Method for alleviating thermal stress damage in laminates

A method is provided for alleviating the stress damage in metallic matrix composites, such as laminated sheet or foil composites. Discontinuities are positively introduced into the interface between the layers so as to reduce the thermal stress produced by unequal expansion of the materials making up the composite. Although a number of discrete elements could be used to form one of the layers and thus carry out this purpose, the discontinuities are preferably produced by simply drilling holes in the metallic matrix layer or by forming grooves in a grid pattern in this layer

Negative refraction with tunable absorption in an active dense gas of atoms

Applications of negative index materials (NIM) presently are severely limited by absorption. Next to improvements of metamaterial designs, it has been suggested that dense gases of atoms could form a NIM with negligible losses. In such gases, the low absorption is facilitated by quantum interference. Here, we show that additional gain mechanisms can be used to tune and effectively remove absorption in a dense gas NIM. In our setup, the atoms are coherently prepared by control laser fields, and further driven by a weak incoherent pump field to induce gain. We employ nonlinear optical Bloch equations to analyze the optical response. Metastable Neon is identified as a suitable experimental candidate at infrared frequencies to implement a lossless active negative index material.Comment: 10 pages, 9 figure

Emporium

Abstract EMPORIUM By John Orth, BFA A thesis submitted in partial fulfillment of the requirements for the degree of Master of Fine Arts at Virginia Commonwealth University. Virginia Commonwealth University, 2017. Major Director: Michael Jones McKean, Associate Professor, Sculpture + Extended Media My MFA thesis project is a ten-minute video installation entitled Emporium, in which I adorn, strap, tie, hang, and wrap the bodies of performers with my sculptures, and then let loose these hybridized bodies in the non-linear dream-time of cinema. Riffing on the fantastical taxonomy of Jorge Luis Borges’s The Celestial Emporium of Benevolent Knowledge, I attempt, as Borges proposes, to penetrate the “divine pattern of the universe” by creating patterns of my own. These patterns required a choreography of process that was new to me, leading me to film in truck stops, to grow water lilies in my studio, to wade into the James River at night, and to build sculptures to be dragged behind my truck at great speeds. By interpreting this classificatory system in video and now through writing, I seek to demonstrate the inherent tendency for this system (and in turn, all such systems of division and signification) to collapse under the weight of their own contradictions. In my invented world, delineations collapse, ooze, seep, vibrate, take root, entwine and decay in defiance of a world that, as of late, seems to encourage excessive polarization and unyielding boundaries. In the following pages, I reinterpret eight of Borges’s categories of classification that I addressed in my thesis videowork. This writing is not ancillary to the video work, but rather it is a new iteration of the project. I apply the same methodology in which I developed the video—addressing these categories metaphorically and poetically rather than literally— to be true to Borges’s intentions and to stay true to my thesis’s aim to always serve as a further point of departure

A search for evidence of large body Earth impacts associated with biological crisis zones in the fossil record

The natural history of the Earth, how the present plant and animal species developed, how others completely died out, etc., was studied. The rock strata sampled and studied were at the time of deposition at sea bottom. It was found that, exactly at the stratigraphic level corresponding to the extinction, a thin clay layer was greatly enriched in the the rare element iridium. It was hypothesized that the excess irridium at the boundary came from a large steroid like object that hit the earth, and that the impact of this object threw up a dust cloud dense enough and long lasting enough to bring about the extinction of a wide variety of plants and animals, producing the unique break in in the fossil record, the cretaceous-tertiary boundary. The same iridium and platinum metals enrichement are found in a thin clay layer that corresponds with the boundary as difined by sudden radical changes in plant populations. The irridium enrichement is confirmed at other fresh water origin rites in the Raton Basin

Interplanetary propulsion using inertial fusion

Inertial fusion can be used to power spacecraft within the solar system and beyond. Such spacecraft have the potential for short-duration manned-mission performance exceeding other technologies. We are conducting a study to assess the systems aspects of inertial fusion as applied to such missions, based on the conceptual engine design of Hyde (1983) we describe the required systems for an entirely new spacecraft design called VISTA that is based on the use of DT fuel. We give preliminary design details for the power conversion and power conditioning systems for manned missions to Mars of total duration of about 100 days. Specific mission performance results will be published elsewhere, after the study has been completed

