18,412 research outputs found
Learning-by-Doing, Learning-by-Exporting, and Productivity: Evidence from Colombia
The empirical evidence on whether participation in export markets increases plant-level productivity has been inconclusive so far. We explain this inconclusiveness by drawing on Arrow's (1962) characterization of learning-by-doing, which suggests focusing on young plants and using measures of export experience rather than export participation. We find strong evidence of learning-by-exporting for young Colombian manufacturing plants between 1981 and 1991: total factor productivity increases 4%-5% for each additional year a plant has exported, after controlling for the effect of current exports on total factor productivity. Learning-by-exporting is more important for young than for old plants and in industries that deliver a larger percentage of their exports to high-income countries.learning, trade, total factor productivity, exports, export-led growth
Learning-by-doing, learning-by-exporting, and productivity : evidence from Colombia
The empirical evidence on whether participation in export markets increases plant-level productivity has been inconclusive so far. The authors explain this inconclusiveness by drawing on Arrow's (1962) characterization of learning-by-doing, which suggests focusing on young plants and using measures of export experience rather than export participation. They find strong evidence of learning-by-exporting for young Colombian manufacturing plants between 1981 and 1991: total factor productivity increases 4-5 percent for each additional year a plant has exported, after controlling for the effect of current exports on total factor productivity. Learning-by-exporting is more important for young than for old plants and in industries that deliver a larger percentage of their exports to high-income countries.Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Educational Sciences,Scientific Research&Science Parks
Fate of the Bose insulator in the limit of strong localization and low Cooper-pair density in ultrathin films
A Bose insulator composed of a low density of strongly localized Cooper pairs develops at the two-dimensional superconductor to insulator transition (SIT) in a number of thin film systems. Investigations of ultrathin amorphous PbBi films far from the SIT described here provide evidence that the Bose insulator gives way to a second insulating phase with decreasing film thickness. At a critical film thickness dc the magnetoresistance changes sign from positive, as expected for boson transport, to negative, as expected for fermion transport, signs of local Cooper-pair phase coherence effects on transport vanish, and the transport activation energy exhibits a kink. Below dc pairing fluctuation effects remain visible in the high-temperature transport while the activation energy continues to rise. These features show that Cooper pairing persists and suggest that the localized unpaired electron states involved in transport are interspersed among regions of strongly localized Cooper pairs in this strongly localized, low Cooper-pair density phase
Collapse of the Cooper pair phase coherence length at a superconductor to insulator transition
We present investigations of the superconductor to insulator transition (SIT)
of uniform a-Bi films using a technique sensitive to Cooper pair phase
coherence. The films are perforated with a nanohoneycomb array of holes to form
a multiply connected geometry and subjected to a perpendicular magnetic field.
Film magnetoresistances on the superconducting side of the SIT oscillate with a
period dictated by the superconducting flux quantum and the areal hole density.
The oscillations disappear close to the SIT critical point to leave a
monotonically rising magnetoresistance that persists in the insulating phase.
These observations indicate that the Cooper pair phase coherence length, which
is infinite in the superconducting phase, collapses to a value less than the
interhole spacing at this SIT. This behavior is inconsistent with the gradual
reduction of the phase coherence length expected for a bosonic, phase
fluctuation driven SIT. This result starkly contrasts with previous
observations of oscillations persisting in the insulating phase of other films
implying that there must be at least two distinct classes of disorder tuned
SITs
Probing the ejecta of evolved massive stars in transition: A VLT/SINFONI K-band survey
Massive evolved stars in transition phases, such as Luminous Blue Variables
(LBVs), B[e] Supergiants (B[e]SGs), and Yellow Hypergiants (YHGs), are not well
understood, and yet crucial steps in determining accurate stellar and galactic
evolution models. The circumstellar environments of these stars reveal their
mass-loss history, identifying clues to both their individual evolutionary
status and the connection between objects of different phases. Here we present
a survey of 25 such evolved massive stars (16 B[e]SGs, 6 LBVs, 2 YHGs, and 1
Peculiar Oe star), observed in the K-band with the Spectrograph for INtegral
Field Observation in the Near-Infrared (SINFONI; R = 4500) on the ESO VLT UT4 8
m telescope. The sample can be split into two categories based on spectral
morphology: one group includes all of the B[e]SGs, the Peculiar Oe star, and
two of the LBVs, while the other includes the YHGs and the rest of the LBVs.
The difference in LBV spectral appearance is due to some objects being in a
quiescent phase and some objects being in an active or outburst phase. CO
emission features are found in 13 of our targets, with first time detections
for MWC 137, LHA 120-S 35, and LHA 115-S 65. From model fits to the CO band
heads, the emitting regions appear to be detached from the stellar surface.
