Size quantization effects in InAs self-assembled quantum dots

3 páginas, 3 figuras. PACS: 73.21.-b; 78.55.Cr; 78.66.Fd; 72.40.+w; 68.35.Ct; 73.40.KpWe study size quantization effects in InAs self-assembled quantum dots (QDs) that are embedded in GaAs. Using capacitance, photoluminescence and photovoltage spectroscopy, we correlate the measured quantized level energies with the quantum dot sizes and densities obtained from transmission electron microscopy. With increasing dot size, we observe a strong redshift of the QD features in all our data. In the capacitance spectra, a band gap renormalization of the two-dimensional wetting layer system appears when the first excited QD state crosses the wetting layer ground state. The relative size dependence and absolute energetic position of the QD transitions determined with photoluminescence provide some information about the influence of lateral confinement and height of the QD.This work was supported by QUEST, a NSF science and technology center (Grant No. DMR91-20007), the Alexander von Humboldt Foundation (KHS), and the Brazilian agency CNPq (GMR).Peer reviewe

Use of chromatin stability assay, mitochondrial stain JC-1, and fluorometric assessment of plasma membrane to evaluate frozen-thawed ram semen

P. 121-133Cryopreservation of semen imposes deleterious effects on spermatozoa, either killing a certain proportion of cells or causing subtle damages on sperm function in the surviving population, changes not easily revealed by conventional assays. We have tested three functional assessment techniques in frozen-thawed ram semen from six adult rams, cryopreserved following eight different protocols (four extenders, and glycerol being added at two temperatures). Semen samples were thawed and the following analyses were carried out: motility (CASA), membrane integrity (Hoescht 33258 and fluorometry), chromatin status (chromatin stability test and fluorescence-assisted cell sorting, FACS) and mitochondrial activity (JC-1 and FACS). Fluorometry outcome did not correlate with the other parameters and showed large variation, albeit discriminating among cryopreservation techniques (P<0.01). Mitochondrial activity correlated, but with low values, with total and progressive motility. However, good sperm motility and high velocity values were associated to high mitochondrial membrane potential. The chromatin stability assay was also successfully carried out, and had a good relationship with male factor (%COMP αt and SD αt parameters). In conclusion, fluorometric assessment of membrane integrity albeit rendering poor results, merits improvement, being a low-cost and handy technique, especially for work in the field. On the other hand, both assessments of chromatin stability and mitochondrial status (JC-1 staining), combined with FACS, are reliable techniques that can be used for the functional assessment of frozen-thawed ram semen.S

Use of lignocellulosic liquid waste from wood hardboard manufacture as bitumen emulsion extender for cold asphalt mixtures for low traffic roads

[Abstract:] During the wet process of manufacturing wood hardboards, a large amount of water contaminated with lignocellulosic waste is generated. With the aim of promoting the circular economy, it is interesting to find new uses for this liquid waste, rich in biopolymer lignin. The present research is a preliminary laboratory analysis of the feasibility of using this industrial waste as bitumen emulsion modifier or extender. To this purpose the lignocellulosic industrial waste was tested as partial substitute of bitumen emulsion for cold asphalt mixtures type grave emulsion. Particularly, GE-2 grave emulsions for low traffic roads have been manufactured. Substitution percentages of 0% (control), 5%, 10%, and 15% were analysed. The envelope water was visually determined. Also the optimum fluid content was obtained by means of the Modified Proctor Test. In addition, the optimum bitumen emulsion content, the compressive strength, and the water resistance of the cold asphalt mixtures were analysed conducting immersion-compression tests. All the tested percentages of lignocellulosic waste led to grave emulsions that could be used for low traffic roads, according to the Spanish specifications. Nevertheless, the results indicate decreased compressive strength with increasing liquid waste percentages. For this reason, only percentages of substitution up to 10% of liquid waste rich in lignin are considered adequate as bitumen emulsion extender

Piglet innate immune response to Streptococcus suis colonization is modulated by the virulence of the strain

