9,599 research outputs found
Hydration and mobility of HO-(aq)
The hydroxide anion plays an essential role in many chemical and biochemical
reactions. But a molecular-scale description of its hydration state, and hence
also its transport, in water is currently controversial. The statistical
mechanical quasi-chemical theory of solutions suggests that HO[H2O]3- is the
predominant species in the aqueous phase under standard conditions. This result
is in close agreement with recent spectroscopic studies on hydroxide water
clusters, and with the available thermodynamic hydration free energies. In
contrast, a recent ab initio molecular dynamics simulation has suggested that
HO[H_2O]4- is the only dominant aqueous solution species. We apply adiabatic ab
initio molecular dynamics simulations, and find good agreement with both the
quasi-chemical theoretical predictions and experimental results. The present
results suggest a picture that is simpler, more traditional, but with
additional subtlety. These coordination structures are labile but the
tri-coordinate species is the prominent case. This conclusion is unaltered with
changes in the electronic density functional. No evidence is found for
rate-determining activated inter-conversion of a HO[H2O]4- trap structure to
HO[H2O]3-, mediating hydroxide transport. The view of HO- diffusion as the
hopping of a proton hole has substantial validity, the rate depending largely
on the dynamic disorder of the water hydrogen-bond network.Comment: 7 pages, 5 figures, additional results include
Direct Observation of Controlled Coupling in an Individual Quantum Dot Molecule
We report the direct observation of quantum coupling in individual quantum
dot molecules and its manipulation using static electric fields. A pronounced
anti-crossing of different excitonic transitions is observed as the electric
field is tuned. Comparison of our experimental results with theory shows that
the observed anti-crossing occurs between excitons with predominant spatially
\emph{direct} and \emph{indirect} character. The electron component of the
exciton wavefunction is shown to have molecular character at the anti-crossing
and the quantum coupling strength is deduced optically. In addition, we
determine the dependence of the coupling strength on the inter-dot separation
and identify a field driven transition of the nature of the molecular ground
state.Comment: 11 pages, 4 figures submitted to Physical Review Letter
Magnetohydrodynamic activity inside a sphere
We present a computational method to solve the magnetohydrodynamic equations
in spherical geometry. The technique is fully nonlinear and wholly spectral,
and uses an expansion basis that is adapted to the geometry:
Chandrasekhar-Kendall vector eigenfunctions of the curl. The resulting lower
spatial resolution is somewhat offset by being able to build all the boundary
conditions into each of the orthogonal expansion functions and by the
disappearance of any difficulties caused by singularities at the center of the
sphere. The results reported here are for mechanically and magnetically
isolated spheres, although different boundary conditions could be studied by
adapting the same method. The intent is to be able to study the nonlinear
dynamical evolution of those aspects that are peculiar to the spherical
geometry at only moderate Reynolds numbers. The code is parallelized, and will
preserve to high accuracy the ideal magnetohydrodynamic (MHD) invariants of the
system (global energy, magnetic helicity, cross helicity). Examples of results
for selective decay and mechanically-driven dynamo simulations are discussed.
In the dynamo cases, spontaneous flips of the dipole orientation are observed.Comment: 15 pages, 19 figures. Improved figures, in press in Physics of Fluid
Reducing Stigma toward the Transgender Community: An Evaluation of a Humanizing and Perspective-Taking Intervention
Transgender (TG) individuals, or those whose gender identities, expressions and/or behaviors differ from their biological sex (Kirk & Kulkarni, 2006) feel there is a pervasive pattern of discrimination and prejudice directed toward them (Lombardi et al., 2001). In comparison to their heterosexual peers, LGBT youth and emerging adults are at increased risk for a host of adverse outcomes including: suicide, depression, harassment, and victimization (IOM, 2011).
Stigma has been characterized as encompassing several components: labeling, making an association between the label and a negative stereotype, separating those who are different as an “out-group” and discriminating. In a recent analysis of the transgender experience, Hill (2002) described three key constructs that can be used to understand negative emotions and behaviors toward transgender individuals: transphobia – an emotional disgust toward gender non-conforming individuals; genderism – a belief that gender non-conforming individuals are pathological or disordered; gender bashing – assault or harassment of gender non-conforming individuals.
