4,007 research outputs found
Abstractions, accounts and grid usability
The vision of the Grid is one of seamless, virtual and constantly changing resources where users need not concern themselves about details, such as exactly where an application is running or where their data is being stored. However, seamless and virtual often imply a lack of control that users may be wary of, or even opposed to. Drawing upon our studies of HCI and of collaborative work, this paper examines whether the Grid development community should be taking this vision literally and argues for the need for accountability of systems âin interactionâ. We give examples of an alternative approach that seeks to provide ways in which administrators, technical support and user communities can make sense of the behaviour of the complex socio-technical ensembles that are the reality of Grids
Sigmoid Neural Transfer Function Realised by Percolation
An experiment using the phenomenon of percolation has been conducted to demonstrate the implementation of neural functionality (summing and sigmoid transfer). A simple analog approximation to digital percolation is implemented. The device consists of a piece of amorphous silicon with stochastic bit-stream optical inputs, in which a current percolating from one end to the other defines the neuron output, also in the form of a stochastic bit stream. Preliminary experimental results are presented
A COMPARISON OF THE PERFECT PUSH-UP⢠TO TRADITIONAL PUSH-UP
The push-up has traditionally been used to help improve arm and shoulder girdle strength and endurance (ASGSE) (Baumgartner, Oh, Chung, and Hales, 2002). The Perfect Push-Up⢠was designed to help improve the work-out that could be obtained while performing push-ups. While the claims from the manufacturer seem appealing there is little to no research to support their claims. The purpose of the current study is to examine the muscle activity and arm kinematics while using the Perfect Push-Up⢠compared to traditional push-ups, thus addressing the claims of an improved work-out
Paedophiles in the community: inter-agency conflict, news leaks and the local press
This article explores the leaking of confidential information about secret Home Office plans to house convicted paedophiles within a local community (albeit inside a prison). It argues that a politics of paedophilia has emerged in which inter-agency consensus on the issue of âwhat to doâ with high-profile sex offenders has broken down. Accordingly, the article situates newspaper âoutingâ of paedophiles in the community in relation to vigilante journalism and leaked information from official agencies. The article then presents research findings from a case study of news events set in train following a whistle-blowing reaction by Prison Officersâ Association officials to Home Office plans. Drawing from a corpus of 10 interviews with journalists and key protagonists in the story, the article discusses both the dynamics of whistle blowing about paedophiles and also what happens after the whistle has blown
Cage-size control of guest vibration and thermal conductivity in Sr8Ga16Si30-xGex
We present a systematic study of thermal conductivity, specific heat,
electrical resistivity, thermopower and x-ray diffraction measurements
performed on single-crystalline samples of the pseudoquaternary type-I
clathrate system Sr8Ga16Si30-xGex, in the full range of 0 < x < 30. All the
samples show metallic behavior with n-type majority carriers. However, the
thermal conductivity and specific heat strongly depend on x. Upon increasing x
from 0 to 30, the lattice parameter increases by 3%, from 10.446 to 10.726 A,
and the localized vibrational energies of the Sr guest ions in the
tetrakaidekahedron (dodecahedron) cages decrease from 59 (120) K to 35 (90) K.
Furthermore, the lattice thermal conductivity at low temperatures is largely
suppressed. In fact, a crystalline peak found at 15 K for x = 0 gradually
decreases and disappears for x > 20, evolving into the anomalous glass-like
behavior observed for x = 30. It is found that the increase of the free space
for the Sr guest motion directly correlates with a continuous transition from
on-center harmonic vibration to off-center anharmonic vibration, with
consequent increase in the coupling strength between the guest's low-energy
modes and the cage's acoustic phonon modes.Comment: 7 pages, 7 figures, submitted to PR
Glasslike vs. crystalline thermal conductivity in carrier-tuned Ba8Ga16X30 clathrates (X = Ge, Sn)
The present controversy over the origin of glasslike thermal conductivity
observed in certain crystalline materials is addressed by studies on
single-crystal x-ray diffraction, thermal conductivity k(T) and specific heat
Cp(T) of carrier-tuned Ba8Ga16X30 (X = Ge, Sn) clathrates. These crystals show
radically different low-temperature k(T) behaviors depending on whether their
charge carriers are electrons or holes, displaying the usual crystalline peak
in the former case and an anomalous glasslike plateau in the latter. In
contrast, Cp(T) above 4 K and the general structural properties are essentially
insensitive to carrier tuning. We analyze these combined results within the
framework of a Tunneling/Resonant/Rayleigh scatterings model, and conclude that
the evolution from crystalline to glasslike k(T) is accompanied by an increase
both in the effective density of tunnelling states and in the resonant
scattering level, while neither one of these contributions can solely account
for the observed changes in the full temperature range. This suggests that the
most relevant factor which determines crystalline or glasslike behavior is the
coupling strength between the guest vibrational modes and the frameworks with
different charge carriers.Comment: 8 pages, 4 figures, 4 tables, submitted to Phys. Rev.
Glass-Like Heat Conduction in High-Mobility Crystalline Semiconductors
The thermal conductivity of polycrystalline semiconductors with type-I
clathrate hydrate crystal structure is reported. Ge clathrates (doped with Sr
and/or Eu) exhibit lattice thermal conductivities typical of amorphous
materials. Remarkably, this behavior occurs in spite of the well-defined
crystalline structure and relatively high electron mobility (). The dynamics of dopant ions and their interaction with the
polyhedral cages of the structure are a likely source of the strong phonon
scattering.Comment: 4 pages, 3 postscript figures, to be published, Phys. Rev. Let
Addressing legal and policy barriers to male circumcision for adolescent boys in South Africa
With millions of adolescents becoming infected with HIV globally, it is essential that barriers to much-needed interventions are reduced for at-risk adolescents. In this article we review the legal and policy framework in South Africa for adolescent access to male circumcision. We are of the view that the framework does confer protection for adolescent boys while enabling access to male circumcision; however, we identify ambiguities and tensions that exist between the Childrenâs Act, regulations and national guidelines. We recommend reform to further enable access by this vulnerable group to this prevention modality
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