Anomalous melting behavior of solid hydrogen at high pressures

Hydrogen is the most abundant element in the universe, and its properties under conditions of high temperature and pressure are crucial to understand the interior of of large gaseous planets and other astrophysical bodies. At ultra high pressures solid hydrogen has been predicted to transform into a quantum fluid, because of its high zero point motion. Here we report first principles two phase coexistence and Z method determinations of the melting line of solid hydrogen in a pressure range spanning from 30 to 600 GPa. Our results suggest that the melting line of solid hydrogen, as derived from classical molecular dynamics simulations, reaches a minimum of 367 K at about 430 GPa, at higher pressures the melting line of the atomics Cs IV phase regain a positive slope. In view of the possible importance of quantum effects in hydrogen at such low temperatures, we also determined the melting temperature of the atomic CsIV phase at pressures of 400, 500, 600 GPa, employing Feynman path integral simulations. These result in a downward shift of the classical melting line by about 100 K, and hint at a possible secondary maximum in the melting line in the region between 500 and 600 GPa, testifying to the importance of quantum effects in this system. Combined, our results imply that the stability field of the zero temperature quantum liquid phase, if it exists at all, would only occur at higher pressures than previously thought.Comment: Submitted to JC

A Probabilistic Approach to the Existence of Solutions to Semilinear Elliptic Equations

We study a semilinear elliptic equation with a pure power nonlinearity with exponent $p>1$, and provide sufficient conditions for the existence of positive solutions. These conditions involve expected exit times from the domain, $D$, where a solution is defined, and expected occupation times in suitable subdomains of $D$. They provide an alternative new approach to the geometric or topological sufficient conditions given in the literature for exponents close to the critical Sobolev exponent. Moreover, unlike standard results, in our probabilistic approach no \emph{a priori} upper bound restriction is imposed on $p$, which might be supercritical. The proof is based on a fixed point argument using a probabilistic representation formula. We also prove a multiplicity result and discuss possible extensions to the existence of sign changing solutions. Finally, we conjecture that necessary conditions for the existence of solutions might be obtained using a similar probabilistic approach. This motivates a series of natural questions related to the characterisation of topological and geometrical properties of a domain in probabilistic terms.Comment: 13 page

CyanoEXpress: A web database for exploration and visualisation of the integrated transcriptome of cyanobacterium Synechocystis sp. PCC6803.

UNLABELLED: Synechocystis sp. PCC6803 is one of the best studied cyanobacteria and an important model organism for our understanding of photosynthesis. The early availability of its complete genome sequence initiated numerous transcriptome studies, which have generated a wealth of expression data. Analysis of the accumulated data can be a powerful tool to study transcription in a comprehensive manner and to reveal underlying regulatory mechanisms, as well as to annotate genes whose functions are yet unknown. However, use of divergent microarray platforms, as well as distributed data storage make meta-analyses of Synechocystis expression data highly challenging, especially for researchers with limited bioinformatic expertise and resources. To facilitate utilisation of the accumulated expression data for a wider research community, we have developed CyanoEXpress, a web database for interactive exploration and visualisation of transcriptional response patterns in Synechocystis. CyanoEXpress currently comprises expression data for 3073 genes and 178 environmental and genetic perturbations obtained in 31 independent studies. At present, CyanoEXpress constitutes the most comprehensive collection of expression data available for Synechocystis and can be freely accessed. AVAILABILITY: The database is available for free at http://cyanoexpress.sysbiolab.eu

CAMBIOS FISICOQUÍMICOS DE ALMIDON DE MAÍZ DURANTE LA FERMENTACION ACIDO LÁCTICA CON Lactobacillus bulgaricus

Lactic acid fermentation with L. bulgaricus induced large changes in the morphology of corn starch granules. The production of amylolytic enzymes as well as lactic acid produced fractures along the granule hilum, which led to disintegration of starch granules at long fermentation times. On the other hand, lactic acid fermentation increased crystallinity and double-helices structures, which led to increased susceptibility to acidic hydrolysis. In fact, thermal analysis results indicated than an improved internal organization of granule residues occurred. In general, the results showed that the fermentation time can be considered as a suitable parameter for modulating the physicochemical properties of corn starch granules. Additionally, it can be postulated that lactic acid fermentation of starchy food matrices has a positive effect on the acidic digestibility of starch granules, by improving the content of resistant starch fractionsLactic acid fermentation (LAF) has been used since antiquity to conserve food including starchy food. The bioaccessibility of starch depends on the food microstructures. Therefore, the understanding of the physicochemical transformations of the starch suffered during LAF will allow to develop an adequate processing of the alimentary matrices. In this work, native corn starch (NCS) dispersions were inoculated with Lactobacillus bulgaricus (2×107 cells ml−1) and fermented for 24 h at 38 ºC. Physicochemical changes of starch granules during fermentation time were monitored by XRD, FTIR and DSC. The crystallinity content achieved a maximum value (39.72±1.02%) after 12 h of fermentation. In contrast, the absorbance ratio 1047/1022 from FTIR measurements increased as the fermentation advanced. Likewise, DSC analysis showed that the gelatinization enthalpy increased 60.0% after 12 h of fermentation, reflecting the production of ordered microstructures. Thus, it is suggested that LAF increased the resistant starch content in corn starch granules

