Deceptively Simple NMR Spectra of Contiguously 13C-enriched Compounds

Contiguously 13C-enriched compounds are widely used in biosynthetic studies, since they effectively label a bonded pair of carbon atoms, rather than an individual atom. Such compounds are referred to as »bond labeled« compounds. With such substrates, the course of biosynthesis can be followed using 13C-NMR spectroscopy. When the enriched carbon atoms are chemically but not magnetically equivalent, the 13C-NMR spectra are unusual, and such spectra have been labeled "deceptively simple«. Furthermore, the use of standard NMR experiments such as DEPT (Distortionless Enhancement by Polarization Transfer) is complicated by the presence of homonuclear coupling between 13C nuclei. At natural abundance, the 13C nucleus is magnetically dilute and shows no homonuclear coupling. This paper analyzes the 13C-NMR spectra of a series of molecules derived from fully 13C-enriched acetylene, and explores some of the complications that arise in applying pulse NMR methods

Structure and Mechanism of the Lincosamide Antibiotic Adenylyltransferase LinB

SummaryLincosamides make up an important class of antibiotics used against a wide range of pathogens, including methicillin-resistant Staphylococcus aureus. Predictably, lincosamide-resistant microorganisms have emerged with antibiotic modification as one of their major resistance strategies. Inactivating enzymes LinB/A catalyze adenylylation of the drug; however, little is known about their mechanistic and structural properties. We determined two X-ray structures of LinB: ternary substrate– and binary product–bound complexes. Structural and kinetic characterization of LinB, mutagenesis, solvent isotope effect, and product inhibition studies are consistent with a mechanism involving direct in-line nucleotidyl transfer. The characterization of LinB enabled its classification as a member of a nucleotidyltransferase superfamily, along with nucleotide polymerases and aminoglycoside nucleotidyltransferases, and this relationship offers further support for the LinB mechanism. The LinB structure provides an evolutionary link to ancient nucleotide polymerases and suggests that, like protein kinases and acetyltransferases, these are proto-resistance elements from which drug resistance can evolve

Vulnerability of Water Supply Systems to Droughts

This summary completion report describes the project work completed in three areas: 1) the development and preliminary testing of drought severity and vulnerability indices, 2) the impacts of Utah\u27s 1977 drought, and 3) an operation comparison of stochastic streamflow models. The drought indices were evaluated for three municipal and three irrigation water supply systems in Utah. It was concluded that a continuous loss function to define the effects of water shortage would be more appropriate than the existing assumption that drought-related lossed occur suddenly at a certain degree of water shortage. Information on the impacts of Utah\u27s 1977 drought was collected by surveys of municipal and rural domestic systems, water users in Salt Lake County, and farmers, stockmen, ranchers, and irrigation company officials. Survey results were used to examine drought effects in different regions of the state and with respect to size of municipal supply systems. Despite severe restrictiosn placed on Salt Lake County water users most did not consider the experience an undue burden. The comparison of five stochastic streamflow models on four Utah streams lead to a preliminary model choice strategy which is based on the historical estimates of the lag-one autocorrelation and Hurst coefficients

Mapping ground instability in areas of geotechnical infrastructure using satellite InSAR and Small UAV Surveying: a case study in Northern Ireland

Satellite Interferometric Synthetic Aperture Radar (InSAR), geological data and Small Unmanned Aerial Vehicle (SUAV) surveying was used to enhance our understanding of ground movement at five areas of interest in Northern Ireland. In total 68 ERS-1/2 images 1992–2000 were processed with the Small Baseline Subset (SBAS) InSAR technique to derive the baseline ground instability scenario of key areas of interest for five stakeholders: TransportNI, Northern Ireland Railways, Department for the Economy, Arup, and Belfast City Council. These stakeholders require monitoring of ground deformation across either their geotechnical infrastructure (i.e., embankments, cuttings, engineered fills and earth retaining structures) or assessment of subsidence risk as a result of abandoned mine workings, using the most efficient, cost-effective methods, with a view to minimising and managing risk to their businesses. The InSAR results provided an overview of the extent and magnitude of ground deformation for a 3000 km2 region, including the key sites of the disused salt mines in Carrickfergus, the Belfast–Bangor railway line, Throne Bend and Ligoniel Park in Belfast, Straidkilly and Garron Point along the Antrim Coast Road, plus other urbanised areas in and around Belfast. Tailored SUAV campaigns with a X8 airframe and generation of very high resolution ortho-photographs and a 3D surface model via the Structure from Motion (SfM) approach at Maiden Mount salt mine collapse in Carrickfergus in 2016 and 2017 also demonstrate the benefits of very high resolution surveying technologies to detect localised deformation and indicators of ground instabilit

