Nutrient Limitation of Periphyton in a Spring-Fed, Coastal Stream in Florida, USA.

There is strong evidence to suggest that ground-water nitrate concentrations have increased in recent years and further increases are expected along portions of the central Gulf coast of Florida. Much of the nitrate enriched groundwater is discharged into surface waters through numerous freshwater springs that are characteristic of the area and the potential for eutrophication of their receiving waters is a legitimate concern. To test the potential effects of elevated nutrient concentrations on the periphyton community an in situ nutrient addition experiment was conducted in the spring-fed Chassahowitzka River, FL, USA, during the summer of 1999. Plastic tubes housing arrays of glass microscope slides were suspended in the stream. Periphyton colonizing the microscope slides was subjected to artificial increases in nitrogen, phosphorus or a combination of both. Slides from each tube were collected at 3- to 4- day intervals and the periphyton communities were measured for chlorophyll concentration. The addition of approximately 10 μg/L of phosphate above ambient concentrations significantly increased the amount of periphyton on artificial substrates relative to controls; the addition of approximately 100 μg/L of nitrate above ambient concentrations did not. The findings from this experiment implicated phosphorus, rather than nitrogen, as the nutrient that potentially limits periphyton growth in this system.(PDF contains 4 pages.)

用激波管研究超音速气固两相流

在激波管里进行了可压缩性气固两相流的实验研究。测量了激波通过颗粒群时的压力的衰减过程。用纹影仪拍摄了激波与颗粒群相互干涉的照片。试验了颗粒群的不同构造对压力衰减的影响。指出了激波反射、聚焦等非线性气动因素是可压缩性气固两相流的关键问题。

障碍物结构对管道中预混火焰加速的影响

在一端封闭、一端开口的火焰传播管中均匀布置障碍物，研究了障碍物结构对管道中预混火焰传播的影响。结果表明，由于障碍物的扰动，火焰不断加速，在阻塞比相同的条件下，最终的火焰稳态速度与障碍物的形状和间距基本无关，其中障碍物间距仅仅影响火焰的加速速率，在障碍物间距约等于火焰传播管内径（W/D ≈ 1.0）时，平均火焰速度达到最大值，火焰到达稳态传播的距离最短。同时，本文用一维简化模型模拟了火焰在障碍物管道中的加速过程，计算结果与实验测试结果在定性上比较吻合，说明在管内火焰速度较低的情况下，用一维可压缩流动近似处理能初步揭示管内火焰的加速机制。

The Characteristics of Semi-Cokes --The Solid Residues from Coal Partial Gasification

In this paper the proximate analysis and ultimate analysis of sulfur in different semi-cokes generated from Rizhao bituminous coal and Beijing anthracite under different temperatures is done. Also the tendency of the contents of volatile, ash, fixed carbon and sulfur in different semi-cokes along with the different preparation temperatures is studied. Then the combustion experiment of semi-cokes in the drop-tube furnace system was carried out, and the kinetic parameters of different semi-cokes ware calculated.

Measurement of Electron Density Profile Behind Strong Shock Waves with a Langmuir Probe

At the shock velocity range of 7~9km/s, the variations of electron density behind strong normal shock waves are measured in a low-density shock tube by using the Langmuir electrostatic probe technique. The electron temperature, calculated based on Park’s three-temperature model, is used in interpreting the probe current data. The peak electron densities determined in the present experiment are shown to be in a good agreement with those predicted by Lin’s calculation. The experimentally obtained ratios of the characteristic ionization distance to the mean free path of freestream ahead of the shock wave are found to be in a good agreement with the existing experiments and Park’s calculation.

Investigation of Vaporized Kerosene Injection in a Supersonic Model Combustor

Characteristics of vaporized aviation kerosene injection in a supersonic model combustor were preliminarily investigated. The electrically storage type heater has a volume capacity of heating kerosene of 0.8 kg up to 670 K at a pressure of 5.5 Mpa. The temperature to cause pressurized kerosene jet being fully vaporized in Quiescent atmosphere was found to be 550 K at 4 Mpa however the pressurized hot kerosene remains in liquid state within the tube. The correspondent jet spray in Mach 2.5 vitiated air cross-flow were visualized by using stop schlieren photograph.It was found the penetration depth of the hot pressurized kerosene jet is approximately same with the temperature varied from 290 K to 550 k. at pressure of 4 Mpa. This results showed that the atomization process of hot kerosene jet spray in supersonic combustor could be bypassed and directly transferred to be gas state at temperature 550 K and pressure of 4 Mpa.

