679 research outputs found
Infrared study of spin crossover Fe-picolylamine complex
Infrared (IR) absorption spectroscopy has been used to probe the evolution of
microscopic vibrational states upon the temperature- and photo-induced spin
crossovers in [Fe(2-picolylamine)3]Cl2EtOH (Fe-pic). To overcome the small
sizes and the strong IR absorption of the crystal samples used, an IR
synchrotron radiation source and an IR microscope have been used. The obtained
IR spectra of Fe-pic show large changes between high-spin and low-spin states
for both the temperature- and the photo- induced spin crossovers. Although the
spectra in the temperature- and photo-induced high-spin states are relatively
similar to each other, they show distinct differences below 750 cm-1. This
demonstrates that the photo-induced high-spin state involves microscopically
different characters from those of the temperature-induced high-spin state. The
results are discussed in terms of local pressure and structural deformations
within the picolylamine ligands, and in terms of their possible relevance to
the development of macroscopic photo-induced phase in Fe-pic.Comment: 6 pages (text) and 6 figures,submitted to J. Phys. Soc. Jp
Brilliant Pebbles: A Method for Detection of Very Large Interstellar Grains
A photon of wavelength lambda ~1 micron interacting with a dust grain of
radius a_p ~ 1 mm (a "pebble") undergoes scattering in the forward direction,
largely within a small characteristic diffraction angle theta_s ~ lambda/a_p ~
100". Though mm-size dust grains contribute negligibly to the interstellar
medium's visual extinction, the signal they produce in scattered light may be
detectable, especially for variable sources. Observations of light scattered at
small angles allows for the direct measurement of the large grain population;
variable sources can also yield tomographic information of the interstellar
medium's mass distribution. The ability to detect brilliant pebble halos
require a careful understanding of the instrument PSF.Comment: 5 pages, ApJL accepte
Upper Limits to Fluxes of Neutrinos and Gamma-Rays from Starburst Galaxies
Loeb and Waxman have argued that high energy neutrinos from the decay of
pions produced in interactions of cosmic rays with interstellar gas in
starburst galaxies would be produced with a large enough flux to be observable.
Here we obtain an upper limit to the diffuse neutrino flux from starburst
galaxies which is a factor of 5 lower than the flux which they predict.
Compared with predicted fluxes from other extragalactic high energy neutrino
sources, starburst neutrinos with PeV energies would have a flux
considerably below that predicted for AGN models. We also estimate an upper
limit for the diffuse GeV -ray flux from starbust galaxies to be
of the observed -ray background, much less than
the component from unresolved blazars.Comment: 4 pages, for Proc. TeV2 Conf., Madison, WI, to be published in J.
Phy
Characterizing Cosmic-Ray Propagation in Massive Star-forming Regions: The Case of 30 Doradus and the Large Magellanic Cloud
Using infrared, radio, and γ-ray data, we investigate the propagation characteristics of cosmic-ray (CR) electrons and nuclei in the 30 Doradus (30 Dor) star-forming region in the Large Magellanic Cloud (LMC) using a phenomenological model based on the radio-far-infrared correlation within galaxies. Employing a correlation analysis, we derive an average propagation length of ~100-140 pc for ~3 GeV CR electrons resident in 30 Dor from consideration of the radio and infrared data. Assuming that the observed γ-ray emission toward 30 Dor is associated with the star-forming region, and applying the same methodology to the infrared and γ-ray data, we estimate a ~20 GeV propagation length of 200-320 pc for the CR nuclei. This is approximately twice as large as for ~3 GeV CR electrons, corresponding to a spatial diffusion coefficient that is ~4 times higher, scaling as (R/GV)δ with δ ≈ 0.7-0.8 depending on the smearing kernel used in the correlation analysis. This value is in agreement with the results found by extending the correlation analysis to include ~70 GeV CR nuclei traced by the 3-10 GeV γ-ray data (δ ≈ 0.66 ± 0.23). Using the mean age of the stellar populations in 30 Dor and the results from our correlation analysis, we estimate a diffusion coefficient D_R ≈ (0.9-1.0) × 10^(27)(R/GV)0.7 cm^(2) s^(–1). We compare the values of the CR electron propagation length and surface brightness for 30 Dor and the LMC as a whole with those of entire disk galaxies. We find that the trend of decreasing average CR propagation distance with increasing disk-averaged star formation activity holds for the LMC, and extends down to single star-forming regions, at least for the case of 30 Dor
Experimental and Numerical Analysis of Wind Turbine
The objective of this Paper is to design and build a self-starting vertical axis wind turbine that is capable of producing power in real world situations. The design of the turbine will include exploration of various self-starting options, as well as the construction of both mode land fullscale turbines. The full-scale turbine will be designed such that it can be connected to a generator and a torque transducer to measure the output power, torque and rotational speed of the turbine. The design will also allow for data collection regarding the effects of blade pitch angles. Here compare both experimental and simulation analysis by using CFD and As a result of the engineering analysis carried out for the NACA 0012 and it had been designed in design software Catia and the flow analysis was carried out in CFD by using Fluent and CFX softwar
The Effect of Starburst Metallicity on Bright X-Ray Binary Formation Pathways
We investigate the characteristics of young ( 1e36
