scholarly journals Hydrothermal alteration and sealing at Turrialba as a mechanism for phreatic eruption triggering

2021 ◽  
Author(s):  
Emily Mick ◽  
John Stix ◽  
J. Maarten de Moor ◽  
Geoffroy Avard
Keyword(s):  
Mineral Assemblage ◽  
Sulphate Content ◽  
Acid Sulphate ◽  
Seal Failure ◽  
Variable Porosity ◽  
Highly Active ◽  
Macro Scale ◽  
Hydrothermal Sealing ◽  
Phreatic Eruptions ◽  
High Concentrations

<p>Turrialba is a basaltic to andesitic Holocene stratovolcano that after decades of quiescence re-activated in 1996 and has been highly active ever since. Turrialba is characterized by a highly active magmatic-hydrothermal system, and we propose that hydrothermal sealing and volatile accumulation are the mechanisms responsible for the reactivation and persistent phreatic activity at Turrialba since 2010. Evidence of sealing is found in pyroclastic breccias from phreatic eruptions as high concentrations of hydrothermal minerals coupled with low intrinsic permeability. The suite of volcanic breccias studied erupted from the main vent between 2014 and 2019 and has an alteration mineral assemblage of SiO<sub>2</sub>polymorphs ± gypsum ± natroalunite ± pyrite. The mineral assemblage is indicative of acid sulphate alteration within the advanced-argillic alteration facies characterized by temperatures of approximately 200-350°C as indicated by the presence of gypsum and natroalunite, the high temperature endmember of the alunite series. Acid sulphate alteration is the result of extreme base leaching by acidic fluids (pH<4) with a high sulphate content. Measurements of permeability and porosity yielded variable porosity and very low to non-existent permeability in all hydrothermal breccia samples. Back-scatter electron (BSE) images reveal nano-, micro- and macro-scale fracture networks discontinuously filled with hydrothermal gypsum and pyrite which are responsible for diminished permeability, supporting the conclusion that hydrothermal sealing is active at Turrialba. Diminished permeability associated with the formation of a seal inhibits the escape of gases, causing them to accumulate below the seal and pressurize the system. Eventual seal failure releasing overpressure and possibly dynamic rapid seal formation result in the frequent phreatic eruptions seen at Turrialba.</p>

scholarly journals Kinetics and specificity of homogeneous protein disulphide-isomerase in protein disulphide isomerization and in thiol-protein-disulphide oxidoreduction

1983 ◽  
Vol 213 (1) ◽  
pp. 235-243 ◽  
Author(s):  
N Lambert ◽  
R B Freedman
Keyword(s):  
Reduced Glutathione ◽  
Physiological Role ◽  
Homologous Proteins ◽  
Ph Optimum ◽  
Oxidoreductase Activity ◽  
Protein Disulphide Isomerase ◽  
Highly Active ◽  
Reducing Conditions ◽  
Order Of Magnitude ◽  
High Concentrations

The protein disulphide-bond isomerization activity of highly active homogeneous protein disulphide-isomerase (measured by re-activation of ‘scrambled’ ribonuclease) is enhanced by EDTA and by phosphate buffers. As shown for previous less-active preparations, the enzyme has a narrow pH optimum around pH 7.8 and requires the presence of either a dithiol or a thiol. The dithiol dithiothreitol is effective at concentrations 100-fold lower than the monothiols reduced glutathione and cysteamine. The enzyme follows Michaelis-Menten kinetics with respect to these substrates; Km values are 4,620 and 380 microM respectively. The enzyme shows apparent inhibition by high concentrations of thiol or dithiol compounds (greater than 10 X Km), but the effect is mainly on the extent of reaction, not the initial rate. This is interpreted as indicating the formation of significant amounts of reduced ribonuclease in these more reducing conditions. The purified enzyme will also catalyse net reduction of insulin disulphide bonds by reduced glutathione (i.e. it has thiol:protein-disulphide oxidoreductase or glutathione:insulin transhydrogenase activity), but this requires considerably higher concentrations of enzyme and reduced glutathione than does the disulphide-isomerization activity. The Km for reduced glutathione in this reaction is an order of magnitude greater than that for the disulphide-isomerization activity, and the turnover number is considerably lower than that of other enzymes that can catalyse thiol-disulphide oxidoreduction. Conventional two-substrate steady-state analysis of the thiol:protein-disulphide oxidoreductase activity indicates that it follows a ternary-complex mechanism. The protein disulphide-isomerase and thiol:protein-disulphide oxidoreductase activities co-purify quantitatively through the final stages of purification, implying that a single protein species is responsible for both activities. It is concluded that previous preparations, from various sources, that have been referred to as protein disulphide-isomerase, disulphide-interchange enzyme, thiol:protein-disulphide oxidoreductase or glutathione:insulin transhydrogenase are identical or homologous proteins. The assay, nomenclature and physiological role of this enzyme are discussed.

