2,755 research outputs found
ATLAST detector needs for direct spectroscopic biosignature characterization in the visible and near-IR
Are we alone? Answering this ageless question will be a major focus for
astrophysics in coming decades. Our tools will include unprecedentedly large
UV-Optical-IR space telescopes working with advanced coronagraphs and
starshades. Yet, these facilities will not live up to their full potential
without better detectors than we have today. To inform detector development,
this paper provides an overview of visible and near-IR (VISIR;
) detector needs for the Advanced Technology
Large Aperture Space Telescope (ATLAST), specifically for spectroscopic
characterization of atmospheric biosignature gasses. We also provide a brief
status update on some promising detector technologies for meeting these needs
in the context of a passively cooled ATLAST.Comment: 8 pages, Presented 9 August 2015 at SPIE Optics + Photonics, San
Diego, C
Immunopathology of CD4+ T Cell-Mediated Autoimmune Responses to Central Nervous System Antigens: Role of IL-16
Multiple sclerosis (MS) is a chronic, inflammatory, demyelinating and degenerative disease of the central nervous system (CNS). While etiology of the disease remains unknown, genetic susceptibility and autoimmune mechanisms in the initiation and progression of the disease have been strongly suggested. Experimental autoimmune encephalomyelitis (EAE) is commonly used to study immune regulation of MS. Infiltration by CD4+ T cells, through blood-brain barrier (BBB), precedes the onset and relapses of MS. CNS migration and homing patterns of T cells are tightly synchronized by astrocyte and microglia derived cytokines and chemokines. Autoimmune, CNS antigenreactive, infiltrating T cells produce and locally release cytokines including but not limited to IFNγ, IL-2, IL-6, IL-16, IL-17, TNFα, and chemokines including CCL2, CCL5 and CXCL10. Chemokine mediated chemotaxis is exclusive for activated cell state and most chemokines do not discriminate between distinct cell types. Conversely, a cytokine IL-16 is a CD4-specific cytokine-ligand and exclusively induces chemotaxis of CD4+T cells, by binding and signaling through CD4, regardless of T cell activation state. In this article we focus on CD4+ T cell-mediated autoimmune responses to CNS antigens because of their importance for immunopathology of MS and EAE. We focus on autoimmune responses to myelin oligodendrocyte glycoprotein (MOG) because of its relevance for immunopathology of MS. We emphasize a role of IL-16 in regulation of CD4+T cell mediated autoimmune responses to MOG in EAE and MS. While a role of IL-16 in regulation of other CD4+T cell mediated autoimmune diseases has been established, its role in regulation of MS remains to be determined. Emerging data from our laboratories have indicated that IL-16-mediated CD4+ T cell chemoattraction has a significant role in regulation of CD4+ T cell-mediated autoimmune responses to CNS antigens. We propose an important function of this cytokine in regulation of relapsing-remitting EAE
Absence of the Rashba effect in undoped asymmetric quantum wells
To an electron moving in free space an electric field appears as a magnetic
field which interacts with and can reorient the electron spin. In semiconductor
quantum wells this spin-orbit interaction seems to offer the possibility of
gate-voltage control in spintronic devices but, as the electrons are subject to
both ion-core and macroscopic structural potentials, this over-simple picture
has lead to intense debate. For example, an externally applied field acting on
the envelope of the electron wavefunction determined by the macroscopic
potential, underestimates the experimentally observed spin-orbit field by many
orders of magnitude while the Ehrenfest theorem suggests that it should
actually be zero. Here we challenge, both experimentally and theoretically, the
widely held belief that any inversion asymmetry of the macroscopic potential,
not only electric field, will produce a significant spin-orbit field for
electrons. This conclusion has far-reaching consequences for the design of
spintronic devices while illuminating important fundamental physics.Comment: 7 pages, 5 fig
Using Modern Technologies to Capture and Share Indigenous Astronomical Knowledge
Indigenous Knowledge is important for Indigenous communities across the globe
and for the advancement of our general scientific knowledge. In particular,
Indigenous astronomical knowledge integrates many aspects of Indigenous
Knowledge, including seasonal calendars, navigation, food economics, law,
