A transcellular water flux induced by light in Nitella

1973 ◽  
Vol 51 (5) ◽  
pp. 1045-1053 ◽  
Author(s):  
D. S. Fensom ◽  
S. L. Barclay ◽  
Sophie Law ◽  
R. G. Thompson
Keyword(s):  
Water Flow ◽  
Plasma Membranes ◽  
Water Flux ◽  
Pond Water ◽  
Basic Flow ◽  
Membrane Properties ◽  
Light Change ◽  
Hydraulic Permeability ◽  
Closed Chamber ◽  
Current Flows

When Nitella cells in artificial pond water (APW) are illuminated in an electroosmometer, water appears to move into the closed chamber of the instrument. This has been termed the "basic flow" of the instrument. A part of this basic flow is thermal expansion but an appreciable part is a water flow through the living cell. This transcellular water flow is increased by illumination of any part of the cell and is mostly removed by 10−3 mM N-dichlorophenyl-N′,N′-dimethylurea (DCMU). It is readily altered by conditioners which alter the membrane properties at one end of the cell compared with the other: carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) at 5 × 10−3 mM, dinitrophenol (DNP), 10−1 mM ouabain, and particularly pH. Asymmetrical changes in the hydraulic permeability of the membrane are indicated as the most probable cause of this water flow.An electric current flows between the two ends of the cell when the cell is differentially illuminated, particularly at the beginning or end of the light change. The current is thought to indicate the presence of some electrogenic pumps on the plasma membranes.

Note on lack of effect of ethylene on water permeability, electroosmotic efficiency, or transcellular water flow of the plasma membranes in Nitella

1977 ◽  
Vol 55 (5) ◽  
pp. 615-616 ◽  
Author(s):  
D. S. Fensom ◽  
S. M. Ross
Keyword(s):  
Water Flow ◽  
Water Permeability ◽  
Plasma Membranes ◽  
Pond Water ◽  
Monovalent Cation ◽  
Hydraulic Permeability ◽  
Water Flows ◽  
Cation Permeability ◽  
Transcellular Osmosis ◽  
Permeation Properties

Ethylene (4.0 mM) in artificial pond water had no significant effect on three permeation properties of the plasma membranes of Nitella 2 h after addition. Neither the hydraulic permeability measured by transcellular osmosis, the passive monovalent cation permeability measured by electroosmosis, nor the 'active' transcellular water flows were altered appreciably by ethylene in solution.

The effect of some growth-regulating compounds upon electroosmotic measurements, transcellular water flow, and Na, K, and Cl influx in Nitella flexilis

1973 ◽  
Vol 51 (5) ◽  
pp. 1055-1070 ◽  
Author(s):  
I. R. Wanless ◽  
Nancy Bryniak ◽  
D. S. Fensom
Keyword(s):  
Water Flow ◽  
Pond Water ◽  
Basic Flow ◽  
Constant Current ◽  
Naphthaleneacetic Acid ◽  
Applied Current ◽  
Osmotic Effect ◽  
Membrane Complex ◽  
Small Constant ◽  
A Cell

By using a small, constant, applied current on a cell of Nitella in artificial pond water, it was possible to compare the effect of different growth-regulating compounds on the apparent electroosmotic water coupling in the cell wall – membrane complex. Indoleacetic acid (IAA) at first enhanced the electro-osmotic effect and then ceased to alter it, but began to change the asymmetric transcellular water flow. Gibberellic acid (GA), when added to IAA, increased this effect, while abscissic acid (ABA) added to IAA decreased it. Some compounds like naphthaleneacetic acid (NAA), alar-83, skatol, or ABA alone, had no effect on the electroosmotic (eo.) coefficient; but NAA, skatol, ABA (alone) changed the asymmetric water flow (basic flow) and some ion influxes. Light-degraded IAA acted in a manner very similar to skatol, which suggests that IAA is quickly converted to skatol in the cell in the presence of light. With light–dark transitions or with IAA, the electroosmotic coefficient changed in a manner parallel to passive ion (Na+ and K+) influx, but was not related to basic flow or Cl− influx changes.Under controlled conditions of low constant current applied to a test cell, it has been shown that a change in apparent eo. coefficient upon auxin addition is largely a reflection of change in the true electroosmotic properties of the cell membrane at the positive end of the cell.

