Double Diffusion Encoding Prevents Degeneracy in Parameter Estimation of Biophysical Models in Diffusion MRI

Purpose: Biophysical tissue models are increasingly used in the interpretation of diffusion MRI (dMRI) data, with the potential to provide specific biomarkers of brain microstructural changes. However, the general Standard Model has recently shown that model parameter estimation from dMRI data is ill-posed unless very strong magnetic gradients are used. We analyse this issue for the Neurite Orientation Dispersion and Density Imaging with Diffusivity Assessment (NODDIDA) model and demonstrate that its extension from Single Diffusion Encoding (SDE) to Double Diffusion Encoding (DDE) solves the ill-posedness and increases the accuracy of the parameter estimation. Methods: We analyse theoretically the cumulant expansion up to fourth order in b of SDE and DDE signals. Additionally, we perform in silico experiments to compare SDE and DDE capabilities under similar noise conditions. Results: We prove analytically that DDE provides invariant information non-accessible from SDE, which makes the NODDIDA parameter estimation injective. The in silico experiments show that DDE reduces the bias and mean square error of the estimation along the whole feasible region of 5D model parameter space. Conclusions: DDE adds additional information for estimating the model parameters, unexplored by SDE, which is enough to solve the degeneracy in the NODDIDA model parameter estimation.Comment: 22 pages, 7 figure

Ornithodoros quilinensis sp. nov. (Acari, Argasidae), a new tick species from the Chacoan region in Argentina

Ornithodoros quilinensis sp. nov. (Acari: Argasidae) is described from larvae collected on the small rodents Graomys centralis (Cricetidae: Sigmodontinae) in Argentina. The diagnostic characters for this new species are a combination of small size (520-540 μm), a dorsal plate oval in shape with a length of approximately 200 μm, 14 pairs of dorsal setae, hypostome short and narrower at the base (length from Ph1 to apex 133 μm (120-141)) with dental formula 2/2 and apex blunt, and the capsule of the Haller's organ irregular in shape and without reticulations. The analysis of the 16S rDNA sequences available for the genus Ornithodoros indicate that, phylogenetically, O. quilinensis represents an independent lineage only related to a Bolivian tick species of the genus Ornithodoros yet not formally described.Fil: Venzal, José M.. Universidad de la Republica, Salto; UruguayFil: Nava, Santiago. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; ArgentinaFil: Mangold, Atilio Jose. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; ArgentinaFil: Mastropaolo, Mariano. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; ArgentinaFil: Casás, Gustavo. UNIVERSIDAD DE LA REPUBLICA (UDELAR); . Universidad de la República; UruguayFil: Guglielmone, Alberto Alejandro. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; Argentin

On the decorrelation filtering of RL05 GRACE data for global applications

In autumn 2012, the new release 05 (RL05) of monthly geopotencial spherical harmonics Stokes coefficients (SC) from GRACE (Gravity Recovery and Climate Experiment) mission was published. This release reduces the noise in high degree and order SC, but they still need to be filtered. One of the most common filtering processing is the combination of decorrelation and Gaussian filters. Both of them are parameters dependent and must be tuned by the users. Previous studies have analyzed the parameters choice for the RL05 GRACE data for oceanic applications, and for RL04 data for global application. This study updates the latter for RL05 data extending the statistics analysis. The choice of the parameters of the decorrelation filter has been optimized to: (1) balance the noise reduction and the geophysical signal attenuation produced by the filtering process; (2) minimize the differences between GRACE and model-based data; (3) maximize the ratio of variability between continents and oceans. The Gaussian filter has been optimized following the latter criteria. Besides, an anisotropic filter, the fan filter, has been analyzed as an alternative to the Gauss filter, producing better statistics.This work has been partly supported by two Spanish Projects from CGL2010-12153-E and AYA2010-22039-C02-01; and two from Generalitat Valenciana, GV/2013/144 and ACOMP-2013-068

Propriedades psicométricas do Questionário Revisado de Bullying/Vitimização de Olweus para Crianças em español

