Salt Exchange Research Articles

Bicarbonate and potassium regulation of the shape of Streptococcus mutans NCTC 10449S.

Morphological changes of S. mutans NCTC 10449S associated with growth in modified Jordan medium and FMC medium (Terleckyj et al., Infect. Immun. 11:649-655, 1975) were studied by scanning electron microscopy. The cells were bacillary in Jordan medium, but coccoid and of unequal size in FMC. Transfer of the cells from Jordan medium to FMC and vice versa reversed their shapes, as did salt exchange between these media. Morphological changes could not be ascribed to either medium pH, concentration of P, or Na+/K+ ratio. However, they were growth dependent, since the changes did not occur when the cells were suspended in salt components alone or in media supplemented with protein synthesis inhibitors. Only a high bicarbonate/K+ ratio, as in FMC, produced spherical cells, whereas cells remained bacillary in medium with a low bicarbonate/K+ ratio, as in Jordan medium. Manipulating this ratio in other media resulted in similar shape changes. Thus, the shape of S. mutans 10449S can be dictated by the ratio of bicarbonate to K+ in the growth medium.

Gravity currents and the release of salt from an inverse estuary

Spencer Gulf, South Australia, forms a remarkable natural system in which marine gravity currents are regularly observed. The most intense of these forms every autumn, when the gulf waters, which are of high salinity after summer evaporation, are cooled to the point where they are much denser than the waters on the shelf. They then slip out of the gulf along the sea floor to be replaced by a surface inflow of less saline shelf water. Here we report the first complete survey of this outflow during a period when salt exchange was both intense and well-defined. The gravity current has been traced across the floor of the continental shelf to the point where it cascades over the shelf break until it finds its own density level at a depth of 250 m. The speed of the current is estimated to be in the region of 0.1 ms−1, and at that rate it would have to flow for three months to remove the salt accumulated in the gulf during summer. There is evidence that the flow is unsteady in character, and is possibly released in regular pulses.

Coupled 13C longitudinal and transverse magnetic relaxation in micellar and non-micellar sodium octanoate

Coupled 13C longitudinal (R1) and transverse (R2) relaxation rates of the CH2-2 group in sodium octanoate have been studied at 20.1, 75.5 and 125.7 MHz. In the non-micellar state there is little cross-correlation between the C—H bonds, but in the micelle cross-correlation is strongly positive. Values of R1, R2 and nuclear Overhauser enhancements can all be interpreted in terms of the simple two-step correlation function proposed by B. Lindman and co-workers. An exchange effect on R2 due to acid–salt exchange was detected.

Effect of dielectric constant on the rate of electron spin exchange of Fremy's salt in solution

The rate of electron spin exchange in aqueous solution of potassium nitrosodisulphonate K2(SO3)2NO, has been investigated by ESR and found to depend on the dielectric constant of the medium. This observation lead to the calculation of the collision diameter 2 nm which corresponds to bimolecular collisions between species carrying two nagative charges.

