Acidity Studies of Deuterated Acids and Bases Commonly Used as Buffers in NMR Studies

Structure based drug development is currently considered to be an important strategy for drug discovery. This strategy requires that critical knowledge of the three dimensional binding site on receptor molecules be known. NMR studies are frequently employed to ascertain important structural data on individual proteins as well as complexes of proteins with ligands. Deuterium labeled acids and bases are frequently used as buffers in deuterium oxide solutions for NMR studies on the structural conformations of bioactive molecules. Since pH is an important factor in any study of the conformational and stereochemical aspects of biologically active molecules, deuterated buffers are an essential part of the NMR experiments. However, the ionization constant for deuterium oxide (1.95 x 1015) is significantly different from that of water. Therefore, a pH comparison of deuterium-labeled acids and bases in deuterium oxide with nondeuterated aqueous acids and bases was conducted. Titration curve comparisons for deuterated and nondeuterated hydrochloric acid, acetic acid, sodium formate, and TRIS (tris[hydroxymethyl] amino methane) are described. Also, the average pKas of deuterated and non-deuterated acetic acid, formic acid, and TRIS are compared

Stratigraphy and chronology of a 15ka sequence of multi-sourced silicic tephras in a montane peat bog, eastern North Island, New Zealand.

We document the stratigraphy, composition, and chronology of a succession of 16 distal, silicic tephra layers interbedded with lateglacial and Holocene peats and muds up to c. 15 000 radiocarbon years (c. 18 000 calendar years) old at a montane site (Kaipo Bog) in eastern North Island, New Zealand. Aged from 665 +/- 15 to 14 700 +/- 95 14C yr BP, the tephras are derived from six volcanic centres in North Island, three of which are rhyolitic (Okataina, Taupo, Maroa), one peralkaline (Tuhua), and two andesitic (Tongariro, Egmont). Correlations are based on multiple criteria: field properties and stratigraphic interrelationships, ferromagnesian silicate mineral assemblages, glass-shard major element composition (from electron microprobe analysis), and radiocarbon dating. We extend the known distribution of tephras in eastern North Island and provide compositional data that add to their potential usefulness as isochronous markers. The chronostratigraphic framework established for the Kaipo sequence, based on both site-specific and independently derived tephra-based radiocarbon ages, provides the basis for fine-resolution paleoenvironmental studies at a climatically sensitive terrestrial site from the mid latitudes of the Southern Hemisphere. Tephras identified as especially useful paleoenvironmental markers include Rerewhakaaitu and Waiohau (lateglacial), Konini (lateglacial-early Holocene), Tuhua (middle Holocene), and Taupo and Kaharoa (late Holocene)

Multi-Wavelength Properties of the 2021 Periastron Passage of PSR B1259-63

PSR B1259-63 is a gamma-ray binary system hosting a radio pulsar orbiting around a O9.5Ve star, LS 2883, with a period of similar to 3.4 years. The interaction of the pulsar wind with the LS 2883 outflow leads to unpulsed broadband emission in the radio, X-ray, GeV, and TeV domains. One of the most unusual features of the system is an outburst of GeV energies around the periastron, during which the energy release substantially exceeds the spin down luminosity under the assumption of the isotropic emission. In this paper, we present the first results of a recent multi-wavelength campaign (radio, optical, and X-ray bands) accompanied by the analysis of publicly available GeV Fermi/LAT data. The campaign covered a period of more than 100 days around the 2021 periastron and revealed substantial differences from previously observed passages. We report a major delay of the GeV flare, weaker X-ray flux during the peaks, which are typically attributed to the times when the pulsar crosses the disk, and the appearance of a third X-ray peak never observed before. We argue that these features are consistent with the emission cone model proposed by us previously, in the case of a sparser and clumpier disk of the Be star

Optical Propagation and Communication

Contains an introduction and reports on four research projects.Maryland Procurement Office Contract MDA 904-87-C-4044National Science Foundation Grant ECS 87-18970U.S. Army Research Office - Durham Contract DAAL03-87-K-0117U.S. Navy - Office of Naval Research Grant N00014-89-J-1163U.S. Air Force - Office of Scientific Research Contract F49620-87-C-004

Research Ethics Recommendations for Whole-Genome Research: Consensus Statement

Interest in whole-genome research has grown substantially over the past few months. This article explores the challenging ethics issues associated with this work

Addressing ethical, social, and cultural issues in global health research.

The purpose of this paper is to encourage reflection among the global health research community and the research ethics community about how a wide range of ethical, social, and cultural (ESC) influences on the conduct, success, and impact of global health research can best be addressed by consultation services in research ethics (CSRE). We draw on lessons we have learned during our experiences with the ESC Program of the Grand Challenges in Global Health initiative to propose key features of CSRE that may prove useful for those designing or implementing similar programs