208 research outputs found
Early and late follow-up of untreated traumatic aortic lesion: a support to delayed surgery
Fuente Fuente, Carlos;Montes Gil, Antonio;Periel Piquer, Montserra
Can the deployment of community health workers for the delivery of HIV services represent an effective and sustainable response to health workforce shortages? Results of a multicountry study
In countries severely affected by HIV/AIDS, shortages of health workers present a major obstacle to scaling up HIV services. Adopting a task shifting approach for the deployment of community health workers (CHWs) represents one strategy for rapid expansion of the health workforce. This study aimed to evaluate the contribution of CHWs with a focus on identifying the critical elements of an enabling environment that can ensure they provide quality services in a manner that is sustainable. The method of work included a collection of primary data in five countries: Brazil, Ethiopia, Malawi, Namibia, and Uganda. The findings show that delegation of specific tasks to cadres of CHWs with limited training can increase access to HIV services, particularly in rural areas and among underserved communities, and can improve the quality of care for HIV. There is also evidence that CHWs can make a significant contribution to the delivery of a wide range of other health services. The findings also show that certain conditions must be observed if CHWs are to contribute to well-functioning and sustainable service delivery. These conditions involve adequate systems integration with significant attention to: political will and commitment; collaborative planning; definition of scope of practice; selection and educational requirements; registration, licensure and certification; recruitment and deployment; adequate and sustainable remuneration; mentoring and supervision including referral system; career path and continuous education; performance evaluation; supply of equipment and commodities. The study concludes that, where there is the necessary support, the potential contribution of CHWs can be optimized and represents a valuable addition to the urgent expansion of human resources for health, and to universal coverage of HIV services
Finding the complement of the invariant manifolds transverse to a given foliation for a 3D flow
A method is presented to establish regions of phase space for 3D vector fields through which pass no co-oriented invariant 2D submanifolds transverse to a given oriented 1D foliation. Refinements are given for the cases of volume-preserving or Cartan-Arnol’d Hamiltonian flows and for boundaryless submanifolds
An approximate renormalization-group transformation for Hamiltonian systems with three degrees of freedom
We construct an approximate renormalization transformation that combines
Kolmogorov-Arnold-Moser (KAM)and renormalization-group techniques, to analyze
instabilities in Hamiltonian systems with three degrees of freedom. This scheme
is implemented both for isoenergetically nondegenerate and for degenerate
Hamiltonians. For the spiral mean frequency vector, we find numerically that
the iterations of the transformation on nondegenerate Hamiltonians tend to
degenerate ones on the critical surface. As a consequence, isoenergetically
degenerate and nondegenerate Hamiltonians belong to the same universality
class, and thus the corresponding critical invariant tori have the same type of
scaling properties. We numerically investigate the structure of the attracting
set on the critical surface and find that it is a strange nonchaotic attractor.
We compute exponents that characterize its universality class.Comment: 10 pages typeset using REVTeX, 7 PS figure
Nonlinear time-series analysis of Hyperion's lightcurves
Hyperion is a satellite of Saturn that was predicted to remain in a chaotic
rotational state. This was confirmed to some extent by Voyager 2 and Cassini
series of images and some ground-based photometric observations. The aim of
this aticle is to explore conditions for potential observations to meet in
order to estimate a maximal Lyapunov Exponent (mLE), which being positive is an
indicator of chaos and allows to characterise it quantitatively. Lightcurves
existing in literature as well as numerical simulations are examined using
standard tools of theory of chaos. It is found that existing datasets are too
short and undersampled to detect a positive mLE, although its presence is not
rejected. Analysis of simulated lightcurves leads to an assertion that
observations from one site should be performed over a year-long period to
detect a positive mLE, if present, in a reliable way. Another approach would be
to use 2---3 telescopes spread over the world to have observations distributed
more uniformly. This may be achieved without disrupting other observational
projects being conducted. The necessity of time-series to be stationary is
highly stressed.Comment: 34 pages, 12 figures, 4 tables; v2 after referee report; matches the
version accepted in Astrophysics and Space Scienc
Regularization of the circular restricted three-body problem using 'similar' coordinate systems
The regularization of a new problem, namely the three-body problem, using
'similar' coordinate system is proposed. For this purpose we use the relation
of 'similarity', which has been introduced as an equivalence relation in a
previous paper (see \cite{rom11}). First we write the Hamiltonian function, the
equations of motion in canonical form, and then using a generating function, we
obtain the transformed equations of motion. After the coordinates
transformations, we introduce the fictitious time, to regularize the equations
of motion. Explicit formulas are given for the regularization in the coordinate
systems centered in the more massive and the less massive star of the binary
system. The 'similar' polar angle's definition is introduced, in order to
analyze the regularization's geometrical transformation. The effect of
Levi-Civita's transformation is described in a geometrical manner. Using the
resulted regularized equations, we analyze and compare these canonical
equations numerically, for the Earth-Moon binary system.Comment: 24 pages, 7 figures; Accepted for publication in Astrophysics and
Space Scienc
Physics of the Riemann Hypothesis
Physicists become acquainted with special functions early in their studies.
Consider our perennial model, the harmonic oscillator, for which we need
Hermite functions, or the Laguerre functions in quantum mechanics. Here we
choose a particular number theoretical function, the Riemann zeta function and
examine its influence in the realm of physics and also how physics may be
suggestive for the resolution of one of mathematics' most famous unconfirmed
conjectures, the Riemann Hypothesis. Does physics hold an essential key to the
solution for this more than hundred-year-old problem? In this work we examine
numerous models from different branches of physics, from classical mechanics to
statistical physics, where this function plays an integral role. We also see
how this function is related to quantum chaos and how its pole-structure
encodes when particles can undergo Bose-Einstein condensation at low
temperature. Throughout these examinations we highlight how physics can perhaps
shed light on the Riemann Hypothesis. Naturally, our aim could not be to be
comprehensive, rather we focus on the major models and aim to give an informed
starting point for the interested Reader.Comment: 27 pages, 9 figure
To what extent could performance-based schemes help increase the effectiveness of prevention of mother-to-child transmission of HIV (PMTCT) programs in resource-limited settings? a summary of the published evidence
<p>Abstract</p> <p>Background</p> <p>In resource-limited settings, HIV/AIDS remains a serious threat to the social and physical well-being of women of childbearing age, pregnant women, mothers and infants.</p> <p>Discussion</p> <p>In sub-Saharan African countries with high prevalence rates, pediatric HIV/AIDS acquired through mother-to-child transmission (MTCT) can in largely be prevented by using well-established biomedical interventions. Logistical and socio-cultural barriers continue, however, to undermine the successful prevention of MTCT (PMTCT). In this paper, we review reports on maternal, neonatal and child health, as well as HIV care and treatment services that look at program incentives.</p> <p>Summary</p> <p>These studies suggest that comprehensive PMTCT strategies aiming to maximize health-worker motivation in developing countries must involve a mix of both financial and non-financial incentives. The establishment of robust ethical and regulatory standards in public-sector HIV care centers could reduce barriers to PMTCT service provision in sub-Saharan Africa and help them in achieving universal PMTCT targets.</p
- …