1,171 research outputs found
Probing the optical readout characteristics of Fabry-Perot ultrasound sensors through realistic modelling
The Fabry-Perot interferometer (FPI) is widely used in photoacoustic imaging (PAI) as an ultrasound (US) sensor due to its high sensitivity to weak US waves. Such high sensitivity is important as it allows for increasing the depth in tissue at which PAI can access, thus strongly influencing its clinical applicability. FPI sensitivity is impacted by many factors including the FPI mirror reflectivity, focussed beam spot size, FPI cavity thickness and aberrations introduced by the optical readout system. Improving FPI sensitivity requires a mathematical model of its optical response which takes all of these factors into account. Previous attempts to construct such a model have been critically limited by unrealistic assumptions. In this work we have developed a general model of FPI optical readout which based upon electromagnetic theory. By making very few assumptions, the model is able to replicate experimental results and allows insight to be gained into the operating principles of the sensor
Outcome and factors associated with hospital mortality in patients with impaired left ventricular function undergoing coronary artery bypass grafting: where do we stand?
Objective: Impaired ventricular function is a known risk factor for mortality after coronary artery bypass grafting however increasingly more patients with impaired ventricular function are referred for surgery. Currently no large data is available from Pakistan regarding this aspect of coronary surgery. Our objectives were to find out the hospital mortality and mid term functional improvement in patients with impaired ventricular function undergoing coronary artery by pass grafting and identify the risk factors for mortality. Methodology: Retrospective analysis of preoperative, operative and postoperative variables of patients with impaired ventricular function who were operated for isolated first time coronary artery bypass between October 2006 to April 2009. Results: Total 190 patients with impaired ventricular function underwent isolated first time coronary artery bypass grafting during this period with a male predominance (82.6%). Mean ejection fraction of the group was 25.4±5.3%. Mean predicted mortality on logistic Euro score was 10.9±2.7%. Actual in hospital mortality of the group was 4.7% which is comparable to contemporary published results. Multivariate analysis identified use of intra aortic balloon pump, non use of internal mammary artery and preoperative NYHA functional class as factors associated with mortality. Conclusion: Coronary artery bypass grafting can be performed in patients with impaired ventricular function with acceptable hospital mortality and mid term functional improvement
Order Effects of Ballot Position without Information-Induced Confirmatory Bias
Candidate list positions have been shown to influence decision making when voters have limited candidate information (e.g. Miller and Krosnick, 1998; Brockington, 2003). Here, a primacy advantage is observed due to a greater number of positive arguments generated for early list candidates (Krosnick, 1991). The present study examined list position effects when an absence of information precludes such a confirmatory bias heuristic. We report the first large scale low-information experimental election where candidate position is fully counterbalanced. Seven hundred and twenty participants voted in a mock election where the position of 6 fictitious and meaningless parties was counterbalanced across the electorate. Analysis by position revealed that significantly fewer votes were allocated to the terminal parties (Experiment 1). In addition, Experiment 1 reported preliminary evidence of an alphabetical bias (consistent with Bagley, 1966). However, this positional bias was not present in a methodological replication using six genuine UK political parties (Experiment 2). This suggests that in situations of pure guessing, the heuristic shifts from the primacy benefiting confirmatory bias to an alternative heuristic that prejudices the first and last parties. These findings suggest that whilst the UK general electoral process may be largely immune to positional prejudice, English local elections (in which there can be multiple candidates from the same party) and multiple preference ranking systems (Scottish Local Government and London Mayoral Elections) could be susceptible to both positional and alphabetical biases
Occurrence and bioconcentration of micropollutants in Silver Perch (Bidyanus bidyanus) in a reclaimed water reservoir
© 2018 This study examined the occurrence of 49 micropollutants in reclaimed water and Silver Perch (Bidyanus bidyanus) living in a reclaimed water reservoir. The numbers of micropollutants detected in reclaimed water, Silver Perch liver, and Silver Perch flesh were 20, 23, and 19, respectively. Concentrations of all micropollutants in reclaimed water, except benzotriazole, were well below the Australian Guideline for Recycled Water (AGRW) values for potable purposes. The concentration of benzotriazole in reclaimed water was 675 ± 130 ng/L while the AGRW value for this compound was 7 ng/L. Not all micropollutants detected in the water phase were identified in the Silver Perch flesh and liver tissues. Likewise, not all micropollutants detected in the Silver Perch flesh and liver were identified in the reclaimed water. In general, micropollutant concentrations in the liver were higher than in the flesh. Perfluorooctane sulfonate (PFOS) was detected at a trace level in reclaimed water well below the AGRW guideline value for potable purposes, but showed a high and medium bioconcentration factor in Silver Perch liver and flesh, respectively. In addition, the risk quotient for PFOS was medium and high when considering its concentration in Silver Perch liver and flesh, respectively. Results reported here highlight the need to evaluate multiple parameters for a comprehensive risk assessment. The results also single out PFOS as a notable contaminant of concern for further investigation
Factors regulating the relationship between total and size-fractionated chlorophyll-a in coastal waters of the Red Sea
This is the final version. Available from the publisher via the DOI in this record.Phytoplankton biomass and size structure are recognized as key ecological indicators.
