776 research outputs found
Application of satellite data to tropic/subtropic moisture coupling
The objective is to utilize various satellite products from a number of satellites together with data observed from platforms available during the FGGE Special Observing Periods to diagnose synoptic scale events in date void regions. The focus is on episodes of northeastward traveling cloud bands which move out of the ITCZ over the eastern North Pacific Ocean. These events are called moisture bursts
Decoherence-driven Cooling of a Degenerate Spinor Bose Gas
We investigate the relationship between the coherence of a partially
Bose-condensed spinor gas and its temperature. We observe cooling of the normal
component driven by decoherence as well the effect of temperature on
decoherence rates.Comment: 4 pages, 2 figure
The Mystery of the Ramsey Fringe that Didn't Chirp
We use precision microwave spectroscopy of magnetically trapped, ultra-cold
87Rb to characterize intra- and inter-state density correlations. The cold
collision shifts for both normal and condensed clouds are measured. The results
verify the presence of the sometimes controversial "factors of two", in
normal-cloud mean-field energies, both within a particular state and between
two distinct spin species. One might expect that as two spin species decohere,
the inter-state factor of two would revert to unity, but the associated
frequency chirp one naively expects from such a trend is not observed in our
data.Comment: Proceedings of the 18th International Conference on Atomic Physics
(ICAP 2002
Thermally Induced Losses in Ultra-Cold Atoms Magnetically Trapped Near Room-Temperature Surfaces
We have measured magnetic trap lifetimes of ultra-cold Rb87 atoms at
distances of 5-1000 microns from surfaces of conducting metals with varying
resistivity. Good agreement is found with a theoretical model for losses
arising from near-field magnetic thermal noise, confirming the complications
associated with holding trapped atoms close to conducting surfaces. A
dielectric surface (silicon) was found in contrast to be so benign that we are
able to evaporatively cool atoms to a Bose-Einstein condensate by using the
surface to selectively adsorb higher energy atoms.Comment: Improved theory curve eliminates discrepancy. JLTP in pres
Duality Between Spatial and Angular Shift in Optical Reflection
We report a unified representation of the spatial and angular Goos-Hanchen
and Imbert-Fedorov shifts that occur when a light beam reflects from a plane
interface. We thus reveal the dual nature of spatial and angular shifts in
optical beam reflection. In the Goos-Hanchen case we show theoretically and
experimentally that this unification naturally arises in the context of
reflection from a lossy surface (e.g., a metal).Comment: 4 pages, 3 figure
Gravitational Instantons and Fluxes from M/F-theory on Calabi-Yau fourfolds
We compactify four-dimensional N=1 gauged supergravity theories on a circle
including fluxes for shift-symmetric scalars. Four-dimensional Taub-NUT
gravitational instantons universally correct the three-dimensional
superpotential in the absence of fluxes. In the presence of fluxes these
Taub-NUT instanton contributions are no longer gauge-invariant. Invariance can
be restored by gauge instantons on top of Taub-NUT instantons. We establish the
embedding of this scenario into M-theory. Circle fluxes and gaugings arise from
a restricted class of M-theory four-form fluxes on a resolved Calabi-Yau
fourfold. The M5-brane on the base of the elliptic fourfold dualizes into the
universal Taub-NUT instanton. In the presence of fluxes this M5-brane is
anomalous. We argue that anomaly free contributions arise from involved
M5-brane geometries dual to gauge-instantons on top of Taub-NUT instantons.
Adding a four-dimensional superpotential to the gravitational instanton
corrections leads to three-dimensional Anti-de Sitter vacua at stabilized
compactification radius. We comment on the possibility to uplift these M-theory
vacua, and to tunnel to four-dimensional F-theory vacua.Comment: 47 pages, 2 figure
The material politics of smart building energy management: A view from Sydney\u27s commercial office space
The potential of cities in leveraging energy transformation is increasingly recognised, with a growing focus on urban built environments. In this paper we focus on smart building energy management as an increasingly pivotal material means through which energy transformation comes to matter in cities, and through which buildings are politicised in the negotiation of energy transformation. We advance a material political analysis of the case of Sydney\u27s premium commercial office building sector to explore how such buildings are conferred with political capacity. We explicitly extend this material politics framework to pluralise the \u27whereabouts\u27 of the politics of energy transformation, expanding recognition of the sites and moments of negotiation through which these politics are enacted, authority shaped, and where trajectories of energy transformation begin to be fashioned. Drawing on this extended conception of politics, the paper traces how the political capacity of buildings comes to matter through smart building energy management platforms as they are negotiated through the context of Sydney\u27s policy settings, the political-economy of the top tier commercial office sector, and building management cultures. We conclude with observations on how smart building energy management platforms might contribute to the shaping of particular trajectories, possibilities and limits for energy transformation advanced through the built environment
TLR2 and TLR4 in Ischemia Reperfusion Injury
Ischemia reperfusion (I/R) injury refers to the tissue damage which occurs when blood supply returns to tissue after a period of ischemia and is associated with trauma, stroke, myocardial infarction, and solid organ transplantation. Although the cause of this injury is multifactorial, increasing experimental evidence suggests an important role for the innate immune system in initiating the inflammatory cascade leading to detrimental/deleterious changes. The Toll-like Receptors (TLRs) play a central role in innate immunity recognising both pathogen- and damage-associated molecular patterns and have been implicated in a range of inflammatory and autoimmune diseases. In this paper, we summarise the current state of knowledge linking TLR2 and TLR4 to I/R injury, including recent studies which demonstrate that therapeutic inhibition of TLR2 has beneficial effects on I/R injury in a murine model of myocardial infarction
Testing General Relativity with Atom Interferometry
The unprecedented precision of atom interferometry will soon lead to
laboratory tests of general relativity to levels that will rival or exceed
those reached by astrophysical observations. We propose such an experiment that
will initially test the equivalence principle to 1 part in 10^15 (300 times
better than the current limit), and 1 part in 10^17 in the future. It will also
probe general relativistic effects--such as the non-linear three-graviton
coupling, the gravity of an atom's kinetic energy, and the falling of light--to
several decimals. Further, in contrast to astrophysical observations,
laboratory tests can isolate these effects via their different functional
dependence on experimental variables.Comment: 4 pages, 1 figure; v2: Minor changes made for publicatio
Influence of optical aberrations in an atomic gyroscope
In atom interferometry based on light-induced diffraction, the optical
aberrations of the laser beam splitters are a dominant source of noise and
systematic effect. In an atomic gyroscope, this effect is dramatically reduced
by the use of two atomic sources. But it remains critical while coupled to
fluctuations of atomic trajectories, and appears as a main source of noise to
the long term stability. Therefore we measure these contributions in our setup,
using cold Cesium atoms and stimulated Raman transitions
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