18,046 research outputs found
Protocluster Discovery in Tomographic Ly Forest Flux Maps
We present a new method of finding protoclusters using tomographic maps of
Ly Forest flux. We review our method of creating tomographic flux maps
and discuss our new high performance implementation, which makes large
reconstructions computationally feasible. Using a large N-body simulation, we
illustrate how protoclusters create large-scale flux decrements, roughly 10
Mpc across, and how we can use this signal to find them in flux maps.
We test the performance of our protocluster finding method by running it on the
ideal, noiseless map and tomographic reconstructions from mock surveys, and
comparing to the halo catalog. Using the noiseless map, we find protocluster
candidates with about 90% purity, and recover about 75% of the protoclusters
that form massive clusters (). We
construct mock surveys similar to the ongoing COSMOS Lyman-Alpha Mapping And
Tomography Observations (CLAMATO) survey. While the existing data has an
average sightline separation of 2.3 Mpc, we test separations of 2 - 6
Mpc to see what can be tolerated for our application. Using
reconstructed maps from small separation mock surveys, the protocluster
candidate purity and completeness are very close what was found in the
noiseless case. As the sightline separation increases, the purity and
completeness decrease, although they remain much higher than we initially
expected. We extended our test cases to mock surveys with an average separation
of 15 Mpc, meant to reproduce high source density areas of the BOSS
survey. We find that even with such a large sightline separation, the method
can still be used to find some of the largest protoclusters.Comment: 18 pages, 12 figure
Observational Requirements for Lyman-alpha Forest Tomographic Mapping of Large-Scale Structure at z ~ 2
The z > 2 Lyman-alpha (Lya) forest traces the underlying dark-matter
distribution on large scales and, given sufficient sightlines, can be used to
create 3D maps of large-scale structure. We examine the observational
requirements to construct such maps and estimate the signal-to-noise as a
function of exposure time and sightline density. Sightline densities at z =
2.25 are n_los = [360, 1200,3300] deg^{-2} at limiting magnitudes of g =[24.0,
24.5,25.0], resulting in transverse sightline separations of d_perp = [3.6,
1.9, 1.2] h^{-1} Mpc, which roughly sets the reconstruction scale. We simulate
these reconstructions using mock spectra with realistic noise properties, and
find that spectra with S/N = 4 per angstrom can be used to generate maps that
clearly trace the underlying dark-matter at overdensities of rho/ ~ 1. For
the VLT/VIMOS spectrograph, exposure times t_exp = [4, 6, 10] hrs are
sufficient for maps with spatial resolution epsilon_3d = [5.0, 3.2, 2.3] h^{-1}
Mpc. Assuming ~ 250 h^{-1} Mpc is probed along the line-of-sight, 1 deg^2 of
survey area would cover a comoving volume of ~ 10^6 h^{-3} Mpc^3 at =2.3,
enabling efficient mapping of large volumes with 8-10m telescopes. These maps
could be used to study galaxy environments, detect proto-clusters, and study
the topology of large-scale structure at high-z.Comment: 18 pages, 10 figures. Accepted by Ap
Genotypic Analysis of the Canine MultiDrug Resistance 1 (ABCB1) gene in Miniature American and Australian Shephards
Canine breeders who are breeding to improve genetics often utilize the ability to test breeding stock for deleterious alleles. A DNA sample, such as a cheek swab or blood sample, is sent to laboratory where they determine genotypes that the owner has requested to know. Once the breeder receives results, they are better able to plan crosses or decide if a dog should be castrated to avoid the inheritance of unwanted diseases. This is particularly important with purebred dogs due to the high ratio of homozygous alleles. I will be using canine DNA for the gene ABCB1 or Multidrug Resistance 1. Samples for this study were collected from the Miniature American Shepherd, Miniature Australian Shepherd, and Australian Shepherd breeds, all which are known to carry the ABCB1 gene. Paw Print Genetics (Spokane, WA) provided 6 DNA samples of known genotype for use as controls
Magnetic susceptibility study of hydrated and non-hydrated NaxCoO2-yH2O single crystals
We have measured the magnetic susceptibility of single crystal samples of
non-hydrated NaxCoO2 (x ~ 0.75, 0.67, 0.5, and 0.3) and hydrated Na0.3CoO2-yH2O
(y ~ 0, 0.6, 1.3). Our measurements reveal considerable anisotropy between the
susceptibilities with H||c and H||ab. The derived anisotropic g-factor ratio
(g_ab/g_c) decreases significantly as the composition is changed from the
Curie-Weiss metal with x = 0.75 to the paramagnetic metal with x = 0.3. Fully
hydrated Na0.3CoO2-1.3H2O samples have a larger susceptibility than
non-hydrated Na0.3CoO2 samples, as well as a higher degree of anisotropy. In
addition, the fully hydrated compound contains a small additional fraction of
anisotropic localized spins.Comment: 6 pages, 5 figure
Measurement of the small-scale structure of the intergalactic medium using close quasar pairs
The distribution of diffuse gas in the intergalactic medium (IGM) imprints a
series of hydrogen absorption lines on the spectra of distant background
quasars known as the Lyman- forest. Cosmological hydrodynamical
simulations predict that IGM density fluctuations are suppressed below a
characteristic scale where thermal pressure balances gravity. We measured this
pressure-smoothing scale by quantifying absorption correlations in a sample of
close quasar pairs. We compared our measurements to hydrodynamical simulations,
where pressure smoothing is determined by the integrated thermal history of the
IGM. Our findings are consistent with standard models for photoionization
heating by the ultraviolet radiation backgrounds that reionized the universe.Comment: Accepted for publication on Scienc
Myeloid suppressor cell depletion augments antitumor activity in lung cancer.