scholarly journals Purification and properties of an esterase from organophosphate-resistant strain of the mosquito Culex quinquefasciatus

1990 ◽  
Vol 266 (1) ◽  
pp. 83-90 ◽  
Author(s):  
A T Merryweather ◽  
J M Crampton ◽  
H Townson
Keyword(s):  
Culex Quinquefasciatus ◽  
Resistant Strain ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Starch Gel Electrophoresis ◽  
Post Translational Modification ◽  
Highly Active ◽  
High Concentrations ◽  
Starch Gels

Organophosphate-resistant and -susceptible strains of Culex quinquefasciatus (mosquito) have been compared on the basis of their esterase activities. The homozygous resistant strain (Dar) shows two highly active esterases after starch-gel electrophoresis, of Rm 0.2 and 0.4, which are absent from susceptible strains (Apo, Mon), and which previous selection studies have shown to be inseparable from organophosphate resistance. After SDS/polyacrylamide-gel electrophoresis and silver staining of total C. quinquefasciatus proteins, a 62 kDa band is observed in strain Dar at high concentrations, and in susceptible strains in trace amounts. After Western blotting, this 62 kDa protein is recognized by antisera raised against the two esterases eluted from starch gels. After chromatofocusing of Dar proteins, the 62 kDa protein is seen to be associated with esterase activity, and of a similar pI to that observed for esterases after isoelectric focusing. Post-translational modification is not required for recognition of the 62 kDa putative esterase, since the protein is immunoprecipitated by the anti-esterase serum from products of translation of Dar mRNA in vitro.

Low-temperature, highly selective, highly stable Nb2O5–NiO/Ni-foam catalyst for the oxidative dehydrogenation of ethane

2018 ◽  
Vol 8 (17) ◽  
pp. 4383-4389 ◽  
Author(s):  
Zhiqiang Zhang ◽  
Guofeng Zhao ◽  
Ruijuan Chai ◽  
Jian Zhu ◽  
Ye Liu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Oxidative Dehydrogenation ◽  
Ni Foam ◽  
Highly Active ◽  
Oxidative Dehydrogenation Of Ethane ◽  
Macro Scale

A Nb2O5–NiO/Ni-foam catalyst engineered from nano- to macro-scale is developed, which is highly active/selective and stable for the oxidative dehydrogenation of ethane to ethylene.

scholarly journals Accumulation of malto-oligosaccharides in the syncytiotrophoblastic cells of first-trimester human placentas

1981 ◽  
Vol 200 (1) ◽  
pp. 93-98 ◽  
Author(s):  
S J Fisher ◽  
R A Laine
Keyword(s):  
Gel Filtration ◽  
First Trimester ◽  
Structural Elements ◽  
Trophoblastic Cells ◽  
Highly Active ◽  
A Cell ◽  
Liver Homogenates ◽  
High Concentrations ◽  
Very High

