3,458 research outputs found
String Junctions and Bound States of Intersecting Branes
We study four-dimensional black hole configurations which result from
wrapping M5-branes on a Calabi-Yau manifold, as well as U-dual realizations.
Our aim is to understand the microscopic degrees of freedom responsible for the
existence of bound states of multiple branes. The details depend on the chosen
U-frame; in some cases, they are massless string junctions. We also identify a
perturbative description in which these states correspond to twisted strings of
intersecting D3-branes at an orbifold singularity. In each case, these are the
preponderant states of the spacetime infrared conformal field theory and
account for the entropy of the blackhole.Comment: 14 pages; 2 figures; uses latex with epsf and hyperref package
Nonperturbative dynamics for abstract (p,q) string networks
We describe abstract (p,q) string networks which are the string networks of
Sen without the information about their embedding in a background spacetime.
The non-perturbative dynamical formulation invented for spin networks, in terms
of causal evolution of dual triangulations, is applied to them. The formal
transition amplitudes are sums over discrete causal histories that evolve (p,q)
string networks. The dynamics depend on two free SL(2,Z) invariant functions
which describe the amplitudes for the local evolution moves.Comment: Latex, 12 pages, epsfig, 7 figures, minor change
Very low-density lipoprotein cholesterol may mediate a substantial component of the effect of obesity on myocardial infarction risk:the Copenhagen General Population Study
On the Lense-Thirring test with the Mars Global Surveyor in the gravitational field of Mars
I discuss some aspects of the recent test of frame-dragging performed by me
by exploiting the Root-Mean-Square (RMS) orbit overlap differences of the
out-of-plane component N of the orbit of the Mars Global Surveyor (MGS)
spacecraft in the gravitational field of Mars. A linear fit of the full time
series of the entire MGS data (4 February 1999-14 January 2005) yields a
normalized slope 1.03 +/- 0.41 (with 95% confidence bounds). Other linear fits
to different data sets confirm the agreement with general relativity. The huge
systematic effects induced by the mismodeling in the martian gravitational
field claimed by some authors are absent in the MGS out-of-plane record. The
non-gravitational forces affect at the same level of the gravitomagnetic one
the in-plane orbital components of MGS, not the out-of-plane one. Moreover,
they experience high-frequency variations which does not matter in the present
case in which secular effects are relevant.Comment: LaTex2e, 8 pages, no figures, no tables, 17 references. It refers to
K. Krogh, Class. Quantum Grav., 24, 5709-5715, 2007 based on
astro-ph/0701653. Final version to appear in CEJP (Central European Journal
of Physics
MiRNA-513a-5p inhibits progesterone receptor expression and constitutes a risk factor for breast cancer : The hOrmone and Diet in the ETiology of breast cancer prospective study
report was to investigate whether many years before the diagnosis of breast cancer miRNA expression is already disregulated. In order to test this hypothesis, we compared miRNAs extracted from leukocytes in healthy women who later developed breast cancer and in women who remain healthy during the whole 15-year follow-up time. Accordantly, we used a case-control study design nested in the hOrmone and Diet in the ETiology of breast cancer (ORDET) prospective cohort study addressing the possibility that miRNAs can serve as both early biomarkers and components of the hormonal etiological pathways leading to breast cancer development in premenopausal women. We compared leukocyte miRNA profiles of 191 incident premenopausal breast cancer cases and profiles of 191 women who remained healthy over a follow-up period of 20 years. The analysis identified 20 differentially expressed miRNAs in women candidate to develop breast cancer versus control women. The upregulated miRNAs, miR-513-a-5p, miR- 513b-5p and miR-513c-5p were among the most significantly deregulated miRNAs. In multivariate analysis, miR-513a-5p upregulation was directly and statistically significant associated with breast cancer risk (OR = 1.69; 95% CI 1.08-2.64; P = 0.0293). In addition, the upregulation of miR-513-a-5p displayed the strongest direct association with serum progesterone and testosterone levels. The experimental data corroborated the inhibitory function of miR-513a-5p on progesterone receptor expression confirming that progesterone receptor is a target of miR-513a-5p. The identification of upregulated miR-513a-5p with its oncogenic potential further validates the use of miRNAs as long-term biomarker of breast cancer risk
Dietary glycemic index, glycemic load, and cancer risk: Results from the EPIC-Italy study
