570 research outputs found
Correlation between the quenching of total GT+ strength and the increase of E2 strength
Relations between the total beta+ Gamow-Teller (GT+) strength and the E2
strength are further examined. It is found that in shell-model calculations for
N=Z nuclei, in which changes in deformation are induced by varying the
single-particle energies, the total GT+ or GT- strength decreases monotonically
with increasing values of the B(E2) from the ground state to the first excited
J=2+ state. Similar trends are also seen for the double GT transition amplitude
(with some exceptions) and for the spin part of the total M1 strength as a
function of B(E2).Comment: 11 pages and 3 figures (Figures will be sent on request
A novel method for sampling the suspended sediment load in the tidal environment using bi-directional time-integrated mass-flux sediment (TIMS) samplers
Identifying the source and abundance of sediment transported within tidal creeks is essential for studying the connectivity between coastal watersheds and estuaries. The fine-grained suspended sediment load (SSL) makes up a substantial portion of the total sediment load carried within an estuarine system and efficient sampling of the SSL is critical to our understanding of nutrient and contaminant transport, anthropogenic influence, and the effects of climate. Unfortunately, traditional methods of sampling the SSL, including instantaneous measurements and automatic samplers, can be labor intensive, expensive and often yield insufficient mass for comprehensive geochemical analysis. In estuaries this issue is even more pronounced due to bi-directional tidal flow. This study tests the efficacy of a time-integrated mass sediment sampler (TIMS) design, originally developed for uni-directional flow within the fluvial environment, modified in this work for implementation the tidal environment under bi-directional flow conditions. Our new TIMS design utilizes an ‘L’ shaped outflow tube to prevent backflow, and when deployed in mirrored pairs, each sampler collects sediment uniquely in one direction of tidal flow. Laboratory flume experiments using dye and particle image velocimetry (PIV) were used to characterize the flow within the sampler, specifically, to quantify the settling velocities and identify stagnation points. Further laboratory tests of sediment indicate that bidirectional TIMS capture up to 96% of incoming SSL across a range of flow velocities (0.3–0.6 m s−1). The modified TIMS design was tested in the field at two distinct sampling locations within the tidal zone. Single-time point suspended sediment samples were collected at high and low tide and compared to time-integrated suspended sediment samples collected by the bi-directional TIMS over the same four-day period. Particle-size composition from the bi-directional TIMS were representative of the array of single time point samples, but yielded greater mass, representative of flow and sediment-concentration conditions at the site throughout the deployment period. This work proves the efficacy of the modified bi-directional TIMS design, offering a novel tool for collection of suspended sediment in the tidally-dominated portion of the watershed
b-physics signals of the lightest CP-odd Higgs in the NMSSM at large tan beta
We investigate the low energy phenomenology of the lighter pseudoscalar
in the NMSSM. The mass can naturally be small due to a global
symmetry of the Higgs potential, which is only broken by trilinear
soft terms. The mass is further protected from renormalization group
effects in the large limit. We calculate the
amplitude at leading order in and work out the contributions to
rare , and radiative -decays and mixing. We obtain
constraints on the mass and couplings and show that masses down to
MeV are allowed. The -physics phenomenology of the NMSSM
differs from the MSSM in the appearance of sizeable renormalization effects
from neutral Higgses to the photon and gluon dipole operators and the breakdown
of the MSSM correlation between the branching ratio and
mixing. For masses above the tau threshold the
can be searched for in processes with branching ratios
\lsim 10^{-3}.Comment: 18 pages, 3 figures; references adde
Heritability of specific language impairment depends on diagnostic criteria
Heritability estimates for specific language impairment (SLI) have been inconsistent. Four twin studies reported heritability of 0.5 or more, but a recent report from the Twins Early Development Study found negligible genetic influence in 4-year-olds. We considered whether the method of ascertainment influenced results and found substantially higher heritability if SLI was defined in terms of referral to speech and language pathology services than if defined by language test scores. Further analysis showed that presence of speech difficulties played a major role in determining whether a child had contact with services. Childhood language disorders that are identified by population screening are likely to have a different phenotype and different etiology from clinically referred cases. Genetic studies are more likely to find high heritability if they focus on cases who have speech difficulties and who have been referred for intervention
Charged Higgs bosons in the Next-to MSSM (NMSSM)
The charged Higgs boson decays and
are studied in the framework of the next-to Minimal Supersymmetric Standard
Model (NMSSM). It is found that the decay rate for can
exceed the rates for the and channels both below and above
the top-bottom threshold. The dominance of is most readily
achieved when has a large doublet component and small mass. We also study
the production process at the LHC followed by the decay
which leads to the signature . We suggest
that is a promising discovery channel for a light charged
Higgs boson in the NMSSM with small or moderate and dominant decay
mode . This signature can also arise from
the Higgsstrahlung process followed by the decay . It is shown that there exist regions of parameter space where these
processes can have comparable cross sections and we suggest that their
respective signals can be distinguished at the LHC by using appropriate
reconstruction methods.Comment: 20 pages, 22 eps figures, more reference adde
Higgs Scalars in the Minimal Non-minimal Supersymmetric Standard Model
We consider the simplest and most economic version among the proposed
non-minimal supersymmetric models, in which the -parameter is promoted to
a singlet superfield, whose all self-couplings are absent from the
renormalizable superpotential. Such a particularly simple form of the
renormalizable superpotential may be enforced by discrete -symmetries which
are extended to the gravity-induced non-renormalizable operators as well. We
show explicitly that within the supergravity-mediated supersymmetry-breaking
scenario, the potentially dangerous divergent tadpoles associated with the
presence of the gauge singlet first appear at loop levels higher than 5 and
therefore do not destabilize the gauge hierarchy. The model provides a natural
explanation for the origin of the -term, without suffering from the
visible axion or the cosmological domain-wall problem. Focusing on the Higgs
sector of this minimal non-minimal supersymmetric standard model, we calculate
its effective Higgs potential by integrating out the dominant quantum effects
due to stop squarks. We then discuss the phenomenological implications of the
Higgs scalars predicted by the theory for the present and future high-energy
colliders. In particular, we find that our new minimal non-minimal
supersymmetric model can naturally accommodate a relatively light charged Higgs
boson, with a mass close to the present experimental lower bound.Comment: 63 pages (12 figures), extended versio
Association of untargeted urinary metabolomics and lung cancer risk among never-smoking women in China
Importance Chinese women have the highest rate of lung cancer among female never-smokers in the world, and the etiology is poorly understood.
