Langevin Equation for the Rayleigh model with finite-ranged interactions

Both linear and nonlinear Langevin equations are derived directly from the Liouville equation for an exactly solvable model consisting of a Brownian particle of mass $M$ interacting with ideal gas molecules of mass $m$ via a quadratic repulsive potential. Explicit microscopic expressions for all kinetic coefficients appearing in these equations are presented. It is shown that the range of applicability of the Langevin equation, as well as statistical properties of random force, may depend not only on the mass ratio $m/M$ but also by the parameter $Nm/M$, involving the average number $N$ of molecules in the interaction zone around the particle. For the case of a short-ranged potential, when $N\ll 1$, analysis of the Langevin equations yields previously obtained results for a hard-wall potential in which only binary collisions are considered. For the finite-ranged potential, when multiple collisions are important ($N\gg 1$), the model describes nontrivial dynamics on time scales that are on the order of the collision time, a regime that is usually beyond the scope of more phenomenological models.Comment: 21 pages, 1 figure. To appear in Phys. Rev.

LA ACUAPONÍA, DIVERSIFICACIÓN PRODUCTIVA SUSTENTABLE

An aquaponics system was evaluated as a model for diversification of food production with a completely randomized experimental design through the variables of water temperature (20-31.5 °C), pH (5.7-7.6) and oxygen (4.0-5.3 mg L-1), applied to parsley (Petroselinum crispum), serrano pepper (Capsicum annuum) and ornamental pepper (Capsicum sp.) with controls grown in traditional cultivation with a 2:1 soil-tezontle substrate, during a 4-month period, along with white tilapia, var. Rocky Mountain (Oreochromis niloticusxO. aureus). Results indicated that the effluent derived was too salty (C4). The tilapia had a weight gain of 206 g in 120 days and a survival of 91%. Serrano pepper grown in aquaponics (11 cm) did not show statistically significant differences in terms of plant growth (P>0.05), compared to traditional cultivation (70 cm). Parsley did not develop in aquaponics due to the salinity. The ornamental pepper had a limited development with a height lower than the control grown in traditional cultivation, so the conclusion is that the effluent limits the selection of species to be cultivated, although the potential for species that tolerate salinity can be seen.Se evaluó un sistema acuapónico como modelo de diversificación productiva de alimentos en un diseño experimental completamente al azar mediante las variables temperatura del agua (20-31.5 °C), pH (5.7-7.6) y oxígeno (4.0-5.3 mg L-1), aplicados a perejil (Petroselinum crispum), chile serrano (Capsicum annuum) y chile de ornato (Capsicum sp.) con testigos en siembra tradicional con sustrato tierra-tezontle 2:1, en un periodo de 4 meses, además de tilapia blanca var. Rocky mountain (Oreochromis niloticusxO. aureus). Los resultados indicaron que el efluente derivado fue muy salino (C4). La tilapia tuvo una ganancia de peso de 206 g en 120 días y sobrevivencia de 91%. El chile serrano cultivado en acuaponía (11 cm) no mostró diferencias estadísticamente significativas en crecimiento de la planta (P>0.05), en comparación con la siembra tradicional (70 cm). El perejil no se desarrolló en acuaponía atribuido a la salinidad. El chile de ornato tuvo un desarrollo limitado con altura menor al testigo bajo siembra tradicional, concluyendo que el efluente delimita la selección de las especies a cultivar, apreciando potencial para especies tolerantes a salinidad

Cardiometabolic Pregnancy Complications in Association With Autism-Related Traits as Measured by the Social Responsiveness Scale in ECHO

Prior work has examined associations between cardiometabolic pregnancy complications and autism spectrum disorder (ASD) but not how these complications may relate to social communication traits more broadly. We addressed this question within the Environmental Inf luences on Child Health Outcomes program, with 6,778 participants from 40 cohorts conducted from 1998–2021 with information on ASD-related traits via the Social Responsiveness Scale. Four metabolic pregnancy complications were examined individually, and combined, in association with Social Responsiveness Scale scores, using crude and adjusted linear regression as well as quantile regression analyses. We also examined associations stratified by ASD diagnosis, and potential mediation by preterm birth and low birth weight, and modification by child sex and enriched risk of ASD. Increases in ASD-related traits were associated with obesity (β = 4.64, 95% confidence interval: 3.27, 6.01) and gestational diabetes (β = 5.21, 95% confidence interval: 2.41, 8.02), specifically, but not with hypertension or preeclampsia. Results among children without ASD were similar to main analyses, but weaker among ASD cases. There was not strong evidence for mediation or modification. Results suggest that common cardiometabolic pregnancy complications may inf luence child ASD-related traits, not only above a diagnostic threshold relevant to ASD but also across the population

