Systematics of Gamow-Teller strengths in mid-fp-shell nuclei

We show that the presently available data on the Gamow-Teller (GT) strength in mid-fp-shell nuclei are proportional to the product of the numbers of valence protons and neutron holes in the full fp-shell. This observation leads to important insights into the mechanism for GT quenching and to a simple parametrization of the Gamow-Teller strengths important for electron capture by fp-shell nuclei in the early stage of supernovae.Comment: 9 pages + 1 figure, Caltech preprint MAP-16

Neutrino capture by r-process waiting-point nuclei

We use the Quasiparticle Random Phase Approximation to include the effects of low-lying Gamow-Teller and first forbidden strength in neutrino capture by very neutron-rich nuclei with N = 50, 82, or 126. For electron neutrinos in what is currently considered the most likely r-process site the capture cross sections are two or more times previous estimates. We briefly discuss the reliability of our calculations and their implications for nucleosynthesis.Comment: 9 pages, 4 figure

Josephson Current in the Presence of a Precessing Spin

The Josephson current in the presence of a precessing spin between various types of superconductors is studied. It is shown that the Josephson current flowing between two spin-singlet pairing superconductors is not modulated by the precession of the spin. When both superconductors have equal-spin-triplet pairing state, the flowing Josephson current is modulated with twice of the Larmor frequency by the precessing spin. It was also found that up to the second tunneling matrix elements, no Josephson current can occur with only a direct exchange interaction between the localized spin and the conduction electrons, if the two superconductors have different spin-parity pairing states.Comment: 5 pages, 1 figur

Selectivity and functional diversity in arbuscular mycorrhizas of co-occurring fungi and plants from a temperate deciduous woodland

1 The arbuscular mycorrhizal (AM) fungi colonizing plants at a woodland site in North Yorkshire (UK) have been characterized from the roots of five plant species (Rubus fruticosus agg. L., Epilobium angustifolium L., Acer pseudoplatanus L., Ajuga reptans L. and Glechoma hederacea L.), and identified using small-subunit rRNA (SSUrRNA) gene amplification and sequencing. 2 Interactions between five plant species from the site and four co-occurring glomalean fungi were investigated in artificial one-to-one AM symbioses. Three of the fungi were isolated from the site; the fourth was a culture genetically similar to a taxon found at the site. Phosphorus uptake and growth responses were compared with non-mycorrhizal controls. 3 Individual fungi colonized each plant with different spatial distribution and intensity. Some did not colonize at all, indicating incompatibility under the conditions used in the experiments. 4 Glomus hoi consistently occupied a large proportion of root systems and outperformed the other fungi, improving P uptake and enhancing the growth of four out of the five plant species. Only G. hoi colonized and increased P uptake in Acer pseudoplatanus, the host plant with which it associates almost exclusively under field conditions. Colonization of all plant species by Scutellospora dipurpurescens was sparse, and beneficial to only one of the host plants (Teucrium scorodonia). Archaeospora trappei and Glomus sp. UY1225 had variable effects on the host plants, conferring a range of P uptake and growth benefits on Lysimachia nummularia and T. scorodonia, increasing P uptake whilst not affecting biomass in Ajuga reptans and Glechoma hederacea, and failing to form mycorrhizas with A. pseudoplatanus. 5 These experimental mycorrhizas show that root colonization, symbiont compatibility and plant performance vary with each fungus-plant combination, even when the plants and fungi naturally co-exist. 6 We provide evidence of physical and functional selectivity in AM. The small number of described AM fungal species (154) has been ascribed to their supposed lack of host specificity, but if the selectivity we have observed is the general rule, then we may predict that many more, probably hard-to-culture glomalean species await discovery, or that members of species as currently perceived may be physiologically or functionally distinct

