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1

Prebiotic condensation reactions in an aqueous medium: A review of condensing agents  

Microsoft Academic Search

Biopolymers are formed by dehydration-type condensation reactions. In aqueous solutions dehydration reactions are very unlikely to happen spontaneously. However, coupling of dehydration-condensation to the hydrolysis of condensing agents could facilitate the synthesis of biopolymers in an aqueous solution. The literature shows that the peptides, nucleosides, nucleotides and oligonucleotides can be formed in this way. A careful study of the literature

Josée Hulshof; Cyril Ponnamperuma

1976-01-01

2

Prebiotic condensation reactions using cyanamide  

NASA Technical Reports Server (NTRS)

Condensation reactions in cyanamide, 4-amino-5-imidazole-carboxamide and cyanamide, imidazole systems under dehydrating conditions at moderate temperatures (60 to 100 deg C) were investigated. The cyanamide, imidazole system was used for synthesis of palmitoylglycerols from ammonium palmitate and glycerol. With the addition of deoxythymidine to the former system, P1, P2-dideoxythymidine 5 prime-phosphate was obtained; the same cyanamide, 4-amino-5-imidazole-carboxamide system was used to synthesize deoxythymidine oligonucleotides using deoxythymidine 5 prime-phosphate and deoxythymidine 5 prime-triphosphate, and peptides using glycine, phenylalanine or isoleucine with adenosine 5 prime-triphosphate. The pH requirements for these reactions make their prebiotic significance questionable; however, it is conceivable that they could occur in stable pockets of low interlayer acidity in a clay such as montmorillonite.

Sherwood, E.; Nooner, D. W.; Eichberg, J.; Epps, D. E.; Oro, J.

1978-01-01

3

Kinetics of Hydration-Dehydration Reactions Considered as Solid Transformations.  

National Technical Information Service (NTIS)

A mechanism is proposed for the dehydration-rehydration process in solid inorganic salts and model rate equations are derived and applied to the observed behavior of potassium carbonate. Quantitative expressions for the effect of pressure on the reaction ...

M. A. Stanish D. D. Perlmutter

1982-01-01

4

The possible role of solid surface area in condensation reactions during chemical evolution - Reevaluation  

NASA Technical Reports Server (NTRS)

Using surface concentration and reaction rate as the main criteria for the feasibility of condensation reactions, four types of prebiotic environments were analyzed: (1) an ocean-sediment system, (2) a dehydrated lagoon bed produced by evaporation, (3) the surface of a frozen sediment, and (4) a fluctuating system where hydration (rainstorms, tidal variations, flooding) and dehydration (evaporation) take place in a cyclic manner. With the possible exception of nucleotides, low adsorption of organomonomers on sediment surfaces of a prebiotic ocean (pH 8) is expected, and significant condensation is considered unlikely. In dehydrated and frozen systems, high surface concentrations are probable and condensation is more likely. In fluctuating environments, condensation rates will be enhanced and the size distribution of the oligomers formed during dehydration may be influenced by a 'redistribution mechanism' in which adsorbed oligomers and monomers are desorbed and redistributed on the solid surface during the next hydration-dehydration cycle.

Lahav, N.; Chang, S.

1976-01-01

5

Dehydration  

MedlinePLUS

... Breastfeeding FAQs Pregnant? Your Baby's Growth First Aid: Dehydration KidsHealth > Parents > First Aid & Safety > Printable Safety Guides > First Aid: Dehydration Print A A A Text Size What's in ...

6

Effect of Dehydration Reaction on Serpentinite Deformation in Torsion  

NASA Astrophysics Data System (ADS)

Dehydration of serpentine to olivine, talc and water during deformation is critical for understanding the possible localization of deformation into shear zones and the generation of earthquakes along subduction zones. In order to investigate the effect of the dehydration reaction on the strength and ductility of serpentinite, torsion experiments were performed using a Paterson high PT torsion rig at constant shear strain rates of 10-4 to 10-5 s-1, temperatures of 550 to 750 ° C and a confining pressure of 300 MPa, to local shear strains up to ? = 3. We deformed two types of serpentinite: antigorite from Val Malenco, Italy, a high-temperature phase of serpentine (stable at T <500 ° C), and lizardite from Elba, Italy, a low-temperature phase of serpentine (stable at T <400 ° C). Most of the samples were shaped in dog-bone geometry with a central hole along their axial direction which acted as a fluid conduit, enabling an easy escape for any released fluid during the dehydration reaction. We also deformed solid bone-shaped specimens to compare the mechanical behavior of solid and hollow specimens. In both cases, porous alumina spacers were placed on both end sides of specimen and led to the atmosphere through the pore pressure line. Thus our experiments were performed under drained conditions. Antigorite deformed in the semi-brittle field at the run conditions. Visible faults formed probably due to reaction-induced fracturing, and the stress started to drop just after the initial peak stress ( ˜350 MPa at 650 to 700 ° C and ˜280 MPa at 750 ° C). Highly comminuted grains with various sizes along the faults were identified as partially dehydrated antigorite (H2O ˜6 wt%) at 650 ° C and olivine and talc at >700 ° C. Mechanical behavior after the peak stress is thought to occur by cataclastic flow, possibly assisted by diffusion mass transfer processes of these fine-grained reactant minerals. We have also investigated the effect of pre-heating on the strength of antigorite. The peak strength of a sample pre-heated at 750 ° C for 3 hr and then deformed at 700 ° C is 70 MPa lower than a sample deformed directly at 700 ° C. This stress reduction occurred due to the presence of a mechanically weaker reaction product (talc) rather than elevated pore pressure because the sample was deformed under completely drained conditions. By contrast, a solid sample was weaker than hollow ones by ˜100 MPa, mainly due to low permeability of the serpentinite. Excess fluid pressure in solid specimens leads to a drop in the effective pressure and appears to have enhanced the dehydration reaction along micro-fractures. Our data shows that dehydration weakening of serpentinite is caused not as much because of excess pore pressure but more because of the weaker mineral assemblages from the reaction. In contrast to semi-brittle faulting in antigorite, deformation of lizardite at 550 ° C to a bulk shear strain of 0.9 was widely distributed, showing typical ductile microstructures such as boudinage and S-C fabric. A well developed secondary foliation (C-plane) and strong lattice preferred orientations of lizardite grains were observed close to the localized shear zones. After the initial peak stress, steady stress values of 250 MPa were measured. We intend to focus on how the localized zones evolve and how the mechanical response changes with increasing shear strain during the reaction.

Vinciguerra, S.; Trovato, C.; Meredith, P. G.; Benson, P. M.; Hirose, T.; Bystricky, M.; Stünitz, H.; Kunze, K.

2003-12-01

7

Dehydration of cyclohexanol as a test reaction for zeolite acidity  

SciTech Connect

Dehydration of cyclohexanol was investigated using a fixed-bed continuous flow reactor with acidic mordenite-type, clinoptilolite-type, and faujasite-type (Y) zeolites as catalysts. The surface acidity of the catalysts employed was studied by IR using pyridine or 2,6-di-tert. butylpyridine as probe molecules. A correlation between the acidity and the rates of dehydration was clearly shown.

Karge, H.G.; Kosters, H.; Wada, Y.

1984-01-01

8

Water incorporation in NAMs after antigorite and chlorite dehydration reactions  

NASA Astrophysics Data System (ADS)

Subduction zones play a fundamental role in the deep water cycle making the Earth unique among other terrestrial planets. Water is incorporated into hydrous minerals during seafloor alteration of the oceanic lithosphere. During subduction of the oceanic lithosphere, dehydration of these hydrous minerals produces a fluid phase. A part of this fluid phase will be recycled back to the Earth's surface through hydrothermal aqueous fluids or through hydrous arc magmas, whereas another part of the water will be transported to the deep mantle by Nominally Anhydrous Minerals (NAMs) such as olivine, pyroxene and garnet. The partitioning of water between these two processes is crucial for our understanding of the mantle-scale water recycling in the Earth. This can be investigated experimentally under water-saturated conditions because this situation is met during dehydration reactions. However relatively low temperature conditions for such reactions make challenging these experiments. An alternative can be found in the natural record. The Alpine Betic-Rif orogen together with Central and Western Alps offer an invaluable diversity of ultramafic lenses that record a significant range of pressure-temperature and cooling rates. Hence these samples portray an excellent data set of 24 samples to survey the transfer of fluids from hydrous phases (brucite, antigorite and chlorite) to NAMs (olivine, orthopyroxene, clinopyroxene and garnet). Well-studied samples from these localities have been selected for water measurement using FTIR spectroscopy. The selected suite comprises the following high-pressure peridotite outcrops: Malenco serpentinite, Cerro del Almirez (1.6-1.9 GPa and 680-710ºC), Alpe Arami (3.2 GPa and 840ºC), Cima di Gagnone (3.0 GPa and 750-800ºC) and Alpe Albion (0.6 GPa and 730ºC). The infrared signature of olivine in all localities contains water (hydroxyl groups) associated to intrinsic defects (mostly point defects related to Ti4+) and extrinsic submicroscopic hydrous lamellae (titanoclinohumite). In the following only water contents related to intrinsic defects are reported. At low temperature (400-450 ºC) the spectra of olivine coexisting with antigorite are dominated by OH associated to silica-vacancies and contains 12-20 wt. ppm H2O (using site-specific infrared OH absorption coefficients from [1]). Olivine in equilibrium with orthopyroxene and chlorite formed after the antigorite breakdown (650-700 ºC) at high pressure (1.6-1.9 GPa) from Cerro del Almirez contains 14-17 ppm and is associated to Ti4+ and abundant extrinsic defects. Surprisingly the associated orthopyroxene is nearly dry (1-3 wt. ppm) resulting in D[opx/ol] 1. After chlorite breakdown (750-800ºC) olivine contains 21-68 wt. ppm H2O. In summary there is a systematic correlation between PT conditions and water content in olivine and orthopyroxene. The dependence is however different for both resulting in significant changes in the water partition coefficient. This dataset represents a first step in the quantification of the water budget in the slab and in the mantle wedge of NAMs coexisting with hydrous phases and after their breakdown. [1] Kovacs, I., O'Neill, H.S.C., Hermann, J., Hauri, E.H., 2010. Site-specific infrared O-H absorption coefficients for water substitution into olivine. Am. Miner. 95, 292-299.

Padrón-Navarta, José Alberto; Hermann, Jörg

2014-05-01

9

Effect of dehydration reactions on earthquake nucleation: Stable sliding, slow transients, and unstable slip  

NASA Astrophysics Data System (ADS)

We study the influence of metamorphic dehydration reactions on the stability of slip in a one-dimensional, spring-slider model. The equations that govern the evolution of the velocity of sliding block and of pore pressure and temperature inside the slip zone are deduced from the mass and energy balance of the multiphases saturated medium and from the kinetics of the dehydration reaction. Such reactions induce two competing effects: a direct increase in pore pressure because they release fluid and a limit in temperature increase because part of the frictional heat is absorbed in the endothermic reactions. The effect of the chemical reaction on the stability of stationary slip is studied. Dehydration reactions increase the critical stiffness at which the system becomes unstable. Depending on the sign of the perturbations, it is shown that dehydration reactions can either (1) trigger a catastrophic increase of pore pressure at quasi-constant temperature leading to vanishing effective stress or (2) trigger an arrest of the fault. Numerical simulations demonstrate the crucial role of initial pore pressure and temperature in the slip zone prior to the onset of the chemical reaction on the subsequent evolution of the system. For highly pressurized fault zones, in which the creep motion of the fault is stable in absence of dehydration reactions, the onset of the reaction can trigger transient slip events induced by chemical pressurization. The magnitude of such events appears to be proportional to the reaction progress. We conclude that metamorphic dehydration reactions strongly modify the nucleation of unstable slip and are a possible origin for slow slip events in subduction zones.

Brantut, N.; Sulem, J.; Schubnel, A.

2011-05-01

10

Seismological evidence for thermally-controlled dehydration reactions in the oceanic crust of the Pacific slab  

Microsoft Academic Search

When the oceanic plate subducts at the trench, the hydrated oceanic crust carries water into the earth in the form of hydrous minerals. Hydrous minerals in the oceanic crust become unstable with increasing pressure and temperature, and dehydration reactions occur accompanied by the release of water to the surroundings. Tsuji et al. (2008) estimated detailed seismic-velocity structure around the Pacific

J. Nakajima; Y. Tsuji; A. Hasegawa

2008-01-01

11

One-pot synthesis of olefins from aromatic ketones via tandem consecutive hydrogenation–dehydration reactions  

Microsoft Academic Search

In this work, the synthesis of aromatic olefins from the corresponding ketones via tandem consecutive hydrogenation–dehydration reactions was studied. The conversion of acetophenone (AP) to styrene (STY) was used as model reaction. Initially, the liquid-phase hydrogenation of AP to 1-phenylethanol (PHE), using cyclohexane as solvent, was investigated at 363K and 10bar over Ni, Co, Cu, Pd and Pt supported on

Nicolás M. Bertero; Carlos R. Apesteguía; Alberto J. Marchi

2011-01-01

12

Thermal dehydration reactions characterized by combined measurements of electrical conductivity and elastic wave velocities  

NASA Astrophysics Data System (ADS)

Combined laboratory measurements of seismic velocities and electrical conductivity as a function of PT and drainage conditions have been performed on various rocks containing hydrous minerals. This paper presents experimental results for evaporite rocks containing gypsum (CaSO4 x 2H2O) and carnallite (KMgCl3 x 6H2O) and for serpentinite. The experiments on the evaporite rocks were carried out in a triaxial cell in the range 20-130 C and 5.0-24.0 MPa confining pressure. The measurements on serpentinite covered the range 20-750 C at pressures of up to 200 MPa and were performed in a cubic pressure apparatus. The thermally induced onset of dehydration was indicated by the pronounced discontinuous behaviour of conductivity, corresponding to a marked drop in the elastic wave velocities. The respective Poisson ratios were inversely correlated with permeability and seem to be a sensitive parameter to describe the reaction-related variations of pore space. The seismic properties can be satisfactory modelled by using the self-consistent approximation of O'Connell and Budiansky, illustrating the effects of variations in pore space and saturation. The dehydration behavior of the various hydrous rock types was found to be different because the changes in the rock physical properties are closely linked to the internally created pore fluid, to the changes in the porosity and pore geometry, and to the resulting pore pressure. Progressive thermal dehydration reactions induce an opening of pore space accompanied by lowered saturation conditions whereby the rate of fluid release depends mainly on temperature and also on the drainage conditions of the system. Our findings, as reflected by the variations in the geophysical parameters, may be of importance for the interpretation of natural dehydration processes in the crust caused by prograde metamorphism.

Popp, T.; Kern, H.

1993-11-01

13

POLLUTION PREVENTION IN INDUSTRIAL CONDENSATION REACTIONS  

EPA Science Inventory

The objective of this project is to develop heterogeneous acid-base catalysts to increase the economic and environmental performance of the current homogeneous catalysts used to make industrially important condensation products. Such products include methyl isobutyl ketone ...

14

Reversion and dehydration reactions of glucose during the dilute sulfuric acid hydrolysis of cellulose  

SciTech Connect

The inaccessibility of all glycosidic bonds necessitates industrial conversion schemes which employ a dilute acid catalyst at high temperatures. Process conditions also promote further reactions of glucose via the reversion and dehydration pathways. Quantitative determination of the yields of the major reversion and dehydration products is important for understanding and predicting the amounts of these materials expected under envisioned industrial operating conditions. Microcrystalline cellulose (Avicel) was hydrolyzed with sulfuric acid (0.0-1.25 wt.%), at high temperatures (160-250/sup 0/C), and at a 3:1 liquid-to-solid ratio. The hydrolysis was monitored by evaluating the amount of cellulose remaining and the yields of glucose, solid humin, levulinic acid, formic acid, hydroxymethylfurfural (HMF), and reversion products as a function of the aforementioned reaction conditions. Analysis of the reversion products required the development of a technique for the quantitation of trace carbohydrates in complex mixtures and led to the development of a reduction/permethylation gas chromatographic procedure. Cellulose hydrolysis followed pseudo-homogeneous first-order kinetics. Glucose yield was adequately described as consecutive first-order reactions. Anhydrosugars formed via reversion followed equilibrium reaction kinetics whereas the disaccharides did not. Total reversion product yields approached 10% at 250/sup 0/C. Quantitative determination of the major dehydration products provided important information concerning the destruction of glucose. HMF was produced in up to 12% yields based on the theoretical amount of glucose available, and furfural was detected in up to 5% yields. A carbon mass balance based on the determined product yields revealed that approximately 90% of all carbon was accounted for at maximum glucose yields.

Helm, R.F.

1987-01-01

15

Metamorphic dehydration reactions control the location of intermediate-depth seismicity  

NASA Astrophysics Data System (ADS)

The cause of intermediate-depth seismicity in subduction zones is not well understood. The viability of proposed mechanisms, that include dehydration embrittlement, shear instablities, and the presence of fluids in general, depends significantly on local conditions, including pressure, temperature, and composition. A number of high resolution seismic studies have improved the location of earthquakes within the slab in Japan, Alaska and Cascadia. Intriguingly, the warm subduction zones of Nankai and Cascadia show that intermediate depth seismicity is located below the oceanic crust. In contrast, the colder subduction zones Alaska, Tohoku and Hokkaido have the upper plane of seismicity confined to the subducting crust, with a systematic deepening of the seismic belt with respect to the top of the slab with depth. We use high resolution thermal-petrological models to determine the metamorphic facies in the downgoing slab and to identify the main phase changes that cause dehydration. In Alaska and Northern Japan, the seismicity occurs at, or at shallower depths than, the blueschist-out boundary. In Nankai and Cascadia the seismicity disappears above the antigorite-out boundary. Seismicity in the lower plane of the double seismic zone in Northern Japan also occurs at pressures and temperatures below the antigorite-out boundary. These observations strongly suggest that intermediate-depth seismicity is limited by the first major dehydration reaction in the crust and mantle and that fluids liberated by this phase change are primarily responsible for causing the earthquakes.

van Keken, Peter E.; Kita, Saeko; Nakajima, Junichi; Abers, Geoff; Hacker, Brad

2013-04-01

16

Semicatalytic hydrogenation and dehydrational condensation in the mechanism of the iso synthesis  

Microsoft Academic Search

Summary 1.In the synthesis of hydrocarbons from carbon monoxide and hydrogen over nonhydrogenating oxide catalysts (Al2O3, ThO2), which is called the iso synthesis, the hydrogenation processes are in the nature of semicatalytic reactions: carbon monoxide molecules are activated at be catalyst surface and are attached to the surface during the reaction, but the hydrogen molecules are thermally activated and react

Yao T. Eidus

1953-01-01

17

Seismological evidence for thermally-controlled dehydration reactions in the oceanic crust of the Pacific slab  

NASA Astrophysics Data System (ADS)

When the oceanic plate subducts at the trench, the hydrated oceanic crust carries water into the earth in the form of hydrous minerals. Hydrous minerals in the oceanic crust become unstable with increasing pressure and temperature, and dehydration reactions occur accompanied by the release of water to the surroundings. Tsuji et al. (2008) estimated detailed seismic-velocity structure around the Pacific slab in the central part of northeastern Japan by double-difference tomography and detected a remarkable low-velocity zone with a thickness of ~10 km, which corresponds to hydrated oceanic crust, at the uppermost part of the slab. The zone gradually disappears at depths of 70-90 km, suggesting the occurrence of intensive dehydration reactions there. This study extends the analysis by Tsuji et al. (2008) to a wider area from Hokkaido to Kanto to investigate whether or not the depth extent of the hydrated oceanic crust in the Pacific slab varies along the arc. Obtained results show a striking along-arc variation in the depth extent of the hydrated oceanic crust. Although the low-velocity oceanic crust is generally distributed down to depths of 70-90 km in Hokkaido and Tohoku, there are two exceptional regions where it is imaged down to deeper depths: 100-140 km in Kanto and 90-110 km in Hokkaido corner (Fig.1). Such preservations of the low-velocity oceanic crust to deeper depths can reflect the delay of dehydration reactions of hydrous minerals, which in turn suggests lower- temperature conditions in the slab. The lateral extent of the low-velocity oceanic crust preserved to deeper depths beneath Kanto corresponds well to that of a region where the Pacific slab is in contact with the overriding Philippine Sea slab. The contact of the Philippine Sea slab with the Pacific slab can hinder effective heat transfer to the Pacific slab from hot mantle wedge, and therefore, the Pacific slab can retain lower temperatures than normal subduction environments. On the other hand, the deeper preservation of the low-velocity oceanic crust beneath Hokkaido corner may be related to low-heat transfer because of accumulated materials above the slab by the fore-arc sliver. Interestingly, the upper-plane seismic belt (Kita et al., 2006; Hasegawa et al, 2007), a belt-like concentration of seismicity at depths of 70-90 km in the upper plane of the double seismic zone, is also shifted to deeper depths only beneath the two regions. These observations suggest that the preservation of the hydrated oceanic crust to deeper depths and deepening of the upper-plane seismic belt in the two regions can be caused by the delay of dehydration reactions resulting from lower-temperature conditions in the Pacific slab.

Nakajima, J.; Tsuji, Y.; Hasegawa, A.

2008-12-01

18

Modeling the controls on excess pore pressure by dehydration reactions in the slow-slip region of subduction zones  

NASA Astrophysics Data System (ADS)

Slow slip and tremor in subduction zones take place where there is abundant evidence for elevated, near lithostatic, pore pressures along the plate interface. In Japan and Cascadia, these depths (~30-45 km) are such that the main source of fluids must be attributed to chemical dehydration reactions. Here we model the consolidation of low porosity (~5%) oceanic crust subducting through the slow slip and tremor zone, and participating in pressure and temperature-dependent dehydration reactions. Pore pressures in excess of lithostatic values, and hence negative effective stresses, are a robust feature of preliminary work that employs parameters consistent with the geometry of the Cascadia subduction margin, and bulk permeabilities in the range 10-25 ? k ? 10-21 m2. In these calculations, the dehydration fluid source is parameterized using the predictions of previous studies that have calculated the amount of bound H2O lost from subducting oceanic crust as a result of broad metamorphic facies transitions. We also report the predictions of a revised model that includes a general kinetic law, which governs the rate of dehydration as a function of temperature and pressure, and provides constraints on the parameters necessary for such kinetic effects to be relevant for the fluid supply by dehydration reactions in the subducting crust. Finally, we investigate the role of lateral fluid migration by including a fluid sink term that is proportional to modeled horizontal pressure gradients. Our results indicate that processes must be active in the slow slip region of subduction zones that are responsible, perhaps periodically, for alleviating excess pore pressures generated by dehydration reactions. Candidate mechanisms include hydraulic fracturing within or below the plate interface, lateral and/or focused fluid migration, or increases in permeability during slow slip events.

Skarbek, R. M.; Rempel, A. W.

2013-12-01

19

High-resolution models of subduction zones: Implications for mineral dehydration reactions and the transport of water into the deep mantle  

Microsoft Academic Search

(1) Arc volcanism is intimately linked to mineral dehydration reactions in the subducting oceanic mantle, crust, and sediments. The location of slab dehydration reactions depends strongly on the temperature and pressure conditions at the top of the subducting plate and hence on the detailed thermal structure of subduction zones. A particularly important physical property of subduction zone thermal models is

Peter E. van Keken; Boris Kiefer; Simon M. Peacock

2002-01-01

20

High-resolution models of subduction zones: Implications for mineral dehydration reactions and the transport of water into the deep mantle  

Microsoft Academic Search

Arc volcanism is intimately linked to mineral dehydration reactions in the subducting oceanic mantle, crust, and sediments. The location of slab dehydration reactions depends strongly on the temperature and pressure conditions at the top of the subducting plate and hence on the detailed thermal structure of subduction zones. A particularly important physical property of subduction zone thermal models is the

Peter E. van Keken; Boris Kiefer; Simon M. Peacock

2002-01-01

21

The reaction mechanism for dehydration process catalyzed by type I dehydroquinate dehydratase from Gram-negative Salmonella enterica  

NASA Astrophysics Data System (ADS)

The fundamental reaction mechanism for the dehydration process catalyzed by type I dehydroquinate dehydratase from Gram-negative Salmonella enterica has been studied by density functional theory calculations. The results indicate that the dehydration process undergoes a two-step cis-elimination mechanism, which is different from the previously proposed one. The catalytic roles of both the highly conserved residue His143 and the Schiff base formed between the substrate and Lys170 have also been elucidated. The structural and mechanistic insight presented here may direct the design of type I dehydroquinate dehydratase enzyme inhibitors as non-toxic antimicrobials, anti-fungals, and herbicides.

Yao, Yuan; Li, Ze-Sheng

2012-01-01

22

A highly efficient oxidative condensation reaction for selective protein conjugation.  

PubMed

We hereby report a mild and efficient coupling reaction between alkyl aldehydes and aryl diamines. In the presence of a Cu(2+) or a Zn(2+) ion, oxygen (O2) in air is able to promote the oxidative condensation of the two readily preparable functional groups, forming stable benzimidazole linkages in neutral aqueous solution at room temperature (RT). We demonstrated that the reaction could be utilized to label a T4 lysozyme protein containing a chemically installed aryl diamine group with a fluorescent aldehyde dye molecule at 37 °C. PMID:24875017

Ji, Ao; Ren, Wei; Ai, Hui-Wang

2014-06-17

23

Exponential enhancement of nuclear reactions in a condensed matter environment  

SciTech Connect

A mechanism that uses the environment to increase the probability of the nuclear reaction when a beam of accelerated nuclei collides with a target nucleus implanted in condensed matter is suggested. The effect considered is exponentially large for low collision energies. For t+p collision the mechanism becomes effective when the energy of the projectile tritium is below 1 KeV per nucleon. The gain in probability of the nuclear reaction is due to a redistribution of energy and momentum of the projectile in several 'preliminary' elastic collisions with the target nucleus and the environmental nuclei in such a way that the final inelastic projectile-target collision takes place with larger relative velocity, which is accompanied by the corresponding decrease of the center of mass energy. This increase of the relative velocity exponentially increases the penetration through the Coulomb barrier.

Kuchiev, M.Yu. [University of New South Wales, Sydney (Australia); Altshuler, B.L. [Physics Department, Princeton University, Princeton, New Jersey 08544 (United States); NEC Research Institute, 4 Independence Way, Princeton, New Jersey 08540 (United States); Flambaum, V.V. [University of New South Wales, Sydney (Australia); Institute for Advanced Study, Einstein Drive, Princeton, New Jersey 08540 (United States)

2004-10-01

24

Hydrotalcite catalysis in ionic liquid medium: a recyclable reaction system for heterogeneous Knoevenagel and nitroaldol condensation  

Microsoft Academic Search

Knoevenagel condensation proceeds efficiently in recyclable [bmim]PF6 and [bmim]BF4 without any catalyst, and hydrotalcites in ionic liquid serve as a safe and recyclable reaction system for both Knoevenagel as well as nitroaldol condensations.

Faiz Ahmed Khan; Jyotirmayee Dash; Rashmirekha Satapathy; Sarasij K. Upadhyay

2004-01-01

25

Condensation  

NSDL National Science Digital Library

In this activity, learners explore the process of condensation. After seeing water vapor condense, learners will help design a test to see if cooling water vapor has an effect on the rate of condensation.

Kessler, James H.; Galvan, Patricia M.

2007-01-01

26

Mining chemical reactions using neighborhood behavior and condensed graphs of reactions approaches.  

PubMed

This work addresses the problem of similarity search and classification of chemical reactions using Neighborhood Behavior (NB) and Condensed Graphs of Reaction (CGR) approaches. The CGR formalism represents chemical reactions as a classical molecular graph with dynamic bonds, enabling descriptor calculations on this graph. Different types of the ISIDA fragment descriptors generated for CGRs in combination with two metrics--Tanimoto and Euclidean--were considered as chemical spaces, to serve for reaction dissimilarity scoring. The NB method has been used to select an optimal combination of descriptors which distinguish different types of chemical reactions in a database containing 8544 reactions of 9 classes. Relevance of NB analysis has been validated in generic (multiclass) similarity search and in clustering with Self-Organizing Maps (SOM). NB-compliant sets of descriptors were shown to display enhanced mapping propensities, allowing the construction of better Self-Organizing Maps and similarity searches (NB and classical similarity search criteria--AUC ROC--correlate at a level of 0.7). The analysis of the SOM clusters proved chemically meaningful CGR substructures representing specific reaction signatures. PMID:22894688

de Luca, Aurélie; Horvath, Dragos; Marcou, Gilles; Solov'ev, Vitaly; Varnek, Alexandre

2012-09-24

27

Variational principles for describing chemical reactions: Condensed reactivity indices  

NASA Astrophysics Data System (ADS)

Two recent papers [P. W. Ayers and R. G. Parr, J. Am. Chem. Soc. 122, 2010 (2000); 123, 2007 (2001)] have shown how variational principles for the energy may be used to derive and elucidate the significance of the chemical reactivity indices of density-functional theory. Here, similar ideas are applied, yielding a systematic, mathematically rigorous, and physically sound approach to condensed reactivity indices. First, we use the variational principle for the energy to derive an expression for the condensed Fukui function index in terms of the condensed hardness kernel. Next, we address an important open problem pertaining to condensed reactivity indices: when (if ever) is the condensed Fukui function for an atom in a molecule negative? In particular, our analysis confirms the observation, hitherto based only on computational evidence, that the Hirshfeld partitioning is optimal for obtaining non-negative Fukui functions. We also hypothesize that the strong diagonal dominance of the condensed hardness kernel is sufficient for the non-negativity of the Fukui function. Errors in the partitioning of molecules into atoms and inadequate treatment of correlation are pinpointed as the most likely causes of negative condensed Fukui functions. We conclude by noting that the condensed Fukui functions are, in some respects, more appropriate indicators of a molecular site's reactivity than the Fukui function itself.

Ayers, Paul W.; Morrison, Robert C.; Roy, Ram K.

2002-05-01

28

Electron microscopic study of dehydration transformations. Part III: High resolution observation of the reaction process FeOOH --> Fe2O3  

Microsoft Academic Search

The dehydration reaction accompanying the goethite-hematite transformation was observed by high resolution electron microscopy. The origin of the satellites which appear during the transformation is discussed from the point of view of structure factor and shape factor. Details of the transformation mechanism have been clarified through these results and from the considerations based on the observations. The transformation goes directly

Fumio Watari; P. Delavignette; J. van Landuty; S. Amelinckx

1983-01-01

29

Hornblende dehydration reactions during magma ascent at Soufrière Hills Volcano, Montserrat  

Microsoft Academic Search

Hornblende phenocrysts in recent andesites of the Soufrière Hills Volcano display reaction rims of microcrystalline plagioclase,\\u000a pyroxene, Fe-oxides and interstitial glass, formed by decompression during magma ascent. Mass balance calculations give the\\u000a following reactions with mineral proportions in agreement with modal abundances:\\u000a \\u000a \\u000a \\u000a \\u000a $$\\\\begin{aligned} 100.0\\\\,{\\\\text{hbl}} & \\\\to 49.8\\\\,{\\\\text{cpx}} + 27.6\\\\,{\\\\text{opx}} + 18.2\\\\,{\\\\text{plag}} + 4.5\\\\,{\\\\text{Ti - mag}} \\\\\\\\ 100.0\\\\,{\\\\text{hbl}} & \\\\to 53.9\\\\,{\\\\text{cpx}}

V. J. E. Buckley; R. S. J. Sparks; B. J. Wood

2006-01-01

30

Ion-molecule condensation reactions: a mechanism for organic synthesis in ionized reducing atmospheres.  

PubMed

The CH3+ ion, formed in ionized methane, undergoes consecutive eliminative condensation reactions with methane to form the carbonium ions C2H5+, i-C3H7+ and t-C4H9+. At T smaller than 500 degrees K, NCH4 greater than 10(16) cm-3 these ions react with NH3 in competitive condensation -- H+ transfer reactions, e.g. C2H5 + NH3 M leads to C2H5NH3+ leads to NH4+ + C2H4 At particle densities of NCH4 smaller than 10(16) cm-3 proton transfer is the only significant reaction channel. At NCH4 greater than 10(17) cm-3 condensation constitutes 5--20% of the overall reactions. The product of the condensation reaction further associates with CO2 to form C2H5NH3+ . CO2; the atomic composition of this cluster ion is identical with the protonated amino acid alanine. The carbonium ions i-C3H7+ and t-C4H9+ condense also with HCN to yield protonated isocyanides. HCNH% also appears to condense with HCN at T greater than 570 degrees K, and form cluster ions with HCN at lower temperatures. The rate constants of the condensation reactions vary with temperature and pressure in a complex manner. Under conditions similar to those on Titan at an altitude of 100 km (T = 100--150 degrees K, NCH4 approximately 10(18) cm-3), with a methane atmosphere containing 1% H2 and traces of NH3 and H2O, ion-molecule condensation reactions followed by H+ transfer are expected to lead to the atmospheric synthesis of C2H6, C3H8, CH3OH, C2H5OH and the terminal ions NH4+, CH3NH3+ and C2H5NH3+. At higher temperatures (250 degrees K smaller than T smaller than 400 degrees K), the synthesis of i-C4H10, i-C3H7OH and t-C4H9OH and of the ions i-C3H7NH3+ and t-C4H9NH3+ is also expected. Electron recombination of the terminal ions may yield amines, imines and nitriles. Cycles of protonation and dissociative recombination of the alkanes and alcohols produced in condensation reactions will also produce unsaturated hydrocarbons, ketones and aldehydes in the ionized atmosphere. PMID:752132

Meot-Ner, M

1978-12-01

31

Tandem Aldol Condensation - Platinacycle-Catalyzed Addition Reactions of Aldehydes, Methyl Ketones and Arylboronic Acids  

PubMed Central

Tandem aldol condensation of aldehydes with methyl ketones followed by anionic four-electron donor-based (Type I) platinacycle-catalyzed addition reactions of arylboronic acids to form ?-arylated ketones is described. Good to excellent yields of ?-arylated ketones were obtained for the tandem reactions of aromatic/aliphatic aldehydes, methyl ketones and arylboronic acids, and moderate yields were observed for the tandem reaction with ?, ?-unsaturated aldehydes as the aldehyde source.

Liao, Yuan-Xi; Hu, Qiao-Sheng

2013-01-01

32

Analytical solution for transient partitioning and reaction of a condensing vapor species in a droplet  

NASA Astrophysics Data System (ADS)

We present the exact analytical solution of the transient equation of gas-phase diffusion of a condensing vapor to, and diffusion and reaction in, an aqueous droplet. Droplet-phase reaction is represented by first-order chemistry. The solution facilitates study of the dynamic nature of the vapor uptake process as a function of droplet size, Henry's law coefficient, and first-order reaction rate constant for conversion in the droplet phase.

Liu, Albert Tianxiang; Zaveri, Rahul A.; Seinfeld, John H.

2014-06-01

33

Condensed Matter Deuterium Cluster Target for Study of Pycnonuclear Reactions  

NASA Astrophysics Data System (ADS)

Fusion reactions have two main classes: thermonuclear and the pycnonuclear. Thermonuclear fusion occurs in low density high temperature plasmas, and is very sensitive to the ion temperature due to Columbic repulsion effects. As the density increases, the Columbic potential barrier is depressed by increased electron screening, allowing fusion at lower temperatures. This type of nuclear reaction is termed a pycnonuclear fusion and is the basis for astrophysical fusion. Ichimarua [1] proposed a laboratory study of this process using explosive mechanical compression of H/D to metallic densities, which would be extremely difficult to implement. Instead, our recent research suggests that metallic-like H/D ``clusters'' can be formed in dislocation loops of thin Palladium foils through electrochemical processes. [2] If this technique is used as a laser compression target, the compressed cluster density would allow study of pycnonuclear reactions. This provides a means of studying astrophysical fusion process, and could also lead to an important non-cryogenic ICF target. [2] [4pt] [1] S. Ichimaru, H. Kitamura. Phys. Plasmas, 6, 2649 (1999) [0pt] [2] G. Miley and X. Yang, Deuterium Cluster Target for Ultra-High Density, 18TH TOFE, San Francisco, CA Sep. 28 -- Oct. 2, 2008

Yang, Xiaoling; George, Miley

2009-11-01

34

Sequential Aldol Condensation - Transition Metal-Catalyzed Addition Reactions of Aldehydes, Methyl Ketones and Arylboronic Acids  

PubMed Central

Sequential aldol condensation of aldehydes with methyl ketones followed by transition metal-catalyzed addition reactions of arylboronic acids to form ?-substituted ketones is described. By using the 1,1?-spirobiindane-7,7?-diol (SPINOL)-based phosphite, an asymmetric version of this type of sequential reaction, with up to 92% ee, was also realized. Our study provided an efficient method to access ?-substituted ketones and might lead to the development of other sequential/tandem reactions with transition metal-catalyzed addition reactions as the key step.

Liao, Yuan-Xi; Xing, Chun-Hui; Israel, Matthew; Hu, Qiao-Sheng

2011-01-01

35

The thermal dehydration of synthetic gypsum  

Microsoft Academic Search

Mass losses vary between 13.7 and 16.5% and heat of dehydration values between 377 and 420 J g?1 for the dehydration of ground and mixed inhomogeneous gypsum samples. As for the dehydration of CaSO4·2H2O, the dehydration of synthetic gypsum proceeds via multi-step reactions. Using a heating rate of 5°C min?1, the very slow dehydration of CaSO4·2H2O and impurities in the

C. A. Strydom; D. L. Hudson-Lamb; J. H. Potgieter; E. Dagg

1995-01-01

36

Chemical reactions in the gas phase and in condensed matter: From wavefunctions to density operators  

NASA Astrophysics Data System (ADS)

This contribution generalizes the treatment of chemical reactions in the gas phase based on the reaction channel decomposition of the wavefunction, by introducing a similar channel decomposition of the statistical density operator valid also for condensed phases such as liquid solutions and solid surfaces. Coupled equations for the channel components of the density operator are derived and a brief presentation is given of their partial Wigner transform, which leads to a general treatment for coupling quantum and classical variables. This provides a general approach for reactions involving electronically excited states in many-atom systems. It is pointed out that reactions involving coupled quantal and classical variables can be correctly described provided (a) initial conditions for trajectories are generated from quantal distributions and (b) the bundle of trajectories for the whole initial classical phase space is propagated coupled to the quantal elements of the density matrix and used in the calculation of reaction flux averages.

Micha, David A.

37

Microwave assisted condensation reactions of 2-aryl hydrazonopropanals with nucleophilic reagents and dimethyl acetylenedicarboxylate.  

PubMed

The reaction of methyl ketones 1a-g with dimethylformamide dimethylacetal (DMFDMA) afforded the enaminones 2a-g, which were coupled with diazotized aromatic amines 3a,b to give the corresponding aryl hydrazones 6a-h. Condensation of compounds 6a-h with some aromatic heterocyclic amines afforded iminoarylhydrazones 9a-m. Enaminoazo compounds 12a,b could be obtained from condensation of 6c with secondary amines. The reaction of 6e,h with benzotriazolylacetone yielded 14a,b. Also, the reaction of 6a,b,d-f,h with glycine and hippuric acid in acetic anhydride afforded pyridazinone derivatives 17a-f. Synthesis of pyridazine carboxylic acid derivatives 22a,b from the reaction of 6b,e with dimethyl acetylenedicarboxylate (DMAD) in the presence of triphenylphosphine at room temperature is also reported. Most of these reactions were conducted under irradiation in a microwave oven in the absence of solvent in an attempt to improve the product yields and to reduce the reaction times. PMID:17960106

Al-Zaydi, Khadijah M; Borik, Rita M

2007-01-01

38

Two-step synthesis of hexaammonium triptycene: an air-stable building block for condensation reactions to extended triptycene derivatives.  

PubMed

A simple two-step synthesis of an air-stable hexaammoniumtriptycene is introduced, which can be used for a variety of transformations by condensation reactions, e.g., to benzimidazole, benzotriazole, and quinoxaline derivatives in high yields. PMID:21688800

Mastalerz, Michael; Sieste, Stefanie; Ceni?, Mila; Oppel, Iris M

2011-08-01

39

Uses and abuses of the Langevin equation for chemical reactions in condensed phases  

NASA Astrophysics Data System (ADS)

The Langevin and Fokker-Planck equations are useful in the description of many classical and quantum mechanical systems. However, these equations are justifiable from molecular considerations under very restricted conditions. These conditions include weak coupling, Brownian motion, and systems with special Hamiltonians. The application of these equations to chemical reactions in condensed phases is fraught with peril, particularly for fluid systems. We examine the molecular derivations of these equations and describe the conditions under which they are justifiable. It is, of course, possible that the equations are useful under other conditions.

Oppenheim, Irwin; Orsky, Alex

1991-12-01

40

Formation of Activated Biomolecules by Condensation on Mineral Surfaces - A Comparison of Peptide Bond Formation and Phosphate Condensation  

NASA Astrophysics Data System (ADS)

Many studies have reported condensation reactions of prebiotic molecules, such as the formation of peptide bonds between amino acids, to occur to some degree on mineral surfaces. We have studied several such reactions on the same divided silica. When drying steps are applied, the equilibria of peptide formation from glycine, and polyphosphate formation from monophosphate, are displaced to the right because these reactions are dehydrating condensations, accompanied by the emission of water. In contrast, the equilibrium of AMP dismutation is not significantly favored by drying. The silica surface plays little role (if any) in the thermochemistry of the condensation reactions, but is does play a significant kinetic role by acting as a catalyst, lowering the condensation temperatures with respect to bulk solids. Of course, the surface also catalyzes the inverse hydrolysis reactions.

Georgelin, Thomas; Jaber, Maguy; Bazzi, Houssein; Lambert, Jean-François

2013-10-01

41

1-( p -Fluorophenyl)-2-(2?-pyridyl)ethanol and 1-( p -fluorophenyl)-2-(2?-pyridyl)ethene obtained from the condensation reaction of 2-picoline and p -fluorophenylaldehyde under catalyst-and solvent-free conditions  

Microsoft Academic Search

The novel intermediate 1-(p-fluorophenyl)-2-(2?-pyridyl)ethanol or 2-[2?-(1-hydroxy-1-(p-fluorophenyl)ethyl]pyridine and the corresponding novel dehydration compound 1-(p-fluorophenyl)-2-(2?-pyridyl)ethene or 2-[p-fluorophenylvinyl]pyridine were obtained from the condensation reaction of p-fluorophenylaldehyde and 2-picoline under catalyst-and solvent-free conditions. The intermediate 1-(p-fluorophenyl)-2-(2?-pyridyl)ethanol was obtained at 42 h reaction time and temperature of 120?C, respectively. 1H-NMR, IR spectroscopic data of the 1-(p-fluorophenyl)-2-(2-pyridyl)ethanol clearly showed the presence of the-CH2-CHOH-group. The compound was

M. Judith Percino; Víctor M. Chapela; Omar Urzúa; Ling-Fa Montiel; Cecilia Rodríguez-Barbarín

2007-01-01

42

Dehydration kinetics of shocked serpentine  

NASA Technical Reports Server (NTRS)

Experimental rates of dehydration of shocked and unshocked serpentine were determined using a differential scanning calorimetric technique. Dehydration rates in shocked serpentine are enhanced by orders of magnitude over corresponding rates in unshocked material, even though the impact experiments were carried out under conditions that inhibited direct impact-induced devolatilization. Extrapolation to temperatures of the Martian surface indicates that dehydration of shocked material would occur 20 to 30 orders of magnitude more rapidly than for unshocked serpentine. The results indicate that impacted planetary surfaces and associated atmospheres would reach chemical equilibrium much more quickly than calculations based on unshocked material would indicate, even during the earliest, coldest stages of accretion. Furthermore, it is suggested that chemical weathering of shocked planetary surfaces by solid-gas reactions would be sufficiently rapid that true equilibrium mineral assemblages should form.

Tyburczy, James A.; Ahrens, Thomas J.

1988-01-01

43

Progress toward chemcial accuracy in the computer simulation of condensed phase reactions  

SciTech Connect

A procedure is described for the generation of chemically accurate computer-simulation models to study chemical reactions in the condensed phase. The process involves (1) the use of a coupled semiempirical quantum and classical molecular mechanics method to represent solutes and solvent, respectively; (2) the optimization of semiempirical quantum mechanics (QM) parameters to produce a computationally efficient and chemically accurate QM model; (3) the calibration of a quantum/classical microsolvation model using ab initio quantum theory; and (4) the use of statistical mechanical principles and methods to simulate, on massively parallel computers, the thermodynamic properties of chemical reactions in aqueous solution. The utility of this process is demonstrated by the calculation of the enthalpy of reaction in vacuum and free energy change in aqueous solution for a proton transfer involving methanol, methoxide, imidazole, and imidazolium, which are functional groups involved with proton transfers in many biochemical systems. An optimized semiempirical QM model is produced, which results in the calculation of heats of formation of the above chemical species to within 1.0 kcal/mol of experimental values. The use of the calibrated QM and microsolvation QM/MM models for the simulation of a proton transfer in aqueous solution gives a calculated free energy that is within 1.0 kcal/mol (12.2 calculated vs. 12.8 experimental) of a value estimated from experimental pKa`s of the reacting species.

Bash, P.A.; Levine, D.; Hallstrom, P. [Argonne National Lab., IL (United States); Ho, L.L. [Yale Univ., New Haven, CT (United States). Dept. of Physics; Mackerell, A.D. Jr. [Univ. of Maryland, Baltimore, MD (United States). Dept. of Pharmaceutical Sciences

1996-03-01

44

Dehydration reactions, mass transfer and rock deformation relationships during subduction of Alpine metabauxites: insights from LIBS compositional profiles between metamorphic veins  

NASA Astrophysics Data System (ADS)

In subduction zones, the significant amounts of aqueous fluid released in the course of the successive dehydration reactions occurring during prograde metamorphism are expected to strongly influence the rock rheology, as well as kinetics of metamorphic reactions and mass transfer efficiency. Mineralized veins, ubiquitous in metamorphic rocks, can be seen as preserved witnesses of fluid and mass redistribution that partly accommodate the rock deformation (lateral segregation). However, the driving forces and mechanisms of mass transfer towards fluid-filled open spaces remain somewhat unclear. The aim of this study is to investigate the vein-forming processes and the modalities of mass transfer during local fluid-rock interactions, and their links with fluid production and rock deformation, with new insights from Laser Induced Breakdown Spectroscopy (LIBS) profiles. This study focuses on karstic pockets (metre scale) of Triassic metabauxites embedded in thick carbonate units, that have been isolated from large-scale fluid flow during HP-LT Alpine metamorphism (W. Vanoise, French Alps). These rocks display several generations of metamorphic veins containing various Al-bearing minerals, which give particular insights into mass transfer processes. It is proposed that the internally-derived fluid (~13 vol% produced by successive dehydration reactions) has promoted the opening of fluid-filled open spaces (euhedral habits of vein minerals) and served as medium for diffusive mass transfer from rock to vein. Based on mineralogical and textural features, two vein types can be distinguished: (1) some veins are filled with newly formed products of either prograde (chloritoid) or retrograde (chlorite) metamorphic reactions; in this case, fluid-filled open spaces seem to offer energetically favourable nucleation/growth sites; (2) the second vein type is filled with cookeite (Li-Al-rich chlorite) or pyrophyllite, that were present in the host rock prior to the vein formation. In this closed chemical system, mass transfer from rock to vein was achieved through the fluid, in a dissolution-transport-precipitation process, possibly stress-assisted. To investigate the modalities of mass transfer towards this second vein type, LIBS profiles were performed in the rock matrix, taking Li concentration as a proxy for cookeite distribution. Cookeite is highly concentrated (40-70 vol%) in regularly spaced veins, and the LIBS profiles show that cookeite is evenly distributed in the rock matrix comprised between two veins. The absence of diffusion profiles suggests that the characteristic diffusion length for Li, Al and Si is greater than or equal to the distance separating two cookeite veins (3-6 cm). This is in agreement with characteristic diffusion lengths calculated from both grain boundary and pore fluid diffusion coefficients, for the estimated duration of the peak of metamorphism. Concerning mass transfer driving forces, phyllosilicates have very different morphologies in the rock matrix (fibers) compared to veins (euhedral crystals): fluid-mineral interfacial energy may be maximal in the small matrix pores, which can maintain higher cookeite solubility than in fluid-filled open spaces. Therefore, as soon as veins open, chemical potential gradients may develop and drive cookeite transfer from rock matrix to veins.

Verlaguet, Anne; Brunet, Fabrice; Goffé, Bruno; Menut, Denis; Findling, Nathaniel; Poinssot, Christophe

2013-04-01

45

Trialkylphosphine-stabilized copper-phenyltellurolate complexes: from small molecules to nanoclusters via condensation reactions.  

PubMed

Reactions of CuCl with Te(Ph)SiMe3 and solublizing trialkylphosphine ligands afford a series of polynuclear copper-phenyltellurolate complexes that has been structurally characterized. The formation of the complexes is found to be highly dependent on the ancillary phosphine ligand used. The synthesis and structures of [Cu2(mu-TePh)2(PMe3)4] 1, [Cu4(mu3-TePh)4(PPr(i)3)3] 2, [Cu5(mu-TePh)3(mu3-TePh)3(PEt3)3][PEt3Ph] 3, and [Cu12Te3(mu3-TePh)6(PEt3)6] 4 are described. The telluride (Te(2-)) ligands in 4 arise from the generation of TePh2 in the reaction mixtures. The subsequent co-condensation of clusters 3 and 4 leads to the generation of the nanometer sized complex [Cu29Te9(mu3-TePh)10(mu4-TePh)2(PEt3)8][PEt3Ph] 5 in good yield, in addition to small amounts of [Cu39(mu3-TePh)10(mu4-TePh)Te16(PEt3)13] 6. These complexes are formed via the photo elimination of TePh2. The cyclic voltammogram of 5 in THF solution exhibits two oxidation waves, assigned to the oxidation of the Cu(I) centers. PMID:11511215

DeGroot, M W; Cockburn, M W; Workentin, M S; Corrigan, J F

2001-08-27

46

Condensation reaction between carbohydrazide and salicylaldehyde: in-line vibrational spectroscopy monitoring and characterization of the reaction products in solution and solid state.  

PubMed

The condensation reaction between carbohydrazide and salicylaldehyde was monitored in-line by using vibrational NIR and Raman spectroscopies and statistical methods. Prior to in-line data analysis the reaction products were fully characterized in solution and solid state in order to check the potential of the in-line approach as a tool for in-process Schiff bases reaction control. It was demonstrated that a combination of vibrational spectroscopy and principal component analysis made it possible to detect and identify the reaction products, e.g. mono(salicylidene)carbohydrazide (1) and bis(salicylidene)carbohydrazide (2) in different solvents, and to determine the reaction end points in real time. Owing to complexity of the reaction mixtures and band overlapping, it was not possible to determine the relative ratio of the reaction products in-line. The off-line analysis showed that 1 was predominant in methanol while the highest portion of 2 was obtained in ethanol. PMID:24664340

Jedna?ak, Tomislav; Novak, Predrag; Hodzic, Aden; Scheibelhofer, Otto; Khinast, Johannes G; Plavec, Janez; Sket, Primož; Parlov, Vukovi? Jelena

2014-01-01

47

Fe?O?@MOF core-shell magnetic microspheres as excellent catalysts for the Claisen-Schmidt condensation reaction.  

PubMed

Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this work, we present a facile fabrication and characterization of a novel type of MOF-based porous catalyst, namely, Fe?O?@MIL-100(Fe) core-shell magnetic microspheres. It has been shown that these catalysts not only exhibit high catalytic activities for the Claisen-Schmidt condensation reactions under environmentally friendly conditions, but remarkably, they can be easily separated and recycled without significant loss of catalytic efficiency after being used for many times. Therefore, compared to other reported catalysts used in the Claisen-Schmidt condensation reactions, these catalysts are green, cheap and more suitable for large scale industrial applications. PMID:24336813

Ke, Fei; Qiu, Ling-Guang; Zhu, Junfa

2014-01-16

48

Fe3O4@MOF core-shell magnetic microspheres as excellent catalysts for the Claisen-Schmidt condensation reaction  

NASA Astrophysics Data System (ADS)

Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this work, we present a facile fabrication and characterization of a novel type of MOF-based porous catalyst, namely, Fe3O4@MIL-100(Fe) core-shell magnetic microspheres. It has been shown that these catalysts not only exhibit high catalytic activities for the Claisen-Schmidt condensation reactions under environmentally friendly conditions, but remarkably, they can be easily separated and recycled without significant loss of catalytic efficiency after being used for many times. Therefore, compared to other reported catalysts used in the Claisen-Schmidt condensation reactions, these catalysts are green, cheap and more suitable for large scale industrial applications.Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this work, we present a facile fabrication and characterization of a novel type of MOF-based porous catalyst, namely, Fe3O4@MIL-100(Fe) core-shell magnetic microspheres. It has been shown that these catalysts not only exhibit high catalytic activities for the Claisen-Schmidt condensation reactions under environmentally friendly conditions, but remarkably, they can be easily separated and recycled without significant loss of catalytic efficiency after being used for many times. Therefore, compared to other reported catalysts used in the Claisen-Schmidt condensation reactions, these catalysts are green, cheap and more suitable for large scale industrial applications. Electronic supplementary information (ESI) available: SEM and TEM images, and GC-MS spectra for chalcones. See DOI: 10.1039/c3nr05051c

Ke, Fei; Qiu, Ling-Guang; Zhu, Junfa

2014-01-01

49

Golden rule kinetics of transfer reactions in condensed phase: The microscopic model of electron transfer reactions in disordered solid matrices  

SciTech Connect

The algorithm for a theoretical calculation of transfer reaction rates for light quantum particles (i.e., the electron and H-atom transfers) in non-polar solid matrices is formulated and justified. The mechanism postulated involves a local mode (an either intra- or inter-molecular one) serving as a mediator which accomplishes the energy exchange between the reacting high-frequency quantum mode and the phonon modes belonging to the environment. This approach uses as a background the Fermi golden rule beyond the usually applied spin-boson approximation. The dynamical treatment rests on the one-dimensional version of the standard quantum relaxation equation for the reduced density matrix, which describes the frequency fluctuation spectrum for the local mode under consideration. The temperature dependence of a reaction rate is controlled by the dimensionless parameter ?{sub 0}=??{sub 0}/k{sub B}T where ?{sub 0} is the frequency of the local mode and T is the temperature. The realization of the computational scheme is different for the high/intermediate (?{sub 0} < 1 ? 3) and for low (?{sub 0}? 1) temperature ranges. For the first (quasi-classical) kinetic regime, the Redfield approximation to the solution of the relaxation equation proved to be sufficient and efficient in practical applications. The study of the essentially quantum-mechanical low-temperature kinetic regime in its asymptotic limit requires the implementation of the exact relaxation equation. The coherent mechanism providing a non-vanishing reaction rate has been revealed when T? 0. An accurate computational methodology for the cross-over kinetic regime needs a further elaboration. The original model of the hopping mechanism for electronic conduction in photosensitive organic materials is considered, based on the above techniques. The electron transfer (ET) in active centers of such systems proceeds via local intra- and intermolecular modes. The active modes, as a rule, operate beyond the kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode/medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems.

