Simultaneously optimizing the interdependent thermoelectric parameters in Ce(Ni1−x_{1-x}Cux_x)2_2Al3_3

Substitution of Cu for Ni in the Kondo lattice system CeNi$_2$Al$_3$ results in a simultaneous optimization of the three interdependent thermoelectric parameters: thermoelectric power, electrical and thermal conductivities, where the electronic change in conduction band induced by the extra electron of Cu is shown to be crucial. The obtained thermoelectric figure of merit $zT$ amounts to 0.125 at around 100 K, comparable to the best values known for Kondo compounds. The realization of ideal thermoelectric optimization in Ce(Ni$_{1-x}$Cu$_x$)$_2$Al$_3$ indicates that proper electronic tuning of Kondo compounds is a promising approach to efficient thermoelectric materials for cryogenic application.Comment: 4 pages, 4 figures. Accepted for publication in Physical Review

Chromosomes and Expression Mechanisms

Introduction Whether one considers a single cell or a multicellular organism, a complex and precisely coordinated series of regulatory events and communications is required to ensure its proper configuration and function. One of the major goals in biology is to understand how cells differentiate into specific types to perform their roles in vivo. Genome sequencing projects have produced enormous amounts of data that are beginning to reveal the blue print of body plans for various organisms. Despite this wealth of new information, we are still far from understanding how cells differentiate. This is, in part, because we are not yet able to fully appreciate how this genetic information is being read by the transcription machineries. It is widely accepted that specific gene expression patterns are responsible for differentiation and maintenance of specific cell types, with mistakes in these regulatory steps often leading to developmental defects and the onset of cancers. Therefore, understanding the mechanisms of transcriptional control is a necessary prerequisite to achieve this major goal in biology. To this end, we need to know more about the substrate of transcription (chromatin), as well as the effectors of transcription (transcription factors). The theme of this issue of Current Opinion in Genetics & Development is the mechanism of transcriptional regulation, with an emphasis on latest topics in this rapidly moving area of research. Because chromatin structure deeply affects transcription at multiple stages, a significant portion of this issue is devoted to the mechanisms related to chromatin regulation

Settlement of a Light Rail Pier Supported on Large Diameter Bored Piles Remediated by Jet Grouting

A support Pier (Pier 161) for a Light Rail line being constructed for the Metro Manila Light Rail Project encountered large settlements after the installation of the Precast Deck Girders. This pier supports bridge crossing across the San Juan River with a total span of sixty (60) meters. This Pier is supported on six (6) 1500 mm diameter bored piles designed to extend down to 17 meters or socketed into bedrock at least 2.0 meters based on design requirements. The structure started to settle during the erection of the superstructure when the dead load reached about 700 metric tons. Total settlement was about 42 mm when the erection was halted at a dead load of about 1600 metric tons. The pier was designed to carry a maximum total load of about 2100 metric tons (DL + LL). Subsequent subsurface investigation conducted by our office indicated that the bored piles were terminated prematurely and were not socketed into bedrock as originally specified. The Bored pile tips were resting on approximately 150 mm of soft to very soft clay and highly weathered bedrock, which is partly natural soil and drill cuttings. Several remediation procedures were considered but finally, Jet grouting was selected . This paper discusses the problems associated with the settlement and the ensuing solution using Jet Grouted Piles

Redshift Dependent Lag-Luminosity Relation in 565 BASTE Gamma Ray Bursts

We compared redshifts $z_Y$ from Yonetoku relation and $z_{lag}$ from the lag-luminosity relation for 565 BASTE GRBs and were surprised to find that the correlation is very low. Assuming that the luminosity is a function of both $z_Y$ and the intrinsic spectral lag $\tau_{lag}$, we found a new redshift dependent lag-luminosity relation as $L=7.5\times 10^{50}{\rm erg/s}(1+z)^{2.53}\tau_{lag}^{-0.282}$ with the correlation coefficient of 0.77 and the chance probability of $7.9\times 10^{-75}$. To check the validity of this method, we examined the other luminosity indicator, Amati relation, using $z_Y$ and the observed fluence and found the correlation coefficient of 0.92 and the chance probability of $5.2\times 10^{-106}$. Although the spectral lag is computed from two channels of BATSE, our new lag-luminosity relation suggests that a possible lag-luminosity relation in the \swift era should also depend on redshift

Non-Equilibrium Ionization States of GRB Environments

Iron spectral features are thought to be the best tracer of a progenitor of gamma-ray bursts (GRBs). The detections of spectral features such as an iron line and/or a Radiative Recombination edge and Continuum (RRC) were reported in four X-ray afterglows of GRBs. However their properties were different each other burst by burst. For example, Chandra observation of GRB 991216 reported both the strong H-like iron line together with its RRC. On the contrary, Yoshida et al. (2001) report only a detection of the strong RRC in GRB 970828 with ASCA. Since it is difficult to produce the strong RRC, we have to consider special condition for the line and/or the RRC forming region. In this paper, we point out a possibility of a ``non-equilibrium ionization state'' for the line and the RRC forming region.Comment: 10pages, 2figures. Accepted for ApJL. This is a companion paper by A.Yoshida et. a

Modulation of Sri Lankan Maha rainfall by the Indian Ocean Dipole

Investigating the September to December rainy season in Sri Lanka associated with the Maha rice growing season provides insights into the Asian monsoon during the boreal fall. Here, the modulation of the Maha rainfall by the tropical air-sea coupled phenomenon referred to as the Indian Ocean Dipole (IOD) is documented. The Maha rainfall has a strong and robust association with the IOD from 1869 to 2000. The anomalously warm sea surface in the western Indian Ocean associated with the positive IOD phase induces large scale convergence in the lower troposphere extending to Sri Lanka leading to the preponderant enhancement of Maha rainfall

Surface Acoustic Wave Single-Electron Interferometry

We propose an experiment to observe interference of a single electron as it is transported along two parallel quasi-one-dimensional channels trapped in a single minimum of a travelling periodic electric field. The experimental device is a modification of the surface acoustic wave (SAW) based quantum processor. Interference is achieved by creating a superposition of spatial wavefunctions between the two channels and inducing a relative phase shift via either a transverse electric field or a magnetic field. The interference can be used to estimate the decoherence time of an electron in this type of solid-state device

Variable Spin-down in the Soft Gamma Repeater SGR 1900+14 and Correlations with Burst Activity

We have analyzed Rossi X-ray Timing Explorer Proportional Counter Array observations of the pulsed emission from SGR 1900+14 during September 1996, June - October 1998, and early 1999. Using these measurements and results reported elsewhere, we construct a period history of this source for 2.5 years. We find significant deviations from a steady spin-down trend during quiescence and the burst active interval. Burst and Transient Source Experiment observations of the burst emission are presented and correlations between the burst activity and spin-down rate of SGR 1900+14 are discussed. We find an 80 day interval during the summer of 1998 when the average spin-down rate is larger than the rate elsewhere by a factor ~ 2.3. This enhanced spin-down may be the result of a discontinuous spin-down event or ``braking glitch'' at the time of the giant flare on 27 August 1998. Furthermore, we find a large discrepancy between the pulsar period and average spin-down rate in X-rays as compared to radio observations for December 1998 and January 1999.Comment: 6 pages, 2 figures, submitted to ApJ Letter