Theoretical and experimental study of the excitonic binding energy in GaAs/AlGaAs single and coupled double quantum wells

This paper discusses the theoretical and experimental results obtained for the excitonic binding energy (Eb) in a set of single and coupled double quantum wells (SQWs and CDQWs) of GaAs/AlGaAs with different Al concentrations (Al%) and inter-well barrier thicknesses. To obtain the theoretical Eb the method proposed by Mathieu, Lefebvre and Christol (MLC) was used, which is based on the idea of fractional-dimension space, together with the approach proposed by Zhao et al., which extends the MLC method for application in CDQWs. Through magnetophotoluminescence (MPL) measurements performed at 4 K with magnetic fields ranging from 0 T to 12 T, the diamagnetic shift curves were plotted and adjusted using two expressions: one appropriate to fit the curve in the range of low intensity fields and another for the range of high intensity fields, providing the experimental Eb values. The effects of increasing the Al% and the inter-well barrier thickness on Eb are discussed. The Eb reduction when going from the SQW to the CDQW with 5 Å inter-well barrier is clearly observed experimentally for 35% Al concentration and this trend can be noticed even for concentrations as low as 25% and 15%, although the Eb variations in these latter cases are within the error bars. As the Zhao's approach is unable to describe this effect, the wave functions and the probability densities for electrons and holes were calculated, allowing us to explain this effect as being due to a decrease in the spatial superposition of the wave functions caused by the thin inter-well barrier.

Heme oxygenase-1 activity is involved in the control of Toxoplasma gondii infection in the lung of BALB/c and C57BL/6 and in the small intestine of C57BL/6 mice

Heme oxygenase-1 (HO-1) is an enzyme that catabolizes free heme, which induces an intense inflammatory response. The expression of HO-1 is induced by different stimuli, triggering an anti-inflammatory response during biological stress. It was previously verified that HO-1 is able to induce indoleamine 2,3-dioxygenase (IDO), an enzyme that is induced by IFN-γ in Toxoplasma gondii infection. To verify the role of HO-1 during in vivo T. gondii infection, BALB/c and C57BL/6 mice were infected with the ME49 strain and treated with zinc protoporphyrin IX (ZnPPIX) or hemin, which inhibit or induce HO-1 activity, respectively. The results show that T. gondii infection induced high levels of HO-1 expression in the lung of BALB/c and C57BL6 mice. The animals treated with ZnPPIX presented higher parasitism in the lungs of both lineages of mice, whereas hemin treatment decreased the parasite replication in this organ and in the small intestine of infected C57BL/6 mice. Furthermore, C57BL/6 mice infected with T. gondii and treated with hemin showed higher levels of IDO expression in the lungs and small intestine than uninfected mice. In conclusion, our data suggest that HO-1 activity is involved in the control of T. gondii in the lungs of both mouse lineages, whereas the hemin, a HO-1 inducer, seems to be involved in the control of parasitism in the small intestine of C57BL/6 mice.

Expression analysis and in silico characterization of intronic long noncoding RNAs in renal cell carcinoma: emerging functional associations

Abstract Background Intronic and intergenic long noncoding RNAs (lncRNAs) are emerging gene expression regulators. The molecular pathogenesis of renal cell carcinoma (RCC) is still poorly understood, and in particular, limited studies are available for intronic lncRNAs expressed in RCC Methods Microarray experiments were performed with custom-designed arrays enriched with probes for lncRNAs mapping to intronic genomic regions. Samples from 18 primary RCC tumors and 11 nontumor adjacent matched tissues were analyzed. Meta-analyses were performed with microarray expression data from three additional human tissues (normal liver, prostate tumor and kidney nontumor samples), and with large-scale public data for epigenetic regulatory marks and for evolutionarily conserved sequences. Results A signature of 29 intronic lncRNAs differentially expressed between RCC and nontumor samples was obtained (false discovery rate (FDR) <5%). A signature of 26 intronic lncRNAs significantly correlated with the RCC five-year patient survival outcome was identified (FDR <5%, p-value ≤0.01). We identified 4303 intronic antisense lncRNAs expressed in RCC, of which 22% were significantly (p <0.05) cis correlated with the expression of the mRNA in the same locus across RCC and three other human tissues. Gene Ontology (GO) analysis of those loci pointed to 'regulation of biological processes’ as the main enriched category. A module map analysis of the protein-coding genes significantly (p <0.05) trans correlated with the 20% most abundant lncRNAs, identified 51 enriched GO terms (p <0.05). We determined that 60% of the expressed lncRNAs are evolutionarily conserved. At the genomic loci containing the intronic RCC-expressed lncRNAs, a strong association (p <0.001) was found between their transcription start sites and genomic marks such as CpG islands, RNA Pol II binding and histones methylation and acetylation. Conclusion Intronic antisense lncRNAs are widely expressed in RCC tumors. Some of them are significantly altered in RCC in comparison with nontumor samples. The majority of these lncRNAs is evolutionarily conserved and possibly modulated by epigenetic modifications. Our data suggest that these RCC lncRNAs may contribute to the complex network of regulatory RNAs playing a role in renal cell malignant transformation.

