基于小波变换和似然无偏估计的胃阻抗信号处理研究

目的：介绍一种基于小波变换和似然无偏估计的胃阻抗信号分析去噪的方法。方法：首先经过多分辨分析将信号进行分离，然后应用Stein似然无偏估计对胃阻抗信号进行自适应软阈值去噪处理。结果：实验结果表明，该方法能够有效滤除由呼吸、血流阻抗等因素造成的干扰。结论：小波分析技术为进一步研究胃动力信号的参数分析提供了新途径。     

英文医学科技论文写作方法与技巧

中国人一些高质量的科学研究因未能在国际期刊发表，痛失了在国际上展示自己工作与成果的机会。要想与国外同仁共享自己的成果，用英文写作必不可少。除英文水平外，英文科技论文还是大有规律可循。笔者根据自己的写作经验，就英文医学科技论文的写作意义、写作规律、方法和技巧作了介绍，以求共同探讨与提高。     

Minimax two-stage-designs with applications to tissue banking case-control studies

'Tissue banks' are created, at least in part, to help medical scientists learn about disease biology on the basis of samples provided by patients on treatment protocols that were competed years earlier.The bank inventory consists of precious non-renewable patient material (such as frozen diagnostic blood or bone marrow), which can be linked to both clinical data and long term follow-up information. Case-control studies, where cases represent clinical failures and controls clinical successes, are ideal for rapidly learning if a laboratory marker might have prognostic significance. While group sequential (multi-stage) methods are widely used in clinical trials, they have rarely been applied in case-control studies. Further, unlike clinical trials where safety and efficiency may actually be in conflict, case-control studies can focus on efficiency. Hence, minimizing the expected sample size is a desirable goal in such a setting. Since the true effect size is never known, and since no prior distribution can be postulated for the effect size, we have opted for the minimax solution. A strategy is developed to determine amongst all two-stage designs with given type I and type II errors, the one for which the maximum expected sample size is minimized. The user is provided with simple tables, whereby one can determine everything necessary to conduct the study from the corresponding calculation for a single-stage design. A matched pair example is given where the suggested design can be modified, to obtain a superior 'two-plus' stage design. The basic idea is to conduct the first stage as planned, but use the estimate of variance to redesign the study, without using the estimate of effect size in the redesign.     

宁夏甘草胭脂蚧发生规律及综合防治技术的研究

通过对甘草胭脂蚧（Porphyrophora ningxiana）的田间调查，生活习性、发生规律、自然种群生命表以及综合防治试验研究，结果表明：该虫一年发生一代，成虫寿命7-10d，卵以卵袋的形式产于2-6cm的土壤中。8月上旬成虫羽化、交尾后入土产卵分泌白色棉团状卵袋。秋、冬季，一部分若虫在寄主上越冬，另一部份若虫和少量卵在土壤中的卵袋内越冬。以一龄若虫寄生甘草根部并造成严重危害，使植株根部腐烂枯死。根据以上生物学特性与发生危害情况，进一步开展了田间分布型调查，组建了甘草胭脂蚧自然种群生命表，开展了室内胭脂蚧发生与土壤含水量关系实验。利用改变栽培方式、局部露根治虫的措施，轮作可降低害虫的危害。田间进行了化学药剂的筛选，采用辛硫磷、毒死蜱、白僵菌杀虫剂在秋、春季，分别对威虫、若虫活动始期和一龄若虫上寄主的关键防治适期进行防治取得了良好的防治效果。     

Facilitated stimulus-response associative learning and long-term memory in mice lacking the NTAN1 amidase of the N-end rule pathway

The N-end rule relates the in vivo half-life of a protein to the identity of its N-terminal residue. Inactivation of the NTAN1 gene encoding the asparagine-specific N-terminal amidase in mice results in impaired spatial memory [26]. The studies described here were designed to further characterize the effects upon learning and memory of inactivating the NTAN1 gene. NTAN1-deficient mice were found to be better than wild-type mice on black-white and horizontal-vertical discrimination learning. They were also better at 8-week Morris maze retention testing when a reversal trial was not included in the testing procedures. In all three tasks NTAN1-deficient mice appeared to use a strong win-stay strategy. It is concluded that inactivating the asparagine-specific branch of the N-end rule pathway in mice results in impaired spatial learning with concomitant compensatory restructuring of the nervous system in favor of non-spatial (stimulus-response) learning.     

