Release of mitochondrial calcium has been shown to occur concomitant with mineral ion loading of matrix vesicles at the onset of mineralization in epiphyseal growth plate cartilage. Matrix vesicles ...contain amorphous calcium phosphate (ACP), a mineral form that usually results from rapid precipitation at high initial levels of Ca2+ and/or inorganic P (Pi). Since the cytosol of growth plate chondrocytes has been found to contain high levels of Pi, rapid release of mitochondrial Ca2+ into the cytosol may cause local precipitation of calcium phosphate and thus be coupled with matrix vesicle formation. Studies were carried out to determine the kinetics and nature of mineral formation that occur when small amounts of Ca2+ are added under various conditions to a Pi buffer composed of electrolytes matched in concentrations and pH to that of the cytosol of epiphyseal chondrocytes. Depending on the manner in which Ca2+ was added, ACP, dicalcium phosphate dihydrate (DCPD), or apatite (HA) first formed. In the presence of ATP, ACP was the only solid phase detected, being stable for at least 24 h. However, in its absence, ACP rapidly transformed into DCPD. Increasing the pH of the reaction buffer from 6.9 to 7.5 increased the amount of ACP initially formed, but DCPD was consistently found upon ACP transformation. Yet at pH 8.0, ACP persisted for at least 24 h. The amount of precipitate formed was proportional to the level of added Ca2+; precipitates formed when as little as 1.0 mmole was added per liter of buffer. Our findings support the possibility that rapid release of mitochondrial Ca2+ may cause localized intracellular precipitation of ACP. Since nascent ACP is known to stimulate membrane fusion and blebbing of vesicles, these findings may explain the presence of ACP in matrix vesicles. The rapid conversion of ACP to DCPD in the absence of ATP under these conditions may also explain the reported occurrence of DCPD in samples of early mineralizing tissue.
We report on studies of the viability and sensitivity of the Askaryan Radio Array (ARA), a new initiative to develop a Teraton-scale ultra-high energy neutrino detector in deep, radio-transparent ice ...near Amundsen-Scott station at the South Pole. An initial prototype ARA detector system was installed in January 2011, and has been operating continuously since then. We describe measurements of the background radio noise levels, the radio clarity of the ice, and the estimated sensitivity of the planned ARA array given these results, based on the first five months of operation. Anthropogenic radio interference in the vicinity of the South Pole currently leads to a few-percent loss of data, but no overall effect on the background noise levels, which are dominated by the thermal noise floor of the cold polar ice, and galactic noise at lower frequencies. We have also successfully detected signals originating from a 2.5km deep impulse generator at a distance of over 3 km from our prototype detector, confirming prior estimates of kilometer-scale attenuation lengths for cold polar ice. These are also the first such measurements for propagation over such large slant distances in ice. Based on these data, ARA-37, the ∼200km2 array now in its initial construction phase, will achieve the highest sensitivity of any planned or existing neutrino detector in the 1016–1019eV energy range.
Childhood mortality remains high in sub-Saharan Africa. In this cluster-randomized, placebo-controlled trial, mortality among children younger than 5 years of age was lower among those who received ...azithromycin than among those who received placebo.
We investigated the oxidation of CH4 on oxygen-pre-covered IrO2(110) surfaces using temperature-programmed reaction spectroscopy (TPRS) and density functional theory (DFT). Our TPRS results show that ...on-top oxygen (Oot) species hinder CH4 adsorption, providing evidence that CH4 adsorbs on coordinatively unsaturated Ir atoms. We also find that the fractional yield of adsorbed CH4 that reacts during TPRS remains constant at ∼70% as the Oot-coverage increases to about 0.5 monolayer for saturation CH4 coverage, demonstrating that O-rich IrO2(110) surfaces are highly active in promoting CH4 C–H bond cleavage. Our results show that Oot atoms promote CH4 oxidation to CO2 as well as H2O formation while suppressing CO and recombinative CH4 desorption, as evidenced by an increase in the fractional yield of CO2 produced during TPRS and a downshift of CO2 and H2O TPRS peak maxima with increasing Oot-coverage. DFT predicts that initial CH4 bond cleavage is highly facile on both stoichiometric and O-rich IrO2(110) and can occur by either H-transfer to an Oot or a bridging O-atom of the surface. Our calculations also predict that oxidation of the CH x species that result from CH4 activation is more facile on O-rich compared with stoichiometric IrO2(110), and that complete oxidation is strongly favored on the O-rich surface, in good agreement with our experimental findings. According to the calculations, key steps in the CH4 oxidation pathway have significantly lower-energy barriers on O-rich vs stoichiometric IrO2(110) because these steps involve reaction with Oot atoms initially present on the surface rather than the abstraction of more strongly bound Obr species. High coverages of O-atoms also enable adsorbed intermediates to oxidize extensively on O-rich IrO2(110), without the intermediates needing to overcome diffusion barriers to access reactive O-atoms. Our results provide insights for understanding CH4 oxidation on IrO2(110) surfaces under reaction conditions at which Oot atoms and adsorbed CH4 can co-exist.
The precise value of the mean neutron lifetime, τ
, plays an important role in nuclear and particle physics and cosmology. It is used to predict the ratio of protons to helium atoms in the primordial ...universe and to search for physics beyond the Standard Model of particle physics. We eliminated loss mechanisms present in previous trap experiments by levitating polarized ultracold neutrons above the surface of an asymmetric storage trap using a repulsive magnetic field gradient so that the stored neutrons do not interact with material trap walls. As a result of this approach and the use of an in situ neutron detector, the lifetime reported here 877.7 ± 0.7 (stat) +0.4/-0.2 (sys) seconds does not require corrections larger than the quoted uncertainties.
