14,957 research outputs found
An efficient flamelet progress-variable method for modeling non-premixed flames in weak electric fields
Combustion stabilization and enhancement of the flammability limits are
mandatory objectives to improve nowadays combustion chambers. At this purpose,
the use of an electric field in the flame region provides a solution which is,
at the same time, easy to implement and effective to modify the flame
structure. The present work describes an efficient flamelet progress-variable
approach developed to model the fluid dynamics of flames immersed in an
electric field. The main feature of this model is that it can use complex
ionization mechanisms without increasing the computational cost of the
simulation. The model is based on the assumption that the combustion process is
not directly influenced by the electric field and has been tested using two
chemi-ionization mechanisms of different complexity in order to examine its
behavior with and without the presence of heavy anions in the mixture. Using a
one- and two-dimensional numerical test cases, the present approach has been
able to reproduce all the major aspects encountered when a flame is subject to
an imposed electric field and the main effects of the different chemical
mechanisms. Moreover, the proposed model is shown to produce a large reduction
in the computational cost, being able to shorten the time needed to perform a
simulation up to 40 times.Comment: 26 pages, 13 figures, paper accepted for publication on Computers and
Fluid
Entanglement control in hybrid optomechanical systems
We demonstrate the control of entanglement in a hybrid optomechanical system
comprising an optical cavity with a mechanical end-mirror and an intracavity
Bose-Einstein condensate (BEC). Pulsed laser light (tuned within realistic
experimental conditions) is shown to induce an almost sixfold increase of the
atom-mirror entanglement and to be responsible for interesting dynamics between
such mesoscopic systems. In order to assess the advantages offered by the
proposed control technique, we compare the time-dependent dynamics of the
system under constant pumping with the evolution due to the modulated laser
light.Comment: Published versio
Entanglement production by quantum error correction in the presence of correlated environment
We analyze the effect of a quantum error correcting code on the entanglement
of encoded logical qubits in the presence of a dephasing interaction with a
correlated environment. Such correlated reservoir introduces entanglement
between physical qubits. We show that for short times the quantum error
correction interprets such entanglement as errors and suppresses it. However
for longer time, although quantum error correction is no longer able to correct
errors, it enhances the rate of entanglement production due to the interaction
with the environment.Comment: 7 pages, 3 figures, published versio
Normal form decomposition for Gaussian-to-Gaussian superoperators
In this paper we explore the set of linear maps sending the set of quantum
Gaussian states into itself. These maps are in general not positive, a feature
which can be exploited as a test to check whether a given quantum state belongs
to the convex hull of Gaussian states (if one of the considered maps sends it
into a non positive operator, the above state is certified not to belong to the
set). Generalizing a result known to be valid under the assumption of complete
positivity, we provide a characterization of these Gaussian-to-Gaussian (not
necessarily positive) superoperators in terms of their action on the
characteristic function of the inputs. For the special case of one-mode
mappings we also show that any Gaussian-to-Gaussian superoperator can be
expressed as a concatenation of a phase-space dilatation, followed by the
action of a completely positive Gaussian channel, possibly composed with a
transposition. While a similar decomposition is shown to fail in the multi-mode
scenario, we prove that it still holds at least under the further hypothesis of
homogeneous action on the covariance matrix
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Nutritional Education and Promotion in Central America Through Dietary Guidelines Development
Malnutrition has been one of the major health problems which affects two of every ten children, under five years old, in Central American countries. During recent years, in addition to malnutrition problems, almost all Central American countries have reported an increase in the incidence of chronic illness such as diabetes, cardio-vascular diseases and some cancers. This tendency has been associated with the increase of overweight and obesity among the adult population, especially among women. Both poor nutrition and over nutrition constitute high priority health problems, which need to be addressed through comprehensive health promotion programs that includes a strong component of nutrition educaiton.
The strategies and actions to promote appropriate diets and healthy lifestyles, that emanated from the last International Conference on Nutrition (FAO 1992), includes:
- nutrition education and dietary guidance for the general public
- training of professionals in health care, agriculture extension and related services
- development of food-services guidelines
- involvement of consumer groups and the food industry
- ensuring food quality and safety
- monitoring and evaluating national food and nutrition situations
- encouraging the availability of the variety of foods needed to meet consumer demand
To accomplish these recommendations many sectors need to take an active role in the promotion of healthy habits. The public sector, including health professionals can work to educate the general public about diet and health. The food industry plays an essential role by responding to consumer demand to produce and market the variety of foods needed for a healthy diet. Both the formal and non-formal education system must play a central role, incorporating nutrition into education in general, and within the context of local culture. In addition to school systems, the health and agriculture sector, public information channels, unions, youth groups and community leaders should take an active role in education and promotion of nutrition healthy lifestyles (FAO 1992).
I believe that the first step, to carry out such a comprehensive nutrition promotion strategy should be the development of dietary guidelines, as the basis of information that every sector should use as they develop their own educational programs, directed to different populations, applying different educational strategies.
The purpose of this document is to present a model of dietary guidelines and graphic design to promote health and nutrition in Central American Countries, as well as a proposal to implement these dietary guidelines. To develop the model of dietary guidelines, experiences from different countries, such as the United States, Mexico and Venezuela were reviewed and adapted. Graphic designs from fourteen countries were reviewed.
