Partial (13)C isotopic enrichment of nucleoside monophosphates: useful reporters for NMR structural studies

Analysis of the (13)C isotopic labeling patterns of nucleoside monophosphates (NMPs) extracted from Escherichia coli grown in a mixture of C-1 and C-2 glucose is presented. By comparing our results to previous observations on amino acids grown in similar media, we have been able to rationalize the labeling pattern based on the well-known biochemistry of nucleotide biosynthesis. Except for a few notable absences of label (C4 in purines and C3′ in ribose) and one highly enriched site (C1′ in ribose), most carbons are randomly enriched at a low level (an average of 13%). These sparsely labeled NMPs give less complex NMR spectra than their fully isotopically labeled analogs due to the elimination of most (13)C–(13)C scalar couplings. The spectral simplicity is particularly advantageous when working in ordered systems, as illustrated with guanosine diphosphate (GDP) bound to ADP ribosylation factor 1 (ARF1) aligned in a liquid crystalline medium. In this system, the absence of scalar couplings and additional long-range dipolar couplings significantly enhances signal to noise and resolution

The cosmological gravitational wave background from primordial density perturbations

We discuss the gravitational wave background generated by primordial density perturbations evolving during the radiation era. At second-order in a perturbative expansion, density fluctuations produce gravitational waves. We calculate the power spectra of gravitational waves from this mechanism, and show that, in principle, future gravitational wave detectors could be used to constrain the primordial power spectrum on scales vastly different from those currently being probed by large-scale structure. As examples we compute the gravitational wave background generated by both a power-law spectrum on all scales, and a delta-function power spectrum on a single scale.Comment: 8 Page

Defaults & Returns on High Yield Bonds: Analysis through 1999 and Default Outlook for 2000-2002

Full year 1999 was again a mixed performance year for the high yield bond market in the United States but for different reasons than the mixed 1998 performance. Once again, total returns were lackluster, registering just +1.73%. But, unlike last year’s companion negative return spread vs. U.S. ten-year Treasuries, the return spread in 1999 was a positive 10.1%, as yield spreads increased significantly and Treasuries tumbled. And again, new issuance of high yield bonds was impressive, topping $100 billion for the third consecutive year, but aggregate defaults increased dramatically to an all-time record level of over$23 billion (face value). The default rate registered a sizeable increase, topping 4% (4.15%) for the first time since 1991 and significantly above the 1.6% level of one year earlier. Combined with a relatively low recovery rate of below 30 cents on the dollar, the default loss rate was 3.2% in 1999, compared to a historical arithmetic annual average of 1.9%. Despite 1999’s low absolute return, net returns (after deducting losses from defaults, rating migrations and interest rate changes) for the 1978-1999 period continued to show an attractive compounded return spread over U.S. Treasury bonds of close to 3.0% per year (2.96%). This report documents the high yield bond market’s risk and return performance by presenting traditional and mortality default rate statistics and providing a matrix of performance statistics over the relevant periods of the market’s evolution. Our analysis covers the 1971-1999 period for defaults and the 1978-1999 period for returns. In addition, we present our annual forecast of expected defaults for the next three years (2000-2002). Our 1999 forecast was for substantially higher defaults than 1998, but we underestimated the record default levels. Default levels and rates were swelled in 1999 due to a number of factors, including the huge new issuance in the 1997-1999 period, a trend toward earlier defaults, deteriorating credit quality of new issues, pockets of industry fragility, and the continued vestige of 1998’s flight to quality. For 2000, we expect default levels to decline to about $17.5 billion and the default rate to regress to around three percent of the amount outstanding

Defaults and Returns on High Yield Bonds: Analysis through 1994

Nineteen-ninety-four was a relatively lackluster year for the high yield market with relatively low defaults combined with slightly negative total returns. When viewed in comparative terms with other fixed income securities markets, however, high yield debt performed quite well. Compared to long term U.S. Government securities, the average yield spread on high yield debt dropped to the lowest year-end level (3.44%) since 1984. This report documents the high yield debt market’s risk and return performance in 1994 by presenting default and mortality statistics and provides a matrix of average returns and other performance statistics over the relevant periods of the market’s evolution. Our analysis covers the period 1971-1994 for defaults and 1978-1994 for returns

Defaults and Returns on High Yield Bonds: Analysis through 1994

Nineteen-ninety-four was a relatively lackluster year for the high yield market with relatively low defaults combined with slightly negative total returns. When viewed in comparative terms with other fixed income securities markets, however, high yield debt performed quite well. Compared to long term U.S. Government securities, the average yield spread on high yield debt dropped to the lowest year-end level (3.44%) since 1984. This report documents the high yield debt market’s risk and return performance in 1994 by presenting default and mortality statistics and provides a matrix of average returns and other performance statistics over the relevant periods of the market’s evolution. Our analysis covers the period 1971-1994 for defaults and 1978-1994 for returns

