1,180 research outputs found
Three-dimensional Maxwellian extended Newtonian gravity and flat limit
In the present work we find novel Newtonian gravity models in three space-time dimensions. We first present a Maxwellian version of the extended Newtonian gravity, which is obtained as the non-relativistic limit of a particular U(1)-enlargement of an enhanced Maxwell Chern-Simons gravity. We show that the extended Newtonian gravity appears as a particular sub-case. Then, the introduction of a cosmological constant to the Maxwellian extended Newtonian theory is also explored. To this purpose, we consider the non-relativistic limit of an enlarged symmetry. An alternative method to obtain our results is presented by applying the semigroup expansion method to the enhanced Nappi-Witten algebra. The advantages of considering the Lie algebra expansion procedure is also discussed
Genetic Polymorphisms Influencing Arsenic Metabolism: Evidence from Argentina
The susceptibility to arsenic-induced diseases differs greatly between individuals, possibly due to interindividual variations in As metabolism that affect retention and distribution of toxic metabolites. To elucidate the role of genetic factors in As metabolism, we studied how polymorphisms in six genes affected the urinary metabolite pattern in a group of indigenous women (n = 147) in northern Argentina who were exposed to approximately 200 μg/L As in drinking water. These women had low urinary percentages of monomethylated As (MMA) and high percentages of dimethylated As (DMA). MMA has been associated with adverse health effects, and DMA has the lowest body retention of the metabolites. The genes studied were arsenic(+III)methyltransferase (AS3MT), glutathione S-transferase omega 1 (GSTO1), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), methylenetetrahydrofolate reductase (MTHFR), and glutathione S-transferases mu 1 (GSTM1) and theta 1 (GSTT1). We found three intronic polymorphisms in AS3MT (G12390C, C14215T, and G35991A) associated with a lower percentage of MMA (%MMA) and a higher percentage of DMA (%DMA) in urine. The variant homozygotes showed approximately half the %MMA compared with wild-type homozygotes. These polymorphisms were in strong linkage, with high allelic frequencies (72–76%) compared with other populations. We also saw minor effects of other polymorphisms in the multivariate regression analysis with effect modification for the deletion genotypes for GSTM1 (affecting %MMA) and GSTT1 (affecting %MMA and %DMA). For pregnant women, effect modification was seen for the folate-metabolizing genes MTR and MTHFR. In conclusion, these findings indicate that polymorphisms in AS3MT—and possibly GSTM1, GSTT1, MTR, and MTHFR—are responsible for a large part of the interindividual variation in As metabolism and susceptibility
Wrinkling of a bilayer membrane
The buckling of elastic bodies is a common phenomenon in the mechanics of
solids. Wrinkling of membranes can often be interpreted as buckling under
constraints that prohibit large amplitude deformation. We present a combination
of analytic calculations, experiments, and simulations to understand wrinkling
patterns generated in a bilayer membrane. The model membrane is composed of a
flexible spherical shell that is under tension and that is circumscribed by a
stiff, essentially incompressible strip with bending modulus B. When the
tension is reduced sufficiently to a value \sigma, the strip forms wrinkles
with a uniform wavelength found theoretically and experimentally to be \lambda
= 2\pi(B/\sigma)^{1/3}. Defects in this pattern appear for rapid changes in
tension. Comparison between experiment and simulation further shows that, with
larger reduction of tension, a second generation of wrinkles with longer
wavelength appears only when B is sufficiently small.Comment: 9 pages, 5 color figure
Características antropométricas y nivel de condición física en relación con el estado ponderal en niños chilenos de edad preescolar
The purpose of this study was to describe anthropometric
and physical fitness characteristics of low-income
Chilean preschool children and to examine whether
weight status influences children’s performance on fitness
tests. A total of 434 preschool children (246 boys;
5.48 ± 0.31 years) participated in our study. Anthropometry
(weight, height, body mass index -BMI- and waist
circumference) and fitness tests (handgrip strength test,
standing long jump and 20 m sprint) were assessed by
trained nutritionists and physical education teachers,
respectively. Significant differences in anthropometry
and fitness tests between boys and girls were found. The
prevalence of overweight was higher in girls; in contrast
to that of obesity. Compared to normal-weight children,
overweight/obese boys and girls were heavier and
had greater waist circumference (P < 0.001), were taller
(P ≤ 0.002), and showed higher performance in handgrip
strength (P ≤ 0.027) but not in standing long jump nor
20 m sprint (P ≥ 0.052). Screening physical fitness levels
in overweight/obese preschool children could be an important
tool in order to design an efficacy physical activity
programme.El objetivo de este estudio fue describir las características
antropométricas y el nivel de condición física de
preescolares chilenos de bajo nivel socioeconómico y examinar
si el estado ponderal influye en el rendimiento de
los niños en las pruebas de condición física. Un total de
434 preescolares (246 niños; 5,48 ± 0,31 años) participaron
en nuestro estudio. Antropometría (peso, talla, índice
de masa corporal –IMC– y perímetro de cintura) y tests
de condición física (test de fuerza de prensión manual,
test de salto de longitud y 20 m sprint) fueron evaluados
por nutricionistas entrenados y profesores de educación
física, respectivamente. Se encontraron diferencias significativas
en antropometría y tests de condición física
entre niños y niñas. La prevalencia de sobrepeso fue
mayor en las niñas; en contraste con la de la obesidad.
