Dehydration Procedure Research Articles

State of Irremovable Water in Solid Polymer Films Examined by Fourier Transform Infrared Spectroscopy I: Poly(Ethylene Glycol) Dimethyl Ether

The state of the sorbed water, including the water that cannot be removed by the reduced pressure and water-sorption processes, into poly(ethylene glycol) dimethyl ether (PEG-DME) film was examined by Fourier transform infrared (FT-IR) spectroscopy. The spectrum of the irremovable water could be obtained without a thermal treatment frequently used as the dehydration procedure. It was found that the irremovable water mainly existed in the crystalline region of PEG-DME film, and that its hydrogen-bonding (HB) structure differed from that of the water sorbed from the air. Moreover, the amount of water having the same HB structure as the irremovable water increased with the water contents. These findings could not be revealed by the spectrum of the sorbed water obtained by the conventional dehydration procedure. The experimental procedure examined here allowed us to investigate the true aspects of the irremovable water and the water-sorption processes.

A 3D porous lanthanide–fumarate framework with water hexamer occupied cavities, exhibiting a reversible dehydration and rehydration procedure

[Sm2(fumarate)3(H2O)4] x 3 H2O, a new porous pillared layer framework with 0D cavities for the accommodation of chair-like hexameric water clusters, possesses three kinds of fumarate ligand with their two COO ends adopting different coordination modes and shows reversible de- and re-hydration behavior.

Nickel-Catalyzed Dimerization of [5]Cumulenes (Hexapentaenes)

Abstract Tetraaryl[5]cumulenes react with low-valent nickel complexes at the second double bond to produce novel [4]radialene derivatives that are head-to-head dimers of [5]cumulenes. The head-to-head dimers are also synthesized by a stepwise route. On the other hand, the nickel-catalyzed dimerization of [5]cumulenes with bulky substituents produces other types of extended [4]radialenes and [5]radialenones depending on the bulkiness of the terminal alkyl substituents. Thus, tetrakis-t-butyl[5]cumulene and 1,4-bis(2,2,6,6-tetramethylcyclohexylidene)[3]cumulene react at the central double bond to give the corresponding [4]radialene and [5]radialenone, whereas 1,4-bis(2,2,5,5-tetramethylcyclopentylidene)[3]cumulene and its benzo-annelated derivative react at the second double bond in a head-to-tail manner to afford the corresponding extended [4]radialenes. Tetrakis-t-butyl[5]radialenone was converted into [5]radialene by using a methylation–dehydration procedure. The extended [4]- and [5]radialenes and [5]radialenones have been fully characterized by spectroscopic analyses, X-ray crystallography, and/or independent chemical synthesis. The properties of these novel exocyclic π-electron systems have been investigated in detail. The aryl-substituted [4]radialenes exhibit facile bond rotation with low energy barriers. The [5]radialene and [5]radialenone form the corresponding cations easily by the addition of an acidic proton. The selectivity of the nickel-catalyzed dimerization of [5]cumulenes is discussed on the basis of theoretical calculations.

Evaluation of Liquid Nitrogen Freeze Drying and Ethanol Dehydration as Methods to Preserve Partially Cooked Starch and Masa Systems

ABSTRACTPreservation of starch structure/properties, including structures formed during partial or complete cooking, are important when the impact of processing conditions is being studied. Two preservation techniques used to study changes in starch during thermal‐mechanical processing are commonly cited in the literature: 1) rapid freezing followed by lyophilization, and 2) a dehydration procedure using alcohols. A comparative determination on how these methods affect various starch structures has not been widely reported. Corn starch samples were collected from the Rapid Visco‐Analyser (RVA) at 3 min (swollen granules, 30°C), at the top of the pasting peak (gelatinized granules, 95°C), at the bottom of the trough (dispersed polymers, 95°C), and a completed RVA sample stored for 120 hr at 4°C (retrograded starch). Samples of masa were obtained by nixtamalizing corn. Differential scanning calorimetry (DSC) endotherms of starch and masa, and X‐ray diffraction (XRD) patterns of masa were evaluated after being preserved by alcohol‐ or freeze‐drying. No significant differences (P > 0.05) between methods were found for onset, end, and peak temperatures (°C), enthalpy (J/g) and % relative crystallinity in any of the samples analyzed. Liquid nitrogen freeze‐drying and ethanol dehydration are both effective methods of preserving various starch systems for structural changes detectible by DSC and XRD; freeze‐drying is generally less expensive and time‐consuming.