Basilevsky, M. V.; Mitina, E. A. [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation)] [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation); Odinokov, A. V. [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation) [Photochemistry Center, Russian Academy of Sciences, 7a, Novatorov ul., Moscow (Russian Federation); National Research Nuclear University “MEPhI,” 31, Kashirskoye shosse, Moscow (Russian Federation); Titov, S. V. [Karpov Institute of Physical Chemistry, 3-1/12, Building 6, Obuha pereulok, Moscow (Russian Federation)] [Karpov Institute of Physical Chemistry, 3-1/12, Building 6, Obuha pereulok, Moscow (Russian Federation)

2013-12-21

50

Golden rule kinetics of transfer reactions in condensed phase: the microscopic model of electron transfer reactions in disordered solid matrices.  

PubMed

The algorithm for a theoretical calculation of transfer reaction rates for light quantum particles (i.e., the electron and H-atom transfers) in non-polar solid matrices is formulated and justified. The mechanism postulated involves a local mode (an either intra- or inter-molecular one) serving as a mediator which accomplishes the energy exchange between the reacting high-frequency quantum mode and the phonon modes belonging to the environment. This approach uses as a background the Fermi golden rule beyond the usually applied spin-boson approximation. The dynamical treatment rests on the one-dimensional version of the standard quantum relaxation equation for the reduced density matrix, which describes the frequency fluctuation spectrum for the local mode under consideration. The temperature dependence of a reaction rate is controlled by the dimensionless parameter ?0 = ??0/k(B)T where ?0 is the frequency of the local mode and T is the temperature. The realization of the computational scheme is different for the high/intermediate (?0 < 1 - 3) and for low (?0 ? 1) temperature ranges. For the first (quasi-classical) kinetic regime, the Redfield approximation to the solution of the relaxation equation proved to be sufficient and efficient in practical applications. The study of the essentially quantum-mechanical low-temperature kinetic regime in its asymptotic limit requires the implementation of the exact relaxation equation. The coherent mechanism providing a non-vanishing reaction rate has been revealed when T ? 0. An accurate computational methodology for the cross-over kinetic regime needs a further elaboration. The original model of the hopping mechanism for electronic conduction in photosensitive organic materials is considered, based on the above techniques. The electron transfer (ET) in active centers of such systems proceeds via local intra- and intermolecular modes. The active modes, as a rule, operate beyond the kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode?medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the present approach to the Marcus ET theory and to the quantum-statistical reaction rate theory [V. G. Levich and R. R. Dogonadze, Dokl. Akad. Nauk SSSR, Ser. Fiz. Khim. 124, 213 (1959); J. Ulstrup, Charge Transfer in Condensed Media (Springer, Berlin, 1979); M. Bixon and J. Jortner, Adv. Chem. Phys. 106, 35 (1999)] underlying it is discussed and illustrated by the results of computations for practically important target systems. PMID:24359347

Basilevsky, M V; Odinokov, A V; Titov, S V; Mitina, E A

2013-12-21

51

Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions  

PubMed Central

Catalytic behavior of isomorphously substituted B-, Al-, Ga-, and Fe-containing extra-large pore UTL zeolites was investigated in Knoevenagel condensation involving aldehydes, Pechmann condensation of 1-naphthol with ethylacetoacetate, and Prins reaction of ?-pinene with formaldehyde and compared with large-pore aluminosilicate zeolite beta and representative Metal-Organic-Frameworks Cu3(BTC)2 and Fe(BTC). The yield of the target product over the investigated catalysts in Knoevenagel condensation increases in the following sequence: (Al)beta < (Al)UTL < (Ga)UTL < (Fe)UTL < Fe(BTC) < (B)UTL < Cu3(BTC)2 being mainly related to the improving selectivity with decreasing strength of active sites of the individual catalysts. The catalytic performance of Fe(BTC), containing the highest concentration of Lewis acid sites of the appropriate strength is superior over large-pore zeolite (Al)beta and B-, Al-, Ga-, Fe-substituted extra-large pore zeolites UTL in Prins reaction of ?-pinene with formaldehyde and Pechmann condensation of 1-naphthol with ethylacetoacetate.

Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; Cejka, Jiri

2013-01-01

52

Dissolution processes, hydrolysis and condensation reactions during geopolymer synthesis: Part II. High Si\\/Al ratio systems  

Microsoft Academic Search

The mechanisms of speciation of aluminate and silicate phases during dissolution and condensation stages of alumino-silicate\\u000a geopolymer reactions characterised by Si\\/Al ? 3, have been investigated and the results compared to predictions of the partial\\u000a charge model. Solid-state nuclear magnetic resonance (NMR) traces indicate that free [Al(OH)4]? species, present in lower silicate formulations such as Si\\/Al ? 1, do not occur in the present

K. Sagoe-Crentsil; L. Weng

2007-01-01

53

Identification of 4-methylspinaceamine - a Pictet – Spengler condensation reaction product of histamine with acetaldehyde - in human urine  

Microsoft Academic Search

This study reports the first identification of 4-methylspinaceamine (4-MSPA)-a Pictet Spengler condensation reaction product of histamine with acetaldehyde-in human urine. 4-MSPA was identified and quantified as follows: the target compound was partially purified by solvent extraction from a urine sample spiked with N-methylpiperazine (N-MP) as an internal standard, then derivatized to a naphthylthiourea derivative with 1-naphthylisothiocyanate (NITC) and finally analyzed

Takeshi Ohya; Masaru Niitsu

2005-01-01

54

Synthesis of 1,5-Benzodiazepine and Its Derivatives by Condensation Reaction Using H-MCM-22 as Catalyst  

PubMed Central

A simple and versatile method for the synthesis of 1,5-benzodiazepines is via condensation of o-phenylenediamines (OPDA) and ketones in the presence of catalytic amount of H-MCM-22 using acetonitrile as solvent at room temperature. In all the cases, the reactions are highly selective and are completed within 1–3?h. The method is applicable to both cyclic and acyclic ketones without significant differences. The reaction proceeds efficiently under ambient conditions with good-to-excellent yields.

Majid, Sheikh Abdul; Khanday, Waheed Ahmad; Tomar, Radha

2012-01-01

55

Thirst, Drinking Behavior, And Dehydration  

NASA Technical Reports Server (NTRS)

Report describes review of physiological mechanisms of involuntary dehydration. Researchers considered cellular dehydration and effects of sodium on thirst, as well as extracellular dehydration and restoration of vascular volume, effects of renin on thirst, and effects of heat.

Greenleaf, John

1996-01-01

56

Oxidative condensation reactions of (diethylenetriamine)cobalt(III) complexes with substituted bis(pyridin-2-yl)methane ligands  

NASA Astrophysics Data System (ADS)

The synthesis and characterisation of Co(III) complexes derived from a condensation reaction with a central or terminal nitrogen of a dien ligand and the ?-carbon of a range of substituted bis(pyridin-2-yl)methane ligands are described. Aerial oxidation of bpm {bis(pyridin-2-yl)methane with Co(II)/dien or direct reaction with Co(dien)Cl 3 provided in low yield a single C-N condensation product 1 (at the primary terminal NH 2) after the pyridyl -CH 2- is formally oxidised to -CH +-. The methyl substituted ligand bpe {1,1-bis(pyridin-2-yl)ethane} behaves likewise, except both terminal (prim) and central (sec) amines condense to yield isomeric products 2 and 3. Two of these three materials have been characterised by single crystal X-ray crystallography. The corresponding reactions for the bis(pyridyl) ligand bpk {bis(pyridin-2-yl)ketone} provided C-N condensation products without the requirement for oxidation at the ?-C center; two carbinolamine complexes in different geometrical configurations resulted, mer-anti-[Co(dienbpc)Cl]ZnCl 4, 5, and unsym- fac-[Co(dienbpc)Cl]ZnCl 4, 6, {dienbpc=[2-(2-aminoethylamino)-ethylamino]-di-pyridin-2-yl-methanol}. In addition, a novel complex, [Co(bpk)(bpd-OH)Cl]ZnCl 4, 4, in which one bidentate N, N-bonded bpk ligand and one tridentate N, O, N-bonded bpd (the diol from bpk+OH -) were coordinated, was obtained via the Co(II)/O 2 synthetic route. When the bpc ligand (bpc=bis(pyridin-2-yl)methanol) was employed directly as a reagent along with dien, no condensation reactions were observed, but rather a single isomeric complex [Co(dien)(bpc)]Cl.ZnCl 4, 7, in which the ligand bpc acted as a N,N,O-bonded tridentate ligand rather than as a N,N-bidentate ligand was isolated. 13C, 1D and 2D 1H NMR studies are reported for all the complexes; they establish the structures unambiguously.

Zhou, Xiangting; Hockless, David C. R.; Willis, Anthony C.; Jackson, W. Gregory

2005-04-01

57

An investigation of the role of water on retrograde/condensation reactions and enhanced liquefaction yields. Final report  

SciTech Connect

While great strides have been made in developing the technology of coal liquefaction processes in recent years, many unsolved problems still remain before a viable and economical process can be achieved. The technological problems that still exist can be solved through a more fundamental understanding of the chemistry associated with each stage of the coal liquefaction process, starting with any pretreatment steps that may be carried out on the coal itself. Western Research Institute, under the a contract from the US Department of Energy, has conducted a study of different methods of coal drying as pretreatment steps before liquefaction. The results of that study are the subject of this report. Coals that were dried or partially dried thermally and with microwaves had lower liquefaction conversions than coals containing equilibrium moisture contents. However, chemically dried coals had conversions equal to or greater than the premoisturized coals. The conversion behavior is consistent with changes in the physical structure and cross linking reactions because of drying. Thermal and microwave drying appear to cause a collapse in the pore structure, thus preventing donor solvents such as tetralin from contacting reactive sites inside the coals. Chemical dehydration does not appear to collapse the pore structure. From the study of the kinetics of the chemical dehydration of coals, it was possible to quantify the amount of water on the surface, the amount readily accessible in pores, and the amount more strongly bonded in the internal structure of the coals. The results indicate that high-rank coals have proportionally less surface and easily accessible water than the lower rank coals.

Miknis, F.P.; Netzel, D.A.; Wallace, J.C. Jr.; Butcher, C.H.; Mitzel, J.M.; Turner, T.F.

1995-02-01

58

Dehydration behavior of eprosartan mesylate dihydrate.  

PubMed

Eprosartan mesylate (SKF 108566-J; EM) is an antihypertensive agent approved for marketing in the USA. EM dihydrate was prepared by three methods, one of which included suspending the anhydrous drug in an aqueous solution of 1.0 M methanesulfonic acid to form a slurry, followed by filtration. The dehydration kinetics of EM dihydrate were derived by analyzing the fit of the isothermal thermogravimetric analytical (TGA) data to numerous kinetic models. EM dihydrate undergoes dehydration in two distinct steps, each involving the loss of 1 mol of water at 25-70 degrees C and 70-120 degrees C, respectively. Recrystallization of EM occurs at approximately 120-140 degrees C after dehydration to the anhydrous phase. This explanation is supported by variable temperature powder X-ray diffractometry. The mechanism of the dehydration reaction is complex, the dependence of the reaction rate on temperature varying as a function of the particles size. For the dihydrate of sieve fraction <125 microm, the kinetics of the first and second dehydration steps are consistent with the Avrami-Erofeev equation (A3, n = 1/3) over the temperature range studied, corresponding to three-dimensional growth of nuclei. In contrast, for the 125-180-microm and 180-250-microm sieve fractions, the kinetics are best described by the two-dimensional phase boundary reaction (R2) at a lower dehydration temperature (i.e., 28.3 degrees C), and by the Avrami-Erofeev equation (A3, n = 1/3) at a higher dehydration temperature (i.e., 93.7 degrees C). The activation energies (15-40 kcal/mol) and frequency factors of the dehydration of EM dihydrate were determined both by Arrhenius plots of the isothermal rates determined by TGA and by Kissinger plots of the nonisothermal differential scanning calorimetric data. Hot stage microscopy of single crystals of EM dihydrate showed random nucleation at the surface and dehydration with the growth of microcrystals along the needle a axis. Cerius(2) molecular modeling software showed the existence of water channels along the a axis and enabled the observed dehydration behavior of EM dihydrate crystals to be explained in terms of the bonding environment of water molecules in the crystal structure. PMID:10514350

Sheng, J; Venkatesh, G M; Duddu, S P; Grant, D J

1999-10-01

59

Dehydration of Magnesium Chloride.  

National Technical Information Service (NTIS)

The patent application discloses a method for dehydrating magnesium chloride hydrates or brines by complexing with amine hydrochlorides. Magnesium chloride hydrate or brine is reacted to an amine hydrochloride to form a complex which is then heated to fir...

H. Dolezal

1975-01-01

60

THE DEHYDRATION OF TOBERMORITE  

Microsoft Academic Search

Tobermorite (Ca 4 (Si6018H2)Ca.4I-IaO ) is a hydrated calcimn silicate mineral with a layer structure which in some respects resembles that of vermiculite. Its dehydration has been studied using single crystals from Ballyeraigy, N. Ireland. The three most frequently encountered hych'ation states are characterized by basal spacings (d002) of 14.0, 11.3 and 9.35~. Dehydration to the 9.35~ state is complete

F. W. TAYLOR

61

Electrolyte Concentrates Treat Dehydration  

NASA Technical Reports Server (NTRS)

Wellness Brands Inc. of Boulder, Colorado, exclusively licensed a unique electrolyte concentrate formula developed by Ames Research Center to treat and prevent dehydration in astronauts returning to Earth. Marketed as The Right Stuff, the company's NASA-derived formula is an ideal measure for athletes looking to combat dehydration and boost performance. Wellness Brands also plans to expand with products that make use of the formula's effective hydration properties to help treat conditions including heat stroke, altitude sickness, jet lag, and disease.

2009-01-01

62

Structural requirements and reaction pathways in condensation reactions of alcohols on Mg{sub y}AlO{sub x} catalysts  

SciTech Connect

The effect of composition and of surface properties on alcohol-coupling reactions was studied on Mg{sub y}AlO{sub x} catalysts using C{sub 2}H{sub 5}OH or {sup 13}CH{sub 3}OH/1-{sup 12}C{sub 3}H{sub 7}OH mixtures as reactants. Samples with Mg/Al ratios of 0.5--9.0 were obtained by thermal decomposition of precipitated hydrotalcite precursors. The nature, density, and strength of surface basic sites were obtained by temperature-programmed desorption (TPD) of CO{sub 2} and by {sup 13}CO{sub 2}/{sup 12}CO isotopic switch methods, whereas the acid site densities were measured by TPD or NH{sub 3}. The catalyst ability for activating H-H bonds was investigated by performing H{sub 2}-D{sub 2} steady-state equilibration reactions. Isotopic tracer studies were carried out in order to probe chain growth pathways in the synthesis of isobutanol. The rates and product selectivity for C{sub 2}H{sub 5}OH or CH{sub 3}OH/C{sub 3}H{sub 7}OH reactions strongly depended on the chemical composition of Mg{sub y}AlO{sub x} samples. In turn, the chemical composition affected the acid-base properties of Mg{sub y}AlO{sub x} samples by modifying surface acid and base site densities and the distribution of strength for such sites. The rate of alcohol dehydration to ethers and olefins increased with increasing Al content. Al-rich Mg{sub y}AlO{sub x} samples contained a high density of Al{sup 3+}{minus}O{sup 2{minus}} site pairs and of moderate strength basic sites, the combination of which promoted the formation of ethylene or propylene from primary alcohols via E{sub 2} elimination pathways. The competitive dehydration to form ethers involved the adsorption of two alcohol molecules on neighboring active sites offering different acid-base properties.

Di Cosimo, J.I.; Apesteguia, C.R.; Gines, M.J.L.; Iglesia, E.

2000-03-10

63

Microwave-assisted four-component, one-pot condensation reaction: an efficient synthesis of annulated pyridines.  

PubMed

A one-pot, effective synthesis of pyridines by a modified Kröhnke procedure is described. Polysubstituted annulated pyridines were synthesized in high yields by four-component, one-pot cyclocondensation reactions of N-phenacylpyridinium bromide, aromatic aldehydes, acetophenones or cyclic ketones in the presence of ammonium acetate and acetic acid, assisted by microwave irradiation. In this procedure, cyclic ketones with two alpha-CH(2) groups yield annulated pyridines with additional alpha-benzylidene groups, which are derived in situ from double aldol condensation of cyclic ketones with two moles of aromatic aldehydes. PMID:17340010

Yan, Chao-Guo; Cai, Xi-Mei; Wang, Qi-Fang; Wang, Ting-Yu; Zheng, Ming

2007-03-21

64

Carbon dioxide hydrationand dehydration kinetics in seawater  

Microsoft Academic Search

Rate constants for the hydration and dehydration reactions of carbon dioxide with water and with hydroxyl ion were measured in seawater by a pH-stat method at salinities (X lO:l) from 3.4 to 37.06 at 25°C and from 5\\

Kenneth S. Johnson

1982-01-01

65

Synthesis of 2,8-dioxabicyclo[3.3.1]nonane derivatives via a sequential Knoevenagel condensation and hetero-Diels-Alder reaction in an aqueous medium.  

PubMed

Utilizing aldehyde-substituted vinylogous carbonates and 1,3-diketones, a simple protocol is presented for the synthesis of 2,8-dioxabicyclo[3.3.1]nonane derivatives via Knoevenagel condensation followed by a hetero-Diels-Alder reaction under green reaction conditions. The structure of a key product is unequivocally confirmed by X-ray crystallography. PMID:24147553

Srinivas, Venu; Koketsu, Mamoru

2013-11-15

66

Plastic and dehydration instabilities of antigorite serpentinite  

NASA Astrophysics Data System (ADS)

We conducted a constant displacement rate test of antigorite serpentinite by a triaxial solid medium deformation apparatus installed at Hiroshima University. Experimental conditions were P = ca. 1.0 GPa, T = 450 C to 800 C, which cover from stability to dehydration conditions of antigorite, and strain rate of digit of 10-5 /sec. Samples were cylindrical shape cored from serpentinite and their sizes were 7 mm x 7 mm and 5 mm x 5 mm in diameter by length. Faults were observed in recovered samples from all temperature conditions. Mechanical data of faulted samples showed stress drop of several 10 MPa during experiments. The followings summarize microstructural observations of the recovered samples, and propose generation processes of fault at stability and dehydration conditions. 1) Stability field (plastic instability): Antigorite grains develop a lattice preferred orientation (LPO) along a fault, which characterized by (001) cleavage face parallel to fault plane. This fact suggests the fault is generated by the following process. i) Antigorite grains on the plane applied by maximum shear stress are preferentially deformed by plastic manner, and then develop the LPO. ii) The arrangement of cleavage face gradually reduces the strength of this plane. iii) Eventually, embrittlement occurs at the critical point when the rock strength along this weak plane becomes smaller than shear stress. 2) Dehydration condition (dehydration instability): Fine grained dehydration phases less than 1 micrometer in size such as olivine and talc are detected as a thin vein along the fault. Moreover, talc and olivine, or antigorite ca. 1 - 5 micrometers in size with angular shape are observed within the fault as a fault gauge. These facts suggest the following generation process of fault. i) Dehydration reaction of antigorite begins on the plane applied by maximum shear stress and expands along this plane. ii) The dehydration gradually reduces the strength of this plane. iii) Eventually, embrittlement occurs at the critical point when the rock strength along this weak plane becomes smaller than shear stress.

Ando, J.; Katayama, I.; Ohfuji, H.; Terada, Y.

2008-12-01

67

Linking the historical and chemical definitions of diabatic states for charge and excitation energy transfer reactions in condensed phase  

NASA Astrophysics Data System (ADS)

Marcus theory of electron transfer (ET) and Förster theory of excitation energy transfer (EET) rely on the Condon approximation and the theoretical availability of initial and final states of ET and EET reactions, often called diabatic states. Recently [Subotnik et al., J. Chem. Phys. 130, 234102 (2009)], diabatic states for practical calculations of ET and EET reactions were defined in terms of their interactions with the surrounding environment. However, from a purely theoretical standpoint, the definition of diabatic states must arise from the minimization of the dynamic couplings between the trial diabatic states. In this work, we show that if the Condon approximation is valid, then a minimization of the derived dynamic couplings leads to corresponding diabatic states for ET reactions taking place in solution by diagonalization of the dipole moment matrix, which is equivalent to a Boys localization algorithm; while for EET reactions in solution, diabatic states are found through the Edmiston-Ruedenberg localization algorithm. In the derivation, we find interesting expressions for the environmental contribution to the dynamic coupling of the adiabatic states in condensed-phase processes. In one of the cases considered, we find that such a contribution is trivially evaluable as a scalar product of the transition dipole moment with a quantity directly derivable from the geometry arrangement of the nuclei in the molecular environment. Possibly, this has applications in the evaluation of dynamic couplings for large scale simulations.

Pavanello, Michele; Neugebauer, Johannes

2011-10-01

68

Rehydration of Dehydrated Foods  

Microsoft Academic Search

Dehydrated products readily take up moisture when immersed in a liquid medium, leading to significant changes in their thermophysical properties. The rehydration kinetics, the structural properties (apparent density, true density, specific volume and internal porosity), the viscoelastic behavior (compression tests), and the flavor losses were investigated during rehydration of various fruits and vegetables. The effect of temperature on the above

M. K. Krokida; C. Philippopoulos

2005-01-01

69

Dehydrated Fried Meat Cakes.  

National Technical Information Service (NTIS)

Dehydrated hamburger cakes, pork sausage patties, fish cakes and the like may be prepared by the process. It may be reconstituted by hot water. The comminuted meat product is mixed with a starchy vegetable component such as corn meal. The product is prefr...

R. Buscemi J. M. Tuomy

1964-01-01

70

Role of Metal Oxides in Nanothermite Reactions: Evidence of Condensed Phase Initiation.  

National Technical Information Service (NTIS)

This work is a culmination of several corresponding studies designed to probe the initiation and reaction of aluminum nanothermite systems. The main diagnostic tool used in this study is a Temperature-Jump/Time-of-Flight Mass Spectrometer (T-Jump/TOFMS), ...

K. T. Sullivan M. R. Zachariah N. W. Piekiel S. Chowdhury

2010-01-01

71

Chemische Reaktionen in kondensierender Atmosphaere. Abschlussbericht. (Chemical reactions in condensing atmosphere. Final report).  

National Technical Information Service (NTIS)

The investigations have deepened understanding in individual points, especially on the S(IV) oxidation in the ground-level atmosphere. These are perhaps the best-known degradation reactions; they lead to production of sulfates and hydrogen ions and repres...

R. Dlugi, R. Forkel, W. Seidl

1990-01-01

72

Reaction engineering of co-condensing (methyl)ethoxysilane mixtures: Kinetic characterization and modeling  

SciTech Connect

Molecular homogeneity frequently plays a decisive role in the effective application of organically modified silicate copolymers. However, methods of directly characterizing copolymerization extent in siloxanes generated from mixed alkoxysilanes are not always available or convenient. The authors present an alternative tool for determining kinetic parameters for models of alkoxysilane hydrolytic copolycondensation. Rather than restricting attention to single step batch reactors, they use a semibatch reactor with varying time of injection of one component. They describe the fitting method and show that all necessary kinetic parameters can be determined from a series of ordinary {sup 29}Si NMR data in a straightforward case study: copolymerization of dimethyldiethoxy silane and trimethylethoxysilane. Under conditions providing no direct {sup 29}Si NMR signature of copolymerization, they find kinetic trends consistent with those previously reported. As further validation, the results of a new series of experiments (varying the ratio of mono-functional to difunctional monomer) are predicted by the semibatch copolymerization model and measured parameters. Based on these results, they are able to calculate the molecular homogeneity in the copolymer products investigated. Even for this relatively simple system, the optimal injection time is a complex function of residence time, but early injection of the faster-condensing monomer gives the best homogeneity at long residence times.

RANKIN,STEPHEN E.; MCCORMICK,ALON V.

2000-01-26

73

Experimental evidence for condensation reactions between sugars and proteins in carbonate skeletons  

SciTech Connect

Melanoidins, condensation products formed from protein and polysaccharide precursors, were once thought to be an important geological sink for organic carbon. The active microbial recycling of the precursors, coupled with an inability to demonstrate the formation of covalent linkages between amino acids and sugars in melanoidins, has shaped a powerful argument against this view. Yet, melanoidins may still be an abundant source of macromolecules in fossil biominerals such as shells, in which the proteins and polysaccharides are well protected from microbial degradation. The authors have modeled diagenetic changes in a biomineral by heating at 90C mixtures of protein, polysaccharides, and finely ground calcite crystals in sealed glass vials. Changes to the protein bovine serum albumin (BSA, fraction V) were monitored by means of gel electrophoresis and immunology. In the presence of water, BSA was rapidly hydrolyzed and remained immunologically reactive for less than 9 h. Under anhydrous conditions the protein was immunologically reactive for the whole period of the experiment (1,281 h), unless mono- or disaccharide sugars were also present. In the presence of these reactive sugars, browning, a discrete increase in molecular weight of the protein, and a concomitant loss of antigenicity confirmed that the sugars were attaching covalently to the protein, forming melanoidins. The authors roughly estimate that, at the global scale, 2.4 {times} 10{sup 6} tons of calcified tissue matrix glycoproteins is processed annually through the melanoidin pathway. This amount would be equivalent to 7 per mil of the total flux of organic carbon into marine sediments.

Collins, M.J.; Westbroek, P.; Muyzer, G. (Leiden Univ. (Netherlands)); De Leeuw, J.W. (Delft Univ. of Technology (Netherlands))

1992-04-01

74

Postmortem diagnosis of hypertonic dehydration.  

PubMed

Beside morphological signs of hypertonic dehydration as tinting of skin, sunken eyes, dry surface of the galea or dry cutting areas of organs, a chemical profile of vitreous humor was proposed as a diagnostic tool for the diagnosis of hypertonic dehydration. The profile consists of an elevation of sodium >155 mmol/l, chloride >135 mmol/l and urea >40 mg/dl. This profile was named dehydration pattern. The value of this dehydration pattern for the diagnosis of hypertonic dehydration will be discussed by a short review of the literature and case reports. So far, the published literature on the dehydration pattern is not a sound scientific basis for the diagnosis of dehydration. PMID:16216704

Madea, Burkhard; Lachenmeier, Dirk W

2005-12-01

75

Experimental evidence for condensation reactions between sugars and proteins in carbonate skeletons  

NASA Astrophysics Data System (ADS)

Melanoidins, condensation products formed from protein and polysaccharide precursors, were once thought to be an important geological sink for organic carbon. The active microbial recycling of the precursors, coupled with an inability to demonstrate the formation of covalent linkages between amino acids and sugars in melanoidins, has shaped a powerful argument against this view. Yet, melanoidins may still be an abundant source of macromolecules in fossil biominerals such as shells, in which the proteins and polysaccharides are well protected from microbial degradation. We have modelled diagenetic changes in a biomineral by heating at 90°C mixtures of protein, polysaccharides and finely ground calcite crystals in sealed glass vials. Changes to the protein bovine serum albumin (BSA, fraction V) were monitored by means of gel electrophoresis and immunology. In the presence of water, BSA was rapidly hydrolyzed and remained immunologically reactive for less than 9 h. Under anhydrous conditions the protein was immunologically reactive for the whole period of the experiment (1281 h), unless mono- or disaccharide sugars were also present. In the presence of these reactive sugars, browning, a discrete increase in molecular weight of the protein and a concomitant loss of antigenicity confirmed that the sugars were attaching covalently to the protein, forming melanoidins. The de novo formation of products cross-reactive with antibodies raised against organic matter isolated from the shells of a fossil mollusc ( Mercenaria mercenaria) indicated that at least in part the model simulated natural diagenesis. We roughly estimate that, at the global scale, 2.4 × 10 6 tonnes of calcified tissue matrix glycoproteins is processed annually through the melanoidin pathway. This amount would be equivalent to 7 per mil of the total flux of organic carbon into marine sediments.

Collins, M. J.; Westbroek, P.; Muyzer, G.; de Leeuw, J. W.

1992-04-01

76

Synthesis of highly substituted 4H-pyrido[1,2-a]pyrimidines via a one-pot three-component condensation reaction.  

PubMed

A one-pot three-component reaction, involving condensation of 2-aminopyridines, aldehydes, and ketones/aldehydes under trifluoromethanesulfonic acid catalysis, provides rapid access to highly substituted novel 4H-pyrido[1,2-a]pyrimidines. PMID:23914724

Yang, Kai; Xiang, Jinbao; Bao, Guochen; Dang, Qun; Bai, Xu

2013-09-01

77

Indium(III) iodide-mediated Strecker reaction in water: an efficient and environmentally friendly approach for the synthesis of ?-aminonitrile via a three-component condensation  

Microsoft Academic Search

A mild, efficient and environmentally friendly method has been developed for the synthesis of ?-aminonitriles via a three-component condensation of aldehyde, amine and TMSCN in the presence of a catalytic amount of indium(III) iodide in water. The reactions proceeded smoothly at room temperature in water to generate the corresponding products in moderate to excellent yields.

Zhi-Liang Shen; Shun-Jun Ji; Teck-Peng Loh

2008-01-01

78

The chemical signatures of progressive dehydration stages in subducted serpentinites  

Microsoft Academic Search

Fluids mediate chemical cycling in subduction zones. Nonetheless, the chemistry of serpentinite-dehydration fluids from down-going slabs and their chemical effects on ascent are only very poorly constrained. We report new data on discontinuous dehydration reactions, including the measurement of individual fluid inclusions in prograde minerals from natural occurrences, and one case study tracing the infiltration of serpentinite-derived fluid in mafic

T. Pettke; C. Spandler; J. Kodolanyi; M. Scambelluri

2009-01-01

79

Preparation of sodium borohydride by the reaction of MgH 2 with dehydrated borax through ball milling at room temperature  

Microsoft Academic Search

A convenient method was developed to synthesize NaBH4 by the reaction of MgH2 with Na2B4O7 through ball milling at room temperature. In order to improve the sodium borohydride yield, Na compounds were added to compensate the Na insufficiency in reactants when MgH2 instead of NaH was used as the reducing agent. It was found that Na2CO3 addition was better than

Z. P. Li; N. Morigazaki; B. H. Liu; S. Suda

2003-01-01

80

Dehydration of fermentative 2,3-butanediol into methyl ethyl ketone  

SciTech Connect

A solid acid catalyst consisted of sulfonic groups covalently bound to an inorganic matrice was developed to dehydrate 2,3-butanediol into methyl ethyl ketone. Rate constant and apparent activation energy of the dehydration reaction were determined. The decay course of the catalyst was a two-stage curve. The catalyst was deactivated more rapidly in the first stage than in the second stage. The strategy of maintaining constant degree of dehydration was employed to lengthen the lifetime of catalyst. Treatment of the 2,3-butanediol containing fermentation broth with activated carbon greatly facilitated the subsequent dehydration reaction.

Tran, A.V.; Chambers, R.P.

1987-01-01

81

Kinetics of volatile extraction from carbonaceous chondrites: Dehydration of talc  

NASA Technical Reports Server (NTRS)

Carbonaceous chondrites are believed to be the primary constituents of near-Earth asteroids and Phobos and Deimos, and are potential resources of fuels that may be exploited for future planetary missions. Calculations of equilibrium phase relations suggest that talc (Ta) and antigorite (Ant) are likely to be the major hydrous phases in the C1 and C2 meteorites (Ganguly and Saxena, 1989), which constitute the most volatile rich classes of carbonaceous chondrites. The dehydration kinetics of talc are studied as a function of temperature, grain size, composition and fluid fugacity, as part of a systematic study of the reaction kinetics of the volatile bearing phases that are either known or likely to be present in carbonaceous chondrites. The dehydration kinetics were investigated at 1 bar, 775 to 875 C by monitoring the in-situ weight loss as a function of time of a natural talc. The talc platelets had a dimension of 0.8 to 1 micron. The run durations varied from 233.3 hours at 775 C (48 percent dehydration) to 20.8 hours at 875 C (80 pct. dehydration). The results can be adequately represented by a given rate equation. Theoretical analysis suggests that the reduction in the concentration of H2O in the environment of dehydrating talc, as would be encountered in processing chondritic materials, will have negligible effect on the rate of dehydration, unless there is a change of reaction mechanism owing to the presence of other volatile species.

Bose, Kunal; Ganguly, Jibamitra

1991-01-01

82

Survey of quality indicators in commercial dehydrated fruits.  

PubMed

Physical and chemical quality parameters (dry matter, aw, protein, carbohydrates, vitamin C, 2-furoylmethyl amino acids, rehydration ratio and leaching loss) have been determined in 30 commercial dehydrated fruits (strawberry, blueberry, raspberry, cranberry, cherry, apple, grapefruit, mango, kiwifruit, pineapple, melon, coconut, banana and papaya). For comparison purposes, strawberry samples processed in the laboratory by freeze-drying and by convective drying were used as control samples. Overall quality of dehydrated fruits seemed to be greatly dependent on processing conditions and, in a cluster analysis, samples which were presumably subjected to osmotic dehydration were separated from the rest of fruits. These samples presented the lowest concentration of vitamin C and the highest evolution of Maillard reaction, as evidenced by its high concentration of 2-furoylmethyl amino acids. This is the first study on the usefulness of this combination of chemical and physical indicators to assess the overall quality of commercial dehydrated fruits. PMID:24360417

Megías-Pérez, Roberto; Gamboa-Santos, Juliana; Soria, Ana Cristina; Villamiel, Mar; Montilla, Antonia

2014-05-01

83

Reaction Mechanisms of Energetic Materials in the Condensed Phase: Long- term Aging, Munition Safety and Condensed-Phase Processes in Propellants and Explosives.  

National Technical Information Service (NTIS)

The achievements of this five-year project are summarized. The primary achievement is the development of a new paradigm to investigate the complex reaction processes that control the behavior of heterogeneous energetic materials in munitions throughout th...

R. Behrens R. L. Swanson

2009-01-01

84

Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP): linking condensation, evaporation and chemical reactions of organics, oxidants and water  

NASA Astrophysics Data System (ADS)

We present a novel kinetic multi-layer model for gas-particle interactions in aerosols and clouds (KM-GAP) that treats explicitly all steps of mass transport and chemical reaction of semi-volatile species partitioning between gas phase, particle surface and particle bulk. KM-GAP is based on the PRA model framework (Pöschl-Rudich-Ammann, 2007), and it includes gas phase diffusion, reversible adsorption, surface reactions, bulk diffusion and reaction, as well as condensation, evaporation and heat transfer. The size change of atmospheric particles and the temporal evolution and spatial profile of the concentration of individual chemical species can be modeled along with gas uptake and accommodation coefficients. Depending on the complexity of the investigated system and the computational constraints, unlimited numbers of semi-volatile species, chemical reactions, and physical processes can be treated, and the model shall help to bridge gaps in the understanding and quantification of multiphase chemistry and microphysics in atmospheric aerosols and clouds. In this study we demonstrate how KM-GAP can be used to analyze, interpret and design experimental investigations of changes in particle size and chemical composition in response to condensation, evaporation, and chemical reaction. For the condensational growth of water droplets, our kinetic model results provide a direct link between laboratory observations and molecular dynamic simulations, confirming that the accommodation coefficient of water at ~270 K is close to unity (Winkler et al., 2006). Literature data on the evaporation of dioctyl phthalate as a function of particle size and time can be reproduced, and the model results suggest that changes in the experimental conditions like aerosol particle concentration and chamber geometry may influence the evaporation kinetics and can be optimized for efficient probing of specific physical effects and parameters. With regard to oxidative aging of organic aerosol particles, we illustrate how the formation and evaporation of volatile reaction products like nonanal can cause a decrease in the size of oleic acid particles exposed to ozone.

Shiraiwa, M.; Pfrang, C.; Koop, T.; Pöschl, U.

2012-03-01

85

Theory of Bose-Einstein condensation mechanism for deuteron-induced nuclear reactions in micro/nano-scale metal grains and particles.  

PubMed

Recently, there have been many reports of experimental results which indicate occurrences of anomalous deuteron-induced nuclear reactions in metals at low energies. A consistent conventional theoretical description is presented for anomalous low-energy deuteron-induced nuclear reactions in metal. The theory is based on the Bose-Einstein condensate (BEC) state occupied by deuterons trapped in a micro/nano-scale metal grain or particle. The theory is capable of explaining most of the experimentally observed results and also provides theoretical predictions, which can be tested experimentally. Scalabilities of the observed effects are discussed based on theoretical predictions. PMID:19440686

Kim, Yeong E

2009-07-01

86

NUMERICAL TECHNIQUES TO SOLVE CONDENSATIONAL AND DISSOLUTIONAL GROWTH EQUATIONS WHEN GROWTH IS COUPLED TO REVERSIBLE REACTIONS (R823186)  

EPA Science Inventory

Noniterative, unconditionally stable numerical techniques for solving condensational and dissolutional growth equations are given. Growth solutions are compared to Gear-code solutions for three cases when growth is coupled to reversible equilibrium chemistry. In all cases, ...

87

Condensation reactions of 3-oxo-2-arylhydrazonopropanals with active methylene reagents: formation of 2-hydroxy- and 2-amino-6-substituted-5-arylazonicotinates and pyrido[3,2-c]cinnolines via 6?-electrocyclization reactions.  

PubMed

3-Oxo-3-phenyl-2-(p-tolylhydrazono)propanal (1a) undergoes condensation with ethyl cyanoacetate in acetic acid in the presence of ammonium acetate to yield either 2-hydroxy-6-phenyl-5-p-tolylazonicotinic acid ethyl ester (6a) or 2-amino-6-phenyl-5-ptolyl-azonicotinic acid ethyl ester (8), depending on the reaction conditions. Similarly, other 3-oxo-3-aryl-2-arylhydrazonopropanals 1a,b condense with active methylene nitriles 2c,d to yield arylazonicotinates 6b,c. In contrast, 2-[(4-nitrophenyl)-hydrazono]-3-oxo-3-phenyl-propanal (1c) reacts with ethyl cyanoacetate to yield ethyl 6-(4-nitrophenyl)-2-oxo-2,6-dihydropyrido[3,2–c]cinnoline-3-carboxylate (11), via a novel 6?-electrocyclization pathway. Finally, 3-oxo-2-(phenylhydrazono)-3-p-tolylpropanal (1d) condenses with 2a-c to yield pyridazinones 13a-c. PMID:22728352

Al-Mousawi, Saleh M; El-Apasery, Morsy A

2012-01-01

88

Interstellar Silicate Analogs for Grain-surface Reaction Experiments: Gas-phase Condensation and Characterization of the Silicate Dust Grains  

NASA Astrophysics Data System (ADS)

Amorphous, astrophysically relevant silicates were prepared by laser ablation of siliceous targets and subsequent quenching of the evaporated atoms and clusters in a helium/oxygen gas atmosphere. The described gas-phase condensation method can be used to synthesize homogeneous and astrophysically relevant silicates with different compositions ranging from nonstoichiometric magnesium iron silicates to pyroxene- and olivine-type stoichiometry. Analytical tools have been used to characterize the morphology, composition, and spectral properties of the condensates. The nanometer-sized silicate condensates represent a new family of cosmic dust analogs that can generally be used for laboratory studies of cosmic processes related to condensation, processing, and destruction of cosmic dust in different astrophysical environments. The well-characterized silicates comprising amorphous Mg2SiO4 and Fe2SiO4, as well as the corresponding crystalline silicates forsterite and fayalite, produced by thermal annealing of the amorphous condensates, have been used as real grain surfaces for H2 formation experiments. A specifically developed ultra-high vacuum apparatus has been used for the investigation of molecule formation experiments. The results of these molecular formation experiments on differently structured Mg2SiO4 and Fe2SiO4 described in this paper will be the topic of the next paper of this series.

Sabri, T.; Gavilan, L.; Jäger, C.; Lemaire, J. L.; Vidali, G.; Mutschke, H.; Henning, T.

2014-01-01

89

Dehydration-driven topotaxy in subduction zones  

NASA Astrophysics Data System (ADS)

Mineral replacement reactions play a fundamental role in the chemistry and the strength of the lithosphere. When externally or internally derived fluids are present, interface-coupled dissolution-precipitation is the driving mechanism for such reactions [1]. One of the microstructural features of this process is a 3D arrangement of crystallographic axes across internal interfaces (topotaxy) between reactant and product phases. Dehydration reactions are a special case of mineral replacement reaction that generates a transient fluid-filled porosity. Among others, the dehydration serpentinite is of special relevance in subduction zones because of the amount of fluids involved (potentially up to 13 wt.%). Two topotatic relationships between olivine and antigorite (the serpentine mineral stable at high temperature and pressure) have been reported in partially hydrated mantle wedge xenoliths [2]. Therefore, if precursor antigorite serpentine has a strong crystallographic preferred orientation (CPO) its dehydration might result in prograde peridotite with a strong inherited CPO. However for predicting the importance of topotactic reactions for seismic anisotropy of subduction zones we also need to consider the crystallization orthopyroxene + chlorite in the prograde reaction and, more importantly, the fact that this dehydration reaction produces a transient porosity of ca. 20 % vol. that results in local fluctuations of strain during compaction and fluid migration. We address this issue by a microstructural comparison between the CPO developed in olivine, orthopyroxene and chlorite during high-pressure antigorite dehydration in piston cylinder experiments (at 750ºC and 20 kbar and 1000ºC and 30 kbar, 168 h) and that recorded in natural samples (Cerro del Almirez, Betic Cordillera, Spain). Experimentally developed CPOs are strong. Prograde minerals show a significant inheritance of the former antigorite foliation. Topotactic relations are dominated by (001)atg//(100)ol// (100)opx//(001)chl. The relation [010]atg// [001]ol //[001]opx can also be inferred but it is weaker. Similar topotactic relations are observed in the Cerro del Almirez samples, but the CPOs are weaker and more complex. The complexity arises from constant interfacial angles and systematic low-index interfacial contacts between orthopyroxene-olivine-chlorite (e.g. (001)chl // (100)opx). As a consequence the inheritance from the antigorite serpentinite is partially obliterated. Compaction-related microstructural features are also present including: (1) smooth bending of the former foliation and diffuse olivine veinlets perpendicular to it, (2) gradual crystallographic misorientation (up to 15º) of prismatic enstatite due to buckling, (3) localized orthoenstatite(Pbca)/low clinoenstatite (P21/c) inversion, and (4) brittle fracturing of prismatic enstatite wrapped by plastically deformed chlorite. These observations suggest that topotactic crystrallographic relations are dominant in undrained systems, but that the mechanisms allowing for compaction and fluid draining significantly affect the final texture in drained systems. Because the second case prevails in subduction zones, compaction mechanisms need to be better understood for modelling the development of CPOs after foliated protoliths in the slab and the mantle wedge. [1] Putnis, A., 2009. Reviews in Mineralogy and Geochemistry 70, 87-124. [2] Boudier, F., et al. 2010 J. Petrology 51, 495-512.

Padrón-Navarta, José Alberto; Tommasi, Andréa; Garrido, Carlos J.

2014-05-01

90

Direct synthesis of dimethyl ether from carbon-monoxide-rich synthesis gas: Influence of dehydration catalysts and operating conditions  

Microsoft Academic Search

Various dehydration catalysts were studied in the synthesis of dimethyl ether (DME) directly from carbon-monoxide-rich synthesis gas under a series of different reaction conditions. The investigated catalyst systems consisted of combinations of a methanol catalyst (CuO\\/ZnO system) with catalysts for methanol dehydration based on ?-Al2O3 or zeolites and ?-Al2O3 was identified as the most favorable dehydration catalyst. Various reaction parameters

Miriam Stiefel; Ruaa Ahmad; Ulrich Arnold; Manfred Döring

2011-01-01

91

Carbohydrate Dehydration Demonstrations.  

ERIC Educational Resources Information Center

Discusses the impact of various factors on the "charring reaction" of a carbohydrate with concentrated sulfuric acid including the type of sugar, the degree of fineness of the sugar crystals, and the amount of water added. (JRH)

Dolson, David A.; And Others

1995-01-01

92

Textbook Forum: Equilibrium Constants of Chemical Reactions Involving Condensed Phases: Pressure Dependence and Choice of Standard State.  

ERIC Educational Resources Information Center

Problems of equilibria in condensed phases (particularly those involving solutes in dilute solutions) are encountered by students in their laboratory work; the thermodynamics of these equilibria is neglected in many textbooks. Therefore, several aspects of this topic are explored, focusing on pressure dependence and choice of standard state. (JN)

Perlmutter-Hayman, Berta

1984-01-01

93

Dehydrating slabs - mechanisms, flow structures, and rates  

NASA Astrophysics Data System (ADS)

In the Tianshan mountains (China) it is possible to study initial eclogitisation of blueschists (i.e. slab dehydration) and the associated fluid flow regime in well-exposed fragments of an oceanic subduction zone. Field evidence shows that the preferential flow field of released slab fluids is highly channelized and that these fluids tend to react with their wall rocks, thereby serving as agents for the mobilisation and transport of trace elements. In some cases, we observed well-developed reaction selvages formed along several-meter long exposed veins. Within these selvages, the degree of eclogitisation -and thus dehydration- increases towards the vein. The petrological and structural observations, however, suggest that an external, slab-derived fluid formed these veins and selvages. The main driving forces behind mineral reactions are variations in composition, temperature, and pressure. We suggest that the observed change of compositions within these selvages is a function of their formation. Temperature variations within a meter scale are negligible in non-magmatic systems, thus leaving pressure as the only variable to change. The observed dehydration selvages and related chemical changes can be explained by adapting the concept of porosity waves. Such a porosity wave has an over-pressured fluid head that produces the pathway through the rock followed by an under-pressured tail, causing a zone of a certain thickness around the pathway to be drained. Modelling of diffusive fluid-mediated transport of Li-concentration and isotopes show that the rates of fluid release are similar to convergence rates and do match those found for melt extraction at mid ocean ridges.

John, Timm; Podladchikov, Yuri; Klemd, Reiner; Magna, Tomas

2010-05-01

94

Dehydrated fluid and seismic deformation in deep subduction zone  

NASA Astrophysics Data System (ADS)

It has been considered that there is a correlation between the double seismic zone and metamorphic dehydration reaction in deep slab. The location of the upper limits of the upper seismic plane correspond to metamorphic facies boundary where H2O contents change in subducting crust; numerous earthquakes from 60 to 110 km depths in the lawsonite-blueschist facies, many earthquakes in the lower crust of the slab from 110 to 150 km depths in the lawsonite-amphibole eclogite facies and few earthquakes in the lawsonite eclogite facies. There is still minor amount of H2O present in the lawsonite eclogite facies. The dehydrated fluid is not the only trigger to cause slab earthquake. Recent petrological researches have revealed that both blueschist and lawsonite eclogite are stable in the same pressure and temperature condition because chemical variation including water content creates both lawsonite-amphibole eclogite and lawsonite eclogite in different portion of subducted crust. It would cause stress localization and hydro-fracturing in the slab in the shallower part (depths ranging from 60 to 110 km) and lawsonite amphibole eclogite in the lower crust in the deeper part (from 110 to 150 km depth) in the upper seismic plane. The lower plane of the double seismic zone, is considered to be related to dehydration reaction in the slab. Metamorphic olivine has been described in vein from serpentinite mylonite. The vein was created by dehydration reaction to decompose antigorite under shear deformation. In the cold slab beneath Tohoku arc, the reaction has a negative slope in P-T space and forms olivine+orthopyroxene+fluid. In the warm slab beneath SW Japan, the reaction has a positive slope in P-T space and forms olivine+talc+fluid. The above these dehydration reactions are well-described in the serpentinite from high P/T metamorphic belt from Spain, and Italy, respectively.

Okamoto, K.

2013-12-01

95

Organocatalytic atroposelective aldol condensation: synthesis of axially chiral biaryls by arene formation.  

PubMed

Axially chiral compounds are of significant importance in modern synthetic chemistry and particularly valuable in drug discovery and development. Nonetheless, current approaches for the preparation of pure atropisomers often prove tedious. We demonstrate here a synthetic method that efficiently transfers the stereochemical information of a secondary amine organocatalyst into the axial chirality of tri-ortho-substituted biaryls. An aromatic ring is formed during the dehydration step of the described aldol condensation cascade, leading to highly enantioenriched binaphthyl derivatives. The fundamental course of the reaction is related to the biosynthesis of aromatic polyketides. PMID:24757165

Link, Achim; Sparr, Christof

2014-05-19

96

Chemistry of the Borax/Glycol Condensate.  

National Technical Information Service (NTIS)

A review of some previous work on borate condensation reactions is given and experimental investigations are reported. The borax-glycol reaction is interpreted as involving a nearly complete degree of condensation, forming a mixture of acidic and basic bo...

G. H. Myers

1967-01-01

97

Dehydration and Oxidation of Cellulose Hydrolysis Products in Acidic Solution  

Microsoft Academic Search

The conversion of cellulose in homogenous solution to hydrolysis, dehydration,and oxidation products was investigated. A reaction sequence involving acetylation and degradation by aqueous acids led to humic acid, hydroxymethylfurfural, and levulinic acid as the isolated end-products. The influence of various reaction parameters upon the yields was studied.In the presence of ferric chloride some furfural was formed in addition to the

Klaus Garves

1981-01-01

98

Human Brain Has Coping Mechanism for Dehydration  

MedlinePLUS

... sharing features on this page, please enable JavaScript. Human Brain Has Coping Mechanism for Dehydration The mind ... Dehydration FRIDAY, July 25, 2014 (HealthDay News) -- The human brain can preserve oxygen to protect itself from ...

99

Zinc Oxide Nanoparticles Catalyzed Condensation Reaction of Isocoumarins and 1,7-Heptadiamine in the Formation of Bis-Isoquinolinones  

PubMed Central

The diversified bis-isoquinolinones were obtained in two steps, utilizing homophthalic acid and various acid chlorides providing 3-substituted isocoumarins in the first step which on further condensation with 1,7-heptadiamine involving C–N bond formation from the lactone in the presence of 10?mol% zinc oxide nanoparticles (ZnO NPs) (<150?nm) afforded the desired bis-isoquinolinones in high yield and purity. The synthesized compounds were then characterized using FTIR, 1H NMR, 13C NMR, and HRMS techniques.

Krishnakumar, Varadhan; Mohan Kumar, Kesarla; Mandal, Badal Kumar; Khan, Fazlur-Rahman Nawaz

2012-01-01

100

Dehydration and the dying patient  

Microsoft Academic Search

This study investigated the relationship between symptoms and dehydration in 82 subjects with malignant disease. Assessment of respiratory tract secretions, thirst, and dry mouth were made during the dying phase, and serum biochemistry was analyzed. Follow-up data were also collected when the patient died. The median time from entry into the study until death was 2 days. All subjects died

John E. Ellershaw; Jane M. Sutcliffe; Cicely M. Saunders

1995-01-01

101

Dehydrated Soups for USAF Aircraft.  

National Technical Information Service (NTIS)

Laboratory tests were conducted on dehydrated soups for the development of soups for use aboard aircraft operating above 15,240 meters (50,000 feet). These tests involved storage studies on seven different commercially available soups after repacking in f...

H. Gorfien A. R. Rahman E. M. Powers D. E. Westcott

1974-01-01

102

Kinetics and transport effects in the dehydration of crystalline potassium carbonate hydrate  

Microsoft Academic Search

The reaction kinetics and physical transport processes governing the thermal dehydration of solid KâCOâ.3\\/2HâO particles were investigated. Isothermal reaction rate data were gathered using a thermogravimetric balance in which narrowly-sized KâCOâ.3\\/2HâO crystals were dehydrated under a water vapor atmosphere at different pressures and temperatures. The magnitudes of the heat and mass transfer resistances external to and within the solid product

M. A. Stanish; D. D. Perlmutter

1983-01-01

103

A reexamination of Biginelli-like multicomponent condensation reaction: one-pot regioselective synthesis of spiro heterobicyclic rings.  

PubMed

A pseudo four-component reaction is described, leading to the efficient regioselective synthesis of sigma symmetric spiro heterobicyclic rings using aldehydes and urea in the presence of cyclic beta-diester or beta-diamides such as Meldrum's acid or barbituric acid derivatives. The reaction needs no added catalyst and proceeds solvent-free conditions at 80 degrees C. PMID:15209166

Shaabani, Ahmad; Bazgir, Ayoob; Bijanzadeh, Hamid Reza

2004-01-01

104

The Market for Dehydrated Vegetables in the United Kingdom.  

National Technical Information Service (NTIS)

Contents: Uses of dehydrated vegetables; The main outlets for dehydrated vegetables; The demand for dehydrated vegetables in the United Kingdom; The pattern of trade; Suppliers of dehydrated vegetables; Tariffs; Prices; Quality; Packing; Prospects; Prospe...

