958 research outputs found
Morphology, fluid Motion and Predation by the Scyphomedusa Aurelia Aurita
Although medusan predators play demonstrably important roles in a variety of marine ecosystems, the mechanics of prey capture and, hence, prey selection, have remained poorly defined. A review of the literature describing the commonly studied medusa Aurelia aurita (Linnaeus 1758) reveals no distinct patterns of prey selectivity and suggests that A. aurita is a generalist and feeds unselectively upon available zooplankton. We examined the mechanics of prey capture by A. aurita using video methods to record body and fluid motions. Medusae were collected between February and June in 1990 and 1991 from Woods Hole, Massachusetts and Narragansett Bay, Rhode Island, USA. Tentaculate A. aurita create fluid motions during swimming which entrain prey and bring them into contact with tentacles. We suggest that this mechanism dominates prey selection by A. aurita. In this case, we predict that medusae of a specific diameter will positively select prey with escape speeds slower than the flow velocities at their bell margins. Negatively selected prey escape faster than the medusan flow velocity draws them to capture surfaces. Faster prey will be captured by larger medusac because flow field velocity is a function of bell diameter. On the basis of prey escape velocities and flow field velocities of A. aurita with diameters of 0.8 to 7.1 cm, we predict that A. aurita will select zooplankton such as barnacle nauplii and some slow swimming hydromedusae, while faster copepods will be negatively selected
ATLASGAL - properties of compact H II regions and their natal clumps
We present a complete sample of molecular clumps containing compact and ultracompact HII (UC HII) regions between ℓ = 10° and 60° and |b| < 1°, identified by combining the APEX Telescope Large Area Survey ofthe Galaxy submm and CORNISH radio continuum surveys with visual examination ofarchival infrared data. Our sample is complete to optically thin, compact and UC HII regions driven by a zero-age main-sequence star of spectral type B0 or earlier embedded within a 1000M clump. In total we identify 213 compact and UC HII regions, associated with 170 clumps. Unambiguous kinematic distances are derived for these clumps and used to estimate their masses and physical sizes, as well as the Lyman continuum fluxes and sizes of their embedded HII regions. We find a clear lower envelope for the surface density of molecular clumps hosting massive star formation of 0.05 g cm, which is consistent with a similar sample of clumps associated with 6.7 GHz masers. The mass of the most massive embedded starsis closely correlated with the mass of their natal clump. Young B stars appearto be significantly more luminous in the ultraviolet than predicted by current stellar atmosphere models. The properties of clumps associated with compact and UC HII regions are very similar to those associated with 6.7 GHz methanol masers and we speculate that there is little evolution in the structure of the molecular clumps between these two phases. Finally, we identifya significant peak in the surface density of compact and UC HII-regions associated with the W49A star-forming complex, noting that this complex is truly one of the most massive and intense regions of star formation in the Galaxy. © 2013 The Authors, Published by Oxford University Press on behalf of the Royal Astronomical Society
Strong Interactions of Single Atoms and Photons near a Dielectric Boundary
Modern research in optical physics has achieved quantum control of strong
interactions between a single atom and one photon within the setting of cavity
quantum electrodynamics (cQED). However, to move beyond current
proof-of-principle experiments involving one or two conventional optical
cavities to more complex scalable systems that employ N >> 1 microscopic
resonators requires the localization of individual atoms on distance scales <
100 nm from a resonator's surface. In this regime an atom can be strongly
coupled to a single intracavity photon while at the same time experiencing
significant radiative interactions with the dielectric boundaries of the
resonator. Here, we report an initial step into this new regime of cQED by way
of real-time detection and high-bandwidth feedback to select and monitor single
Cesium atoms localized ~100 nm from the surface of a micro-toroidal optical
resonator. We employ strong radiative interactions of atom and cavity field to
probe atomic motion through the evanescent field of the resonator. Direct
temporal and spectral measurements reveal both the significant role of
Casimir-Polder attraction and the manifestly quantum nature of the atom-cavity
dynamics. Our work sets the stage for trapping atoms near micro- and
nano-scopic optical resonators for applications in quantum information science,
including the creation of scalable quantum networks composed of many
atom-cavity systems that coherently interact via coherent exchanges of single
photons.Comment: 8 pages, 5 figures, Supplemental Information included as ancillary
fil
Cavity Induced Interfacing of Atoms and Light
This chapter introduces cavity-based light-matter quantum interfaces, with a
single atom or ion in strong coupling to a high-finesse optical cavity. We
discuss the deterministic generation of indistinguishable single photons from
these systems; the atom-photon entanglement intractably linked to this process;
and the information encoding using spatio-temporal modes within these photons.
