Dynamic changes of the extracellular matrix after acute tako-tsubo cardiomyopathy

Funding Tenovus Scotland. Grant number G13/10.Peer reviewedPublisher PD

Statistical Entropy of Nonextremal Four-Dimensional Black Holes and U-Duality

We identify the states in string theory which are responsible for the entropy of near-extremal rotating four-dimensional black holes in $N=8$ supergravity. For black holes far from extremality (with no rotation), the Bekenstein-Hawking entropy is exactly matched by a mysterious duality invariant extension of the formulas derived for near-extremal black holes states.Comment: 9 pages, harvma

210Po and 210Pb distributions during a phytoplankton bloom in the North Atlantic: Implications for POC export

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Horowitz, E. J., Cochran, J. K., Bacon, M. P., & Hirschberg, D. J. 210Po and 210Pb distributions during a phytoplankton bloom in the North Atlantic: implications for POC export. Deep-Sea Research Part I: Oceanographic Research Papers, 164, (2020): 103339, doi:10.1016/j.dsr.2020.103339.During the North Atlantic Bloom Experiment (NABE) of the Joint Global Ocean Flux Study (JGOFS), water column sampling for particulate and dissolved 210Po and 210Pb was performed four times (26 April and 4, 20, 30 May 1989) during a month-long Lagrangian time-series occupation of the NABE site, as well as one-time samplings at stations during transit to and from the site. There are few prior studies documenting short-term changes in 210Po and 210Pb profiles over the course of a phytoplankton bloom, and we interpret the profiles in terms of the classical “steady-state” (SS) approach used in most studies, as well as by using a non-steady state approach suggested by the temporal evolution of the profiles. Changes in 210Po profiles during a bloom are expectable as this radionuclide is scavenged and exported. During NABE, 210Pb profiles also displayed non-steady state, with significant increases in upper water column inventory occurring midway through the experiment. Export of 210Po from the upper 150 m using the classic “steady-state” model shows increases from 0.5 ± 8.5 dpm m−2 d−1 to 68.2 ± 4.2 dpm m−2 d−1 over the ~one-month occupation. Application of a non-steady state model, including changes in both 210Pb and 210Po profiles, gives higher 210Po export fluxes. Detailed depth profiles of particulate organic carbon (>0.8 μm) and particulate 210Po (>0.4 μm) are available from the 20 and 30 May samplings and show maxima in POC/Po at ~37 m. Applying the POC/210Po ratios at 150 m to the “steady state” 210Po fluxes yields POC export from the upper 150 m of 8.2 ± 1.5 mmol C m− 2 d−1 on 20 May and 6.0 ± 1.6 mmol C m−2 d−1 on 30 May. The non-steady state model applied to the interval 20 to 30 May yields POC export of 24.3 mmol C m−2 d−1. The non-steady state (NSS) 210Po-derived POC fluxes are comparable to, but somewhat less than, those estimated previously from 234Th/238U disequilibrium for the same time interval (37.3 and 45.0 mmol m−2 d−1, depending on the POC/Th ratio used). In comparison, POC fluxes measured with a floating sediment trap deployed at 150 m from 20 to 30 May were 11.6 mmol m−2 d−1. These results suggest that non-steady state Po-derived POC fluxes during the NABE agree well with those derived from 234Th/238U disequilibrium and agree with sediment trap fluxes within a factor of ~2. However, unlike the 234Th-POC flux proxy, non-steady stage changes in profiles of 210Pb, the precursor of 210Po, must be considered.We are grateful to T. Hammar and A. Fleer (WHOI) for assistance at sea and in the laboratory. This work was supported originally by National Science Foundation (United States) grant OCE-8819544 to JKC and more recently by OCE-1736591. We thank Stephen Thurston (American Museum of Natural History) for graphics assistance Robert Aller, Steven Beaupre, and two anonymous reviewers for helpful comments

Relativistic mean-field study of neutron-rich nuclei

A relativistic mean-field model is used to study the ground-state properties of neutron-rich nuclei. Nonlinear isoscalar-isovector terms, unconstrained by present day phenomenology, are added to the model Lagrangian in order to modify the poorly known density dependence of the symmetry energy. These new terms soften the symmetry energy and reshape the theoretical neutron drip line without compromising the agreement with existing ground-state information. A strong correlation between the neutron radius of 208Pb and the binding energy of valence orbitals is found: the smaller the neutron radius of 208Pb, the weaker the binding energy of the last occupied neutron orbital. Thus, models with the softest symmetry energy are the first ones to drip neutrons. Further, in anticipation of the upcoming one-percent measurement of the neutron radius of 208Pb at the Thomas Jefferson Laboratory, a close relationship between the neutron radius of 208Pb and neutron radii of elements of relevance to atomic parity-violating experiments is established.Comment: 14 pages, 5 figure