Numerical Investigation of Toroidal Shock Wave Focusing

In this paper,focusing of a toroidal shock wave propagating from a shock tube of an- nular cross-section into a cylindrical chamber was investigated numerically with the dispersion- controlled scheme. For CFD validation, the numerical code was rst applied to calculate both viscous and inviscid ows at a low Mach number of 1.5, which was compared with the experi- ment results and got better consistency. Then the validated code was used to calculate several cases for high Mach numbers. From the result, several major factors that in uent the ow, such as the Mach number and the viscosity, were analyzed detailedly and along with the high Mach number some unusual ow structure was observed and explained theoretically

Measurement and Calculation of Vibrational Temperature behind Strong Shock Waves

In the present paper the measured values of vibrational temperature behind strong shock waves are compared with theoretical ones. The histories of vibrational temperature behind strong shock waves in a shock tube were measured using two monochromators. The test gas was pure nitrogen at 100-300Pa, and the speeds of shock waves were 5.0-6.0km/s. The electronic temperature of N-2(+) was also approximately determined from experiment and compared with the experimental vibrational temperature. The results show that the presented calculational method is effective, and the electronic energy of N2+ is excited much faster than its vibrational energy. One Langmuir probe was used to determine the effective time of region 2. The influence of viscosity in the shock tube is also analyzed.

Research progress on high-enthalpy and hypersonic flows

The research progress on high-enthalpy and hypersorlic flows having been achieved in the Institute of Mechanics, Chinese Academy of Sciences, is reported in this paper. The paper consists of three main parts: The first part is on the techniques to develop advanced hypersonic test facilities, in which the detonation-driven shock-reflected tunnel and the detonation-driven shock-expanded tube are introduced. The shock tunnel can be used for generating hypersonic flows of a Mach number ranging from 10 to 20, and the expansion tube is applicable to simulate the flows with a speed of 7 similar to 10km/s. The second part is dedicated to the shock tunnel nozzle flow diagnosis to examine properties of the hypersonic flows thus created. The third part is on experiments and numerical simulations. The experiments include measuring the aerodynamic pitching moment and heat transfer in hypersonic flows, and the numerical work reports nozzle flow simulations and flow non-equilibrium effects on the possible experiments that may be carried out on the above-mentioned hypersonic test facilities.

高频感应等离子体风洞的流场研究

高频感应等离子体风洞适合于基础研究特别是用于防热材料的催化特性的研究，本文用实验测量和数值模拟了该风洞的温度场和速度场。温度场是用OSA （Optical Spectrum Analyzer）进行光谱分析得到的，同时用水冷总压和静压探针对风洞的流场进行测量得到了速度场的空间分布。数值模拟采用完全二维的高频感应等离子模型，我们通过求解相关的能量方程、流体动力学方程和电磁场方程得到了相应的温度场和流场。比较了数值模拟结果与实现测量结果，并给出了不同运行参数下的典型数值结果。

障碍物扰动对半开口管道中火焰传播特性的影响

自从1926年Chanman和Wheeler率先开创有障碍物管道中的火焰传播研究工作以来，管道中障碍物扰动引起的火焰加速现象引起了广泛的关注。由于这类现象在燃烧科学上的学术意义及其在生产中诸如安全问题等方面的实际意义，人们相继进行了一系列的研究工作。归纳起来，可以分为两大类：1）封闭管道的火焰传播。人们在不同形状的管道或容器中研究了障碍物对火焰加速的影响，在理论分析和数值计算方面也作了一些有益的工作；2）开口管道的火焰传播。相对于闭口管道，开口管道中的火焰传播研究则逊色得多。这方面尚缺乏系统的实验数据，理论方面的分析也欠缺得多。但当前在实际中，并不乏开口体系的应用，如，现已广泛应用于电力系统的一种燃气除灰装置，是一燃烧气体燃料的半开口系统。因此，研究半开口管道中非稳态燃烧的加速机制具有重要意义。在本论文工作中，通过大量的实验研究，比较系统地研究了障碍物的扰动对预混火焰传播特性的影响。实验在一长L=5m、内径D＝80mm的一端封闭、一端开口的火焰传播管内进行，管内均匀布置障碍物，通过改变障碍物的形状、间距、阻塞比大小，同时选用五种不同的可燃气体，探索了障碍物结构对预混湍流火焰加速和管内压力上升的影响。实验表明，对于敏感气体如氢气和乙炔，由于障碍物扰动产生的影响，火焰不断加速，并最终达到一准稳定状态；在适当的条件下，火焰传播状态可由爆燃向爆轰转变，此时火焰速度发生跃变；而对干不敏感气体如甲烷，则爆燃转爆轰现象不容易发生。在不同的火焰传播状态，障碍物结构特性对火焰速度和压力产生的影响各不相同。在缓燃态，随着阻塞比的变化，最大火焰速度先上升后下降，在BR=0.3～0.4之间存在一最大值；在銮塞态，最大火焰速度受阻塞比变化的影响不明显，略低于燃烧产物的声速；在阻塞比BR＝0.5附近，压力达到最大值。而在爆轰态，随着阻塞比的增加，最大火焰速度和压力逐渐降低，爆燃转爆轰的浓度范围变小。由于在有障碍物的管道中，火焰速度很容易达到声速（变塞态）或超声速（爆轰态），必须考虑流体的马赫数效应。本文在前人研究成果的基础上，给出了湍流马赫数修正的可压缩性两方程湍流模型，模拟了半开口狭长管道中重复布置的障碍物引起的湍流火焰加速现象。最大火焰速度和管内压力的计算结果与实验测量值吻合良好，这表明用修正后的湍流模型能够比较真实地模拟障碍物管内预混火焰的发展过程。通过对管道内障碍物扰动引起的燃烧波加速的机理和技术研究，对流场扰动对燃烧波产生和发展的影响规律有了比较全面的了解，研究结果对气脉冲除灰技术的完善具有直接的指导意义。

