Phase Dehydration Research Articles

Wollastonite at the Sterling Hill Fe?Zn?Mn ore body, Ogdensburg, New Jersey

Wollastonite occurs abundantly at the Sterling Hill Fe–Zn–Mn ore deposit, Ogdensburg, New Jersey, one of the few occurrences of wollastonite in regionally metamorphosed rocks; it is absent from the surrounding Franklin marble. Wollastonite occurs in two distinct bands along the inner margins of the synclinal ore deposit. Minerals associated with wollastonite include calcite, grossular-andradite, diopsidic pyroxene, alkali feldspar, and rarely vesuvianite, quartz or bustamite. Assuming the generally accepted values of 750 °C at 5 kbar at Sterling Hill during metamorphism in the Grenville Orogeny, thermodynamic modeling of reactions involving garnet and wollastonite suggest XCO2 ∼0.35 in the wollastonite-bearing rocks. Infiltrating metamorphic fluid rich in H2O was necessary for the formation of wollastonite; at XCO2 of 0.35, the calculated minimum volumetric water:rock ratio is 0.51. The source of the water is believed to be the dehydration of water-rich phases in adjacent ores or mafic rocks. The chemical compositions, textures, stratigraphy, and calculated metamorphic conditions show that wollastonite formed from calcite and quartz at the peak of the Grenville Orogeny.

Raman spectra of phase C (superhydrous phase B) at various pressures and temperatures

Variations of Raman spectra of phase C, or the superhydrous phase B, were investigated up to about 420 kbar at room temperature and in the range 80–873 K at atmospheric pressure. With the exception of the 3355 cm -1 OH band, the frequency of all observable Raman bands of phase C increases monotonously with increasing pressure. However, the frequency for the two well-defined OH bands at pressures greater than about 100 kbar depends strongly on the presence of shear stress. With the exceptions of the three OH bands and the ambient 325 cm -1 band, the frequency of all other Raman bands of phase C decreases with increasing temperature within the experimental uncertainties and the range investigated. Phase C appears to be intact up to the highest temperature attainable in the present study. However, Raman spectra obtained at various conditions seem to suggest that amorphization may start to occur in phase C above 773 K, but dehydration is not completed at the highest temperature studied. It is interesting to find that amorphization occurs at lower temperature than dehydration in phase C. The pressure and temperature effects on the Raman frequencies of phase C are different in many aspects from those observed earlier in phases A and B.

Effects of fluid ingestion on cognitive function after heat stress or exercise-induced dehydration

This study investigated the effects of heat exposure, exercise-induced dehydration and fluid ingestion on cognitive performance. Seven healthy men, unacclimatized to heat, were kept euhydrated or were dehydrated by controlled passive exposure to heat (H, two sessions) or by treadmill exercise (E, two sessions) up to a weight loss of 2.8%. On completion of a 1-h recovery period, the subjects drank a solution containing 50 g l −1 glucose and 1.34 g l −1 NaCl in a volume of water corresponding to 100% of his body weight loss induced by dehydration. (H1 and E1) or levels of fluid deficit were maintained (H0, E0). In the E0, H0 and control conditions, the subject drank a solution containing the same quantity of glucose diluted in 100 ml of water. Psychological tests were administered 30 min after the dehydration phase and 2 h after fluid ingestion. Both dehydration conditions impaired cognitive abilities (i.e. perceptive discrimination, short-term memory), as well as subjective estimates of fatigue, without any relevant differences between the methods. By 3.5 h after fluid deficit, dehydration (H0 and E0) no longer had any adverse effect, although the subjects felt increasingly tired. Thus, there was no beneficial effect of fluid ingestion (H1 and E1) on the cognitive variables. However, long-term memory retrieval was impaired in both control and dehydration situations, whereas there was no decrement in performance in the fluid ingestion condition (H1, E1).

