2,403 research outputs found
Trade Reforms and Market Selection: Evidence from Manufacturing Plants in Colombia
We use plant output and input prices to decompose the profit margin into four parts: productivity, demand shocks, mark-ups and input costs. We find that each of these market fundamentals are important in explaining plant exit. We then use variation across sectors in tariff changes after the Colombian trade reform to assess whether the impact of market fundamentals on plant exit changed with in creased international competition. We find that greater international competition magnifies the impact of productivity, and other market fundamentals, on plant exit. A dynamic simulation that compares the distribution of productivity with and without the trade reform shows that improvements in market selection from trade reform help to weed out the least productive plants and increase average productivity. In addition, we find that trade liberalization increases productivity of incumbent plants and improves the allocation of activity within industries.trade liberalization, plant exit, market selection
Scanning Tunneling Spectroscopy of Bi2Sr2CuO6+d: New Evidence for the Common Origin of the Pseudogap and Superconductivity
Using scanning tunneling spectroscopy, we investigated the temperature dependence of the quasiparticle density of states of overdoped Bi2Sr2CuO6+δ between 275 mK and 82 K. Below Tc = 10 K, the spectra show a gap with well-defined coherence peaks at ±Δp≃12 meV, which disappear at Tc. Above Tc, the spectra display a clear pseudogap of the same magnitude, gradually filling up and vanishing at T*≃68 K. The comparison with Bi2Sr2CaCu2O8+δ demonstrates that the pseudogap and the superconducting gap scale with each other, providing strong evidence that they have a common origin
Negative frequency tuning of a carbon nanotube nano-electromechanical resonator
A suspended, doubly clamped single wall carbon nanotube is characterized as
driven nano-electromechanical resonator at cryogenic temperatures.
Electronically, the carbon nanotube displays small bandgap behaviour with
Coulomb blockade oscillations in electron conduction and transparent contacts
in hole conduction. We observe the driven mechanical resonance in dc-transport,
including multiple higher harmonic responses. The data shows a distinct
negative frequency tuning at finite applied gate voltage, enabling us to
electrostatically decrease the resonance frequency to 75% of its maximum value.
This is consistently explained via electrostatic softening of the mechanical
mode.Comment: 4 pages, 4 figures; submitted for the IWEPNM 2013 conference
proceeding
Trade Reforms and Market Selection: Evidence from Manufacturing Plants in Colombia
We use plant output and input prices to decompose the profit margin into four parts: productivity, demand shocks, mark-ups and input costs. We find that each of these market fundamentals are important in explaining plant exit. We then use variation across sectors in tariff changes after the Colombian trade reform to assess whether the impact of market fundamentals on plant exit changed with increased international competition. We find that greater international competition magnifies the impact of productivity, and other market fundamentals, on plant exit. A dynamic simulation that compares the distribution of productivity with and without the trade reform shows that improvements in market selection from trade reform help to weed out the least productive plants and increase average productivity. In addition, we find that trade liberalization increases productivity of incumbent plants and improves the allocation of activity within industries.
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Distinct ligand binding sites in integrin alpha3beta1 regulate matrix adhesion and cell-cell contact.