Hepatocyte Growth Factor Receptor c-Met Instructs T Cell Cardiotropism and Promotes T Cell Migration to the Heart via Autocrine Chemokine Release

© 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)This study was funded by the British Heart Foundation (RG/09/002/2642 to F.M.M.-B.) and the Medical Research Council of the UK (G0901084 to F.M.M.-B.). ImageStream X was funded by the Wellcome Trust (101604/Z/13/Z). This work forms part of the research themes contributing to the translational research portfolio of Barts and the London Cardiovascular Biomedical Research Unit, which is supported and funded by the National Institute of Health Research

Isotope Effect in the Presence of Magnetic and Nonmagnetic Impurities

The effect of impurities on the isotope coefficient is studied theoretically in the framework of Abrikosov-Gor'kov approach generalized to account for both potential and spin-flip scattering in anisotropic superconductors. An expression for the isotope coefficient as a function of the critical temperature is obtained for a superconductor with an arbitrary contribution of spin-flip processes to the total scattering rate and an arbitrary degree of anisotropy of the superconducting order parameter, ranging from isotropic s-wave to d-wave and including anisotropic s-wave and mixed (s+d)-wave as particular cases. It is found that both magnetic and nonmagnetic impurities enhance the isotope coefficient, the enhancement due to magnetic impurities being generally greater than that due to nonmagnetic impurities. From the analysis of the experimental results on La-Sr-Cu-M-O high temperature superconductor, it is concluded that the symmetry of the pairing state in this system differs from a pure d-wave.Comment: 4 pages, 3 figure

Defaults & Returns on High Yield Bonds: Analysis Through 1998 and Default Outlook for 1999-2001

Nineteen-ninety-eight was a mixed performance year for the high yield bond market in the United States , with much below average returns and spreads over default-risk-free Treasury Bonds but continued relatively low default rates and losses and another record year of new insurance. Returns and new insurance were excellent through the first seven months of the year but returns reversed and new issues dried up, temporarily, in the wake of August's Russians default and the emerging market turmoil, causing another short-term flight to quality. Returns in 1998 on high yield bonds in the U.S. were slightly above 4.0% for the entire year, about 8.5% lower than historical averages. Return spreads also were much below average (-8.7%). The default rate was again relatively low, 1.60%, and losses from default 1.1%. Despite 1998's low relative return, net returns (after deducting losses from defaults) over the last two decades continue to show a compound result over 12% per year and spreads over U.S. Treasuries of over 2.5% per year. New insurance of high yield debt in 1998 totaled a record $152 billion, with$120 billion of the total in the first seven and a half months. This report documents the high yield debt market's risk and return performance by presenting default and morality statistics and providing a matrix of average returns and other performance statistics over relevant periods of the market's evolution. Our analysis covers the period 1971-1998 for defaults and 1978-1998 for returns. In addition, we present our annual forecast of expected defaults for the next three years (1999-2001). Two other reports, published by the NYU Salomon Center, comprehensively document the performance of defaulted public bonds and bank loans and the default rate experience on syndicated bank loans

Studies on atmospheric gravity wave activity in the troposphere and lower stratosphere over a tropical station at Gadanki

MST radars are powerful tools to study the mesosphere, stratosphere and troposphere and have made considerable contributions to the studies of the dynamics of the upper, middle and lower atmosphere. Atmospheric gravity waves play a significant role in controlling middle and upper atmospheric dynamics. To date, frontal systems, convection, wind shear and topography have been thought to be the sources of gravity waves in the troposphere. All these studies pointed out that it is very essential to understand the generation, propagation and climatology of gravity waves. In this regard, several campaigns using Indian MST Radar observations have been carried out to explore the gravity wave activity over Gadanki in the troposphere and the lower stratosphere. The signatures of the gravity waves in the wind fields have been studied in four seasons viz., summer, monsoon, post-monsoon and winter. The large wind fluctuations were more prominent above 10 km during the summer and monsoon seasons. The wave periods are ranging from 10 min-175 min. The power spectral densities of gravity waves are found to be maximum in the stratospheric region. The vertical wavelength and the propagation direction of gravity waves were determined using hodograph analysis. The results show both down ward and upward propagating waves with a maximum vertical wave length of 3.3 km. The gravity wave associated momentum fluxes show that long period gravity waves carry more momentum flux than the short period waves and this is presented