36,331 research outputs found
Three-body Hydrogen Bond Defects Contribute Significantly to the Dielectric Properties of the Liquid Water-Vapor Interface
In this Letter, we present a simple model of aqueous interfacial molecular
structure and we use this model to isolate the effects of hydrogen bonding on
the dielectric properties of the liquid water-vapor interface. By comparing
this model to the results of atomistic simulation we show that the anisotropic
distribution of molecular orientations at the interface can be understood by
considering the behavior of a single water molecule interacting with the
average interfacial density field via an empirical hydrogen bonding potential.
We illustrate that the depth dependence of this orientational anisotropy is
determined by the geometric constraints of hydrogen bonding and we show that
the primary features of simulated orientational distributions can be reproduced
by assuming an idealized, perfectly tetrahedral hydrogen bonding geometry. We
also demonstrate that non-ideal hydrogen bond geometries are required to
produce interfacial variations in the average orientational polarization and
polarizability. We find that these interfacial properties contain significant
contributions from a specific type of geometrically distorted three-body
hydrogen bond defect that is preferentially stabilized at the interface. Our
findings thus reveal that the dielectric properties of the liquid water-vapor
interface are determined by collective molecular interactions that are unique
to the interfacial environment.Comment: 5 pages, 4 figure, S
Characterizing Hydration Properties Based on the Orientational Structure of Interfacial Water Molecules
In this manuscript, we present a general computational method for
characterizing the molecular structure of liquid water interfaces as sampled
from atomistic simulations. With this method, the interfacial structure is
quantified based on the statistical analysis of the orientational
configurations of interfacial water molecules. The method can be applied to
generate position dependent maps of the hydration properties of heterogeneous
surfaces. We present an application to the characterization of surface
hydrophobicity, which we use to analyze simulations of a hydrated protein. We
demonstrate that this approach is capable of revealing microscopic details of
the collective dynamics of a protein hydration shell.Comment: 13 pages, 6 figure
Limits on Vectorlike Leptons from Searches for Anomalous Production of Multi-Lepton Events
We consider extensions of the Standard Model by vectorlike leptons and set
limits on a new charged lepton, , using the ATLAS search for anomalous
production of multi-lepton events. It is assumed that only one Standard Model
lepton, namely the muon, dominantly mixes with vectorlike leptons resulting in
possible decays , , and
. We derive generally applicable limits on the new
lepton treating the branching ratios for these processes as free variables. We
further interpret the general limits in two scenarios with
originating predominantly from either the doublet or the
singlet. The doublet case is more constrained as a result of larger production
cross-section and extra production processes and
in addition to , where is a new neutral state accompanying
. We find that some combinations of branching ratios are poorly
constrained, whereas some are constrained up to masses of more than 500 GeV. In
the doublet case, assuming BR, all masses below
about 300 GeV are ruled out. Even if this condition is relaxed and additional
decay modes, and , are allowed,
below the Higgs threshold still almost all of the parameter space (of
independent branching ratios) is ruled out. Nevertheless, even assuming the
maximal production cross-section, which coincides with the doublet case, the
new charged lepton can still be as light as the LEP-II limit allows. We discuss
several possible improvements of current experimental analyses that would
dramatically reduce the allowed parameter space, even with current data.Comment: 24 pages, 11 figure
A New Avenue to Charged Higgs Discovery in Multi-Higgs Models
Current searches for the charged Higgs at the LHC focus only on the
, , and final states. Instead, we consider the process where is a heavy neutral Higgs boson,
is a charged Higgs boson, and is a light Higgs boson, with mass
either below or above the threshold. The cross-section for this
process is typically large when kinematically open since
can be the dominant decay mode of the charged Higgs. The final state we
consider has two leptons and missing energy from the doubly leptonic decay of
the and possibly additional jets; it is therefore constrained by
existing SM Higgs searches in the channel. We extract these
constraints on the cross-section for this process as a function of the masses
of the particles involved. We also apply our results specifically to a type-II
two Higgs doublet model with an extra Standard-Model-singlet and obtain new and
powerful constraints on and . We point out that a
slightly modified version of this search, with more dedicated cuts, could be