The content of this document is presented in four sections: the first one presents a bibliographic review of dietary guidelines development in the United States and Latin American countries. The second demonstrates the adaptation and application of these concepts to the development of the Guatemalan dietary guidelines and graphic design. The third section introduces a bibliographic review of the recommendations to implement dietary guidelines in the United States, as well as my suggestion to develop and implement dietary guidelines in Central American countries. In the last section I present some ideas about the application of non-formal education strategies, to adapt the dietary guidelines at community level.
This document will be translated into Spanish, and will be reviewed by a team of nutritionists, communicators and educators from the Institute of Nutrition of Central America and Panama. After that, this document will be disseminated to other Latin American countries and could be used as the basis to develop dietary guidelines in Latin American countries
Analysis of the SET/FTY720 Complex by NMR Reveals a Unique Mechanism for the Activation of PP2A
Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase with tumor suppressor function. PP2A holoenzyme contains numerous combinations of its various isoforms of scaffolding (A), regulatory (B), and catalytic (C) subunits. In many cancer types, an endogenous PP2A inhibitor, inhibitor 2 of PP2A (SET) oncoprotein, is overexpressed, resulting in PP2A inhibition, leading to enhanced cell growth, and attenuation of cell death. It is known that targeting SET with bioactive sphingolipid ceramide or sphingolipid analogue drug FTY720 leads to the reactivation of PP2A, leading to necroptosis. However, structural details of the interaction between SET and FTY720 (or ceramide) with regards to mechanism of the PP2A activation have been unknown. Here, we report the first in solution examination of SET-sphingolipid complex by NMR spectroscopy. Data revealed that FTY720 binding may result in a structural shift in the N-terminal region of SET, which prevents its oligomerization. This then leads to the release of SET from the catalytic subunit of a specific PP2A holoenzyme, which comprises PP2AAβ, PP2A-B56γ, and PP2ACα subunits, for increased PP2A activity, while SET remains associated with the PP2A-B56γ. The activation of this specific PP2A holoenzyme by SET-FTY720 complex then regulates a number of downstream effector proteins involved in various biological functions, such as tumor suppressor non-muscle myosin IIA. Attenuation of FTY720-SET association by point mutations enhances SET- PP2A inhibitory complex, leading to resistance to PP2A activation, which is recapitulated by R71A and E111A SET mutations
Influence of electromagnetic interferences on the gravimetric sensitivity of surface acoustic waveguides
Surface acoustic waveguides are increasing in interest for (bio)chemical
detection. The surface mass modification leads to measurable changes in the
propagation properties of the waveguide. Among a wide variety of waveguides,
Love mode has been investigated because of its high gravimetric sensitivity.
The acoustic signal launched and detected in the waveguide by electrical
transducers is accompanied by an electromagnetic wave; the interaction of the
two signals, easily enhanced by the open structure of the sensor, creates
interference patterns in the transfer function of the sensor. The influence of
these interferences on the gravimetric sensitivity is presented, whereby the
structure of the entire sensor is modelled. We show that electromagnetic
interferences generate an error in the experimental value of the sensitivity.
This error is different for the open and the closed loop configurations of the
sensor. The theoretical approach is completed by the experimentation of an
actual Love mode sensor operated under liquid in open loop configuration. The
experiment indicates that the interaction depends on the frequency and the mass
modifications.Comment: 28 pages, 8 figure
Cavity-aided quantum parameter estimation in a bosonic double-well Josephson junction
We describe an apparatus designed to make non-demolition measurements on a
Bose-Einstein condensate (BEC) trapped in a double-well optical cavity. This
apparatus contains, as well as the bosonic gas and the trap, an optical cavity.
We show how the interaction between the light and the atoms, under appropriate
conditions, can allow for a weakly disturbing yet highly precise measurement of
the population imbalance between the two wells and its variance. We show that
the setting is well suited for the implementation of quantum-limited estimation
strategies for the inference of the key parameters defining the evolution of
the atomic system and based on measurements performed on the cavity field. This
would enable {\it de facto} Hamiltonian diagnosis via a highly controllable
quantum probe.Comment: 8 pages, 5 figures, RevTeX4; Accepted for publication in Phys. Rev.
The First Fermi-LAT SNR Catalog SNR and Cosmic Ray Implications
Galactic cosmic ray (CRs) sources, classically proposed to be Supernova
Remnants (SNRs), must meet the energetic particle content required by direct
measurements of high energy CRs. Indirect gamma-ray measurements of SNRs with
the Fermi Large Area Telescope (LAT) have now shown directly that at least
three SNRs accelerate protons. With the first Fermi LAT SNR Catalog, we have
systematically characterized the GeV gamma-rays emitted by 279 SNRs known
primarily from radio surveys. We present these sources in a multiwavelength
context, including studies of correlations between GeV and radio size, flux,
and index, TeV index, and age and environment tracers, in order to better
understand effects of evolution and environment on the GeV emission. We show
that previously sufficient models of SNRs' GeV emission no longer adequately
describe the data. To address the question of CR origins, we also examine the
SNRs' maximal CR contribution assuming the GeV emission arises solely from
proton interactions. Improved breadth and quality of multiwavelength data,
including distances and local densities, and more, higher resolution gamma-ray
data with correspondingly improved Galactic diffuse models will strengthen this
constraint.Comment: 8 pages, 10 figures; in Proceedings of the 34th International Cosmic
Ray Conference (ICRC 2015), The Hague (The Netherlands
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