculations. The fiber-optic sensor system was applied to two problems of ultrasonic exposimetry in which the favorable features of the measurement technique were exploited. Shock waves from an electromagnetic lithotripter were investigated by use of the wide bandwidth of the system, and the subharmonic in an ultrasonic cleaner was detected, which indicates cavitation.     

Dynamic range and sensitivity adaptation in a silicon spikingneuron

We propose an adaptive procedure that enables a spiking neuron, whether artificial or biological, to make optimal use of its dynamic range and gain. We discuss an analog electronic circuit implementation of this algorithm using a biologically realistic artificial "silicon" neuron. The adaptation procedure adapts the neuron's firing threshold and the sensitivity (or gain) of its current-frequency relationship to match the DC offset (or mean) and the dynamic range (or variance) of the time-varying somatic input current. The neuron extracts the minimum and maximum levels of the reconstructed somatic current signals from the cell's own spike trains. These are used to regulate the somatic leak conductance in order to shift the somatic current-frequency relation and to adjust a calcium-activated potassium conductance to change the dynamic range of the cell's somatic current-frequency relationship. We report experimental data from a test neuron-built using analog subthreshold CMOS VLSI technology-that shows the expected behavior.     

Influence of patient age and co-morbidity on outcome of a collaborative care pathway after radical prostatectomy and cystoprostatectomy

PURPOSE: We determined whether standardized care patterns developed with a collaborative care methodology can be applied successfully across all patient groups with favorable effects on cost and quality. MATERIALS AND METHODS: We retrospectively analyzed financial and clinical outcomes in 109 radical retropubic prostatectomy and 47 radical cystectomy cases. Patients older than 70 years and/or with an American Society of Anethesiology status of 3 or greater were compared to younger, healthier patients undergoing these procedures. RESULTS: Standardized care patterns resulted in favorable financial and clinical outcomes in high and low risk patient groups. The only apparent difference was an increased need for rehospitalization after discharge for patients undergoing radical prostatectomy with a high American Society of Anesthesiology status. CONCLUSIONS: Standardized care patterns developed with a collaborative care methodology provide a high quality, cost-efficient approach to medical care. This methodology is applicable to all patient groups and is highly compatible with current medical practice.     

Highly-efficient gene transfer with retroviral vectors into human T lymphocytes on fibronectin

Genetically modified lymphocytes have been successfully used for correction of ADA deficiency in children and in controlling graft-versus-host disease (GvHD) after allogeneic bone marrow transplantation. Low transduction efficiencies are, however, limiting for gene therapeutic strategies based on lymphocytes. In this study we compared protocols for highly efficient gene transfer into human T cells using retroviral vector-containing supernatant. We showed that infection of both human primary T cells and CD4+ Jurkat cells is most efficient on the matrix component fibronectin. Transduction was carried out with a retroviral vector encoding both the human intracytoplasmatically truncated low-affinity nerve growth factor receptor (deltaLNGFR) as a gene transfer marker and the Herpes simplex virus thymidine kinase for negative selection. Based on LNGFR expression genetically modified cells were enriched to near purity by magnetic cell sorting (MACS). Enriched cells could be shown to be highly sensitive to ganciclovir.     

Is image selection a useful strategy to decrease the transmission time in teleradiology? A study using 100 emergency cranial CTs

This study examines the suitability of working with a selection of images in a teleradiology consulting system in neurological or neurosurgical emergency situations. The teleradiology system was based on IBM-compatible personal computers, video digitization for data acquisition, and data transmission by Integrated System Digital Network. Forty normal and 60 abnormal emergency cranial computed tomograms were shown to a radiologist on call who presented all cases he regarded as pathologic to a neuroradiologic expert by teleradiology. To reduce transmission time, only a selection of images from the CT study was presented (up to four images per case). For each case the on-call radiologist's diagnosis (D(on-call)), the expert's diagnosis on the teleradiology screen (D(monitor)), and the expert's diagnosis on the original film (D(original)) was documented, together with an estimation of the agreement between those diagnoses. There was clinically relevant disagreement between the on-call radiologist's diagnosis and the neuroradiologist's diagnosis based on the image selection on the teleradiology monitor in 23% of cases. A clinically important discrepancy between the neuroradiologist's diagnosis based on the image selection and his diagnosis using the original films was found in 30% of cases. This was due to the presence of clinically relevant information on images not transferred by the on-call radiologist. Image quality of the transferred images was sufficient in all cases. Drastic selection of images from a complete CT study leads to a high rate of incorrect diagnoses and is not appropriate to reduce transmission time in teleradiology.     

Response of V79 cells to low doses of X-rays and negative pi-mesons: clonogenic survival and DNA strand breaks

Mammalian cells are hypersensitive to very low doses of X-rays (< 0.2 Gy), a response which is followed by increased radioresistance up to 1 Gy. Increased radioresistance is postulated to be a response to DNA damage, possibly single-strand breaks, and it appears to be a characteristic of low linear energy transfer (LET) radiation. Here we demonstrate a correspondence between the extent of the increased radioresistance and linear energy transfer of 250 kVp X-rays and plateau and Bragg peak negative pi-mesons. The results support our hypothesis since the size of the increased radioresistant response appears to correspond to the number of radiation induced single-strand breaks. Furthermore, since survival prior to the increased radioresistant response (< 0.2 Gy) was LET-independent, these data support the notion that the increased radioresistant response may dictate the overall survival response to higher doses. However, while these data provide further circumstantial evidence for the involvement of DNA strand breaks in the triggering of increased radioresistance, more direct conclusions cannot be made. The data are not accurate enough to detect structure in the single-strand break profiles, the production of single-strand breaks being apparently linear with dose.     

Processing of the Borna disease virus glycoprotein gp94 by the subtilisin-like endoprotease furin

Open reading frame IV (ORF-IV) of Borna disease virus (BDV) encodes a protein with a calculated molecular mass of ca. 57 kDa (p57), which increases after N glycosylation to 94 kDa (gp94). The unglycosylated and glycosylated proteins are proteolytically cleaved by the subtilisin-like protease furin. Furin most likely recognizes one of three potential cleavage sites, namely, an arginine at position 249 of the ORF-IV gene product. The furin inhibitor decRVKRcmk decreases the production of infectious BDV significantly, indicating that proteolytic cleavage of the gp94 precursor molecule is necessary for the full biological activity of the BDV glycoprotein.