used to possibly discover the charged Higgs, either with existing data or in
the future.Comment: 38 pages, 14 figure
A New Phase at Finite Quark Density from AdS/CFT
We explore phases of N=2 super Yang-Mills theory at finite quark density by
introducing quark chemical potential in a D3-D7 setup. We formulate the
thermodynamics of brane embeddings and find that we need to renormalize the
finite chemical potential due to the divergence of the thermodynamic potentials
and we find that the density versus chemical potential equation of state has
rich structure. This yields two distinct first order phase transitions in a
small window of quark density. In order words, there is a new first order phase
transition in the region of deconfined quarks. In this new phase, the chemical
potential is a decreasing function of the density. We suggest that this might
be relevant to the difference in sQGP--wQGP phases of QCD.Comment: 4 pages, revte
Country Image, Perceived Product Quality and Purchase Intention: the Moderating Roles of Quality Warranty Certificate and Country-Image Transferred Strategies
This article aims at researching on the relationship of country image and customer perception on product quality and purchasing intention in South Korean. Additionally, the moderating roles of product quality warranty and country image transferred strategies are also taken into investigation in this empirical research. In order to make a research on these areas, questionnaire forms were distributed by emails and sending hard copies to 350 target samples in South Korea including Koreans and foreigners who have been living in South Korea and 215 forms were returned back and analyzed by SPSS v.21. The results indicated that gender, age groups and nationalities can significantly influence consumers' perception on the relationship country image and product quality. Surprisingly, the image of origin country produced products does not really affect consumers' perceived product quality, but the image of manufacturing country has a strong and significant influence on consumers' perception in terms of product quality. More interestingly, country image transferred strategy is ineffective in altering consumers' psychological perceptions on country image and perceived product quality. Apart from this, product quality warranty is still workable for boosting consumers' confidence in consuming products in Korean context. Even though this empirical research was considerably and carefully implemented, there are still some significant limitations in practice. The limitations and suggestion are finally introduced and explained
Recommended from our members
Sleep dysfunction and EEG alterations in mice overexpressing alpha-synuclein.
BackgroundSleep disruptions occur early and frequently in Parkinson's disease (PD). PD patients also show a slowing of resting state activity. Alpha-synuclein is causally linked to PD and accumulates in sleep-related brain regions. While sleep problems occur in over 75% of PD patients and severely impact the quality of life of patients and caregivers, their study is limited by a paucity of adequate animal models.ObjectiveThe objective of this study was to determine whether overexpression of wildtype alpha-synuclein could lead to alterations in sleep patterns reminiscent of those observed in PD by measuring sleep/wake activity with rigorous quantitative methods in a well-characterized genetic mouse model.MethodsAt 10 months of age, mice expressing human wildtype alpha-synuclein under the Thy-1 promoter (Thy1-aSyn) and wildtype littermates underwent the subcutaneous implantation of a telemetry device (Data Sciences International) for the recording of electromyograms (EMG) and electroencephalograms (EEG) in freely moving animals. Surgeries and data collection were performed without knowledge of mouse genotype.ResultsThy1-aSyn mice showed increased non-rapid eye movement sleep during their quiescent phase, increased active wake during their active phase, and decreased rapid eye movement sleep over a 24-h period, as well as a shift in the density of their EEG power spectra toward lower frequencies with a significant decrease in gamma power during wakefulness.ConclusionsAlpha-synuclein overexpression in mice produces sleep disruptions and altered oscillatory EEG activity reminiscent of PD, and this model provides a novel platform to assess mechanisms and therapeutic strategies for sleep dysfunction in PD
N3LO NN interaction adjusted to light nuclei in ab exitu approach
We use phase-equivalent transformations to adjust off-shell properties of
similarity renormalization group evolved chiral effective field theory NN
interaction (Idaho N3LO) to fit selected binding energies and spectra of light
nuclei in an ab exitu approach. We then test the transformed interaction on a
set of additional observables in light nuclei to verify that it provides
reasonable descriptions of these observables with an apparent reduced need for
three- and many-nucleon interactions.Comment: Revised text due to journal referee comments. 6 pages, 2 figure
- …