Each star with ^12CO features also shows ^13CO emission, signaling an evolved
nature. Based on the level of ^13C enrichment, we conclude that many of the
B[e]SGs are likely in a pre-Red Supergiant phase of their evolution. There
appears to be a lower luminosity limit of log L/L_solar = 5.0 below which CO is
not detected. The lack of CO features in several high luminosity B[e]SGs and
variability in others suggests that they may in fact be LBV candidates,
strengthening the connection between these two very similar transition phases.Comment: 20 pages, 13 figures, 7 tables. Accepted for publication in A&
Automatic identification of gait events using an instrumented sock
Background: textile-based transducers are an emerging technology in which piezo-resistive properties of materials
are used to measure an applied strain. By incorporating these sensors into a sock, this technology offers the
potential to detect critical events during the stance phase of the gait cycle. This could prove useful in several
applications, such as functional electrical stimulation (FES) systems to assist gait.
Methods: we investigated the output of a knitted resistive strain sensor during walking and sought to determine
the degree of similarity between the sensor output and the ankle angle in the sagittal plane. In addition, we
investigated whether it would be possible to predict three key gait events, heel strike, heel lift and toe off, with a
relatively straight-forward algorithm. This worked by predicting gait events to occur at fixed time offsets from
specific peaks in the sensor signal.
Results: our results showed that, for all subjects, the sensor output exhibited the same general characteristics as
the ankle joint angle. However, there were large between-subjects differences in the degree of similarity between
the two curves. Despite this variability, it was possible to accurately predict gait events using a simple algorithm.
This algorithm displayed high levels of trial-to-trial repeatability.
Conclusions: this study demonstrates the potential of using textile-based transducers in future devices that provide active gait assistance
Impacts of in vivo and in vitro exposures to tamoxifen: comparative effects on human cells and marine organisms
Tamoxifen (TAM) is a first generation-SERM administered for hormone receptor-positive (HER+) breast cancer in both pre- and post-menopausal patients and may undergo metabolic activation in organisms that share similar receptors and thus face comparable mechanisms of response. The present study aimed to assess whether environmental trace concentrations of TAM are bioavailable to the filter feeder M. galloprovincialis (100âŻngâŻL-1) and to the deposit feeder N. diversicolor (0.5, 10, 25 and 100âŻngâŻL-1) after 14âŻdays of exposure. Behavioural impairment (burrowing kinetic), neurotoxicity (AChE activity), endocrine disruption by alkali-labile phosphate (ALP) content, oxidative stress (SOD, CAT, GPXs activities), biotransformation (GST activity), oxidative damage (LPO) and genotoxicity (DNA damage) were assessed. Moreover, this study also pertained to compare TAM cytotoxicity effects to mussels and targeted human (i.e. immortalized retinal pigment epithelium - RPE; and human transformed endothelial cells - HeLa) cell lines, in a range of concentrations from 0.5âŻngâŻL-1 to 50âŻÎŒgâŻL-1. In polychaetes N. diversicolor, TAM exerted remarkable oxidative stress and damage at the lowest concentration (0.5âŻngâŻL-1), whereas significant genotoxicity was reported at the highest exposure level (100âŻngâŻL-1). In mussels M. galloprovincialis, 100âŻngâŻL-1 TAM caused endocrine disruption in males, neurotoxicity, and an induction in GST activity and LPO byproducts in gills, corroborating in genotoxicity over the exposure days. Although cytotoxicity assays conducted with mussel haemocytes following in vivo exposure was not effective, in vitro exposure showed to be a feasible alternative, with comparable sensitivity to human cell line (HeLa).info:eu-repo/semantics/publishedVersio
Age-related differences during visual search: the role of contextual expectations and cognitive control mechanisms
We explored the efficacy of drawing pictures as an encoding strategy to enhance memory performance in healthy older adults and individuals with probable dementia. In an incidental encoding phase, participants were asked to either draw a picture or write out each word from a set of 30 common nouns for 40 seconds each. Episodic memory for the target words was compared in a group of healthy older adults to individuals with probable dementia (MMSE/MOCA range 4 to 25). In two experiments we showed that recall and recognition performance was higher for words that were drawn than written out during encoding, for both participant groups. We suggest that incorporating visuo-perceptual information into memory enhanced performance by increasing reliance on visual-sensory brain regions, which are relatively intact in these populations. Our findings demonstrate that drawing is a valuable technique leading to measurable gains in memory performance for individuals with probable dementia
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