Water atomised aluminium alloy powders

The new rapid solidification (RS) process based on high-pressure water atomisation (WA) of the melt for manufacturing of advanced aluminium alloys was realised in the form of a pilot plant. The problems of safe operation in the course of Al alloy powder production and powder quality were solved by the use of water solutions of inhibitors, by the control of suspension temperature and hydrogen ion exponent (pH), by the hydraulic classification of atomised products, and by the optimisation of dehydration procedure. The rate of powder–water interaction strongly depends on the value of pH. While the rate of room temperature reactions is very slow at pH 3.0–4.0, the increase of pH to 6.0 leads to an intensive powder oxidation. A set of powder metallurgy (PM) alloys for various applications was produced on the base of water atomised powders. The characteristics of tensile strength of such alloys essentially exceed those of cast materials of similar compositions.

A VERSATILE METHOD FOR THE CONVERSION OF ALDOXIMES TO NITRILES USING SILICA GEL/THIONYL CHLORIDE

A simple convenient procedure for dehydration of aldoximes has been developed using silica gel/thionyl chloride in heterogeneous conditions. The method has been found to be effective for a wide range of aromatic oximes.

Cellulose derivative-hyaluronic acid-based microporous hydrogels cross-linked through divinyl sulfone (DVS) to modulate equilibrium sorption capacity and network stability.

The aim of this work is to obtain a chemically cross-linked hydrogel from hyaluronic acid and cellulose derivatives that exhibits sensitivity to variation of the composition of the external absorbing medium and an equilibrium sorption capacity higher than a common hyaluronic acid-based hydrogel, in view of its potential use in prevention of postsurgical soft tissue adhesion. This has been achieved by chemical stabilization of hyaluronic acid (HA) and cellulose derivatives, hydroxyethylcellulose (HEC) and carboxymethylcellulose (CMCNa) through the difunctional cross-linker divinyl sulfone. Significant increase in sorption capacity, both in water and in water solutions at different ionic strength, has been observed for these samples in comparison with hydrogels obtained through chemical stabilization of hyaluronic acid. Moreover, different dehydration procedures adopted for the xerogel synthesis have been used, which resulted in a modulation of the equilibrium sorption capacity. Hyaluronic acid stability has been confirmed by means of NMR analysis.

Lanthanum fixation by Myxococcus xanthus: cellular location and extracellular polysaccharide observation

Myxococcus xanthus is a soil bacterium of the myxobacteria group and is abundant in almost all soils. Its role in soil ecology is considered significant. One noteworthy characteristic of the bacterium is that it produces large quantities of extracellular polymeric substances (EPS). It is also known that its biomass has the capacity to fix heavy metals. Here it is reported that M. xanthus was able to accumulate 0.6 mmol of La per g of wet biomass and/or 0.99 mmol per g of dry biomass. Transmission Electron Microscopy (TEM) observation of M. xanthus cells treated with La showed that a substantial amount of this cation was fixed in the EPS and in the cell wall. Smaller amounts were also observed in the cytoplasm. Fixed La appeared as phosphate in all cellular locations. The results given here also show that the use of La enables TEM observation of the M. xanthus EPS as a dense fibrillar net surrounding the cells. This technique is relatively easy and prevents EPS collapse, which occurs frequently during the fixation and dehydration procedures commonly used in preparations for TEM observations. Since antibodies are no longer required, the La stain can be carried out without delaying bacterial cell cultivation or isolation. In addition, the presence of La in cell cytoplasm without cell degeneration suggests that this microorganism could be used as a model in the study of bacteria–lanthanide interactions.

