957 research outputs found
What Drives Car Attitudes: An Analysis of How Demographics and Environmental Views Relate to Car Attitudes
Successfully marketing new, clean, car technologies to consumers requires an advertising strategy that fits consumersâ priorities and attitudes towards cars. We created a survey to study how attitudes towards cars are associated with demographics and environmental views. Our study examined car preferences and environmental concerns of a sample of Gettysburg College students in comparison to a national sample obtained from Amazonâs Mechanical Turk. Overall, we concluded that environmental beliefs are a significantly better prediction of car behaviors than demographics. We found that on average people would pay more for a car with a higher fuel economy, but not enough to cover the higher price of newer, cleaner technologies, such as hybrid cars. Gettysburg College studentsâ environmental concern scores were significantly higher on average than that of the general American population. Survey respondents from both samples supported devoting more research and resources to hybrid, electric, and biofuel technologies. However, in regards to their personal purchases they ranked safety and other qualities of the car as higher priorities than greenhouse gas emissions or fuel economy. According to our results, marketing electric cars as safe and reliable is a better strategy than marketing their high fuel economy
The Role of Surface Entropy in Statistical Emission of Massive Fragments from Equilibrated Nuclear Systems
Statistical fragment emission from excited nuclear systems is studied within
the framework of a schematic Fermi-gas model combined with Weisskopf's detailed
balance approach. The formalism considers thermal expansion of finite nuclear
systems and pays special attention to the role of the diffuse surface region in
the decay of hot equilibrated systems. It is found that with increasing
excitation energy, effects of surface entropy lead to a systematic and
significant reduction of effective emission barriers for fragments and,
eventually, to the vanishing of these barriers. The formalism provides a
natural explanation for the occurrence of negative nuclear heat capacities
reported in the literature. It also accounts for the observed linearity of
pseudo-Arrhenius plots of the logarithm of the fragment emission probability
{\it versus} the inverse square-root of the excitation energy, but does not
predict true Arrhenius behavior of these emission probabilities
Liquid-Gas Coexistence and Critical Behavior in Boxed Pseudo-Fermi Matter
A schematic model is presented that allows one to study the behavior of
interacting pseudo-Fermi matter locked in a thermostatic box. As a function of
the box volume and temperature, the matter is seen to show all of the familiar
charactersitics of a Van der Waals gas, which include the coexistence of two
phases under certain circumstances and the presence of a critical point
The 1/N expansion of colored tensor models
In this paper we perform the 1/N expansion of the colored three dimensional
Boulatov tensor model. As in matrix models, we obtain a systematic topological
expansion, with more and more complicated topologies suppressed by higher and
higher powers of N. We compute the first orders of the expansion and prove that
only graphs corresponding to three spheres S^3 contribute to the leading order
in the large N limit.Comment: typos corrected, references update
The complete 1/N expansion of colored tensor models in arbitrary dimension
In this paper we generalize the results of [1,2] and derive the full 1/N
expansion of colored tensor models in arbitrary dimensions. We detail the
expansion for the independent identically distributed model and the topological
Boulatov Ooguri model
QCD with chiral 4-fermion interactions (QCD)
Lattice QCD with staggered quarks is augmented by the addition of a chiral
4-fermion interaction. The Dirac operator is now non-singular at ,
decreasing the computing requirements for light quark simulations by at least
an order of magnitude. We present preliminary results from simulations at
finite and zero temperatures for , with and without gauge fields.Comment: 3 pages. uuencoded, gzipped, tared LateX with 2 encapsulated
postscript figures. Uses epscrc2.sty. Talk presented at LATTICE96(chirality
in qcd). Title changed; minor changes at beginning and end of paper and
reference
The Four-Fermi Model in Three Dimensions at Non-Zero Density and Temperature
The Four Fermi model with discrete chiral symmetry is studied in three
dimensions at non-zero chemical potential and temperature using the Hybrid
Monte Carlo algorithm. The number of fermion flavors is chosen large
to compare with analytic results. A first order chiral symmetry restoring
transition is found at zero temperature with a critical chemical potential
in good agreement with the large calculations. The critical index
of the correlation length is measured in good agreement with analytic
calculations. The two dimensional phase diagram (chemical potential vs.
