2,702 research outputs found
Structure and Dynamics of amorphous Silica Surfaces
We use molecular dynamics computer simulations to study the equilibrium
properties of the surface of amorphous silica. Two types of geometries are
investigated: i) clusters with different diameters (13.5\AA, 19\AA, and
26.5\AA) and ii) a thin film with thickness 29\AA. We find that the shape of
the clusters is independent of temperature and that it becomes more spherical
with increasing size. The surface energy is in qualitative agreement with the
experimental value for the surface tension. The density distribution function
shows a small peak just below the surface, the origin of which is traced back
to a local chemical ordering at the surface. Close to the surface the partial
radial distribution functions as well as the distributions of the bond-bond
angles show features which are not observed in the interior of the systems. By
calculating the distribution of the length of the Si-O rings we can show that
these additional features are related to the presence of two-membered rings at
the surface. The surface density of these structures is around 0.6/nm^2 in good
agreement with experimental estimates. From the behavior of the mean-squared
displacement at low temperatures we conclude that at the surface the cage of
the particles is larger than the one in the bulk. Close to the surface the
diffusion constant is somewhat larger than the one in the bulk and with
decreasing temperature the relative difference grows. The total vibrational
density of states at the surface is similar to the one in the bulk. However, if
only the one for the silicon atoms is considered, significant differences are
found.Comment: 30 pages of Latex, 16 figure
Beyond the Small-Angle Approximation For MBR Anisotropy from Seeds
In this paper we give a general expression for the energy shift of massless
particles travelling through the gravitational field of an arbitrary matter
distribution as calculated in the weak field limit in an asymptotically flat
space-time. It is {\it not} assumed that matter is non-relativistic. We
demonstrate the surprising result that if the matter is illuminated by a
uniform brightness background that the brightness pattern observed at a given
point in space-time (modulo a term dependent on the oberver's velocity) depends
only on the matter distribution on the observer's past light-cone. These
results apply directly to the cosmological MBR anisotropy pattern generated in
the immediate vicinity of of an object like a cosmic string or global texture.
We apply these results to cosmic strings, finding a correction to previously
published results for in the small-angle approximation. We also derive the
full-sky anisotropy pattern of a collapsing texture knot.Comment: 23 pages, FERMILAB-Pub-94/047-
Explaining the Frequency of Alcohol Consumption in a Conflict Zone: Jews and Palestinians in Israel
Experiencing stress and exposure to terrorism may have an adverse effect on health risk behaviors. Few studies have examined alcohol use among adults living in Israel under chronic, stressful terrorism-related conditions. In this study, we examined the relationships of demographics, past stressful events, and terrorism exposure to the frequency of alcohol use and the mediating roles of depressive and post-traumatic stress disorder (PTSD) symptoms. We used three waves of data from a 2007–2008 nationally representative sample of Jewish and Palestinian adults in Israel. We assessed past stressful events, in addition to direct and indirect exposures to terrorism. Results indicated that past stressful events and exposure to terrorism were not directly associated with alcohol use, but were indirectly associated and mediated by depressive and PTSD symptomology. Mental health symptoms were differentially associated with alcohol use. More frequent drinking was mediated by higher levels of depression, including for women and Palestinians; however, PTSD symptom severity was related to less frequent drinking. Mental health may play a prominent role in the frequency of alcohol use among adults exposed to terrorism in Israel. Alcohol use, as a coping mechanism, may differ by demographic characteristics (gender and ethnicity) and psychological symptomology for adults living in a conflict zone in Israel
The construction of identities in narratives about serious leisure occupations
Engagement in occupation contributes to the shaping of identity throughout the human life. The act of telling about such engagement involves interaction based on symbolic meaning; the speaker constructing an identity by conveying how the occupation is personally meaningful. This study explored meaning in narratives told by people who engage in serious leisure occupations. A total of 78 narratives were extracted from interviews with 17 people who invest considerable time and other resources into their leisure. Analysis focused on the content, structure and performance of each narrative in order to explore meaning. The meanings were organised into a framework based around three dimensions: the located self, the active self and the changing self. Each dimension has facets that the individual might emphasise, constructing a unique identity. The framework offers a structured basis for conceptualising how occupation contributes to the shaping of the internalised self and the socially situated identity