J. D. Winter

1968-01-01

105

Distortions in the photocycle of bacteriorhodopsin at moderate dehydration.  

PubMed Central

The photoreaction of bacteriorhodopsin was studied in moderately dehydrated films (relative humidities between 100 and 65%). Time-resolved difference spectra from a gated optical multichannel analyzer, between 100 ns and 100 ms after photoexcitation, were decomposed into sums of difference spectra of the intermediates K, L, M, N, and O, and the kinetics obtained were fitted to various alternative schemes. The data confirm the model of a single reaction sequence with reversible reactions we proposed recently for purple membrane suspensions (Váró, G., and J. K. Lanyi. Biochemistry. 1990. 29:2241-2250) but including reversibility also for the reaction K in equilibrium with L in addition to L in equilibrium with M, M in equilibrium with N, and N in equilibrium with O. With increasing dehydration the kinetics were increasingly dominated by the reverse reactions. As before, fitting the data required the existence of two M species in series: L in equilibrium with M1 in equilibrium with M2 in equilibrium with N. The M1 in equilibrium with M2 reaction was greatly slowed at lower humidities. This step might be the switch for the unidirectional transfer of protons. With increasing dehydration recovery of BR occurred less and less via the N intermediate and increasingly via direct shunts from the two M species. As indicated earlier by electrical measurements with similarly dried bacteriorhodopsin films (Váró, G., and L. Keszthelyi, 1983. Biophys. J. 43:47-51). The latter are pathways not necessarily associated with net proton translocation.

Varo, G; Lanyi, J K

1991-01-01

106

Distortions in the photocycle of bacteriorhodopsin at moderate dehydration  

SciTech Connect

The photoreaction of bacteriorhodopsin was studied in moderately dehydrated films (relative humidities between 100 and 65%). Time-resolved difference spectra from a gated optical multichannel analyzer, between 100 ns and 100 ms after photoexcitation, were decomposed into sums of difference spectra of the intermediates K, L, M, N, and O, and the kinetics obtained were fitted to various alternative schemes. The data confirm the model of a single reaction sequence with reversible reactions we proposed recently for purple membrane suspensions but including reversibility also for the reaction K in equilibrium with L in addition to L in equilibrium with M, M in equilibrium with N, and N in equilibrium with O. With increasing dehydration the kinetics were increasingly dominated by the reverse reactions. As before, fitting the data required the existence of two M species in series: L in equilibrium with M1 in equilibrium with M2 in equilibrium with N. The M1 in equilibrium with M2 reaction was greatly slowed at lower humidities. This step might be the switch for the unidirectional transfer of protons. With increasing dehydration recovery of BR occurred less and less via the N intermediate and increasingly via direct shunts from the two M species. As indicated earlier by electrical measurements with similarly dried bacteriorhodopsin films. The latter are pathways not necessarily associated with net proton translocation.

Varo, G.; Lanyi, J.K. (Univ. of California, Irvine (USA))

1991-02-01

107

Use of hypodermoclysis to manage dehydration.  

PubMed

Older people, particularly those who are frail, are vulnerable to dehydration. Management of dehydration in older people can be more complex than in younger adults because of the physical effects of ageing. As the population ages, nurses will increasingly care for older patients in every setting. This article provides an overview of the physiological changes that affect the ability of older people to maintain a normal fluid balance. Risk factors for dehydration are reviewed and strategies for the prevention, detection and management of dehydration are discussed. The article focuses on subcutaneous fluid replacement for the management of dehydration in older adults. PMID:21736101

Scales, Katie

2011-06-01

108

The effect of condensed water on the poorly-soluble volatile organic compounds oxidation: kinetics and mechanism of an aqueous phase isoprene reaction with hydroxyl radical and ozone  

NASA Astrophysics Data System (ADS)

Increasing attention has been paid to the aqueous phase chemistry of organic compounds in the atmosphere. Noticeably, the aqueous phase reaction of the poorly-soluble volatile organic compounds (PSVOCs) has not been much concerned in the atmospheric chemical processes. A number of studies on the adsorption of poorly-soluble gases at air-liquid interface suggested a much higher interface concentration compared to the gas phase concentration. Considering the large global abundance of the poorly-soluble but highly reactive VOCs and the large collective surface of liquid droplets in the atmosphere, it may be important to study the chemical processes of VOCs on the surface of droplets. However, currently little information is available regarding the kinetics and mechanism of the aqueous phase chemical processes of PSVOCs. Here, we focused on the aqueous hydroxyl radical/ozone initiated oxidation of isoprene. For example, we determined the rate constant for the aqueous reaction of isoprene with hydroxyl radical as 1.2 {±}1010 M-1s-1 at 283 K, and observed that the ratio of the yields of MVK to MACR in the aqueous phase isoprene oxidation was approximately double that observed for the corresponding gas phase reaction. On the basis of a box model simulation, we hypothesized that this might be explained by a water-induced enhancement in the self-reaction of a hydroxy isoprene peroxyl radical (HOCH2C(CH3)(O2)CH=CH2) produced in the aqueous reaction. For the aqueous phase ozone oxidation, interestingly, two unknown peroxides were not observed under aqueous conditions, whereas they were detected in the gas phase reaction under dry and humid conditions; the combined yield of MAC and MVK, as well as the total yield of peroxides observed in the aqueous isoprene ozonolysis is much higher than that in the corresponding gas phase reaction under dry and humid conditions. We suggest that these high yields of carbonyls and peroxides are related to the condensed water's greater capability of stabilizing the energy rich Criegee radicals compared with the water vapor. Finally, we evaluated the relative importance of aqueous surface hydroxyl radical/ozone oxidation of isoprene. Our study suggests that air-liquid interface reaction may be an important pathway for atmospheric chemical evolution of isoprene, and the condensed water would considerably affect the kinetics and mechanisms of the reactions. However, further studies are needed for better understanding the relative importance of aqueous chemical processes of isoprene, as well as other PSVOCs, in particular, with an special emphasis on the key parameters, such as the oxidant concentration on the droplet surface, the residence time of PSVOCs on the surface of droplets, and the interface reaction rate constant of the PSVOCs.

Huang, D.; zhang, X.; Wang, H.; Chen, Z.; Zhao, Y.; Shen, X.

2011-12-01

109

DFT study of the mechanism of the reaction of aminoguanidine with methylglyoxal.  

PubMed

We have studied the mechanism of the reaction between aminoguanidine (AG) and methylglyoxal (MG) by carrying out Dmol3/DFT calculations, obtaining intermediates, transition-state structures, and free-energy profiles for all of the elementary steps of the reaction. Designed models included explicit water solvent, which forms hydrogen-bond networks around the reactants and intermediate molecules, facilitating intramolecular proton transfer in some steps of the reaction mechanism. The reaction take place in four steps, namely: (1) formation of a guanylhydrazone-acetylcarbinol adduct by condensation of AG and MG; (2) dehydration of the adduct; (3) formation of an 1,2,4-triazine derivative by ring closure; and (4) dehydration with the formation of 5-methyl 3-amino-1,2,4-triazine as the final product. From a microkinetic point of view, the first dehydration step was found to be the rate-determining step for the reaction, with the reaction having an apparent activation energy of 12.65 kcal mol?¹. Additionally, some analogous structures of intermediates and transition states for the reaction between AG and 2,3-dicarbonyl-phosphatidylethanolamine, a possible intermediate in Amadori-glycated phosphatidylethanolamine (Amadori-PE) autooxidation, were obtained to evaluate the reaction above a phosphatidylethanolamine (PE) surface. Our results are in agreement with experimental results obtaining by other authors, showing that AG is efficient at trapping dicarbonyl compounds such as methylglyoxal, and by extension these compounds joined to biomolecules such as PE in environments such as surfaces and their aqueous surroundings. PMID:24705776

Solís-Calero, Christian; Ortega-Castro, Joaquín; Hernández-Laguna, Alfonso; Muñoz, Francisco

2014-04-01

110

CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: Nanoporous AlN particle production from a solid-state metathesis reaction  

NASA Astrophysics Data System (ADS)

This paper reports that nanoporous AlN particles are synthesized from solid-state metathesis reactions using AlCl3 and Mg3N2 as reactants. The samples are characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction, high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible (UV-vis) absorption spectroscopy and Raman spectroscopy. The results show that samples with walls 10 nm in thickness and pores between 10 nm and 100 nm in diameter were produced successfully from these reactions, and their band gap and vibration modes agree with those of AlN bulk crystal.

Yan, Guo-Jun; Chen, Guang-De; Wu, Ye-Long

2009-07-01

111

Cyclopentyl methyl ether: a green co-solvent for the selective dehydration of lignocellulosic pentoses to furfural.  

PubMed

The effects of cyclopentyl methyl ether (CPME) addition during the aqueous xylose dehydration reaction to furfural are reported here. These investigations were conducted by using pure xylose and Cynara cardunculus (cardoon) lignocellulose as sugar source and H(2)SO(4) as catalyst. The research was also applied to aqueous solutions containing NaCl, since it has been previously demonstrated that NaCl incorporation to these reaction mixtures remarkably increases the furfural formation rate. It has been found that CPME incorporation inhibits the formation of undesired products (resins, condensation products and humins). Thus, cardoon lignocellulosic pentoses were selectively transformed into furfural (near 100%) at the following reaction conditions: 1 wt.% H(2)SO(4), 4 wt.% biomass referred to aqueous solution, 30 min reaction, 443 K, CPME/aqueous phase mass ratio equals to 2.33, and NaCl/aqueous solution mass ratio of 0.4. In contrast, no effect was observed for cellulosic glucose transformation into hydroxymethylfurfural and levulinic acid at identical reaction conditions. PMID:23128237

Campos Molina, M J; Mariscal, R; Ojeda, M; López Granados, M

2012-12-01

112

Dehydration melting of tonalites. Part I. Beginning of melting  

NASA Astrophysics Data System (ADS)

The beginning of dehydration melting in the tonalite system (biotite-plagioclase-quartz) is investigated in the pressure range of 2 12 kbar. A special method consisting of surrounding a crystal of natural plagioclase (An45) with a biotite-quartz mixture, and observing reactions at the plagioclase margin was employed for precise determination of the solidus for dehydration melting. The beginning of dehydration melting was worked out at 5 kbar for a range of compositions of biotite varying from iron-free phlogopite to iron-rich Ann70, with and without titanium, fluorine and extra aluminium in the biotite. The dehydration melting of phlogopite + plagioclase (An45) + quartz begins between 750 and 770°C at pressures of 2 and 5 kbar, at approximately 740°C at 8 kbar and between 700 and 730°C at 10 kbar. At 12 kbar, the first melts are observed at temperatures as low as 700°C. The data indicate an almost vertical dehydration melting solidus curve at low pressures which bends backward to lower temperatures at higher pressures (> 5 kbar). The new phases observed at pressures ? 10 kbar are melt + enstatite + clinopyroxene + potassium feldspar ± amphibole. In addition to these, zoisite was also observed at 12 kbar. With increasing temperature, phlogopite becomes enriched in aluminium and deficient in potassium. Substitution of octahedral magnesium by aluminium and titanium in the phlogopite, as well as substitution of hydroxyl by fluorine, have little effect on the beginning of dehydration melting temperatures in this system. The dehydration melting of biotite (Ann50) + plagioclase (An45) + quartz begins 50°C below that of phlogopite bearing starting composition. Solid reaction products are orthopyroxene + clinopyroxene + potassium feldspar ± amphibole. Epidote was also observed above 8 kbar, and garnet at 12 kbar (750°C). The experiments on the iron-bearing system performed at ? 5 kbar were buffered with NiNiO. The f O 2 in high pressure runs lies close to CoCoO. With the substitution of octahedral magnesium and iron by aluminium and titanium, and replacement of hydroxyl by fluorine in biotite, the beginning of dehydration melting temperatures in this system increase up to 780°C at 5 kbar, which is 70°C above the beginning of dehydration melting of the assemblage containing biotite (Ann50) of ideal composition. The dehydration melting at 5 kbar in the more iron-rich Ann70-bearing starting composition begins at 730°C, and in the Ann25-bearing assemblage at 710°C. This indicates that quartz-biotite-plagioclase assemblages with intermediate compositions of biotite (Ann25 and Ann50) melt at lower temperatures as compared to those containing Fe-richer or Mg-richer biotites. This study shows that the dehydration melting of tonalites may begin at considerably lower temperatures than previously thought, especially at high pressures (>5 kbar).

Singh, J.; Johannes, Wilhelm

1996-09-01

113

Dissolution processes, hydrolysis and condensation reactions during geopolymer synthesis: Part I—Low Si\\/Al ratio systems  

Microsoft Academic Search

Initial geopolymeric reaction processes governing dissolution of solid aluminosilicate particles in alkali solutions have\\u000a been investigated using conventional experimental techniques, and the data analysed by speciation predictions of the partial\\u000a charge model (PCM). For metakaolin powders activated with 5.0 M NaOH, solid-state nuclear magnetic resonance (NMR) spectra\\u000a disclose the existence of monomeric [Al(OH)4]? species after two hours of dissolution, consistent with

L. Weng; K. Sagoe-Crentsil

2007-01-01

114

Accumulation of acid sites on natural clinoptilolite under recurring dehydration  

NASA Astrophysics Data System (ADS)

A new 1H NMR approach was applied to study the influence of recurring dehydration on the acidity of a natural Ca-rich zeolite clinoptilolite. It has been found that thermal cycling progressively increases the rate of the proton exchange between water molecules in the rehydrated state. The observed effect is interpreted as a result of the irreversible accumulation of specific structural defects represented by Brønsted acid sites: each dehydration at 720 K adds to the acid sites in an amount of the order of 10-3 per unit cell. The number of these defects, detected by NMR in hydrated mineral, is in reasonable agreement with their amount estimated for the dehydrated state with an IR-spectroscopy CO-probe method. A comparison of the results obtained for two distinct zeolite samples shows that the Ca2+ ions are of first importance in the dehydration-induced formation of the active acid sites. The barrier for the proton-transfer reaction between the acid sites and H2O molecules in hydrated clinoptilolite is found to be 46 kJ mol-1, which is not too different from the value of 54 kJ mol-1 reported recently for natural chabazite.

Moroz, N. K.; Afanassyev, I. S.; Paukshtis, E. A.; Valueva, G. P.

115

The physiological effects of dehydration caused by sweat loss. [athletes  

NASA Technical Reports Server (NTRS)

The mechanisms of fluid loss in the human body while sweating due to physical exercise are discussed. Trained and untrained persons were examined and compared. Since sweat is hypotonous, a disruption in the hydrosalinic balance occurs; the consequences of this finding, also pertaining to the fluid and electrolytic substitution, are presented. Further explanations on the problem of dehydration refer to reactions of individual organ systems, to alterations in bodily capabilities as well as to questions relating to sex and age.

Israel, S.

1981-01-01

116

Clinical signs of dehydration in children.  

PubMed

102 children with acute gastroenteritis were thought by the admitting junior doctors to be 5% or more dehydrated. As judged by subsequent weight recovery in hospital, the main indicators of mild to moderate dehydration were decreased peripheral perfusion, deep breathing, decreased skin turgor, high urea, low pH, and a large base deficit; a history of increased thirst was just short of statistical significance. Dehydration was not indicated by a history of oliguria, by the presence of restlessness or lethargy, sunken eyes, dry mouth, or a sunken fontanelle or by the absence of tears. Clinical signs of dehydration became apparent at 3-4% rather than 5% dehydration. The degree of dehydration was overestimated by a mean of 3.2%; this caused unnecessary hospital admissions and overtreatment with intravenous fluid. PMID:2570294

Mackenzie, A; Barnes, G; Shann, F

1989-09-01

117

Iron Oxide-Supported Copper Oxide Nanoparticles (Nanocat-Fe-CuO): Magnetically Recyclable Catalysts for the Synthesis of Pyrazole Derivatives, 4-Methoxyaniline, and Ullmann-type Condensation Reactions  

EPA Science Inventory

An efficient and benign protocol is reported for the synthesis of 4-methoxyaniline, medicinally important pyrazole derivatives, and Ullmann-type condensation reaction using magnetically separable and reusable magnetite-supported copper (nanocat-Fe-CuO) nanoparticles under mild co...

118

Dehydration  

MedlinePLUS

... too much, for example, from exercising in hot weather Fever Vomiting or diarrhea Urinating too much (uncontrolled ... when you are well. Drink more when the weather is hot or you are exercising. If anyone ...

119

The effect of clay dehydration on land subsidence in the Yun-Lin coastal area, Taiwan  

Microsoft Academic Search

The smectite dehydration theory developed by Ransom and Helgeson was applied for simulation of land subsidence in the Yun-Lin\\u000a coastal area, Taiwan. The volumetric reduction of smectite clay at equilibrium state was computed by assuming that the dehydration\\u000a of interlayer water in smectite clay can be described with a regular solid solution reaction. By using the in situ stratigraphic\\u000a data

C.-W. Liu; W.-S. Lin; C. Shang; S.-H. Liu

2001-01-01

120

Orifluoroacetylation and dehydration of 20-hydroxyecdysone acetonides. Synthesis of stachisterone B  

Microsoft Academic Search

Orifluoroacetylation of the 25(OH)-group with subsequent dehydration of the 14(OH)-group takes place in the reaction of 20-hydroxyecdysone 20,22-acetonide and 2,3:20,22-diacetonide with trifluoroacetic anhydride in the presence of pyridine. Dehydration of the 14(OH)-group gives rise to stachisterone B derivatives, which are hydrolyzed to give the phytoecdysteroid stachisterone B.

V. N. Odinokov; I. V. Galyautdinov; D. V. Nedopekin; L. M. Khalilov

2003-01-01

121

A dehydration mechanism for the stratosphere  

NASA Technical Reports Server (NTRS)

Although mean circulations are generally credited with dehydration of the earth's stratosphere, convective instability in the tropics converts mean circulations to small residuals of local convective circulations. The effects of large cumulonimbus which penetrate the stratosphere and form huge anvils in the lower stratosphere are discussed with respect to hydration and dehydration of the stratosphere. Radiative heating at anvil base combined with cooling at anvil top drives a dehydration engine considered essential to explain the dry stratosphere. Seasonal and longitudinal variations in dehydration potentials are examined with maximum potential attributed to Micronesian area during winter and early spring.

Danielsen, E. F.

1982-01-01

122

Understanding clinical dehydration and its treatment.  

PubMed

Dehydration in clinical practice, as opposed to a physiological definition, refers to the loss of body water, with or without salt, at a rate greater than the body can replace it. We argue that the clinical definition for dehydration, ie, loss of total body water, addresses the medical needs of the patient most effectively. There are 2 types of dehydration, namely water loss dehydration (hyperosmolar, due either to increased sodium or glucose) and salt and water loss dehydration (hyponatremia). The diagnosis requires an appraisal of the patient and laboratory testing, clinical assessment, and knowledge of the patient's history. Long-term care facilities are reluctant to have practitioners make a diagnosis, in part because dehydration is a sentinel event thought to reflect poor care. Facilities should have an interdisciplinary educational focus on the prevention of dehydration in view of the poor outcomes associated with its development. We also argue that dehydration is rarely due to neglect from formal or informal caregivers, but rather results from a combination of physiological and disease processes. With the availability of recombinant hyaluronidase, subcutaneous infusion of fluids (hypodermoclysis) provides a better opportunity to treat mild to moderate dehydration in the nursing home and at home. PMID:18519109

Thomas, David R; Cote, Todd R; Lawhorne, Larry; Levenson, Steven A; Rubenstein, Laurence Z; Smith, David A; Stefanacci, Richard G; Tangalos, Eric G; Morley, John E

2008-06-01

123

Organobase-catalyzed three-component reactions for the synthesis of 4H-2-aminopyrans, condensed pyrans and polysubstituted benzenes.  

PubMed

Novel routes for the preparation of 2-amino-4H-pyran-3-carbonitrile 9, amino-arylbenzoic acid ester derivatives 13a,b, 2-aminotetrahydro-4H-chromene-3-carbonitrile 18, 3-amino-4-cyanotetrahydronaphthalene-2-carboxylic acid ester 26 and 4-amino-3,5-dicyanophthalic acid ester derivatives 37a-c were developed. The synthetic methods utilize one-pot reactions of acetylene carboxylic acid esters, ?,?-unsaturated nitriles and/or active methylenenitriles in the presence of L-proline or DABCO. Plausible mechanisms are suggested for the formation of the products. Finally, these compounds were used for the efficient synthesis of 6-amino-5-cyanonicotinic acid ester derivatives 31a,b, ethyl 4-amino-5H-pyrano[2,3-d]pyrimidine-6-carboxylates 33a,b, 4-amino-6H-pyrrolo[3,4-g]quinazoline-9-carbonitrile 39, and 1,7-diamino-6-(N'-hydroxycarbamimidoyl)-3-oxo-5-phenyl-3H-isoindole-4-carboxylate (40). PMID:24454567

Moustafa, Moustafa Sherief; Al-Mousawi, Saleh Mohammed; Selim, Maghraby Ali; Mosallam, Ahmed Mohamed; Elnagdi, Mohamed Hilmy

2014-01-14

124

Amine catalyzed condensation of tetraethylorthosilicate  

NASA Technical Reports Server (NTRS)

The catalysis of the condensation of hydrolyzed metal alkoxides by amines has been mentioned in the literature, but there has been no systematic study of their influence on the rate of the condensation reaction of the alkoxide and the microstructure of the resultant gel.

Jones, S.

2001-01-01

125

Non-volcanic tremor and discontinuous slab dehydration  

NASA Astrophysics Data System (ADS)

Non-volcanic tremor is a recently discovered fault slip style occurring with remarkable regularity in space near the down-dip end of the locked zone on several subduction thrust interfaces. The physical mechanisms and the controls on the location of tremor have not yet been determined. We calculate the stable mineral assemblages and their water content in the subducting slab, and find that slab dehydration is not continuous, but rather restricted to a few reactions localised in pressure-temperature space. Along geothermal gradients applicable to Shikoku and Cascadia - where tremor has been relatively easy to detect - tremor locations correlate with discontinuous and localised voluminous water release from the breakdown of lawsonite and chlorite + glaucophane respectively. The shape of the pressure-temperature path for subducting slabs prevents fluid release at depths above and below where these dehydration reactions occur. We conclude that abundant tremor activity requires metamorphic conditions where localised dehydration occurs during subduction, and this may explain why tremor appears more abundant in some subduction zones than others.

Fagereng, Åke; Diener, Johann F. A.

2011-08-01

126

Spectral effects of dehydration on phyllosilicates  

NASA Technical Reports Server (NTRS)

Six phyllosilicates were progressively dehydrated under controlled conditions in an effort to study the spectral effects of their dehydration. The spectra obtained at each level of hydration provide information that may be used in future spectroscopic observations of the planets, as well as a data set which compliments the existing body of terrestrial soil knowledge.

Bruckenthal, E. A.; Singer, R. B.

1987-01-01

127

Osmotic Dehydration of Tropical Fruits and Vegetables  

Microsoft Academic Search

Because of the microstructural complexity of plant tissue, osmotic dehydration cannot simply be explained as a pure osmotic process in which cell membranes act as a semipermeable barrier allowing water to pass through. Instead, osmotic dehydration is considered a process in which many simultaneous mechanisms, acting at different levels, are responsible for mass transport. Different compositional and structural profiles are

K. O. Falade; J. C. Igbeka

2007-01-01

128

An Efficient Method for Site-specific 18F-Labeling of Biomolecules Using the Rapid Condensation Reaction between 2-Cyanobenzothiazole and Cysteine  

PubMed Central

An efficient method based on a rapid condensation reaction between 2–cyanobenzothiazole (CBT) and cysteine has been developed for 18F–labeling of N–terminal cysteine–bearing peptides and proteins. An 18F–labeled dimeric cRGD ([18F]CBTRGD2) has been synthesized with an excellent radiochemical yield (92% based on radio–HPLC conversion, 80% decay–corrected and isolated yield) and radiochemical purity (>99%) under mild conditions using 18F–CBT, and shown good in vivo tumor targeting efficiency for PET imaging. The labeling strategy was also applied to the site–specific 18F–labeling of a protein, Renilla lucifierase (RLuc8) with a cysteine residue at its N–terminus. The protein labeling was achieved with 12% of decay–corrected radiochemical yield and more than 99% radiochemical purity. This strategy should provide a general approach for an efficient and site–specific 18F–labeling of various peptides and proteins for in vivo molecular imaging applications.

Jeon, Jongho; Shen, Bin; Xiong, Liqin; Miao, Zheng; Lee, Kyung Hyun; Rao, Jianghong; Chin, Frederick T.

2012-01-01

129

Condensation Polymers with Controlled Structure.  

National Technical Information Service (NTIS)

The polymerization procedure that had been used in the first year of funding was improved dramatically during the current period. A homogenous condensation system for the Modified Schotten-Baumann reaction at ambient temperatures has been found (NMP:THF =...

U. W. Suter W. R. Meyer F. T. Gentile

1986-01-01

130

Dehydration and Performance on Clinical Concussion Measures in Collegiate Wrestlers  

PubMed Central

Context: The effects of dehydration induced by wrestling-related weight-cutting tactics on clinical concussion outcomes, such as neurocognitive function, balance performance, and symptoms, have not been adequately studied. Objective: To evaluate the effects of dehydration on the outcome of clinical concussion measures in National Collegiate Athletic Association Division I collegiate wrestlers. Design: Repeated-measures design. Setting: Clinical research laboratory. Patients or Other Participants: Thirty-two Division I healthy collegiate male wrestlers (age = 20.0 ± 1.4 years; height = 175.0 ± 7.5 cm; baseline mass = 79.2 ± 12.6 kg). Intervention(s): Participants completed preseason concussion baseline testing in early September. Weight and urine samples were also collected at this time. All participants reported to prewrestling practice and postwrestling practice for the same test battery and protocol in mid-October. They had begun practicing weight-cutting tactics a day before prepractice and postpractice testing. Differences between these measures permitted us to evaluate how dehydration and weight-cutting tactics affected concussion measures. Main Outcome Measures: Sport Concussion Assessment Tool 2 (SCAT2), Balance Error Scoring System, Graded Symptom Checklist, and Simple Reaction Time scores. The Simple Reaction Time was measured using the Automated Neuropsychological Assessment Metrics. Results: The SCAT2 measurements were lower at prepractice (P = .002) and postpractice (P < .001) when compared with baseline. The BESS error scores were higher at postpractice when compared with baseline (P = .015). The GSC severity scores were higher at prepractice (P = .011) and postpractice (P < .001) than at baseline and at postpractice when than at prepractice (P = .003). The number of Graded Symptom Checklist symptoms reported was also higher at prepractice (P = .036) and postpractice (P < .001) when compared with baseline, and at postpractice when compared with prepractice (P = .003). Conclusions: Our results suggest that it is important for wrestlers to be evaluated in a euhydrated state to ensure that dehydration is not influencing the outcome of the clinical measures.

Weber, Amanda Friedline; Mihalik, Jason P.; Register-Mihalik, Johna K.; Mays, Sally; Prentice, William E.; Guskiewicz, Kevin M.

2013-01-01

131

Artificially dehydrated lucerne for horses.  

PubMed

Artificially dehydrated lucerne produced in the United Kingdom has been shown to be a better source of nutrients for horses than grass hay. Horses eat more lucerne when it is pelleted, and the processing has little effect on its nutritive value. Lucerne does not appear to contain any antinutritional factors of significance to horses. Lucerne contains readily available calcium and protein and can thus be used as a cereal-balancer or to upgrade poor quality roughages. Because lucerne is a good source of digestible nutrients it has therapeutic applications, including the correction of electrolyte imbalances and hoof horn problems, and it can be used for intragastric nutrition and for feeding old horses. PMID:7846834

Cuddeford, D

1994-10-29

132

Intermediate-depth earthquake faulting by dehydration embrittlement with negative volume change  

NASA Astrophysics Data System (ADS)

Earthquakes are observed to occur in subduction zones to depths of approximately 680km, even though unassisted brittle failure is inhibited at depths greater than about 50km, owing to the high pressures and temperatures. It is thought that such earthquakes (particularly those at intermediate depths of 50-300km) may instead be triggered by embrittlement accompanying dehydration of hydrous minerals, principally serpentine. A problem with failure by serpentine dehydration is that the volume change accompanying dehydration becomes negative at pressures of 2-4GPa (60-120km depth), above which brittle fracture mechanics predicts that the instability should be quenched. Here we show that dehydration of antigorite serpentinite under stress results in faults delineated by ultrafine-grained solid reaction products formed during dehydration. This phenomenon was observed under all conditions tested (pressures of 1-6GPa temperatures of 650-820°C), independent of the sign of the volume change of reaction. Although this result contradicts expectations from fracture mechanics, it can be explained by separation of fluid from solid residue before and during faulting, a hypothesis supported by our observations. These observations confirm that dehydration embrittlement is a viable mechanism for nucleating earthquakes independent of depth, as long as there are hydrous minerals breaking down under a differential stress.

Jung, Haemyeong; Green, Harry W., II; Dobrzhinetskaya, Larissa F.

2004-04-01

133

Dehydration of xylose into furfural over micro-mesoporous sulfonic acid catalysts  

Microsoft Academic Search

Surfactant-templated micro-mesoporous silicas possessing sulfonic acid groups (SAGs) have been prepared, characterized, and tested as catalysts in the dehydration of d-xylose to furfural. All of the materials possessed catalytic activity. In general, selectivity to furfural was lower for a poorly ordered microporous hybrid material, prepared via the co-condensation of (3-mercaptopropyl)trimethoxysilane with bis(trimethoxysilylethyl)benzene, than for mesoporous MCM-41 silica anchored with SAGs

Ana S. Dias; Martyn Pillinger; Anabela A. Valente

2005-01-01

134

Water-loss dehydration and aging.  

PubMed

This review defines water-loss and salt-loss dehydration. For older people serum osmolality appears the most appropriate gold standard for diagnosis of water-loss dehydration, but clear signs of early dehydration have not been developed. In older adults, lower muscle mass, reduced kidney function, physical and cognitive disabilities, blunted thirst, and polypharmacy all increase dehydration risk. Cross-sectional studies suggest a water-loss dehydration prevalence of 20-30% in this population. Water-loss dehydration is associated with higher mortality, morbidity and disability in older people, but evidence is still needed that this relationship is causal. There are a variety of ways we may be able to help older people reduce their risk of dehydration by recognising that they are not drinking enough, and being helped to drink more. Strategies to increase fluid intake in residential care homes include identifying and overcoming individual and institutional barriers to drinking, such as being worried about not reaching the toilet in time, physical inability to make or to reach drinks, and reduced social drinking and drinking pleasure. Research needs are discussed, some of which will be addressed by the FP7-funded NU-AGE (New dietary strategies addressing the specific needs of elderly population for a healthy ageing in Europe) trial. PMID:24333321

Hooper, Lee; Bunn, Diane; Jimoh, Florence O; Fairweather-Tait, Susan J

2014-01-01

135

Condensation polyimides  

NASA Technical Reports Server (NTRS)

Polyimides belong to a class of polymers known as polyheterocyclics. Unlike most other high temperature polymers, polyimides can be prepared from a variety of inexpensive monomers by several synthetic routes. The glass transition and crystalline melt temperature, thermooxidative stability, toughness, dielectric constant, coefficient of thermal expansion, chemical stability, mechanical performance, etc. of polyimides can be controlled within certain boundaries. This versatility has permitted the development of various forms of polyimides. These include adhesives, composite matrices, coatings, films, moldings, fibers, foams and membranes. Polyimides are synthesized through both condensation (step-polymerization) and addition (chain growth polymerization) routes. The precursor materials used in addition polyimides or imide oligomers are prepared by condensation method. High molecular weight polyimide made via polycondensation or step-growth polymerization is studied. The various synthetic routes to condensation polyimides, structure/property relationships of condensation polyimides and composite properties of condensation polyimides are all studied. The focus is on the synthesis and chemical structure/property relationships of polyimides with particular emphasis on materials for composite application.

Hergenrother, P. M.

1989-01-01

136

Ultrasonic Dehydration for Liquid Dental Meals.  

National Technical Information Service (NTIS)

This report summarizes the work accomplished in the successful completion of Phase I of this SBIR Project. It includes: (1) Examination of several options for the use of ultrasonic energy in the dehydration process of liquid dental meals, (2) Identificati...

S. P. Babin J. F. Figuerea R. M. Rae S. Clarke

1994-01-01

137

Problem: Thirst, Drinking Behavior, and Involuntary Dehydration  

NASA Technical Reports Server (NTRS)

The phenomenon of involuntary dehydration, the delay in full restoration of a body water deficit by drinking, has been described extensively but relatively little is known about its physiological mechanism. It occurs primarily in humans when they are exposed to various stresses including exercise, environmental heat and cold, altitude, water immersion, dehydration, and perhaps microgravity, singly and in various combinations. The level of involuntary dehydration is approximately proportional to the degree of total stress imposed on the body. Involuntary dehydration appears to be controlled by more than one factor including social customs that influence what is consumed, the capacity and rate of fluid absorption from the gastrointestinal system, the level of cellular hydration involving the osmotic-vasopressin interaction with sensitive cells or structures in the central nervous system, and, to a lesser extent, hypovolemic-angiotensin II stimuli. Since humans drink when there is no apparent physiological stimulus, the psychological component should always be considered when investigating the total mechanisms for drinking.

Greenleaf, John E.

1992-01-01

138

Central atrial natriuretic peptide in dehydration.  

PubMed

To test the effect of dehydration on brain atrial natriuretic peptide (ANP) concentrations in areas important to salt appetite, water balance and cardiovascular regulation, we subjected rats to dehydration and rehydration and measured ANP concentration in 18 brain areas, as well as all relevant peripheral parameters. Water deprivation decreased body weight, blood pressure, urine volume, and plasma ANP, while it increased urine and plasma osmolality, angiotensin II, and vasopressin. ANP greatly increased in 17 and 18 brain areas (all cut cerebral cortex) by 24 h. Rehydration for 12 h corrected all changes evoked by dehydration, including elevated ANP levels in brain. We conclude that chronic dehydration results in increased ANP in brain areas important to salt appetite and water balance. These results support a role for ANP as a neuroregulatory substance that participates in salt and water balance. PMID:17451053

Bahner, Udo; Geiger, Helmut; Palkovits, Miklós; Lenkei, Zsolt; Luft, Friedrich C; Heidland, August

2007-03-30

139

Yb(OTf) 3 catalyzed condensation reaction of ?-naphthol and aldehyde in ionic liquids: a green synthesis of aryl-14 H-dibenzo[ a, j]xanthenes  

Microsoft Academic Search

A facile, efficient and green synthesis of aryl-14H-dibenzo[a,j]xanthenes has been developed by one-pot condensation of ?-naphthol and substituted benzaldehydes in the presence of ytterbium triflates in ionic liquids.

Weike Su; Dong Yang; Can Jin; Bo Zhang

2008-01-01

140

Dehydration processes using membranes with hydrophobic coating  

DOEpatents

Processes for removing water from organic compounds, especially polar compounds such as alcohols. The processes include a membrane-based dehydration step, using a membrane that has a dioxole-based polymer selective layer or the like and a hydrophilic selective layer, and can operate even when the stream to be treated has a high water content, such as 10 wt % or more. The processes are particularly useful for dehydrating ethanol.

Huang, Yu; Baker, Richard W; Aldajani, Tiem; Ly, Jennifer

2013-07-30

141

Observations of denitrification and dehydration in the winter polar stratospheres  

NASA Technical Reports Server (NTRS)

It is argued that denitrification of the Arctic stratosphere can be explained by the selective growth and sedimentation of aerosol particles rich in nitric acid. Because reactive nitrogen species moderate the destruction of ozone by chlorine-catalyzed reactions by sequestering chlorine in reservoir species such as ClONO2, the possibility of the removal of reactive nitrogen without dehydration should be allowed for in attempts to model ozone depletion in the Arctic. Indeed, denitrification along with elevated concentrations of reactive chlorine observed in 1989 indicate that the Arctic was chemically primed for ozone destruction without an extended period of temperatures below the frost point, as is characteristic of the Antarctic.

Fahey, D. W.; Kelly, K. K.; Kawa, S. R.; Tuck, A. F.; Loewenstein, M.

1990-01-01

142

Dehydration kinetics of howlite, ulexite, and tunellite using thermogravimetric data  

Microsoft Academic Search

In this study, some boron mineral samples (howlite, ulexite and tunellite) have been analysed by DTA and TG methods. The thermochemical reactions of these boron compounds have been studied. The dehydration kinetic parameters for howlite, ulexite and tunellite were activation energies: 65.0, 39.5 and 50.4kJmol?1; the pre-exponential factors: 50.8×105, 6.60×105, 32.4×105s?1 and rate constants: 70.1, 113.1 and 82.3s?1, respectively, at

Yunus Erdo?an; Ay?e Zeybek; Ay?e ?ahin; Ayhan Demirba?

1999-01-01

143

Crystal structures of phosphoketolase: thiamine diphosphate-dependent dehydration mechanism.  

PubMed

Thiamine diphosphate (ThDP)-dependent enzymes are ubiquitously present in all organisms and catalyze essential reactions in various metabolic pathways. ThDP-dependent phosphoketolase plays key roles in the central metabolism of heterofermentative bacteria and in the pentose catabolism of various microbes. In particular, bifidobacteria, representatives of beneficial commensal bacteria, have an effective glycolytic pathway called bifid shunt in which 2.5 mol of ATP are produced per glucose. Phosphoketolase catalyzes two steps in the bifid shunt because of its dual-substrate specificity; they are phosphorolytic cleavage of fructose 6-phosphate or xylulose 5-phosphate to produce aldose phosphate, acetyl phosphate, and H(2)O. The phosphoketolase reaction is different from other well studied ThDP-dependent enzymes because it involves a dehydration step. Although phosphoketolase was discovered more than 50 years ago, its three-dimensional structure remains unclear. In this study we report the crystal structures of xylulose 5-phosphate/fructose 6-phosphate phosphoketolase from Bifidobacterium breve. The structures of the two intermediates before and after dehydration (?,?-dihydroxyethyl ThDP and 2-acetyl-ThDP) and complex with inorganic phosphate give an insight into the mechanism of each step of the enzymatic reaction. PMID:20739284

Suzuki, Ryuichiro; Katayama, Takane; Kim, Byung-Jun; Wakagi, Takayoshi; Shoun, Hirofumi; Ashida, Hisashi; Yamamoto, Kenji; Fushinobu, Shinya

2010-10-29

144

Linked strategy for the production of fuels via formose reaction  

PubMed Central

Formose reaction converts formaldehyde to carbohydrates. We found that formose reaction can be used linking the biomass gasification with the aqueous-phase processing (APP) to produce liquid transportation fuel in three steps. First, formaldehyde from syn-gas was converted to triose. This was followed by aldol condensation and dehydration to 4-hydroxymethylfurfural (4-HMF). Finally, 4-HMF was hydrogenated to produce 2,4-dimethylfuran (2,4-DMF) or C9-C15 branched-chain alkanes as liquid transportation fuels. In the linked strategy, high energy-consuming pretreatment as well as expensive and polluting hydrolysis of biomass were omitted, but the high energy recovery of APP was inherited. In addition, the hexoketoses via formose reaction could be converted to HMFs directly without isomerization. A potential platform molecule 4-HMF was formed simultaneously in APP.

Deng, Jin; Pan, Tao; Xu, Qing; Chen, Meng-Yuan; Zhang, Ying; Guo, Qing-Xiang; Fu, Yao

2013-01-01

145

Oil shale heat-capacity relations and heats of pyrolysis and dehydration  

Microsoft Academic Search

New relations are developed for calculating enthalpy changes during heating, retorting, or cooling of raw, spent, or burned oil shales of various compositions. The relations describe the sensible heats of the minerals, kerogen, and char, and the reaction heats of kerogen pyrolysis and bound-water dehydration. The mineral sensible heat is obtained by summing the ''handbook'' enthalpy values of the constituent

1987-01-01

146

Dehydration kinetics of talc at 1 bar  

NASA Technical Reports Server (NTRS)

Experimental results on the dehydration kinetics of talc, which is likely to be a major potential resource for water and hydrogen in carbonaceous chondrites, is presented. The rate of dehydration of an essentially pure Mg-end member natural talc, (Mg(.99)Fe(.01))3Si4O10(OH)2, was studied by measuring in situ weight change under isothermal condition at 1 bar as a function of time in the temperature range 775 to 985 C. The grain size of the starting material was 0.7 to 1 micron. It was found that the data up to 50 to 60 percent dehydration can be fitted by an equation of the form alpha = exp(-Kt(exp n)), where alpha is the weight fraction of talc remaining, K is a rate constant and n is a numerical constant for a given temperature. For any set of isothermal data, there is a major change in the value of n for larger dehydration. For up to approximately 50 percent dehydration, all rate constants can be described by an Arrheniun relation with an activation energy of 432 (+/- 30) kJ/mol; n has a nearly constant value of 0.54 between 775 and 875 C, but increases almost linearly according to n = -10.77 + 0.012T C at T greater than or equal to 875 C.

Ganguly, J.; Bose, K.

1991-01-01

147

Polariton condensates  

SciTech Connect

Most students of physics know about the special properties of Bose-Einstein condensates (BECs) as demonstrated in the two best-known examples: superfluid helium-4, first reported in 1938, and condensates of trapped atomic gases, first observed in 1995. (See the article by Wolfgang Ketterle in PHYSICS TODAY, December 1999, page 30.) Many also know that superfluid {sup 3}He and superconducting metals contain BECs of fermion pairs. An underlying principle of all those condensed-matter systems, known as quantum fluids, is that an even number of fermions with half-integer spin can be combined to make a composite boson with integer spin. Such composite bosons, like all bosons, have the property that below some critical temperature--roughly the temperature at which the thermal de Broglie wavelength becomes comparable to the distance between the bosons--the total free energy is minimized by having a macroscopic number of bosons enter a single quantum state and form a macroscopic, coherent matter wave. Remarkably, the effect of interparticle repulsion is to lead to quantum mechanical exchange interactions that make that state robust, since the exchange interactions add coherently.

Snoke, David; Littlewood, Peter [University of Pittsburgh, Pennsylvania (United States); University of Cambridge (United Kingdom)

2010-08-15

148

Structural characterization and dehydration kinetics of Kirka inderite mineral: Application of non-isothermal models  

SciTech Connect

Coats-Redfern, Arrhenius, Ozawa, Kissinger, and Doyle non-isothermal kinetic models were used to calculate the dynamic kinetic parameters for dehydration reaction of Mg-borate mineral, inderite (Kirka - Turkey) based on thermogravimetric analysis, derivative thermogravimetric analysis and differential thermal analysis. Dehydration experiments were carried out at different heating rates of 2, 5, 10, 15, and 20 deg. C/min in a pure nitrogen atmosphere. Structural and morphological properties have been characterized by X-Ray diffraction, Fourier transform-infrared spectroscopy, Scanning electron microscopy-energy dispersive spectroscopy, and Inductively coupled plasma-optical emission spectroscopy techniques.

Figen, Aysel Kantuerk, E-mail: akanturk@yildiz.edu.tr [Yildiz Technical University, Department of Chemical Engineering, Davutpasa Campus., N.127, Esenler, Istanbul (Turkey); Yilmaz, Muege Sari, E-mail: mugesari@yildiz.edu.tr [Yildiz Technical University, Department of Chemical Engineering, Davutpasa Campus., N.127, Esenler, Istanbul (Turkey); Piskin, Sabriye, E-mail: piskin@yildiz.edu.tr [Yildiz Technical University, Department of Chemical Engineering, Davutpasa Campus., N.127, Esenler, Istanbul (Turkey)

2010-06-15

149

Dehydration of 3-hydroxyacyl-CoA in brain very-long-chain fatty acid synthesis  

Microsoft Academic Search

Rat brain microsomes actively dehydrate 3-hydroxyacyl-CoAs. Using chemically synthesized [1-14C] (R,S) 3-hydroxyeicosanoyl-CoA, we investigated the biochemical characteristics of the dehydration and reduction steps of stearoyl-CoA elongation.The reaction products, separated and identified as trans2,3-enoyl-CoAs and, in the presence of NADPH, as saturated acyl-CoAs, were released from the enzyme as thioesters which were partly hydrolysed. A kinetic analysis of the two coupled

Anja Knoll; Jean-Jacques Bessoule; Françoise Sargueil; Claude Cassagne

1999-01-01

150

A new one-pot three-component condensation reaction for the synthesis of 2,3,4,6-tetrasubstituted pyridines.  

PubMed

The one-pot three-component condensation of a beta-ketoester, ammonia and an alkynone in the presence of a Brønsted or Lewis acid or Amberlyst 15 ion exchange resin provided 2,3,6-trisubstituted or 2,3,4,6-tetrasubstituted pyridines directly in good yield and with total regiocontrol. PMID:12196948

Bagley, Mark C; Dale, James W; Bower, Justin

2002-08-21

151

Dehydration mechanism of optical clearing in tissue  

NASA Astrophysics Data System (ADS)

Previous studies identified various mechanisms of light scattering reduction in tissue induced by chemical agents. Our results suggest that dehydration is an important mechanism of optical clearing in collagenous and cellular tissue. Photographic and optical coherence tomography images indicate that air-immersed skin and tendon specimens become similarly transparent to glycerol-immersed specimens. Transmission electron microscopy images reveal that dehydration causes individual scattering particles such as collagen fibrils and organelles to become more densely packed, but does not significantly alter size. A heuristic particle-interaction model predicts that the scattering particle volume fraction increase can contribute substantially to optical clearing in collagenous and cellular tissue.

Rylander, Christopher G.; Stumpp, Oliver F.; Milner, Thomas E.; Kemp, Nathaniel J.; Mendenhall, John M.; Diller, Kenneth R.; Welch, Ashley J.

2006-07-01

152

Catalytic activity of zirconium phosphate and some derived phases in the dehydration of alcohols and isomerization of butenes  

SciTech Connect

The catalytic activity of ..cap alpha..-Zr(HPO/sub 4/)/sub 2/ x H/sub 2/O prepared by different methods and of phases derived from it by heating between 200 and 1100/sup 0/C or by ion exchange with Na/sup +/, Cs/sup +/, or Ag/sup +/, has been investigated by means of different acid-catalyzed test reactions, namely, isopropanol, 1- or 2-butanol dehydration, and 1-butene isomerization. The active centers of both Zr(HPO/sub 4/)/sub 2/ and ZrP/sub 2/O/sub 7/ phases are mainly the surface Broensted sites, as indicated by the strong decrease or annihilation of their catalytic activity after surface Cs/sup +/ poisoning. An explanation of the low residual activity detected for same samples is given. As deduced from the products of 1-butene isomerization, the acidic sites are generally of medium strength. However, on heating between 350 and 700/sup 0/C, when partial or total condensation of hydrogen phosphate to P-O-P groups occurs (with progressive formation of the layered pyrophosphate phase) they transform into sites of medium-high strength.

La Ginestra, A.; Patrono, P.; Berardelli, M.L.; Galli, P.; Ferragina, C.; Massucci, M.A.

1987-02-01

153

Factors Influencing the Condensation of 4-Aminoantipyrine with Phenols.  

National Technical Information Service (NTIS)

Phenolic compounds condense with 4-Aminoantipyrine and by subsequent oxidation under alkaline conditions produces a color the intensity of which is proportional to the phenol concentration. These condensation and oxidation reactions have been applied to t...

S. D. Faust F. C. Lorentz

1964-01-01

154

Aldol condensation reactions of tricarbonyliron complexes. Towards building blocks for the synthesis of carbomycin B\\/tylosin macrolide antibiotics and fluorinated analogs  

Microsoft Academic Search

Tricarbonyliron complexes of ?-methoxyheptadienone 3 and octadienone 8 were reacted as silyl enol ethers with protected ?-hydroxypropanal and TiCl4, to give the syn–syn aldol condensation products 4 and 11 as major, isolated diastereomers (61 and 45%). Products 4 and 11 were converted into key intermediates of previous total syntheses of carbonolide B and tylonide, in a few steps, including the

Michel Franck-Neumann; Philippe Geoffroy; Fabien Gumery

2000-01-01

155

ADVANCED DEHYDRATOR DESIGN SAVES GAS AND REDUCES HAP EMISSIONS  

EPA Science Inventory

Glycol dehydrators remove water from gas pipe lines. An advanced dehydrator by Engineered Concepts, Farmington, NM, saves a significant amount of gas, while reducing hazardous air pollutants, volatile organic compounds and CO2 air pollutants...

156

Dehydration in the Winter Arctic Tropopause Region  

NASA Technical Reports Server (NTRS)

Recent work has shown that limited amounts of tropospheric air can penetrate as much as 1 km into the middleworld stratosphere during the arctic winter. This, coupled with temperatures that are cold enough to produce saturation mixing ratios of less than 5 ppmv at the tropopause, results in stratospheric cloud formation and upper tropospheric dehydration. Even though these "cold outbreaks" occupy only a small portion of the area in the arctic (1-2%), their importance is magnified by an order of magnitude because of the air flow through them. This is reinforced by evidence of progressive drying through the winter measured during SOLVE-1. The significance of this process lies in its effect on the upper tropospheric water content of the middle and high latitude tropopause region, which plays an important role in regulating the earth's radiative balance. There appears to be significant year-to-year variability in the incidence of the cold outbreaks. This work has two parts. First, we describe case studies of dehydration taken from the SOLVE and SOLVE2 aircraft sampling missions during the Arctic winters of 2000 and 2003 respectively. Trajectory based microphysical modeling is employed to examine the sensitivity of the dehydration to microphysical parameters and the nature of sub-grid scale temperature fluctuations. We then examine the year-to-year variations in potential dehydration using a trajectory climatology.

Pfister, Leonhard; Jensen, Eric; Podolske, James; Selkirk, Henry; Anderson, Bruce; Avery, Melody; Diskin. Glenn

2004-01-01

157

Pervaporation dehydration of isopropanol with chitosan membranes  

Microsoft Academic Search

Homogeneous and composite chitosan based membranes were prepared by the solution casting technique. The membranes were investigated for the pervaporation dehydration of isopropanol-water systems. The effects of feed concentration and temperature on the separation performance of the membranes were studied. In terms of the pervaporation separation index (PSI), the composite membrane was more productive than the homogeneous membrane for pervaporation

M. Ghazali; M. Nawawi; Robert Y. M. Huang

1997-01-01

158

Water, water everywhere: dehydration in the elderly.  

PubMed

Dehydration is a common disorder in the frail elderly patient. Understanding the mechanisms by which fluid and electrolyte abnormalities occur, as well as the implications of specific laboratory values, is key to providing optimal diagnosis and treatment. Management of fluid abnormalities relies on gradual rehydration with the proper fluids to restore both fluid and electrolytes. PMID:16548671

Sacks, Gordon S; Martin, Caren McHenry

2005-11-01

159

Geothermal demonstration: Zunil food dehydration facility  

Microsoft Academic Search

A food dehydration facility was constructed near the town of Zunil, Guatemala, to demonstrate the use of geothermal energy for industrial applications. The facility, with some modifications to the design, was found to work quite satisfactorily. Tests using five different products were completed during the time geothermal energy was used in the plant. During the time the plant was not

O. Maldonado; J. Altseimer; G. R. Thayer; L. Cooper; A. Caicedo

1991-01-01

160

Bioethanol dehydration: State of the art  

Microsoft Academic Search

This article is a survey of the present-day methods of dehydration of ethanol resulting from fermentation processes. The existing\\u000a separation techniques for water-ethanol mixtures of various compositions are compared, and the conditions under which each\\u000a particular technique is preferable are formulated.

A. K. Frolkova; V. M. Raeva

2010-01-01

161

Thermoelastic behavior and dehydration process of cancrinite  

NASA Astrophysics Data System (ADS)

The high-temperature thermoelastic behavior of a natural cancrinite has been investigated by in situ single-crystal X-ray diffraction. The unit-cell volume variation as a function of temperature ( T) exhibits a continuous trend up to 748 K (hydrous expansion regime). The unit-cell edges expansion clearly shows an anisotropic expansion scheme ( ? a < ? c ). At 748 K, a dehydration process takes place, and a series of unit-cell parameter measurements at constant temperature (748 K) for a period of 12 days indicate that the dehydration process continued for the entire period of time, until the cell parameters were found to be constant. After the dehydration process is completed, the structure expands almost linearly with increasing temperature up to 823 K, where a sudden broadening of the diffraction peaks, likely due to the impending decomposition, did not allow the collection of further data points. Even with a very limited temperature range for the anhydrous regime, we observed that the behavior of the two (i.e., hydrous and anhydrous) high-temperature structures is similar in terms of (1) volume thermal expansion coefficient and (2) thermoelastic anisotropy. The structure refinements based on the data collected at 303, 478 and 748 K (after the dehydration), respectively, showed a change in the mechanism of tilting of the quasi-rigid (Si,Al)O4 tetrahedra, following the loss of H2O molecules, ascribable to the high-temperature Na+ coordination environment within the cages.

Gatta, G. D.; Comboni, D.; Alvaro, M.; Lotti, P.; Cámara, F.; Domeneghetti, M. C.

