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排序方式: 共有1514条查询结果,搜索用时 15 毫秒
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Martins Silvia S.; Mazzotti Guido; Chilcoat Howard D. 《Canadian Metallurgical Quarterly》2006,14(3):275
Background: Despite increases in ecstasy (MDMA) use in the United States, little is known about characteristics linked with recent-onset ecstasy use, especially psychiatric symptoms and deviant behaviors. Aims: To test whether individuals with high levels of other drug use are more likely to be recent-onset ecstasy users; to test whether psychiatric symptoms in adults are associated with recent-onset ecstasy use; to explore the association between recent-onset ecstasy use and concomitant deviant behaviors in adolescents and adults. Methods: Data from the 2001 National Survey on Drug Use and Health. Findings: Recent-onset ecstasy use was significantly more likely to occur among adolescents and adults (18-34 years old) who engaged in deviant behaviors during the past year as compared with those who did not engage in deviant behaviors during the past year. Higher levels of deviancy indicated a higher likelihood of being a recent-onset ecstasy user, and associations were strongest with nonviolent deviant behaviors such as selling illegal drugs and stealing. Associations between deviant behaviors and recent-onset ecstasy use were similar in strength to associations between deviant behaviors and recent-onset cocaine and marijuana use, respectively. Adults who had past-year psychiatric symptoms (both depressive and panic symptoms) were twice as likely to be recent-onset ecstasy users as compared with those without past-year psychiatric symptoms. Greater levels of drug involvement increased the odds of being a recent-onset ecstasy user. Conclusion: Recent-onset ecstasy use seems to be associated with a range of other behavioral problems and may reflect one aspect of a larger problem behavior syndrome. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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介绍北方交通大学与比利时鲁汶大学、布鲁塞尔自由大学、比利时铁路公司合作,在巴黎至布鲁塞尔之间高速铁路线上的Antoing大桥进行的二次高速铁路桥梁动力试验。试验桥梁由跨度50m的多跨预应力混凝土简支槽型梁构成,试验中列车速度达265-310km/h。通过现场试验和实验结果分析,得到了桥梁的频率、振型、阻尼等自振特性,以及桥梁在高速列车作用下的动挠度、梁和桥墩的横向和竖向加速度、橡胶支座的相对位移、梁体的动应变等动力响应特性。试验经验和测试结果对于充实高速铁路桥梁动力分析理论、改进数值分析模型、验证计算结果、提高高速铁路桥梁的动力设计水平、保证行车安全,具有重要的意义。 相似文献
4.
Roberto Leoni Bruno Buonomo Gabriella Castellano Francesco Mattioli Guido Torrioli Luciana Di Gaspare Florestano Evangelisti 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,520(1-3):44-47
We discuss the performance, of a normal metal hot electron bolometer (NHEB) that we have measured at 0.3 K. We found that the noise equivalent power was limited by the amplifier noise. To improve the NHEB power response and to make it more robust and reliable we propose to substitute the normal metal with heavily doped silicon. The heavily doped silicon behaves like a metal with lower carrier concentration and has a smaller electron–phonon thermal coupling. We have fabricated superconductor-doped silicon-superconductor contacts (S-Sm-S) and we have used them as thermometers and coolers. 相似文献
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BACKGROUND: We report a prospective comparative study of the efficacy of three commercial cell lines in the isolation of the parainfluenza (PI) virus from nasopharyngeal samples. MATERIAL AND METHODS: In a 16 months period we studied all nasopharyngeal samples from patients with the suspension of a viral respiratory infection. The compared cell lines were LLC-MK2 and MDCK. All samples were processed by the shell-vial assay, incubated 3 days at 36 degrees C. The monolayers were stained by an indirect immunofluorescence assay with a monoclonal antibody against the nucleoprotein of the PI virus. RESULTS: In the study period 746 samples were analyzed, 46 PI virus were isolated, all belonged to the serotype 3. The LLC-MK2 cell line isolated 44 viruses (95.6%) and the MDCK cell line 41 (89.1%), no statistically significant differences were detected (p = 0.14) (qualitative sensitivity). In 84.8% of positive samples, the PI virus was isolated simultaneously in the two cell lines. Neither cell line isolated all PI virus. No statistical differences were detected in the quantitative sensitivity, although the LLC-MK2 cell line detected a slightly more samples with a low viral load (70.4 vs 68.2%). CONCLUSIONS: In view of the results obtained in this study, we believe that anyone of the two cell lines would be used in the isolation of the PI virus from respiratory samples. 相似文献
7.
