1,724 research outputs found
Motor brush wear measured with strain gages
Balanced bridge circuit, supplied with low-voltage direct current and connected to a readout device, measures remaining brush material, rate of brush wear, armature runout, and brush signature
The GALFA-HI Compact Cloud Catalog
We present a catalog of 1964 isolated, compact neutral hydrogen clouds from
the Galactic Arecibo L-Band Feed Array Survey Data Release One (GALFA-HI DR1).
The clouds were identified by a custom machine-vision algorithm utilizing
Difference of Gaussian kernels to search for clouds smaller than 20'. The
clouds have velocities typically between |VLSR| = 20-400 km/s, linewidths of
2.5-35 km/s, and column densities ranging from 1 - 35 x 10^18 cm^-2. The
distances to the clouds in this catalog may cover several orders of magnitude,
so the masses may range from less than a Solar mass for clouds within the
Galactic disc, to greater than 10^4 Solar Masses for HVCs at the tip of the
Magellanic Stream. To search for trends, we separate the catalog into five
populations based on position, velocity, and linewidth: high velocity clouds
(HVCs); galaxy candidates; cold low velocity clouds (LVCs); warm, low
positive-velocity clouds in the third Galactic Quadrant; and the remaining warm
LVCs. The observed HVCs are found to be associated with previously-identified
HVC complexes. We do not observe a large population of isolated clouds at high
velocities as some models predict. We see evidence for distinct histories at
low velocities in detecting populations of clouds corotating with the Galactic
disc and a set of clouds that is not corotating.Comment: 34 Pages, 9 Figures, published in ApJ (2012, ApJ, 758, 44), this
version has the corrected fluxes and corresponding flux histogram and masse
Ongoing Galactic Accretion: Simulations and Observations of Condensed Gas in Hot Halos
Ongoing accretion onto galactic disks has been recently theorized to progress
via the unstable cooling of the baryonic halo into condensed clouds. These
clouds have been identified as analogous to the High-Velocity Clouds (HVCs)
observed in HI in our Galaxy. Here we compare the distribution of HVCs observed
around our own Galaxy and extra-planar gas around the Andromeda galaxy to these
possible HVC analogs in a simulation of galaxy formation that naturally
generates these condensed clouds. We find a very good correspondence between
these observations and the simulation, in terms of number, angular size,
velocity distribution, overall flux and flux distribution of the clouds. We
show that condensed cloud accretion only accounts for ~ 0.2 M_solar / year of
the current overall Galactic accretion in the simulations. We also find that
the simulated halo clouds accelerate and become more massive as they fall
toward the disk. The parameter space of the simulated clouds is consistent with
all of the observed HVC complexes that have distance constraints, except the
Magellanic Stream which is known to have a different origin. We also find that
nearly half of these simulated halo clouds would be indistinguishable from
lower-velocity gas and that this effect is strongest further from the disk of
the galaxy, thus indicating a possible missing population of HVCs. These
results indicate that the majority of HVCs are consistent with being infalling,
condensed clouds that are a remnant of Galaxy formation.Comment: 10 pages, 6 figures, ApJ Accepted. Some changes to techniqu
H^+_2$ in a strong magnetic field described via a solvable model
We consider the hydrogen molecular ion in the presence of a strong
homogeneous magnetic field. In this regime, the effective Hamiltonian is almost
one dimensional with a potential energy which looks like a sum of two Dirac
delta functions. This model is solvable, but not close enough to our exact
Hamiltonian for relevant strenght of the magnnetic field. However we show that
the correct values of the equilibrium distance as well as the binding energy of
the ground state of the ion, can be obtained when incorporating perturbative
corrections up to second order. Finally, we show that exists for
sufficiently large magnetic fields
Prognostic and predictive value of circulating tumor cells and CXCR4 expression as biomarkers for a CXCR4 peptide antagonist in combination with carboplatin-etoposide in small cell lung cancer: exploratory analysis of a phase II study.
