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Various Segments (various + segment)
Selected AbstractsDesign of an Ultrasound Contrast Agent for Myocardial PerfusionECHOCARDIOGRAPHY, Issue 2000Michel Schneider Ph.D. Myocardial contrast echography (MCE) has been a major research objective in cardiovascular ultrasound for almost two decades. The design of a contrast agent fulfilling the needs of MCE requires taking into consideration a number of points: a basic decision has to be made whether a deposit agent or a free-flowing agent would be more appropriate and whether an agent active at low/medium mechanical index (MI) is preferable to an agent active only at high MI; only a small percentage of the cardiac output enters the coronary microcirculation, which means that highly sensitive bubble detection methods, such as harmonic imaging or pulse inversion, are needed; the low velocity of blood in the microcirculation that leads to extensive bubble destruction during imaging means that intermittent imaging and/or an agent active at low MI is (are) required; the duration of the contrast effect must be sufficient to allow a complete examination and is affected by the rate of contrast administration; the performance of the contrast agent should not be equipment-dependent. The ultimate goal in MCE is to be able to quantify blood flow in the various segments to determine if adequate oxygenation is achieved. Ultrasound-mediated bubble destruction followed by the measurement of bubble replenishment kinetics opens new perspectives for quantification. SonoVue is a free-flowing ultrasound contrast agent made of sulphur hexafluoride microbubbles stabilized by a highly elastic phospholipid monolayer. SonoVue is able to produce myocardial opacification at a wide range of acoustic pressures and in particular at Mis as low as 0.1. Its performance is not equipment-dependent. Good results for myocardial opacification have been observed in all animal species tested (dogs, minipigs, rabbits), using continuous as well as intermittent imaging. Trials are in progress to demonstrate the clinical utility of SonoVue for rest and stress perfusion studies, in particular for the diagnosis of CAD, the detection of myocardial infarction, the assessment of the success of interventions and myocardial viability, and the detection of hibernating myocardium. [source] TV viewing and physical activity: a segment analysis for social marketingINTERNATIONAL JOURNAL OF NONPROFIT & VOLUNTARY SECTOR MARKETING, Issue 3 2008Satyendra Singh Elevated television viewing and physical inactivity promote sedentary behavior, leading to obesity. Yet, modifying the behavior has received a limited academic investigation. Thus, the purpose of this exploratory study is to develop segments relating to such behavior, and propose TV viewing-reduction and physical activity-enhancing strategies for the various segments. Using data from a mall, the multiple regression and analysis of variance (ANOVA) led to the identification of four segments: alert, inactive, action, and ideal. Results indicate that those engaged in physical activity appear to watch less TV, and that age and gender do not have a significant impact on TV viewing. The managers can use the findings, segments, and strategies to create appeals for target social marketing. Copyright © 2007 John Wiley & Sons, Ltd. [source] Morphological mechanisms for regulating blood flow through hepatic sinusoidsLIVER INTERNATIONAL, Issue 1 2000Robert S. McCuskey Abstract: This review summarizes what is known about the various morphological sites that regulate the distribution of blood flow to and from the sinusoids in the hepatic microvascular system. These sites potentially include the various segments of the afferent portal venules and hepatic arterioles, the sinusoids themselves, and central and hepatic venules. Given the paucity of smooth muscle in the walls of these vessels, various sinusoidal lining cells have been suggested to play a role in regulating the diameters of sinusoids and influencing the distribution and velocity of blood flow in these vessels. While sinusoidal endothelial cells have been demonstrated to be contractile and to exhibit sphincter function, attention has recently focused on the perisinusoidal stellate cell as the cell responsible for controlling the sinusoidal diameter. A very recent study, however, suggested that the principal site of vasoconstriction elicited by ET-1 was the pre-terminal portal venule. This raised the question of whether or not the diameters of sinusoids might decrease due to passive recoil when inflow is reduced or eliminated and intra-sinusoidal pressure falls. In more recent in vivo microscopic studies, clamping of the portal vein dramatically reduced sinusoidal blood flow as well as the diameters of sinusoids. The sinusoidal lumens rapidly returned to their initial diameters upon restoration of portal blood flow suggesting that sinusoidal blood pressure normally distends the sinusoidal wall which can recoil when the pressure drops. Stellate cells may be responsible for this reaction given the nature of their attachment to parenchymal cells by obliquely oriented microprojections from the lateral edges of their subendothelial processes. This suggests that care must be exercised when interpreting the mechanism for the reduction of sinusoidal diameters following drug administration without knowledge of changes occurring to the portal venous and hepatic inflow. [source] An innovative method of die design and evaluation of flow balance for thermoplastics extrusion profilesPOLYMER ENGINEERING & SCIENCE, Issue 9 2009Abbas Zolfaghari In this article, a computational and experimental method for flow balancing of a U-shaped die profile with nonuniform thicknesses is presented. The approach was to implement a flow restricting mechanism along the melt flow path. A parametric study based on the restrictor dimensions was carried out to attain a preliminary optimal design. Simulations were performed using Fluent software to analyze the flow velocity at the die exit. Experimental study was then carried out at various restrictor positions for the purpose of attaining a desirable flow balance. The velocity at various segments of the die exit was measured utilizing an innovative procedure by implementing the "separating blades." Experimental findings were compared with those of simulations which showed an acceptable agreement. The results suggest that a flexible die can be designed to achieve a flow balance under various processing conditions. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] A multi-attribute trade-off approach for advancing the management of marine wildlife tourism: a quantitative assessment of heterogeneous visitor preferencesAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009Christina A.D. Semeniuk Abstract 1.Wildlife tourism can be prone to unmitigated development to promote visitor satisfaction that is all too often progressed at the cost of ecological integrity. A manager is thus faced with the dual task of enhancing the tourist experience and protecting the wildlife species. Accordingly, this mandate requires research into how tourists would respond to proposed wildlife-management plans. 2.This study examines the heterogeneity of tourist preferences for wildlife management at a stingray-feeding attraction in the Cayman Islands, using a latent class stated preference choice model. A sample of visitors to Stingray City Sandbar (SCS) evaluated hypothetical wildlife viewing experiences in a discrete choice experiment. Its scenarios were characterized by seven attributes such as animal-feeding and handling rules, ecological outcomes, social crowding, and management cost (defined as a conservation access fee). 3.The latent class segmentation identified two groups in the population: approximately 68% preferred the implementation of fairly strict management rules, while the other 32% valued more the maintenance of status quo with its intensive human , wildlife interactions. Despite the differences between the ,pro-management' and the ,pro-current' segments, both exhibited a preference for the continuation of feeding and handling the stingrays (albeit at different levels of intensity) suggesting that one effective way to implement any management actions is to alter the promotional and marketing strategies for SCS. Other survey questions on trip experience, conservation values, and socio-demographics were used to define these classes further, with the main distinguishing trait being the level of concern for potential impacts occurring at SCS. The discrepancies between the two segments became most obvious when calculating their respective market shares of support for alternative management strategies. 4.This approach to determining visitor preferences can help explain how the various segments will be affected by management options, and therefore can provide the basis for developing feasible strategies that will assist wildlife managers in maximizing tourist satisfaction while achieving wildlife-protection goals. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||