erg/s) High-Mass X-ray Binaries (HMXBs) and find the population to be strongly
metallicity-dependent. We separate the model populations among two distinct
formation pathways: (1) systems undergoing active Roche Lobe Overflow (RLO),
and (2) wind accretion systems with donors in the (super)giant (SG) stage,
which we find to dominate the HMXB population. We find metallicity to primarily
affect the number of systems which move through each formation pathway, rather
than the observable parameters of systems which move through each individual
pathway. We discuss the most important model parameters affecting the HMXB
population at both low and high metallicities. Using these results, we show
that (1) the population of ultra-luminous X-Ray sources can be consistently
described by very bright HMXBs which undergo stable Roche Lobe overflow with
mild super-Eddington accretion and (2) the HMXB population of the bright
starburst galaxy NGC~1569 is likely dominated by one extremely metal-poor
starburst cluster.Comment: 12 pages, 10 figures, Accepted by Ap
Precision Astrometry with the Very Long Baseline Array: Parallaxes and Proper Motions for 14 Pulsars
Astrometry can bring powerful constraints to bear on a variety of scientific
questions about neutron stars, including their origins, astrophysics,
evolution, and environments. Using phase-referenced observations at the VLBA,
in conjunction with pulsar gating and in-beam calibration, we have measured the
parallaxes and proper motions for 14 pulsars. The smallest measured parallax in
our sample is 0.13+-0.02 mas for PSR B1541+09, which has a most probable
distance of 7.2+1.3-1.1 kpc. We detail our methods, including initial VLA
surveys to select candidates and find in-beam calibrators, VLBA
phase-referencing, pulsar gating, calibration, and data reduction. The use of
the bootstrap method to estimate astrometric uncertainties in the presence of
unmodeled systematic errors is also described. Based on our new
model-independent estimates for distance and transverse velocity, we
investigate the kinematics and birth sites of the pulsars and revisit models of
the Galactic electron density distribution. We find that young pulsars are
moving away from the Galactic plane, as expected, and that age estimates from
kinematics and pulsar spindown are generally in agreement, with certain notable
exceptions. Given its present trajectory, the pulsar B2045-16 was plausibly
born in the open cluster NGC 6604. For several high-latitude pulsars, the
NE2001 electron density model underestimates the parallax distances by a factor
of two, while in others the estimates agree with or are larger than the
parallax distances, suggesting that the interstellar medium is irregular on
relevant length scales. The VLBA astrometric results for the recycled pulsar
J1713+0747 are consistent with two independent estimates from pulse timing,
enabling a consistency check between the different reference frames.Comment: 16 pages, 9 figures, 4 tables; results unchanged; revised version
accepted by Ap
Immunogenicity of a Prime-Boost Vaccine Containing the Circumsporozoite Proteins of Plasmodium vivax in Rodents
Plasmodium vivax is the most widespread and the second most prevalent malaria-causing species in the world. Current measures used to control the transmission of this disease would benefit from the development of an efficacious vaccine. in the case of the deadly parasite P. falciparum, the recombinant RTS,S vaccine containing the circumsporozoite antigen (CSP) consistently protects 30 to 50% of human volunteers against infection and is undergoing phase III clinical trials in Africa with similar efficacy. These findings encouraged us to develop a P. vivax vaccine containing the three circulating allelic forms of P. vivax CSP. Toward this goal, we generated three recombinant bacterial proteins representing the CSP alleles, as well as a hybrid polypeptide called PvCSP-All-CSP-epitopes. This hybrid contains the conserved N and C termini of P. vivax CSP and the three variant repeat domains in tandem. We also generated simian and human recombinant replication-defective adenovirus vectors expressing PvCSP-All-CSP-epitopes. Mice immunized with the mixture of recombinant proteins in a formulation containing the adjuvant poly(I.C) developed high and long-lasting serum IgG titers comparable to those elicited by proteins emulsified in complete Freund's adjuvant. Antibody titers were similar in mice immunized with homologous (protein-protein) and heterologous (adenovirus- protein) vaccine regimens. the antibodies recognized the three allelic forms of CSP, reacted to the repeated and nonrepeated regions of CSP, and recognized sporozoites expressing the alleles VK210 and VK247. the vaccine formulations described in this work should be useful for the further development of an anti-P. vivax vaccine.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)PNPDCoordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES)Universidade Federal de São Paulo, Escola Paulista Med, Ctr Terapia Celular & Mol CTCMol, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, São Paulo, BrazilWistar Inst Anat & Biol, Philadelphia, PA 19104 USAMalaria Vaccine & Drug Dev Ctr, Cali, ColombiaUniv Fed Santa Catarina, Dept Microbiol Imunol & Parasitol, Florianopolis, SC, BrazilUniv São Paulo, Fac Ciencias Farmaceut, Dept Anal Clin & Toxicol, São Paulo, BrazilNYU, Sch Med, Dept Pathol, Michael Heidelberger Div, New York, NY USAUniversidade Federal de São Paulo, Escola Paulista Med, Ctr Terapia Celular & Mol CTCMol, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, São Paulo, BrazilFAPESP: 2009/15432-4FAPESP: 2012/13032-5CNPq: 471087/2013-0Web of Scienc
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