The Crystal Packing of 4,7-Dichloro- and 4,7-Dibromobenzo[C]Furazan 1-Oxide

The molecular structures of 4,7-dichlorobenzo[c]furazan 1-oxide, C6H2Cl2N2O2, (I), and 4,7-dibromobenzo[c]furazan 1-oxide, C6H2Br2N2O2, (II), are normal. Compound (I) occurs in two polymorphic forms. One polymorph contains one molecule in the asymmetric unit, organized into two-dimensional sheets involving intermolecular N...Cl and O...Cl interactions. The second polymorph has three molecules in the asymmetric unit, organized into two crystallographically different two-dimensional sheets with similar interactions. Compound (II) is isomorphous with the second polymorph of (I). The three two-dimensional sheets in the two polymorphs comprise a set of three two-dimensional polymorphic arrangements

The Crystal Packing of 4,7-Dichloro- and 4,7-Dibromobenzo[C]Furazan 1-Oxide

The molecular structures of 4,7-dichlorobenzo[c]furazan 1-oxide, C6H2Cl2N2O2, (I), and 4,7-dibromobenzo[c]furazan 1-oxide, C6H2Br2N2O2, (II), are normal. Compound (I) occurs in two polymorphic forms. One polymorph contains one molecule in the asymmetric unit, organized into two-dimensional sheets involving intermolecular N...Cl and O...Cl interactions. The second polymorph has three molecules in the asymmetric unit, organized into two crystallographically different two-dimensional sheets with similar interactions. Compound (II) is isomorphous with the second polymorph of (I). The three two-dimensional sheets in the two polymorphs comprise a set of three two-dimensional polymorphic arrangements

Methyl reorientation in methylphenanthrenes. II. Solid-state proton spin-lattice relaxation in the 1-CH3, 9-CH3, and 1-CD3, 9-CH3 systems

We report proton Zeeman relaxation rates R as a function of temperature T at 8.5 and 53 MHz in polycrystalline 1,9-dimethylphenanthrene (1,9-DMP) and l-trideuteriomethyl-9-methylphenanthrene (1, 9-DMP[1-d3]). The data are interpreted using a Davidson-Cole spectral density for intramolecular reorientation and the implications of this are discussed. R vs T−1data for 1,9-DMP[1-d3] are used to determine the parameters that characterize the reorientation of the 9-methyl group. By assuming that the parameters characterizing the dynamics of the 9-methyl group are the same in 1,9-DMP and 1,9-DMP[1-d3], we subtract out the R vs T−1 contribution of the 9-methyl group in 1,9-DMP to determine the parameters that characterize the dynamics of the 1-methyl group. We find that the barrier for reorientation of the 9-methyl group is larger than the barrier for the 1-methyl group and this is discussed in terms of the various contributions to the barrier

Methyl Reorientation in Methylphenanthrenes: 1. Solid-State Proton Spin-Lattice Relaxation in the 3-Methyl, 9-Methyl, and 3,9-Dimethyl Systems

We have investigated the dynamics of methyl group reorientation in solid methyl‐substituted phenanthrenes. The temperature dependence of the proton spin–lattice relaxation rates has been measured in polycrystalline 3‐methylphenanthrene (3‐MP), 9‐methylphenanthrene (9‐MP), and 3,9‐dimethylphenanthrene (3,9‐DMP) at Larmor frequencies of 8.50, 22.5, and 53.0 MHz. The data are interpreted using a Davidson–Cole spectral density which implies either that the correlation functions for intramolecular reorientation are nonexponential or that there is a distribution of exponential correlation times. Comparing the fitted parameters that characterize the relaxation data for the three molecules shows that the individual contributions to the relaxation rate from the 3‐ and 9‐methyls in 3,9‐DMP can be separated and that the parameters specifying each are similar to the equivalent group in the two single methylphenanthrenes. The 9‐methyl group is characterized by effective activation energies of 10.6±0.6 and 12.5±0.9 kJ/mol in 9‐MP and 3,9‐DMP, respectively, whereas the 3‐methyl group is characterized by effective activation energies of 5.2±0.8 and 5±1 kJ/mol in 3‐MP and 3,9‐DMP, respectively. The agreement between the fitted and calculated values of the spin–lattice interaction strength, assuming only intramethyl proton dipole–dipole interactions need be considered, is excellent. A comparison between experimentally determined correlation times and those calculated from a variety of very simple dynamical models is given, and the results suggest, as have several previous studies, that at high temperatures where tunneling plays no role, methyl reorientation is a simple, thermally activated, hopping process. We have also analyzed many published data in methyl‐substituted phenanthrenes, anthracenes, and naphthalenes (14 molecules) in the same way as we did for the phenanthrene data presented here, and a consistent picture for the dynamics of methyl reorientation emerges

