4,593 research outputs found
Linear and nonlinear waveguides induced by optical vortex solitons
We study, numerically and analytically, linear and nonlinear waveguides
induced by optical vortex solitons in a Kerr medium. Both fundamental and
first-order guided modes are analyzed, as well as the cases of effectively
defocusing and focusing nonlinearity.Comment: 3 pages, 3 figures, changed conten
A transparent 3D printed device for assembling droplet hydrogel bilayers (DHBs)
We report a new approach for assembling droplet hydrogel bilayers (DHBs) using a transparent 3D printed device. We characterise the transparency of our platform, confirm bilayer formation using electrical measurements and show that single-channel recordings can be obtained using our reusable rapid prototyped device. This method significantly reduces the cost and infrastructure required to develop devices for DHB assembly and downstream study
Haldane exclusion statistics and second virial coefficient
We show that Haldanes new definition of statistics, when generalised to
infinite dimensional Hilbert spaces, is equal to the high temperature limit of
the second virial coefficient. We thus show that this exclusion statistics
parameter, g , of anyons is non-trivial and is completely determined by its
exchange statistics parameter . We also compute g for quasiparticles in
the Luttinger model and show that it is equal to .Comment: 11 pages, REVTEX 3.
A human coronavirus responsible for the common cold massively kills dendritic cells but not monocytes
Copyright @ 2012, American Society for Microbiology.Human coronaviruses are associated with upper respiratory tract infections that occasionally spread to the lungs and other organs. Although airway epithelial cells represent an important target for infection, the respiratory epithelium is also composed of an elaborate network of dendritic cells (DCs) that are essential sentinels of the immune system, sensing pathogens and presenting foreign antigens to T lymphocytes. In this report, we show that in vitro infection by human coronavirus 229E (HCoV-229E) induces massive cytopathic effects in DCs, including the formation of large syncytia and cell death within only few hours. In contrast, monocytes are much more resistant to infection and cytopathic effects despite similar expression levels of CD13, the membrane receptor for HCoV-229E. While the differentiation of monocytes into DCs in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4 requires 5 days, only 24 h are sufficient for these cytokines to sensitize monocytes to cell death and cytopathic effects when infected by HCoV-229E. Cell death induced by HCoV-229E is independent of TRAIL, FasL, tumor necrosis factor alpha, and caspase activity, indicating that viral replication is directly responsible for the observed cytopathic effects. The consequence of DC death at the early stage of HCoV-229E infection may have an impact on the early control of viral dissemination and on the establishment of long-lasting immune memory, since people can be reinfected multiple times by HCoV-229E
Single photon generation by pulsed excitation of a single dipole
The fluorescence of a single dipole excited by an intense light pulse can
lead to the generation of another light pulse containing a single photon. The
influence of the duration and energy of the excitation pulse on the number of
photons in the fluorescence pulse is studied. The case of a two-level dipole
with strongly damped coherences is considered. The presence of a metastable
state leading to shelving is also investigated.Comment: 17 pages, 4 figures, submitted to PR
Non-Gaussian states for continuous variable quantum computation via Gaussian maps
We investigate non-Gaussian states of light as ancillary inputs for
generating nonlinear transformations required for quantum computing with
continuous variables. We consider a recent proposal for preparing a cubic phase
state, find the exact form of the prepared state and perform a detailed
comparison to the ideal cubic phase state. We thereby identify the main
challenges to preparing an ideal cubic phase state and describe the gates
implemented with the non-ideal prepared state. We also find the general form of
operations that can be implemented with ancilla Fock states, together with
Gaussian input states, linear optics and squeezing transformations, and
homodyne detection with feed forward, and discuss the feasibility of continuous
variable quantum computing using ancilla Fock states.Comment: 8 pages, 6 figure
Engineering cavity-field states by projection synthesis
We propose a reliable scheme for engineering a general cavity-field state.
This is different from recently presented strategies,where the cavity is
supposed to be initially empty and the field is built up photon by photon
through resonant atom-field interactions. Here, a coherent state is previously
injected into the cavity. So, the Wigner distribution function of the desired
state is constructed from that of the initially coherent state. Such an
engineering process is achieved through an adaptation of the recently proposed
technique of projection synthesis to cavity QED phenomena.Comment: 5 ps pages plus 3 included figure
Two Wide Planetary-Mass Companions to Solar-Type Stars in Upper Scorpius
At wide separations, planetary-mass and brown dwarf companions to solar type
stars occupy a curious region of parameters space not obviously linked to
binary star formation or solar-system scale planet formation. These companions
provide insight into the extreme case of companion formation (either binary or
planetary), and due to their relative ease of observation when compared to
close companions, they offer a useful template for our expectations of more
typical planets. We present the results from an adaptive optics imaging survey
for wide (50-500 AU) companions to solar type stars in Upper Scorpius. We
report one new discovery of a ~14 M_J companion around GSC 06214-00210, and
confirm that the candidate planetary mass companion 1RXS J160929.1-210524
detected by Lafreniere et al (2008) is in fact co-moving with its primary star.
In our survey, these two detections correspond to ~4% of solar type stars
having companions in the 6-20 M_J mass and 200-500 AU separation range. This
figure is higher than would be expected if brown dwarfs and planetary mass
companions were drawn from an extrapolation of the binary mass function.
Finally, we discuss implications for the formation of these objects.Comment: 11 Pages, 7 Figures, Accepted for Ap
Theory of Circle Maps and the Problem of One-Dimensional Optical Resonator with a Periodically Moving Wall
We consider the electromagnetic field in a cavity with a periodically
oscillating perfectly reflecting boundary and show that the mathematical theory
of circle maps leads to several physical predictions. Notably, well-known
results in the theory of circle maps (which we review briefly) imply that there
are intervals of parameters where the waves in the cavity get concentrated in
wave packets whose energy grows exponentially. Even if these intervals are
dense for typical motions of the reflecting boundary, in the complement there
is a positive measure set of parameters where the energy remains bounded.Comment: 34 pages LaTeX (revtex) with eps figures, PACS: 02.30.Jr, 42.15.-i,
42.60.Da, 42.65.Y
In situ measurements of tropical cloud properties in the West African Monsoon: upper tropospheric ice clouds, Mesoscale Convective System outflow, and subvisual cirrus
In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6) cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm.
Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10−4 g m−3. All known in situ measurements of subvisual tropopause cirrus are compared and an exponential fit on the size distributions is established for modelling purposes.
A comparison of aerosol to ice crystal number concentrations, in order to obtain an estimate on how many ice particles may result from activation of the present aerosol, yielded low ratios for the subvisual cirrus cases of roughly one cloud particle per 30 000 aerosol particles, while for the MCS outflow cases this resulted in a high ratio of one cloud particle per 300 aerosol particles
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