scholarly journals Engineering the Surface and Mechanical Properties of Water Desalination Membranes Using Ultralong Carbon Nanotubes

Membranes ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 106 ◽  
Author(s):  
Yehia M. Manawi ◽  
Kui Wang ◽  
Viktor Kochkodan ◽  
Daniel J. Johnson ◽  
Muataz A. Atieh ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Aspect Ratio ◽  
Water Flux ◽  
Contact Angles ◽  
Water Desalination ◽  
Membrane Properties ◽  
Porous Membranes ◽  
Water Contact ◽  
And Performance

In this work, novel polysulphone (PS) porous membranes for water desalination, incorporated with commercial and produced carbon nanotubes (CNT), were fabricated and analyzed. It was demonstrated that changing the main characteristics of CNT (e.g., loading in the dope solutions, aspect ratio, and functionality) significantly affected the membrane properties and performance including porosity, water flux, and mechanical and surface properties. The water flux of the fabricated membranes increased considerably (up to 20 times) along with the increase in CNT loading. Conversely, yield stress and Young’s modulus of the membranes dropped with the increase in the CNT loading mainly due to porosity increase. It was shown that the elongation at fracture for PS/0.25 wt. % CNT membrane was much higher than for pristine PS membrane due to enhanced compatibility of commercial CNTs with PS matrix. More pronounced effect on membrane’s mechanical properties was observed due to compatibility of CNTs with PS matrix when compared to other factors (i.e., changes in the CNT aspect ratio). The water contact angle for PS membranes incorporated with commercial CNT sharply decreased from 73° to 53° (membrane hydrophilization) for membranes with 0.1 and 1.0 wt. % of CNTs, while for the same loading of produced CNTs the water contact angles for the membrane samples increased from 66° to 72°. The obtained results show that complex interplay of various factors such as: loading of CNT in the dope solutions, aspect ratio, and functionality of CNT. These features can be used to engineer membranes with desired properties and performance.

scholarly journals Flow of Antarctic Bottom Water from the Vema Channel 

2020 ◽  
Author(s):  
Eugene G Morozov ◽  
Dmitry I. Frey ◽  
Roman Y. Tarakanov
Keyword(s):  
Continental Slope ◽  
Water Flow ◽  
North Atlantic ◽  
Bottom Water ◽  
The Other ◽  
Antarctic Bottom Water ◽  
The North ◽  
The North Atlantic ◽  
Current Flows ◽  
Western Wall

Abstract We analyze measurements of bottom currents and thermohaline properties of water north of the Vema Channel with the goal to find pathway continuations of Antarctic Bottom Water flow from the Vema Channel into the Brazil Basin. The analysis is based on CTD/LADCP casts north of the Vema Channel. The flow in the deep Vema Channel consists of two branches. The deepest current flows along the bottom in the center of the channel and the other branch flows above the western wall of the channel. We found two smaller channels of the northern continuation of the deeper bottom flow. These flows become weak and almost disappear at a latitude of 25°30’S. The upper current flows at a depth of 4100-4200 m along the continental slope. We traced this current up to 24°S over a distance exceeding 250 km. This branch transports bottom water that eventually fills the deep basins of the North Atlantic.

scholarly journals Preparation and Characterization of MWCNTs/PVDF Conductive Membrane with Cross-Linked Polymer PVA and Study on Its Anti-Fouling Performance

Membranes ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 703
Author(s):  
Yi Ding ◽  
Zhansheng Guo ◽  
Xinan Dong ◽  
Hong You ◽  
Junxue Mei ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Mass Loss Rate ◽  
Pure Water ◽  
Water Flux ◽  
Membrane Properties ◽  
Elongation Ratio ◽  
Functional Layer ◽  
Conductive Membranes ◽  
Pure Water Flux ◽  
Conductive Membrane

