Hydration Procedure Research Articles

Study on Hydration Mechanism of Phosphoaluminate Cement

Phosphoaluminate cement (PAC) is a kind of new cementitious material which has many special properties compared to Portland cement (PC). PAC sets quickly and develops early-high strength. In order to investigate the hydration mechanism, the hydration products and microstructure of PAC were studied with x-ray diffraction (XRD), electron scanning microscope (SEM) and electrochemical impedance spectroscopy (EIS). Heat evolution of PAC was also measured. The results show that the hydration mechanism of PAC is different from Portland cement, which is caused by the special minerals including CxP, CA(P), phase L, and so on. The main hydration products of PAC are calcium phosphorus aluminates hydrate (C-A-P-H), calcium phosphate hydrate (C-P-H), aluminates hydrate (C-A-H), the corresponding hydration microcrystal as well as gels. Also, there is no calcium hydroxide produced during hydration. The hydration procedure of PAC is divided into four stages which are dissolution and induction, acceleration, deceleration, stabilization.

The effect of stromal hydration on surgical outcomes for cataract patients who received a hydrogel ocular bandage.

Purpose:The purpose of this study was to examine the effect of stromal hydration on surgical outcomes for patients who received the new hydrogel ocular bandage (ReSure™ Adherent Ocular Bandage, Ocular Therapeutix, Inc, Bedford, MA, USA) following routine cataract surgery.Methods:This post-hoc, single-masked study was conducted with 310 patients who were scheduled to undergo unilateral clear corneal cataract surgery with phacoemulsification and intraocular lens implantation. Incisions were closed with stromal hydration (270 patients) or without stromal hydration (40 patients) based on physician standard of care. All patients received the hydrogel bandage at the conclusion of the procedure. Ocular assessments of stromal edema, flare, corneal staining, anterior chamber cells, best-corrected visual acuity, and intraocular pressure were made 24 hours after surgery.Results:Significantly more patients experienced stromal edema in the group with stromal hydration (26.3% versus 10.0%, respectively; P = 0.028). A higher percentage of patients experienced corneal staining when stromal hydration was performed (20.4% versus 2.5%; P = 0.004). The mean BCVA (best-corrected visual acuity) also was significantly different between the groups (logMAR of 0.164 with stromal hydration versus 0.095 without hydration; P = 0.007). No significant differences were observed between the study groups in terms of flare, anterior chamber cells, or intraocular pressure.Conclusion:Cataract surgery without stromal hydration provided better surgical outcomes than the traditional hydration procedure when used in conjunction with a new hydrogel bandage.

A new route to mass production of metal hydroxide/oxide hydroxide nanoparticles

Aluminum hydroxide/oxide hydroxide nanofibers were self-assembled by hydration of highly activated aluminum powder using no surfactants or templates. The activation was performed by milling aluminum powder with sodium chloride as nano-miller. Transmission electron microscopy images and X-ray diffraction patterns confirm that this method leads to smaller size of aluminum particles (less than 50 nm) and increases the lattice strain. These factors provide conditions under which hydration procedure proceeds until it reaches the core of aluminum particles. The synthesized powder consists of nanofibers with thickness less then 10 nm and average length of 120 nm and specific surface area of 309 m 2 g −1. The process is convenient, highly efficient and capable to be implemented in mass production. It may be extended to produce hydroxide/oxide hydroxide nanopowders of other metals, as well.

Unusual Hysteresis Loop in the Adsorption−Desorption of Water in NaY Zeolite at Very Low Pressure

We report the observation of an unusual hysteresis loop in the water adsorption−desorption isotherm in NaY in the very low pressure range. Vacuum equilibrium thermodesorption and n-pentane adsorption experiments combined with grand canonical Monte Carlo simulations show that this hysteresis phenomenon is consecutive to the trapping of water in sodalite cages. We propose that the adsorption−desorption of water in NaY occurs as follows. (i) Initial adsorption of a few water molecules on the most accessible cations located on sites II in the supercages. The solvation of these cations makes the sodalite cages accessible to water. (ii) Complete filling of supercages and sodalite cages associated with a migration of nonframework cations from D6R prisms to sodalite cages. (iii) Desorption of water from supercages with water still trapped in the sodalite cages. (iiii) Thermally activated desorption of water from sodalite cages. Thus, according to the hydration procedure used, the residual water can be located eit...

