35,637 research outputs found

    Closing the design loop on HiMAT (highly maneuverable aircraft technology)

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    The design methodology used in the HiMAT program and the wind tunnel development activities are discussed. Selected results from the flight test program are presented and the strengths and weaknesses of testing advanced technology vehicles using the RPV concept is examined. The role of simulation on the development of digital flight control systems and in RPV's in particular is emphasized

    Patterns of Financing: A Comparison Between White- and African-American Young Firms

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    Based on Kauffman Firm Survey data, examines differences in start-up and follow-on capital injections into and capital use by firms with African-American and white owners. Explores how access to capital affects the racial gap in new business formation

    Spectral asymptotics of periodic elliptic operators

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    We demonstrate that the structure of complex second-order strongly elliptic operators HH on Rd{\bf R}^d with coefficients invariant under translation by Zd{\bf Z}^d can be analyzed through decomposition in terms of versions HzH_z, z∈Tdz\in{\bf T}^d, of HH with zz-periodic boundary conditions acting on L2(Id)L_2({\bf I}^d) where I=[0,1>{\bf I}=[0,1>. If the semigroup SS generated by HH has a H\"older continuous integral kernel satisfying Gaussian bounds then the semigroups SzS^z generated by the HzH_z have kernels with similar properties and z↦Szz\mapsto S^z extends to a function on Cd∖{0}{\bf C}^d\setminus\{0\} which is analytic with respect to the trace norm. The sequence of semigroups S(m),zS^{(m),z} obtained by rescaling the coefficients of HzH_z by c(x)→c(mx)c(x)\to c(mx) converges in trace norm to the semigroup S^z\hat{S}^z generated by the homogenization H^z\hat{H}_z of HzH_z. These convergence properties allow asymptotic analysis of the spectrum of HH.Comment: 27 pages, LaTeX article styl

    The milliped genus Euryurus Koch, 1847 (Polydesmida: Euryuridae) west of the Mississippi River; occurrence of E. leachii (Gray, 1832) on Crowley’s Ridge, Arkansas

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    The milliped genus Euryurus Koch, 1847, and the species, E. leachii (Gray, 1832) (Polydesmida: Euryuridae), are recorded from three sites on the northern part of Crowley’s Ridge (Cross, Lee, and Poinsett counties), Arkansas, where the only prior familial records are of Auturus evides (Bollman, 1887). Coupled with the published locality of E. leachii in Phillips Co., at the southern extremity of the Ridge, the only known occurrences of both the genus and species in Arkansas and west of the Mississippi River are in this physiographic feature. The Arkansas population is geographically peripheral but anatomically intermediate between the two recognized subspecies, E. l. leachii and E. l. fraternus Hoffman, 1978, and we do not assign it to a race. Molecular investigations seem necessary to resolve relationships in the “E. leachii complex.

    Tracking TCRß sequence clonotype expansions during antiviral therapy using high-throughput sequencing of the hypervariable region

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    To maintain a persistent infection viruses such as hepatitis C virus (HCV) employ a range of mechanisms that subvert protective T cell responses. The suppression of antigen-specific T cell responses by HCV hinders efforts to profile T cell responses during chronic infection and antiviral therapy. Conventional methods of detecting antigen-specific T cells utilize either antigen stimulation (e.g., ELISpot, proliferation assays, cytokine production) or antigen-loaded tetramer staining. This limits the ability to profile T cell responses during chronic infection due to suppressed effector function and the requirement for prior knowledge of antigenic viral peptide sequences. Recently, high-throughput sequencing (HTS) technologies have been developed for the analysis of T cell repertoires. In the present study, we have assessed the feasibility of HTS of the TCRβ complementarity determining region (CDR)3 to track T cell expansions in an antigen-independent manner. Using sequential blood samples from HCV-infected individuals undergoing antiviral therapy, we were able to measure the population frequencies of >35,000 TCRβ sequence clonotypes in each individual over the course of 12 weeks. TRBV/TRBJ gene segment usage varied markedly between individuals but remained relatively constant within individuals across the course of therapy. Despite this stable TRBV/TRBJ gene segment usage, a number of TCRβ sequence clonotypes showed dramatic changes in read frequency. These changes could not be linked to therapy outcomes in the present study; however, the TCRβ CDR3 sequences with the largest fold changes did include sequences with identical TRBV/TRBJ gene segment usage and high junction region homology to previously published CDR3 sequences from HCV-specific T cells targeting the HLA-B*0801-restricted 1395HSKKKCDEL1403 and HLA-A*0101-restricted 1435ATDALMTGY1443 epitopes. The pipeline developed in this proof of concept study provides a platform for the design of future experiments to accurately address the question of whether T cell responses contribute to SVR upon antiviral therapy. This pipeline represents a novel technique to analyze T cell dynamics in situations where conventional antigen-dependent methods are limited due to suppression of T cell functions and highly diverse antigenic sequences

    Vitrification and determination of the crystallization time scales of the bulk-metallic-glass-forming liquid Zr58.5Nb2.8Cu15.6Ni12.8Al10.3

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    The crystallization kinetics of Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 were studied in an electrostatic levitation (ESL) apparatus. The measured critical cooling rate is 1.75 K/s. Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 is the first bulk-metallic-glass-forming liquid that does not contain beryllium to be vitrified by purely radiative cooling in the ESL. Furthermore, the sluggish crystallization kinetics enable the determination of the time-temperature-transformation (TTT) diagram between the liquidus and the glass transition temperatures. The shortest time to reach crystallization in an isothermal experiment; i.e., the nose of the TTT diagram is 32 s. The nose of the TTT diagram is at 900 K and positioned about 200 K below the liquidus temperature

    Emerging Technologies Challenging Current Legal Paradigms

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    U.S. patent law has made assumptions about where new inventions will be created, who will create them, and how they will be infringed. Throughout history, emerging technologies have challenged these paradigms. This decade’s emerging technologies will allow humans to create in virtual worlds, connect billions of every day devices via the Internet, and use artificial intelligence to invent across technology fields. If countries like the U.S. wish to encourage inventors to seek patent protection in these emerging areas, then a paradigm shift in the law must occur. Specifically, the law must clarify patent eligibility, recognize the increasing role of artificial intelligence in inventing, and continue to develop the doctrinal framework for enforcing interactive patents
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