2,504 research outputs found
On the Chinese Exchange Rate Regime: an Attempt to Flexibility during 2015
This study will demonstrate, through an econometric and asset allocation approach, if and
how the Chinese exchange rate regime was changing during 2015. Particularly, China to improve its
exchange rate formation system implemented, during July and August 2015, three depreciation as a
step toward a market-oriented exchange rate. This situation, along with the new right of the RMB to
be an international currency in SDR should generate a loss of weight about the USD in the Chinese
basket peg. For this reason, moving from Frankel-Weiâs basic econometric model - but with some
appropriate changes - our objective is to verify if the Chinese monetary policy about the exchange
rate has affected the inner balance of the Chinese basket-peg leading it towards a flexible exchange
rate regime
Quantum Spin Hall Effect in Graphene
We study the effects of spin orbit interactions on the low energy electronic
structure of a single plane of graphene. We find that in an experimentally
accessible low temperature regime the symmetry allowed spin orbit potential
converts graphene from an ideal two dimensional semimetallic state to a quantum
spin Hall insulator. This novel electronic state of matter is gapped in the
bulk and supports the quantized transport of spin and charge in gapless edge
states that propagate at the sample boundaries. The edge states are non chiral,
but they are insensitive to disorder because their directionality is correlated
with spin. The spin and charge conductances in these edge states are calculated
and the effects of temperature, chemical potential, Rashba coupling, disorder
and symmetry breaking fields are discussed.Comment: 4 pages, published versio
Nanotube Piezoelectricity
We combine ab initio, tight-binding methods and analytical theory to study
piezoelectric effect of boron nitride nanotubes. We find that piezoelectricity
of a heteropolar nanotube depends on its chirality and diameter and can be
understood starting from the piezoelectric response of an isolated planar
sheet, along with a structure specific mapping from the sheet onto the tube
surface. We demonstrate that coupling between the uniaxial and shear
deformation are only allowed in the nanotubes with lower chiral symmetry. Our
study shows that piezoelectricity of nanotubes is fundamentally different from
its counterpart in three dimensional (3D) bulk materials.Comment: 4 pages, with 3 postscript figures embedded. Uses REVTEX4 macros.
Also available at
http://www.physics.upenn.edu/~nsai/preprints/bn_piezo/index.htm
The Ah receptor: adaptive metabolism, ligand diversity, and the xenokine model
Author Posting. © American Chemical Society, 2020. This is an open access article published under an ACS AuthorChoice License. The definitive version was published in Chemical Research in Toxicology, 33(4), (2020): 860-879, doi:10.1021/acs.chemrestox.9b00476.The Ah receptor (AHR) has been studied for almost five decades. Yet, we still have many important questions about its role in normal physiology and development. Moreover, we still do not fully understand how this protein mediates the adverse effects of a variety of environmental pollutants, such as the polycyclic aromatic hydrocarbons (PAHs), the chlorinated dibenzo-p-dioxins (âdioxinsâ), and many polyhalogenated biphenyls. To provide a platform for future research, we provide the historical underpinnings of our current state of knowledge about AHR signal transduction, identify a few areas of needed research, and then develop concepts such as adaptive metabolism, ligand structural diversity, and the importance of proligands in receptor activation. We finish with a discussion of the cognate physiological role of the AHR, our perspective on why this receptor is so highly conserved, and how we might think about its cognate ligands in the future.This review is dedicated in memory of the career of Alan Poland, one of the truly great minds in pharmacology and toxicology. This work was supported by the National Institutes of Health Grants R35-ES028377, T32-ES007015, P30-CA014520, P42-ES007381, and U01-ES1026127, The UW SciMed GRS Program, and The Morgridge Foundation. The authors would like to thank Catherine Stanley of UW Media Solutions for her artwork
Common path interference in Zener tunneling is a universal phenomenon
We show that the probability of electric field induced interband tunneling in
solid state systems is generically a non-monotonic (oscillatory) function of
the applied field. This unexpected behavior can be understood as arising due to
a common path interference between two distinct tunneling solutions. The
phenomenon is insensitive to magnetic field, and arises whenever the low energy
dispersion relation contains higher order terms in addition to the usual
term. Such higher order terms are generically present, albeit with small
co-efficient, so that the oscillatory Zener tunneling is a universal
phenomenon. However, the first `Zener oscillation' occurs at a transmission
probability which is exponentially small when the co-efficient of the higher
order terms is small. This explains why this oscillatory aspect of Zener
tunneling has been hitherto overlooked, despite its universality. The common