Skyrmion Excitations in Quantum Hall Systems

Using finite size calculations on the surface of a sphere we study the topological (skyrmion) excitation in quantum Hall system with spin degree of freedom at filling factors around $\nu=1$. In the absence of Zeeman energy, we find, in systems with one quasi-particle or one quasi-hole, the lowest energy band consists of states with $L=S$, where $L$ and $S$ are the total orbital and spin angular momentum. These different spin states are almost degenerate in the thermodynamic limit and their symmetry-breaking ground state is the state with one skyrmion of infinite size. In the presence of Zeeman energy, the skyrmion size is determined by the interplay of the Zeeman energy and electron-electron interaction and the skyrmion shrinks to a spin texture of finite size. We have calculated the energy gap of the system at infinite wave vector limit as a function of the Zeeman energy and find there are kinks in the energy gap associated with the shrinking of the size of the skyrmion. breaking ground state is the state with one skyrmion of infinite size. In the presence of Zeeman energy, the skyrmion size is determined by the interplay of the Zeeman energy and electron-electronComment: 4 pages, 5 postscript figures available upon reques

A model for net-baryon rapidity distribution

In nuclear collisions, a sizable fraction of the available energy is carried away by baryons. As the baryon number is conserved, the net-baryon $B-\bar{B}$ retains information on the energy-momentum carried by the incoming nuclei. A simple and consistent model for net-baryon production in high energy proton-proton and nucleus-nucleus collisions is presented. The basic ingredients of the model are valence string formation based on standard PDFs with QCD evolution and string fragmentation via the Schwinger mechanism. The results of the model are presented and compared with data at different centre-of-mass energies and centralities, as well as with existing models. These results show that a good description of the main features of net-baryon data is possible in the framework of a simplistic model, with the advantage of making the fundamental production mechanisms manifest.Comment: 9 pages, 12 figures; in fig. 11 a) the vertical scale was correcte

Grilled, Barbecued, and Smoked Meat Intake and Survival Following Breast Cancer

Background: Grilled, barbecued, and smoked meat intake, a prevalent dietary source of polycyclic aromatic hydrocarbon (PAH) carcinogens, may increase the risk of incident breast cancer. However, no studies have examined whether intake of this PAH source influences survival after breast cancer. Methods: We interviewed a population-based cohort of 1508 women diagnosed with first primary invasive or in situ breast cancer in 1996 and 1997 at baseline and again approximately five years later to assess grilled/barbecued and smoked meat intake. After a median of 17.6 years of follow-up, 597 deaths, of which 237 were breast cancer related, were identified. Multivariable Cox regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality as related to prediagnosis intake, comparing high (above the median) to low intake, as well as postdiagnosis changes in intake, comparing every combination of pre-/postdiagnosis intake to low pre-/postdiagnosis intake. All statistical tests were two-sided. Results: High prediagnosis grilled/barbecued and smoked meat intake was associated with increased risk of all-cause mortality (HR = 1.23, 95% CI = 1.03 to 1.46). Other associations were noted, but estimates were not statistically significant. These include high prediagnosis smoked beef/lamb/pork intake and increased all-cause (HR = 1.17, 95% CI = 0.99 to 1.38, Ptrend = .10) and breast cancer–specific (HR = 1.23, 95% CI = 0.95 to 1.60, Ptrend = .09) mortality. Also, among women with continued high grilled/barbecued and smoked meat intake after diagnosis, all-cause mortality risk was elevated 31% (HR = 1.31, 95% CI = 0.96 to 1.78). Further, breast cancer–specific mortality was decreased among women with any pre- and postdiagnosis intake of smoked poultry/fish (HR = 0.55, 95% CI = 0.31 to 0.97). Conclusion: High intake of grilled/barbecued and smoked meat may increase mortality after breast cancer