Streptococcus suis is a zoonotic pathogen of swine involved in arthritis, polyserositis, and meningitis. Colonization of piglets by S. suis is very common and occurs early in life. The clinical outcome of infection is influenced by the virulence of the S. suis strains and the immunity of the animals. Here, the role of innate immunity was studied in cesarean-derived colostrum-deprived piglets inoculated intranasally with either virulent S. suis strain 10 (S10) or non-virulent S. suis strain T15. Colonization of the inoculated piglets was confirmed at the end of the study by PCR and immunohistochemistry. Fever (≥40.5 °C) was more prevalent in piglets inoculated with S10 compared to T15 at 4 h after inoculation. During the 3 days of monitoring, no other major clinical signs were detected. Accordingly, only small changes in transcription of genes associated with the antibacterial innate immune response were observed at systemic sites, with S10 inducing an earlier response than T15 in blood. Local inflammatory response to the inoculation, evaluated by transcriptional analysis of selected genes in nasal swabs, was more sustained in piglets inoculated with the virulent S10, as demonstrated by transcription of inflammation-related genes, such as IL1B, IL1A, and IRF7. In contrast, most of the gene expression changes in trachea, lungs, and associated lymph nodes were observed in response to the non-virulent T15 strain. Thus, S. suis colonization in the absence of systemic infection induces an innate immune response in piglets that appears to be related to the virulence potential of the colonizing strain

Evidence of magnetic accretion in an SW Sex star: discovery of variable circular polarization in LS Pegasi

We report on the discovery of variable circular polarization in the SW Sex star LS Pegasi. The observed modulation has an amplitude of ~0.3 % and a period of 29.6 minutes, which we assume as the spin period of the magnetic white dwarf. We also detected periodic flaring in the blue wing of Hbeta, with a period of 33.5 minutes. The difference between both frequencies is just the orbital frequency, so we relate the 33.5-min modulation to the beat between the orbital and spin period. We propose a new accretion scenario in SW Sex stars, based on the shock of the disk-overflown gas stream against the white dwarf's magnetosphere, which extends to the corotation radius. From this geometry, we estimate a magnetic field strength of B(1) ~ 5-15 MG. Our results indicate that magnetic accretion plays an important role in SW Sex stars and we suggest that these systems are probably Intermediate Polars with the highest mass accretion rates.Comment: Accepted by ApJ Letters. LaTeX, 14 pages, 3 PostScript figure

TDPAC characterization of Ni<SUB>2</SUB>HfF<SUB>8</SUB>·12H<SUB>2</SUB>O and its decomposition products

The hyperfine interaction in Ni2HfF8·12H2O has been determined between 77 K and 1100 K by means of the time-differential perturbed angular correlation technique. From 200 K on, the one-site phase existing at lower temperatures undergoes a gradual phase transition until, at room temperature, the populations of both phases attain a 2:1 ratio. While the quadrupole frequencies characterizing them exhibit aT; 3/2 thermal dependence, their population ratio seems to obey a Boltzmann distribution. At 350 K, when the η-value of the high temperature phase electric field gradient approaches its maximum value, the starting compound decomposes to NiHfF6·6H2O. A kinetics study of the Ni2HfF8·12H2O recovery at room temperature seems to indicate that a tri-dimensional diffusion mechanism is responsible for the corresponding reaction process. The first decomposition product of NiHfF6·6H2O left to atmospheric pressure is found to be NiHfF6·4H2O at 368 K and, between 414 K and 590 K, the high temperature cubic phase of NiHfF6 and Hf2OF6 can be simultaneously observed. Finally, monoclinic HfO2 appears from 1020 K on, having been preceded by an interaction which can be though of as depicting a preliminary stage in hafnia formation.Facultad de Ciencias Exacta

Birkhoff's Theorem for Three-Dimensional AdS Gravity

All three-dimensional matter-free spacetimes with negative cosmological constant, compatible with cyclic symmetry are identified. The only cyclic solutions are the 2+1 (BTZ) black hole with SO(2) x R isometry, and the self-dual Coussaert-Henneaux spacetimes, with isometry groups SO(2) x SO(2,1) or SO(2) x SO(2).Comment: 11 pages, RevTeX4; minor typos corrected, Ref. added, accepted for publication in Phys. Rev.