Study of Sewage Sludge Pyrolysis Mechanism and Mathematical Modeling

The pyrolysis of sewage sludge, with and without ZnCl2 activation, was monitored using TGA-FTIR, with the results utilized in a proposed decomposition mechanism. For the pyrolysis of sludge without ZnCl2 activation, three global stages of mass loss occurred and are proposed as dehydration, initial depolymerization, and deep degradation. For the pyrolysis of sludge with ZnCl2 activation, apart from these three stages, an additional mass loss stage could be also observed at high temperature. It is suggested this results from the evaporation of ZnCl2. To make a comparison between these two cases, it was found that the pyrolysis of sludge with ZnCl2 activation had a longer dehydration phase and a shorter degradation phase. Based on the speculated mechanism, a kinetic model of four consecutive competitive reactions was adopted to simulate the pyrolysis of sewage sludge with and without ZnCl2 activation. Globally, the proposed model was able to fit the experimental data very well for both cases, with the correl...

Changes in chalazal cell walls and in the peroxidase enzymes of the crease region during grain development in barley.

In an investigation of the role of peroxidase enzymes in the differentiation of the tissues of the crease region of barley, plants of winter barley cv. Halcyon were grown from anthesis onwards in controlled conditions at a constant temperature of 16 degrees C. Four ears were harvested at 2-d intervals from 6 d after anthesis (daa) until 50 daa. Grains from mid-ear were used for (i) fresh and dry weight determinations, (ii) extraction of crease tissue for the determination of peroxidase activity and for the separation of isozymes of peroxidase by isoelectric focusing (IEF) and (iii) detection of lignin and suberin in the tissues of the crease using autofluorescence and cytochemistry. Peroxidase activity was located histochemically in the crease tissue of cv. Chariot. Scanning electron microscopy studies were carried out on developing grains of cv. Blenheim. Maximum grain water content was achieved at 14 daa. Lignin and suberin were detected in the walls of the chalazal cells from 18 daa onwards. No changes in the staining of chalazal cell walls were detected at the end of grain filling (32 daa), but loss of autofluorescence and staining were observed at 42 daa, just prior to the final, rapid phase of grain dehydration. Peroxidase activity per fresh weight of crease tissue was high at 6 daa and low at 22 daa. It was also low between 32 and 40 daa, but it rose again from 42 daa onwards. IEF demonstrated that both anionic and cationic isozymes of peroxidase were present in crease tissue, the pattern of bands showing some marked changes during the course of grain development.

Seeds obtained from a hydrated polymorph permit crystallisation of an elusive anhydrous organometallic zwitterion

Single crystals of the anhydrous polymorphic modification of the organometallic zwitterion [CoIII(η5-C5H4CO2H)(η5-C5H4CO2)] can only be obtained by seeding the solution with seeds prepared after stepwise dehydration and consequent phase transition at 506 K of the hydrated material [CoIII(η5-C5H4CO2H)(η5-C5H4CO2)]·3H2O.

Photosynthetic Performance and Water Use Efficiency of the Fern Cheilanthes Persica

Morphological, anatomical and physiological frond traits of Cheilanthes persica (Bory) Mett. ex Kuhn were studied to analyze its adaptive strategy. Mean frond life span is about 340 d. Mature fronds are characterized by 91 g m-2 areal dry mass (ADM) and 217 g m-2 succulence. The reduction of frond water content in July (dehydration phase) caused a 51 % decrease in frond surface area (SA). Fronds were dry in August (desiccation phase); nevertheless, in September they showed an increased SA (rehydration phase). Chlorophyll (Chl) a/b ratio, above 3, and the well developed palisade parenchyma (two layers, total thickness of 103.9 µm) are typical for sun leaves. Chl and carotenoid contents and net photosynthetic rate (PN) increased during frond development until the highest values in April-May (maturity phase). When mean air temperature reached 31.3 °C, stomatal conductance (gs) decreased by 34 % and PN by 33 %. The high pigment contents can dissipate the excess of radiant energy, particularly under unfavourable conditions, when PN is low. Rather high PN was found during the rehydration stage. The pronounced decline of mesophyll activity during the declining phase was confirmed by the lowest PN.