The integrin alpha3beta1 mediates cellular adhesion to the matrix ligand laminin-5. A second integrin ligand, the urokinase receptor (uPAR), associates with alpha3beta1 via a surface loop within the alpha3 beta-propeller (residues 242-246) but outside the laminin binding region, suggesting that uPAR-integrin interactions could signal differently from matrix engagement. To explore this, alpha3-/- epithelial cells were reconstituted with wild-type (wt) alpha3 or alpha3 with Ala mutations within the uPAR-interacting loop (H245A or R244A). Wt or mutant-bearing cells showed comparable expression and adhesion to laminin-5. Cells expressing wt alpha3 and uPAR dissociated in culture, with increased Src activity, up-regulation of SLUG, and down-regulation of E-cadherin and gamma-catenin. Src kinase inhibition or expression of Src 1-251 restored the epithelial phenotype. The H245A and R244A mutants were unaffected by coexpression of uPAR. We conclude that alpha3beta1 regulates both cell-cell contact and matrix adhesion, but through distinct protein interaction sites within its beta-propeller. These studies reveal an integrin- and Src-dependent pathway for SLUG expression and mesenchymal transition
Exclusive channels in semi-inclusive production of pions and kaons
We investigate the role of exclusive channels in semi-inclusive
electroproduction of pions and kaons. Using the QCD factorization theorem for
hard exclusive processes we evaluate the cross sections for exclusive
pseudoscalar and vector meson production in terms of generalized parton
distributions and meson distribution amplitudes. We investigate the
uncertainties arising from the modeling of the nonperturbative input
quantities. Combining these results with available experimental data, we
compare the cross sections for exclusive channels to that obtained from quark
fragmentation in semi-inclusive deep inelastic scattering. We find that rho^0
production is the only exclusive channel with significant contributions to
semi-inclusive pion production at large z and moderate Q^2. The corresponding
contribution to kaon production from the decay of exclusively produced phi and
K^* is rather small.Comment: 33 pages, 18 figure
Evaluation of the antioxidant capacity of betalainic fruits and vegetables
The present investigation determined total phenolics, ascorbic acid, betalain contents and the corresponding antioxidant capacities of betalain-bearing fruits and vegetables. In addition to differently coloured Swiss chard petioles (Beta vulgaris L. ssp. cicla [L.] Alef. cv. ‘Bright Lights’) and hypocotyls of white, yellow, and red beetroot varieties (Beta vulgaris L. ssp. vulgaris, cv. ‘Albina Vereduna’, cv. ‘Burpee’s Golden’, and cv. ‘Rote Kugel 2’), juices from cactus pears (Opuntia ficus-indica [L.] Mill. cv. ‘Gialla’ and cv. ‘Rossa’) and pitaya fruits (Hylocereus polyrhizus [Weber] Britton & Rose, H. undatus [Haworth] Britton & Rose, Selenicereus megalanthus [K. Schumann ex Vaupel] Moran) were included in this study. Antioxidant capacities were determined by application of the TEAC and FRAP assays, respectively, resulting in differing rankings of the commodities investigated. In both test systems, highest antioxidant capacity was shown for red beetroot extract while for the remaining samples no straightforward order could be established
COMPARATIVE ANALYSIS OF THE KINEMATICS AND KINETICS OF FORWARD AND BACKWARD HUMAN LOCOMOTION
Although common in occurrence one of the least studied modes
of human motion is backward locomotion. Backward walking and jogging are currently being used as components of physical therapy for persons who have suffered trauma or submitted to surgery on the lower extremity or back as well as stroke patients. (Gray, 1985, Bates and McCaw, 1986; Kramer and Reid, 1981; Bates, Morrison, Hamill, 1984).
Anecdotal reports of reduced noxious stress and beneficial
proprioceptive stimulation have perpetuated the use of this form of physical therapy. Position specific sport training necessitates backward locomotion to engender efficient game performances. In numerous sport activities the defensive techniques employed entail retreating or "jockeying" maneuvers. Evasive offensive techniques likewise include backward travel. Some coaches and athletes are supplementing their conventional fitness training regimens with backwards running claiming enhanced hip extensor overloading with the resulting strength adaptation (Morton, 1985)
Spin dynamics in p-doped semiconductor nanostructures subject to a magnetic field tilted from the Voigt geometry
We develop a theoretical description of the spin dynamics of resident holes
in a p-doped semiconductor quantum well (QW) subject to a magnetic field tilted
from the Voigt geometry. We find the expressions for the signals measured in
time-resolved Faraday rotation (TRFR) and resonant spin amplification (RSA)
experiments and study their behavior for a range of system parameters. We find
that an inversion of the RSA peaks can occur for long hole spin dephasing times
and tilted magnetic fields. We verify the validity of our theoretical findings
by performing a series of TRFR and RSA experiments on a p-modulation doped
GaAs/Al_{0.3}Ga_{0.7}As single QW and showing that our model can reproduce
experimentally observed signals.Comment: 9 pages, 3 figures; corrected typo
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