Based on carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), a MWCNTs/PVDF conductive membrane was prepared by a vacuum filtration cross-linking method. The surface compositions and morphology of conductive membranes were studied by X-ray photoelectron spectroscopy and high-resolution field emission scanning electron microscopy, respectively. The effects of cross-linked polymeric polyvinyl alcohol (PVA) on the conductive membrane properties such as the porosity, pore size distribution, pure water flux, conductivity, hydrophilicity, stability and antifouling properties were investigated. Results showed that the addition of PVA to the MWCNTs/PVDF conductive membrane decreased the pure water flux, porosity and the conductivity. However, the hydrophilicity of the modified MWCNTs/PVDF conductive membrane was greatly improved, and the contact angle of pure water was reduced from 70.18° to 25.48° with the addition of PVA contents from 0 wt% to 0.05 wt%. Meanwhile, the conductive membranes with higher content had a relatively higher stability. It was found that the conductive functional layer of the conductive membrane had an average mass loss rate of 1.22% in the 30 min ultrasonic oscillation experiment. The tensile intensity and break elongation ratio of the conductive membrane are improved by the addition of PVA, and the durability of the conductive membrane with PVA was superior to that without PVA added. The electric assisted anti-fouling experiments of modified conductive membrane indicated that compared with the condition without electric field, the average flux attenuation of the conductive membrane was reduced by 11.2%, and the membrane flux recovery rate reached 97.05%. Moreover, the addition of PVA could accelerate the clean of the conductive membranes.

Field Metabolic-Rate, Water Flux, and Food-Requirements of Short-Nosed Bandicoots, Isoodon-Obesulus (Marsupialia, Peramelidae)

1991 ◽  
Vol 39 (3) ◽  
pp. 299 ◽  
Author(s):  
KA Nagy ◽  
SD Bradshaw ◽  
BT Clay
Keyword(s):  
Metabolic Rate ◽  
Dry Matter ◽  
Produced Water ◽  
Water Flux ◽  
Pond Water ◽  
Doubly Labelled Water ◽  
Fresh Matter ◽  
Water Influx ◽  
Study Population ◽  
Field Metabolic Rates

Field metabolic rates (FMRS) and water influx rates of free-living short-nosed bandicoots (Isoodon obesulus) were measured via the doubly labelled water technique. Bandicoots ranging in body mass from 775 to 1825 g (mean = 1230 g) had FMRS averaging 0.908 mL CO2 g-1 h-1, or 644 kJ d-1. This is about 2.7 times predicted basal metabolic rate. Water influx rates during the autumn measurement period were comparatively low, averaging 88.8 mL kg-1 d-1, or 103 mL d-1 for a 1230 g animal. Feeding rate (dry matter intake) was estimated to be 45 g d-1, assuming that the food was half invertebrates and half plant tissues (dry matter basis). Performed and metabolically produced water from the food can completely account for total water intake, indicating that bandicoots did not drink the rainwater or pond water that was available. The study population (estimated density = 0.63 bandicoots ha-1) consumed food at a rate of about 62 g fresh matter ha-1 d-1 (equivalent to 27 g dry matter or 605 kJ ha-1 d-1), which is similar to the food requirements of populations of small eutherian and marsupial insectivores in other habitats.

