Preliminary design analysis for the solar optical telescope main mirror actuator

The resolution of the SOT Gregorian telescope was maintained if the conic foci of the elliptical secondary and parabolic primary were made to coincide within plus or minus 38 microns across the prime focus plane and to within 5 microns in focus. An error in coincidence across the focal plane caused all point images to show additional coma with all the comatic tails pointing in the same direction. An error in focus became magnified by the square of the magnification of the secondary and simply increased the diameter of the point source. Offsetting or rastering the sun may be accomplished by swinging the primary in an arc about the point of coincidence of the conic foci so long as the coincidence is kept to within the tolerance stated

Coaxial inverted geometry transistor having buried emitter

The invention relates to an inverted geometry transistor wherein the emitter is buried within the substrate. The transistor can be fabricated as a part of a monolithic integrated circuit and is particularly suited for use in applications where it is desired to employ low actuating voltages. The transistor may employ the same doping levels in the collector and emitter, so these connections can be reversed

Evaluating the Applicability of the Fokker-Planck Equation in Polymer Translocation: A Brownian Dynamics Study

Brownian dynamics (BD) simulations are used to study the translocation dynamics of a coarse-grained polymer through a cylindrical nanopore. We consider the case of short polymers, with a polymer length, N, in the range N=21-61. The rate of translocation is controlled by a tunable friction coefficient, gamma_{0p}, for monomers inside the nanopore. In the case of unforced translocation, the mean translocation time scales with polymer length N as ~ (N-N_p)^alpha, where N_p is the average number of monomers in the nanopore. The exponent approaches the value alpha=2 when the pore friction is sufficiently high, in accord with the prediction for the case of the quasi-static regime where pore friction dominates. In the case of forced translocation, the polymer chain is stretched and compressed on the cis and trans sides, respectively, for low gamma_{0p}. However, the chain approaches conformational quasi-equilibrium for sufficiently large gamma_{0p}. In this limit the observed scaling of with driving force and chain length supports the FP prediction that is proportional to N/f_d for sufficiently strong driving force. Monte Carlo simulations are used to calculate translocation free energy functions for the system. The free energies are used with the Fokker-Planck equation to calculate translocation time distributions. At sufficiently high gamma_{0p}, the predicted distributions are in excellent agreement with those calculated from the BD simulations. Thus, the FP equation provides a valid description of translocation dynamics for sufficiently high pore friction for the range of polymer lengths considered here. Increasing N will require a corresponding increase in pore friction to maintain the validity of the FP approach. Outside the regime of low N and high pore friction, the polymer is out of equilibrium, and the FP approach is not valid.Comment: 13 pages, 11 figure

Observational manifestations of solar magneto-convection -- center-to-limb variation

We present the first center-to-limb G-band images synthesized from high resolution simulations of solar magneto-convection. Towards the limb the simulations show "hilly" granulation with dark bands on the far side, bright granulation walls and striated faculae, similar to observations. At disk center G-band bright points are flanked by dark lanes. The increased brightness in magnetic elements is due to their lower density compared with the surrounding intergranular medium. One thus sees deeper layers where the temperature is higher. At a given geometric height, the magnetic elements are cooler than the surrounding medium. In the G-band, the contrast is further increased by the destruction of CH in the low density magnetic elements. The optical depth unity surface is very corrugated. Bright granules have their continuum optical depth unity 80 km above the mean surface, the magnetic elements 200-300 km below. The horizontal temperature gradient is especially large next to flux concentrations. When viewed at an angle, the deep magnetic elements optical surface is hidden by the granules and the bright points are no longer visible, except where the "magnetic valleys" are aligned with the line of sight. Towards the limb, the low density in the strong magnetic elements causes unit line-of-sight optical depth to occur deeper in the granule walls behind than for rays not going through magnetic elements and variations in the field strength produce a striated appearance in the bright granule walls.Comment: To appear in ApJL. 6 pages 4 figure

On the Use of Group Theoretical and Graphical Techniques toward the Solution of the General N-body Problem

Group theoretic and graphical techniques are used to derive the N-body wave function for a system of identical bosons with general interactions through first-order in a perturbation approach. This method is based on the maximal symmetry present at lowest order in a perturbation series in inverse spatial dimensions. The symmetric structure at lowest order has a point group isomorphic with the S_N group, the symmetric group of N particles, and the resulting perturbation expansion of the Hamiltonian is order-by-order invariant under the permutations of the S_N group. This invariance under S_N imposes severe symmetry requirements on the tensor blocks needed at each order in the perturbation series. We show here that these blocks can be decomposed into a basis of binary tensors invariant under S_N. This basis is small (25 terms at first order in the wave function), independent of N, and is derived using graphical techniques. This checks the N^6 scaling of these terms at first order by effectively separating the N scaling problem away from the rest of the physics. The transformation of each binary tensor to the final normal coordinate basis requires the derivation of Clebsch-Gordon coefficients of S_N for arbitrary N. This has been accomplished using the group theory of the symmetric group. This achievement results in an analytic solution for the wave function, exact through first order, that scales as N^0, effectively circumventing intensive numerical work. This solution can be systematically improved with further analytic work by going to yet higher orders in the perturbation series.Comment: This paper was submitted to the Journal of Mathematical physics, and is under revie

Analysis of defect structure in silicon. Characterization of SEMIX material. Silicon sheet growth development for the large area silicon sheet task of the low-cost solar array project

Statistically significant quantitative structural imperfection measurements were made on samples from ubiquitous crystalline process (UCP) Ingot 5848 - 13C. Important correlation was obtained between defect densities, cell efficiency, and diffusion length. Grain boundary substructure displayed a strong influence on the conversion efficiency of solar cells from Semix material. Quantitative microscopy measurements gave statistically significant information compared to other microanalytical techniques. A surface preparation technique to obtain proper contrast of structural defects suitable for quantimet quantitative image analyzer (QTM) analysis was perfected and is used routinely. The relationships between hole mobility and grain boundary density was determined. Mobility was measured using the van der Pauw technique, and grain boundary density was measured using quantitative microscopy technique. Mobility was found to decrease with increasing grain boundary density

Limestone As a buffering Agent in High-Concentrate Diets

In recent years, there has been evidence indicating that limestone in excess of normal requirement levels for calcium has beneficial effects for ruminants. Research at this station has shown that limestone supplementation is effective in preventing phosphatic urinary calculi formation in ruminants when fed at higher levels than normally recommended. Work at other stations has shown positive effects on weight gain from limestone added to highconcentrate diets, which was attributed to buffering action within the digestive tract. In short-term finishing periods, buffer supplementation may help ruminants adapt to high-grain diets if roughage has been their major feedstuff in the past. Graded levels of limestone were fed in this experiment to determine beneficial effects in protecting lambs from the effects of rumen acidosis during an extremely short adaptation period and to determine the optimum level of supplementation needed to improve performance during the longer term finishing period

Sodium Bentonite and Sodium Bicarbonate in High-Concentrate Beef Cattle Diets

Sodium bentonite and sodium bicarbonate alter conditions in the rumen and may offer animals protection from some of the harmful effects of rumen acidosis. The potential benefits that may be derived from use of these materials have become increasingly important as backgrounding periods are extended and finishing periods are shortened. The experiment reported herein were designed to investigate the effectiveness of these materials, individually or in combination, in the adaptation of beef cattle to high-concentrate diets