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Circulation System (circulation + system)
Selected AbstractsPrincipal features of impact-generated hydrothermal circulation systems: mineralogical and geochemical evidenceGEOFLUIDS (ELECTRONIC), Issue 3 2005MIKHAIL V. NAUMOVArticle first published online: 14 JUL 200 Abstract Any hypervelocity impact generates a hydrothermal circulation system in resulting craters. Common characteristics of hydrothermal fluids mobilized within impact structures are considered, based on mineralogical and geochemical investigations, to date. There is similarity between the hydrothermal mineral associations in the majority of terrestrial craters; an assemblage of clay minerals,zeolites,calcite,pyrite is predominant. Combining mineralogical, geochemical, fluid inclusion, and stable isotope data, the distinctive characteristics of impact-generated hydrothermal fluids can be distinguished as follows: (i) superficial, meteoric and ground water and, possibly, products of dehydration and degassing of minerals under shock are the sources of hot water solutions; (ii) shocked target rocks are sources of the mineral components of the solutions; (iii) flow of fluids occurs mainly in the liquid state; (iv) high rates of flow are likely (10,4 to 10,3 m s,1); (v) fluids are predominantly aqueous and of low salinity; (vi) fluids are weakly alkaline to near-neutral (pH 6,8) and are supersaturated in silica during the entire hydrothermal process because of the strong predominance of shock-disordered aluminosilicates and fusion glasses in the host rocks; and (vii) variations in the properties of the circulating solutions, as well as the spatial distribution of secondary mineral assemblages are controlled by tempera ure gradients within the circulation cell and by a progressive cooling of the impact crater. Products of impact-generated hydrothermal processes are similar to the hydrothermal mineralization in volcanic areas, as well as in modern geothermal systems, but impacts are always characterized by a retrograde sequence of alteration minerals. [source] The Indian Ocean dipole , the unsung driver of climatic variability in East AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2007Rob Marchant Abstract A growing body of evidence suggests that an independent ocean circulation system in the Indian Ocean, the Indian Ocean dipole (IOD), is partly responsible for driving climate variability of the surrounding landmasses. The IOD had traditionally been viewed as an artefact of the El Niño,Southern Oscillation (ENSO) system although increasingly the evidence is amassing that it is separate and distinct phenomenon. We review the causes of the IOD, how it develops within the Indian Ocean, the relationships with ENSO, and the consequences for East African climate dynamics and associated impacts on ecosystems, in particular along the Eastern Arc Mountains of Kenya and Tanzania. We evaluate current research initiatives focussed on characterizing and constraining the IOD and examine how effective these will be in determining climate change impacts on East African ecosystems and how such predictive capacity can be used in developing policy. Résumé Un nombre croissant de preuves suggère qu'un système indépendant de circulation des eaux de l'océan Indien, le Dipôle de l'océan Indien (IOD), est partiellement responsable de la variabilité du climat des terres environnantes. L'IOD est habituellement considéré comme un artéfact de l'Oscillation Méridionale El Niño (ENSO) bien que les preuves s'accumulent pour montrer que c'est un phénomène séparé et distinct. Nous revoyons les causes de l'IOD, comment il se développe au sein de l'océan Indien, ses liens avec l'ENSO et ses conséquences pour la dynamique du climat de l'Afrique de l'Est, ainsi que son impact sur les écosystèmes, particulièrement sur la chaîne des montagnes orientales au Kenya et en Tanzanie. Nous évaluons les initiatives de recherches actuelles qui visent à caractériser et à circonscrire l'impact de l'IOD et nous examinons dans quelle mesure elles seront efficaces pour déterminer les impacts du changement climatique sur les écosystèmes est-africains et comment on pourra se servir d'un tel moyen de prévision pour mettre au point des politiques. [source] A novel CD4-conjugated ultraviolet light-activated photocatalyst inactivates HIV-1 and SIV efficiently,JOURNAL OF MEDICAL VIROLOGY, Issue 8 2008Koushi Yamaguchi Abstract In this study, we found that the electric potential derived from the redox reaction of ultraviolet (UV)-illuminated CD4-conjugated titanium dioxide (TiO2) inactivated a wide range of high-titered primary HIV-1 isolates, regardless of virus co-receptor usage or genetic clade. In vitro incubation of HIV-1 isolates with CD4-conjugated TiO2 (CD4-TiO2) followed by UV illumination led to inhibition of viral infectivity in both H9 cells and peripheral blood mononuclear cells as well as to the complete inactivation of plasma virions from HIV-1-infected individuals. Treatment with a newly established extra-corporeal circulation system with the photocatalyst in rhesus macaques completely inactivated plasma virus in the system and effectively reduced the infectious plasma viral load. Furthermore, plasma viremia and infectious viral loads were controlled following a second therapeutic photocatalyst treatment during primary SIVmac239 infection of macaques. Our findings suggest that this therapeutic immunophysical strategy may help control human immunodeficiency viral infection in vivo. J. Med. Virol. 