Abstract Factors linked to glucose metabolism are involved in the etiology of several cancers. High glycemic index (GI) or high glycemic load (GL) diets, which chronically raise postprandial blood glucose, may increase cancer risk by affecting insulin-like growth factor. We prospectively investigated cancer risk and dietary GI/GL in the EPIC-Italy cohort. After a median 14.9 years, 5112 incident cancers and 2460 deaths were identified among 45,148 recruited adults. High GI was associated with increased risk of colon and bladder cancer. High GL was associated with: increased risk of colon cancer; increased risk of diabetes-related cancers; and decreased risk of rectal cancer. High intake of carbohydrate from high GI foods was significantly associated with increased risk of colon and diabetes-related cancers, but decreased risk of stomach cancer; whereas high intake of carbohydrates from low GI foods was associated with reduced colon cancer risk. In a Mediterranean population with high and varied carbohydrate intake, carbohydrates that strongly raise postprandial blood glucose may increase colon and bladder cancer risk, while the quantity of carbohydrate consumed may be involved in diabetes-related cancers. Further studies are needed to confirm the opposing effects of high dietary GL on risks of colon and rectal cancers
A new wrinkle on the enhancon
We generalize the basic enhancon solution of Johnson, Peet and Polchinski by
constructing solutions without spherical symmetry. A careful consideration of
boundary conditions at the enhancon surface indicates that the interior of the
supergravity solution is still flat space in the general case. We provide some
explicit analytic solutions where the enhancon locus is a prolate or oblate
sphere.Comment: 19 pages, no figure
Dietary total antioxidant capacity and colorectal cancer in the Italian EPIC cohort
Background
Colorectal cancer is the third most common cancer worldwide. Diet has been hypothesized as involved in colorectal cancer etiology, but few studies on the influence of total dietary antioxidant intake on colorectal cancer risk have been performed.
Methods
We investigated the association between colorectal cancer risk and the total antioxidant capacity (TAC) of the diet, and also of intake of selected antioxidants, in 45,194 persons enrolled in 5 centers (Florence, Naples, Ragusa, Turin and Varese) of the European Prospective
Investigation into Cancer and Nutrition (EPIC) Italy study. TAC was estimated by the Trolox equivalent antioxidant capacity (TEAC) assay. Hazard ratios (HRs) for developing colorectal cancer, and colon and rectal cancers separately, adjusted for confounders, were estimated for tertiles of TAC by Cox modeling, stratifying by center.
Results
Four hundred thirty-six colorectal cancers were diagnosed over a mean follow-up of 11.28 years. No significant association between dietary TAC and colorectal cancer incidence was found. However for the highest category of TAC compared to the lowest, risk of developing colon cancer was lower (HR: 0.63; 95% CI: 0.44\u20130.89, P trend: 0.008). By contrast, increasing TAC intake was associated with significantly increasing risks of rectal cancer (2nd tertile HR: 2.09; 95%CI: 1.19\u20133.66; 3rd tertile 2.48 95%CI: 1.32\u20134.66; P trend 0.007). Intakes of
vitamin C, vitamin E, and
f-carotene were not significantly associated with colorectal cancer risk. Conclusions
Further prospective studies are needed to confirm the contrasting effects of high total antioxidant intake on risk of colon and rectal cancers
Social Interactions vs Revisions, What is important for Promotion in Wikipedia?
In epistemic community, people are said to be selected on their knowledge
contribution to the project (articles, codes, etc.) However, the socialization
process is an important factor for inclusion, sustainability as a contributor,
and promotion. Finally, what does matter to be promoted? being a good
contributor? being a good animator? knowing the boss? We explore this question
looking at the process of election for administrator in the English Wikipedia
community. We modeled the candidates according to their revisions and/or social
attributes. These attributes are used to construct a predictive model of
promotion success, based on the candidates's past behavior, computed thanks to
a random forest algorithm.
Our model combining knowledge contribution variables and social networking
variables successfully explain 78% of the results which is better than the
former models. It also helps to refine the criterion for election. If the
number of knowledge contributions is the most important element, social
interactions come close second to explain the election. But being connected
with the future peers (the admins) can make the difference between success and
failure, making this epistemic community a very social community too
Friend or foe? The current epidemiologic evidence on selenium and human cancer risk.
Scientific opinion on the relationship between selenium and the risk of cancer has undergone radical change over the years, with selenium first viewed as a possible carcinogen in the 1940s then as a possible cancer preventive agent in the 1960s-2000s. More recently, randomized controlled trials have found no effect on cancer risk but suggest possible low-dose dermatologic and endocrine toxicity, and animal studies indicate both carcinogenic and cancer-preventive effects. A growing body of evidence from human and laboratory studies indicates dramatically different biological effects of the various inorganic and organic chemical forms of selenium, which may explain apparent inconsistencies across studies. These chemical form-specific effects also have important implications for exposure and health risk assessment. Overall, available epidemiologic evidence suggests no cancer preventive effect of increased selenium intake in healthy individuals and possible increased risk of other diseases and disorders
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