As an alternative to previously developed catalytic FeCrAlloy fibre mat burners based on perovskite catalysts, new catalytic burners have been developed based on Pd catalyst on lantana-stabilised Al2O3 and different fibre structures (NIT100A, NIT100S and NIT200S by ACOTECH NV). All development steps are considered, shifting from catalyst preparation (based on combustion synthesis of γ-Al2O3) to the optimisation of lantana and Pd loadings, from the definitions of the best catalyst-deposition conditions (washcoating) to the catalytic burners performances, determined in an ad hoc developed combustion chamber. The results show almost half pollutants emissions and better performance compared to various non-catalytic counterparts, especially as far as CO and NOx emissions are concerned. Some flame instability problems were though registered, especially for one of the catalytic burner mattresses employed, at low specific power inputs and excesses of air (<375 kW/m2 and <12%, respectively). Further, PdO/Pd transition is shown to influence the dynamic behaviour of the catalytic burners. 相似文献
8.
The design of feedback-linearization and poles-placement controllers for discrete-time non-linear plants, using Input/Output/State measurements only, is typically addressed via indirect design. In this paper we propose the use of a new technique, based on a Virtual Input Direct Design (VID2) approach. The main feature of such a technique is to reduce the control design problem into a standard non-linear mapping approximation problem, without calling for the preliminary construction of an appropriate model of the plant. As compared with the existing methods, the new one requires less computational effort, while taking full advantage of the non-linear approximation software tools already available. In this paper, the new method is described, a simple theoretical analysis is given, and some numerical examples are presented. 相似文献
9.
Influence of electroosmotic treatment on the hydro-mechanical behaviour of clayey silts: preliminary experimental results 总被引:1,自引:0,他引:1
Laura Gabrieli Cristina Jommi Guido Musso Enrique Romero 《Journal of Applied Electrochemistry》2008,38(7):1043-1051
Preliminary results of an investigation focused on the influence of electrokinetic treatment on the mechanical and hydraulic
behaviour of clayey soils are presented. The experimental programme aims at providing a contribution to the sustainability
of contaminant extraction or containment via electroosmosis. Changes in the hydraulic and mechanical properties of two illitic
clayey soils, subjected to a DC electric field, were investigated. Samples of the two soils were subjected to electrokinetic
filtration, for different periods of time, and under different constant loads. Afterwards, they were tested under one-dimensional
compression to detect changes in stiffness and hydraulic conductivity due to the electrical treatment. After the application
of a DC field for a few hours, a small reversible increment in the average soil stiffness was observed, with respect to the
untreated soil, while the hydraulic conductivity was not affected substantially. Dramatic changes of the mechanical and hydraulic
soil properties, correlated to changes of the soil pH, were observed following non-conditioned electrokinetic treatment with
duration of the order of days. 相似文献
10.
MA Reina Perticone A López Garciá ME Gorra J Daneri 《Canadian Metallurgical Quarterly》1998,64(11):489-497
BACKGROUND AND AIM: Several authors have focused on a causal link between the onset of neurological complications after lumbar injections and the fact that epithelial cells may be drawn into the vertebral canal during these procedures. Complications may arise both early (cephalea, septic and aseptic meningitis) and late (epidermoid tumours). The authors aimed to evaluate whether skin fragments which are carried down by the needle during subarachnoid anesthesia may even be present in the epidural or subarachnoid space three days later and may therefore justify the onset of the above neurological syndromes. METHODS: Five adult cats under narcosis underwent subarachnoid anesthesia using disposable 22G Quincke type needles. Between 0.7 and 1 ml isobaric bupivacaine at 0.50% was injected. The presence of the motor block of the lower limbs was ascertained once the effects of general anesthesia wore off. On the third day, again under general anesthesia, cardio-respiratory arrest was provoked by intravenous injection. Samples of meninges were collected in the injection area. After fixation in a phosphate glutaraldehyde buffer, dehydration in acetone, dehydration by critical point and gold metalisation, the samples were examined using SEM. RESULTS: No epidermal cells were found on the surface of the meninges. On the other hand, a squamous epithelial cell was observed which drained inside a sectioned epidural vessel towards the systemic circulation. CONCLUSIONS: This study confirms the possibility that, after subarachnoid anesthesia using 22G Quincke needles, skin fragments may enter the spinal canal. The permanence or otherwise of the epithelial fragments on the third day depends on the size of the fragment drawn down and the efficacy of the drainage system which removes isolated epithelial cells. This phenomenon may justify the self-limiting character of cephalea and meningisms which, even if not treated, regress in a few days, as well as the scarce development of epidermoid tumours. 相似文献