7,832 research outputs found
Attraction of Culex mosquitoes to aldehydes from human emanations.
Anecdotes related to preferential mosquito bites are very common, but to date there is no complete explanation as to why one out of two people systematically receives more mosquito bites than the other when both are equally accessible. Here we tested the hypothesis that two constituents of skin emanations, 6-methyl-5-heptan-2-one (6-MHO) and geranylacetone (GA), are natural repellents and may account for differential attraction in different ratios. We studied skin emanations from two human subjects, confirmed in behavioral assays that female southern house mosquitoes are significantly more attracted to subject A (attractant) than to subject N (non-attractant), and tested their 6-MHO/GA ratios in a dual-choice olfactometer. Although repelling at high doses, 6-MHO/GA mixtures were not active at the levels emitted by human skin. We found, however, differential attraction elicited by the aldehydes in the ratios produced by subjects A and N. When tested in a dose commensurate with the level released from human skin and in the ratio produced by subject A, the aldehyde mixture significantly attracted mosquitoes. By contrast, an aldehyde mixture at the same ratio released by subject N did not attract mosquitoes. We, therefore, hypothesized that aldehydes may play a role in the commonly observed differential attraction
Faceted anomalous scaling in the epitaxial growth of semiconductor films
We apply the generic dynamical scaling theory (GDST) to the surfaces of CdTe
polycrystalline films grown in glass substrates. The analysed data were
obtained with a stylus profiler with an estimated resolution lateral resolution
of m. Both real two-point correlation function and power spectrum
analyses were done. We found that the GDST applied to the surface power spectra
foresees faceted morphology in contrast with the self-affine surface indicated
by the local roughness exponent found via the height-height correlation
function. This inconsistency is explained in terms of convolution effects
resulting from the finite size of the probe tip used to scan the surfaces. High
resolution AFM images corroborates the predictions of GDST.Comment: to appear in Europhysics Letter
Modelling of epitaxial film growth with a Ehrlich-Schwoebel barrier dependent on the step height
The formation of mounded surfaces in epitaxial growth is attributed to the
presence of barriers against interlayer diffusion in the terrace edges, known
as Ehrlich-Schwoebel (ES) barriers. We investigate a model for epitaxial growth
using a ES barrier explicitly dependent on the step height. Our model has an
intrinsic topological step barrier even in the absence of an explicit ES
barrier. We show that mounded morphologies can be obtained even for a small
barrier while a self-affine growth, consistent with the Villain-Lai-Das Sarma
equation, is observed in absence of an explicit step barrier. The mounded
surfaces are described by a super-roughness dynamical scaling characterized by
locally smooth (faceted) surfaces and a global roughness exponent .
The thin film limit is featured by surfaces with self-assembled
three-dimensional structures having an aspect ratio (height/width) that may
increase or decrease with temperature depending on the strength of step
barrier.Comment: To appear in J. Phys. Cond. Matter; 3 movies as supplementary
materia
The scenario of two-dimensional instabilities of the cylinder wake under EHD forcing: A linear stability analysis
We propose to study the stability properties of an air flow wake forced by a dielectric barrier discharge (DBD) actuator, which is a type of electrohydrodynamic (EHD) actuator. These actuators add momentum to the flow around a cylinder in regions close to the wall and, in our case, are symmetrically disposed near the boundary layer separation point.
Since the forcing frequencies, typical of DBD, are much higher than the natural shedding frequency of the flow, we will be considering the forcing actuation as stationary.
In the first part, the flow around a circular cylinder modified by EHD actuators will be experimentally studied by means of particle image velocimetry (PIV). In the second part, the EHD actuators have been numerically implemented as a boundary condition on the cylinder surface. Using this boundary condition, the computationally obtained base flow is then compared with the experimental one in order to relate the control parameters from both methodologies.
After validating the obtained agreement, we study the Hopf bifurcation that appears once the flow starts the vortex shedding through experimental and computational approaches. For the base flow derived from experimentally obtained snapshots, we monitor the evolution of the velocity amplitude oscillations. As to the computationally obtained base flow, its stability is analyzed by solving a global eigenvalue problem obtained from the linearized Navier–Stokes equations. Finally, the critical parameters obtained from both approaches are compared
The genetics of colored sequence synesthesia: Evidence of linkage to chromosome 16q and genetic heterogeneity for the condition
Synesthesia is a perceptual condition in which normal sensory stimulation can trigger anomalous sensory experiences. For example, synesthetes may experience colors in response to sounds, tastes in response to words, or smells in response to touch. We here focus on colored sequence synesthesia, in which color experiences are triggered by learned ordinal sequences such as letters, numbers, weekdays and months. Although synesthesia has been noted in the scientific literature for over a century, it is understood only at the level of the phenomenology, and not at the molecular and neural levels. We have performed a linkage analysis to identify the first genetic loci responsible for the increased neural crosstalk underlying colored sequence synesthesia. Our analysis has identified a 23 MB region on chromosome 16 as a putative locus for the trait. Our data provide the first step in understanding neural crosstalk from its molecular basis to its behavioral consequences, opening a new inroad into the understanding of the multisensory brain
Orientation dynamics of weakly Brownian particles in periodic viscous flows
Evolution equations for the orientation distribution of axisymmetric
particles in periodic flows are derived in the regime of small but non-zero
Brownian rotations. The equations are based on a multiple time scale approach
that allows fast computation of the relaxation processes leading to statistical
equilibrium. The approach has been applied to the calculation of the effective
viscosity of a thin disk suspension in gravity waves.Comment: 16 pages, 7 eps figures include
Produção de mudas de coqueiros, Cocos nucifera L., pelo sistema alternativo.
Apresenta método de produção alternativa de mudas de coqueiro.bitstream/item/81099/1/CPATC-COM.-TEC.-22-98.pd
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Factors associated with postpartum depressive symptomatology in Brazil: The Birth in Brazil National Research Study, 2011/2012
Background: Depression is one of the most common postpartum mental disorders. Many sociodemographic and individuals risk factors are associated with maternal depression but the impact of high levels of birth intervention is unclear. The Brazilian context is characterized by excessive intervention and frequent non-compliance with recommended obstetric protocols. This study therefore examined the impact of sociodemographic, individual, and obstetric risk factors in postpartum depression.
Methods: The Birth in Brazil research study is a national study of 23,894 postpartum women. Information about depression was obtained by telephone interview at 6 to 18 months after birth and was measured using the Edinburgh Postnatal Depression Scale.
Results: The prevalence of probable cases of depression was 26.3%. A multivariate model identified significant sociodemographic and individual risk factors as: brown skin color (OR = 1.15 CI 1.01-1.31), lower economic class (OR=1.70 CI 1.41-2.06), alcohol use (OR= 1.41 CI 1.09-1.84) and a history of mental disorders (OR= 3.13 CI 1.80-5.44). Significant obstetric factors were unplanned pregnancy (OR=1.22 CI 1.05-1.43 for wanted later and OR= 1.38 CI 1.20-1.60 for never wanted), multiparity (OR=1.97 CI 1.58-2.47 for 3 or more children), and poor care during birth (OR= 2.02 CI 1.28-3.20) or of the newborn (OR=2.16 CI 1.51-3.10). Obstetric interventions and complications were not associated with maternal depression.
Limitations: Depression was measured only once so we are not able to examine the course over time. The associational and reverse causality cannot be ruled out for some variables.
Conclusions: The prevalence of postpartum depression is high in Brazilian women six months after birth. Poor care of women and babies during birth is more important in postpartum depression than physical obstetric or neonatal intervention and complications
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