RESIK and RHESSI observations of the 20 September 2002 flare

Soft X-ray spectra 3.33 A - 6.15 A from the RESIK instrument on CORONAS-F constitute a unique database for the study of the physical conditions of solar flare plasmas, enabling the calculation of differential emission measures. The two RESIK channels for the shortest wavelengths overlap with the lower end of RHESSI spectral energy range, which is located around 3 keV, making it possible to compare both data sets. We aim to compare observations from RESIK and RHESSI spectrometers and cross-correlate these instruments. Observations are compared with synthetic spectra calculated based on the results of one-dimensional hydrodynamical (1D-HD) modelling. The analysis was performed for the flare on 20 September 2002. We estimated the geometry of the flaring loop, necessary for 1D-HD modelling, based on images from RHESSI and SOHO/EIT. The distribution of non-thermal electrons (NTEs) was determined from RHESSI spectra. The 1D-HD model assumes that non-thermal electrons with a power-law spectrum were injected at the apex of the flaring loop. The NTEs then heat and evaporate the chromosphere, filling the loop with hot and dense plasma radiating in soft X-rays. The total energy of electrons was constrained by comparing observed and calculated fluxes from GOES 1 - 8 A data. We determined the temperature and density at every point of the flaring loop throughout the evolution of the flare, calculating the resulting X-ray spectra. The synthetic spectra calculated based on the results of hydrodynamic modelling for the 20 September 2002 flare are consistent within a factor of two with the observed RESIK spectra during most of the duration of the flare. This discrepancy factor is probably related to the uncertainty on the cross-calibration between RESIK and RHESSI instruments

Half-BPS cosmic string in N=2 supergravity in the presence of a dilaton

We construct new half-BPS cosmic string solutions in D=4 N=2 supergravity compatible with a consistent truncation to N=1 supergravity where they describe D-term cosmic strings. The constant Fayet-Iliopoulos term in the N=1 D-term is not put in by hand but is geometrically engineered by a gauging in the mother N=2 supergravity theory. The coupling of the N=2 vector multiplets is characterized by a cubic prepotential admitting an axion-dilaton field, a common property of many compactifications of string theory. The axion-dilaton field survives the truncation to N=1 supergravity. On the string configuration the BPS equations constrain the dilaton to be an arbitrary constant. All the cosmic string solutions with different values of the dilaton have the same energy per unit length but different lenght scales.Comment: 52 pages; typos correcte

Model Systems of Precursor Cellular Membranes: Long-Chain Alcohols Stabilize Spontaneously Formed Oleic Acid Vesicles

AbstractOleic acid vesicles have been used as model systems to study the properties of membranes that could be the evolutionary precursors of more complex, stable, and impermeable phospholipid biomembranes. Pure fatty acid vesicles in general show high sensitivity to ionic strength and pH variation, but there is growing evidence that this lack of stability can be counterbalanced through mixtures with other amphiphilic or surfactant compounds. Here, we present a systematic experimental analysis of the oleic acid system and explore the spontaneous formation of vesicles under different conditions, as well as the effects that alcohols and alkanes may have in the process. Our results support the hypothesis that alcohols (in particular 10- to 14-C-atom alcohols) contribute to the stability of oleic acid vesicles under a wider range of experimental conditions. Moreover, studies of mixed oleic-acid-alkane and oleic-acid-alcohol systems using infrared spectroscopy and Langmuir trough measurements indicate that precisely those alcohols that increased vesicle stability also decreased the mobility of oleic acid polar headgroups, as well as the area/molecule of lipid

Economic and Environmental Assessment of Bacterial Poly(3-Hydroxybutyrate) Production from the Organic Fraction of Municipal Solid Waste

The management of municipal solid waste is a major logistic and environmental problem worldwide. Nonetheless, the organic fraction of municipal solid waste (OFMSW) is a valuable source of nutrients which can be used for a variety of purposes, according to the Circular Economy paradigm. Among the possible applications, the bioproduction of a biodegradable polyester, poly(3-hydroxybutyrate) [P(3HB)], using OFMSW as carbon platform is a promising strategy. Here, an economic and environmental assessment of bacterial P(3HB) production from OFMSW is presented based on previously published results. The SuperPro Designer (R) software was used to simulate P(3HB) production under our experimental parameters. Two scenarios were proposed depending on the fermentation medium: (1) enzymatic hydrolysate of OFMSW supplemented with glucose and plum waste juice; and (2) basal medium supplemented with glucose and plum waste juice. According to our results, both scenarios are not economically feasible under our experimental parameters. In Scenario 1, the low fermentation yield, the cost of the enzymes, the labour cost and the energy consumption are the factors that most contribute to that result. In Scenario 2, the cost of the extraction solvent and the low fermentation yield are the most limiting factors. The possibility of using process waste as raw material for the generation of other products must be investigated to enhance economic feasibility. From an environmental viewpoint, the photochemical oxidation potential (derived from the use of anisole as extraction solvent) and the generation of acid rain and global warming effect (caused by the burning of fuels for power generation) are the most relevant impacts associated to P(3HB) production under our experimental parameters.Jon Kepa Izaguirre was the recipient of a predoctoral fellowship from the Basque Governmen

