Process Of Rehydration Research Articles

Correlation between surface forces and surface reactivity in the setting of plaster by atomic force microscopy

The setting of mineral binders (cement, plaster, etc.) arises as a direct consequence of surface reactivity by a process of dissociation and rehydration. This transformation induces a complete change of surface forces, of which the nature remains still unknown. The general process of the setting has been studied by means of plaster (CaSO 4·0.5H 2O) crystals, chosen for an experimental convenience. The surface alteration (growth, dissolution, atomic resolution) of the plaster crystal with respect to the introduction of the calcium sulfate solution has been followed by using atomic force microscopy (AFM. Alternatively, this apparatus has been adapted by gluing a plaster microcrystal on the end of a microcantilever to quantitatively measure in situ the interactions between two plaster crystals in the condition of the setting. Kinetic comparison between force measurements and surface images leads to the conclusion of physical and chemical phenomena involved during the setting.

Effect of an osmotic differential on the efficiency of gene transfer by electroporation of fish spermatozoa

This study examined the efficiency of an osmotic differential to promote the influx of extracellular medium and hence the uptake of foreign DNA into common carp sperm cells during electroporation. Carp spermatozoa diluted in a hyposmotic solution (<290 mOsm/kg) become motile, but rapidly lose their fertility. Thus, spermatozoa were first dehydrated in a hyperosmotic solution (590 mOsm/kg) and subsequently rehydrated with a hyposmotic solution (130 mOsm/kg) containing pRSV-CAT DNA to regain the original osmotic pressure of the seminal fluid (about 300 mOsm/kg). Electroporation (pRSV-CAT DNA concentration of 30 ng/μl, field strength of 3.5 kV/cm, pulse length of 500 μs) was applied during the process of rehydration. The success rates of gene transfer assessed in 30-day-old fish were 66% for electroporation during the rehydration process of dehydrated sperm, 8% for electroporation in isosmotic conditions, and 20% for electroporation in hyperosmotic conditions. These results suggest that electroporation during rehydration of dehydrated sperm can greatly enhance the uptake of foreign DNA leading to increased gene transfer frequencies.

Dehydration of onion: some theoretical and practical considerations

SummaryYellow globe type onion slices were dehydrated with air at different temperatures and flow rates. Drying‐rate curves were constructed and used for the calculation of critical moisture content, drying constant, effective diffusivity of moisture through the slices and energy of activation for diffusion. Rehydration rates at 25 and 40°C were also determined and found to be independent of drying conditions. An attempt to relate the process of moisture removal to the process of rehydration was made and a possible diffusion mechanism based on the concept of internal and external resistances is discussed.

Some Observations on the Process of Dehydration and Rehydration of Gypsum by Means of Proton Magnetic Resonance

Abstract 1) On the thermal dehydration in vacuo, the characteristic single sharp peak of proton resonance was observed for the specimens dehydrated at the temperature from 70 to 150°C. It is assumed that this single sharp peak is attributed to the zeolitic water probably existing in the space of the crystal lattice of soluble anhydrite and that this zeolitic water can be interpreted as being a part of the water molecules which originate from dihydrate during the thermal decomposition. 2) Calcium sulfate hemihydrate was formed by the rehydration of gypsum dehydrated in vacuo. This hemihydrate showed the proton resonance spectrum corresponding to the signal of three spin type with an intensive center peak. This intensive center peak can be interpreted as an indication of the movable water existing in the space of the crystal lattice of hemihydrate. 3) This hemihydrate was considerably stable under the atmosphere of saturated water vapor. This was ascertained by the NMR measurements.

647. The dehydration of gypsum. Part III. A study of the process of dehydration and rehydration of gypsum by adsorption methods

647. The dehydration of gypsum. Part III. A study of the process of dehydration and rehydration of gypsum by adsorption methods