806 research outputs found
Implications of Corporate Capital Structure Theory for Banking Institutions
This paper applies some recent advances in corporate capital structure theory to the determination of optimal capital in banking. The effects of corporate and personal taxes, government regulation, the technology of producing deposit services and the costs of bankruptcy and agency problems are all discussed in the context of the U.S. commercial banking system. The analysis suggests explanations for why commercial banks tend to have relatively less capital than nonfinancial firms, why commercial bank leverage has tended to increase over time and why large banks tend to have relatively less capital than small banks.
Decisive role of nuclear quantum effects on surface mediated water dissociation at finite temperature
Water molecules adsorbed on inorganic substrates play an important role in
several technological applications. In the presence of light atoms in
adsorbates, nuclear quantum effects (NQE) influence properties of these
systems. In this work, we explore the impact of NQE on the dissociation of
water wires on stepped Pt(221) surfaces. By performing ab initio molecular
dynamics simulations with van der Waals corrected density functional theory, we
note that several competing minima for both intact and dissociated structures
are accessible at finite temperatures, making it important to assess whether
harmonic estimates of the quantum free energy are sufficient to determine the
relative stability of the different states. We perform ab initio path integral
molecular dynamics (PIMD) in order to calculate these contributions taking into
account conformational entropy and anharmonicities at finite temperatures. We
propose that when when adsorption is weak and NQE on the substrate are
negligible, PIMD simulations can be performed through a simple partition of the
system, resulting in considerable computational savings. We calculate the
contribution of NQE to the free energies, including anharmonic terms. We find
that they result in an increase of up to 20% of the quantum contribution to the
dissociation free energy compared to harmonic estimates. We also find that the
dissociation has a negligible contribution from tunneling, but is dominated by
ZPE, which can enhance the rate by three orders of magnitude. Finally we
highlight how both temperature and NQE indirectly impact dipoles and the
redistribution of electron density, causing work function to changes of up to
0.4 eV with respect to static estimates. This quantitative determination of the
change in work function provides a possible approach to determine
experimentally the most stable configurations of water oligomers on the stepped
surfaces
An exactly solvable model for driven dissipative systems
We introduce a solvable stochastic model inspired by granular gases for
driven dissipative systems. We characterize far from equilibrium steady states
of such systems through the non-Boltzmann energy distribution and compare
different measures of effective temperatures. As an example we demonstrate that
fluctuation-dissipation relations hold, however with an effective temperature
differing from the effective temperature defined from the average energy.Comment: Some further clarifications. No changes in results or conclusion
Interference in Bohmian Mechanics with Complex Action
In recent years, intensive effort has gone into developing numerical tools
for exact quantum mechanical calculations that are based on Bohmian mechanics.
As part of this effort we have recently developed as alternative formulation of
Bohmian mechanics in which the quantum action, S, is taken to be complex [JCP
{125}, 231103 (2006)]. In the alternative formulation there is a significant
reduction in the magnitude of the quantum force as compared with the
conventional Bohmian formulation, at the price of propagating complex
trajectories. In this paper we show that Bohmian mechanics with complex action
is able to overcome the main computational limitation of conventional Bohmian
methods -- the propagation of wavefunctions once nodes set in. In the vicinity
of nodes, the quantum force in conventional Bohmian formulations exhibits rapid
oscillations that pose severe difficulties for existing numerical schemes. We
show that within complex Bohmian mechanics, multiple complex initial conditions
can lead to the same real final position, allowing for the description of nodes
as a sum of the contribution from two or more crossing trajectories. The idea
is illustrated on the reflection amplitude from a one-dimensional Eckart
barrier. We believe that trajectory crossing, although in contradiction to the
conventional Bohmian trajectory interpretation, provides an important new tool
for dealing with the nodal problem in Bohmian methods
Slow and Smooth: A Bayesian Theory for the Combination of Local Motion Signals in Human Vision
In order to estimate the motion of an object, the visual system needs to combine multiple local measurements, each of which carries some degree of ambiguity. We present a model of motion perception whereby measurements from different image regions are combined according to a Bayesian estimator --- the estimated motion maximizes the posterior probability assuming a prior favoring slow and smooth velocities. In reviewing a large number of previously published phenomena we find that the Bayesian estimator predicts a wide range of psychophysical results. This suggests that the seemingly complex set of illusions arise from a single computational strategy that is optimal under reasonable assumptions
EXPERIMENTAL STUDY TO ASSESS THE IMPACT OF TIMERS ON USER SUSCEPTIBILITY TO PHISHING ATTACKS
Social engineering costs organizations billions of dollars. It exploits the weakest link of information systems security, the users. It is well-documented in literature that users continue to click on phishing emails costing them and their employers significant monetary resources and data loss. Training does not appear to mitigate the effects of phishing much; other solutions are warranted. Kahneman introduced the concepts of System-One and System-Two thinking. System-One is a quick, instinctual decision-making process, while System-Two is a process by which humans use a slow, logical, and is easily disrupted. The key aim of our experimental field study was to investigate if requiring the user to pause by presenting a countdown or count-up timer when a possible phishing email is opened will influence the user to enter System-Two thinking. In this study, we designed, developed, and empirically tested a Pause-and-Think (PAT) mobile app that presented a user with a warning dialog and a countdown or count-up timer. Our goal was to determine whether requiring users to wait with a colored warning and a timer has any effect on phishing attempts. The study was completed in three phases with 42 subject matter experts and 107 participants. The results indicated that a countdown timer set at 3-seconds accompanied by red warning text was most effective on the user’s ability to avoid clicking on a malicious link or attachment. Recommendations for future research include enhancements to the PAT mobile app and investigating what effect the time of day has on susceptibility to phishing
Carotenoid Derivates in Achiote (Bixa orellana) Seeds: Synthesis and Health Promoting Properties
Bixa orellana (family Bixaceae) is a neotropical fast growing perennial tree of great agro-industrial value because its seeds have a high carotenoid content, mainly bixin. It has been used since pre-colonial times as a culinary colorant and spice, and for healing purposes. It is currently used as a natural pigment in the food, in pharmaceutical, and cosmetic industries, and it is commercially known as annatto. Recently, several studies have addressed the biological and medical properties of this natural pigment, both as potential source of new drugs or because its ingestion as a condiment or diet supplement may protect against several diseases. The most documented properties are anti-oxidative; but its anti-cancer, hypoglucemic, antibiotic and anti-inflammatory properties are also being studied. Bixin’s pathway elucidation and its regulation mechanisms are critical to improve the produce of this important carotenoid. Even though the bixin pathway has been established, the regulation of the genes involved in bixin production remains largely unknown. Our laboratory recently published B. orellana’s transcriptome and we have identified most of its MEP (methyl-D-erythritol 4-phosphate) and carotenoid pathway genes. Annatto is a potential source of new drugs and can be a valuable nutraceutical supplement. However, its nutritional and healing properties require further study
Quantized representation of some nonlinear integrable evolution equations on the soliton sector
The Hirota algorithm for solving several integrable nonlinear evolution
equations is suggestive of a simple quantized representation of these equations
and their soliton solutions over a Fock space of bosons or of fermions. The
classical nonlinear wave equation becomes a nonlinear equation for an operator.
The solution of this equation is constructed through the operator analog of the
Hirota transformation. The classical N-solitons solution is the expectation
value of the solution operator in an N-particle state in the Fock space.Comment: 12 page
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