13,939 research outputs found
Contamination cannot explain the lack of large-scale power in the cosmic microwave background radiation
Several anomalies appear to be present in the large-angle cosmic microwave
background (CMB) anisotropy maps of WMAP. One of these is a lack of large-scale
power. Because the data otherwise match standard models extremely well, it is
natural to consider perturbations of the standard model as possible
explanations. We show that, as long as the source of the perturbation is
statistically independent of the source of the primary CMB anisotropy, no such
model can explain this large-scale power deficit. On the contrary, any such
perturbation always reduces the probability of obtaining any given low value of
large-scale power. We rigorously prove this result when the lack of large-scale
power is quantified with a quadratic statistic, such as the quadrupole moment.
When a statistic based on the integrated square of the correlation function is
used instead, we present strong numerical evidence in support of the result.
The result applies to models in which the geometry of spacetime is perturbed
(e.g., an ellipsoidal Universe) as well as explanations involving local
contaminants, undiagnosed foregrounds, or systematic errors. Because the
large-scale power deficit is arguably the most significant of the observed
anomalies, explanations that worsen this discrepancy should be regarded with
great skepticism, even if they help in explaining other anomalies such as
multipole alignments.Comment: 9 pages. Submitted to Phys. Rev.
Perturbing forces in the lunar gravitational potential, part 3 Final report
Spherical harmonics for evaluating perturbing forces on lunar satellite due to nonsymmetric mass distribution of moo
RTCC requirements for mission G - Landing site determination using onboard observations, part 2 Final report
Computer programs for evaluation of telemetered rendezvous radar tracking data of orbiting command module and lunar module landing site determinatio
Vibration and stress analysis of soft-bonded shuttle insulation tiles. Modal analysis with compact widely space stringers
An efficient iterative procedure is described for the vibration and modal stress analysis of reusable surface insulation (RSI) of multi-tiled space shuttle panels. The method, which is quite general, is rapidly convergent and highly useful for this application. A user-oriented computer program based upon this procedure and titled RESIST (REusable Surface Insulation Stresses) has been prepared for the analysis of compact, widely spaced, stringer-stiffened panels. RESIST, which uses finite element methods, obtains three dimensional tile stresses in the isolator, arrestor (if any) and RSI materials. Two dimensional stresses are obtained in the tile coating and the stringer-stiffened primary structure plate. A special feature of the program is that all the usual detailed finite element grid data is generated internally from a minimum of input data. The program can accommodate tile idealizations with up to 850 nodes (2550 degrees-of-freedom) and primary structure idealizations with a maximum of 10,000 degrees-of-freedom. The primary structure vibration capability is achieved through the development of a new rapid eigenvalue program named ALARM (Automatic LArge Reduction of Matrices to tridiagonal form)
Thermal stress analysis of reusable surface insulation for shuttle
An iterative procedure for accurately determining tile stresses associated with static mechanical and thermally induced internal loads is presented. The necessary conditions for convergence of the method are derived. An user-oriented computer program based upon the present method of analysis was developed. The program is capable of analyzing multi-tiled panels and determining the associated stresses. Typical numerical results from this computer program are presented
A study of the dynamics of rotating space stations with elastically connected counterweight and attached flexible appendages. Volume 1: Theory
The formulation of a mathematical model for predicting the dynamic behavior of rotating flexible space station configurations was conducted. The overall objectives of the study were: (1) to develop the theoretical techniques for determining the behavior of a realistically modeled rotating space station, (2) to provide a versatile computer program for the numerical analysis, and (3) to present practical concepts for experimental verification of the analytical results. The mathematical model and its associated computer program are described
Microstructured optical fibres for gas sensing: design fabrication and post-fab processing
Air/silica Microstructured Optical Fibers (MOFs) offer new prospects for fiber based sensor devices. In this paper, two topics of particular significance for gas sensing using air guiding Photonic Bandgap Fibers (PBGFs) are discussed. First, we address the issue of controlling the modal properties of PBGFs and demonstrate a single mode, polarization maintaining air guiding PBGF. Secondly, we present recent improvements of a femtosecond laser machining technique for fabricating fluidic channels in PBGFs, which allowed us to achieve cells with multiple side access channels and low additional loss
Prevention of ulcer disease in goldfish by means of vaccination
A vaccine comprising cells of Aeromonas bestiarum grown in tryptic soy broth and atypical A. salmonicida cells produced in iron-limited and iron-supplemented media protected goldfish Carassius auratus when administered by immersion (dosage ≈ 5 × 107 cells/mL for 60 s) followed after 28 d by an oral booster (dosage = 5 × 107 cells/g of feed), which was fed for 7 d so that each fish received about 1 g of vaccine-containing feed. After challenge by intramuscular injection of a virulent culture of atypical A. salmonicida, the relative percent survival (RPS) was more than 90%. The approach was more successful than using a commercial furunculosis vaccine with or without supplementation with A. bestiarum or atypical A. salmonicida cells. Moreover, a smooth derivative of the virulent rough culture of atypical A. salmonicida was less effective as a vaccine candidate, yielding an RPS of only 65%. Low antibody titers of 1:39–1:396 were found in the vaccinated fish. The vaccinated fish had a significantly higher proportion of dead head kidney macrophages (10.9 ± 3.5%; P = 0.0149) than did the controls (6.8 ± 3.1%). However, differences in the number of erythrocytes and leukocytes, the level of phagocytic and lysozyme activities, and the proportion of lymphocytes, monocytes, and polymorphonuclear cells were not statistically significant between the two groups
Absorption of Energy at a Metallic Surface due to a Normal Electric Field
The effect of an oscillating electric field normal to a metallic surface may
be described by an effective potential. This induced potential is calculated
using semiclassical variants of the random phase approximation (RPA). Results
are obtained for both ballistic and diffusive electron motion, and for two and
three dimensional systems. The potential induced within the surface causes
absorption of energy. The results are applied to the absorption of radiation by
small metal spheres and discs. They improve upon an earlier treatment which
used the Thomas-Fermi approximation for the effective potential.Comment: 19 pages (Plain TeX), 2 figures, 1 table (Postscript
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