Isolation and characterization of genes expressed during early events of the dehydration process in the resurrection plant Craterostigma plantagineum

Summary The resurrection plant Craterostigma plantagineum Hochst. (Fam. Scrophulariaceae) is unique in its ability to survive severe desiccation. To analyze the primary response of this plant to drought, genes were identified that are either transiently expressed or down-regulated during early phases of dehydration. A cDNA library was prepared using as template mRNA isolated from 1 h dried leaves. The library was differentially screened employing three experimental strategies. Partial sequencing of the isolated cDNAs and comparison of the cDNA sequences with those from the public data bases revealed that 49% of the cDNA clones displayed significant sequence similarity to previously identified genes. Northern and reverse Northern analysis confirmed that all genes so far tested showed differential expression upon drought stress: 58 % were transiently expressed, 35.8% were down-regulated and 6.2 % were found to be up-regulated during dehydration. The identification of a large spectrum of differentially expressed genes with diverse cellular functions points to a complex molecular response to drought stress in the resurrection plant C. plantagineum .

Volatile Compounds in Spanish Paprika

The volatile compounds extracted from both sweet and hot samples of commercial Spanish paprika were analyzed by gas chromatography/mass spectrometry (GC-MS). Sixty-one peaks were detected in the volatile extracts of which 55 were identified, only 24 were present in all four samples. The substances identified belonged to several chemical classes: phenols, aldehydes, acids, ketones, alcohols, ethers, nitrogen compounds, aromatic hydrocarbons, alkanes, esters, and lactones. Acetic acid was by far the most abundant compound followed by 1,3- and 2,3-butanediol, acetoine, 3-methylbutanal, ethyl acetate, and dimethoxyphenol. Many of the volatiles probably originated in smoke, applied during the dehydration phase. Products derived from the carbohydrate metabolism and the Strecker degradation were found. The presence of 2-methoxy-3-isobutylpyrazine, the characteristic aroma compound of fresh capsicum, was not detected. Of the volatiles isolated, acetic acid, phenols, ethyl acetate, methyl-branched aldehydes and acids, and other carbonyls would be expected to contribute to the overall paprika flavor.

The bioavailability of febantel in dehydrated camels

In the present study the bioavailability of febantel paste and febantel suspension was investigated in the fully hydrated and the dehydrated camel. The serum concentrations of febantel and its metabolites, fenbendazole, oxfendazole and fenbendazole sulfone were determined by high performance liquid chromatography following extraction with ether. The exposure to febantel and its metabolites in fully hydrated camels was significantly higher in camels dosed with febantel paste compared to febantel suspension, as measured by AUC and Cmax. The AUC and Cmax of fenbendazole and oxfendazole were significantly lower in dehydrated camels as compared to control camels dosed with febantel paste. The systemic availability of febantel suspension in control and dehydrated camels was very low and differences between dehydration and control phases were insignificant. The low systemic availability of febantel in camels dosed with febantel suspension may cause nematodes to become resistant to this anthelmintic. It is, thus, suggested to increase the dose of febantel paste in dehydrated camels in order to increase the exposure to febantel and its metabolites. The binding of febantel, fenbendazole, oxfendazole and fenbendazole sulfone to camels' serum proteins was over 85%. Oxfendazole was only about 70% bound. Dehydration of 10 days did not affect the binding of these benzimidazole derivatives to serum proteins.

Dehydration of the cyclodextrins: A model system for the interactions of biomolecules with water

The thermodynamics of hydration of biomolecules is experimentally studied in the β-cyclodextrin (β-CD), which contains water molecules in a range of configurations and has been proposed as a model system for complex biomolecules. The thermal measurements point to the role of a structural transition from the hydrated β-CD (phase I) to a ‘‘dehydrated’’ form (phase II). We show that dehydration in phase I is assisted by a ‘‘compensation mechanism’’ for which β-CD contributes a constant amount of energy for each H2O mole. Despite the presence of different types of H2O’s, water losses in phase I are accurately described in terms of this energy and the isosteric molar enthalpy of dehydration. Moreover, in going from the fully hydrated to the fully dehydrated form, the contribution of β-CD to dehydration is over all equal to the enthalpy of transition from phase I to phase II. Our analysis yields the changes of an enthalpy associated with the biomolecule alone as a function of the water content. In the case of β-CD, we can sketch a qualitative phase diagram, which assists the interpretation of details of our thermal experiments. The role of kinetic factors in the attainment of the thermodynamic equilibrium is investigated with 2H-NMR in samples recrystallized from heavy water. We find that, over a wide range of hydration levels, water molecules have a liquidlike diffusion, which, together with the compensation mechanism, explains the fast and nearly reversible dehydration of the β-CD.

