731 research outputs found
linus: Conveniently explore, share, and present large-scale biological trajectory data in a web browser
In biology, we are often confronted with information-rich, large-scale trajectory data, but exploring and communicating patterns in such data can be a cumbersome task. Ideally, the data should be wrapped with an interactive visualisation in one concise packet that makes it straightforward to create and test hypotheses collaboratively. To address these challenges, we have developed a tool, linus, which makes the process of exploring and sharing 3D trajectories as easy as browsing a website. We provide a python script that reads trajectory data, enriches them with additional features such as edge bundling or custom axes, and generates an interactive web-based visualisation that can be shared online. linus facilitates the collaborative discovery of patterns in complex trajectory data
Пневматический привод для шарового крана Ду 200
Работа направлена на разработку пневматического привода применяемого на газо-нефти проводах, работа включает конструкторскую часть с разработкой компоновки, моделей, схем устройства и технологическую часть с технологией изготовления отдельных деталей привода.The work is aimed at developing a pneumatic drive used on gas and oil wires, the work includes the design part with the development of the layout, models, device circuits and the technological part with the manufacturing technology of individual drive parts
Linear optical absorption spectra of mesoscopic structures in intense THz fields: free particle properties
We theoretically study the effect of THz radiation on the linear optical
absorption spectra of semiconductor structures. A general theoretical
framework, based on non-equilibrium Green functions, is formulated, and applied
to the calculation of linear optical absorption spectrum for several
non-equilibrium mesoscopic structures. We show that a blue-shift occurs and
sidebands appear in bulk-like structures, i.e., the dynamical Franz-Keldysh
effect [A.-P. Jauho and K. Johnsen, Phys. Rev. Lett. 76, 4576 (1996)]. An
analytic calculation leads to the prediction that in the case of superlattices
distinct stable steps appear in the absorption spectrum when conditions for
dynamical localization are met.Comment: 13 Pages, RevTex using epsf to include 8 ps figures. Submitted to
Phys. Rev. B (3 April 97
Superfluid Dynamics of a Bose-Einstein Condensate in a Periodic Potential
We investigate the superfluid properties of a Bose-Einstein condensate (BEC)
trapped in a one dimensional periodic potential. We study, both analytically
(in the tight binding limit) and numerically, the Bloch chemical potential, the
Bloch energy and the Bogoliubov dispersion relation, and we introduce {\it two}
different, density dependent, effective masses and group velocities. The
Bogoliubov spectrum predicts the existence of sound waves, and the arising of
energetic and dynamical instabilities at critical values of the BEC
quasi-momentum which dramatically affect its coherence properties. We
investigate the dependence of the dipole and Bloch oscillation frequencies in
terms of an effective mass averaged over the density of the condensate. We
illustrate our results with several animations obtained solving numerically the
time-dependent Gross-Pitaevskii equation.Comment: 13 pages, 7 figures, movies and published paper available at
http://www.iop.org/EJ/abstract/1367-2630/5/1/11
Schrodinger cat states prepared by Bloch oscillation in a spin-dependent optical lattice
We propose to use Bloch oscillation of ultra-cold atoms in a spin-dependent
optical lattice to prepare schrodinger cat states. Depending on its internal
state, an atom feels different periodic potentials and thus has different
energy band structures for its center-of-mass motion. Consequently, under the
same gravity force, the wave packets associated with different internal states
perform Bloch oscillation of different amplitudes in space and in particular
they can be macroscopically displaced with respect to each other. In this way,
a cat state can be prepared.Comment: 4 pages, 3 figures; slightly modifie
A quantum point contact for neutral atoms
We show that the conductance of neutral atoms through a tightly confining
waveguide constriction is quantized in units of lambda_dB^2/pi, where lambda_dB
is the de Broglie wavelength of the incident atoms. Such a constriction forms
the atom analogue of an electron quantum point contact and is an example of
quantum transport of neutral atoms in an aperiodic system. We present a
practical constriction geometry that can be realized using a microfabricated
magnetic waveguide, and discuss how a pair of such constrictions can be used to
study the quantum statistics of weakly interacting gases in small traps.Comment: 5 pages with 3 figures. To appear in Phys. Rev. Let
Bloch oscillations of magnetic solitons in anisotropic spin-1/2 chains
We study the quantum dynamics of soliton-like domain walls in anisotropic
spin-1/2 chains in the presence of magnetic fields. In the absence of fields,
domain walls form a Bloch band of delocalized quantum states while a static
field applied along the easy axis localizes them into Wannier wave packets and
causes them to execute Bloch oscillations, i.e. the domain walls oscillate
along the chain with a finite Bloch frequency and amplitude. In the presence of
the field, the Bloch band, with a continuum of extended states, breaks up into
the Wannier-Zeeman ladder -- a discrete set of equally spaced energy levels. We
calculate the dynamical structure factor in the one-soliton sector at finite
frequency, wave vector, and temperature, and find sharp peaks at frequencies
which are integer multiples of the Bloch frequency. We further calculate the
uniform magnetic susceptibility and find that it too exhibits peaks at the
Bloch frequency. We identify several candidate materials where these Bloch
oscillations should be observable, for example, via neutron scattering
measurements. For the particular compound CoCl_2.2H_2O we estimate the Bloch
amplitude to be on the order of a few lattice constants, and the Bloch
frequency on the order of 100 GHz for magnetic fields in the Tesla range and at
temperatures of about 18 Kelvin.Comment: 31 single-spaced REVTeX pages, including 7 figures embedded with eps
Time Periodic Behavior of Multiband Superlattices in Static Electric Fields
We use an analytic perturbation expansion for the two-band system of tight
binding electrons to discuss Bloch oscillations and Zener tunneling within this
model. We make comparison with recent numerical results and predict
analytically the frequency of radiation expected from Zener tunneling,
including its disappearance, as a function of the system parameters.Comment: 12 pages, no figure include
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