Changes In Solute Concentration Research Articles

Ammonia–water absorption cycle: a prospective way to transport low-grade heat energy over long distance

The ammonia–water absorption cycle could transfer thermal energy into chemical energy by the change in solution concentration, which low-grade heat released by industry-concentrated areas could be utilized to provide heating or cooling in the user site over long distance. No heat insulation is required for the transportation pipelines and the energy consumption is reduced greatly. The simulation researches show that thermal coefficient of performance (COP) is at 0.5 and exergy efficiency is >0.2 when generation temperature is at 110°C to provide cooling in summer; thermal COP is at 0.6 and exergy efficiency is >0.3 to provide heating in winter. Electrical COP as high as 50 could be realized if the transportation distance is >50 km. Therefore, the COP of the system is determined by thermal COP (nearly equal). An experimental prototype has been built to testify this theory. Thermal COP is 0.43 when chilled water at 8°C is obtained in summer. In winter, thermal COP is 0.45 when hot water at 58°C is obtained. The deviations between experimental and simulation results are ∼20%. The economic assessment based on the reasonable assumptions shows that the investment cost of the transportation pipelines of a 500 MW, 50 km system could be recovered within 15 months, in which the whole system costs could be recovered within 4 years. Copyright , Oxford University Press.

Special features of formation of omega-phase in titanium alloys due to hardening

Special features of formation of athermal ω-phase in titanium alloys of the Ti – Nb, Ti – V, and Ti2AlNb-base systems are considered from the standpoint of changes in the electron concentration of the β-solid solution. The conditions of formation of ω-phase with anomalous (“raft”) morphology are determined. A dislocation model explaining the morphological features is suggested. The effect of hydrogen alloying of titanium alloys on the process of formation of ω-phase in hardening is described. Amethod for computing electron concentration for titanium alloys with hydrogen is suggested.

Routes of Epithelial Water Flow: Aquaporins versus Cotransporters

The routes water takes through membrane barriers is still a matter of debate. Although aquaporins only allow transmembrane water movement along an osmotic gradient, cotransporters are believed to be capable of water transport against the osmotic gradient. Here we show that the renal potassium-chloride-cotransporter (KCC1) does not pump a fixed amount of water molecules per movement of one K+ and one Cl−, as was reported for the analogous transporter in the choroid plexus. We monitored water and potassium fluxes through monolayers of primary cultured renal epithelial cells by detecting tiny solute concentration changes in the immediate vicinity of the monolayer. KCC1 extruded K+ ions in the presence of a transepithelial K+ gradient, but did not transport water. KCC1 inhibition reduced epithelial osmotic water permeability Pf by roughly one-third, i.e., the effect of inhibitors was small in resting cells and substantial in hormonal stimulated cells that contained high concentrations of aquaporin-2 in their apical membranes. The furosemide or DIOA (dihydroindenyl-oxy-alkanoic acid)-sensitive water flux was much larger than expected when water passively followed the KCC1-mediated ion flow. The inhibitory effect of these drugs on water flux was reversed by the K+–H+ exchanger nigericin, indicating that KCC1 affects water transport solely by K+ extrusion. Intracellular K+ retention conceivably leads to cell swelling, followed by an increased rate of endocytic AQP2 retrieval from the apical membrane.

A unified constitutive model for quasi-static flow responses of pure Ta and Ta–W alloys

This study aims to develop a unified constitutive model describing the flow behaviors of pure Ta and Ta–W alloys over a wide range of strain rate and temperature. The model was based on the previously suggested model by Nemat-Nasser and Isaacs [3] and was further extended to capture the hardening effects caused by the changes in solute contents and concentrations, and grain size; while interstitial solutes (C, N, and O) increased the thermal stress, substitutional solute (W) increased both the thermal and athermal stresses. The results showed that the developed model can provide a reasonable prediction on the flow behaviors of pure Ta and Ta–W alloys (Ta–2.47W, Ta–5.2W, and Ta–9.8W) with different grain sizes of 0.3–45μm over a strain rate range of 1–10−6s−1 and a temperature range of 77–900K without any change in the material constants used.

