The cerebrovascular effects of adrenaline, noradrenaline and dopamine infusions under propofol and isoflurane anaesthesia in sheep

Publisher's copy made available with the permission of the publisher © Australian Society of AnaesthetistsInfusions of catecholamines are frequently administered to patients receiving propofol or isoflurane anaesthesia. Interactions between these drugs may affect regional circulations, such as the brain. The aim of this animal (sheep) study was to determine the effects of ramped infusions of adrenaline, noradrenaline (10, 20, 40 µg/min) and dopamine (10, 20, 40 µg/kg/min) on cerebral blood flow (CBF), intracranial pressure (ICP), cerebrovascular resistance (CVR) and cerebral metabolic rate for oxygen (CMRO₂). These measurements were made under awake physiological conditions, and during continuous propofol (15 mg/min) or 2% isoflurane anaesthesia. All three catecholamines significantly and equivalently increased mean arterial pressure from baseline in a dose-dependent manner in the three cohorts (P0.05). Under propofol (n=6) and isoflurane (n=6), all three catecholamines significantly increased CBF (P<0.001). Dopamine caused the greatest increase in CBF, and was associated with significant increases in ICP (awake: P<0.001; propofol P<0.05; isoflurane P<0.001) and CVR (isoflurane P<0.05). No significant changes in CMRO₂ were demonstrated. Under propofol and isoflurane anaesthesia, the cerebrovascular effects of catecholamines were significantly different from the awake, physiological state, with dopamine demonstrating the most pronounced effects, particularly under propofol. Dopamine-induced hyperaemia was associated with other cerebrovascular changes. In the presence of an equivalent effect on mean arterial pressure, the exaggerated cerebrovascular effects under anaesthesia appear to be centrally mediated, possibly induced by propofol- or isoflurane-dependent changes in blood-brain barrier permeability, thereby causing a direct influence on the cerebral vasculature.http://www.aaic.net.au/Article.asp?D=200205

Energy efficiency of iron-boron-silicon metallic glasses in sulfuric acid solutions

A criterion of the energy efficiency of iron–boron–silicon metallic glasses in sulfuric acid solutions is proposed for the first time. The criterion has been derived based on calculating the limit of the ratio value of the conductivity of a metallic glass in aqueous solution to the conductivity of the metallic glass in air. In other words, the conductivity ratio of a metallic glass in aqueous solution to the conductivity of the metallic glass in air  = 1, was applied to determine the energy efficiency of the metallic glass in the aqueous solution when the conductivity of a metallic glass in air became equal (decreased) to the steady conductivity of the metallic glass in aqueous solution as a function of time of the exposure of the metallic glass to the aqueous solution. This criterion was not only used to determine the energy efficiency of different metallic glasses, but also, the criterion was used to determine the energy efficiency of metallic glasses exposed to a wide range of sulfuric acid concentrations. These conductivity values were determined by the electrochemical impedance spectroscopy (EIS). In addition, the criterion can be applied under diverse test conditions with a predetermined period of the operational life of the metallic glasses as functional materials. Furthermore, variations of the energy efficiency of the metallic glasses as a function of the acid concentration and time were produced by fitting the experimental data to a numerical model using a nonlinear regression method. The profiles of the metallic glasses exhibit a less conservative behavior of the energy efficiency than the proposed analytical criterion

Comparing and validating models of driver steering behaviour in collision avoidance and vehicle stabilisation

A number of driver models were fitted to a large data set of human truck driving, from a simulated near-crash, low-friction scenario, yielding two main insights: steering to avoid a collision was best described as an open-loop manoeuvre of predetermined duration, but with situation-adapted amplitude, and subsequent vehicle stabilisation could to a large extent be accounted for by a simple yaw rate nulling control law. These two phenomena, which could be hypothesised to generalise to passenger car driving, were found to determine the ability of four driver models adopted from the literature to fit the human data. Based on the obtained results, it is argued that the concept of internal vehicle models may be less valuable when modelling driver behaviour in non-routine situations such as near-crashes, where behaviour may be better described as direct responses to salient perceptual cues. Some methodological issues in comparing and validating driver models are also discussed

A framework for automatic semantic video annotation

The rapidly increasing quantity of publicly available videos has driven research into developing automatic tools for indexing, rating, searching and retrieval. Textual semantic representations, such as tagging, labelling and annotation, are often important factors in the process of indexing any video, because of their user-friendly way of representing the semantics appropriate for search and retrieval. Ideally, this annotation should be inspired by the human cognitive way of perceiving and of describing videos. The difference between the low-level visual contents and the corresponding human perception is referred to as the ‘semantic gap’. Tackling this gap is even harder in the case of unconstrained videos, mainly due to the lack of any previous information about the analyzed video on the one hand, and the huge amount of generic knowledge required on the other. This paper introduces a framework for the Automatic Semantic Annotation of unconstrained videos. The proposed framework utilizes two non-domain-specific layers: low-level visual similarity matching, and an annotation analysis that employs commonsense knowledgebases. Commonsense ontology is created by incorporating multiple-structured semantic relationships. Experiments and black-box tests are carried out on standard video databases for action recognition and video information retrieval. White-box tests examine the performance of the individual intermediate layers of the framework, and the evaluation of the results and the statistical analysis show that integrating visual similarity matching with commonsense semantic relationships provides an effective approach to automated video annotation

