3,097 research outputs found
Utilization survey of prototype structural test article
A survey was conducted of six aerospace companies and two NASA agencies to determine how prototype structural test articles are used in flight operations. The prototype structures are airframes and similar devices which are used for testing and generally are not flown. The survey indicated the following: (1) prototype test articles are not being discarded after development testing is complete, but are used for other purposes, (2) only two cases of prototypes being refurbished and flown were identified, (3) protective devices and inspection techniques are available to prevent or minimize test article damage, (4) substitute programs from design verification are availabel in lieu of using prototype structural articles, and (5) there is a trend away from dedicated test articles. Four options based on these study results were identified to reduce test and hardware costs without compromising reliability of the flight program
Morphology of Three Imported Aphthona Flea Beetles Used as Biological Control Agents of Leafy Spurge
The following morphological study of the three imported Aphtona flea beetles supplies a detailed description of selected structures that will distinguish each of the three imported species and will separate them from a common native fle beetle (Glyptina atriventris) found at South Dakota release sites
In Vitro and In Vivio Evaluation of a Moisture Treatment Cream Containing Three Critical Elements of Natural Skin Moisturization
Objectives
To evaluate skin barrier and hydration effects of a new rebalancing moisture treatment (TRMT) and to assess efficacy and tolerability in subjects with photodamaged skin. Methods
In an epidermal skin model, tissues (n = 5/group) were topically treated with 25 ”L of TRMT, 25 ”L of a marketâleading moisturizer (MLM), or untreated for 60 minutes. Hydration was measured at 0, 15, and 30 minutes. Tissues were harvested for gene expression analysis of markers associated with skin barrier and hydration: Claudin (CLD), Aquaporin (AQP), Hyaluronic Acid Syntheses (HAS), and Hyaluronidase (HYAL). A clinical study evaluated twiceâdaily application of TRMT, assessing changes in fine lines/wrinkles, brightness, texture, erythema, and tolerability from baseline through week 8. Hydration was measured using electrical impedance. Results
TRMT and MLM demonstrated significant increases in hydration vs untreated tissue at each timepoint (P \u3c .005), with greater hydration effects observed for TRMT vs MLM. TRMTâtreated tissues demonstrated greater expression of CLD, AQP, and HA, and reduced expression of HYAL vs untreated and MLMâtreated tissues. Twiceâdaily application of TRMT demonstrated significant improvements at 2 weeks in fine lines/wrinkles (P \u3c .001), brightness (P \u3c .0001), texture (P \u3c .0004), and hydration (P \u3c .004). At 8 weeks, statistically significant improvements were achieved in all categories. Conclusion
In an epidermal skin model, TRMT demonstrated significant increases in hydration, greater hydration effects, and expression of key markers associated with skin barrier and hydration vs a MLM. Twiceâdaily application of TRMT was well tolerated and resulted in early, significant improvements in hydration and visible improvements in skin brightness, texture, fine lines/wrinkles, and erythema at 8 weeks
Free-field propagation of high intensity noise
Research on high intensity (finite amplitude) acoustic waves shows that nonlinear distortion effects generally result in a shift of energy to higher frequencies. The higher intensities associated with supersonic jets would therefore indicate that high frequency enhancement of the spectrum should occur, resulting in the differences observed between subsonic and supersonic jets. A 10,000 acoustic watt source installed in an anechoic chamber generates sound levels such that acoustic shocks are readily observable. Dual frequency excitation of the source produces a strong parametric effect with a difference frequency comparable in level to the primary frequency. The test set up and recording equipment being used to determine the finite amplitude noise representative of an actual supersonic jet are described as well as the development of a computer program based on Burger's equation. The spectra of 1/2 octave band, 1 kHz sine wave, and dual frequency input and output are presented in graphs along with waveforms at Z = .025, 0.1, and 1.0
Theory of imaging a photonic crystal with transmission near-field optical microscopy
While near-field scanning optical microscopy (NSOM) can provide optical
images with resolution much better than the diffraction limit, analysis and
interpretation of these images is often difficult. We present a theory of
imaging with transmission NSOM that includes the effects of tip field,
tip/sample coupling, light propagation through the sample and light collection.