The Influence of Gustatory and Olfactory Experiences on Responsiveness to Reward in the Honeybee

BackgroundHoneybees (Apis mellifera) exhibit an extraordinarily tuned division of labor that depends on age polyethism. This adjustment is generally associated with the fact that individuals of different ages display different response thresholds to given stimuli, which determine specific behaviors. For instance, the sucrose-response threshold (SRT) which largely depends on genetic factors may also be affected by the nectar sugar content. However, it remains unknown whether SRTs in workers of different ages and tasks can differ depending on gustatory and olfactory experiences.MethodologyGroups of worker bees reared either in an artificial environment or else in a queen-right colony, were exposed to different reward conditions at different adult ages. Gustatory response scores (GRSs) and odor-memory retrieval were measured in bees that were previously exposed to changes in food characteristics.Principal FindingsResults show that the gustatory responses of pre-foraging-aged bees are affected by changes in sucrose solution concentration and also to the presence of an odor provided it is presented as scented sucrose solution. In contrast no differences in worker responses were observed when presented with odor only in the rearing environment. Fast modulation of GRSs was observed in older bees (12–16 days of age) which are commonly involved in food processing tasks within the hive, while slower modulation times were observed in younger bees (commonly nurse bees, 6–9 days of age). This suggests that older food-processing bees have a higher plasticity when responding to fluctuations in resource information than younger hive bees. Adjustments in the number of trophallaxis events were also found when scented food circulated inside the nest, and this was positively correlated with the differences in timing observed in gustatory responsiveness and memory retention for hive bees of different age classes.ConclusionsThis work demonstrates the accessibility of chemosensory information in the honeybee colonies with respect to incoming nectar. The modulation of the sensory-response systems within the hive can have important effects on the dynamics of food transfer and information propagation.

Solubility determination of organometallic complexes in supercritical carbon dioxide by chromatographic impulse response method

The solubilities of organometallic complexes in supercritical CO 2 were determined from retention factors measured by the chromatographic impulse response (CIR) method, in which a solute was pulse-injected into a supercritical CO 2 flowing in a polymer coated open capillary column, and the response curve, i.e. time change of solute concentration, was monitored at the exit of the column. The retention factor and binary diffusion coefficient were simultaneously obtained as two parameters so that the fitting error between response curves of solute species measured and calculated was minimized. The validities of the method and the apparatus employed in this study were verified by determining the solubilities of naphthalene, which have extensively been reported in the literature. Then, the solubilities of organometallic complexes such as ferrocene and cobalt (III) acetylacetonate in supercritical CO 2 were determined. The data determined in this study were in good agreement with the literature data. The solubilities were also correlated with the Chrastil equation including the three adjustable parameters.

Do quantitative vessel and pit characters account for ion‐mediated changes in the hydraulic conductance of angiosperm xylem?

• The hydraulic conductance of angiosperm xylem has been suggested to vary with changes in sap solute concentrations because of intervessel pit properties. • The magnitude of the 'ionic effect' was linked with vessel and pit dimensions in 20 angiosperm species covering 13 families including six Lauraceae species. • A positive correlation was found between ionic effect and vessel grouping parameters, especially the portion of vessel walls in contact with neighbouring vessels. Species with intervessel contact fraction (F(C)) values < 0.1 showed an ionic effect between 2% and 17%, while species with F(C) values > 0.1 exhibited a response between 10% and 32%. The ionic effect increased linearly with the mean fraction of the total vessel wall area occupied by intervessel pits as well as with the intervessel contact length. However, no significant correlation occurred between the ionic effect and total intervessel pit membrane area per vessel, vessel diameter, vessel length, vessel wall area, and intervessel pit membrane thickness. • Quantitative vessel and pit characters are suggested to contribute to interspecific variation of the ionic effect, whereas chemical properties of intervessel pit membranes are likely to play an additional role.

Near-infrared spectroscopy for the quantitative determination of mass transfer and water absorption kinetics by a polymer solution

This article reports a new method to quantify the water absorption kinetics and the mass transfer in a polymer solution by using near-infrared (NIR) spectroscopy and partial least-squares (PLS) models, while it is exposed to a humid atmosphere. Polymer solutions used in this study were made with highly polar solvents exhibiting both a high affinity for water and a low volatility such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. Poly(ethersulfone) and poly(etherimide) were chosen as polymer models as the method could provide useful information for coating process and membrane fabrication monitoring. Whereas gravimetric kinetics yield data on the overall mass transfer, including both water absorption and solvent evaporation, in situ analyses using NIR can quantify separately the solvent and nonsolvent concentration change in the polymer solution. Quantitative models were developed using PLS regression to predict the local water, polymer, and solvent weight fractions in the polymer solution. The method was proved to be suitable for the different studied systems and allowed to infer mass transfers until the onset of the phase separation process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1960–1969, 2010

Rapid changes in plasma cortisol, osmolality, and respiration in response to salinity stress in tilapia ( Oreochromis mossambicus)