The expression of a small heat shock gene is activated during induction of tobacco pollen embryogenesis by starvation*

ABSTRACTA tobacco (Nicotiana tabacum L.) cDNA clone, Nthsp 18P, encoding a class I low‐molecular‐weight heat shock protein (LMW HSP), has been isolated from a mid‐biccllular pollen cDNA library by hcterologous hybridization with a low‐molecular‐weight heat shock cDNA clone of alfalfa. Northern analysis showed that Nthsp 18P expression is activated at normal temperature during the dehydration phase of in situ pollen development, just before anthesis. Induction of pollen embryogenesis by an in vitro starvation treatment of mid‐bicellular tobacco pollen was accompanied by a dramatic increase in the levels of the Nthsp 18P transcript, which accumulated in embryogenic pollen grains at 25°C; lower levels of this transcript were also detected in early pollen‐derived embryos. A similar pattern of expression was observed in transgcnic tobacco plants containing the promoter of Gmhsp 17.3‐B, a soybean homologue of the Nthsp 18P gene, fused to the GUS reporter gene. This is the first characterized gene shown to be transcriptionally activated during the induction of pollen embryogenesis.

Evaporitic and biosiliceous cyclic sedimentation in the Miocene of the Gulf of Suez—Depositional and diagenetic aspects

The Middle to Late Miocene evaporite-bearing formations which outcrop along the Gebel Zeit and Gems highs in the southwestern Gulf of Suez (Egypt), consist of thick calcium sulphate beds rhythmically interbedded with marlstones, siltstones and claystones containing various amounts of biogenic silica, as well as pure diatomites. The calcium sulphate beds are composed mainly of gypsum and anhydrite. Subaqueous crustallisation in subpermanent brine ponds of marine origin predominated during deposition of the selenite and laminated gypsum. Early diagenetic interstitial growth of nodular anhydrite occurred episodically when the water level dropped, in response to increasing salinity associated with the precipitation of halite in the deeper troughs. Nevertheless, most of the nodular facies resulted from the burial conversion of gypsum to anhydrite which has been sometimes rehydrated into gypsum. A last phase of gypsum dehydration has occurred at the surface, related to the present hot and dry climatic conditions. The biosiliceous deposits contain either well preserved (opal-A) or diagenetically altered (opal-CT, clinoptilolite, quartz and even clays) diatom frustules. Such diagenetic changes are commonly described in the oceanic biosiliceous deposits. The fossil content of these diatomitic layers implies shallow-marine conditions on the shelves of highs induced by block faulting. The cyclic succession of evaporited and biosiliceous deposits recorded the alternation of high sea level stands associated with high organic productivity, probably enhanced by seasonal input of nutrients and low sea level stands associated with hypersaline conditions and evaporite deposition. Locally, the sharp contact between the diatomites and gypsum argues for a rapid evolution of salinity towards high concentration (up to gypsum saturation and more). The formation of finely laminated diatomitic sediments is known to require either high organic productivity or anoxic conditions in bottom/intermediate waters, and eventually both processes. In the Gebel Zeit and Gemsa areas, a local association of the biosiliceous sediments with diagenetic carbonates and native sulphur, resulting from processes of bacterial sulphate reduction, confirms that anoxic conditions occurred in the deep-water body or in the sediments. Large amounts of organic compounds were involved in these diagenetic processes. Immature organic matter was consumed during an early diagenetic stage of transformation. It is assumed that this organic matter was supplied either by the biosilica-rich interbeds or the organic-rich laminated carbonates. The initial organic content of the biogenic deposits was impoverished as early as the first stages of sedimentation and diagenesis. Although a large part of the organic matter could have been destroyed by these early diagenetic processes and further oxidation in outcrops, these sediments can be considered as potential source rocks in nearby less exposed sequences.

