789 research outputs found
Fabrication of Microstructure Arrays on Photosensitive Glass by Femtosecond Laser
A maskless technique for the fabrication of U-shaped microstructure arrays on the surface of photosensitive glass by femtosecond laser-induced modification is developed. This technique is followed by heat treatment to crystallize the modified area, and the specimen is then placed in acid solution for chemical etching. The surface roughness of the microstructures is further improved by a secondary annealing process. The fabricated photosensitive glass is used as a mold template, and replicated plano-convex cylindrical arrays by UV-replica are also presented. The focusing ability of the microlens arrays on the glass mold and replicate is demonstrated. DOI: 10.2961/jlmn.2012.01.002
Conductance oscillations of a spin-orbit stripe with polarized contacts
We investigate the linear conductance of a stripe of spin-orbit interaction
in a 2D electron gas; that is, a 2D region of length along the transport
direction and infinite in the transverse one in which a spin-orbit interaction
of Rashba type is present. Polarization in the contacts is described by means
of Zeeman fields. Our model predicts two types of conductance oscillations:
Ramsauer oscillations in the minority spin transmission, when both spins can
propagate, and Fano oscillations when only one spin propagates. The latter are
due to the spin-orbit coupling with quasibound states of the non propagating
spin. In the case of polarized contacts in antiparallel configuration Fano-like
oscillations of the conductance are still made possible by the spin orbit
coupling, even though no spin component is bound by the contacts. To describe
these behaviors we propose a simplified model based on an ansatz wave function.
In general, we find that the contribution for vanishing transverse momentum
dominates and defines the conductance oscillations. Regarding the oscillations
with Rashba coupling intensity, our model confirms the spin transistor
behavior, but only for high degrees of polarization. Including a position
dependent effective mass yields additional oscillations due to the mass jumps
at the interfaces.Comment: 8.5 pages, 9 figure
Greenspace and mortality in the U.K. Biobank: Longitudinal cohort analysis of socio-economic, environmental, and biomarker pathways
Exposure to natural greenspace benefits health through direct and indirect pathways: increasing physical activity, improving mental health, relieving social isolation, reducing exposure to extreme temperature, noise, and air pollution. Understanding the etiologic pathway of greenspace and health is needed. Here, we used a large cohort follow-up data from the U.K. Biobank to quantify the magnitude of behavioural factors, psychological factors, biomarkers/physiological measurements, co-morbid diseases, and environmental exposure as potential mediators in the relationship between greenspace and mortality. We estimated hazard ratios (HR) with Cox proportional hazards models, and undertook exploratory mediation analyses to quantify the relative contribution of five types of mediators. Our results indicate greenspace was strongly associated with lower mortality risks [per IQR of public greenspace (HR = 0.90 (95% CI 0.86-0.84)) and domestic gardens (HR = 0.91, (95% CI 0.88–0.94))]. The protective associations were especially pronounced among those with lower individual-level socioeconomic status or living in places with area-level deprivation. Exploratory mediation analysis detected benefits in pathways through reducing air pollution, relieving social isolation and depression, increased physical activity and time spent outdoor, better lung function (FEV1/FVC), and having higher serum vitamin D levels
Rate-equation calculations of the current flow through two-site molecular device and DNA-based junction
Here we present the calculations of incoherent current flowing through the
two-site molecular device as well as the DNA-based junction within the
rate-equation approach. Few interesting phenomena are discussed in detail.
Structural asymmetry of two-site molecule results in rectification effect,
which can be neutralized by asymmetric voltage drop at the molecule-metal
contacts due to coupling asymmetry. The results received for poly(dG)-poly(dC)
DNA molecule reveal the coupling- and temperature-independent saturation effect
of the current at high voltages, where for short chains we establish the
inverse square distance dependence. Besides, we document the shift of the
conductance peak in the direction to higher voltages due to the temperature
decrease.Comment: 12 pages, 6 figure
Regio- and stereoselective organocatalyzed relay glycosylations to synthesize 2-amino-2-deoxy-1,3-dithioglycosides
Herein, we describe a novel methodology for the regio-and stereoselectiveconvergent synthesis of 2-amino-2-deoxy-dithioglycosides via one-potrelay glycosylation of 3-O-acetyl-2-nitroglucal donors.This unique organo-catalysis relay glycosylation features excellentsite- and stereoselectivity, good to excellent yields, mild reactionconditions, and broad substrate scope. 2-Amino-2-deoxy-glucosides/mannosidesbearing 1,3-dithio-linkages were efficiently obtained from 3-O-acetyl-2-nitroglucal donors in both stepwise and one-potglycosylation protocols. The dithiolated O-antigen of E. coli serogroup 64 was successfully synthesizedusing this newly developed method.Bio-organic Synthesi
Origin of the low-mass electron pair excess in light nucleus-nucleus collisions
We report measurements of electron pair production in elementary p+p and d+p
reactions at 1.25 GeV/u with the HADES spectrometer. For the first time, the
electron pairs were reconstructed for n+p reactions by detecting the proton
spectator from the deuteron breakup. We find that the yield of electron pairs
with invariant mass Me+e- > 0.15 GeV/c2 is about an order of magnitude larger
in n+p reactions as compared to p+p. A comparison to model calculations
demonstrates that the production mechanism is not sufficiently described yet.
The electron pair spectra measured in C+C reactions are compatible with a
superposition of elementary n+p and p+p collisions, leaving little room for
additional electron pair sources in such light collision systems.Comment: 11 pages, 2 figures, \usepackage{epsfig
Hydrogen bond activated glycosylation under mild conditions
Herein, we report a new glycosylation system for the highly efficient and stereoselective formation of glycosidic bonds using glycosyl N-phenyl trifluoroacetimidate (PTFAI) donors and a charged thiourea hydrogen-bond-donor catalyst. The glycosylation protocol features broad substrate scope, controllable stereoselectivity, good to excellent yields and exceptionally mild catalysis conditions. Benefitting from the mild reaction conditions, this new hydrogen bond-mediated glycosylation system in combination with a hydrogen bond-mediated aglycon delivery system provides a reliable method for the synthesis of challenging phenolic glycosides. In addition, a chemoselective glycosylation procedure was developed using different imidate donors (trichloroacetimidates, N-phenyl trifluoroacetimidates, N-4-nitrophenyl trifluoroacetimidates, benzoxazolyl imidates and 6-nitro-benzothiazolyl imidates) and it was applied for a trisaccharide synthesis through a novel one-pot single catalyst strategy.Bio-organic Synthesi
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
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