The Flare-energy Distributions Generated by Kink-unstable Ensembles of Zero-net-current Coronal Loops

It has been proposed that the million degree temperature of the corona is due to the combined effect of barely-detectable energy releases, so called nanoflares, that occur throughout the solar atmosphere. Alas, the nanoflare density and brightness implied by this hypothesis means that conclusive verification is beyond present observational abilities. Nevertheless, we investigate the plausibility of the nanoflare hypothesis by constructing a magnetohydrodynamic (MHD) model that can derive the energy of a nanoflare from the nature of an ideal kink instability. The set of energy-releasing instabilities is captured by an instability threshold for linear kink modes. Each point on the threshold is associated with a unique energy release and so we can predict a distribution of nanoflare energies. When the linear instability threshold is crossed, the instability enters a nonlinear phase as it is driven by current sheet reconnection. As the ensuing flare erupts and declines, the field transitions to a lower energy state, which is modelled by relaxation theory, i.e., helicity is conserved and the ratio of current to field becomes invariant within the loop. We apply the model so that all the loops within an ensemble achieve instability followed by energy-releasing relaxation. The result is a nanoflare energy distribution. Furthermore, we produce different distributions by varying the loop aspect ratio, the nature of the path to instability taken by each loop and also the level of radial expansion that may accompany loop relaxation. The heating rate obtained is just sufficient for coronal heating. In addition, we also show that kink instability cannot be associated with a critical magnetic twist value for every point along the instability threshold

A chemical probe unravels the reactive proteome of health-associated catechols

Catechol-containing natural products are common constituents of foods, drinks, and drugs. Natural products carrying this motif are often associated with beneficial biological effects such as anticancer activity and neuroprotection. However, the molecular mode of action behind these properties is poorly understood. Here, we apply a mass spectrometry-based competitive chemical proteomics approach to elucidate the target scope of catechol-containing bioactive molecules from diverse foods and drugs. Inspired by the protein reactivity of catecholamine neurotransmitters, we designed and synthesised a broadly reactive minimalist catechol chemical probe based on dopamine. Initial labelling experiments in live human cells demonstrated broad protein binding by the probe, which was largely outcompeted by its parent compound dopamine. Next, we investigated the competition profile of a selection of biologically relevant catechol-containing substances. With this approach, we characterised the protein reactivity and the target scope of dopamine and ten biologically relevant catechols. Strikingly, proteins associated with the endoplasmic reticulum (ER) were among the main targets. ER stress assays in the presence of reactive catechols revealed an activation of the unfolded protein response (UPR). The UPR is highly relevant in oncology and cellular resilience, which may provide an explanation of the health-promoting effects attributed to many catechol-containing natural products.Molecular Physiolog

Solar Stereoscopy with STEREO/EUVI A and B spacecraft from small (6 deg) to large (170 deg) spacecraft separation angles

We performed for the first time stereoscopic triangulation of coronal loops in active regions over the entire range of spacecraft separation angles ($\alpha_{sep}\approx 6^\circ, 43^\circ, 89^\circ, 127^\circ$, and $170^\circ$). The accuracy of stereoscopic correlation depends mostly on the viewing angle with respect to the solar surface for each spacecraft, which affects the stereoscopic correspondence identification of loops in image pairs. From a simple theoretical model we predict an optimum range of $\alpha_{sep} \approx 22^\circ-125^\circ$, which is also experimentally confirmed. The best accuracy is generally obtained when an active region passes the central meridian (viewed from Earth), which yields a symmetric view for both STEREO spacecraft and causes minimum horizontal foreshortening. For the extended angular range of $\alpha_{sep}\approx 6^\circ-127^{\circ}$ we find a mean 3D misalignment angle of $\mu_{PF} \approx 21^\circ-39^\circ$ of stereoscopically triangulated loops with magnetic potential field models, and $\mu_{FFF} \approx 15^\circ-21^\circ$ for a force-free field model, which is partly caused by stereoscopic uncertainties $\mu_{SE} \approx 9^\circ$. We predict optimum conditions for solar stereoscopy during the time intervals of 2012--2014, 2016--2017, and 2021--2023.Comment: Solar Physics, (in press), 22 pages, 9 figure

