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81.
MM Anceschi JJ Piazze Garnica V Unfer MR Di Benedetto EV Cosmi 《Canadian Metallurgical Quarterly》1996,24(4):355-362
Our aim was to determine the diagnostic accuracy and reliability of four tests for the assessment of fetal lung maturity (FLM): shake test, optical density at 650 nm (OD650), lecithin to sphingomyelin ratio (L/S) by planimetry and stechiometry, and presence of phosphatydylglycerol. Amniotic fluid was obtained from 74 patients at various gestational ages. The shake test and the OD650 were performed according to published methods L/S was determined by TLC (thin-layer chromatography) and the ratio assessed by planimetry and stechiometrically by measurement of organic phosphorus from the chromatographic spots. PG was assessed similarly by TLC. When correlated with gestational age at amniocentesis, all tests correlated positively: shake test (r = 0.46, p < 0.005); OD650 (r = 0.31, p < 0.005); planimetric L/S (r = 0.77, p < 0.005); stechiometric L/S (r = 0.52, p < 0.005) and PG (r = 0.54, p < 0.005). The diagnostic accuracy of each test was as follows: the shake test and the OD650 had a sensitivity of 50%, while the steciometric L/S had a sensitivity of 75%, the planimetric L/S and the presence of PG were 100%. All four tests demonstrated a specificity greater than 64%, the highest for the PG presence being (83%) and the shake test (86%). Predictive negative values for lung maturity were > 93% for all tests, with the highest for the planimetric L/S and presence of PG being (100%). The study confirms that the determination of L/S ratio is still superior to other tests in terms of overall diagnostic accuracy. In addition, it was found that presence of PG was highly associated with the absence of respiratory complications in the newborn. 相似文献
82.
The problem of the non-causal inversion of linear multivariable discrete-time systems is analyzed in the geometric approach framework and is solved through the computation of convolution profiles which guarantee perfect tracking under the assumption of infinite-length preaction and postaction time intervals. It is shown how the shape of the convolution profiles is related to both the relative degree and the invariant zeros of the plant. A computational setting for the convolution profiles is derived by means of the standard geometric approach tools. Feasibility constraints are also taken into account. A possible implementation scheme, based on a finite impulse response system acting on a stabilized control loop, is provided. 相似文献
83.
薄膜磁头磁轭制备工艺研究 总被引:1,自引:1,他引:0
本文重点讨论了用不同的工艺方法来制备薄膜磁头中的关键元件-磁轭。采用多次光刻的方法克服湿法工艺中磁性膜NiFe层的侧向钻蚀问题,从而实现对磁轭几何尺寸的精确控制,并对几种工艺方法的优缺点作了比较详细的分析。 相似文献
84.
C Alli F Avanzini G Bettelli M Bonati F Colombo R Corso M Di Tullio MG Gentile L Sangalli E Taioli 《Canadian Metallurgical Quarterly》1992,6(4):281-286
The present study set out to assess the feasibility of long-term moderate dietary sodium restriction in patients with mild hypertension in general practice. After screening and a run-in phase of 6-8 weeks, a total of 77 previously undiagnosed mildly hypertensive patients were identified. Half of them were randomized to receive a few simple dietary instructions from their general practitioners in order to reduce salt usage; the others were randomized to receive no advice. The patients were followed up for 12 months with quarterly visits. A total of 56 patients (72.7%) completed the study, 26 on a low-sodium diet (LD) and 30 on their usual diet (UD). At each visit in the diet phase, patients provided 24h urine, which was analysed for volume and sodium concentration in order to assess their sodium intake. Blood pressure, heart the rate and body weight were recorded. The mean urinary sodium excretion for all diet phase visits overlapped in the two groups (177.0 +/- 32.9 vs. 169.3 +/- 49.4 mEq/24h respectively in the LD and UD groups). Nevertheless the mean systolic and diastolic blood pressures for all diet phase visits were significantly lower in the LD than in UD group (144.2 +/- 11.1/91.6 +/- 6.4 and 148.0 +/- 13.7/95.6 +/- 4.7 mmHg respectively, P less than 0.01). Our data suggest that it is not feasible at present to reduce sodium intake in mild hypertensives with simple and inexpensive dietary instructions, the only ones suitable for widespread application in general practice. 相似文献
85.
