Dynamics of heavy-Rydberg ion-pair formation in K(14p,20p)-SF6, CCl4ﾠcollisions

The dynamics of formation of heavy-Rydberg ion-pair states throughﾠelectron transferﾠin K(np)-SF6, CCl4ﾠcollisions is examined byﾠmeasuringﾠtheﾠvelocity,ﾠangular, and bindingﾠenergyﾠdistributions of the product ion pairs. The results areﾠanalyzedﾠwith the aid of a Monte Carlo collision code that models both the initial electron capture and the subsequent evolution of the ion pairs. The model simulations are in good agreement with the experimental data and highlight the factors such asﾠRydberg atomﾠsize, the kineticﾠenergyﾠof relativeﾠmotionﾠof theﾠRydberg atomﾠand target particle, and (in the case of attaching targets that dissociate) the energetics ofﾠdissociationﾠthat can be used to control the properties of the product ion-pair states

Comparison of the association between different ozone indicators and daily respiratory hospitalization in Guangzhou, China

Background: Epidemiological studies have widely proven the impact of ozone (O3) on respiratory mortality, while only a few studies compared the association between different O3 indicators and health. Methods: This study explores the relationship between daily respiratory hospitalization and multiple ozone indicators in Guangzhou, China, from 2014 to 2018. It uses a time-stratified case–crossover design. Sensitivities of different age and gender groups were analyzed for the whole year, the warm and the cold periods. We compared the results from the single-day lag model and the moving average lag model. Results: The results showed that the maximum daily 8 h average ozone concentration (MDA8 O3) had a significant effect on the daily respiratory hospitalization. This effect was stronger than for the maximum daily 1 h average ozone concentration (MDA1 O3). The results further showed that O3 was positively associated with daily respiratory hospitalization in the warm season, while there was a significantly negative association in the cold season. Specifically, in the warm season, O3 has the most significant effect at lag 4 day, with the odds ratio (OR) equal to 1.0096 [95% confidence intervals (CI): 1.0032, 1.0161]. Moreover, at the lag 5 day, the effect of O3 on the 15–60 age group was less than that on people older than 60 years, with the OR value of 1.0135 (95% CI: 1.0041, 1.0231) for the 60+ age group; women were more sensitive than men to O3 exposure, with an OR value equal to 1.0094 (95% CI: 0.9992, 1.0196) for the female group. Conclusion: These results show that different O3 indicators measure different impacts on respiratory hospitalization admission. Their comparative analysis provided a more comprehensive insight into exploring associations between O3 exposure and respiratory health.</p

Search for Small Trans-Neptunian Objects by the TAOS Project

The Taiwan-America Occultation Survey (TAOS) aims to determine the number of small icy bodies in the outer reach of the Solar System by means of stellar occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9) telescopes have been installed at Lulin Observatory in Taiwan to simultaneously monitor some thousand of stars for such rare occultation events. Because a typical occultation event by a TNO a few km across will last for only a fraction of a second, fast photometry is necessary. A special CCD readout scheme has been devised to allow for stellar photometry taken a few times per second. Effective analysis pipelines have been developed to process stellar light curves and to correlate any possible flux changes among all telescopes. A few billion photometric measurements have been collected since the routine survey began in early 2005. Our preliminary result of a very low detection rate suggests a deficit of small TNOs down to a few km size, consistent with the extrapolation of some recent studies of larger (30--100 km) TNOs.Comment: 4 pages, 3 figures, IAU Symposium 23

Hydrogen sulphide and nitric oxide mitigate the negative impacts of waterlogging stress on wheat (Triticum aestivum L.)

Nitric oxide (NO) and hydrogen sulphide (H2S) are important gaseous signalling molecules that regulate key physiochemical mechanisms of plants under environmental stresses. A number of attempts have been made to improve waterlogging tolerance in plants, but with limited success. Having said that, NO and H2S are vital signalling molecules, but their role in mitigating waterlogging effects on crop plants is not well established. We investigated the efficacy of exogenous NO and H2S to alleviate waterlogging effects in two wheat cultivars (Galaxy-2013 and FSD-2008). Waterlogging produced a noticeable reduction in plant growth, yield, chlorophyll, soluble sugars and free amino acids. Besides, waterlogging induced severe oxidative damage seen as higher cellular TBARS and H2O2 content. Antioxidant enzyme activity increased together with a notable rise in Fe2+ and Mn2+ content. Proline content was higher in waterlogged plants compared with non-waterlogged plants. In contrast, waterlogging caused a substantial decline in endogenous levels of essential nutrients (K+, Ca2+ and Mg2+). Waterlogged conditions led to Fe2+ and Mn2+ toxicity due to rapid reduction of Fe3+ and Mn3+ in the soil. Exogenous NO and H2S significantly protected plants from waterlogging effects by enhancing the oxidative defence and regulating nutritional status. Besides, the protective effects of exogenous NO were more prominent as compared with effects of H2S. Further, we did not study the effect of H2S and NO on photosynthetic attributes and expression of stress-related genes. Therefore, future studies should examine the effects of H2S and NO on wheat physiology and gene expression under waterlogging