2014-05-01

162

Dehydration of incoming sediments at the Japan Trench  

NASA Astrophysics Data System (ADS)

In the 2011 Tohoku-oki earthquake, the seismic fault slip propagated close to the axis of the Japan Trench and caused an extremely large tsunami (Ide et al., 2011). It is generally considered that ductile deformation of unconsolidated sediments is commonly prominent in the aseismic shallow parts of the subduction zone. Therefore, it is unknown how the seismic rupture reached the nearby trench axis. The plate-boundary megathrust of the Japan Trench is characterized by a prominent seismic reflector, suggesting that the megathrust may host highly pressurized fluids (Kimura et al., 2012). Based on the result of Deep Sea Drilling Project (DSDP) Leg 56 at site 436 (reference, 1977), it is expected that the subducting sediments at the Japan Trench mainly consist of vitric diatomaceous and radiolarian ooze with pelagic clay intervals. Opal-A in the pelagic sediments transforms into quartz, and smectite transforms into illite. Kinetic modeling demonstrated that these reactions will progress with active dehydration at 50-60 km horizontally away from the deformation front and with a temperature of 100-120°C. This region coincides with the plate-boundary marked by a prominent seismic reflector, and suggests that the main source of highly pressured fluids is the dehydration of pelagic sediments (Kimura et al., 2012). However, detailed dehydration processes are still unclear mainly due to lack of quantitative sediment composition data. Therefore, in this study, we examined whole rock composition including amorphous silica of the core samples recovered at site 436 as well as those from the Japan Trench by the IODP 343 Japan Trench Fast Drilling Project (JFAST). Analysis of amorphous silica at site 436 documents that dehydration of the sediments is able to contribute to excess pressure at the shallow part of the megathrust if they underthrust as the same composition. At the drilling site of JFAST, a plate-boundary shear zone was identified around 820 mbsf, which was supposed to cause the 2011 Tohoku-oki earthquake (Chester., et al., 2012). Our analysis showed that the shear zone is characterized by extremely high concentration of smectite (~70 wt.%). These results suggest that the abundant smectite may have possibly fostered localized rupture and slip during the earthquake, because smectite has low frictional coefficient.

Shimizu, M.; Kameda, J.; Hamada, Y.; Kimura, G.

2013-12-01

163

Understanding Condensation  

NSDL National Science Digital Library

Monica Hartman, Assistant Director for Science in St. Clair County, Michigan, conducted this research while she was the learning specialist in a small suburban district just outside a large Midwestern city. While teaching full time in this district she was also completing her doctoral program in education at the University of Michigan. In this chapter, she tells the story of a "science talk" about condensation among fifth graders. She acted as a source and facilitator of change as she and the fifth-grade teacher worked collaboratively to help students share responsibility for their own learning. She describes their continual assessment of student understanding that occurred as their students struggled to explain observations and as they, the teachers, carefully resisted the temptation to end the struggle by saying "that's right!"

Hartman, Monica

2007-12-01

164

Diagenesis and dehydration of subducting oceanic crust within seismogenic subduction zones  

NASA Astrophysics Data System (ADS)

Diagenesis and dehydration of subducting oceanic crust is thought to have strong influence on mechanical and hydrologic properties of seismogenic plate interfaces beneath the accretionary wedges (Kameda et al., 2011). In this work, we analyzed five representative pillow basalts exposed in the ancient accretionary complex, the Shimanto belt in southwest Japan, in order to derive details on a suite of mineral reactions within the subducting oceanic crust. Based on the vitrinite reflectance measurement of terrigenous sediments accompanied by these rocks, they are estimated to have been subjected to burial diagenenesis at 150-300 C. Whole rock and clay-fraction X-ray diffraction (XRD) analyses indicate that sequential saponite to chlorite transformation through mixed-layer phases proceeds under the relatively constant bulk rock composition. Such clay mineral reaction may persist to deep crustal level (~290 C) and contribute to bulk dehydration as a dominant fluid supplier to the plate-boundary fault system. The dehydration may cause abnormal fluid pressurization around the plate-boundary fault zone with a maximum at a certain horizon below the fault (within the intact oceanic crust), resulting in underplating of the upper basement rock into the overriding accretionary prism. Such dehydration-induced weakening process well explains the thickness distribution of the accreted basaltic crust fragments as observed in the onland exposures (Kimura and Ludden, 1995). The breakage of the oceanic crust potentially nucleates seismic slip to propagate along the seismogenic plate interface.

Kameda, J.; Yamaguchi, A.; Hamada, Y.; Hashimoto, Y.; Kimura, G.

2012-12-01

165

Condensed atmospheric photooxidation mechanisms for isoprene  

Microsoft Academic Search

Two condensed mechanisms for the atmospheric reactions of isoprene, which differ in the number of species used to represent isoprene's reactive products, have been developed for use in ambient air quality modehng. They are based on a detailed isoprene mechanism that has recently been developed and extensively evaluated against environmental chamber data. The new condensed mechanisms give very close predictions

William P. L. Carter

1996-01-01

166

Process for dehydrating ethanol and for the production of gasohol therefrom  

SciTech Connect

Process is claimed for dehydrating aqueous ethanol, utilizing a highpressure distillation (With a single distillation column) of an aqueous ethanol admixture (Preferably one derived from a conventional ethanol fermentation process), to achieve a vapor phase ethanol-water admixture containing about 90 percent, by weight, of ethanol. The vaporous admixture is then dried, in the presence of CO/sub 2/, with a crystalline zeolite type 3a, utilizing the ''pressure energy'' derived from the distillation to allow the product ethanol to condense at ambient temperatures, and then, if desired, employing the resultant dried ethanol product in the production of gasohol.

Fornoff, L.L.

1981-06-16

167

Rate of Nucleation in Condensed Systems  

Microsoft Academic Search

On the basis of the nucleation theory developed by Volmer, Becker, and co-workers, and the theory of absolute reaction rates, an expression is derived for the absolute rate of nucleation in condensed systems.

D. Turnbull; J. C. Fisher

1949-01-01

168

Chemistry and anelasticity in dehydrated sandstone  

NASA Astrophysics Data System (ADS)

Preliminary acoustic measurements of a dehydrated sample of Berea sandstone indicated a dramatic change in elastic and anelastic properties near 45C. With an improved temperature control system we have characterized the change, a softening of the modulus and an increase in dissipation, in detail. We have attempted to fit a finite-element model of a silica grain-bond network to the data and discuss ideas for the connection between water content and nonlinearity. Berea is a complex sandstone with several components beyond the silica frame, so in order to simplify the sample, we are working with a very nonlinear Fontainebleau sandstone and we present new data from both Nonlinear Resonant Ultrasound Spectroscopy (NRUS) and Dynamic Acoustic Elastic Testing on a dehydrated 99.5% silica rock.

Darling, T. W.; Miller, R. A.

2012-12-01

169

Rice water solution in diarrheal dehydration  

Microsoft Academic Search

Diarrheal disorders and complications related to diarrhea especially dehydration continue to be a major problem in developing\\u000a countries like India. Though oral rehydration with salt, sugar and water is a well accepted mode of treatment in uncomplicated\\u000a cases, still ORS packets (WHO formula) or sugar (sucrose ORS formula) are not readily available in every house or hospital\\u000a rice water with

B. R. Sathanakrishnan; V. S. Sankaranarayanan

1985-01-01

170

ON DEHYDRATION OF BOUND WATER OF SEPIOLITE  

Microsoft Academic Search

Bound water of sepiolite dehydrates in two steps in the temperature range of 250-650~ as shown in the TG-curve. These steps are described here as steps II and III. At step II, half of the bound water is removed; other half at step III. From step II to IlL discontinuous changes are confirmed in such properties as activation energy of

ROSHI NAGATA; SUSUMU SHIMODA; TOSHIO SUDO

1974-01-01

171

Dehydration-induced drinking in humans  

NASA Technical Reports Server (NTRS)

The human tendency to experience a delay in rehydration (involuntary dehydration) after fluid loss is considered. The two primary factors contributing to involuntary dehydration are probably upright posture, and extracellular fluid and electrolyte loss by sweating from exercise and heat exposure. First, as the plasma sodium and osmotic concentrations remain virtually unchanged for supine to upright postural changes, the major stimuli for drinking appear to be associated with the hypovolemia and increase in the renin-angiotension system. Second, voluntary drinking during the heat experiments was 146% greater than in cool experiments; drinking increased by 109% with prior dehydration as opposed to normal hydration conditions; and drinking was increased by 41% after exercise as compared with the resting condition. Finally, it is concluded that the rate of sweating and the rate of voluntary fluid intake are highly correlated, and that the dispogenic factors of plasma volume, osmolality, and plasma renin activity are unrelated to sweat rate, but are likely to induce drinking in humans.

Greenleaf, J. E.

1982-01-01

172

Evolution of microstructure and elastic wave velocities in dehydrated gypsum samples  

NASA Astrophysics Data System (ADS)

We report on changes in P and S-wave velocities and rock microstructure induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air, at ambient pressure, and temperatures between 378 and 423 K. Dehydration did not proceed homogeneously but via a reaction front moving sample inwards separating an outer highly porous rim from the remaining gypsum which, above approximately 393 (±5) K, concurrently decomposed into hemihydrate. Overall porosity was observed to continuously increase with reaction progress from approximately 2% for fully hydrated samples to 30% for completely dehydrated ones. Concurrently, P and S-wave velocities linearly decreased with porosity from 5.2 and 2.7 km/s to 1.0 and 0.7 km/s, respectively. It is concluded that a linearized empirical Raymer-type model extended by a critical porosity term and based on the respective time dependent mineral and pore volumes reasonably replicates the P and S-wave data in relation to reaction progress and porosity.

Milsch, Harald; Priegnitz, Mike

2012-12-01

173

Simulation of nonlinear optical signals via approximate solutions of the quantum-classical Liouville equation: Application to the pump-probe spectroscopy of a condensed phase electron transfer reaction  

NASA Astrophysics Data System (ADS)

The equation-of-motion phase-matching approach provides an efficient way for calculating a system's time-dependent polarization in any phase-matching direction subject to weak laser fields of arbitrary shape. Within this approach, we introduce the Poisson Bracket Mapping Equation and Forward-Backward methods, two approximate solutions of the quantum-classical Liouville equation, for simulating the laser-induced response of a quantum subsystem in a classical environment. We illustrate this approach by calculating the transient absorption signal in a model photo-induced condensed phase electron transfer reaction. The results are found to be in reasonable agreement with the exact results, which is promising for applications to realistic systems.

Martinez, Franz; Rekik, Najeh; Hanna, Gabriel

2013-06-01

174

Effect of thermal dehydration and rehydration on Na-magadiite structure.  

PubMed

The effect caused by dehydration and rehydration of the synthetic Na-magadiite was investigated by TGA, XRD, SEM, and (29)Si NMR. Thermal analysis of Na-magadiite presented two well-defined loss mass stages between 20 and 150 degrees C and another between 270 and 310 degrees C, both related to the removal of interlayer water. The swelling behavior of Na-magadiite was studied by thermal dehydration data obtained at 150 and 300 degrees C, and respective rehydration by water addition. X-ray patterns showed that the dehydration of Na-magadiite at 150 and 300 degrees C provoked the basal spacing decrease. The XRD also showed that only the material treated at 150 degrees C returned to the original structure with the rehydration. (29)Si NMR spectra showed that after rehydration, the Q(3)/Q(4) relationship presented the same value for Na-magadiite treated at 150 degrees C. However, this Q(3)/Q(4) value decreased when the treatment was done at 300 degrees C. Kinetic studies of thermal decomposition showed that the dehydration of magadiite is based on a phase boundary-controlled reaction, caused by contracting areas. The exfoliation of lamellas with thermal treatment can explain this behavior, as observed in SEM images. PMID:19026425

Moura, Aline O; Prado, Alexandre G S

2009-02-15

175

An experimental investigation of antigorite dehydration in natural silica-enriched serpentinite  

Microsoft Academic Search

Piston cylinder experiments were performed to constrain the pressure and temperature conditions for two high-pressure antigorite dehydration reactions found in silica-enriched serpentinites from Cerro del Almirez (Nevado-Filábride Complex, Betic Cordillera, southern Spain). At 630-660°C and pressures greater than 1.6 GPa, antigorite first reacts with talc to form orthopyroxene ± chlorite + fluid. We show that orthopyroxene + antigorite is restricted

José Alberto Padrón-Navarta; Jörg Hermann; Carlos J. Garrido; Vicente López Sánchez-Vizcaíno; María Teresa Gómez-Pugnaire

2010-01-01

176

Uptake of thiol anti-browning agents by cabbage on blanching and reactivity during dehydration  

Microsoft Academic Search

The uptake of the anti-browning agents, mercaptoethanesulphonic acid, cysteine, N-acetylcysteine, glutathione and leucinylcysteine (leu-cys), by cabbage from blanch liquor at pH 5.8 is measured and used to obtain the amounts of these thiols which undergo reaction when the vegetable is subsequently dehydrated. This behaviour is compared with that of sulphite species S(IV). The most reactive thiol was leu-cys, which was

A. S. Edwards; B. L. Wedzicha

1997-01-01

177

Powder X-ray thermodiffraction study of mirabilite and epsomite dehydration. Effects of direct IR-irradiation on samples.  

PubMed

This paper investigates the thermal and irradiation-dependent dehydration and kinetics occurring in Na2SO4.10H2O (mirabilite) and MgSO4.7H2O (epsomite) at room conditions by using powder X-ray thermodiffraction. An improved version of a first optically stimulated X-ray diffractometer prototype was used. Specific software for the thermodiffraction study was developed (XPowder PLUS) and a filter inserted between the lamp (heating system) and the sample. The results show that these salts are thermal and irradiation sensitive. The temperature and kinetic rates of the salt conversions differed depending on direct exposure to high-intensity radiation (photodehydration) or whether the radiation was blocked by the filter (thermodehydration). In general, radiation-induced dehydration triggers the transformation at lower temperature and accelerates the kinetic reaction more than when the filter is used. Mirabilite dehydration starts with the initial radiation impacts, unlike epsomite. Thermodehydration and photodehydration of mirabilite is a non-isothermal reaction occurring through an amorphous-mediated step. Radiation damage in epsomite leads to isothermal dehydration, whereas non-isothermal dehydration occurs when epsomite is thermally damaged. In both cases, no amorphous material was observed. Because of the weaker bond between cation and oxygen atom in mirabilite, its thermal and radiation stability is lower than in epsomite. These results have important implications for the prevention of salt weathering of porous materials found in the cultural heritage. PMID:17500533

Cardell, Carolina; Sánchez-Navas, Antonio; Olmo-Reyes, F José; Martín-Ramos, J Daniel

2007-06-15

178

Dehydration of isobutanol to isobutene in a slurry reactor  

SciTech Connect

The April 1990 Alternative Fuels Proposal to the Department of Energy involved the development of new technology, based on the liquid phase process, for conversion of coal-derived synthesis gas to oxygenated hydrocarbon fuels, fuel additives, and fuel intermediates. The objective of this work was to develop a slurry reactor based process for the dehydration of isobutanol to isobutene. The isobutene can serve as a feedstock for the high octane oxygenated fuel additive methyl tertiary-butyl either (MTBE). Alumina catalysts were investigated because of their wide use as a dehydration catalyst. Four commercially available alumina catalysts (Catapal B, Versal B, Versal GH, and Al-3996R) were evaluated for both activity and selectivity to the branched olefin. All four catalysts demonstrated conversions greater than 80% at 290 C, while conversions of near 100% could be obtained at 330 C. The reaction favors low pressures and moderate to low space velocities. A yield of 0.90 mole isobutene per mole reacted isobutanol or better was obtained at conversions of 60--70% and higher. From 75 to 98% conversion, the four catalysts all provide isobutene yields ranging from 0.92 to 0.94 with the maximum occurring around 90% conversion. At low conversions, the concentration of diisobutyl ether becomes significant while the concentration of linear butenes is essentially a linear function of isobutanol conversion. Doping the catalyst with up to 0.8 wt % potassium showed a modest increase in isobutene selectivity; however, this increase was more than offset by a reduction in activity. Investigations using a mixed alcohols feed (consistent with isobutanol synthesis from syngas) demonstrated a small increase in the C4 iso-olefin selectivity over that observed for a pure isobutanol feed. 55 refs.

Latshaw, B.E.

1994-02-01

179

Dehydration of plutonium or neptunium trichloride hydrate  

DOEpatents

A process is described for preparing anhydrous actinide metal trichlorides of plutonium or neptunium by reacting an aqueous solution of an actinide metal trichloride selected from the group consisting of plutonium trichloride or neptunium trichloride with a reducing agent capable of converting the actinide metal from an oxidation state of +4 to +3 in a resultant solution, evaporating essentially all the solvent from the resultant solution to yield an actinide trichloride hydrate material, dehydrating the actinide trichloride hydrate material by heating the material in admixture with excess thionyl chloride, and recovering anhydrous actinide trichloride.

Foropoulos, J. Jr.; Avens, L.R.; Trujillo, E.A.

1992-03-24

180

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Co-Adsorption of CO in NO—CO Reaction on a Metal Catalytic Surface Studied by Computer Simulation  

NASA Astrophysics Data System (ADS)

The effect of co-adsorption of CO molecules in the NO-CO reaction on a metal catalytic surface like Pt(001) is studied by applying the Langmuir-Hinshelwood mechanism using the Monte Carlo simulations. The system is investigated by two approaches of NO adsorption; dissociatively at two empty surface sites and molecularly at a single vacant site. The elementary steps are the same as those in the conventional Ziff-Gulari-Barshad model. With the additional reaction step of co-adsorption, the sustained production of CO2 is obtained, which has never been seen on a square lattice without introducing additional parameters. The most interesting result is the elimination of continuous second order phase transition, i.e. the production of CO2 starts as soon as the partial pressure of CO departs from zero, which is in accordance with the experimental observations. The effect of co-adsorption probability on the phase diagrams has also been studied.

Waqar, Ahmad

2009-03-01

181

Reactivity of a condensed–type lignin model compound in the Mannich reaction and preparation of cationic surfactant from sulfuric acid lignin  

Microsoft Academic Search

The chemical conversion of phenolized sulfuric acid lignin (P-SAL), prepared from sulfuric acid lignin (SAL) by phenolation\\u000a with sulfuric acid catalyst, to novel cationic surfactant was investigated. To elucidate the chemical reactivity of the P-SAL\\u000a to a Mannich reaction, 1-guaiacyl-1-p-hydroxyphenylethane (I) as a simple phenolized sulfuric acid lignin model compound was reacted with dimethylamine and formaldehyde. Quantitative\\u000a analysis of the

Yasuyuki Matsushita; Seiichi Yasuda

2003-01-01

182

Olfactory contributions to dehydration-induced anorexia in weanling rats.  

PubMed

By 20 days of age, dehydration produces a clear anorexia, even though weanling rats have had only limited feeding and drinking experience. Their lack of ingestive experience makes weanlings good subjects for studying the physiological mechanisms subserving anorexic phenomena because learned contributions are unlikely to add significant complications. Twenty-day-old rats dehydrated by hypertonic saline injection were anorexic when offered milk or solid food (rat chow), but not when offered sucrose solutions (Experiment I). However, when the scent of almond was associated with sucrose solutions, or with water, intake of these solutions was depressed by dehydration (Experiment II). Thus for dehydrated rats, olfactory stimulation may help produce dehydration-induced anorexia. Making rats anosmic by intransal lavage with ZnSO4 (Experiment III) eliminated the anorexia to almond-scented water and partially eliminated that to milk. For these fluids, an odor cue seems a requirement for the occurrence of dehydration-anorexia. In Experiment IV, we found that dehydration-anorexia did not occur when milk was infused directly into pups' mouths. This finding suggests that the inhibitory process mediating dehydration-anorexia influences the approach to food and not the actual consumatory response that occurs once food is in the mouth. The inhibition of feeding produced by dehydration, therefore, may depend largely on olfactory cues, and seems to operate at a distance, as rats locate and approach food. PMID:7152117

Bruno, J P; Hall, W G

1982-11-01

183

The effects of dehydration, moderate alcohol consumption, and rehydration on cognitive functions.  

PubMed

This study investigated the impact of mild-moderate dehydration on alcohol-induced deteriorations in cognitive functions. Sixteen healthy males participated in a single-blind, placebo-controlled cross-over design study involving 4 experimental trials (separated by ?7 d). In each trial, participants were dehydrated by 2.5% body mass through exercise. After 1 h recovery in a thermo-neutral environment (22 ± 2 °C, 60-70% relative humidity) 4 tasks from the Cambridge Neuropsychological Test Automated Battery (CANTAB) were administered to the participants (test 1). In two of the trials, participants were provided with water equivalent to either 50% or 150% body mass loss and given salt (NaCl) capsules (50 mmol/L). A set volume of alcohol or placebo was then consumed in each trial, incorporating the conditions: dehydration-placebo (DP), dehydration-alcohol (DA), partial rehydration-alcohol (PA), and full rehydration-alcohol (FA). The same 4 CANTAB tasks were then re-administered (test 2). Subjective ratings of mood and estimates of alcohol intoxication and driving impairment were also recorded in each trial. Alcohol consumption caused deterioration on 3 of the 4 CANTAB measures (viz., choice reaction time, executive function and response inhibition). This reduction in performance was exacerbated when participants were dehydrated compared to trials where full rehydration occurred. Subjective ratings of impairment and intoxication were not significantly different between any of the trials where alcohol was consumed; however ratings for alcohol trials were significantly higher than in the placebo trial. These findings suggest that rehydration after exercise that causes fluid loss can attenuate alcohol-related deterioration of cognitive functions. This may pose implications for post match fluid replacement if a moderate amount of alcohol is also consumed. PMID:23352231

Irwin, Christopher; Leveritt, Michael; Shum, David; Desbrow, Ben

2013-05-01

184

Cryoprotective dehydration is widespread in Arctic springtails.  

PubMed

Cryoprotective dehydration (CPD) is a cold tolerance strategy employed by small invertebrates that readily lose water by evaporation when subjected to sub-zero temperatures in the presence of ice. Until now, relatively few species have been investigated using methods by which CPD can be shown. In the present study we investigated the cold tolerance strategy of seven soil arthropod species from the high Arctic Spitzbergen, and compared water content and water loss, body fluid melting points (MP) and survival under cold and desiccating conditions. We tested the hypothesis that CPD is a commonly occurring cold hardiness strategy among soil arthropods. We found that four springtail species (Hypogastrura viatica, Folsomia quadrioculata, Oligaphorura groenlandica and Megaphorura arctica; Collembola) went through severe dehydration and MP equilibration with ambient temperature, and thus overwinter by employing CPD, whereas a beetle (Atheta graminicola) and one of the springtails (Isotoma anglicana) were typical freeze avoiding species over-wintering by supercooling. Desiccation tolerance of the red velvet mite (Neomolgus littoralis) was also investigated; very low water loss rates of this species indicated that it does not survive winter by use of CPD. All in all, the results of the present study confirm the hypothesis that CPD is an effective over-wintering strategy which is widespread within soil arthropods. PMID:21396373

Sørensen, Jesper Givskov; Holmstrup, Martin

2011-08-01

185

Dehydration parameters and standards for laboratory mice.  

PubMed

Water deprivation and restriction are common features of many physiologic and behavioral studies; however, there are no data-driven humane standards regarding mice on water deprivation or restriction studies to guide IACUC, investigators, and veterinarians. Here we acutely deprived outbred CD1 mice of water for as long as 48 h or restricted them to a 75% or 50% water ration; physical and physiologic indicators of dehydration were measured. With acute water deprivation, the appearance and attitude of mice deteriorated after 24 h, and weight loss exceeded 15%. Plasma osmolality was increased, and plasma volume decreased with each time interval. Plasma corticosterone concentration increased with duration of deprivation. There were no differences in any dehydration measures between mice housed in conventional static cages or ventilated racks. Chronic water restriction induced no significant changes compared with ad libitum availability. We conclude that acute water deprivation of as long as 24 h produces robust physiologic changes; however, deprivation in excess of 24 h is not recommended in light of apparent animal distress. Although clearly thirsty, mice adapt to chronic water restriction of as much as 50% of the ad libitum daily ration that is imposed over an interval of as long as 8 d. PMID:23849404

Bekkevold, Christine M; Robertson, Kimberly L; Reinhard, Mary K; Battles, August H; Rowland, Neil E

2013-01-01

186

Mild to moderate dehydration combined with moderate alcohol consumption has no influence on simulated driving performance.  

PubMed

Objective: Many people consume alcoholic beverages following a period of physical activity that results in fluid loss through sweating (e.g., after sports, work). Adequate rehydration following physical activity may not occur, consequently resulting in the consumption of alcohol in a dehydrated state. This may have serious implications for the safety of individuals operating motor vehicles. Therefore, this study investigated the impact of mild-moderate dehydration in combination with moderate alcohol consumption on simulated driving performance. Methods: Fourteen healthy males participated in a placebo-controlled crossover design study involving 4 experimental trials (separated by 4 days or more). In each trial, participants were dehydrated by ?2 percent body mass through exercise. After a 30-min recovery, participants completed a 15-min computerized simulated driving task (drive 1). In 2 of the trials, participants were provided with water equivalent to either 50 or 150 percent body mass loss and also received salt capsules (NaCl, 50 mmol/L). A set volume of alcohol or placebo was then consumed in each trial, incorporating the conditions: dehydration-placebo (DP), dehydration-alcohol (DA), partial rehydration-alcohol (PA), and full rehydration-alcohol (FA). The volume of the alcoholic beverage was individually calculated and intended to raise the blood alcohol content (BAC) to ?0.05 percent. The same driving task was then readministered (drive 2). Primary outcome measures of driving consisted of standard deviation of lateral position (SDLP), number of side and center line crossings (LC), number of failures to stop at red traffic signals (FTS), number of impacts/collisions with other vehicles or objects (IMP), and time to collision with a specified lead vehicle (TTC). In addition, reaction time (RT) and incorrect inhibition response (IIR) behavior to critical events were collected throughout each experimental drive. Subjective ratings of mood and estimates of alcohol intoxication and driving impairment were also recorded in each trial. Results: No effects of trial condition were observed on any of the driving performance measures or on subjective ratings of mood, alcohol intoxication, and driving impairment. SDLP was higher following the consumption of alcohol compared to the placebo trial. However, no differences in SDLP were recorded between the alcohol trials, indicating that hydration level had no observable interaction with alcohol to influence SDLP performance. Conclusions: Overall, it appears that dehydration does not exacerbate impairment in driving performance caused by mild-moderate alcohol intoxication. Further research is required to clarify the effects of alcohol and dehydration at various alcohol doses. PMID:24867575

Irwin, Christopher; Leveritt, Michael; Shum, David H K; Desbrow, Ben

2014-08-18

187

Optimizing process vacuum condensers  

SciTech Connect

Vacuum condensers play a critical role in supporting vacuum processing operations. Although they may appear similar to atmospheric units, vacuum condensers have their own special designs, considerations and installation needs. By adding vacuum condensers, precondensers and intercondensers, system cost efficiency can be optimized. Vacuum-condensing systems permit reclamation of high-value product by use of a precondenser, or reduce operating costs with intercondensers. A precondenser placed between the vacuum vessel and ejector system will recover valuable process vapors and reduce vapor load to an ejector system--minimizing the system`s capital and operating costs. Similarly, an intercondenser positioned between ejector stages can condense motive steam and process vapors and reduce vapor load to downstream ejectors as well as lower capital and operating costs. The paper describes vacuum condenser systems, types of vacuum condensers, shellside condensing, tubeside condensing, noncondensable gases, precondenser pressure drop, system interdependency, equipment installation, and equipment layout.

Lines, J.R.; Tice, D.W. [Graham Mfg. Co., Batavia, NY (United States)

1997-09-01

188

Methanol and 2-methyl-1-propanol (isobutanol) coupling to ethers and dehydration over Nafion H: Selectivity, kinetics, and mechanism  

SciTech Connect

The dehydration of a mixture of methanol and isobutanol has been studied over the sulfonic acid Nafion H catalyst. Dehydration products consisted of dimethyl ether (DME), di-isobutyl ether (DIBE), methyl-isobutyl ether (MIBE), butenes, octenes, and traces of methyl-tertiarybutyl ether (MTBE). At low temperatures and high alcohol pressures (P [ge] 150 kPa), the dehydration product slate was dominated by ether formation with selectivity within the ethers significantly in favor of the mixed ether, MIBE. The rates of ether and butene formation as a function of alcohol pressure could be described by Langmuir-Hinshelwood kinetics in which competitive adsorption of the two alcohols on the surface -SO[sub 3]H sites was the dominant feature. The kinetics of isobutanol dehydration to isobutene were consistent with a dual-site mechanism involving the cooperative action of a free surface -SO[sub 3]H site and an adjacent adsorbed alcohol molecule. Dehydration to ethers was consistent with the reaction of two adsorbed alcohols, also by a dual-site mechanism. As a consequence, dehydration to symmetric ethers showed saturation-type kinetics as a function of alcohol pressure, while the rate of isobutene formation went through a distinct maximum. Due to the competitive adsorption of methanol and isobutanol, the mixed ether MIBE was formed at a maximum rate with an optimum ratio of partial pressures of the two alcohols. The high selectivity to MIBE was explained by stronger adsorption of isobutanol on the catalyst surface as compared to methanol. The absence of MTBE and the predominance of products such as MIBE and 2,5-dimethylhexene suggests that dehydration to give free carbenium ions that subsequently rearrange to the more stable tertiary intermediate was not occurring. It was proposed that the alcohols react with the -SO[sub 3]H groups to give oxonium ions or esters. These intermediates couple to give the product ethers or octenes. 24 refs., 13 figs., 1 tab.

Nunan, J.G.; Klier, K.; Herman, R.G. (Lehigh Univ., Bethlehem, PA (United States))

1993-02-01

189

Photo-initiated Reactions of Methylglyoxal and Other Organics in the Condensed Phase: Impact on UV-vis Absorbance of Aerosols  

NASA Astrophysics Data System (ADS)

Solar ultraviolet-visible (UV-vis) radiation can initiate photochemical reactions of organic compounds in aerosols that may be important sinks for the particle-phase reactants as well as sources for new organic products in both the particle and gas phases. Furthermore, the optical characteristics of organic aerosols may be altered by the photochemical destruction (or production) of organics that absorb solar UV-vis radiation. Here we present laboratory results that demonstrate that solar irradiation (simulated with a xenon lamp) of solutions of organic compounds can either increase or decrease the UV-vis absorbance of the solution depending on conditions--namely acidity. For example, UV-vis irradiation of aqueous solutions of methylglyoxal resulted in solutions that absorbed less UV radiation than the original, while irradiation of methylglyoxal in concentrated (~50wt%) sulfuric acid solutions resulted in solutions that absorbed more UV radiation. In order to identify the molecules and/or reactions responsible for these changes in optical properties, we used High Performance Liquid Chromatography (HPLC) and Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR) spectroscopy to monitor loss of organic reactant and the appearance of photo-products. These results are used to evaluate the potential impacts of particle-phase organic photochemistry on the optical properties of atmospheric organic aerosols.

Brown, L. C.; Rodgers, J. M.; Iraci, L. T.; van Wyngarden, A. L.

2008-12-01

190

Brønsted Instead of Lewis Acidity in Functionalized MIL-101Cr MOFs for Efficient Heterogeneous (nano-MOF) Catalysis in the Condensation Reaction of Aldehydes with Alcohols.  

PubMed

Porous chromium(III) 2-nitro-, 2-amino-, and nonfunctionalized terephthalate (MIL-101Cr) metal organic frameworks are heterogeneous catalysts for diacetal formation from benzaldehyde and methanol (B-M reaction) as well as other aldehydes and alcohols. MIL-101Cr-NO2 obtained by direct reaction between CrO3 and 2-nitro-terephthalate showed the highest activity with 99% conversion in the B-M reaction in 90 min and turnover numbers of 114. The activity decreased in the order MIL-101Cr-NO2 > MIL-101Cr > MIL-101Cr-NH2. Within different samples of nonfunctionalized MIL-101Cr the activity increased with surface area. Methanol gas sorption of the different MIL materials correlates with the BET surface area and pore volume but not with the diacetalization activity. Benzaldehyde adsorption from heptane showed no significant difference for the different MILs. Gas sorption studies of CD3CN to probe for a higher Lewis acidity in MIL-101Cr-NO2 remained inconclusive. A high B-M catalytic activity of wet MIL-101Cr-NO2 excluded significant contributions from coordinatively unsaturated Lewis-acid sites. pH measurements of methanol dispersions of the MIL materials gave the most acidic pH (as low as 1.9) for MIL-101Cr-NO2, which significantly increased over MIL-101Cr (3.0) to MIL-101Cr-NH2 (3.3). The increase in acidity is of short range or a surface effect to the heterogeneous MIL particles as protons dissociating from the polarized aqua ligands (Cr-OH2) have to stay near the insoluble counteranionic framework. The variation in Brønsted acidity of MIL-101Cr-NO2 > MIL-101Cr ? MIL-101Cr-NH2 correlates with the withdrawing effect of NO2 and the diacetalization activity. The catalytic B-M activity of soluble, substitution-inert, and acidic Cr(NO3)3·9H2O supports the Brønsted-acid effect of the MIL materials. Filtration and centrifugation experiments with MIL-101Cr-NO2 revealed that about 2/3 of the catalytic activity comes from nano-MOF particles with a diameter below 200 nm. The MIL-101Cr-NO2 catalysts can be recycled five times with very little loss in activity. The diacetalization activity of MIL-101Cr-NO2 decreases with the alcohol chain length from methanol over ethanol, n-propanol, n-butanol, to almost inactive n-pentanol, while conversions for benzaldehyde, paratolylaldehyde, 4-chlorobenzaldehyde, and cyclohexanone all reach 90% or more after 90 min. PMID:25006999

Herbst, Annika; Khutia, Anupam; Janiak, Christoph

2014-07-21

191

Dehydration-melting of amphibolite at 10 kbar: the effects of temperature and time  

Microsoft Academic Search

We have simulated the dehydration-melting of a natural, low-K, calcic amphibolite (67.4% hornblende, 32.5% anorthite) in piston-cylinder experiments at 10 kbar and 750–1000°C, for 1–9 days. The solidus temperature is lower than 750°C; garnet appears at 850°C. The overall reaction is: Hb+P?L+Cpx+Al-Hb+Ca-Hb+Ga+Opx. Three stages of reaction are: (1) melting dominated by the growth of clinopyroxene and garnet, with little change

Michael B. Wolf; Peter J. Wyllie

1994-01-01

192

Inorganic compounds for passive solar energy storage: Solid-state dehydration materials and high specific heat materials  

NASA Astrophysics Data System (ADS)

Two classes of hydrated inorganic salts have been studied to assess their potential as materials for passive solar energy storage. The materials are part of the quaternary system CaO-Al2O3-SO3-H2O and related chemical systems, and the two classes are typified by ettringite, a trisubstituted salt, and Friedel's salt, a monosubstituted salt. The trisubstituted salts were studied for their possible application in latent heat storage, utilizing a low-temperature dehydration reaction, and both classes were studies for their application in sensible heat storage. In order to assess their potential for energy storage, the salts have been synthesized, characterized by several analytical techniques, and thermal properties measured. The dehydration data of that the trisubstituted salts vary somewhat with chemical composition, with the temperature of the onset of dehydration ranging from 6(0)C to 33(0)C, and enthalpy changes on dehydration ranging from 60 to 200 cal/g. Heat capacity is less variable with composition; values for the trisubstituted phases are 30 cal/g/(0)C and for the monosubstituted phases between 0.23 and 0.28 cal/g/(0)C. Preliminary experiments indicate that the dehydration is reversible, and suggest that the materials might have additional potential as solar desiccant materials. These thermal data demonstrate the trisubstituted salts have potential as latent heat storage materials, and that both classes of salts have potential as sensible heat storage materials.

Struble, L. J.; Brown, P. W.

1986-04-01

193

Recent developments in osmotic dehydration: methods to enhance mass transfer  

Microsoft Academic Search

Osmotic dehydration, due to its energy and quality related advantages, is gaining popularity as a complimentary processing step in the chain of integrated food processing. Generally, osmotic dehydration being a slow process, there has been a need for additional ways to increase the mass transfer without adversely affecting the quality. This gave the required motivation for many recent advances in

N. K. Rastogi; K. S. M. S. Raghavarao; K. Niranjan; D. Knorr

2002-01-01

194

Vacuum impregnation for development of new dehydrated products  

Microsoft Academic Search

Vacuum impregnation (VI) of structured foods implies the partial release of gas from pores and its substitution by an external liquid. Therefore, important changes in physicochemical and structural properties take place in the food and these affect its behavior in drying operations (air-drying (AD) and\\/or osmotic dehydration (OD)). The adequate control of VI prior to dehydration may be used as

Pedro Fito; Amparo Chiralt; José M Barat; Ana Andrés; Javier Mart??nez-Monzó; Nuria Mart??nez-Navarrete

2001-01-01

195

Characterization of the Thermal Dehydration of Zirconium Oxide Halide Octahydrates.  

National Technical Information Service (NTIS)

The compounds ZrOX2.8H2O (X = Cl, Br) dehydrate thermally in a stepwise manner to the respective hexahydrates, tetrahydrates, and finally ZrO2. Dehydration is complete at 700C. The intermediate hydrates have been isolated and characterized. Several region...

D. A. Powers H. B. Gray

1972-01-01

196

Retention of nutrients in green leafy vegetables on dehydration.  

PubMed

The objective of the study was to investigate the influence of dehydration on nutrient composition of Amaranthus gangeticus, Chenopodium album, Centella asiatica, Amaranthus tricolor and Trigonella foenum graecum. The green leafy vegetables (GLV) were steam blanched for 5 min after pretreatment and dried in an oven at 60 °C for 10-12 h. The fresh and dehydrated samples were analyzed for selected proximate constituents, vitamins, minerals, antinutrients and dialyzable minerals. Dehydration seems to have little effect on the proximate, mineral and antinutrient content of the GLV. Among the vitamins, retention of ascorbic acid was 1-14%, thiamine 22-71%, total carotene 49-73% and ?-carotene 20-69% respectively, of their initial content. Dialyzable iron and calcium in the fresh vegetables ranged between 0.21-3.5 mg and 15.36-81.33 mg/100 g respectively, which reduced to 0.05-0.53 mg and 6.94-58.15 mg/100 g on dehydration. Dehydration seems to be the simplest convenient technology for preserving these sources of micronutrients, especially when they are abundantly available. Irrespective of the losses of vitamins that take place during dehydration, dehydrated GLV are a concentrated natural source of micronutrients and they can be used in product formulations. Value addition of traditional products with dehydrated GLV can be advocated as a feasible food-based approach to combat micronutrient malnutrition. PMID:24425998

Gupta, Sheetal; Gowri, B S; Lakshmi, A Jyothi; Prakash, Jamuna

2013-10-01

197

Geothermal vegetable dehydration at Brady`s Hot Springs, Nevada  

Microsoft Academic Search

This article describes the utilization of the Brady`s Springs geothermal resource for heat generation used in the food dehydration process. This geothermal system is located in the Forty-Mile Desert area of Nevada. Geothermal Food Processors, Inc. of Reno, Nevada started construction of the geothermal vegetable dehydration plant in 1978, and the plant started operations in 1979. The industrial process of

1994-01-01

198

Osmotic dehydration of Aloe vera ( Aloe barbadensis Miller)  

Microsoft Academic Search

Aloe vera possess immunomodulatory, anti-inflammatory, antibacteria effects and wound and burn healing properties, but it is a very unstable product due to its high water content. Osmotic dehydration can be used to obtain stable products from aloe. In this work the effect of osmotic dehydration (OD) on Aloe vera (Aloe barbadensis Miller) leaves was studied. Peeled and unpeeled Aloe vera

P. García-Segovia; C. Mognetti; A. Andrés-Bello; J. Martínez-Monzó

2010-01-01

199

Flavour quality of dehydrated lime [ Citrus aurantifolia (Christm.) Swingle  

Microsoft Academic Search

The hydro-distilled volatile oils of fresh and dehydrated lime [Citrus aurantifolia (Christm.) Swingle] fruit were subjected to GC and GC–MS. A total of 32 compounds, constituting > 98% of the volatiles of fresh lime fruit, were identified. Five sesquiterpene hydrocarbons and two sesquiterpene alcohols were found and identified for the first time in lime fruit. The volatiles from the dehydrated

A. Ramesh Yadav; A. S. Chauhan; M. N. Rekha; L. J. M. Rao; R. S. Ramteke

2004-01-01

200

Dehydration of serpentinized slab mantle: Seismic evidence from southwest Japan  

Microsoft Academic Search

The seismicity in the subducting Philippine Sea slab (PHS) beneath southwest Japan shows a variety of modes of occurrence. We try to explain this variety on the basis of dehydration embrittlement in the subducting oceanic crust and\\/or mantle. The PHS subducting along the Nankai Trough shows commonly a single narrow seismic zone shallower than 60 km, which may reflect dehydration

Tetsuzo Seno; Dapeng Zhao; Yoji Kobayashi; Masao Nakamura

2001-01-01

201

Corannulene ethers via Ullmann condensation.  

PubMed

Penta-aryloxycorannulene derivatives, which were previously considered difficult synthetic targets, are efficiently achieved via the Cu(I)-catalyzed Ullmann condensation reaction between 1,3,5,7,9-pentachlorocorannulene and a broad variety of substituted phenols. The reaction proceeds under air and mild conditions that are compatible even with 4-bromophenol. These findings open new avenues for easy preparation of other symmetrically substituted pentagonal building blocks that can be used for the preparation of new materials and new supramolecular architectures. PMID:19905024

Gershoni-Poranne, Renana; Pappo, Doron; Solel, Ephrath; Keinan, Ehud

2009-11-19

202

Avoiding failed reconstitution of ultradeformable liposomes upon dehydration.  

PubMed

Although freeze-drying is an ordinarily used technique to dehydrate conventional liposomes, we have found that ultradeformable liposomes (UDLs) suffered irreversible aggregation when rehydrated upon freeze-drying (99.4% water elimination), even in high sugar content (4/1 sucrose/lipid mass ratio). When dehydrated by speed vac and vacuum drying, two alternative techniques that rendered less pronounced dehydration (94.27 and 96.2% water elimination, respectively) and avoid ice formation, however, UDL could only be successfully rehydrated when vacuum dried in 4/1 sucrose/lipid mass ratios. Conventional liposomes, on the other hand, were successfully reconstituted upon dehydrated by the three methods in lower sugar content (2/1 sucrose/lipid mass ratio). These results indicated that the 27% mole sodium cholate within the UDL lipid matrix was responsible for a greater and differential mechanical sensitivity of the bilayers to the different dehydration stress, as compared to conventional liposomes. PMID:19429279

Montanari, J; Roncaglia, D I; Lado, L A; Morilla, M J; Romero, E L

2009-05-01

203

Dehydration of xylose to furfural over MCM-41-supported niobium-oxide catalysts.  

PubMed

A series of silica-based MCM-41-supported niobium-oxide catalysts are prepared, characterized by using XRD, N2 adsorption-desorption, X-ray photoelectron spectroscopy, Raman spectroscopy, and pyridine adsorption coupled to FTIR spectroscopy, and tested for the dehydration of D-xylose to furfural. Under the operating conditions used all materials are active in the dehydration of xylose to furfural (excluding the MCM-41 silica support). The xylose conversion increases with increasing Nb2 O5 content. At a loading of 16 wt % Nb2 O5 , 74.5 % conversion and a furfural yield of 36.5 % is achieved at 170 °C, after 180 min reaction time. Moreover, xylose conversion and furfural yield increase with the reaction time and temperature, attaining 82.8 and 46.2 %, respectively, at 190 °C and after 100 min reaction time. Notably, the presence of NaCl in the reaction medium further increases the furfural yield (59.9 % at 170 °C after 180 min reaction time). Moreover, catalyst reutilization is demonstrated by performing at least three runs with no loss of catalytic activity and without the requirement for an intermediate regeneration step. No significant niobium leaching is observed, and a relationship between the structure of the catalyst and the activity is proposed. PMID:23512820

García-Sancho, Cristina; Sádaba, Irantzu; Moreno-Tost, Ramón; Mérida-Robles, Josefa; Santamaría-González, José; López-Granados, Manuel; Maireles-Torres, Pedro

2013-04-01

204

Dehydration of Synthetic Hydrated Kaolinites: A Model for the Dehydration of Halloysite(10?)  

Microsoft Academic Search

Several hydrates can be synthesized from well-crystallized kaolinites; of importance to the present work are a 10-Zk hydrate (called the QS-10 hydrate), an 8.6-~k hydrate, and two kinds of partially dehydrated mixed-layer hydrates. One kind is a series of unstable materials with d(001) varying contin- uously between 10 and 8.6\\/~, and the other kind is stable with d(001) approximately centered

P. M. Costanzo; R. F. GIESE

1985-01-01

205

PL CONDENSER EVALUATION REPORT  

Microsoft Academic Search

The air-cooled steam condenser and sub-cooler developed for use with the ; PL series of natural circulation boiling water nuclear power plants are designed ; to condense 13,000 lb\\/hr at 10% moisture at 15 in. Hg and to subcool the ; condensate to 100 deg F at an ambient temperature of 60 deg F. The design heat ; load at

V. R. Mardoc; R. G. Young

1961-01-01

206

Efficient condensate removal  

Microsoft Academic Search

Achieving stable control of product temperatures on reboilers and other steam\\/product heat exchangers has long been a problem area where conventional steam control and condensate trapping methods were used. Application of a non-electric condensate pump and steam trap sidesteps the problem. Removal of condenser under all conditions, from full load to zero load, is readily achieved. Steam flow control then

Armer

1988-01-01

207

Condensation in Microchannels  

Microsoft Academic Search

Condensation in microchannels has applications in a wide variety of advanced microthermal devices. Presented here is a review of both experimental and theoretical analyses of condensation in these microchannels, with special attention given to the effects of channel diameter and surface conditions on the flow regimes of condensing flows occurring in these channels. This review suggests that surface tension, rather

Yongping Chen; Mingheng Shi; Ping Cheng; G. P. Peterson

2008-01-01

208

Cluster condensation reactions. Transformation of two triangular trinuclear clusters into a hexanuclear cluster containing a novel edge-fused bitetrahedral structure  

SciTech Connect

The carbene-containing cluster complex Os/sub 3/(CO)/sub 9/(C(H)NMe/sub 2/)..mu..-SMe)(..mu..-H) (1) was prepared in 56% yield from the reaction of Os/sub 3/(CO)/sub 10/(..mu..-SMe)(..mu..-H) with CH/sub 2/(NMe/sub 2/)/sub 2/. UV irradiation of 1 yielded the complex Os/sub 3/(CO)/sub 8/(..mu..-CNMe/sub 2/)(..mu..-SMe)(..mu..-H)/sub 2/ (2) in 68% yield. Compound 2 contains a bridging (dimethylamino)carbyne ligand that was formed by an ..cap alpha..-CH activation of the carbene ligand in 1. Thermal decarbonylation of 2 resulted in the formation of the hexaosmium cluster complex Os/sub 6/-(CO)/sub 12/(..mu..-CNMe/sub 2/)/sub 2/(..mu..-SMe)/sub 2/(..mu..-H)/sub 2/ (3) in 65% yield. Compound 3 was characterized by a single-crystal X-ray diffraction analysis. The structure was solved by a combination of direct methods and difference Fourier techniques and was refined (2701 reflections) to the final values of the residuals R = 0.048 and R/sub w/ = 0.050. The structure consists of six osmium atoms arranged in the form of two tetrahedral clusters that have one edge in common. There are two bridging (dimethylamino)carbyne ligands and two triply bridging methanethiolato ligands that appear to serve as three-electron donors instead of the usual five-electron-donor configuration. 18 references, 3 figures, 4 tables.

Adams, R.D.; Babin, J.E.

1987-04-08

209

Ethanol dehydration to ethylene in a stratified autothermal millisecond reactor.  

PubMed

The concurrent decomposition and deoxygenation of ethanol was accomplished in a stratified reactor with 50-80 ms contact times. The stratified reactor comprised an upstream oxidation zone that contained Pt-coated Al(2)O(3) beads and a downstream dehydration zone consisting of H-ZSM-5 zeolite films deposited on Al(2)O(3) monoliths. Ethanol conversion, product selectivity, and reactor temperature profiles were measured for a range of fuel:oxygen ratios for two autothermal reactor configurations using two different sacrificial fuel mixtures: a parallel hydrogen-ethanol feed system and a series methane-ethanol feed system. Increasing the amount of oxygen relative to the fuel resulted in a monotonic increase in ethanol conversion in both reaction zones. The majority of the converted carbon was in the form of ethylene, where the ethanol carbon-carbon bonds stayed intact while the oxygen was removed. Over 90% yield of ethylene was achieved by using methane as a sacrificial fuel. These results demonstrate that noble metals can be successfully paired with zeolites to create a stratified autothermal reactor capable of removing oxygen from biomass model compounds in a compact, continuous flow system that can be configured to have multiple feed inputs, depending on process restrictions. PMID:21834091

Skinner, Michael J; Michor, Edward L; Fan, Wei; Tsapatsis, Michael; Bhan, Aditya; Schmidt, Lanny D

2011-08-22

210

In utero extracellular dehydration modifies thirst in neonatal rats.  

PubMed

The main aim of this study was to investigate the effect of maternal extracellular dehydration during pregnancy in rats on the development of thirst mechanisms in the offspring. Pregnant rats underwent three episodes of extracellular dehydration induced by injecting s.c. 15ml/kg b.w. of a 20% wt/vol solution of polyethylene glycol (PEG) in saline. The treatment given on days 14, 17 and 20 postconception is thought to induce endocrine and natriophilic responses similar to those elicited by vomiting. The offspring were tested for their responses to three different thirst stimuli at 2, 4 and 6 days of age. Like the controls, the offspring from PEG-treated mothers responded to beta stimulation by isoproterenol at 6 days of age. However, they failed to respond to cellular dehydration (NaCl hypertonic injection) at 2 days of age or to extracellular dehydration by PEG on day 4. In conclusion, offspring exposed to in utero extracellular dehydration do not respond to cellular dehydration at 2 days of age or to extracellular dehydration at 4 days of age, whereas control pups had already developed an appropriate response to these stimuli. According to these results, it therefore seems that in utero conditions determine the development of adaptive thirst responses in offspring. PMID:18524414

Perillan, C; Costales, M; Vijande, M; Arguelles, J

2008-11-01

211

Immobilisation increases yeast cells' resistance to dehydration-rehydration treatment.  

PubMed

This study was performed with the goal of revealing if the dehydration procedure used in our new immobilisation method noticeably decreases the viability of yeast cells in immobilised preparations. Various yeasts were used in this research: Saccharomyces cerevisiae cells that were rather sensitive to dehydration and had been aerobically grown in an ethanol-containing medium, a recombinant strain of S. cerevisiae grown in aerobic conditions which were completely non-resistant to dehydration and an anaerobically grown bakers' yeast strain S. cerevisiae, as well as a fairly resistant Pichia pastoris strain. Experiments performed showed that immobilisation of all these strains essentially increased their resistance to a dehydration-rehydration treatment. The increase of cells' viability (compared with control cells dehydrated in similar conditions) was from 30 to 60%. It is concluded that a new immobilisation method, which includes a dehydration stage, does not lead to an essential loss of yeast cell viability. Correspondingly, there is no risk of losing the biotechnological activities of immobilised preparations. The possibility of producing dry, active yeast preparations is shown, for those strains that are very sensitive to dehydration and which can be used in biotechnology in an immobilised form. Finally, the immobilisation approach can be used for the development of efficient methods for the storage of recombinant yeast strains. PMID:24886905

Borovikova, Diana; Rozenfelde, Linda; Pavlovska, Ilona; Rapoport, Alexander

2014-08-20

212

Transient dehydration of lungs in tail-suspended rats  

NASA Technical Reports Server (NTRS)

The fluid balance in the lungs of rats exposed to head-down tilt is examined. Six Munich-Wister rats were suspended for 7 days and 10 Sprague-Dawley rats for 14 days using the technique of Morey (1979). The water contents of the lungs of the suspended and a control group are calculated and compared. The data reveal that the two-days suspended rats had dehydrated lungs; however, the lungs of the 14-day suspended and control group rats were similar. It is noted that the dehydration in the 2-day suspended rats is caused by general dehydration not the head-tilt position.

Hargens, A. R.; Steskal, J.; Morey-Holton, E. R.

1985-01-01

213

Thermal dehydration of magnesium acetate tetrahydrate: formation and in situ crystallization of anhydrous glass.  

PubMed

The kinetics and mechanism of the thermal dehydration of magnesium acetate tetrahydrate were investigated as a typical example of the glass formation process via the thermal decomposition of solids. Formation of an intermediate fluid phase was identified as the characteristic phenomenon responsible for the formation of anhydrous glass. Thermal dehydration from the surface fluid layer regulates the zero-order-like rate behavior of the mass-loss process with an apparent activation energy E(a) ? 70-80 kJ mol(-1). Because of variations in the mechanism of release of the water vapor with changes in the reaction temperature range, the mass-loss behavior is largely dependent on the particle size of the sample and heating conditions. The formation of hollow anhydrous glass is the novel finding of the present study. The mechanism of formation is discussed in terms of complementary interpretations of the morphological changes and kinetic behavior of the thermal dehydration. On further heating, the as-produced anhydrous glass exhibits a glass transition phenomenon at approximately 470 K with an E(a) ? 550-560 kJ mol(-1), and subsequently crystallizes via the three-dimensional growth of nuclei controlled by diffusion. The crystallization process is characterized by an E(a) ? 280 kJ mol(-1) and an enthalpy change ?H = -13.3 kJ mol(-1), resulting in the formation of smaller, rounded particles of crystalline anhydrate. PMID:23157569

Koga, Nobuyoshi; Suzuki, Yasumichi; Tatsuoka, Tomoyuki

2012-12-13

214

Condensed phase preparation of 2,3-pentanedione  

DOEpatents

A condensed phase process for the preparation of purified 2,3-pentanedione from lactic acid and an alkali metal lactate is described. The process uses elevated temperatures between about 200.degree. to 360.degree. C. for heating a reaction mixture of lactic acid and an alkali metal lactate to produce the 2,3-pentanedione in a reaction vessel. The 2,3-pentanedione produced is vaporized from the reaction vessel and condensed with water.

