Water flux and sediment transport within a forested landscape: the role of connectivity, subsurface flow, and slope length scale on transport mechanism

2013 ◽  
Vol 27 (26) ◽  
pp. 4091-4102 ◽  
Author(s):  
Afshin Ghahramani ◽  
Yoshiharu Ishikawa
Keyword(s):  
Sediment Transport ◽  
Transport Mechanism ◽  
Water Flux ◽  
Subsurface Flow ◽  
Length Scale ◽  
Slope Length

Computational studies of the mitochondrial carrier family SLC25. Present status and future perspectives

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Andrea Pasquadibisceglie ◽  
Fabio Polticelli
Keyword(s):  
Transport Mechanism ◽  
Experimental Studies ◽  
Intermembrane Space ◽  
Mitochondrial Carrier ◽  
Mitochondrial Homeostasis ◽  
The Matrix ◽  
Mitochondrial Carrier Family ◽  
Mitochondrial Intermembrane Space ◽  
Computational Analyses

Abstract The members of the mitochondrial carrier family, also known as solute carrier family 25 (SLC25), are transmembrane proteins involved in the translocation of a plethora of small molecules between the mitochondrial intermembrane space and the matrix. These transporters are characterized by three homologous domains structure and a transport mechanism that involves the transition between different conformations. Mutations in regions critical for these transporters’ function often cause several diseases, given the crucial role of these proteins in the mitochondrial homeostasis. Experimental studies can be problematic in the case of membrane proteins, in particular concerning the characterization of the structure–function relationships. For this reason, computational methods are often applied in order to develop new hypotheses or to support/explain experimental evidence. Here the computational analyses carried out on the SLC25 members are reviewed, describing the main techniques used and the outcome in terms of improved knowledge of the transport mechanism. Potential future applications on this protein family of more recent and advanced in silico methods are also suggested.

Role of the General Pediatrician in Neonatology: Relevance of Recent Advances

1981 ◽  
Vol 3 (3) ◽  
pp. 71-76
Author(s):  
Ann R. Stark
Keyword(s):  
Newborn Infant ◽  
Transport Mechanism ◽  
Major Influence ◽  
Recent Advances ◽  
General Pediatrician ◽  
Life Saving

The general pediatrician plays important roles even as neonatology becomes more specialized: first in the evaluation of the newborn infant and in the organization of resources for care; and second as a major influence in the education of the parents. Awareness of significant advances will allow appropriate counseling of parents and obstetricians. Inasmuch as perinatal centers can provide care for mothers and babies that other hospitals cannot, pediatricians must ensure that the regionalization network and transport mechanism are established so that life-saving advances are available for their patients. Then, the pediatrician and the obstetrician, as members of a team, can provide the best possible care to mother and infant.

scholarly journals The Na+/H+ exchanger isoform 3 is required for active paracellular and transcellular Ca2+ transport across murine cecum

2013 ◽  
Vol 305 (4) ◽  
pp. G303-G313 ◽  
Author(s):  
Juraj Rievaj ◽  
Wanling Pan ◽  
Emmanuelle Cordat ◽  
R. Todd Alexander
Keyword(s):  
Water Movement ◽  
Water Flux ◽  
Wild Type Mouse ◽  
Wild Type ◽  
Rt Pcr ◽  
Ussing Chambers ◽  
Voltage Clamps ◽  
Paracellular Absorption ◽  
Mouse Intestine