Conformations of closed DNA

We examine the conformations of a model for a short segment of closed DNA. The molecule is represented as a cylindrically symmetric elastic rod with a constraint corresponding to a specification of the linking number. We obtain analytic expressions leading to the spatial configuration of a family of solutions representing distortions that interpolate between the circular form of DNA and a figure-eight form that represents the onset of interwinding. We are also able to generate knotted loops. We suggest ways to use our approach to produce other configurations relevant to studies of DNA structure. The stability of the distorted configurations is assessed, along with the effects of fluctuations on the free energy of the various configurations.Comment: 39 pages in REVTEX with 14 eps figures. Submitted to Phys. Rev. E. This manuscript updates, expands and revises, to a considerable extent, a previously posted manuscript, entitled "Conformations of Circular DNA," which appeared as cond-mat/970104

A novel enhancer regulates MGMT expression and promotes temozolomide resistance in glioblastoma

Temozolomide (TMZ) was used for the treatment of glioblastoma (GBM) for over a decade, but its treatment benefits are limited by acquired resistance, a process that remains incompletely understood. Here we report that an enhancer, located between the promoters of marker of proliferation Ki67 (MKI67) and O6-methylguanine-DNA-methyltransferase (MGMT) genes, is activated in TMZ-resistant patient-derived xenograft (PDX) lines and recurrent tumor samples. Activation of the enhancer correlates with increased MGMT expression, a major known mechanism for TMZ resistance. We show that forced activation of the enhancer in cell lines with low MGMT expression results in elevated MGMT expression. Deletion of this enhancer in cell lines with high MGMT expression leads to a dramatic reduction of MGMT and a lesser extent of Ki67 expression, increased TMZ sensitivity, and impaired proliferation. Together, these studies uncover a mechanism that regulates MGMT expression, confers TMZ resistance, and potentially regulates tumor proliferation

Analytical prediction and experimental measurement for mode conversion and scattering of plate waves at non-symmetric circular blind holes in isotropic plates

A model for guided wave scattering from non-symmetric blind holes in isotropic plates using Poisson and Mindlin plate wave theories for in-plane and flexural wave modes, respectively, is presented. It makes use of the wave function expansion technique and coupling conditions at the defect boundary in order to evaluate the scattered far fields of the three fundamental guided wave modes. The results were compared to other analytical models as well as experimental measurements for mode conversion from S0 to A0. Measurements agreed well with predictions confirming the validity of the model, highlighting at the same time the strong frequency dependence of the scattering and mode conversion behaviour

Origin and Properties of the Gap in the Half-Ferromagnetic Heusler Alloys

We study the origin of the gap and the role of chemical composition in the half-ferromagnetic Heusler alloys using the full-potential screened KKR method. In the paramagnetic phase the C1_b compounds, like NiMnSb, present a gap. Systems with 18 valence electrons, Z_t, per unit cell, like CoTiSb, are semiconductors, but when Z_t > 18 antibonding states are also populated, thus the paramagnetic phase becomes unstable and the half-ferromagnetic one is stabilized. The minority occupied bands accommodate a total of nine electrons and the total magnetic moment per unit cell in mu_B is just the difference between Z_t and $2 \times 9$. While the substitution of the transition metal atoms may preserve the half-ferromagnetic character, substituting the $sp$ atom results in a practically rigid shift of the bands and the loss of half-metallicity. Finally we show that expanding or contracting the lattice parameter by 2% preserves the minority-spin gap.Comment: 11 pages, 7 figures New figures, revised tex

Anthropogenic influences on heavy precipitation during the 2019 extremely wet rainy season in Southern China

Anthropogenic forcings have reduced the likelihood of heavy precipitation in southern China like the 2019 March-July event by about 60