Miller, Dennis J. (Okemos, MI); Perry, Scott M. (Beaumont, TX); Fanson, Paul T. (Stockbridge, MI); Jackson, James E. (Haslett, MI)

1998-01-01

215

Dehydration of n-butanol on zeolite H-ZSM-5 and amorphous aluminosilicate: Detailed mechanistic study and the effect of pore confinement  

SciTech Connect

This study of the catalytic dehydration of n-butanol on zeolite H-ZSM-5 and amorphous aluminosilicate confirms the reaction scheme proposed earlier by the authors for isobutanol dehydration. The rate constant for n-butanol dehydration on H-ZSM-5 (determined from in situ FTIR kinetic studies by monitoring the growth of the water deformation peak at 1640 cm{sup -1}) is shown to be the true dehydration rate constant (1.7 x 10{sup -4}s{sup -1} at 100{degrees}C). On the other hand, the rate constants determined from GC steady-state kinetic studies (temperature interval 105-185{degrees}C) are effective ones, giving activation energies of 22{+-}2 kcal/mol and 33{+-}2 kcal/mol for complete dehydration and dehydration to butene only, respectively. By studying the dehydration reaction under different conditions (flow and static reactors, steady-state and non-steady-state regimes) and on samples with rather similar acid strengths but different porous systems (H-ZSM-5-microporous channels with diameter {approximately}5.5 {angstrom}, and amorphous aluminosilicate-pores of average diameter {approximately}50 {angstrom}), it was shown that depending on the concentration of butanol in the immediate vicinity of the active alkoxide intermediate {exists}-OC{sub 4}H{sub 9}, different reaction paths are utilized. High concentrations of alcohol favor ether formation, whereas low ones favour butene. This also explains the so-called {open_quotes}stop effect{close_quotes} observed in GC experiments, where an increase in the rate of butene formation occurs when the flow of alcohol is stopped and replaced with a flow of pure helium. Here, decreasing the concentration of alcohol in the micropores results in more of the alkoxide intermediate transforming to butene rather than to ether (which was the case at steady state). 28 refs., 17 figs., 3 tabs.

Makarova, M.A.; Paukshtis, E.A.; Zamaraev, K.I. [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation)] [and others] [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation); and others

1994-09-01

216

Renal tubular vasopressin receptors downregulated by dehydration  

SciTech Connect

Receptors for arginine vasopressin (AVP) were characterized in tubular epithelial basolateral membranes (BL membranes) prepared from the kidneys of male Spraque-Dawley rats. Association of ({sup 3}H)AVP was rapid, reversible, and specific. Saturation studies revealed a single class of saturable binding sites with a maximal binding (B{sub max}) of 184 {plus minus} 15 fmol/mg protein. The V{sub 2} receptor antagonist was more than 3,700 times as effective in displacing ({sup 3}H)AVP than was the V{sub 1} antagonist. To investigate the physiological regulation of vasopressin receptors, the effects of elevated levels of circulating AVP on receptor characteristics were studied. Seventy-two-hour water deprivation significantly elevated plasma osmolality and caused an 11.5-fold increase in plasma (AVP). Scatchard analysis revealed a 38% decreased in the number of AVP receptors on the BL membranes from dehydrated animals. The high-affinity binding sites on the BL membranes fit the pharmacological profile for adenylate cyclase-linked vasopressin receptors (V{sub 2}), which mediate the antidiuretic action of the hormone. The authors conclude that physiologically elevated levels of AVP can downregulate vasopressin receptors in the kidney.

Steiner, M.; Phillips, M.I. (Univ. of Florida, Gainesville (USA))

1988-03-01

217

Comparison of clinical and biochemical markers of dehydration with the clinical dehydration scale in children: a case comparison trial  

PubMed Central

Background The clinical dehydration scale (CDS) is a quick, easy-to-use tool with 4 clinical items and a score of 1–8 that serves to classify dehydration in children with gastroenteritis as no, some or moderate/severe dehydration. Studies validating the CDS (Friedman JN) with a comparison group remain elusive. We hypothesized that the CDS correlates with a wide spectrum of established markers of dehydration, making it an appropriate and easy-to-use clinical tool. Methods This study was designed as a prospective double-cohort trial in a single tertiary care center. Children with diarrhea and vomiting, who clinically required intravenous fluids for rehydration, were compared with minor trauma patients who required intravenous needling for conscious sedation. We compared the CDS with clinical and urinary markers (urinary electrolytes, proteins, ratios and fractional excretions) for dehydration in both groups using receiver operating characteristic (ROC) curves to determine the area under the curve (AUC). Results We enrolled 73 children (male?=?36) in the dehydration group and 143 (male?=?105) in the comparison group. Median age was 32 months (range 3–214) in the dehydration and 96 months (range 2.6-214 months, p?dehydration group and 0 in the comparison group (p?dehydrated group: difference in heart rate, diastolic blood pressure, urine sodium/potassium ratio, urine sodium, fractional sodium excretion, serum bicarbonate, and creatinine measurements. The best markers for dehydration were urine Na and serum bicarbonate (ROC AUC?=?0.798 and 0.821, respectively). CDS was most closely correlated with serum bicarbonate (Pearson r?=?-0.3696, p?=?0.002). Conclusion Although serum bicarbonate is not the gold standard for dehydration, this study provides further evidence for the usefulness of the CDS as a dehydration marker in children. Trial registration Registered at ClinicalTrials.gov (NCT00462527) on April 18, 2007.

2014-01-01

218

25. BUILDING NO. 527, DEHYDRATING HOUSE, DETAIL OF SOLVENT RECOVERY ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

25. BUILDING NO. 527, DEHYDRATING HOUSE, DETAIL OF SOLVENT RECOVERY DUCTS. SOUTH SIDE OF BUILDING. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

219

Effects of dehydration on performance in man: Annotated bibliography  

NASA Technical Reports Server (NTRS)

A compilation of studies on the effect of dehydration on human performance and related physiological mechanisms. The annotations are listed in alphabetical order by first author and cover material through June 1973.

Greenleaf, J. E.

1973-01-01

220

NOVEL POLYMERIC MEMBRANE FOR DEHYDRATION OF ORGANIC SOLVENTS  

EPA Science Inventory

Pervaporation has emerged as an economically viable alternative technology for dehydration of organic solvents, removal of organic compounds and organic/organic separations. Development of a membrane system with suitable flux and selectivity characteristics plays a critical role...

221

A Study of the Microbiology of Selected Dehydrated Food Products.  

National Technical Information Service (NTIS)

Progress is reported on a bacteriological survey of 35 dehydrated foods. The following microbial groups are enumerated: (1) total aerobic (2) coliform (3) anaerobic spores and (4) Salmonella. In addition, the prefreezing, freezing and drying effects on su...

F. E. Wells

1964-01-01

222

Dehydration of hydrogen contact lenses in vitro and in vivo.  

PubMed

An attempt was made to derive a model for predicting the extent of hydrogel lens dehydration in vivo (delta Wv) by using a contact lens refractometer to (1) measure the water content (W) of eight lenses ranging from 36.5 to 85.8% water before and after 90 min lens wear by six subjects; and (2) measure the rate of dehydration of the same lenses in vitro (delta Wt), in a controlled, randomized, double-masked experiment. A significant correlation was demonstrated between W and the rate of change of delta Wt (the dehydration rate, D), whereby lenses of higher water content dehydrate at a slower rate. No correlation was found between W and delta Wv or between D and delta Wv, thus precluding the development of a predictive model. Possible reasons for this failure, and directions for further research, are discussed. PMID:3269505

Efron, N; Young, G

1988-01-01

223

Effects of Dehydration on Performance in Man: Annotated Bibliography.  

National Technical Information Service (NTIS)

A compilation of studies on the effect of dehydration on human performance and related physiological mechanisms. The annotations are listed in alphabetical order by first author and cover material through June 1973. (Author)

J. E. Greenleaf

1973-01-01

224

Enhancement of Peritoneal Fluid Absorption by Dehydration, Mercaptomerin and Vasopressin.  

National Technical Information Service (NTIS)

The effects of dehydration, mercaptomerin (Thiomerin) and vasopressin on kinetics of transperitoneal fluid and solute absorption were compared in 40 dogs. Rate of absorption of intraperitoneally administered 0.9% saline was measured serially for 6 hrs by ...

L. Shear J. J. Castellot J. H. Shinaberger L. Poole K. G. Barry

1966-01-01

225

EFFECTS OF OSMOTIC DEHYDRATION ON AIR-DRYING AND ON CHARACTERISTICS OF DRIED PUMPKIN (Cucurbita moschata)  

Microsoft Academic Search

Vegetable dehydration by immersion in osmotic solutions followed by air-drying is a technology that has seen a rising interest because it can improve the dehydrated product quality in terms of their sensorial and nutritional characteristics. Effects of osmotic dehydration on physical and chemical properties of dried pumpkin were evaluated. Pumpkin (Cucurbita moschata) slices (0.4 cm thickness) were osmotically dehydrated in

M. A. Mauro; C. C. Garcia; M. Kimura

226

The dehydration process of gypsum under high pressure  

NASA Astrophysics Data System (ADS)

The effects of pressure on the dehydration of gypsum materials were investigated up to 633 K and 25 GPa by using Raman spectroscopy and synchrotron X-ray diffraction with an externally heated diamond anvil cell. At 2.5 GPa, gypsum starts to dehydrate around 428 K, by forming bassanite, CaSO4 hemihydrate, which completely dehydrates to ?-anhydrite at 488 K. All the sulphate modes decrease linearly between 293 and 427 K with temperature coefficients ranging from -0.119 to -0.021 cm-1 K-1, where an abrupt change in the ?3 mode and in the OH-stretching region indicates the beginning of dehydration. Increasing the temperature to 488 K, the OH-stretching modes completely disappear, marking the complete dehydration and formation of ?-anhydrite. Moreover, the sample changes from transparent to opaque to transparent again during the dehydration sequence gypsum-bassanite-?-anhydrite, which irreversibly transforms to ?-anhydrite form at 593 K. These data compared with the dehydration temperature at room pressure indicate that the dehydration temperature increases with pressure with a ? P/? T slope equal to 230 bar/K. Synchrotron X-ray diffraction experiments show similar values of temperature and pressure for the first appearance of bassanite. Evidence of phase transition from ?-anhydrite structure to the monazite type was observed at about 2 GPa under cold compression. On the other hand at the same pressure (2 GPa and 633 K), ?-anhydrite was found, indicating a positive Clausis-Clayperon slope of the transition. This transformation is completely reversible as showed by the Raman spectra on the sample recovered after phase transition.

Comodi, P.; Kurnosov, A.; Nazzareni, S.; Dubrovinsky, L.

2012-01-01

227

External Validation and Comparison of Three Pediatric Clinical Dehydration Scales  

PubMed Central

Objective To prospectively validate three popular clinical dehydration scales and overall physician gestalt in children with vomiting or diarrhea relative to the criterion standard of percent weight change with rehydration. Methods We prospectively enrolled a non-consecutive cohort of children ? 18 years of age with an acute episode of diarrhea or vomiting. Patient weight, clinical scale variables and physician clinical impression, or gestalt, were recorded before and after fluid resuscitation in the emergency department and upon hospital discharge. The percent weight change from presentation to discharge was used to calculate the degree of dehydration, with a weight change of ? 5% considered significant dehydration. Receiver operating characteristics (ROC) curves were constructed for each of the three clinical scales and physician gestalt. Sensitivity and specificity were calculated based on the best cut-points of the ROC curve. Results We approached 209 patients, and of those, 148 were enrolled and 113 patients had complete data for analysis. Of these, 10.6% had significant dehydration based on our criterion standard. The Clinical Dehydration Scale (CDS) and Gorelick scales both had an area under the ROC curve (AUC) statistically different from the reference line with AUCs of 0.72 (95% CI 0.60, 0.84) and 0.71 (95% CI 0.57, 0.85) respectively. The World Health Organization (WHO) scale and physician gestalt had AUCs of 0.61 (95% CI 0.45, 0.77) and 0.61 (0.44, 0.78) respectively, which were not statistically significant. Conclusion The Gorelick scale and Clinical Dehydration Scale were fair predictors of dehydration in children with diarrhea or vomiting. The World Health Organization scale and physician gestalt were not helpful predictors of dehydration in our cohort.

Jauregui, Joshua; Nelson, Daniel; Choo, Esther; Stearns, Branden; Levine, Adam C.; Liebmann, Otto; Shah, Sachita P.

2014-01-01

228

Condensed Matter Physics  

NSDL National Science Digital Library

Founded in 1993 by the Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, the journal Condensed Matter Physics is a peer-reviewed, English-language journal covering such aspects of condensed matter as phase transition theory, statistical mechanics of spin and spin-electron systems, metals and alloys, liquids, solutions, electrolytes, surface phenomena, and plasma physics. Selected issues of Condensed Matter Physics from January 1994 to March 2000 are now available free, online in LaTeX format.

229

An experimental investigation of antigorite dehydration in natural silica-enriched serpentinite  

Microsoft Academic Search

Piston cylinder experiments were performed to constrain the pressure and temperature conditions for two high-pressure antigorite\\u000a dehydration reactions found in silica-enriched serpentinites from Cerro del Almirez (Nevado–Filábride Complex, Betic Cordillera,\\u000a southern Spain). At 630–660°C and pressures greater than 1.6 GPa, antigorite first reacts with talc to form orthopyroxene ± chlorite + fluid.\\u000a We show that orthopyroxene + antigorite is restricted to high-pressure metamorphism of silica-enriched serpentinite. This

José Alberto Padrón-Navarta; Jörg Hermann; Carlos J. Garrido; Vicente López Sánchez-Vizcaíno; María Teresa Gómez-Pugnaire

2010-01-01

230

Whole transcriptome organisation in the dehydrated supraoptic nucleus  

PubMed Central

The supraoptic nucleus (SON) is part of the central osmotic circuitry that synthesises the hormone vasopressin (Avp) and transports it to terminals in the posterior lobe of the pituitary. Following osmotic stress such as dehydration, this tissue undergoes morphological, electrical and transcriptional changes to facilitate the appropriate regulation and release of Avp into the circulation where it conserves water at the level of the kidney. Here, the organisation of the whole transcriptome following dehydration is modelled to fit Zipf's law, a natural power law that holds true for all natural languages, that states if the frequency of word usage is plotted against its rank, then the log linear regression of this is -1. We have applied this model to our previously published euhydrated and dehydrated SON data to observe this trend and how it changes following dehydration. In accordance with other studies, our whole transcriptome data fit well with this model in the euhydrated SON microarrays, but interestingly, fit better in the dehydrated arrays. This trend was observed in a subset of differentially regulated genes and also following network reconstruction using a third-party database that mines public data. We make use of language as a metaphor that helps us philosophise about the role of the whole transcriptome in providing a suitable environment for the delivery of Avp following a survival threat like dehydration.

Hindmarch, C.C.T.; Franses, P.; Goodwin, B.; Murphy, D.

2013-01-01

231

Evaluation of in situ smectite dehydration as a pore water freshening mechanism in the Nankai Trough, offshore southwest Japan  

NASA Astrophysics Data System (ADS)

Pore water freshening has been observed within sediments near the trench at numerous subduction zones. Constraining the relative contributions of long-distance updip flow of freshened fluids and in situ clay dehydration holds important implications for margin-scale fluid flow but remains unresolved because the evolution of pore water chemistry expected due to in situ clay dehydration and the budget of fresh water release have generally not been carefully quantified. Here, we address this problem at the well-studied Nankai Trough offshore SW Japan, where Deep Sea Drilling Project and Ocean Drilling Program drilling have sampled the sedimentary section along two transects: the Muroto transect and the Ashizuri transect, located ˜100 km southwest along strike. Broad low-chloride anomalies with minimum concentrations significantly below typical seawater values were documented along the Muroto transect at Sites 1173, 1174, and 808 and indicate progressive freshening with increasing burial. In contrast, freshening at Site 1177 along the Ashizuri transect (˜24 km seaward of the trench) is characterized by a series of sharp excursions from seawater values. We use a one-dimensional model to simulate sedimentation, thermal history, clay dehydration, and chemical diffusion, in order to quantify the component of pore water freshening attributable to in situ smectite dehydration. We find that simulated reaction progress is in close agreement with observations. The peak magnitude of pore water freshening is reasonably well predicted within the lowermost ˜150 m of the section but consistently underpredicted at intermediate depths. The residual pore water freshening profiles (not explained by smectite dehydration) reach peak magnitudes of ˜50-75 mM and approximately straddle the décollement at Sites 1174 and 808. We suggest that these residuals may reflect either an additional in situ dehydration process or a contribution from updip fluid migration along the fault. Our conclusion differs from that of previous studies, which have suggested that most of the observed geochemical anomaly could be generated by in situ smectite dehydration with as little as 15 wt% initial smectite. This substantial discrepancy is readily explained by the high sensitivity of pore water freshening to assumed porosity at the time of dehydration.

Saffer, Demian M.; McKiernan, Alexander W.

2009-02-01

232

Arctic stratospheric dehydration - Part 2: Microphysical modeling  

NASA Astrophysics Data System (ADS)

Large areas of synoptic-scale ice PSCs (polar stratospheric clouds) distinguished the Arctic winter 2009/2010 from other years and revealed unprecedented evidence of water redistribution in the stratosphere. A unique snapshot of water vapor repartitioning into ice particles was obtained under extremely cold Arctic conditions with temperatures around 183 K. Balloon-borne, aircraft and satellite-based measurements suggest that synoptic-scale ice PSCs and concurrent reductions and enhancements in water vapor are tightly linked with the observed de- and rehydration signatures, respectively. In a companion paper (Part 1), water vapor and aerosol backscatter measurements from the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) and LAPBIAT-II (Lapland Atmosphere-Biosphere Facility) field campaigns have been analyzed in detail. This paper uses a column version of the Zurich Optical and Microphysical box Model (ZOMM) including newly developed NAT (nitric acid trihydrate) and ice nucleation parameterizations. Particle sedimentation is calculated in order to simulate the vertical redistribution of chemical species such as water and nitric acid. Despite limitations given by wind shear and uncertainties in the initial water vapor profile, the column modeling unequivocally shows that (1) accounting for small-scale temperature fluctuations along the trajectories is essential in order to reach agreement between simulated optical cloud properties and observations, and (2) the use of recently developed heterogeneous ice nucleation parameterizations allows the reproduction of the observed signatures of de- and rehydration. Conversely, the vertical redistribution of water measured cannot be explained in terms of homogeneous nucleation of ice clouds, whose particle radii remain too small to cause significant dehydration.

Engel, I.; Luo, B. P.; Khaykin, S. M.; Wienhold, F. G.; Vömel, H.; Kivi, R.; Hoyle, C. R.; Grooß, J.-U.; Pitts, M. C.; Peter, T.

2014-04-01

233

Potassium and Silver Salts of Tungstophosphoric Acid as Catalysts in Dehydration of Ethanol and Hydration of Ethylene  

Microsoft Academic Search

Potassium and silver salts of tungstophosphoric acid (HPW) with varying amounts of the cations KxH3?xPW12O40 and AgxH3?xPW12O40 have been prepared as pure or supported on silica using the incipient wetness method. Their catalytic properties in two reactions have been studied. The vapor-phase dehydration of ethanol carried out in a conventional flow-type reactor under atmospheric pressure at temperatures varying from 398

J. Haber; K. Pamin; L. Matachowski; B. Napruszewska; J. Po?towicz

2002-01-01

234

Materials in Condensing Boilers.  

National Technical Information Service (NTIS)

This is a review of corrosion and materials problems in condensing boilers for oil and gas. In the condensing boiler the fluegas is cooled below the water dewpoint of 45-48sub(o)C with gasoil and 55-58sub(o)C with natural gas. Materials for the three zone...

P. Jansen

1985-01-01

235

Incorporated evaporative condenser  

Microsoft Academic Search

The incorporated evaporative condenser developed in this work comprises of a system of fins, basin of water condensates, circuit pump and system of drop cloud via spraying. In the whole provision a system of drop collector is also included for the minimisation of water escapes now essential for the operation of system. Actually, the present work aims on the development

Michalis Gr. Vrachopoulos; Andronikos E. Filios; Georgios T. Kotsiovelos; Eleftherios D. Kravvaritis

2007-01-01

236

Diamond Formation in association with Deep Mantle Dehydration Zones  

NASA Astrophysics Data System (ADS)

INTRODUCTION. During the last 25 years a series of publications have documented the occurrence of inclusions in diamonds that show mineral compositions and mineral associations predicted for mantle rocks at deeper levels than the mantle lithosphere (e.g Harte et al., 1999; Harte & Cayzer, 2007). Although the diamonds bearing deep mantle inclusions are not abundant in absolute terms they are widespread and have been reported from cratonic blocks on all major continents. DEPTH ZONES OF INCLUSION SUITES. The silicate inclusions and their mineral associations form a series showing good correlation with mineral assemblages expected in basic and ultrabasic rock compositions at depth. However, there is a strong bias towards assemblages from two principal zones: (1)uppermost Transition zone and Asthenosphere. (2)lowermost Transition Zone and uppermost Lower Mantle. In the case of (1) the assemblages are predominantly of majorite garnet, and majorite garnet + cpx with an affinity to eclogitic bulk compositions. In many of these inclusions the cpx appears to have exsolved from the majoritic garnet and the depth of origin of the initial inclusions may be near the top of the Transition Zone. The assemblages from (2) are predominantly of peridotic affinity and involve fPer as well as silicates. They indicate material from three depth zones near the upper mantle to lower mantle boundary (UM/LM boundary). 2a) Upper/Lower Mantle Boundary association - inclusions of: Mg2SiO4, fPer, majorite/TAPP, MgSi-perovskite(mpv), CaSi-perovskite (cpv). 2b) uppermost Lower Mantle association with: Mpv(Al-poor), fPer and cpv, majorite/tapp 2c)lower Mantle association with: Mpv(Al-rich) with fPer, and corundum. DISCUSSION. The above features show that the formation of deep mantle diamonds is concentrated in a zone around the top of the Transition Zone (ca 400-500 kms deep), and a zone at 600-800 kms embracing the bottom of the Transition Zone and the top of Lower Mantle. Associations including Mg2SiO4 with and fPer + mpv indicate the preservation of UM/LM boundary reaction, which from experimental data is expected to be sharply constrained in depth, though the presence of H2O will broaden the reaction zone due to the potential stability of hydrous ringwoodite. Considerations of the preservation of hydrous peridotitic assemblages in subduction zones (Komabayashi, 2006, AGU monograph), show that an initially cool subducted slab may preserve hydrous assemblages to the lower part of the upper mantle and into the lower mantle. Here stagnation and warming of the slab may cause dehydration with the formation of fluids/melts which provide the potential location for diamond formation. At the top of the Transition Zone, Bercovici and Karato (2003, Nature 245) have suggested the existence of a melt zone. The location of this melt zone at its intersection with the upper surface of a subducting slab, provides an ideal location for the crystallisation of the majorite assemblages from around the top of the Transition Zone. This also accords with the crustal carbon isotope signatures in the host diamonds and the wide variations in REE abundances in the majorites. Deep diamond inclusions provide strong evidence for dehydration zones near the top and bottom of the Transition Zone.

Harte, B.

2009-12-01

237

Ice Cloud Formation and Dehydration in the Tropical Tropopause Layer  

NASA Technical Reports Server (NTRS)

Stratospheric water vapor is important not only for its greenhouse forcing, but also because it plays a significant role in stratospheric chemistry. Several recent studies have focused on the potential for dehydration due to ice cloud formation in air rising slowly through the tropical tropopause layer (TTL). Holton and Gettelman showed that temperature variations associated with horizontal transport of air in the TTL can drive ice cloud formation and dehydration, and Gettelman et al. recently examined the cloud formation and dehydration along kinematic trajectories using simple assumptions about the cloud properties. In this study, a Lagrangian, one-dimensional cloud model has been used to further investigate cloud formation and dehydration as air is transported horizontally and vertically through the TTL. Time-height curtains of temperature are extracted from meteorological analyses. The model tracks the growth, advection, and sedimentation of individual cloud particles. The regional distribution of clouds simulated in the model is comparable to the subvisible cirrus distribution indicated by SAGE II. The simulated cloud properties and cloud frequencies depend strongly on the assumed supersaturation threshold for ice nucleation. The clouds typically do not dehydrate the air along trajectories down to the temperature minimum saturation mixing ratio. Rather the water vapor mixing ratio crossing the tropopause along trajectories is 10-50% larger than the saturation mixing ratio. I will also discuss the impacts of Kelvin waves and gravity waves on cloud properties and dehydration efficiency. These simulations can be used to determine whether observed lower stratospheric water vapor mixing ratios can be explained by dehydration associated with in situ TTL cloud formation alone.

Jensen, Eric; Gore, Warren J. (Technical Monitor)

2002-01-01

238

How valid are clinical signs of dehydration in infants?  

PubMed

Our objective was to determine the ability of several clinical signs of dehydration to distinguish among degrees of dehydration in infants with acute diarrhea. The design was a prospective cohort study in a pediatric referral hospital in Cairo, Egypt. Infant boys, 3-18 months old, with a history of acute diarrhea (5 or more watery stools per day for no more than 7 days) were eligible, except those with frank protein-energy malnutrition, serious nongastrointestinal illness, or being exclusively breast-fed. Several clinical signs of dehydration were assessed upon study entry. Subjects were then rehydrated with an oral rehydration solution and fed a standardized diet until diarrhea ceased (no watery or loose stools for 16 h). The main outcome measure was percent body weight gain at rehydration and at resolution of illness. Data from 135 subjects were available for analysis. Average (SD) rehydration phase duration was 5.2 (2.1) h, and average (SD) duration of illness was 54.5 (38) h. Multiple regression analysis selected prolonged skinfold, altered neurologic status, sunken eyes, and dry oral mucosa as the clinical signs that correlated best with percent dehydration (R2 for model 0.244, p < 0.001). Mean weight gain for the two assessment systems was 3.6-3.9% for mild, 4.9-5.3% for moderate, and 9.5-9.8% for severe dehydration. The most valid clinical signs of dehydration include prolonged skinfold, altered neurologic status, sunken eyes, and dry oral mucosa. Children with clinical signs of mild or moderate dehydration have fluid deficits on the order of 3 or 5% body weight, respectively. PMID:8788288

Duggan, C; Refat, M; Hashem, M; Wolff, M; Fayad, I; Santosham, M

1996-01-01

239

Enantioselective dehydration of butan-2-ol using zeolite Y modified with dithiane oxides  

SciTech Connect

Modification of zeolite H-Y by dithiane oxides (2-R-1,3-dithiane 1-oxide; R = H, CH{sub 3}, C{sub 6}H{sub 5}) is shown to enhance significantly its activity for the acid catalyzed gas phase dehydration of butan-2-ol. The rate enhancement is observed for catalysts that are prepared by adding the dithiane oxide to the zeolite synthesis gel or by adsorption of the dithiane oxide onto commercial samples of zeolite H-Y. The origin of the rate enhancement is considered to result from a specific interaction between the dithiane oxide modifier with both the extra-framework and framework aluminum in the zeolite. Modification of zeolite H-Y with (R)-1,3-dithiane 1-oxide enhances the conversion of (S)-butan-2-ol compared to (R)-butan-2-ol in the temperature range 110-150{degrees}C when the two enantiomers are reacted separately. Modification with (S)-2-phenyl-1,3-dithiane 1-oxide gives a catalyst for which (R)-butan-2-ol is the most reactive of the two enantiomers. Reaction of racemic butan-2-ol over these chirally modified H-Y zeolites demonstrates that this modification procedure makes the zeolite enantiomerically discriminating and one enantiomer preferentially reacts, although both are present in the micropores under the reaction conditions. This effect is considered to be due to enantioselective rate enhancement, since, although the rate of dehydration of both enantiomers is enhanced in the chiral environment, the dehydration rate of one enantiomer is accelerated relative to the other. It is suggested that the effect is due to preferential adsorption at the chiral active site. 34 refs., 7 figs., 6 tabs.

Feast, S.; Siddiqui, H.; Bethell, D. [Univ. of Liverpool (United Kingdom)] [and others] [Univ. of Liverpool (United Kingdom); and others

1997-04-15

240

Freeze-Tolerant Condensers  

NASA Technical Reports Server (NTRS)

Two condensers designed for use in dissipating heat carried by working fluids feature two-phase, self-adjusting configurations such that their working lengths automatically vary to suit their input power levels and/or heat-sink temperatures. A key advantage of these condensers is that they can function even if the temperatures of their heat sinks fall below the freezing temperatures of their working fluids and the fluids freeze. The condensers can even be restarted from the frozen condition. The top part of the figure depicts the layout of the first condenser. A two-phase (liquid and vapor) condenser/vapor tube is thermally connected to a heat sink typically, a radiatively or convectively cooled metal panel. A single-phase (liquid) condensate-return tube (return artery) is also thermally connected to the heat sink. At intervals along their lengths, the condenser/vapor tube and the return artery are interconnected through porous plugs. This condenser configuration affords tolerance of freezing, variable effective thermal conductance (such that the return temperature remains nearly constant, independently of the ultimate sink temperature), and overall pressure drop smaller than it would be without the porous interconnections. An additional benefit of this configuration is that the condenser can be made to recover from the completely frozen condition either without using heaters, or else with the help of heaters much smaller than would otherwise be needed. The second condenser affords the same advantages and is based on a similar principle, but it has a different configuration that affords improved flow of working fluid, simplified construction, reduced weight, and faster recovery from a frozen condition.

Crowley, Christopher J.; Elkouhk, Nabil

2004-01-01

241

Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography-Mass Spectroscopy (GC-MS)  

ERIC Educational Resources Information Center

Dehydrations of "cis"- and "trans"-2-methylcyclohexanol mixtures were carried out with 60% sulfuric acid at 78-80 [degrees]C as a function of time and the products were identified by gas chromatography-mass spectroscopy (GC-MS) analysis. The compounds identified in the reaction mixtures include alkenes, 1-, 3-, and 4-methylcyclohexenes and…

Clennan, Malgorzata M.; Clennan, Edward L.

2011-01-01

242

Effect of elevated stress and temperature on smectite dehydration in subducting sediments - an experimental approach  

NASA Astrophysics Data System (ADS)

Smectite-rich subduction inputs have been in the focus of convergent margin researchers because of their mechanical weakness, their ability to store water in interlayer sites and to release it at greater depth. The release of bound water in smectite during the transition to illite is widely acknowledged to cause the omnipresent fluid freshening at convergent margins. Freshened fluids are often considered as tracer for lateral fluid flow because illitization occurs at greater depths with temperatures >60°C. Instead, laboratory experiments showed that smectite is able to dehydrate partially when an effective stress level of ~1.3 MPa is exceeded. This observation is still poorly constrained when regarding the hydrogeochemistry of subduction zones. To shed light on this process the set-up of a backpressured uniaxial consolidation apparatus (hydrothermal oedometer) was chosen, which provides a large spectrum of pressure (P) and temperature (T) conditions. Three hydrothermal consolidation tests were conducted at constant temperatures of 20°C, 60°C and 100°C up to stresses of 70 MPa. The specimen used was a smectite-rich silty claystone to emphasize dehydration reactions. It is mineralogically similar to smectite-rich end members from the Nankai Trough subduction zone (Japan), Barbados accretionary wedge and Costa Rica margin. The fluids expelled at different stress intervals during the compaction tests were analyzed for major and trace elements to evaluate potential fluid-rock interaction with increasing PT conditions in the shallow subduction zone. The results confirm that smectite dehydration starts at stresses as low as ~2 MPa. However, the interlayer collapse can be also related to the decreasing availability of water in the water-rock system. This assumption is favored by the good accordance with literature data of the experimentally determined relationship between smectite's basal spacing and the water-smectite mass ratio. In addition, the data from the room-temperature experiment was sufficient to formulate for the first time a relationship between the water-rock mass ratio (w/r) and the dehydrated smectite fraction in the sediment. This allows a holistic view of 3 different depth-temperature stages of smectite dehydration in the subduction zone. In shallow parts (approx. <250 mbsf) and in overpressured layers where the sediment is able to maintain w/r mass ratios greater than 0.44 g/g and the temperature is low no smectite dehydration occurs. At greater depth where w/r mass ratios are smaller 0.44 g/g dehydration generates low chlorinity fluids. The fluid freshening is associated with less K and Mg and increased concentrations of Na as well as volatile elements (B, Li, Si). This is caused by the change in cation selectivity towards weakly hydrated ions when the interlayer collapse from 18.5 Å to a 15.4 Å hydrate and the increasing temperature. The third stage is characterized by temperatures >60 °C and w/r mass ratios smaller 0.44 g/g. The previous processes are accentuated by higher temperatures and smaller w/r mass ratios but the pore fluid is overprinted by the smectite-illite transition.

Huepers, A.; Kopf, A.

2010-12-01

243

Garnet growth as a proxy for progressive dehydration in subduction zones  

NASA Astrophysics Data System (ADS)

The release of volatiles from subducting lithologies is a crucial triggering process for arc magmatism, seismicity, the growth and maturation of continents, and the global geological H2O-CO2 cycle. While numerous models have been developed to predict slab volatile release, it has proven challenging to reconstruct and test these fluid fluxes released from specific lithologies in the rock record. Here we show that the growth of garnet may be used as a proxy for progressive devolatilization at blueschist to eclogite facies conditions in subduction zones. Generally, as garnet grows in a subducting rock, fluid is produced due to metamorphic dehydration reactions. Using rigorous thermodynamic analysis, which includes the crucial effects of phase fractionation, we model the proportional relationship between garnet and water production in common lithologies (pelitic sediment and hydrated MORB) along three representative subduction geotherms. The results show that several dehydration reactions contribute to garnet growth especially within a crucial span of the subduction zone (~1.5 to 2.5 GPa) within which slab-mantle decoupling has been predicted to occur in some models and volatile fluxes may be focused. The water:garnet production ratio varies during garnet growth, constrained by the specific hydrous reactant phases that are breaking down, but the average water:garnet production ratios are surprisingly consistent regardless of composition and geotherm. Over the garnet growth interval ~400 to 700 C (and corresponding depths for each geotherm) the average production ratio for altered MORB compositions is 0.52 (wt % water per vol % garnet) in cooler geotherms (Honshu and Nicaragua) and 0.27 in hotter (Cascadia) geotherms, with predictably lower ratios if the input basalt previously experienced less hydrous alteration. Over the same interval the water production ratios are approximately 50 % lower for pelite (0.24 and 0.13, respectively). Lower temperature water release is not correlated with garnet growth (it occurs before garnet stability), and higher temperature garnet growth is not correlated with dehydration (as the system is essentially anhydrous); fortunately, the chemistry of garnet produced at these conditions is readily identifiable. Taken together, these results suggest that garnet abundance, its P-T growth span, and any constraints on its growth chronology may be used to indirectly but accurately reconstruct dehydration fluxes for natural samples in the blueschist-eclogite rock record.

Caddick, M. J.; Baxter, E. F.

2012-12-01

244

Evolution of microstructure and elastic wave velocities in dehydrated gypsum samples  

NASA Astrophysics Data System (ADS)

This study aims at contributing to the experimental database of changes in rock physical properties, particularly elastic wave velocities, induced by devolatilization reactions. Cylindrical samples of natural gypsum were dehydrated in air for up to 800 h at ambient pressure and temperatures between 378 and 423 K. Subsequently, the transformation kinetics, reaction induced changes in microstructure and porosity and the concurrent evolution of the sample P and S-wave velocities were constrained. Weighing the heated samples in predefined time intervals yielded the reaction progress where the stoichiometric mass balance indicated an ultimate dehydration to anhydrite regardless of temperature. Porosity was observed to continuously increase with reaction progress from approximately 2 % for fully hydrated samples to 30 % for completely dehydrated ones, whilst the initial bulk volume was preserved. In a first set, P-wave velocity was measured at ambient conditions with ultrasonic transducers indicating a linear decrease with porosity from 5.2 km/s at 2 % to 1.0 km/s at 30 %. Results of a second set of ultrasonic measurements for both P and S-waves will be presented as well aiming at a spatially resolved wave velocity dependence on microstructure. For P-waves three different effective medium models - Voigt, Wyllie (Reuss), and Nur - were compared to the data. The linear dependence of P-wave velocity on porosity observed is best represented by the Voigt bound. The Voigt bound, however, overestimates the measured values significantly. The Wyllie-Equation (the Reuss bound) does not replicate the linear decrease in P-wave velocity with porosity and generally underestimates the data. However, at porosities above approximately 25 % the agreement with measured values is excellent. The Nur-Model yields a nonlinear dependence but replicates the data best for model-inherent critical porosities between 0.25 and 0.3. Thin section micrographs taken on selected samples reveal a sharp reaction front progressively migrating sample inwards. SEM imaging confirmed this observation, additionally showing (1) that the cylindrical outer rim consists of a highly porous network within an anhydrite matrix and (2) that the remaining inner cylinder appears unaltered at 388 K whereas bassanite needles progressively turning into anhydrite can be found at 398 K.

Milsch, H.; Priegnitz, M.

2012-04-01

245

Functional and technological potential of dehydrated Phaseolus vulgaris L. flours.  

PubMed

The effect of cooking followed by dehydration was evaluated on the bioactive composition, antioxidant activity and technological properties of two varieties (Negro 8025 and Bayo Madero) of common beans. Quercetin, rutin, and phenolic acids were the most abundant phenolics found. Cooking processes resulted in decreased values of some phenolic compounds and antioxidant capacity. A subsequent dehydration increased TEAC values, resistant starch content and decreased starch digestibility. Oligosaccharides and dietary fibre were preserved in both treatments. Variety had a strong impact on phytochemical profile, being Negro 8025 that exhibited the highest content of most of the compounds assessed. Water absorption index (WAI) and oil absorption capacity (OAC) were determined in order to measure technological suitability. Dehydration produced flours with stable WAI and low oil pick up. The results suggest that the flours of Negro 8025 beans have a good potential to be considered as functional ingredient for healthy food products. PMID:24837948

Ramírez-Jiménez, A K; Reynoso-Camacho, R; Mendoza-Díaz, S; Loarca-Piña, G

2014-10-15

246

Dehydration Process of Protein Crystals by Micro-Brillouin Scattering  

NASA Astrophysics Data System (ADS)

Polymorphism and dehydration process have been studied by the micro-Brillouin scattering technique in hen egg white lysozyme crystals without cross-linking. Two types of crystal with tetragonal and monoclinic systems have been successfully grown by the two-liquid interface method. The dehydration processes of tetragonal and monoclinic crystals have been investigated by the exposure of crystals to open air. Sound velocity increases markedly owing to the increase in intermolecular interaction between lysozyme molecules, while the attenuation of sound wave decreases markedly owing to the decrease in friction generated by mobile water. The time dependences of sound velocity in two crystals have been discussed on the basis of the Avrami-Erofe’ev model. It is found that a monoclinic crystal dehydrates much faster than a tetragonal one.

Hashimoto, Eiji; Aoki, Yuichiro; Seshimo, Yuichi; Sasanuma, Keita; Ike, Yuji; Kojima, Seiji

2008-05-01

247

Isothermal dehydration of thin films of water and sugar solutions  

NASA Astrophysics Data System (ADS)

The process of quasi-isothermal dehydration of thin films of pure water and aqueous sugar solutions is investigated with a dual experimental and theoretical approach. A nanoporous paper disk with a homogeneous internal structure was used as a substrate. This experimental set-up makes it possible to gather thermodynamic data under well-defined conditions, develop a numerical model, and extract needed information about the dehydration process, in particular the water activity. It is found that the temperature evolution of the pure water film is not strictly isothermal during the drying process, possibly due to the influence of water diffusion through the cellulose web of the substrate. The role of sugar is clearly detectable and its influence on the dehydration process can be identified. At the end of the drying process, trehalose molecules slow down the diffusion of water molecules through the substrate in a more pronounced way than do the glucose molecules.

Heyd, R.; Rampino, A.; Bellich, B.; Elisei, E.; Cesàro, A.; Saboungi, M.-L.

2014-03-01

248

Simple and effective treatment of acute dehydrating diarrhoeas including cholera.  

PubMed

General treatment for diarrhea, including infantile and cholera-related diarrhea, is discussed. Prompt and complete replacement of water and electrolytes lost through diarrhea must be the aim of all treatment. To do this, a solution of electrolytes and glucose is given either orally or intravenously, depending on the severity of the diarrhea-caused dehydration. To avoid misdiagnosis, a brief physical examination and history must be taken beforehand. Symptoms useful in distingushing mild from severe dehydration are listed. Severe dehydration includes extreme weakness, even unconsciousness in children, a weak and fast pulse, sunken eyes, and cool skin. Intravenous treatment should be started at once in such cases. Method of administration and dosage quantities for different weights of patient are given. The necessary ingredients for oral rehydration therapy should be available at all treatment centers, including rural dispensaries. Rehydration treatment should be continued until diarrhea stops. A normal diet should also be continued if possible. PMID:12336958

Mkandawire, A C

1980-04-01

249

Luminescence induced by dehydration of kaolin - Association with electron-spin-active centers and with surface activity for dehydration-polymerization of glycine  

NASA Technical Reports Server (NTRS)

Experimental data concerning emission of light upon dehydration as a function of preheating and pre-gamma-irradiation are correlated with reported studies of electron-spin resonance (ESR) activity after similar pretreatments. The effect of these pretreatments on the kaolin-promoted incorporation of glycine into peptide oligomers in a wet/cold, hot/dry fluctuating environment is compared to their effect on the ESR and luminescent signals. The existence of spectroscopically active centers appears to be loosely anticorrelated with reaction yield; these yields are increased by increasing the overall energy content of the material. It is concluded that some part of the chemical yield is produced by a mechanism involving intrinsic, excited electronic states of the clay crystal lattice. These states may be derived from thermally, interfacially, and/or mechanically induced charge reorganization within interspersed energy levels in the band structure of the material.

Coyne, L.; Hovatter, W.; Sweeney, M.

1983-01-01

250

Effect of experimental and sample factors on dehydration kinetics of mildronate dihydrate: mechanism of dehydration and determination of kinetic parameters.  

PubMed

The dehydration kinetics of mildronate dihydrate [3-(1,1,1-trimethylhydrazin-1-ium-2-yl)propionate dihydrate] was analyzed in isothermal and nonisothermal modes. The particle size, sample preparation and storage, sample weight, nitrogen flow rate, relative humidity, and sample history were varied in order to evaluate the effect of these factors and to more accurately interpret the data obtained from such analysis. It was determined that comparable kinetic parameters can be obtained in both isothermal and nonisothermal mode. However, dehydration activation energy values obtained in nonisothermal mode showed variation with conversion degree because of different rate-limiting step energy at higher temperature. Moreover, carrying out experiments in this mode required consideration of additional experimental complications. Our study of the different sample and experimental factor effect revealed information about changes of the dehydration rate-limiting step energy, variable contribution from different rate limiting steps, as well as clarified the dehydration mechanism. Procedures for convenient and fast determination of dehydration kinetic parameters were offered. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci. PMID:24729295

B?rzi?š, Agris; Acti?š, Andris

2014-06-01

251

Mechanisms of liquefaction and pyrolysis reactions of biomass  

Microsoft Academic Search

In the liquefaction process, the micellar-like broken down fragments produced by hydrolysis are degraded to smaller compounds by dehydration, dehydrogenation, deoxygenation and decarboxylation. These compounds once produced, rearrange through condensation, cyclization and polymerization, leading to new compounds. Thermal depolymerization and decomposition of biomass, cellulose, hemicelluloses and products were formed as well as a solid residue of charcoal. The mechanism of

A. Demirba?

2000-01-01

252

Ice Cloud Formation and Dehydration in the Tropical Tropopause Layer  

NASA Technical Reports Server (NTRS)

Stratospheric water vapor is important not only for its greenhouse forcing, but also because it plays a significant role in stratospheric chemistry. several recent studies have focused on the potential for dehydration due to ice cloud formation in air rising slowly through the tropical tropopause layer. Holton and Gettelman showed that temperature variations associated with horizontal transport of air in the tropopause layer can drive ice cloud formation and dehydration, and Gettelman et al. recently examined the cloud formation and dehydration along kinematic trajectories using simple assumptions about the cloud properties. In this study, we use a Lagrangian, one-dimensional cloud model to further investigate cloud formation and dehydration as air is transported horizontally and vertically through the tropical tropopause layer. Time-height curtains of temperature are extracted from meteorological analyses. The model tracks the growth and sedimentation of individual cloud particles. The regional distribution of clouds simulated in the model is comparable to the subvisible cirrus distribution indicated by SAGE II. The simulated cloud properties depend strongly on the assumed ice supersaturation threshold for ice nucleation. with effective nuclei present (low supersaturation threshold), ice number densities are high (0.1--10 cm(circumflex)-3), and ice crystals do not grow large enough to fall very far, resulting in limited dehydration. With higher supersaturation thresholds, ice number densities are much lower (less than 0.01 cm(circumflex)-3), and ice crystals grow large enough to fall substantially; however, supersaturated air often crosses the tropopause without cloud formation. The clouds typically do not dehydrate the air along trajectories down to the temperature minimum saturation mixing ratio. Rather the water vapor mixing ratio crossing the tropopause along trajectories is typically 10-50% larger than the saturation mixing ratio.

Jensen, Eric; Pfister, Leonhard; Gore, Warren J. (Technical Monitor)

2002-01-01

253

Heat shock proteins contribute to mosquito dehydration tolerance  

PubMed Central

This study examines the responses of heat shock protein transcripts, Hsp70 and Hsp90, to dehydration stress in three mosquito species, Aedes aegypti, Anopheles gambiae and Culex pipiens. We first defined the water balance attributes of adult females of each species, monitored expression of the hsp transcripts in response to dehydration, and then knocked down expression of the transcripts using RNA interference (RNAi) to evaluate potential functions of the Hsps in maintenance of water balance. Fully hydrated females of all three species contained nearly the same amount of water (66–68%), but water loss rates differed among the species, with A. aegypti having the lowest water loss rate (2.6%/h), followed by C.pipiens (3.3%/h), and A. gambiae (5.1%/h). In all three species water could be replaced only by drinking water (or blood). Both A. aegypti and C. pipiens tolerated a loss of 36% of their body water, but A. gambiae was more vulnerable to water loss, tolerating a loss of only 29% of its body water. Dehydration elicited expression of hsp70 in all three species, but only C. pipiens continued to express this transcript during rehydration. Hsp90 was constitutively expressed and expression levels remained fairly constant during dehydration and rehydration, except expression was not noted during rehydration of C. pipiens. Injection of dsRNA to knock down expression of hsp70 (83% reduction) and hsp90 (46% reduction) in A. aegypti did not alter water content or water loss rates, but the dehydration tolerance was lower. Instead of surviving a 36% water loss, females were able to survive only a 28% water loss in response to RNAi directed against hsp70 and a 26% water loss when RNAi was directed against hsp90. These results indicate a critical function for these Hsps in mosquito dehydration tolerance

Benoit, Joshua B.; Lopez-Martinez, Giancarlo; Phillips, Zachary P.; Patrick, Kevin R.; Denlinger, David L.

2009-01-01

254

THE COLOR GLASS CONDENSATE.  

SciTech Connect

The Color Glass Condensate is a state of high density gluonic matter which controls the high energy limit of hadronic interactions. Its properties are important for the initial conditions for matter produced at RHIC.

MCLERRAN,L.

2001-08-26

255

Key condenser failure mechanisms  

SciTech Connect

Eight practical lessons highlight many of the factors that can influence condenser tube corrosion at coal-fired utilities and the effects contaminant in-leakage can have on steam generating units. 1 ref., 4 figs.

Buecker, B.

2009-04-15

256

Forecasting Aircraft Condensation Trails.  

National Technical Information Service (NTIS)

Aircraft condensation trails (contrails) are caused by aircraft aerodynamics or engine exhaust in the proper atmospheric conditions. Engine-exhaust trails are the most common and are discussed in this report. Jet aircraft contrail-formation graphs facilit...

1981-01-01

257

Ghost condensate busting  

SciTech Connect

Applying the Thomas-Fermi approximation to renormalizable field theories, we construct ghost condensation models that are free of the instabilities associated with violations of the null-energy condition.

Bilic, Neven [Rudjer Boskovic Institute, 10002 Zagreb (Croatia)] [Rudjer Boskovic Institute, 10002 Zagreb (Croatia); Tupper, Gary B; Viollier, Raoul D, E-mail: bilic@thphys.irb.hr, E-mail: gary.tupper@uct.ac.za, E-mail: raoul.viollier@uct.ac.za [Centre of Theoretical Physics and Astrophysics, University of Cape Town, Rondebosch 7701 (South Africa)

2008-09-15

258

Efficient dehydration of fructose to 5-hydroxymethylfurfural catalyzed by a recyclable sulfonated organic heteropolyacid salt.  

PubMed

The dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) with room temperature ionic liquids (ILs) is a way of producing liquid fuels from renewable resources, but separation of products and IL is energy intensive. In this work, a heteropolyacid salt of an IL-forming cation functionalized with a propanesulfonate group, 1-(3-sulfonicacid)propyl-3-methyl imidazolium phosphotungstate ([MIMPS](3)PW(12)O(40)), was used as a catalyst-rather than as a solvent-in the conversion of fructose to 5-HMF. The maximum yield of 5-HMF was 99.1% at 120°C after 2h using sec-butanol as solvent, and the catalyst was separated from the reaction mixture by a simple process at the end of the reaction and reused six times without loss of activity. PMID:22201545

Qu, Yongshui; Huang, Chongpin; Zhang, Jie; Chen, Biaohua

2012-02-01

259

[Severe dehydration in a newborn following ambulatory birth].  

PubMed

A nine day-old girl was hospitalised because of breast-feeding problems and life-threatening hypernatremic dehydration; weight loss was 30% of birth weight and s-Na 187 mmol/l. The question is raised whether there could be an association to the current changes in the perinatal health care in Denmark. The case emphasizes the necessity of a sufficient safety net beneath the newborn children in order to minimise the risk of breast-feeding problems and re-hospitalizing. Neonatal problems such as marked weight loss, dehydration, hypernatremia and marked jaundice are potentially preventable. PMID:21917222

Thøstesen, Lisbeth Marianne; Fenger-Grøn, Jesper

2011-09-12

260

Ductile Deformation of Dehydrating Serpentinite Evidenced by Acoustic Signal Monitoring  

NASA Astrophysics Data System (ADS)

Serpentinite dehydration is believed to be responsible for triggering earthquakes at intermediate depths (i.e., 60-300 km) in subduction zones. Based on experimental results, some authors have proposed mechanisms that explain how brittle deformation can occur despite high pressure and temperature conditions [1]. However, reproducing microseismicity in the laboratory associated with the deformation of dehydrating serpentinite remains challenging. A recent study showed that, even for fast dehydration kinetics, ductile deformation could take place rather than brittle faulting in the sample [2]. This latter study was conducted in a multi-anvil apparatus without the ability to control differential stress during dehydration. We have since conducted controlled deformation experiments in the deformation-DIA (D-DIA) on natural serpentinite samples at sector 13 (GSECARS) of the APS. Monochromatic radiation was used with both a 2D MAR-CCD detector and a CCD camera to determine the stress and the strain of the sample during the deformation process [3]. In addition, an Acoustic Emission (AE) recording setup was used to monitor the microseismicity from the sample, using piezo-ceramic transducers glued on the basal truncation of the anvils. The use of six independent transducers allows locating the AEs and calculating the corresponding focal mechanisms. The samples were deformed at strain rates of 10-5-10-4 s-1 under confining pressures of 3-5 GPa. Dehydration was triggered during the deformation by heating the samples at rates ranging from 5 to 60 K/min. Before the onset of the dehydration, X-ray diffraction data showed that the serpentinite sustained ~1 GPa of stress which plummeted when dehydration occurred. Although AEs were recorded during the compression and decompression stages, no AEs ever accompanied this stress drop, suggesting ductile deformation of the samples. Hence, unlike many previous studies, no evidence for fluid embrittlement and anticrack generation was found in our experiments. These results suggest that dehydration of serpentinite alone cannot be responsible for intermediate earthquakes. The recovered samples microstructures are currently studied in the SEM and further experiments are planned on partially hydrated samples (i.e., containing olivine), capable of sustaining higher stress levels. 1. Jung, H. and H.W. Green, International Geology Review, 2004. 46(12): p. 1089-1102. 2. Gasc, J., et al., Physics of the Earth and Planetary Interiors, 2011. 189(3-4): p. 121-133. 3. Wang, Y.B., et al., Review of Scientific Instruments, 2003. 74(6): p. 3002-3011.

Gasc, J.; Hilairet, N.; Wang, Y.; Schubnel, A. J.

2012-12-01

261

A bulge-induced dehydration failure mode of nanocomposite hydrogel  

NASA Astrophysics Data System (ADS)

Since hydrogels are very soft and usually weak in swollen state, they pose unique challenges to traditional mechanical experiments. The mechanical property of nanocomposite poly(N-isopropylacrylamide) hydrogel was characterized by the bulge test in this investigation. A dehydration failure phenomenon of the hydrogel was found and the failure mechanism was presented. A criterion is proposed that when strain reaches the threshold, water molecules migrate out of the polymer networks and the dehydration failure occurs. The critical strain keeps constant for orifices with different diameters. This failure mode can be applied in the controllable release of drugs.

Tang, Jingda; Yu, Zejun; Sun, Youyi; Pei, Yongmao; Fang, Daining

2013-10-01

262

EPR study on gamma-irradiated fruits dehydrated via osmosis  

NASA Astrophysics Data System (ADS)

The shape and time stability of the electron paramagnetic resonance (EPR) spectra of non- and ?-irradiated papaya, melon, cherry and fig samples dehydrated via osmosis are reported. It is shown that non-irradiated samples are generally EPR silent whereas ?-irradiated exhibit "sugar-like" EPR spectra. The recorded EPR spectra are monitored for a period of 7 months after irradiation (stored at low humidity and in the dark). The results suggest longer period of unambiguous identification of the radiation processing of osmose dehydrated fruits. Therefore, the Protocol EN 13708,2001 issued by CEN is fully applicable for the studied fruit samples.

Yordanov, N. D.; Aleksieva, K.

2007-06-01

263

A multiprotein bicarbonate dehydration complex essential to carboxysome function in cyanobacteria.  