Bullying is an important risk factor for the mental health of children and adolescents, since victim’s present higher levels of emotional problems while those who carry it out show greater behavioural problems. Despite its relevance, few instruments exist for its measurement in school-age children. The present study sought to evaluate the psychometric properties of the Revised Olweus Bully/Victim Questionnaire in a Spanish-speaking sample, with the particularity of being the first analysis of Spanish-speaking children. A quantitative study was carried out, implementing AFE, AFC, and Spearman's correlations. An intentional sample of 670 Argentinian children, male (48 %) and female (52 %), from 10 to 12 years old (mean age= 10.80; SD = 0.72) answered this test, such as the Friendship Quality Scale and the Kovacs Depression Inventory. The results indicated a factorial structure of two dimensions called victimization and bullying that coincided with those postulated by the author of the questionnaire. Cronbach's and Omega's alphas were satisfactory. The evidence of concurrent validity with the perception of the quality of friendship and depression was confirmed. The results indicated that this questionnaire presented adequate psychometric properties in its adaptation to Argentinian Spanish.El bullying es un importante factor de riesgo para la salud mental de niños y adolescentes, ya que las víctimas presentan mayores niveles de problemas emocionales; mientras que los acosadores muestran mayores problemas de conducta. A pesar de su relevancia, existen pocos instrumentos para su medición en niños de edad escolar. El presente estudio buscó evaluar las propiedades psicométricas del Cuestionario Revisado de Bullying/Victimización de Olweus en una muestra de habla hispana, con la particularidad de ser el primer análisis de habla hispana en niños. Se realizó un estudio instrumental, implementando AFE, AFC y correlaciones de Pearson. Una muestra intencional de 670 niños argentinos, varones (48 %) y mujeres (52 %), de 10 a 12 años (edad media = 10.80; DE = .72) contestaron el cuestionario, la Escala de Calidad de la Amistad y el Inventario de Depresión de Kovacs. Los resultados indicaron una estructura factorial de dos dimensiones: victimización y bullying, que coincidieron con las postuladas por el autor del cuestionario. Los valores de los coeficientes alfas de Cronbach y de omega de McDonald fueron satisfactorios. Se confirmó la evidencia de validez concurrente con la percepción de la calidad de la amistad y la depresión. El cuestionario presentó adecuadas propiedades psicométricas en su adaptación al español argentino.  O bullying é um importante fator de risco para a saúde mental de crianças e adolescentes, uma vez que as vítimas apresentam maiores níveis de problemas emocionais enquanto aqueles que o praticam apresentam maiores problemas comportamentais. Apesar de sua relevância, existem poucos instrumentos para sua mensuração em crianças em idade escolar. O presente estudo procurou avaliar as propriedades psicométricas do Questionário Revisado de Bullying/ Vitimização de Olweus em uma amostra de língua espanhol, com a particularidade de ser a primeira análise em língua espanhola em crianças. Foi realizado um estudo instrumental, implementando AFE, AFC e correlações de Pearson. Uma amostra intencional de 670 crianças argentinas, meninos (48 %) e meninas (52 %), com idades de 10 a 12 anos (média de idade = 10,80; DP = 0,72) responderam ao questionário, a Escala de Qualidade da Amizade e o Inventário de Depressão de Kovacs. Os resultados indicaram uma estrutura fatorial de duas dimensões denominadas vitimização e bullying, que coincidiram com as postuladas pelo autor do questionário. Os valores dos coeficientes alfas de Cronbach e Omega de McDonald foram satisfatórios. Foi confirmada a evidência de validade concorrente com a qualidade percebida da amizade e a depressão. O questionário apresentou propriedades psicométricas adequadas em sua adaptação ao espanhol argentino

Sulfite-reducing clostridia in the sediment of a high mountain lake (Laguna Grande, Gredos, Spain) as indicators of fecal pollution

We studied the vertical distribution of sulfite-reducing clostridia in the sediment of a Spanish high-mountain lagoon (Laguna Grande de Gredos, central Spain), with optimal sediment characteristics (temperature < 20°C) to maintain spores without growing. This allowed us to assess the original numbers of sulfite-reducing clostridia endospores settled, without postdepositional growing. Sulfite-reducing clostridia are normal inhabitants of the intestinal microbiota of humans and other mammals. These microorganisms may form endospores, which allow the bacteria to survive in almost any habitat, either terrestrial or aquatic, waiting for favorable conditions for growth. Sulfite-reducing clostridia could be suitable indicators of past human pollution because they have a great longevity in natural habitats and they cannot multiply at temperatures below 20°C or in the presence of O2. We found a great increase in the numbers of clostridia (expressed as colony-forming units per gram [CFU/g] of dry weight of sediment) since the 1970s, which reflects the rise of human pressure caused by the practice of outdoor activities.Clostridia CFU/g rose dramatically after the faulty operation of the depuration system of a mountain refuge built close to the lagoon. We compared the vertical distribution of clostridia CFU/g from Laguna Grande sediments with those from a neighbor lagoon (Laguna Cimera), which showed less tourist pressure and no direct disposal of sewage. Finally, we agree with the usefulness of the numbers of sulfitereducing clostridia as indicators of past pollution

