Quark stars and quantum-magnetically induced collapse

Quark matter is expected to exist in the interior of compact stellar objects as neutron stars or even the more exotic strange stars, based on the Bodmer-Witten conjecture. Bare strange quark stars and (normal) strange quark-matter stars, those possessing a baryon (electron-supported) crust, are hypothesized as good candidates to explain the properties of a set of peculiar stellar sources as the enigmatic X-ray source RX J1856.5-3754, some pulsars as PSR B1828-11 and PSR B1642-03, and the anomalous X-ray pulsars and soft gamma-ray repeaters. In the MIT bag model, quarks are treated as a degenerate Fermi gas confined to a region of space having a vacuum energy density $B_{bag}$ (the Bag constant). In this note, we modif{}y the MIT Bag Model by including the electromagnetic interaction. We also show that this version of the MIT model implies the anisotropy of the Bag pressure due to the presence of the magnetic field. The equations of state of degenerate quarks gases are studied in the presence of ultra strong magnetic fields. The behavior of a system made-up of quarks having (or not) anomalous magnetic moment is reviewed. A structural instability is found, which is related to the anisotropic nature of the pressures in this highly magnetized matter. The conditions for the collapse of this system are obtained and compared to a previous model of neutron stars build-up on a neutron gas having anomalous magnetic moment.Comment: 11 pages, 2 figure

Negative Pressures in QED Vacuum in an External Magnetic Field

Our aim is to study the electron-positron vacuum pressures in presence of a strong magnetic field $B$. To that end, we obtain a general energy-momentum tensor, depending on external parameters, which in the zero temperature and zero density limit leads to vacuum expressions which are approximation-independent. Anisotropic pressures arise, and in the tree approximation of the magnetic field case, the pressure along $B$ is positive, whereas perpendicular to $B$ it is negative. Due to the common axial symmetry, the formal analogy with the Casimir effect is discussed, for which in addition to the usual negative pressure perpendicular to the plates, there is a positive pressure along the plates. The formal correspondence between the Casimir and black body energy-momentum tensors is analyzed. The fermion hot vacuum behavior in a magnetic field is also briefly discussed

Chronic Stress Triggers Expression of Immediate Early Genes and Differentially Affects the Expression of AMPA and NMDA Subunits in Dorsal and Ventral Hippocampus of Rats

Indexación: Web of Science; Scopus.Previous studies in rats have demonstrated that chronic restraint stress triggers anhedonia, depressive-like behaviors, anxiety and a reduction in dendritic spine density in hippocampal neurons. In this study, we compared the effect of repeated stress on the expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptor subunits in dorsal and ventral hippocampus (VH). Adult male Sprague-Dawley rats were randomly divided into control and stressed groups, and were daily restrained in their motion (2.5 h/day) during 14 days. We found that chronic stress promotes an increase in c-Fos mRNA levels in both hippocampal areas, although it was observed a reduction in the immunoreactivity at pyramidal cell layer. Furthermore, Arc mRNAs levels were increased in both dorsal and VH, accompanied by an increase in Arc immunoreactivity in dendritic hippocampal layers. Furthermore, stress triggered a reduction in PSD-95 and NR1 protein levels in whole extract of dorsal and VH. Moreover, a reduction in NR2A/NR2B ratio was observed only in dorsal pole. In synaptosomal fractions, we detected a rise in NR1 in dorsal hippocampus (DH). By indirect immunofluorescence we found that NR1 subunits rise, especially in neuropil areas of dorsal, but not VH. In relation to AMPA receptor (AMPAR) subunits, chronic stress did not trigger any change, either in dorsal or ventral hippocampal areas. These data suggest that DH is more sensitive than VH to chronic stress exposure, mainly altering the expression of NMDA receptor (NMDAR) subunits, and probably favors changes in the configuration of this receptor that may influence the function of this area.https://www.frontiersin.org/articles/10.3389/fnmol.2017.00244/ful

