Observational manifestations of solar magneto-convection -- center-to-limb variation

We present the first center-to-limb G-band images synthesized from high resolution simulations of solar magneto-convection. Towards the limb the simulations show "hilly" granulation with dark bands on the far side, bright granulation walls and striated faculae, similar to observations. At disk center G-band bright points are flanked by dark lanes. The increased brightness in magnetic elements is due to their lower density compared with the surrounding intergranular medium. One thus sees deeper layers where the temperature is higher. At a given geometric height, the magnetic elements are cooler than the surrounding medium. In the G-band, the contrast is further increased by the destruction of CH in the low density magnetic elements. The optical depth unity surface is very corrugated. Bright granules have their continuum optical depth unity 80 km above the mean surface, the magnetic elements 200-300 km below. The horizontal temperature gradient is especially large next to flux concentrations. When viewed at an angle, the deep magnetic elements optical surface is hidden by the granules and the bright points are no longer visible, except where the "magnetic valleys" are aligned with the line of sight. Towards the limb, the low density in the strong magnetic elements causes unit line-of-sight optical depth to occur deeper in the granule walls behind than for rays not going through magnetic elements and variations in the field strength produce a striated appearance in the bright granule walls.Comment: To appear in ApJL. 6 pages 4 figure

A molecular line study of NGC 1333/IRAS 4

Molecular line surveys and fully sampled spectral line maps at 1.3 and 0.87 mm are used to examine the physical and chemical characteristics of the extreme Class I sources IRAS 4A and 4B in the L1450/NGC 1333 molecular cloud complex. A very well collimated, jetlike molecular outflow emanates from IRAS 4A, with a dynamical age of a few thousand years. Symmetric, clumpy structure along the outflow lobes suggests that there is considerable variability in the mass-loss rate or wind velocity even at this young age. Molecular emission lines toward IRAS 4A and 4B are observed to be weak in the velocity range corresponding to quiescent material surrounding the young stellar objects (YSOs). Depletion factors of 10-20 are observed for αll molecules, including CO, even for very conservative mass estimates from the measured millimeter and submillimeter dust continuum. However, abundances scaled with respect to CO are similar to other dark molecular cloud cores. Such depletions could be mimicked by high dust optical depths or increased grain emissivities at the observing frequencies of 230 and 345 GHz, but the millimeter and submillimeter spectral energy distributions suggest that this is unlikely over the single-dish size scales of 5000-10,000 AU. Dense, outflowing gas is found to be kinematically, but not spatially, distinct from the quiescent material on these size scales. If CO is used as a chemical standard for the high-velocity gas, we find substantial enhancements in the abundances of several molecules in outflowing material, most notably CS, SiO, and CH_30H. The SiO emission is kinematically well displaced from the bulk cloud velocity and likely arises from directly shocked material. As is the case for CO, however, the outflow features from more volatile species are centered near the cloud velocity and are often characterized by quite low rotational temperatures. We suggest that grain-grain collisions induced by velocity shear zones surrounding the outflow axes transiently desorb the grain mantles, resulting in large abundance enhancements of selected species. Similar results have recently been obtained in several other low-mass YSOs, where the outflowing gas is often both kinematically and spatially distinct, and are illustrative of the ability of accretion and outflow processes to simultaneously modify the composition of the gas and dust surrounding young stars

Crossover from time-correlated single-electron tunneling to that of Cooper pairs

We have studied charge transport in a one-dimensional chain of small Josephson junctions using a single-electron transistor. We observe a crossover from time-correlated tunneling of single electrons to that of Cooper pairs as a function of both magnetic field and current. At relatively high magnetic field, single-electron transport dominates and the tunneling frequency is given by f=I/e, where I is the current through the chain and e is the electron's charge. As the magnetic field is lowered, the frequency gradually shifts to f=I/2e for I>200 fA, indicating Cooper-pair transport. For the parameters of the measured sample, we expect the Cooper-pair transport to be incoherent.Comment: 5 pages, 4 figures; v2: minor changes, clarifications, addition

Combustion of Chemical Substances and the Impact on the Environment of the Fire Products: 1/3 Scale Room Furnace Experiments

This report describes the results obtained from fire tests in a 1/3-scale room. The aim of the study was to investigate how changes in external radiation and oxygen supply affect the production of smoke and toxic gases. The ventilation was varied to simulate under- and well-ventilated fires. The thermal exposure to the materials was varied to simulate fires of different sizes. Fifty-nine tests were performed, with polystyrene, FR polystyrene, polypropylene, nylon and PVC. Measurements were made of the contents of O2, CO2, CO, NOx, and HC in the exhaust gases. The impact of external radiation was mainly to increase the pyrolysis rate, and thus the rate of heat release, and to drive the fire into under-ventilation. The degree of ventilation proved to have the greatest impact on the combustion efficiency. The smoke production was almost constant for polypropylene and nylon. The CO production appeared to be the most complex of the parameters to describe, and the expected increase in CO yield at low yields of CO2 could not be seen. The generation of NOx was low for the two substances without chemically bound nitrogen, but for nylon, the generation was significant. The production of low molecular weight HC was essentially constant for all three materials. Almost all the carbon was recovered in wellventilated fires, but at under-ventilated conditions, only 30% of the carbon from the he1 was detected. The toxic potency of the exhaust gases was estimated using the N-gas model, and proved to be relatively low. Lack of oxygen and the production of carbon oxide had the greatest impact on the toxicity for polystyrene and polypropylene, while NO, represented the main part for nylon. The survival fraction and the decomposition products from the original materials are not considered in the model. It can therefore not be assumed that the model reflects all aspects of the toxicity problem