Tecnologia de quebra do coco babaçu (Orbignya speciosa)

The babassu nut (Orbignya speciosa) consists of fours parts: the epicarp, mesocarp, endocarp and kernel. Currently the babassu nut is collected and cracked manually by women and children, which is one of the social problems of the Brazil's North/Norwest region. The purpose of this work was to develop an effective technique for removing the shell of the babassu nut. Characterizations were made of the volume, mass, real density, length, transversal perimeter and distance between the epicarp and the kernel. These data were analyzed to establish a correlation between the amount of kernels in each babassu nut and the average of the values of the parameters under study. To determine the compressive force required to break babassu nuts, six experiments were carried out involving: a) untreated nuts; b) nuts peeled by abrasion; c) nuts dried at 120 °C; d) dried at 120 °C and peeled by abrasion; e) dried at 120 °C peeled by abrasion, hydrated and frozen at -18 °C; and f) dried at 120 °C, peeled by abrasion, hydrated and puffed. An estimate was made of the average time required to remove the epicarp and mesocarp in the shelling procedure, and of the time required to reach mass equilibrium in the drying and hydration procedure.

Stabilization of gamma alumina slurry for chemical–mechanical polishing of copper

Stabilization of γ-alumina suspension for chemical–mechanical polishing (CMP) of copper was investigated. Citric acid and poly(acrylic acid) (PAA) ( M w = 5000 ) were used as dispersant. The stability of suspension was evaluated from the changes in viscosity, particle size and zeta potential. It appears that metastable γ-alumina mainly due to its high specific surface area and to the presence of aluminol groups on its surface is progressively transformed to bayerite ( β-Al(OH) 3) by hydration procedure. Citric acid molecules were adsorbed onto γ-alumina surface effectively and exhibited the excellent hydration inhibition effect. Although citrate–alumina surface complexes give barrier to the flocculation, the repulsion potential is based mainly on the electrostatic repulsion, thereby steric hindrance caused by the adsorption of these small molecules is very weak. The electrosteric repulsion, which provides more effective dispersion stability than electrostatic repulsion force, can be expected by using polyelectrolyte such as PAA; however, adsorbed layers of PAA onto solid/liquid interface are loosely formed. Therefore, a large amount of PAA was required to inhibit the surface hydration of γ-alumina suspension, thereby the excess addition of PAA decreased the electrosteric repulsion and re-bridging of the dispersant between particles caused an increase in suspension viscosity. Therefore, synergistic effect can be expected in mixed dispersant system of citric acid and PAA, since small citric acid molecules are adsorbed faster than PAA, inhibiting the progress of surface hydration, and then adsorbed PAA layers exhibit the effective electrosteric repulsion interaction between particles with a small amount compared with PAA alone. It was revealed that the γ-alumina slurry dispersed by mixed dispersant exhibited the improved removal rate of Cu layer by CMP polishing test.

동결 건조된 리포솜의 안정화에 있어서 말토스의 영향

Liposome powders were prepared by a freeze-drying method for the application to the field of drug carrier. The effect of maltose as a liposome stabilizer was studied on the stability and the drug-loading efficiency of the freeze-dried liposome powders. The particle size of liposomes before and after freeze-drying was determined to evaluate the liposome stability. The drug-loading efficiency was measured by Fluorescence spectrophotometer using calcein as a model drug. When maltose was added after the preparation of the liposomes, the liposomes was stable, compared to the case of maltose addition at the hydration procedure. By the addition of maltose, the liposome was stable for 30 days at , while the particle size of the liposome without maltose increased with time. The liposome showed relatively high stability when the maltose/lipids molar ratio was 3 and 6.

Metakaolin as a main cement constituent. Exploitation of poor Greek kaolins

Abstract In this work, the properties and the hydration procedure of cements containing metakaolin were monitored for periods up to 180 days. Four metakaolins, derived from poor Greek kaolins, as well as a commercial metakaolin of high purity were used. Cement mortars and pastes, with 0%, 10% and 20% replacement of cement with the above metakaolins, were examined. Strength development, water demand and setting time were determined in all samples. In addition, XRD and TGA were applied in order to study the hydration products and the hydration rate in the cement–metakaolin pastes. It is concluded that metakaolin has a very positive effect on the cement strength after 2 days and specifically at 28 and 180 days. The blended cements demand significantly more water than the relatively pure cement and the water demand increase is higher, the higher the metakaolin content. The produced metakaolins as well as the commercial one give similar hydration products after 28 days and the pozzolanic reaction is accelerated between 7 and 28 days, accompanied by a steep decrease of Ca(OH) 2 content. Finally, it is concluded that a 10% metakaolin content seems to be, generally, more favorable than 20%. The produced metakaolins, derived from poor Greek kaolins, as well as the commercial one impart similar properties with respect to the cement strength development, the setting and the hydration.

