An exploratory study of the behaviour of crude oil spills under ice

An experimental spill of 0.38 m³ of warm (55°C) crude oil under the ice cover of a fresh water pond with an underwater viewing port is described. Temperatures, dissolved hydrocarbon concentrations and oil slick behaviour and areas were determined. Some oil recovery and disposal methods were tested. An attempt has been made to quantify the rates of heat and mass transfer from the oil using reported values for transfer coefficients. The results indicate that the oil slick adopted a thickness of about 2 cm under the ice, that heat transfer from the oil was relatively fast and complete, that dissolution mass transfer is slow resulting in oil concentrations in the water of only 18 to 287 μg/l in the vicinity of the spill. Some recommendations are made for further studies to elucidate the nature and rates of the relevant physical processes and thus assist in assessing the environmental impact of under-ice oil spills.     

平面四杆机构高阶和复合点阶综合的CAD几何法

提出四连杆机构高阶和复合点近似综合的CAD几点法，确定机构连杆的位置、速度和加速度与轨迹曲线的点，一阶导数和二阶导数的等效关系，基于几何约束和尺寸驱动技术，构造一个基本四连杆模拟机构，再根据机构高阶和复合点阶综合的任务，由基本四连杆模拟机构分别构造出高阶和复合点阶近似综合模拟机构，采用修改尺寸和尺寸动态变化技术，检查和分析尺寸变化对机构的影响因素，干涉情况，确定机构的理想形状，计算机模拟结果表明，该方法不仅快捷，直观，而且具有求解精度高和重复性好的优点，为连杆机构的高阶和复合点阶综合提供有效的工具。     

Pneumococcal immune complexes in the diagnosis of lower respiratory infections in children

BACKGROUND: In recent years serologic methods have been applied to assess pneumococcal etiology of pneumonia and other respiratory tract infections. Antigen and antibody assays have shown to be insensitive, especially in young children. The aim of this study was to evaluate the usefulness of circulating immune complexes in the diagnosis of pneumococcal lower respiratory infection in children. MATERIAL AND METHODS: Pneumococcal immune complexes (IC) containing antibodies to species-specific C-polysaccharide, to mixtures of type-specific capsular polysaccharides or to a protein antigen, pneumolysin, were studied in the sera of 449 children with lower respiratory tract infection. RESULTS: Circulating ICs were found in 68 (15%) children; 46 (68%) of them were demonstrated in acute and 43 in convalescent serum. In 5 (7%) of the 68 IC-positive patients pneumococcal antigen was present in acute serum; those patients formed 18% of the 28 cases with antigenemia. An antibody response between paired sera to any of the 3 pneumococcal antigens studied was observed in 14 (21%) IC-positive children; they formed 23% of the 60 cases with an antibody response. In total ICs were positive in 51% of all the 134 pneumococcal cases diagnosed by any method. CONCLUSIONS: We conclude that the measurement of circulating ICs is more sensitive than other serologic methods for the diagnosis of pneumococcal lower respiratory infection. In infants, however, it was as insensitive as antigen and antibody assays.     

Vertical external-cavity surface-emitting laser for dual-wavelength generation

We report an optically pumped vertical external-cavity surface-emitting laser that is designed for emission at two wavelengths simultaneously. Single transverse mode continuous-wave (CW) operation is demonstrated at the wavelengths of 984 and 1042 nm. The device produces a CW optical power of 140 mW for the 984-nm component and 115 mW for the 1042-nm component, exhibiting over 10% efficiency. At a high pump power, self-pulsation of the components appeared on top of the CW-mode components. The maximum total output of 1 W was obtained at the pump power of 9 W.     

Ion-implanted capacitively coupled silicon strip detectors with integrated polysilicon bias resistors processed on a 100 mm wafer

Double-sided silicon strip detectors with integrated coupling capacitors and polysilicon resistors have been processed on a 100 mm wafer. A detector with an active area of 19 × 19 mm² was connected to LSI readout electronics and tested. The strip pitch of the detector is 25 μm on the p-side and 50 μm on the n-side. The readout pitch is 50 μm on both sides. The number of readout strips is 774 and the total number of strips is 1161. On the p-side a signal-to-noise of 35 has been measured using a ⁹⁰Sr β-source. The n-side has been studied using a laser.     