The intronic long noncoding RNA ANRASSF1 recruits PRC2 to the RASSF1A promoter, reducing the expression of RASSF1A and increasing cell proliferation

The down-regulation of the tumor-suppressor gene RASSF1A has been shown to increase cell proliferation in several tumors. RASSF1A expression is regulated through epigenetic events involving the polycomb repressive complex 2 (PRC2); however, the molecular mechanisms modulating the recruitment of this epigenetic modifier to the RASSF1 locus remain largely unknown. Here, we identify and characterize ANRASSF1, an endogenous unspliced long noncoding RNA (lncRNA) that is transcribed from the opposite strand on the RASSF1 gene locus in several cell lines and tissues and binds PRC2. ANRASSF1 is transcribed through RNA polymerase II and is 5'-capped and polyadenylated; it exhibits nuclear localization and has a shorter half-life compared with other lncRNAs that bind PRC2. ANRASSF1 endogenous expression is higher in breast and prostate tumor cell lines compared with non-tumor, and an opposite pattern is observed for RASSF1A. ANRASSF1 ectopic overexpression reduces RASSF1A abundance and increases the proliferation of HeLa cells, whereas ANRASSF1 silencing causes the opposite effects. These changes in ANRASSF1 levels do not affect the RASSF1C isoform abundance. ANRASSF1 overexpression causes a marked increase in both PRC2 occupancy and histone H3K27me3 repressive marks, specifically at the RASSF1A promoter region. No effect of ANRASSF1 overexpression was detected on PRC2 occupancy and histone H3K27me3 at the promoter regions of RASSF1C and the four other neighboring genes, including two well-characterized tumor suppressor genes. Additionally, we demonstrated that ANRASSF1 forms an RNA/DNA hybrid and recruits PRC2 to the RASSF1A promoter. Together, these results demonstrate a novel mechanism of epigenetic repression of the RASSF1A tumor suppressor gene involving antisense unspliced lncRNA, in which ANRASSF1 selectively represses the expression of the RASSF1 isoform overlapping the antisense transcript in a location-specific manner. In a broader perspective, our findings suggest that other non-characterized unspliced intronic lncRNAs transcribed in the human genome might contribute to a location-specific epigenetic modulation of genes.

Involvement of formyl peptide receptors in the stimulatory effect of crotoxin on macrophages co-cultivated with tumour cells

Crotoxin (CTX) is the main neurotoxic component of Crotalus durissus terrificus snake venom. It inhibits tumour growth and modulates the function of macrophages, which are essential cells in the tumour microenvironment. The present study investigated the effect of CTX on the secretory activity of monocultured macrophages and macrophages co-cultivated with LLC-WRC 256 cells. The effect of the macrophage secretory activities on tumour cell proliferation was also evaluated. Macrophages pre-treated with CTX (0.3 μg/mL) for 2 h were co-cultivated with LLC-WRC 256 cells, and the secretory activity of the macrophages was determined after 12, 24 and 48 h. The co-cultivation of CTX-treated macrophages with the tumour cells caused a 20% reduction in tumour cell proliferation. The production of both H2O2 and NO was increased by 41% and 29% after 24 or 48 h of co-cultivation, respectively, compared to the values for the co-cultures of macrophages of control. The level of secreted IL-1β increased by 3.7- and 3.2-fold after 12 h and 24 h of co-cultivation, respectively. Moreover, an increased level of LXA4 (25%) was observed after 24 h of co-cultivation, and a 2.3- and 2.1-fold increased level of 15-epi-LXA4 was observed after 24 h and 48 h, respectively. Boc-2, a selective antagonist of formyl peptide receptors, blocked both the stimulatory effect of CTX on the macrophage secretory activity and the inhibitory effect of these cells on tumour cell proliferation. Taken together, these results indicate that CTX enhanced the secretory activity of macrophages, which may contribute to the antitumour activity of these cells, and that activation of formyl peptide receptors appears to play a major role in this effect.

