683 research outputs found
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Controlled deformation of vesicles by flexible structured media
Liquid crystalline (LC) materials, such as actin or tubulin networks, are known to be capable of deforming the shape of cells. Here, elements of that behavior are reproduced in a synthetic system, namely, a giant vesicle suspended in a LC, which we view as a first step toward the preparation of active, anisotropic hybrid systems that mimic some of the functionality encountered in biological systems. To that end, we rely on a coupled particle-continuum representation of deformable networks in a nematic LC represented at the level of a Landau–de Gennes free energy functional. Our results indicate that, depending on its elastic properties, the LC is indeed able to deform the vesicle until it reaches an equilibrium, anisotropic shape. The magnitude of the deformation is determined by a balance of elastic and surface forces. For perpendicular anchoring at the vesicle, a Saturn ring defect forms along the equatorial plane, and the vesicle adopts a pancake-like, oblate shape. For degenerate planar anchoring at the vesicle, two boojum defects are formed at the poles of the vesicle, which adopts an elongated, spheroidal shape. During the deformation, the volume of the topological defects in the LC shrinks considerably as the curvature of the vesicle increases. These predictions are confirmed by our experimental observations of spindle-like shapes in experiments with giant unilamellar vesicles with planar anchoring. We find that the tension of the vesicle suppresses vesicle deformation, whereas anchoring strength and large elastic constants promote shape anisotropy
Testing integrability with a single bit of quantum information
We show that deterministic quantum computing with a single bit (DQC1) can
determine whether the classical limit of a quantum system is chaotic or
integrable using O(N) physical resources, where is the dimension of the
Hilbert space of the system under study. This is a square root improvement over
all known classical procedures. Our study relies strictly on the random matrix
conjecture. We also present numerical results for the nonlinear kicked top.Comment: Minor changes taking into account Howard Wiseman's comment:
quant-ph/0305153. Accepted for publication in Phys. Rev.
Physical mechanisms and parameters for models of microstructure evolution under irradiation in Fe alloys – Part I: Pure Fe
This paper is the first of three that overview the main mechanisms that drive the microstructure evolution in Fe alloys under irradiation. It focuses on pure α-Fe and compiles the parameters that describe quantitatively the mobility and stability of point-defects and especially their clusters, including possible reactions and criteria to decide when they should react. These parameters are the result of several years of calculations and application in microstructure evolution models. They are mainly collected from the literature and the parameter choice tries to reconcile different sets of values that, while being in general qualitatively similar, are often quantitatively not coincident. A few calculation results are presented here for the first time to support specific approximations concerning defect properties or features. Since calculations cannot cover all possible defect configurations, the definition of these parameters often requires educated guesses to fill knowledge gaps. These guesses are here listed and discussed whenever relevant. This is therefore a “hands-on” paper that: (i) collects in a single report most microstructure evolution parameters that are found in the literature for irradiated α-Fe, including a discussion of the most important mechanisms at play based on current knowledge; (ii) selects a ready-to-use set that can be employed in microstructure evolution models, such as those based on object kinetic Monte Carlo (OKMC) methods. This work also identifies parameters that are needed, but not known, hopefully prompting corresponding calculations in the future.This work has received funding from the Euratom research and training programme 2014-2018 under grant agreement No. 755039 (M4F project). This research also contributes to the Joint Programme on Nuclear Materials of the European Energy Research Alliance (EERA-JPNM)
Implementation of UV rotational Raman channel to improve aerosol retrievals from multiwavelength lidar
Vibrational Raman effect is widely used in atmospheric lidar systems, but rotational Raman present several advantages. We have implemented a new setup in the ultraviolet branch of an existing multiwavelength lidar system to collect signal from rotational Raman lines of Oxygen and Nitrogen. We showed that, with an appropriate filter wavelength selection, the systematic error introduced in the particle optical properties due to temperature dependence was less than 4%. With this new setup, we have been able to retrieve aerosol extinction and backscatter coefficients profiles at 355 nm with 1-h time resolution during daytime and up to 1-min time resolution during nighttime.Grupo de Física de la Atmósfera (RNM119