AGOA: A Hydration Procedure and Its Application to the 1-Phenyl-beta-Carboline Molecule

A new procedure, named AGOA, has been developed and implemented in a computer program written in FORTRAN 77 to explore the hydration structures of polar solutes using its molecular electrostatic potential (MEP). This procedure can be generalized to polar solvents other than water. It has been tested for several small molecules, and applied to complex molecules of pharmacological interest, such as the beta-carbolinic systems derived from indole. This is a stringent, but not general, test of the AGOA procedure and shows its robustness, flexibility and low computational costs, since either semiempirical or ab initio wavefunctions can be employed. The comparisons with procedures based upon the geometry optimization of the solute-water complex show the superior performance of the AGOA procedure for the anti and syn beta-carboline conformers, reassuring its use to comprehend and to quantify the specific interactions involved in solvent effects.

Robust polymeric microchannel coatings for microchip-based analysis of neat PCR products.

Several silica coatings have been evaluated for replicate PCR product analysis in capillaries and electrophoretic microchips. Silica coatings are an essential component to many electrophoretic separations, and this importance is magnified in microchips, where separation distances are minimized. Increasing the resistance of coatings to separation conditions improves the reproducibility and longevity of the coated microchip, which allows for the full potential of these devices (rapid separations, high through-put, and longevity) to be realized. In this study, several coating parameters have been evaluated experimentally and through the literature to produce a coating with high resistance to the separation conditions of interest, neat PCR product separations. Coating degradation induced under these conditions was tested for several coatings, and the influence of surface hydroxylation, surface hydration, silanization solvent, silanizing reagent, catalysis, endcapping, and polymerization procedure are discussed. Under the testing conditions, a coating (coating E) prepared by silanization with chlorodimethyloctylsilane in toluene with a polymer layer of poly(vinylpyrrolidone) attached by a hydrogen abstraction method [Srinivasan, K.; Pohl, C.; Avdalovic, N. Anal. Chem. 1997, 69, 2798-2805] was most resistant. This coating was tested for longevity on electrophoretic microchips and was compared to the traditional coating of polyacrylamide. The coatings produced similar resolution and efficiencies; however, coating E provided more reproducible migration times and had performed for 635 analyses when testing was terminated. This procedure provides a reproducible, resistant surface coating, thus allowing for replicate analysis of neat PCR product on microchips.

Hydration products of C3A, C3S and Portland cement in the presence of CaCO3

The subject of this work is the effect of calcium carbonate on the hydration products of C3A, C3S and cement. Pastes made from C3A and C3S containing 0%, 10%, 20% and 35% w/w of chemical grade CaCO3, as well as pastes made from Portland cement containing 0%, 10%, 20% and 35% w/w limestone, were examined after 1, 2, 7 and 28 days of hydration. The hydration products in C3S and C3A pastes containing CaCO3, as well as in limestone cement pastes, were identified by means of powder diffraction. The effect of calcium carbonate on the hydration procedure was also recorded. It is concluded that in pastes containing CaCO3, either as a chemical reagent or as a limestone constituent, the ettringite's transformation to monosulfate is delayed, while calcium aluminate monocarbonate is preferably formed instead of monosulfate even at early ages. In addition, the hydration of C3S is accelerated and formation of some carbosilicate is observed.

Gas permeability of geosynthetic clay liners

Series of gas permeability tests were performed on partially saturated needle-punched geosynthetic clay liners (GCLs) with nitrogen (N 2) as the gas permeant medium. The hydration procedure was found to have a strong influence on the gas permeability of the GCLs. For the range of overburden pressures considered in the present investigation, a reasonable linear relationship on a linear-log scale has been observed between the permeability and the volumetric water content. A decrease of around 1 to 1.5 order of magnitude in the permeability of a granular bentonite type of GCL and about 2 to 3 order of magnitude in the permeability of a powder bentonite type of GCL have been observed for the range of volumetric water content studied (46%< ϑ<73%). A well defined linear relationship was found to exist between the permeability and the air content. This relationship is independent of the overburden pressure and is specific to each type of GCL. The size and shape of the gravel in the drainage layer immediately above the GCL was found to affect its gas permeability, when subjected to high overburden pressure.

Pharmacokinetics and antidiuretic effect of a new vasopressin analogue (F992) in overhydrated male volunteers.