Time scales of circulation and mixing processes of San Francisco Bay waters

Conceptual models for tidal period and low-frequency variations in sea level, currents, and mixing processes in the northern and southern reaches of San Francisco Bay describe the contrasting characteristics and dissimilar processes and rates in these embayments: The northern reach is a partially mixed estuary whereas the southern reach (South Bay) is a tidally oscillating lagoon with density-driven exchanges with the northern reach. The mixed semidiurnal tides are mixtures of progressive and standing waves. The relatively simple oscillations in South Bay are nearly standing waves, with energy propagating down the channels and dispersing into the broad shoal areas. The tides of the northern reach have the general properties of a progressive wave but are altered at the constriction of the embayments and gradually change in an upstream direction to a mixture of progressive and standing waves. The spring and neap variations of the tides are pronounced and cause fortnightly varying tidal currents that affect mixing and salinity stratification in the water column. Wind stress on the water surface, freshwater inflow, and tidal currents interacting with the complex bay configuration are the major local forcing mechanisms creating low-frequency variations in sea level and currents. These local forcing mechanisms drive the residual flows which, with tidal diffusion, control the water-replacement rates in the estuary. In the northern reach, the longitudinal density gradient drives an estuarine circulation in the channels, and the spatial variation in tidal amplitude creates a tidally-driven residual circulation. In contrast, South Bay exhibits a balance between wind-driven circulation and tidally-driven residual circulation for most of the year. During winter, however, there can be sufficient density variations to drive multilayer (2 to 3) flows in the channel of South Bay. Mixing models (that include both diffusive and dispersive processes) are based on time scales associated with salt variations at the boundaries and those associated with the local forcing mechanisms, while the spatial scales of variations are dependent upon the configuration of the embayments. In the northern reach, where the estuarine circulation is strong, the salt flux is carried by the mean advection of the mean salt field. Where large salinity gradients are present, the tidal correlation part of the salt flux is of the same order as the advective part. Our knowledge of mixing and exchange rates in South Bay is poor. As this embayment is nearly isohaline, the salt flux is dominated entirely by the mean advection of the mean salt field. During and after peaks in river discharge, water mixing becomes more dynamic, with a strong density-driven current creating a net exchange of both water mass and salt. These exchanges are stronger during neap tides. Residence times of the water masses vary seasonally and differ between reaches. In the northern reach, residence times are on the order of days for high winter river discharge and of months for summer periods. The residence times for South Bay are fairly long (on the order of several months) during summer, and typically shorter (less than a month) during winter when density-driven exchanges occur.

Observations of a loop current frontal eddy intrusion onto the West Florida Shelf

Hydrographic and satellite data from the west Florida shelf between April 1–7, 1982 showed the intrusion of a Loop Current frontal eddy onto the shelf. Data were examined to describe the structure of this feature and study effects of its intrusion on water masses in the outer shelf region. A frontal eddy, consisting of a warm filament separated from the main current by a region of cooler water, propagated southeastward at 30 cm/s intruding onto the shelf near 26°N between April 4 and 6. Temperature‐salinity (T‐S) properties revealed that water in the filament was Loop Current water that had been contiguous with 80 m deeper Loop Current water in the main body of the current; water in the cold region was Continental Edge water, a transitional water mass with cooler, fresher T‐S characteristics. Upwelling of deeper Loop Current water occurred under this region, and elevated nutrient concentrations were found in the upwelled dome under the cold region. Interleaving occurred along water mass boundaries enabling the exchange of heat and salt. This mixing and the supply of cool, nutrient‐rich water to the outer shelf was the major consequence of the intrusion. The length scale and speed of this Loop Current frontal eddy was similar to Gulf Stream frontal eddies through the upwelling was not as intense as in intrusions of Gulf Stream frontal eddies.

A Numerical Experiment on Water and Salt Exchange through the Akashi and the Naruto Straits

Abstract To study the relation between the water-volume exchange rates Ev and the salt-exchange rates Ez of the Akashi and the Naruto Straits in the Seto Inland Sea of Japan, we use an observed salt distribution near the straits, the calculated Eulerian velocity of the M2 current and the calculated location of about 20 000 labeled particles tracked during an M2 period. The salt-exchange rate Ez was about one-third and one-twelfth that of the water-volume exchange rate Ev for the Akashi Strait and the Naruto Strait, respectively. In general, the exchange rates of Ez and Ev do not equal each other, because Ez largely depends on the spatial distribution of salt near a strait. Therefore, Ez is not an adequate measure for the tidal exchange. We found that the salt distribution near the straits and the salt-exchange rates Ez were dependent on the deformation of a water column and that this deformation is produced not only by the velocity shear of the nonlinear tidal current but also by tide-induced transient ed...

