Coastal Tidally-driven Circulation and the Role of Water Exchange in the Linkage Between Tropical Coastal Ecosystems

1997 ◽  
Vol 45 (2) ◽  
pp. 177-187 ◽  
Author(s):  
J.U. Kitheka
Keyword(s):  
Water Exchange ◽  
Coastal Ecosystems ◽  
Tidally Driven

Pressure cycles and the water economy of insects

1988 ◽  
Vol 318 (1190) ◽  
pp. 377-407 ◽  
Keyword(s):  
Body Temperature ◽  
Water Exchange ◽  
Vapour Phase ◽  
The Body ◽  
Tracheal System ◽  
Water Economy ◽  
Insect Wings ◽  
Pressure Cycle ◽  
Respiratory Gases

Water exchange between insects and their environment via the vapour phase includes influx and efflux components. The pressure cycle theory postulates that insects (and some other arthropods) can regulate the relative rates of influx and efflux of water vapour by modulating hydrostatic pressures at a vapour-liquid interface by compressing or expanding a sealed, gas-filled cavity. Some such cavities, like the tracheal system, could be compressed by elevated pressure in all or part of the haemocoele. Others, perhaps including the muscular rectum of flea prepupae, could be compressed by intrinsic muscles. Maddrell Insect Physiol . 8, 199 (1971)) suggested a pressure cycle mechanism of this kind to account for rectal uptake of water vapour in Thermobia but did not find it compatible with quantitative information then available. Newer evidence conforms better with the proposed mechanism. Cyclical pressure changes are of widespread occurrence in insects and have sometimes been shown to depend on water status. Evidence is reviewed for the role of the tracheal system as an avenue for net exchange of water between the insect and its environment. Because water and respiratory gases share common pathways, most published findings fail to distinguish between the conventional view that the tracheal system has evolved as a site for distribution and exchange of respiratory gases and that any water exchange occurring in it is generally incidental and nonadaptive, and the theory proposed here. The pressure cycle theory offers a supplementary explanation not incompatible with evidence so far available. The relative importance of water economy and respiratory exchange in the functioning of compressible cavities such as the tracheal system remains to be explored. Some further implications of the pressure cycle theory are discussed. Consideration is given to the possible involvement of vapour-phase transport in the internal redistribution of water within the body. It is suggested that some insect wings may constitute internal vapour-liquid exchange sites, where water can move from the body fluids to the intratracheal gas. Ambient and body temperature must influence rates of vapour-liquid mass transfer. If elevated body temperature promotes evaporative discharge of the metabolic water burden that has been shown to accumulate during flight in some large insects, their minimum threshold thoracic temperature for sustained flight may relate to the maintenance of water balance. The role of water economy in the early evolution of insect wings is considered. Pressure cycles might help to maintain water balance in surface-breathing insects living in fresh and saline waters, but the turbulence of the surface of the open sea might prevent truly marine forms from using this mechanism.

The Role of Water Exchange in Attaining Maximum Relaxivities for Dendrimeric MRI Contrast Agents

1996 ◽  
Vol 2 (12) ◽  
pp. 1607-1615 ◽  
Author(s):  
Éva Tóth ◽  
Dirk Pubanz ◽  
Sylvain Vauthey ◽  
Lothar Helm ◽  
André E. Merbach
Keyword(s):  
Contrast Agents ◽  
Water Exchange ◽  
Mri Contrast Agents ◽  
Mri Contrast

scholarly journals Role of eNOS in water exchange index maintenance-MRI studies

2017 ◽  
Vol 886 ◽  
pp. 012002 ◽  
Author(s):  
D Atochin ◽  
M Litvak ◽  
S Huang ◽  
Y R Kim ◽  
P Huang
Keyword(s):  
Water Exchange ◽  
Mri Studies ◽  
Index Maintenance

scholarly journals Role of elision water exchange in formation of the Yamalo-Kara depression hydrodynamic field

2019 ◽  
pp. 248-261
Author(s):  
D. A. Novikov
Keyword(s):  
Water Exchange ◽  
Oil And Gas ◽  
Water Pressure ◽  
Hydrodynamic Characteristics ◽  
Gas Generation ◽  
Pressure System ◽  
Stage Of Development ◽  
Capacitive Properties ◽  
Unique Material

The unique material has been compiled on the hydrodynamics of oil and gas deposits of the Yamalo-Kara Depression for the first time in the last 30 years. The main feature of the region is the wide development of abnormally high formation pressures (Ka to 2.21) in both Jurassic and Lower Cretaceous horizons. Studying the filtration-capacitive properties and hydrodynamic characteristics of the Jurassic-Cretaceous reservoirs allows to established the predominate role of the elision water exchange in the formation of the modern hydrodynamic structure. At the depth of about 2–2.5 km elisional lithostatic system begins to acquire the features of elisional thermo-dehydration system. The extensive zones of piezomaxima (Bolshekhetskaya and Karskaya megasyneclise) at the present stage of development of the water-pressure basin system became internal areas of water pressure (supply) with a maximum degree of hydrogeological closeness. The vast zones of piezomaxima (the Bolshekhetskaya and Karskaya megasyneclises) became the inner regions of water pressuring (feeding) with the maximal degree of hydrogeological closeness of the interior at the current stage of the development of the water-pressure system in the basin. The areas of piezominima extending along the main sites of oil and gas generation are related to the largest zones of oil and gas accumulation (Vankoro-Suzunskaya, Bovanenkovskaya, Urengoyskaya and others). Currently, two types of natural water-pressure systems has been established in the region under investigation: elision in the inner regions (dominating within the Yamalo-Kara depression) and infiltration — in the basin margins of the West Siberian sedimentary basin.

