2,200 research outputs found
Suppression of surface roughening during ion bombardment of semiconductors
Ion beams are used routinely for processing of semiconductors, particularly
sputtering, ion implantation and direct-write fabrication of nanostructures.
However, the utility of ion beam techniques is limited by crystal damage and
surface roughening. Damage can be reduced or eliminated by performing
irradiation at elevated temperatures. However, at these conditions, surface
roughening is highly problematic due to thermal mobility of adatoms and surface
vacancies. Here we solve this problem using hydrogen gas, which we use to
stabilize surface mass flow and suppress roughening during ion bombardment of
elemental and compound semiconductors. We achieve smooth surfaces during
ion-beam processing, and show that the method can be enhanced by radicalizing
H2 gas using a remote plasma source. Our approach is broadly applicable, and
expands the utility of ion beam techniques for the processing and fabrication
of functional materials and nanostructures.Comment: 14 pages, 5 figure
The ACS Virgo Cluster Survey II. Data Reduction Procedures
The ACS Virgo Cluster Survey is a large program to carry out multi-color
imaging of 100 early-type members of the Virgo Cluster using the Advanced
Camera for Surveys (ACS) on the Hubble Space Telescope. Deep F475W and F850LP
images (~ SDSS g and z) are being used to study the central regions of the
program galaxies, their globular cluster systems, and the three-dimensional
structure of Virgo itself. In this paper, we describe in detail the data
reduction procedures used for the survey, including image registration,
drizzling strategies, the computation of weight images, object detection, the
identification of globular cluster candidates, and the measurement of their
photometric and structural parameters.Comment: 33 pages, 8 figures. Accepted for publication in ApJS. Also available
at http://www.physics.rutgers.edu/~pcote/acs/publications.htm
Proposal for the implementation of physician assistants in Uganda
Non-communicable diseases are on the rise throughout Uganda and the management of four chronic disease states -- hypertension, diabetes, breast cancer, and prostate cancer -- have shown to be inadequate. This gap in chronic disease care leaves room for an educational intervention in the training of medical professionals and the implementation of a novel workforce. Similar to the model seen in the United States, this research aims to create a cohort of physician assistant students at the Makerere University College of Health Sciences in Kampala, Uganda. Physician assistants in the United States provide medical care in many ways, including primary care where chronic diseases can be managed. The cohort of physician assistant students in this study will be trained alongside their medical student counterparts, however, their curriculum will focus on the management of chronic disease. This will be accomplished through shortening and restructuring the didactic and clinical medical school curriculum such that a greater focus is on the management of chronic conditions. Physician assistant and medical students in this study will be assessed for both knowledge and clinical skills gained over the course of their training regarding the management of the four chronic disease states noted above. Knowledge of chronic disease states will be tested with the administration of pre- and post- examinations at the orientation of their medical training and after their completion, respectively. Further, all students will be assessed for their views and will self-evaluate their skills regarding interprofessional collaboration at the orientation of their medical training and after their completion. This study aims to demonstrate how a novel workforce of trained clinicians, known as physician assistants, can display competency in the management of chronic conditions as means to aid a growing healthcare concern throughout Uganda. A secondary outcome being examined in this study is how training these future clinicians together with medical students will improve their views on interprofessional collaboration as means to provide optimal care to patients and enhanced interconnectedness between clinicians in Uganda
Framework for engineering of spin defects in hexagonal boron nitride by focused ion beams
Hexagonal boron nitride (hBN) is gaining interest as a wide bandgap van der
Waals host of optically active spin defects for quantum technologies. Most
studies of the spin-photon interface in hBN focus on the negatively charged
boron vacancy (VB-) defect, which is typically fabricated by ion irradiation.