80:1322,1331, 2008. © 2008 Wiley-Liss, Inc. [source] The effect of gravity on surface temperatures of plant leavesPLANT CELL & ENVIRONMENT, Issue 4 2003Y. KITAYA ABSTRACT A fundamental study was conducted to develop a facility having an adequate air circulation system for growing healthy plants over a long-term under microgravity conditions in space. To clarify the effects of gravity on heat exchange between plant leaves and the ambient air, surface temperatures of sweet potato and barley leaves and replica leaves made of wet paper and copper were evaluated at gravity levels of 0.01, 1.0, 1.5 and 2.0 g for 20 s each during parabolic aeroplane flights. Thermal images were captured using infrared thermography at an air temperature of 26 °C, a relative humidity of 18% and an irradiance of 260 W m,2. Mean leaf temperatures increased by 0.9,1.0 °C with decreasing gravity levels from 1.0 to 0.01 g and decreased by 0.5 °C with increasing gravity levels from 1.0 to 2.0 g. The increase in leaf temperatures was at most 1.9 °C for sweet potato leaves over 20 s as gravity decreased from 1.0 to 0.01 g. The boundary layer conductance to sensible heat exchange decreased by 5% when the gravity decreased from 1.0 to 0.01 g at the air velocity of 0.2 m s,1. The decrease in the boundary layer conductance with decrease in the gravity levels was more significant in a lower air velocity. Heat exchange between leaves and the ambient air was more retarded at lower gravity levels because of less sensible and latent heat transfers with less heat convection. [source] Comparative Assessment of Coagulation Changes Induced by Two Different Types of Heart,Lung MachineARTIFICIAL ORGANS, Issue 1 2010Niels Rahe-Meyer Abstract The cardiopulmonary bypass (CPB) used in heart surgery has a deleterious effect on hemostasis. The aim of our study was to assess by means of standard laboratory and point-of-care methods changes induced by CPB in coagulation parameters, particularly in platelet function, and to determine whether these changes differ depending on the type of heart,lung machine (HLM) used: minimal extracorporeal circulation system (MECC) and standard HLM. The study enrolled 88 patients scheduled for coronary artery bypass surgery performed on pump. Forty-four interventions were performed with MECC and 44 with standard HLM. Blood was sampled preoperatively, after 30 min on CPB, after weaning from CPB, and 24 h postoperatively. Coagulation and platelet function were assessed using multiple electrode aggregometry (MEA), rotation thromboelastometry, as well as standard laboratory tests. Rotation thromboelastometry and standard laboratory reflected significantly impaired hemostasis after weaning from CPB but no significant differences between the two groups at different time points. Aggregation decreased significantly in both groups as early as 30 min after the institution of CPB (P < 0.05, Mann,Whitney U -test) and recovered within the first 24 h postoperatively, without reaching the preoperative level. Intraoperatively, aggregometry values reflected a significantly more severe reduction of platelet function in standard HLM group than in the MECC group (P < 0.01, ProcMixed test). Our findings suggest that MEA and thromboelastometry reflect impairment of coagulation in cardiac surgery performed on different types of HLM and that platelet function is less affected by MECC than by standard HLM. [source] Optimal Pressure Regulation of the Pneumatic Ventricular Assist Device With Bellows-Type DriverARTIFICIAL ORGANS, Issue 8 2009Jung Joo Lee Abstract The bellows-type pneumatic ventricular assist device (VAD) generates pneumatic pressure with compression of bellows instead of using an air compressor. This VAD driver has a small volume that is suitable for portable devices. However, improper pneumatic pressure setup can not only cause a lack of adequate flow generation, but also cause durability problems. In this study, a pneumatic pressure regulation system for optimal operation of the bellows-type VAD has been developed. The optimal pneumatic pressure conditions according to various afterload conditions aiming for optimal flow rates were investigated, and an afterload estimation algorithm was developed. The developed regulation system, which consists of a pressure sensor and a two-way solenoid valve, estimates the current afterload and regulates the pneumatic pressure to the optimal point for the current afterload condition. Experiments were performed in a mock circulation system. The afterload estimation algorithm showed sufficient performance with the standard deviation of error, 8.8 mm Hg. The flow rate could be stably regulated with a developed system under various afterload conditions. The shortcoming of a bellows-type VAD could be handled with this simple pressure regulation system. [source] Principal features of impact-generated hydrothermal circulation systems: mineralogical and geochemical