增加折叠电流保护的电路

对许多需要数安培供电电流的应用而言，三端输出可调线性稳压器有易用．低成本和完全片上过载保护等特点，如美国国家半导体公司的LM317。增加数个元器件可以使三端稳压器具备一种高速度的短路限流能力，从而提高可靠性。限流器可将最大输出电流限制在一个安全的恒定水平IMAX上，避免稳压器的损坏。当出现一个故障状况时，传输晶体管上的功耗近似于VIN×IMAX。要让设计的稳压器能承受过载，就需要谨慎地选择元器件的额定值（经常是留了过大的余地），除非可以在故障发生时降低或折叠（foldback）输出电流。     

Asymptotic Bias and Variance of Conventional Bispectrum Estimates for 2-D Signals

In this paper, we derive the asymptotic bias and variance of conventional bispectrum estimates of 2-D signals. Two methods have been selected for the estimation: the first one – the indirect method – is the Fourier Transform of the weighted third order moment, while the second one – the direct method – is the expectation of the Fourier component product. Most of the developments are known for 1-D signals and the first contribution of this paper is the rigorous extension of the results to 2-D signals. The calculation of the bias of the direct method is a totally original contribution. Nevertheless, we did all calculations (bias and variance) for both method in order to be able to compare the results. The second contribution of this paper consists of the comparison of the theoretical bispectrum estimate bias and variance with the measured bias and variance for two 2-D signals. The first studied signal is the output of a non-minimal phase linear system driven by a non-symmetric noise. The second signal is the output of a non-linear system with Gaussian input data. In order to assess the results, we performed the comparison for both methods with different sets of parameters. We show that the maximum bias coefficient is the one of the 1-D case multiplied by the dimensionality of the signal for both methods. We also show that the estimate variance coefficient is the 1-D case coefficient with a power equal to the signal dimensionality.Received October 21, 2002; Revised December 2003; Accepted March 25, 2004; First Online Version published in December 2004     

Primary pericardial mesothelioma

This study reports the results of analysis concerning some chemical characteristics of 63 samples of tomato juice and paste. Copper was determined by atomic absorption spectrometry and its average content was 32 ppm. This is not a critical value for human health and results below the upper limit provided by law of several european and not european countries.     

A classification of endocervical curettings

The influence of inborn errors of metabolism on the amino acid content, the structure and growth of human hair has been studied in patients suffering from Phenylketonuria, Cystinosis, Homocystinuria and Tyrosinosis. Examiniation of hairs under the scanning electron microscope reveals defects and abnormalities such as a plicated pattern of the cuticula in patients with Phenylketonuria and Cystinosis. The amino acid content of the hydrolized hair keratin of all patients was within normal range and did not reveal significant changes of phenylalanine, cystine, homocystine, methionine or tyrosine. Disturbance in hair growth was determined by evaluation of standardized hair root samples. The results indicate an increase in hair root atrophy with increasing severity of the disorder of amino acid metabolism.     

Long-term exposure to jet fuel: an investigation on occupationally exposed workers with special reference to the nervous system

In the present study the results of a neurological and neurophysiological health examination of 29 aircraft factory workers chronically exposed to jet fuel vapors are presented. The exposed subjects were classified into a heavily exposed and a less heavily exposed group. The examination included a standardized clinical neurological examination, measurements of the conduction velocities in the peripheral nerves, and threshold determinations of vibratory sensations in the extremities. All 13 persons examined in the heavily exposed group and 7 of the 16 in the less heavily exposed group stated that they had repeatedly experienced acute effects (dizziness, respiratory tract symptoms, heart palpitations, a feeling of pressure on the chest, nausea, headache) of the jet fuel vapors in the inhaled air. A high rate of symptoms indicative of neurasthenia and psychasthenia and symptoms and signs indicative of polyneuropathy was observed both in the heavily exposed group and in the two groups combined in comparison with reference groups. Considering the presented facts concerning (a) the acute effects on repeated occasions, (b) the high rates of symptoms indicative of neurasthenia and psychasthenia and symptoms and signs indicative of polyneuropathy, and (c) the differences in the observations made between the two groups with varying degrees of exposure to jet fuel, the authors interpreted the results as indicative of a possible effect of long-term exposure to jet fuel on the nervous system.     

Stomach motility and lyspafen

The effects of spermidine and spermine at varying concentrations upon the replicative ability of human fibroblasts in cell culture have been studied. The average concentrations of spermidine causing a 50% inhibition of prolifertion (ID50) after 3 days of growth for three normal cell strains and three strains derived from patients with cystic fibrosis (CF) were 4.4 X 10(-6) +/- 1.2 M and 6.2 X 10(-6) +/- 2.1 M, respectively. The values for spermine were 2.0 X 10(-6) +/- 0.5 M for normal and 2.2 X 10(-6) +/- 0.1 M for fibroblasts from cystic fibrosis patients. No significant difference between the replicative ability of normal and CF cell strains was seen over a wide range of polyamine concentrations employed for a period of up to 3 days.     

Arterial radio-anatomy of the extrahepatic biliary system (author's transl)

The uni-arterial vascularisation of the lateral bilary duct makes it impossible to systematise the arteries which supply the common bile duct. Only the cystic artery is seen at coelio-mesenteric catheterization. The techniques essential for visualisation of the cystic artery are discussed, on the basis of one hundred coelio-mesenteric arteriograms: frequency of demonstration, origin, course, termination, calibre and length. The frequent finding of opacification of the wall of the gall bladder under normal conditions is stressed.