However, VB- fabrication methods often lack robustness and reproducibility when
applied to thin flakes (less than 10 nm) of hBN. Here we identify mechanisms
that both promote and inhibit VB- generation and optimize ion beam parameters
for site-specific fabrication of optically active VB- centers. We emphasize
conditions accessible by high resolution focused ion beam (FIB) systems, and
present a framework for VB- fabrication in hBN flakes of arbitrary thickness
for applications in quantum sensing and quantum information processing.Comment: 11 pages, 5 figure
The ACS Virgo Cluster Survey. VIII. The Nuclei of Early-Type Galaxies
(Abridged) The ACS Virgo Cluster Survey is an HST program to obtain
high-resolution, g and z-band images for 100 early-type members of the Virgo
Cluster, spanning a range of ~460 in blue luminosity. Based on this large,
homogeneous dataset, we present a sharp upward revision in the frequency of
nucleation in early-type galaxies brighter than M_B ~ -15 (66 < f_n < 82%), and
find no evidence for nucleated dwarfs to be more concentrated to the center of
Virgo than their non-nucleated counterparts. Resolved stellar nuclei are not
present in galaxies brighter than M_B ~ -20.5, however, there is no clear
evidence from the properties of the nuclei, or from the overall incidence of
nucleation, for a change at M_B ~ -17.6, the traditional dividing point between
dwarf and giant galaxies. On average, nuclei are ~3.5 mag brighter than a
typical globular cluster and have a median half-light radius ~4.2 pc. Nuclear
luminosities correlate with nuclear sizes and, in galaxies fainter than M_B ~
-17.6, nuclear colors. Comparing the nuclei to the "nuclear clusters" found in
late-type spiral galaxies reveals a close match in terms of size, luminosity
and overall frequency, pointing to a formation mechanism that is rather
insensitive to the detailed properties of the host galaxy. The mean
nuclear-to-galaxy luminosity ratio is indistinguishable from the mean
SBH-to-bulge mass ratio, calculated in early-type galaxies with detected
supermassive black holes (SBHs). We argue that compact stellar nuclei might be
the low-mass counterparts of the SBHs detected in the bright galaxies, and that
one should think in terms of "Central Massive Objects" -- either SBHs or
compact stellar nuclei -- that accompany the formation of almost all early-type
galaxies and contain a mean fraction ~0.3% of the total bulge mass.Comment: ApJ Supplements, accepted. Updated references. The manuscript is 61
pages, including 6 tables and 28 figures. Figures included in this submission
are low resolution; a version of the paper containing high-resolution color
figures can be downloaded from the ACSVCS website:
http://www.cadc.hia.nrc.gc.ca/community/ACSVCS/publications.html#acsvcs
Roles of vimentin in health and disease
In this review, Ridge et al. discuss the essential functions of vimentin IFs revealed from studies of Vim(-/-) mice and cells derived from them.More than 27 yr ago, the vimentin knockout (Vim(-/-)) mouse was reported to develop and reproduce without an obvious phenotype, implying that this major cytoskeletal protein was nonessential. Subsequently, comprehensive and careful analyses have revealed numerous phenotypes in Vim(-/-) mice and their organs, tissues, and cells, frequently reflecting altered responses in the recovery of tissues following various insults or injuries. These findings have been supported by cell-based experiments demonstrating that vimentin intermediate filaments (IFs) play a critical role in regulating cell mechanics and are required to coordinate mechanosensing, transduction, signaling pathways, motility, and inflammatory responses. This review highlights the essential functions of vimentin IFs revealed from studies of Vim(-/-) mice and cells derived from them
Interoperability of GPON and WiMAX for network capacity enhancement and resilience
This paper was published in Journal of Optical Networking and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/JON/Issue.cfm. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law. Copyright Optical Society of America.The interoperability of standard WiMAX and GPON is shown to overcome the wireless spectrum congestion and provide resilience for GPON through the use of overlapping radio cells. The application of centralised control in the optical line terminal (OLT) and time division multiplexing for upstream transmission enables efficient dynamic bandwidth allocation for wireless users on a single wavelength as well as minimised optical beat interference at the optical receiver. The viability of bidirectional transmission of multiple un-coded IEEE802.16d channels by means of a single radio frequency (RF) subcarrier at transmission rates of 50 Mbits/s and 15 Mbits/s downstream and upstream respectively for distances of up to 21 km of integrated GPON and WiMAX micro-cell links is demonstrated.Peer reviewe
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