141 research outputs found
A new fabrication method for precision antenna reflectors for space flight and ground test
Communications satellites are using increasingly higher frequencies that require increasingly precise antenna reflectors for use in space. Traditional industry fabrication methods for space antenna reflectors employ successive modeling techniques using high- and low-temperature molds for reflector face sheets and then a final fit-up of the completed honeycomb sandwich panel antenna reflector to a master pattern. However, as new missions are planned at much higher frequencies, greater accuracies will be necessary than are achievable using these present methods. A new approach for the fabrication of ground-test solid-surface antenna reflectors is to build a rigid support structure with an easy-to-machine surface. This surface is subsequently machined to the desired reflector contour and coated with a radio-frequency-reflective surface. This method was used to fabricate a 2.7-m-diameter ground-test antenna reflector to an accuracy of better than 0.013 mm (0.0005 in.) rms. A similar reflector for use on spacecraft would be constructed in a similar manner but with space-qualified materials. The design, analysis, and fabrication of the 2.7-m-diameter precision antenna reflector for antenna ground tests and the extension of this technology to precision, space-based antenna reflectors are described
Fast IR laser mapping ellipsometry for the study of functional organic thin films
Fast infrared mapping with sub millimeter lateral resolution as well as time resolved infrared studies of kinetic processes of functional organic thin films require a new generation of infrared ellipsometers. We present a novel laboratory based infrared IR laser mapping ellipsometer, in which a laser is coupled to a variableangle rotating analyzer ellipsometer. Compared to conventional Fourier transform infrared FT IR ellipsometers, the IR laser ellipsometer provides ten to hundredfold shorter measurement times down to 80 ms per measured spot, as well as about tenfold increased lateral resolution of 120 amp; 956;m, thus enabling mapping of small sample areas with thin film sensitivity. The ellipsometer, equipped with a HeNe laser emitting at about 2949 cm amp; 8722;1, was applied for the optical characterization of inhomogeneous poly 3 hexylthiophene [P3HT] and poly N isopropylacrylamide [PNIPAAm] organic thin films used for opto electronics and bioapplications. With the constant development of tunable IR laser sources, laser based infrared ellipsometry is a promising technique for fast in depth mapping characterization of thin films and blend
A Hierarchical Multilevel Markov Chain Monte Carlo Algorithm with Applications to Uncertainty Quantification in Subsurface Flow
In this paper we address the problem of the prohibitively large computational
cost of existing Markov chain Monte Carlo methods for large--scale applications
with high dimensional parameter spaces, e.g. in uncertainty quantification in
porous media flow. We propose a new multilevel Metropolis-Hastings algorithm,
and give an abstract, problem dependent theorem on the cost of the new
multilevel estimator based on a set of simple, verifiable assumptions. For a
typical model problem in subsurface flow, we then provide a detailed analysis
of these assumptions and show significant gains over the standard
Metropolis-Hastings estimator. Numerical experiments confirm the analysis and
demonstrate the effectiveness of the method with consistent reductions of more
than an order of magnitude in the cost of the multilevel estimator over the
standard Metropolis-Hastings algorithm for tolerances
Clinical and morphological phenotype of the filamin myopathy: a study of 31 German patients
Mutations in the filamin C gene (FLNC) cause a myofibrillar myopathy (MFM), morphologically characterized by focal myofibrillar destruction and abnormal accumulation of several proteins within skeletal muscle fibres. We studied 31 patients from four German families to evaluate the phenotype of filaminopathy. All patients harboured the same p.W2710X mutation in FLNC. Haplotype analysis suggested a founder mutation in these German filaminopathy families. The mean age at onset of clinical symptoms was 44 +/â 6 years (range, 24-57 years). Slowly progressive muscle weakness was mostly pronounced proximally, initially affecting the lower extremities and involving the upper extremities in the course of disease progression, similar to the distribution of weakness seen in limb-girdle muscular dystrophies (LGMD). Patients frequently developed respiratory muscle weakness. About one-third of the patients showed cardiac abnormalities comprising conduction blocks, tachycardia, diastolic dysfunction and left ventricular hypertrophy indicating a cardiac involvement in filaminopathy. Serum creatine kinase levels varied from normal up to 10-fold of the upper limit. Magnetic resonance imaging studies showed a rather homogenous pattern of muscle involvement in the lower extremities differing from that in other types of MFM. Myopathological features included perturbation of myofibrillar alignment, accumulation of granulofilamentous material similar to that seen in primary desminopathies and abnormal intracellular protein deposits typical of MFM. Decreased activities of oxidative enzymes and fibre hypertrophy seem to be early features, whereas dystrophic changes were present in advanced stages of filaminopathy. Rimmed vacuoles were detected in only a few cases. The intracellular aggregates were composed of a variety of proteins including filamin C, desmin, myotilin, Xin, dystrophin and sarcoglycans. Therapy is so far limited to symptomatic treatment. The German filaminopathy cohort, the largest group of patients studied so far, shares phenotypic features with LGMD and presents with characteristic histopathological findings of MF
Complexity Analysis of Accelerated MCMC Methods for Bayesian Inversion
We study Bayesian inversion for a model elliptic PDE with unknown diffusion
coefficient. We provide complexity analyses of several Markov Chain-Monte Carlo
(MCMC) methods for the efficient numerical evaluation of expectations under the
Bayesian posterior distribution, given data . Particular attention is
given to bounds on the overall work required to achieve a prescribed error
level . Specifically, we first bound the computational complexity
of "plain" MCMC, based on combining MCMC sampling with linear complexity
multilevel solvers for elliptic PDE. Our (new) work versus accuracy bounds show
that the complexity of this approach can be quite prohibitive. Two strategies
for reducing the computational complexity are then proposed and analyzed:
first, a sparse, parametric and deterministic generalized polynomial chaos
(gpc) "surrogate" representation of the forward response map of the PDE over
the entire parameter space, and, second, a novel Multi-Level Markov Chain Monte
Carlo (MLMCMC) strategy which utilizes sampling from a multilevel
discretization of the posterior and of the forward PDE.
