Finite-temperature properties of frustrated classical spins coupled to the lattice

We present extensive Monte Carlo simulations for a classical antiferromagnetic Heisenberg model with both nearest ($J_1$) and next-nearest ($J_2$) exchange couplings on the square lattice coupled to the lattice degrees of freedom. The Ising-like phase transition, that appears for $J_2/J_1>1/2$ in the pure spin model, is strengthened by the spin-lattice coupling, and is accompanied by a lattice deformation from a tetragonal symmetry to an orthorhombic one. Evidences that the universality class of the transition does not change with the inclusion of the spin-lattice coupling are reported. Implications for ${\rm Li_2VOSiO_4}$, the prototype for a layered $J_1{-}J_2$ model in the collinear regime, are also discussed.Comment: 6 pages and 8 figure

Caracterização de Latossolos com horizontes A Húmico sob diferentes usos na Região Serrana do Rio de Janeiro.

Horizontes com altos teores de carbono e grandes espessuras, são observados em diferentes classes de solos e regiões do Brasil, no entanto, ainda pouco entendida a sua formação e dinâmica na paisagem, bem como a influência do uso com cultivo agrícola. O trabalho teve como objetivo avaliar os atributos químicos, físicos e a composição isotópica do carbono em amostras de Latossolos com horizonte A húmico sob diferentes usos no município de Bom Jardim, RJ. Foram coletadas amostras de solos com horizontes A húmico sob floresta, eucalipto, café, pastagem, olericultura e maracujá. Os solos foram avaliados quanto à morfologia, composição química, física e isotópica do carbono (δ13C). Os horizontes A húmicos apresentam variações nos atributos químicos devido a aplicação de insumos agrícolas. O efeito do uso nos atributos do solo pode ser observado pelos menores teores de C org nos horizontes superficiais sob olericultura, pastagem e maracujá. A amplitude dos valores de δ13C demonstram que a vegetação pretérita e atual apresenta-se com mistura de plantas C3 e C4, mas com predomínio de C3 e as pequenas diferenças nos valores do δ13C entre os usos nos horizontes superficiais evidenciam o poder tamponante da matéria orgânica

Os jovens na "era do jazz" ou "os belos e os malditos"

Os anos vinte foram anos de grande bulício e agitação em todas as esferas da vida social, cultural, económica e política. Porém, nenhum aspecto foi tão comentado e tratado com auras de maior sensacionalismo do que a dita revolta dos jovens: uma simples alusão aos anos 20 tem o efeito de evocar a primeira visita ao "speakeasy" (bar secreto escondido no subsolo); a primeira experiência sexual - que a privacidade e intimidade do automóvel proporcionavam -; a procura de uma felicidade concreta e imediata, etc. Contudo, a revolta dos jovens constituiu simplesmente o corolário de um desdém pelas condições económico - sociais vigentes, e não se confinou aos Estados Unidos da América, mas atingiu todo o mundo ocidental, em resultado da primeira grande guerra do século. Dado o "boom" na indústria americana, com as suas fábricas gigantescas e ruidosas e a resultante agressividade em larga escala, o culto da elegância nos modos e no porte (que a época anterior favorecera) foi progressivamente abandonado: com guerra ou sem guerra, cada vez se tornava mais difícil para os jovens adoptarem padrões de comportamento que não se ajustassem ao mundo de negócios em que teriam de competir

Ages and Metallicities of Hickson Compact Group Galaxies

Hickson Compact Groups (HCGs) constitute an interesting extreme in the range of environments in which galaxies are located, as the space density of galaxies in these small groups are otherwise only found in the centres of much larger clusters. The work presented here uses Lick indices to make a comparison of ages and chemical compositions of galaxies in HCGs with those in other environments (clusters, loose groups and the field). The metallicity and relative abundance of `$\alpha$-elements' show strong correlations with galaxy age and central velocity dispersion, with similar trends found in all environments. However, we show that the previously reported correlation between $\alpha$-element abundance ratios and velocity dispersion disappears when a full account is taken of the the abundance ratio pattern in the calibration stars. This correlation is thus found to be an artifact of incomplete calibration to the Lick system. Variations are seen in the ranges and average values of age, metallicity and $\alpha$-element abundance ratios for galaxies in different environments. Age distributions support the hierarchical formation prediction that field galaxies are on average younger than their cluster counterparts. However, the ages of HCG galaxies are shown to be more similar to those of cluster galaxies than those in the field, contrary to the expectations of current hierarchical models. A trend for lower velocity dispersion galaxies to be younger was also seen. This is again inconsistent with hierarchical collapse models, but is qualitatively consistent with the latest N-body-SPH models based on monolithic collapse in which star formation continues for many Gyr in low mass halos.Comment: 18 pages. Submitted for publication in MNRA

