Stellar Abundances in the Early Galaxy and Two r-Process Components

We present quantitative predictions for the abundances of r-process elements in stars formed very early in the Galactic history using a phenomenological two-component r-process model based on the I129 and Hf182 inventory in the early solar system. This model assumes that a standard mass of the ISM dilutes the debris from an individual supernova. High frequency supernova H events and low frequency supernova L events are proposed in the model with characteristics determined by the meteoritic data on I129 and Hf182. The yields in an H or L event are obtained from these characteristics and the solar r-process abundances under the assumption that the yield template for the high mass (A > 130) nuclei associated with W182 or the low mass (A < or = 130) nuclei associated with I127 is the same for both the H and L events and follows the corresponding solar r-pattern in each mass region. The abundance of Eu, not Fe, is proposed as a key guide to the age of very metal-poor stars. We predict that stars with log epsilon (Eu) = -2.98 to -2.22 were formed from an ISM contaminated most likely by a single H event within the first 10**7 yr of the Galactic history and should have an Ag/Eu abundance ratio less than the corresponding solar r-process value by a factor of at least 10. Many of the very metal-poor stars observed so far are considered here to have been formed from an ISM contaminated by many (about 10) r-process events. Stars formed from an ISM contaminated only by a pure L event would have an Ag/Eu ratio higher than the corresponding solar r-process value but would be difficult to find due to the low frequency of the L events. However, variations in the relative abundances of the low and high mass regions should be detectable in very metal-poor stars.Comment: 46 pages, 19 figures, to appear in the Schramm Memorial Volume of Physics Report

The Origin of the Heavy Elements: Recent Progress in the Understanding of the r-Process

There has been significant progress in the understanding of the r-process over the last ten years. The conditions required for this process have been examined in terms of the parameters for adiabatic expansion from high temperature and density. There have been many developments regarding core-collapse supernova and neutron star merger models of the r-process. Meteoritic data and observations of metal-poor stars have demonstrated the diversity of r-process sources. Stellar observations have also found some regularity in r-process abundance patterns and large dispersions in r-process abundances at low metallicities. This review summarizes the recent results from parametric studies, astrophysical models, and observational studies of the r-process. The interplay between nuclear physics and astrophysics is emphasized. Some suggestions for future theoretical, experimental, and observational studies of the r-process are given.Comment: typos in Eqs. (30) and (31) correcte

Precise determination of relative and absolute &#946;&#946;-decay rates of <SUP>128</SUP>Te and <SUP>130</SUP>Te

Double beta decay of 128Te has been confirmed and the ratio of half-lives for &#946;&#946; decay of 130Te and 128Te has been precisely determined as T&#189;130/T&#189;128=(3.52&#177;0.11)&#215;10-4 by ion-counting mass spectrometry of Xe in ancient Te ores, using techniques that reduce interferences due to trapped Xe. We have also detected excesses of 126Xe originating in high energy reactions of cosmic ray muons and their secondaries on Te; such reactions make minor contributions to the measured 128Xe excesses in the Te ores. The Xe measurements, combined with common Pb dating of the ores, yield a 130Te half-life of (2.7&#177;0.1)&#215;1021 yr and thus a 128Te half-life of (7.7&#177;0.4)&#215;1024 yr, the longest radioactive decay lifetime measured to date. These results give limits on the effective Majorana mass of the neutrino (&lt;1.1-1.5 eV) and right-handed currents (||&lt;&#951;&gt;||&lt;5.3&#215;10-8) comparable to the best obtained from direct neutrinoless &#946;&#946;-decay searches. They also imply new limits on unconventional Majorons not constrained by measurements of the Z0 decay width

Neutrino mass limits from a precise determination of &#946;&#946;-decay rates of <SUP>128</SUP>Te and <SUP>130</SUP>Te

Double beta decay of 128Te has been confirmed and the ratio of half-lives for &#946;&#946; decay of 130Te and 128Te has been determiend as 130Te&#189;/128Te&#189;=(3.52&#177;0.11)&#215;10-4 by ion-counting mass spectrometry of Xe in ancient Te ores. The Xe measurements, combined with common Pb dating, yield a 130Te half-life of (2.7&#177;0.1)&#215;1021 yr and thus a 128Te half-life of (7.7&#177;0.4)&#215;1024 yr. These results give limits on the effective Majorana mass of the neutrino (&lt;1.1-1.5 eV) and right-handed currents (||&lt;&#951;&gt;||&gt;5.3&#215;10-8) comparable to the best obtained from direct neutrinoless &#946;&#946;-decay searches. They also imply new limits on nonstandard Majorons not constrained by measurements of the Z0 decay width

Micromachined Pipette Arrays

Index Terms-Gel electrophoresis, metallic microchannels, micromachined pipettes, microscale sample loading, pipette arrays

Polymeric insulator-based dielectrophoresis (iDEP) for the monitoring of water-borne pathogens

We have successfully demonstrated selective trapping, concentration, and release of various biological organisms and inert beads by insulator-based dielectrophoresis within a polymeric microfluidic device. The microfluidic channels and internal features, in this case arrays of insulating posts, were initially created through standard wet-etch techniques in glass. This glass chip was then transformed into a nickel stamp through the process of electroplating. The resultant nickel stamp was then used as the replication tool to produce the polymeric devices through injection molding. The polymeric devices were made of Zeonor® 1060R, a polyolefin copolymer resin selected for its superior chemical resistance and optical properties. These devices were then optically aligned with another polymeric substrate that had been machined to form fluidic vias. These two polymeric substrates were then bonded together through thermal diffusion bonding. The sealed devices were utilized to selectively separate and concentrate a biological pathogen simulants. These include spores that were selectively concentrated and released by simply applying D.C. voltages across the plastic replicates via platinum electrodes in inlet and outlet reservoirs. The dielectrophoretic response of the organisms is observed to be a function of the applied electric field and post size, geometry and spacing. Cells were selectively trapped against a background of labeled polystyrene beads and spores to demonstrate that samples of interest can be separated from a diverse background. We have implemented and demonstrated here a methodology to determine the concentration factors obtained in these devices