12,905 research outputs found
Detection of electrode asymmetry in electrochemical noise analysis
The electrochemical noise resistance is a calculation that can be used for estimating the rate of corrosion of a pair of metal samples purely from the electrochemical noise that they generate. Ideally these metal samples (electrodes) would be identical, but it is not uncommon, for various reasons, for the electrodes to be significantly different. In that case, the theory linking the noise resistance to the more conventional electrochemical parameter, the polarisation resistance, breaks down. This link is important because it is only via the polarisation resistance that noise resistance can be used for corrosion rate estimation. It is therefore important to be able to detect an asymmetric electrode pair. This paper describes how the cross correlation between voltage and current noise can be used to detect an asymmetr
Dynamic trust models for ubiquitous computing environments
A significant characteristic of ubiquitous computing is the need for interactions of highly mobile entities to be secure: secure both for the entity and the environment in which the entity operates. Moreover, ubiquitous computing is also characterised by partial views over the state of the global environment, implying that we cannot guarantee that an environment can always verify the properties of the mobile entity that it has just received. Secure in this context encompasses both the need for cryptographic security and the need for trust, on the part of both parties, that the interaction is functioning as expected. In this paper we make a broad assumption that trust and cryptographic security can be considered as orthogonal concerns (i.e. an entity might encrypt a deliberately incorrect answer to a legitimate request). We assume the existence of reliable encryption techniques and focus on the characteristics of a model that supports the management of the trust relationships between two entities during an interaction in a ubiquitous environment
Initial states and infrared physics in locally de Sitter spacetime
The long wavelength physics in a de Sitter region depends on the initial
quantum state. While such long wavelength physics is under control for massive
fields near the Hartle-Hawking vacuum state, such initial states make unnatural
assumptions about initial data outside the region of causal contact of a local
observer. We argue that a reasonable approximation to a maximum entropy state,
one that makes minimal assumptions outside an observer's horizon volume, is one
where a cutoff is placed on a surface bounded by timelike geodesics, just
outside the horizon. For sufficiently early times, such a cutoff induces
secular logarithmic divergences with the expansion of the region. For massive
fields, these effects sum to finite corrections at sufficiently late times. The
difference between the cutoff correlators and Hartle-Hawking correlators
provides a measure of the theoretical uncertainty due to lack of knowledge of
the initial state in causally disconnected regions. These differences are
negligible for primordial inflation, but can become significant during epochs
with very long-lived de Sitter regions, such as we may be entering now.Comment: 19 pages, 4 figures, references adde
Holographic representation of local bulk operators
The Lorentzian AdS/CFT correspondence implies a map between local operators
in supergravity and non-local operators in the CFT. By explicit computation we
construct CFT operators which are dual to local bulk fields in the
semiclassical limit. The computation is done for general dimension in global,
Poincare and Rindler coordinates. We find that the CFT operators can be taken
to have compact support in a region of the complexified boundary whose size is
set by the bulk radial position. We show that at finite N the number of
independent commuting operators localized within a bulk volume saturates the
holographic bound.Comment: 36 pages, LaTeX, 4 eps figure
A study of blood contamination of Siqveland matrix bands
AIMS To use a sensitive forensic test to measure blood contamination of used Siqveland matrix bands following routine cleaning and sterilisation procedures in general dental practice. MATERIALS AND METHODS: Sixteen general dental practices in the West of Scotland participated. Details of instrument cleaning procedures were recorded for each practice. A total of 133 Siqveland matrix bands were recovered following cleaning and sterilisation and were examined for residual blood contamination by the Kastle-Meyer test, a well-recognised forensic technique. RESULTS: Ultrasonic baths were used for the cleaning of 62 (47%) bands and retainers and the remainder (53%) were hand scrubbed prior to autoclaving. Overall, 21% of the matrix bands and 19% of the retainers gave a positive Kastle-Meyer test, indicative of residual blood contamination, following cleaning and sterilisation. In relation to cleaning method, 34% of hand-scrubbed bands and 32% of hand-scrubbed retainers were positive for residual blood by the Kastle-Meyer test compared with 6% and 3% respectively of ultrasonically cleaned bands and retainers (P less than 0.001). CONCLUSIONS: If Siqveland matrix bands are re-processed in the assembled state, then adequate pre-sterilisation cleaning cannot be achieved reliably. Ultrasonic baths are significantly more effective than hand cleaning for these items of equipment
Instrumentation for hydrogen slush storage containers
Hydrogen liquid and slush tank continuous inventory during ground storag
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