7,391 research outputs found
"Interaction-Free" Imaging
Using the complementary wave- and particle-like natures of photons, it is
possible to make ``interaction-free'' measurements where the presence of an
object can be determined with no photons being absorbed. We investigated
several ``interaction-free'' imaging systems, i.e. systems that allow optical
imaging of photosensitive objects with less than the classically expected
amount of light being absorbed or scattered by the object. With the most
promising system, we obtained high-resolution (10 \mu m), one-dimensional
profiles of a variety of objects (human hair, glass and metal wires, cloth
fibers), by raster scanning each object through the system. We discuss possible
applications and the present and future limits for interaction-free imaging.Comment: 10 pages, 6 encapsulated Postscript figure files, accepted for
publication in Physical Review
Study of zero-gravity, vapor/liquid separators
Heat exchange, mechanical separation, surface tension, and dielectrophoretic methods of separating vapor from liquid at zero gravity for vapor ventin
Aerodynamic data on a large semispan tilting wing with 0.5-diameter chord, double-slotted flap, and both left-hand and right-hand rotation of a single propeller
Longitudinal aerodynamic data on large-scale semispan V/STOL tilt-wing configuration having single propeller with left and right hand rotatio
Grover's search algorithm: An optical approach
The essential operations of a quantum computer can be accomplished using
solely optical elements, with different polarization or spatial modes
representing the individual qubits. We present a simple all-optical
implementation of Grover's algorithm for efficient searching, in which a
database of four elements is searched with a single query. By `compiling' the
actual setup, we have reduced the required number of optical elements from 24
to only 12. We discuss the extension to larger databases, and the limitations
of these techniques.Comment: 6 pages, 5 figures. To appear in a special issue of the Journal of
Modern Optics -- "The Physics of Quantum Information
Mass Models and Sunyaev-Zeldovich Effect Predictions for a Flux Limited Sample of 22 Nearby X-Ray Clusters
We define a 90% complete, volume-limited sample of 31 z<0.1 x-ray clusters
and present a systematic analysis of public ROSAT PSPC data on 22 of these
objects. Our efforts are undertaken in support of the Penn/OVRO SZE survey, and
to this end we present predictions for the inverse Compton optical depth
towards all 22 of these clusters. We have performed detailed Monte Carlo
simulations to understand the effects of the cluster profile uncertainties on
the SZE predictions given the OVRO 5.5-meter telescope beam and switching
patterns; we find that the profile uncertainties are one of the least
significant components of our error budget for SZE-based distance measurements.
We also present baryonic masses and baryon mass fractions derived under the
assumption of hydrostatic equilibrium for these 22 clusters. The mean baryonic
mass fraction within R_500 \sim 500 h^-1 kpc is (7.02 \pm 0.28) x 10^-2 h^-3/2,
or (19.8 \pm 0.8) x 10^-2 for h=0.5. We confirm the Allen et al. (1993) claim
of an excess absorbing column density towards Abell 478, but do not find
similar anomalies in the other 21 clusters in our sample. We also find some
evidence for an excess of soft counts in the ROSAT PSPC data.
A measurement of H_o using these models and OVRO SZE determinations will be
presented in a second paper.Comment: 51 pages, 6 figures included in text. Added comparison of different
cosmologies; accepted for publication in Ap
Viral evasion of innate immune defense: The case of resistance of pandemic H1N1 influenza A virus to human mannose-binding proteins
Mannose-binding lectins effectively inhibit most seasonal strains of influenza A virus and contribute to the innate host defense vs. these viruses. In contrast, pandemic IAV strains are largely resistant to these lectins, likely contributing to increased spread and worse outcomes. In this paper, we evaluated the inhibition of IAV by mannose-binding lectins of human, bacterial, and fungal origin to understand and possibly increase activity vs. the pandemic IAV. A modified version of the human surfactant protein D (SP-D) neck and carbohydrate recognition domain (NCRD) with combinatorial substitutions at the 325 and 343 positions, previously shown to inhibit pandemic H3N2 IA
High-efficiency quantum interrogation measurements via the quantum Zeno effect
The phenomenon of quantum interrogation allows one to optically detect the
presence of an absorbing object, without the measuring light interacting with
it. In an application of the quantum Zeno effect, the object inhibits the
otherwise coherent evolution of the light, such that the probability that an
interrogating photon is absorbed can in principle be arbitrarily small. We have
implemented this technique, demonstrating efficiencies exceeding the 50%
theoretical-maximum of the original ``interaction-free'' measurement proposal.
