What can the braking indices tell us about pulsars' nature?

As a result of observational difficulties, braking indices of only six rotation-powered pulsars are obtained with certainty, all of which are remarkably smaller than the value ($n=3$) expected for pure magnetodipole radiation model. This is still a real fundamental question not being well answered after nearly forty years of the discovery of pulsar. The main problem is that we are shamefully not sure about the dominant mechanisms that result in pulsars' spin-down. Based on the previous works, the braking index is re-examined, with a conclusion of suggesting a constant gap potential drop for pulsars with magnetospheric activities. New constrains on model parameters from observed braking indices are presented.Comment: 10 pages, 4 figures, submitted to "Advances in Space Research" (Proceedings of COSPAR 2006

Gastric cancer and Helicobacter pylori: a combined analysis of 12 case control studies nested within prospective cohorts

BACKGROUND: The magnitude of the association between Helicobacter pylori and incidence of gastric cancer is unclear. H pylori infection and the circulating antibody response can be lost with development of cancer; thus retrospective studies are subject to bias resulting from classifi- cation of cases as H pylori negative when they were infected in the past. AIMS: To combine data from all case control studies nested within prospective cohorts to assess more reliably the relative risk of gastric cancer associated with H pylori infection.To investigate variation in relative risk by age, sex, cancer type and subsite, and interval between blood sampling and cancer diagnosis. METHODS: Studies were eligible if blood samples for H pylori serology were collected before diagnosis of gastric cancer in cases. Identified published studies and two unpublished studies were included. Individual subject data were obtained for each. Matched odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated for the association between H pylori and gastric cancer. RESULTS: Twelve studies with 1228 gastric cancer cases were considered. The association with H pylori was restricted to noncardia cancers (OR 3.0; 95% CI 2.3–3.8) and was stronger when blood samples for H pylori serology were collected 10+ years before cancer diagnosis (5.9; 3.4–10.3). H pylori infection was not associated with an altered overall risk of cardia cancer (1.0; 0.7–1.4). CONCLUSIONS: These results suggest that 5.9 is the best estimate of the relative risk of non-cardia cancer associated with H pylori infection and that H pylori does not increase the risk of cardia cancer. They also support the idea that when H pylori status is assessed close to cancer diagnosis, the magnitude of the non-cardia association may be underestimated

Light cone QCD sum rules study of the semileptonic heavy ΞQ\Xi_{Q} and ΞQ′\Xi'_{Q} transitions to Ξ\Xi and Σ\Sigma baryons

The semileptonic decays of heavy spin--1/2, $\Xi_{b(c)}$ and $\Xi'_{b(c)}$ baryons to the light spin-- 1/2, $\Xi$ and $\Sigma$ baryons are investigated in the framework of the light cone QCD sum rules. In particular, using the most general form of the interpolating currents for the heavy baryons as well as the distribution amplitudes of the $\Xi$ and $\Sigma$ baryons, we calculate all form factors entering the matrix elements of the corresponding effective Hamiltonians in full QCD. Having calculated the responsible form factors, we evaluate the decay rates and branching fractions of the related transitions.Comment: 30 Pages, 5 Figures and 18 Table

Female chromosome X mosaicism is age-related and preferentially affects the inactivated X chromosome

To investigate large structural clonal mosaicism of chromosome X, we analysed the SNP microarray intensity data of 38,303 women from cancer genome-wide association studies (20,878 cases and 17,425 controls) and detected 124 mosaic X events42Mb in 97 (0.25%) women. Here we show rates for X-chromosome mosaicism are four times higher than mean autosomal rates; X mosaic events more often include the entire chromosome and participants with X events more likely harbour autosomal mosaic events. X mosaicism frequency increases with age (0.11% in 50-year olds; 0.45% in 75-year olds), as reported for Y and autosomes. Methylation array analyses of 33 women with X mosaicism indicate events preferentially involve the inactive X chromosome. Our results provide further evidence that the sex chromosomes undergo mosaic events more frequently than autosomes, which could have implications for understanding the underlying mechanisms of mosaic events and their possible contribution to risk for chronic diseases

Detectable clonal mosaicism and its relationship to aging and cancer

In an analysis of 31,717 cancer cases and 26,136 cancer-free controls from 13 genome-wide association studies, we observed large chromosomal abnormalities in a subset of clones in DNA obtained from blood or buccal samples. We observed mosaic abnormalities, either aneuploidy or copy-neutral loss of heterozygosity, of >2 Mb in size in autosomes of 517 individuals (0.89%), with abnormal cell proportions of between 7% and 95%. In cancer-free individuals, frequency increased with age, from 0.23% under 50 years to 1.91% between 75 and 79 years (P = 4.8 × 10(-8)). Mosaic abnormalities were more frequent in individuals with solid tumors (0.97% versus 0.74% in cancer-free individuals; odds ratio (OR) = 1.25; P = 0.016), with stronger association with cases who had DNA collected before diagnosis or treatment (OR = 1.45; P = 0.0005). Detectable mosaicism was also more common in individuals for whom DNA was collected at least 1 year before diagnosis with leukemia compared to cancer-free individuals (OR = 35.4; P = 3.8 × 10(-11)). These findings underscore the time-dependent nature of somatic events in the etiology of cancer and potentially other late-onset diseases

Patterns of sexual behaviors among unmarried adolescents and youth in three Asian cities

We examined patterns of sexual behaviors of unmarried adolescents and youth (UAY) in three Asian cities (Shanghai, Taipei, and Hanoi) and identified factors related to the timing of initial sexual experience. From analysis of a sample of 16 554 UAY aged 15–24 years recruited from Shanghai, Taipei, and Hanoi plus data collected from face-to-face interviews complemented by computer-assisted self-interviews for intimate questions, we learned: UAY in Shanghai, Taipei, and Hanoi have different sexual behaviors. Affluent economic status increases the likelihood of early initial sexual experiences. Higher educational attainment may delay initial intercourse. Compared with Shanghai UAY, study participants from Taipei and Hanoi were 3.64 times and 0.33 times as likely to participate intercourse. These data can provide a basis for developing effective government policies and social interventions