24,154 research outputs found
Ground test experience with large composite structures for commercial transports
The initial ground test of each component resulted in structural failure at less than ultimate design loads. While such failures represent major program delays, the investigation and analysis of each failure revealed significant lessons for effective utilization of composites in primary structure. Foremost among these are secondary loads that produce through-the-thickness forces which may lead to serious weaknesses in an otherwise sound structural design. The sources, magnitude, and effects of secondary loads need to be thoroughly understood and accounted for by the designers of composite primary aircraft structures
Population polygons of tektite specific gravity for various localities in australasia
Comparison of specific gravity of tektites from australia, asia, texas, and czechoslovaki
Some gamma-ray shielding measurements made at altitudes greater than 115000 feet using large Ge(Li) detectors
A series of balloon-flight experiments at altitudes greater than 115,000 feet were conducted to gain information relative to the use of composite shields (passive and/or active) for shielding large-volume, lithium-drifted, germanium (Ge(Li)) detectors used in gamma-ray spectrometers. Data showing the pulse-height spectra of the environmental gamma radiation as measured at 5.3 and 3.8 gms sq cm residual atmosphere with an unshielded diode detector are also presented
The vortex dynamics of a Ginzburg-Landau system under pinning effect
It is proved that the vortices are attracted by impurities or inhomogeities
in the superconducting materials. The strong H^1-convergence for the
corresponding Ginzburg-Landau system is also proved.Comment: 23page
Modulation of Natural Killer Cell Cytotoxicity in Human Cytomegalovirus Infection: The Role of Endogenous Class I Major Histocompatibility Complex and a Viral Class I Homolog
Natural killer (NK) cells have been implicated in early immune responses against certain viruses, including cytomegalovirus (CMV). CMV causes downregulation of class I major histocompatibility complex (MHC) expression in infected cells; however, it has been proposed that a class I MHC homolog encoded by CMV, UL18, may act as a surrogate ligand to prevent NK cell lysis of CMV-infected cells. In this study, we examined the role of UL18 in NK cell recognition and lysis using fibroblasts infected with either wild-type or UL18 knockout CMV virus, and by using cell lines transfected with the UL18 gene. In both systems, the expression of UL18 resulted in the enhanced killing of target cells. We also show that the enhanced killing is due to both UL18-dependent and -independent mechanisms, and that the killer cell inhibitory receptors (KIRs) and CD94/NKG2A inhibitory receptors for MHC class I do not play a role in affecting susceptibility of CMV-infected fibroblasts to NK cellâmediated cytotoxicity
Seasonal abundance of small cladocerans in Lake Mangakaware, Waikato, New Zealand
The seasonal changes in the dynamics and life histories of the Cladocera in Lake Mangakaware, North Island, New Zealand, were studied over 19 months by sampling at weekly or 2-weekly intervals. Lake Mangakaware is a 13.3 ha polymictic lake with high nutrient status, low Secchi disc transparencies, and an unstable thermal regime. The four planktonic cladoceran species (Bosmina longirostris, B. meridionalis, Ceriodaphnia pulchella, and C. dubia) exhibited disjunct population maxima. Only B. longirostris was perennially present. All species exhibited low fecundities and low lipid content, indicating that food resources were limited and that competitive interactions and resistance to starvation were probably important in determining species success. Increases in body size in cooler seasons were unrelated to clutch size, giving further support for the view that available food was limited. These results are consistent with previous experimental findings that subtle differences in life history can determine seasonal success and the outcome of competition between similar species
Phasing diffuse scattering. Application of the SIR2002 algorithm to the non-crystallographic phase problem
A new phasing algorithm has been used to determine the phases of diffuse
elastic X-ray scattering from a non-periodic array of gold balls of 50 nm
diameter. Two-dimensional real-space images, showing the charge-density
distribution of the balls, have been reconstructed at 50 nm resolution from
transmission diffraction patterns recorded at 550 eV energy. The reconstructed
image fits well with scanning electron microscope (SEM) image of the same
sample. The algorithm, which uses only the density modification portion of the
SIR2002 program, is compared with the results obtained via the
Gerchberg-Saxton-Fienup HIO algorithm. In this way the relationship between
density modification in crystallography and the HiO algorithm used in signal
and image processing is elucidated.Comment: 7 pages, 12 figure
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