3,787 research outputs found
Charged Black Hole in a Canonical Ensemble
We consider the thermodynamics of a charged black hole enclosed in a cavity.
The charge in the cavity and the temperature at the walls are fixed so that we
have a canonical ensemble. We derive the phase structure and stability of black
hole equilibrium states. We compare our results to that of other work which
uses asymptotically anti-de Sitter boundary conditions to define the
thermodynamics. The thermodynamic properties have extensive similarities which
suggest that the idea of AdS holography is more dependent on the existence of
the boundary than on the exact details of asymptotically AdS metrics.Comment: 9 pages; 4 multipart figure
Genetics and genetic tools in coral reef management 2011
This report forms a synthesis of current knowledge and future applications of genetics
in coral reef management. It is divided up into three parts, (1) the coral host, (2) the
Symbiodinium, and (3) other coral associated microbes. Within each of these parts
current knowledge is summarised and examples are provided to illustrate how this
knowledge may be applicable to the management of the Great Barrier Reef. The
synthesis ends with a summary of how it is all linked together and possible future
developments, uses and risks associated with the use of genetics in coral reef
management. Words in dark blue with a dotted underline are part of the glossary,
which can be found at the end of the document
On correlation between protein secondary structure, backbone bond angles, and side-chain orientations
We investigate the fine structure of the sp3 hybridized covalent bond
geometry that governs the tetrahedral architecture around the central
C carbon of a protein backbone, and for this we develop new
visualization techniques to analyze high resolution X-ray structures in Protein
Data Bank. We observe that there is a correlation between the deformations of
the ideal tetrahedral symmetry and the local secondary structure of the
protein. We propose a universal coarse grained energy function to describe the
ensuing side-chain geometry in terms of the C carbon orientations. The
energy function can model the side-chain geometry with a sub-atomic precision.
As an example we construct the C-C structure of HP35 chicken
villin headpiece. We obtain a configuration that deviates less than 0.4 \.A in
root-mean-square distance from the experimental X-ray structure
Two-Dimensional Flow Nanometry of Biological Nanoparticles for Accurate Determination of Their Size and Emission Intensity
Biological nanoparticles (BNPs) are of high interest due to their key role in
various biological processes and use as biomarkers. BNP size and molecular
composition are decisive for their functions, but simultaneous determination of
both properties with high accuracy remains challenging, which is a severe
limitation. Surface-sensitive microscopy allows one to precisely determine
fluorescence or scattering intensity, but not the size of individual BNPs. The
latter is better determined by tracking their random motion in bulk, but the
limited illumination volume for tracking this motion impedes reliable intensity
determination. We here show that attaching BNPs (specifically, vesicles and
functionalized gold NPs) to a supported lipid bilayer, subjecting them to a
hydrodynamic flow, and tracking their motion via surface-sensitive imaging
enable to determine their diffusion coefficients and flow-induced drift
velocities and to accurately quantify both BNP size and emission intensity. For
vesicles, the high accuracy is demonstrated by resolving the expected
radius-squared dependence of their fluorescence intensity.Comment: 28 pages, 5 figure
Elastic Energy and Phase Structure in a Continuous Spin Ising Chain with Applications to the Protein Folding Problem
We present a numerical Monte Carlo analysis of a continuos spin Ising chain
that can describe the statistical proterties of folded proteins. We find that
depending on the value of the Metropolis temperature, the model displays the
three known nontrivial phases of polymers: At low temperatures the model is in
a collapsed phase, at medium temperatures it is in a random walk phase, and at
high temperatures it enters the self-avoiding random walk phase. By
investigating the temperature dependence of the specific energy we confirm that
the transition between the collapsed phase and the random walk phase is a phase
transition, while the random walk phase and self-avoiding random walk phase are
separated from each other by a cross-over transition. We also compare the
predictions of the model to a phenomenological elastic energy formula, proposed
by Huang and Lei to describe folded proteins.Comment: 12 pages, 23 figures, RevTeX 4.
Memory and rejuvenation in a spin glass
The temperature dependence of the magnetisation of a Cu(Mn) spin glass (
57 K) has been investigated using weak probing magnetic fields ( =
0.5 or 0 Oe) and specific thermal protocols. The behaviour of the zero-field
cooled, thermoremanent and isothermal remanent magnetisation on (re-)cooling
the system from a temperature (40 K) where the system has been aged is
investigated. It is observed that the measured magnetisation is formed by two
parts: (i) a temperature- and observation time-dependent thermally activated
relaxational part governed by the age- and temperature-dependent response
function and the (latest) field change made at a lower temperature, superposed
on (ii) a weakly temperature-dependent frozen-in part. Interestingly we observe
that the spin configuration that is imprinted during an elongated halt in the
cooling, if it is accompanied by a field induced magnetisation, also includes a
unidirectional excess magnetisation that is recovered on returning to the
ageing temperature.Comment: EPL style; 7 pages, 5 figure
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