PubMed

Carboxysomes are proteinaceous biochemical compartments that constitute the enzymatic "back end" of the cyanobacterial CO2-concentrating mechanism. These protein-bound organelles catalyze HCO3- dehydration and photosynthetic CO2 fixation. In Synechocystis sp. strain PCC6803 these reactions involve the beta-class carbonic anhydrase (CA), CcaA, and Form 1B ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). The surrounding shell is thought to be composed of proteins encoded by the ccmKLMN operon, although little is known about how structural and catalytic proteins integrate to form a functional carboxysome. Using biochemical activity assays and molecular approaches we have identified a catalytic, multiprotein HCO3- dehydration complex (BDC) associated with the protein shell of Synechocystis carboxysomes. The complex was minimally composed of a CcmM73 trimer, CcaA dimer, and CcmN. Larger native complexes also contained RbcL, RbcS, and two or three immunologically identified smaller forms of CcmM (62, 52, and 36 kDa). Yeast two-hybrid analyses indicated that the BDC was associated with the carboxysome shell through CcmM73-specific protein interactions with CcmK and CcmL. Protein interactions between CcmM73 and CcaA, CcmM73 and CcmN, or CcmM73 and itself required the N-terminal gamma-CA-like domain of CcmM73. The specificity of the CcmM73-CcaA interaction provided both a mechanism to integrate CcaA into the fabric of the carboxysome shell and a means to recruit this enzyme to the BDC during carboxysome biogenesis. Functionally, CcaA was the catalytic core of the BDC. CcmM73 bound H14CO3- but was unable to catalyze HCO3- dehydration, suggesting that it may potentially regulate BDC activity. PMID:17993516

Cot, Swan S-W; So, Anthony K-C; Espie, George S

2008-02-01

264

Characterization and Thermal Dehydration Kinetics of Highly Crystalline Mcallisterite, Synthesized at Low Temperatures  

PubMed Central

The hydrothermal synthesis of a mcallisterite (Mg2(B6O7(OH)6)2·9(H2O)) mineral at low temperatures was characterized. For this purpose, several reaction temperatures (0–70°C) and reaction times (30–240?min) were studied. Synthesized minerals were subjected to X-ray diffraction (XRD), fourier transform infrared (FT-IR), and Raman spectroscopies and scanning electron microscopy (SEM). Additionally, experimental analyses of boron trioxide (B2O3) content and reaction yields were performed. Furthermore, thermal gravimetry and differential thermal analysis (TG/DTA) were used for the determination of thermal dehydration kinetics. According to the XRD results, mcallisterite, which has a powder diffraction file (pdf) number of “01-070-1902,” was formed under certain reaction parameters. Pure crystalline mcallisterite had diagnostic FT-IR and Raman vibration peaks and according to the SEM analysis, for the minerals which were synthesized at 60°C and 30?min of reaction time, particle size was between 398.30 and 700.06?nm. Its B2O3 content and reaction yield were 50.80 ± 1.12% and 85.80 ± 0.61%, respectively. Finally, average activation energies (conversion values (?) that were selected between 0.1 and 0.6) were calculated as 100.40?kJ/mol and 98.31?kJ/mol according to Ozawa and Kissinger-Akahira-Sunose (KAS) methods, respectively.

Senberber, Fatma Tugce

2014-01-01

265

Characterization and thermal dehydration kinetics of highly crystalline mcallisterite, synthesized at low temperatures.  

PubMed

The hydrothermal synthesis of a mcallisterite (Mg2(B6O7(OH)6)2 · 9(H2O)) mineral at low temperatures was characterized. For this purpose, several reaction temperatures (0-70°C) and reaction times (30-240 min) were studied. Synthesized minerals were subjected to X-ray diffraction (XRD), fourier transform infrared (FT-IR), and Raman spectroscopies and scanning electron microscopy (SEM). Additionally, experimental analyses of boron trioxide (B2O3) content and reaction yields were performed. Furthermore, thermal gravimetry and differential thermal analysis (TG/DTA) were used for the determination of thermal dehydration kinetics. According to the XRD results, mcallisterite, which has a powder diffraction file (pdf) number of "01-070-1902," was formed under certain reaction parameters. Pure crystalline mcallisterite had diagnostic FT-IR and Raman vibration peaks and according to the SEM analysis, for the minerals which were synthesized at 60°C and 30 min of reaction time, particle size was between 398.30 and 700.06 nm. Its B2O3 content and reaction yield were 50.80 ± 1.12% and 85.80 ± 0.61%, respectively. Finally, average activation energies (conversion values (?) that were selected between 0.1 and 0.6) were calculated as 100.40 kJ/mol and 98.31 kJ/mol according to Ozawa and Kissinger-Akahira-Sunose (KAS) methods, respectively. PMID:24719585

Moroydor Derun, Emek; Senberber, Fatma Tugce

2014-01-01

266

Entrapment and condensation of DNA in neutral reverse micelles.  

PubMed Central

DNA condensation and compaction is induced by a variety of condensing agents such as polycations. The present study analyzed the structure of plasmid DNA (DNA) in the small inner space of reverse micelles formed from nonionic surfactants (isotropic phase). Spectroscopic studies indicated that DNA was dissolved in an organic solvent in the presence of a neutral detergent. Fluorescent quenching of ethidium bromide and of rhodamine covalently attached to DNA suggested that the DNA within neutral, reverse micelles was condensed. Circular dichroism indicated that the DNA structure was C form (member of B family) and not the dehydrated A form. Concordantly, NMR experiments indicated that the reverse micelles contained a pool of free water, even at a ratio of water to surfactant (Wo) of 3.75. Electron microscopic analysis also indicated that the DNA was in a ring-like structure, probably toroids. Atomic force microscopic images also revealed small, compact particles after the condensed DNA structures were preserved using an innovative cross-linking strategy. In the lamellar phase, the DNA was configured in long strands that were 20 nm in diameter. Interestingly, such DNA structures, reminiscent of "nanowires," have apparently not been previously observed.

Budker, Vladimir G; Slattum, Paul M; Monahan, Sean D; Wolff, Jon A

2002-01-01

267

Evidence for Human Adaptive Response to Dehydration: Increase of Circulating Protein Mass,  

National Technical Information Service (NTIS)

Previously, it was believed that humans do not adapt to dehydration. Data are presented here showing that within 15 hours after dehydration is reached, humans increase circulating protein mass to facilitate the redistribution of body water from the inters...

M. N. Sawka C. B. Wenger

1987-01-01

268

Locating QTL for osmotic adjustment and dehydration tolerance in rice  

Microsoft Academic Search

Research was conducted to identify and map quantit- ative trait loci (QTL) associated with dehydration tolerance and osmotic adjustment of rice. Osmotic adjustment capacity and lethal osmotic potential were determined for 52 recombinant inbred lines grown in a controlled environment under conditions of a slowly developed stress. The lines were from a cross between an Indica cultivar, Co39, of lowland

J. M. Lilley; M. M. Ludlow; S. R. McCouch; J. C. O'Toole

1996-01-01

269

Progressive cellular dehydration and proteolysis in critically ill patients  

Microsoft Academic Search

SummaryBackground According to a recent hypothesis, the profound loss of body protein that occurs in critically ill patients is triggered and maintained by cell shrinkage secondary to cellular dehydration. We tested this hypothesis by studying sequential changes in intracellular water, total body protein, total body potassium, and intracellular potassium in patients receiving intensive care for blunt trauma or sepsis.Methods Nine

P. J Finn; L. D Plank; M. A Clark; A. B Connolly; G. L Hill

1996-01-01

270

Horizontal transport and the dehydration of the stratosphere  

Microsoft Academic Search

The coldest tropopause temperatures occur over the equatorial West Pacific during Northern Hemisphere winter. Horizontal transport through this ``cold trap'' region causes air parcels that reach the tropopause at other longitudes to be dehydrated to the very low saturation mixing ratios characteristic of the cold trap, and hence can explain why observed tropical stratospheric water vapor mixing ratios are often

James R. Holton; Andrew Gettelman

2001-01-01

271

Dehydration and melting experiments constrain the fate of subducted sediments  

Microsoft Academic Search

Geochemical tracers demonstrate that elements are cycled from subducted sediments into the arc melting regime at subduction zones, although the transfer mechanism is poorly understood. Are key elements (Th, Be, Rb) lost during sediment dehydration or is sediment melting required? To investigate this question, we conducted phase equilibria and trace element partitioning experiments on a pelagic red clay for conditions

Marie C. Johnson; Terry Plank

1999-01-01

272

Science Study Aids 1: Dehydration for Food Preservation.  

ERIC Educational Resources Information Center

This publication is the first of a series of seven supplementary investigative materials for use in secondary science classes providing up-to-date research-related investigations. This unit is structured for grades 9 through 12. It is concerned with the osmatic dehydration of fruits. The guide provides students with information about food…

Boeschen, John; And Others

273

DEHYDRATION OF ALCOHOLS VIA PREVAPORATION USING A NOVEL HYDROPHILIC MEMBRANE  

EPA Science Inventory

Pervaporation has emerged as an economically viable alternative technology for the dehydration of organic solvents, removal of organic compounds from water and organic/organic separations. Development of a suitable membrane system with high flux and high selectivity plays a criti...

274

DEHYDRATION OF ALCOHOLS VIA PERVAPORATION USING A NOVEL HYDROHILIC MEMBRANE  

EPA Science Inventory

Pervaporation has emerged as an economically viable alternative technology for the dehydration of organic solvents, removal of organic compounds from water and organic/organic separations. Development of a suitable membrane system with high flux and high selectivity plays a criti...

275

Ample Water, Avoiding Dehydration Can Prevent Renal Calculi  

MedlinePLUS

A Summer Menace Ample Water, Avoiding Dehydration Can Prevent Renal Calculi By Jan Ehrman On the front page... Talk about a summer bummer. They could ... should be drinking at least 12 glasses of water each day, especially during the summer.” kidney stones— ...

276

Study of wound dressing structure and hydration/dehydration properties  

NASA Astrophysics Data System (ADS)

Hydrogels manufactured by radio-induced crosslinking and simultaneous sterilisation of hydrogels of PVP, PEG and agar, according to the Rosiak method, have many desirable properties for using as wound dressings. However, some properties need to be improved or better controlled. The membranes need to be strong enough to be freely used. Another important property to be controlled is the capacity of absorption of exudate and the kinetics of drying. Therefore, it was necessary to understand the role of main parameters (agar, PVP, PEG concentration and dose) in the structure of the net and in the hydration and dehydration properties. The structure of the membranes was studied by sol analysis and the hydrating/dehydrating properties were studied by isothermal thermogravimetric analysis. The gel content for all samples were always in agreement with expected values considering that only PVP undergoes crosslinking. The hydrating and dehydration results did not show variation with the tested parameters. It was concluded that the network was solely composed of crosslinked PVP plasticezed by the other compounds. The properties of hydration/dehydration is related rather to diffusion than to capillarity or osmose and to the chemical retention of water in the polymeric matrix.

Lugão, A. B.; Machado, L. D. B.; Miranda, L. F.; Alvarez, M. R.; Rosiak, J. M.

1998-06-01

277

Dehydrated Kitchen Waste as a Feedstuff for Laying Hens  

Microsoft Academic Search

An experiment was conducted to determine the effects of dehydrated kitchen waste (DKW) product as a feedstuff for laying hens. Fresh food wastes of a retirement house were prepared for the experiment. This was mostly leftover food, plate scrapings and cooking residue. The kitchen waste was blended and dried by the temperature in the heater set at 80 to 85

2005-01-01

278

Poultry Excreta Dehydration and Utilization: System Development and Demonstration.  

National Technical Information Service (NTIS)

A manure handling and drying system involving caged layers with daily manure collection, air drying, and dehydration in a flash-type dryer has been studied. Objectives of the study were to: (1) Develop a complete manure handling system to maximize polluti...

H. C. Zindel T. S. Chang C. J. Flegal D. Polin C. C. Sheppard

1977-01-01

279

Crustal Dehydration and Overpressure Development on the San Andreas Fault  

Microsoft Academic Search

Previous authors have hypothesized that the apparent weakness of the San Andreas Fault may be explained by fluid overpressures resulting from the combination of crustal dehydration of the Franciscan mélange and the presence of a low-permeability serpentinite cap at its geologic contact with the Great Valley Sequence. We previously evaluated this hypothesis by calculating the spatial and temporal distribution of

P. M. Fulton; D. M. Saffer; B. A. Bekins

2005-01-01

280

Potential of calorimetry to study osmotic dehydration of food materials  

Microsoft Academic Search

A new method, thermocalorimetry, was developed to study osmotic dehydration. The kinetic data from the method was comparable to more traditional methods in the determination of rate constants for water loss. Thermocalorimetry measurements indicated a 2–3 kinetic phases, a relatively rapid process followed by a relatively slow process. The first phase is possibly due to water removal from the cut

C. Tortoe; J. Orchard; A. Beezer; M. O’Neil

2007-01-01

281

Dehydration of isobutanol to isobutene in a slurry reactor  

Microsoft Academic Search

The April 1990 Alternative Fuels Proposal to the Department of Energy involved the development of new technology, based on the liquid phase process, for conversion of coal-derived synthesis gas to oxygenated hydrocarbon fuels, fuel additives, and fuel intermediates. The objective of this work was to develop a slurry reactor based process for the dehydration of isobutanol to isobutene. The isobutene

Latshaw

1994-01-01

282

Cellular Dehydration and Hypovolaemia are Additive in producing Thirst  

Microsoft Academic Search

CELLULAR dehydration1-4 and hypovolaemia5-7 are both conditions which cause thirst, and because both occur in thirst associated with water deprivation, it is essential for theoretical accounts of drinking behaviour8,9 to understand how the two dipsogenic stimuli interact.

John D. Corbit

1968-01-01

283

Hypodermoclysis to treat dehydration: a review of the evidence.  

PubMed

Dehydration is a serious acute condition in older adults associated with significant morbidity and mortality. Hypodermoclysis (HDC; the infusion of fluids into the subcutaneous tissue) can provide an alternative to intravenous (i.v.) rehydration of older adults. This article reviews the relevant literature on the use of HDC to treat mild to moderate dehydration in older adults. A comprehensive search of the literature was conducted to identify research reports on the use of HDC to treat dehydration in older adults. Articles published in English during the previous 10 years were reviewed to reflect current standards of practice. One systematic review; two randomized, controlled trials; and six cohort studies were identified and appraised. Only one study was conducted in the United States; the remainder were conducted in Europe, Asia, and Canada. The evidence indicated that HDC is as effective as i.v. rehydration of older adults with mild to moderate dehydration. The literature cites advantages of HDC over i.v. hydration, including the same number of or fewer complications, cost savings, greater patient comfort, and less nursing time to start and maintain the infusion. It remains unclear from the literature why HDC is used infrequently in the United States. PMID:17971137

Remington, Ruth; Hultman, Todd

2007-12-01

284

Responses of plants to dehydration stress: a molecular analysis  

Microsoft Academic Search

Over more than a decade molecular techniques have been applied to analyse the response of plants to drought with the objective to identify genes which contribute to drought tolerance. The studies have used a variety of experimental strategies, and they have resulted in the characterization of a large number of genes which are expressed upon dehydration. A very prominent group

Dorothea Bartels; Antonella Furini; Jonathan Ingram; Francesco Salamini

1996-01-01

285

Chemical Clearing and Dehydration of GFP Expressing Mouse Brains  

PubMed Central

Generally, chemical tissue clearing is performed by a solution consisting of two parts benzyl benzoate and one part benzyl alcohol. However, prolonged exposure to this mixture markedly reduces the fluorescence of GFP expressing specimens, so that one has to compromise between clearing quality and fluorescence preservation. This can be a severe drawback when working with specimens exhibiting low GFP expression rates. Thus, we screened for a substitute and found that dibenzyl ether (phenylmethoxymethylbenzene, CAS 103-50-4) can be applied as a more GFP-friendly clearing medium. Clearing with dibenzyl ether provides improved tissue transparency and strikingly improved fluorescence intensity in GFP expressing mouse brains and other samples as mouse spinal cords, or embryos. Chemical clearing, staining, and embedding of biological samples mostly requires careful foregoing tissue dehydration. The commonly applied tissue dehydration medium is ethanol, which also can markedly impair GFP fluorescence. Screening for a substitute also for ethanol we found that tetrahydrofuran (CAS 109-99-9) is a more GFP-friendly dehydration medium than ethanol, providing better tissue transparency obtained by successive clearing. Combined, tetrahydrofuran and dibenzyl ether allow dehydration and chemical clearing of even delicate samples for UM, confocal microscopy, and other microscopy techniques.

Saghafi, Saiedeh; Weiler, Reto; Dodt, Hans-Ulrich

2012-01-01

286

Dehydrating of flax fiber with microwave heating for biocomposite production.  

PubMed

The feasibility of microwave dehydrating flax fiber was evaluated using a commercial domestic microwave oven at four power settings representing 200, 300, 400 and 500 Watt (W) power level. Due to the possibility of local heating and consequent fiber degradation, the changes in color of the flax fiber at different levels of temperature were also investigated. The dehydration processes at various power levels were simulated by Page model. Based on visual inspection, color analysis and scanning electron microscopy (SEM) of the fiber, it was revealed that discoloration of the fiber occurred at about 170 degrees C. At 200 and 300 W power level, after 10 minutes of dehydrating, the moisture content of the fiber reached from initial 7.9% close to 2.0 and 1.0%, respectively. For 400 W power level, the moisture content of the fiber dropped to 0. 10% in about 9.5 minutes. Major discoloration of the fiber was noticed when dehydration was proceed beyond 4.5 minutes for 500 W treatment. The Page model very well fitted the experimental data. The coefficients of determination calculated from the model and the experimental data increased with increase in applied microwave power PMID:17278791

Panigrahi, Satyanarayan; Ghazanfari, Ahmad; Meda, Venkatesh

2006-01-01

287

Effects of acute dehydration on brain morphology in healthy humans.  

PubMed

Dehydration can affect brain structure which has important implications for human health. In this study, we measured regional changes in brain structure following acute dehydration. Healthy volunteers received a structural MRI scan before and after an intensive 90-min thermal-exercise dehydration protocol. We used two techniques to determine changes in brain structure: a manual point counting technique using MEASURE, and a fully automated voxelwise analysis using SIENA. After the exercise regime, participants lost (2.2% +/- 0.5%) of their body mass. Using SIENA, we detected expansion of the ventricular system with the largest change occurring in the left lateral ventricle (P = 0.001 corrected for multiple comparisons) but no change in total brain volume (P = 0.13). Using manual point counting, we could not detect any change in ventricular or brain volume, but there was a significant correlation between loss in body mass and third ventricular volume increase (r = 0.79, P = 0.03). These results show ventricular expansion occurs following acute dehydration, and suggest that automated longitudinal voxelwise analysis methods such as SIENA are more sensitive to regional changes in brain volume over time compared with a manual point counting technique. PMID:18064587

Kempton, Matthew J; Ettinger, Ulrich; Schmechtig, Anne; Winter, Edward M; Smith, Luke; McMorris, Terry; Wilkinson, Iain D; Williams, Steven C R; Smith, Marcus S

2009-01-01

288

Dehydrating Magnesium Chloride by Double-Salt Decomposition.  

National Technical Information Service (NTIS)

Federal Bureau of Mines studies show that some organic hydrochlorides can be used as dehydrating agents for producing anhydrous MgCl2 from hydrates and brines. Double salts are formed, and these salts dissociate without decomposition of the magnesium chlo...

D. C. Seidel J. T. May V. E. Edlund

1978-01-01

289

Dehydration Kinetics and Glass Transition of Poly(Acrylic Acid).  

National Technical Information Service (NTIS)

The kinetics of dehydration and decarboxylation as well as the glass transition temperature as a function of anhydride content were measured for poly(acrylic acid). It was found that the glass transition of PAA is of the order of 103C and increases with i...

A. Eisenberg T. Yokoyama E. Sambalido

1968-01-01

290

Dehydration Selectively Increases Dopamine Synthesis in Tuberohypophyseal Dopaminergic Neurons  

Microsoft Academic Search

The concentration of dopamine (DA) and the accumulation of DOPA following the administration of a decarboxylase inhibitor were determined in the rat striatum, median eminence and posterior pituitary, regions containing terminals of nigrostriatal, tuberoinfundibular and tuberohypophyseal DA nerves, respectively. Severe dehydration (2 days water deprivation followed by 3 days of 2% NaCI substituted for drinking water) incressed the concentration of

R. H. Alper; K. T. Demarest; K. E. Moore

1980-01-01

291

mPGES-1-derived PGE2 mediates dehydration natriuresis  

PubMed Central

PGE2 is a natriuretic factor whose production is elevated after water deprivation (WD) but its role in dehydration natriuresis is not well-defined. The goal of the present study was to investigate the role of microsomal prostaglandin E synthase-1 (mPGES-1) in dehydration natriuresis. After 24-h WD, wild-type (WT) mice exhibited a significant increase in 24-h urinary Na+ excretion accompanied with normal plasma Na+ concentration and osmolality. In contrast, WD-induced elevation of urinary Na+ excretion was completely abolished in mPGES-1 knockout (KO) mice in parallel with increased plasma Na+ concentration and a trend increase in plasma osmolality. WD induced a 1.8-fold increase in urinary PGE2 output and a 1.6-fold increase in PGE2 content in the renal medulla of WT mice, both of which were completely abolished by mPGES-1 deletion. Similar patterns of changes were observed for urinary nitrate/nitrite and cGMP. The natriuresis in dehydrated WT mice was associated with a significant downregulation of renal medullary epithelial Na channel-? mRNA and protein, contrasting to unaltered expressions in dehydrated KO mice. By quantitative RT-PCR, WD increased the endothelial nitric oxide synthase (eNOS), inducible NOS, and neuronal NOS expressions in the renal medulla of WT mice by 3.9-, 1.48-, and 2.6-fold, respectively, all of which were significantly blocked in mPGES-1 KO mice. The regulation of eNOS expression was further confirmed by immunoblotting. Taken together, our results suggest that mPGES-1-derived PGE2 contributes to dehydration natriuresis likely via NO/cGMP.

Jia, Zhanjun; Liu, Gang; Sun, Ying; Kakizoe, Yutaka; Guan, Guangju; Zhang, Aihua; Zhou, Shu-Feng

2013-01-01

292

Mantle wedge infiltrated with saline fluids from dehydration and decarbonation of subducting slab.  

PubMed

Slab-derived fluids play an important role in heat and material transfer in subduction zones. Dehydration and decarbonation reactions of minerals in the subducting slab have been investigated using phase equilibria and modeling of fluid flow. Nevertheless, direct observations of the fluid chemistry and pressure-temperature conditions of fluids are few. This report describes CO2-bearing saline fluid inclusions in spinel-harzburgite xenoliths collected from the 1991 Pinatubo pumice deposits. The fluid inclusions are filled with saline solutions with 5.1 ± 1.0% (wt) NaCl-equivalent magnesite crystals, CO2-bearing vapor bubbles, and a talc and/or chrysotile layer on the walls. The xenoliths contain tremolite amphibole, which is stable in temperatures lower than 830 °C at the uppermost mantle. The Pinatubo volcano is located at the volcanic front of the Luzon arc associated with subduction of warm oceanic plate. The present observation suggests hydration of forearc mantle and the uppermost mantle by slab-derived CO2-bearing saline fluids. Dehydration and decarbonation take place, and seawater-like saline fluids migrate from the subducting slab to the mantle wedge. The presence of saline fluids is important because they can dissolve more metals than pure H2O and affect the chemical evolution of the mantle wedge. PMID:23716664

Kawamoto, Tatsuhiko; Yoshikawa, Masako; Kumagai, Yoshitaka; Mirabueno, Ma Hannah T; Okuno, Mitsuru; Kobayashi, Tetsuo

2013-06-11

293

Dehydration Injury in Germinating Soybean (Glycine max L. Merr.) Seeds 1  

PubMed Central

The sensitivity of soybean (Glycine max L. Merr. cv Maple Arrow) seeds to dehydration changed during germination. Seeds were tolerant of dehydration to 10% moisture if dried at 6 hours of imbibition, but were susceptible to dehydration injury if dried at 36 hours of imbibition. Dehydration injury appeared as loss of germination, slower growth rates of isolated axes, hypocotyl and root curling, and altered membrane permeability. Increased electrolyte leakage due to dehydration treatment was observed only from isolated axes but not from cotyledons, suggesting that cotyledons are more tolerant of dehydration. The transition from a dehydration-tolerant to a dehydration-susceptible state coincided with radicle elongation. However, the prevention of cell elongation by osmotic treatment in polyethylene glycol (?6 bars) or imbibition in 20 micrograms per milliliter cycloheximide did not prevent the loss of dehydration tolerance suggesting that neither cell elongation nor cytoplasmic protein synthesis was responsible for the change in sensitivity of soybean seeds to dehydration. Furthermore, the rate of dehydration or rate of rehydration did not alter the response to the dehydration stress.

Senaratna, Tissa; McKersie, Bryan D.

1983-01-01

294

Keeping condensers clean  

SciTech Connect

The humble condenser is among the biggest contributors to a steam power plant's efficiency. But although a clean condenser can provide great economic benefit, a dirty one can raise plant heat rate, resulting in large losses of generation revenue and/or unnecessarily high fuel bills. Conventional methods for cleaning fouled tubes range form chemicals to scrapers to brushes and hydro-blasters. This article compares the available options and describes how one power station, Omaha Public Power District's 600 MW North Omaha coal-fired power station, cleaned up its act. The makeup and cooling water of all its five units comes from the Missouri River. 6 figs.

Wicker, K.

2006-04-15

295

Vortices in condensate mixtures  

SciTech Connect

In a condensate made of two different atomic molecular species, Onsager's quantization condition implies that around a vortex, the velocity field cannot be the same for the two species. We explore some simple consequences of this observation. Thus, if the two condensates are in slow relative translation one over the other, the composite vortices are carried at a velocity that is a fraction of the single-species velocity. This property is valid for attractive interaction and below a critical velocity which corresponds to a saddle-node bifurcation.

Josserand, Christophe; Pomeau, Yves [Laboratoire de Modelisation en Mecanique, UPMC-CNRS UMR 7607, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Laboratoire de Physique Statistique de l'Ecole Normale Superieure, 24 Rue Lhomond, 75231 Paris Cedex 05 (France); Departement of Mathematics, University of Arizona, Tucson, AZ 85720 (United States)

2005-08-15

296

Simple Simulations of DNA Condensation  

SciTech Connect

Molecular dynamics simulations of a simple, bead-spring model of semiflexible polyelectrolytes such as DNA are performed. All charges are explicitly treated. Starting from extended, noncondensed conformations, condensed structures form in the simulations with tetravalent or trivalent counterions. No condensates form or are stable for divalent counterions. The mechanism by which condensates form is described. Briefly, condensation occurs because electrostatic interactions dominate entropy, and the favored Coulombic structure is a charge ordered state. Condensation is a generic phenomena and occurs for a variety of polyelectrolyte parameters. Toroids and rods are the condensate structures. Toroids form preferentially when the molecular stiffness is sufficiently strong.

STEVENS,MARK J.

2000-07-12

297

Municipal Landfill Gas Condensate,  

National Technical Information Service (NTIS)

New regulations relative to air emissions from municipal landfills may require the installation of gas collection systems at landfills. As landfill gas (LFG) is collected, water and other vapors in the gas condense in the system or are purposely removed i...

J. Briggs

1987-01-01

298

Cloud Condensation Nuclei  

Microsoft Academic Search

In this study the supersaturation spectra of Cloud Condensation Nuclei (CCN) and the size distribution spectra of aerosols were investigated. These studies were conducted because it is believed that atmospheric aerosols, especially CCN, can affect the climate of the Earth. First, the size distributions of aerosols and the number concentrations of CCN were measured at different times in different meteorological

Qiang Ji

1995-01-01

299

Condensate removal device  

DOEpatents

A condensate removal device is disclosed which incorporates a strainer in unit with an orifice. The strainer is cylindrical with its longitudinal axis transverse to that of the vapor conduit in which it is mounted. The orifice is positioned inside the strainer proximate the end which is remoter from the vapor conduit.

Maddox, James W. (Newport News, VA); Berger, David D. (Alexandria, VA)

1984-01-01

300

Critical Temperature and Condensate Fraction of a Fermion Pair Condensate  

SciTech Connect

We report on measurements of the critical temperature and the temperature dependence of the condensate fraction for a fermion pair condensate of {sup 6}Li atoms. Bragg spectroscopy is employed to determine the critical temperature and the condensate fraction after a fast magnetic field ramp to the molecular side of the Feshbach resonance. Our measurements reveal evidence of level off of the critical temperature and limiting behavior of condensate fraction near the unitarity limit.

Inada, Yasuhisa; Kuwata-Gonokami, Makoto [ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo 113-8656 (Japan); Horikoshi, Munekazu; Mukaiyama, Takashi [ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Nakajima, Shuta; Ueda, Masahito [ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2008-10-31

301

Effect of feeding dehydrated and ensiled tanniferous sainfoin (Onobrychis viciifolia) on nitrogen and mineral digestion and metabolism of lambs.  

PubMed

The effects of tanniferous sainfoin on digestion and metabolism have been investigated in 12 lambs in an incomplete cross-over design (n = 6). Effects of condensed tannins (CT) were evaluated by comparing dehydrated and ensiled sainfoin treated with and without polyethylene glycol (PEG). Dehydrated and ensiled grass-clover mixtures served as controls. The lambs were fed the treatment diets, including a mineral supplement, for 21 d. During the last 7 d excreta, rumen fluid and blood were sampled. The CT of sainfoin decreased rumen fluid ammonia concentration (p < 0.001) and increased the plasma concentration mainly of essential amino acids (p < 0.001). Body retention of phosphorus, calcium and magnesium was lower with sainfoin compared to PEG-treated sainfoin (p < 0.05). Sainfoin without PEG resulted in lower digestibilities of organic matter and neutral detergent fibre than sainfoin with PEG and the grass-clover mixture (p < 0.001). Ensiling of sainfoin led to the lowest N-retention. In conclusion, the reduction in ruminal ammonia and urine-N losses by sainfoin CT did not improve N-retention. PMID:18030920

Scharenberg, Anna; Arrigo, Yves; Gutzwiller, Andreas; Wyss, Ueli; Hess, Hans D; Kreuzer, Michael; Dohme, Frigga

2007-10-01

302

Biomarker reproducibility in exhaled breath condensate collected with different condensers  

Microsoft Academic Search

Optimal collection and analysis of exhaled breath condensate (EBC) are prerequisites for standardisation and reproducibility of assessments. The present study aimed to assess reproducibility of EBC volume, hydrogen peroxide (H2O2), 8-isoprostane and cytokine measurements using different condensers, including a newly developed glass condenser. At four points in time, 30 healthy subjects performed sequential EBC collections randomly using the following four

P. P. Rosias; C. M. Robroeks; A. Kester; G. J. den Hartog; W. K. Wodzig; G. T. Rijkerse; L. J. Zimmermann; C. P. van Schayck; Q. Jobsis; E. Dompeling

2008-01-01

303

Dehydration and crystallization of amorphous calcium carbonate in solution and in air  

PubMed Central

The mechanisms by which amorphous intermediates transform into crystalline materials are poorly understood. Currently, attracting enormous interest is the crystallization of amorphous calcium carbonate, a key intermediary in synthetic, biological and environmental systems. Here we attempt to unify many contrasting and apparently contradictory studies by investigating this process in detail. We show that amorphous calcium carbonate can dehydrate before crystallizing, both in solution and in air, while thermal analyses and solid-state nuclear magnetic resonance measurements reveal that its water is present in distinct environments. Loss of the final water fraction—comprising less than 15% of the total—then triggers crystallization. The high activation energy of this step suggests that it occurs by partial dissolution/recrystallization, mediated by surface water, and the majority of the particle then crystallizes by a solid-state transformation. Such mechanisms are likely to be widespread in solid-state reactions and their characterization will facilitate greater control over these processes.

Ihli, Johannes; Wong, Wai Ching; Noel, Elizabeth H.; Kim, Yi-Yeoun; Kulak, Alexander N.; Christenson, Hugo K.; Duer, Melinda J.; Meldrum, Fiona C.

2014-01-01

304

Dehydration and crystallization of amorphous calcium carbonate in solution and in air.  

PubMed

The mechanisms by which amorphous intermediates transform into crystalline materials are poorly understood. Currently, attracting enormous interest is the crystallization of amorphous calcium carbonate, a key intermediary in synthetic, biological and environmental systems. Here we attempt to unify many contrasting and apparently contradictory studies by investigating this process in detail. We show that amorphous calcium carbonate can dehydrate before crystallizing, both in solution and in air, while thermal analyses and solid-state nuclear magnetic resonance measurements reveal that its water is present in distinct environments. Loss of the final water fraction--comprising less than 15% of the total--then triggers crystallization. The high activation energy of this step suggests that it occurs by partial dissolution/recrystallization, mediated by surface water, and the majority of the particle then crystallizes by a solid-state transformation. Such mechanisms are likely to be widespread in solid-state reactions and their characterization will facilitate greater control over these processes. PMID:24469266

Ihli, Johannes; Wong, Wai Ching; Noel, Elizabeth H; Kim, Yi-Yeoun; Kulak, Alexander N; Christenson, Hugo K; Duer, Melinda J; Meldrum, Fiona C

2014-01-01

305

The Mechanism of 2-Furaldehyde Formation from d-Xylose Dehydration in the Gas Phase. A Tandem Mass Spectrometric Study  

NASA Astrophysics Data System (ADS)

The mechanism of reactions occurring in solution can be investigated also in the gas phase by suited mass spectrometric techniques, which allow to highlight fundamental mechanistic features independent of the influence of the medium and to clarifying controversial hypotheses proposed in solution studies. In this work, we report a gas-phase study performed by electrospray triple stage quadrupole mass spectrometry (ESI-TSQ/MS) on the dehydration of d-xylose, leading mainly to the formation of 2-furaldehyde (2-FA). It is generally known in carbohydrate chemistry that the thermal acid catalyzed dehydration of pentoses leads to the formation of 2-FA, but several aspects on the solution-phase mechanism are controversial. Here, gaseous reactant ions corresponding to protonated xylose molecules obtained from ESI of a solution containing d-xylose and ammonium acetate as protonating reagent were allowed to undergo collisionally activated decomposition (CAD) into the triple stage quadrupole analyzer. The product ion mass spectra of protonated xylose are characterized by the presence of ionic intermediates arising from xylose dehydration, which were structurally characterized by their fragmentation patterns. As expected, the xylose triple dehydration leads to the formation of the ion at m/z 97, corresponding to protonated 2-FA. On the basis of mass spectrometric evidences, we demonstrated that in the gas phase, the formation of 2-FA involves protonation at the OH group bound to the C1 atom of the sugar, the first ionic intermediate being characterized by a cyclic structure. Finally, energy resolved product ion mass spectra allowed to obtain information on the energetic features of the d-xylose?2-FA conversion.

Ricci, Andreina; Piccolella, Simona; Pepi, Federico; Garzoli, Stefania; Giacomello, Pierluigi

2013-07-01

306

Synthesis and crystal structure of Schiff bases obtained by condensation of 2-aminopyridines with acrylic aldehydes  

Microsoft Academic Search

We synthesized a series of novel imines by reactions of 2-amino-4-methylpyridine with (hetero)aromatic derivatives of acrolein in the presence of molecular sieves (as a dehydrating and acid-catalyzing agent). We determined the molecular and crystal structure of two 2-pyridylazomethines containing the CH=CH–CH=N group by X-ray diffraction analysis.

I. Iovel; L. Golomba; S. Belyakov; E. Lukevics

2000-01-01

307

Methods for dehydration of sugars and sugar alcohols  

DOEpatents

The invention includes a method of dehydration of a sugar using a dehydration catalyst and a co-catalyst within a reactor. A sugar is introduced and H.sub.2 is flowed through the reactor at a pressure of less than or equal to about 300 psig to convert at least some of the sugar into an anhydrosugar product. The invention includes a process for producing isosorbide. A starting material comprising sorbitol is flowed into a reactor. H.sub.2 is counter flowed through the reactor. The starting material is exposed to a catalyst in the presence of a co-catalyst which comprises at least one metal. The exposing is conducted at a hydrogen pressure of less than or equal to 300 psig within the reactor and the hydrogen removes at least some of any water present during the exposing and inhibits formation of colored byproducts.

Holladay, Johnathan E [Kennewick, WA; Hu, Jianli [Kennewick, WA; Zhang, Xinjie [Burlington, MA; Wang, Yong [Richland, WA

2010-08-10

308

Dehydration and oxidation of cellulose hydrolysis products in acidic solution  

SciTech Connect

The dehydration of cotton cellulose in aqueous solutions in the presence of Ac/sub 2/O, AcOH, HCl, H/sub 2/SO/sub 4/ or HBr proceeded by hydrolysis to carbohydrates with acetate groups, followed by conversion to 5-(hydroxymethyl)furfural (I) and then, to levulinic acid (II) accompanied by humic acids. For the formation of I, HCl was a more efficient and selective catalyst than H/sub 2/SO/sub 4/, and the formation of II was promoted by high acid and H/sub 2/O concentrations in the medium. The addition of FeCl/sub 3/ to the dehydration mixture with HCl and continuous distillation led to the isolation of furfural.

Garves, K.

1981-01-01

309

The hydration/dehydration behavior of aspartame revisited.  

PubMed

Aspartame, l-aspartyl-l-phenylalanine methyl ester, has two hydrates (IA and IB), a hemi-hydrate (IIA) and an anhydrate (IIB). The hydration/dehydration behavior of aspartame was investigated using hot-humidity stage X-ray powder diffraction (XRPD) and molecular mechanics modeling in combination with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results of this study are compared to earlier studies on aspartame as described in literature. It is shown that earlier transition studies were hampered by incomplete conversions and wrong assignment of the forms. The combination of the techniques applied in this study now shows consistent results for aspartame and yields a clear conversion scheme for the hydration/dehydration behavior of the four forms. PMID:18207687

Guguta, C; Meekes, H; de Gelder, R

2008-03-13

310

Nocturnal lagophthalmos: never seen before in hypernatraemic dehydration.  

PubMed

We present two cases in which a 10-month-old male infant and another 15-month-old female child presented with symptoms of sleeping with their eyes wide open (lagophthalmos) with features of gastroenteritis (GE) and dehydration. The first child had been seen and discharged the previous day from the paediatric emergency department (ED) with a diagnosis of GE. He presented the following day with sleeping discomfort with his eyes wide open and ongoing symptoms of GE. The second child presented to the ED with features of GE. She was found to be sleeping in the ED with her eyes wide open. Investigations of both children revealed hypernatraemic dehydration. Correction of the electrolyte imbalance in both cases over a period of 48 h led to the resolution of symptoms. PMID:24728900

Rai, Birendra; Moka, Sudha; Sharif, Farhana

2014-01-01

311

Hydrothermal Dehydration of Aqueous Fructose Solutions in a Closed System  

SciTech Connect

The synthesis of materials with targeted size and shape has attracted much attention. Specifically, colloidal spheres with targeted and uniform sizes have opened the door for a variety of applications associated with drug delivery, and manipulation of light (photonic band-gap crystals). Surface modification is a key to realizing many of these applications owing to the inherent inert surface.The remarkable transformation of carbohydrate molecules including sugars to homogeneous carbon spheres is found to readily occur by a dehydration mechanism and subsequent sequestering in aqueous solutions that are heated at 160-180oC in a pressurized vessel. Under such conditions, these molecules actually dehydrate even though they are dissolved in water. Size-tunable metal and metal oxides with uniform shells have also been prepared by using carbon spheres as templates.

Yao, Chunhua; Shin, Yongsoon; Wang, Li Q.; Windisch, Charles F.; Samuels, William D.; Arey, Bruce W.; Wang, Chong M.; Risen Jr., William M.; Exarhos, Gregory J.

2007-10-25

312

30. BUILDING NO. 527, DEHYDRATING PRESSES, LOOKING SOUTH. ALUMINUM NARROWGUAGE ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

30. BUILDING NO. 527, DEHYDRATING PRESSES, LOOKING SOUTH. ALUMINUM NARROW-GUAGE GONDOLA CAR IN LEFT BACKGROUND BROUGHT MOISTENED GUN COTTON FROM REST HOUSE (BUILDING NO. 320-B) IN CANS. (ONE OF THESE CANS IS ON UNLOADING PLATFORM RUNNING BESIDE PRESSES). CONTENTS OF CANS WERE UNLOADED INTO PRESSES BY HAND. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

313

Microwave-assisted air dehydration of apple and mushroom  

Microsoft Academic Search

Microwave-assisted hot-air dehydration of apple and mushroom was performed with low-power microwave energy. The purpose of the investigation was to compare hot-air drying and microwave-assisted hot-air drying. The air velocity, the microwave output power and the air temperature were the variables in the experiments. The microwave energy was supplied by either microwave applicators with transverse magnetic (TM) modes as dominant

Tomas Funebo; Thomas Ohlsson

1998-01-01

314

Selective brain cooling in goats: effects of exercise and dehydration.  

PubMed Central

1. Measurements of brain and central blood temperature (Tbr and Tbl), metabolic rate (MR) and respiratory evaporative heat loss (REHL) were made in trained goats walking on a treadmill at 4.8 km h-1 at treadmill inclines of 0, 5, 10, 15 and 20% when they were fully hydrated and at 0% when they had been deprived of water for 72 h. 2. In hydrated goats, exercise MR increased progressively with increasing treadmill incline. Both Tbl and Tbr rose during exercise, but Tbl always rose more than Tbr, and selective brain cooling (SBC = Tbl - Tbr) increased linearly with Tbl. Significant linear relationships were also present between REHL and Tbl and between SBC and REHL. Neither the slope of the regression relating SBC to Tbl nor the threshold Tbl for onset of SBC was affected by exercise intensity. Manual occlusion of the angularis oculi veins decreased SBC in a walking goat, while occlusion of the facial veins increased SBC. 3. Dehydrated goats had higher levels of Tbl, Tbr and SBC during exercise, but the relationship between SBC and Tbl was the same in hydrated and dehydrated animals. In dehydrated animals, REHL at a given Tbl was lower and SBC was thus maintained at reduced rates of REHL. 4. It is concluded that SBC is a linear function of body core temperature in exercising goats and REHL appears to be a major factor underlying SBC in exercise. The maintenance of SBC in spite of reduced REHL in dehydrated animals could be a consequence of increased vascular resistance in the facial vein and increased flow of cool nasal venous blood into the cranial cavity.

Baker, M A; Nijland, M J

1993-01-01

315

PHOTOSYNTHESIS AND METABOLITE LEVELS IN DEHYDRATING LEAVES OF REAUMURIA SOONGORICA  

Microsoft Academic Search

Reaumuria soongorica (Pall.) Maxim., a perennial semishrub, is able to survive almost complete tissue dehy- dration when water is withheld from it, and then the stem can rehydrate on rewatering. In this work, a series of experiments were conducted to characterize the drought-induced changes in two-year-old Reaumuria soongori- ca. The plants were subjected to dehydration by withholding water for 15

YUBING LIU; TENGGUO ZHANG; JIN WANG

2008-01-01

316

28. BUILDING NO. 527, DEHYDRATING HOUSE, LOOKING SOUTH AT NORTH ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

28. BUILDING NO. 527, DEHYDRATING HOUSE, LOOKING SOUTH AT NORTH (REAR) ELEVATION OF PRELIMINARY SOLVENT RECOVERY WING. RAILS LEADING FROM DOORS CARRIED STANDARD GUAGE R.R. CARTS ONTO SMALL FLATCARS RIDING IN TRACKS IN FOREGROUND. FROM HERE THE CARS WERE TAKEN TO BUILDING NO. 533, SOLVENT RECOVERY. BUILDING NO. 540, LOADING DOCK (STORAGE FOR POWDER BUGGIES) IN BACKGROUND LEFT. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

317

Dehydration dynamics of analcime by in situ synchrotron powder diffraction  

SciTech Connect

The continuous structural transformation of tetragonal analcime (Na{sub 15.87}Al{sub 15.20}Si{sub 32.64}O{sub 96}{center_dot}16.3H{sub 2}O) upon dehydration was studied, using Rietveld structure analysis of temperature-resolved powder diffraction data collected using synchrotron radiation. The variation of the a-c axis length difference and normalized intensity of the (200) reflection as a function of temperature suggest that tetragonal analcime evolves toward a cubic structure at high temperature. The removal of water was accompanied by a spreading of the initial Na sites into many positions bonded to the framework O atoms. The migration of H{sub 2}O molecules through the [111] channels during dehydration caused the six-member ring apertures to open as widely as possible: this was accompanied by a twisting of the tetragonal prism, constituting the analcime framework, which led to an opposite tilting of tetrahedra connecting the prisms. These modifications induced by water diffusion are not energetically favored because they would increase the elasticity energy of the system, and require a substantial thermal activation energy. The analcime framework reached a maximum distortion at about 650 K, the temperature of complete water loss, then underwent a relaxation process during which the T-O-T angles were restored to the starting value. The relative variation of cell volume associated with the opening of wide six-member ring channels during water migration, and then due to the framework relaxation process after complete dehydration, provides an explanation of the negative thermal expansion (i.e., volume contraction) effect in dehydrated analcime, which is complementary to that based on the Rigid Unit Modes theory

Cruciani, G. [Univ. di Ferrara (Italy). Istituto di Mineralogia; Gualtieri, A. [Univ. di Modena (Italy). Dipt. di Scienze della Terra

1999-01-01

318

Increased Insensible Water Loss Contributes to Aging Related Dehydration  

PubMed Central

Dehydration with aging is attributed to decreased urine concentrating ability and thirst. We further investigated by comparing urine concentration and water balance in 3, 18 and 27 month old mice, consuming equal amounts of water. During water restriction, 3 month old mice concentrate their urine sufficiently to maintain water balance (stable weight). 18 month old mice concentrate their urine as well, but still lose weight (negative water balance). 27 month old mice do not concentrate their urine as well and lose even more weight than the 18 month old mice, indicating a larger negative water balance. Negative water balance in older mice is accompanied by increased vasopressin excretion, providing further evidence of dehydration. All 3 groups maintain water balance while consuming only the water in gel food containing 56% water. However, both older groups excrete a smaller volume of urine of higher osmolality, indicating greater extra urinary water loss. Since their feces also contain less water, the excess water lost by the older mice apparently is through other routes, presumably insensible loss through the respiratory tract and skin. The greater insensible water loss occurs at an earlier age (18 months) than decreased urine concentrating ability (27 months). We propose that insensible water loss through skin and respiration increases with age, making a major contribution to aging related dehydration.

Dmitrieva, Natalia I.; Burg, Maurice B.

2011-01-01

319

Inhibition of plasma vasopressin after drinking in dehydrated humans  

NASA Technical Reports Server (NTRS)

The effects of nonosmotic and nonvolumetric factors on vasopressin secretion in dehydrated humans has been investigated experimentally, before and after drinking. The subjects of the experiment were five adult men and three adult women weighing 69-77 kg. In order to determine the influence of nonosmotic and nonvolumetric factors on vasopressin secretion, measurements were obtained of the following blood hematological indices: serum Na(+) content; serum K(+) content; osmolality; and hemoglobin. Measurements of hematocrit, plasma arginine vasopressin (AVP), aldosterone, and renin activity were also obtained. It is found that dehydration increased mean serum Na(+) content, osmolality,and AVP. No significant changes were observed in renin activity, hemoglobin, hematocrit, or plasma volume, while plasma aldosterone increased from 11.1 ng/dl after dehydration to 15.6 ng/dl between 30 and 60 min after drinking. A rapid fall of AVP content following rehydration occurred in the absence of changes in the primary regulators of AVP osmolality and plasma volume, with no change in blood pressure. On the basis of the experimental results, it is suggested that oropharyngeal factors may be the mechanism, for the observed decrease in AVP following rehydration.

Geelen, G.; Keil, L. C.; Kravik, S. E.; Wade, C. E.; Thrasher, T. N.; Barnes, P. R.; Pyka, G.; Nesvig, C.; Greenleaf, J. E.

1984-01-01

320

Electrical conductivity of amphibole-bearing rocks: influence of dehydration  

NASA Astrophysics Data System (ADS)

We investigated the electrical conductivity of amphibole-bearing rocks under the conditions of the middle to lower crust. Alternating current measurements were performed in the frequency range of 10-106 Hz in a cubic-anvil high-pressure apparatus at 0.5-1.0 GPa and 373-873 K. The electrical conductivity of these rocks is weakly temperature dependent below ~800 K with modest anisotropy and relatively low conductivity (~5 × 10-3 S/m at ~750 K with the activation enthalpy of 64-67 kJ/mol). However, the electrical conductivity starts to increase with temperature more rapidly above ~800 K (activation enthalpy of 320-380 kJ/mol). The infrared spectroscopy observations indicate that dehydration occurs in this high temperature regime. The observed high activation enthalpy and the reproducibility suggest that the enhanced conductivity is not due to the direct effect caused by the generation of conductive fluids. Dehydration of amphibole is associated with the oxidation of iron (from ferrous to ferric), and we suggest that the increased conductivity associated with dehydration is caused by oxidation. This effect may explain high electrical conductivity observed in some regions of the continental crust.

Wang, Duojun; Guo, Yingxing; Yu, Yingjie; Karato, Shun-ichiro

2012-07-01

321

Steam condensate corrosion; mechanism; prevention  

Microsoft Academic Search

Steam condensate is a potential corrosion problem in most industries, and because of the tremendous cost involved to protect piping and condensate recovery systems, the problem is greatly increased. The various stages of steam condensate are discussed from its beginning as raw water, through its conversion to steam in a boiler, and to its disposal to a steam consumer, such

1966-01-01

322

Atomic structure and dehydration mechanism of amorphous silica: Insights from 29Si and 1H solid-state MAS NMR study of SiO2 nanoparticles  

NASA Astrophysics Data System (ADS)

Detailed knowledge of the atomic structure of hydrous species on surface of amorphous silica and the effect of temperature and particle size on their atomic configurations are essential to understand the nature of fluids–amorphous silicates interactions and the dehydration processes in the amorphous oxides. Here, we report the 29Si, 1H MAS, and 1H–29Si heteronuclear correlation (HetCor) NMR spectra of 7 nm and 14 nm amorphous silica nanoparticles—a model system for natural amorphous silica—where previously unknown details of changes in their atomic structures with varying dehydration temperature and particle size are revealed. Diverse hydroxyl groups with varying atomic configurations and molecular water apparently show distinct dehydration trends. The dehydration (i.e., removal of water) of amorphous silica nanoparticles mostly results in the increase of isolated silanol by removing water molecules from hydrogen-bonded silanols associated water molecules. With further increase in dehydration temperature, the intensity of isolated silanol peak decreases above ˜873 K, suggesting that the condensation of isolated silanol may occur mainly above ˜873 K. The entire dehydration (and dehydroxylation) process completes at ˜1473 K. Both the water (i.e., physisorbed water and hydrogen-bonded water) and hydrogen-bonded silanol species show a dramatic change in the slope of intensity variation at ˜873 K, indicating that most of silanols is hydrogen-bonded to water rather than to other silanols. The fraction of hydrogen-bonded proton species is also much smaller in 14 nm amorphous silica nanoparticles than in 7 nm amorphous silica nanoparticles mainly due to the presences of larger fractions of water and hydrogen-bonded silanol species. 29Si NMR results show that with increasing dehydration temperature, the fraction of Q4 species apparently increases at the expense of Q2 and Q3 species. The fractions of Q2 and Q3 structures in 7 nm amorphous silica nanoparticles are larger than those in 14 nm amorphous silica nanoparticles. Dehydration of 7 nm amorphous silica nanoparticles occurs at a lower temperature than that of 14 nm amorphous silica nanoparticles. 29Si MAS NMR results show that a possible simultaneous dehydroxylation can also occur with removal of the hydrogen bonded silanol in the 7 nm silica nanoparticles. The energy penalty of dehydroxylation estimated from 29Si MAS NMR spectra varies with Q species and is smaller in 7 nm than in 14 nm amorphous silica nanoparticles. These results demonstrate that the particle size of nanoparticles plays an important role in controlling the hydrogen contents, and thus overall hydrogen bond strength of hydroxyl groups and atomic structure of silanols can control dehydroxylation of amorphous silica nanoparticles. The structural information and mechanistic details obtained from the current study provide insights into the structure of hydrous species and dehydration mechanisms in crystalline and amorphous silicates in diverse geological settings, highlighting usually unknown effects of particle size on the dehydration processes.

Kim, Hyun Na; Lee, Sung Keun

2013-11-01

323

Gravitational vacuum condensate stars  

PubMed Central

A new final state of gravitational collapse is proposed. By extending the concept of Bose–Einstein condensation to gravitational systems, a cold, dark, compact object with an interior de Sitter condensate pv = -?v and an exterior Schwarzschild geometry of arbitrary total mass M is constructed. These regions are separated by a shell with a small but finite proper thickness ? of fluid with equation of state p = +?, replacing both the Schwarzschild and de Sitter classical horizons. The new solution has no singularities, no event horizons, and a global time. Its entropy is maximized under small fluctuations and is given by the standard hydrodynamic entropy of the thin shell, which is of the order kB?Mc/, instead of the Bekenstein–Hawking entropy formula, SBH = 4?kBGM2/c. Hence, unlike black holes, the new solution is thermodynamically stable and has no information paradox.