MicroRNA Profiling and Bioinformatics Target Analysis in Dorsal Hippocampus of Chronically Stressed Rats: Relevance to Depression Pathophysiology

Indexación: Scopus.1Laboratory of Neuroplasticity and Neurogenetics, Faculty of Chemical and Pharmaceutical Sciences, Department of Biochemistry and Molecular Biology, Universidad de Chile, Santiago, Chile, 2National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Durham, NC, United States, 3Centro de Genómica y Bioinformática, Facultad de Ciencias, Universidad Mayor, Santiago, Chile, 4Millennium Institute for Integrative Biology (iBio), FONDAP Center for Genome Regulation, Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, Santiago, Chile, 5Department of Kinesiology, Faculty of Health Sciences, Universidad Católica del Maule, Talca, Chile, 6Escuela de Química y Farmacia, Facultad de Medicina, Universidad Andres Bello, Santiago, Chile.This study was supported by the following grants: FONDECYT 1120528 (JLF), Fondo Central de Investigación, Universidad de Chile ENL025/16 (JLF), ES090079 (JAC). Research in RG and EV laboratories is funded by Instituto Milenio iBio – Iniciativa Científica Milenio MINECON.Studies conducted in rodents subjected to chronic stress and some observations in humans after psychosocial stress, have allowed to establish a link between stress and the susceptibility to many complex diseases, including mood disorders. The studies in rodents have revealed that chronic exposure to stress negatively affects synaptic plasticity by triggering changes in the production of trophic factors, subunit levels of glutamate ionotropic receptors, neuron morphology, and neurogenesis in the adult hippocampus. These modifications may account for the impairment in learning and memory processes observed in chronically stressed animals. It is plausible then, that stress modifies the interplay between signal transduction cascades and gene expression regulation in the hippocampus, therefore leading to altered neuroplasticity and functioning of neural circuits. Considering that miRNAs play an important role in post-transcriptional-regulation of gene expression and participate in several hippocampus-dependent functions; we evaluated the consequences of chronic stress on the expression of miRNAs in dorsal (anterior) portion of the hippocampus, which participates in memory formation in rodents. Here, we show that male rats exposed to daily restraint stress (2.5 h/day) during 7 and 14 days display a differential profile of miRNA levels in dorsal hippocampus and remarkably, we found that some of these miRNAs belong to the miR-379-410 cluster. We confirmed a rise in miR-92a and miR-485 levels after 14 days of stress by qPCR, an effect that was not mimicked by chronic administration of corticosterone (14 days). Our in silico study identified the top-10 biological functions influenced by miR-92a, nine of which were shared with miR-485: Nervous system development and function, Tissue development, Behavior, Embryonic development, Organ development, Organismal development, Organismal survival, Tissue morphology, and Organ morphology. Furthermore, our in silico study provided a landscape of potential miRNA-92a and miR-485 targets, along with relevant canonical pathways related to axonal guidance signaling and cAMP signaling, which may influence the functioning of several neuroplastic substrates in dorsal hippocampus. Additionally, the combined effect of miR-92a and miR-485 on transcription factors, along with histone-modifying enzymes, may have a functional relevance by producing changes in gene regulatory networks that modify the neuroplastic capacity of the adult dorsal hippocampus under stress. © 2018 Muñoz-Llanos, García-Pérez, Xu, Tejos-Bravo, Vidal, Moyano, Gutiérrez, Aguayo, Pacheco, García-Rojo, Aliaga, Rojas, Cidlowski and Fiedler.https://www.frontiersin.org/articles/10.3389/fnmol.2018.00251/ful

Remark on charge conjugation in the non relativistic limit

We study the non relativistic limit of the charge conjugation operation $\cal C$ in the context of the Dirac equation coupled to an electromagnetic field. The limit is well defined and, as in the relativistic case, $\cal C$, $\cal P$ (parity) and $\cal T$ (time reversal) are the generators of a matrix group isomorphic to a semidirect sum of the dihedral group of eight elements and $\Z_2$. The existence of the limit is supported by an argument based in quantum field theory. Also, and most important, the limit exists in the context of galilean relativity. Finally, if one complexifies the Lorentz group and therefore the galilean spacetime $x_\mu$, then the explicit form of the matrix for $\cal C$ allows to interpret it, in this context, as the complex conjugation of the spatial coordinates: $\vec{x} \to \vec{x}^*$. This result is natural in a fiber bundle description.Comment: 8 page

