涡旋式压缩机中的蒸气喷射

这篇论文定量分析了在应用于空调及制冷场合时，在涡旋压缩机中应用蒸气喷射技术带来的潜在优势。蒸气喷射将压缩过程划分为两个阶段，减小压缩机功耗和降低蒸发器吸气流量，从而提高其容量。另外比较了两套均采用涡旋压缩机并且同为三冷吨容量的系统(一套使用蒸气喷射技术而另一套则不使用)。建立了一个多级压缩机模型，考虑了过压缩和欠压缩并根据一个单级系统得到了验证。详细的数学模拟模型预测表明，对于空调系统来说COP将提高约6～8％，而压缩机排量将降低16％。对于制冷装置来说，也能获得类似的好处。     

Mechanisms of cement hydration

The current state of knowledge of cement hydration mechanisms is reviewed, including the origin of the period of slow reaction in alite and cement, the nature of the acceleration period, the role of calcium sulfate in modifying the reaction rate of tricalcium aluminate, the interactions of silicates and aluminates, and the kinetics of the deceleration period. In addition, several remaining controversies or gaps in understanding are identified, such as the nature and influence on kinetics of an early surface hydrate, the mechanistic origin of the beginning of the acceleration period, the manner in which microscopic growth processes lead to the characteristic morphologies of hydration products at larger length scales, and the role played by diffusion in the deceleration period. The review concludes with some perspectives on research needs for the future.     

Air-side thermal hydraulic performance of multi-louvered fin aluminum heat exchangers

An experimental study on the air-side heat transfer and pressure drop characteristics for multi-louvered fin and flat tube heat exchangers has been performed. For 45 heat exchangers with different louver angles (15–29°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm), a series of tests were conducted for the air-side Reynolds numbers of 100–600, at a constant tube-side water flow rate of 0.32 m³/h. The inlet temperatures of the air and water for heat exchangers were 21 and 45°C, respectively. The air-side thermal performance data were analyzed using effectiveness-NTU method for cross-flow heat exchanger with both fluid unmixed conditions. The heat transfer coefficient and pressure drop data for heat exchangers with different geometrical configurations were reported in terms of Colburn j-factor and Fanning friction factor f, as functions of Reynolds number based on louver pitch. The general correlations for j and f factors are developed and compared to other correlations. The f correlation indicates that the flow depth is one of the important parameters for the pressure drop.     

Managing the uncertainties of low-level radioactive waste disposal

A special program developed by the authors, called Pombe, identifies protein coding regions in the Schizosaccharomyces pombe genome. Linear discriminant analysis was applied to predict 5'-terminal, internal, 3'-terminal exons (coding-exon) and introns. The accuracy of the prediction was tested by cross verifications. The sensitivity, specificity and correlation coefficient for the internal exon prediction were 98.5%, 99.9% and 98.3% respectively at the nucleotide level. Open reading frames were studied and used to predict intron-less genes: 99.0% of such genes were identified with correct stopping sites. The gene structure was determined by dynamic programming and the prediction achieved 97.0% correlation coefficient at the nucleotide level. The program is available at http:(/)/clio.cshl.org/genefinder.     

A minimal role for selectins in the recruitment of leukocytes into the inflamed liver microvasculature

A two-step paradigm for leukocyte recruitment has been established in a number of tissues including the mesentery, skin, and muscle, and necessitates an initial rolling step via the selectins before firm leukocyte adhesion via the integrins. In view of the many inflammatory diseases that involve the liver, we investigated the importance of rolling and the selectins in the hepatic microvasculature and compared the responses to that of the commonly used mesentery or cremaster microvasculature. We visualized the liver microvasculature using intravital microscopy and we determined that within the liver the majority of leukocytes adhere within the sinusoids (80%) in response to a chemotactic stimulus such as FMLP (20% in postsinusoidal venules) whereas leukocytes adhere exclusively within postcapillary venules in tissue like the mouse cremaster. In the sinusoids, the adhesive response to FMLP is not dependent upon selectins inasmuch as adhesion was not reduced in the sinusoidal vessels of P-selectin-deficient mice or E-selectin/P-selectin- deficient animals in the presence or absence of L-selectin antibody. No rolling or adhesion was detected in response to FMLP in the selectin-deficient cremaster microvasculature. Immunoneutralization of selectins with fucoidan in wildtype mice eliminated rolling and adhesion in the cremaster but failed to affect adhesion in the liver sinusoids in response to FMLP. More long-term leukocyte recruitment with lipopolysaccharide (4 h) was also impaired in the cremaster but not the liver microvasculature in selectin-deficient animals. Leukocyte adhesion in the sinusoids was reduced in P-selectin-deficient mice also lacking intercellular adhesion molecule-1 (ICAM-1). This study for the first time demonstrates that selectins are not an essential step for leukocyte recruitment into the inflamed liver microvasculature.     

Thermodynamics and Kinetics of Surface Area Changes of Faceted Particles

An equation is derived that describes the influence of particle size and shape on the free energies of particles of anisotropic specific surface free energies. When the specific surface free energy is isotropic, the general equation reduces directly to the Gibbs–Thomson equation for the chemical potential of spherical drops and predicts the accepted driving force for neck growth between two spherical particles. The general equation is also used to obtain equations for the chemical potentials of particles of non-equilibrium shapes and to derive alternate rate equations for different possible rate-controlling steps of mass transport when faceted {100} ridge/channel arrays etched into a {100} single-crystal surface decrease in depth to reduce the surface free energy. Edge free energies are suggested to sometimes play important roles in determining the sequence of shape changes that occur when particles of non-equilibrium shapes are annealed.     

Cardiac tamponade in Taiwan

We describe two sibs with chorioretinal dystrophy, hypogonadotrophic hypogonadism, and cerebellar ataxia, Boucher-Neuh?user syndrome, a rare but distinct pleiotropic single gene disorder with an autosomal recessive pattern of inheritance. The cases presented illustrate that this syndrome is still poorly recognised. We provide a review and analysis of previously reported cases and the differential diagnosis, which might aid in the identification of additional cases.     

Creep and relaxation of cement paste caused by stress‐induced dissolution of hydrated solid components

The creep and relaxation of cement paste caused by dissolving solid hydration products is evaluated in this work. According to the second law of thermodynamics, dissolution or precipitation of solid constituents may be altered by the change in stress/strain fields inside cement paste via alteration of the stress power or strain energy. Thus, it is hypothesized that stress‐induced dissolution can affect the overall creep/relaxation behavior of cement composites. A novel, fully coupled thermodynamic, mechanical, and microstructural model (TM²) that uses the finite element method was developed to predict the time‐evolving properties of cement paste under prescribed strains and to test the hypothesis. In the model, the strain energy was incorporated to accurately predict the effect of stress and strain fields on cement microstructure change. From the simulation results, depending on the stress/strain levels and the choice of the domain (over which the thermodynamic equilibrium is enforced), stress‐induced dissolution of solid constituents can lead to significant creep/relaxation.