In vivo assessment of specific cytotoxic T lymphocyte killing

The direct killing of target cells by cytotoxic T lymphocytes (CTLs) plays a fundamental role in protective immunity to viral, bacterial, protozoan and fungi infections, as well as to tumor cells. In vivo cytotoxic assays take into account the interaction of target and effector cells in the context of the proper microenvironment making the analysis biologically more relevant than in vitro cytotoxic assays. Thus, the development, improvement and validation of in vivo methods are necessary in view of the importance of the results they may provide. We describe and discuss in this manuscript a method to evaluate in vivo specific cytotoxic T lymphocyte killing. We used as model system mice immunized with human recombinant replication-deficient adenovirus 5 (HAd5) containing different transgenes as the trigger of a CTL-mediated immune response. To these mice, we adoptively transferred syngeneic cells labeled with different vital fluorescent dyes. Donor cells were pulsed (target) or not (control non-target) with distinct CD8 T-cell epitopes, mixed in a 1:1 ratio and injected i.v. into immunized or non-immunized recipient mice. After 18-24h, spleen cells are collected and analysed by flow cytometry. A deviation from the 1:1 ratio of control and target cell populations indicates antigen specific lysis of target cells

Bounds on the density of sources of ultra-high energy cosmic rays from the Pierre Auger Observatory

We derive lower bounds on the density of sources of ultra-high energy cosmic rays from the lack of significant clustering in the arrival directions of the highest energy events detected at the Pierre Auger Observatory. The density of uniformly distributed sources of equal intrinsic intensity was found to be larger than ~(0.06 - 5) × '10 POT. -4' 'Mpc POT. -3' at 95% CL, depending on the magnitude of the magnetic deflections. Similar bounds, in the range (0.2 - 7) × '10 POT. -4' 'Mpc POT. -3', were obtained for sources following the local matter distribution.

Spectroscopic investigation and heat generation of Yb3+/Ho3+ codoped aluminosilicate glasses looking for the emission at 2 μm

Energy transfer (ET) and heat generation processes in Yb3+/Ho3+-codoped low-silica calcium aluminosilicate glasses were investigated using thermal lens (TL) and photoluminescence measurements looking for the emission around 2.0 μm. Stepwise ET processes from Yb3+ to Ho3+, upon excitation at 0.976 μm, produced highly efficient emission in the mid-infrared range at around 2.0 μm, with high fluorescence quantum efficiency (η1 ∼ 0.85 and independent of Ho3+ concentration) and relatively very low thermal loading (<0.4) for concentration up to 1.5% of Ho2O3. An equation was deduced for the description of the TL results that provided the absolute value of η1 and the number of emitted photons at 2.0 μm per absorbed pump photon by the Yb3+ ions, the latter reaching 60% for the highest Ho3+ concentration. These results suggest that the studied codoped system would be a promising candidate for the construction of photonic devices, especially for medical applications.

Theoretical and experimental studies on the electronic, optical, and structural properties of poly-pyrrole-2-carboxylic acid films

A theoretical approach is used here to explain experimental results obtained from the electrosynthesis of polypyrrole-2-carboxylic acid (PPY-2-COOH) films in nonaqueous medium. An analysis of the Fukui function (reactivity index) indicates that the monomer (pyrrole-2-carboxylic acid, PY-2-COOH), and dimers and trimers are oxidized in the C4 or C5 positions of the heterocyclic ring of the PY-2-COOH structure. After calculating the heat of formation using semiempirical Austin Model 1 post-Hartree-Fock parameterization for dimer species, both C4 and C5 positions adjacent to the aromatic rings of PPY-2-COOH were considered the most susceptible ones to oxidative coupling reactions. The ZINDO-S/CI semiempirical method was used to simulate the electronic transitions typically seen in the UV-VIS-NIR range in monomer and oligomers with different conjugation lengths. The use of an electrochemical quartz crystal microbalance provides sufficient information to propose a polymerization mechanism of PY-2-COOH based on molecular modeling and experimental results.

Photoluminescence of core-shell nanoparticles made from yttrium stabilized zirconia powder grain coated with alumina

A YSZ@Al2O3 nanocomposite was obtained by Al2O3 coating on the surface of yttrium stabilized zirconia via a polymeric precursor method. The resulting core–shell structures were characterized by X-ray diffraction, scanning electron microscopy, transmission electronic microscopy and PL spectra. The TEM micrographs clearly show a homogeneous Al2O3 shell around the ZrO2 core. The observed PL is related to surface–interface defects. Such novel technologies can, in principle, explore materials which are not available in the bulk single crystal form but their figure-of-merit is dramatically dependent on the surface–interface defect states.