We have also predicted and experimentally verified a previously unsuspected
dependence on loss; efficiencies of up to 73% were observed and the feasibility
of efficiencies up to 85% was demonstrated.Comment: 4 pages, 3 postscript figures. To appear in Phys. Rev. Lett;
submitted June 11, 199
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Alzheimer's Associated β-Amyloid Protein Inhibits Influenza A Virus and Modulates Viral Interactions with Phagocytes
Accumulation of β-Amyloid (βA) is a key pathogenetic factor in Alzheimer's disease; however, the normal function of βA is unknown. Recent studies have shown that βA can inhibit growth of bacteria and fungi. In this paper we show that βA also inhibits replication of seasonal and pandemic strains of H3N2 and H1N1 influenza A virus (IAV) in vitro. The 42 amino acid fragment of βA (βA42) had greater activity than the 40 amino acid fragment. Direct incubation of the virus with βA42 was needed to achieve optimal inhibition. Using quantitative PCR assays βA42 was shown to reduce viral uptake by epithelial cells after 45 minutes and to reduce supernatant virus at 24 hours post infection. βA42 caused aggregation of IAV particles as detected by light transmission assays and electron and confocal microscopy. βA42 did not stimulate neutrophil H2O2 production or extracellular trap formation on its own, but it increased both responses stimulated by IAV. In addition, βA42 increased uptake of IAV by neutrophils. βA42 reduced viral protein synthesis in monocytes and reduced IAV-induced interleukin-6 production by these cells. Hence, we demonstrate for the first time that βA has antiviral activity and modulates viral interactions with phagocytes
Reduced influenza viral neutralizing activity of natural human trimers of surfactant protein D
BACKGROUND. Surfactant protein D (SP-D) plays important roles in innate host defense against influenza A virus (IAV) infection. Common human polymorphisms of SP-D have been found in many human populations and associated with increased risk of certain infections. We recently reported that the Thr/Thr 11 form of SP-D is associated with low serum levels and assembles predominantly as trimers as opposed to the more common multimeric forms of SP-D. METHODS. Preliminary experiments were done to establish the effects of different monoclonal antibodies against SP-D on ability of SP-D to bind to or neutralize the virus. We then purified natural human trimeric and multimeric forms of SP-D from amniotic fluid and tested ability of these preparations to bind to IAV, to inhibit infectivity and hemagglutination activity of IAV in vitro. RESULTS. In initial experiments mAbs directed against different areas on the CRD of SP-D were found to have differing effects on antiviral activity. Using an mAb that did not interfere with antiviral activity of SP-D, we confirm that natural SP-D trimers had reduced ability to bind to IAV. In addition, the trimers had reduced ability to neutralize IAV as compared to natural human SP-D multimers as well as reduced hemagglutination inhibiting activity against several strains of IAV. Natural SP-D trimers also had different interactions with human neutrophil peptide defensins (HNPs) in viral neutralization assays as compared to multimeric SP-D. CONCLUSION. These studies indicate that a common human polymorphic form of SP-D may modulate host defense against IAV and give impetus to clinical studies correlating this genotype with risk for IAV infection in susceptible groups. We also show that mAbs directed against different areas on the carbohydrate recognition domain of SP-D can be useful for dissecting out different functional properties of the protein
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