1,673 research outputs found
Interpreting the Hours-Technology time-varying relationship
We investigate the time varying relation between hours and technology shocks using a structural business cycle model. We propose an RBC model with a Constant Elasticity of Substitution (CES) production function that allows for capital- and labor-augmenting technology shocks. We estimate the model with Bayesian techniques. In the full sample, we find (i) evidence in favor of a less than unitary elasticity of substitution (rejecting Cobb-Douglas) and (ii) a sizable role for capital augmenting shock for business cycles fluctuations. In rolling sub-samples, we document that the transmission of technology shocks to hours worked has been varying over time. We argue that this change is due to the increase of the elasticity of factor substitution. That is, labor and capital became less complementary throughout the sample inducing a change in the sign and size of the response of hours. We conjecture that this change may have been induced by a change in the skill composition of the labor input.Hours Worked and Business Cycles, Bayesian Methods.
Smale flows on
In this paper, we use abstract Lyapunov graphs as a combinatorial tool to
obtain a complete classification of Smale flows on
. This classification gives necessary and
sufficient conditions that must be satisfied by an abstract Lyapunov graph in
order for it to be associated to a Smale flow on
Optimized generation of spatial qudits by using a pure phase spatial light modulator
We present a method for preparing arbitrary pure states of spatial qudits,
namely, D-dimensional (D > 2) quantum systems carrying information in the
transverse momentum and position of single photons. For this purpose, a set of
D slits with complex transmission are displayed on a spatial light modulator
(SLM). In a recent work we have shown a method that requires a single
phase-only SLM to control independently the complex coefficients which define
the quantum state of dimension D. The amplitude information was codified by
introducing phase gratings inside each slit and the phase value of the complex
transmission was added to the phase gratings. After a spatial filtering process
we obtained in the image plane the desired qudit state. Although this method
has proven to be a good alternative to compact the previously reported
architectures, it presents some features that could be improved. In this paper
we present an alternative scheme to codify the required phase values that
minimizes the effects of temporal phase fluctuations associated to the SLM
where the codification is carried on. In this scheme the amplitudes are set by
appropriate phase gratings addressed at the SLM while the relative phases are
obtained by a lateral displacement of these phase gratings. We show that this
method improves the quality of the prepared state and provides very high
fidelities of preparation for any state. An additional advantage of this scheme
is that a complete 2\pi modulation is obtained by shifting the grating by one
period, and hence the encoding is not limited by the phase modulation range
achieved by the SLM. Numerical simulations, that take into account the phase
fluctuations, show high fidelities for thousands of qubit states covering the
whole Bloch sphere surface. Similar analysis are performed for qudits with D =
3 and D = 7.Comment: 12 pages, 7 figure
Misallocation, Access to Finance, and Public Credit: Firm-Level Evidence
Using a database of 23,000 firms in 45 economies, we test the quantitative
importance of access to finance and access to public and private credit for the
determination of misallocation. We first derive measures of factor market and
size distortions, and then use these measures within a regression framework to
test the significance of self-declared access-to-finance obstacles as well as the
effect of access to a credit line issued by either a government-owned or private
bank. We find that access-to-finance obstacles and private credit increase the
dispersion of distortions. Public credit has a very small effect. For firms that do
not face financial obstacles, public credit increases the dispersion of distortions;
for firms that face financial obstacles, it slightly decreases dispersion. Public
credit does not appear to compensate for the distortions that exist in private
credit markets. Quantitatively, however, financial variables explain a very small
part of the dispersion of factor market and size distortions
Reanalysis of the FEROS observations of HIP 11952
Aims. We reanalyze FEROS observations of the star HIP 11952 to reassess the
existence of the proposed planetary system. Methods. The radial velocity of the
spectra were measured by cross-correlating the observed spectrum with a
synthetic template. We also analyzed a large dataset of FEROS and HARPS
archival data of the calibrator HD 10700 spanning over more than five years. We
compared the barycentric velocities computed by the FEROS and HARPS pipelines.
Results. The barycentric correction of the FEROS-DRS pipeline was found to be
inaccurate and to introduce an artificial one-year period with a semi-amplitude
of 62 m/s. Thus the reanalysis of the FEROS data does not support the existence
of planets around HIP 11952.Comment: 7 pages, 8 figures, 1 tabl
Dynamics of gravity driven three-dimensional thin films on hydrophilic-hydrophobic patterned substrates
We investigate numerically the dynamics of unstable gravity driven
three-dimensional thin liquid films on hydrophilic-hydrophobic patterned
substrates of longitudinal stripes and checkerboard arrangements. The thin film
can be guided preferentially on hydrophilic longitudinal stripes, while fingers
develop on adjacent hydrophobic stripes if their width is large enough. On
checkerboard patterns, the film fingering occurs on hydrophobic domains, while
lateral spreading is favoured on hydrophilic domains, providing a mechanism to
tune the growth rate of the film. By means of kinematical arguments, we
quantitatively predict the growth rate of the contact line on checkerboard
arrangements, providing a first step towards potential techniques that control
thin film growth in experimental setups.Comment: 30 pages, 12 figure
Mutation and SARS-CoV-2 strain competition under vaccination in a modified SIR model
The crisis caused by the COVID-19 outbreak around the globe raised an
increasing concern about the ongoing emergence of variants of SARS-CoV-2 that
may evade the immune response provided by vaccines. New variants appear due to
mutation, and as the cases accumulate, the probability of the emergence of a
variant of concern increases. In this article, we propose a modified SIR model
with waning immunity that captures the competition of two strain classes of an
infectious disease under the effect of vaccination with a highly contagious and
deadly strain class emerging from a prior strain due to mutation. When these
strains compete for a limited supply of susceptible individuals, changes in the
efficiency of vaccines may affect the behaviour of the disease in a non-trivial
way, resulting in complex outcomes. We characterise the parameter space
including intrinsic parameters of the disease, and using the vaccine
efficiencies as control variables. We find different types of transcritical
bifurcations between endemic fixed points and a disease-free equilibrium and
identify a region of strain competition where the two strain classes coexist
during a transient period. We show that a strain can be extinguished either due
to strain competition or vaccination, and we obtain the critical values of the
efficiency of vaccines to eradicate the disease. Numerical studies using
parameters estimated from publicly reported data agree with our theoretical
results. Our mathematical model could be a tool to assess quantitatively the
vaccination policies of competing and emerging strains using the dynamics in
epidemics of infectious diseases.Comment: 28 pages, 8 figure
Investigation of the calcification response of foraminifera and pteropods to high CO2 environments in the Pleistocene, Paleogene and Cretaceous
Diffantom: Whole-Brain Diffusion MRI Phantoms Derived from Real Datasets of the Human Connectome Project.
Food allergies are believed to be on the rise and currently management relies on the avoidance of the food. Hen's egg allergy is after cow's milk allergy the most common food allergy; eggs are used in many food products and thus difficult to avoid. A technological process using a combination of enzymatic hydrolysis and heat treatment was designed to produce modified hen's egg with reduced allergenic potential. Biochemical (SDS-PAGE, Size exclusion chromatography and LC-MS/MS) and immunological (ELISA, immunoblot, RBL-assays, animal model) analysis showed a clear decrease in intact proteins as well as a strong decrease of allergenicity. In a clinical study, 22 of the 24 patients with a confirmed egg allergy who underwent a double blind food challenge with the hydrolysed egg remained completely free of symptoms. Hydrolysed egg products may be beneficial as low allergenic foods for egg allergic patients to extent their diet. This article is protected by copyright. All rights reserved
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