Synthetic and structural studies of mixed sodium bis(trimethylsilyl)amide/sodium halide aggregates in the presence of η2-N,N-, η3-N,N,N/N,O,N-, and η4-N,N,N,N-donor ligands

When the important utility amide sodium bis(trimethylsilyl)amide is combined with hydrocarbon-soluble molecular forms of sodium halide salts, a complex structural chemistry is observed. Through utilization of several different multidentate donor molecules, it is possible to isolate a series of compounds that have structural motifs previously not observed in sodium chemistry

Monodentate coordination of the normally chelating chiral diamine (R,R)-TMCDA

After isolating an unusual binuclear, but monosolvated NaHMDS complex [{(R,R)-TMCDA}·(NaHMDS)2]∞ which polymerises via intermolecular electrostatic Na···MeHMDS interactions, further (R,R)-TMCDA was added to produce the discrete binuclear amide [κ2-{(R,R)-TMCDA}·(NaHMDS)2{κ1-(R,R)-TMCDA}], whose salient feature is the unique monodentate coordination of one of the chiral diamine ligands

A biophysical model of prokaryotic diversity in geothermal hot springs

Recent field investigations of photosynthetic bacteria living in geothermal hot spring environments have revealed surprisingly complex ecosystems, with an unexpected level of genetic diversity. One case of particular interest involves the distribution along hot spring thermal gradients of genetically distinct bacterial strains that differ in their preferred temperatures for reproduction and photosynthesis. In such systems, a single variable, temperature, defines the relevant environmental variation. In spite of this, each region along the thermal gradient exhibits multiple strains of photosynthetic bacteria adapted to several distinct thermal optima, rather than the expected single thermal strain adapted to the local environmental temperature. Here we analyze microbiology data from several ecological studies to show that the thermal distribution field data exhibit several universal features independent of location and specific bacterial strain. These include the distribution of optimal temperatures of different thermal strains and the functional dependence of the net population density on temperature. Further, we present a simple population dynamics model of these systems that is highly constrained by biophysical data and by physical features of the environment. This model can explain in detail the observed diversity of different strains of the photosynthetic bacteria. It also reproduces the observed thermal population distributions, as well as certain features of population dynamics observed in laboratory studies of the same organisms

Structural studies of cesium, lithium/cesium and sodium/cesium bis(trimethylsilyl)amide (HMDS) complexes

Reacting cesium fluoride with an equimolar n-hexane solution of lithium bis(trimethylsilyl)amide (LiHMDS), allows the isolation of CsHMDS (1) in 80% yield (after sublimation). This preparative route to 1 negates the need for pyrophoric Cs metal or organocesium reagents in its synthesis. If a 2:1 LiHMDS:CsF ratio is employed the heterobimetallic polymer [LiCs(HMDS)2]∞ 2 was isolated (57% yield). By combining equimolar quantities of NaHMDS and CsHMDS in hexane/toluene [NaCs(HMDS)2(toluene)]∞ 3 was isolated (62% yield). Attempts to prepare the corresponding potassium-cesium amide failed, and instead yielded the known monometallic polymer [Cs(HMDS)(toluene)]∞ 4. With the aim of expanding the structural diversity of Cs(HMDS) species, 1 was reacted with several different Lewis basic donor molecules of varying denticity; namely, (R,R)-N,N,N′,N′-tetramethylcyclohexane-1,2-diamine [(R,R)-TMCDA] and N,N,Nʹ,Nʹ-tetramethylethylenediamine (TMEDA), N,N,Nʹ,Nʹʹ,Nʹʹ-pentamethyldiethylenetriamine (PMDETA), tris[2-(dimethylamino)ethyl]amine (Me6-TREN) and tris[2-(2-methoxyethoxy)ethyl]amine (TMEEA). These reactions yielded dimeric [Cs(HMDS)·donor]2 5-7 [where donor is (R,R)-TMCDA, TMEDA and PMDETA respectively], the tetranuclear ‘open’-dimer [{Me6-TREN·Cs(HMDS)}2{Cs(HMDS)}2] 8 and the monomeric Cs(HMDS)·TMEEA 9. Complexes 2,3 and 5-9 were characterized by X-ray crystallography and in solution by multinuclear NMR spectroscopy