DNA methylation of FKBP5 and response to exposure-based psychological therapy

Differential DNA methylation of the HPA-axis related gene FKBP5 has recently been shown to be associated with varying response to environmental influences, and may play a role in how well people respond to psychological treatments. Participants (n=111) received exposure-based CBT for agoraphobia with or without panic disorder, or specific phobias. Percentage DNA methylation levels were measured for the promoter region and intron 7 of FKBP5. The association between percentage reduction in clinical severity and change in DNA methylation was tested using linear mixed models. The effect of genotype (rs1360780) was tested by the inclusion of an interaction term. The association between change in DNA methylation and FKBP5 expression was examined. Change in percentage DNA methylation at one CpG site of intron 7 was associated with percentage reduction in severity (β=-4.26, p=3.90x10-4), where a decrease in DNA methylation was associated with greater response to therapy. An interaction was detected between rs1360780 and changes in DNA methylation in the promoter region of FKBP5 on treatment outcome (p=0.045), but did not survive correction for multiple testing. Changes in DNA methylation were not associated with FKBP5 expression. Decreasing DNA methylation at one CpG site of intron 7 of FKBP5 was strongly associated with decreasing anxiety severity following exposure-based CBT. In addition, there was suggestive evidence that allele-specific methylation at the promoter region may also be associated with treatment response. The results of this study add to the growing literature demonstrating the role of biological processes such as DNA methylation in response to environmental influences

Electronic and optical spectra in a diluted magnetic semiconductor multilayer

The effects of random distribution of magnetic impurities with concentration $x$ in a semiconductor alloy multilayer at a paramagnetic temperature are investigated by means of coherent potential approximation and tight-binding model. The change in the electronic states and the optical absorption spectrum with $x$ is calculated for weak and strong exchange interactions between carrier spins and localized spin moments on magnetic ions. We find that the density of states and optical absorption are strongly layer-dependent due to the quantum size effects. The electronic and optical spectra are broadened due to the spin fluctuations of magnetic ions and in the case of strong exchange interaction, an energy gap appears in both spectra. Furthermore, the interior layers show higher contribution in the optical absorption of the system. The results can be helpful for magneto-optical devices at a paramagnetic temperature.Comment: 7 pages, 5 figure

The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks

Aims. Photodissociation by UV light is an important destruction mechanism for CO in many astrophysical environments, ranging from interstellar clouds to protoplanetary disks. The aim of this work is to gain a better understanding of the depth dependence and isotope-selective nature of this process. Methods. We present a photodissociation model based on recent spectroscopic data from the literature, which allows us to compute depth-dependent and isotope-selective photodissociation rates at higher accuracy than in previous work. The model includes self-shielding, mutual shielding and shielding by atomic and molecular hydrogen, and it is the first such model to include the rare isotopologues C17O and 13C17O. We couple it to a simple chemical network to analyse CO abundances in diffuse and translucent clouds, photon-dominated regions, and circumstellar disks. Results. The photodissociation rate in the unattenuated interstellar radiation field is 2.6e-10 s^-1, 30% higher than currently adopted values. Increasing the excitation temperature or the Doppler width can reduce the photodissociation rates and the isotopic selectivity by as much as a factor of three for temperatures above 100 K. The model reproduces column densities observed towards diffuse clouds and PDRs, and it offers an explanation for both the enhanced and the reduced N(12CO)/N(13CO) ratios seen in diffuse clouds. The photodissociation of C17O and 13C17O shows almost exactly the same depth dependence as that of C18O and 13C18O, respectively, so 17O and 18O are equally fractionated with respect to 16O. This supports the recent hypothesis that CO photodissociation in the solar nebula is responsible for the anomalous 17O and 18O abundances in meteorites.Comment: Accepted by A&

Site-specific O-glycosylation of members of the low-density lipoprotein receptor superfamily enhances ligand interactions

15 pags, 8 figs, 1 tab. -- This article contains supplementary material (Table S1, Figs. S1–S4, and Data Sets S1–S4.1)The low-density lipoprotein receptor (LDLR) and related receptors are important for the transport of diverse biomolecules across cell membranes and barriers. Their functions are especially relevant for cholesterol homeostasis and diseases, including neurodegenerative and kidney disorders. Members of the LDLR-related protein family share LDLR class A (LA) repeats providing binding properties for lipoproteins and other biomolecules. We previously demonstrated that short linker regions between these LA repeats contain conserved O-glycan sites. Moreover, we found that O-glycan modifications at these sites are selectively controlled by the GalNAc-transferase isoform, GalNAc-T11. However, the effects of GalNAc-T11–mediated O-glycosylation on LDLR and related receptor localization and function are unknown. Here, we characterized O-glycosylation of LDLR-related proteins and identified conserved O-glycosylation sites in the LA linker regions of VLDLR, LRP1, and LRP2 (Megalin) from both cell lines and rat organs. Using a panel of gene-edited isogenic cell line models, we demonstrate that GalNAc-T11–mediated LDLR and VLDLR O-glycosylation is not required for transport and cell-surface expression and stability of these receptors but markedly enhances LDL and VLDL binding and uptake. Direct ELISA-based binding assays with truncated LDLR constructs revealed that O-glycosylation increased affinity for LDL by 5-fold. The molecular basis for this observation is currently unknown, but these findings open up new avenues for exploring the roles of LDLR-related proteins in disease.This work was supported by the Læge Sofus Carl Emil Friis og hustru Olga Doris Friis’ Legat, the Kirsten og Freddy Johansen Fonden, the Lundbeck Foundation, the A.P. Møller og Hustru Chastine Mc-Kinney Møllers Fond til Almene Formaal, the Mizutani Foundation, the Novo Nordisk Foundation, the Danish Research Council Sapere Aude Research Talent Grant (to K. T. S.), and the Danish National Research Foundation (DNRF107). The authors declare that they have no conflicts of interest with the contents of this articl