Prospective study of carotid endarterectomy and contralateral carotid occlusion

A total of 700 patients who had carotid endarterectomy (CEA) in the UK and Ireland during a 6-month interval between March and August 1994 were studied prospectively. Some 108 patients (15.4 per cent) had a contralateral internal carotid artery occlusion. Previous reports have shown an associated stroke rate of about 10 per cent in these patients. This study assessed complications and outcome for patients undergoing CEA with contralateral internal carotid artery occlusion compared with those without. The indications for surgery were comparable between the two groups although the patients with occlusion had a slightly higher incidence of arrhythmia and stroke. Intraoperative shunts were used in a significantly higher proportion of those with occlusion (83.3 versus 64.7 per cent, P = 0.0001). The combined death and stroke rate for patients with occlusion was 5.6 per cent compared with 2.4 per cent for the remainder (P not significant). On the basis of the present data, CEA with a contralateral carotid artery occlusion carries only a slight increase in the rate of postoperative stroke and death. This increase was not statistically significant and is lower than that reported previously.     

RBS/channelling study of ion-implanted and proton-exchanged LiNbO3:Nd:MgO planar waveguides

We present a structural study of two Nd³⁺/MgO codoped LiNbO₃ waveguides fabricated by two different methods: ion-implantation and proton-exchange. Rutherford backscattering spectrometry in combination with channelling was used to study the influence of the waveguide fabrication method on the possible modification of the LiNbO₃ crystal structure within the waveguiding layer. The results show that the ion-implanted waveguide mainly maintains the same properties as the virgin crystal, apart from a deterioration of a thin surface layer, whilst the proton-exchanged waveguide exhibits a quite different behaviour, although its surface is less damaged.     

中频变频器UFV故障探析

本文对中频变频器的UFV故障进行了系统试验和原因分析，并对UFV故障的关键因素进行了详细探析。     

Oral glutamine challenge in cirrhotics pre- and post-liver transplantation: a psychometric and analyzed EEG study

Latent or sub-clinical hepatic encephalopathy is a recognized complication of cirrhosis and is thought to represent one end of the spectrum of neuropsychiatric impairment, which occurrs as a result of portal-systemic shunting. We studied the psychometric, analyzed electroencephalography (EEG), and venous blood ammonia responses to an oral glutamine challenge in 17 patients with cirrhosis and in 4 normal controls. The cirrhotics were attending for liver transplant assessment and had no clinical evidence of hepatic encephalopathy. The oral glutamine challenge was repeated following liver transplantation. Five of sixteen patients (31%) showed impaired performance on at least one of the baseline psychometric tests. There was a correlation between fasting venous ammonia and choice reaction time (r = .7, P < .01). Following glutamine challenge there was a significant increase in blood ammonia from a mean fasting value ranging between 58 micromol/L to 120 micromol/L (P < .01), between significant prolongation of reaction times of 387 ms to 428 ms (P < .01), and an increase in mean EEG amplitude between 68.5 microV to 78.6 microV (P < .001). Four normal controls who were challenged with glutamine and 6 cirrhotic patients who were challenged with water showed no change in any of these parameters. Following orthotopic liver transplantation (OLT) the eight patients studied had normal baseline psychomotor performance with significant improvements in digit symbol, digit span, information processing, number connection tests (P < .05), and reaction time (P < .005). Posttransplantation, there were no significant changes in blood ammonia, analyzed EEG, or choice reaction time in response to oral glutamine challenge (six patients). We conclude that short lived changes in blood ammonia (in cirrhotics) can cause significant impairment of sensitive tests of brain function and that psychometric performance is improved following OLT.     

Computationally efficient methods for bit-error rate evaluation inweakly coherent optical systems

A semianalytical method to estimate the bit-error rate performance of nonsynchronous ASK and FSK optical heterodyne systems is presented. This approach takes into account numerous system details with an accuracy similar to Monte-Carlo simulation, but with a computation time reduced by several orders of magnitude. An analytical approximation, based on a closed-form expression for the decision variable moment generating function, is also presented. The results obtained with the semianalytical method and the analytical approximation are compared to Monte-Carlo simulation results and to measurements obtained on a practical FSK system     

土质边坡稳定分析中条分法与有限元法的比较

对比分析了土质边坡稳定性计算中条分法和有限元法的特点，讨论了在有限元法中边坡稳定系数的计算方法，并针对铜钟水电站库区左岸滑坡分别采用条分法和有限元法研究其稳定性，计算结果表明两种计算方法得到的滑坡稳定系数规律相同，但条分法计算值一般大于有限元值，反映出条分法中部分基本假设与实际情况存在一定差异。     

Uniform Polarization Scattering With Fiber-Coil-Based Polarization Controllers

A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PCs can be used to emulate both first- and second-order polarization-mode dispersions     

Total and acid-soluble fluoride content of infant cereals, beverages and biscuits from Brazil

Total fluoride (TF) and HCl 0.01 M ('gastric juice')-soluble fluoride (SF) were analysed in infant foods, beverages and calcium-rich biscuits. Samples were divided into seven categories: children cereals (A), chocolate-flavoured milk (B), soy beverages (C), filled biscuits (D), non-filled biscuits (E), wafer biscuits (F) and corn starch biscuits (G). Mean TF concentrations ± SD (amplitude, unit µg F ml^-1 or µg F g^-1) were: (A) 4.25 ± 3.04 (0.20 - 7.84, n = 6); (B) 0.34 ± 0.47 (0.05-1.27, n = 6); (C) 0.15 ± 0.07 (0.09-0.29, n = 8); (D) 8.44 ± 1.76 (7.65-10.47, n = 4); (E) 12.41 ± 1.15 (10.69-13.68, n = 4); (F) 0.35 ± 0 (0.34-0.36, n = 4) and (G) 7.77 ± 1.12 (6.86-8.68, n = 2). Five samples of cereals, one sample of chocolate-flavoured milk and 10 samples of biscuits were analysed for SF. In cereals analysed for SF, all fluoride was soluble, while for the chocolate-flavoured milk, approximately 50% of TF was soluble. Regarding the biscuits analysed for SF approximately 20% of TF was soluble. It was observed that some of the cereals and beverages, and most of the biscuits analysed, might be important contributors to total daily fluoride intake. When consumed just once per day, cereals and beverages might supply up to 25% of the maximum recommended daily fluoride intake (0.07 mg F kg^-1 body weight) for a 2-year-old child (12 kg). For the filled, non-filled and corn starch biscuits, when 3, 32 or 20 units of them, respectively, are consumed just once per day, they may supply up to 16% of the maximum recommended daily fluoride intake. However, only approximately 25% of fluoride absorption occurs from the stomach and 75% from the small intestine. Therefore, a higher fluoride bioavailability is possible.