6,576 research outputs found
Can the correlated stability conjecture be saved?
Correlated stability conjecture (CSC) proposed by Gubser and Mitra [1,2]
linked the thermodynamic and classical (in)stabilities of black branes. In [3]
it was shown that the thermodynamic instabilities, specifically the negative
specific heat, indeed result in the instabilities in the hydrodynamic spectrum
of holographically dual plasma excitations. Counter-examples of CSC were
presented in the context of black branes with scalar hair undergoing a
second-order phase transition [4,5]. The latter translationary invariant
horizons have scalar hair, raising the question whether the asymptotic
parameters of the scalar hair can be appropriately interpreted as additional
charges leading to a generalization of the thermodynamic stability criterion.
In this paper we show that the generalization of the thermodynamic stability
criterion of this type can not save CSC. We further present a simple
statistical model which makes it clear that thermodynamic and dynamical
(in)stabilities generically are not correlated.Comment: 9 pages, 2 figures; v2: JHEP versio
Characterisation of gastroenteritis associated adenoviruses in South Africa
Objective. To analyse adenovirus (Ad) numbers and types associated with paediatric gastro-enteritis in South AfricaSetting. Gauteng, 1994-1996.Methods. A total of 234 paediatric diarrhoeal stool samples were screened for Ad using commercial enzyme-linked iInmunosorbent assays (EUSAs). Adenoviral isolates were typed, where possibie, using restriction enzyme analysis.Results. Ad was detected in 23 (9.8%) specimens, of which 8 (34.8%) were found by subgroup F-specilic EUSA to contain Ad40 or 41. Six of these isolates were typed and 2 could not be typed. Of the remaining 15 specimens, 2 isolates had restriction profiles that did not correspond with known Ads, while 2were identified as Ad31 and 1 as a subgroup CAd. The remaining 10 specimens negative for Ad40/41 were noncultivable and could not be typed.Conclusions. The high percentage of non-eultivable Ads other than Ad40/41 is unusual, and may possibly indicate the prevalence of hexon variants of Ad40/41 or of emerging Ad types in South Africa
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The development and sea trials of a subsea holographic camera for large volume in-situ recording of marine organisms
We describe the development, construction and sea testing of an underwater holographic camera (HoloCam) for in situ recording of marine organisms and particles in large volumes of sea water. HoloCam comprises a laser, power supply,
holographic recording optics and plate holders, a water-tight housing and a support frame. Added to this are control electronics such that the entire camera is remotely operable and controllable from ship or dock-side. Uniquely the camera can simultaneously record both in-line and off-axis holograms using a pulsed frequency doubled Nd-YAG laser. In-line holography is capable of producing images of organisms with a resolution of better than 10 Pm (at concentrations up to a few thousand per cubic centimetre at the smallest sizes). Off-axis holograms of aquatic systems of up to 50,000 cm3 volume, have been recorded. Following initial laboratory testing, the holo-camera was evaluated in an observation tank and ultimately was tested in Loch Etive, Scotland. In-line and off-axis holograms were recorded to a depth of 100 m. We will present results on the test dives and evaluation of the camera performance
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HoloCam: A subsea holographic camera for recording marine organisms and particles
The HoloCam system is a major component of a multi-national multi-discipline project known as HoloMar (funded by the European Commission under the MAST III initiative). The project is concerned with the development of pulsed laser holography to analyse and monitor the populations of living organisms and inanimate particles within the world's oceans. We describe here the development, construction and evaluation of a prototype underwater camera, the purpose of which is to record marine organisms and particles, in-situ. Recording using holography provides several advantages over conventional sampling methods in that it allows non-intrusive, non-destructive, high-resolution imaging of large volumes (up to 10^5 cm^3) in three dimensions. The camera incorporates both in-line and off-axis holographic techniques, which allows particles from a few micrometres to tens of centimetres to be captured. In tandem with development of the HoloCam, a dedicated holographic replay system and an automated data extraction and image processing facility are being developed. These will allow, optimisation of the images recorded by the camera, identification of species and particle concentration plotting
Maladaptation and the paradox of robustness in evolution
Background. Organisms use a variety of mechanisms to protect themselves
against perturbations. For example, repair mechanisms fix damage, feedback
loops keep homeostatic systems at their setpoints, and biochemical filters
distinguish signal from noise. Such buffering mechanisms are often discussed in
