38 research outputs found
New Five Dimensional Black Holes Classified by Horizon Geometry, and a Bianchi VI Braneworld
We introduce two new families of solutions to the vacuum Einstein equations
with negative cosmological constant in 5 dimensions. These solutions are static
black holes whose horizons are modelled on the 3-geometries nilgeometry and
solvegeometry. Thus the horizons (and the exterior spacetimes) can be foliated
by compact 3-manifolds that are neither spherical, toroidal, hyperbolic, nor
product manifolds, and therefore are of a topological type not previously
encountered in black hole solutions. As an application, we use the
solvegeometry solutions to construct Bianchi VI braneworld cosmologies.Comment: LaTeX, 20 pages, 2 figures Typographical errors corrected, and
references to printed matter added in favour of preprints where possibl
Anti-de Sitter no-hair, AdS/CFT and the brane-world
We study the asymptotic behavior of the bulk spacetimes with the negative
cosmological constant in the context of the brane-world scenario. We show that,
in Euclidean bulk, or in Lorentzian static bulk, some sequences of
hypersurfaces with the positive Ricci scalar evolve to the warped geometries
like the anti-de Sitter spacetime. Based on the AdS/CFT correspondence, we
discuss that the positivity of the Ricci scalar is related to the stability of
CFT on the brane. In addition, the brane-world is described from the
holographic point of view. The asymptotic local structure of the conformal
infinity is also investigated.Comment: 6 pages, minor changes, to appear in Phys. Rev.
Anti-de Sitter Quotients: When Are They Black Holes?
We point out that the BTZ black holes, and their relatives, can be defined in
a cleaner way than they originally were. The covering space can be taken to be
anti-de Sitter space, period, while scri splits up into components due to
Misner singularities. Our definition permits us to choose between two
conflicting claims concerning BTZ black holes in 3+1 dimensions.Comment: 16 pages, 4 figures; minor polish adde
Accreting Millisecond X-Ray Pulsars
Accreting Millisecond X-Ray Pulsars (AMXPs) are astrophysical laboratories
without parallel in the study of extreme physics. In this chapter we review the
past fifteen years of discoveries in the field. We summarize the observations
of the fifteen known AMXPs, with a particular emphasis on the multi-wavelength
observations that have been carried out since the discovery of the first AMXP
in 1998. We review accretion torque theory, the pulse formation process, and
how AMXP observations have changed our view on the interaction of plasma and
magnetic fields in strong gravity. We also explain how the AMXPs have deepened
our understanding of the thermonuclear burst process, in particular the
phenomenon of burst oscillations. We conclude with a discussion of the open
problems that remain to be addressed in the future.Comment: Review to appear in "Timing neutron stars: pulsations, oscillations
and explosions", T. Belloni, M. Mendez, C.M. Zhang Eds., ASSL, Springer;
[revision with literature updated, several typos removed, 1 new AMXP added
Dietary and lifestyle determinants of acrylamide and glycidamide hemoglobin adducts in non-smoking postmenopausal women from the EPIC cohort
Purpose Acrylamide was classified as 'probably carcinogenic' to humans in 1994 by the International Agency for Research on Cancer. In 2002, public health concern increased when acrylamide was identified in starchy, plant-based foods, processed at high temperatures. The purpose of this study was to identify which food groups and lifestyle variables were determinants of hemoglobin adduct concentrations of acrylamide (HbAA) and glycidamide (HbGA) in 801 non-smoking postmenopausal women from eight countries in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Methods Biomarkers of internal exposure were measured in red blood cells (collected at baseline) by high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) . In this cross-sectional analysis, four dependent variables were evaluated: HbAA, HbGA, sum of total adducts (HbAA + HbGA), and their ratio (HbGA/HbAA). Simple and multiple regression analyses were used to identify determinants of the four outcome variables. All