2,367 research outputs found
Electrodynamics of Amorphous Media at Low Temperatures
Amorphous solids exhibit intrinsic, local structural transitions, that give
rise to the well known quantum-mechanical two-level systems at low
temperatures. We explain the microscopic origin of the electric dipole moment
of these two-level systems: The dipole emerges as a result of polarization
fluctuations between near degenerate local configurations, which have nearly
frozen in at the glass transition. An estimate of the dipole's magnitude, based
on the random first order transition theory, is obtained and is found to be
consistent with experiment. The interaction between the dipoles is estimated
and is shown to contribute significantly to the Gr\"{u}neisen parameter anomaly
in low glasses. In completely amorphous media, the dipole moments are
expected to be modest in size despite their collective origin. In partially
crystalline materials, however, very large dipoles may arise, possibly
explaining the findings of Bauer and Kador, J. Chem. Phys. {\bf 118}, 9069
(2003).Comment: Submitted for publication; April 27, 2005 versio
MicroRNA-143 is a potential tumor suppressor targeting DNA methyltransferases 3a in colorectal cancer
Gastroenterology, 2009, v. 136 n. 5, suppl.1, p. A165, abstract no. 10692009 DDW (Digestive Disease Week) Abstract Supplement , AGA (American Gastroenterological Association) Institute Topic Forum, Oral sessions: Scientific sessions: Microrna and digestive cancers, Oral presentation no. 1069postprin
Discovery of high affinity inhibitors of Leishmania donovani N-myristoyltransferase
N-Myristoyltransferase (NMT) is a potential drug target in Leishmania parasites. Scaffold-hopping from published inhibitors yielded the serendipitous discovery of a chemotype selective for Leishmania donovani NMT; development led to high affinity inhibitors with excellent ligand efficiency. The binding mode was characterised by crystallography and provides a structural rationale for selectivity
Three geographically separate domestications of Asian rice
Domesticated rice (Oryza sativa L.) accompanied the dawn of Asian civilization(1) and has become one of world's staple crops. From archaeological and genetic evidence various contradictory scenarios for the origin of different varieties of cultivated rice have been proposed, the most recent based on a single domestication(2,3). By examining the footprints of selection in the genomes of different cultivated rice types, we show that there were three independent domestications in different parts of Asia. We identify wild populations in southern China and the Yangtze valley as the source of the japonica gene pool, and populations in Indochina and the Brahmaputra valley as the source of the indica gene pool. We reveal a hitherto unrecognized origin for the aus variety in central India or Bangladesh. We also conclude that aromatic rice is a result of a hybridization between japonica and aus, and that the tropical and temperate versions of japonica are later adaptations of one crop. Our conclusions are in accord with archaeological evidence that suggests widespread origins of rice cultivation(1,4). We therefore anticipate that our results will stimulate a more productive collaboration between genetic and archaeological studies of rice domestication, and guide utilization of genetic resources in breeding programmes aimed at crop improvement.European Research Council [339941]info:eu-repo/semantics/publishedVersio
Performance Analysis of Dual-Hop MIMO AF Relaying Network with Multiple Interferences
In this paper, we investigate the performance of a dual-hop multiple-input-multiple-output (MIMO) amplify-and-forward (AF) relay network, where the source, relay, and destination are all equipped with multiple antennas. By using maximum ratio transmission (MRT) at the transmitter and maximum ratio combining (MRC) at the receiver, we first obtain the output signal-to-interference-plus-noise ratio (SINR) of the dual-hop AF relay system, considering multiple cochannel interferences (CCIs), as well as noise at the relay. Then, we derive an exact closed-form expression for the outage probability (OP), and the asymptotic result of OP at high SNR, which can be used to calculate the array gain and diversity order. Finally, computer simulations are conducted to validate the performance analysis. Our new analytical expressions not only provide a fast and efficient method to evaluate the system performance but enable us to gain valuable insights into the effects of key parameters on the MIMO AF relaying network performance that benefits from implementing multiple antennas at each of the three nodes as well
- …