Cryopreservation of axillary shoot tips of in vitro-grown grape (Vitis) by a two-step vitrification protocol

Axillary shoot tips of in vitro grape(Vitis vinifera L. cv. CabernetSauvignon) were successfully cryopreservedby vitrification. Axillary shoot tipswere excised from 4- and 5-month oldplantlets were cultured onsolidified 1/2 MS medium with 1 mg l-1BA at 25 °C. Shoot tips wereprecultured on solidified mediumsupplemented with 0.3 M sucrose for 3 daysand then treated with a mixture of 2 Mglycerol plus 0.4 M sucrose (LS solution)for 20 min at 25 °C. They were thendehydrated with PVS2 for 80 min at0 °C before being plunged into LN for1 hr. Samples were then warmed rapidly inwater at 40 °C. The recovery of theshoot tips amounted to approximately 60%.To enhance further recovery, a two-stepdehydration procedure by vitrification wasexamined. Osmo-protected shoot tips werefirst dehydrated with a 50% PVS2 (halfstrength of the solution) for 30 min,followed by PVS2 for 50 min at 0 °C.This revised dehydration procedure improvedshoot recovery from 60 to 80%. Thisprocedure by vitrification was applied toten other species/cultivars of Vitiswith an average recovery of 64%. Thismethod incorporates a simple and reliableapproach for providing high levels ofgrowth recovery. It also appears promisingfor the cryopreservation of Vitisgermplasm.

Cobalt oxide preparation from waste LiCoO 2 by electrochemical–hydrothermal method

Cobalt ions, extracted from waste LiCoO 2 by using a nitric acid leaching solution, are potentiostatically transformed into cobalt hydroxide on a titanium electrode and cobalt oxide is then obtained via a dehydration procedure. In linear sweep voltammetry, distinct cathodic current peak is observed and indicates that hydroxide ions are formed near the electrode via the electroreduction of dissolved oxygen and nitrate ions give rise to an increase in the local surface pH of the titanium. Under appropriate pH conditions, island-shaped cobalt hydroxide is precipitated on the titanium substrate and heat treatment of the cobalt hydroxide results in the formation of cobalt oxide.

Effect of industrial processing on alfalfa cell walls

Thermal treatment is one of the widely used methods for feedstuff preservation. The aim of this study was to evaluate possible cell wall alterations during the industrial-scale drying of alfalfa. Alfalfa is mainly dehydrated and pelleted using two drying treatments. First a thermal treatment at 70 °C is applied to the chopped raw material, prior to the main dehydration procedure which involves a temperature of about 600 °C for a restricted time (15 min). The different steps of the dehydration process did not cause significant changes in alfalfa cell wall composition, but the proportion of labile ether-linked lignin structure (β-O-4) increased after the thermal shock. Chemical fractionation of cell wall carbohydrates showed that pectins were less accessible to extraction with ammonium oxalate after alfalfa drying. Moreover, xylanase (endo enzyme) was more effective on cell walls obtained from heated material. These results suggested that heat processing causes some changes in interpolymer bonds (covalent and hydrogen bonds) between pectins and the lignin/hemicellulose matrix, whereby the cell wall network is modified. © 2002 Society of Chemical Industry

Synthesis of ultrafine-particle La0.7Sr0.3MnO3 via chelate homogenization and microwave processing

Ultrafine La0.7Sr0.3MnO3 powders were prepared via homogenization in chelate solutions, followed by microwave dehydration, using polynuclear heterometallic diethylenetriaminepentaacetates as precursors. To assess the effect of the dehydration procedure on the phase composition and grain size of La0.7Sr0.3MnO3 ceramics, three routes were tested: concentration of chelate solutions by evaporation until the formation of a glassy precursor, microwave dehydration of chelate solutions, and a combination of gelation and microwave dehydration. Phase-pure La0.7Sr0.3MnO3 with a crystallite size of 30–40 nm (as determined by transmission electron microscopy) could be obtained via microwave dehydration of heterobimetallic precursor solutions, followed by calcination at a temperature as low as 800°C.