A cell-surface microvillar fraction that was isolated from the syncytiotrophoblastic cells of first-trimester human placentas was found to contain very high concentrations (890 +/- 32 microgram of hexose/mg of protein) of a class of low-molecular-weight oligosaccharides that were comprised entirely of glucose. T.l.c. and gel filtration showed that the saccharides contained from one to six glucose residues. The structures of the most prominent members of the series, a tetra- and a tri-saccharide, were determined. The anomeric configuration of the glucose residues was alpha, and methylation linkage analysis gave terminal and 4-linked hexose residues. These malto-oligosaccharides contained one reducing terminus per molecule, indicating that they were free and not bound to other structural elements of the cells. Within the placenta they appeared to be concentrated in the first-trimester trophoblastic cells, since crude membrane and particulate fractions isolated from either term trophoblastic cells or cultured placental fibroblasts did not contain detectable amounts of glucose oligomers. This series of oligosaccharides was similar to the products that are formed when glycogen is degraded by alpha-amylase in liver homogenates and may be indicative of a similar, highly active enzymic reaction closely associated with the brush border of the syncytiotrophoblastic cells of the first-trimester human placenta. Although the role of these oligosaccharides remains obscure they are probably involved in foetal metabolism.

Seasonal fluctuations in mineral sulphur under subterranean clover pasture in southern New South Wales

Soil Research ◽  
1968 ◽  
Vol 6 (1) ◽  
pp. 131 ◽  
Author(s):  
CH Williams
Keyword(s):  
Plant Uptake ◽  
Surface Soil ◽  
New South ◽  
Subterranean Clover ◽  
Sulphate Content ◽  
South Wales ◽  
Sulphate Sulphur ◽  
Soil Temperatures ◽  
High Concentrations ◽  
Clover Pasture

Seasonal changes in sulphate sulphur were studied in a soil under subterranean clover pasture. Fluctuations in sulphate content were found to be similar to those in nitrate. Both sulphate and nitrate accumulated in the surface soil during summer, immediately after senescence of the pasture. High concentrations were maintained throughout the summer-autumn period and these decreased to low values in winter and spring. The higher values in summer probably resulted from mineralization of soil organic matter under favourable moisture and temperature conditions, and lack of plant uptake. Minor fluctuations were associated with partial leaching by rainwater. The low values in winter and spring were probably brought about by leaching and plant uptake, together with low rates of mineralization at low soil temperatures.

scholarly journals FURTHER STUDIES ON THE PROPERTIES OF PURE VACCINE VIRUS CULTIVATED IN VIVO

1918 ◽  
Vol 27 (3) ◽  
pp. 425-442 ◽  
Author(s):  
Hideyo Noguchi
Keyword(s):  
Vaccine Virus ◽  
Entire Body ◽  
Distilled Water ◽  
Injurious Effect ◽  
Ringer’S Solution ◽  
Highly Active ◽  
Cent Saline ◽  
High Concentrations ◽  
Saline Solutions