temperature) is mapped out quantitatively. Finite size effects on relatively
small lattices and non-zero fermion mass effects are seen to smooth out the
chiral transition dramatically.Comment: 21 pages, sorry, no figure
Ab initio Quantum and ab initio Molecular Dynamics of the Dissociative Adsorption of Hydrogen on Pd(100)
The dissociative adsorption of hydrogen on Pd(100) has been studied by ab
initio quantum dynamics and ab initio molecular dynamics calculations. Treating
all hydrogen degrees of freedom as dynamical coordinates implies a high
dimensionality and requires statistical averages over thousands of
trajectories. An efficient and accurate treatment of such extensive statistics
is achieved in two steps: In a first step we evaluate the ab initio potential
energy surface (PES) and determine an analytical representation. Then, in an
independent second step dynamical calculations are performed on the analytical
representation of the PES. Thus the dissociation dynamics is investigated
without any crucial assumption except for the Born-Oppenheimer approximation
which is anyhow employed when density-functional theory calculations are
performed. The ab initio molecular dynamics is compared to detailed quantum
dynamical calculations on exactly the same ab initio PES. The occurence of
quantum oscillations in the sticking probability as a function of kinetic
energy is addressed. They turn out to be very sensitive to the symmetry of the
initial conditions. At low kinetic energies sticking is dominated by the
steering effect which is illustrated using classical trajectories. The steering
effects depends on the kinetic energy, but not on the mass of the molecules.
Zero-point effects lead to strong differences between quantum and classical
calculations of the sticking probability. The dependence of the sticking
probability on the angle of incidence is analysed; it is found to be in good
agreement with experimental data. The results show that the determination of
the potential energy surface combined with high-dimensional dynamical
calculations, in which all relevant degrees of freedon are taken into account,
leads to a detailed understanding of the dissociation dynamics of hydrogen at a
transition metal surface.Comment: 15 pages, 9 figures, subm. to Phys. Rev.
Potentially modifiable predictors of adverse neonatal and maternal outcomes in pregnancies with gestational diabetes mellitus: can they help for future risk stratification and risk-adapted patient care?
Gestational diabetes mellitus (GDM) exposes mothers and their offspring to short and long-term complications. The objective of this study was to identify the importance of potentially modifiable predictors of adverse outcomes in pregnancies with GDM. We also aimed to assess the relationship between maternal predictors and pregnancy outcomes depending on HbA1c values and to provide a risk stratification for adverse pregnancy outcomes according to the prepregnancy BMI (Body mass index) and HbA1c at the 1st booking.
This prospective study included 576 patients with GDM. Predictors were prepregnancy BMI, gestational weight gain (GWG), excessive weight gain, fasting, 1 and 2-h glucose values after the 75 g oral glucose challenge test (oGTT), HbA1c at the 1st GDM booking and at the end of pregnancy and maternal treatment requirement. Maternal and neonatal outcomes such as cesarean section, macrosomia, large and small for gestational age (LGA, SGA), neonatal hypoglycemia, prematurity, hospitalization in the neonatal unit and Apgar score at 5 min < 7 were evaluated. Univariate and multivariate regression analyses and probability analyses were performed.
One-hour glucose after oGTT and prepregnancy BMI were correlated with cesarean section. GWG and HbA1c at the end pregnancy were associated with macrosomia and LGA, while prepregnancy BMI was inversely associated with SGA. The requirement for maternal treatment was correlated with neonatal hypoglycemia, and HbA1c at the end of pregnancy with prematurity (all p < 0.05). The correlations between predictors and pregnancy complications were exclusively observed when HbA1c was â„5.5% (37 mmol/mol). In women with prepregnancy BMI â„ 25 kg/m <sup>2</sup> and HbA1c â„ 5.5% (37 mmol/mol) at the 1st booking, the risk for cesarean section and LGA was nearly doubled compared to women with BMI with < 25 kg/m <sup>2</sup> and HbA1c < 5.5% (37 mmol/mol).
Prepregnancy BMI, GWG, maternal treatment requirement and HbA1c at the end of pregnancy can predict adverse pregnancy outcomes in women with GDM, particularly when HbA1c is â„5.5% (37 mmol/mol). Stratification based on prepregnancy BMI and HbA1c at the 1st booking may allow for future risk-adapted care in these patients
Kinetics of Ordering in Fluctuation-Driven First-Order Transitions: Simulations and Dynamical Renormalization
Many systems where interactions compete with each other or with constraints
are well described by a model first introduced by Brazovskii. Such systems
include block copolymers, alloys with modulated phases, Rayleigh-Benard Cells
and type-I superconductors. The hallmark of this model is that the fluctuation
spectrum is isotropic and has a minimum at a nonzero wave vector represented by
the surface of a d-dimensional hyper-sphere. It was shown by Brazovskii that
the fluctuations change the free energy structure from a to a
form with the disordered state metastable for all quench depths.
The transition from the disordered to the periodic, lamellar structure changes
from second order to first order and suggests that the dynamics is governed by
nucleation. Using numerical simulations we have confirmed that the equilibrium
free energy function is indeed of a form. A study of the dynamics,
however, shows that, following a deep quench, the dynamics is described by
unstable growth rather than nucleation. A dynamical calculation, based on a
generalization of the Brazovskii calculations shows that the disordered state
can remain unstable for a long time following the quench.Comment: 18 pages, 15 figures submitted to PR
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