2,288 research outputs found
Spinorial Characterizations of Surfaces into 3-dimensional pseudo-Riemannian Space Forms
We give a spinorial characterization of isometrically immersed surfaces of
arbitrary signature into 3-dimensional pseudo-Riemannian space forms. For
Lorentzian surfaces, this generalizes a recent work of the first author in
to other Lorentzian space forms. We also characterize
immersions of Riemannian surfaces in these spaces. From this we can deduce
analogous results for timelike immersions of Lorentzian surfaces in space forms
of corresponding signature, as well as for spacelike and timelike immersions of
surfaces of signature (0,2), hence achieving a complete spinorial description
for this class of pseudo-Riemannian immersions.Comment: 9 page
Cracklike Dynamics at the Onset of Frictional Sliding
We propose an elasto-plastic inspired friction model which incorporates
interfacial stiffness. Steady state sliding friction is characterized by a
generic nonmonotonic behavior, including both velocity weakening and
strengthening branches. In 1D and upon the application of sideway loading, we
demonstrate the existence of transient cracklike fronts whose velocity is
independent of sound speed, which we propose to be analogous to the recently
discovered slow interfacial rupture fronts. Most importantly, the properties of
these transient inhomogeneously loaded fronts are determined by steady state
front solutions at the {\em minimum} of the sliding friction law, implying the
existence of a new velocity scale and a "forbidden gap" of rupture velocities.
We highlight the role played by interfacial stiffness and supplement our
analysis with 2D scaling arguments.Comment: 4 pages, 2 figure
Noise induced rupture process: Phase boundary and scaling of waiting time distribution
A bundle of fibers has been considered here as a model for composite
materials, where breaking of the fibers occur due to a combined influence of
applied load (stress) and external noise. Through numerical simulation and a
mean-field calculation we show that there exists a robust phase boundary
between continuous (no waiting time) and intermittent fracturing regimes. In
the intermittent regime, throughout the entire rupture process avalanches of
different sizes are produced and there is a waiting time between two
consecutive avalanches. The statistics of waiting times follows a Gamma
distribution and the avalanche distribution shows power law scaling, similar to
what have been observed in case of earthquake events and bursts in fracture
experiments. We propose a prediction scheme that can tell when the system is
expected to reach the continuous fracturing point from the intermittent phase.Comment: 6 pages, 8 figure
Dynamic instabilities of fracture under biaxial strain using a phase field model
We present a phase field model of the propagation of fracture under plane
strain. This model, based on simple physical considerations, is able to
accurately reproduce the different behavior of cracks (the principle of local
symmetry, the Griffith and Irwin criteria, and mode-I branching). In addition,
we test our model against recent experimental findings showing the presence of
oscillating cracks under bi-axial load. Our model again reproduces well
observed supercritical Hopf bifurcation, and is therefore the first simulation
which does so
Predicting the long-term impact of antiretroviral therapy scale-up on population incidence of tuberculosis.
OBJECTIVE: To investigate the impact of antiretroviral therapy (ART) on long-term population-level tuberculosis disease (TB) incidence in sub-Saharan Africa. METHODS: We used a mathematical model to consider the effect of different assumptions about life expectancy and TB risk during long-term ART under alternative scenarios for trends in population HIV incidence and ART coverage. RESULTS: All the scenarios we explored predicted that the widespread introduction of ART would initially reduce population-level TB incidence. However, many modelled scenarios projected a rebound in population-level TB incidence after around 20 years. This rebound was predicted to exceed the TB incidence present before ART scale-up if decreases in HIV incidence during the same period were not sufficiently rapid or if the protective effect of ART on TB was not sustained. Nevertheless, most scenarios predicted a reduction in the cumulative TB incidence when accompanied by a relative decline in HIV incidence of more than 10% each year. CONCLUSIONS: Despite short-term benefits of ART scale-up on population TB incidence in sub-Saharan Africa, longer-term projections raise the possibility of a rebound in TB incidence. This highlights the importance of sustaining good adherence and immunologic response to ART and, crucially, the need for effective HIV preventive interventions, including early widespread implementation of ART
Raped, beaten and bruised: military institutional abuse, identity wounds and veteran suicide
The Australian government has recently established a Royal Commission on Defence and Veteran Suicide (DVSRC). Veteran suicide rates for those who have left the Australian Defence Force (ADF) are higher than the national average and there has been little success in reducing this over an extended period of time. Veteran suicide is poorly understood, and the collected data is imprecise and incomplete. Deployment trauma and Post-traumatic stress disorder (PTSD i.e. a mental health lens) are taken for granted as the principal causes. This article presents a case study on institutional abuse in the ADF which led to the veteran attempting suicide on numerous occasions. The article draws upon the mental health and moral injury knowledge but questions their centrality and dominance. Military Institutional Abuse (MIA) and its consequent identity wounds are explained as institutional causes of military trauma. We argue that these institutional abuse processes and their consequences, occurring within military moral geographies, lead to suicidal ideation and attempt. These are situated within wider relations of civil society, the state, and the military
Failure time and microcrack nucleation
The failure time of samples of heterogeneous materials (wood, fiberglass) is
studied as a function of the applied stress. It is shown that in these
materials the failure time is predicted with a good accuracy by a model of
microcrack nucleation proposed by Pomeau. It is also shown that the crack
growth process presents critical features when the failure time is approached.Comment: 13 pages, 4 figures, submitted to Europhysics Letter
How do liquids confined at the nanoscale influence adhesion?
Liquids play an important role in adhesion and sliding friction. They behave
as lubricants in human bodies especially in the joints. However, in many
biological attachment systems they acts like adhesives, e.g. facilitating
insects to move on ceilings or vertical walls. Here we use molecular dynamics
to study how liquids confined at the nanoscale influence the adhesion between
solid bodies with smooth and rough surfaces. We show that a monolayer of liquid
may strongly affect the adhesion.Comment: 5 pages, 9 color figures. Some figures are in Postscript Level 3
format. Minimal changes with respect to the previous version. Added doi and
reference to the published article also inside the pape
Towards equity and sustainability of rural and remote health services access: supporting social capital and integrated organisational and professional development
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Background: Access to rural health services is compromised in many countries including Australia due to workforce
shortages. The issues that consequently impact on equity of access and sustainability of rural and remote health
services are complex.
Discussion: The purpose of this paper is to describe a number of approaches from the literature that could form the
basis of a more integrated approach to health workforce and rural health service enhancement that can be supported
by policy. A case study is used to demonstrate how such an approach could work.
Summary: Disjointed health services are common in rural areas due to the ‘tyranny of distance.’ Recruitment and
retention of health professionals in rural areas and access to and sustainability of rural health services is therefore
compromised. Strategies to address these issues tend to have a narrow focus. An integrated approach is needed to
enhance rural workforce and health services; one that develops, acknowledges and accounts for social capital
and social relations within the rural community.
Keywords: Rural workforce, Recruitment and retention, Professional development, Organisational development,
Community engagement, Social capital, Rural health service access, Policy development, Chronic conditions,
Complex car
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