Manual for obscuration code with space station applications

The Obscuration Code, referred to as SHADOW, is a user-oriented computer code to determine the case shadow of an antenna in a complex environment onto the far zone sphere. The surrounding structure can be composed of multiple composite cone frustums and multiply sided flat plates. These structural pieces are ideal for modeling space station configurations. The means of describing the geometry input is compatible with the NEC-BASIC Scattering Code. In addition, an interactive mode of operation has been provided for DEC VAX computers. The first part of this document is a user's manual designed to give a description of the method used to obtain the shadow map, to provide an overall view of the operation of the computer code, to instruct a user in how to model structures, and to give examples of inputs and outputs. The second part is a code manual that details how to set up the interactive and non-interactive modes of the code and provides a listing and brief description of each of the subroutines

Stabilization and control of electrostatic accelerators.

The research carried out on the stabilization control and protection of two Van de Graaff electrostatic nuclear accelerators is described in this thesis. The system at Oxford consists of a single ended and a tandem accelerator with two different kinds of stabilizers; the results presented here are directly applicable to most electrostatic accelerators. As an end result of the mathematical analysis, the behaviour of the single ended injector with combined liner and spray control is formulated. The stabilizer designed for the injector, based on the analysis, incorporates automatic switch over to the auxiliary generating voltmeter stabilizer loop. The automatic gain control introduced into the slit amplifiers eliminates the necessity of manual gain adjustments for different operating conditions. The energy resolution of the injector was measured by using alpha capture resonance in [15]N. It was 0.65 keV at 4.46 MeV. The analysis presented here describes the behaviour of the corona stabilizer as used on the tandem. The predicted limitations due to the time delay and dispersion of the ions in high pressure gas are in good agreement with the measured performance figures. The two loop stabilizer with the auxiliary generating voltmeter loop provides facilities for semi-automatic operation. The resolution of the tandem was +/-1 keV by measuring the [28]Si(p,p)[28]Si resonance at 5.83 MeV. Multiple breakdowns on both the injector and the tandem were prevented by the introduction of the protection circuit. The circuit design was based on the analysis of the breakdown behaviour of the generators as described. The predicted performance of the circuit and its effect on the accelerators is well verified by the observed behaviour of the generators after total breakdown. The study of the computer controlled generator operation is described in Chapter 5. For the interfacing the internationally accepted Camac system is recommended

Finite volume form factors in the presence of integrable defects

We developed the theory of finite volume form factors in the presence of integrable defects. These finite volume form factors are expressed in terms of the infinite volume form factors and the finite volume density of states and incorporate all polynomial corrections in the inverse of the volume. We tested our results, in the defect Lee-Yang model, against numerical data obtained by truncated conformal space approach (TCSA), which we improved by renormalization group methods adopted to the defect case. To perform these checks we determined the infinite volume defect form factors in the Lee-Yang model exactly, including their vacuum expectation values. We used these data to calculate the two point functions, which we compared, at short distance, to defect CFT. We also derived explicit expressions for the exact finite volume one point functions, which we checked numerically. In all of these comparisons excellent agreement was found.Comment: pdflatex, 34 pages, many figure

The Polar Regions of Cassiopeia A: The Aftermath of a Gamma Ray Burst?

Probably not, but it is interesting nevertheless to investigate just how close Cas A might have come to generating such an event. Focusing on the northeast jet filaments, we analyze the polar regions of the recently acquired very deep 1 Ms Chandra X-ray observation. We infer that the so-called "jet" regions are indeed due to jets emanating from the explosion center, and not due to polar cavities in the circumstellar medium at the time of explosion. We place limits on the equivalent isotropic explosion energy in the polar regions (around 2.3 x 10^52 ergs), and the opening angle of the x-ray emitting ejecta (around 7 degrees), which give a total energy in the NE jet of order 10^50 ergs; an order of magnitude or more lower than inferred for "typical" GRBs. While the Cas A progenitor and explosion exhibit many of the features associated with GRB hosts, e.g. extensive presupernova mass loss and rotation, and jets associated with the explosion, we speculate that the recoil of the compact central object, with velocity 330 km/s, may have rendered the jet unstable. In such cases the jet rapidly becomes baryon loaded, if not truncated altogether. Although unlikely to have produced a gamma ray burst, the jets in Cas A suggest that such outflows may be common features of core-collapse SNe.Comment: 35 pages, 7 figures, accepted by Ap

Documentation of the GLAS fourth order general circulation model. Volume 1: Model documentation

The volume 1, of a 3 volume technical memoranda which contains a documentation of the GLAS Fourth Order General Circulation Model is presented. Volume 1 contains the documentation, description of the stratospheric/tropospheric extension, user's guide, climatological boundary data, and some climate simulation studies