dependent variables (except HbGA/HbAA) and all independent variables were log-transformed (log2) to improve normality. Median (25th-75th percentile) HbAA and HbGA adduct levels were 41.3 (32.8-53.1) pmol/g Hb and 34.2 (25.4-46.9) pmol/g Hb, respectively. Results The main food group determinants of HbAA, HbGA, and HbAA + HbGA were biscuits, crackers, and dry cakes. Alcohol intake and body mass index were identified as the principal determinants of HbGA/HbAA. The total percent variation in HbAA, HbGA, HbAA + HbGA, and HbGA/HbAA explained in this study was 30, 26, 29, and 13 %, respectively. Conclusions Dietary and lifestyle factors explain a moderate proportion of acrylamide adduct variation in non-smoking postmenopausal women from the EPIC cohort
Circulating concentrations of vitamin D in relation to pancreatic cancer risk in European populations
Evidence from in vivo, in vitro and ecological studies are suggestive of a protective effect of vitamin D against pancreatic cancer (PC). However, this has not been confirmed by analytical epidemiological studies. We aimed to examine the association between pre-diagnostic circulating vitamin D concentrations and PC incidence in European populations. We conducted a pooled nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC) and the Nord-TrĂžndelag Health Study's second survey (HUNT2) cohorts. In total, 738 primary incident PC cases (EPIC nâ=â626; HUNT2 nâ=â112; median follow-upâ=â6.9 years) were matched to 738 controls. Vitamin D [25(OH)D2 and 25(OH)D3 combined] concentrations were determined using isotope-dilution liquid chromatography-tandem mass spectrometry. Conditional logistic regression models with adjustments for body mass index and smoking habits were used to estimate incidence rate ratios (IRRs) and 95% confidence intervals (95%CI). Compared with a reference category of >50 to 75 nmol/L vitamin D, the IRRs (95% CIs) were 0.71 (0.42â1.20); 0.94 (0.72â1.22); 1.12 (0.82â1.53) and 1.26 (0.79â2.01) for clinically pre-defined categories of â€25; >25 to 50; >75 to 100; and >100 nmol/L vitamin D, respectively (p for trendâ=â0.09). Corresponding analyses by quintiles of season-standardized vitamin D concentrations also did not reveal associations with PC risk (p for trendâ=â0.23). Although these findings among participants from the largest combination of European cohort studies to date show increasing effect estimates of PC risk with increasing pre-diagnostic concentrations of vitamin D, they are not statistically significant
Circulating concentrations of vitamin D in relation to pancreatic cancer risk in European populations
Evidence from in vivo, in vitro and ecological studies are suggestive of a protective effect of vitamin D against pancreatic cancer (PC). However, this has not been confirmed by analytical epidemiological studies. We aimed to examine the association between pre-diagnostic circulating vitamin D concentrations and PC incidence in European populations. We conducted a pooled nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC) and the Nord-TrĂžndelag Health Study's second survey (HUNT2) cohorts. In total, 738 primary incident PC cases (EPIC n = 626; HUNT2 n = 112; median follow-up = 6.9 years) were matched to 738 controls. Vitamin D [25(OH)D2 and 25(OH)D3 combined] concentrations were determined using isotope-dilution liquid chromatography-tandem mass spectrometry. Conditional logistic regression models with adjustments for body mass index and smoking habits were used to estimate incidence rate ratios (IRRs) and 95% confidence intervals (95%CI). Compared with a reference category of >50 to 75 nmol/L vitamin D, the IRRs (95% CIs) were 0.71 (0.42-1.20); 0.94 (0.72-1.22); 1.12 (0.82-1.53) and 1.26 (0.79-2.01) for clinically pre-defined categories of â€25; >25 to 50; >75 to 100; and >100 nmol/L vitamin D, respectively (p for trend = 0.09). Corresponding analyses by quintiles of season-standardized vitamin D concentrations also did not reveal associations with PC risk (p for trend = 0.23). Although these findings among participants from the largest combination of European cohort studies to date show increasing effect estimates of PC risk with increasing pre-diagnostic concentrations of vitamin D, they are not statistically significant