A time-domain recursive method to analyse transient wave propagation across rock joints

The present investigation is concerned with transient wave propagation in a rock mass with a set of parallel joints by using a recursive method. According to the displacement field of a rock mass with a set of parallel joints, the interaction between four plane waves (two longitudinal-waves and two transverse-waves) and a joint is analysed first. With the displacement discontinuity model and the time shifting function, the wave propagation equation based on the recursive method in time domain for obliquely longitudinal-(P) or transverse-(S) waves across a set of parallel joints is established. The joints are assumed linearly elastic. The analytical solution obtained by the proposed method is compared with the existing results for some special cases, including oblique incidence across a single joint and normal incidence across a set of parallel joints. By verification, it is found that the solutions by the proposed method match very well with the existing methods. The applicability and limitations of the new method are then discussed for incident waves with different propertie

Oligothiophene/graphene supramolecular ensembles managing light induced processes: Preparation, characterization, and femtosecond transient absorption studies leading to charge‐separation

Advances  in  organic  synthetic  chemistry  combined  with  the  exceptional  electronic  properties  of  carbon  allotropes,  particularly graphene, is the basis to design and fabricate novel electron donor-­‐acceptor ensembles with desired properties for technological applications. Thiophene-­‐based materials, mainly thiophene-­‐containing polymers, are known for  their  notable  electronic  properties.  In  this  frame  moving  from  polymer  to  oligomer  forms,  new  fundamental  information would help to the better understanding of their electrochemical and photophysical properties. Furthermore, a successful  combination  of  their  electronic  properties  with  those  of  graphene  is  a  challenging  goal.  In  this  work  two  oligothiophene compounds consists of three and nine thiophene-­‐rings, abbreviated as 3T and 9T, respectively, were synthesized and noncovalently associated with liquid phase exfoliated few-­‐layered graphene sheets (abbreviated as eG), forming donor-­‐acceptor 3T/eG and 9T/eG nanoensembes. Markedly, intra-­‐ensemble electronic interactions between the two  components  in  the  ground  and  excited  states  were  evaluated  with  the  aid  of  UV-­‐Vis  and  photoluminescence  spectroscopy. Furthermore, redox assays revealed an one-­‐electron oxidation of 3T accompanied by one-­‐electron reduction due  to  eG  in  3T/eG,  while  two  reversible  one-­‐electron  oxidations  of  9T  accompanied  by  one-­‐electron  reduction  of  eG  9T/eG. The electrochemical band gap for 3T/eG and 9T/eG ensembles were calculated and verified that the negative free-­‐energy change for the charge-­‐separated state of 3T/eG and 9T/eG via the singlet excited state of 3T and 9T respectively, were  thermodynamically  favorable.  Finally,  results  of  transient  pump-­‐probe  spectroscopic  studies  at  the  femtosecond  time scale were supportive of charge transfer type interactions in the 3T/eG and 9T/eG ensembles. The estimated rates for intra-­‐ensemble charge separation were found to be 9.52 x 109 s-­‐1 and 2.2 x 1011 s-­‐1, respectively, for 3T/eG and 9T/eG in THF, revealing moderate to ultrafast photoinduced events in the oligothiophene/graphene supramolecular ensemble

Time--Distance Helioseismology Data Analysis Pipeline for Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory (SDO/HMI) and Its Initial Results

The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) provides continuous full-disk observations of solar oscillations. We develop a data-analysis pipeline based on the time-distance helioseismology method to measure acoustic travel times using HMI Doppler-shift observations, and infer solar interior properties by inverting these measurements. The pipeline is used for routine production of near-real-time full-disk maps of subsurface wave-speed perturbations and horizontal flow velocities for depths ranging from 0 to 20 Mm, every eight hours. In addition, Carrington synoptic maps for the subsurface properties are made from these full-disk maps. The pipeline can also be used for selected target areas and time periods. We explain details of the pipeline organization and procedures, including processing of the HMI Doppler observations, measurements of the travel times, inversions, and constructions of the full-disk and synoptic maps. Some initial results from the pipeline, including full-disk flow maps, sunspot subsurface flow fields, and the interior rotation and meridional flow speeds, are presented.Comment: Accepted by Solar Physics topical issue 'Solar Dynamics Observatory

Adult physical activity and breast cancer risk in women with a family history of breast cancer

Background: Recreational physical activity has been consistently associated with reduced breast cancer risk. Less is known about how family history of breast cancer affects the association and whether it varies by menopausal status. Methods: The Sister Study is a cohort of 50,884 women who had a sister with breast cancer but no prior breast cancer themselves at enrollment. Women reported all recreational sport/exercise activities they participated in over the past 12 months. Hours/week and MET-hours/week of physical activity were considered in association with breast cancer risk. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated with Cox regression. Extent of family history, examined as a modifier, was characterized by a Bayesian score incorporating characteristics of the family structure. Results: During follow-up (average 8.4 years), 3,023 cases were diagnosed. Higher hours/week (HR ≥7vs<1 = 0.77; 95% CI, 0.66–0.90) and MET-hours/week (HR quartile4vs1 = 0.75; 95% CI, 0.67–0.85) of physical activity were associated with reduced postmenopausal breast cancer risk. Hours/week and MET-hours/week were associated with suggestively increased premenopausal breast cancer risk (MET-hours/week HR quartile4vs1 = 1.25; 95% CI, 0.98–1.60). Associations did not vary with extent of family history. However, the increased risk in premenopausal women may be limited to those with stronger family history. Conclusions: In women with a family history of breast cancer, physical activity was associated with reduced postmenopausal, but not premenopausal, breast cancer risk and was not modified by extent of family history. Impact: This was the first study to examine the association between physical activity and breast cancer risk in a large population with a family history of breast cancer

