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61.
A panel of individuals from diverse ethnocultural backgrounds and representing a variety of genetic disorders presented their consumer perspectives on genetic programs, testing and services. Their remarks emphasized how misunderstanding and miscommunication between health care professionals and many of the populations for whom they provide services can lead to unfilled genetic service needs. Panelists recommended that health care professionals become more aware and knowledgeable about the diversity of customs, beliefs and cultures of those receiving their services. Only by building a foundation of trust and mutual respect will genetic testing, research and services become more accessible to individuals from diverse populations, their families and their communities. 相似文献
62.
63.
Interaction of von Karman vortices and intersecting main streams in staggered tube bundles 总被引:2,自引:0,他引:2
Flow visualization, heat transfer and pressure drop characteristics in flow through staggered tube bundles have been regarded
as classical, with results well-documented. However, the mechanism of producing such results has been left untouched. Applications
of staggered tube bundles are abundant in industry, for example as heat exchange devices like the shell-and-tube type and
fuel bundles in nuclear reactor cores. An experimental study is recorded in the present paper which investigates the interaction
of von Karman vortices and intersecting main streams in staggered tube bundles. Flow visualization by means of the particle
tracing method, laser Doppler velocimetry (LDV) and pressure drop measurements using a piezometer are conducted. A modified Reynolds number appropriate to flow through
a staggered tube arrangement is defined together with a pressure drop coefficient. Auto-correlation and power spectrum analyses
of signals obtained from LDV measurements yield an optimum spectrum frequency which is correlated against the Reynolds number. It is concluded that flow
characteristics in staggered tube bundles are determined by the interaction between the von Karman vortex street and X-shaped
interacting main streams.
Received: 4 August 1997 / Accepted: 3 October 1998 相似文献
64.
航天器轨道机动可达域是表征其在未来时间可能到达空间位置集合的有效方式,对维护航天器在轨安全、改善空间态势感知能力具有重要意义.现有关于可达域计算的方法仍然存在模型复杂、初值敏感性高导致计算效果较差等缺点,因此有必要发展更加简洁有效的可达域包络求解算法.本文基于近心点坐标系建立了基于未来可达位置矢量极值求解的可达域求解模型,首先定义任意指向的矢量描述方法并给出未来该指向位置是否可达的判据;其次,设置转移轨道面内机动方位角,将可达域求解问题转化为当前可达位置矢量方向的单变量极值求解问题,利用极值点处可达域包络面函数梯度需为零的条件确定转移轨道面机动方位角的取值,从而确定航天器的轨道机动可达域;此外根据二体轨道动力学特性,利用包络的对称性减少可达域求解计算量;最后通过蒙特卡洛打靶仿真对提出的可达域求解方法进行仿真验证.结果表明,本文方法对航天器单脉冲轨道机动可达域的计算结果与蒙特卡洛打靶仿真吻合良好,模型更加简洁且计算精度优于现有方法. 相似文献
65.
Shen-Hua Hu Jun-Jie YanJin-Shi Wang Yang LiJi-Ping Liu 《International Journal of Multiphase Flow》2007
This paper experimentally studied the effect of macroscopic temperature gradient on Marangoni condensation of ethanol–water vapor mixtures under a wide range of concentrations. For each concentration, the experiment was performed at different velocities and pressures. An oblique copper block was employed to create surface temperature gradient. The results indicated that local heat flux was varied along transversal condensation surface, which was caused by surface temperature gradient. This difference in heat flux might be attributed to the variation of condensate thickness on condensation surface. In addition, a mean heat transfer coefficient was derived along transversal condensation surface. For low ethanol concentration (0.5%, 1%), the coefficient kept a high value over a relative wide range of vapor-to-surface temperature difference (<10 K) and could be augmented as much as 15% as compared with literature under similar experimental condition. Moreover, the mean heat transfer coefficient generally increased with increasing velocity or pressure for all concentrations of the ethanol–water mixtures. 相似文献
66.
Nitriles were prepared from alkyl and aryl carboxylic acids in dry media conditions, under microwave irradiation. Heating of the carboxylic acid, urea and amidosulfonic acid adsorbed on alumina support in a microwave oven affords nitriles in 20–93% yields. 相似文献
67.
A novel synthesis of belinostat (1) starting from 3-nitrobenzaldehyde has been developed. The key step in this sequence involves the conversion of (2E)-3-(3-aminophenyl)acrylic acid methyl ester to (2E)-3-(3-chlorosulfonylphenyl)acrylic acid methyl ester via diazotization and sulfonylation. 相似文献
68.
Bo Yang R. R. Wu N. C. Polfer G. Berden J. Oomens M. T. Rodgers 《Journal of the American Society for Mass Spectrometry》2013,24(10):1523-1533
The gas-phase structures of alkali metal cation-cytosine complexes generated by electrospray ionization are probed via infrared multiple photon dissociation (IRMPD) action spectroscopy and theoretical calculations. IRMPD action spectra of five alkali metal cation–cytosine complexes exhibit both similar and distinctive spectral features over the range of ~1000–1900 cm-1. The IRMPD spectra of the Li+(cytosine), Na+(cytosine), and K+(cytosine) complexes are relatively simple but exhibit changes in the shape and shifts in the positions of several bands that correlate with the size of the alkali metal cation. The IRMPD spectra of the Rb+(cytosine) and Cs+(cytosine) complexes are much richer as distinctive new IR bands are observed, and the positions of several bands continue to shift in relation to the size of the metal cation. The measured IRMPD spectra are compared to linear IR spectra of stable low-energy tautomeric conformations calculated at the B3LYP/def2-TZVPPD level of theory to identify the conformations accessed in the experiments. These comparisons suggest that the evolution in the features in the IRMPD action spectra with the size of the metal cation, and the appearance of new bands for the larger metal cations, are the result of the variations in the intensities at which these complexes can be generated and the strength of the alkali metal cation-cytosine binding interaction, not the presence of multiple tautomeric conformations. Only a single tautomeric conformation is accessed for all five alkali metal cation–cytosine complexes, where the alkali metal cation binds to the O2 and N3 atoms of the canonical amino-oxo tautomer of cytosine, M+(C1). Figure
? 相似文献
69.
70.