669 research outputs found
Metabolomics--a new exciting field within the "omics" sciences.
keine DOI, kein abstract (Editorial!)/keg18.8.1
A Waveguide for Bose-Einstein Condensates
We report on the creation of Bose-Einstein condensates of Rb in a
specially designed hybrid, dipole and magnetic trap. This trap naturally allows
the coherent transfer of matter waves into a pure dipole potential waveguide
based on a doughnut beam. Specifically, we present studies of the coherence of
the ensemble in the hybrid trap and during the evolution in the waveguide by
means of an autocorrelation interferometer scheme. By monitoring the expansion
of the ensemble in the waveguide we observe a mean field dominated acceleration
on a much longer time scale than in the free 3D expansion. Both the
autocorrelation interference and the pure expansion measurements are in
excellent agreement with theoretical predictions of the ensemble dynamics
Phase Fluctuations in Bose-Einstein Condensates
We demonstrate the existence of phase fluctuations in elongated Bose-Einstein
Condensates (BECs) and study the dependence of those fluctuations on the system
parameters. A strong dependence on temperature, atom number, and trapping
geometry is observed. Phase fluctuations directly affect the coherence
properties of BECs. In particular, we observe instances where the phase
coherence length is significantly smaller than the condensate size. Our method
of detecting phase fluctuations is based on their transformation into density
modulations after ballistic expansion. An analytic theory describing this
transformation is developed.Comment: 11 pages, 7 figure
Localization and Anomalous Transport in a 1-D Soft Boson Optical Lattice
We study the dynamics of Bose-Einstein condensed atoms in a 1-D optical
lattice potential in a regime where the collective (Josephson) tunneling energy
is comparable with the on-site interaction energy, and the number of particles
per lattice site is mesoscopically large. By directly imaging the motion of
atoms in the lattice, we observe an abrupt suppression of atom transport
through the array for a critical ratio of these energies, consistent with
quantum fluctuation induced localization. Directly below the onset of
localization, the frequency of the observed superfluid transport can be
explained by a phonon excitation but deviates substantially from that predicted
by the hydrodynamic/Gross-Pitaevskii equations.Comment: 14 pages, 5 figure
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
Adaptable-radius, time-orbiting magnetic ring trap for Bose-Einstein condensates
We theoretically investigate an adjustable-radius magnetic storage ring for
laser-cooled and Bose-condensed atoms. Additionally, we discuss a novel
time-dependent variant of this and other ring traps. Time-orbiting ring traps
provide a high optical access method for spin-flip loss prevention near a
storage ring's circular magnetic field zero. Our scalable storage ring will
allow one to probe the fundamental limits of condensate Sagnac interferometry.Comment: 5 pages, 3 figures. accepted in J Phys
Agricultura e inovação: estudo sobre a viabilidade de uso do 'pĂł de rocha' em sistemas de produção agrĂcola.
O uso dos chamados remineralizadores de solo, "pĂł de rocha" (rochagem / ?rocks-for-crops?), Ă© uma tĂ©cnica que vem se expandindo com o passar dos anos. O trabalho visa observar o comportamento das culturas anuais de soja e milho durante trĂŞs safras consecutivas, utilizando pĂł de rocha (remineralizador), como fonte principal da adubação verificando viabilidade econĂ´mica e tĂ©cnica de uso da tĂ©cnica. O projeto está sendo conduzido na Fazenda Campanário municĂpio de ItaquiraĂ, estado de Mato Grosso do Sul, Brasil, a partir da safra de soja 2018/2019. SĂŁo trĂŞs tratamentos sendo T1, utilizando adubo quĂmico solĂşvel na base de plantio, T2 e T3 utilizando 12 e 6 toneladas de pĂł de rocha de origem basáltica respectivamente, 30 dias apĂłs o plantio. O acompanhamento da área para tomada dos dados e observações Ă© semanal, com visitas in loco, tendo maior frequĂŞncia a partir do perĂodo de implantação da cultura atĂ© sua colheita. Foram coletadas informações como: datas de plantio, emergĂŞncia e colheita da cultura Tipos de manejos efetuados para o controle das pragas, doenças e plantas invasoras. A coleta do solo para análise Ă© realizada depois da retirada de cada cultura. Análises foliares sĂŁo realizadas durante o desenvolvimento da cultura.EIGEDIN 2019
Observation of Phase Fluctuations in Bose-Einstein Condensates
The occurrence of phase fluctuations due to thermal excitations in
Bose-Einstein condensates (BECs) is studied for a variety of temperatures and
trap geometries. We observe the statistical nature of the appearence of phase
fluctuations and characterize the dependence of their average value on
temperature, number of particles and the trapping potential. We find pronounced
phase fluctuations for condensates in very elongated traps in a broad
temperature range. The results are of great importance for the realization of
BEC in quasi 1D geometries, for matter wave interferometry with BECs, as well
as for coherence properties of guided atom laser beams.Comment: 4 pages, 4 figure
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
Extension of Bogoliubov theory to quasi-condensates
We present an extension of the well-known Bogoliubov theory to treat low
dimensional degenerate Bose gases in the limit of weak interactions and low
density fluctuations. We use a density-phase representation and show that a
precise definition of the phase operator requires a space discretisation in
cells of size . We perform a systematic expansion of the Hamiltonian in
terms of two small parameters, the relative density fluctuations inside a cell
and the phase change over a cell. The resulting macroscopic observables can be
computed in one, two and three dimensions with no ultraviolet or infrared
divergence. Furthermore this approach exactly matches Bogoliubov's approach
when there is a true condensate. We give the resulting expressions for the
equation of state of the gas, the ground state energy, the first order and
second order correlations functions of the field. Explicit calculations are
done for homogeneous systems.Comment: 32 pages, 2 figures; typos corrected in revised versio
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