We elucidated a time course for cortisol release in tilapia as it corresponds to changes in plasma osmolytes and respiration. Following exposure of freshwater (FW) tilapia to 25‰ seawater (SW), we measured plasma osmolality, [Na +], [K +], [Cl −], hematocrit, cortisol concentration, oxygen-consumption rate (ṀO2), and ventilation frequency over 5 days and compared them to FW control fish. Cortisol increased rapidly by 3 h and remained elevated for 3 days. Plasma osmolality, [Na +], and [Cl −] were elevated at 6–8 h, peaked 24 h following SW exposure, and then decreased to near-FW levels by 3 days. ṀO2 increased at 24 h post-SW exposure relative to FW, while ventilation frequency increased by 3 h. Overall, we interpret changes in cortisol as resulting from a change in salinity, in contrast to changes in plasma solute concentrations that could be due to adjustments resulting from the fish's cortisol response as it faces osmoregulatory distress. Increases in oxygen-consumption rate at 24 h and ventilation frequency at 3 h are likely as a result of the cellular stress response occurring during salinity stress. No significant changes in blood hematocrit were observed, which suggests that tilapia are capable of rapidly counteracting dehydration during acute hyperosmotic stress.

Computational prediction of the osmoregulation network in Synechococcus sp. WH8102

BackgroundOsmotic stress is caused by sudden changes in the impermeable solute concentration around a cell, which induces instantaneous water flow in or out of the cell to balance the concentration. Very little is known about the detailed response mechanism to osmotic stress in marine Synechococcus, one of the major oxygenic phototrophic cyanobacterial genera that contribute greatly to the global CO2 fixation.ResultsWe present here a computational study of the osmoregulation network in response to hyperosmotic stress of Synechococcus sp strain WH8102 using comparative genome analyses and computational prediction. In this study, we identified the key transporters, synthetases, signal sensor proteins and transcriptional regulator proteins, and found experimentally that of these proteins, 15 genes showed significantly changed expression levels under a mild hyperosmotic stress.ConclusionsFrom the predicted network model, we have made a number of interesting observations about WH8102. Specifically, we found that (i) the organism likely uses glycine betaine as the major osmolyte, and others such as glucosylglycerol, glucosylglycerate, trehalose, sucrose and arginine as the minor osmolytes, making it efficient and adaptable to its changing environment; and (ii) σ38, one of the seven types of σ factors, probably serves as a global regulator coordinating the osmoregulation network and the other relevant networks.

Fully Coupled THMC Modeling of Wellbore Stability with Thermal and Solute Convection Considered

Wellbore stability analysis is an important topic in petroleum geomechanics. Analytical and numerical analysis of wellbore stability involves the study of interactions among pressure, temperature and chemical changes, and the mechanical response of the rock, a coupled thermal–hydraulic–mechanical–chemical (THMC) process. Thermal and solute convection have usually been overlooked in numerical models. This is appropriate for shales with extremely low permeability, but for shales with intermediate and high permeability (e.g., shale with a disseminated microfissure network), thermal and solute convection should be considered. The challenge of considering advection lies in the numerical oscillation encountered when implementing the traditional Galerkin finite element approach for transient advection–diffusion problems. In this article, we present a fully coupled THMC model to analyze the stress, pressure, temperature, and solute concentration changes around a wellbore. In order to overcome spurious spatial temperature oscillations in the convection-dominated thermal advection–diffusion problem, we place the transient problem into an advection– diffusion-reaction problem framework, which is then efficiently addressed by a stabilized finite element approach, the subgrid scale/gradient subgrid scale method (SGS/GSGS).

Use of Alkali–Silica Reaction-Affected Recycled Concrete Aggregate in Hot-Mix Asphalt

The effects of using alkali–silica reaction-affected recycled concrete aggregate (ASR-RCA) in hot-mix asphalt (HMA) were investigated. The goal of the study was to determine if the asphalt binder provided sufficient moisture protection to prevent reexpansion of existing ASR gel or occurrence of new ASR. Expansion tests were performed with a dilatometer on RCAs to determine the possibility of new ASR occurring in reactive aggregates in the HMA. Micro-Deval and freeze–thaw tests measure higher mass loss in ASR-RCAs than that in virgin aggregates, which is caused by preexisting aggregate microcracks and ASR gel in ASR-RCAs. Moisture damage testing indicated good moisture resistance of HMA mixtures made with ASR-RCA, especially when compared with virgin siliceous aggregate. Expansion testing indicated that both ASR-RCAs were still reactive with 0.5 N sodium hydroxide (NaOH) solution saturated with calcium hydroxide (CaOH2) at 60°C. Expansion testing of HMA specimens in NaOH + CaOH2 solution at 60°C indicated a reaction between the asphalt binder and the solution, but little ASR. However, expansion testing in deicer solution at the same temperature indicated that some ASR may have occurred along with the primary binder-solution interaction. The volume change characteristics associated with the binder–solution interaction with and without ASR was supported by the change in pH and alkali concentration of the test solution. The potential distress mechanisms are identified, and possible remedial measures as guidelines are recommended for the use of ASR-RCA in HMA.

