3,630 research outputs found
The effects of multiple repairs on Inconel 718 weld mechanical properties
Inconel 718 weldments were repaired 3, 6, 9, and 13 times using the gas tungsten arc welding process. The welded panels were machined into mechanical test specimens, postweld heat treated, and nondestructively tested. Tensile properties and high cycle fatigue life were evaluated and the results compared to unrepaired weld properties. Mechanical property data were analyzed using the statistical methods of difference in means for tensile properties and difference in log means and Weibull analysis for high cycle fatigue properties. Statistical analysis performed on the data did not show a significant decrease in tensile or high cycle fatigue properties due to the repeated repairs. Some degradation was observed in all properties, however, it was minimal
Boundary-detection algorithm for locating edges in digital imagery
The author has identified the following significant results. Initial development of a computer program which implements a boundary detection algorithm to detect edges in digital images is described. An evaluation of the boundary detection algorithm was conducted to locate boundaries of lakes from LANDSAT-1 imagery. The accuracy of the boundary detection algorithm was determined by comparing the area within boundaries of lakes located using digitized LANDSAT imagery with the area of the same lakes planimetered from imagery collected from an aircraft platform
Soil moisture and evapotranspiration predictions using Skylab data
The author has identified the following significant results. Multispectral reflectance and emittance data from the Skylab workshop were evaluated for prediction of evapotranspiration and soil moisture for an irrigated region of southern Texas. Wavelengths greater than 2.1 microns were required to spectrally distinguish between wet and dry fallow surfaces. Thermal data provided a better estimate of soil moisture than did data from the reflective bands. Thermal data were dependent on soil moisture but not on the type of agricultural land use. The emittance map, when used in conjunction with existing models, did provide an estimate of evapotranspiration rates. Surveys of areas of high soil moisture can be accomplished with space altitude thermal data. Thermal data will provide a reliable input into irrigation scheduling
A global fit of top quark effective theory to data
In this paper we present a global fit of beyond the Standard Model (BSM)
dimension six operators relevant to the top quark sector to currently available
data. Experimental measurements include parton-level top-pair and single top
production from the LHC and the Tevatron. Higher order QCD corrections are
modelled using differential and global K-factors, and we use novel fast-fitting
techniques developed in the context of Monte Carlo event generator tuning to
perform the fit. This allows us to provide new, fully correlated and
model-independent bounds on new physics effects in the top sector from the most
current direct hadron-collider measurements in light of the involved
theoretical and experimental systematics. As a by-product, our analysis
constitutes a proof-of-principle that fast fitting of theory to data is
possible in the top quark sector, and paves the way for a more detailed
analysis including top quark decays, detector corrections and precision
observables.Comment: Additional references and preprint code added. Minor error in
generation of plots fixed, no conclusions affecte
Results from TopFitter
We discuss a global fit of top quark BSM couplings, phrased in the
model-independent language of higher-dimensional effective operators, to the
currently available data from the LHC and Tevatron. We examine the interplay
between inclusive and differential measurements, and the complementarity of LHC
and Tevatron results. We conclude with a discussion of projections for
improvement over LHC Run II.Comment: 5 pages, 4 figures, proceedings of the 9th International Workshop on
the CKM Unitarity Triangle, 28 November - 3 December 2016, Tata Institute for
Fundamental Research (TIFR), Mumbai, Indi
Quantum walks on Cayley graphs
We address the problem of the construction of quantum walks on Cayley graphs.
Our main motivation is the relationship between quantum algorithms and quantum
walks. In particular, we discuss the choice of the dimension of the local
Hilbert space and consider various classes of graphs on which the structure of
quantum walks may differ. We completely characterise quantum walks on free
groups and present partial results on more general cases. Some examples are
given, including a family of quantum walks on the hypercube involving a
Clifford Algebra.Comment: J. Phys. A (accepted for publication
Effects of site, silviculture and seedlot on wood density and estimated wood stiffness in radiata pine at mid-rotation
APOBEC3G induces a hypermutation gradient: purifying selection at multiple steps during HIV-1 replication results in levels of G-to-A mutations that are high in DNA, intermediate in cellular viral RNA, and low in virion RNA
<p>Abstract</p> <p>Background</p> <p>Naturally occurring Vif variants that are unable to inhibit the host restriction factor APOBEC3G (A3G) have been isolated from infected individuals. A3G can potentially induce G-to-A hypermutation in these viruses, and hypermutation could contribute to genetic variation in HIV-1 populations through recombination between hypermutant and wild-type genomes. Thus, hypermutation could contribute to the generation of immune escape and drug resistant variants, but the genetic contribution of hypermutation to the viral evolutionary potential is poorly understood. In addition, the mechanisms by which these viruses persist in the host despite the presence of A3G remain unknown.</p> <p>Results</p> <p>To address these questions, we generated a replication-competent HIV-1 Vif mutant in which the A3G-binding residues of Vif, Y<sup>40</sup>RHHY<sup>44</sup>, were substituted with five alanines. As expected, the mutant was severely defective in an A3G-expressing T cell line and exhibited a significant delay in replication kinetics. Analysis of viral DNA showed the expected high level of G-to-A hypermutation; however, we found substantially reduced levels of G-to-A hypermutation in intracellular viral RNA (cRNA), and the levels of G-to-A mutations in virion RNA (vRNA) were even further reduced. The frequencies of hypermutation in DNA, cRNA, and vRNA were 0.73%, 0.12%, and 0.05% of the nucleotides sequenced, indicating a gradient of hypermutation. Additionally, genomes containing start codon mutations and early termination codons within <it>gag </it>were isolated from the vRNA.</p> <p>Conclusion</p> <p>These results suggest that sublethal levels of hypermutation coupled with purifying selection at multiple steps during the early phase of viral replication lead to the packaging of largely unmutated genomes, providing a mechanism by which mutant Vif variants can persist in infected individuals. The persistence of genomes containing mutated <it>gag </it>genes despite this selection pressure indicates that dual infection and complementation can result in the packaging of hypermutated genomes which, through recombination with wild-type genomes, could increase viral genetic variation and contribute to evolution.</p
- …