Testing the Bottom-Up and Top-Down Models of Self-Esteem: A Meta-Analysis of Longitudinal Studies

The present meta-analysis tests the bottom-up and top-down models of self-esteem, by synthesizing the available longitudinal evidence on prospective effects between global and domain-specific self-esteem. The bottom-up model assumes that people’s domain-specific self-esteem influences their global self-esteem, whereas the top-down model assumes the reverse direction of effects. Eight domains of self-esteem were assessed: academic abilities, physical appearance, athletic abilities, morality, romantic relationships, social acceptance, mathematics, and verbal abilities. We conducted a comprehensive search of the literature, which led to the inclusion of data from 43 independent samples (total N = 24,668). One-stage meta-analytic structural equation modeling was used to estimate the coefficients of interest. There was no evidence of publication bias. Overall, the results indicated a pattern of reciprocal prospective effects between global and domain-specific self-esteem. Bottom-up effects were significant in all domains except verbal abilities (mean effect sizes ranged from .05 to .19). Top-down effects were significant in all domains except mathematics (mean effect sizes ranged from .05 to .12, except .01 in the mathematics domain). None of the moderators tested (i.e., age, gender, measure, time lag, and publication year) was significant in any of the domains, which strengthens the generalizability of the results. In sum, the findings provide support for both bottom-up and top-down effects, suggesting a reciprocal relation model between global and domain-specific self-esteem. The discussion addresses the implications of the findings for research in the field of self-esteem

The link between low self-esteem and eating disorders: A meta-analysis of longitudinal studies

In this meta-analysis, we synthesized the available longitudinal evidence on prospective effects between self-esteem and eating pathology (i.e., restrained eating, bulimic behavior, binge eating, eating concern, negative body image, and drive for thinness). The analyses were based on 48 independent samples, including 19,187 participants. Mean age was 19.3 years (range = 7–48). As effect-size measure, we used standardized regression coefficients, controlled for prior levels of the predicted variables. Results suggested reciprocal prospective effects between low self-esteem and eating pathology. Self-esteem negatively predicted total eating pathology over time (β = −.08), and total eating pathology negatively predicted self-esteem over time (β = −.09). Overall, results for specific categories of eating pathology were similar. Moderator analyses indicated that the effects did not differ across age, gender, sample type (clinical vs. nonclinical), and time lag between assessments. In sum, the results support a reciprocal relations model of low self-esteem and eating disorders

Chemical fractionation of siderophile elements in impactites from Australian meteorite craters

The abundance pattern of siderophile elements in terrestrial and lunar impact melt rocks was used extensively to infer the nature of the impacting projectiles. An implicit assumption made is that the siderophile abundance ratios of the projectiles are approximately preserved during mixing of the projectile constituents with the impact melts. As this mixture occurs during flow of strongly shocked materials at high temperatures, however there are grounds for suspecting that the underlying assumption is not always valid. In particular, fractionation of the melted and partly vaporized material of the projectile might be expected because of differences in volatility, solubility in silicate melts, and other characteristics of the constituent elements. Impactites from craters with associated meteorites offer special opportunities to test the assumptions on which projectile identifications are based and to study chemical fractionation that occurred during the impact process

Vacuum energy in the presence of a magnetic string with delta function profile

We present a calculation of the ground state energy of massive spinor fields and massive scalar fields in the background of an inhomogeneous magnetic string with potential given by a delta function. The zeta functional regularization is used and the lowest heat kernel coefficients are calculated. The rest of the analytical calculation adopts the Jost function formalism. In the numerical part of the work the renormalized vacuum energy as a function of the radius $R$ of the string is calculated and plotted for various values of the strength of the potential. The sign of the energy is found to change with the radius. For both scalar and spinor fields the renormalized energy shows no logarithmic behaviour in the limit $R\to 0$, as was expected from the vanishing of the heat kernel coefficient $A_2$, which is not zero for other types of profiles.Comment: 30 pages, 10 figure