Electric field of a pointlike charge in a strong magnetic field and ground state of a hydrogenlike atom

In an external constant magnetic field, so strong that the electron Larmour length is much shorter than its Compton length, we consider the modification of the Coulomb potential of a point charge owing to the vacuum polarization. We establish a short-range component of the static interaction in the Larmour scale, expressed as a Yukawa-like law, and reveal the corresponding "photon mass" parameter. The electrostatic force regains its long-range character in the Compton scale: the tail of the potential follows an anisotropic Coulomb law, decreasing away from the charge slower along the magnetic field and faster across. In the infinite-magnetic-field limit the potential is confined to an infinitely thin string passing though the charge parallel to the external field. This is the first evidence for dimensional reduction in the photon sector of quantum electrodynamics. The one-dimensional form of the potential on the string is derived that includes a delta-function centered in the charge. The nonrelativistic ground-state energy of a hydrogenlike atom is found with its use and shown not to be infinite in the infinite-field limit, contrary to what was commonly accepted before, when the vacuum polarization had been ignored. These results may be useful for studying properties of matter at the surface of extremely magnetized neutron stars.Comment: 45 pages, 6 figures, accepted to Phys. Rev.

Examination of the Feynman-Hibbs Approach in the Study of NeN_N-Coronene Clusters at Low Temperatures

Feynman-Hibbs (FH) effective potentials constitute an appealing approach for investigations of many-body systems at thermal equilibrium since they allow us to easily include quantum corrections within standard classical simulations. In this work we apply the FH formulation to the study of Ne$_N$-coronene clusters ($N=$ 1-4, 14) in the 2-14 K temperature range. Quadratic (FH2) and quartic (FH4) contributions to the effective potentials are built upon Ne-Ne and Ne-coronene analytical potentials. In particular, a new corrected expression for the FH4 effective potential is reported. FH2 and FH4 cluster energies and structures -obtained from energy optimization through a basin-hoping algorithm as well as classical Monte Carlo simulations- are reported and compared with reference path integral Monte Carlo calculations. For temperatures $T> 4$ K, both FH2 and FH4 potentials are able to correct the purely classical calculations in a consistent way. However, the FH approach fails at lower temperatures, especially the quartic correction. It is thus crucial to assess the range of applicability of this formulation and, in particular, to apply the FH4 potentials with great caution. A simple model of $N$ isotropic harmonic oscillators allows us to propose a means of estimating the cut-off temperature for the validity of the method, which is found to increase with the number of atoms adsorbed on the coronene molecule

A Mixed Heterobimetallic Y/Eu-MOF for the Cyanosilylation and Hydroboration of Carbonyls