Diagnosis of invasive candidiasis by enzyme-linked immunosorbent assay using the N-terminal fragment of Candida albicans hyphal wall protein I

Background: The diagnosis of invasive candidiasis is difficult because there are no specific clinical manifestations of the disease and colonization and infection are difficult to distinguish. In the last decade, much effort has been made to develop reliable tests for rapid diagnosis of invasive candidiasis, but none of them have found widespread clinical use. Results: Antibodies against a recombinant N-terminal fragment of the Candida albicans germ tube-specific antigen hyphal wall protein 1 (Hwp1) generated in Escherichia coli were detected by both immunoblotting and ELISA tests in a group of 36 hematological or Intensive Care Unit patients with invasive candidiasis and in a group of 45 control patients at high risk for the mycosis who did not have clinical or microbiological data to document invasive candidiasis. Results were compared with an immunofluorescence test to detect antibodies to C. albicans germ tubes (CAGT). The sensitivity, specificity, positive and negative predictive values of a diagnostic test based on the detection of antibodies against the N-terminal fragment of Hwp1 by immunoblotting were 27.8 %, 95.6 %, 83.3 % and 62.3 %, respectively. Detection of antibodies to the N-terminal fragment of Hwp1 by ELISA increased the sensitivity (88.9 %) and the negative predictive value (90.2 %) but slightly decreased the specificity (82.6 %) and positive predictive values (80 %). The kinetics of antibody response to the N-terminal fragment of Hwp1 by ELISA was very similar to that observed by detecting antibodies to CAGT. Conclusion: An ELISA test to detect antibodies against a recombinant N-terminal fragment of the C. albicans germ tube cell wall antigen Hwp1 allows the diagnosis of invasive candidiasis with similar results to those obtained by detecting antibodies to CAGT but without the need of treating the sera to adsorb the antibodies against the cell wall surface of the blastospore.

Hydroelectric Voltage Generation Based On Water-Filled Single-Walled Carbon Nanotubes

A DFT/MD mutual iterative method was employed to give insights into the mechanism of voltage generation based on water-fitted single-walled carbon nanotubes (SWCNTs). Our calculations showed that a constant voltage difference of several mV would generate between the two ends of a carbon nanotube, due to interactions between the water dipole chains and charge carriers in the tube. Our work validates this structure of a water-fitted SWCNT as a promising candidate for a synthetic nanoscale power cell, as well as a practical nanopower harvesting device at the atomic level. 

Transport Properties And Induced Voltage In The Structure Of Water-Filled Single-Walled Boron-Nitrogen Nanotubes

Density functional theory/molecular dynamics simulations were employed to give insights into the mechanism of voltage generation based on a water-filled single-walled boron-nitrogen nanotube (SWBNNT). Our calculations showed that (1) the transport properties of confined water in a SWBNNT are different from those of bulk water in view of configuration, the diffusion coefficient, the dipole orientation, and the density distribution, and (2) a voltage difference of several millivolts would generate between the two ends of a SWBNNT due to interactions between the water dipole chains and charge carriers in the tube. Therefore, this structure of a water-filled SWBNNT can be a promising candidate for a synthetic nanoscale power cell as well as a practical nanopower harvesting device.

Transport properties and induced voltage in the structure of water-filled single-walled boron-nitrogen nanotubes

Density functional theory/molecular dynamics simulations were employed to give insights into the mechanism of voltage generation based on a water-filled single-walled boron-nitrogen nanotube (SWBNNT). Our calculations showed that (1) the transport properties of confined water in a SWBNNT are different from those of bulk water in view of configuration the diffusion coefficient the dipole orientation and the density distribution and (2) a voltage difference of several millivolts would generate between the two ends of a SWBNNT due to interactions between the water dipole chains and charge carriers in the tube. Therefore this structure of a water-filled SWBNNT can be a promising candidate for a synthetic nanoscale power cell as well as a practical nanopower harvesting device.