1,623 research outputs found
A tunable radiation source by coupling laser-plasma-generated electrons to a periodic structure
Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV=m ïŹeld strength can be achieved by using appropriate grating parameter
Room temperature ferromagnetism in chemically synthesized ZnO rods
We report structural and magnetic properties of pure ZnO rods using X-ray
diffraction (XRD), magnetization hysteresis (M-H) loop and near edge x-ray fine
structure spectroscopy (NEXAFS) study at O K edge. Sample of ZnO was prepared
by co-precipitation method. XRD and selective area electron diffraction
measurements infer that ZnO rods exhibit a single phase polycrystalline nature
with wurtzite lattice. Field emission transmission electron microscopy, field
emission scanning electron microscopy micrographs infers that ZnO have rod type
microstructures with dimension 200 nm in diameter and 550 nm in length. M-H
loop studies performed at room temperature display room temperature
ferromagnetism in ZnO rods. NEXAFS study reflects absence of the oxygen
vacancies in pure ZnO rods.Comment: 8 Pages, 3 Figure
Preparation and ferroelectric properties of (124)-oriented SrBi4Ti4O15 ferroelectric thin film on (110)-oriented LaNiO3 electrode
A (124)-oriented SrBi4Ti4O15 (SBTi) ferroelectric thin film with high volume
fraction of {\alpha}SBTi(124)=97% was obtained using a metal organic
decomposition process on SiO2/Si substrate coated by (110)-oriented LaNiO3
(LNO) thin film. The remanent polarization and coercive field for
(124)-oriented SBTi film are 12.1 {\mu}C/cm2 and 74 kV/cm, respectively. No
evident fatigue of (124)-oriented SBTi thin film can be observed after
1{\times}10e9 switching cycles. Besides, the (124)-oriented SBTi film can be
uniformly polarized over large areas using a piezoelectric-mode atomic force
microscope. Considering that the annealing temperature was 650{\deg}C and the
thickness of each deposited layer was merely 30 nm, a long-range epitaxial
relationship between SBTi(124) and LNO(110) facets was proposed. The epitaxial
relationship was demonstrated based on the crystal structures of SBTi and LNO.Comment: 11 pages, 4 figures, published in Journal of Materials Science:
Materials in Electronics (JMSE), 19 (2008), 1031-103
Melting behavior of ultrathin titanium nanowires
The thermal stability and melting behavior of ultrathin titanium nanowires
with multi-shell cylindrical structures are studied using molecular dynamic
simulation. The melting temperatures of titanium nanowires show remarkable
dependence on wire sizes and structures. For the nanowire thinner than 1.2 nm,
there is no clear characteristic of first-order phase transition during the
melting, implying a coexistence of solid and liquid phases due to finite size
effect. An interesting structural transformation from helical multi-shell
cylindrical to bulk-like rectangular is observed in the melting process of a
thicker hexagonal nanowire with 1.7 nm diameter.Comment: 4 pages, 4 figure
Low Temperature Measurements by Infrared Spectroscopy in CoFeO Ceramic
In this paper results of new far-infrared and middle-infrared measurements
(wavenumber range of 4000cm-1 - 100cm-1) in the range of the temperature from
300K to 8K of the CoFe2O4 ceramic are presented. The bands positions and their
shapes are the same in the wide temperature range. The quality of the sample
was investigated by X-ray, EDS and EPMA studies. The CoFe2O4 reveals the cubic
structure (Fd-3m) in the temperature range from 85K to 360 K without any traces
of distortion. On the current level of knowledge the polycrystalline CoFe2O4
does not exhibit phase transition in the temperature range from 8 K to 300 K.Comment: 10 pages, 6 figure
Coupling Modes and Stoichiometry of Clâ/HCO3â Exchange by slc26a3 and slc26a6
The SLC26 transporters are a family of mostly luminal Clâ and HCO3â transporters. The transport mechanism and the Clâ/HCO3â stoichiometry are not known for any member of the family. To address these questions, we simultaneously measured the HCO3â and Clâ fluxes and the current or membrane potential of slc26a3 and slc26a6 expressed in Xenopus laevis oocytes and the current of the transporters expressed in human embryonic kidney 293 cells. slc26a3 mediates a coupled 2Clâ/1HCO3â exchanger. The membrane potential modulated the apparent affinity for extracellular Clâ of Clâ/HCO3â exchange by slc26a3. Interestingly, the replacement of Clâ with NO3â or SCNâ uncoupled the transport, with large NO3â and SCNâ currents and low HCO3â transport. An apparent uncoupled current was also developed during the incubation of slc26a3-expressing oocytes in HCO3â-buffered Clâ-free media. These findings were used to develop a turnover cycle for Clâ and HCO3â transport by slc26a3. Clâ and HCO3â flux measurements revealed that slc26a6 mediates a 1Clâ/2HCO3â exchange. Accordingly, holding the membrane potential at 40 and â100 mV accelerated and inhibited, respectively, Clâ-mediated HCO3â influx, and holding the membrane potential at â100 mV increased HCO3â-mediated Clâ influx. These findings indicate that slc26a6 functions as a coupled 1Clâ/2HCO3â exchanger. The significance of isoform-specific Clâ and HCO3â transport stoichiometry by slc26a3 and slc26a6 is discussed in the context of diseases of epithelial Clâ absorption and HCO3â secretion
