5,673 research outputs found
Central Neurocytoma: A Review of Clinical Management and Histopathologic Features.
Central neurocytoma (CN) is a rare, benign brain tumor often located in the lateral ventricles. CN may cause obstructive hydrocephalus and manifest as signs of increased intracranial pressure. The goal of treatment for CN is a gross total resection (GTR), which often yields excellent prognosis with a very high rate of tumor control and survival. Adjuvant radiosurgery and radiotherapy may be considered to improve tumor control when GTR cannot be achieved. Chemotherapy is also not considered a primary treatment, but has been used as a salvage therapy. The radiological features of CN are indistinguishable from those of other brain tumors; therefore, many histological markers, such as synaptophysin, can be very useful for diagnosing CNs. Furthermore, the MIB-1 Labeling Index seems to be correlated with the prognosis of CN. We also discuss oncogenes associated with these elusive tumors. Further studies may improve our ability to accurately diagnose CNs and to design the optimal treatment regimens for patients with CNs
Improving Cosmological Distance Measurements by Reconstruction of the Baryon Acoustic Peak
The baryon acoustic oscillations are a promising route to the precision
measure of the cosmological distance scale and hence the measurement of the
time evolution of dark energy. We show that the non-linear degradation of the
acoustic signature in the correlations of low-redshift galaxies is a
correctable process. By suitable reconstruction of the linear density field,
one can sharpen the acoustic peak in the correlation function or, equivalently,
restore the higher harmonics of the oscillations in the power spectrum. With
this, one can achieve better measurements of the acoustic scale for a given
survey volume. Reconstruction is particularly effective at low redshift, where
the non-linearities are worse but where the dark energy density is highest. At
z=0.3, we find that one can reduce the sample variance error bar on the
acoustic scale by at least a factor of 2 and in principle by nearly a factor of
4. We discuss the significant implications our results have for the design of
galaxy surveys aimed at measuring the distance scale through the acoustic peak.Comment: 5 pages, LaTeX. Submitted to the Astrophysical Journa
Reliable Multivalued Conductance States in TaOx, Memristors through Oxygen Plasma-Assisted Electrode Deposition with in Situ-Biased Conductance State Transmission Electron Microscopy Analysis
Transition metal oxide-based memristors have widely been proposed for applications toward artificial synapses. In general, memristors have two or more electrically switchable stable resistance states that device researchers see as an analogue to the ion channels found in biological synapses. The mechanism behind resistive switching in metal oxides has been divided into electrochemical metallization models and valence change models. The stability of the resistance states in the memristor vary widely depending on: oxide material, electrode material, deposition conditions, film thickness, and programming conditions. So far, it has been extremely challenging to obtain reliable memristors with more than two stable multivalued states along with endurances greater than similar to 1000 cycles for each of those states. Using an oxygen plasma-assisted sputter deposition method of noble metal electrodes, we found that the metal-oxide interface could be deposited with substantially lower interface roughness observable at the nanometer scale. This markedly improved device reliability and function, allowing for a demonstration of memristors with four completely distinct levels from similar to 6 x 10(-6) to similar to 4 x 10(-8) S that were tested up to 10(4) cycles per level. Furthermore through a unique in situ transmission electron microscopy study, we were able to verify a redox reaction-type model to be dominant in our samples, leading to the higher degree of electrical state controllability. For solid-state synapse applications, the improvements to electrical properties will lead to simple device structures, with an overall power and area reduction of at least 1000 times when compared to SRAM.11Ysciescopu
Baryon Acoustic Oscillations in the Sloan Digital Sky Survey Data Release 7 Galaxy Sample
The spectroscopic Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) galaxy
sample represents the final set of galaxies observed using the original SDSS
target selection criteria. We analyse the clustering of galaxies within this
sample, including both the Luminous Red Galaxy (LRG) and Main samples, and also
include the 2-degree Field Galaxy Redshift Survey (2dFGRS) data. Baryon
Acoustic Oscillations are observed in power spectra measured for different
slices in redshift; this allows us to constrain the distance--redshift relation
at multiple epochs. We achieve a distance measure at redshift z=0.275, of
r_s(z_d)/D_V(0.275)=0.1390+/-0.0037 (2.7% accuracy), where r_s(z_d) is the
comoving sound horizon at the baryon drag epoch,
D_V(z)=[(1+z)^2D_A^2cz/H(z)]^(1/3), D_A(z) is the angular diameter distance and
H(z) is the Hubble parameter. We find an almost independent constraint on the
ratio of distances D_V(0.35)/D_V(0.2)=1.736+/-0.065, which is consistent at the
1.1sigma level with the best fit Lambda-CDM model obtained when combining our
z=0.275 distance constraint with the WMAP 5-year data. The offset is similar to
that found in previous analyses of the SDSS DR5 sample, but the discrepancy is
now of lower significance, a change caused by a revised error analysis and a
change in the methodology adopted, as well as the addition of more data. Using
WMAP5 constraints on Omega_bh^2 and Omega_ch^2, and combining our BAO distance
measurements with those from the Union Supernova sample, places a tight
constraint on Omega_m=0.286+/-0.018 and H_0 = 68.2+/-2.2km/s/Mpc that is robust
to allowing curvature and non-Lambda dark energy. This result is independent of
the behaviour of dark energy at redshifts greater than those probed by the BAO
