635 research outputs found
Ramos do Cooperativismo: cenário da região centro oeste do Brasil.
O cooperativismo é um modelo econômico com características próprias, baseado em princípios definidos pela Aliança Cooperativa Internacional - ACI. Está presente no Brasil desde o final do século XIX, contemplando hoje seus diferentes ramos, e em todos os Estados brasileiros e Distrito Federal. Na região centro oeste do país, temos hoje 575 cooperativas ativas, sendo 178 do ramo agropecuário, em Mato Grosso do Sul das 71 cooperativas, 26 são deste ramo. O desenvolvimento de forma sustentável é um desafio para as instituições e governos, assim, devido a sua natureza, o cooperativismo pode ser uma alternativa de promover o crescimento da economia, o desenvolvimento local de maneira sustentável? O que percebemos é que o crescente número de negócios de natureza cooperativa que vêm se firmando no país pode ser um sinal de que o caminho para alcançar tal desenvolvimento foi encontrado, uma vez que a maior parte das cooperativas do país já existem a mais de 20 anos, algumas mais de 40 demonstrando a solidez e sustentabilidade do negócio. Também evidenciando que ainda há espaço para crescimento.Anais do VI EIGEDIN
Breakdown of superfluidity of an atom laser past an obstacle
The 1D flow of a continuous beam of Bose-Einstein condensed atoms in the
presence of an obstacle is studied as a function of the beam velocity and of
the type of perturbing potential (representing the interaction of the obstacle
with the atoms of the beam). We identify the relevant regimes:
stationary/time-dependent and superfluid/dissipative; the absence of drag is
used as a criterion for superfluidity. There exists a critical velocity below
which the flow is superfluid. For attractive obstacles, we show that this
critical velocity can reach the value predicted by Landau's approach. For
penetrable obstacles, it is shown that superfluidity is recovered at large beam
velocity. Finally, enormous differences in drag occur when switching from
repulsive to attractive potential.Comment: 15 pages, 6 figure
The Lieb-Liniger Model as a Limit of Dilute Bosons in Three Dimensions
We show that the Lieb-Liniger model for one-dimensional bosons with repulsive
-function interaction can be rigorously derived via a scaling limit
from a dilute three-dimensional Bose gas with arbitrary repulsive interaction
potential of finite scattering length. For this purpose, we prove bounds on
both the eigenvalues and corresponding eigenfunctions of three-dimensional
bosons in strongly elongated traps and relate them to the corresponding
quantities in the Lieb-Liniger model. In particular, if both the scattering
length and the radius of the cylindrical trap go to zero, the
Lieb-Liniger model with coupling constant is derived. Our bounds
are uniform in in the whole parameter range , and apply
to the Hamiltonian for three-dimensional bosons in a spectral window of size
above the ground state energy.Comment: LaTeX2e, 19 page
Homeless drug users' awareness and risk perception of peer "Take Home Naloxone" use – a qualitative study
BACKGROUND
Peer use of take home naloxone has the potential to reduce drug related deaths. There appears to be a paucity of research amongst homeless drug users on the topic. This study explores the acceptability and potential risk of peer use of naloxone amongst homeless drug users. From the findings the most feasible model for future treatment provision is suggested.
METHODS
In depth face-to-face interviews conducted in one primary care centre and two voluntary organisation centres providing services to homeless drug users in a large UK cosmopolitan city. Interviews recorded, transcribed and analysed thematically by framework techniques.
RESULTS
Homeless people recognise signs of a heroin overdose and many are prepared to take responsibility to give naloxone, providing prior training and support is provided. Previous reports of the theoretical potential for abuse and malicious use may have been overplayed.
CONCLUSION
There is insufficient evidence to recommend providing "over the counter" take home naloxone" to UK homeless injecting drug users. However a programme of peer use of take home naloxone amongst homeless drug users could be feasible providing prior training is provided. Peer education within a health promotion framework will optimise success as current professionally led health promotion initiatives are failing to have a positive impact amongst homeless drug users
Agricultura e inovação: estudo sobre a viabilidade de uso do 'pó de rocha' em sistemas de produção agrícola.
