2,137 research outputs found
Quantitative Relativistic Effects in the Three-Nucleon Problem
The quantitative impact of the requirement of relativistic invariance in the
three-nucleon problem is examined within the framework of Poincar\'e invariant
quantum mechanics. In the case of the bound state, and for a wide variety of
model implementations and reasonable interactions, most of the quantitative
effects come from kinematic factors that can easily be incorporated within a
non-relativistic momentum-space three-body code.Comment: 15 pages, 15 figure
Relativity and the low energy nd Ay puzzle
We solve the Faddeev equation in an exactly Poincare invariant formulation of
the three-nucleon problem. The dynamical input is a relativistic
nucleon-nucleon interaction that is exactly on-shell equivalent to the high
precision CDBonn NN interaction. S-matrix cluster properties dictate how the
two-body dynamics is embedded in the three-nucleon mass operator. We find that
for neutron laboratory energies above 20 MeV relativistic effects on Ay are
negligible. For energies below 20 MeV dynamical effects lower the nucleon
analyzing power maximum slightly by 2% and Wigner rotations lower it further up
to 10 % increasing thus disagreement between data and theory. This indicates
that three-nucleon forces must provide an even larger increase of the Ay
maximum than expected up to now.Comment: 29 pages, 2 ps figure
Village Baseline Study: Site Analysis Report for Kaffrine â Kaffrine, Senegal
The village baseline study of Toune MosquĂ©e village in the CCAFS benchmark site Kaffrine in Senegal took place from June 2 to 4, 2011. Natural resources in the village are in a progressive state of degradation. The âprotectedâ forest has almost disappeared, the soils have low fertility and are degraded, and crop production is not sufficient to meet the food needs of a family throughout the year. Families must buy food to fill the gap in production. For that they harvest and sell forest products, which creates a vicious cycle of resource degradation.
The male and female groups identified 35 organisations operating in the village including informal groups, state services, associations, NGOs and Muslim brotherhoods. While 18 of those work on food security issues, only 4 are involved in the management and protection of natural resources. Very few agricultural extension and training opportunities target women despite the womenâs significant role in agriculture and livestock production.
Women obtain information on livestock feeding techniques from people and organisations such as the horticultural project, womenâs associations, and water and forest services. Men get information on soil inputs and soil fertility management from other farmers, organisations, radio and television, and from community leaders, notably the office of the village chief and the mosque on Fridays. The radio is the form of media most commonly used by the women but few women own a radio
Electromagnetically induced transparency and dynamic Stark effect in coupled quantum resonators
In this work we reproduce the phenomenology of the electromagnetically
induced transparency and dynamic Stark effect in a dissipative system composed
by two coupled bosonic fields under linear and nonlinear amplification process.
Such a system can be used as a quantum switch in networks of oscillators
First Order Relativistic Three-Body Scattering
Relativistic Faddeev equations for three-body scattering at arbitrary
energies are formulated in momentum space and in first order in the two-body
transition-operator directly solved in terms of momentum vectors without
employing a partial wave decomposition. Relativistic invariance is incorporated
within the framework of Poincare invariant quantum mechanics, and presented in
some detail.
