3,077 research outputs found
Charged False Vacuum Bubbles and the AdS/CFT Correspondence
We initiate a study of cosmology within the framework of Maldacena's AdS/CFT
correspondence. We present a comprehensive analysis of the classical motion of
a charged domain wall that separates an external Reissner-Nordstrom region of
spacetime (with small or vanishing cosmological constant) from an internal
de-Sitter region. The possible associated spacetime diagrams are drawn,
although in the classical case, an unambiguous prediction of what occurs at
late times in the interior region is not possible, since singularities and
Cauchy horizons form. We argue that, when the asymptotic region is anti-de
Sitter, the AdS/CFT correspondence gives a prescription for resolving the
curvature singularities and evolving solutions across the expected Cauchy
horizon. Some of our solutions contain inflating interiors, and we provide
evidence these can be patched onto solutions with smooth initial data,
circumventing an obstacle found by Farhi and Guth to creating an inflating
universe in the laboratory.Comment: 21 pages, 6 figures, latex, references and some comments adde
C-reactive protein: associations with haematological variables, cardiovascular risk factors and prevalent cardiovascular disease
C-reactive protein (CRP) has been proposed as a risk factor for cardiovascular disease; however, this association is confounded by mutual relationships with both classical and haematological cardiovascular risk factors. We, therefore, measured CRP with a high-sensitivity assay in stored plasma samples from 414 men and 515 women in the north Glasgow MONICA (MONItoring trends in CArdiovascular diseases) survey, to study its correlation with haematological variables, classical risk factors and prevalent cardiovascular disease. CRP correlated with age, oral contraceptive use, menopause and most classical cardiovascular risk factors (except blood pressure). CRP also correlated with plasma levels of the pro-inflammatory cytokine interleukin 6, and haematocrit, viscosity, red cell aggregation, white cell count, and coagulation factors [fibrinogen, factor (F) VII in women, FVIII, FIX] and inhibitors (antithrombin and protein C in women; protein S) but not coagulation activation markers. CRP was significantly associated with prevalent cardiovascular disease in both men (P = 0.03) and women (P = 0.009), however, the association became non-significant after adjustment for firstly classical risk factors, then fibrinogen. We conclude that correlations with classical and haematological risk factors account for a substantial component of the association of CRP with prevalent cardiovascular disease, but there is evidence of a residual, independent effect among women
Conservation of Supergravity Currents from Matrix Theory
In recent work by Kabat and Taylor, certain Matrix theory quantities have
been identified with the spatial moments of the supergravity stress-energy
tensor, membrane current, and fivebrane current. In this note, we determine the
relations between these moments required by current conservation, and prove
that these relations hold as exact Matrix Theory identities at finite N. This
establishes conservation of the effective supergravity currents (averaged over
the compact circle). In addition, the constraints of current conservation allow
us to deduce Matrix theory quantities corresponding to moments of the spatial
current of the longitudinal fivebrane charge, not previously identified.Comment: 11 pages, LaTeX, typos correcte
Does sticky blood predict a sticky end? Associations of blood viscosity, haematocrit and fibrinogen with mortality in the West of Scotland
There is increasing evidence that blood viscosity and its major determinants (haematocrit, plasma viscosity and fibrinogen) are associated with an increased risk of incident cardiovascular events; however, their associations with mortality are not established. We therefore studied the associations of these variables with cardiovascular events and total mortality in 1238 men and women aged 25-64 years, followed for 13 years in the first North Glasgow MONICA (MONItoring CArdiovascular disease) survey and West of Scotland centres in the Scottish Heart Health Study. After adjustment for age and sex, increasing whole blood viscosity, plasma viscosity, haematocrit and fibrinogen (analysed by both von Clauss and heat precipitation assays) were significantly associated with mortality. Only the association for fibrinogen (von Clauss assay) remained significant after adjustment for major cardiovascular risk factors. We conclude that clottable fibrinogen may be independently associated with mortality. However, the significance of this association, and the extent to which viscosity is associated with mortality, remain to be established in larger studies and meta-analyses
Ages on weathered Plio-Pleistocene tephra sequences, western North Island, New Zealand
Using the zircon fission-track method, we have obtained five ages on members of two strongly-weathered silicic, Pliocene-Pleistocene tephra sequences, the Kauroa and Hamilton Ash formations, in western North Island, New Zealand. These are the first numerical ages to be obtained directly on these deposits. Of the Kauroa Ash sequence, member K1 (basal unit) was dated at 2.24 ± 0.29 Ma, confirming a previous age of c. 2.25 Ma obtained (via tephrochronology)from K/Ar ages on associated basalt lava. Members K2 and K3 gave indistinguishable ages between 1.68 ± 0.12 and 1.43 ± 0.17 Ma. Member K12, a correlative of Oparau Tephra and probably also Ongatiti Ignimbrite, was dated at 1.28 ± 0.11 Ma, consistent with an age of 1.23 ± 0.02 Ma obtained by various methods on Ongatiti Ignimbrite. Palaeomagnetic measurements indicated that members K13 to K15 (top unit, Waiterimu Ash) are aged between c. 1.2 Ma and 0.78 Ma. Possible sources of the Kauroa Ash Formation include younger volcanic centres in the southern Coromandel Volcanic Zone or older volcanic centres in the Taupo Volcanic Zone, or both. Of the Hamilton Ash sequence, the basal member Ohinewai Ash (HI) was dated at 0.38 ± 0.04 Ma. This age matches those obtained by various methods on Rangitawa Tephra of 0.34-0.35 Ma, supporting correlation with this Whakamaru-caldera derived deposit. The origin of the other Hamilton Ash beds is unknown but various younger volcanic centres in the Taupo Volcanic Zone are possible sources. The topmost member, Tikotiko Ash (H6-H7), is estimated to be aged between c. 0.18 and 0.08 Ma. Various silicic pyroclastic deposits documented in North Island and in marine cores may be co-eval with members of the Kauroa Ash and Hamilton Ash sequences on the basis of their age
Preliminary Sunyaev Zel'dovich Observations of Galaxy Clusters with OCRA-p
We present 30 GHz Sunyaev Zel'dovich (SZ) observations of a sample of four
galaxy clusters with a prototype of the One Centimetre Receiver Array (OCRA-p)
which is mounted on the Torun 32-m telescope. The clusters (Cl0016+16,
MS0451.6-0305, MS1054.4-0321 and Abell 2218) are popular SZ targets and serve
as commissioning observations. All four are detected with clear significance
(4-6 sigma) and values for the central temperature decrements are in good
agreement with measurements reported in the literature. We believe that
systematic effects are successfully suppressed by our observing strategy. The
relatively short integration times required to obtain these results demonstrate
the power of OCRA-p and its successors for future SZ studies.Comment: 9 pages, 2 figures. Accepted by MNRAS, online earl
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