Reaction Of Seawater Research Articles

Hydration of Portland cement with seawater toward concrete sustainability: Phase evolution and thermodynamic modelling

To mitigate the shortage of freshwater resource in the island and coastal regions, using seawater (SW) for concrete mix can provide significant economic and environmental benefits. To achieve a safe and reliable application, in-depth investigation is needed on hydration of Portland cement in SW. The composition of solid and liquid phases in hydrated Portland cement was quantitively determined and analysed in this study. The use of SW not only significantly increases the hydration rate of clinker but also affects the evolution of phase assemblage. Both the thermodynamic calculations and experimental determinations indicates the formation of Friedel's salt (FS) instead of sulfo-AFm in hydrated cement by SW, implying sulfate ions cannot compete with chloride ions to combine with AFm phases. The characteristic reaction in SW leads to higher sulfate concentration, thus indirectly hindering ettringite (AFt) conversion at the late stage. Through the experimental quantification of thermogravimetric analysis and X-ray diffraction analysis, the kinetic model of clinker dissolution was modified to be more suitable for the hydration of Portland cement in SW. The calculation from coupled models exhibits a novel method to evaluate the evolution of phases in cement hydration. Through model calculations, 3.70% higher solid volume and 12.2% lower liquid volume were obtained in the cement-SW paste at the end of the hydration, which may cause the mechanical properties to be more sensitive under environmental humidity and the temperature.

Table salt as a catalyst for the oxidation of aromatic alcohols and amines to acids and imines in aqueous medium: effectively carrying out oxidation reactions in sea water

A simple, efficient, sustainable and economical method for the oxidation of alcohols and amines has been developed using chloride, a sea abundant anionic catalyst for the synthesis of a range of carboxylic acids, ketones and imines.

C2GT: intercepting CERN neutrinos to Gran Sasso in the Gulf of Taranto to measure θ13

Today’s greatest challenge in accelerator-based neutrino physics is to measure the mixing angle θ13 which is known to be much smaller than the solar mixing angle θ12 and the atmospheric mixing angle θ23. A non-zero value of the angle θ13 is a prerequisite for observing CP violation in neutrino mixing. In this paper, we discuss a deep-sea neutrino experiment with 1.5 Mt fiducial target mass in the Gulf of Taranto with the prime objective of measuring θ13. The detector is exposed to the CERN neutrino beam to Gran Sasso in off-axis geometry. Monochromatic muon neutrinos of ≈ 800 MeV energy are the dominant beam component. Neutrinos are detected through quasi-elastic, charged-current reactions in sea water; electrons and muons are detected in a large-surface, ring-imaging Cherenkov detector. The profile of the seabed in the Gulf of Taranto allows for a moveable experiment at variable distances from CERN, starting at 1100 km. From the oscillatory pattern of the disappearance of muon neutrinos, the experiment will measure sin2θ23 and especially Δm2 23 with high precision. The appearance of electron neutrinos will be observed with a sensitivity to P(νμ→νe) as small as 0.0035 (90% CL) and sin2θ13 as small as 0.0019 (90% CL; for a CP phase angle δ=0° and for normal neutrino mass hierarchy).

The Limulus sperm motility-initiating peptide initiates acrosome reactions in sea water lacking potassium.

During fertilization in Limulus, the spermatozoa first attach to the egg and then undergo an acrosomal reaction. In this reaction, the acrosomal vesicle exocytoses, and a long, preformed acrosomal filament is extruded (and subsequently penetrates the egg chorion). The egg surface component that triggers the acrosome reaction has not yet been solubilized; therefore, previous studies have examined either spontaneous acrosome reactions or acrosome reactions that were triggered by eggs (or insoluble egg fragments), elevated extracellular Ca2+, or Ca2+ ionophores. In this study, we report a new method for initiating acrosome reactions in Limulus sperm. When the Limulus sperm motility-initiating peptide (SMI) is added to sperm in K+-free sea water, greater than 90% acrosome reactions are initiated within 5 min. However, less than 5% acrosome reactions occur either in K+-free sea water lacking SMI or when SMI is added to sperm in either normal sea water or K+- and Ca2+-free sea water. Experiments with K+ ionophores (nigericin and valinomycin), a K+ channel blocking agent (tetraethyl ammonium), an Na+ ionophore (monensin), and reagents that increase the intracellular pH (monensin, nigericin, and NH4Cl) indicate that changes in intracellular K+, Na+, or H+ do not mediate SMI-initiated acrosome reactions. The K+/Ca2+ ratio determines whether or not SMI will initiate acrosome reactions, with greater than 50% acrosome reactions being initiated when this ratio is below 0.3. In that K+ movement does not appear to be the critical event, possibly the K+/Ca2+ ratio either determines the rate of Ca2+ entry or controls the conformation of sperm surface molecules to allow SMI to initiate acrosome reactions in low K+.