Prediction of vesico-ureteric reflux in childhood urinary tract infection: a multivariate approach

In this study, independent predictors obtained from patient history, physical examination and laboratory results for vesico-ureteric reflux (VUR) in children of 0-5 y with a first urinary tract infection (UTI) were assessed and the added value of renal ultrasound (US) investigated. Information was collected from children visiting the paediatric outpatient department with a first proven UTI, defined as a urine monoculture with ≥105 organism/ml, with clinical symptoms and possible white cell count ≥20 per high-power field of spun fresh urine. Children with neurologic bladder dysfunction were excluded. VUR was determined by voiding cystourethrography (VCUG) and graded from I to V. The diagnostic value of predictors was judged using multivariate logistic modelling with the area under the receiver operating characteristic (ROC area). A risk score was derived based on the regression coefficients of the independent predictors in the logistic model. In 140 children (51 boys and 89 girls) VUR was diagnosed in 37. Independent predictors for VUR were male gender, age, family history for uropathology, serum C-reactive protein level (CRP) and dilatation of the urinary tract on US. The ROC area of this model was 0.78 (95% CI: 0.69-0.87). This prediction model identified 12% (95% CI: 7-18) of the patients without VUR without missing one case of VUR. If we used VUR ≥ grade 3 as a threshold, the model assessed VUR to be absent in 34% (95% CI: 26-42). Conclusion: A prediction rule based on age, gender, family history, CRP and US results is useful in assessing the probability of VUR in the individual child with a first UTI and may help the physician to make decisions about performing additional imaging techniques. Prospective validation of the model in future patients, however, will be necessary before applying the rule in practice.     

Applications of dosimetry modeling to assessment of neurotoxic risk

Risk assessment procedures can be improved through better understanding and use of tissue dose information and linking tissue dose level to adverse outcomes. For volatile organic compounds, such as toluene and trichloroethylene (TCE), blood and brain concentrations can be estimated with physiologically based pharmacokinetic (PBPK) models. Acute changes in the function of the nervous system can be linked to the concentration of test compounds in the blood or brain at the time of neurological assessment. This set of information enables application to a number of risk assessment situations. For example, we have used this approach to recommend duration adjustments for acute exposure guideline levels (AEGLs) for TCE such that the exposure limits for each exposure duration yield identical tissue concentrations at the end of the exposure period. We have also used information on tissue concentration at the time of assessment to compare sensitivity across species, adjusting for species-specific pharmacokinetic differences. Finally this approach has enabled us to compare the relative sensitivity of different compounds on a tissue dose basis, leading to expression of acute solvent effects as ethanol-dose equivalents for purposes of estimating cost–benefit relationships of various environmental control options.     

Sequential urn designs with elimination for comparing K > or =3 treatments

A fully sequential procedure is proposed for comparing K > or =3 treatments with immediate binary responses. The procedure uses an adaptive urn design to randomize patients to the treatments and stopping rules are incorporated for eliminating less promising treatments. Simulation is used to assess the performance of the procedure for several adaptive urn designs, in terms of expected numbers of treatment failures and allocation proportions, and the effect on estimation at the end of the trial is also addressed. It is concluded that the drop-the-loser rule is more effective than equal allocation and all of the other designs considered. The practical benefits of the procedure are illustrated using the results of a three-treatment lung cancer study. It is then shown how the sequential elimination procedure may be used in dose-finding studies and its performance is compared with a recently proposed method. Several possible extensions to the work are briefly indicated.     

Simple Trends in NMR Spectra of Vinyl Polymers: The 1H NMR Spectrum of Poly(propylene)

Summary: The tacticity spreading of chemical shifts in the proton NMR spectrum of poly(propylene) in solution has been analyzed first qualitatively, taking advantage of known trends in both proton chemical shift and conformational statistics of vinyl polymers as summarized in the telephone rule, and then quantitatively using ab initio computations, empirical additivity schemes of proton chemical shifts, and conformational averages according to models of different rotational isomeric states. The very good results obtained, both qualitatively and quantitatively, stem from the relatively easy parametrization of proton chemical shift and establish a successful application of the telephone rule, also for proton NMR spectra.

Anti and syn labeling of methylene hydrogens in m and r diads.