Methyl Reorientation in Methylphenanthrenes: 1. Solid-State Proton Spin-Lattice Relaxation in the 3-Methyl, 9-Methyl, and 3,9-Dimethyl Systems

We have investigated the dynamics of methyl group reorientation in solid methyl‐substituted phenanthrenes. The temperature dependence of the proton spin–lattice relaxation rates has been measured in polycrystalline 3‐methylphenanthrene (3‐MP), 9‐methylphenanthrene (9‐MP), and 3,9‐dimethylphenanthrene (3,9‐DMP) at Larmor frequencies of 8.50, 22.5, and 53.0 MHz. The data are interpreted using a Davidson–Cole spectral density which implies either that the correlation functions for intramolecular reorientation are nonexponential or that there is a distribution of exponential correlation times. Comparing the fitted parameters that characterize the relaxation data for the three molecules shows that the individual contributions to the relaxation rate from the 3‐ and 9‐methyls in 3,9‐DMP can be separated and that the parameters specifying each are similar to the equivalent group in the two single methylphenanthrenes. The 9‐methyl group is characterized by effective activation energies of 10.6±0.6 and 12.5±0.9 kJ/mol in 9‐MP and 3,9‐DMP, respectively, whereas the 3‐methyl group is characterized by effective activation energies of 5.2±0.8 and 5±1 kJ/mol in 3‐MP and 3,9‐DMP, respectively. The agreement between the fitted and calculated values of the spin–lattice interaction strength, assuming only intramethyl proton dipole–dipole interactions need be considered, is excellent. A comparison between experimentally determined correlation times and those calculated from a variety of very simple dynamical models is given, and the results suggest, as have several previous studies, that at high temperatures where tunneling plays no role, methyl reorientation is a simple, thermally activated, hopping process. We have also analyzed many published data in methyl‐substituted phenanthrenes, anthracenes, and naphthalenes (14 molecules) in the same way as we did for the phenanthrene data presented here, and a consistent picture for the dynamics of methyl reorientation emerges

Pulsar Wind Nebulae in EGRET Error Boxes

A remarkable number of pulsar wind nebulae (PWN) are coincident with EGRET gamma-ray sources. X-ray and radio imaging studies of unidentified EGRET sources have resulted in the discovery of at least 6 new pulsar wind nebulae (PWN). Stationary PWN (SPWN) appear to be associated with steady EGRET sources with hard spectra, typical for gamma-ray pulsars. Their toroidal morphologies can help determine the geometry of the pulsar which is useful for constraining models of pulsed gamma-ray emission. Rapidly moving PWN (RPWN) with more cometary morphologies seem to be associated with variable EGRET sources in regions where the ambient medium is dense compared to what is typical for the ISM.Comment: 8 pages, 5 figures, to appear in the proceedings of "The Multiwavelength Approach to Unidentified Sources", ed. G. Romero & K.S. Chen