The aim of the present study was to study the pharmacokinetics, the antidiuretic effects and the safety of [D-Phe2, Thi3, alpha-Me-Abu4, Hyp7, D-Arg8]dC1-vasopressin, a new antidiuretic peptide (F992, Ferring, Sweden), administered as intravenous infusion to orally overhydrated male volunteers. Eight healthy male volunteers participated in this open study consisting of two parts: a dose titration study and a safety study. In the dose titration study ascending doses of F992 were administered to volunteers in pairs in order to find a dose that within 1 h after the infusion, in both subjects, caused a reduction of the urine flow rate to below 5 ml x min(-1) (target dose). Subsequently, this target dose was administered to all volunteers. In the safety study the target dose was doubled and given to all volunteers. On each study occasion, in both study parts, the subjects were orally overhydrated with water. F992 was administered as i.v. infusion approximately 1.5 h after the start of the hydration procedure. Throughout the study days, blood was sampled for determination of plasma concentrations of F992 and for safety evaluation. Urine was collected at intervals in order to estimate flow rate and osmolality. The target dose was found to be 4.0 microg as this dose fulfilled the criteria regarding antidiuretic effect, consequently 8.0 microg was administered to all subjects in the safety study. After infusion of 4.0 and 8.0 microg, the median half-lives of elimination were 4.72 (range 3.99-6.53) h and 3.85 (range 3.04-11.08) h, respectively. The plasma clearance and the volume of distribution at steady state were estimated to be 0.88 (SD 0.24) ml x min(-1) x kg(-1) and 326 (SD 68) ml x kg(-1)] after infusion of 4 microg. After the highest dose (8 microg), the corresponding estimates were 0.86 (SD 0.32) ml x min(-1) x kg(-1) and 299 (SD 81) ml x kg(-1), respectively. Significantly (P = 0.033) different maximum mean urine osmolalities were produced after infusion of 4.0 and 8.0 microg of F992 (534 (SD 318) vs 732 (SD 189) mOsmol x kg(-1)). The median times to reach these values showed some tendency to be longer for the highest dose, however statistical significance was not reached. No serious adverse events were observed during the study. We found it safe to administer F992 as infusion to overhydrated male volunteers. The results suggest that F992 has a longer half-life and a lower potency than the widely used peptide desmopressin.

Pharmacokinetics and antidiuretic effect of intravenous administration of desmopressin in orally overhydrated male volunteers.

In order to study the antidiuretic activity of desmopressin in healthy human subjects, a study design has previously been used with subjects orally hydrated. The objective of the present study was to investigate the pharmacokinetics and the antidiuretic activity of desmopressin administered as an intravenous infusion to eight orally hydrated male volunteers. After initial ingestion of water corresponding to 15 ml.kg-1 body weight, the overhydration was maintained by replacing the urinary fluid loss by drinking-water. Desmopressin (4 micrograms) was administered intravenously over 10 min. 1.5 hr after the start of the hydration procedure. Blood was sampled and urine was collected at intervals throughout the study day (9.5 hr). The terminal half-life of elimination (t1/2,) of desmopressin was calculated to be 2.97 +/- 0.24 (S.E.M.) hr while the clearance was 1.77 +/- 0.10 ml.min.-1.kg-1 and the volume of distribution at steady state was 373 +/- 30 ml.kg-1. The infusion caused a marked and long-lasting reduction of the urine flow rate. Four hr after the start of the infusion the mean urine osmolality was 909 +/- 46 mOsm.kg-1.

Minimal Radius of Curvature of Lipid Bilayers in the Gel Phase State Corresponds to the Dimension of Biomembrane Structures “Caveolae”

Caveolae are membrane invaginations with a radius of curvature in the range of 40 nm for the bulb; 10–15 nm is the minimal radius for lipid bilayers in the liquid-crystalline Lα(liquid-disordered:ld) phase state. A minimal radius of 20–30 nm could be detected for the gel phase state by analysis of convex–concave bilayer deformations. Circular protrusions with a diameter in the range of only about 40 nm are closed by a flat lid, and those with diameters of 60 nm or more are closed by hemispherical caps. These structures are found primarily in phosphatidylcholine/sterol mixtures, where the gel phase state “liquid ordered” (lo) has been introduced. As a further example the mixture of dimyristoylphosphatidylcholine (DMPC) with an unusual sterol (diflucortolon-21-valerat) is presented. In the usual hydration at temperatures above the phase transition the deformation requires an incubation at 4°C for several weeks or months to form. Using a low temperature hydration procedure (at 4°C), surprisingly bilayers of pure DMPC and DPPC (dipalmitoylphosphatidylcholine) are found to deform in the same convex–concave manner, and this takes place within hours and days. The dependence on hydration protocol is also observed for formation of a sponge-like bilayer network with 30–35 nm radius of curvature in brain sphingomyelin and its mixtures with cholesterol. Caveolae are microdomains enriched in cholesterol and sphingomyelin and are simultaneously discussed to be in thelostate. Direct evidence by investigation of bilayers formed by the lipids isolated from caveolae is still lacking, but structures similar to caveolae which are in the gel phase state (very probably thelostate) are also formed by lipids extracted from bacterial membranes. A further analogy exists because both natural lipid mixtures (brain sphingomyelin and bacterial lipids) transform during heating from the curved bilayer structures into microvesicles above the phase transition. Internalization of caveolae is a process of vesicle formation.