Acrosomal reaction of the Thyone sperm. III. The relationship between actin assembly and water influx during the extension of the acrosomal process.

In an attempt to investigate the role of water influx in the extension of the acrosomal process of Thyone sperm, we induced the acrosomal reaction in sea water whose osmolarity varied from 50 to 150% of that of sea water. (a) Video sequences of the elongation of the acrosomal processes were made; plots of the length of the acrosomal process as a function of (time)1/2 produced a straight line except at the beginning of elongation and at the end in both hypotonic and hypertonic sea water (up to 1.33 times the osmolarity of sea water), although the rate of elongation was fastest in hypotonic sea water and was progressively slower as the tonicity was raised. (b) Close examination of the video sequences revealed that regardless of the tonicity of the sea water, the morphology of the acrosomal processes were similar. (c) From thin sections of fixed sperm, the amount of actin polymerization that takes place is roughly coupled to the length of the acrosomal process formed so that sperm with short processes only polymerize a portion of the actin that must be present in those sperm. From these facts we conclude that the influx of water and the release of actin monomers from their storage form in the profilactin (so that these monomers can polymerize) are coupled. The exact role of water influx, why it occurs, and whether it could contribute to the extension of the acrosomal process by a hydrostatic pressure mechanism is discussed.

On the selective adsorption of cations in the cell wall of the green algaValonia utricularis

The selective adsorption of the cations Na+, K+, Mg++ and Ca++ by the cell wall of the Mediterranean algaValonia utricularis (Siphonocladales, Chlorophyceae) from sea water of 40 %. S was investigated by extraction of cell-wall preparations, eluted before in 1.1 mol methanol (adjusted to pH 8) with 0.1 n formic acid in a Soxhlet apparatus. Na+ and K+ were determined by flame photometry, Mg++ and Ca++ by complexometric titration with EDTA. From calculation of the dry weight:fresh weight ratios and the chloride determinations in the eluates, the Donnan free-space fraction of the total cell-wall volume was calculated to about 35 %, and the analytical results of the cation concentrations in the extracts expressed asμVal cm−3 DFS. This calculation is based on the assumption that the acidic groups of the noncellulosic matrix material, carrying negative charges by dissociation at the reaction of sea water (ph about 8) are responsible for the adsorption of cations by exhibition of a Donnan effect. The results obtained show clearly that besides the divalent cations Mg++ and Ca++, which according to the physico-chemical laws of the Donnan distribution must be relatively accumulated to the second power of the monovalent ones, potassium is also enriched by selective adsorption, and the K+:Na+ ratio increased significantly compared with that in sea water. This seems to indicate that the strength of attraction between the cations and the negative sites is dependent on the radii of the ions and the state of hydration and/or polarisation of the ions and binding sites.

HUNTITE, A MINERAL USED IN ANTIQUITY

ABSTRACTSAn unusual occurrence of huntite CaMg3(CO3)4, found in a wooden box pertaining to the cargo of a sunken Roman ship of imperial age in the Golfo di Procchio on the north coast of Elba is described. The huntite has been identified on the basis of chemical analysis, thermo‐gravimetric analysis, differential thermal analysis, X‐ray diffraction and electron microscope images. Having ruled out its origin by the reaction of sea water on some pre‐existing material it is concluded that the huntite represented the original content of the box. The origin and the provenance of huntite and its possible use are discussed.

Scales from phosphate treated sea water

The reaction of sea water with sodium tri-polyphosphate, a compound found in Hagevap sea water phosphate additive, has been examined and precipitates so prepared, in fresh and fully hydrolysed forms, have been examined by X-Ray powder diffraction analysis. Constituent compounds have been identified in the powder patterns and compared with patterns of industrial phosphate scales and sludges. The powder pattern “fog” or diffuse halo commonly associated with such scales has been re-examined and found to contain detail sufficient to characterise the commonest form of polyphosphate found—as β-calcium orthophosphate, or Whitlockite.