Intestinal calcium (Ca2+) absorption occurs via paracellular and transcellular pathways. Although the transcellular route has been extensively studied, mechanisms mediating paracellular absorption are largely unexplored. Unlike passive diffusion, secondarily active paracellular Ca2+ uptake occurs against an electrochemical gradient with water flux providing the driving force. Water movement is dictated by concentration differences that are largely determined by Na+ fluxes. Consequently, we hypothesized that Na+ absorption mediates Ca2+ flux. NHE3 is central to intestinal Na+ absorption. NHE3 knockout mice (NHE3−/−) display impaired intestinal Na+, water, and Ca2+ absorption. However, the mechanism mediating this latter abnormality is not clear. To investigate this, we used Ussing chambers to measure net Ca2+ absorption across different segments of wild-type mouse intestine. The cecum was the only segment with net Ca2+ absorption. Quantitative RT-PCR measurements revealed cecal expression of all genes implicated in intestinal Ca2+ absorption, including NHE3. We therefore employed this segment for further studies. Inhibition of NHE3 with 100 μM 5-( N-ethyl- N-isopropyl) amiloride decreased luminal-to-serosal and increased serosal-to-luminal Ca2+ flux. NHE3−/− mice had a >60% decrease in luminal-to-serosal Ca2+ flux. Ussing chambers experiments under altered voltage clamps (−25, 0, +25 mV) showed decreased transcellular and secondarily active paracellular Ca2+ absorption in NHE3−/− mice relative to wild-type animals. Consistent with this, cecal Trpv6 expression was diminished in NHE3−/− mice. Together these results implicate NHE3 in intestinal Ca2+ absorption and support the theory that this is, at least partially, due to the role of NHE3 in Na+ and water absorption.

scholarly journals THE ROLE OF SUBSURFACE FLOW DYNAMIC ON SPATIAL AND TEMPORAL VARIATION OF WATER CHEMISTRY IN A HEADWATER CATCHMENT

2016 ◽  
Vol 8 (1) ◽  
pp. 17
Author(s):  
Tadashi Tanaka
Keyword(s):  
Water Chemistry ◽  
Temporal Variation ◽  
Random Process ◽  
Riparian Zone ◽  
Subsurface Flow ◽  
Solute Concentration ◽  
Spatial And Temporal Variation ◽  
Flow Dynamic ◽  
Headwater Catchment

Variation of water chemistry does not merely occur due to in situ chemical process, but also transport process. The study was carried out to address the role of subsurface flow dynamic on spatial and temporal variation of water chemistry in a headwater catchment. Hydrometric and hydrochemistry measurements were done in transect with nested piezometers, tensiometers, and suction samplers at different depths across hillslope and riparian zone in a 5.2 ha first-order drainage of the Kawakami experimental basin, Nagano, Central Japan from August 2000 to August 2001. Spatial variation of solute concentration was defined by the standard deviation and coefficient of variation of the seasonal observed concentrations. Autocorrelation analysis was performed to define temporal variation of solute concentration. The results showed that spatial variation of water chemistry was mainly influenced by the variation of subsurface flow through the hillslope and riparian zone. Solute concentration in the deep riparian groundwater was almost three times higher than that in the hillslope segment. A prominent downward flow in deep riparian groundwater zone provided transport of solutes to the deeper layer. Time series analysis showed that in the deep riparian groundwater, Ca2+, Mg2+, SO42- and HCO3- concentrations underwent a random process, Na+ concentration of a random process superimposed by a trend process, and SiO2 of a random process superimposed by a periodic process. Near the riparian surface, SO42- concentration was composed of a random process superimposed by a periodic process, whereas other solutes were mainly in a random process. In the hillslope soil water, there was no trend observed for the Na+ concentration, but there were for Ca2+ and Mg2+. The magnitude and direction of subsurface flow across hillslope and riparian zone created transport and deposition processes that changed solute concentration spatially and temporally.

scholarly journals Role of Liposomes Composite as Drug Transport Mechanism

2021 ◽  
pp. 230-243
Keyword(s):  
Drug Delivery ◽  
Lipid Bilayers ◽  
Transport Mechanism ◽  
Drug Transport ◽  
Phospholipid Bilayer ◽  
Drug Transporter ◽  
Delivery Methods ◽  
Second Stage ◽  
Novel Drug

Liposomes are spherical shaped vesicles comprising of at least one phospholipid bilayer that serve as a novel drug delivery framework. They are microscopic structures in which a fluid system is totally encased by a film made out of lipid bilayers. It varies in size, conformation, charge and drug transporter stacked with assortment of particles, for example, small molecules of drug, plasmids, nucleotides or proteins and so on. Ongoing advances in nanotherapeutics have brought about engineered liposomes rising in nanomedicine, giving better restorative control of diseased states. This has made ready for the improvement of second-stage liposomes for increased efficiency and could at last lead to a change in perspective from the regular drug delivery methods.

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