ceremony, and social structure. We aim to develop innovative ways of capturing,
managing, and disseminating Indigenous astronomical knowledge for Indigenous
communities and the general public for the future. Capturing, managing, and
disseminating this knowledge in the digital environment poses a number of
challenges, which we aim to address using a collaborative project involving
experts in the higher education, library, and industry sectors. Using
Microsoft's WorldWide Telescope and Rich Interactive Narratives technologies,
we propose to develop software, media design, and archival management solutions
to allow Indigenous communities to share their astronomical knowledge with the
world on their terms and in a culturally sensitive manner.Comment: Australian Academic & Research Libraries, Vol. 45(2), pp. 101-11
Controlling trapping potentials and stray electric fields in a microfabricated ion trap through design and compensation
Recent advances in quantum information processing with trapped ions have
demonstrated the need for new ion trap architectures capable of holding and
manipulating chains of many (>10) ions. Here we present the design and detailed
characterization of a new linear trap, microfabricated with scalable
complementary metal-oxide-semiconductor (CMOS) techniques, that is well-suited
to this challenge. Forty-four individually controlled DC electrodes provide the
many degrees of freedom required to construct anharmonic potential wells,
shuttle ions, merge and split ion chains, precisely tune secular mode
frequencies, and adjust the orientation of trap axes. Microfabricated
capacitors on DC electrodes suppress radio-frequency pickup and excess
micromotion, while a top-level ground layer simplifies modeling of electric
fields and protects trap structures underneath. A localized aperture in the
substrate provides access to the trapping region from an oven below, permitting
deterministic loading of particular isotopic/elemental sequences via
species-selective photoionization. The shapes of the aperture and
radio-frequency electrodes are optimized to minimize perturbation of the
trapping pseudopotential. Laboratory experiments verify simulated potentials
and characterize trapping lifetimes, stray electric fields, and ion heating
rates, while measurement and cancellation of spatially-varying stray electric
fields permits the formation of nearly-equally spaced ion chains.Comment: 17 pages (including references), 7 figure
Spatially uniform single-qubit gate operations with near-field microwaves and composite pulse compensation
We present a microfabricated surface-electrode ion trap with a pair of
integrated waveguides that generate a standing microwave field resonant with
the 171Yb+ hyperfine qubit. The waveguides are engineered to position the wave
antinode near the center of the trap, resulting in maximum field amplitude and
uniformity along the trap axis. By calibrating the relative amplitudes and
phases of the waveguide currents, we can control the polarization of the
microwave field to reduce off-resonant coupling to undesired Zeeman sublevels.
We demonstrate single-qubit pi-rotations as fast as 1 us with less than 6 %
variation in Rabi frequency over an 800 um microwave interaction region. Fully
compensating pulse sequences further improve the uniformity of X-gates across
this interaction region.Comment: 14 pages, 8 figure
Solar and atmospheric neutrino oscillations with three flavours
We analyze the solar and the atmospheric neutrino problems in the context of
three flavour neutrino oscillations. We assume a mass hierarchy in the vacuum
mass eigenvalues , but make no approximation
regarding the magnitudes of the mixing angles. We find that there are small but
continuous bands in the parameter space where the constraints imposed by the
current measurements of , and Kamiokande
experiments are satisfied at level. The allowed parameter space
increases dramatically if the error bars are enlarged to . The
electron neutrino survival probability has different energy dependence in
different regions of the parameter space. Measurement of the recoil electron
energy spectrum in detectors that use scattering may distinguish
between some of the allowed regions of parameter space. Finally we use the
results for the parameter space admitted by the solar neutrinos as an input for
the atmospheric neutrino problem and show that there exists a substantial
region of parameter space in which both problems can be solved.Comment: 25 pages plus eight figures. Uses Revtex. Postcript files for figures
sent separately as a uuencoded fil
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