Supplementary Materials The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal12030299/s1. Table S1: Elemental analysis of compounds Y/Eu-MOF. Table S2: ICP-AES results of compound Y/Eu-MOF. Table S3: Crystallographic data and structure refinement details of compound Y/Eu-MOF. Table S4: Selected bond lengths (Å) and angles (°) for compound Y/Eu-MOF. Table S5: Table of the continuous Shape Measurements for the MN3O6 coordination environment. Table S6: Table of the continuous Shape Measurements for the MO8 coordination environment. Table S7: Electrophoretic mobility and ζ-potential dependence, with the pH of the Y/Eu-MOFs particles dispersed in water. Conductivity fixed at 330 µS/cm. Table S8: Optimization of the reaction conditions in the hydroboration reaction. Table S9: Green metrics calculated for Y/Eu-MOF catalyst. Table S10: Catalytic cyanosilylation of benzaldehyde performances of Ln-MOFs, as reported in the literature. Figure S1: Figure of the pattern matching analysis and experimental PXRD for Y/Eu-MOF. Figure S2: Figure of the infrared spectra of the ligand and Y/Eu-MOF. Figure S3: SEM and EDS mapping of bulk material of Y/Eu-MOF. Figure S4: Images and particle size distribution (an overall of 250 particles) in the deposited fraction of Y/Eu-MOF catalyst non-suspended in water (about a 68% of the total amount), determined from optical microscope images. Figure S5: Images and particle size distribution (an overall of 250 particles) of Y/Eu-MOF crystals in the fraction steadily suspended in water (about a 32% of the total amount), determined from optical microscope images. Figure S6: Comparation of the particle size distribution of Y/Eu-MOF in the fraction steadily suspended in water and the non-suspended, determined from optical microscope images. Figure S7: Calibration line of conductivity (µS/cm) vs [NaCl] (mol/L). Figure S8: ζ-potential (mV) dependence with the pH of the Y/Eu-MOF. All the measurements were performed with constant conductivity of 330 µS/cm. Figure S9: Electrophoretic mobility (µm·cm/V·s) dependence with the pH of the Y/Eu-MOF. All the measurements were performed with constant conductivity of 330 µS/cm. Figure S10: Study of the recyclability of Y/Eu-MOF (0.5 mol%) catalyst on the cyanosilylation and hydroboration reaction of acetophenone as carbonyl substrate. Figure S11: Analysis of the TOF (h−1) obtained in the cyanosilylation reaction of acetophenone at different times of reaction with Y/Eu-MOF (0.5 mol%), with the optimized reaction conditions. Figure S12: Analysis of the TOF (h−1) obtained in the hydroboration reaction acetophenone at different times of reaction with Y/Eu-MOF (0.5 mol%), with the optimized reaction conditions. Scheme S1: Reaction conditions used for the study of recyclability of Y/Eu-MOF catalysts in the cyanosilylation reaction. Scheme S2: Reaction conditions used for the study of recyclability of Y/Eu-MOF catalysts in the hydroboration reaction. Scheme S3: Leaching test, carried out after the first and second cycles.Funding: This research has been funded by the State Research Agency (grants CTQ2017-84334-R and PGC2018-102052-B-C21) of the Spanish Ministry of Science, Innovation and Universities, the European Union (European Regional Development Fund—ERDF), Junta de Andalucía (P20_01041, UAL2020-AGR-B1781, B-FQM-734-UGR20 and FQM-394). E.E., S.R., and J.P. acknowledge the Government of the Basque Country, Juan de la Cierva Incorporación (grant no. IJC2019-038894-I) and University of Almeria (grant no. HIPATIA2021_04) for their respective fellowsHerein, to the best of our knowledge, the first heterobimetallic Y/Eu porous metal–organic framework (MOF), based on 3-amino-4-hydroxybenzoic acid (H2L) ligand, with the following formulae {[Y3.5Eu1.5L6(OH)3(H2O)3]·12DMF}n (in advance, namely Y/Eu-MOF), is described. The three-dimensional structure has been synthesized by solvothermal routes and thoroughly characterized, by means of single crystal X-ray diffraction, powder X-ray diffraction, electronic microscopy, ICP-AES, electrophoretic mobility, and FTIR spectra. Intriguingly, the porous nature allows for coordinated solvent molecules displacement, yielding unsaturated metal centers, which can act as a Lewis acid catalyst. This novel supramolecular entity has been tested in cyanosilylation and hydroboration reactions on carbonyl substrates of a diverse nature, exhibiting an extraordinary activity.Cierva Incorporación IJC2019-038894-IState Research Agency CTQ2017-84334-R, PGC2018-102052-B-C21University of Almeria HIPATIA2021_04Ministerio de Ciencia, Innovación y UniversidadesEuropean CommissionEuropean Regional Development FundJunta de Andalucía B-FQM-734-UGR20, FQM-394, IJC2019-038894-I, P20_01041, UAL2020-AGR-B178