We apply this theory to analyze experimental NSOM images of a nanochannel glass
(NCG) array obtained in transmission mode. The NCG is a triangular array of
dielectric rods in a dielectric glass matrix with a two-dimensional photonic
band structure. We determine the modes for the NCG photonic crystal and
simulate the observed data. The calculations show large contrast at low
numerical aperture (NA) of the collection optics and detailed structure at high
NA consistent with the observed images. We present calculations as a function
of NA to identify how the NCG photonic modes contribute to and determine the
spatial structure in these images. Calculations are presented as a function of
tip/sample position, sample index contrast and geometry, and aperture size to
identify the factors that determine image formation with transmission NSOM in
this experiment.Comment: 28 pages of ReVTex, 14 ps figures, submitted to Phys. Rev.
Correlated defects, metal-insulator transition, and magnetic order in ferromagnetic semiconductors
The effect of disorder on transport and magnetization in ferromagnetic III-V
semiconductors, in particular (Ga,Mn)As, is studied theoretically. We show that
Coulomb-induced correlations of the defect positions are crucial for the
transport and magnetic properties of these highly compensated materials. We
employ Monte Carlo simulations to obtain the correlated defect distributions.
Exact diagonalization gives reasonable results for the spectrum of valence-band
holes and the metal-insulator transition only for correlated disorder. Finally,
we show that the mean-field magnetization also depends crucially on defect
correlations.Comment: 4 pages RevTeX4, 5 figures include
Fluorescence Imaging of Underexpanded Jets and Comparison with CFD
An experimental study of underexpanded and highly underexpanded axisymmetric nitrogen free jets seeded with 0.5% nitric oxide (NO) and issuing from a sonic orifice was conducted at NASA Langley Research Center. Reynolds numbers based on nozzle exit conditions ranged from 770 to 35,700, and nozzle exit-to-ambient jet pressure ratios ranged from 2 to 35. These flows were non-intrusively visualized with a spatial resolution of approximately 0.14 mm x 0.14 mm x 1 mm thick and a temporal resolution of 1 s using planar laser-induced fluorescence (PLIF) of NO, with the laser tuned to the strongly-fluorescing UV absorption bands of the Q1 band head near 226.256 nm. Three laminar cases were selected for comparison with computational fluid dynamics (CFD). The cases were run using GASP (General Aerodynamic Simulation Program) Version 4. Comparisons of the fundamental wavelength of the jet flow showed good agreement between CFD and experiment for all three test cases, while comparisons of Mach disk location and Mach disk diameter showed good agreement at lower jet pressure ratios, with a tendency to slightly underpredict these parameters with increasing jet pressure ratio
Characterizing the -ray Emission from FR0 Radio Galaxies
FR0 galaxies constitute the most abundant jet population in the local
Universe. With their compact jet structure, they are broadband photon emitters
and have been proposed as multi-messenger sources. Recently, these sources have
been detected for the first time in rays. Using a revised FR0 catalog,
we confirm that the FR0 population as a whole are -ray emitters, and we
also identify two significant sources. For the first time, we find a
correlation between the 5 GHz core radio luminosity and -ray luminosity
in the 1 - 800 GeV band, having a 4.5 statistical significance. This is
clear evidence that the jet emission mechanism is similar in nature for FR0s
and the well-studied canonical FR (FRI and FRII) radio galaxies. Furthermore,
we perform broadband SED modeling for the significantly detected sources as
well as the subthreshold source population using a one-zone SSC model. Within
the maximum jet power budget, our modeling shows that the detected gamma rays
from the jet can be explained as inverse Compton photons. To explain the
multi-wavelength observations for these galaxies, the modeling results
stipulate a low bulk Lorentz factor and a jet composition far from
equipartition, with the particle energy density dominating over the magnetic
field energy density.Comment: 24 pages, 9 figures, 2 tables. Submitted to the Astrophysical Journa
Mirror Energy Differences at Large Isospin Studied through Direct Two-Nucleon Knockout
The first spectroscopy of excited states in 52Ni (Tz=2) and 51Co (Tz=-3/2)
has been obtained using the highly selective two-neutron knockout reaction.
Mirror energy differences between isobaric analogue states in these nuclei and
their mirror partners are interpreted in terms of isospin nonconserving
effects. A comparison between large scale shell-model calculations and data
provides the most compelling evidence to date that both electromagnetic and an
additional isospin nonconserving interactions for J=2 couplings, of unknown
origin, are required to obtain good agreement.Comment: Accepted for publication in Physical Review Letter
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