O uso dos chamados remineralizadores de solo, "pó de rocha" (rochagem / ?rocks-for-crops?), é uma técnica que vem se expandindo com o passar dos anos. O trabalho visa observar o comportamento das culturas anuais de soja e milho durante três safras consecutivas, utilizando pó de rocha (remineralizador), como fonte principal da adubação verificando viabilidade econômica e técnica de uso da técnica. O projeto está sendo conduzido na Fazenda Campanário município de Itaquiraí, estado de Mato Grosso do Sul, Brasil, a partir da safra de soja 2018/2019. São três tratamentos sendo T1, utilizando adubo químico solúvel na base de plantio, T2 e T3 utilizando 12 e 6 toneladas de pó de rocha de origem basáltica respectivamente, 30 dias após o plantio. O acompanhamento da área para tomada dos dados e observações é semanal, com visitas in loco, tendo maior frequência a partir do período de implantação da cultura até sua colheita. Foram coletadas informações como: datas de plantio, emergência e colheita da cultura Tipos de manejos efetuados para o controle das pragas, doenças e plantas invasoras. A coleta do solo para análise é realizada depois da retirada de cada cultura. Análises foliares são realizadas durante o desenvolvimento da cultura.EIGEDIN 2019
Non-equilibrium coherence dynamics in one-dimensional Bose gases
Low-dimensional systems are beautiful examples of many-body quantum physics.
For one-dimensional systems the Luttinger liquid approach provides insight into
universal properties. Much is known of the equilibrium state, both in the
weakly and strongly interacting regime. However, it remains a challenge to
probe the dynamics by which this equilibrium state is reached. Here we present
a direct experimental study of the coherence dynamics in both isolated and
coupled degenerate 1d Bose gases. Dynamic splitting is used to create two 1d
systems in a phase coherent state. The time evolution of the coherence is
revealed in local phase shifts of the subsequently observed interference
patterns. Completely isolated 1d Bose gases are observed to exhibit a universal
sub-exponential coherence decay in excellent agreement with recent predictions
by Burkov et al. [Phys. Rev. Lett. 98, 200404 (2007)]. For two coupled 1d Bose
gases the coherence factor is observed to approach a non-zero equilibrium value
as predicted by a Bogoliubov approach. This coupled-system decay to finite
coherence is the matter wave equivalent of phase locking two lasers by
injection. The non-equilibrium dynamics of superfluids plays an important role
in a wide range of physical systems, such as superconductors, quantum-Hall
systems, superfluid Helium, and spin systems. Our experiments studying
coherence dynamics show that 1d Bose gases are ideally suited for investigating
this class of phenomena.Comment: to appear in natur
Maximal length of trapped one-dimensional Bose-Einstein condensates
I discuss a Bogoliubov inequality for obtaining a rigorous bound on the
maximal axial extension of inhomogeneous one-dimensional Bose-Einstein
condensates. An explicit upper limit for the aspect ratio of a strongly
elongated, harmonically trapped Thomas-Fermi condensate is derived.Comment: 6 pages; contributed paper for Quantum Fluids and Solids, Trento
2004, to appear in JLT
Low-dimensional Bose gases
We present an improved many-body T-matrix theory for partially Bose-Einstein
condensed atomic gases by treating the phase fluctuations exactly. The
resulting mean-field theory is valid in arbitrary dimensions and able to
describe the low-temperature crossover between three, two and one-dimensional
Bose gases. When applied to a degenerate two-dimensional atomic hydrogen gas,
we obtain a reduction of the three-body recombination rate which compares
favorably with experiment. Supplementing the mean-field theory with a
renormalization-group approach to treat the critical fluctuations, we also
incorporate into the theory the Kosterlitz-Thouless transition that occurs in a
homogeneous Bose gas in two dimensions. In particular, we calculate the
critical conditions for the Kosterlitz-Thouless phase transition as a function
of the microscopic parameters of the theory. The proposed theory is further
applied to a trapped one-dimensional Bose gas, where we find good agreement
with exact numerical results obtained by solving a nonlinear Langevin field
equation.Comment: 14 pages, 13 figures, revte
Probing quantum and thermal noise in an interacting many-body system
The probabilistic character of the measurement process is one of the most
puzzling and fascinating aspects of quantum mechanics. In many-body systems
quantum mechanical noise reveals non-local correlations of the underlying
many-body states. Here, we provide a complete experimental analysis of the
shot-to-shot variations of interference fringe contrast for pairs of
independently created one-dimensional Bose condensates. Analyzing different
system sizes we observe the crossover from thermal to quantum noise, reflected
in a characteristic change in the distribution functions from Poissonian to
Gumbel-type, in excellent agreement with theoretical predictions based on the
Luttinger liquid formalism. We present the first experimental observation of
quasi long-range order in one-dimensional atomic condensates, which is a
hallmark of quantum fluctuations in one-dimensional systems. Furthermore, our
experiments constitute the first analysis of the full distribution of quantum
noise in an interacting many-body system
Collective oscillations of a 1D trapped Bose gas
Starting from the hydrodynamic equations of superfluids, we calculate the
frequencies of the collective oscillations of a harmonically trapped Bose gas
for various 1D configurations. These include the mean field regime described by
Gross-Pitaevskii theory and the beyond mean field regime at small densities
described by Lieb-Liniger theory. The relevant combinations of the physical
parameters governing the transition between the different regimes are
discussed.Comment: 4 pages, 2 figure
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