Recent work on minority stress posits a distal-proximal model of stress in which a person identifies with and makes proximal, distal social attitudes that can have negative effects on their psychological well-being (Meyer, 2003). Thus, stigmatized attitudes and behaviors not only have the potential to contribute to violence or discriminatory behavior but also have a direct impact on the psychological health of the target individual. Thus, the question of how to change negative attitudes and behaviors toward TG individuals is paramount.
Researchers have sought to develop interventions aimed at reducing stigma with three basic strategies identified: protest, education and contact (Corrigan & Penn, 1999). However, to date only two such strategies have garnered empirical support: contact and education. In relation to mental illness, education strategies have received limited support (Holmes et al., 1999; see Luty et al., 2007 for an exception). In contrast, contact-based interventions yield the most dramatic changes in attitudes and behaviors; contact involving media depictions have also been demonstrated to yield positive attitude change. Comparing traditional diagnosis-centered teaching about mental illness to a humanizing approach that required students to write a first-person narrative about suffering from a mental illness, Mann and Himelein (2008) found that attitudes changed only when students were required to adopt the perspective of a mentally ill individual. In their recent meta-analysis, Pettigrew and Tropp (2006) demonstrated that contact reduces prejudice and is particularly effective when it occurs under favorable conditions (e.g., conditions of equality, cooperation, and institutional support). While a wealth of research has supported the contact hypothesis related to changing negative attitudes toward ethnic minorities, the mentally ill, the homeless, gays/lesbians and other stigmatized groups, there have been a limited number of studies evaluating associations between contact and attitudes toward the TG community (Harvey, 2002; Hill & Willoughby, 2005) and no controlled studies to evaluate the efficacy of such methods.
The current study extends work evaluating anti-stigma interventions to the TG community and seeks to evaluate whether attitude change will differ between participants receiving basic education about the transgender community and those who are educated about TG through media depictions of TG families and are asked to engage in a perspective-taking task. We hypothesize that participants in the humanizing condition who view a documentary and write a first-person narrative of transgender experiences will show a more significant change in transphobia, genderist attitudes and desire for social distance across time relative to participants in the education-only condition signaling less stigmatized and prejudicial attitudes at post-test.
Hodson (2011) recently examined the existing contact literature and found that, consistent with Pettigrew’s (1998) focus on individual differences, intergroup contact was effective (and perhaps even more effective) among individuals who were intolerant and cognitively rigid. Religious fundamentalism has been associated with anti-homosexual sentiment (Fulton et al., 1999). Whether religiosity is similarly associated with negative attitudes toward TG individuals will be explored. Whether religiosity and prior contact with the LGBTQ community will moderate intervention outcomes will also be explored
Hydrodynamic and magnetohydrodynamic computations inside a rotating sphere
Numerical solutions of the incompressible magnetohydrodynamic (MHD) equations
are reported for the interior of a rotating, perfectly-conducting, rigid
spherical shell that is insulator-coated on the inside. A previously-reported
spectral method is used which relies on a Galerkin expansion in
Chandrasekhar-Kendall vector eigenfunctions of the curl. The new ingredient in
this set of computations is the rigid rotation of the sphere. After a few
purely hydrodynamic examples are sampled (spin down, Ekman pumping, inertial
waves), attention is focused on selective decay and the MHD dynamo problem. In
dynamo runs, prescribed mechanical forcing excites a persistent velocity field,
usually turbulent at modest Reynolds numbers, which in turn amplifies a small
seed magnetic field that is introduced. A wide variety of dynamo activity is
observed, all at unit magnetic Prandtl number. The code lacks the resolution to
probe high Reynolds numbers, but nevertheless interesting dynamo regimes turn
out to be plentiful in those parts of parameter space in which the code is
accurate. The key control parameters seem to be mechanical and magnetic
Reynolds numbers, the Rossby and Ekman numbers (which in our computations are
varied mostly by varying the rate of rotation of the sphere) and the amount of
mechanical helicity injected. Magnetic energy levels and magnetic dipole
behavior are exhibited which fluctuate strongly on a time scale of a few eddy
turnover times. These seem to stabilize as the rotation rate is increased until
the limit of the code resolution is reached.Comment: 26 pages, 17 figures, submitted to New Journal of Physic
Использование подхода социальной семиотики в мультимодальном анализе: исследование обучения в школах, музеях и больницах
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