Germination of Perennial Ryegrass and Annual Bluegrass Seeds Subjected to Hydration‐Dehydration Cycles

Seeds that encounter widely fluctuating water conditions during germination could die, become dormant, lose hydration‐dependent steps toward radicle emergence through dehydration, or incrementally accumulate events required for radicle emergence. These alternatives were evaluated with seeds of perennial ryegrass (Lolium perenne L.) and annual bluegrass (Poa annua L. var. annua) exposed to repeated hydration‐dehydration episodes. Seeds were cycled between liquid (hydration phase, Ψ = 0 MPa)and vapor (dehydration phase, Ψ = − 4 or − 10 MPa) environments for up to 16.5 cycles or 328 h, with phase durations of 8, 16, or 24 h. Cycling generally resulted in delayed, but more uniform germination. Cycled seeds required fewer hours in contact with liquid water to germinate than did continuously hydrated seeds and were not killed by repeated dehydration for up to 24 h at −10 MPa. Coleorhiza tissue that emerged from perennial ryegrass seeds following accumulation of 24 hydration‐phase hours retracted during dehydration, but this did not negatively affect radicle emergence upon subsequent rehydration. Annual bluegrass seeds were prevented from germinating by 8‐h hydration phases coupled with 16‐ or 24‐h dehydration phases at − 10 MPa. Upon transfer to continuous hydration, however, seeds germinated within 36 h. These data support the hypothesis that seeds of perennial ryegrass and annual bluegrass can progress toward germination with intermittent hydration.

A model for the prebiotic synthesis of peptides which throws light on the origin of the genetic code and the observed chirality of life

A model is proposed which indicates that peptides could have been synthesized on RNA templates. L-amino acids are selectively trapped and orientated in clefts in an apparently stable RNA structure attached to a solid phase. Each cleft is bounded by three bases which correspond to the codon for that amino acid. Rotation during a dehydration phase orientates the amino acids so that peptide bond formation can occur by condensation. Rehydration releases the formed peptides.

Changes in abscisic acid and its β-D-glucopyranosyl ester levels during tomato (Lycopersicon esculentum Mill.) seed development

The role of abscisic acid (ABA) in tomato (Lycopersicon esculentum Mill.) zygotic embryogenesis was analysed. ABA and ABA ß-D-glucopyranosyl ester (ABA-GE) changes were determined in seeds and fruit tissues - placenta and mesocarp - during seed development, which was defined with eight embryo stages: from globular (stage 1) to mature embryo (stage 8). In whole seeds, ABA changes paralleled fresh and dry weight pattern curves and could be characterized by a high increase during embryo growth followed by a decrease as the seed matured and dehydrated. Moreover this dehydration phase led, at stage 8, to a new ABA distribution within the seed, preferentially into integument and embryo. Fruit tissue analyses provided new information about the ABA origin in seeds. ABA-GE levels were also measured and the results suggested different ABA metabolism in seed and fruit tissues.

Thermal decomposition of [(CH 3) 4N]M IIIF 4·H 2O compounds of iron and aluminum

Within investigations about thermal dehydration and decomposition of fluorometallate hydrates also the thermal behaviour of [(CH 3) 4N]M IIIF 4·H 2O (M III= Fe, Al) has been studied by thermal analysis, X-ray, i.r., and EPR investigations. As it has been shown from the crystal structure determination the structure consists of centrosymmetrical dimeric anions [Fe 2F 8(H 2O) 2] 2− with fluorine double bridges [1]. Strong intramolecular and additional intermolecular H-bonds have been found. The thermal decomposition of the Fe compound starts at about 200°C with the liberation of water. The dehydrate phase [(CH 3) 4N]FeF 4 is stable up to 380°C and decomposes between 400–450° in two steps. The decomposition is accompanied by the reduction of Fe III to Fe II by the [(CH 3) 4N] cation. The end product of the thermal decomposition is FeF 2. The Al compound is dehydrated at lower temperatures (140°C) but the formed [(CH 3) 4N]AlF 4 phase is not so stable as the Fe compound respectively and rehydrates very fast on air. The decomposition of [(CH 3) 4N]AlF 4 proceeds between 450–500°C leading to α-AlF 3 and a new cubic form of AlF 3. Assumptions about the reaction mechanisms and the structural constitution of especially the [(CH 3) 4N]M IIIF 4 phases will be made.

