2,986 research outputs found
Domain wall displacement in Py square ring for single nanometric magnetic bead detection
A new approach based on the domain wall displacement in confined
ferromagnetic nanostructures for attracting and sensing a single nanometric
magnetic particles is presented. We modeled and experimentally demonstrated the
viability of the approach using an anisotropic magnetoresistance device made by
a micron-size square ring of Permalloy designed for application in magnetic
storage. This detection concept can be suitable to biomolecular recognition,
and in particular to single molecule detection.Comment: 8pages, 3figure
Two Clusters with Radio-quiet Cooling Cores
Radio lobes inflated by active galactic nuclei at the centers of clusters are
a promising candidate for halting condensation in clusters with short central
cooling times because they are common in such clusters. In order to test the
AGN-heating hypothesis, we obtained Chandra observations of two clusters with
short central cooling times yet no evidence for AGN activity: Abell 1650 and
Abell 2244. The cores of these clusters indeed appear systematically different
from cores with more prominent radio emission. They do not have significant
central temperature gradients, and their central entropy levels are markedly
higher than in clusters with stronger radio emission, corresponding to central
cooling times ~ 1 Gigayear. Also, there is no evidence for fossil X-ray
cavities produced by an earlier episode of AGN heating. We suggest that either
(1) the central gas has not yet cooled to the point at which feedback is
necessary to prevent it from condensing, possibly because it is conductively
stabilized, or (2) the gas experienced a major heating event Gyr in
the past and has not required feedback since then. The fact that these clusters
with no evident feedback have higher central entropy and therefore longer
central cooling times than clusters with obvious AGN feedback strongly suggests
that AGNs supply the feedback necessary to suppress condensation in clusters
with short central cooling times.Comment: ApJ Letter, in pres
Ultraviolet absorption: Experiment MA-059
A technique devised to permit the measurement of atmospheric species concentrations is described. This technique involves the application of atomic absorption spectroscopy and the quantitative observation of resonance fluorescence in which atomic or molecular species scatter resonance radiation from a light source into a detector. A beam of atomic oxygen and atomic nitrogen resonance radiation, strong unabsorbable oxygen and nitrogen radiation, and visual radiation was sent from Apollo to Soyuz. The density of atomic oxygen and atomic nitrogen between the two spacecraft was measured by observing the amount of resonance radiation absorbed when the line joining Apollo and Soyuz was perpendicular to their velocity with respect to the ambient atmosphere. Results of postflight analysis of the resonance fluorescence data are discussed
Simulation Studies of Nanomagnet-Based Architecture
We report a simulation study on interacting ensembles of Co nanomagnets that
can perform basic logic operations and propagate logic signals, where the state
variable is the magnetization direction. Dipole field coupling between
individual nanomagnets drives the logic functionality of the ensemble and
coordinated arrangements of the nanomagnets allow for the logic signal to
propagate in a predictable way. Problems with the integrity of the logic signal
arising from instabilities in the constituent magnetizations are solved by
introducing a biaxial anisotropy term to the Gibbs magnetic free energy of each
nanomagnet. The enhanced stability allows for more complex components of a
logic architecture capable of random combinatorial logic, including horizontal
wires, vertical wires, junctions, fanout nodes, and a novel universal logic
gate. Our simulations define the focus of scaling trends in nanomagnet-based
logic and provide estimates of the energy dissipation and time per nanomagnet
reversal
Evidence for Rapid Redshift Evolution of Strong Cluster Cooling Flows
We present equivalent widths of the [OII] and Ha nebular emission lines for
77 brightest cluster galaxies (BCGs) selected from the 160 Square Degree
X-ray survey. We find no [OII] or Ha emission stronger than -15
angstroms or -5 angstroms, respectively, in any BCG. The corresponding emission
line luminosities lie below 6E40 erg/s, which is a factor of 30 below that of
NGC1275 in the Perseus cluster. A comparison to the detection frequency of
nebular emission in BCGs lying at redshifts above z = 0.35 drawn from the
Brightest Cluster Survey (Crawford et al. 1999) indicates that we should have
detected roughly one dozen emission-line galaxies, assuming the two surveys are
selecting similar clusters in the X-ray luminosity range 10E42 erg/s to 10E45
erg/s. The absence of luminous nebular emission (ie., Perseus-like systems) in
our sample is consistent with an increase in the number density of {\it strong}
cooling flow (cooling core) clusters between and today. The decline
in their numbers at higher redshift could be due to cluster mergers and AGN
heating.Comment: Accepted for publication in Ap
Life Satisfaction and Perceived Meaningfulness of Learning Experience among First-Year Traditional Graduate Social Work Students
