14,848 research outputs found
Spatial accessibility and social inclusion: The impact of Portugal's last health reform
Health policies seek to promote access to health care and should provide appropriate geographical accessibility to each demographical functional group. The dispersal demand of health‐careservices and the provision for such services atfixed locations contribute to the growth of inequality intheir access. Therefore, the optimal distribution of health facilities over the space/area can lead toaccessibility improvements and to the mitigation of the social exclusion of the groups considered mostvulnerable. Requiring for such, the use of planning practices joined with accessibility measures. However,the capacities of Geographic Information Systems in determining and evaluating spatial accessibility inhealth system planning have not yet been fully exploited. This paper focuses on health‐care services planningbased on accessibility measures grounded on the network analysis. The case study hinges on mainlandPortugal. Different scenarios were developed to measure and compare impact on the population'saccessibility. It distinguishes itself from other studies of accessibility measures by integrating network data ina spatial accessibility measure: the enhanced two‐stepfloating catchment area. The convenient location forhealth‐care facilities can increase the accessibility standards of the population and consequently reducethe economic and social costs incurred. Recently, the Portuguese government implemented a reform thataimed to improve, namely, the access and equity in meeting with the most urgent patients. It envisaged,in terms of equity, the allocation of 89 emergency network points that ensured more than 90% of thepopulation be within 30 min from any one point in the network. Consequently, several emergency serviceswere closed, namely, in rural areas. This reform highlighted the need to improve the quality of the emergencycare, accessibility to each care facility, and equity in their access. Hence, accessibility measures becomean efficient decision‐making tool, despite its absence in effective practice planning. According to anapplication of this type of measure, it was possible to verify which levels of accessibility were decreased,including the most disadvantaged people, with a larger time of dislocation of 12 min between 2001 and 2011
Optical Properties of Strained Graphene
The optical conductivity of graphene strained uniaxially is studied within
the Kubo-Greenwood formalism. Focusing on inter-band absorption, we analyze and
quantify the breakdown of universal transparency in the visible region of the
spectrum, and analytically characterize the transparency as a function of
strain and polarization. Measuring transmittance as a function of incident
polarization directly reflects the magnitude and direction of strain. Moreover,
direction-dependent selection rules permit identification of the lattice
orientation by monitoring the van-Hove transitions. These photoelastic effects
in graphene can be explored towards atomically thin, broadband optical
elements
A conjugate for the Bargmann representation
In the Bargmann representation of quantum mechanics, physical states are
mapped into entire functions of a complex variable z*, whereas the creation and
annihilation operators and play the role of
multiplication and differentiation with respect to z*, respectively. In this
paper we propose an alternative representation of quantum states, conjugate to
the Bargmann representation, where the roles of and
are reversed, much like the roles of the position and momentum operators in
their respective representations. We derive expressions for the inner product
that maintain the usual notion of distance between states in the Hilbert space.
Applications to simple systems and to the calculation of semiclassical
propagators are presented.Comment: 15 page
Irreversible magnetization under rotating fields and lock-in effect on ErBa_2Cu_3O_7 single crystal with columnar defects
We have measured the irreversible magnetization M_i of an ErBa_2Cu_3O_7
single crystal with columnar defects (CD), using a technique based on sample
rotation under a fixed magnetic field H. This method is valid for samples whose
magnetization vector remains perpendicular to the sample surface over a wide
angle range - which is the case for platelets and thin films - and presents
several advantages over measurements of M_L(H) loops at fixed angles. The
resulting M_i(\Theta) curves for several temperatures show a peak in the CD
direction at high fields. At lower fields, a very well defined plateau
indicative of the vortex lock-in to the CD develops. The H dependence of the
lock-in angle \phi_L follows the H^{-1} theoretical prediction, while the
temperature dependence is in agreement with entropic smearing effects
corresponding to short range vortex-defects interactions.Comment: 7 pages, 6 figures, to be published in Phys. Rev.
Aharonov-Bohm signature for neutral excitons in type-II quantum dot ensembles
It is commonly believed that the Aharonov-Bohm (AB) effect is a typical
feature of the motion of a charged particle interacting with the
electromagnetic vector potential. Here we present a magnetophotoluminescence
study of type-II InP/GaAs self-assembled quantum dots, unambiguously revealing
the Aharonov-Bohm-type oscillations for neutral excitons when the hole ground
state changes its angular momentum from lh = 0 to lh = 1, 2, and 3. The hole
ring parameters derived from a simple model are in excellent agreement with the
structural parameters for this system.Comment: Revised version, 10 pages, 3 figure
Vacuum fluctuations of a scalar field near a reflecting boundary and their effects on the motion of a test particle
The contribution from quantum vacuum fluctuations of a real massless scalar
field to the motion of a test particle that interacts with the field in the
presence of a perfectly reflecting flat boundary is here investigated. There is
no quantum induced dispersions on the motion of the particle when it is alone
in the empty space. However, when a reflecting wall is introduced, dispersions
occur with magnitude dependent on how fast the system evolves between the two
scenarios. A possible way of implementing this process would be by means of an
idealized sudden switching, for which the transition occurs instantaneously.
Although the sudden process is a simple and mathematically convenient
idealization it brings some divergences to the results, particularly at a time
corresponding to a round trip of a light signal between the particle and the
wall. It is shown that the use of smooth switching functions, besides
regularizing such divergences, enables us to better understand the behavior of
the quantum dispersions induced on the motion of the particle. Furthermore, the
action of modifying the vacuum state of the system leads to a change in the
particle energy that depends on how fast the transition between these states is
implemented. Possible implications of these results to the similar case of an
electric charge near a perfectly conducting wall are discussed.Comment: 17 pages, 8 figure
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