Background Circulating tumor cells (CTCs) and chemokine (C-X-C motif) receptor 4 (CXCR4) expression in CTCs and tumor tissue were evaluated as prognostic or predictive markers of CXCR4 peptide antagonist LY2510924 plus carboplatin-etoposide (CE) versus CE in extensive-stage disease small cell lung cancer (ED-SCLC). Methods This exploratory analysis of a phase II study evaluated CXCR4 expression in baseline tumor tissue and peripheral blood CTCs and in post-treatment CTCs. Optimum cutoff values were determined for CTC counts and CXCR4 expression in tumors and CTCs as predictors of survival outcome. Kaplan-Meier estimates and hazard ratios were used to determine biomarker prognostic and predictive values. Results There was weak positive correlation at baseline between CXCR4 expression in tumor tissue and CTCs. Optimum cutoff values were H-score ≥ 210 for CXCR4+ tumor, ≥7% CTCs with CXCR4 expression (CXCR4+ CTCs), and ≥6 CTCs/7.5 mL blood. Baseline H-score for CXCR4+ tumor was not prognostic of progression-free survival (PFS) or overall survival (OS). Baseline CXCR4+ CTCs ≥7% was prognostic of shorter PFS. CTCs ≥6 at baseline and cycle 2, day 1 were prognostic of shorter PFS and OS. None of the biomarkers at their respective optimum cutoffs was predictive of treatment response of LY2510924 plus CE versus CE. Conclusions In patients with ED-SCLC, baseline CXCR4 expression in tumor tissue was not prognostic of survival or predictive of LY2510924 treatment response. Baseline CXCR4+ CTCs ≥7% was prognostic of shorter PFS. CTC count ≥6 at baseline and after 1 cycle of treatment were prognostic of shorter PFS and OS
Risk factors and outcomes of contrast-induced nephropathy in hospitalised South Africans
Background. Despite ranking third as a cause of hospital-acquired acute kidney injury (AKI), iatrogenic contrast-induced nephropathy (CIN) impacts significantly on morbidity and mortality and is associated with high hospital costs. In sub-Saharan Africa, the rates and risk factors for CIN and patient outcomes remain unexplored.Methods. We conducted a prospective observational study at the Charlotte Maxeke Johannesburg Academic Hospital, South Africa, from 1 July 2014 to 30 July 2015. Hospitalised patients undergoing computed tomography scan contrast media administration and angiography were consecutively recruited to the study and followed up for development of AKI. CIN was defined as an increase in serum creatinine >25% or an absolute increase of >44 μmol/L from baseline at 48 - 72 hours post exposure to contrast media. Outcome variables were the occurrence of CIN, length of hospitalisation and in-hospital mortality.Results. We recruited 371 hospitalised patients with a mean (standard deviation) age of 49.3 (15.9). The rates of CIN, assessed using an absolute or relative increase in serum creatinine from baseline, were 4.6% and 16.4%, respectively. Anaemia was an independent predictor for the development of CIN (risk ratio (RR) 1.71, 95% confidence interval (CI) 1.01 - 2.87; p=0.04). The median serum albumin was 34 g/L (interquartile range (IQR) 29 - 39.5) and 38 g/L (IQR 31 - 42) in the CIN and control groups, respectively (p=0.01), and showed a significant trend for CIN development (RR 1.68, 95% CI 0.96 - 2.92; p=0.06). Mortality was significantly increased in the CIN group (22.4% v. 6.8%; p<0.001), and CIN together with anaemia increased mortality twofold (RR 2.39, 95% CI 1.20 - 4.75; p=0.01) and threefold (RR 3.32, 95% CI 1.48 - 7.43; p=0.003), respectively.Conclusions. CIN has a relatively high incidence in sub-Saharan Africa and predicts poorer clinical outcomes. The presence of CIN and anaemia positively predicted mortality. Caution should be exercised in patients with hypoalbuminaemia and anaemia undergoing contrast media administration
Minnesota K-12 Education: The Current Debate, The Present Condition.