Equilibrium and metastable phases formed at successive ordering of Jahn-Teller distortions in Cu(H2O)6·SiF6 crystals

The first-order phase transitions and dehydration in solid solutions Cu1-xMex(H2O)6·SiF6 (Me = Zn, Fe, Ni) are studied at temperatures from 14 K to 300 K using the roentgenography, adiabatic calorimetry and Mossbauer spectroscopy. As temperature decreases the identified phases from the sequence: dynamically disordered (R3, z = 1), partially disordered (R3, = 4), ordered (P1, z = 2). A possibility for the existence of the Jahn-Teller glass crystalline phase (the result of the quenching of partially ordered phase at v > 20 K/min), its devitrification and ordering of the distortions of Jahn-Teller complexes in the phase the structure of which has not yet been determined is substantiated.It is shown that the interaction of Jahn-Teller complexes [Cu(H2O)6]2+ is the general mechanism of all the transformations. The role of the Jahn-Teller dynamics in phase formation is found. The results are interpreted within the framework of the four-sublattice model which is in good agreement with the experiment.

Structural Analysis of Metadickite

The structure of metadickite, which was a dehydration phase of a dickite from Shokozan mine, Hiroshima, Japan calcined at 600°C for 24 h, was investigated by X‐ray radial distribution function (RDF) analysis and the correlation method. The RDF curve showed the coordination numbers of both Si and Al atoms to be four and the structural regularity was observed up to ∼0.8 nm. Several structural models for metadickite were examined by the correlation method and the most likely model is considered to be the arrangement built up of SiO4 tet‐rahedral sheets, similar to the original dickite, and an adjacent edge‐shared AlO4 tetrahedral chain, with a 6‐4‐4 type oxygen atom distribution.

Island arc and continent-building magmatism — A review of petrogenic models based on experimental petrology and geochemistry

Detailed geochemical and petrological studies of igneous rock suites in island arc and continental marginal environments have revealed the complexity of magmatism in these regions. Rocks once collectively termed the orogenic calc-alkaline suite are now recognized as forming a continuum between tholeiitic, calc-alkaline and alkaline suites. Although this diversity of rock types has inspired varied and overlapping hypotheses of origin, the application of experimental and geochemical data do limit the appropriate choice of a genetic hypothesis for individual magma suites in convergent plate regions. Also a number of hypotheses of origin may be linked to give an integrated model of the growth of island arcs and continental crust and certain geochemical parameters are distinctive in tracingthisprogressive development. Minor phases such as titanochondrodite, titanoclinohumite and sphene have a critical bearing on key geochemical parameters. Water plays a key role in the integrated model for generation of magmas in convergent plate regions. In the first stage, release of water through dehydration of phases in subducted material controls large-scale melting processes in the mantle, forming the early and most “primitive” tholeiitic magmas in the island arc suite (c.f. Ringwood, 1974), where olivine plays a dominating fractionating role. These magmas form a modified and thickened crust in plate collision regimes. Once this thickened crust has developed, subsequent calc-alkaline magmatism becomes more complex, involving a number of possible sources or processes, including (a) silicic melt from eclogite in the subduction zone, (b) melts from “contaminated” peridotite and (c) relatively shallow level, hydrous, often amphibole-dominated fractionation in the thickened crust. Key trace element abundances can constrain the involvement of these sources or processes. Further magmatic activity in island arcs is related to deeper and low degrees melting, with mica breakdown making an important contribution and jadeitic clinopyroxene remaining.as a residual mantle phase. This produces high-K calc-alkaline rocks transitional into the alkaline suite. Finally, in both “mature” island arcs and continental margins where crustal thicknesses exceed 35 km, continued access of water from the subduction zone and/or underplating of the crust by mantle- or subduction zone-derived magmas, causes partial melting of the crust. The resultant magmas are dominantly silicic and plutonic or ignimbritic. An increasing amount of experimental, geochemical and mineralogical evidence indicates a prominent role for “mature” sedimentary material being involved in melting at depth and the generation of volcanic and plutonic magmas in evolved island arc or continental marginal environments. REE provide useful additional constraints on the genesis of these rocks, as they do for other rocks in the island arc suite.