Entropy in the natural time-domain

A surrogate data analysis is presented, which is based on the fluctuations of the ``entropy'' $S$ defined in the natural time-domain [Phys. Rev. E {\bf 68}, 031106, 2003]. This entropy is not a static one as, for example, the Shannon entropy. The analysis is applied to three types of time-series, i.e., seismic electric signals, ``artificial'' noises and electrocardiograms, and ``recognizes'' the non-Markovianity in all these signals. Furthermore, it differentiates the electrocardiograms of healthy humans from those of the sudden cardiac death ones. If $\delta S$ and $\delta S_{shuf}$ denote the standard deviation when calculating the entropy by means of a time-window sweeping through the original data and the ``shuffled'' (randomized) data, respectively, it seems that the ratio $\delta S_{shuf}/\delta S$ plays a key-role. The physical meaning of $\delta S_{shuf}$ is investigated.Comment: Published in Physical Review

Transvaginal ultrasound simulation and its effect on trainee confidence levels: A replacement for initial clinical training?

Introduction: The ScanTrainer transvaginal ultrasound simulator has been developed to facilitate initial training of transvaginal ultrasound skills without patient contact. Due to the intimate nature of the examination and in some cases, limited training opportunities, the need for simulation-based education in ultrasound has gained momentum. Currently, research into the effectiveness of the ScanTrainer is limited. Methods: A mixed method study was conducted in a single institution between October 2011 and January 2012. Participants were recruited using convenience sampling and allocated to the control (clinical training) or experimental (simulation training) group following a pre-test. After 10 hours of their allocated transvaginal ultrasound training method a post-test assessment was conducted and the results statistically analysed. Participants then experienced the alternative method of training and completed questionnaires. The results were used to inform semi-structured interviews for each group. Interview transcripts were interpreted using theme analysis. Results: A small number of doctors completed the study, nine (82%) out of the 11 recruited. The majority of participants (89%) felt that practice on the ScanTrainer can increase confidence prior to attempting a real transvaginal ultrasound scan. Average scores showed that the simulation training group outperformed the clinical training group on overall score and each of the five post-test components. No statistically significant differences were demonstrated for overall score (U = 13, P = 0.556) or the five components (P = 0.190–1). Conclusions: Transvaginal ultrasound training on the ScanTrainer has the potential to replace initial clinical training; however, further larger trials are required to evaluate. Clinically significant outcomes exist if the ScanTrainer training is proven to be more effective than initial clinical training. The ScanTrainer prepares a trainee and builds confidence to progress to clinical scanning, which has the potential to improve the patient experience

A New Method for Classifying Flares of UV Ceti Type Stars: Differences Between Slow and Fast Flares

In this study, a new method is presented to classify flares derived from the photoelectric photometry of UV Ceti type stars. This method is based on statistical analyses using an independent samples t-test. The data used in analyses were obtained from four flare stars observed between 2004 and 2007. The total number of flares obtained in the observations of AD Leo, EV Lac, EQ Peg, and V1054 Oph is 321 in the standard Johnson U band. As a result flares can be separated into two types, slow and fast, depending on the ratio of flare decay time to flare rise time. The ratio is below 3.5 for all slow flares, while it is above 3.5 for all fast flares. Also, according to the independent samples t-test, there is a difference of about 157 s between equivalent durations of slow and fast flares. In addition, there are significant differences between amplitudes and rise times of slow and fast flares.Comment: 46 pages, 7 figures, 4 tabels, 2010AJ....140..483

A stochastic evolutionary model for capturing human dynamics

The recent interest in human dynamics has led researchers to investigate the stochastic processes that explain human behaviour in various contexts. Here we propose a generative model to capture the dynamics of survival analysis, traditionally employed in clinical trials and reliability analysis in engineering. We derive a general solution for the model in the form of a product, and then a continuous approximation to the solution via the renewal equation describing age-structured population dynamics. This enables us to model a wide range of survival distributions, according to the choice of the mortality distribution. We provide empirical evidence for the validity of the model from a longitudinal data set of popular search engine queries over 114 months, showing that the survival function of these queries is closely matched by the solution for our model with power-law mortality