evidenceGEOFLUIDS (ELECTRONIC), Issue 3 2005MIKHAIL V. NAUMOVArticle first published online: 14 JUL 200 Abstract Any hypervelocity impact generates a hydrothermal circulation system in resulting craters. Common characteristics of hydrothermal fluids mobilized within impact structures are considered, based on mineralogical and geochemical investigations, to date. There is similarity between the hydrothermal mineral associations in the majority of terrestrial craters; an assemblage of clay minerals,zeolites,calcite,pyrite is predominant. Combining mineralogical, geochemical, fluid inclusion, and stable isotope data, the distinctive characteristics of impact-generated hydrothermal fluids can be distinguished as follows: (i) superficial, meteoric and ground water and, possibly, products of dehydration and degassing of minerals under shock are the sources of hot water solutions; (ii) shocked target rocks are sources of the mineral components of the solutions; (iii) flow of fluids occurs mainly in the liquid state; (iv) high rates of flow are likely (10,4 to 10,3 m s,1); (v) fluids are predominantly aqueous and of low salinity; (vi) fluids are weakly alkaline to near-neutral (pH 6,8) and are supersaturated in silica during the entire hydrothermal process because of the strong predominance of shock-disordered aluminosilicates and fusion glasses in the host rocks; and (vii) variations in the properties of the circulating solutions, as well as the spatial distribution of secondary mineral assemblages are controlled by tempera ure gradients within the circulation cell and by a progressive cooling of the impact crater. Products of impact-generated hydrothermal processes are similar to the hydrothermal mineralization in volcanic areas, as well as in modern geothermal systems, but impacts are always characterized by a retrograde sequence of alteration minerals. [source] An Initial Analysis of River Discharge and Rainfall in Coastal New South Wales, Australia Using Wavelet TransformsGEOGRAPHICAL RESEARCH, Issue 3 2001H. Kirkup In many coastal catchments of south eastern New South Wales, Australia, changes in river morphology are a response to human impact superimposed on spatial and temporal patterns of variability in precipitation and discharge. Understanding, and preferably quantifying, spatial and temporal patterns of hydrologic variability are essential to understanding natural changes, and to separate these from artificial changes in river systems. Prediction and management of water resources are also dependent upon this understanding. We assess the variability in precipitation and discharge using the wavelet transform which projects the time series of data into a three dimensional surface of frequency, amplitude and time. The analysis reveals that changes across time often reflect changes in individual seasons and may be linked to changes in particular seasonal atmospheric circulation systems. Strong perturbations in the analysis of one catchment are consistent with documented, geomorphically-effective, flooding sequences. The characteristics of the series in the transformed data reveal interesting differences at certain times and scales which may be a reflection of changes in larger scale atmospheric processes. [source] Nanofluids: A novel promising flow stabilizer in natural circulation systemsAICHE JOURNAL, Issue 1 2009Arun Kumar Nayak First page of article [source] The impact of mesoscale convective systems on the surface and boundary-layer structure in West Africa: Case-studies from the AMMA campaign 2006THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 648 2010Juliane Schwendike Abstract Within the framework of the AMMA project, atmospheric, surface and soil observations were performed during the pre-onset phase of the monsoon (Special Observing Period SOP 1) and during the summer monsoon (SOP 2) in 2006. Based on several case-studies the paper investigates the impact of mesoscale convective systems (MCSs) on the surface and boundary layer (PBL), the recovery time of the surface and the PBL after MCS passages, and the differences between the two monsoon phases. In the pre-MCS environment the mean conditional and convective instabilities were higher in SOP 1 than in SOP 2 (e.g. CAPE = 1815 J kg,1 and CAPE = 1295 J kg,1, respectively). In both monsoon phases these instabilities, which were strongly reduced by MCSs, recovered within less than 2 days. Precipitation of the MCSs and the resulting soil moisture increase caused a significant decrease in the surface temperature by up to 10 K and an increase in evapotranspiration by up to 2.5 mm d,1. In both phases of the monsoon, these surface anomalies and, hence, the conditions favourable for triggering MCSs by thermally induced circulation systems, diminished largely within 2 to 3 days. Due to the repeated passage of the first MCSs at intervals of a few days during SOP 1, the surface properties exhibited trends towards higher soil moisture, evapotranspiration and humidity, and lower albedo, temperature and Bowen ratio. After two weeks only, the mean conditions present in the summer monsoon were reached. In SOP 2 no significant trends could be detected. Copyright © 2010 Royal Meteorological Society [source] | |||||||||||||