A virus biosensor with single virus-particle sensitivity based on fluorescent vesicle labels and equilibrium fluctuation analysis

Biosensors allowing for the rapid and sensitive detection of viral pathogens in environmental or clinical samples are urgently needed to prevent disease outbreaks and spreading. We present a bioanalytical assay for the detection of whole viral particles with single virus sensitivity. Specifically, we focus on the detection of human norovirus, a highly infectious virus causing gastroenteritis. In our assay configuration, virus-like particles are captured onto a supported lipid bilayer containing a virus-specific glycolipid and detected after recognition by a glycolipid-containing fluorescent vesicle. Read-out is performed after illumination of the vesicle labels by total internal reflection fluorescence microscopy. This allows for visualization of individual vesicles and for recording of their binding kinetics under equilibrium conditions (equilibrium fluctuation analysis), as demonstrated previously. In this work we extend the concept and demonstrate that this simple assay setup can be used as a bioanalytical assay for the detection of virus particles at a limit of detection of 16 fM. Furthermore, we demonstrate how the analysis of the single vesicle-virus-like particle interaction dynamics can contribute to increase the accuracy and sensitivity of the assay by discriminating specific from non-specific binding events. This method is suggested to be generally applicable, provided that these events display different interaction kinetics

Giant Cross Kerr Effect for Propagating Microwaves Induced by an Artificial Atom

We have investigated the cross Kerr phase shift of propagating microwave fields strongly coupled to an artificial atom. The artificial atom is a superconducting transmon qubit in an open transmission line. We demonstrate average phase shifts of 11 degrees per photon between two coherent microwave fields both at the single-photon level. At high control power, we observe phase shifts up to 30 degrees. Our results provide an important step towards quantum gates with propagating photons in the microwave regime.Comment: 5 pages, 4 figure

Proteolytic Processing of OPA1 Links Mitochondrial Dysfunction to Alterations in Mitochondrial Morphology

Many muscular and neurological disorders are associated with mitochondrial dysfunction and are often accompanied by changes in mitochondrial morphology. Mutations in the gene encoding OPA1, a protein required for fusion of mitochondria, are associated with hereditary autosomal dominant optic atrophy type I. Here we show that mitochondrial fragmentation correlates with processing of large isoforms of OPA1 in cybrid cells from a patient with myoclonus epilepsy and ragged-red fibers syndrome and in mouse embryonic fibroblasts harboring an error-prone mitochondrial mtDNA polymerase {gamma}. Furthermore, processed OPA1 was observed in heart tissue derived from heart-specific TFAM knock-out mice suffering from mitochondrial cardiomyopathy and in skeletal muscles from patients suffering from mitochondrial myopathies such as myopathy encephalopathy lactic acidosis and stroke-like episodes. Dissipation of the mitochondrial membrane potential leads to fast induction of proteolytic processing of OPA1 and concomitant fragmentation of mitochondria. Recovery of mitochondrial fusion depended on protein synthesis and was accompanied by resynthesis of large isoforms of OPA1. Fragmentation of mitochondria was prevented by overexpressing OPA1. Taken together, our data indicate that proteolytic processing of OPA1 has a key role in inducing fragmentation of energetically compromised mitochondria. We present the hypothesis that this pathway regulates mitochondrial morphology and serves as an early response to prevent fusion of dysfunctional mitochondria with the functional mitochondrial network

Comparison of the Near-Threshold Production of eta- and K-Mesons in Proton-Proton Collisions

The pp -> pp eta and pp -> pLambda K^+ reactions near threshold are dominated by the first and second S_11 resonance respectively. It is shown that a one-pion-exchange model exciting these isobars reproduces well the ratio of the production cross sections. The consequences for this and other channels are discussed.Comment: 10 pages, LaTeX2e, 1 eps-figur

Decrease in the incidence of total hip arthroplasties in patients with rheumatoid arthritis - results from a well defined population in south Sweden

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field.INTRODUCTION: One aim of modern pharmacologic treatment in rheumatoid arthritis (RA) is to prevent joint destruction and reduce the need for surgery. Our purpose was to investigate secular trends in the incidence of primary total hip and knee arthroplasties in a well defined sample of patients with RA. METHODS: Prevalent cases with RA in 1997 and incident cases from 1997 to 2007 in a community based register in Malmö, south Sweden, were included. Based on a structured review of the medical records, patients were classified according to the 1987 ACR criteria for RA. This cohort was linked to the Swedish Hip Arthroplasty Register (through December 2006) and the Swedish Knee Arthroplasty Register (through October 2007). Patients with a registered total hip or knee arthroplasty before 1997 or before RA diagnosis were excluded. Incidence rates for the period of introduction of TNF inhibitors (1998 to 2001) were compared to the period when biologics were part of the established treatment for severe RA (2002 to 2006/2007). RESULTS: In the cohort (n = 2,164; 71% women) a primary hip arthroplasty was registered for 115 patients and a primary knee arthroplasty for 82 patients. The incidence of primary total hip arthroplasties decreased from the period 1998 to 2001 (12.6/1,000 person-years (pyr)) to 2002 to 2006 (6.6/1,000 pyr) (rate ratio (RR) 0.52; 95% confidence interval (CI) 0.35 to 0.76). There was a trend towards an increase of primary knee arthroplasties (incidence 4.8/1,000 pyr vs. 6.8/1,000 pyr; RR 1.43; 95% CI 0.89 to 2.31). CONCLUSIONS: Our investigation shows a significant decrease in the incidence of total hip arthroplasties in patients with RA after 2001. Possible explanations include a positive effect on joint damage from more aggressive pharmacological treatment.The Swedish Research Council Lund University Crafoord Foundation Swedish Rheumatism Associatio