4,576 research outputs found
Targeting inflammatory pathways in axial spondyloarthritis.
The triggers and pathogenesis of axial spondyloarthritis (axSpA) are not yet completely understood. However, therapeutic agents targeting tumor necrosis factor-α and interleukin-17 inflammatory pathways have proven successful in suppressing many of the clinical symptoms and signs of axSpA, giving us an indication of which pathways are responsible for initiating and maintaining the inflammation. The mechanisms that eventuate in syndesmophytes and ankyloses are less clear. This review addresses these two critical pathways of inflammation, discussing their nature and these factors that may activate or enhance the pathways in patients with axSpA. In addition, genetic and other markers important to the inflammatory pathways implicated in axSpA are explored, and prognostic biomarkers are discussed. Treatment options available for the management of axSpA and their associated targets are highlighted
Proceedings of the Third Cryocooler Conference
Mechanical and non-mechanical types of small cryocoolers in the temperature range of 4 to 80 K are discussed. Applications of these small cryocoolers include the cooling of infrared detectors, cryopumps, small superconducting devices and magnets, and electronic devices
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Universal slow plasmons and giant field enhancement in atomically thin quasi-two-dimensional metals
Plasmons depend strongly on dimensionality: while plasmons in three-dimensional systems start with finite energy at wavevector q = 0, plasmons in traditional two-dimensional (2D) electron gas disperse as ωp∼q√. However, besides graphene, plasmons in real, atomically thin quasi-2D materials were heretofore not well understood. Here we show that the plasmons in real quasi-2D metals are qualitatively different, being virtually dispersionless for wavevectors of typical experimental interest. This stems from a broken continuous translational symmetry which leads to interband screening; so, dispersionless plasmons are a universal intrinsic phenomenon in quasi-2D metals. Moreover, our ab initio calculations reveal that plasmons of monolayer metallic transition metal dichalcogenides are tunable, long lived, able to sustain field intensity enhancement exceeding 107, and localizable in real space (within ~20 nm) with little spreading over practical measurement time. This opens the possibility of tracking plasmon wave packets in real time for novel imaging techniques in atomically thin materials
Phonon-assisted optical absorption in silicon from first principles
The phonon-assisted interband optical absorption spectrum of silicon is
calculated at the quasiparticle level entirely from first principles. We make
use of the Wannier interpolation formalism to determine the quasiparticle
energies, as well as the optical transition and electron-phonon coupling matrix
elements, on fine grids in the Brillouin zone. The calculated spectrum near the
onset of indirect absorption is in very good agreement with experimental
measurements for a range of temperatures. Moreover, our method can accurately
determine the optical absorption spectrum of silicon in the visible range, an
important process for optoelectronic and photovoltaic applications that cannot
be addressed with simple models. The computational formalism is quite general
and can be used to understand the phonon-assisted absorption processes in
general
Spin Polarization and Transport of Surface States in the Topological Insulators Bi2Se3 and Bi2Te3 from First Principles
We investigate the band dispersion and the spin texture of topologically
protected surface states in the bulk topological insulators Bi2Se3 and Bi2Te3
by first-principles methods. Strong spin-orbit entanglement in these materials
reduces the spin-polarization of the surface states to ~50% in both cases; this
reduction is absent in simple models but of important implications to
essentially any spintronic application. We propose a way of controlling the
magnitude of spin polarization associated with a charge current in thin films
of topological insulators by means of an external electric field. The proposed
dual-gate device configuration provides new possibilities for electrical
control of spin.Comment: 4+ pages, 3 figure
Excitonic Effects and Optical Spectra of Single-Walled Carbon Nanotubes
Many-electron effects often dramatically modify the properties of reduced
dimensional systems. We report calculations, based on an many-electron Green's
function approach, of electron-hole interaction effects on the optical spectra
of small-diameter single-walled carbon nanotubes. Excitonic effects
qualitatively alter the optical spectra of both semiconducting and metallic
tubes. Excitons are bound by ~ 1 eV in the semiconducting (8,0) tube and by ~
100 meV in the metallic (3,3) tube. These large many-electron effects explain
the discrepancies between previous theories and experiments.Comment: 6 pages, 3 figures, 2 table
Engineering the Next Generation of Solid State Proton Conductors: Synthesis and Properties of Ba_(3−x)K_(x)H_(x)(PO_4)_2
A new series of compounds with general chemical formula Ba_(3−x)K_(x)H_(x)(PO_4)_2 has been successfully prepared. This particular stoichiometry was targeted as a candidate solid-state proton conductor because of its anticipated structural similarity to known M_(3)H(XO_4)_2 superprotonic conductors (M = Cs, Rb, NH4, K; X = Se, S) and to the known trigonal compound Ba_(3)(PO_4)_2. The materials were synthesized from aqueous solution using barium acetate, dipotassium hydrogen phosphate, and potassium hydroxide as starting materials. Through variations in the initial solution stoichiometry or the synthesis temperature, the final stoichiometry could be controlled from x ~ 0.5 to ~1. X-ray powder diffraction, energy dispersive spectroscopy chemical analysis, ^(1)H magic angle spinning (MAS) nuclear magnetic spectroscopy, and thermogravimetric analysis were all employed to establish potassium and proton incorporation. The diffraction data confirmed crystallization of a trigonal phase, and chemical analysis showed the (Ba+K):P ratio to be 3:2, consistent with the target stoichiometry. The conductivity of the Ba_(3−x)K_(x)H_(x)(PO_4)_2 materials, as measured by A.C. impedance spectroscopy, is about 3 orders of magnitude greater than the end-member Ba_(3)(PO_4)_2 material with only a slight dependence on x, however, it is substantially lower than that of typical superprotonic conductors and of the M_(3)H(XO_4)_2 materials in particular. The close proximity of Ba to the hydrogen bond site is proposed to explain this behavior. At 250 °C, the conductivity is 2.4 × 10^(−5) S/cm for the composition x = 0.80, which, when combined with the water insolubility and the relatively high thermal stability, may render Ba_(3−x)K_(x)H_(x)(PO_4)_2 an attractive alternative in selected electrochemical applications to known superprotonic conductors
Harnessing Rural Radio for Climate Change Mitigation and Adaptation in the Philippines
The working paper documents the pilot rural radio campaign, dubbed as 'Climate Change i-Broadkas Mo', implemented by the CGIAR Research Program on Climate Change, Agriculture and Food Security in Southeast Asia (CCAFS SEA) and the Philippine Federation of Rural Broadcasters (PFRB)​ in strategic regions of the Philippines from 2015 to 2018. The radio campaign provided PFRB affiliated broadcasters with scripts and ready-to-be-aired (RTBA) interviews on climate-smart agriculture. The lessons learned from the project can be used to enhance the capacities of rural broadcasters on climate change reporting and to create a demand for radio-based distance learning, not only in Northern Philippines, but in similar regions in Southeast Asia
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