Desulfurization yield of calcium hydroxide/fly-ash mixtures. Thermogravimetric determination

Abstract This work reports the thermogravimetric characterization of the solid products resulting from the low temperature reaction between SO2 and mixed solids containing hydrated mixtures of calcium hydroxide and fly-ashes. The latter sorbents were obtained after a pressurized hydration procedure of coal fly-ashes and commercial calcium hydroxide following a factorial design of the experiments. The analysis of the TG curves performed in a high temperature thermobalance allowed calculation of yield of the desulfurization reaction expressed as mol SO 2 mol Ca , a parameter needed for the design and optimization of desulfurization processes.

Step-by-step observation of the hydration of C3S by magic-angle spinning 29Si nuclear magnetic resonance: the masking effect of D2O

High-resolution solid-state 29Si nuclear magnetic resonance (NMR) characterization of hydrated C3S provides a means of selectively observing the hydrogen-containing phases. In particular, by applying the cross-polarization (CP) technique, we demonstrated that a contrast can be obtained, not only for hydrated against anhydrous phases, but also for hydrogen-hydrated against deuterium-hydrated phases. Selectively deuterated samples were thus prepared by a H2O/D2O alternated hydration procedure. The progress of the polycondensation of orthosilicates as derived by H2O was followed, demonstrating that a separate microphase of anhydrous C3S prevailingly reacted at any step. An induction period, showing a low reactivity and mainly formation of Qo hydrated was observed during the first hydration steps of selectively deuterated samples. The efficiency of the masking effect of D2O was also indirectly proven by comparison with calorimetric measurements.

Supported aqueous-phase, rhodium hydroformylation catalysts I. New methods of preparation

Improved methods for the preparation of supported aqueous phase (SAP) catalysts are described. An in situ preparation of the supported rhodium complex and a more effective hydration procedure are presented. SAP catalysts are also prepared by a self-assembly experiment in which the separated components of a SAP catalyst spontaneously adopt a SAP configuration under reaction conditions.

The effect of surface carbonation on the hydration of CaO

CaO rapidly reacts with water, even with vapor phase. To control the hydration rate of CaO, several methods have been suggested. In the present work, to study the effect of surface carbonation on the hydration rate of CaO, densified CaO is carbonated and the hydration procedure is analyzed by microconduction calorimeter and scanning electron microscope. CaCO3 film formed on CaO surface makes protective layer and contributes to delaying the initial stage of hydration by creating induction period. From the experimental results, the determining mechanism of induction period is proved to be the diffusion of water molecule through CaCO3 protective layer.

Turgor and osmotic relations of the desert shrub Larrea tridentata

Abstract Leaf water relations characteristics of creosote bush, Larrea tridentata, were studied in view of previous reports that its leaves commonly experience zero or negative turgor under dry conditions. Leaf turgor loss point () was determined by a pressure‐volume method for samples subjected to a hydration procedure and for untreated samples. Hydration caused to increase by as much as 3 M Pa. Hydration of samples also caused changes in other leaf water relations characteristics such as symplastic solute content, tissue elasticity and symplasmic water fraction, but total leaf solute content was unchanged. Comparison of our field plant water potential data with values of obtained by the two methods resulted in predictions of turgor loss during part or all of a diurnal cycle based on hydrated samples, and turgor maintenance (at least 0.3 MPa) based on untreated samples. Pooled data for obtained from both partially hydrated and untreated samples showed that L. tridentata maintains fairly constant levels of turgor over a wide range of leaf water potential. Dilution of cell contents by apoplastic water introduced significant errors in psychrometric determinations of osmotic potential in both frozen and thawed leaf tissue and expressed cell sap. Use of these values of osmotic potential resulted in predictions of zero turgor at all plant water potentials measured in the field.