Effect of a polymeric protective coating on optical and electrical properties of poly (p-phenylene vinylene) derivatives

The resistance to photodegradation of poly [(2-methoxy-5-n-hexyloxy)-p-phenylene vinylene] (OC1OC6-PPV) films was significantly enhanced by the use of poly(vinyl alcohol) 99% hydrolyzed as protective coating. The deposition of poly(vinyl alcohol) onto OC1OC6-PPV films did not affect the absorption and the emission spectra of the luminescent polymer. The protected film showed 5% drop on the absorbance at 500nm after 270 hours of light exposure while the unprotected film completely degraded in the same conditions. The conductivity of the protected film remained stable (around 7 × 10-10 S/m) while the value for the unprotected one dropped around two orders of magnitude after 100 hours of light exposure.

Synthesis and photovoltaic performance of a fluorene-bithiophene copolymer

We present the synthesis of a copolymer structure, poly(9,9′-n-di-hexyl-2,7-fluorene-alt-2,5- bithiophene), referred to herein as LaPPS43, and its physico-chemical characterization. Thin films of this polymer mixed with phenyl-C61-butyric acid methyl ester (PCBM) were used as the active layer in photovoltaic devices using the ITO/PEDOT:PSS/LaPPS43: PCBM/Ca/Al bulk heterojunction structure. The devices of different active layer thicknesses were electrically studied using J-V curves and the Photo-Celiv technique. The obtained results show that LaPPS43 combined with PCBM is a promising system for photovoltaic devices. Device performance is discussed in terms of the mean drift distance x for charge carriers. Photophysical data showed that the excitonic species are all localized in the aggregated forms. The mechanism of exciton formation and dissociation is also discussed.

Estado, política y petróleo : La historia política neuquina y el rol del petróleo en el modelo de provincia, 1958-1990

Nuestro objetivo no es concretar un estudio técnico-económico sobre el petróleo en Neuquén, ni tampoco la historia de las actividades productivas y/o energéticas de la provincia; en rigor, el intento se centra en debatir y aportar reflexiones sobre la definición energética de la provincia - proceso lento pero consistente - que se inicia desde que reviste el status de territorio nacional, desmitificando presupuestos vinculados al impacto del desarrollismo en materia petrolífera, sin que ello implique desconocer la incidencia de esa política nacional en el rubro.

Rupturas políticas y disputas de sentido en el movimiento estudiantil reformista : Un acercamiento a la relación entre universidad y política entre "dos intervenciones", 1955-1966

Este trabajo ha sido elaborado como una primera indagación sobre la relación entre Universidad y política entre 'dos intervenciones', la de 1955 y la de 1966, haciendo especial énfasis en un actor específico: el movimiento estudiantil reformista, sus conflictos y transformaciones en el período en cuestión. Tales cambios se pensaron a partir de dos dimensiones: respecto de los procesos más significativos de la coyuntura política nacional, y de las transformaciones propias de la vida universitaria y estudiantil. Teniendo en cuenta ambos aspectos, hemos delineado una periodización que nos permitió ubicar coyunturas específicas en las que tuvieron lugar cuestionamientos al reformismo como 'modelo de universidad' y desplazamientos en el mapa político estudiantil. Por otra parte, y para realizar un completo abordaje del tema, hemos reconstruido la trayectoria histórica del Reformismo, en tanto 'modelo de universidad' e identidad político-ideológica de amplios sectores de la juventud, desde sus orígenes en la Córdoba de 1918 hasta el año 1955, pasando por los 'traumas' que el peronismo va a significarle

Estado, política y petróleo : La historia política neuquina y el rol del petróleo en el modelo de provincia, 1958-1990

Nuestro objetivo no es concretar un estudio técnico-económico sobre el petróleo en Neuquén, ni tampoco la historia de las actividades productivas y/o energéticas de la provincia; en rigor, el intento se centra en debatir y aportar reflexiones sobre la definición energética de la provincia - proceso lento pero consistente - que se inicia desde que reviste el status de territorio nacional, desmitificando presupuestos vinculados al impacto del desarrollismo en materia petrolífera, sin que ello implique desconocer la incidencia de esa política nacional en el rubro.