KINETICS CONSIDERATIONS CONCERNING THE OXIDATIVE DEGRADATION BY PHOTO-FENTON PROCESS OF SOME ANTIBIOTICS

The aim of this study is the evaluation of photo-Fenton as a suitable advanced oxidation process to degrade ampicillin and streptomycin antibiotics. The degradation was studied by monitoring the organic substrate concentration changes in aqueous solution as a function of reaction time using COD analysis. The oxidation process follows two successive stages. In the first stage (I) the oxidation of the antibiotics takes place with high reaction rate, leading to intermediate oxidation products. In the second stage (II) the reaction rate is much lower, the intermediate compounds being more resistant towards the oxidation process. For each oxidation stage, the process follows a pseudo-first-order kinetics according to the Lagergren model, the first-order kinetic constants being k1 I (magnitude order of 10-3 s-1) and k1 II (magnitude order of 10-4 s-1). The kinetics constant k1 I and k1 II values are correlated with the nature and structure of the antibiotic and the intermediate oxidation products, which determine the oxidation reactivity.

수용액 합성법에 의한 ZnO 이중 나노구조물의 합성

Double-layered ZnO nanostructures have been synthesized by aqueous solution method on (001) plane of ZnO nanorod. A stepwise changing of aqueous solution concentration gave rise to a new nano-structured layer consisting of either multiple of nanorods or nanowires with much smaller radii than that of the ZnO nanorod on which the new layer was grown. As the first step the ZnO nanorods have been grown to have the (001) preferential orientation in the aqueous solution consisting of 0.1M zinc nitrate and 0.1 M HMT. This preferentially aligned ZnO nanorods have been regrown in either a less diluted solution of 0.01M zinc nitrate and 0.01 M HMT or a more diluted solution of 0.005M zinc nitrate and 0.01 M HMT. A new nano-layer consisting of numerous aligned nanorods or nanowires has been produced on the (001) planes of ZnO nanorods. The growth mechanism for this double layered ZnO nanostructure is ascribed to the (001) polar surface energy instability and inhibition of (001) plane growth due to the step-wise change of aqueous solution concentration; ZnO nuclei formed on the (001) plane grow preferentially in (010) plane instead of (001) plane to reduce the total surface energy. Surface area of ZnO nanostructure can be increased in orders of magnitudes by forming a new layer consisting of smaller nanorods/nanowires on (001) plane of ZnO nanorods.

Does habitat of Atriplex halimus L. affect plant strategy for osmotic adjustment?

The impact of water stress was analysed in the xero-halophyte Mediterranean shrub Atriplex halimus using two Tunisian populations originating from a sub-humid coastal site (Monastir) or from a semi-arid area (Kairouan). Seedlings were exposed for 10 days to nutrient solution containing either 0 or 15% polyethylene glycol. Water potential (Ψw), osmotic potential (Ψs), osmotic potential at full turgor [Ψs(100)], relative water content (RWC), shoot dry weight (DW) and changes in solute concentrations were quantified every 2 days throughout the stress period and inorganic solutes contents were determined at the end of the treatment. The water deficit induced a decrease in Ψw, Ψs and RWC in both populations, recorded changes being higher in plants of Monastir than those of Kairouan while the shoot dry weight was reduced in a similar extent in stressed plants from both populations. Water deficit induced an increase in proline, glycinebetaine and sugar concentrations. Proline accumulated as early as after the 24-h stress treatment while, glycinebetaine required more than 6 days of stress to accumulate. At the end of the stress period, the plants of Kairouan population accumulated higher amounts of proline than those of Monastir, while an opposite trend was reported for glycinebetaine. Both populations specifically accumulated Na+ in response to drought stress, suggesting that this element could play a physiological role in the stress response of this xero-halophyte species. Presented results suggest that the non-recyclable osmotic solute glycinebetaine does not necessarily preferentially accumulates in population facing permanent water stress and that other strategy than osmotic adjustment might be involved in drought tolerance of A. halimus.

