驱动压电陶瓷的高压放大器

概述了高压放大器的基本组成，以及采用高压稳压电源措施，提高高压放大器的性能，并简述了高压放大器输出级的工作原理，给出了过渡保护方法。     

The lack of long-term detrimental effects on liver allografts caused by donor-specific anti-HLA antibodies

Recent reports indicate a higher incidence of both acute and chronic liver allograft rejection when, at the time of transplantation, the recipients serum contains donor-specific anti-HLA antibodies. From 9/89 to 5/91, 133 liver allografts were performed at our institution. Thirteen liver recipients had donor-specific IgG anti-HLA antibodies (complement-fixing) at the time of transplantation. In eleven patients, antibodies reacted to donor class I antigens while in 1 patient the donor-specific antibody had class II reactivity. Twelve patients have been followed for a minimum of 12 months (median 18 months, range 28-12 months). No hyperacute rejection was seen in any of the cases and four patients had acute rejections. Thus far only one of the twelve patients has biopsy evidence suggestive of chronic liver injury. The remaining have normal liver enzymes and bilirubin. Three of these twelve patients died (one from a myocardial infarction and the others from sepsis) accounting for a one-year graft survival of 75%. There was no significant statistical difference in the one-year graft survival in those recipients without donor-specific antibodies (i.e., 80.5%). In eight of the twelve patients, pretransplant preformed antibody level (PRA) was > 50%. In six of the thirteen patients donor-specific antibody was present at dilutions greater than 1:64. As previously reported, the donor-specific antibody disappeared from the serum posttransplant within hours and did not reappear. In vitro studies demonstrated no factor in portal or hepatic artery blood that could inhibit rabbit complement mediated lysis of anti-HLA antibodies. We conclude that it is not a contraindication to do liver transplants in the presence of donor-specific anti-HLA antibodies.     

Determinants of genital human papillomavirus infection among cytologically normal women attending the University of New Mexico student health center

OBJECTIVES: To confirm the risk factors for genital human papillomavirus (HPV) infection. GOAL OF THIS STUDY: To investigate risk factors for HPV detection apart from the correlated risk factors for cervical neoplasia. STUDY DESIGN: Cervical human papillomavirus (HPV) DNA was assessed in 357 cytologically normal women attending the University of New Mexico student health center. Cervical swab samples were obtained for HPV DNA detection and typing using a PCR-based DNA amplification system. Possible determinants of cervical HPV were examined including age, ethnicity, history of sexually transmitted disease, oral contraceptive use, smoking, age at first intercourse, lifetime number of sex partners, marital status, and history of pregnancy. RESULTS: A 44.3% overall prevalence of cervical HPV was observed. On univariate analysis, factors associated with increasing HPV prevalence included higher lifetime number of sex partners and single marital status. After adjustment for potential confounding variables, we found that HPV prevalence increased with higher lifetime number of sexual partners. CONCLUSION: These findings, along with those from the companion reports in this issue of the journal, support the sexual route of transmission of the virus.     

Use of a modified non-rebreathing mask during upper intestinal endoscopy

BACKGROUND AND STUDY AIMS: Recently, attention has been drawn to the significant occurrence of respiratory and other complications during upper intestinal endoscopy. This prospective study was designed to compare the incidence and severity of oxygen desaturation when two different methods of oxygen delivery were used during elective oesophagogastroduodenoscopy. PATIENTS AND METHODS: After local medical ethics committee approval and written informed consent, one hundred patients undergoing elective oesophagogastroduodenoscopy were randomly allocated to receive supplemental oxygen at either four litres per minute via nasal specular or ten litres per minute through a specially modified non-rebreathing mask. Oxygen saturations during endoscopy facilitated by midazolam sedation were recorded, and non-parametric tests were used to compare the oxygen saturations in the two groups. RESULTS: The mean oxygen saturations were significantly better during the procedure for American Society of Anesthesiology (ASA) grade 2 and 3 patients who received oxygen with the modified mask than for those who received oxygen via nasal specular (98.6% vs. 97.0%, P = 0.004 for ASA grade 2 and 98.4% vs. 95.5, P = 0.006 for ASA grade 3). CONCLUSIONS: For ASA grade 2 and 3 patients, the modified non-rebreathing mask significantly improves oxygen saturations during upper intestinal endoscopy. This technique should be more widely used for patients at moderate and high risk.     

Efficacy of surgical treatment in traumatic central cord syndrome

BACKGROUND: Controversy surrounds the treatment of traumatic central cord syndrome (TCCS), as there are strong advocates for nonsurgical treatment for most patients. However, conservative treatment has been shown to yield a longer period of discomfort from pain and weakness in certain cases. METHODS: In a retrospective review of 114 patients presenting with acute or chronic TCCS from 1988-94, four different age groups were separately observed under different treatments. Motor and sensory recovery were assessed. RESULTS: Better results were achieved in younger patients, with or without radiographic abnormalities, and in patients with clinically correlated encroaching cord lesions who received early surgical decompression. CONCLUSIONS: Surgical intervention for TCCS must be addressed with careful clinical and radiographic survey. Removal of offending lesions in the subacute period results in significant motor and sensory improvement in short-term and long-term follow-up.     

Memory complaints in epilepsy: correlations with cognitive performance and neuroticism

Experimental results are presented to show that the adhesion force is the single most important limiting factor in high-resolution atomic force microscopy of DNA in air, prepared by the cytochrome-C-assisted spreading method. It is also shown that humidity plays a minor role in the control of probe force. Using a pure carbon film as the substrate to clean the AFM tip prior to imaging, it is demonstrated that 4-6 nm resolution on DNA can be routinely obtained by the atomic force microscope with commercial Si3N4 pyramid cantilevers. We also show that in organic solvents a resolution of up to 3 nm can be obtained under optimal conditions.     

参考信号频率自调整的数字相敏检波器算法的研究

本文提出了一种不需要外接同频参考信号的数字相敏检波器算法。该算法首先提取计算机产生的参考信号与被测信号频率的差值，然后根据该差值调整参考信号的频率直到满足要求。本文还讨论了数字相敏检波器的幅频特性，仿真试验表明理论分析与实际结果是一致的。该算法可以用于同频参考信号不能获得时正弦信号的幅度和相位测量。     

实现多层混合刻蚀薄膜大面积均匀的方法浅探

采用多层光刻工艺结合氩离子铣的混合刻蚀方法，刻蚀高Ｔｃ超导ＹＢａＣｕＯ／ＺｒＯ２（１００）薄膜图形，取得了较好的结果。在进行氩离子镜的工艺步骤中，使用普通氩离子铣设备（离子束斑极不均匀），但采取了一定的措施─－使被刻样品在刻蚀台座上可移动，模糊地实现了薄膜的相对＂大面积＂（直径φ≥２０ｍｍ）均匀刻蚀─－可同时刻蚀２～３片６ｍｍ×１０ｍｍ薄膜，并且被刻蚀部分表面起伏约在１０ｎｍ左右。图形样品的最小线条达２μｍ，其Ｔｃ、Ｊｃ人与刻蚀前薄膜的Ｔｃ、Ｊｃ相当，即：ＴＣ为８５～９０Ｋ，Ｊｃ～１０６Ａ／ｃｍ２（在７７Ｋ下）。