Residential Flashover Prevention with Reduced Water Flow: Phase 2

2021 ◽  
Author(s):  
Nicholas Dow ◽  
◽  
Daniel Madrzykowski
Keyword(s):  
Water Flow ◽  
Fire Suppression ◽  
Water Flux ◽  
Sprinkler System ◽  
Low Flow ◽  
Fire Growth ◽  
Solid Cone ◽  
Prevention System ◽  
Discharge Density ◽  
Reduced Water

The purpose of this study was to investigate the feasibility of a residential flashover prevention system with reduced water flow requirements relative to a residential sprinkler system designed to meet NFPA~13D requirements. The flashover prevention system would be designed for retrofit applications where water supplies are limited. In addition to examining the water spray's impact on fire growth, this study utilized thermal tenability criteria as defined in UL 199, Standard for Automatic Sprinklers for Fire-Protection Service. The strategy investigated was to use full cone spray nozzles that would discharge water low in the fire room and directly onto burning surfaces of the contents in the room. Where as current sprinkler design discharges water in a manner that cools the hot gas layer, wets the walls and wets the surface of the contents in the fire room. A series of eight full-scale, compartment fire experiments with residential furnishings were conducted with low flow nozzles. While the 23~lpm (6~gpm) of water was the same between experiments, the discharge density or water flux around the area of ignition varied between 0.3~mm/min (0.008~gpm/ft**2) and 1.8~mm/min (0.044~gpm/ft**2). Three of the experiments prevented flashover. Five of the experiments resulted in the regrowth of the fire while the water was flowing. Regrowth of the fire led to untenable conditions, per UL 199 criteria, in the fire room. At approximately the same time as the untenability criteria were reached, the second sprinkler in the hallway activated. In a completed system, the activation of the second sprinkler would reduce the water flow to the fire room, which would potentially lead to flashover. The variations in the burning behavior of the sofa resulted in shielded fires which led to the loss of effectiveness of the reduced flow solid cone water sprays. As a result of these variations, a correlation between discharge density at the area of ignition and fire suppression performance could not be determined given the limited number of experiments. An additional experiment using an NFPA~13D sprinkler system, flowing 30~lpm (8 gpm), demonstrated more effective suppression than any of the experiments with a nozzle. The success of the sprinkler compared with the unreliable suppression performance of the lower flow nozzles supports the minimum discharge density requirements of 2~mm/min (0.05~gpm/ft**2) from NFPA~13D. The low flow nozzle system tested in this study reliably delayed fire growth, but would not reliably prevent flashover.

Selective permeability barrier to urea in shark rectal gland

2005 ◽  
Vol 289 (1) ◽  
pp. F83-F89 ◽  
Author(s):  
Joshua D. Zeidel ◽  
John C. Mathai ◽  
John D. Campbell ◽  
Wily G. Ruiz ◽  
Gerard L. Apodaca ◽  
...  
Keyword(s):  
Activation Energy ◽  
Epithelial Cells ◽  
Water Flow ◽  
Water Permeability ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Water Flux ◽  
Rectal Gland ◽  
Basolateral Membranes ◽  
Urea Permeability

Elasmobranchs such as the dogfish shark Squalus acanthius achieve osmotic homeostasis by maintaining urea concentrations in the 300- to 400-mM range, thus offsetting to some degree ambient marine osmolalities of 900–1,000 mosmol/kgH2O. These creatures also maintain salt balance without losing urea by secreting a NaCl-rich (500 mM) and urea-poor (18 mM) fluid from the rectal gland that is isotonic with the plasma. The composition of the rectal gland fluid suggests that its epithelial cells are permeable to water and not to urea. Because previous work showed that lipid bilayers that permit water flux do not block flux of urea, we reasoned that the plasma membranes of rectal gland epithelial cells must either have aquaporin water channels or must have some selective barrier to urea flux. We therefore isolated apical and basolateral membranes from shark rectal glands and determined their permeabilities to water and urea. Apical membrane fractions were markedly enriched for Na-K-2Cl cotransporter, whereas basolateral membrane fractions were enriched for Na-K-ATPase. Basolateral membrane osmotic water permeability (Pf) averaged 4.3 ± 1.3 × 10−3 cm/s, whereas urea permeability averaged 4.2 ± 0.8 × 10−7 cm/s. The activation energy for water flow averaged 16.4 kcal/mol. Apical membrane Pf averaged 7.5 ± 1.6 × 10−4 cm/s, and urea permeability averaged 2.2 ± 0.4 × 10−7 cm/s, with an average activation energy for water flow of 18.6 kcal/mol. The relatively low water permeabilities and high activation energies argue strongly against water flux via aquaporins. Comparison of membrane water and urea permeabilities with those of artificial liposomes and other isolated biological membranes indicates that the basolateral membrane urea permeability is fivefold lower than would be anticipated for its water permeability. These results indicate that the rectal gland maintains a selective barrier to urea in its basolateral membranes.