Mazur, Pawel O.; Mottola, Emil

2004-01-01

324

Modeling of B concentrations and isotopic compositions in subducted slabs and dehydration fluids  

NASA Astrophysics Data System (ADS)

The oceanic lithosphere plays a key role regarding global scale element cycles. Seawater-rock interaction at the ocean floor causes intense chemical modification of the basaltic oceanic crust and possibly also the upper parts of the oceanic mantle. Later subduction of the modified oceanic lithosphere leads to dehydration, which again enables redistribution of major and trace elements in the subducted slab. This dehydration process is responsible for arc volcanism, subduction-related ore formation but also controls the distribution of elements that are recycled into the upper plate and the atmosphere and those that are incorporated into refractory minerals and are recycled into the deeper mantle. Regarding the water budget and thus the element transport in a subduction zone, the potentially hydrated oceanic mantle plays a major role as it can store large amounts of water in hydrous minerals, such as chlorite and serpentine. The pressure and temperature conditions as well as the fluid-rock interaction within the subducted slab controls whether water - and elements solved therein - can escape the slab or are deeply subducted and recycled into the Earth's mantle. Boron concentrations and isotopic compositions are excellent tracers for the contribution of oceanic lithospheric mantle to the water and trace element budget in subduction zones: boron is incorporated at significant amounts in serpentine, it is highly fluid mobile and its two stable isotopes (10B and 11B) undergo equilibrium fractionation between fluid and solid phases. In this contribution, thermal and thermodynamic models of subduction of oceanic lithosphere are combined with trace element and isotope partitioning data in order to quantify boron concentrations and its isotopic composition in coexisting fluid and solid phases during devolatilisation, fluid migration and fluid-rock interaction in a subducted slab. The results show that fluid-mobile elements undergo complex liberation and resorption processes during fluid migration in a dehydrating slab, which leads to re-enrichment of previously leached lithologies. Such internal redistribution of trace elements within the slab enables recycling of fluid mobile elements beyond the dehydration interval into the deep mantle beyond sub-arc depths. Further, this study shows that across arc variations of the isotopic composition of boron in arc volcanics can be used as indicator for the hydration state of the subducted oceanic mantle lithosphere. Increases in boron concentrations and ?11B in rear- and back-arc volcanic rocks, as observed for example in Kamchatka and Northern Japan, can be explained by dehydration of serpentinized upper oceanic mantle.This release occurs over a small pressure and temperature range and, despite intense fluid-rock interaction in the slab crust, the associated trace element signal is transferred to the slab surface and into the mantle wedge. The position of the serpentinite-out reaction and thus the associated trace element signal is dependent on the thermal structure within the slab. Consequently complex across-arc variations in boron concentrations and boron isotopic compositions can be used as constraining parameters in thermomechanical subduction zone models.

Konrad-Schmolke, Matthias

2013-04-01

325

Analysis of Dehydration and Strength in Elite Badminton Players  

PubMed Central

Background The negative effects of dehydration on aerobic activities are well established. However, it is unknown how dehydration affects intermittent sports performance. The purpose of this study was to identify the level of dehydration in elite badminton players and its relation to muscle strength and power production. Methodology Seventy matches from the National Spanish badminton championship were analyzed (46 men’s singles and 24 women’s singles). Before and after each match, jump height and power production were determined during a countermovement jump on a force platform. Participants’ body weight and a urine sample were also obtained before and after each match. The amount of liquid that the players drank during the match was also calculated by weighing their individual drinking bottles. Results and Discussion Sweat rate during the game was 1.14±0.46 l/h in men and 1.02±0.64 l/h in women. The players rehydrated at a rate of 1.10±0.55 l/h and 1.01±0.44 l/h in the male and female groups respectively. Thus, the dehydration attained during the game was only 0.37±0.50% in men and 0.32±0.83% in women. No differences were found in any of the parameters analyzed during the vertical jump (men: from 31.82±5.29 to 32.90±4.49 W/kg; p>0.05, women: from 26.36±4.73 to 27.25±4.44 W/kg; p>0.05). Post-exercise urine samples revealed proteinuria (60.9% of cases in men and 66.7% in women), leukocyturia (men?=?43.5% and women?=?50.0%) and erythrocyturia (men?=?50.0% and women?=?21.7%). Conclusions Despite a moderate sweat rate, badminton players adequately hydrated during a game and thus the dehydration attained was low. The badminton match did not cause muscle fatigue but it significantly increased the prevalence of proteinuria, leukocyturia and erythrocyturia.

Abian-Vicen, Javier; Del Coso, Juan; Gonzalez-Millan, Cristina; Salinero, Juan Jose; Abian, Pablo

2012-01-01

326

Effects of dehydration on organ metabolism in the frog Pseudacris crucifer : hyperglycemic responses to dehydration mimic freezing-induced cryoprotectant production  

Microsoft Academic Search

The metabolic effects of evaporative water loss at 5 °C were assessed for both fall- and spring-collected spring peepersPsuedacris crucifer. Frogs readily endured the loss of 50% of total body water. During dehydration organ water content was defended with no change in water content in skeletal muscle, gut, and kidney of 50% dehydrated frogs and reduced water content in liver,

T. A. Churchill; K. B. Storey

1994-01-01

327

Pore formation during dehydration of a polycrystalline gypsum sample observed and quantified in a time-series synchrotron X-ray micro-tomography experiment  

NASA Astrophysics Data System (ADS)

We conducted an in-situ X-ray micro-computed tomography heating experiment at the Advanced Photon Source (USA) to dehydrate an unconfined 2.3 mm diameter cylinder of Volterra Gypsum. We used a purpose-built X-ray transparent furnace to heat the sample to 388 K for a total of 310 min to acquire a three-dimensional time-series tomography dataset comprising nine time steps. The voxel size of 2.2 ?m3 proved sufficient to pinpoint reaction initiation and the organization of drainage architecture in space and time. We observed that dehydration commences across a narrow front, which propagates from the margins to the centre of the sample in more than four hours. The advance of this front can be fitted with a square-root function, implying that the initiation of the reaction in the sample can be described as a diffusion process. Novel parallelized computer codes allow quantifying the geometry of the porosity and the drainage architecture from the very large tomographic datasets (20483 voxels) in unprecedented detail. We determined position, volume, shape and orientation of each resolvable pore and tracked these properties over the duration of the experiment. We found that the pore-size distribution follows a power law. Pores tend to be anisotropic but rarely crack-shaped and have a preferred orientation, likely controlled by a pre-existing fabric in the sample. With on-going dehydration, pores coalesce into a single interconnected pore cluster that is connected to the surface of the sample cylinder and provides an effective drainage pathway. Our observations can be summarized in a model in which gypsum is stabilized by thermal expansion stresses and locally increased pore fluid pressures until the dehydration front approaches to within about 100 ?m. Then, the internal stresses are released and dehydration happens efficiently, resulting in new pore space. Pressure release, the production of pores and the advance of the front are coupled in a feedback loop.

Fusseis, F.; Schrank, C.; Liu, J.; Karrech, A.; Llana-Fúnez, S.; Xiao, X.; Regenauer-Lieb, K.

2012-03-01

328

Characterization of Solute Efflux from Dehydration Injured Soybean (Glycine max L. Merr) Seeds 1  

PubMed Central

Soybean (Glycine max L. Merr) seeds lose their tolerance of dehydration between 6 and 36 hours of imbibition. Soybean axes and cotyledons were excised 6 hours (tolerant of dehydration) and 36 hours (susceptible) after commencing imbibition and subsequently dehydrated to 10% moisture. Kinetics of the efflux of potassium, phosphate, amino acid, sugar, protein, and total electrolytes were compared in the four treatments during rehydration. Only slight differences were observed in the kinetics of solute efflux between the two cotyledon treatments dehydrated at 6 and 36 hours suggesting that the cotyledons may retain their tolerance of dehydration at this stage of germination. Several symptoms of injury were observed in the axes dehydrated at 36 hours. An increase in the initial leakage of solutes during rehydration, as quantified by the y-intercept of the linear regression line for solute efflux between 2 and 8 hours suggests an increased incidence of cell rupture. An increase in the rate of solute efflux (slope of regression line between 2 and 8 hours) from fully rehydrated axes was observed in comparison to axes dehydrated at 6 hours. The Arrhenius activation energy for potassium, phosphate, and amino acid efflux decreased and for protein remained unchanged. Both observations indicate an increase in membrane permeability in dehydration-injured tissue. Increasing the H+ concentration of the external solution increased K+ efflux from both control and dehydrated/rehydrated samples, increased sugar efflux from axes at 6 hours imbibition but decreased sugar efflux from axes at 36 hours imbibition, indicating changes in membrane properties during germination. The dehydration treatment did not alter the pattern of the pH response of axes dehydrated at 6 or 36 hours but did increase the quantity of potassium and sugar efflux from dehydration injured axes. These results are interpreted as indicating that dehydration of soybean axes at 36 hours of imbibition increased both the incidence of cell rupture during rehydration and altered membrane permeability of the rehydrated tissue.

Senaratna, Tissa; McKersie, Bryan D.

1983-01-01

329

Structural Characterization and Cage-Condensation Reactions of the Coupled-Cage Borane 1:2'-(B2H8)2: New Routes to Higher Single-Cage Boranes and Carboranes,  

National Technical Information Service (NTIS)

We recently reported the development of high-yield, catalytic synthetic routes to boron-boron-coupled polyhedral boranes and carboranes via transition-metal-promoted dehydrocondensation reactions. The facile formation of multicage systems is potentially o...

J. J. Briguglio P. J. Carroll E. W. Corcoran L. G. Sneddon

1986-01-01

330

Michael Condensation in a Two-Phase System: The Application of Inverse Phase-Transfer Catalysis to the Reaction of Butyl Acrylate with Diethylamine in a Water–Heptane System  

Microsoft Academic Search

The kinetics of a heterogeneous reaction of fat-soluble butyl acrylate (BA) with water-soluble diethylamine (DEA) in a two-phase water–heptane system in the presence and absence of small amounts of water-soluble surfactants was studied by the methods of inverse phase-transfer and interfacial catalysis. It was found that the rate of the reaction in either a homogeneous medium or the two-phase system

G. S. Simonyan; N. M. Beileryan

2002-01-01

331

Deep-level magma dehydration and ascent rates at Mt. Etna (Sicily, Italy)  

NASA Astrophysics Data System (ADS)

Magma ascent velocity, v (dH/dt; H = depth, t = time),can be determined from ascent rate (dP/dt), and rate of cooling (dT/dt): v= 1/(rgpg) (dP/dT)(dT/dt) where r is magma density, P is pressure, T is temperature and g is the acceleration of gravity. This equation for v provides a key to investigating the relationships between initial ascent rate of magma and the depths of magma dehydration, and v can be calculated using pressure and temperature (P - PH2O - T) estimates from mineral-liquid thermobarometry, and cooling rates inferred from Crystal Size Distribution (CSD) theory. For recent Mt. Etna lava flows, both dP/dT and dT/dt have been well characterized based, respectively, on clinopyroxene thermobarometry, and clinopyroxene CSDs (the latter yields dT/dt = 2x10-6 °C/s). Deep-level (>20 km) magma ascent rates range from practically 0 (where clinopyroxene P - T estimates form a cluster, and so dP/dT ? 0), to about 10 m/hr for flows that yield very steep P - T trajectories. Many lava flows at Mt. Etna yield P - T paths that follow a hydrous (about 3% water) clinopyroxene saturation surface, which closely approximates water contents obtained from melt inclusions. Independent assessments of deep level water content yield ascent rates of ~1 m/hr, in agreement with the slowest rates derived for magma effusion or vapor-driven ascent (~0.001 to >0.2 m/s, or 3.6 to 720 m/hr). Changes in P - T slopes, as obtained by pyroxene thermobarometry, indicate an upward acceleration of magma, which may be due to the onset of deep-level magma dehydration linked to the non-ideal behavior of water and CO2 mixtures that induce a deep-level maximum of water loss at P ? 0.4 MPa at T ? 1200 ° C for a CO2 content >1000ppm. Melt inclusion data on CO2 and H2O contents are successfully reproduced and interpreted in a context of magma dehydration induced by a CO2 flux possibly deriving by decarbonation reaction of the carbonate fraction of the Capo D'Orlando flysch.

Armienti, P.; Perinelli, C.; Putirka, K.

2012-04-01

332

Seed dehydration and the establishment of desiccation tolerance during seed maturation is altered in the Arabidopsis thaliana mutant atem6-1.  

PubMed

The end of orthodox seed development is typified by a developmentally regulated period of dehydration leading to the loss of bulk water from the entire structure. When dehydration occurs, the cytoplasm condenses and intracellular components become more crowded, providing an environment amenable to numerous undesirable interactions that can lead to protein aggregation, denaturation and organelle-cell membrane fusion. Acquisition of desiccation tolerance, or the ability to withstand these very low water potentials and consequent molecular crowding, has been correlated with the accumulation of various protective compounds including proteins and sugars. Among these are the late embryogenesis abundant (LEA) proteins, a diverse class of highly abundant, heat-stable proteins that accumulate late in embryo maturation coincident with the acquisition of desiccation tolerance. Previous work led us to hypothesize that the protein ATEM6, one of the two Arabidopsis thaliana group 1 LEA proteins, is involved in regulating the rate at which water is lost from the maturing embryo; homozygous atem6-1 mutants display premature dehydration of seeds at the distal end of the silique. Here we demonstrate that rehydrated, mature seeds from atem6-1 mutant plants lose more water during subsequent air drying than wild-type seeds, consistent with a role for ATEM6 protein in water binding/loss during embryo maturation. In addition, and possibly as a result of premature dehydration, mutant seeds along the entire length of the silique acquire desiccation tolerance earlier than their wild-type counterparts. We further demonstrate precocious, and perhaps elevated, expression of the other A. thaliana group 1 LEA protein, ATEM1, that may compensate for loss or ATEM6 expression. However, this observation could also be consistent with acceleration of the entire normal maturation program in atem6-1 mutant embryos. Interestingly, ATEM6 protein does not appear to be required in mature seeds for viability or efficient germination. PMID:19073649

Manfre, Alicia J; LaHatte, Gabrielle A; Climer, Cynthia R; Marcotte, William R

2009-02-01

333

Confinement Contains Condensates  

SciTech Connect

Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have commonly been viewed as constant empirical mass-scales that fill all spacetime, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence, and incidentally expose misconceptions in a recent Comment.

Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.

2012-03-12

334

Optimisation of osmotic dehydration of carrot cubes in sucrose-salt solutions using response surface methodology  

Microsoft Academic Search

Osmotic dehydration of carrot cubes in ternary solution of water, sucrose and sodium chloride at different solution concentrations,\\u000a temperatures and process durations were analysed for water loss and solute gain during osmotic dehydration. The osmotically\\u000a pre-treated carrot cubes were further dehydrated in a cabinet dryer at 65 °C and were then rehydrated in water at ambient\\u000a temperature of water for 10–12 h

Bahadur Singh; Parmjit S. Panesar; A. K. Gupta; John F. Kennedy

2007-01-01

335

Water Loss and Gene Expression of Rice ( Oryza sativa L.) Plants Under Dehydration  

Microsoft Academic Search

This study aims to determine physiological and molecular alterations as exposed to dehydration stress in rice plant. Rice\\u000a seedlings were grown in a nutrient solution within a managed environment chamber prior to the imposition of the dehydration\\u000a stress. Dehydration was imposed through uprooting and exposing to controlled environment condition (25°C, RH 50%, and 290\\u000a PAR). Water loss of intact plant

T.-R. Kwon; J.-O. Lee; S.-K. Lee; S.-C. Park

336

Surface structures of supported tungsten oxide catalysts under dehydrated conditions  

Microsoft Academic Search

The molecular structures of the WO3\\/support (Al2O3, TiO2, Nb2O5, ZrO2, SiO2, and MgO) catalysts under in situ dehydrated conditions have been investigated by Raman spectroscopy. The series of catalysts was synthesized by the aqueous incipient wetness method. The WO3\\/support catalysts, with the exception of the WO3SiO2 and WO3MgO catalysts, possess a highly distorted, octahedrally coordinated surface tungsten oxide species with

Du Soung Kim; Marlene Ostromecki; Israel E. Wachs

1996-01-01

337

Strange Disoriented Chiral Condensates  

NASA Astrophysics Data System (ADS)

Enhancement of omega and anti-omega baryon production in Pb+Pb collisions at the CERN SPS can be explained by the formation of many small regions of disordered chiral condensate. This explanation implies that neutral and charged kaons as well as pions must exhibit novel isospin fluctuations. Fluctuations due to transient behavior of the Polyakov Loop condensate can produce similar phenomena. Kapusta and Gavin have computed the distribution of the fraction of neutral pions and kaons from such regions. We proposed robust statistical observables that can be used to extract the novel isospin fluctuations from background contributions in neutral/charged pion and K-short/K-charged correlation measurements at RHIC and LHC. The STAR experiment is currently examining K-short/K-charged correlations. Note that Pruneau, Voloshin and Gavin have proposed similar observables to study net-charge fluctuations. To obtain a baseline for comparison to RHIC and SPS experiments, Abdel-Aziz and Gavin compute these observables using numerical simulations using HIJING and URQMD event generators. We also obtain limits on the size and number of disordered regions by comparing to photon and charged-pion searches from WA98 and other SPS experiments. We will compare to the first results from STAR K-short/K-charged analysis.

Abdel-Aziz, Mohamed; Gavin, Sean

2002-10-01

338

The effects of anaerobic fermentation on dehydrated sludge.  

PubMed

Dehydrated sludge with two concentrations of total suspended solids (high: 50 g/L TSS; low: 20 g/L TSS) were studied for 20 d to investigate the effects of anaerobic fermentation on sludge properties. The results showed that the soluble chemical oxygen demand (SCOD) of high-concentration sludge was 16.53 g/L, much higher than that from the low one. The SCOD/total nitrogen ratio of high-concentration sludge varied from 8 to 14.29 g/g, indicating that the sludge could serve as a carbon source for biological denitrification. High-concentration sludge showed a short-chain fatty acid yield of 11.29 g COD/L, much higher than that from low-concentration sludge. The specific resistance of the sludge to filtration (SRF) increased with fermentation time. The quantity of low-speed centrifugation substances (LSCS) was the main factor that influenced the reduction of dehydration. The correlation coefficient between the SRF and protein content in the LSCS layer was significantly positive. PMID:23752399

Lu, Haowen; Dai, Ruihua; Liu, Yan; Song, Anan; Liu, Xiang

2013-01-01

339

Hypernatraemic dehydration in the Hail region of Saudi Arabia.  

PubMed

Infants presenting with hypernatraemic dehydration were studied prospectively in order to describe its incidence and the predisposing factors. Five hundred and twenty children with gastroenteritis were admitted to the Paediatric Unit of Hail General Hospital over a 1-year period from 1 June 1985 to 1 June 1986. Twenty-five children (4.8%) had hypernatraemia (Na+ greater than 150 mmol/l) and all 25 were under 1 year of age, 23 (92%) being under 6 months. Twenty (80%) came from families living in the villages and had a poor educational background. All the babies were bottle-fed. The majority of the mothers did not know how to prepare food hygienically and with the appropriate water/milk proportions. Most of the infants presented with high fever (+39 degrees C) and the majority were underweight for their age. Two babies died and one had evidence of neurological damage. This study indicates that the incidence of hypernatraemic dehydration is significant in this region and causes serious morbidity and mortality. It confirms the importance of breast-feeding and the need to educate the public in the proper preparation of bottle feeds when breast-feeding is not possible. PMID:1703742

Mehasi, A I; Murthy, K

1990-01-01

340

Dehydration of scandium chloride hydrate: synthesis and molecular structures of ScCl 3(? 2DME)(MeCN), ScCl 3(diglyme) and [Sc 2(?-OH) 2(H 2O) 10]Cl 4·2H 2O  

Microsoft Academic Search

Various dehydration procedures have been evaluated for ScCl3·6H2O. The ScCl3(DME)(MeCN) 1 and ScCl3(diglyme) 2 [diglyme=MeO(CH2CH2O)2Me] adducts have been synthesized by a ligand-exchange reaction from ScCl3(THF)3 in acetonitrile. The diglyme adduct could also be obtained by dehydration of ScCl3·6H2O by trimethylchlorosilane in diethylether in the presence of the ligand. The complexes were characterized by FT–IR, 1H NMR and by X-ray diffraction.

Valérie Ripert; Liliane G. Hubert-Pfalzgraf; Jacqueline Vaissermann

1999-01-01

341

Safety of chlorination reactions  

Microsoft Academic Search

Chlorination reactions are part of various processes in the chemical industry, to manufacture heavy chemicals, specialty chemicals, pesticides and pharmaceuticals, in inorganic and organic chemistry. They are a valuable tool in organic synthesis.The hazard of processing chlorine involves:u- Gas phase explosion;- Runaway reaction or thermal explosion in the condensed phase.Gas phase explosion hazard with chlorine as an oxidizer is present

Jean-Louis Gustin; Alexandre Fines

1996-01-01

342

Potentially Prebiotic Syntheses of Condensed Phosphates  

NASA Technical Reports Server (NTRS)

In view of the importance of a prebiotic source of high energy phosphates, we have investigated a number of potentially prebiotic processes to produce condensed phosphates from orthophosphate and cyclic trimetaphosphate from tripolyphosphate. The reagents investigated include polymerizing nitriles, acid anhydrides, lactones, hexamethylene tetramine and carbon suboxide. A number of these processes give substantial yields of pyrophosphate from orthophosphate and trimetaphosphate from tripolyphosphate. Although these reactions may have been applicable in local areas, they are not sufficiently robust to have been of importance in the prebiotic open ocean.

Keefe, Anthony D.; Miller, Stanley L.

1996-01-01

343

Condensation Processes in Geothermal Systems  

NASA Astrophysics Data System (ADS)

We model condensation processes in geothermal systems to understand how this process changes fluid chemistry. We assume two processes operate in geothermal systems: 1) condensation of a vapor phase derived by boiling an aqueous geothermal fluid into a cool near surface water and 2) condensation of a magmatic vapor by a deep circulating meteoric thermal fluid. It is assumed that the condensation process has two stages. Initially the condensing fluid is under saturated in gaseous species. Condensation of the vapor phase continues until the pressure on the fluid equals the sum of the partial pressures of water and the dissolved gaseous species. At that time bubbles flux through the condensing fluid. In time the fluid and fluxing gas phase come to equilibrium. Calculation shows that during the second stage of the condensation process the liquid phase becomes enriched in more soluble gaseous species like CO2 and H2S, and depleted in less soluble species like CH4 and N2. Stage 2 condensation processes can therefore be monitored by ratios of more and less condensable species like CO2/N2. Condensation of vapor released by boiling geothermal fluids results in liquids with high concentrations of H2S and CO2 like is seen in geothermal system steam-heated waters. Condensation of a magmatic vapor into circulating meteoric water has been proposed, but not well demonstrated. We compare to our models the Cerro Prieto, Mexico gas analysis data set collected over twelve years time by USGS personnel. It was assumed for modeling that the Cerro Prieto geothermal fluids are circulating meteoritic fluids with N2/Ar ratios about 40 to which is added a magmatic vapor with N2/Ar ratio = 400. The Cerro Prieto analyses show a strong correlation between N2/Ar and CO2/N2 as predicted by calculation. Two dimensional image plots of well N2/Ar + CO2/N2 show a bull's-eye pattern on the geothermal field. Image plots of analyses collected over a year or less time show N2/Ar and CO2/N2 hot spots. Plotting data for individual wells show a hysteresis like loops on time vs. CO2/N2 diagrams. Our analysis demonstrates that condensation of magmatic vapor into convecting meteoric waters is a viable process. Condensation explains variations in Cerro Prieto geothermal system gas chemistry and is compatible with helium isotope data. Locally condensation appears to wax and wane over a time periods of about 10 years.

Norman, D. I.; Moore, J. N.

2005-12-01

344

Mechanism of the dehydration of D-fructose to 5-hydroxymethylfurfural in dimethyl sulfoxide at 150 ?C: An NMR study  

PubMed Central

The anomeric composition of D-fructose in dimethyl sulfoxide changes when the solution is heated from room temperature to 150 °C, with a small increase in the ?-furanose form at the expense of the ?-pyranose tautomer. Additionally, a small amount of ?-pyranose form was also observed at 150 °C. A mechanism is proposed for the dehydration of D-fructose to 5-hydroxymethylfurfural in DMSO at 150 °C, where the solvent acts as the catalyst. A key intermediate in the reaction was identified as (4R,5R)-4-hydroxy-5-hydroxymethyl-4,5-dihydrofuran-2-carbaldehyde by using 1H and 13C NMR spectra of the sample during the reaction.

Amarasekara, Ananda S.; Williams, LaToya D.; Ebede, Chidinma C.

2008-01-01

345

Microgravity condensing heat exchanger  

NASA Technical Reports Server (NTRS)

A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.

Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)

2011-01-01

346

Addition polymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and Bis-dienes. 2: Evidence for thermal dehydration occurring in the cure process  

NASA Technical Reports Server (NTRS)

Diels-Alder cycloaddition copolymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and anthracene end-capped polyimide oligomers appear, by thermogravimetric analysis (TGA), to undergo dehydration at elevated temperatures. This would produce thermally stable pentiptycene units along the polymer backbone, and render the polymers incapable of unzipping through a retro-Diels-Alder pathway. High resolution solid 13C nuclear magnetic resonance (NMR) of one formulation of the polymer system before and after heating at elevated temperatures, shows this to indeed be the case. NMR spectra of solid samples of the polymer before and after heating correlated well with those of the parent pentiptycene model compound before and after acid-catalyzed dehydration. Isothermal gravimetric analyses and viscosities of the polymer before and after heat treatment support dehydration as a mechanism for the cure reaction.

Meador, Mary Ann B.; Olshavsky, Michael A.; Meador, Michael A.; Ahn, Myong-Ku

1988-01-01

347

Zirconium-catalyzed Nagata reaction for the synthesis of 2-aryl-1,3,2-aryldioxaborins via a mild three-component condensation of phenols, aldehydes, and boronic acid  

Microsoft Academic Search

An efficient ZrCl4-catalyzed ortho-hydroxyalkylation of phenols with aldehydes promoted by 3,5-bis(trifluoromethyl)phenyl boronic acid, leading to the formation of 2-aryl-1,3,2-aryldioxaborins, was investigated and optimized. The reaction afforded the desired aryldioxaborins in good to excellent yields under mild conditions at room temperature. The electron-deficient boronic acid promoter was essential. Electron-rich phenols react faster, and both alkyl and aryl aldehydes are suitable substrates.

Hongchao Zheng; Dennis G. Hall

2010-01-01

348

Condensed Explosive Gas Dynamic Laser.  

National Technical Information Service (NTIS)

The condensed explosive of a gas dynamic laser is a condensed mixture of one or more nonhydrogenous organic explosive compounds, such as TNM, with a sufficient amount of aluminum or zirconium powder to supply energy to the products so that a temperature o...

J. Hershkowitz M. Y. D. Lanzerotti

1978-01-01

349

Counterion condensation on ionic oligomers  

NASA Astrophysics Data System (ADS)

The Ramanathan-Woodbury formulas representing the charge density critical for the onset of counterion condensation on finite-length polymers are derived by three alternate methods, an extension of Debye-Huckel theory, a theory of end effects, and by density functional theory. For charged oligomers with length of the same order as the Debye length, the threshold for condensation is the same as for polymers of length much greater than the Debye lenght. However, the threshold depends both on length and salt concentration if the oligomer is shorter than the Debye length, in such a way as to recede to infinity as the ratio of oligomer length to Debye length tends to zero (i.e., condensation vanishes in this limit). The extended Debye-Huckel theory additionally provides a new result for the partition function of the condensed layer, showing that the free energy of the condensed counterions is different on an oligomer and a polymer, even when the fractional extent of condensation is the same. The end effect theory discloses a hitherto unnoticed connection between the number of counterions condensed at the ends of a long polymer and the number condensed on a short oligomer.

Manning, Gerald S.; Mohanty, Udayan

1997-02-01

350

Nuclear Fusion in a Solid via a Bose Bloch Condensate.  

National Technical Information Service (NTIS)

A theory of solid state fusion is presented based on the formation of a D(+) bosonic Bloch condensate within a metal deuteride. The first step towards fusion is a coalescence reaction which converts a 4-fold occupation state of zero point motion size into...

S. R. Chubb T. A. Chubb

1990-01-01

351

An asymptotic theory of condensed two-phase flame propagation  

Microsoft Academic Search

A model is presented for flame propagation though a condensed combustible mixture in which the limiting component of the mixture melts during the reaction process. An asymptotic analysis, valid for large activation energies, is employed to derive a two-term expansion for the steady, planar adiabatic flame speed. A linear stability analysis is then used to show that for sufficiently large

Stephen B. Margolis

1983-01-01

352

Dehydration of the upper troposhere and lower stratosphere by subdivisible cirrus clouds near the tropical tropopause  

Microsoft Academic Search

The extreme dryness of the lower stratosphere is believed to be caused by freeze-drying air as it enters the stratosphere through the cold tropical troposphere. Previous investigations have been focused on dehydration occurring at the tops of deep convective cloud systems. However, recent observations of a ubiquitous stratiform cirrus cloud layer near the tropical tropopause suggest the possibility of dehydration

Eric J. Jensen; Owen B. Toon; Leonard Pfister; Henry B. Selkirk

1996-01-01

353

DEHYDRATION OF FRUITS AND VEGETABLES - RECENT DEVELOPMENTS IN PRINCIPLES AND TECHNIQUES  

Microsoft Academic Search

Advances in dehydration techniques and development of novel drying methods have in recentyears enabled the preparation of a wide range of dehydrated products and convenience foods from fruits and vegetables meeting the quality, stability and functional requirements coupled with economy. This has been made possible by the sustained experimental studies over the years to understand the theoretical and fundamental aspects

K. S. Jayaraman; D. K. Das Gupta

1992-01-01

354

Evaluation and treatment of cancer-related fluid deficits: volume depletion and dehydration  

Microsoft Academic Search

Fluid deficits should be divided into two categories (dehydration and volume depletion) according to pathophysiology and into 3 categories (hyponatremic, hypernatremic, and isotonic) according to the plasma sodium concentration. Dehydration (total water deficit especially intracellular) is always hypernatremic, while volume depletion (intravascular water and sodium deficit) is either hyponatremic, hypernatremic, or isotonic. There are no clear clinical differences among the

N. Sarhill; D. Walsh; K. Nelson; M. Davis

2001-01-01

355

Waste grape skins thermal dehydration: potential release of colour, phenolic and aroma compounds into wine  

Microsoft Academic Search

Exploitation of grape waste material is scarce. One of the main issues to deal with is its high moisture content, as it causes spoilage and degradation of valuable compounds. In order to assess this limitation, four different Vitis vinifera waste grape skins from the juice industry were dehydrated at 60, 90 and 100°C. Characterisation of dehydrated waste grape skins (DWGS)

Miguel A. Pedroza; Manuel Carmona; Francisco Pardo; M. Rosario Salinas; Amaya Zalacain

2012-01-01

356

Dehydration does not affect the radial pressures produced by the earthworm Aporrectodea caliginosa  

Microsoft Academic Search

As a soil dries, the earthworms in that soil dehydrate and become less active. Moisture stress may weaken an earthworm, lowering the radial pressure that the animal can produce. This possibility was investigated for the earthworm Aporrectodea caliginosa (Savigny). Pressures were compared for saturated earthworms (worms taken from saturated soil) and stressed earthworms (worms that had been partially dehydrated by

Robert J. Stovold; W. Richard Whalley; Peter J. Harris

2003-01-01

357

The “dehydrated” lumbar intervertebral disk on MR, its anatomy, biochemistry and biomechanics  

Microsoft Academic Search

# Springer-Verlag 2011 MR imaging of the lumbar spine often reveals disks with lower than normal signal in the nucleus pulposus without decreased disk height or abnormal contours of the annulus fibrosus. These are often referred to as “dehydrated”, “desiccated” or “dark” disks. The clinical significance of dehydrated disks may not be generally known. Official reports of MR images tend

Vitcor Haughton

2011-01-01

358

Mass Transfer Modeling and Shrinkage Consideration during Osmotic Dehydration of Fruits and Vegetables  

Microsoft Academic Search

During osmotic dehydration of fruits and vegetables, as water and\\/or other substances are removed from the material, shrinkage follows depending on the extent of net mass loss. Mass transfer is usually predicted through modeling. However, common models developed for osmotic dehydration of fruits and vegetables make assumptions that often deviate far from reality, including large heterogeneity, variability and complexity in

Hilaire Nahimana; Min Zhang; Arun S. Mujumdar; Zhansheng Ding

2011-01-01

359

Dehydration Behaviour of Borax Pentahydrate to Anhydrous Borax by MultiStage Heating in a Fluidized  

Microsoft Academic Search

In order to optimize the anhydrous borax process in a fluidized bed calcinator, it is absolutely necessary to study the dehydration behaviour of borax pentahydrate. It was found that the basic feature of the dehydration of borax pentahydrate to anhydrous borax is concerned with the conditions employed. The bulk density and sodium borate content of the end product were determined

Omer S AH; A. Nusret BULUTCU

360

Effect of blanching\\/osmotic dehydration combined methods on quality and stability of minimally processed strawberries  

Microsoft Academic Search

The combined effect of blanching [steam (S) or microwave (MW)] and osmotic dehydration at atmospheric pressure (OD) or pulsed vacuum treatments (PVOD), on some physiochemical and quality parameters of strawberry (aw, pH, color, firmness, polyphenoloxidase enzyme activity and microstructure), as well as on microbial stability of processed samples, was analyzed. Pulsed vacuum osmotic dehydration with 65 Brix sucrose solution of

J Moreno; A Chiralt; I Escriche; J. A Serra

2000-01-01

361

Rehydration properties of precooked whole beans (Phaseolus vulgaris) dehydrated at room temperature  

Microsoft Academic Search

The aim of this research was to study the rehydration behavior of precooked whole beans (Phaseolus vulgaris) dehydrated at room temperature (25°C) and soaked in water at three temperatures (40, 60, and 80°C). The water absorption of the beans was determined by the gain in weight. The dehydration kinetic at room temperature of the beans was adequately described by the

J. A. Ulloa; C. R. Bonilla-Sánchez; M. A. Ortíz-Jiménez; P. Rosas-Ulloa; J. C. Ramírez-Ramírez; B. E. Ulloa-Rangel

2012-01-01

362

Modelling of water\\/organic vapor dehydration by glassy polymer membranes  

Microsoft Academic Search

Hydrophilic glassy polymers are suitable membranes for the dehydration of water\\/organic vapor mixtures. Vapor permeation is the predominant process for the dehydration of organic vapors employing glassy polymers. The permeation of vapor mixtures through this type of membrane is usually analyzed in terms of a dual-mode transport model which fails to predict well the separation behavior of a vapor mixture.

A. Salem; A. A. Ghoreyshi

2006-01-01

363

Calorimetric studies of freeze-induced dehydration of phospholipids.  

PubMed Central

Differential scanning calorimetry (DSC) was used to determine the amount of water that freezes in an aqueous suspension of multilamellar dipalmitoylphosphatidylcholine (DPPC) liposomes. The studies were performed with dehydrated suspensions (12-20 wt% water) and suspensions containing an excess of water (30-70 wt% water). For suspensions that contained > or = 18 wt% water, two ice-formation events were observed during cooling. The first was attributed to heterogeneous nucleation of extraliposomal ice; the second was attributed to homogeneous nucleation of ice within the liposomes. In suspensions with an initial water concentration between 13 and 16 wt%, ice formation occurred only after homogeneous nucleation at temperatures below -40 degrees C. In suspensions containing < 13 wt% water, ice formation during cooling was undetectable by DSC, however, an endotherm resulting from ice melting during warming was observed in suspensions containing > or = 12 wt% water. In suspensions containing < 12 wt% water, an endotherm corresponding to the melting of ice was not observed during warming. The amount of ice that formed in the suspensions was determined by using an improved procedure to calculate the partial area of the endotherm resulting from the melting of ice during warming. The results show that a substantial proportion of water associated with the polar headgroup of phosphatidylcholine can be removed by freeze-induced dehydration, but the amount of ice depends on the thermal history of the samples. For example, after cooling to -100 degrees C at rates > or = 10 degrees C/min, a portion of water in the suspension remains supercooled because of a decrease in the diffusion rate of water with decreasing temperature. A portion of this supercooled water can be frozen during subsequent freeze-induced dehydration of the liposomes under isothermal conditions at subfreezing storage temperature Ts. During isothermal storage at Ts > or = -40 degrees C, the amount of unfrozen water decreased with decreasing Ts and increasing time of storage. After 30 min of storage at Ts = -40 degrees C and subsequent cooling to -100 degrees C, the amount of water associated with the polar headgroups was < 0.1 g/g of DPPC. At temperatures > -50 degrees C, the amount of unfrozen water associated with the polar headgroups of DPPC decreased with decreasing temperature in a manner predicted from the desorption isotherm of DPPC. However, at lower temperatures, the amount of unfrozen water remained constant, in large part, because the unfrozen water underwent a liquid-to-glass transformation at a temperature between -50 degrees and -140 degrees C.

Bronshteyn, V L; Steponkus, P L

1993-01-01

364

Formation processes of high-dimensional Mo?O frameworks in tetrakis(2-hydroxypropane-1,3-diaminium) hexatriacontamolybdate hydrate (C3H12N2O)4[Mo36O112(H2O)16-m]·nH2O crystals: Solid-phase structural conversions under restricted dehydration conditions  

NASA Astrophysics Data System (ADS)

We found that the hexatriacontamolybdate [Mo36O112(H2O)16]8- (?{Mo36}) compound of 1,3-diamino-2-propanol (?OHC3-DA) forms seven structural phases with the formula (?OHC3-DA)4{Mo36}·nH2O. They showed a range of dimensionality: three zero-dimensional (0D), two 1D, and two 2D Mo?O framework structures consisting of {Mo36} anions. Two of the phases have 0D framework structures crystallized in the mother solution. The remaining five phases were obtained when the crystals of these two 0D phases were aged in resin. The dense 2D framework ({Mo36}-nanosheet) of the title compound was formed via solid-phase condensation reactions under restricted dehydration conditions such as in resin-coated crystals, unlike the loose {Mo36}-nanosheet of the (C3?DA)4{Mo36}·nH2O. The formation processes of the related high-dimensional Mo?O frameworks were guided by hydrogen-bonding contacts initially formed between {Mo36} anions in the crystal. There were two different conversion routes: the one starting from the phase consisting of {Mo36} hydrogen-bonded at their head/foot parts lead to the dense 2D nanosheet, while the other originating from the phase consisting of {Mo36} hydrogen-bonded at their trunk parts, to 1D {Mo36}-nanochain with rare triple oxygen bridges. These routes had neither branching nor intercrossing.

Eda, Kazuo; Koduka, Tatsuya; Iriki, Yuichi; Stanley Whittingham, M.

2013-03-01

365

Pyropia yezoensis can utilize CO2 in the air during moderate dehydration  

NASA Astrophysics Data System (ADS)

Pyropia yezoensis, an intertidal seaweed, experiences regular dehydration and rehydration with the tides. In this study, the responses of P. yezoensis to dehydration and rehydration under high and low CO2 concentrations ((600-700)×10-6 and (40-80)×10-6, named Group I and Group II respectively) were investigated. The thalli of Group I had a significantly higher effective photosystem II quantum yield than the thalli of Group II at 71% absolute water content (AWC). There was little difference between thalli morphology, total Rubisco activity and total protein content at 100% and 71% AWC, which might be the basis for the normal performance of photosynthesis during moderate dehydration. A higher effective photosystem I quantum yield was observed in the thalli subjected to a low CO2 concentration during moderate dehydration, which might be caused by the enhancement of cyclic electron flow. These results suggested that P. yezoensis can directly utilize CO2 in ambient air during moderate dehydration.

Zhou, Wei; He, Linwen; Yang, Fang; Lin, Apeng; Zhang, Baoyu; Niu, Jianfeng; Wang, Guangce

2014-03-01

366

Characterization of dehydration-induced luminescence of kaolinite  

NASA Technical Reports Server (NTRS)

The dehydration-induced luminescence of a colloidal kaolinite is investigated experimentally, with particular attention given to the effect of various treatments on the luminescence characteristics. It is found that the total photon count of the emitted light is linearly related to the film thickness up to a thickness of 30 microns; mechanical stress in the form of grinding increases the photon output and produces extensive changes in the emission kinetics. A direct check of the emission wavelength dependence (by using color filters) indicates that roughly 75 percent of the emission occurs in the wavelength range below 410 nm. It is also found that incorporation of fluorescent molecules into the kaolinite paste increases the photon output and may indicate the transfer of ultraviolet photons to the fluorescent probe.

Lahav, N.; Coyne, L.; Lawless, J. G.

1985-01-01

367

Oxpentifylline and cetiedil citrate improve deformability of dehydrated sickle cells.  

PubMed Central

Erythrocytes from 14 patients with homozygous sickle cell anaemia were treated with the calcium ionophore A23187 to induce loss of cellular potassium and water. The dehydrated cells showed a decrease in filterability (loss of deformability) through pores of 5 micron diameter. Oxpentifylline and cetiedil citrate, which preserve erythrocyte cation and water content, had a significant (p less than 0.01) protective effect against loss of deformability at a concentration of 1 mumol/l. Oxpentifylline showed no adverse effect on the rheology, morphology, or haemolysis of sickle cells at concentrations up to 500 mumol/l. Drugs that act on the erythrocyte membrane to maintain cell hydration are of potential rheological benefit in sickle cell anaemia.

Stuart, J; Stone, P C; Bilto, Y Y; Keidan, A J

1987-01-01

368

Expeditious Pechmann Condensation by Using Biodegradable Cellulose Sulfuric Acid as a Solid Acid Catalyst  

Microsoft Academic Search

A facile synthesis of coumarins was performed in excellent yields via Pechmann condensation by using different type of phenols and ethylacetoacetates under solvent–free media using both conventional method and microwave irradiation in short reaction times is described. The reaction workup is very simple, and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent

B. Suresh Kuarm; J. Venu Madhav; S. Vijaya Laxmi; B. Rajitha; Y. Thirupathi Reddy; P. Narsimha Reddy; Peter A. Crooks

2010-01-01

369

Low serum urea level in dehydrated patients with central diabetes insipidus.  

PubMed Central

Dehydrated patients usually present with an elevated serum urea level, owing in part to increased renal reabsorption of urea mediated by antidiuretic hormone (ADH). We carried out a study to examine whether, during dehydration, the variations in the serum urea level could discriminate patients with central diabetes insipidus (CDI) from those with dehydration not due to CDI. We studied retrospectively 27 episodes of dehydration in 23 patients with CDI and 14 episodes in 14 patients without CDI. The mean serum urea level was 2.9 mmol/L in the CDI group and 15.4 mmol/L in the patients without CDI (p less than 0.001); the mean serum sodium level was 155 mmol/L in both groups. All the patients with CDI had a sodium/urea ratio greater than 24.2, whereas the ratio was less than 21.7 in all the patients without CDI. In the patients with CDI a positive correlation was found between the magnitude of diuresis and the percentage decrease in the serum urea level compared with the level before dehydration (p less than 0.001). In the patients with CDI the serum urea level returned to the level before dehydration after the administration of vasopressin; a striking increase in the clearance of urea, which exceeded the creatinine clearance, was observed during dehydration in the three patients in whom clearance studies were done. The results suggest that serum urea values can be used to distinguish patients dehydrated because of CDI from those with hypertonic dehydration but without ADH deficiency and that during dehydration the net reabsorption of urea is dependent on the renal action of ADH.

Comtois, R; Bertrand, S; Beauregard, H; Vinay, P

1988-01-01

370

An organ-specific role for ethylene in rose petal expansion during dehydration and rehydration  

PubMed Central

Dehydration is a major factor resulting in huge loss from cut flowers during transportation. In the present study, dehydration inhibited petal cell expansion and resulted in irregular flowers in cut roses, mimicking ethylene-treated flowers. Among the five floral organs, dehydration substantially elevated ethylene production in the sepals, whilst rehydration caused rapid and elevated ethylene levels in the gynoecia and sepals. Among the five ethylene biosynthetic enzyme genes (RhACS1–5), expression of RhACS1 and RhACS2 was induced by dehydration and rehydration in the two floral organs. Silencing both RhACS1 and RhACS2 significantly suppressed dehydration- and rehydration-induced ethylene in the sepals and gynoecia. This weakened the inhibitory effect of dehydration on petal cell expansion. ?-glucuronidase activity driven by both the RhACS1 and RhACS2 promoters was dramatically induced in the sepals, pistil, and stamens, but not in the petals of transgenic Arabidopsis. This further supports the organ-specific induction of these two genes. Among the five rose ethylene receptor genes (RhETR1–5), expression of RhETR3 was predominantly induced by dehydration and rehydration in the petals. RhETR3 silencing clearly aggravated the inhibitory effect of dehydration on petal cell expansion. However, no significant difference in the effect between RhETR3-silenced flowers and RhETR-genes-silenced flowers was observed. Furthermore, RhETR-genes silencing extensively altered the expression of 21 cell expansion-related downstream genes in response to ethylene. These results suggest that induction of ethylene biosynthesis by dehydration proceeds in an organ-specific manner, indicating that ethylene can function as a mediator in dehydration-caused inhibition of cell expansion in rose petals.

Liu, Daofeng; Liu, Xiaojing; Gao, Junping

2013-01-01

371

An organ-specific role for ethylene in rose petal expansion during dehydration and rehydration.  

PubMed

Dehydration is a major factor resulting in huge loss from cut flowers during transportation. In the present study, dehydration inhibited petal cell expansion and resulted in irregular flowers in cut roses, mimicking ethylene-treated flowers. Among the five floral organs, dehydration substantially elevated ethylene production in the sepals, whilst rehydration caused rapid and elevated ethylene levels in the gynoecia and sepals. Among the five ethylene biosynthetic enzyme genes (RhACS1-5), expression of RhACS1 and RhACS2 was induced by dehydration and rehydration in the two floral organs. Silencing both RhACS1 and RhACS2 significantly suppressed dehydration- and rehydration-induced ethylene in the sepals and gynoecia. This weakened the inhibitory effect of dehydration on petal cell expansion. ?-glucuronidase activity driven by both the RhACS1 and RhACS2 promoters was dramatically induced in the sepals, pistil, and stamens, but not in the petals of transgenic Arabidopsis. This further supports the organ-specific induction of these two genes. Among the five rose ethylene receptor genes (RhETR1-5), expression of RhETR3 was predominantly induced by dehydration and rehydration in the petals. RhETR3 silencing clearly aggravated the inhibitory effect of dehydration on petal cell expansion. However, no significant difference in the effect between RhETR3-silenced flowers and RhETR-genes-silenced flowers was observed. Furthermore, RhETR-genes silencing extensively altered the expression of 21 cell expansion-related downstream genes in response to ethylene. These results suggest that induction of ethylene biosynthesis by dehydration proceeds in an organ-specific manner, indicating that ethylene can function as a mediator in dehydration-caused inhibition of cell expansion in rose petals. PMID:23599274

Liu, Daofeng; Liu, Xiaojing; Meng, Yonglu; Sun, Cuihui; Tang, Hongshu; Jiang, Yudong; Khan, Muhammad Ali; Xue, Jingqi; Ma, Nan; Gao, Junping

2013-05-01

372

Gasification Effects in the Heterogeneous Ignition of a Condensed Fuel by a Hot Gas.  

National Technical Information Service (NTIS)

An analysis is presented to describe the heterogeneous ignition of a condensed fuel suddenly exposed to a hot oxidizing atmosphere. The exothermic heterogeneous reaction, generating gaseous products, is considered to be of the Arrhenius type with an activ...

M. Kindelan A. Linan

1976-01-01

373

Spring dehydration in the Antarctic stratospheric vortex observed by HALOE  

NASA Technical Reports Server (NTRS)

The distribution of dehydrated air in the middle and lower stratosphere during the 1992 Southern Hemisphere spring is investigated using Halogen Occultation Experiment (HALOE) observations and trajectory techniques. Comparisons between previously published Version 9 and the improved Version 16 retrievals on the 700-K isentropic surface show very slight (0.05 ppmv) increases in Version 16 CH4 relative to Version 9 within the polar vortex. Version 16 H2O mixing ratios show a reduction of 0.5 ppmv relative to Version 9 within the polar night jet and a reduction of nearly 1.0 ppmv in middle latitudes when compared to Version 9. The version 16 HALOE retrievals show low mixing ratios of total hydrogen (2CH4 + H2O) within the polar vortex on both 700 and 425 K isentropic surfaces relative to typical middle-stratospheric 2CH4 + H2O mixing ratios. The low 2CH4 + H2O mixing ratios are associated with dehydration. Slight reductions in total hydrogen, relative to typical middle-stratospheric values, are found at these levels throughout the Southern Hemisphere during this period. Trajectory calculations show that middle-latitude air masses are composed of a mixture of air from within the polar night jet and air from middle latitudes. A strong kinematic barrier to large-scale exchange is found on the poleward flank of the polar night jet at 700 K. A much weaker kinematic barrier is found at 425 K. The impact of the finite tangent pathlength of the HALOE measurements is investigated using an idealized tracer distribution. This experiment suggests that HALOE should be able to resolve the kinematic barrier, if it exists.

Pierce, R. Bradley; Grose, William L.; Russell, James M., III; Tuck, Adrian F.; Swinbank, Richard; O'Neill, Alan

1994-01-01

374

Advancing microwave technology for dehydration processing of biologics.  

PubMed

Our prior work has shown that microwave processing can be effective as a method for dehydrating cell-based suspensions in preparation for anhydrous storage, yielding homogenous samples with predictable and reproducible drying times. In the current work an optimized microwave-based drying process was developed that expands upon this previous proof-of-concept. Utilization of a commercial microwave (CEM SAM 255, Matthews, NC) enabled continuous drying at variable low power settings. A new turntable was manufactured from Ultra High Molecular Weight Polyethylene (UHMW-PE; Grainger, Lake Forest, IL) to provide for drying of up to 12 samples at a time. The new process enabled rapid and simultaneous drying of multiple samples in containment devices suitable for long-term storage and aseptic rehydration of the sample. To determine sample repeatability and consistency of drying within the microwave cavity, a concentration series of aqueous trehalose solutions were dried for specific intervals and water content assessed using Karl Fischer Titration at the end of each processing period. Samples were dried on Whatman S-14 conjugate release filters (Whatman, Maidestone, UK), a glass fiber membrane used currently in clinical laboratories. The filters were cut to size for use in a 13 mm Swinnex(®) syringe filter holder (Millipore(™), Billerica, MA). Samples of 40 ?L volume could be dehydrated to the equilibrium moisture content by continuous processing at 20% with excellent sample-to-sample repeatability. The microwave-assisted procedure enabled high throughput, repeatable drying of multiple samples, in a manner easily adaptable for drying a wide array of biological samples. Depending on the tolerance for sample heating, the drying time can be altered by changing the power level of the microwave unit. PMID:24835259

Cellemme, Stephanie L; Van Vorst, Matthew; Paramore, Elisha; Elliott, Gloria D

2013-10-01

375

Effect of dehydration prior to cryopreservation of large equine embryos.  

PubMed

Cryopreservation of equine embryos>300microm in diameter results in low survival rates using protocols that work well for smaller equine embryos. These experiments tested the potential benefit of incorporating a dehydration step prior to standard cryopreservation procedures. Forty-six, day 7-8, grade 1, equine embryos 300-1350microm in diameter were subjected to one of the following treatments: (A) 2 min in 0.6M galactose, 10min in 1.5M glycerol, slow freeze (n=21); (B) 10min in 1.5M glycerol, slow freeze (n=15); (C) 2min in 0.6M galactose, 10min in 1.5M glycerol, followed by exposure to thaw solutions, then culture medium (n=5); (D) transferred directly to culture medium (n=5). Frozen embryos were thawed and subjected to a three-step cryoprotectant removal. Five embryos from each treatment were evaluated morphologically after 24 and 48h culture (1=excellent, 5=degenerate/dead). All treatments had at least 4/5 embryos with a quality score >or=3 at these time points except treatment B (2/5 at 24h, 1/5 at 48h). Subsequent embryos from treatment A (n=16) or B (n=10) were matched in sets of two for size and treatment, thawed, and immediately transferred in pairs to 13 recipients. Only two recipient mares were pregnant; one received two 400microm embryos from treatment A, and the other one 400 and one 415microm embryo from treatment B. There was no advantage of incorporating a 2min dehydration step into the cryopreservation protocol for large equine embryos. PMID:19375416

Barfield, J P; McCue, P M; Squires, E L; Seidel, G E

2009-08-01

376

Effect of Dehydration Prior to Cryopreservation of Large Equine Embryos  

PubMed Central

Cryopreservation of equine embryos > 300 ?m in diameter results in low survival rates using protocols that work well for smaller equine embryos. These experiments tested the potential benefit of incorporating a dehydration step prior to standard cryopreservation procedures. Forty-six, d 7–8, grade 1, equine embryos ? 400 ?m in diameter were subjected to one of the following treatments: (A) 2-min in 0.6 M galactose, 10 min in 1.5 M glycerol, slow freeze (n=21); (B) 10 min in 1.5 M glycerol, slow freeze (n=15); (C) 2 min in 0.6 M galactose, 10 min in 1.5 M glycerol, followed by exposure to thaw solutions, then culture medium (n=5); (D) transferred directly to culture medium (n=5). Frozen embryos were thawed and subjected to a 3-step cryoprotectant removal. Five embryos from each treatment were evaluated morphologically after 24 and 48 h culture (1=excellent, 5=degenerate/dead). All treatments had at least 4/5 embryos with a quality score ? 3 at these time points except treatment B (2/5 at 24 h, 1/5 at 48 h). Subsequent embryos from treatment A (n=16) or B (n=10) were matched in sets of two for size and treatment, thawed, and immediately transferred in pairs to 13 recipients. Only two recipient mares were pregnant; one received two 400 ?m embryos from treatment A, and the other one 400 ?m and one 415 ?m embryo from treatment B. There was no advantage of incorporating a 2 min dehydration step into the cryopreservation protocol for large equine embryos.

Barfield, JP; McCue, PM; Squires, EL; Seidel, GE

2009-01-01

377

Recovery of human mesenchymal stem cells following dehydration and rehydration.  