and supernova measurements. (abridged)Comment: 22 pages, 16 figures, minor changes to match version published in
MNRA
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey : measuring DA and H at z = 0.57 from the baryon acoustic peak in the Data Release 9 spectroscopic Galaxy sample
We present measurements of the angular diameter distance to and Hubble parameter at z = 0.57 from the measurement of the baryon acoustic peak in the correlation of galaxies from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey. Our analysis is based on a sample from Data Release 9 of 264 283 galaxies over 3275 square degrees in the redshift range 0.43 < z < 0.70. We use two different methods to provide robust measurement of the acoustic peak position across and along the line of sight in order to measure the cosmological distance scale. We find DA(0.57) = 1408 ± 45 Mpc and H(0.57) = 92.9 ± 7.8 km s−1 Mpc−1 for our fiducial value of the sound horizon. These results from the anisotropic fitting are fully consistent with the analysis of the spherically averaged acoustic peak position presented in Anderson et al. Our distance measurements are a close match to the predictions of the standard cosmological model featuring a cosmological constant and zero spatial curvature.Publisher PDFPeer reviewe
Probing ISM Structure in Trumpler 14 & Carina I Using The Stratospheric Terahertz Observatory 2
We present observations of the Trumpler 14/Carina I region carried out using
the Stratospheric Terahertz Observatory 2 (STO2). The Trumpler 14/Carina I
region is in the west part of the Carina Nebula Complex, which is one of the
most extreme star-forming regions in the Milky Way. We observed Trumpler
14/Carina I in the 158 m transition of [C\,{\sc ii}] with a spatial
resolution of 48 and a velocity resolution of 0.17 km s. The
observations cover a 0.25 by 0.28 area with central position
{\it l} = 297.34, {\it b} = -0.60. The kinematics show that
bright [C\,{\sc ii}] structures are spatially and spectrally correlated with
the surfaces of CO clouds, tracing the photodissociation region and ionization
front of each molecular cloud. Along 7 lines of sight that traverse Tr 14 into
the dark ridge to the southwest, we find that the [C\,{\sc ii}] luminosity from
the HII region is 3.7 times that from the PDR. In same los we find in the PDRs
an average ratio of 1:4.1:5.6 for the mass in atomic gas:dark-CO gas: molecular
gas traced by CO. Comparing multiple gas tracers including HI 21cm, [C\,{\sc
ii}], CO, and radio recombination lines, we find that the HII regions of the
Carina Nebula Complex are well-described as HII regions with one-side freely
expanding towards us, consistent with the champagne model of ionized gas
evolution. The dispersal of the GMC in this region is dominated by EUV
photoevaporation; the dispersal timescale is 20-30 Myr.Comment: ApJ accepte
VirMAP for Cancer: Characterization of the Intratumoral Virome in Virally-Associated Cancers and a Resource for Investigators
View full abstracthttps://openworks.mdanderson.org/leading-edge/1040/thumbnail.jp
Halo Occupation Distribution Modeling of Clustering of Luminous Red Galaxies
We perform Halo Occupation Distribution (HOD) modeling to interpret
small-scale and intermediate-scale clustering of 35,000 luminous early-type
galaxies and their cross-correlation with a reference imaging sample of normal
L* galaxies in the Sloan Digital Sky Survey. The modeling results show that
most of these luminous red galaxies (LRGs) are central galaxies residing in
massive halos of typical mass M ~ a few times 10^13 to 10^14 Msun/h, while a
few percent of them have to be satellites within halos in order to produce the
strong auto-correlations exhibited on smaller scales. The mean luminosity Lc of
central LRGs increases with the host halo mass, with a rough scaling relation
of Lc \propto M^0.5. The halo mass required to host on average one satellite
LRG above a luminosity threshold is found to be about 10 times higher than that
required to host a central LRG above the same threshold. We find that in
massive halos the distribution of L* galaxies roughly follows that of the dark
matter and their mean occupation number scales with halo mass as M^1.5. The HOD
modeling results also allows for an intuitive understanding of the
scale-dependent luminosity dependence of the cross-correlation between LRGs and
L_* galaxies. Constraints on the LRG HOD provide tests to models of formation
and evolution of massive galaxies, and they are also useful for cosmological
parameter investigations. In one of the appendices, we provide LRG HOD
parameters with dependence on cosmology inferred from modeling the two-point
auto-correlation functions of LRGs.Comment: 21 pages, 10 figures, accepted for publication in Ap
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey : baryon acoustic oscillations in the Data Releases 10 and 11 Galaxy samples
We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations (BAO) in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey, which is part of the Sloan Digital Sky Survey III. Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately 8500 square degrees and the redshift range 0.2 < z < 0.7. We also compare these results with those from the publicly released DR9 and DR10 samples. Assuming a concordance Λ cold dark matter (ΛCDM) cosmological model, the DR11 sample covers a volume of 13 Gpc3 and is the largest region of the Universe ever surveyed at this density. We measure the correlation function and power spectrum, including density-field reconstruction of the BAO feature. The acoustic features are detected at a significance of over 7σ in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, rd, which has a value of rd,fid = 149.28 Mpc in our fiducial cosmology. We find DV = (1264 ± 25 Mpc)(rd/rd,fid) at z = 0.32 and DV = (2056 ± 20 Mpc)(rd/rd,fid) at z = 0.57. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line of sight yields measurements at z = 0.57 of DA = (1421 ± 20 Mpc)(rd/rd,fid) and H = (96.8 ± 3.4 km s−1 Mpc−1)(rd,fid/rd). Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat CDM model with a cosmological constant.Publisher PDFPeer reviewe
- …