THERMODYNAMICS OF ASPHALTENE PRECIPITATION AND DISSOLUTION INVESTIGATION OF TEMPERATURE AND SOLVENT EFFECTS

Petroleum asphaltenes have been precipitated in solvent mixtures of n-heptane and toluene at various temperatures, likewise n-heptane asphaltenes have been dissolved in under similar conditions. This give added evidence to apparent hysteresis phenomenon between the two processes. The Asphaltenes have been characterized showing that although data is scattered convergence to certain structural parameters as incipient flocculation is approached. The asphaltenes are seen to consist of an associating and a non-associating part. The solubility of asphaltenes has been correlated/modelled using the Flory-Huggins equation using two different terms for the Flory parameter. A process for evaluation of best choice of solubility parameter and molar volume for the asphaltenes is proposed. Dissolution processes are seen to be best fitted by the equations. Based on these findings the asphaltenes are proposed to be formed by a colloidal and a true solution part.     

Childhood fibrous dysplasia presenting as blindness: a skull base approach for resection and immediate reconstruction

Fibrous dysplasia is an abnormal fibroosseous process of bone of unknown cause. The incidence of skull involvement varies, painless enlargement being the most common presenting symptom. Change in vision is a rare but recognized finding. We report a 3-year-old boy with extreme fibrous dysplasia involving the skull base, who presented with blindness. He underwent exposure osteotomies of the frontal bones and orbits to provide access for skull base tumor removal. The orbital roofs were reconstructed with microplate-fixed cranial grafts. One and one half years after tumor excision followed by immediate reconstruction, the boy retains facial symmetry, and his ocular function has not deteriorated.     

Transport of K in PVC matrix membranes containing valinomycin

We report impedance measurements on PVC matrix membranes which contain KBPh₄ with varying proportions of valinomycin. In agreement with our earlier measurements the value of the bulk membrane resistance (R_b) is much larger in the presence of valinomycin, indicating that the mobility of K⁺ is greatly reduced by the valinomycin. R_b shows a linear variation with valinomycin/K⁺ ratio between 0 and 1, but it is invariant at higher valinomycin/K⁺ ratios. Thus there is no evidence for a special transport mechanism for K⁺ in these membranes.     

汽车电子系统要求低静态电流

如今的汽车电子系统越来越复杂。同时，汽车环境对任何电子产品来说都是很大的挑战，因为汽车电子系统要求运行电压很宽，并且有很大的瞬态电压和温度变化。另外，性能要求也越来越高，需要多个供应电压以满足系统的不同要求。典型的     

Results of a User Study on 2D Hurricane Visualization

We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter‐clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter‐clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields.     

单片同步降压型转换器LTC3416

许多微处理器和数字信号处理器(DSP)需要一个核心电源和一个在启动期间必须进行排序的输入／输出(I／O)电源。如果未经过适当的电源排序，可能发生闭锁或过流，从而损害微处理器的I／O端口或诸如存储器、逻辑电路、现场可编程门阵列(FPGA)或数据转换器之类支持设备的I／O端口。为了确保在主电源电压未被适当偏置之前I／O负载不被驱动，对核心电源电压和I／O电源电压进行跟踪是必要的。