path interference is also destroyed by the presence of odd powers of in the
low energy dispersion relation. Since odd powers of are strictly absent
only when the tunneling barrier lies along an axis of mirror symmetry, it
follows that the robustness of the oscillatory behavior depends on the
orientation of the tunneling barrier. Bilayer graphene is identified as a
particularly good material for observation of common path interference, due to
its unusual nearly isotropic dispersion relation, where the term makes
the leading contribution
Enhanced self-field critical current density of nano-composite YBa(2)Cu(3)O(7) thin films grown by pulsed-laser deposition
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ EPLA, 2008.Enhanced self-field critical current density Jc of novel, high-temperature superconducting thin films is reported. Layers are deposited on (001) MgO substrates by laser ablation of YBa2Cu3O7âÎŽ(Y-123) ceramics containing Y2Ba4CuMOx (M-2411, M=Ag, Nb, Ru, Zr) nano-particles. The Jc of films depends on the secondary-phase content of the ceramic targets, which was varied between 0 and 15âmol%. Composite layers (2âmol% of Ag-2411 and Nb-2411) exhibit Jc values at 77âK of up to 5.1âMA/cm2, which is 3 to 4 times higher than those observed in films deposited from phase pure Y-123 ceramics. Nb-2411 grows epitaxially in the composite layers and the estimated crystallite size is ~10ânm.The Austrian Science Fund, the Austrian Federal Ministry of Economics and Labour, the European Science Foundation and the Higher Education Commission of Pakistan
Plasmon reflections by topological electronic boundaries in bilayer graphene
Domain walls separating regions of AB and BA interlayer stacking in bilayer
graphene have attracted attention as novel examples of structural solitons,
topological electronic boundaries, and nanoscale plasmonic scatterers. We show
that strong coupling of domain walls to surface plasmons observed in infrared
nanoimaging experiments is due to topological chiral modes confined to the
walls. The optical transitions among these chiral modes and the band continua
enhance the local ac conductivity, which leads to plasmon reflection by the
domain walls. The imaging reveals two kinds of plasmonic standing-wave
interference patterns, which we attribute to shear and tensile domain walls. We
compute the electronic structure of both wall varieties and show that the
tensile wall contain additional confined bands which produce a
structure-specific contrast of the local conductivity. The calculated plasmonic
interference profiles are in quantitative agreement with our experiments.Comment: 14 pages, 5 figure
Probing Spin-Charge Relation by Magnetoconductance in One-Dimensional Polymer Nanofibers
Polymer nanofibers are one-dimensional organic hydrocarbon systems containing
conducting polymers where the non-linear local excitations such as solitons,
polarons and bipolarons formed by the electron-phonon interaction were
predicted. Magnetoconductance (MC) can simultaneously probe both the spin and
charge of these mobile species and identify the effects of electron-electron
interactions on these nonlinear excitations. Here we report our observations of
a qualitatively different MC in polyacetylene (PA) and in polyaniline (PANI)
and polythiophene (PT) nanofibers. In PA the MC is essentially zero, but it is
present in PANI and PT. The universal scaling behavior and the zero (finite) MC
in PA (PANI and PT) nanofibers provide evidence of Coulomb interactions between
spinless charged solitons (interacting polarons which carry both spin and
charge)
Re â Training Needs of Mechanical Engineering Technologists for Improved Performance in Scientific Equipment Development Institutes in Nigeria.
Following constant complains by our schools on short falls in the supply of laboratory apparatus and even when available they are sub â standard, this study was conducted to determine the re-training needs of mechanical engineering technologists who are directly involved in the production of these laboratory apparatus  for improved performance in Scientific Equipment Development Institutes (SEDI) in Nigeria. Two research questions and 2 hypotheses were formulated to guide the study. The study was conducted in the two Scientific Development Institutes located at Minna and Enugu. A survey research design approach was adopted. The entire population of 82 mechanical engineers and 140 mechanical engineering technologists served as the respondents. No sampling was done. A 50 item structured questionnaire was used to collect the relevant data for the study. Data collected were analyzed using frequency counts, standard deviation, mean and t â test statistics. Results from analysis of data showed that all the 50 proposed items were accepted as retraining needs of mechanical engineering technologists. Specifically, the study revealed that the technologists were most deficient in areas of the use of automatic, NC, and CNC machines. It was recommended that as a matter of urgency government should put in place various strategies of retraining such as partnership with production industries, workshops, seminars and short term trainings outside the country. Key words: Re-training, performance, technologists, industries, scientific equipmen
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