激光辐照石墨-镍悬浮液制备碳包覆颗粒的研究

用球磨机湿法球磨微米级镍粉和石墨制备石墨与镍的悬浮液,然后用脉冲激光辐照.用扫描电镜、X射线衍射和透射电镜等对球磨和激光辐照后的产物进行表征.结果表明:球磨细化了镍粉,并使镍粉和石墨混合均匀,使其可悬浮于水介质中;然后激光辐照悬浮液得到了细小的碳包覆镍纳米颗粒.通过对碳包覆颗粒形成机制的初步探索,认为激光作用会使镍和碳气化并形成镍碳混合蒸气,在脉冲过后的冷却过程中碳和镍碰撞溶解,而温度的不断降低会促使过饱和的碳从镍中析出,从而形成包覆,获得了细小的碳包覆颗粒.     

Conditional lineage ablation to model human diseases

Cell loss contributes to the pathogenesis of many inherited and acquired human diseases. We have developed a system to conditionally ablate cells of any lineage and developmental stage in the mouse by regulated expression of the diphtheria toxin A (DTA) gene by using tetracycline-responsive promoters. As an example of this approach, we targeted expression of DTA to the hearts of adult mice to model structural abnormalities commonly observed in human cardiomyopathies. Induction of DTA expression resulted in cell loss, fibrosis, and chamber dilatation. As in many human cardiomyopathies, transgenic mice developed spontaneous arrhythmias in vivo, and programmed electrical stimulation of isolated-perfused transgenic hearts demonstrated a strikingly high incidence of spontaneous and inducible ventricular tachycardia. Affected mice showed marked perturbations of cardiac gap junction channel expression and localization, including a subset with disorganized epicardial activation patterns as revealed by optical action potential mapping. These studies provide important insights into mechanisms of arrhythmogenesis and suggest that conditional lineage ablation may have wide applicability for studies of disease pathogenesis.     

Mathematical model for computer simulation and control of steelmaking

A dynamic model for computer simulation and control of steelmaking has been developed. It is essentially based on multicomponent mixed transport control theory with the incorporation of energy balance calculations. The model is applicable to both steelmaking in electric furnaces as well as in oxygen steelmaking converters. The adjustable parameters of the model for simulation of oxygen steelmaking are gas evolution rate (G_co). oxygen flux factor (F_o) and emulsification factor (EM). These simulation parameters, when combined with on-line measurement of off-gas composition and temperature, enable complete dynamic control of the process. The model developed is applied, as an example, to an industrially produced heat in a top blown oxygen steelmaking converter and the results of simulation are discussed.     

Successful video-assisted thoracoscopic bullectomy and Nd-YAG laser ablation

We report here two cases of giant/multiple emphysematous bullae treated with video-assisted thoracoscopy. The first case was a 35-year-old male who was referred to our hospital because an abnormal shadow was casually pointed out in a chest roentgenogram. Chest computed tomographic scan showed giant bulla in the left upper lobe. The second patient was a 37-year-old male who had a symptom of shortness of breath on exertion. Chest roentgenogram and computed tomographic scan revealed multiple bullae at bilateral apical regions. They were performed resection of bulla with stapler and Nd-YAG laser ablation to the emphysematous surroundings using video-assisted thoracoscopy. They had recovered sufficiently to be discharged from our hospital. We think Nd-YAG laser ablation is effective to prevent postoperative air leakage and recurrence of bullae because it makes surrounding tissue tight and continuous.     

Technology for in situ ablation by laparoscopic and image-guided interstitial laser hyperthermia

The effects of low level lead exposure on synaptic plasticity in hippocampal regions CA1 and CA3 were determined in adult rats in vitro. In the CA3 region the NMDA (N-methyl-D-aspartate)-independent mossy fiber-CA3 synapse potentiation was not influenced by chronic pre- and postnatal lead exposure, while in the same rats, in the CA1 region the NMDA-dependent long-term potentiation was slightly reduced as compared to controls. Paired-pulse facilitation was neither impaired in CA1 nor in CA3 region in the lead-exposed rats. These findings suggest that NMDA-dependent forms of synaptic plasticity are more susceptible to chronic low level lead exposure than NMDA-independent forms of potentiation or paired-pulse facilitation.     

Mathematical model for nitrogen control in oxygen steelmaking

A mathematical model was developed to quantify the effects of different operational parameters on the nitrogen content of steel produced during oxygen steelmaking. The model predicts nitrogen removal by the CO produced during decarburization and how the final nitrogen content is affected by different process variables. These variables include the type of coolants used (scrap, direct reduced iron (DRI), etc.), the sulfur content of the metal, combined gas blowing practices, and the nitrogen content in the hot metal, scrap and oxygen blown. The model is a mixed control model that incorporates mass transfer and chemical kinetics. It requires a single parameter that reflects the surface area and mass-transfer coefficient that is determined from the rate of decarburization. The model also computes the rate of decarburization and the change in surface active elements, such as sulfur and oxygen, that affect the rate of the nitrogen reaction. Nitrogenization of steel in the converter is also predicted with the model. The computed results are in good agreement with plant data and observations.     