PubMed

As cell therapies advance from research laboratories to clinical application, there is the need to transport cells and tissues across long distances while maintaining cell viability and function. Currently cells are successfully stored and shipped under liquid nitrogen vapor. The ability to store these cells in the desiccated state at ambient temperature would provide tremendous economic and practical advantage. Human mesenchymal stem cells (hMSCs) have broad potential uses in tissue engineering and regeneration since they can differentiate along multiple lineages and support hematopoeisis. The current research applied recent technological advances in the dehydration and storage of human fibroblasts to hMSCs. Three conditions were tested: air-dried, air-dried and stored under vacuum (vacuum only), and incubated with 50 mM trehalose + 3% glycerol and then air-dried and stored under vacuum (vacuum + trehalose). Plates containing dehydrated hMSCs were shipped from San Diego to Baltimore overnight in separate FedEx cardboard boxes. The hMSCs were rehydrated with 3 ml of hMSC medium and were able to regain their spindle-shaped morphology and adhesive capability. In addition, they maintained high viability and proliferation capacity. Rehydrated and passaged cells continued to express the characteristic hMSC surface antigen panel. Additionally, cells showed constitutive levels of mRNA for a stromal factor and, when exposed to reagents known to induce differentiation, demonstrated upregulation of two tissue-specific messages indicative of differentiation potential for fat and bone. While our preliminary findings are encouraging, we still need to address consistency and duration of storage by considering factors such as cell water content, oxygen concentration, and the presence of free radicals. PMID:11846472

Gordon, S L; Oppenheimer, S R; Mackay, A M; Brunnabend, J; Puhlev, I; Levine, F

2001-09-01

378

Diamond Formation in Dehydration Zones in the deep Upper Mantle and Lower Mantle  

NASA Astrophysics Data System (ADS)

Introduction. During the last 25 years a series of publications have documented the occurrence of inclusions in diamonds that show mineral compositions and mineral associations predicted for mantle rocks at deeper levels than the mantle lithosphere (e.g Harte et al., 1999; Harte & Cayzer, 2007). Although the diamonds bearing deep mantle inclusions are not abundant in absolute terms they are widespread and have been reported from cratonic blocks on all major continents. As with natural diamonds in general these deep diamonds appear to have grown in fluids/melts. Depth Zones indicated by inclusion suites. The silicate inclusions and their mineral associations form a series showing good correlation with mineral assemblages expected in basic and ultrabasic rock compositions at depth. However, there is a strong bias towards assemblages from two principal zones: (1)uppermost Transition zone and Asthenosphere (upper TZ group)) (2)lowermost Transition Zone and uppermost Lower Mantle (UM/LM group) In the case of (1) the assemblages are predominantly of majorite garnet, and majorite garnet + cpx with an affinity to eclogitic bulk compositions. In many of these inclusions the cpx appears to have exsolved from the majoritic garnet and the depth of origin of the initial inclusions may often be near the top of the Transition Zone. The assemblages from (2) are predominantly of peridotic affinity and involve fPer as well as silicates. They indicate material from three depth zones near the upper mantle to lower mantle boundary (UM/LM boundary). 2a) Upper/Lower Mantle Boundary association - inclusions of: Mg2SiO4, fPer, maj/tapp, mpv, cpv 2b) uppermost Lower Mantle association with: Mpv(Al-poor) with fPer and cpv,maj/tapp 2c)lower Mantle association with: Mpv(Al-rich) with fPer, and crn [fPer:ferropericlase; maj:majorite; tapp:tetragonal-almandine-pyrope phase; mpv:MgSiperovskite; cpv:CaSiperovskite] Discussion. The above features show that the formation of deep mantle diamonds is concentrated in a zone around the top of the Transition Zone (ca 400 kms deep), and a zone at 600-800 kms embracing the bottom of the Transition Zone and the top of Lower Mantle. Associations including Mg2SiO4 with and fPer + MgSi-perovskite indicate the preservation of UM/LM boundary reaction, which from experimental data is expected to be sharply constrained in depth, though the presence of H2O will broaden the reaction zone due to the potential stability of hydrous ringwoodite. Considerations of the preservation of hydrous peridotitic assemblages in subduction zones (Komabayashi, 2006, AGU monograph), show that an initially cool subducted slab may preserve hydrous assemblages to the lower part of the upper mantle and into the lower mantle. Here stagnation and warming of the slab may cause dehydration with the formation fluids/melts. Such fluids/melts provide the potential location for diamond formation and thereby provide an explanation for the abundance of inclusion assemblages from around the UM/LM boundary. At the top of the Transition Zone, there is potential for dehydration to occur where hydrous wadsleyite converts to olivine. The intersection with the upper surface of a subducting slab with potential dehydration zone provides an ideal location for the crystallisation of the majorite assemblages from around the top of the Transition Zone. This also accords with the crustal carbon isotpe signatures in the host diamonds and the wide variations in REE abundances in the majorites.

Harte, Ben

2010-05-01

379

Characterization of spacecraft humidity condensate  

NASA Technical Reports Server (NTRS)

When construction of Space Station Freedom reaches the Permanent Manned Capability (PMC) stage, the Water Recovery and Management Subsystem will be fully operational such that (distilled) urine, spent hygiene water, and humidity condensate will be reclaimed to provide water of potable quality. The reclamation technologies currently baselined to process these waste waters include adsorption, ion exchange, catalytic oxidation, and disinfection. To ensure that the baseline technologies will be able to effectively remove those compounds presenting a health risk to the crew, the National Research Council has recommended that additional information be gathered on specific contaminants in waste waters representative of those to be encountered on the Space Station. With the application of new analytical methods and the analysis of waste water samples more representative of the Space Station environment, advances in the identification of the specific contaminants continue to be made. Efforts by the Water and Food Analytical Laboratory at JSC were successful in enlarging the database of contaminants in humidity condensate. These efforts have not only included the chemical characterization of condensate generated during ground-based studies, but most significantly the characterization of cabin and Spacelab condensate generated during Shuttle missions. The analytical results presented in this paper will be used to show how the composition of condensate varies amongst enclosed environments and thus the importance of collecting condensate from an environment close to that of the proposed Space Station. Although advances were made in the characterization of space condensate, complete characterization, particularly of the organics, requires further development of analytical methods.

Muckle, Susan; Schultz, John R.; Sauer, Richard L.

1994-01-01

380

Mesoporous siliconiobium phosphate as a pure Brønsted acid catalyst with excellent performance for the dehydration of glycerol to acrolein.  

PubMed

The development of solid acid catalysts that contain a high density of Brønsted acid sites with suitable acidity, as well as a long lifetime, is one of great challenges for the efficient dehydration of glycerol to acrolein. Herein, we report on a mesoporous siliconiobium phosphate (NbPSi-0.5) composite, which is a promising solid Brønsted acid that is a potential candidate for such a high-performance catalyst. A variety of characterization results confirm that NbPSi-0.5 contains nearly pure Brønsted acid sites and has well-defined large mesopores. In addition, NbPSi-0.5 contains a similar amount of acid sites and exhibits weaker acidity than that of the highly acidic niobium phosphate and HZSM-5 zeolite. NbPSi-0.5 is quite stable and has a high activity for the dehydration of glycerol. The stability of NbPSi-0.5 is about three times higher than that of the reported catalyst. The significantly enhanced catalytic performance of NbPSi-0.5 can be attributed to 1) nearly pure Brønsted acidity, which suppresses side reactions that lead to coke formation; 2) a significant reduction of pore blocking due to the mesopores; and 3) a decrease in the amount and oxidation temperature of coke. PMID:23132784

Choi, Youngbo; Park, Dae Sung; Yun, Hyeong Jin; Baek, Jayeon; Yun, Danim; Yi, Jongheop

2012-12-01

381

Role of ion-neutral complexes during acid-catalyzed dehydration of ethanol in the gas phase  

SciTech Connect

Acid-catalyzed dehydration of ethanol in the gas phase has been studied both theoretically and experimentally. Molecular orbital calculations have been done at the MP3/6-31G*//6-31G* level with correction of the zero-point vibrational energy. Protonated ethanol, 1 is predicted to isomerize easily into the C{sub 2}H{sub 4} {hor ellipsis} H {hor ellipsis} OH{sub 2}{sup +} complex, 2 (activation energy 120 kJ/mol). This result is in agreement with the observation of a near statistical hydrogen exchange preceding the dehydration reaction 1 {yields} C{sub 2}H{sub 4} + H{sub 3}O{sup +}. In the case of the water-solvated ion C{sub 2}H{sub 5}OH{sub 2} {hor ellipsis} OH{sub 2}{sup +}, 5, isomerization into a proton-bound complex C{sub 2}H{sub 4} {hor ellipsis} H{sub 5}O{sub 2}{sup +}, 6, needs a larger amount of energy (ca. 180 kJ/mol). Again the calculations agree with experiments: the important activation energy for the process 5 {yields} 6 prevents hydrogen exchanges and ethene elimination. Extension of these calculations to higher systems is discussed.

Bouchoux, G.; Hoppilliard, Y. (Ecole Polytechnique, Palaiseau (France))

1990-12-05

382

A critical evaluation of crustal dehydration as the cause of an overpressured and weak San Andreas Fault  

USGS Publications Warehouse

Many plate boundary faults, including the San Andreas Fault, appear to slip at unexpectedly low shear stress. One long-standing explanation for a "weak" San Andreas Fault is that fluid release by dehydration reactions during regional metamorphism generates elevated fluid pressures that are localized within the fault, reducing the effective normal stress. We evaluate this hypothesis by calculating realistic fluid production rates for the San Andreas Fault system, and incorporating them into 2-D fluid flow models. Our results show that for a wide range of permeability distributions, fluid sources from crustal dehydration are too small and short-lived to generate, sustain, or localize fluid pressures in the fault sufficient to explain its apparent mechanical weakness. This suggests that alternative mechanisms, possibly acting locally within the fault zone, such as shear compaction or thermal pressurization, may be necessary to explain a weak San Andreas Fault. More generally, our results demonstrate the difficulty of localizing large fluid pressures generated by regional processes within near-vertical fault zones. ?? 2009 Elsevier B.V.

Fulton, P. M.; Saffer, D. M.; Bekins, B. A.

2009-01-01

383

Treatment of arsenic-contaminated groundwater by a low cost activated alumina adsorbent prepared by partial thermal dehydration  

Microsoft Academic Search

Experimental investigations were carried out to remove arsenic from contaminated groundwater by low cost activated alumina based adsorbent prepared by partial thermal dehydration. Activated alumina based adsorbent with high surface area was prepared following partial thermal dehydration of gibbsite precursor and an attempt was made to study the effects of dehydration temperature, residence time, rate of increase of temperature and

Mou Sen; Parimal Pal

2009-01-01

384

Effects of dehydration on organ metabolism in the frog Pseudacris crucifer: hyperglycemic responses to dehydration mimic freezing-induced cryoprotectant production.  

PubMed

The metabolic effects of evaporative water loss at 5 degrees C were assessed for both fall- and spring-collected spring peepers Pseudacris crucifer. Frogs readily endured the loss of 50% of total body water. During dehydration organ water content was defined with no change in water content in skeletal muscle, gut, and kidney of 50% dehydrated frogs and reduced water content in liver, brain and heart. Dehydration stimulated a rapid and massive increase in liver glucose production. In fall-collected frogs liver glucose rose by 120-fold to 2690 +/- 400 nmol.mg protein-1 or 220 mumol.g ww-1 in 50% dehydrated frogs and glucose in other organs increased by 2.6- to 60-fold. Spring-collected frogs showed the same qualitative response to dehydration although absolute glucose levels were lower, rising maximally by 8.4-fold in liver. Glucose synthesis was supported by glycogenolysis in liver and changes in the levels of glycolytic intermediates in liver indicated that an inhibitory block at the phosphofructokinase locus during desiccation helped to divert hexose phosphates into the production of glucose. Liver energy status (ATP, total adenylates, energy charge) was maintained even after the loss of 35% of total body water but at 50% dehydration all parameters showed a sharp decline; for example, energy charge fell from about 0.85 to 0.42. Severe dehydration also led to an accumulation of lactate in four organs, probably hypoxia-induced due to impaired circulation.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7860806

Churchill, T A; Storey, K B

1994-01-01

385

Detonation theory for condensed phase explosives with anisotropic properties  

NASA Astrophysics Data System (ADS)

Detonation theory for condensed phase explosives with anisotropic properties is relevant to energetic materials that are crystals in their unreacted state and have anisotropic material properties due to their underlying molecular structure. For example, crystalline, molecular explosives like PETN and azides, depending on which crystal face is shocked, initiate detonation at different shock pressures. We discuss our recent efforts to construct a theory of sustained detonation that has strong directionally dependent effects and properties. We propose a continuum, phase-field theory that is capable of describing the transition from anisotropic unreacted solid to reacted condensed products. The material behavior is allowed to include anisotropic elasticity, heat conduction and reaction.

Stewart, D. Scott; Fried, Laurence E.; Szuck, Matthew

2012-03-01

386

Production of ?-PARTICLE Condensate States in Heavy-Ion Collisions  

NASA Astrophysics Data System (ADS)

The fragmentation of quasi-projectiles from the nuclear reaction 40Ca+12C at 25 MeV/nucleon was used to produce excited states candidates to ?-particle condensation. The experiment was performed at LNS-Catania using the CHIMERA multidetector. Accepting the emission simultaneity and equality among the ?-particle kinetic energies as experimental criteria for deciding in favor of the condensate nature of an excited state, we analyze the 02^ + and 22+ states of 12C and the 06^ + state of 16O. A sub-class of events corresponding to the direct 3-? decay of the Hoyle state is isolated.

Raduta, Ad. R.; Borderie, B.; Le Neindre, N.; Napolitani, P.; Rivet, M. F.; Geraci, E.

387

Adsorption of the compounds encountered in monosaccharide dehydration in zeolite beta.  

PubMed

A comprehensive study of the adsorption of the compounds involved in the reaction of dehydration of fructose to 5-hydroxymethyl furfural (HMF) on the zeolite H-BEA with SiO2/Al2O3 = 18 has been carried out. Furthermore, a method for the estimation of the real adsorption loading from the experimentally measured excess adsorption is developed and applied to calculate the adsorption isotherms both in the case of single-solute and multisolute mixtures. It was found that zeolite H-BEA adsorbs HMF and levulinic acid from water mixtures to greater extent than sugars and formic acid, which prefer to partition in the aqueous phase. HMF and levulinic acid adsorption isotherms could be fitted in a Redlich-Peterson isotherm model, while the adsorption of formic acid is better fitted using the Freundlich model and sugars via the Henry model. Adsorption loadings decreased with increasing temperature (0, 25, and 40 °C), which is characteristic of an exothermic process. From the temperature dependence of the isotherms, the limiting heat of adsorption at zero coverage was determined using van't Hoff equation. Given the importance and the complexity of multicomponent systems, several experiments of adsorption of multisolute solutions have been carried out. In most of the cases, the ideal adsorbed solution theory (IAST) has been proven to satisfactorily predict adsorption from multisolute mixtures using as input the single-solute isotherms. PMID:23642168

León, Marta; Swift, T Dallas; Nikolakis, Vladimiros; Vlachos, Dionisios G

2013-06-01

388

Acid-catalyzed dehydration of fructose into 5-hydroxymethylfurfural by cellulose-derived amorphous carbon.  

PubMed

Carbonaceous solid (CS) catalysts with --SO?H, --COOH, and phenolic --OH groups were prepared by incomplete hydrothermal carbonization of cellulose followed by either sulfonation with H?SO? to give carbonaceous sulfonated solid (CSS) material or by both chemical activation with KOH and sulfonation to give activated carbonaceous sulfonated solid (a-CSS) material. The obtained carbon products (CS, CSS, and a-CSS) were amorphous; the CSS material had a small surface area (<0.5?m² g?¹) and a high --SO?H group concentration (0.953?mmol?g?¹), whereas the a-CSS material had a large surface area (514?m² ?g ?¹) and a low --SO?H group concentration (0.172?mmol?g?¹). The prepared materials were evaluated as catalysts for the dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) in the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]). Remarkably high 5-HMF yields (83?%) could be obtained efficiently (80?°C and 10?min reaction time). CSS and a-CSS catalysts had similar catalytic activities and efficiencies for the conversion of fructose to 5-HMF in [BMIM][Cl]; this could be explained by the trade-off between --SO?H group concentration (high for CSS) and surface area (high for a-CSS). The cellulose-derived catalysts and ionic liquid exhibited constant activity for five successive recycles, and thus, the methods developed provide a renewable strategy for biomass conversion. PMID:22927099

Qi, Xinhua; Guo, Haixin; Li, Luyang; Smith, Richard L

2012-11-01

389

Catalytic dehydration of fructose to 5-hydroxymethylfurfural over Nb2O5 catalyst in organic solvent.  

PubMed

The catalytic dehydration of fructose to 5-hydroxymethylfurfural (HMF) in DMSO was performed over Nb2O5 derived from calcination of niobic acid at various temperatures (300-700 °C). The catalysts were characterized by powder X-ray diffraction, N2 physical adsorption, temperature-programed desorption of NH3, n-butylamine titration using Hammett indicators, infrared spectroscopy of adsorbed pyridine, and X-ray photoelectron spectroscopy. It was found that both catalytic activity and surface acid sites decrease with increasing calcination temperatures. The Nb2O5 derived from calcination of niobic acid at 400 °C reveals the maximum yield of HMF among all the catalysts, although the amount of acid sites on the catalyst is lower than that on the sample calcined at 300 °C. The results suggest that the presence of larger amounts of strong acid sites on the surface of the Nb2O5 calcined at 300 °C may promote side reactions. The Nb2O5 prepared at 400 °C shows 100% fructose conversion with 86.2% HMF yield in DMSO at 120 °C after 2 h. The activity of the catalyst decreases gradually during recycle because of coke deposition; however, it can be fully recovered by calcination at 400 °C for 2 h, suggesting that this catalyst is of significance for practical applications. PMID:23348242

Wang, Fenfen; Wu, Hai-Zhen; Liu, Chun-Ling; Yang, Rong-Zhen; Dong, Wen-Sheng

2013-03-01

390

Effects of Dehydration on the Viscoelastic Properties of Vocal Folds in Large Deformations  

PubMed Central

Summary Dehydration may alter vocal fold viscoelastic properties, which may hamper phonation. The effects of water loss induced by an osmotic-pressure potential on vocal fold tissue viscoelastic properties were investigated. Porcine vocal folds were dehydrated by immersion in a hypertonic solution, and quasi-static and low-frequency dynamic traction tests were performed for elongations of up to 50%. Digital image correlation was used to determine local strains from surface deformations. The elastic modulus and the loss factor were then determined for normal and dehydrated tissues. An eight-chain hyperelastic model was used to describe the observed nonlinear stress-stretch behavior. Contrary to expectations, the mass history indicated that the tissue absorbed water during cyclic extension when submerged in a hypertonic solution. During loading history, the elastic modulus was increased for dehydrated tissues as a function of strain. The response of dehydrated tissues was much less affected when the load was releasing. This calls more attention to the modeling of vocal folds in micromechanics modeling. The internal hysteresis, which is often linked to phonation effort, increased significantly with water loss. The effects of dehydration on the viscoelastic properties of vocal fold tissue were quantified in a systematic way. The results will contribute to a better understanding of the basic biomechanics of voice production and ultimately will help establish objective dehydration and phonotrauma criteria.

Miri, Amir K.; Barthelat, Francois; Mongeau, Luc

2012-01-01

391

Thirst perception in dehydrated sickle cell disease patients in steady state.  

PubMed

Liberal fluid intake is one of the key management strategies in sickle cell anaemia [SCA] patients in steady state, but less work has been done on the desire of patients to drink water. Using the Visual Analogue Scale we studied thirst perception [TP] in 20 euhydrated SCA patients and 28 control [HbA] subjects, as well as during dehydration in 13 SCA patients and 9 HbA subjects. Serum and urine samples were collected and analyzed for Na, K ions, creatinine concentrations and haematocrit and specific gravity of urine were determined. During euhydration, TP was significantly [P<0.05] higher in male SCA patients compared to the HbA subjects. In females, TP in SCA patient was not statistically significant compared with HbA subjects. After 13 hours of dehydration, TP was significantly [P<0.05] reduced in female. While dehydration increased TP in HbA subjects, it reduced TP in SCA patients. Fluid intakes after dehydration in SCA patients were not significantly different from the control HbA subjects in both male and female. It can be concluded that female SCA patients do not have normal response to dehydration with regards to TP after a period of dehydration. Since dehydration stimulates the release of vasoactive hormones like vasopressin, this may explain why female patients are less prone to crisis than their male counterparts. PMID:20234751

Ozoene, J O; Enosolease, M E; Ajayi, O I; Agoreyo, F O; Obika, L F O

2009-12-01

392

Unusual effect of water vapor pressure on dehydration of dibasic calcium phosphate dihydrate.  

PubMed

Dibasic calcium phosphate occurs as an anhydrate (DCPA; CaHPO?) and as a dihydrate (DCPD; CaHPO?•2H?O). Our objective was to investigate the unusual behavior of these phases. Dibasic calcium phosphate dihydrate was dehydrated in a (i) differential scanning calorimeter (DSC) in different pan configurations; (ii) variable-temperature X-ray diffractometer (XRD) at atmospheric and under reduced pressure, and in sealed capillaries; and (iii) water vapor sorption analyzer at varying temperature and humidity conditions. Dehydration was complete by 210°C in an open DSC pan and under atmospheric pressure in the XRD. Unlike "conventional" hydrates, the dehydration of DCPD was facilitated in the presence of water vapor. Variable-temperature XRD in a sealed capillary and DSC in a hermetic pan with pinhole caused complete dehydration by 100°C and 140°C, respectively. Under reduced pressure, conversion to the anhydrate was incomplete even at 300°C. The increase in dehydration rate with increase in water vapor pressure has been explained by the Smith-Topley effect. Under "dry" conditions, a coating of poorly crystalline product is believed to form on the surface of particles and act as a barrier to further dehydration. However, in the presence of water vapor, recrystallization occurs, creating cracks and channels and facilitating continued dehydration. PMID:24081471

Kaushal, Aditya M; Vangala, Venu R; Suryanarayanan, Raj

2011-04-01

393

Condensation in Well Insulated Houses.  

National Technical Information Service (NTIS)

The performance was investigated of well insulated houses in Aberdeen (Scotland). Condensation problems were reported in two areas, the bedroom ceilings adjacent to outside walls and in the loft. It was found that misalignment of insulation material above...

G. W. Brundrett G. Poultney J. Waddington R. Bentley

1980-01-01

394

Experimental Soft Condensed Matter Group  

NSDL National Science Digital Library

The home page of the David Weitz group at Harvard. We study the physics of soft condensed matter, including colloids, emulsions, gels, glasses, polymers, foams, and biological samples. We are beginning work in biophysics.

Weitz, David

2003-10-10

395

Flow Boiling and Condensation Experiment  

NASA Video Gallery

The Flow Boiling and Condensation Experiment is another investigation that examines the flow of a mixture of liquids and the vapors they produce when in contact with hot space system equipment. Coo...

396

Counterion Correlations on Condensed Biopolymers  

NASA Astrophysics Data System (ADS)

Like-charged polyelectrolytes condense into ordered phases in the presence of multivalent ions. The physical origin of the attractive interaction required for this condensation has been intensely debated, but no clear consensus has emerged, although counterion correlations appear to play a key role. In order to elucidate the nature of these interactions, we have performed structural measurements of condensed phases formed between multivalent ions and a range of rod-like polyelectrolytes, including cytoskeletal F-actin, and Fd and M13 filamentary virus particles.šDirect measurements of the counterion density and correlations in different condensed phases will be presented, along with the temperature dependence of these phases. This work was supported by NSF DMR-0071761, DOE DEFG02-91ER45439, the Beckman Young Investigator Program, and the Cystic Fibrosis Foundation.

Angelini, Tommy; Butler, John; Ho, James; Liang, Hongjun; Wong, Gerard

2002-03-01

397

Dynamic tracking of mica breakdown reactions with electrochemical measurements  

Microsoft Academic Search

The breakdown of hydrous minerals involves multiple reactions of dehydration and often oxidation of ferric iron. Such reactions are important in mantle metasomatism, metamorphic petrology and material sciences. Here we track these reactions dynamically over the temperature range from 400° to 1100° C using Y-doped ZrO2 sensors in a novel manner, comparable to differential thermal analyses. This contrasts to the

Dorothee J. M. Burkhard; Gene C. Ulmer

1995-01-01

398

Condenser vibration analysis by microcomputer  

SciTech Connect

A computer program is presented through which surface condenser tubing undergoes vibration stress analysis and support plate spacing. The program generates the following data: synomic drag force of steam as it flows over the tubes; weight of the tube; weight of the water in the tube; and the weight of the exterior condensate. A deflection chart is given. The computer program takes about seven seconds to run the program and the results are printed out.

Miller, S.S.

1985-11-01

399

Stability of detonations for an idealized condensed-phase model  

NASA Astrophysics Data System (ADS)

The stability of travelling wave Chapmanvon Neumannring type is formulated for a general system that incorporates the idealized gas and condensed-phase (liquid or solid) detonation models. The general model consists of a two-component mixture with a one-step irreversible reaction between reactant and product. The reaction rate has both temperature and pressure sensitivities and has a variable reaction order. The idealized condensed-phase model assumes a pressure-sensitive reaction rate, a constant-=3, and invokes the strong shock limit. A linear stability analysis of the steady, planar, ZND detonation wave for the general model is conducted using a normal-mode approach. An asymptotic analysis of the eigenmode structure at the end of the reaction zone is conducted, and spatial boundedness (closure) conditions formally derived, whose precise form depends on the magnitude of the detonation overdrive and reaction order. A scaling analysis of the transonic flow region for ChapmanJouguet detonations. Neutral stability boundaries are calculated for the idealized condensed-phase model for one- and two-dimensional perturbations. Comparisons of the growth rates and frequencies predicted by the normal-mode analysis for an unstable detonation are made with a numerical solution of the reactive Euler equations. The numerical calculations are conducted using a new, high-order algorithm that employs a shock-fitting strategy, an approach that has significant advantages over standard shock-capturing methods for calculating unstable detonations. For the idealized condensed-phase model, nonlinear numerical solutions are also obtained to study the long-time behaviour of one- and two-dimensional unstable Chapman-Jouguet ZND waves.

Short, M.; Anguelova, I. I.; Aslam, T. D.; Bdzil, J. B.; Henrick, A. K.; Sharpe, G. J.

400

Dehydration Behavior of Metapelites and Metabasites at Very low to low Grade Metamorphic Conditions  

NASA Astrophysics Data System (ADS)

Thermodynamic calculations have been undertaken in the system Na-Ca-K-Fe-Mg-Al-Si-Ti-H-O with the PERPLE_X software package (Connolly, 1990 and updates) for a better understanding of the dehydration behavior of metapelites and metabasites during prograde metamorphism. To obtain reasonable results for the temperature range 150-450° C at pressures up to 25 kbar, the subsequent solid solution models were introduced being compatible with the applied thermodynamic data set of Holland & Powell (1998 and updates): a three component model for Mg-Fe2+-Fe3+-pumpellyite, a two component model for Fe2+-Mg- stilpnomelane, a four component amphibole model (tremolite - Fe2+-tremolite - glaucophane - Mg- riebeckite), and a four component Na-pyroxene model (acmite - jadeite - diopside - hedenbergite). The water contents released by prograde metamorphism up to 450° C from MORB and psammopelitic compositions on top of oceanic crust, were obtained by calculating P-T pseudosections. Metabasite contains 6-7 wt% H2O bound to minerals at 150° C depending on the oxidation state. Along geotherms lower than 7° C/km typical for young subduction zones, no water is released up to 400° C. However, reduction of the rock causes release of small amounts of water. Metapsammopelitic rocks also store about 6 wt% H2O in minerals at 150° C. Considerable amounts of water are liberated by mineral reactions already in the temperature range 150-250° C also at the above mentioned low geotherms. This behavior determines the rheological characteristics of the upper oceanic crust during early subduction. If water is exclusively released in the sedimentary portion of the downgoing crust only this material gets weakened to be scraped off to form accretionary wedges. At geotherms of 15-20° C/km both lithologies show significant dehydration at very low metamorphic grade. For instance, in cold frontal paleoaccretionary prisms of the Chilean Coastal Cordillera metapelites by far dominate whereas in hotter basal accretionary prisms both low grade basic oceanic crust and continental sediments occur. We also hypothesize that accretionary wedge complexes with a clear dominance of sediments should not have formed in hot subduction zones typical for Precambrian Earth.

Massonne, H.; Willner, A. P.

2007-12-01

401

Slab dehydration versus melting: primary arc magma genesis for arc crust formation  

NASA Astrophysics Data System (ADS)

Whether subducting slab melts or simply dehydrates is a key question for understanding the generation of primary magmas above subduction zones. Chemical composition of the primary magma is the fundamental constraint, both for understanding crust formation and mantle return in subduction zones. There are two endmember ideas about arc primary magma genesis; one suggests mantle melting by slab fluid fluxing (basalt to high-Mg andesite) and the other suggests slab melting to form primary magma immediately (adakite) or after slab melt-mantle reaction (high-Mg andesite to basalt). Geodynamic and petrological models suggest that both are plausible, depending on the temperature structure in the mantle wedge and slab. To test these models, we have improved our petrological/geochemical model (ABS2; Kimura et al. G-cubed 2009)), which we now call ABS3, to additionally simulate (1) prograde metamorphism and melting phase relationships of the slab to calculate slab fluid/melt compositions, and (2) mantle peridotite melting induced by slab fluid/melt-fluxing for the primary arc magma compositions. The ABS3 model uses 23 incompatible trace elements and Sr-Nd-Pb isotopes to fit primary basalt/andesite compositions found in arcs and can be adjusted for variable subduction zone inputs via oceanic slab subduction and mantle peridotite convection. Intensive and extensive parameters for slab dehydration/melting and mantle peridotite melting conditions are found by iterative fitting, providing geochemical constrains for the primary magmas and slab-mantle conditions. We have compared magmas from old-cold subduction zones (NE Japan, Izu arcs) and young-hot subduction zones (SW Japan, early Bonin arcs). The results indicate that low-K volcanic front tholeiites in cold subduction zone alone are from slab fluid fluxed mantle melting whereas medium-K rear arc basalts in the same arcs are slab melt fluxed. High-Mg andesites and some adakites can be generated by intensive slab melt flux to the mantle wedge whereas boninites require ultra-depleted high-T mantle wedge with slight addition of both slab melts and fluids.

Kimura, J.; Hacker, B. R.; van Keken, P. E.; Kawabata, H.; Yoshida, T.; Stern, R. J.

2009-12-01

402

Dehydration of Oxygenated Hydrocarbons and Related Reactions over an Amorphous Silica-Alumina Catalyst.  

National Technical Information Service (NTIS)

The amorphous silica-alumina catalyst used (silica/alumina ratio of 90) produced a product spectrum in methanol (or dimethylether) conversion very similar to that of zeolite H-ZSM-5. Its activity was similar to that of H-ZSM-5 with a comparable silica/alu...

R. L. Espinoza C. M. Stander

1981-01-01

403

Molecular and structural preservation of dehydrated bio-tissue for THz spectroscopy  

NASA Astrophysics Data System (ADS)

Terahertz transmission through freshly excised biological tissue is limited by the tissue's high water content. Tissue fixation methods that remove water, such as fixation in Formalin, destroy the structural information of proteins hence are not suitable for THz applications. Dehydration is one possible method for revealing the tissue's underlying molecular structure and components. In this study, we measured the THz responses over time of dehydrating fresh, necrotic and lyophilized rat tissue. Our results show that as expected, THz absorption increases dramatically with drying and tissue freshness can be maintained through lyophilization. Dehydrated biological tissue with retained molecular structure can be useful for future laser-based THz wave molecular analysis.

Png, Gretel M.; Choi, Jin Wook; Guest, Ian; Ng, Brian W.-H.; Mickan, Samuel P.; Abbott, Derek; Zhang, Xi-Cheng

2007-12-01

404

On the dehydration mechanism of Mg(OH){sub 2} by a high-energy electron beam  

SciTech Connect

The dehydration process in Mg(OH){sub 2} induced by high-energy electron irradiation is studied by in situ electron energy loss spectroscopy. During dehydration, both the low energy-loss spectra and the Mg L{sub 23} edge show the existence of partially oxidized Mg- or O-deficient MgO in the dehydrated products, which is not seen in the thermally dehydrated MgO. This indicates that the dehydration mechanism under the electron beam may be different from the mechanism involved in a thermal process.

Su Dong; Jiang, Nan; Spence, John C. H. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); He Feng; Petuskey, William T. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States)

2008-09-15

405

Different gene-specific mechanisms determine the 'revised-response' memory transcription patterns of a subset of A. thaliana dehydration stress responding genes  

PubMed Central

Plants that have experienced several exposures to dehydration stress show increased resistance to future exposures by producing faster and/or stronger reactions, while many dehydration stress responding genes in Arabidopsis thaliana super-induce their transcription as a ‘memory’ from the previous encounter. A previously unknown, rather unusual, memory response pattern is displayed by a subset of the dehydration stress response genes. Despite robustly responding to a first stress, these genes return to their initial, pre-stressed, transcript levels during the watered recovery; surprisingly, they do not respond further to subsequent stresses of similar magnitude and duration. This transcriptional behavior defines the ‘revised-response’ memory genes. Here, we investigate the molecular mechanisms regulating this transcription memory behavior. Potential roles of abscisic acid (ABA), of transcription factors (TFs) from the ABA signaling pathways (ABF2/3/4 and MYC2), and of histone modifications (H3K4me3 and H3K27me3) as factors in the revised-response transcription memory patterns are elucidated. We identify the TF MYC2 as the critical component for the memory behavior of a specific subset of MYC2-dependent genes.

Liu, Ning; Ding, Yong; Fromm, Michael; Avramova, Zoya

2014-01-01

406

Bonding by Hydroxide-Catalyzed Hydration and Dehydration  

NASA Technical Reports Server (NTRS)

A simple, inexpensive method for bonding solid objects exploits hydroxide-catalyzed hydration and dehydration to form silicate-like networks in thin surface and interfacial layers between the objects. The method can be practiced at room temperature or over a wide range of temperatures. The method was developed especially to enable the formation of precise, reliable bonds between precise optical components. The bonds thus formed exhibit the precision and transparency of bonds formed by the conventional optical-contact method and the strength and reliability of high-temperature frit bonds. The method also lends itself to numerous non-optical applications in which there are requirements for precise bonds and/or requirements for bonds, whether precise or imprecise, that can reliably withstand severe environmental conditions. Categories of such non-optical applications include forming composite materials, coating substrates, forming laminate structures, and preparing objects of defined geometry and composition. The method is applicable to materials that either (1) can form silicate-like networks in the sense that they have silicate-like molecular structures that are extensible into silicate-like networks or (2) can be chemically linked to silicate-like networks by means of hydroxide-catalyzed hydration and dehydration. When hydrated, a material of either type features surface hydroxyl (-OH) groups. In this method, a silicate-like network that bonds two substrates can be formed either by a bonding material alone or by the bonding material together with material from either or both of the substrates. Typically, an aqueous hydroxide bonding solution is dispensed and allowed to flow between the mating surfaces by capillary action. If the surface figures of the substrates do not match precisely, bonding could be improved by including a filling material in the bonding solution. Preferably, the filling material should include at least one ingredient that can be hydrated to have exposed hydroxyl groups and that can be chemically linked, by hydroxide catalysis, to a silicate-like network. The silicate-like network could be generated in situ from the filling material and/or substrate material, or could be originally present in the bonding material.

Gwo, Dz-Hung

2008-01-01

407

Photochemical activity of Titan's low-altitude condensed haze.  

PubMed

Titan, the largest moon of Saturn and similar to Earth in many aspects, has unique orange-yellow colour that comes from its atmospheric haze, whose formation and dynamics are far from well understood. Present models assume that Titan's tholin-like haze formation occurs high in atmosphere through gas-phase chemical reactions initiated by high-energy solar radiation. Here we address an important question: Is the lower atmosphere of Titan photochemically active or inert? We demonstrate that indeed tholin-like haze formation could occur on condensed aerosols throughout the atmospheric column of Titan. Detected in Titan's atmosphere, dicyanoacetylene (C?N?) is used in our laboratory simulations as a model system for other larger unsaturated condensing compounds. We show that C4N2 ices undergo condensed-phase photopolymerization (tholin formation) at wavelengths as long as 355 nm pertinent to solar radiation reaching a large portion of Titan's atmosphere, almost close to the surface. PMID:23552063

Gudipati, Murthy S; Jacovi, Ronen; Couturier-Tamburelli, Isabelle; Lignell, Antti; Allen, Mark

2013-01-01

408

Condensation inside tubes: Condensate film coefficient for vertical downflow  

NASA Astrophysics Data System (ADS)

ESDU 91024 presents a procedure for calculating the local (point) condensate film heat transfer coefficient at a prescribed vapor mass flux and the mean coefficient for the case when the saturation temperature is approximately constant over the entire condensing length. It applies to flow regimes in which the flow is controlled by vapor shear at the film interface or by gravity with either a wavy laminar flow or a turbulent film. Critria to establish the transition from mist-annular to annular flow and from annular to slug flow are included. The procedure applies to co-current downward flow; for reflux condensation ESDU 89038 should be consulted. The method depends on a correlation for the local coefficient extracted from the literature that was tested against experimental data also taken from the literature. No significant trends were seen with condensate or vapor phase Reynolds number, interfacial shear stress, vapor mass fraction, or flow regime parameter (a parameter giving a non-dimensional gas phase velocity). Typical correlation plots illustrate that behavior and show that the data correlate within 30 percent. The treatment of vapor desuperheating is considered, and the effect of condensate sub-cooling is treated. Step-by-step calculation procedures are presented and their use illustrated by a worked example.

1991-11-01

409

Hypodermoclysis for control of dehydration in terminal-stage cancer.  

PubMed

Many of those involved in palliative care have justifiable objections to the introduction of intravenous hydration in patients with dehydration-associated symptoms and advanced cancer. Researchers from the University of Buenos Aires carried out a randomized, comparative and prospective trail to determine the usefulness of hypodermoclysis in the control of thirst, chronic nausea and delirium. Forty-two patients were randomized into two groups. Both groups received drugs subcutaneously (haloperidol 2.5 mg every 4 hours to control delirium and/or metoclopramide 10 mg every 4 hours to control chronic nausea). The study group also received 1000 ml 5% dextrose in water infusion plus 140 milliequivalent per litre (mEq/L) sodium chloride, at a rate of 42 ml/hour per day. Both groups showed significant and equal improvements in relief of thirst and chronic nausea at 24 hours. After 48 hours, this improvement was maintained in the group that received hydration, but only for the relief of chronic nausea. Delirium did not improve significantly in either group during the 48-hour trial period. Current data suggest that decisions on rehydration of patients with terminal-phase cancer should be based more on the patient's comfort than on providing optimal hydration. PMID:12411847

Cerchietti, L; Navigante, A; Sauri, A; Palazzo, F

2000-09-01

410

Dehydration in cancer patients: to treat or not to treat.  

PubMed

Many patients in the terminal phase of their illness experience reduced oral intake before death, due to causes related to their cancer or its treatment. When oral intake is not adequate, dehydration and malnutrition are the obvious results. But these terminally ill patients present a challenge to healthcare providers: to rehydrate these patients or not and, if so, how? Adequate hydration levels are much lower in terminal patients with cancer than in normal adults. Healthcare professionals should assess the patient's hydration needs through personal history, physical examination, and laboratory evaluation before considering the advantages and disadvantages of rehydration, as well as the wishes of the patient and his or her family. In doubtful cases, a short trial of hydration may be appropriate. If hydration is considered, there are a number of methods to consider based on the needs of the patient, including intravenous administration, hypodermoclysis, and proctoclysis. The subcutaneous route is an excellent alternative due to its simplicity, low cost, and feasibility in the home setting. PMID:15605914

Dalal, Shalini; Bruera, Eduardo

2004-01-01

411

Vat dye sorption onto crude dehydrated sewage sludge.  

PubMed

In this work, sewage sludge is used as a textile dye adsorbent. A sample of crude dehydrated sewage sludge issued from an urban wastewater treatment plant (high-rate aeration, activated sludge process, Sahline, Tunisia) is utilized for vat dye retention. The main objective of this work is to evaluate the "efficiency" of the crude material on vat dye sorption. However, no treatment to modify any of the adsorbent properties was considered. Although the relatively low specific surface area (about 3.2m(2)g(-1)) compared to more conventional adsorbents, the used material shows very interesting retention capacities when used with water pollutants. The pseudo, first and second order kinetic models have been used to investigate the retention mechanism. When linearized, the pseudo-second order fit, for the both used dyes, in a better way the obtained experimental results than the pseudo-first order kinetic model. For equilibrium dye uptake amount it is found that the used material has a capacity (Langmuir Freundlich monolayer) of 73.1mg/g to fix the VAT RED 10 and 58.7 mg/g to fix the VAT ORANGE 11. PMID:18809247

Dhaouadi, H; M'henni, F

2009-05-30

412

Possible contributions of pileus clouds to TTL dehydration  

NASA Astrophysics Data System (ADS)

Measurements from CRYSTAL-FACE show that thin tropopause cirrus (TTC) was frequently present above anvil cirrus. TTC was typically a hundred times more tenuous, about 20 K colder, and had similar horizontal dimensions to the anvil. Photography, as well as analysis of the cloud dynamics, chemistry, and isotopic ratios has led to a hypothesis that the tropopause cirrus formed initially as cap-shaped pileus clouds over deep convective turrets. The pileus spread as stratiform layers over the anvil, where they were shielded from heating from terrestrial infrared radiation. Here we propose possible implications of pileus cloud formation to the process of stratospheric dehydration. In the moist stratified tropopause transition layer (TTL), isentropes are bent upwards ahead of deep convection. A thin pileus cloud may form if isentropic surfaces are raised sufficiently that air is cooled to the point of homogeneous ice nucleation. If the TTL was initially supersaturated with respect to ice (as is often observed), once the convection subsides and the isentropes flatten, a stratiform TTC cloud lingers. As the anvil beneath the TTC thins, the TTC is increasingly exposed to radiative heating from the earth's surface, and it is lofted upwards. If it precipitates it may contribute to the dessication of the lower stratosphere.

Garrett, T. J.

2004-12-01

413

Pore formation during dehydration of polycrystalline gypsum observed and quantified in a time-series synchrotron radiation based X-ray micro-tomography experiment  

NASA Astrophysics Data System (ADS)

We conducted an in-situ X-ray micro-computed tomography heating experiment at the Advanced Photon Source (USA) to dehydrate an unconfined 2.3 mm diameter cylinder of Volterra Gypsum. We used a purpose-built X-ray transparent furnace to heat the sample to 388 K for a total of 310 min to acquire a three-dimensional time-series tomography dataset comprising nine time steps. The voxel size of 2.2 ?m3 proved sufficient to pinpoint reaction initiation and the organization of drainage architecture in space and time. We observed that dehydration commences across a narrow front, which propagates from the margins to the centre of the sample in more than four hours. The advance of this front can be fitted with a square-root function, implying that the initiation of the reaction in the sample can be described as a diffusion process. Novel parallelized computer codes allow quantifying the geometry of the porosity and the drainage architecture from the very large tomographic datasets (6.4 × 109 voxel each) in unprecedented detail. We determined position, volume, shape and orientation of each resolvable pore and tracked these properties over the duration of the experiment. We found that the pore-size distribution follows a power law. Pores tend to be anisotropic but rarely crack-shaped and have a preferred orientation, likely controlled by a pre-existing fabric in the sample. With on-going dehydration, pores coalesce into a single interconnected pore cluster that is connected to the surface of the sample cylinder and provides an effective drainage pathway. Our observations can be summarized in a model in which gypsum is stabilized by thermal expansion stresses and locally increased pore fluid pressures until the dehydration front approaches to within about 100 ?m. Then, the internal stresses are released and dehydration happens efficiently, resulting in new pore space. Pressure release, the production of pores and the advance of the front are coupled in a feedback loop. We discuss our findings in the context of previous studies.

Fusseis, F.; Schrank, C.; Liu, J.; Karrech, A.; Llana-Fúnez, S.; Xiao, X.; Regenauer-Lieb, K.

2011-10-01

414

Dehydration and Denitrification in the Arctic Polar Vortex During the 1995-1996 Winter  

NASA Technical Reports Server (NTRS)

Dehydration of more than 0.5 ppmv water was observed between 18 and 19 km (theta approximately 450-465 K) at the edge of the Arctic polar vortex on February 1, 1996. More than half the reactive nitrogen (NO(y)) had also been removed, with layers of enhanced NO(y) at lower altitudes. Back trajectory calculations show that air parcels sampled inside the vortex had experienced temperatures as low as 188 K within the previous 12 days, consistent with a small amount of dehydration. The depth of the dehydrated layer (approximately 1 km) and the fact that trajectories passed through the region of ice saturation in one day imply selective growth of a small fraction of particles to sizes large enough (>10 micrometers) to be irreversibly removed on this timescale. Over 25% of the Arctic vortex in a 20-30 K range Transport of theta is estimated to have been dehydrated in this event.

Hintsa, E. J.; Newman, P. A.; Jonsson, H. H.; Webster, C. R.; May, R. D.; Herman, R. L.; Lait, L. R.; Schoeberl, M. R.; Elkins, J. W.; Wamsley, P. R.; Dutton, G. S.; Bui, T. P.; Kohn, D. W.; Anderson, J. G.

1998-01-01

415

Dehydration and Denitrification in the Arctic Polar Vortex During the 1995-1996 Winter  

NASA Technical Reports Server (NTRS)

Dehydration of more than 0.5 ppmv water was observed between 18 and 19 km (theta about 450-465 K) at the edge of the Arctic polar vortex on February 1, 1996. More than half the reactive nitrogen (NO(sub y)) had also been removed, with layers of enhanced (sub y) at lower altitudes. Back trajectory calculations show that air parcels sampled inside the vortex had experienced temperatures as low as 188 K within the previous 12 days, consistent with a small amount of dehydration. The depth of the dehydrated layer (about 1 km) and the fact that trajectories passed through the region of ice saturation in one day imply selective growth of a small fraction of particles to sizes large enough (>10 micron) to be irreversibly removed on this timescale. Over 25% of the Arctic vortex in a 20-30 K range of theta is estimated to have been dehydrated in this event.

Hintsa, E. J.; Newman, P. A.; Jonsson, H. H.; Webster, C. R.; May, R. D.; Herman, R. L.; Lait, L. R.; Schoeberl, M. R.; Elkins, J. W.; Wamsley, P. R.; Dutton, G. S.; Bui, T. P.; Kohn, D. W.; Anderson, J. G.

1998-01-01

416

Dehydration and Denitrification in the Arctic Polar Vortex During the 1995-1996 Winter  

NASA Technical Reports Server (NTRS)

Dehydration of more than 0.5 ppmv water was observed between 18 and 19 km (theta = 450-465 K) at the edge of the Arctic polar vortex on February 1, 1996. More than half the reactive nitrogen (NOy) had also been removed, with layers of enhanced NOy at lower altitudes. Back trajectory calculations show that air parcels sampled inside the vortex had experienced temperatures as low as 188 K within the previous 12 days, consistent with a small amount of dehydration. The depth of the dehydrated layer (approx. 1 km) and the fact that trajectories passed through the region of ice saturation in one day imply selective growth of a small fraction of particles to sizes large enough (>10 micrometers) to be irreversibly removed on this timescale. Over 25% of the Arctic vortex in a 20-30 K range of theta is estimated to have been dehydrated in this event.

Hintsa, E. J.; Newman, P. A.; Jonsson, H. H.; Webster, C. R.; May, R. D.; Herman, R. L.; Lait, L. R.; Schoerberl, M. R.; Elkins, J. W.; Wamsley, P. R.

1998-01-01

417

Dehydration and Denitrification in the Arctic Polar Vortex During the 1995-1996 Winter  

NASA Technical Reports Server (NTRS)

Dehydration of more than 0.5 ppmv water was observed between 18 and 19 km (0-450-465 K) at the edge of the Arctic polar vortex on February 1, 1996. More than half the reactive nitrogen (NO(y)) had also been removed, with layers of enhanced NO(y) at lower altitudes. Back trajectory calculations show that air parcels sampled inside the vortex had experienced temperatures as low as 188 K within the previous 12 days, consistent with a small amount of dehydration. The depth of the dehydrated layer (approximately 1 km) and the fact that trajectories passed through the region of ice saturation in one day imply selective growth of a small fraction of particles to sizes large enough (>10 microns) to be irreversibly removed on this timescale. Over 25% of the Arctic vortex in a 20-30 K range of 0 is estimated to have been dehydrated in this event.

Hintsa, E. J.; Newman, P. A.; Jonsson, H. H.; Webster, C. R.; May, R. D.; Herman, R. L.; Lait, L. R.; Schoeberl, M. R.; Elkins, J. W.; Wamsley, P. R.; Dutton, G. S.; Bui, T. P.; Kohn, D. W.; Anderson, J. G.

1998-01-01

418

Dehydration of Mars Relevant Ferric Sulfates at High Temperatures Studied by Laser Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

We explored the dehydration of Mars relevant ferric sulfates using laser Raman spectroscopy, which provides important clue to uncover the mystery of relatively rarely detected ferric sulfates on martian surface by orbital remote sensing.

Liu, Y.; Wang, A.

2014-06-01

419

The Micro Raman Spectroscopy for Analysis of the Gypsum Dehydration by Simulated Space Weathering  

NASA Astrophysics Data System (ADS)

Herein, a simulated space weathering of hydrated sulfates (gypsum, CaSO_4.2H_20) by CO_2 low temperature plasma was reported. Gypsum dehydration is a significant process of weathering analyzed by micro-laser Raman spectroscopy.

Wu, Z. C.; Ni, Y. H.; Ling, Z. C.; Wu, H.

2014-06-01

420

Liquid-phase and vapor-phase dehydration of organic/water solutions  

DOEpatents

Processes for dehydrating an organic/water solution by pervaporation or vapor separation using fluorinated membranes. The processes are particularly useful for treating mixtures containing light organic components, such as ethanol, isopropanol or acetic acid.

Huang, Yu (Palo Alto, CA); Ly, Jennifer (San Jose, CA); Aldajani, Tiem (San Jose, CA); Baker, Richard W. (Palo Alto, CA)

2011-08-23

421

Method and Apparatus for Heated, Pressure-Swing High Pressure Air Dehydration.  

National Technical Information Service (NTIS)

Method and apparatus for separating gases, especially for removing water vapor from a gas such as air. This invention uses a short-cycle process which produces reduction in dewpoint (for dehydrating gas separation processes) or change in gas concentration...

R. Blizzard C. T. Schell H. J. Skurch

1995-01-01

422

Review of Magnesium Nitrate as a Dehydrating Agent for Use in the Manufacture of Nitrocellulose.  

National Technical Information Service (NTIS)

A recent GAO review of the production base modernization program for the manufacture of nitrocellulose (NC) resulted in a recommendation that further modernization be deferred until a new nitration process employing magnesium nitrate as a dehydrating agen...

M. Netzler T. W. Lott

1974-01-01

423

A NOVEL HYDROPHILIC POLYMER MEMBRANE FOR THE DEHYDRATION OF ORGANIC SOLVENTS  

EPA Science Inventory

Novel hydrophilic polymer membranes based on polyallylamine ydrochloride- polyvinylalcohol are developed. The high selectivity and flux characteristics of these membranes for the dehydration of organic solvents are evaluated using pervaporation technology and are found to be ver...

424

76 FR 4284 - Grant of Authority for Subzone Status; Tulkoff Food Products, Inc. (Dehydrated Garlic), Baltimore...  

Federal Register 2010, 2011, 2012, 2013

...Tulkoff Food Products, Inc. (Dehydrated Garlic), Baltimore, MD Pursuant to its authority...establish a special-purpose subzone at the garlic products manufacturing facility of Tulkoff...activity related to the manufacture of garlic products at the Tulkoff Food...

2011-01-25

425

Coseismic dehydration in clay-bearing faults and implications for slip weakening, frictional heating, and earthquake energetics  

NASA Astrophysics Data System (ADS)

Transient frictional heating during earthquake slip induces dehydroxylation of phyllosilicate minerals. As this reaction is endothermic and releases H2O, it may affect dynamic fault weakening and the energetics of earthquakes. To elucidate this question, we chose illite-muscovite as a representative example of the phyllosilicates in active crustal faults. We first measured the specific heat capacity and thermal diffusivity of an illite-muscovite specimen, and their temperature dependencies, and determined the weight loss and enthalpy of the dehydroxylation reaction to be 5.22 wt% and 0.2895 kJ g-1, respectively. We applied Friedman analysis to the weight loss data from heating experiments and found that the dehydroxylation reactions were well fitted by two-step reactions of an n-dimensional nucleation mechanism according to the Avrami-Erofeev equation with n = 0.5 (first step) and two-dimensional diffusion (second step). On the basis of these experimental results, we performed numerical analyses of dynamic fault weakening, taking into account the dehydroxylation reaction of illite-muscovite. We demonstrated that the fluids released by dehydroxylation contribute to pressurization of pore fluids and induce a decrease in effective normal stress on faults, and that the dehydroxylation reaction absorbs heat from the energy released at the fault during earthquake slip. These processes collectively inhibit temperature increases during slip. The ratio of the energy used for the reaction to the work on the fault at the condition of 2 km depth, 1 cm slip-zone thickness, and 0.38 frictional coefficient reached 14.5%. Therefore, coseismic dehydration of phyllosilicate minerals significantly affects slip weakening, frictional heating, and energetics in clay-rich faults.

Hirono, T.; Tanikawa, W.

2011-12-01

426

Condensation modes in magnetized plasmas  

NASA Technical Reports Server (NTRS)

Condensation modes in magnetized cylindrical plasmas, with concentration on how magnetic field affects the stability were studied. It is found that the effects of magnetic field (shear, twist, and strength) on the condensation modes are different depending on the wave vector. For modes whose wave vector is not perpendicular to magnetic field lines the plasma motion is mainly along the field lines; the effects of magnetic field on the modes are negligible except on the heat flow parallel to the field line. For a mode which is localized near a surface where the wave vector is perpendicular to the field line, the plasma moves perpendicular to the line carrying the field