Knowledge about life satisfaction and learning experience among first-year graduate students is sparse, despite its relevance to instructional decisions, academic support, and success of students. Adequate knowledge is crucial, as it may help graduate students manage personal and professional life changes associated with graduate education. Using a convenience sample of 118 first-year traditional social work graduate students in a northeastern U.S. university the study examined associations of life satisfaction and peer support with perception of meaningfulness of learning experience, as well as associations of gender, marital status, family support and perceived stress with life satisfaction. Results suggest that receiving higher peer support was associated with perceived meaningfulness of learning experience, whereas being female, being married, having lower perceived stress, and receiving higher family support were associated with life satisfaction. Reciprocal predictive relationship between life satisfaction and perceived meaningfulness of learning experience was found. In general, findings suggest that stress and support are important variables to consider in understanding life satisfaction and learning experience of first-year traditional social work graduate students and highlight the importance of peer and family support to navigating challenges of graduate education. Most importantly, findings have implications for social work education, highlighting how instructor’s utilization of instructional approaches that facilitate peer support may help ease transition into graduate education or help prevent drop out during the first year graduate students are most vulnerable to dropping out. Altogether, findings highlight why exploring perceived meaningfulness of learning experience and life satisfaction is crucial for identifying supportive needs of graduate students. Keywords: Life satisfaction; learning experience; perceived stress; family support; peer support
Frequent genomic copy number gain and overexpression of GATA-6 in pancreatic carcinoma
Multiple genetic alterations are well recognized as contributing to pancreatic carcinogenesis, although the finding of recurrent copy number changes indicates additional targets remain to be found. The objective of this study was to identify novel targets of genetic alteration that contribute to pancreatic cancer development or progression. We used Representational Oligonucleotide Microarray Analysis (ROMA) to identify copy number changes in pancreatic cancer xenografts, and validated these findings using FISH, quantitative PCR, Western blotting and immunohistochemical labeling. With this approach, we identified a 0.36-Mb amplification at 18q11.2 containing two known genes, GATA-6 and cTAGE1. Using a cutoff value of 3.0 fold compared to haploid controls, copy number gain or amplification was confirmed in 4 of 42 (9.5%) pancreatic carcinomas analyzed. Combined genetic and transcriptional analyses showed consistent overexpression of GATA-6 in all carcinomas with 18q11.2 gain, as well as in the majority of pancreatic cancers examined (17 of 30 cancers, 56.7%) that did not have gain of this region. By contrast, overexpression of cTAGE1 was rare in these same cancers suggesting GATA-6 is the true target of this copy number increase. GATA-6 mRNA overexpression corresponded to robust nuclear protein expression in cancer cell lines and resected tissues consistent with its role as a transcription factor. Intense nuclear labeling was significantly increased in PanIN-3 lesions and infiltrating carcinomas compared to normal duct epithelium (p < 0.000001 and p < 0.003, respectively). Forced overexpression of GATA6 in MiaPaca2 cells resulted in increased proliferation and growth in soft-agar. Gain and overexpression of the development-related transcription factor GATA-6 may play an important and hitherto unrecognized role in pancreatic carcinogenesis
Polarization Diagnostics for Cool Core Cluster Emission Lines
The nature of the interaction between low-excitation gas filaments at ~104 K, seen in optical line emission, and diffuse X-ray emitting coronal gas at ~107 K in the centers of galaxy clusters remains a puzzle. The presence of a strong, empirical correlation between the two gas phases is indicative of a fundamental relationship between them, though as yet of undetermined cause. The cooler filaments, originally thought to have condensed from the hot gas, could also arise from a merger or the disturbance of cool circumnuclear gas by nuclear activity. Here, we have searched for intrinsic line emission polarization in cool core galaxy clusters as a diagnostic of fundamental transport processes. Drawing on developments in solar astrophysics, direct energetic particle impact induced polarization holds the promise to definitively determine the role of collisional processes such as thermal conduction in the ISM physics of galaxy clusters, while providing insight into other highly anisotropic excitation mechanisms such as shocks, intense radiation fields, and suprathermal particles. Under certain physical conditions, theoretical calculations predict of the order of 10% polarization. Our observations of the filaments in four nearby cool core clusters place stringent upper limits ( 0.1%) on the presence of emission line polarization, requiring that if thermal conduction is operative, the thermal gradients are not in the saturated regime. This limit is consistent with theoretical models of the thermal structure of filament interfacesPeer reviewe
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