We propose a new perspective on the hierarchy of climate models which goes beyond the "classical" climate modeling pyramid that is restricted mainly to atmospheric processes. Most notably, we ...introduce a new indicator, called "integration", which characterizes the number of interacting components of the climate system being explicitly described in a model. The location of several model types, from conceptual to comprehensive, is presented in a new spectrum of climate system models. In particular, the location of the Earth system Models of Intermediate Complexity (EMICs) in this spectrum is discussed in some detail and examples are given, which indicate that there is currently a broad range of EMICs in use. In some EMICs, the number of processes and/or the detail of description is reduced for the sake of simulating the feedbacks between as many components of the climate system as feasible. Others, with a lesser degree of interaction, or "integration", are used for long-term ensemble simulations to study specific aspects of climate variability. EMICs appear to be closer to comprehensive coupled models of atmospheric and oceanic circulation (CGCMs) than to "conceptual" or "box" models. We advocate that EMICs be considered as complementary to CGCMs and conceptual models, because we believe that there is an advantage of having a spectrum of climate system models which are designed to tackle specific aspects of climate and which together provide the proper tool for climate system modeling.PUBLICATION ABSTRACT
ABSTRACT We present initial results from the Dark Energy Spectroscopic Instrument (DESI) complete calibration of the colour–redshift relation (DC3R2) secondary target survey. Our analysis uses 230 k ...galaxies that overlap with KiDS-VIKING ugriZYJHKs photometry to calibrate the colour–redshift relation and to inform photometric redshift (photo-z) inference methods of future weak lensing surveys. Together with emission line galaxies (ELGs), luminous red galaxies (LRGs), and the Bright Galaxy Survey (BGS) that provide samples of complementary colour, the DC3R2 targets help DESI to span 56 per cent of the colour space visible to Euclid and LSST with high confidence spectroscopic redshifts. The effects of spectroscopic completeness and quality are explored, as well as systematic uncertainties introduced with the use of common Self-Organizing Maps trained on different photometry than the analysis sample. We further examine the dependence of redshift on magnitude at fixed colour, important for the use of bright galaxy spectra to calibrate redshifts in a fainter photometric galaxy sample. We find that noise in the KiDS-VIKING photometry introduces a dominant, apparent magnitude dependence of redshift at fixed colour, which indicates a need for carefully chosen deep drilling fields, and survey simulation to model this effect for future weak lensing surveys.
Background
Radiofrequency ablation of malignant biliary strictures has been offered for the last 3 years, but only limited data have been published.
Aim
To assess the safety, efficacy, and survival ...outcomes of patients receiving endoscopic radiofrequency ablation.
Methods
Between April 2010 and December 2013, 69 patients with unresectable neoplastic lesions and malignant biliary obstruction underwent 98 radiofrequency ablation sessions with stenting.
Results
A total of 69 patients (22 male, aged 66.1 ± 13.3) were included in the registry. The etiology of malignant biliary stricture included unresectable cholangiocarcinoma (
n
= 45), pancreatic cancer (
n
= 19), gallbladder cancer (
n
= 2), gastric cancer (
n
= 1), and liver metastasis from colon cancer (
n
= 3). Seventy-eight percentage of patients had prior chemotherapy. All strictures were stented post-radiofrequency ablation with either plastic stents or metal stents. The mean stricture length treated was 14.3 mm. There was a statistically significant improvement in stricture diameter post-ablation (
p
< 0.0001). The likelihood of stricture improvement was significantly greater in pancreatic cancer-associated strictures RR 1.8 (95 % 1.03–5.38). Seven patients (10 %) had adverse events, not linked directly to radiofrequency ablation. Median survival was 11.46 months (6.2–25 months).
Conclusion
Radiofrequency ablation is effective and safe in malignant biliary obstruction and seems to be associated with improved survival.
ABSTRACT
The abundance, temperature, and clustering of metals in the intergalactic medium are important parameters for understanding their cosmic evolution and quantifying their impact on ...cosmological analysis with the Ly α forest. The properties of these systems are typically measured from individual quasar spectra redward of the quasar’s Ly α emission line, yet that approach may provide biased results due to selection effects. We present an alternative approach to measure these properties in an unbiased manner with the two-point statistics commonly employed to quantify large-scale structure. Our model treats the observed flux of a large sample of quasar spectra as a continuous field and describes the one-dimensional, two-point statistics of this field with three parameters per ion: the abundance (column density distribution), temperature (Doppler parameter), and clustering (cloud–cloud correlation function). We demonstrate this approach on multiple ions (e.g. ${\rm C\, \small {\rm IV}}$ , ${\rm Si\, \small {\rm IV}}$ , and ${\rm Mg\, \small {\rm II}}$ ) with early data from the Dark Energy Spectroscopic Instrument (DESI) and high-resolution spectra from the literature. Our initial results show some evidence that the ${\rm C\, \small {\rm IV}}$ abundance is higher than previous measurements and evidence for abundance evolution over time. The first full year of DESI observations will have over an order of magnitude more quasar spectra than this study. In a future paper, we will use those data to measure the growth of clustering and its impact on the Ly α forest, as well as test other DESI analysis infrastructure such as the pipeline noise estimates and the resolution matrix.
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