The Cerenkov effect revisited: from swimming ducks to zero modes in gravitational analogs

We present an interdisciplinary review of the generalized Cerenkov emission of radiation from uniformly moving sources in the different contexts of classical electromagnetism, superfluid hydrodynamics, and classical hydrodynamics. The details of each specific physical systems enter our theory via the dispersion law of the excitations. A geometrical recipe to obtain the emission patterns in both real and wavevector space from the geometrical shape of the dispersion law is discussed and applied to a number of cases of current experimental interest. Some consequences of these emission processes onto the stability of condensed-matter analogs of gravitational systems are finally illustrated.Comment: Lecture Notes at the IX SIGRAV School on "Analogue Gravity" in Como, Italy from May 16th-21th, 201

Rebuilding Resilient Shrimp Aquaculture in South-east Asia: Disease Management, Coastal Ecology and Decision Making

We contend there are currently two competing scenarios for the sustainable development of shrimp aquaculture in coastal areas of South-east Asia. First, a landscape approach where farming techniques for small-scale producers are integrated into intertidal areas in a way that the ecological functions of mangroves are maintained and disease controlled. Second, a closed-system approach where problems of disease and effluent are eliminated in closed recirculation ponds behind the intertidal zone controlled by industrial-scale producers. Moving towards either scenario requires a better understanding of the scaled interaction between the ecological, social and political dynamics underlying processes of change and possible threats to the resilience of mangrove forested coastal ecosystems. We discuss how the analytical concepts of resilience, uncertainty, risk and scale can contribute to a social-ecological system understanding of decision making related to shrimp production by exploring their use in the empirical research areas of coastal ecology, shrimp health management and epidemiology, livelihoods and governance in response to the two scenarios. The challenge for the science-policy divide is to ensure that the complexity of social and ecological change in coastal areas, as understood from these empirical areas, is simplified but not made so simple that management becomes ineffective in steering production to rebuild resilience and maintain social and ecological stability. The discussion leads to a transdisciplinary research agenda that can contribute to sustainable shrimp aquaculture in coastal areas.Other chapters from this boo

Coronary Artery Stenoses: Accuracy of 64-Detector Row CT Angiography in Segments with Mild, Moderate, or Severe Calcification-A Subanalysis of the CORE-64 Trial

Purpose: To evaluate the influence of cross-sectional arc calcification on the diagnostic accuracy of computed tomography (CT) angiography compared with conventional coronary angiography for the detection of obstructive coronary artery disease (CAD). Materials and Methods: Institutional Review Board approval and written informed consent were obtained from all centers and participants for this HIPAA-compliant study. Overall, 4511 segments from 371 symptomatic patients (279 men, 92 women; median age, 61 years [interquartile range, 53-67 years]) with clinical suspicion of CAD from the CORE-64 multi-center study were included in the analysis. Two independent blinded observers evaluated the percentage of diameter stenosis and the circumferential extent of calcium (arc calcium). The accuracy of quantitative multidetector CT angiography to depict substantial (>50%) stenoses was assessed by using quantitative coronary angiography (QCA). Cross-sectional arc calcium was rated on a segment level as follows: noncalcified or mild (180 degrees) calcification. Univariable and multivariable logistic regression, receiver operation characteristic curve, and clustering methods were used for statistical analyses. Results: A total of 1099 segments had mild calcification, 503 had moderate calcification, 338 had severe calcification, and 2571 segments were noncalcified. Calcified segments were highly associated (P < .001) with disagreement between CTA and QCA in multivariable analysis after controlling for sex, age, heart rate, and image quality. The prevalence of CAD was 5.4% in noncalcified segments, 15.0% in mildly calcified segments, 27.0% in moderately calcified segments, and 43.0% in severely calcified segments. A significant difference was found in area under the receiver operating characteristic curves (noncalcified: 0.86, mildly calcified: 0.85, moderately calcified: 0.82, severely calcified: 0.81; P < .05). Conclusion: In a symptomatic patient population, segment-based coronary artery calcification significantly decreased agreement between multidetector CT angiography and QCA to detect a coronary stenosis of at least 50%.Cardiovascular Aspects of Radiolog

Analysis of bolus formation in micropipette ejection systems

The ejection of drugs from micropipettes is practiced frequently in biomedical research and clinical studies however, little is known about the dynamics of this process. The fundamentals of disperse fluid injection via a capillary into an ambient immiscible fluid have been investigated extensively. Here, we experimentally investigate the bolus formation in micropipette ejection systems, where the injection and ambient fluid are the same. We experimentally measure the temporal evolution of the bolus formation in the same fluid. There are three different bolus formation mechanisms that arise from different Re t regimes: a) a nearly spherical bolus, b) a pear-like bolus, and c) a large distortion or axial jet. We examine the scaled dimensions of the bolus, R b/D t, L b/D t, H/D t, and α, as a function of the dimensionless parameters such as tip Reynolds number, Re t, dimensionless value of g/(D t . V t), the dimensionless time, tV t/D t, and the distance between the edge of the micropipette and the free surface, D/D t. The bolus radius for 0.2 < Re t < 30 grows according to t 1/2 in the entire time range, which allows us to estimate the time for complete bolus formation