Postdiagnosis changes in cigarette smoking and survival following breast cancer

Background: The purpose of this study was to examine whether at-diagnosis smoking and postdiagnosis changes in smoking within five years after breast cancer were associated with long-termall-cause and breast cancer-specific mortality. Methods: A population-based cohort of 1508 women diagnosed with first primary in situ or invasive breast cancer in 1996 to 1997 were interviewed shortly after diagnosis and again approximately five years later to assess smoking history. Participants were followed for vital status through December 31, 2014. After 18+ years of follow-up, 597 deaths were identified, 237 of which were breast cancer related. Multivariable Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Results: Compared with never smokers, risk of all-cause mortality was elevated among the 19% of at-diagnosis smokers (HR=1.69, 95% CI=1.36 to 2.11), those who smoked 20 or more cigarettes per day (HR=1.85, 95% CI=1.42 to 2.40), women who had smoked for 30 or more years (HR=1.62, 95% CI=1.28 to 2.05), and women who had smoked 30 or more pack-years (HR=1.82, 95% CI=1.39 to 2.37). Risk of all-cause mortality was further increased among the 8% of women who were at-/postdiagnosis smokers (HR=2.30, 95% CI=1.56 to 3.39) but was attenuated among the 11% women who quit smoking after diagnosis (HR=1.83, 95% CI=1.32 to 2.52). Compared with never smokers, breast cancer-specific mortality risk was elevated 60% (HR=1.60, 95% CI=0.79 to 3.23) among at-/postdiagnosis current smokers, but the confidence interval included the null value and elevated 175% (HR=2.75, 95% CI=1.26 to 5.99) when we considered postdiagnosis cumulative pack-years. Conclusions: Smoking negatively impacts long-term survival after breast cancer. Postdiagnosis cessation of smoking may reduce the risk of all-cause mortality. Breast cancer survivors may benefit from aggressive smoking cessation programs starting as early as the time of diagnosis

Dietary sugar/starches intake and Barrett’s esophagus: a pooled analysis

Barrett’s esophagus (BE) is the key precursor lesion of esophageal adenocarcinoma, a lethal cancer that has increased rapidly in westernized countries over the past four decades. Dietary sugar intake has also been increasing over time, and may be associated with these tumors by promoting hyperinsulinemia. The study goal was to examine multiple measures of sugar/starches intake in association with BE. This pooled analysis included 472 BE cases and 492 controls from two similarly conducted case–control studies in the United States. Dietary intake data, collected by study-specific food frequency questionnaires, were harmonized across studies by linking with the University of Minnesota Nutrient Database, and pooled based on study-specific quartiles. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for age, sex, race, total energy intake, study indicator, body mass index, frequency of gastro-esophageal reflux, and fruit/vegetable intake. In both studies, intake of sucrose (cases vs. controls, g/day: 36.07 vs. 33.51; 36.80 vs. 35.06, respectively) and added sugar (46.15 vs. 41.01; 44.18 vs. 40.68, respectively) were higher in cases than controls. BE risk was increased 79% and 71%, respectively, for associations comparing the fourth to the first quartile of intake of sucrose (ORQ4vs.Q1 = 1.79, 95% CI = 1.07–3.02, Ptrend = 0.01) and added sugar (ORQ4vs.Q1 = 1.71, 95% CI = 1.05–2.80, Ptrend = 0.15). Intake of sweetened desserts/beverages was associated with 71% increase in BE risk (ORQ4vs.Q1 = 1.71, 95% CI = 1.07–2.73, Ptrend = 0.04). Limiting dietary intake of foods and beverages that are high in added sugar, especially refined table sugar, may reduce the risk of developing BE

Mapping the Two-Component Atomic Fermi Gas to the Nuclear Shell-Model

The physics of a two-component cold fermi gas is now frequently addressed in laboratories. Usually this is done for large samples of tens to hundreds of thousands of particles. However, it is now possible to produce few-body systems (1-100 particles) in very tight traps where the shell structure of the external potential becomes important. A system of two-species fermionic cold atoms with an attractive zero-range interaction is analogous to a simple model of nucleus in which neutrons and protons interact only through a residual pairing interaction. In this article, we discuss how the problem of a two-component atomic fermi gas in a tight external trap can be mapped to the nuclear shell model so that readily available many-body techniques in nuclear physics, such as the Shell Model Monte Carlo (SMMC) method, can be directly applied to the study of these systems. We demonstrate an application of the SMMC method by estimating the pairing correlations in a small two-component Fermi system with moderate-to-strong short-range two-body interactions in a three-dimensional harmonic external trapping potential.Comment: 13 pages, 3 figures. Final versio