9,267 research outputs found
A Theory of Capital Structure with Strategic Defaults and Priority Violations
We reformulate the classic CSV model of financial contracting from Townsend (1979) and Gale & Hellwig (1985) to tackle criticisms raised against it voiced by Hart (1995), such as lack of optimal behavior at the repayment stage and an inability to allow for outside equity. As a result, we obtain a theory of capital structure that accommodates empirical regularities such as bankruptcies, strategic defaults of debt obligations, and violations of absolute priority rules as parts of the equilibrium description.Cash Diversion, Costly State Verification, Outside Equity, Financial Contracts.
Integral equations of scattering in one dimension
A self-contained discussion of integral equations of scattering is presented
in the case of centrally-symmetric potentials in one dimension, which will
facilitate the understanding of more complex scattering integral equations in
two and three dimensions. The present discussion illustrates in a simple
fashion the concept of partial-wave decomposition, Green's function,
Lippmann-Schwinger integral equations of scattering for wave function and
transition operator, optical theorem and unitarity relation. We illustrate the
present approach with a Dirac delta potential.Comment: 12 pages, accepted in American Journal of Physic
Bounds on the electromagnetic interactions of excited spin-3/2 leptons
We discuss possible deviations from QED produced by a virtual excited
spin-3/2 lepton in the reaction . Data recorded
by the OPAL Collaboration at a c.m. energy are used to
establish bounds on the nonstandard-lepton mass and coupling strengths.Comment: Latex, 5 pages, 7 ps figures. To be published in Phys. Rev.
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Increased DNA Copy Number Variation Mosaicism in Elderly Human Brain.
Aging is a complex process strongly determined by genetics. Previous reports have shown that the genome of neuronal cells displays somatic genomic mosaicism including DNA copy number variations (CNVs). CNVs represent a significant source of genetic variation in the human genome and have been implicated in several disorders and complex traits, representing a potential mechanism that contributes to neuronal diversity and the etiology of several neurological diseases and provides new insights into the normal, complex functions of the brain. Nonetheless, the features of somatic CNV mosaicism in nondiseased elderly brains have not been investigated. In the present study, we demonstrate a highly significant increase in the number of CNVs in nondiseased elderly brains compared to the blood. In two neural tissues isolated from paired postmortem samples (same individuals), we found a significant increase in the frequency of deletions in both brain areas, namely, the frontal cortex and cerebellum. Also, deletions were found to be significantly larger when present only in the cerebellum. The sizes of the variants described here were in the 150-760 kb range, and importantly, nearly all of them were present in the Database of Genomic Variants (common variants). Nearly all evidence of genome structural variation in human brains comes from studies detecting changes in single cells which were interpreted as derived from independent, isolated mutational events. The observations based on array-CGH analysis indicate the existence of an extensive clonal mosaicism of CNVs within and between the human brains revealing a different type of variation that had not been previously characterized
Quantum scattering in one dimension
A self-contained discussion of nonrelativistic quantum scattering is
presented in the case of central potentials in one space dimension, which will
facilitate the understanding of the more complex scattering theory in two and
three dimensions. The present discussion illustrates in a simple way the
concept of partial-wave decomposition, phase shift, optical theorem and
effective-range expansion.Comment: 8 page
Water activity in lamellar stacks of lipid bilayers: "Hydration forces" revisited
Water activity and its relationship with interactions stabilising lamellar
stacks of mixed lipid bilayers in their fluid state are investigated by means
of osmotic pressure measurements coupled with small-angle x-ray scattering. The
(electrically-neutral) bilayers are composed of a mixture in various
proportions of lecithin, a zwitterionic phospholipid, and Simulsol, a non-ionic
cosurfactant with an ethoxylated polar head. For highly dehydrated samples the
osmotic pressure profile always exhibits the "classical" exponential decay as
hydration increases but, depending on Simulsol to lecithin ratio, it becomes
either of the "bound" or "unbound" types for more water-swollen systems. A
simple thermodynamic model is used for interpreting the results without
resorting to the celebrated but elusive "hydration forces"Comment: 24 pages, 12 figures. Accepted for publication in The European
Physical Journal
A Nuclear Physics Program at the ATLAS Experiment at the CERN Large Hadron Collider
The ATLAS collaboration has significant interest in the physics of
ultra-relativistic heavy ion collisions. We submitted a Letter of Intent to the
United States Department of Energy in March 2002. The following document is a
slightly modified version of that LOI. More details are available at:
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/SM/ionsComment: Letter of Intent submitted to the United States Department of Energy
Nuclear Physics Division in March 2002 (revised version
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On conductance-based neural field models
This technical note introduces a conductance-based neural field model that combines biologically realistic synaptic dynamics—based on transmembrane currents—with neural field equations, describing the propagation of spikes over the cortical surface. This model allows for fairly realistic inter-and intra-laminar intrinsic connections that underlie spatiotemporal neuronal dynamics. We focus on the response functions of expected neuronal states (such as depolarization) that generate observed electrophysiological signals (like LFP recordings and EEG). These response functions characterize the model's transfer functions and implicit spectral responses to (uncorrelated) input. Our main finding is that both the evoked responses (impulse response functions) and induced responses (transfer functions) show qualitative differences depending upon whether one uses a neural mass or field model. Furthermore, there are differences between the equivalent convolution and conductance models. Overall, all models reproduce a characteristic increase in frequency, when inhibition was increased by increasing the rate constants of inhibitory populations. However, convolution and conductance-based models showed qualitatively different changes in power, with convolution models showing decreases with increasing inhibition, while conductance models show the opposite effect. These differences suggest that conductance based field models may be important in empirical studies of cortical gain control or pharmacological manipulations
Incidência de Diatraea saccharalis (Fabr.) (Lepidoptera: pyralidae) nas culturas do milho e do sorgo em sistema de plantio direto e convencional, com e sem tratamento de sementes.
Evaluation of parasite resistance to commonly used commercial anthelmintics in meat goats on humid subtropical pasture
Anthelmintic-resistant gastrointestinal nematode parasites are a threat to small ruminant industry sustainability. Meat goat does were administered one of four anthelmintics orally (ivermectin (n = 18), moxidectin (n = 18), levamisole hydrochloride (n = 17), or albendazole (n = 19)) or water (n = 18). Fecal samples were collected pretreatment and 12 days post-treatment. Fecal egg counts (FEC) were determined by the modified McMaster technique. The FEC reduction percentages (FECR%) were calculated using three equations. Log transformed FEC means were analyzed by treatment, sire breed of doe, and doe age. Sire breed affected (P \u3c 0.05) pretreatment FEC, but not post-treatment FEC (P = 0.12). Pretreatment FEC did not differ (P = 0.21) by treatment group. Posttreatment FEC varied (P \u3c 0.05) by treatment. Anthelmintic resistance determinations were based on FECR% falling below 90% or 80%, dependent on equation applied. Resistance was detected to all four anthelmintics using each equation. These results suggest the need for alternative methods of internal parasite control in goats
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