Estímulos para la liberación de aldosterona durante una actividad física intensa y de larga duración

Objetivo: establecer los posibles factores causales de la secreción de aldosterona durante una actividad física intensa y de larga duración, bajo condiciones ambientales neutras, en nueve corredores de fondo. Materiales y métodos: después de 10 minutos de calentamiento, en banda rodante con una pendiente del 1% y al 55% de la capacidad física de trabajo máxima (PWCmax), siguieron 90 minutos de carrera, al 80%; finalmente, 90 minutos de recuperación pasiva. No se hizo reposición hídrica durante DH (deshidratado); durante RH (rehidratado) se repuso el 51% del peso corporal perdido en DH. Resultados: en DH hubo pérdida de peso corporal y reducción porcentual del volumen plasmático (%VP). Se observaron hiperosmolaridad, hipernatremia, hipercaliemia, hiperaldosteronemia, pero no hiperreninemia. Al hacer corrección por hemoconcentración y calcular el porcentaje de cambio de las variables en estudio, sólo se observaron hipercaliemia e hiperaldosteronemia. En RH la pérdida de peso corporal fue menor, pero la reducción %VP fue similar; se evitaron la hiperosmolaridad y la hipernatremia, pero no la hipercaliemia durante el ejercicio ni la hiperaldosteronemia durante todo el procedimiento, un comportamiento similar al observado al hacer corrección por hemoconcentración. Conclusiones: Durante la realización de una actividad física intensa la concentración plasmática de aldosterona presentó un incremento proporcional a la duración del ejercicio e independiente de la reducción porcentual del volumen plasmático. La hipersecreción de aldosterona es, al parecer, multicausal y el potasio es uno de los factores determinantes.

Rapid plastic embedding is compatible with colorimetric detection following whole mount in situ hybridization in plant specimens

In performing in situ hybridizations, nonisotopic nucleic acid labeling coupled with colorimetric detection offers a safer, easier and more rapid alternative to using radioactively labeled nucleic acid probes and microscopic autoradiography. Whole mount in situ hybridization is also advantageous, because many samples can be processed identically and the reduced handling of specimens greatly reduces the risk of exposing tissues to RNase(s). The thickness of whole mount specimens, however, often prevents accurate determination of sites of expression within specific tissues. Although post-hybridization embedding and sectioning is a solution to this problem, the precipitate formed following the common colorimetric detection procedure is soluble in the organic solvents used for dehydration prior to embedding. We have developed a dehydration and embedding procedure that takes advantage of the compatibility of L.R. White® resin containing 10% (v/v) polyethylene glycol 400, and heat polymerized. The addition of the plasticizer allows L.R. White® embedded tissues to be sectioned at 10 μm providing excellent signal contrast.

Commercial baker's yeast stability as affected by intracellular content of trehalose, dehydration procedure and the physical properties of external matrices.

The effects of vacuum-drying and freeze-drying on the cell viability of a commercial baker's yeast, Saccharomyces cerevisiae, strain with different endogenous contents of trehalose were analyzed. An osmotolerant Zygosaccharomyces rouxii strain was used for comparative purposes. Higher viability values were observed in cells after vacuum-drying than after freeze-drying. Internal concentrations of trehalose in the range 10-20% protected cells in both dehydration processes. Endogenous trehalose concentrations did not affect the water sorption isotherm nor the Tg values. The effect of external matrices of trehalose and maltodextrin was also studied. The addition of external trehalose improved the survival of S. cerevisiae cells containing 5% internal trehalose during dehydration. Maltodextrin (1.8 kDa) failed to protect vacuum-dried samples at 40 degrees C. The major reduction in the viability during the freeze-drying process of the sensitive yeast cells studied was attributed to the freezing step. The suggested protective mechanisms for each particular system are vitrification and the specific interactions of trehalose with membranes and/or proteins. The failure of maltodextrins to protect cells was attributed to the fact that none of the suggested mechanisms of protection could operate in these systems.