With the aim to quantify the relationship between these two ecological indicators in
tropical waters and understand controlling factors, we analyzed the total chlorophyll-a
concentration, a measure of phytoplankton biomass, and its partitioning into three
size classes of phytoplankton, using a series of observations collected at coastal
sites in the central Red Sea. Over a period of 4 years, measurements of flow
cytometry, size-fractionated chlorophyll-a concentration, and physical-chemical variables
were collected near Thuwal in Saudi Arabia. We fitted a three-component model
to the size-fractionated chlorophyll-a data to quantify the relationship between
total chlorophyll and that in three size classes of phytoplankton [pico- (<2µm),
nano- (2–20µm) and micro-phytoplankton (>20µm)]. The model has an advantage over
other more empirical methods in that its parameters are interpretable, expressed as
the maximum chlorophyll-a concentration of small phytoplankton (pico- and combined
pico-nanophytoplankton, C
m
p
and C
m
p,n
, respectively) and the fractional contribution of
these two size classes to total chlorophyll-a as it tends to zero (Dp and Dp,n). Residuals
between the model and the data (model minus data) were compared with a range of
other environmental variables available in the dataset. Residuals in pico- and combined
pico-nanophytoplankton fractions of total chlorophyll-a were significantly correlated with
water temperature (positively) and picoeukaryote cell number (negatively). We conducted
a running fit of the model with increasing temperature and found a negative relationship
between temperature and parameters C
m
p
and C
m
p,n
and a positive relationship between
temperature and parameters Dp and Dp,n. By harnessing the relative red fluorescence
of the flow cytometric data, we show that picoeukaryotes, which are higher in cell
number in winter (cold) than summer (warm), contain higher chlorophyll per cell than other
picophytoplankton and are slightly larger in size, possibly explaining the temperature
shift in model parameters, though further evidence is needed to substantiate this
Brewin et al. Total and Size-Fractionated Chlorophyll-a in the Red Sea
finding. Our results emphasize the importance of knowing the water temperature and
taxonomic composition of phytoplankton within each size class when understanding their
relative contribution to total chlorophyll. Furthermore, our results have implications for the
development of algorithms for inferring size-fractionated chlorophyll from satellite data,
and for how the partitioning of total chlorophyll into the three size classes may change in
a future oceanUK National Centre for Earth Observation (NCEO)King Abdullah University for Science and Technology (KAUST) Office of Sponsored Research (OSR): Virtual Red Sea Initiativ
On the intuitive understanding of interrogating Fabry-Perot etalon with a focused beam
Polymer film Fabry-Perot (FP) sensors are commonly used to detect ultrasound for Photoacoustic (PA) imaging providing high resolution 3D images. Such high image quality is possible due to their low Noise Equivalent Pressure (NEP) because of their broadband response and small acoustic element size. The acoustic element size is small (<100 μm) as defined, to first approximation, by the spot size of the focused interrogation beam. However, it has been difficult until now to gain an accurate intuitive understanding of the working principle of FP sensors interrogated with a focused beam. To overcome this limitation a highly realistic rigorous model of the FP sensor's optical response has used to establish a new intuitive understanding. The origin of fringe depth reduction and asymmetry associated with the FP sensors optical response is explained using the model developed
Design of Resonant Optical Cavities for Ultrasound Detection using Rigorous Electromagnetic Modelling
Detection of very weak ultrasound waves with a Fabry-Perot interferometer has enabled a new range of biomedical applications such as photoacoustic imaging. We propose a realistic model of the optical readout of this device valid for arbitrary focussed readout beams and optical fibre based detection
Asthma hospitalisation trends from 2010 to 2015: variation among rural and metropolitan Australians