Based on a Malfliet-Tjon type interaction, observables for elastic and
break-up scattering are calculated up to projectile energies of 1 GeV. The
influence of kinematic and dynamic relativistic effects on those observables is
systematically studied. Approximations to the two-body interaction embedded in
the three-particle space are compared to the exact treatment.Comment: 26 pages, 13 figure
Dynamical Casimir effect for a massless scalar field between two concentric spherical shells
In this work we consider the dynamical Casimir effect for a massless scalar
field -- under Dirichlet boundary conditions -- between two concentric
spherical shells. We obtain a general expression for the average number of
particle creation, for an arbitrary law of radial motion of the spherical
shells, using two distinct methods: by computing the density operator of the
system and by calculating the Bogoliubov coefficients. We apply our general
expression to breathing modes: when only one of the shells oscillates and when
both shells oscillate in or out of phase. We also analyze the number of
particle production and compare it with the results for the case of plane
geometry.Comment: Final version. To apear in Physical Review
Organisational structures and processes for health and well-being: insights from work integration social enterprise
Background: Previous research on employee well-being for those who have experienced social and economic disadvantage and those with previous or existing mental health conditions has focused mainly on programmatic interventions. The purpose of this research was to examine how organisational structures and processes (such as policies and culture) influence well-being of employees from these types of backgrounds. Methods: A case study ethnographic approach which included in-depth qualitative analysis of 93 semi-structured interviews of employees, staff, and managers, together with participant observation of four social enterprises employing young people. Results: The data revealed that young people were provided a combination of training, varied work tasks, psychosocial support, and encouragement to cultivate relationships among peers and management staff. This was enabled through the following elements: structure and space; funding, finance and industry orientation; organisational culture; policy and process; and fostering local service networks. The findings further illustrate how organisational structures at these workplaces promoted an inclusive workplace environment in which participants self-reported a decrease in anxiety and depression, increased self-esteem, increased self-confidence and increased physical activity. Conclusions: Replicating these types of organisational structures, processes, and culture requires consideration of complex systems perspectives on implementation fidelity which has implications for policy, practice and future research
Action of the gravitational field on the dynamical Casimir effect
In this paper we analyze the action of the gravitational field on the
dynamical Casimir effect. We consider a massless scalar field confined in a
cuboid cavity placed in a gravitational field described by a static and
diagonal metric. With one of the plane mirrors of the cavity allowed to move,
we compute the average number of particles created inside the cavity by means
of the Bogoliubov coefficients computed through perturbative expansions. We
apply our result to the case of an oscillatory motion of the mirror, assuming a
weak gravitational field described by the Schwarzschild metric. The regime of
parametric amplification is analyzed in detail, demonstrating that our computed
result for the mean number of particles created agrees with specific associated
cases in the literature. Our results, obtained in the framework of the
perturbation theory, are restricted, under resonant conditions, to a short-time
limit.Comment: 2 Figures, comments are welcom
Non-Hermitian Swanson model with a time-dependent metric
We provide further non-trivial solutions to the recently proposed time-dependent Dyson and quasi-Hermiticity relation. Here we solve them for the generalized version of the non-Hermitian Swanson Hamiltonian with time-dependent coefficients. We construct time-dependent solutions by employing the Lewis-Riesenfeld method of invariants and discuss concrete physical applications of our results
The hibernating South American marsupial, Dromiciops gliroides, displays torpor-sensitive microRNA expression patterns
When faced with adverse environmental conditions, the marsupial Dromiciops gliroides uses either daily or seasonal torpor to support survival and is the only known hibernating mammal in South America. As the sole living representative of the ancient Order Microbiotheria, this species can provide crucial information about the evolutionary origins and biochemical mechanisms of hibernation. Hibernation is a complex energy-saving strategy that involves changes in gene expression that are elicited in part by microRNAs. To better elucidate the role of microRNAs in orchestrating hypometabolism, a modified stem-loop technique and quantitative PCR were used to characterize the relative expression levels of 85 microRNAs in liver and skeletal muscle of control and torpid D. gliroides. Thirty-nine microRNAs were differentially regulated during torpor; of these, 35 were downregulated in liver and 11 were differentially expressed in skeletal muscle. Bioinformatic analysis predicted that the downregulated liver microRNAs were associated with activation of MAPK, PI3K-Akt and mTOR pathways, suggesting their importance in facilitating marsupial torpor. In skeletal muscle, hibernation-responsive microRNAs were predicted to regulate focal adhesion, ErbB, and mTOR pathways, indicating a promotion of muscle maintenance mechanisms. These tissue-specific responses suggest that microRNAs regulate key molecular pathways that facilitate hibernation, thermoregulation, and prevention of muscle disuse atrophy.Link_to_subscribed_fulltex
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