S=1/2S=1/2 Chain-Boundary Excitations in the Haldane Phase of 1D S=1S=1 Systems

The $s=1/2$ chain-boundary excitations occurring in the Haldane phaseof $s=1$ antiferromagnetic spin chains are investigated. The bilinear-biquadratic hamiltonian is used to study these excitations as a function of the strength of the biquadratic term, $\beta$, between $-1\le\beta\le1$. At the AKLT point, $\beta=-1/3$, we show explicitly that these excitations are localized at the boundaries of the chain on a length scale equal to the correlation length $\xi=1/\ln 3$, and that the on-site magnetization for the first site is $=2/3$. Applying the density matrixrenormalization group we show that the chain-boundaryexcitations remain localized at the boundaries for $-1\le\beta\le1$. As the two critical points $\beta=\pm1$ are approached the size of the $s=1/2$ objects diverges and their amplitude vanishes.Comment: 4 Pages, 4 eps figures. Uses RevTeX 3.0. Submitted to PR

POSITION PAPER OF THE CATALAN SOCIETY OF GASTROENTEROLOGY ABOUT HEPATIC ELASTOGRAPHY 2022

After almost 20 years using transient elastography (TE) for the non-invasive diagnosis of liver fibrosis, its use has been extended to population screening, evaluation of steatosis and complications of cirrhosis. For this reason, the "Catalan Society of Digestology" commissioned a group of experts to update the first Document carried out in 2011.The working group (8 doctors and 4 nurses) prepared a panel of questions based on the online survey "Hepatic Elastography in Catalonia 2022" following the PICO structure and the Delphi method.The answers are presented with the level of evidence, the degree of recommendation and the final consensus after being evaluated by 2 external reviewers.TE uses the simplest and most reliable elastographic method to quantify liver fibrosis, assess steatosis, and determine the risk of complications in patients with cirrhosis.Copyright © 2022 Elsevier España, S.L.U. All rights reserved

GAPS-megacities: A new global platform for investigating persistent organic pollutants and chemicals of emerging concern in urban air

A pilot study was initiated in 2018 under the Global Atmospheric Passive Sampling (GAPS) Network named GAPS-Megacities. This study included 20 megacities/major cities across the globe with the goal of better understanding and comparing ambient air levels of persistent organic pollutants and other chemicals of emerging concern, to which humans residing in large cities are exposed. The first results from the initial period of sampling are reported for 19 cities for several classes of flame retardants (FRs) including organophosphate esters (OPEs), polybrominated diphenyl ethers (PBDEs), and halogenated flame retardants (HFRs) including new flame retardants (NFRs), tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDD). The two cities, New York (USA) and London (UK) stood out with ∼3.5 to 30 times higher total FR concentrations as compared to other major cities, with total concentrations of OPEs of 15,100 and 14,100 pg/m, respectively. Atmospheric concentrations of OPEs significantly dominated the FR profile at all sites, with total concentrations in air that were 2–5 orders of magnitude higher compared to other targeted chemical classes. A moderately strong and significant correlation (r = 0.625, p < 0.001) was observed for Gross Domestic Product index of the cities with total OPEs levels. Although large differences in FR levels were observed between some cities, when averaged across the five United Nations regions, the FR classes were more evenly distributed and varied by less than a factor of five. Results for Toronto, which is a ‘reference city’ for this study, agreed well with a more in-depth investigation of the level of FRs over different seasons and across eight sites representing different urban source sectors (e.g. traffic, industrial, residential and background). Future sampling periods under this project will investigate trace metals and other contaminant classes, linkages to toxicology, non-targeted analysis, and eventually temporal trends. The study provides a unique urban platform for evaluating global exposome.A global study across 20 megacities/major cities reporting urban air concentrations of flame retardants and plasticizers.Authors thank the United Nations Environment Programme (UNEP) and the Chemicals Management Plan (CMP) for financial support. The worldwide implementation of the Global Monitoring Plan is made possible thanks to the generous contributions to the Stockholm Convention Voluntary Trust Fund from the Governments of Japan, Norway, Sweden, and through the European Commission’s Thematic Programme for Environment andSustainable Management of Natural Resources, including Energy (ENRTP). Further, the contribution of the projects to support POPs monitoring activities in regions, funded through the Global Environment Facility (GEF) and the Strategic Approach to International Chemicals Management (SAICM), is greatly acknowledged. Monitoring activities and data collection and analysis are implemented in the five UN regions in cooperation with strategic partners and through the involvement of Regional Organization Groups and Global Coordination Group. We also thank Yasuyuki Shibata and Yoshikatsu Takazawa (Tokyo, Japan); Juan Mu~noz-Arnanz (Madrid, Spain) and Dilek €Ozkan and Sinan Kızıltug (_Istanbul, Turkey) for their help and assistance in the sampling campaign