Wasserstruktur und Permeation: Die Aktivierungsenergie und der molekulare Mechanismus der Wasserpermeation

1967 ◽  
Vol 22 (8) ◽  
pp. 885-890 ◽  
Author(s):  
Josef Weigl
Keyword(s):  
Membrane Proteins ◽  
Hydrogen Bonds ◽  
Water Permeability ◽  
Plasma Membranes ◽  
Water Structure ◽  
Activation Energies ◽  
Membrane Properties ◽  
Pure Liquid ◽  
Tissue Water ◽  
Prolonged Contact

The exchange of tissue water of corn roots with ambient water was investigated using D2O, a gaschromatographic method, and a technique which avoids prolonged contact of tissue water with atmospheric water.The exchange experiments were performed at 10°, 20°, and 25 °C and the activation energies for different exchange phases were calculated by a method involving a graphical determination of the relative exchange rates at certain H2O/D2O gradients. Log10 of the rates were plotted versus 1/T as usual and the activation energies were calculated from the slopes of the straight lines. The energy of activation of the exchange process increased from 4.4 kcal-mol-1 in an initial phase (exchange of surface water and free space water) to 6.3 kcal·mol-1 in later phases which represent the processes of permeation through plasma and plasma membranes. This suggests that the hydrogen bonds of permeating water have a mean energy of 6 —7 kcal·mol-1 resulting from interaction with membrane (and plasma) constituents.The theory is proposed that cell membranes contain water phases with hydrogen bonds stronger than those in pure liquid water. These water phases are assumed to be located mainly within apolar portions of globular membrane proteins. Not solely a continous lipid layer, but a specific arrangement of polar and apoiar portions of globular membrane proteins is regarded to be essential for semipermeability and other membrane properties. Results from various authors were considered in establishing the general working hypothesis that agents like apoiar compounds which increase water structure decrease water permeability, and agents like salts which disrupt water structure increase water permeability.

scholarly journals Interplay of the Factors Affecting Water Flux and Salt Rejection in Membrane Distillation: A State-of-the-Art Critical Review

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2841
Author(s):  
Lin Chen ◽  
Pei Xu ◽  
Huiyao Wang
Keyword(s):  
Water Flux ◽  
Feed Solution ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Membrane Properties ◽  
Membrane Thickness ◽  
Membrane Pore ◽  
Factors Affecting ◽  
Term Operation ◽  
Salt Rejection

High water flux and elevated rejection of salts and contaminants are two primary goals for membrane distillation (MD). It is imperative to study the factors affecting water flux and solute transport in MD, the fundamental mechanisms, and practical applications to improve system performance. In this review, we analyzed in-depth the effects of membrane characteristics (e.g., membrane pore size and distribution, porosity, tortuosity, membrane thickness, hydrophobicity, and liquid entry pressure), feed solution composition (e.g., salts, non-volatile and volatile organics, surfactants such as non-ionic and ionic types, trace organic compounds, natural organic matter, and viscosity), and operating conditions (e.g., temperature, flow velocity, and membrane degradation during long-term operation). Intrinsic interactions between the feed solution and the membrane due to hydrophobic interaction and/or electro-interaction (electro-repulsion and adsorption on membrane surface) were also discussed. The interplay among the factors was developed to qualitatively predict water flux and salt rejection considering feed solution, membrane properties, and operating conditions. This review provides a structured understanding of the intrinsic mechanisms of the factors affecting mass transport, heat transfer, and salt rejection in MD and the intra-relationship between these factors from a systematic perspective.

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