BackgroundMyeloid derived suppressor cells (MDSC) are important regulators of immune responses. We evaluated the mechanistic role of MDSC depletion on antigen presenting cell (APC), NK, T cell activities and therapeutic vaccination responses in murine models of lung cancer.Principal findingsIndividual antibody mediated depletion of MDSC (anti-Gr1 or anti-Ly6G) enhanced the antitumor activity against lung cancer. In comparison to controls, MDSC depletion enhanced the APC activity and increased the frequency and activity of the NK and T cell effectors in the tumor. Compared to controls, the anti-Gr1 or anti-Ly6G treatment led to increased: (i) CD8 T cells, (ii) NK cells, (iii) CD8 T or NK intracytoplasmic expression of IFNΞ³, perforin and granzyme (iv) CD3 T cells expressing the activation marker CD107a and CXCR3, (v) reduced CD8 T cell IL-10 production in the tumors (vi) reduced tumor angiogenic (VEGF, CXCL2, CXCL5, and Angiopoietin1&2) but enhanced anti-angiogenic (CXCL9 and CXCL10) expression and (vii) reduced tumor staining of endothelial marker Meca 32. Immunocytochemistry of tumor sections showed reduced Gr1 expressing cells with increased CD3 T cell infiltrates in the anti-Gr1 or anti-Ly6G groups. MDSC depletion led to a marked inhibition in tumor growth, enhanced tumor cell apoptosis and reduced migration of the tumors from the primary site to the lung compared to controls. Therapeutic vaccination responses were enhanced in vivo following MDSC depletion with 50% of treated mice completely eradicating established tumors. Treated mice that rejected their primary tumors acquired immunological memory against a secondary tumor challenge. The remaining 50% of mice in this group had 20 fold reductions in tumor burden compared to controls.SignificanceOur data demonstrate that targeting MDSC can improve antitumor immune responses suggesting a broad applicability of combined immune based approaches against cancer. This multifaceted approach may prove useful against tumors where MDSC play a role in tumor immune evasion
Dexfenfluramine and the oestrogen-metabolizing enzyme CYP1B1 in the development of pulmonary arterial hypertension
<p>Aims: Pulmonary arterial hypertension (PAH) occurs more frequently in women than men. Oestrogen and the oestrogen-metabolising enzyme cytochrome P450 1B1 (CYP1B1) play a role in the development of PAH. Anorectic drugs such as dexfenfluramine (Dfen) have been associated with the development of PAH. Dfen mediates PAH via a serotonergic mechanism and we have shown serotonin to up-regulate expression of CYP1B1 in human pulmonary artery smooth muscle cells (PASMCs). Thus here we assess the role of CYP1B1 in the development of Dfen-induced PAH.</p>
<p>Methods and results: Dfen (5 mg kgβ1 dayβ1 PO for 28 days) increased right ventricular pressure and pulmonary vascular remodelling in female mice only. Mice dosed with Dfen showed increased whole lung expression of CYP1B1 and Dfen-induced PAH was ablated in CYP1B1β/β mice. In line with this, Dfen up-regulated expression of CYP1B1 in PASMCs from PAH patients (PAH-PASMCs) and Dfen-mediated proliferation of PAH-PASMCs was ablated by pharmacological inhibition of CYP1B1. Dfen increased expression of tryptophan hydroxylase 1 (Tph1; the rate-limiting enzyme in the synthesis of serotonin) in PAH-PASMCs and both Dfen-induced proliferation and Dfen-induced up-regulation of CYP1B1 were ablated by inhibition of Tph1. 17Ξ²-Oestradiol increased expression of both Tph1 and CYP1B1 in PAH-PASMCs, and Dfen and 17Ξ²-oestradiol had synergistic effects on proliferation of PAH-PASMCs. Finally, ovariectomy protected against Dfen-induced PAH in female mice.</p>
<p>Conclusion: CYP1B1 is critical in the development of Dfen-induced PAH in mice in vivo and proliferation of PAH-PASMCs in vitro. CYP1B1 may provide a novel therapeutic target for PAH.</p>
A deep X-ray observation of supernova remnant G304.6+0.1 (Kes 17) with Suzaku
In this paper, we present the analysis of a deep (99.6 ks) observation of
G304.6 + 0.1 with the X-ray Imaging Spectrometer on board {\it Suzaku}
satellite. The X-ray spectral data are well-fitted with a plasma model
consisting of a thermal component in collisional ionization equilibrium and a
non-thermal component. The thermal emission is well fitted with VMEKAL model
with an electron temperature of keV, a high absorbing
column density of and near/lower
solar abundances which indicate that the X-ray emitting plasma of G304.6 + 0.1
is dominated by swept-up ambient medium. The non-thermal component is well
fitted with a power-law model with photon index of . We found
a relatively high electron density cm, age
yr, and X-ray emitting mass {M\sun} at an adopted distance of d=10 kpc. Using the morphological
and spectral X-ray data, we confirm that the remnant is a new member of
mixed-morphology supernova remnants.Comment: 8 pages, 4 figures, 2 table
Evolution of the Density of States Gap in a Disordered Superconductor
It has only recently been possible to study the superconducting state in the
attractive Hubbard Hamiltonian via a direct observation of the formation of a
gap in the density of states N(w). Here we determine the effect of random
chemical potentials on N(w) and show that at weak coupling, disorder closes the
gap concurrently with the destruction of superconductivity. At larger, but
still intermediate coupling, a pseudo-gap in N(w) remains even well beyond the
point at which off-diagonal long range order vanishes. This change in the
elementary excitations of the insulating phase corresponds to a crossover
between Fermi- and Bose-Insulators. These calculations represent the first
computation of the density of states in a finite dimensional disordered fermion
model via the Quantum Monte Carlo and maximum entropy methods.Comment: 4 pages, 4 figure
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