Furthermore, we show how to establish a time-reversal of the aforementioned
emission process to use a coupled atom-cavity system as a quantum memory. Along
the line, we also discuss the performance and characterisation of cavity
photons in elementary linear-optics arrangements with single beam splitters for
quantum-homodyne measurements.Comment: to appear as a book chapter in a compilation "Engineering the
Atom-Photon Interaction" published by Springer in 2015, edited by A.
Predojevic and M. W. Mitchel
Ears of the Armadillo: Global Health Research and Neglected Diseases in Texas
Neglected tropical diseases (NTDs) have\ud
been recently identified as significant public\ud
health problems in Texas and elsewhere in\ud
the American South. A one-day forum on the\ud
landscape of research and development and\ud
the hidden burden of NTDs in Texas\ud
explored the next steps to coordinate advocacy,\ud
public health, and research into a\ud
cogent health policy framework for the\ud
American NTDs. It also highlighted how\ud
U.S.-funded global health research can serve\ud
to combat these health disparities in the\ud
United States, in addition to benefiting\ud
communities abroad
Analogue peptides for the immunotherapy of human acute myeloid leukemia
Accepted manuscript. The final publication is available at: http://link.springer.com/article/10.1007%2Fs00262-015-1762-9The use of peptide vaccines, enhanced by adjuvants, has shown some efficacy in clinical trials. However, responses are often short-lived and rarely induce notable memory responses. The reason is that self-antigens have already been presented to the immune system as the tumor develops, leading to tolerance or some degree of host tumor cell destruction. To try to break tolerance against self-antigens, one of the methods employed has been to modify peptides at the anchor residues to enhance their ability to bind major histocompatibility complex molecules, extending their exposure to the T-cell receptor. These modified or analogue peptides have been investigated as stimulators of the immune system in patients with different cancers with variable but sometimes notable success. In this review we describe the background and recent developments in the use of analogue peptides for the immunotherapy of acute myeloid leukemia describing knowledge useful for the application of analogue peptide treatments for other malignancies
Quantum nature of a strongly-coupled single quantum dot-cavity system
Cavity quantum electrodynamics (QED) studies the interaction between a
quantum emitter and a single radiation-field mode. When an atom is in strong
coupling with a cavity mode1,2, it is possible to realize key quantum
information processing (QIP) tasks, such as controlled coherent coupling and
entanglement of distinguishable quantum systems. Realizing these tasks in the
solid state is clearly desirable, and coupling semiconductor self-assembled
quantum dots (QDs) to monolithic optical cavities is a promising route to this
end. However, validating the efficacy of QDs in QIP applications requires
confirmation of the quantum nature of the QD-cavity system in the strong
coupling regime. Here we find a confirmation by observing quantum correlations
in photoluminescence (PL) from a photonic crystal (PC) nanocavity3-5
interacting with one, and only one, QD located precisely at the cavity electric
field maximum. When off-resonance, photon emission from the cavity mode and QD
excitons is anti-correlated at the level of single quanta, proving that the
mode is driven solely by the QD despite an energy mis-match between cavity and
excitons. When tuned into resonance, the exciton and photon enter the
strong-coupling regime of cavity-QED and the QD lifetime reduces by a factor of
120. The photon stream from the cavity becomes anti-bunched, proving that the
coupled exciton/photon system is in the quantum anharmonic regime. Our
observations unequivocally show that QIP tasks requiring the quantum nonlinear
regime are achievable in the solid state.Comment: 14 pages 4 figure
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