Sociology Back to the Publics

This article is a reading of the `new sociology' that is mainly identified with the works of C. Wright Mills and Alvin Gouldner. Its main argument is that during the past 40 years the new sociology gave back a public face to sociology. This distinguishes it from the `old sociology' that had not been able to free itself from `private' social values. It is argued that Mills' power elite and Gouldner's coming crisis theses provided the foundation for a common enterprise among many `new sociologists' to develop a critical and public sociology that would seek to shape what Mills called the `democratic society of publics'.`New sociologists' share a critique of modern societies, namely, that though most modern societies have formal democracies, a substantial democratic social structure of publics is often lacking, due to the erosion of the public sphere by private values

What fraction of stars formed in infrared galaxies at high redshift?

Star formation happens in two types of environment: ultraviolet-bright starbursts (like 30 Doradus and HII galaxies at low redshift and Lyman-break galaxies at high redshift) and infrared-bright dust-enshrouded regions (which may be moderately star-forming like Orion in the Galaxy or extreme like the core of Arp 220). In this work I will estimate how many of the stars in the local Universe formed in each type of environment, using observations of star-forming galaxies at all redshifts at different wavelengths and of the evolution of the field galaxy population.Comment: 7 pages, 0 figs, to appear in proceedings of "Starbursts - From 30 Doradus to Lyman break galaxies", edited by Richard de Grijs and Rosa M. Gonzalez Delgado, published by Kluwe

Deep Inelastic Scattering from off-Shell Nucleons

We derive the general structure of the hadronic tensor required to describe deep-inelastic scattering from an off-shell nucleon within a covariant formalism. Of the large number of possible off-shell structure functions we find that only three contribute in the Bjorken limit. In our approach the usual ambiguities encountered when discussing problems related to off-shellness in deep-inelastic scattering are not present. The formulation therefore provides a clear framework within which one can discuss the various approximations and assumptions which have been used in earlier work. As examples, we investigate scattering from the deuteron, nuclear matter and dressed nucleons. The results of the full calculation are compared with those where various aspects of the off-shell structure are neglected, as well as with those of the convolution model.Comment: 36 pages RevTeX, 9 figures (available upon request), ADP-93-210/T128, PSI-PR-93-13, accepted for publication in Physical Review

Spin battery operated by ferromagnetic resonance

Precessing ferromagnets are predicted to inject a spin current into adjacent conductors via Ohmic contacts, irrespective of a conductance mismatch with, for example, doped semiconductors. This opens the way to create a pure spin source spin battery by the ferromagnetic resonance. We estimate the spin current and spin bias for different material combinations.Comment: The estimate for the magnitude of the spin bias is improved. We find that it is feasible to get a measurable signal of the order of the microwave frequency already for moderate rf intensitie

Autoimmune lymphoproliferative syndrome (ALPS) in a child from consanguineous parents: a dominant or recessive disease?

Autoimmune lymphoproliferative syndrome (ALPS) is characterized by autoimmune features and lymphoproliferations and is generally caused by defective Fas-mediated apoptosis. This report describes a child with clinical features of ALPS without detectable Fas expression on freshly isolated blood leukocytes. Detection of FAS transcripts via real-time quantitative PCR made a severe transcriptional defect unlikely. Sequencing of the FAS gene revealed a 20-nucleotide duplication in the last exon affecting the cytoplasmic signaling domain. The patient was homozygous for this mutation, whereas the consanguineous parents and the siblings were heterozygous. The patient reported here is a human homologue of the Fas-null mouse, inasmuch as she carries an autosomal homozygous mutation in the FAS gene and she shows the severe and accelerated ALPS phenotype. The heterozygous family members did not have the ALPS phenotype, indicating that the disease-causing FAS mutation in this family is autosomal recessive