A Model for the Exchange of Water and Salt Between the Baltic and the Skagerrak

Abstract A model for the exchange of salt and water between the Baltic and the Sea (the Skagerrak) is presented. Because of strong inter-basin interactions in the Baltic entrance area, the model must include the Kattegat and the Belt Sea. These are modeled by horizontally homogeneous two-layer sub-models. The most prominent dynamical properties of the sub-models are wind-driven entrainment flows and rotational-baroclinic, hydraulic controls. The model is driven by a meteorologically forced barotropic transport Qh [calculated from the freshwater supply to the Baltic (Qf) and the sea level fluctuations in the Kattegat], and turbulent entrainment flows coupled to the wind speed W and, in the Belt Sea, also to the barotropic transport. The most important bathymetric features of the basins are included. The model equations are integrated numerically for a test period of 1½ years. The stratification in the Kattegat, as well as in the Belt Sea, is quite well predicted. It is found that approximately one-half of ...

A simple heat-salt oscillator

A theoretical study is made of a simple mixed-layer model, in the form of a well-mixed constant-depth layer, forced from above by a heat flux k T ( T A − T) and salinity flux k S ( S A − S), where T A and S A are two reference values and T and S the temperature and salinity of the layer. The layer has a turbulent exchange of heat and salt with underlying water, kept at constant temperature and salinity, which is small in a statically stable case; large in a statically unstable case. If k T > k S , self-sustained oscillations may occur. In one cycle, a fast temperature rise, a slower salinity increase, and a final relaxation when the layer adjusts to the conditions of the underlying water, are observed.

Salt and water balance and antennal gland function in three pacific species of terrestrial crab (Gecarcoidea lalandii, Cardisoma carnifex, Birgus latro). I. Urine production and salt exchanges in hydrated crabs

AbstractRates of inulin clearance and urine production were determined in Gecarcoidea lalandii on full‐strength seawater‐moist sand, in Cardisoma carnifex on 800 mOsm seawater‐moist sand; and in Birgus latro with access to distilled water for drinking. Urine production in G. lalandii was 3.4 ± 0.6 ml·100 g−1·d−1, and the inulin U/B ratio was 0.77 ± 0.01 (n = 6). The urine production rate for C. carnifex was 3.2 ± 0.5 ml·100 g−1·d−1, and the inulin U/B ratio was 0.95 ± 0.01 (n = 6). We were unable to collect urine from B. latro, but the inulin clearance rate was over twice that observed in either G. lalandii or C. carnifex. The inulin U/B ratios we observed were less than unity, which indicated a secretion of fluid into the urine. In general, this secreted solution was slightly hyperosmotic, isoionic with respect to sodium and slightly hyperionic with respect to chloride, but appeared to be of minimal use in salt regulation. Unidirectional sodium fluxes were determined in C. carnifex and B. latro, and compared with the estimated urinary sodium fluxes. The antennal gland appears to be the major site of sodium loss. Under our experimental conditions, the antennal gland was the major site for the loss of salt and water, and it appears to be of minimal use in the retention of salts.

Exchange of water, salt, nutrients and photoplankton between Peel Inlet, Western Australia, and the indian Ocean

Two 5-day intensive exercises were undertaken to measure the exchange between Peel Inlet and the Indian Ocean under summer and winter conditions. During both exercises there were tides of small amplitude, with a periodicity of 24 h, typical of this part of the Western Australian coast. There was a substantial net gain of water by the estuary on both occasions (25-28% of estuary volume) due to longer term oscillations in water level which gave increased ocean levels of c. 22 cm during each study. In the summer exercise estuarine nutrient concentrations approximated those in the ocean, so that nutrient flux depended largely on long- term volume exchange as controlled by meteorological tides. There was a net gain of both nutrients and marine phytoplankton to the estuary. However, in the winter exercise river inflow produced low salinity and high nutrient levels in the estuary and, despite the net gain of water by the inlet, there was a large loss of nutrients and phytoplankton to the sea where they were apparently removed by longshore currents from near the mouth of the inlet channel.

