6,745 research outputs found

    Ionized Gas Kinematics and Morphology in Sgr B2 Main on 1000 AU Scales

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    We have imaged the Sgr B2 Main region with the Very Large Array in the BnA configuration (θbeam\theta_{beam} = 0\farcs13) in both the H52α\alpha (45.453 GHz) radio recombination line (RRL) and 7 mm continuum emission. At a distance of 8500 pc, this spatial resolution corresponds to a physical scale of 0.005 pc (\sim1100 AU). The current observations detect H52α\alpha emission in 12 individual ultracompact (UC) and hypercompact (HC) HII regions. Two of the sources with detected H52 α\alpha emission have broad (Δ\DeltaVFWHM_{FWHM}\sim50 \kms) recombination lines, and two of the sources show lines with peaks at more than one velocity. We use line parameters from the H52α\alpha lines and our previous H66α\alpha line observations to determine the relative contribution of thermal, pressure and kinematic broadening, and electron density. These new observations suggest that pressure broadening can account for the broad lines in some of the sources, but that gas motions (e.g. turbulence, accretion or outflow) contribute significantly to the broad lines in at least one of the sources (Sgr B2 F3).Comment: 10 pages, 2 figure

    Algebras related to posets of hyperplanes

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    We compare two noncommutative algebras which are related to arrangements of hyperplanes. For three special arrangements the induced approximately finite dimensional CC^*-algebra and the graded Orlik-Solomon-algebra are investigated

    Capital stranding cascades: The impact of decarbonisation on productive asset utilisation

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    This article develops a novel methodological framework to investigate the exposure of eco- nomic systems to the risk of physical capital stranding. Combining Input-Output (IO) and network theory, we define measures to identify both the sectors likely to trigger relevant capital stranding cascades and those most exposed to capital stranding risk. We show how, in a sample of ten European countries, mining is among the sectors with the highest external asset strand- ing multipliers. The sectors most affected by capital stranding triggered by decarbonisation include electricity and gas; coke and refined petroleum products; basic metals; and transporta- tion. From these sectors, stranding would frequently cascade down to chemicals; metal products; motor vehicles water and waste services; wholesale and retail trade; and public administration. Finally, we provide an estimate for the lower-bound amount of assets at risk of transition-related stranding, which is in the range of 0.6-8.2% of the overall productive capital stock for our sample of countries, mainly concentrated in the electricity and gas sector, manufacturing, and mining. These results confirm the systemic relevance of transition-related risks on European societies.Series: Ecological Economic Paper

    Ligand entry in human ileal bile acid-binding protein is mediated by histidine protonation

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    Abstract Human ileal bile acid-binding protein (hI-BABP) has a key role in the intracellular transport of bile salts. To explore the role of histidine protonation in the binding process, the pH-dependence of bile salt binding and internal dynamics in hI-BABP was investigated using NMR spectroscopy and biophysical tools. Thermodynamic and kinetic measurements show an increase in the overall binding affinity and the association rate constant of the first binding step below the pKa of the histidines, suggesting that ligand binding is favoured by the protonated state. The overlap between residues exhibiting a high sensitivity to pH in their backbone amide chemical shifts and protein regions undergoing a global ms conformational exchange indicate a connection between the two processes. According to 15N NMR relaxation dispersion analysis, the slow motion is most pronounced at and above the pKa of the histidines. In agreement with the NMR measurements, MD simulations show a stabilization of the protein by histidine protonation. Hydrogen-bonding and van der Waals interactions mediating the flow of information between the C/D- and G/H-turn regions hosting the three histidines, suggest a complex way of pH-governed allosteric regulation of ligand entry involving a transition between a closed and a more open protein state

    Hydrogen-bonding synthons in lamotrigine salts: 3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazin-2-ium 2-[(2-carboxyphenyl)disulfanyl]benzoate in its monohydrate and anhydrous forms

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    Lamotrigine is a drug used in the treatment of epilepsy and related convulsive diseases. The drug in its free form is rather inadequate for pharmacological use due to poor absorption by the patient, which limits its bioavailability. On the other hand, the lamotrigine mol­ecule is an excellent hydrogen-bonding agent and this has been exploited intensively in the search for better formulations. The formulation presently commercialized (under the brand name Lamictal) is rather complex and includes a number of anions in addition to the active pharmaceutical ingredient (API). The title salts of lamotrigine, namely 3,5-di­amino-6-(2,3-di­chloro­phen­yl)-1,2,4-triazin-2-ium 2-[(2-carb­oxy­phen­yl)di­sul­fan­yl]benzoate monohydrate, C9H8Cl2N5+·C14H9O4S2-·H2O, (I), and the anhydrate, C9H8Cl2N5+·C14H9O4S2-, (II), contain a lamotriginium cation (L), a hydrogen di­thio­dibenzoate monoanion (D) and, in the case of (I), a disordered solvent water mol­ecule. Both L and D present their usual configurations severely twisted around their central C-C and S-S bonds, respectively. The supra­molecular structure generated by the many available donor and acceptor sites is characterized by a planar anti­symmetric motif of the form D-L-L-D, i.e. the structural building block. Although this characteristic motif is extremely similar in both structures, its conformation involves different donors and acceptors in its R22(8) central L-L homosynthon. The lateral R22(8) D-L hetero­synthons are, on the other hand, identical. These substructures are further connected by strong hydrogen bonds into broad two-dimensional structures, in turn weakly linked to each other. Even if the homo- and heterosynthons in (I) and (II) are rather frequent in lamotrigine structural chemistry, the composite tetra­meric synthon appears to be much less common. The occurrence of these motifs among lamotrigine salts and cocrystals is analyzed.Fil: Freire Espeleta, Eleonora. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Polla, Griselda Ines. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; ArgentinaFil: Baggio, Ricardo Fortunato. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentin

    Mitochondrial DNA Variation Among Populations of Rhynchophorus ferrugineus (Coleoptera: Curculionidae) From Pakistan.

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    The Red Palm Weevil (RPW) Rhynchophorus ferrugineus (Olivier) is a voracious pest of palm species. In recent decades its range has expanded greatly, particularly impacting the date palm industry in the Middle East. This has led to conjecture regarding the origins of invasive RPW populations. For example, in parts of the Middle East, RPW is commonly referred to as the "Pakistani weevil" in the belief that it originated there. We sought evidence to support or refute this belief. First reports of RPW in Pakistan were from the Punjab region in 1918, but it is unknown whether it is native or invasive there. We estimated genetic variation across five populations of RPW from two provinces of Pakistan, using sequences of the mitochondrial cytochrome oxidase subunit I gene. Four haplotypes were detected; two (H1 and H5) were abundant, accounting for 88% of specimens across the sampled populations, and were previously known from the Middle East. The remaining haplotypes (H51 and H52) were newly detected (in global terms) and there was no geographic overlap in their distribution within Pakistan. Levels of haplotype diversity were much lower than those previously recorded in accepted parts of the native range of RPW, suggesting that the weevil may be invasive in Pakistan. The affinity of Pakistani haplotypes to those reported from India (and the geographical proximity of the two countries), make the latter a likely "native" source. With regards the validity of the name "Pakistani weevil", we found little genetic evidence to justify it
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