4,213 research outputs found
Lithography-Free, Omnidirectional, CMOS-Compatible AlCu Alloys for Thin-Film Superabsorbers
Superabsorbers based on metasurfaces have recently enabled the control of light at the nanoscale in unprecedented ways. Nevertheless, the subâwavelength features needed to modify the absorption band usually require complex fabrication methods, such as electronâbeam lithography. To overcome the scalability limitations associated with the fabrication of metallic nanostructures, engineering the optical response of superabsorbers by metal alloying is proposed, instead of tuning the geometry/size of the nanoscale building blocks. The superior performance of thin film AlCu alloys as the metallic component of planar bilayer superabsorbers is numerically demonstrated. This alloy outperforms its pure constituents as well as other metals, such as Ag, Au, and Cr. As a model system, a Si/AlCu structure is analyzed that presents \u3e99% absorption at selected wavelength ranging from the visible to the nearâinfrared regions of the spectrum, depending on the subwavelength thickness of the semiconductor. The multiâwavelength nearâunity absorption behavior of Si/AlCu persists even for oblique angle of incidence, up to 70°. Additionally, the findings are validated by fabricating and testing aâSi/AlCu superabsorbers, where good agreement is found between the numerically and experimentally determined optical response. The system investigated here is relevant for integration in complementary metalâoxideâsemiconductor (CMOS) technologies
On a Testing Methodology for the Mechanical Property Assessment of a New Low-Cost Titanium Alloy Derived from Synthetic Rutile
Mechanical property data of a low-cost titanium alloy derived directly from synthetic rutile is reported. A small-scale testing approach comprising consolidation via field-assisted sintering technology, followed by axisymmetric compression testing, has been designed to yield mechanical property data from small quantities of titanium alloy powder. To validate this approach and provide a benchmark, Ti-6Al-4V powder has been processed using the same methodology and compared with material property data generated from thermo-physical simulation software. Compressive yield strength and strain to failure of the synthetic rutile-derived titanium alloy were revealed to be similar to that of Ti-6Al-4V
Simulation Study on JLEIC High Energy Bunched Electron Cooling
In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during the collision at the collider ring. Different with other electron coolers using DC electron beam, the proposed electron cooler at the JLEIC ion collider ring uses high energy bunched electron beam, provided by an ERL. In this paper, we report some recent simulation study on how the electron cooling rate will be affected by the bunched electron beam properties, such as the correlation between the longitudinal position and momentum, the bunch size, and the Larmor emittance
The detection of the imprint of filaments on cosmic microwave background lensing
Galaxy redshift surveys, such as 2dF, SDSS, 6df, GAMA and VIPERS, have shown
that the spatial distribution of matter forms a rich web, known as the cosmic
web. The majority of galaxy survey analyses measure the amplitude of galaxy
clustering as a function of scale, ignoring information beyond a small number
of summary statistics. Since the matter density field becomes highly
non-Gaussian as structure evolves under gravity, we expect other statistical
descriptions of the field to provide us with additional information. One way to
study the non-Gaussianity is to study filaments, which evolve non-linearly from
the initial density fluctuations produced in the primordial Universe. In our
study, we report the first detection of CMB (Cosmic Microwave Background)
lensing by filaments and we apply a null test to confirm our detection.
Furthermore, we propose a phenomenological model to interpret the detected
signal and we measure how filaments trace the matter distribution on large
scales through filament bias, which we measure to be around 1.5. Our study
provides a new scope to understand the environmental dependence of galaxy
formation. In the future, the joint analysis of lensing and Sunyaev-Zel'dovich
observations might reveal the properties of `missing baryons', the vast
majority of the gas which resides in the intergalactic medium and has so far
evaded most observations
Are Great Disks Defined by Satellite Galaxies in Milky-Way Type Halos Rare in CDM model?
We study the spatial distribution of satellite galaxies by assuming that they
follow the dark matter distribution. This assumption is supported by
semi-analytical studies based on high-resolution numerical simulations. We find
that for a Milky-Way type halo, if only a dozen satellite galaxies are
observed, then they can lie on a ``great'' disk with an rms height of about 40
kpc. The normal to the plane is roughly isotropic on the sky. These results are
consistent with the observed properties of the satellite galaxies in the Milky
Way. If, however, the satellite galaxies follow the distribution of
substructure selected by present mass, then great disks similar to the one in
the Milky Way are rare and difficult to reproduce, in agreement with the
conclusion reached by Kroupa et al. (2004).Comment: Major revised, new figure and text added, to appear in A&
Magnetic susceptibility of EuTe/PbTe Heisenberg superlattices: experimental and theoretical studies
We report results on the temperature dependence of the susceptibilities of a
set of MBE-grown short-period EuTe/PbTe antiferromagnetic superlattices having
different EuTe layer thicknesses. In-plane and orthogonal susceptibilities have
been measured and display a strong anisotropy at low temperature, confirming
the occurrence of a magnetic phase transition in the thicker samples, as seen
also in neutron diffraction studies. We suggest that dipolar interactions
stabilize antiferromagnetic long-range order in an otherwise isotropic system
and we present numerical and analytical results for the low-temperature
orthogonal susceptibility.Comment: 30 pages, 8 ps figures, RevTe
A warped m=2 water maser disc in V778 Cyg?