P. Bocchetta C. Sunseri A. Bottino G. Capannelli G. Chiavarotti S. Piazza F. Di Quarto 《Journal of Applied Electrochemistry》2002,32(9):977-985
Alumina membranes were fabricated by anodizing aluminium metal in 0.15 M oxalic acid. The growth kinetics of the porous layer were investigated in the temperature range –1 to 16 °C using linear potential scans up to 70 V. The faradaic efficiencies of metal oxidation and of porous layer formation, determined by applying Faraday's law, were found to be independent of both temperature and electrical charge. SEM analysis of the metal-side and solution-side surfaces revealed different morphologies. After dissolution of the barrier layer in phosphoric acid, the metal-side surface showed circular pores whose size of about 90 nm was found to be uniform and independent of temperature. The pore population was also practically independent of temperature and a value of about 4 × 1013 pores m–2 was determined. On the solution-side surface the presence of a deposit partially occluding the mouths of pores was observed. This coating could be removed by chemical etching in NaOH or thermal treatment at 870 °C, where decomposition of oxalate occurs. This supports the hypothesis that the deposit consists of an aluminium salt containing oxalate anions precipitated from the solution. The results show that it is possible to control the morphological characteristics of the anodic alumina membranes by careful choice of experimental conditions. 相似文献
86.
L Sigurdsson A Flores PE Putnam PE Hyman C Di Lorenzo 《Canadian Metallurgical Quarterly》1997,131(5):751-754
We describe the clinical features and long-term outcome of 11 children who had persistent gastroparesis after an acute viral illness, eight of whom tested positive for rotavirus. Gastric emptying was delayed in the 10 children evaluated with scintigraphy. Antroduodenal manometry confirmed postprandial antral hypomotility in 10 subjects. All children recovered within 6 to 24 months. 相似文献
87.
Humin Cheng Jiming Ma Zhenguo Zhao Di Qiang Yongxiang Li Xi Yao 《Journal of the American Ceramic Society》1992,75(5):1123-1128
A pure, acicular lead titanate (PbTiO3 ) fine powder with a white color has been prepared by hydrothermal synthesis. It is a new phase of PbTiO3 with I 4 symmetry, cell parameters of a = 12.358 Å and b = 14.541 Å, and a density of 6.80 g.cm−3 . The influences of pH (12.5 to 14.4), Pb/Ti ratio (1.0 to 1.6) in the feedstock, reaction temperature (130° to 230°C), time (0.25 to 4 h), starting materials, and additives on the formation of acicular PbTiO3 under hydrothermal conditions have been investigated. The acicular PbTiO3 with I 4 symmetry, referred to as the PX phase, can be converted to the perovskite-type (PE phase) of PbTiO3 at about 605°C while its acicular morphology is essentially unchanged. The preferable conditions for preparing pure acicular PX-phase PbTiO3 are that the pH is 13.0 to 14.0, Pb/Ti ratio is >1.3, reaction temperature is 170° to 200°C, time is 0.5 to 1.0 h, titanium butoxide (Ti[O(CH2 )3 CH3 ]4 ) is the starting material, and poly(vinyl alcohol) is an additive. The acicular grain of the PX phase is usually less than 100 nm in diameter and more than 1000 nm in length. 相似文献
88.
89.
90.
Multiresidue method for pesticides in drinking water using a graphitized carbon black cartridge extraction and liquid chromatographic analysis 总被引:2,自引:0,他引:2
A general liquid-solid extraction procedure for the isolation of pesticides from groundwater and drinking water for high-performance liquid chromatography (HPLC) is presented. This simple and rapid procedure involved passing a 2-L sample through a 250-mg graphitized carbon black (Carbopack B) cartridge at a flow rate of 150-160 mL/min. By taking advantage of the presence of positively charged active centers on the Carbopack B surface, a stepwise elution system allowed the complete separation of base-neutral pesticides from acidic ones. After partial solvent removal, the components in the two fractions were separated and quantified by gradient elution, reversed-phase HPLC with ultraviolet (UV) detection. The performance of the Carbopack cartridge was compared with that of a 500-mg C-18 bonded silica cartridge. With the Carbopack cartridge, the grand mean measurement accuracy of the 35 pesticides considered was 95%. With the C-18 cartridge, the grand mean measurement accuracy of the analytes was 76%. Compared to the C-18 cartridge, additional advantages of using a Carbopack cartridge are that the extraction procedure is about 7 times shorter, no pH adjustment of the environmental sample is necessary for trapping acidic compounds, and one cartridge instead of two suffices to extract base-neutral and acidic pesticides, making the Carbopack cartridge more adaptable than the C-18 one for field use. The detection limits by this method of all the pesticides considered were between 0.003 and 0.07 micrograms/L. 相似文献