Etiology of pneumonia and other common childhood infections requiring hospitalization and parenteral antimicrobial therapy. SE-TU Study Group

The etiology of acute lower respiratory tract infections (mostly pneumonia) in children is well characterized, but these are only some of the community-acquired infections warranting parenteral antimicrobial therapy. We prospectively evaluated all such infections among children aged 3 months to 15 years by use of blood cultures, examination of nasopharyngeal aspirates, and serologies for 15 viral, 7 bacterial, and 1 protozoal agent. Immunocompromised patients and those with urinary tract infection, meningitis, or osteoarticular infection were excluded. In all, 170 children were included. The pathogenic agent was identified in 62% of the cases. Bacteria were detected in 54%, and a pneumococcus was found in 59% of the cases identified. Viruses were found in 15% overall. Sole bacterial or viral infections were detected in 47.1% and 8.1%, respectively. Since thorough screening established the etiology in less than two-thirds of patients ill enough to be hospitalized and treated parenterally, better diagnostics are needed, especially to identify those who would truly benefit from antimicrobial therapy.     

Chlamydia pneumoniae and acute myocardial infarction in Jerusalem

BACKGROUND: A number of studies in European and North American populations have reported associations between Chlamydia pneumoniae seropositivity and coronary heart disease (CHD). Our objective was to assess the association of IgG and IgA antibodies to C. pneumoniae with acute myocardial infarction (MI) in a population-based case-control study in a Middle Eastern country. METHODS: Eligible cases aged 25-64 with a first acute MI were ascertained through an active surveillance system in Jerusalem hospitals between 1987 and 1989 (85% response). Controls were Jerusalem residents aged 25-64 sampled from the national population registry (83% response). Data on sociodemographic variables, CHD history and risk factors were collected by interview. Chlamydia serology, available for 93% of eligible participants, was performed by microimmunofluorescence on frozen stored samples using the TWAR antigen. Altogether, 251 male and 51 female cases, and 324 male and 162 female controls were analysed. RESULTS: Overall, high IgG titres (> or = 128) were not associated with increased risk of acute MI (Odds ratio [OR] = 0.74 for men [95% confidence interval (CI): 0.47-1.17] and 0.91 for women [95% CI: 0.43-1.94]); neither were high IgA titres (> or = 80) (OR = 1.11 for men [95% CI: 0.71-1.73] and 1.15 for women [95% CI: 0.33-4.0]). At IgG and IgA titres of > 32 and > 20 respectively there was also no relation. CONCLUSIONS: An association of C. pneumoniae seropositivity with acute MI was not confirmed in this population with a very high IgG seropositivity prevalence of 84% in males and 69% in females. However, we cannot exclude the possibility that a postulated recent outbreak obscured an association with chronic C. pneumoniae infection.     

Energy harvesting with a cymbal type piezoelectric transducer from low frequency compression

In this paper a piezoelectric energy harvester based on a Cymbal type structure is presented. A piezoelectric disc ?35?mm was confined between two convex steel discs ?35?mm acting as a force amplifier delivering stress to the PZT and protecting the harvester. Optimization was performed and generated voltage and power of the harvester were measured as functions of resistive load and applied force. At 1.19?Hz compression frequency with 24.8?N force a Cymbal type harvester with 250?μm thick steel discs delivered an average power of 0.66?mW. Maximum power densities of 1.37?mW/cm³ and 0.31?mW/cm³ were measured for the piezo element and the whole component, respectively. The measured power levels reported in this article are able to satisfy the demands of some monitoring electronics or extend the battery life of a portable device.     

A correlation for the solubility of hydrocarbons in water

A correlation has been developed for the solubility of C₄ to C₁₀ hydrocarbons in water at 25°C and atmospheric pressure. The excess Gibbs free energy is correlated in terms of an effective molar volume which is related to the actual molar volume adjusted to include the effects of the degree of branching, the number of olefinic and acetylenic bonds and the number of aromatic and cycloalkane rings. The root mean square deviation between 59 correlated and experimental solubilities is 20%. The range of solubilities is from 0.052 to 5150 g hydrocarbon per 10⁶ g water. The correlation provides a rational procedure for the estimation of solubility of other hydrocarbons.