The silicate carbon star V778 Cyg is a source of 22 GHz water maser emission
which was recently resolved by MERLIN. Observations revealed an elongated
S-like structure along which the velocities of the maser features show a linear
dependence on the impact parameter. This is consistent with a doubly-warped m=2
disc observed edge-on. Water masers and silicate dust emission (detected by
IRAS and ISO) have a common origin in O-rich material and are likely to be
co-located in the disc. We propose a detailed self-consistent model of a masing
gas-dust disc around a companion to the carbon star in a binary system, which
allows us to estimate the companion mass of 1.7 +- 0.1 M_sun, the disc radius
of 40 +-3 AU and the distance between companions of about 80 AU. Using a
dust-gas coupling model for water masing, we calculate the maser power
self-consistently, accounting for both the gas and the dust energy balances.
Comparing the simulation results with the observational data, we deduce the
main physical parameters of the masing disc, such as the gas and dust
temperatures and their densities. We also present an analysis of the stability
of the disc.Comment: 7 pages, 5 figures. This paper is accepted for publication in MNRA
What Are the Barriers and Motivators to Exercise in 50-65 Year-Old Adults?
Introduction. The benefit of exercise in adults has been well established. Research has demonstrated improved cardiovascular health, decreased bone fractures, and increased mental capacity. While the benefits of exercise has clearly been demonstrated, personal barriers to exercise are yet to be fully elucidated. Thus, in collaboration with the YMCA, this study aimed to clarify barriers to exercise in 50-65 year-old adults.https://scholarworks.uvm.edu/comphp_gallery/1085/thumbnail.jp
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Wolfram syndrome: new pathophysiological insights and therapeutic strategies.
UNLABELLED: Wolfram Syndrome (WS) is an ultra-rare, progressive neurodegenerative disease characterized by early-onset diabetes mellitus and irreversible loss of vision, secondary to optic nerve degeneration. Visual loss in WS is an important cause of registrable blindness in children and young adults and the pathological hallmark is the preferential loss of retinal ganglion cells within the inner retina. In addition to optic atrophy, affected individuals frequently develop variable combinations of neurological, endocrinological, and psychiatric complications. The majority of patients carry recessive mutations in the WFS1 (4p16.1) gene that encodes for a multimeric transmembrane protein, wolframin, embedded within the endoplasmic reticulum (ER). An increasingly recognised subgroup of patients harbor dominant WFS1 mutations that usually cause a milder phenotype, which can be limited to optic atrophy. Wolframin is a ubiquitous protein with high levels of expression in retinal, neuronal, and muscle tissues. It is a multifunctional protein that regulates a host of cellular functions, in particular the dynamic interaction with mitochondria at mitochondria-associated membranes. Wolframin has been implicated in several crucial cellular signaling pathways, including insulin signaling, calcium homeostasis, and the regulation of apoptosis and the ER stress response. There is currently no cure for WS; management remains largely supportive. This review will cover the clinical, genetic, and pathophysiological features of WS, with a specific focus on disease models and the molecular pathways that could serve as potential therapeutic targets. The current landscape of therapeutic options will also be discussed in the context of the latest evidence, including the pipeline for repurposed drugs and gene therapy. PLAIN LANGUAGE SUMMARY: Wolfram syndrome - disease mechanisms and treatment options Wolfram syndrome (WS) is an ultra-rare genetic disease that causes diabetes mellitus and progressive loss of vision from early childhood. Vision is affected in WS because of damage to a specialized type of cells in the retina, known as retinal ganglion cells (RGCs), which converge at the back of the eye to form the optic nerve. The optic nerve is the fast-conducting cable that transmits visual information from the eye to the vision processing centers within the brain. As RGCs are lost, the optic nerve degenerates and it becomes pale in appearance (optic atrophy). Although diabetes mellitus and optic atrophy are the main features of WS, some patients can develop more severe problems because the brain and other organs, such as the kidneys and the bladder, are also affected. The majority of patients with WS carry spelling mistakes (mutations) in the WFS1 gene, which is located on the short arm of chromosome 4 (4p16.1). This gene is highly expressed in the eye and in the brain, and it encodes for a protein located within a compartment of the cell known as the endoplasmic reticulum. For reasons that still remain unclear, WFS1 mutations preferentially affect RGCs, accounting for the prominent visual loss in this genetic disorder. There is currently no effective treatment to halt or slow disease progression and management remains supportive, including the provision of visual aids and occupational rehabilitation. Research into WS has been limited by its relative rarity and the inability to get access to eye and brain tissues from affected patients. However, major advances in our understanding of this disease have been made recently by making use of more accessible cells from patients, such as skin cells (fibroblasts), or animal models, such as mice and zebrafish. This review summarizes the mechanisms by which WFS1 mutations affect cells, impairing their function and eventually leading to their premature loss. The possible treatment strategies to block these pathways are also discussed, with a particular focus on drug repurposing (i.e., using drugs that are already approved for other diseases) and gene therapy (i.e., replacing or repairing the defective WFS1 gene)
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