Extinction-related Angström exponent characterization of submicrometric volume fraction in atmospheric aerosol particles
The AEAOD– ΔAEAOD grid proposed by Gobbi et al. (2007) is a graphical method used to visually represent the spectral characterization of aerosol optical depth (AOD), i.e. Angström exponent (AE) and its curvature, in order to infer the fine mode contribution (η) to the total AOD and the size of the fine mode aerosol particles. Perrone et al. (2014) applied this method for the wavelengths widely used in lidar measurements. However, in neither case does the method allow for a direct relationship between η and the fine mode fraction contribution to the total aerosol population. Some discussions are made regarding the effect of shape and composition to the classical AE-ΔAE plot. The potential use of particle backscatter measurements, widely used in aerosol characterization methods together with extinction measurements, is also discussed in the AE-ΔAE grid context. A modification is proposed that yields the submicron contribution to the total volume concentration by using particle extinction data, and a comparison to experimental measurements is made. Our results indicate that the use of a modified AE-ΔAE grid plot to directly obtain submicrometric and micrometric mode fraction to the total aerosol population is feasible if a volume-based bimodal particle size distribution is used instead of a number-based one.Andalusia Regional Government through project P12-RNM-2409Spanish Ministry of Sciences, Innovation and Universities (CGL2016-81092 and CGL2017 -90884 - REDT
Vocalizaciones asociadas al comportamiento colonial de Cacicus chrysonotus leucoramphus (Icteridae) en Colombia
In order to assess the association between the vocalizations and the displayed behaviors of the Golden-shouldered Mountain Cacique (Cacicus chrysonotus leucoramphus), we sampled both acoustic and behavioral features at three sites in the Andes of Nariño, southern Colombia. We obtained seven vocalization types, six of them associated with at least one of the three identified behavioral categories (vigilance, alertness, and territorial defense), and one linked with a courtship exhibition. Vocalizations with higher values of bandwidth and frequency modulations were associated with territorial behavior, whereas those with lower values of bandwidth and few frequency modulations were associated with vigilance and alert. Results showed similarities in the acoustic structure of vocalizations and the related social context with other species as the C. cela and C. haemorrhous. C. c. leucoramphus uses specific types of vocalizations in a particular social context, with some vocalizations used in different behaviors. This study describes for the first time the social context in which vocalizations are associated with their behaviors.Con el objetivo de evaluar la asociación entre las vocalizaciones y los comportamientos del cacique montano norteño (Cacicus chrysonotus leucoramphus), se tomaron registros acústicos y conductuales de la especie en cuatro localidades de los Andes de Nariño, en el sur de Colombia. Se registraron seis tipos de vocalizaciones asociadas a por lo menos una de las tres categorías conductuales identificadas (vigilancia, alerta y defensa territorial), y una vocalización registrada en un único evento de cortejo. Vocalizaciones con valores más altos de ancho de banda y modulación de frecuencia resultaron asociadas a defensa territorial, mientras que vocalizaciones con valores bajos de ancho de banda y poca modulación cumplieron funciones de vigilancia y alerta. Los resultados indican similitudes en el comportamiento vocal y social con respecto a estudios en otras especies como Cacicus cela y Cacicus haemorrhous. C. c. leucoramphus utiliza vocalizaciones específicas en un determinado contexto conductual, pudiendo algunas de ellas ser reutilizadas en varios comportamientos. Este estudio describe por primera vez el contexto social en el que se asocian las vocalizaciones y conductas en esta especie
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Development and characterization of films with propolis to inhibit mold contamination in the dairy industry
Due to the number of polyphenols with multiple biological activities, propolis has high potential to be used as an active agent in food protective films. Therefore, this study aimed to develop and characterize a sodium alginate film with ethanolic extract of propolis (EEP) for its potential use as protective active packaging against filamentous fungi in ripened cheese. Three different concentrations of EEP were analyzed: 0, 5 and 10% w/v. The films obtained were characterized, assessing thermal and physicochemical properties, as well as the concentration of polyphenols in the EEP and antifungal activity of the active films. The incorporation of EEP in the films generated thermal stability with respect to the loss of mass. Total color values (ΔE) of the films were affected by the incorporation of the different concentrations of EEP, showing a decrease in luminosity (L*) of the films, while the chromatic parameters a* and b* increased in direct proportion to the EEP concentration. Antifungal activity was observed with a fungistatic mode of action, stopping the growth of the fungus in cheeses without development of filamentous molds, thus increasing the shelf life of the ripened cheese under the analytical conditions, over 30 days at room temperature. Overall, EEP can be used to prevent growth and proliferation of spoilage microorganisms in cheese