Effect of polymer solution concentration on the swelling and mechanical properties of glycol chitosan superporous hydrogels

AbstractThis study examined the effect of the polymer solution concentration on the swelling and mechanical properties of glycol chitosan (GCS) superporous hydrogels (SPHs). GCS SPHs were synthesized using a gas blowing method using glyoxal as the crosslinking agent at different polymer solution concentrations. A small change in the GCS solution concentration resulted in a remarkable change in compression strength and swelling kinetics without any significant loss in equilibrium water imbibing capacity. The increase in mechanical strength accompanied by the decrease in swelling kinetics was caused by the generation of smaller pores during the gelation process of the reactant systems associated with a higher polymer solution viscosity. The apparent diffusion coefficients for a variety of GCS/simulated gastric fluid solution systems were determined from the theoretical fitting of experimental dynamic swelling data, explaining the effects of the solution concentration and crosslinking density on the swelling kinetics. The diffusion coefficients determined in this study are expected to be used as the basic information in estimating the swelling kinetics of samples in different dimension. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Piezoresistive cantilever array sensor for consolidated bioprocess monitoring

Cellulolytic microbes occur in diverse natural niches and are being screened for industrial modification and utility. A microbe for consolidated bioprocessing (CBP) development can rapidly degrade pure cellulose and then ferment the resulting sugars into fuels. To identify and screen for novel microbes for CBP, we have developed a piezoresistive cantilever array sensor which is capable of simultaneous monitoring of glucose and ethanol concentration changes in a phosphate buffer solution. 4-mercaptophenylboronic acid and polyethyleneglycol-thiol are employed to functionalize each piezoresistive cantilever for glucose and ethanol sensing, respectively. Successful concentration measurements of glucose and ethanol with minimal interferences are obtained with our cantilever array sensor.

PREDICTION OF SOLUTE CONCENTRATION CHANGES ALONG PULSED SIEVE PLATE EXTRACTION COLUMNS

Pulsed columns are one of the most important extraction columns that have extensive application in different industries. Obtaining the solute concentration in different heights of the column has a great influence on achieving the physical property changes of the phases along the column. An experimental work of mass transfer in a pilot pulsed sieve plate extraction column at different operating conditions is carried out in this research, and the solute concentration in different heights of the column is obtained for two different systems with medium and high interfacial tensions. The solute concentration changes along the column are calculated using previous models in the literature and the model presented for achieving the effective diffusivity in a previous work of the present authors. Comparison of the experimental results and the models is made and the best one is suggested.

Experimental investigation on heat transportation over long distance by ammonia–water absorption cycle

An ammonia–water absorption cycle is suggested to transport heat over long distance, in which thermal energy is transferred into chemical energy in the heat source site by the change of solution concentration. So there is no heat insulation requirement for the transportation pipelines. In the user site the chemical energy could be released with heating or cooling. An experimental prototype has been built to investigate the system performance. The experiments include two parts: heating is obtained from absorber (user site) in transition season by ammonia–water absorption heat pump cycle, in which a hot water outlet temperature at about 64 °C can be reached and the system COP is 0.47 (absorption temperature at 66 °C). Cooling is obtained from evaporator (user site) in summer by ammonia–water absorption refrigeration cycle, in which a chilled medium outlet temperature at about 8 °C can be reached and the system COP is 0.43 (evaporation temperature at 4.6 °C). The investigation of the transportation parameters also shows that the pump electric consumption can be reduced greatly in comparison with the conventional heat transportation method. The ammonia–water absorption cycle is a potential and efficient way of heat transportation over long distance.

Inhibition of nucleation and growth of ice by poly(vinyl alcohol) in vitrification solution

Control of ice formation is crucial in cryopreservation of biological substances. Successful vitrification using several additives that inhibit ice nucleation in vitrification solutions has previously been reported. Among these additives, here we focused on a synthetic polymer, poly(vinyl alcohol) (PVA), and investigated the effects of PVA on nucleation and growth of ice in 35% (w/w) aqueous 1,2-propanediol solution by using a differential scanning calorimetry (DSC) system equipped with a cryomicroscope. First, the freezing temperature of the solution was measured using the DSC system, and then the change in ice fraction in the solution during cooling was evaluated based on images obtained using the cryomicroscope, at different concentrations of PVA between 0% and 3% (w/w). Based on the ice fraction, the change in residual solution concentration during cooling was also evaluated and then plotted on the state diagram of aqueous 1,2-propanediol solution. Results indicated that, when the partially glassy and partially frozen state was intentionally allowed, the addition of PVA effectively inhibited not only ice nucleation but also ice growth in the vitrification solution. The effect of PVA on ice growth in the vitrification solution was explained based on kinetic limitations mainly due to mass transport. The interfacial kinetics also might limit ice growth in the vitrification solution only when the ice growth rate decreased below a critical value. This coincides with the fact that PVA exhibits a unique antifreeze activity in the same manner as antifreeze proteins when ice growth rate is lower than a critical value.