The influence of degeneracy on the emitter efficiency of a bipolar transistor

An expression for the emitter efficiency is derived taking the degeneracy of the emitter into account. It is found that, even if there is no recombination of minority carriers in the emitter, degeneracy reduces the emitter efficiency. In addition this first order theory explains experimental results on temperature dependence of current gain and predicts an optimum emitter design for a fixed type of emitter profile

A fast algorithm for the calculation of junction capacitance and its application for impurity profile determination

A fast algorithm is described which calculates the space charge layer width and junction capacitance for an arbitrary impurity profile and for plane, cylindrical and spherical junctions. The algorithm is based on the abrupt space charge edge (ASCE) approximation. A method to use the algorithm for the determination of impurity profiles for two-sided junctions is presented. An expression is derived for the built-in voltage to be used for capacitance calculations with the ASCE approximation. Experimental evidence is given that the algorithm permits very accurate capacitance calculations and also predicts the exact temperature dependence of the junction capacitance

Texture and Microstructure of Soybean Curd (Tofu) as Affected by Different Coagulants

The coagulating properties of five coagulants and the nature of the curd obtained from soymilk was investigated . Viscosity changes during coagulation were studied using a Namctrc Vibrating Sphere Viscometer and texture measurements were made by compression and computer assisted analysis. pH and amount of solids in the whey were determined. The microstructure of the tofu was examined by sca nning electron microscopy. It was observed that CaCI2.2H20 and MgCI2.6H20 coagulaled the milk in stantl y while CaS04 .1/2H20. glucono delta l a~tonc (GOL) and MgS04 .7H20 acted comparatively slowly. The t exture of the curd was greatly influenced by type and concerHra tion of coagulant. Curd obtained with CaCI2.2H20 and MgCI2.6H20 was coarse, granular and hard , whereas CaS04. I/2H 20 and GDL (fresh solution) gave a very smooth . soft and uniform curd . Among the five coagulants studied, 0.75% CaSO_. and 0.4% GDL (fresh solution) appeared to be most suitable for making tofu of high bulk weight and smooth texture

A STUDY ON THE MECHANISM OF INTERCELLULAR ADHESION : Effects of Neuraminidase, Calcium, and Trypsin on the Aggregation of Suspended HeLa Cells

Aggregation of suspended HeLa cells is increased on removal of cell surface sialic acid. Calcium ions promote aggregation whereas magnesium ions have no effect. The calcium effect is abolished by previous treatment of the cells with neuraminidase. Trypsinization of the HeLa cells followed by thorough washing diminishes the rate of mutual cell aggregation. Subsequent incubation with neuraminidase restores the aggregation rate to the original value before trypsin treatment. Cells which had acquired a greater tendency for aggregation after removal of peripheral sialic acid lose this property when subsequently treated with trypsin. Calcium ions have no aggregative effect on trypsinized cells. In contrast to HeLa cells, aggregation of human erythrocytes was not increased after treatment with neuraminidase or on addition of calcium. The results with HeLa cells are interpreted as follows: (a) Trypsin-releasable material confers adhesiveness upon the cells. (b) The adhesive property of this material is counteracted by the presence of cell surface sialic acids. (c) Calcium ions exert their effect by attenuating the adverse effect of sialic acid

Outcomes of transnasal endoscopic repair of cerebrospinal fluid leaks: a prospective cohort study

Abstract Background Although cerebrospinal fluid (CSF) leak repair of the anterior and middle skull base defect by endonasal endoscopic surgery (EES) presents one of the more difficult challenges, it has shown high success rates with less morbidity. Our objective is to evaluate the outcomes of transnasal endoscopic repair of CSF leak regarding success rate, impact on olfaction, and sinonasal function. Methods A prospective cohort study was conducted to evaluate the CSF leak repair outcomes related to the site, size of the defect, surgical techniques, and the materials that been used through Smell Identification Test (SIT), 22-item Sino-Nasal Outcome Test (SNOT-22), Perioperative Sinus Endoscopy score (POSE), and Lund-MacKay Scoring (LM) of CT scan. Results Twenty-one patients were enrolled in the study; 12 out of 21 were females with a higher prevalence of traumatic causes of 61.9%. Different techniques and materials were used for the repair with a success rate recorded at 90.5% after the first closure attempt. The mean standard deviation (SD) scores postoperatively (after 6 months) was markedly decreased in SNOT 22 with mean (SD) 5.55 ± 3.6, slightly increase in POSE (mean ± SD = 0.43 ± 0.6), and slightly decrease in SIT (mean ± SD =10.31 ± 4.7) and LM (mean ± SD = 0.57 ± 0.7). Conclusion Transnasal endoscopic CSF leak repair is an effective technique for skull base defect closure with a high success rate and no valuable morbidity to sinonasal function other than mild hyposmia in patients where nasoseptal (NSF) and septal flap have been used. Trial registration The study was approved by the institutional review board and ethics committee of (The Arab Board of Health Specializations) with order no. (453) on 1April 2018

Anisotropic composite polymer for high magnetic force in microfluidic systems

International audienceAnisotropic carbonyl iron-PolyDiMethylSiloxane (PDMS) composites were developed and implemented in microfluidic devices to serve as magnetic flux concentrators. These original materials provide technological solutions for heterogeneous integration with PDMS. Besides microfabrication advantages, they offer interesting modular magnetic properties. Applying an external magnetic field during the PDMS reticulation leads to the formation of 1D-agglomerates of magnetic particles, organized in the non-magnetic polymer matrix. This induces an increase of susceptibility as compared to composites with randomly dispersed particles. In this report, we explored the gain in reachable magnetophoretic forces in operating microfluidic devices, from the study of magnetic micro-beads motion injected in the microchannel. We show that even at relatively large distances from the magnetically-functionalized channel wall, the anisotropic composite leads to a factor two increase in the magnetophoretic force. Finally, further investigations based on finite element description suggest that the measured benefit of anisotropic composite polymers does not only rely on the global susceptibility increase but also on the local magnetic field gradients originating from the microstructure