1. The virulence of vaccine virus for the testicular tissues increases until its maximum is finally reached. The selective increase is not associated with any loss, reduction, or modification in its virulence for the skin. A highly potent testicular vaccine is also highly active for the skin. 2. The testicular strain of vaccine virus has no more tendency to localize in various organs than the ordinary skin strain. Both may localize in adjacent lymph nodes when introduced intravenously, subcutaneously, or intratesticularly in sufficiently large quantities, but other organs are not involved. 3. Intravenous inoculation of an excessive amount of a powerful vaccine virus (1 to 2 cc. of undiluted stock emulsion), irrespective of whether it is from the testis or the skin, will result in a generalized eruption over the entire body surface of rabbits. The eruption may be confluent on mucous membranes of the mouth, nostrils, genitalia, etc. Intratesticular or subcutaneous inoculations of the same virus fail to produce this effect. 4. Subcutaneous or intravenous introduction of much smaller quantities of the virus does not cause an appreciable local or general reaction in the rabbit. But the animals which have once received these injections become refractory to a subsequent vaccination as applied to the skin. It seems probable that an active immunity has been conferred. 5. Experiments on the viability and resistance of the testicular strain of vaccine virus indicate that the virus is best preserved when emulsified with Ringer's solution or 0.9 per cent saline solution. Distilled water, while apparently one of the best diluents, fails to keep the virus active as long as Ringer's or saline solutions. As would be expected, the lower the temperature is, the longer the virus retains its viability. At 18° or 37°C., the deterioration of the virus proceeds rapidly. However, a small part of the virus survives after many weeks' standing at 37°C. 6. Of the two most commonly employed chemical agents for the ripening (eliminating bacteria) process of the green vaccine pulp, glycerol and phenol, the latter is the less injurious. Phenol in concentration above 2 per cent destroys the virus within 24 hours at any temperature, but it has almost no injurious effect when used in 0.5 to 1 per cent. On the other hand, glycerol is a powerful vaccinicide. When used in full strength it destroys the virus within 24 hours, even at 4°C. In a concentration of 40 per cent, that ordinarily recommended for the ripening, the virus retains some of its virulence for about half a year at 4°C., while at higher temperatures the same concentration kills the virus within 1 to 2 months. The virus preserved in distilled water or Ringer's solution under similar temperature conditions remains more active during this period. From this it may be concluded that glycerol is not an indifferent agent, as is assumed by many, but a powerful vaccinicide when used in high concentrations. The injurious effect is markedly accelerated at 18° or 37°C. 7. The vaccine virus retains its virulence better in a sealed tube containing either hydrogen, nitrogen, or air than in an open receptacle. The virus deteriorates when placed in a sealed tube with oxygen or carbon dioxide. 8. Desiccation decreases to a considerable degree the virulence of the vaccine virus. In the dried state the virus retains its viability about as long as does the emulsion, but it is not protected from the deterioration caused by age under various conditions. 9. Iodine is a powerful disinfectant for the vaccine virus, but its sodium and potassium salts have no effect. Various bile salts destroy the vaccine virus when employed in sufficient concentration.

Arginine-Specific Cysteine Proteinase from Porphyromonas gingivalis as a Convenient Tool in Protein Chemistry

2001 ◽  
Vol 382 (9) ◽  
pp. 1399-1404 ◽  
Author(s):  
A. Banbula ◽  
P. Mak ◽  
M. Smoluch ◽  
J. Travis ◽  
J. Potempa
Keyword(s):  
Porphyromonas Gingivalis ◽  
Cysteine Proteinase ◽  
Enzymatic Digestion ◽  
Specific Protein ◽  
Protein Chemistry ◽  
Protein Cleavage ◽  
Peptide Bonds ◽  
Highly Active ◽  
High Concentrations ◽  
Triton X

Abstract RgpB, a cysteine proteinase produced by Porphyromonas gingivalis, exhibits proteolytic activity selectively directed against peptide bonds containing an arginine residue in the P1 position. Here we show that this enzyme can be used for very efficient and specific protein cleavage. RgpB is highly active even at high concentrations of denaturing agents, including urea (up to 6 M) and SDS (0.1%), both of them being commonly used for solubilization of insoluble proteins and peptides. Moreover, RgpB is able to digest polypeptide chains in buffers supplemented with 1% Triton X-100, 1% octyl or decylpyranoside, detergents employed for the enzymatic digestion of proteins transferred onto nitrocellulose membranes. These features render RgpB a suitable tool for use in protein chemistry.

Anti-Leishmanial Activity of Novel Homo- and Heteroleptic Bismuth(III) Thiocarboxylates

2013 ◽  
Vol 66 (10) ◽  
pp. 1297 ◽  
Author(s):  
Philip C. Andrews ◽  
Peter C. Junk ◽  
Lukasz Kedzierski ◽  
Roshani M. Peiris
Keyword(s):  
Mammalian Cells ◽  
Leishmania Major ◽  
Lone Pair ◽  
Phenyl Group ◽  
Distorted Octahedral Geometry ◽  
X Ray Crystallography ◽  
Highly Active ◽  
Thiobenzoic Acid ◽  
High Concentrations