Additive subdistribution hazards regression for competing risks data in case-cohort studies

In survival data analysis, a competing risk is an event whose occurrence precludes or alters the chance of the occurrence of the primary event of interest. In large cohort studies with long-term follow-up, there are often competing risks. Further, if the event of interest is rare in such large studies, the case-cohort study design is widely used to reduce the cost and achieve the same efficiency as a cohort study. The conventional additive hazards modeling for competing risks data in case-cohort studies involves the cause-specific hazard function, under which direct assessment of covariate effects on the cumulative incidence function, or the subdistribution, is not possible. In this paper, we consider an additive hazard model for the subdistribution of a competing risk in case-cohort studies. We propose estimating equations based on inverse probability weighting methods for the estimation of the model parameters. Consistency and asymptotic normality of the proposed estimators are established. The performance of the proposed methods in finite samples is examined through simulation studies and the proposed approach is applied to a case-cohort dataset from the Sister Study

Effects of Allelic Variation in Glutenin Subunits and Gliadins on Baking-Quality in Near-isogenic Lines of Common Wheat cv. Longmai 19

Two lines, L-19-613 and L-19-626, were produced from the common wheat cultivar Longmai 19 (L-19) by six consecutive backcrosses using biochemical marker-assisted selection. L-19 (Glu-D1a, Glu-A3c/Gli-A1?; Gli-A1? is a gene coding for unnamed gliadin) and L-19-613 (Glu-D1d, Glu-A3c/Gli-A1?) formed a set of near-isogenic lines (NILs) for HMW-GS, while L-19-613 and L-19-626 (Glu-D1d, Glu-A3e/Gli-A1m) constituted another set of NILs for the LMW-GS/gliadins. The three L-19 NILs were grown in the wheat breeding nursery in 2007 and 2008. The field experiments were designed using the three-column contrast arrangement method with four replicates. The three lines were ranked as follows for measurements of gluten strength, which was determined by the gluten index, Zeleny sedimentation, the stability and breakdown time of the farinogram, the maximum resistance and area of the extensogram, and the P andWvalues of the alveogram: L-19-613 > L-19-626 > L-19. The parameters listed above were significantly different between lines at the 0.05 or 0.01 level. The Glu-D1 and Glu-A3/Gli-A1 loci had additive effects on the gluten index, Zeleny sedimentation, stability, breakdown time, maximum resistance, area, P and W values. Although genetic variation at the Glu-A3/Gli-A1 locus had a great influence on wheat quality, the genetic difference between Glu-D1d and Glu-D1a at the Glu-D1 locus was much larger than that of Glu-A3c/Gli-A1? and Glu-A3e/Gli-A1m at the Glu-A3/Gli-A1 locus. Glu-D1d had negative effects on the extensibility and the L value compared with Glu-D1a. In contrast, Glu-A3c/Gli-A1? had a positive effect on these traits compared with Glu-A3e/Gli-A1m

Studies of Prototype CsI(Tl) Crystal Scintillators for Low-Energy Neutrino Experiments

Crystal scintillators provide potential merits for the pursuit of low-energy low-background experiments. A CsI(Tl) scintillating crystal detector is being constructed to study low-energy neutrino physics at a nuclear reactor, while projects are underway to adopt this technique for dark matter searches. The choice of the geometrical parameters of the crystal modules, as well as the optimization of the read-out scheme, are the results of an R&D program. Crystals with 40 cm in length were developed. The detector requirements and the achieved performance of the prototypes are presented. Future prospects for this technique are discussed.Comment: 32 pages, 14 figure

Can surface flux transport account for the weak polar field in cycle 23?

To reproduce the weak magnetic field on the polar caps of the Sun observed during the declining phase of cycle 23 poses a challenge to surface flux transport models since this cycle has not been particularly weak. We use a well-calibrated model to evaluate the parameter changes required to obtain simulated polar fields and open flux that are consistent with the observations. We find that the low polar field of cycle 23 could be reproduced by an increase of the meridional flow by 55% in the last cycle. Alternatively, a decrease of the mean tilt angle of sunspot groups by 28% would also lead to a similarly low polar field, but cause a delay of the polar field reversals by 1.5 years in comparison to the observations.Comment: 9 pages, 8 figures, Space Science Reviews, accepte

Structural and dielectric properties of Sr2_{2}TiO4_{4} from first principles

We have investigated the structural and dielectric properties of Sr$_{2}$TiO$_{4}$,the first member of the Sr$_{n+1}$Ti$_{n}$O$_{3n+1}$ Ruddlesden-Popper series, within density functional theory. Motivated by recent work in which thin films of Sr$_{2}$TiO$_{4}$ were grown by molecular beam epitaxy (MBE) on SrTiO$_{3}$ substrates, the in-plane lattice parameter was fixed to the theoretically optimized lattice constant of cubic SrTiO$_{3}$ (n=$\infty$), while the out-of-plane lattice parameter and the internal structural parameters were relaxed. The fully relaxed structure was also investigated. Density functional perturbation theory was used to calculate the zone-center phonon frequencies, Born effective charges, and the electronic dielectric permittivity tensor. A detailed study of the contribution of individual infrared-active modes to the static dielectric permittivity tensor was performed. The calculated Raman and infrared phonon frequencies were found to be in agreement with experiment where available. Comparisons of the calculated static dielectric permittivity with experiments on both ceramic powders and epitaxial thin films are discussed.Comment: 11 pages, 1 figure, 8 tables, submitted to Phys. Rev.