terms of robustness, which may be measured by reduced sensitivity of
performance to perturbations. Methodology/Principal Findings. I use a
mathematical model to analyze the evolutionary dynamics of robustness in order
to understand aspects of organismal design by natural selection. I focus on two
characters: one character performs an adaptive task; the other character
buffers the performance of the first character against perturbations. Increased
perturbations favor enhanced buffering and robustness, which in turn decreases
sensitivity and reduces the intensity of natural selection on the adaptive
character. Reduced selective pressure on the adaptive character often leads to
a less costly, lower performance trait. Conclusions/Significance. The paradox
of robustness arises from evolutionary dynamics: enhanced robustness causes an
evolutionary reduction in the adaptive performance of the target character,
leading to a degree of maladaptation compared to what could be achieved by
natural selection in the absence of robustness mechanisms. Over evolutionary
time, buffering traits may become layered on top of each other, while the
underlying adaptive traits become replaced by cheaper, lower performance
components. The paradox of robustness has widespread implications for
understanding organismal design
Comparison of the Near-Threshold Production of eta- and K-Mesons in Proton-Proton Collisions
The pp -> pp eta and pp -> pLambda K^+ reactions near threshold are dominated
by the first and second S_11 resonance respectively. It is shown that a
one-pion-exchange model exciting these isobars reproduces well the ratio of the
production cross sections. The consequences for this and other channels are
discussed.Comment: 10 pages, LaTeX2e, 1 eps-figur
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A holographic system for subsea recording and analysis of plankton and other marine particles
We report here details of the design, development, initial testing and field-deployment of the HOLOMAR system for in-situ subsea holography and analysis of marine plankton and nonliving particles. HOLOMAR comprises a submersible holographic camera ("HoloCam") able to record in-line and off-axis holograms at depths down to 100 m, together with specialised reconstruction hardware ("HoloScan") linked to custom image processing and classification software. The HoloCam consists of a laser and power supply, holographic recording optics and holographic plate holders, a water-tight housing and a support frame. It utilises two basic holographic geometries, in-line and off-axis such that a wide range of species, sizes and concentrations can be recorded. After holograms have been recorded and processed they are reconstructed in full three-dimensional detail in air in a dedicated replay facility. A computer-controlled microscope, using video cameras to record the image at a given depth, is used to digitise the scene. Specially written software extracts a binarised image of an object in its true focal plane and is classified using a neural network. The HoloCam was deployed on two separate cruises in a Scottish sea loch (Loch Etive) to a depth of 100 m and over 300 holograms were recorded
Determining bacterial and host contributions to the human salivary metabolome
BACKGROUND: Salivary metabolomics is rapidly advancing. AIM AND METHODS: To determine the extent to which salivary metabolites reflects host or microbial metabolic activity whole-mouth saliva (WMS), parotid saliva (PS) and plasma collected contemporaneously from healthy volunteers were analysed by (1)H-NMR spectroscopy. Spectra underwent principal component analysis and k-means cluster analysis and metabolite quantification. WMS samples were cultured on both sucrose and peptide-enriched media. Correlation between metabolite concentration and bacterial load was assessed. RESULTS: WMS contained abundant short-chain fatty acids (SCFAs), which were minimal in PS and plasma. WMS spectral exhibited greater inter-individual variation than those of PS or plasma (6.7 and 3.6 fold, respectively), likely reflecting diversity of microbial metabolomes. WMS bacterial load correlated strongly with SCFA levels. Additional WMS metabolites including amines, amino acids and organic acids were positively correlated with bacterial load. Lactate, urea and citrate appeared to enter WMS via PS and the circulation. Urea correlated inversely with WMS bacterial load. CONCLUSIONS: Oral microbiota contribute significantly to the WMS metabolome. Several WMS metabolites (lactate, urea and citrate) are derived from the host circulation. WMS may be particularly useful to aid diagnosis of conditions reflective of dysbiosis. WMS could also complement other gastrointestinal fluids in future metabolomic studies
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MICE Hall PPS â User's Guide
This document describes the use of the MICE Hall Personnel Protection System ("PPS"). The PPS uses hardware logic and interlocks to track the state of ISIS, the MICE Hall and some experiment subsystems, so as to prevent or limit certain activities during unsuitable situations and therefore ensure the safety of personnel in the Hall
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