Energy-Water-Salinity: Upper Colorado River Basin

Coal, oil shale, and uranium resource developments in the Upper Colorado River Basin are expected to consume large amounts of water that will alter both the quantity and quality of downstream flows. An evaluation of the water resource impacts from alternative energy developments will assure a continued high level of water use throughout the Colorado River. A mathematical model that simulates the salt and water exchange phase of potential fuel conversions has been developed. The analysis is based on a subbasin division of the Upper Colorado River Basin utilizing a minimum cost linear programming algorithm. Model results are presented for minimum cost energy developments, marginal value of water, and impacts of interstate water transfers.

Darbo Jula: The Role of a Mandinka Jula Clan in the Long-Distance Trade of the Gambia River and Its Hinterland

Through the peak years of the Gambia River slave trade, a clan with the surname Darbo was one of several Mandinka jula (merchant) clans whose members participated in the carriage and exchange of slaves, cloth, iron, salt, European manufactures, and other commodities between the lower Gambia and its broad eastern hinterland. Itinerant merchants had conducted long-distance trade along a general Gambia-Niger axis for several centuries prior to Portuguese arrival on the Senegambian coast. Thereafter, the growing demand for slaves at coastal and riverine points led to an increase in the east-west flow of merchandise. Most slaves exported from the Gambia through the middle of the seventeenth century came from populations living reasonably close to the river's banks, but for the century or more after 1650 Gambian slave exports came increasingly from the river's eastern hinterland, the several hundred miles of savannas stretching between the upper reaches of the navigable Gambia and the upper Niger. From this region merchants conveyed slaves of the Tanda, Mandinka, and Bambara ethnic groups down the Gambia for what was normally ultimate exchange into the Atlantic slave trade. Well placed to conduct this longdistance trade were members of the Darbo clan of jula. Like segments of other Mandinka jula clans, extended families of Darbo jula were settled in commercial villages along the river, where over the years they had developed social and economic ties with local residents and with members of the ruling families of the appropriate Gambian Mandinka states. From these locations, and with the aid of their strong local and regional influence, Darbo jula were able to participate actively and regularly in the long-distance trade of the Gambia-Niger commercial axis. Such a study as this, of the commercial operations of a specific jula clan and the importance of the clan's social integration in its overall economic success, takes on added meaning when placed in the proper context of longdistance trading operations in the larger Western Sudan. Therefore, relevant background information on the broad Western Sudanic trading complex, the general landlord-stranger types of relationships that made possible efficient long-distance trading, and jula clans in general precedes the more particular study of the Darbo jula.

Mechanisms of elimination reactions—XXVI: The α'-β mechanism in elimination reactions of sulforium salts

Tracer studies with β-deuterated sulfonium salts have shown that the α'-β, or ylid mechanism can be the major path of elimination in the reaction of sulfonium salts with t-butoxide in t-butyl alcohol, while the E2 reaction is dominant with hydroxide in water or n-butoxide in n-butyl alcohol. The structure of the sulfonium salt also affects the propensity toward α'-β elimination, with 3-pentyl > 3-propyl and eyclopentyl > 3-pentyl > cyclohexyl. The S-methyl protons of the sulfonium salt exchange at a rate much faster than that of the elimination reaction. A strongly basic medium and a syn-periplanar arrangement of the α-C-S and β-C-H bonds seem to be the two most important factors favoring the α'-β mechanism.