Plane waves with weak singularities

We study a class of time dependent solutions of the vacuum Einstein equations which are plane waves with weak null singularities. This singularity is weak in the sense that though the tidal forces diverge at the singularity, the rate of divergence is such that the distortion suffered by a freely falling observer remains finite. Among such weak singular plane waves there is a sub-class which do not exhibit large back reaction in the presence of test scalar probes. String propagation in these backgrounds is smooth and there is a natural way to continue the metric beyond the singularity. This continued metric admits string propagation without the string becoming infinitely excited. We construct a one parameter family of smooth metrics which are at a finite distance in the space of metrics from the extended metric and a well defined operator in the string sigma model which resolves the singularity.Comment: 22 pages, Added references and clarifying comment

Statistical Origin of Black Hole Entropy in Matrix Theory

The statistical entropy of black holes in M-theory is considered. Assuming Matrix theory is the discretized light-cone quantization of a theory with eleven-dimensional Lorentz invariance, we map the counting problem onto the original Gibbons-Hawking calculation of the thermodynamic entropy.Comment: 9 pages, harvmac, (v2 References added, typo fixed), (v3 Some clarifying comments added.

Black Hole Hair Removal: Non-linear Analysis

BMPV black holes in flat transverse space and in Taub-NUT space have identical near horizon geometries but different microscopic degeneracies. It has been proposed that this difference can be accounted for by different contribution to the degeneracies of these black holes from hair modes, -- degrees of freedom living outside the horizon. In this paper we explicitly construct the hair modes of these two black holes as finite bosonic and fermionic deformations of the black hole solution satisfying the full non-linear equations of motion of supergravity and preserving the supersymmetry of the original solutions. Special care is taken to ensure that these solutions do not have any curvature singularity at the future horizon when viewed as the full ten dimensional geometry. We show that after removing the contribution due to the hair degrees of freedom from the microscopic partition function, the partition functions of the two black holes agree.Comment: 40 pages, LaTe

Brane cosmology with a bulk scalar field

We consider ``cosmologically symmetric'' (i.e. solutions with homogeneity and isotropy along three spatial dimensions) five-dimensional spacetimes with a scalar field and a three-brane representing our universe. We write Einstein's equations in a conformal gauge, using light-cone coordinates. We obtain explicit solutions: a. assuming proportionality between the scalar field and the logarithm of the (bulk) scale factor; b. assuming separable solutions. We then discuss the cosmology in the brane nduced by these solutions.Comment: 24 pages, Latex, no figur

Spatial Hypersurfaces in Causal Set Cosmology

Within the causal set approach to quantum gravity, a discrete analog of a spacelike region is a set of unrelated elements, or an antichain. In the continuum approximation of the theory, a moment-of-time hypersurface is well represented by an inextendible antichain. We construct a richer structure corresponding to a thickening of this antichain containing non-trivial geometric and topological information. We find that covariant observables can be associated with such thickened antichains and transitions between them, in classical stochastic growth models of causal sets. This construction highlights the difference between the covariant measure on causal set cosmology and the standard sum-over-histories approach: the measure is assigned to completed histories rather than to histories on a restricted spacetime region. The resulting re-phrasing of the sum-over-histories may be fruitful in other approaches to quantum gravity.Comment: Revtex, 12 pages, 2 figure

AdS/CFT and the Information Paradox

The information paradox in the quantum evolution of black holes is studied within the framework of the AdS/CFT correspondence. The unitarity of the CFT strongly suggests that all information about an initial state that forms a black hole is returned in the Hawking radiation. The CFT dynamics implies an information retention time of order the black hole lifetime. This fact determines many qualitative properties of the non-local effects that must show up in a semi-classical effective theory in the bulk. We argue that no violations of causality are apparent to local observers, but the semi-classical theory in the bulk duplicates degrees of freedom inside and outside the event horizon. Non-local quantum effects are required to eliminate this redundancy. This leads to a breakdown of the usual classical-quantum correspondence principle in Lorentzian black hole spacetimes.Comment: 16 pages, harvmac, reference added, minor correction