Angular Correlations in the ß Decay of

We present the first measurement of the α-ß-ν angular correlation in the Gamow-Teller ß^{+} decay of ^{8}B. This was accomplished using the Beta-decay Paul Trap, expanding on our previous work on the ß^{-} decay of ^{8}Li. The ^{8}B result is consistent with the V-A electroweak interaction of the standard model and, on its own, provides a limit on the exotic right-handed tensor current relative to the axial-vector current of |C_{T}/C_{A}|^{2}<0.013 at the 95.5% confidence level. This represents the first high-precision angular correlation measurements in mirror decays and was made possible through the use of an ion trap. By combining this ^{8}B result with our previous ^{8}Li results, we demonstrate a new pathway for increased precision in searches for exotic currents.

Direct Mass Measurements to Inform the Behavior of

Nuclear isomer effects are pivotal in understanding nuclear astrophysics, particularly in the rapid neutron-capture process where the population of metastable isomers can alter the radioactive decay paths of nuclei produced during astrophysical events. The ß-decaying isomer ^{128m}Sb was identified as potentially impactful since the ß-decay pathway along the A=128 isobar funnels into this state bypassing the ground state. We report the first direct mass measurements of the ^{128}Sb isomer and ground state using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. We find mass excesses of -84564.8(25) keV and -84608.8(21) keV, respectively, resulting in an excitation energy for the isomer of 43.9(33) keV. These results provide the first key nuclear data input for understanding the role of ^{128m}Sb in nucleosynthesis, and we show that it will influence the flow of the rapid neutron-capture process.

Improved Limit on Tensor Currents in the Weak Interaction from

The electroweak interaction in the standard model is described by a pure vector-axial-vector structure, though any Lorentz-invariant component could contribute. In this Letter, we present the most precise measurement of tensor currents in the low-energy regime by examining the ß-ν[over ¯] correlation of trapped ^{8}Li ions with the Beta-decay Paul Trap. We find a_{ßν}=-0.3325±0.0013_{stat}±0.0019_{syst} at 1σ for the case of coupling to right-handed neutrinos (C_{T}=-C_{T}^{'}), which is consistent with the standard model prediction.

Precision Mass Measurements of Neutron-Rich Neodymium and Samarium Isotopes and Their Role in Understanding Rare-Earth Peak Formation.

The Canadian Penning Trap mass spectrometer at the Californium Rare Isotope Breeder Upgrade (CARIBU) facility was used to measure the masses of eight neutron-rich isotopes of Nd and Sm. These measurements are the first to push into the region of nuclear masses relevant to the formation of the rare-earth abundance peak at A∼165 by the rapid neutron-capture process. We compare our results with theoretical predictions obtained from "reverse engineering" the mass surface that best reproduces the observed solar abundances in this region through a Markov chain Monte Carlo technique. Our measured masses are consistent with the reverse-engineering predictions for a neutron star merger wind scenario.

First results from the CARIBU facility: mass measurements on the r-process path.

The Canadian Penning Trap mass spectrometer has made mass measurements of 33 neutron-rich nuclides provided by the new Californium Rare Isotope Breeder Upgrade facility at Argonne National Laboratory. The studied region includes the 132Sn double shell closure and ranges in Z from In to Cs, with Sn isotopes measured out to A=135, and the typical measurement precision is at the 100 ppb level or better. The region encompasses a possible major waiting point of the astrophysical r process, and the impact of the masses on the r process is shown through a series of simulations. These first-ever simulations with direct mass information on this waiting point show significant increases in waiting time at Sn and Sb in comparison with commonly used mass models, demonstrating the inadequacy of existing models for accurate r-process calculations.

Prey life-history and bioenergetic responses across a predation gradient.

To evaluate the importance of non-consumptive effects of predators on prey life histories under natural conditions, an index of predator abundance was developed for naturally occurring populations of a common prey fish, the yellow perch Perca flavescens, and compared to life-history variables and rates of prey energy acquisition and allocation as estimated from mass balance models. The predation index was positively related to maximum size and size at maturity in both male and female P. flavescens, but not with life span or reproductive investment. The predation index was positively related to size-adjusted specific growth rates and growth efficiencies but negatively related to model estimates of size-adjusted specific consumption and activity rates in both vulnerable (small) and invulnerable (large) size classes of P. flavescens. These observations suggest a trade-off between growth and activity rates, mediated by reduced activity in response to increasing predator densities. Lower growth rates and growth efficiencies in populations with fewer predators, despite increased consumption suggests either 1) a reduction in prey resources at lower predator densities or 2) an intrinsic cost of rapid prey growth that makes it unfavourable unless offset by a perceived threat of predation. This study provides evidence of trade-offs between growth and activity rates induced by predation risk in natural prey fish populations and illustrates how behavioural modification induced through predation can shape the life histories of prey fish species.