Tuning Magnetic Avalanches in Mn12-ac

Using micron-sized Hall sensor arrays to obtain time-resolved measurements of the local magnetization, we report a systematic study in the molecular magnet Mn$_{12}$-acetate of magnetic avalanches controllably triggered in different fixed external magnetic fields and for different values of the initial magnetization. The speeds of propagation of the spin-reversal fronts are in good overall agreement with the theory of magnetic deflagration of Garanin and Chudnovsky \cite{Garanin}.Comment: 8 pages, 7 figures; discussion expanded and revise

The Interaction of Microwaves with Materials of Different Properties

Electromagnetic radiation, such as microwaves, are all the time reflected, transmitted, and/or absorbed by any kind of matter, glasses, conductors, water, ferrites, and so forth. Magnetic materials absorb greatly microwaves. The more magnetic, the more microwaves are absorbed. The aim of this chapter is to present the fundamental physics of the absorption of microwave power (energy per unit time) by ferrimagnetic and ferromagnetic matter in the nano and micro size scale. The magnetic moments and their collective modes are the basic microscopic absorbers under in-resonance and out-of-resonance conditions. Experimental setups and measurement techniques are described. The profiles of microwave absorption are described and connected to the micromagnetic environment that elicits such absorption. Section by section and the overall microwave power absorption profiles are related to the micromagnetic structures. Emphasis is made on nano- and micromagnets. These interactions of microwaves with nano- and micromagnets serve to infer microscopic magnetic information

Nitrile butadiene rubber composites reinforced with reduced graphene oxide and carbon nanotubes show superior mechanical, electrical and icephobic properties

In this article, we examine the effects of two different nanostructured carbons when they are incorporated in a rubber matrix in terms of mechanical and electrical properties as well as the icephobic behaviour of the nanocomposites when swollen. Nitrile butadiene rubber composites reinforced with thermally reduced graphene oxide or multiwalled carbon nanotubes or both of them were prepared and characterized. At a particular hybrid filler loading, tensile and electrical tests showed a significant improvement of the composite. From the swelling studies, after the immersion, the nanocomposites experienced a reduction of the cross-link density that promotes weakening of ice adhesion, being this effect more evident for those samples prepared with hybrid fillers. In view of the composite formulations, that utilize commercially available elastomers and fillers, these findings would be applicable to the automotive and aviation sectors, where the demand for multifunctional rubbers is increasing.N.M.P. is supported by the European Commission H2020 under the Graphene Flagship Core 1 No. 696656 (WP14 00Polymer composites>) and FET Proactive >Neurofibres> grant No. 732344. M.A.L.M. thanks the support from the MINECO project MAT2016- 81138-R. SERMS srl (Terni - Italy) is kindly aknowledged for aging the composites in climatic chamberPeer Reviewe

Effect of Primidone on Dentate Nucleus γ-Aminobutyric Acid Concentration in Patients With Essential Tremor

OBJECTIVES: It is not known whether current use of the medication primidone affects brain γ-aminobutyric acid (GABA) concentrations. This is an important potential confound in studies of the pathophysiology of essential tremor (ET), one of the most common neurological diseases. We compared GABA concentrations in the dentate nucleus in 6 ET patients taking primidone versus 26 ET patients not taking primidone. METHODS: (1)H magnetic resonance spectroscopy was performed using a 3.0-T Siemens Tim Trio scanner. The MEGA-PRESS J-editing sequence was used for GABA detection in 2 cerebellar volumes of interest (left and right) that included the dentate nucleus. RESULTS: The right dentate GABA concentration was similar in the 2 groups (2.21 ± 0.46 [on primidone] vs 1.93 ± 0.39 [not on primidone], P = 0.15), as was the left dentate GABA concentration (1.61 ± 0.35 [on primidone] vs 1.67 ± 0.34 [not on primidone], P = 0.72). The daily primidone dose was not associated with either right or left dentate GABA concentrations (P = 0.89 and 0.76, respectively). CONCLUSIONS: We did not find a difference in dentate GABA concentrations between 6 ET patients taking daily primidone and 26 ET patients not taking primidone. Furthermore, there was no association between daily primidone dose and dentate GABA concentration. These data suggest that it is not necessary to exclude ET patients on primidone from magnetic resonance spectroscopy studies of dentate GABA concentration, and if assessment of these concentrations was to be developed as a biomarker for ET, primidone usage would not confound interpretation of the results