A review and analysis of the debate on public education in Minnesota, the book includes a history of educational change in Minnesota, a description of trends in the early 1980s affecting schools in Minnesota, challenges facing education today, and a policy framework for understanding Minnesota public education.CURA/College of Education Project on the Future of K-12 Public Education in Minnesota
Entanglement and Timing-Based Mechanisms in the Coherent Control of Scattering Processes
The coherent control of scattering processes is considered, with electron
impact dissociation of H used as an example. The physical mechanism
underlying coherently controlled stationary state scattering is exposed by
analyzing a control scenario that relies on previously established entanglement
requirements between the scattering partners. Specifically, initial state
entanglement assures that all collisions in the scattering volume yield the
desirable scattering configuration. Scattering is controlled by preparing the
particular internal state wave function that leads to the favored collisional
configuration in the collision volume. This insight allows coherent control to
be extended to the case of time-dependent scattering. Specifically, we identify
reactive scattering scenarios using incident wave packets of translational
motion where coherent control is operational and initial state entanglement is
unnecessary. Both the stationary and time-dependent scenarios incorporate
extended coherence features, making them physically distinct. From a
theoretical point of view, this work represents a large step forward in the
qualitative understanding of coherently controlled reactive scattering. From an
experimental viewpoint, it offers an alternative to entanglement-based control
schemes. However, both methods present significant challenges to existing
experimental technologies
An Accurate Distance to High-Velocity Cloud Complex C
We report an accurate distance of d = 10+/-2.5kpc to the high-velocity cloud
Complex C. Using high signal-to-noise Keck/HIRES spectra of two
horizontal-branch stars, we have detected CaII K absorption lines from the
cloud. Significant non-detections toward a further 3 stars yield robust lower
distance limits. The resulting HI mass of Complex C is 4.9^{+2.8}_{-2.2} x 10^6
Msun; a total mass of 8.2^{+4.6}_{-2.6} x 10^6 Msun is implied, after
corrections for helium and ionization. At 10kpc, Complex C has physical
dimensions 3x15 kpc, and if it is as thick as it is wide, then the average
density is log ~ -2.5. We estimate the contribution of Complex C to the mass
influx may be as high as ~0.14 Msun/yr.Comment: Resubmitted to ApJ. 8 figure
Cold gas in massive early-type galaxies: The case of NGC 1167
We present a study of the morphology and kinematics of the neutral hydrogen
in the gas-rich (M_HI=1.5x10^{10}Msun), massive early-type galaxy NGC 1167,
which was observed with the Westerbork Synthesis Radio Telescope (WSRT). The HI
is located in a 160kpc disk (~3xD_25) and has low surface density (<2Msun
pc^{-2}). The disk shows regular rotation for r<65kpc but several signs of
recent and ongoing interaction and merging with fairly massive companions are
observed. No population of cold gas clouds is observed - in contrast to what is
found in some spiral galaxies. This suggests that currently the main mechanism
bringing in cold gas to the disk is the accretion of fairly massive satellite
galaxies, rather than the accretion of a large number of small gas clumps. NGC
1167 is located in a (gas-) rich environment: we detect eight companions with a
total HI mass of ~6x10^9Msun within a projected distance of 350kpc. Deep
optical images show a disrupted satellite at the northern edge of the HI disk.
The observed rotation curve shows a prominent bump of about 50km/s (in the
plane of the disk) at r=1.3xR_25. This feature in the rotation curve occurs at
the radius where the HI surface density drops significantly and may be due to
large-scale streaming motions in the disk. We suspect that both the streaming
motions and the HI density distribution are the result of the
interaction/accretion with the disrupted satellite. Like in other galaxies with
wiggles and bumps in the rotation curve, HI scaling describes the observed
rotation curve best. We suggest that interactions create streaming motions and
features in the HI density distribution and that this is the reason for the
success of HI scaling in fitting such rotation curves.Comment: 17 pages, 11 figures; A&A in pres
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