Survival of Chlorophyllous and Nonchlorophyllous Fern Spores through Exposure to Liquid Nitrogen

Survival of Chlorophyllous and Nonchlorophyllous Fern Spores through Exposure to Liquid Nitrogen

Formation of defect-free polyimide hollow fiber membranes for gas separations

Ultra-thin and defect-free polyimide hollow fiber membranes were formed using a dry-jet, wet quench process with spin dopes both with and without volatile solvents. Fibers were spun from the commercially available polyimide, Matrimid ® 5218, and were precipitated in an aqueous quench bath. Spin dopes comprised volatile and non-volatile solvents, polymer, and non-solvent. The influences of dope composition, spinning parameters, and dehydration procedures on the membrane morphology and performance were investigated. Without post-treatment (i.e., defect repair), the fibers exhibited skin thicknesses on the order of 1000 Å and O 2/N 2 selectivities ranging from 90 to 100% of those determined for dense, solution-cast films. The 250 μm OD/125 μm ID fibers were spun at take-up rates comparable to those used in commercial processes (i.e., 50 m/min) and had macrovoid-free morphologies.

Evaluation of LR white resin for histology of the undecalcified rat tibia

Histology of plastic embedded undecalcified bone represents a challenging problem to the histotechnologist. We outline here an exploration of LR White resin as a suitable medium for histologic study of undecalcified rat tibia. A procedure was developed for light microscopy of rat tibia embedded in LR White and sectioned by sawing-grinding technics. The specimens were fixed in 10% neutral buffered formalin or alcohol-acetic acid-formol, dehydrated in ethanol, defatted in chloroform followed by resin infiltration and heat-curing of embedded blocks. The procedure of dehydration, defatting, infiltration, and polymerization can be completed within 10 days. Cold curing with accelerator provided by the manufacturer did not yield superior results compared to blocks cured with heat. Thick sections were obtained using a diamond wire saw, attached to plexiform slides, then ground and polished. Surface staining with Von Kossa silver reagent or toluidine blue revealed satisfactory morphological preservation of the mineralized bone sections. Artifacts like small bubbles appeared occasionally and could not be avoided despite prolonged infiltration or cold curing of blocks. Our method is relatively simple for base-line histologic study of rat tibia. The method offers advantages such as easy adaptability, reliable stainability, contrast, and resolution of bone architecture and marrow cells. Two other embedding media, Micro-Bed resin and Unicryl, were also tested, but produced inferior results.

Cryopreservation of in vitro Grown Fern Gametophytes

Cryopreservation of in vitro Grown Fern Gametophytes

A new method for preparing electron microscopic specimens of Helicobacter pylori.

Abstract A new method for preparing electron microscopic specimens of Helicobacter pylori was developed and used to examine the ultrastructure of this bacterium. We have also investigated the morphological changes in the bacterium when exposed to amoxicillin using our new method. Bacterial specimens for electron microscopy are usually prepared by collecting the bacteria by centrifugation during the fixation and dehydration processes. In our new method the bacteria are filtered through and adsorbed onto a filter before fixation, and the entire filter containing the adhered bacteria is fixed and dehydrated. Using this method we were able to obtain electron photomicrographs in which the external appearances or internal structures of the bacteria were well conserved. The advantages of this method are that it uses only a small amount of bacterial suspension, shortens the time required for the dehydration procedure, and keeps the artifacts to the minimum. Amoxicillin treatment resulted in coccoid form with blebs in the bacterial surface and the appearance of vacuoles, granules, and an area of low electron density in the cytoplasm at one and four minimum inhibitory concentrations. These changes were consistent with results previously reported in the literature.