Two new thiocarboxylic acids, p-bromothiobenzoic BTA and thionaphthoic acid TNA, and five new homo- and heteroleptic bismuth(iii) compounds derived from thiocarboxylic acids: [Bi{S(C=O)C6H4Br}3] 1, [PhBi{S(C=O)C6H4Br}2] 2, [Bi{S(C=O)C10H7}3] 3, [PhBi{S(C=O)C10H7}2] 4, and [Ph2Bi{S(C=O)C10H7}] 5 were synthesised and fully characterised. The solid-state structure of complex [PhBi{S(C=O)C6H4Br}2] 2 was confirmed by X-ray crystallography. In complex 2, the two thiocarboxylate ligands are coordinated to the bismuth(iii) centre in a didentate fashion, forming a distorted octahedral geometry in which the phenyl group and the lone pair are oriented axial to the plane formed by the two thiocarboxylate ligands. Long-range Bi–S interactions (3.54 Å) link these monomeric units to form a one-dimensional polymer. These compounds, in addition to six previously synthesised complexes: [Bi{SC(=O)C6H5}3] 6, [PhBi{SC(=O)C6H5}2] 7, [Ph2Bi{SC(=O)C6H5}] 8, [Bi{SC(=O)C6H4NO2}3] 9, [PhBi{SC(=O)C6H4NO2}2] 10, and [PhBi{SC(=O)C6H4SO3}] 11, and the thiocarboxylic acids themselves, were assessed for their in vitro activity against Leishmania major promastigotes, and for general toxicity against human fibroblast cells. The thiocarboxylic acids, with the exception of thiobenzoic acid and sulfothiobenzoic acid, were toxic to both L. major parasites and the mammalian cells at high concentrations of 50–100 μM. The bismuth(iii) thiocarboxylate derivatives proved to be more active than the corresponding acids. Among these, the heteroleptic phenyl-substituted bismuth(iii) complexes 2, 4, 5, and 7 were highly active, showing IC50 (half maximal inhibitory concentration) values ranging from 0.39 to 4.69 μM, and a clear ligand dependence on activity.

scholarly journals Influence of Different Peritoneal Dialysis Fluids on theIn VitroActivity of Cefepime, Ciprofloxacin, Ertapenem, Meropenem and Tobramycin againstEscherichia Coli

2016 ◽  
Vol 36 (6) ◽  
pp. 662-668 ◽  
Author(s):  
Manuel Kussmann ◽  
Linda Schuster ◽  
Sarah Wrenger ◽  
Petra Pichler ◽  
Gottfried Reznicek ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Peritoneal Dialysis ◽  
Antimicrobial Agents ◽  
Highly Active ◽  
Microbiological Outcome ◽  
Mueller Hinton ◽  
Baxter Healthcare ◽  
High Concentrations ◽  
The Impact

BackgroundPeritonitis is a major problem among patients on peritoneal dialysis (PD). The influence of diverse PD fluids on the activity of frequently used antibiotics has been insufficiently investigated. Thus, the present study set out to investigate the impact of different PD fluids on the activity of cefepime, ciprofloxacin, ertapenem, meropenem, and tobramycin against Escherichia coli.MethodsTime-kill curves in 4 different PD fluids (Dianeal PDG4, Extraneal, Nutrineal PD4 and Physioneal 40, all Baxter Healthcare Corp., Deerfield, IL, USA) were performed over 24 hours with 4 different concentrations (1 x minimum inhibitory concentration [MIC], 4 x MIC, 8 x MIC, 30 x MIC) of each antibiotic evaluated and without antibiotics as control. Cation-adjusted Mueller Hinton broth (CA-MHB) was used as comparator solution.ResultsIn all PD fluids investigated, bacterial growth and antimicrobial activity of all antibiotics tested was significantly reduced compared with the CA-MHB comparator solution. Except at high concentrations of 30 x MIC, cefepime, ertapenem and meropenem demonstrated a strongly reduced activity in all PD fluids investigated. Ciprofloxacin and tobramycin were highly active and bactericidal in all PD fluids and demonstrated dose-dependent activity.ConclusionThe antimicrobial activity of cefepime, ertapenem and meropenem is limited or even nullified in certain PD fluids in vitro, whereas ciprofloxacin and tobramycin show excellent activity. The choice of PD fluids can impact the activity of antimicrobial agents and might influence microbiological outcome. Further studies are required to verify the clinical relevance of our findings.

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