3,363 research outputs found
3D tomography of cells in micro-channels
We combine confocal imaging, microfluidics and image analysis to record
3D-images of cells in flow. This enables us to recover the full 3D
representation of several hundred living cells per minute. Whereas 3D confocal
imaging has thus far been limited to steady specimen, we overcome this
restriction and present a method to access the 3D shape of moving objects. The
key of our principle is a tilted arrangement of the micro-channel with respect
to the focal plane of the microscope. This forces cells to traverse the focal
plane in an inclined manner. As a consequence, individual layers of passing
cells are recorded which can then be assembled to obtain the volumetric
representation. The full 3D information allows for a detailed comparisons with
theoretical and numerical predictions unfeasible with e.g.\ 2D imaging. Our
technique is exemplified by studying flowing red blood cells in a micro-channel
reflecting the conditions prevailing in the microvasculature. We observe two
very different types of shapes: `croissants' and `slippers'. Additionally, we
perform 3D numerical simulations of our experiment to confirm the observations.
Since 3D confocal imaging of cells in flow has not yet been realized, we see
high potential in the field of flow cytometry where cell classification thus
far mostly relies on 1D scattering and fluorescence signals
Quark confinement and color transparency in a gauge-invariant formulation of QCD
We examine a nonlocal interaction that results from expressing the QCD
Hamiltonian entirely in terms of gauge-invariant quark and gluon fields. The
interaction couples one quark color-charge density to another, much as electric
charge densities are coupled to each other by the Coulomb interaction in QED.
In QCD, this nonlocal interaction also couples quark color-charge densities to
gluonic color. We show how the leading part of the interaction between quark
color-charge densities vanishes when the participating quarks are in a color
singlet configuration, and that, for singlet configurations, the residual
interaction weakens as the size of a packet of quarks shrinks. Because of this
effect, color-singlet packets of quarks should experience final state
interactions that increase in strength as these packets expand in size. For the
case of an SU(2) model of QCD based on the {\em ansatz} that the
gauge-invariant gauge field is a hedgehog configuration, we show how the
infinite series that represents the nonlocal interaction between quark
color-charge densities can be evaluated nonperturbatively, without expanding it
term-by-term. We discuss the implications of this model for QCD with SU(3)
color and a gauge-invariant gauge field determined by QCD dynamics.Comment: Revtex, 23 pages; contains additional references with brief comments
on sam
Demonstrating the feasibility of standardized application program interfaces that will allow mobile/portable terminals to receive services combining UMTS and DVB-T
Crucial to the commercial exploitation of any service combining UMTS and DVB-T is the availability of standardized API’s adapted to the hybrid UMTS and DVB-T network and to the technical limitations of mobile/portable terminals. This paper describes work carried out in the European Commission Framework Program 5 (FP5) project CONFLUENT to demonstrate the feasibility of such Application Program Interfaces (API’s) by enabling the reception of a Multimedia Home Platform (MHP) based application transmitted over DVB-T on five different terminals with parts of the service running on a mobile phone
Particle Spectrum of the Supersymmetric Standard Model from the Massless Excitations of a Four Dimensional Superstring
A superstring action is quantised with Neveu Schwarz(NS) and Ramond(R)
boundary conditions. The zero mass states of the NS sector are classified as
the vector gluons, W-mesons, -mesons and scalars containing Higgs. The
fifteen zero mass fermions are obtained from the Ramond sector. A space time
supersymmetric Hamiltonian of the Standard Model is presented without any
conventional SUSY particles
Journalists views and use of social media: Cision Social Journalism Study 2012: global report
The annual Social Journalism Study conducted by Cision and Canterbury Christ Church University, UK, is charting the changes of how journalists and media professionals use social media for work. Unique to this year’s study is the identification of five profile groups of professional social media users who differ in terms of patterns of use, attitude and knowledge.These groups are: Architects, Hunters, Observers, Promoters and Sceptics. This report also includes a Social Journalism Barometer which was developed to assess social media involvement, practice, knowledge and attitudes among journalists and media professionals in different countries. To put journalists in the wider social context of the changing use of technology, we also included a comparison to Forrester’s Social Technographics® framework of general population‘s use of social media
Matched filters for coalescing binaries detection on massively parallel computers
We discuss some computational problems associated to matched filtering of
experimental signals from gravitational wave interferometric detectors in a
parallel-processing environment. We then specialize our discussion to the use
of the APEmille and apeNEXT processors for this task. Finally, we accurately
estimate the performance of an APEmille system on a computational load
appropriate for the LIGO and VIRGO experiments, and extrapolate our results to
apeNEXT.Comment: 19 pages, 6 figure
Softening of First-Order Phase Transition on Quenched Random Gravity Graphs
We perform extensive Monte Carlo simulations of the 10-state Potts model on
quenched two-dimensional gravity graphs to study the effect of
quenched coordination number randomness on the nature of the phase transition,
which is strongly first order on regular lattices. The numerical data provides
strong evidence that, due to the quenched randomness, the discontinuous
first-order phase transition of the pure model is softened to a continuous
transition, representing presumably a new universality class. This result is in
striking contrast to a recent Monte Carlo study of the 8-state Potts model on
two-dimensional Poissonian random lattices of Voronoi/Delaunay type, where the
phase transition clearly stayed of first order, but is in qualitative agreement
with results for quenched bond randomness on regular lattices. A precedent for
such softening with connectivity disorder is known: in the 10-state Potts model
on annealed Phi3 gravity graphs a continuous transition is also observed.Comment: Latex + 5 postscript figures, 10 pages of text, figures appende
Well-posedness and stability results for the Gardner equation
In this article we present local well-posedness results in the classical
Sobolev space H^s(R) with s > 1/4 for the Cauchy problem of the Gardner
equation, overcoming the problem of the loss of the scaling property of this
equation. We also cover the energy space H^1(R) where global well-posedness
follows from the conservation laws of the system. Moreover, we construct
solitons of the Gardner equation explicitly and prove that, under certain
conditions, this family is orbitally stable in the energy space.Comment: 1 figure. Accepted for publication in Nonlin.Diff Eq.and App
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