Further evidence for the importance of an androgen response element in the factor IX promoter.

Previous work involving the characterizing of a factor IX promoter mutation (-26 G-->C) of a 21-year-old patient with severe haemophilia B suggested that an androgen response element (ARE) was present in the wild-type factor IX promoter but was disrupted in this patient. However, other theories not involving this ARE have been suggested for the mechanism of recovery in the more typical (Leyden) promoter patients, so that the ARE hypothesis requires further evidence if it is to be accepted. We now present a case history and functional data on another 48-year-old severe haemophilia B patient (UK232) with a different (G-->A) mutation at the same position, -26. This mutation impairs transactivation of the minimal factor IX promoter region (-220-->+43) by HNF4 in transient transfection experiments in HepG2 and HeLa cells. It disrupts binding of both androgen receptor (AR) and HNF4 to oligonucleotides spanning this region (-40-->-9) in competition gel mobility shift assays. It impairs AR/testosterone transactivation of these oligonucleotides (-40-->-9) when tetramerized upstream of a CAT reporter gene in cotransfection assays in HeLa cells. And, finally, no clinical recovery has occurred since puberty. These results strengthen the evidence for the importance of nucleotide -26, both for the normal transcription of the gene in response to HNF4 and for the proposed Leyden recovery mechanism in response to AR and testosterone acting directly through the factor IX ARE.

Qualitative analysis of temporal information in Iliad: implications for linking Iliad to an electronic medical record as a knowledge server.

In linking Iliad to an electronic medical record (EMR) as a knowledge server, our objective is to convert the date and time stamped data from the EMR to the temporal representations existing in the Iliad knowledge base. First, an empirical analysis of Iliad's temporal information content is described: categorizing, estimating the amount (22%), and offering a temporal template to canonically represent it. Second, we analyze the effect of history and physical examination temporal information on the diagnostic performance of the system using data from 241 real cases. Third, we discuss knowledge engineering mapping techniques to convert time information found in EMRs. We conclude that the Iliad system includes a large amount of explicit and implicit time information and this information improves the system's diagnostic accuracy, both in terms of diagnosis ranking and confidence.

The high frequency of the -6G-->A factor IX promoter mutation is the result both of a founder effect and recurrent mutation at a CpG dinucleotide.

We report a new Liverpool family with a mild haemophilia B Leyden phenotype caused by a -6G-->A mutation in a CpG dinucleotide in the promoter of the clotting factor IX gene. This mutation had previously been identified in three other U.K. pedigrees and six others worldwide. To investigate whether these mutations were of independent origin, the haplotype was determined for eight polymorphic loci, within or immediately adjacent to the factor IX gene, for nine of the 10 existing patients. Six probands had identical haplotypes, including all four U.K. probands, suggesting that they arose from a common founder. The other three probands differed in haplotype from the common haplotype, and from each other, suggesting that they were independent mutations at this CpG dinucleotide.

Iliad and Medical HouseCall: evaluating the impact of common sense knowledge on the diagnostic accuracy of a medical expert system.

Diagnostic expert systems are gaining acceptance among physicians. Recently, a comparative study of the performance of four major commercial diagnostic programs demonstrated that the information they produce contains a certain amount of irrelevancy that the trained physician ignores. Medical HouseCall is a consumer health information expert system based on a medical expert system for physicians, Iliad. To enhance the usefulness of Medical HouseCall to health care consumers, we are interested in significantly reducing the amount of irrelevancy contained in the diagnostic differential list. Testing with over 470 'textbook' cases revealed that a large part of the irrelevancy can be eliminated by adding universal and medical 'common sense' knowledge. Using four performance measures, we compared, on a subset of cases, the differential lists from two versions of the program: the refined knowledge base (1995) and an older version (1994) 'pre-common sense'. The results suggest that the performance of a diagnostic expert system can be significantly improved with the addition of common sense knowledge.