For both of these strategies we derive asymptotic bounds on work versus
accuracy, and hence asymptotic bounds on the computational complexity of the
algorithms. In particular we provide sufficient conditions on the regularity of
the unknown coefficients of the PDE, and on the approximation methods used, in
order for the accelerations of MCMC resulting from these strategies to lead to
complexity reductions over "plain" MCMC algorithms for Bayesian inversion of
PDEs.
Novel biomaterials: plasma-enabled nanostructures and functions
Material processing techniques utilizing low-temperature plasmas as the main process tool feature many unique capabilities for the fabrication of various nanostructured materials. As compared with the neutral-gas based techniques and methods, the plasma-based approaches offer higher levels of energy and flux controllability, often leading to higher quality of the fabricated nanomaterials and sometimes to the synthesis of the hierarchical materials with interesting properties. Among others, nanoscale biomaterials attract significant attention due to their special properties towards the biological materials (proteins, enzymes), living cells and tissues. This review briefly examines various approaches based on the use of low-temperature plasma environments to fabricate nanoscale biomaterials exhibiting high biological activity, biological inertness for drug delivery system, and other features of the biomaterials make them highly attractive. In particular, we briefly discuss the plasma-assisted fabrication of gold and silicon nanoparticles for bio-applications; carbon nanoparticles for bioimaging and cancer therapy; carbon nanotube-based platforms for enzyme production and bacteria growth control, and other applications of low-temperature plasmas in the production of biologically-active materials
Molecular Characterization of Human Breast Tumor Vascular Cells
A detailed understanding of the assortment of genes that are expressed in breast tumor vessels is needed to facilitate the development of novel, molecularly targeted anti-angiogenic agents for breast cancer therapies. Rapid immunohistochemistry using factor VIII-related antibodies was performed on sections of frozen human luminal-A breast tumors (n = 5) and normal breast (n = 5), followed by laser capture microdissection of vascular cells. RNA was extracted and amplified, and fluorescently labeled cDNA was synthesized and hybridized to 44,000-element long-oligonucleotide DNA microarrays. Statistical analysis of microarray was used to compare differences in gene expression between tumor and normal vascular cells, and Expression Analysis Systematic Explorer was used to determine enrichment of gene ontology categories. Protein expression of select genes was confirmed using immunohistochemistry. Of the 1176 genes that were differentially expressed between tumor and normal vascular cells, 55 had a greater than fourfold increase in expression level. The extracellular matrix gene ontology category was increased while the ribosome gene ontology category was decreased. Fibroblast activation protein, secreted frizzled-related protein 2, Janus kinase 3, and neutral sphingomyelinase 2 proteins localized to breast tumor endothelium as assessed by immunohistochemistry, showing significantly greater staining compared with normal tissue. These tumor endothelial marker proteins also exhibited increased expression in breast tumor vessels compared with that in normal tissues. Therefore, these genetic markers may serve as potential targets for the development of angiogenesis inhibitors
Overview of the PALM model system 6.0
In this paper, we describe the PALM model system 6.0. PALM (formerly an abbreviation for Parallelized Largeeddy Simulation Model and now an independent name) is a Fortran-based code and has been applied for studying a variety of atmospheric and oceanic boundary layers for about 20 years. The model is optimized for use on massively parallel computer architectures. This is a follow-up paper to the PALM 4.0 model description in Maronga et al. (2015). During the last years, PALM has been significantly improved and now offers a variety of new components. In particular, much effort was made to enhance the model with components needed for applications in urban environments, like fully interactive land surface and radiation schemes, chemistry, and an indoor model. This paper serves as an overview paper of the PALM 6.0 model system and we describe its current model core. The individual components for urban applications, case studies, validation runs, and issues with suitable input data are presented and discussed in a series of companion papers in this special issue
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