Constraining the electric charges of some astronomical bodies in Reissner-Nordstrom spacetimes and generic r^-2-type power-law potentials from orbital motions

We put model-independent, dynamical constraints on the net electric charge Q of some astronomical and astrophysical objects by assuming that their exterior spacetimes are described by the Reissner-Nordstroem metric, which induces an additional potential U_RN \propto Q^2 r^-2. Our results extend to other hypothetical power-law interactions inducing extra-potentials U_pert = r^-2 as well (abridged).Comment: LaTex2e, 16 pages, 3 figures, no tables, 128 references. Version matching the one at press in General Relativity and Gravitation (GRG). arXiv admin note: substantial text overlap with arXiv:1112.351

Template-free synthesis of CoMoO4 rods and their characterization

The effect of pressure and temperature on the synthesis of cobalt-molybdenum oxides and their characterisation is herein reported. The synthesis was performed under hydrothermal conditions without any template. It was found that the experimental conditions affect the physical properties of the CoMoO4. SEM images demonstrate that the synthesised powder is comprised of rods, and the width of the structures is about 100 nm but the length varies from about 5 μm to less than 1 μm. Low temperature and pressure favour the formation of longer rods. © 2013 Elsevier Ltd. All rights reserved

Stepwise cycloadditions of mesoionic systems: thionation of thioisomunchnones by isothlocyanates

An unusual thionation strategy of mesoionic compounds with aryl isothiocyanates enables a facile synthesis of 1,3-thiazolium-4-thiolate systems. The mechanistic pathway of such a transformation most likely involves a stepwise 1,3-dipolar cycloaddition, which is supported by theoretical calculations performed with a two-layer hybrid method (B3LYP/6-31G(d):PM3)

Chiral N-acyloxazolidines: synthesis, structure, and mechanistic insights

A series of chiral imines derived from 1-amino-1-deoxyalditols such as D-glucamine, a rather unexplored raw material from the chiral pool, have been serendipitiously transformed into a novel family of N-acetyl-1,3-oxazolidines by means of an unexpected acetylation. The structure of these substances is supported by spectroscopic and crystallographic data. The acetylates also trigger a complex dynamic transformation, in which an initially configured trans oxazolidine converts into a more stable cis-configured derivative. Both isomers can also exist as rotational conformers (E,Z) as a consequence of the restricted rotation around the N-acetyl bond. The barriers to rotation have been determined by variable-temperature experiments. Overall, this transformation most likely involves the intermediacy of a chiral iminium ion, which has been documented in the synthesis of nitrogen heterocycles, thus explaining the experimental facts

Optimal optical fiber for high spatial resolution in scanning electrochemical and photoelectrochemical microscopy

High-resolution analytical techniques based on scanned microprobes over surfaces are useful to investigate reactions at different materials in solution, with possibilities for remote sensing. One of these techniques is Scanning Electrochemical and Photoelectrochemical Microscopy (SPECM), which allows to investigate both electrochemical and photoelectrochemical reactions either concurrently or simultaneously over a semiconductor surface. SPECM is based on the use of an optical fiber coated with a noble metal and isolated from its surrounding media with a polymer film. Spatial resolution for this technique strongly depends on the characteristics of the probe, for instance numerical aperture or the characteristics of optical fiber tips. According to this, there is an increasing need for reducing the optical probe sizes, as well as the illumination spot size, in order to improve spatial resolution for this technique. Usually, optical scanning probes are prepared by chemically etching an optical fiber in HF solutions or by heating and stretching an optical fiber locally with an oscillating flame or a CO 2 laser beam. In this work, the goal of this study is to establish the optimal tip diameter and the total length of the taper in order to obtain a good transmission efficiency and thus to improve the sensitivity of the SPECM technique

An efficient and highly diastereoselective synthesis of C-glycosylated 1,3-oxazolidines from N-methyl-D-glucamine

A one-pot procedure for preparing chiral 1,3-oxazolidines derived from N-methyl-d-glucamine and aryl aldehydes is described. It has been carried out by using readily available reagents and operationally simple conditions allowing the preparation of the acyclic C-nucleoside analogs in high yields. The structure of these derivatives has been fully characterized by NMR correlations and single-crystal X-ray diffraction. Some reactions also provide access to the corresponding tetrahydro-1,3-oxazines by an alternative ring closure. Mechanistic considerations account for the observed steric course