Speed Limits in General Relativity

Some standard results on the initial value problem of general relativity in matter are reviewed. These results are applied first to show that in a well defined sense, finite perturbations in the gravitational field travel no faster than light, and second to show that it is impossible to construct a warp drive as considered by Alcubierre (1994) in the absence of exotic matter.Comment: 7 pages; AMS-LaTeX; accepted for publication by Classical and Quantum Gravit

Suburbs, Networks, and Attitudes

This paper addresses the question of whether suburban residence is related to greater involvement and interest in the locality. Five alternative models are presented: in particular, one which predicts a "localizing" effect as a consequence of the peripheral location of suburbs. Examination of published research and analyses of two surveys suggest that suburbanites are more locally oriented and involved than are city residents. (And when not, they tend to be more isolated.) This is accounted for largely by self-selection based on individual traits, but also by contextual effects, and, to some extent, by peripheral location

Plasma Urea Concentrations of Pigs on Commercial Operations

Research was conducted on commercial swine operations to determine whether plasma urea concentrations could be used as an indicator of the protein requirement of growing-finishing pigs. The research consisted of a 30-question survey and an on-farm visit to collect blood and feed samples. The survey included questions about genetics, nutrition, housing and health. Results showed that when plasma urea concentrations were analyzed across all phases of production, barrows had greater plasma urea concentrations than gilts. Plasma urea concentrations varied between the different phases of production, with nursery pigs having the lowest plasma urea concentrations, followed by growing and finishing pigs, respectively. An increase in dietary crude protein resulted in an increase of plasma urea in barrows and gilts in all phases of production. The comparison of dietary crude protein concentrations and age of the pigs at the time of blood collection indicates that the majority of the diets were over-formulated for crude protein. The effects of sex, crude protein, and phase of production on plasma urea concentrations in pigs raised on commercial operations were similar to those in a research setting. These results suggest that within an individual swine operation, plasma urea is a useful indicator of the protein requirement of growing-finishing pigs

Local Cortical Tension by Myosin II Guides 3D Endothelial Cell Branching

SummaryA key feature of angiogenesis is directional control of endothelial cell (EC) morphogenesis and movement [1]. During angiogenic sprouting, endothelial “tip cells” directionally branch from existing vessels in response to biochemical cues such as VEGF or hypoxia and migrate and invade the surrounding extracellular matrix (ECM) in a process that requires ECM remodeling by matrix metalloproteases (MMPs) [2–4]. Tip EC branching is mediated by directional protrusion of subcellular pseudopodial branches [5, 6]. Here, we seek to understand how EC pseudopodial branching is locally regulated to directionally guide angiogenesis. We develop an in vitro 3D EC model system in which migrating ECs display branched pseudopodia morphodynamics similar to those in living zebrafish. Using this system, we find that ECM stiffness and ROCK-mediated myosin II activity inhibit EC pseudopodial branch initiation. Myosin II is dynamically localized to the EC cortex and is partially released under conditions that promote branching. Local depletion of cortical myosin II precedes branch initiation, and initiation can be induced by local inhibition of myosin II activity. Thus, local downregulation of myosin II cortical contraction allows pseudopodium initiation to mediate EC branching and hence guide directional migration and angiogenesis

Nonlinear Bloch modes in two-dimensional photonic lattices

We generate experimentally different types of two-dimensional Bloch waves of a square photonic lattice by employing the phase imprinting technique. We probe the local dispersion of the Bloch modes in the photonic lattice by analyzing the linear diffraction of beams associated with the high-symmetry points of the Brillouin zone, and also distinguish the regimes of normal, anomalous, and anisotropic diffraction through observations of nonlinear self-action effects.Comment: 11 pages, 8 figure

The Use of Plasma Urea as an Indicator of Protein Status in Growing-Finishing Pigs

An experiment is being conducted on commercial swine operations to determine if plasma urea concentration can be used as an indicator of protein status in growing-finishing pigs. Swine producers in Eastern Nebraska are being selected to participate in this on-farm study. The experiment includes the completion of a 30-question survey and an on-farm visit for the collection of blood and feed samples. The survey includes questions about genetics, nutrition, housing and health. Preliminary results suggest that crude protein is overfed in most finishing diets. Gilts consistently have lower plasma urea concentrations than barrows when gilts and barrows are fed the same diet during the finishing growth period. This confirms the concept that gilts utilize protein more efficiently for lean growth. These results suggest that within an individual swine operation, plasma urea is a useful indicator of protein status in growing-finishing pigs

Generation of the second-harmonic Bessel beams via nonlinear Bragg diffraction

We generate conical second-harmonic radiation by transverse excitation of a two-dimensional annular periodically-poled nonlinear photonic structure with a fundamental Gaussian beam. We show that these conical waves are the far-field images of the Bessel beams generated in a crystal by parametric frequency conversion assisted by nonlinear Bragg diffraction.Comment: 4 pages, 5 figures. submitte

Beliefs-Driven Price Association

In addition to being a function of traditional fundamentals such as cash-flow persistence and the discount rate, the equilibrium association between a security price and a value-relevant statistic can simply be a function of what rational investors believe the association will be. We refer to this phenomenon as beliefs-driven price association (BPA). By explicitly considering the phenomenon of BPA, we show that the price response to information releases can vary over time even if the risk-free interest rate and investor preferences are static and the earnings/cash flow generating process is stable. This observation suggests, for example, that price-to-earnings associations and price volatility can vary over time even if a stable pattern of economic fundamentals suggests otherwise. The possibility of BPA suggests that measures of the cost of capital, information content, and growth prospects inferred from observed market prices will be confounded. While we do not predict when periods of BPA will arise, we provide empirically testable predictions about how prices should behave during periods of BPA. In particular, we predict that, during sufficiently long periods of high (positive or negative) BPA, price volatility, price levels, and expected returns will be higher than would be implied by a fundamental valuation framework. Finally, while BPA in the pricing of one security does not cause BPA in the pricing of other securities, the price levels of those other securities will be affected if the securities with BPA are sufficiently large relative to the market as a whole