Objective To assess the association between metabolomics and lung cancer risk among never-smoking women.
Design, Setting, and Participants This nested case-control study included 275 never-smoking female patients with lung cancer and 289 never-smoking cancer-free control participants from the prospective Shanghai Women’s Health Study recruited from December 28, 1996, to May 23, 2000. Validated food frequency questionnaires were used for the collection of dietary information. Metabolomic analysis was conducted from November 13, 2015, to January 6, 2016. Data analysis was conducted from January 6, 2016, to November 29, 2018.
Exposures Untargeted ultra-high-performance liquid chromatography–tandem mass spectrometry and nuclear magnetic resonance metabolomic profiles were characterized using prediagnosis urine samples. A total of 39 416 metabolites were measured.
Main Outcomes and Measures Incident lung cancer.
Results Among the 564 women, those who developed lung cancer (275 participants; median [interquartile range] age, 61.0 [52-65] years) and those who did not develop lung cancer (289 participants; median [interquartile range] age, 62.0 [53-66] years) at follow-up (median [interquartile range] follow-up, 10.9 [9.0-11.7] years) were similar in terms of their secondhand smoke exposure, history of respiratory diseases, and body mass index. A peak metabolite, identified as 5-methyl-2-furoic acid, was significantly associated with lower lung cancer risk (odds ratio, 0.57 [95% CI, 0.46-0.72]; P < .001; false discovery rate = 0.039). Furthermore, this peak was weakly correlated with self-reported dietary soy intake (ρ = 0.21; P < .001). Increasing tertiles of this metabolite were associated with lower lung cancer risk (in comparison with first tertile, odds ratio for second tertile, 0.52 [95% CI, 0.34-0.80]; and odds ratio for third tertile, 0.46 [95% CI, 0.30-0.70]), and the association was consistent across different histological subtypes and follow-up times. Additionally, metabolic pathway analysis found several systemic biological alterations that were associated with lung cancer risk, including 1-carbon metabolism, nucleotide metabolism, oxidative stress, and inflammation.
Conclusions and Relevance This prospective study of the untargeted urinary metabolome and lung cancer among never-smoking women in China provides support for the hypothesis that soy-based metabolites are associated with lower lung cancer risk in never-smoking women and suggests that biological processes linked to air pollution may be associated with higher lung cancer risk in this population
Astroparticle Physics with a Customized Low-Background Broad Energy Germanium Detector
The MAJORANA Collaboration is building the MAJORANA DEMONSTRATOR, a 60 kg
array of high purity germanium detectors housed in an ultra-low background
shield at the Sanford Underground Laboratory in Lead, SD. The MAJORANA
DEMONSTRATOR will search for neutrinoless double-beta decay of 76Ge while
demonstrating the feasibility of a tonne-scale experiment. It may also carry
out a dark matter search in the 1-10 GeV/c^2 mass range. We have found that
customized Broad Energy Germanium (BEGe) detectors produced by Canberra have
several desirable features for a neutrinoless double-beta decay experiment,
including low electronic noise, excellent pulse shape analysis capabilities,
and simple fabrication. We have deployed a customized BEGe, the MAJORANA
Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and
shield at the Kimballton Underground Research Facility in Virginia. This paper
will focus on the detector characteristics and measurements that can be
performed with such a radiation detector in a low-background environment.Comment: Submitted to NIMA Proceedings, SORMA XII. 9 pages, 4 figure
Colossal dielectric constants in transition-metal oxides
Many transition-metal oxides show very large ("colossal") magnitudes of the
dielectric constant and thus have immense potential for applications in modern
microelectronics and for the development of new capacitance-based
energy-storage devices. In the present work, we thoroughly discuss the
mechanisms that can lead to colossal values of the dielectric constant,
especially emphasising effects generated by external and internal interfaces,
including electronic phase separation. In addition, we provide a detailed
overview and discussion of the dielectric properties of CaCu3Ti4O12 and related
systems, which is today's most investigated material with colossal dielectric
constant. Also a variety of further transition-metal oxides with large
dielectric constants are treated in detail, among them the system La2-xSrxNiO4
where electronic phase separation may play a role in the generation of a
colossal dielectric constant.Comment: 31 pages, 18 figures, submitted to Eur. Phys. J. for publication in
the Special Topics volume "Cooperative Phenomena in Solids: Metal-Insulator
Transitions and Ordering of Microscopic Degrees of Freedom
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