TDPAC study of the thermal evolution of the quadrupole parameters in NiTiF<SUB>6</SUB>·6H<SUB>2</SUB>O between 30 and 400 K

The thermal evolution of the quadrupole parameters determined using the time differential perturbed angular correlation technique at titanium sites, in NiTiF6·6H2O is presented. The study of the thermal behavior of the hyperfine quadrupole interaction allows one to observe the occurrence of a structural phase transition around 140 K. The thermal evolution of the hyperfine quadrupole frequency of the high temperature phase was interpreted in terms of the flip motion of the water molecules through an ad hoc model. Parameters associated with the model are in good agreement with independent data obtained by Raman scattering. The agreement gives support to the model to be a valuable tool to study the dynamics of molecular groups in crystalline hydrates.Facultad de Ciencias Exacta

The Use of Flavylium Salts as Dynamic Inhibitor Moieties for Human Cb5R

Authors would like to acknowledge the Biochemistry Department in the Faculty of Medicine at the Universidad Autónoma de Madrid for the equipment and support for some of the required reagent purchases. FCT/MCTES is also acknowledged for supporting the National Portuguese NMR Network (ROTEIRO/0031/2013-PINFRA/22161/2016, co-financed by FEDER through COMPETE 2020, POCI, PORL. We thank José Paulo da Silva for the HRMS-ESI analysis. Publisher Copyright: © 2022 by the authors.Cytochrome b5 reductase (Cb5R) is a flavoprotein that participates in the reduction of multiple biological redox partners. Co-localization of this protein with nitric oxide sources has been observed in neurons. In addition, the generation of superoxide anion radical by Cb5R has been observed. A search for specific inhibitors of Cb5R to understand the role of this protein in these new functions has been initiated. Previous studies have shown the ability of different flavonoids to inhibit Cb5R. Anthocyanins are a subgroup of flavonoids responsible for most red and blue colors found in flowers and fruits. Although usually represented by the flavylium cation form, these species are only stable at rather acidic pH values (pH ≤ 1). At higher pH values, the flavylium cation is involved in a dynamic reaction network comprising different neutral species with the potential ability to inhibit the activities of Cb5R. This study aims to provide insights into the molecular mechanism of interaction between flavonoids and Cb5R using flavylium salts as dynamic inhibitors. The outcome of this study might lead to the design of improved specific enzyme inhibitors in the future.publishersversionpublishe

Isometry in mesosaurs: Implications for growth patterns in early amniotes

Mesosaurs were small amphibious tetrapods that lived in western Gondwana during the Early Permian or even earlier, when temperate Permo-Carboniferous conditions initiated after the glaciations that affected the southern region of Pangea. In this contribution, we applied traditional linear regression morphometrics to analyse proportions of both the skull and limb bones in more than 100 mesosaur specimens. The analyses revealed that all mesosaur bones scale remarkably close to a model of geometrical similarity (isometry), and that this pattern is particularly strong in long bones and also in the skull. These results indicate that juvenile and adult mesosaurs do not display appreciable change in bone proportions, meaning that there are few or no noticeable differences between them during growth. The well-defined isometry, and particularly, the high interrelation between metatarsals and phalanges permit us to suggest that the mesosaur hind limb is subject to notable modularity. This evidence strongly argues that the differences previously described to support three mesosaur species in Western Gondwana, might instead reflect natural intraspecific variability, taphonomic features or even possible sexual dimorphism, as recently suggested. Our study also reinforces the general plesiomorphic structure of the mesosaur skeleton, which along with some cranial specializations for ecological fitness and the evidence of strong isometric growth as we demonstrate herein, may suggest new hypotheses of relationships for mesosaurs which thus would position them as more basal amniotes than previously thought