Theory of High-Force DNA Stretching and Overstretching
Single molecule experiments on single- and double stranded DNA have sparked a
renewed interest in the force-extension of polymers. The extensible Freely
Jointed Chain (FJC) model is frequently invoked to explain the observed
behavior of single-stranded DNA. We demonstrate that this model does not
satisfactorily describe recent high-force stretching data. We instead propose a
model (the Discrete Persistent Chain, or ``DPC'') that borrows features from
both the FJC and the Wormlike Chain, and show that it resembles the data more
closely. We find that most of the high-force behavior previously attributed to
stretch elasticity is really a feature of the corrected entropic elasticity;
the true stretch compliance of single-stranded DNA is several times smaller
than that found by previous authors. Next we elaborate our model to allow
coexistence of two conformational states of DNA, each with its own stretch and
bend elastic constants. Our model is computationally simple, and gives an
excellent fit through the entire overstretching transition of nicked,
double-stranded DNA. The fit gives the first values for the elastic constants
of the stretched state. In particular we find the effective bend stiffness for
DNA in this state to be about 10 nm*kbt, a value quite different from either
B-form or single-stranded DNAComment: 33 pages, 11 figures. High-quality figures available upon reques
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Bone turnover markers to explain changes in lumbar spine BMD with abaloparatide and teriparatide: results from ACTIVE.
Summary
Early PINP changes correlate with 18-month lumbar spine BMD changes and the correlation was greater with abaloparatide versus teriparatide. The uncoupling index was similar between the two agents.
Introduction
We evaluated the relationship between early PINP changes and subsequent changes in spine BMD following abaloparatide and teriparatide treatments. We also explored the use of an âuncoupling indexâ (UI), the balance between bone formation and bone resorption, which we hypothesised would be similar in response to these treatment groups.
Methods
Blood samples were taken for measurement of bone turnover markers (BTMs) s-PINP and s-CTX at baseline, 1, 3, 6, 12, and 18 months from 189 abaloparatide patients and 227 teriparatide patients randomly selected from all participants who completed the study. BMD was measured by DXA at baseline, 6, 12, and 18 months. Correlations were calculated between log ratio of BTMs from baseline to 3 months and percent change from baseline in BMD at 18 months. A UI was calculated using log transformation and subtraction of the standard deviate for s-CTX from the standard deviate for s-PINP for each patient.
Results
Early BTM changes were associated with subsequent BMD changes for both treatments. Pearson correlations for the log ratio of PINP over baseline at 3 months and BMD percent change from baseline at 18 months were larger (Pâ<â0.0001) with abaloparatide (râ=â0.561) than teriparatide (râ=â0.198). The mean UI at 1 month was greater for abaloparatide versus teriparatide (1.743 and 1.493, respectively; Pâ=â0.03) but was similar at 3 months or later time points.
Conclusions
Early s-PINP changes correlate with percentage change in lumbar spine BMD 18 months after treatment with both abaloparatide and teriparatide, though the correlation with abaloparatide was greater. The UI was similar between abaloparatide and teriparatide suggesting that the balance between formation and resorption markers was similar
Mass measurements of neutron-deficient Y, Zr, and Nb isotopes and their impact on rp and Îœp nucleosynthesis processes
© 2018 The Authors. Published by Elsevier B.V. This manuscript is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence (CC BY-NC-ND 4.0). For further details please see: https://creativecommons.org/licenses/by-nc-nd/4.0/Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of 82Zr and 84Nb were measured for the first time with an uncertainty of âŒ10 keV, and the masses of 79Y, 81Zr, and 83Nb were re-determined with a higher precision. The latter are significantly less bound than their literature values. Our new and accurate masses remove the irregularities of the mass surface in this region of the nuclear chart. Our results do not support the predicted island of pronounced low α separation energies for neutron-deficient Mo and Tc isotopes, making the formation of ZrâNb cycle in the rp-process unlikely. The new proton separation energy of 83Nb was determined to be 490(400) keV smaller than that in the Atomic Mass Evaluation 2012. This partly removes the overproduction of the p-nucleus 84Sr relative to the neutron-deficient molybdenum isotopes in the previous Îœp-process simulations.Peer reviewe
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