Frictional melt homogenisation during fault slip: Geochemical, textural and rheological fingerprints

info:eu-repo/semantics/publishe

Relational Quantum Mechanics

I suggest that the common unease with taking quantum mechanics as a fundamental description of nature (the "measurement problem") could derive from the use of an incorrect notion, as the unease with the Lorentz transformations before Einstein derived from the notion of observer-independent time. I suggest that this incorrect notion is the notion of observer-independent state of a system (or observer-independent values of physical quantities). I reformulate the problem of the "interpretation of quantum mechanics" as the problem of deriving the formalism from a few simple physical postulates. I consider a reformulation of quantum mechanics in terms of information theory. All systems are assumed to be equivalent, there is no observer-observed distinction, and the theory describes only the information that systems have about each other; nevertheless, the theory is complete.Comment: Substantially revised version. LaTeX fil

Amenability of groups and GG-sets

This text surveys classical and recent results in the field of amenability of groups, from a combinatorial standpoint. It has served as the support of courses at the University of G\"ottingen and the \'Ecole Normale Sup\'erieure. The goals of the text are (1) to be as self-contained as possible, so as to serve as a good introduction for newcomers to the field; (2) to stress the use of combinatorial tools, in collaboration with functional analysis, probability etc., with discrete groups in focus; (3) to consider from the beginning the more general notion of amenable actions; (4) to describe recent classes of examples, and in particular groups acting on Cantor sets and topological full groups

The Reddening Towards Cassiopeia A's Supernova: Constraining the 56Ni Yield

We present new reddening measurements towards the young supernova remnant Cassiopeia A, using two techniques not previously applied to this object. Our observations of the near-infrared [Fe II] 1.257 micron and 1.644 micron lines show the extinction to be highly variable across the remnant, increasing towards the west and the south, consistent with previous radio and X-ray observations. While the absolute value of AV as determined by the [Fe II] lines is uncertain due to conflicting calculations and observations of their intrinsic flux ratio, parts of the remnant without previous optical measurements show comparatively higher reddening. We find AV = 6.2 +/- 0.6 from the broadband shape of the infrared synchrotron emission of a knot within 13" of the expansion center. Given this reddening, the apparent faintness of the nascent supernova, and iron mass constraints from X-ray observations, we estimate an ejected mass of 56Ni of 0.058 - 0.16 MSun. Taken with gamma-ray observations of the 44Ti decay chain, this nickel mass is broadly consistent with the solar 44Ca/56Fe ratio.Comment: 8 pages, 6 figures, accepted for publication in The Astrophysical Journa

Probing the Evolution of IR Properties of z~6 Quasars: Spitzer Observations

We present Spitzer observations of thirteen z~6 quasars using the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS). All the quasars except SDSS J000552.34-000655.8 (SDSS J0005-0006) were detected with high S/N in the four IRAC channels and the MIPS 24um band, while SDSS J0005-0006 was marginally detected in the IRAC 8.0um band, and not detected in the MIPS 24um band. We find that most of these quasars have prominent emission from hot dust as evidenced by the observed 24um fluxes. Their spectral energy distributions (SEDs) are similar to those of low-redshift quasars at rest-frame 0.15-3.5 um, suggesting that accretion disks and hot-dust structures for these sources already have reached maturity. However, SDSS J0005-0006 has an unusual SED that lies significantly below low-redshift SED templates at rest-frame 1 and 3.5 um, and thus shows a strong near-IR (NIR) deficit and no hot-dust emission. Type I quasars with extremely small NIR-to-optical flux ratios like SDSS J0005-0006 are not found in low-redshift quasar samples, indicating that SDSS J0005-0006 has different dust properties at high redshift. We combine the Spitzer observations with X-ray, UV/optical, mm/submm and radio observations to determine bolometric luminosities for all the quasars. We find that the four quasars with central black-hole mass measurements have Eddington ratios of order unity.Comment: 22 pages, 5 figures, accepted by A