Global-String and Vortex Superfluids in a Supersymmetric Scenario
The main goal of this work is to investigate the possibility of finding the
supersymmetric version of the U(1)-global string model which behaves as a
vortex-superfluid. To describe the superfluid phase, we introduce a
Lorentz-symmetry breaking background that, in an approach based on
supersymmetry, leads to a discussion on the relation between the violation of
Lorentz symmetry and explicit soft supersymmetry breakings. We also study the
relation between the string configuration and the vortex-superfluid phase. In
the framework we settle down in terms of superspace and superfields, we
actually establish a duality between the vortex degrees of freedom and the
component fields of the Kalb-Ramond superfield. We make also considerations
about the fermionic excitations that may appear in connection with the vortex
formation.Comment: 9 pages. This version presented the relation between Lorentz symmetry
violation by the background and the appearance of terms that explicitly break
SUS
Developing young people's sense of self and place through sport
Previous research has recognized positive health implications, both physical and mental, as an outcome of participation in leisure pursuits. They provide opportunities for self-expression and stress reduction, as well as an environment in which people can socialize. Leisure activities, specifically sport activities, can play a significant role in young people's identity development. This paper explores the leisure activities in which young people in Adelaide, Australia participate. It examines the role of leisure activities in terms of young people's identity and feelings towards their hometown. This study consisted of semi-structured focus groups conducted with 24 senior high school students, followed by a survey resulting in 226 useable responses. Respondents were aged between 16 and 18 years of age. From the range of activities identified and explored, the results revealed sports activities to have the greatest impact on young people's lives. The results demonstrated that frequency of participation has a significant effect on young people's involvement levels and how they identify with the activity
Correction to: An isogenic neurovascular unit model comprised of human induced pluripotent stem cell-derived brain microvascular endothelial cells, pericytes, astrocytes, and neurons
Abstract
Following publication of the original article [1], the author has reported that in Figure 1 (b and c) the y-axis TEER (© x cm2) should be replaced with TEER (Ω x cm2).
Erratum for
An isogenic neurovascular unit model comprised of human induced pluripotent stem cell-derived brain microvascular endothelial cells, pericytes, astrocytes, and neurons. [Fluids Barriers CNS. 2019
"Oh! What a tangled web we weave": Englishness, communicative leisure, identity work and the cultural web of the English folk morris dance scene
In this paper, we consider the relationship between Englishness and the English folk morris dance scene, considering how the latter draws from and reinforces the former. Englishness is considered within the context of the cultural web; a tool more often applied to business management but linked to a sociological viewpoint here. By doing so, we draw the connections between this structured business model and the cultural identity of Englishness. Then, we use the framework of the cultural web and theories of leisure, culture and identity to understand how morris dancers see their role as dancers and ‘communicative leisure’ agents in consciously defending Englishness, English traditions and inventions, the practices and traditions of folk and morris, and the various symbolic communities they inhabit. We argue that most morris dancers in our research become and maintain their leisured identities as dancers because they are attracted to the idea of tradition – even if that tradition is invented and open to change
Respectable Drinkers, Sensible Drinking, Serious Leisure: Single-Malt Whisky Enthusiasts and the Moral Panic of Irresponsible Others
In the public discourse of policy-makers and journalists, drinkers of (excessive) alcohol are portrayed either as irresponsible, immoral deviants or as gullible victims. In other words, the public discourse engenders a moral panic about alcohol-crazed individuals, who become what Cohen [1972. Folk devil and moral panics. London: Routledge] identifies as folk devils: the Other, abusing alcohol to create anti-social disorder. However, alcohol-drinking was, is and continues to be an everyday practice in the leisure lives of the majority of people in the UK. In this research article, I want to explore the serious leisure of whisky-tasting to provide a counter to the myth of the alcohol-drinker as folk devil, to try to construct a new public discourse of sensible drinking. I will draw on ethnographic work at whisky-tastings alongside interviews and analysis of on-line discourses. I show that participation in whisky-tasting events creates a safe space in which excessive amounts of alcohol are consumed, yet the norms of the particular habitus ensure that such drinking never leads to misbehaviour. In doing so, however, I will note that the respectability of whisky-drinking is associated with its masculine, white, privileged habitus – the folk devil becomes someone else, someone Other
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