Precision Health for Chagas Disease: Integrating Parasite and Host Factors to Predict Outcome of Infection and Response to Therapy

Chagas disease, caused by the infection with the protozoan parasite Trypanosoma cruzi, is clinically manifested in approximately one-third of infected people by inflammatory heart disease (cardiomyopathy) and, to a minor degree, gastrointestinal tract disorders (megaesophagus or megacolon). Chagas disease is a zoonosis transmitted among animals and people through the contact with triatomine bugs, which are found in much of the western hemisphere, including most countries of North, Central and South America, between parallels 45° north (Minneapolis, USA) and south (Chubut Province, Argentina). Despite much research on drug discovery for T. cruzi, there remain only two related agents in widespread use. Likewise, treatment is not always indicated due to the serious side effects of these drugs. On the other hand, the epidemiology and pathogenesis of Chagas disease are both highly complex, and much is known about both. However, it is still impossible to predict what will happen in an individual person infected with T. cruzi, because of the highly variability of parasite virulence and human susceptibility to infection, with no definitive molecular predictors of outcome from either side of the host-parasite equation. In this Minireview we briefly discuss the current state of T. cruzi infection and prognosis and look forward to the day when it will be possible to employ precision health to predict disease outcome and determine whether and when treatment of infection may be necessary.Fil: Martinez, Santiago Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Romano, Patricia Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Engman, David M.. Cedars Sinai Medical Center; Estados Unidos. Northwestern University; Estados Unidos. University of California at Los Angeles; Estados Unido

Cartilage Appearance Using an Environmental Scanning Electron Microscope.

Because of technical principles, samples to be observed with electron microscopy need to be fixed in a chemical process and exposed to vacuum conditions that can produce some changes in the morphology of the specimen. The aim of this work was to obtain high-resolution images of the fresh articular cartilage surface with an environmental scanning electron microscope (ESEM), which is an instrument that permits examination of biological specimens without fixation methods in a 10 Torr chamber pressure, thus minimizing the risk of creating artifacts in the structure. Samples from weight-bearing areas of femoral condyles of New Zealand white rabbits were collected and photographed using an ESEM. Images were analyzed using a categorization based in the Jurvelin classification system modified by Hong and Henderson. Appearance of the observed elevations and depressions as described in the classification were observed, but no fractures or splits of cartilage surface, thought to be artifacts, were detected. The ESEM is a useful tool to obtain images of fresh articular cartilage surface appearance without either employing fixation methods or exposing the specimen to extreme vacuum conditions, reducing the risk of introducing artifacts within the specimen. For all these reasons it could become a useful tool for quality control of the preservation process of osteochondral allografting in a bank of musculoskeletal tissues

A genome-wide 20 K citrus microarray for gene expression analysis

<p>Abstract</p> <p>Background</p> <p>Understanding of genetic elements that contribute to key aspects of citrus biology will impact future improvements in this economically important crop. Global gene expression analysis demands microarray platforms with a high genome coverage. In the last years, genome-wide EST collections have been generated in citrus, opening the possibility to create new tools for functional genomics in this crop plant.</p> <p>Results</p> <p>We have designed and constructed a publicly available genome-wide cDNA microarray that include 21,081 putative unigenes of citrus. As a functional companion to the microarray, a web-browsable database <abbrgrp><abbr bid="B1">1</abbr></abbrgrp> was created and populated with information about the unigenes represented in the microarray, including cDNA libraries, isolated clones, raw and processed nucleotide and protein sequences, and results of all the structural and functional annotation of the unigenes, like general description, BLAST hits, putative Arabidopsis orthologs, microsatellites, putative SNPs, GO classification and PFAM domains. We have performed a Gene Ontology comparison with the full set of Arabidopsis proteins to estimate the genome coverage of the microarray. We have also performed microarray hybridizations to check its usability.</p> <p>Conclusion</p> <p>This new cDNA microarray replaces the first 7K microarray generated two years ago and allows gene expression analysis at a more global scale. We have followed a rational design to minimize cross-hybridization while maintaining its utility for different citrus species. Furthermore, we also provide access to a website with full structural and functional annotation of the unigenes represented in the microarray, along with the ability to use this site to directly perform gene expression analysis using standard tools at different publicly available servers. Furthermore, we show how this microarray offers a good representation of the citrus genome and present the usefulness of this genomic tool for global studies in citrus by using it to catalogue genes expressed in citrus globular embryos.</p