Exact Maximal Height Distribution of Fluctuating Interfaces

We present an exact solution for the distribution P(h_m,L) of the maximal height h_m (measured with respect to the average spatial height) in the steady state of a fluctuating Edwards-Wilkinson interface in a one dimensional system of size L with both periodic and free boundary conditions. For the periodic case, we show that P(h_m,L)=L^{-1/2}f(h_m L^{-1/2}) for all L where the function f(x) is the Airy distribution function that describes the probability density of the area under a Brownian excursion over a unit interval. For the free boundary case, the same scaling holds but the scaling function is different from that of the periodic case. Numerical simulations are in excellent agreement with our analytical results. Our results provide an exactly solvable case for the distribution of extremum of a set of strongly correlated random variables.Comment: 4 pages revtex (two-column), 1 .eps figure include

Documentation of the GLAS fourth order general circulation model. Volume 2: Scalar code

Volume 2, of a 3 volume technical memoranda contains a detailed documentation of the GLAS fourth order general circulation model. Volume 2 contains the CYBER 205 scalar and vector codes of the model, list of variables, and cross references. A variable name dictionary for the scalar code, and code listings are outlined

Documentation of the GLAS fourth order general calculation model. Volume 3: Vectorized code for the Cyber 205

Volume 3 of a 3-volume technical memoranda which contains documentation of the GLAS fourth order genera circulation model is presented. The volume contains the CYBER 205 scalar and vector codes of the model, list of variables, and cross references. A dictionary of FORTRAN variables used in the Scalar Version, and listings of the FORTRAN Code compiled with the C-option, are included. Cross reference maps of local variables are included for each subroutine

Adding value to physics labs to help build confident, knowledgeable teachers

Abstract: This pilot study is being conducted by an interdisciplinary team and is funded through the University of Wollongong Education Strategies Development Fund. The project focuses on the first-year physics laboratories of pre- service teachers enrolled in Bachelor of Science Education degrees. It aims to make the laboratory experience more aligned to the needs of future science and physics teachers, contributing to their confidence in using apparatus in the classroom and their effectiveness as communicators who can explain concepts fluently from a background of deep understanding. According to Mulhall (2006) and Johnston and Millar (2000), misconceptions are common even among successful physics students and explicit teaching strategies that address conceptual change are needed to correct misconceptions. However, our approach is also of value to general physics students. Our approach has three strands. The first involves identifying experiments in our labs that have content in common with compulsory practical investigations in the NSW year 11 / 12 physics syllabus. Experimental procedures and instructions for these labs are being modified to create explicit links between concepts, apparatus and procedures in the first-year labs and those in the school syllabus. Secondly, we are incorporating peer instruction using qualitative multiple-choice questions designed to probe conceptual understanding. These will be included in the laboratory manual, at strategic points in the experimental procedure. Students will discuss and agree on responses before proceeding with the experiment. This approach is based on the work of Mazur (1996), Crouch and Mazur (2001) and Cox and Junkin III (2002) who reported that it developed confidence in communication and was effective in challenging misconceptions. Finally, in designing the laboratory manual we will employ principles of Cognitive Load Theory to decrease extraneous cognitive load and make learning more efficient ( Chandler & Sweller, 1991; Paas, Renkl & Sweller, 2004; Purnell, Solman & Sweller, 1991). Our project will run from February 2009 until January 2010. Syllabus mapping has been carried out to identify appropriate experiments for the study, and three have been selected. High school physics teachers have been interviewed to discuss corresponding practical investigations in the school syllabus and findings are being used to inform the modifications to the procedures and manual for our laboratories, which will run in Spring Session 2009. The impact of the modified experiments will be compared with that of the unmodified experiments, and with previous years’ results. This conference paper elaborates on the theoretical background of our strategies and reports on our progress

Isotopic and genetic methods reveal the role of the gut microbiome in mammalian host essential amino acid metabolism.

Intestinal microbiota perform many functions for their host, but among the most important is their role in metabolism, especially the conversion of recalcitrant biomass that the host is unable to digest into bioavailable compounds. Most studies have focused on the assistance gut microbiota provide in the metabolism of carbohydrates, however, their role in host amino acid metabolism is poorly understood. We conducted an experiment on Mus musculus using 16S rRNA gene sequencing and carbon isotope analysis of essential amino acids (AAESS) to quantify the community composition of gut microbiota and the contribution of carbohydrate carbon used by the gut microbiome to synthesize AAESS that are assimilated by mice to build skeletal muscle tissue. The relative abundances of Firmicutes and Bacteroidetes inversely varied as a function of dietary macromolecular content, with Firmicutes dominating when mice were fed low-protein diets that contained the highest proportions of simple carbohydrates (sucrose). Mixing models estimated that the microbial contribution of AAESS to mouse muscle varied from less than 5% (threonine, lysine, and phenylalanine) to approximately 60% (valine) across diet treatments, with the Firmicute-dominated microbiome associated with the greatest contribution. Our results show that intestinal microbes can provide a significant source of the AAESS their host uses to synthesize structural tissues. The role that gut microbiota play in the amino acid metabolism of animals that consume protein-deficient diets is likely a significant but under-recognized aspect of foraging ecology and physiology