Mathematical modelling of the soil desalinization process

Of the many physical and chemical factors influencing the migration of salt in the ground, only molecular-filtration diffusion, convective transport, and salt exchange between the porous soil skeleton and the moving solution are usually taken into account [1]. The salt-exchange process is of a diffusion nature (“internal” diffusion) and depends on the types of soil and the nature of their salinization. We may assume that soils of a heavy mechanical composition (clay, heavy loam) possessing high moisture-retention capacity are most appropriately modelled by a heterogeneous porous medium with porosity m = m1 + m2, where m1 denotes the volume of transit pores occupied by the moving solution and m2, the volume of terminal pores, filled with a stationary solution (“bound” moisture). In this case, the internal diffusion mass-exchange process between both types of pores is described [2, 3] in the form of Freundlich-type isotherms, $$\alpha {{\partial N} \mathord{\left/ {\vphantom {{\partial N} {\partial t}}} \right. \kern-\nulldelimiterspace} {\partial t}} = c - N,$$ (0.1) where c (x, t) and N (x, t) are the concentrations of solutions in the transit and terminal pores, respectively, t is the time, x is a coordinate, and α is the kinetic parameter. Salinization of soil of light mechanical composition (sand, light loam) with low moisture-retention capacity is associated with the presence of salts in the solid phase. We must write kinetic equations for salt dissolution in place of Eq. (0.1). Some types of these equations have been previously presented [1–5]. In this work, three problems modelling the soil desalinization process and admitting analytic solutions for arbitrarily given initial salinization are considered. It is assumed here that the “internal” diffusion process occurs sufficiently rapidly (or infinitely rapidly) in comparison with the “external” diffusion process and convection.

Oceanography of an Arctic bay

The present investigations have revealed the simultaneous existence of two systems of convective circulation within an Arctic bay, an immediate response to ice growth leading to the establishment of a homogeneous upper layer and a deep-reaching system involving the entire water body. The former occurs everywhere due to salt rejection at the ice-water interface. The latter originates in the shallows of the bay where convection of the former type reaches the bottom. Here the restriction in circulation leads to an excess accumulation of expelled salt. The densit of the water in the shallows may then exceed that of the basin water and flow down the slopes. The heat budget of the bay was found to be nearly locally balanced over the year, there being little net exchange with outside waters. Salt exchanges were limited to the summer months, the salt outflow due to entrainment with runoff being roughly balanced by an inflow at depth after the main runoff has ceased.

Extra-branchial pathways of salt exchange in a teleost fish

1. 1. Effects of ligation of the dendritic organ of the catfish Cnidoglanis macrocephalus were examined at several salinities. 2. 2. Significantly reduced survival was found at certain salinities. 3. 3. The plasma sodium concentrations of experimental fish (dendritic organ ligated) were significantly higher than control fish (intact) in hyperosmotic salinities, and significantly lower in hypoosmotic salinities. 4. 4. In a number of instances urine taken by direct puncture of the bladder was shown to be hyperosmotic to the plasma. In one case the urine was also more concentrated than the external medium. 5. 5. The high osmotic concentration of the bladder-urine was not always due to high sodium concentration, indicating the presence of some other osmotically active constituent. There were instances, however, of bladder-urine more concentrated with respect to sodium than the plasma. 6. 6. It was suggested that in Cnidoglanis there may be several major pathways of sodium exchange with the environment.

Rapid Salt Exchange by Coupled Ultrafiltration and Dialysis in Anisotropic Hollow Fibers

Abstract Anisotropic hollow fibers allow construction of a dialyzing system that provides extremely large membrane surface in a small laboratory-sized system. Possessing the added property of high ultrafiltration flux, these fibers reduce salt exchange times from days to hours. In this system the exchange of salt by dialytic transport is largely unaffected by recirculation rate, solute type, or content, but is strongly affected by those variables which affect molecular diffusion, such as microsolute size and temperature. In contrast, diafiltration (convective salt removal by ultrafiltration), which primarily relates to solvent transport through the membrane, can be changed by operating pressure, polarizability of the macrosolute, as well as those conditions which tend to influence this latter phenomenon.

Luminescence and site distribution of Mn 2+ in βAl 2O 3

The luminescence spectra of Mn 2+ in β alumina prepared by diffusion at high temperature and by exchange in molten MnCl 2 at moderate temperatures are compared. High temperature diffusion distributes Mn 2+ over the tetrahedral sites of the spinel block and gives rise to a green emission at 510 nm. Molten salt exchange places Mn 2+ on the easily exchangeable Na + site and generates a characteristic orange (590 nm) emission.

Observations on the Exchange of Salt Between the Xylem and Neighbouring Cells inZea maysPrimary Roots

Observations on the Exchange of Salt Between the Xylem and Neighbouring Cells in<i>Zea mays</i>Primary Roots