On the Role of the High-Spin State in the Water Exchange Reaction of Hexaaquocobalt(III)

1981 ◽  
Vol 1 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Jay R. Winkler ◽  
Steven F. Rice ◽  
Harry B. Gray
Keyword(s):  
Exchange Reaction ◽  
High Spin ◽  
Spin State ◽  
Water Exchange ◽  
High Spin State

Idiopathic intracranial hypertension

Neurology ◽  
2018 ◽  
Vol 91 (11) ◽  
pp. 515-522 ◽  
Author(s):  
Stéphanie Lenck ◽  
Ivan Radovanovic ◽  
Patrick Nicholson ◽  
Mojgan Hodaie ◽  
Timo Krings ◽  
...  
Keyword(s):  
Intracranial Hypertension ◽  
Idiopathic Intracranial Hypertension ◽  
Interstitial Fluid ◽  
Water Exchange ◽  
Venous Blood ◽  
Glymphatic System ◽  
Associated Conditions ◽  
Outflow Pathway ◽  
The Brain

The recent discoveries of the glymphatic and lymphatic systems of the brain have helped advance our understanding of CSF physiology and may allow new insights in the understanding of idiopathic intracranial hypertension (IIH). The clinical and radiologic presentations of IIH appear to be related to congestion of the glymphatic system associated with an overflow of the lymphatic CSF outflow pathway. By revisiting the role of “vascular arachnoid granulations” in the brain, we hypothesize that an initial impairment of the transport of interstitial fluid from the glymphatic system to the venous blood of the dural sinuses may trigger the hydrodynamic cascade of IIH. Furthermore, we speculate that, similar to other water-exchange systems in the brain, a specific subtype of aquaporin is involved in this transport. This theory may eventually help to provide an underlying explanation for IIH and its associated conditions, since in most of them, the expression of several aquaporins is altered.

scholarly journals Temporal Variability in Thermally Driven Cross-Shore Exchange: The Role of Semidiurnal Tides

2018 ◽  
Vol 48 (7) ◽  
pp. 1513-1531 ◽  
Author(s):  
Hugo N. Ulloa ◽  
Kristen A. Davis ◽  
Stephen G. Monismith ◽  
Geno Pawlak
Keyword(s):  
Temporal Variability ◽  
Dynamic Balance ◽  
Turbulent Transport ◽  
Tidal Flow ◽  
Momentum Balance ◽  
Direct Role ◽  
Thermally Driven ◽  
The Cross ◽  
Tidally Driven

AbstractWe examine temporal variability of thermally driven baroclinic cross-shore exchange in the context of a tropical fringing reef system focusing on the role of tidally driven alongshore flow. Ensemble diurnal phase averaging of cross-shore flow at the Kilo Nalu Observatory (KNO) in Oahu, Hawaii, shows a robust diurnal signal associated with an unsteady buoyancy/diffusive dynamic balance, although significant variability is observed at subdiurnal time scales. In particular, persistent fortnightly variability in the cross-shore diurnal flow pattern is consistent with modulation by the semidiurnal alongshore tidal flow. The alongshore flow plays a direct role in the cross-shore exchange momentum balance via Coriolis acceleration but also affects the cross-shore circulation indirectly via its influence on vertical turbulent diffusion. An idealized linear theoretical model for thermally driven cross-shore flow is formulated using the long-term time-averaged diurnal dynamic balance at KNO as a baseline. The model is driven at leading order by the surface heat flux, with contributions from the alongshore flow and cross-shore wind appearing as linear perturbations. Superposition of the idealized solutions for Coriolis and time-varying eddy viscosity perturbations are able to reproduce key aspects of the fortnightly variability. Modifying the model to consider a more realistic alongshore flow and considering effects of nightly convection lead to further improvements in comparisons with KNO observations. The ability of the theoretical approach to reproduce the fortnightly patterns indicates that semidiurnal variations in the alongshore flow are effective in modulating the cross-shore flow via Coriolis and vertical turbulent transport mechanisms.

The role of unstirred layers for water exchange across the blood-brain barrier

1981 ◽  
Vol 21 (1) ◽  
pp. 117-127 ◽  
Author(s):  
Clifford S. Patlak ◽  
Olaf B. Paulson
Keyword(s):  
Blood Brain Barrier ◽  
Water Exchange ◽  
Brain Barrier ◽  
Unstirred Layers ◽  
Blood Brain
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