Ready ... Go: Amplitude of the fMRI Signal Encodes Expectation of Cue Arrival Time

What happens when the brain awaits a signal of uncertain arrival time, as when a sprinter waits for the starting pistol? And what happens just after the starting pistol fires? Using functional magnetic resonance imaging (fMRI), we have discovered a novel correlate of temporal expectations in several brain regions, most prominently in the supplementary motor area (SMA). Contrary to expectations, we found little fMRI activity during the waiting period; however, a large signal appears after the “go” signal, the amplitude of which reflects learned expectations about the distribution of possible waiting times. Specifically, the amplitude of the fMRI signal appears to encode a cumulative conditional probability, also known as the cumulative hazard function. The fMRI signal loses its dependence on waiting time in a “countdown” condition in which the arrival time of the go cue is known in advance, suggesting that the signal encodes temporal probabilities rather than simply elapsed time. The dependence of the signal on temporal expectation is present in “no-go” conditions, demonstrating that the effect is not a consequence of motor output. Finally, the encoding is not dependent on modality, operating in the same manner with auditory or visual signals. This finding extends our understanding of the relationship between temporal expectancy and measurable neural signals

First Searches for Optical Counterparts to Gravitational-Wave Candidate Events

During the Laser Interferometer Gravitational-wave Observatory and Virgo joint science runs in 2009-2010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for follow-up observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GW-optical observations of this type

All-Sky Search for Periodic Gravitational Waves in the Full S5 LIGO Data

We report on an all-sky search for periodic gravitational waves in the frequency band 50-800 Hz and with the frequency time derivative in the range of 0 through -6 x 10(exp -9) Hz/s. Such a signal could be produced by a nearby spinning and slightly non-axisymmetric isolated neutron star in our galaxy. After recent improvements in the search program that yielded a 10x increase in computational efficiency, we have searched in two years of data. collected during LIGO's fifth science run and have obtained the most sensitive all-sky upper limits on gravitational wave strain to date. Near 150 Hz our upper limit on worst-case linearly polarized strain amplitude h(sub 0) is 1 x 10(exp -24), while at the high end of our frequency ra.nge we achieve a worst-case upper limit of 3.8 x 10(exp -24) for all polarizations and sky locations. These results constitute a factor of two improvement upop. previously published data. A new detection pipeline utilizing a Loosely Coherent algorithm was able to follow up weaker outliers, increasing the volume of space where signals can be detected by a factor of 10, but has not revealed any gravitational wave signals. The pipeline has been tested for robustness with respect to deviations from the model of an isolated neutron star, such as caused by a low-mass or long.period binary companion