Genome Wide Meta-Analysis identifies common genetic signatures shared by heart function and Alzheimer’s disease

Genètica de malalties; Medicina molecularGenética de enfermedades; Medicina molecularDisease genetics; Molecular medicineEchocardiography has become an indispensable tool for the study of heart performance, improving the monitoring of individuals with cardiac diseases. Diverse genetic factors associated with echocardiographic measures have been previously reported. The impact of several apoptotic genes in heart development identified in experimental models prompted us to assess their potential association with human cardiac function. This study aimed at investigating the possible association of variants of apoptotic genes with echocardiographic traits and to identify new genetic markers associated with cardiac function. Genome wide data from different studies were obtained from public repositories. After quality control and imputation, a meta-analysis of individual association study results was performed. Our results confirmed the role of caspases and other apoptosis related genes with cardiac phenotypes. Moreover, enrichment analysis showed an over-representation of genes, including some apoptotic regulators, associated with Alzheimer’s disease. We further explored this unexpected observation which was confirmed by genetic correlation analyses. Our findings show the association of apoptotic gene variants with echocardiographic indicators of heart function and reveal a novel potential genetic link between echocardiographic measures in healthy populations and cognitive decline later on in life. These findings may have important implications for preventative strategies combating Alzheimer’s disease

Changes in vitamin c and color during cooking of green peppers (capsicum annuum l)

La calidad del pimentón es valorada principalmente por el sabor, el color, y el contenido de vitamina C. En este estudio se exploró el efecto de la cocción en las características fisicoquímicas de los frutos de pimentón verde. Se pesaron 150 g cortados en tamaños de 2,2 cm de largo y 1,3 cm de ancho y se sometieron a los tratamientos térmicos (vapor y agua durante 5 min, y microondas 760 W durante 2 min), se enfriaron rápidamente y se procedió a determinar el pH y acidez, concentración de vitamina C por el método Indofenol, contenido de clorofila total por espectrofotometría a 652 nm y las coordenadas de color superficial. Después de los tratamientos térmicos, la concentración de vitamina C, el contenido de clorofila y la acidez presentaron diferencias signi-ficativas (p< 0,05), por el contrario pH, L*, a*, b*, C* y h° no se vieron afectados estadísticamente. La vitamina C varió entre 147,84 ± 4,36 y 79,31± 5,44 mg de ácido ascórbico/100 g de pimentón. La clorofila total oscilo entre 4,44 ± 0,04 y 2,61± 0,04 mg de clorofila/100 g de pimentón. En la acidez se registraron valores entre 0,10 ± 0,005 y 0,07 ± 0,001 % ácido cítrico. El método de cocción por microondas obtiene el mayor nivel de retención de vitamina C, y el color superficial del pimentón verde no es afectado por los diferentes métodos de cocción evaluados en este estudio.The quality of pepper is mainly valued for flavor, color, and vitamin C. This study explored the effect of cooking on the physicochemical characteristics of the fruits of green pepper. Weighed 150 g, cut to size of 2.2 cm long and 1.3 cm wide and subjected to heat treatment (steam and water for 5 min, and 760 W microwave for 2 min), and quenched proceeded to determine the pH and acidity, vitamin C concentration by the indophenol method, total chlorophyll content by spectrophotometry at 652 nm and the surface color coordinates. After heat treatment the concentration of vitamin C, chlorophyll content and acidity significant differences (p <0.05), in contrast pH, L *, a *, b *, C * and h ° not statistically affected. Vitamin C ranged from 147.84 ± 4.36 and 79.31 ± 5.44 mg ascorbic acid/100 g fresh weight. The total chlorophyll ranged from 4.44 ± 0.04 and 2.61 ± 0.04 mg/ 100 of pepper. In the acidity values were between 0.10 ± 0.005 and 0.07 ± 0.001% citric acid. The microwave cooking method obtains the highest level of retention of vitamin C, and the surface color of green pepper is not affected by the different cooking methods evaluated in this study