Red Blood Cell Distribution Width (RDW) Predicts COVID-19 Severity: A Prospective, Observational Study from the Cincinnati SARS-CoV-2 Emergency Department Cohort

Since previous evidence has demonstrated that red blood cell distribution width (RDW) may be a useful prognostic parameter in many critical illnesses and infectious diseases, we investigated the utility of RDW for monitoring patients with coronavirus disease 2019 (COVID-19). The study population consisted of 49 COVID-19 patients, including 16 (32.6%) with severe illness, 12 (24.5%) with severe acute kidney injury (AKI), and 8 (16.3%) requiring renal replacement therapy (RRT). The predictive value of blood tests, performed during emergency department evaluation, was then addressed. A progressive increase of RDW was observed with advancing COVID-19 severity. The area under the curve (AUC) of RDW was 0.73 for predicting severe illness, 0.80 for severe AKI, and 0.83 for RRT, respectively. In multivariate analysis, elevated RDW was associated with 9-fold and 16-fold increased odds of severe COVID-19 and AKI, respectively. The results of this study suggest that RDW should be part of routine laboratory assessment and monitoring of COVID-19

Nonsingular and accelerated expanding universe from effective Yang-Mills theory

The energy-momentum tensor coming from one-parameter effective Yang- Mills theory is here used to describe the matter-energy content of the homogeneous and isotropic Friedmann cosmology in its early stages. The behavior of all solutions is examined. Particularly, it is shown that only solutions corresponding to an open model allow the universe to evolve into an accelerated expansion. This result appears as a possible mechanism for an inflationary phase produced by a vector field. Further, depending on the value of some parameters characterizing the system, the resulting models are classified as singular or nonsingular.Comment: 15 pages, 7 figures, some discussions were simplified and new remarks were introduce

Self-assembled hyaluronan nanocapsules for the intracellular delivery of anticancer drugs

Preparation of sophisticated delivery systems for nanomedicine applications generally involve multi-step procedures using organic solvents. In this study, we have developed a simple self-assembling process to prepare docetaxel-loaded hyaluronic acid (HA) nanocapsules by using a self-emulsification process without the need of organic solvents, heat or high shear forces. These nanocapsules, which comprise an oily core and a shell consisting of an assembly of surfactants and hydrophobically modified HA, have a mean size of 130 nm, a zeta potential of −20 mV, and exhibit high docetaxel encapsulation efficiency. The nanocapsules exhibited an adequate stability in plasma. Furthermore, in vitro studies performed using A549 lung cancer cells, showed effective intracellular delivery of docetaxel. On the other hand, blank nanocapsules showed very low cytotoxicity. Overall, these results highlight the potential of self-emulsifying HA nanocapsules for intracellular drug delivery

Identification of a non-host semiochemical from tick-resistant donkeys (Equus asinus) against Amblyomma sculptum ticks

Amblyomma sculptum is a tick affecting animal and human health across Argentina, Bolivia, Paraguay and Brazil. Donkeys, Equus asinus, are known to be resistant to A. sculptum, suggesting that they can produce non-host tick semiochemicals (allomones), as already demonstrated for some other vertebrate host/pest interactions, whereas horses, Equus caballus, are considered as susceptible hosts. In this study, we tested the hypothesis that donkeys produce natural repellents against A. sculptum, by collecting sebum from donkeys and horses, collecting the odour from sebum extracts, and identifying donkey-specific volatile compounds by gas chromatography (GC) and coupled GC-mass spectrometry (GC–MS). From the complex collected blends, five main compounds were identified in both species. Hexanal, heptanal and (E)-2-decenal were found predominantly in donkey extracts, whilst ethyl octanoate and ethyl decanoate were found predominantly in horse extracts. One compound, (E)-2-octenal, was detected exclusively in donkey extracts. In Y-tube olfactometer bioassays 36 different A. sculptum nymphs were tested for each extract, compound and concentration. The dry sebum extracts and the compounds identified in both species induced neither attraction nor repellency. Only (E)-2-octenal, the donkey-specific compound, displayed repellency, with more nymphs preferring the arm containing the solvent control when the compound was presented in the test arm across four concentrations tested (p < 0.05, Chi-square test). A combination of a tick attractant (ammonia) and (E)-2-octenal at 0.25M also resulted in preference for the control arm (p < 0.05, Chi-square test). The use of semiochemicals (allomones) identified from less-preferred hosts in tick management has been successful for repelling brown dog ticks, Rhipicephalus sanguineus sensu lato from dog hosts. These results indicate that (E)-2-octenal could be used similarly to interfere in tick host location and be developed for use in reducing A. sculptum numbers on animal and human hosts