转炉冶炼脱磷过程数学模型

在对复吹转炉脱磷过程的机理分析的基础上,应用冶金热力学、动力学、传输原理和反应工程学理论,建立了转炉冶炼脱磷过程数学模型,确定了模型的有关参数.模型的     

汽车钢淬透性数学模型建立

在测定 2 0CrMnTi、4 0MnBH、2 0MnVBH钢淬透性及试样的化学成分基础之上 ,利用计算机采用逐步回归分析方法进行了回归运算 ,得到淬透性与化学成分的关系———回归方程 ,根据回归方程求出了不同窄淬透带规格所对应控制的化学成分范围     

Mathematical model for post combustion in smelting reduction

Post combustion in the top space of iron bath smelting reduction furnaces is analysed with three-dimensional mathematical modelling. Momentum transport and continuity equations in combination with a k-? model of turbulence are numerically solved for the gas flow field. Combustion reactions are modelled by a set of transport equations based on the SCRS combustion model and its extension to the k-?-g model. A two-stage combustion scheme is formulated to include carbon transfer and combustion. Heat transfer to bath and droplets is approximated including radiation. Computation results for rectangular reactors are presented with velocity patterns and combustion fields. The complex shapes of post combustion flames are demonstrated. Process parameters are varied to study their influence on combustion and heat transfer to the bath. Effects of the injection geometry are illustrated.     

Mathematical model for burden distribution in blast furnace

Burden distribution in a blast furnace is vital to its smooth running. However, it is difficult to directly measure the burden distribution for an operating blast furnace. Therefore, mathematical models have been applied to guide the charging process to achieve the desired burden distribution. The accuracies of such models depend on the prediction of falling curve, stockline profile formation, and burden descent mode. In this study, a new stockline profile formation model is proposed in which new equations have been developed for the inner and outer repose angle by considering the influence of the burden flow's vertical and horizontal velocity at the apex of the stockline profile. Validation of this new stockline profile formation model is provided through comparison between calculated results and experimental data for stockline profile. A stepped burden descending strategy, in which the burden would descend through a specified distance after each ring charging process, is proposed corresponding to the successive charging process. The influence of the burden descending strategy on the falling point, the final burden profile and radial depth ratio of ore to coke is also analysed. The result shows that the burden descending strategy greatly affects the final burden distribution, especially in the peripheral region.     

Stereological analysis of spherical particles: Experimental assessment and comparison to laser diffraction

Spherical polymer particles in five different size ranges from ∼2 to 200 μm were measured by optical microscopy/image analysis of polished cross sections. From the two-dimensional (2-D) section-size distributions, two stereological techniques were employed to determine the three-dimensional (3-D) particle-size distributions: the classical Schwartz-Saltykov (SS) method, further developed by Takahashi and Suito, and the technique of Harayama, which was applied by Basak and Sengupta (HBS). The objectives of this study were to assess the viability of image analysis and the SS or HBS techniques as quantitative particle analysis methods and to compare them to laser diffraction (LD) of loose powders. It was found that the image analysis/stereology (IA/S) and LD results agreed within about 15 pct over most of the size range studied. Moreover, the IA/S technique accurately estimates experimental particle-size distributions with nonsymmetric or multimodal characteristics. Stereological parameters were studied, such as the number of size classes (histogram step intervals), and methods of displaying the size distributions were compared to develop best practices. The effect of oversight of small particles, which is an area of concern with stereological techniques, was also investigated in terms of changes to the mean and standard deviations of the 3-D particle-size distributions.     

Mathematical model for the AIDS epidemic's evolution in Romania

The individuals are distributed in 9 risk groups (adults and children), in which an HIV transmission way is predominant. Taking into account a simplified graph of the HIV infection evolution, kinetic equations for the number of individuals from each risk group--situated in various stages of HIV infection--are written. The approximative solutions of these equations give us: the characteristic exponents of the temporal evolutions of the main and secondary local epidemics; the ratios Ci/Bi and Di/Bi of asymptomatically contaminated and dead (as consequence of AIDS)--versus symptomatically contaminated; the onset of local epidemics in various risk groups; the relative amplitude of the secondary local epidemics versus the main local ones.     

Mathematical model for on-line heat treatment of steel bars

A mathematical model to predict steel bar thermal behaviour during continuous quenching after the finishing mill has been developed. The model includes process variables, such as finishing rolling speed, finishing temperature, rod size and chemical composition, water flowrate and mechanical design of the cooling device. It was found that empirical correlations for the heat-transfer coefficient belonging to water spray systems are suitable to simulate fast cooling employing submerged water-cooling tubes. Martensite depth is strongly influenced by the bar diameter and water velocity inside the submerged tube. Mist spray systems are not as effective as submerged tubes for cooling steel bars, although, the initial cooling rates are higher. The % volume of martensite is a direct function of the self-tempering temperature, and independent of the fast cooling device.     

Visual laser ablation of the prostate for patients with acute urinary retention

Examination of the long-term relation of a single fibrinogen determination to initial and recurrent atherosclerotic cardiovascular events over 20 years of follow-up revealed a powerful and comparably independent impact on initial events in both sexes but an influence on recurrent events only in men.     

Mathematical model for addiction: Application to Multiple Risk Factor Intervention Trial data for smoking.

Describes habituation and addiction, both psychological and physiological, using the simple equations of the mathematical model of ideodynamics. The parameters in these equations were optimized to smoking data from the Multiple Risk Factor Intervention Trial (MRFIT) program. With only 4 constant parameters, it was possible to calculate accurate time trends for recidivism to smoking among quitters, time trends for secondary cessation among recidivists, and final percentage of smokers in a population with both recidivism and secondary cessation occurring simultaneously. These same parameters further permit predictions for the long-range success of intervention programs to decrease substance dependency. Ideodynamics can also predict time trends of public opinion based on stories in the mass media. (PsycINFO Database Record (c) 2010 APA, all rights reserved)