17,368 research outputs found

    A Note on Systems of Linear Equations

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    This note is a comment on reference [1] and a generalization of the method there presented. We consider a system of m linear equations in n unknowns x_1, x_2,...x_n (1) Σ^(n)_(j=1) a_(ij)x_j = c_i i=1, 2,...m, a_(ij), c_i real or A∙x=c in matrix notation. We distinguish three cases: (I) There is no finite vector x satisfying (1) (inconsistent case); (II) There is a unique vector x satisfying (1); (III) There are an infinity of vectors x satisfying (1), such that their endpoints lie on some line, plane, or higher-dimensional linear manifold

    Development of lubricating oils suitable for use with liquid oxidizers Final summary report, 4 Dec. 1969 - 4 Oct. 1970

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    Development of lubricating oils suitable for use with liquid oxidizer

    ESRC IAA Workshop: Towards Maximising International PhD Students' Experience: Extended Summary

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    Interband Light Absorption at a Rough Interface

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    Light absorption at the boundary of indirect-band-gap and direct-forbidden gap semiconductors is analyzed. It is found that the possibility of the electron momentum nonconservation at the interface leads to essential enhancement of absorption in porous and microcrystalline semiconductors. The effect is more pronounced at a rough boundary due to enlargement of the share of the interface atoms.Comment: LATEX, 19 pages, 4 PostScript figure

    Portable high-speed photometry systems for observing occultations

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    Because of their high spatial resolution, stellar occultations have proven extremely effective for learning about planetary upper atmospheres, asteroids, and planetary rings. The ring orbit studies for Uranus have been particularly fruitful because researchers have been able, through occultations, to obtain data of high spatial resolution (approximately 2 km) at the rate of 1 to 2 times per year. THe occultation program at M.I.T. involves: (1) identifying the scientific questions that can be answered by occultation events, (2) predicting the zone of visibilty for the useful events, (3) maintaining and improving a set of portable high-speed photometric systems, (4) obtaining the observations, and (5) reducing the data and interpreting the results. Accomplishments during the past year include: (1) a comprehensive analysis of stellar occultation data to obtain an oblateness for Uranus at the 10 ubar level of 0.0193 plus or minus 0.0010, a value consistent with the planet being in hydrostatic equilibrium and undergoing rotation at the period found by Voyger; (2) establishing an upper limit of 0.004 km on the equivalent depth of 1986U1R from 2.2 micrometer occultation data; (3) the discovery of low-amplitude waves on the edges of the epsilon ring of Uranus; and (4) the acquisition of several hundred charge coupled device strip scans of 6 weeks at Mauna Kea for the purpose of generating a prediction for the stellar occultation of Pluto

    The intersection of race, sexual orientation, socioeconomic status, trans identity, and mental health outcomes

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    The present study examined patterns in trans individuals’ multiple identities and mental health outcomes. Cluster 1 (socioeconomic and racial privilege; n = 239) was characterized by individuals who identified as trans women or cross-dressers, lesbian, bisexual, or questioning; had associates degrees; reported household incomes of 60,000ormoreayear;andwerenonLatinoWhite.Cluster2(educationalprivilege;n=191)wascharacterizedbyindividualswhoidentifiedastransmenorgenderqueer,gay,orqueer;hadabachelorsdegree;reportedhouseholdincomesof60,000 or more a year; and were non-Latino White. Cluster 2 (educational privilege; n = 191) was characterized by individuals who identified as trans men or genderqueer, gay, or queer; had a bachelor’s degree; reported household incomes of 10,000 or less a year; and were people of color. There was a pattern of individuals in Cluster 1 who identified with two privileged identities (identifying as White and having higher household incomes), whereas individuals in Cluster 2 identified only formal education as a privilege. Individuals in Cluster 2 reported statistically significant levels of anxiety. Implications of these results for future research and clinical practice are examined.Accepted manuscrip

    Comparative Analysis of the Major Polypeptides from Liver Gap Junctions and Lens Fiber Junctions

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    Gap junctions from rat liver and fiber junctions from bovine lens have similar septilaminar profiles when examined by thin-section electron microscopy and differ only slightly with respect to the packing of intramembrane particles in freeze-fracture images. These similarities have often led to lens fiber junctions being referred to as gap junctions. Junctions from both sources were isolated as enriched subcellular fractions and their major polypeptide components compared biochemically and immunochemically. The major liver gap junction polypeptide has an apparent molecular weight of 27,000, while a 25,000-dalton polypeptide is the major component of lens fiber junctions. The two polypeptides are not homologous when compared by partial peptide mapping in SDS. In addition, there is not detectable antigenic similarity between the two polypeptides by immunochemical criteria using antibodies to the 25,000-dalton lens fiber junction polypeptide. Thus, in spite of the ultrastructural similarities, the gap junction and the lens fiber junction are comprised of distinctly different polypeptides, suggesting that the lens fiber junction contains a unique gene product and potentially different physiological properties

    A generalized vortex lattice method for subsonic and supersonic flow applications

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    If the discrete vortex lattice is considered as an approximation to the surface-distributed vorticity, then the concept of the generalized principal part of an integral yields a residual term to the vorticity-induced velocity field. The proper incorporation of this term to the velocity field generated by the discrete vortex lines renders the present vortex lattice method valid for supersonic flow. Special techniques for simulating nonzero thickness lifting surfaces and fusiform bodies with vortex lattice elements are included. Thickness effects of wing-like components are simulated by a double (biplanar) vortex lattice layer, and fusiform bodies are represented by a vortex grid arranged on a series of concentrical cylindrical surfaces. The analysis of sideslip effects by the subject method is described. Numerical considerations peculiar to the application of these techniques are also discussed. The method has been implemented in a digital computer code. A users manual is included along with a complete FORTRAN compilation, an executed case, and conversion programs for transforming input for the NASA wave drag program

    A Survey of the Arithmetical Concepts of Children in the Elementary Grades Pertaining to the Use of Money

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    It was the purpose of this study: (1) to survey the present concepts of money and its use, in a specific elementary grade level, in a cross section of a city that included all socio-economic levels; (2) to determine the extent to which knowledge of economic concepts is related to socio-economic level; and (3) make suggestions as to areas where greater emphasis towards understanding of money concepts should be placed
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