En comparación con los preescolares con normopeso, los
niños y niñas con sobrepeso/obesidad pesaron más y tuvieron
mayor perímetro de cintura (P < 0.001), eran más
altos (P ≤ 0.002) y mostraron mayor rendimiento en el test
de fuerza de prensión manual (P ≤ 0.027), pero no en el
test de salto de longitud ni en el test de sprint de 20 m
(P ≥ 0.052). Detectar los niveles de condición física en preescolares
con sobrepeso/obesidad puede ser una herramienta
importante para diseñar programas eficaces de
actividad física.They would like to thank the “Corporación Municipal
de Educación y Salud” of Ñuñoa for funding the study.
Likewise, we thank Francisco B. Ortega from the University
of Granada, Spain, for his valuable comments
on an earlier draft. Cristina Cadenas-Sánchez is supported
by a grant from the Spanish Ministry of Economy
and Competitiveness (BES-2014-068829)
CARACTERIZACIÓN DE LAS PROPIEDADES NUTRICIONALES Y ANTIOXIDANTES DE SEMILLAS DE QUINUA (Chenopodium quinoa WILLD.)
[EN] Interest in the cultivation of quinoa pseudo-cereal (Chenopodium quinoa Willd.) has increased in recent years due to its nutritional value, as well as its antioxidant capacity and phytochemical content. The chemical composition of quinoa seeds and their bioactive compounds can differ between varieties. In this study, the nutritional composition, antioxidant properties and total phenolic content of Yellow quinoa seeds cultivated in Mexico were evaluated. The results were compared with four commercial quinoa varieties from Peru: Yellow, Black, Red and Peruvian Yellow. The chemical composition of seeds in this study varied as a function of germplasm and growing conditions. In general, samples were characterized by their high carbohydrate content, followed by protein, lipids and fiber. The Yellow quinoa grown in Mexico stood out for its high phenolic content, as well as for its antioxidant activity, probably influenced by the presence of saponins.Carranza-Concha, J.; Chairez-Huerta, SG.; Contreras-Martinez, CS.; García Martínez, EM. (2021). Characterization of nutritional and antioxidant properties of Quinoa seeds (Chenopodium quinoa WILLD.). Revista Fitotecnia Mexicana. 44(3):357-366. http://hdl.handle.net/10251/18680435736644
Extra-embryonic tissue spreading directs early embryo morphogenesis in killifish
The spreading of mesenchymal-like cell layers is critical for embryo morphogenesis and tissue repair, yet we know little of this process in vivo. Here we take advantage of unique developmental features of the non-conventional annual killifish embryo to study the principles underlying tissue spreading in a simple cellular environment, devoid of patterning signals and major morphogenetic cell movements. Using in vivo experimentation and physical modelling we reveal that the extra-embryonic epithelial enveloping cell layer, thought mainly to provide protection to the embryo, directs cell migration and the spreading of embryonic tissue during early development. This function relies on the ability of embryonic cells to couple their autonomous random motility to non-autonomous signals arising from the expansion of the extra-embryonic epithelium, mediated by cell membrane adhesion and tension. Thus, we present a mechanism of extra-embryonic control of embryo morphogenesis that couples the mechanical properties of adjacent tissues in the early killifish embryo
Evaluation of Plant-Based Byproducts as Green Fining Agents for Precision Winemaking
Consumers are increasingly looking for foods, including wine, that are free of animal-derived proteins. This study seeks to evaluate patatin, a new, plant-based and allergen-free fining agent, by comparing it with the fining agents polyvinipolypyrrolidone, bovine serum albumin, and methylcellulose. Specifically, its effects on the phenolic profile of enological tannins were analyzed with four spectrophotometric assays: OD 280 nm, Folin–Ciocâlteu, Adams–Harbertson, and methylcellulose. In addition, changes in the polyphenol composition of Sangiovese red wine were determined by UV-Vis spectrophotometry and HPLC with adsorption trials, and the solid–liquid interaction in a wine solution was modeled by both Langmuir and Freundlich equations. Our findings highlight the occurrence of systematic proportional error between the selected spectrophotometric assays. As a result, direct comparisons of protein precipitation assays can be made only among results obtained with the same spectrophotometric method. However, it is clear that patatin has an impact on the phenolic profile of Sangiovese red wine: it removes simple phenolics (gallic acid, (+)-catechin, (–)-epicatechin, epicatechin gallate, syringic acid, fertaric acid, coutaric acid, and rutin) as well as both oligomeric and polymeric tannins to different extents. In concentrations of less than 1 g/L, the patatin isotherm showed a linear relation between the equilibrium concentration and the quantity absorbed, obeying the Freundlich model reasonably well (KF 1.46; 1/n 1.07; R2 0.996 with 1/n > 1). Thus, the adsorption process is strongly dependent on the fining dosage
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