Statistical validation of Aeolus L2A particle backscatter coefficient retrievals over ACTRIS/EARLINET stations on the Iberian Peninsula
The Global Observing System (GOS) has encountered some limitations due to a lack of worldwide
real-time wind measurements. In this context, the European Space Agency (ESA) has developed the Aeolus satellite
mission, based on the ALADIN (Atmospheric Laser Doppler Instrument) Doppler wind lidar; this mission
aims to obtain near-real-time wind retrievals at the global scale. As spin-off products, the instrument retrieves
aerosol optical properties such as particle backscatter and extinction coefficients. In this work, a validation of Aeolus
reprocessed (baseline 10) co-polar backscatter coefficients (
part
Aeolus) is presented through an intercomparison
with analogous ground-based measurements taken at the ACTRIS (Aerosols, Clouds and Trace gases Research
InfraStructure Network)/EARLINET (European Aerosol Research Lidar Network) stations of Granada (Spain),
Évora (Portugal) and Barcelona (Spain) over the period from July 2019 until October 2020. Case studies are first
presented, followed by a statistical analysis. The stations are located in a hot spot between Africa and the rest
of Europe, which guarantees a variety of aerosol types, from mineral dust layers to continental/anthropogenic
aerosol, and allows us to test Aeolus performance under different scenarios. The so called Aeolus-like profiles
(
part
Aeolus like;355) are obtained from total particle backscatter coefficient and linear particle depolarization
ratio (
part
linear) profiles at 355 and 532 nm measured from the surface, through a thorough bibliographic review of
dual-polarization measurements for relevant aerosol types. Finally, the study proposes a relation for the spectral
conversion of
part
linear, which is implemented in the Aeolus-like profile calculation. The statistical results show
the ability of the satellite to detect and characterize significant aerosol layers under cloud-free conditions, along
with the surface effect on the lowermost measurements, which causes the satellite to largely overestimate copolar
backscatter coefficients. Finally, the Aeolus standard correct algorithm middle bin (SCAmb) shows a better
agreement with ground-based measurements than the standard correct algorithm (SCA), which tends to retrieve negative and meaningless coefficients in the clear troposphere. The implementation of Aeolus quality flags entails
a vast reduction in the number of measurements available for comparison, which affects the statistical
significance of the results
Relation between the Global Burden of Disease and Randomized Clinical Trials Conducted in Latin America Published in the Five Leading Medical Journals
Background: Since 1990 non communicable diseases and injuries account for the majority of death and disability-adjusted life years in Latin America. We analyzed the relationship between the global burden of disease and Randomized Clinical Trials (RCTs) conducted in Latin America that were published in the five leading medical journals.Methodology/Principal Findings: We included all RCTs in humans, exclusively conducted in Latin American countries, and published in any of the following journals: Annals of Internal Medicine, British Medical Journal, Journal of the American Medical Association, Lancet, and New England Journal of Medicine. We described the trials and reported the number of RCTs according to the main categories of the global burden of disease. Sixty-six RCTs were identified. Communicable diseases accounted for 38 (57%) reports. Maternal, perinatal, and nutritional conditions accounted for 19 (29%) trials. Non-communicable diseases represent 48% of the global burden of disease but only 14% of reported trials. No trial addressed injuries despite its 18% contribution to the burden of disease in 2000.Conclusions/Significance: A poor correlation between the burden of disease and RCTs publications was found. Non communicable diseases and injuries account for up to two thirds of the burden of disease in Latin America but these topics are seldom addressed in published RCTs in the selected sample of journals. Funding bodies of health research and editors should be aware of the increasing burden of non communicable diseases and injuries occurring in Latin America to ensure that this growing epidemic is not neglected in the research agenda and not affected by publication bias
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