Runaway Massive Binaries and Cluster Ejection Scenarios

The production of runaway massive binaries offers key insights into the evolution of close binary stars and open clusters. The stars HD 14633 and HD 15137 are rare examples of such runaway systems, and in this work we investigate the mechanism by which they were ejected from their parent open cluster, NGC 654. We discuss observational characteristics that can be used to distinguish supernova ejected systems from those ejected by dynamical interactions, and we present the results of a new radio pulsar search of these systems as well as estimates of their predicted X-ray flux assuming that each binary contains a compact object. Since neither pulsars nor X-ray emission are observed in these systems, we cannot conclude that these binaries contain compact companions. We also consider whether they may have been ejected by dynamical interactions in the dense environment where they formed, and our simulations of four-body interactions suggest that a dynamical origin is possible but unlikely. We recommend further X-ray observations that will conclusively identify whether HD 14633 or HD 15137 contain neutron stars.Comment: Accepted to ApJ, 11 page

PSR J2021+3651: A Young Radio Pulsar Coincident with an Unidentified EGRET Gamma-ray Source

We report on a deep search for radio pulsations toward five unidentified ASCA X-ray sources coincident with EGRET gamma-ray sources. This search has led to the discovery of a young and energetic pulsar using data obtained with the new Wideband Arecibo Pulsar Processor. PSR J2021+3651 is likely associated with the X-ray source AX J2021.1+3651, which in turn is likely associated with the COS B high energy gamma-ray source 2CG 075+00, also known as GeV J2020+3658 or 3EG J2021+3716. PSR J2021+3651 has a rotation period P = 104 ms and P_dot = 9.6x10^{-14}, implying a characteristic age ~17 kyr and a spin-down luminosity E_dot ~ 3.4x10^{36}ergs/s. The dispersion measure DM ~ 371 pc cm^{-3} is by far the highest of any observed pulsar in the Galactic longitude range 55 < l < 80. This DM suggests a distance d > 10 kpc, and a high gamma-ray efficiency of \~15%, but the true distance may be closer if there is a significant contribution to the DM from excess gas in the Cygnus region. The implied luminosity of the associated X-ray source suggests the X-ray emission is dominated by a pulsar wind nebula unresolved by ASCA.Comment: 6 pages, 2 figures, submitted to ApJ

Archaeology and Language: The Indo-Iranians

This review of recent archaeological work in Central Asia and Eurasia attempts to trace and date the movements of the IndoIraniansspeakers of languages of the eastern branch of ProtoIndoEuropean that later split into the Iranian and Vedic families. Russian and Central Asian scholars working on the contemporary but very different Andronovo and Bactrian Margiana archaeological complexes of the 2d millennium b.c. have identified both as IndoIranian, and particular sites so identified are being used for nationalist purposes. There is, however, no compelling archaeological evidence that they had a common ancestor or that either is IndoIranian. Ethnicity and language are not easily linked with an archaeological signature, and the identity of the IndoIranians remains elusive

Interview with Laura Fortunato, Winner of the 2011 Gabriel W. Lasker Prize

An international jury composed of Michael Crawford (University of Kansas, USA), Dennis O\u27Rourke (University of Utah, USA), and Stephen Shennan (University College London, UK) has awarded the Gabriel Ward Lasker Prize 2011 to Dr. Laura Fortunato for her articles entitled Reconstructing the History of Residence Strategies in Indo-European–Speaking Societies and Reconstructing the History of Marriage Strategies in Indo-European–Speaking Societies considered as the best contribution to the 83rd volume of Human Biology (2011). Laura Fortunato is an Omidyar Fellow at the Santa Fe Institute in Santa Fe, New Mexico. She received her Ph.D. in anthropology from University College London in 2009; her doctoral research focused on the evolution of kinship and marriage systems. In particular, she has investigated the evolution of marriage strategies, wealth transfers at marriage, residence strategies, and inheritance strategies. Laura\u27s current research activities apply conceptual and methodological tools developed in evolutionary biology to a diverse range of topics in anthropology, from matrilineal kinship organization to cultural evolution