Abstract Background Asthma remains a leading cause of illness, where primary care can assist to reduce hospitalisations through prevention, controlling acute episodes, and overall management of asthma. In Victoria, Asthma hospitalisations were as high as 3.1 hospitalisations per 1000 population in 1993–94. The primary aims of this study are to: determine if changes in asthma hospitalisations have occurred between 2010 and 2015; determine the key factors that impact asthma hospitalisation over time; and verify whether rural and urban asthma hospitalisations are disparate. A secondary aim of the study is to compare 2010–2015 results with asthma data prior to 2010. Methods Hospital separation data from 1 July 2010 to 30 June 2015 were obtained through the Victorian Admitted Episodes Dataset and other agencies. Data included sex, age, Local Government Area, private or public patient, length of stay, and type of discharge. Asthma and predictor variables were analysed according to hospital separation rates after adjusting for smoking and sex. Hierarchical multiple regression examined the association between asthma and predictor variables. Results During the study period, 49,529 asthma hospital separations occurred, of which 77.5% were in metropolitan hospitals, 55.4% hospital separations were aged 0–14 years, and 21.7% were privately funded. State-wide hospital separations were 1.85 per 1000 population and were consistently higher in metropolitan compared to rural areas (1.93 vs 1.64 per 1000 population). When data among metropolitan adults aged 15 and over were analysed, an increase in the proportion of smokers in the population was reflected by an increase in the number of hospital separations (Adj OR 1.035). Further, among rural and metropolitan children aged 0–14 the only predictor of asthma hospital separations was sex, where metropolitan male children had higher odds of separation than metropolitan females of the same age (Adj OR 4.297). There was no statistically meaningful difference for separation rates between males and females in rural areas. Conclusions We demonstrated a higher overall hospital separation rate in metropolitan Victoria. For children in metropolitan areas, males were hospitalised at higher rates than females, while the inverse was demonstrated for children residing in rural areas. Therefore, optimising asthma management requires consideration of the patient’s age, gender and residential context. Primary health care may play a leading role in increasing health literacy for patients in order to improve self-management and health-seeking behaviour
Visual parameter optimisation for biomedical image processing
Background: Biomedical image processing methods require users to optimise input parameters to ensure high quality
output. This presents two challenges. First, it is difficult to optimise multiple input parameters for multiple
input images. Second, it is difficult to achieve an understanding of underlying algorithms, in particular, relationships
between input and output.
Results: We present a visualisation method that transforms users’ ability to understand algorithm behaviour by
integrating input and output, and by supporting exploration of their relationships. We discuss its application to a
colour deconvolution technique for stained histology images and show how it enabled a domain expert to
identify suitable parameter values for the deconvolution of two types of images, and metrics to quantify
deconvolution performance. It also enabled a breakthrough in understanding by invalidating an underlying
assumption about the algorithm.
Conclusions: The visualisation method presented here provides analysis capability for multiple inputs and outputs
in biomedical image processing that is not supported by previous analysis software. The analysis supported by our
method is not feasible with conventional trial-and-error approaches
Metastatic collecting duct carcinoma of the kidney treated with sunitinib
Collecting duct carcinoma (CDC) of the kidney is a rare and aggressive malignant tumor arising from the distal collecting tubules which has been shown to have a poor response to several kinds of systemic therapy. We present a case of metastatic CDC that responded favorably to a multiple tyrosine kinase inhibitor, sunitinib, achieving a partial response in both lung and skeletal metastases. To our knowledge, this is the first report showing therapeutic activity of sunitinib against CDC. Considering these findings, it would be worthwhile prospectively investigating the role of multiple tyrosine kinase inhibitors, particularly sunitinib, in the management of metastatic CDC
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