Radioisomerization and Photoisomerization of Liquid 2 -Butenes in the Presence of Sulfur Compounds

1974 ◽  
Vol 52 (12) ◽  
pp. 2337-2340 ◽  
Author(s):  
Guy J. Collin ◽  
Patrick M. Perrin ◽  
François X. Garneau
Keyword(s):  
Molecular Weight ◽  
Hydrogen Sulfide ◽  
Liquid Phase ◽  
Molecular Oxygen ◽  
Carbon Disulfide ◽  
Sulfur Hexafluoride ◽  
The Other ◽  
Isomerization Reaction ◽  
Low Molecular Weight ◽  
Cis And Trans

The liquid phase radiolysis and photolysis of cis- and trans-2-butenes were studied in the presence of various additives. A very efficient isomerization of 2-butenes was achieved by the addition of thiols of low molecular weight (hydrogen sulfide, methyl and isopropyl mercaptans). In the absence of molecular oxygen, we have observed G values (trans-2-butene) of the order of 90 000. On the other hand, little or no isomerization occurred in the presence of carbon disulfide, sulfur hexafluoride, and tert-dodecylmercaptan. Although the majority of the additives have no effect on the 2-butene:hydrogen sulfide system, conjugated diolefins block the isomerization reaction. These diolefins disappear from the reaction mixture.

scholarly journals Bridge-therapy with enoxaparin in the preoperative period of endarterectomy

2010 ◽  
Vol 68 (5) ◽  
pp. 775-777
Author(s):  
Jair Leopoldo Raso ◽  
Rogério Zenóbio Darwich ◽  
Francisco de Lucca Jr ◽  
Romeu Valle Santana ◽  
Marco Túlio Tanure ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Mortality Rate ◽  
Prospective Study ◽  
Low Molecular Weight Heparin ◽  
The Other ◽  
Low Molecular Weight ◽  
Preoperative Period ◽  
Safe Strategy ◽  
A Prospective Study ◽  
Bridge Therapy

Cervical clot is one of the complications of endarterectomy. This risk may be higher in patients using aspirin or clopidogrel. On the other hand, stroke may occur if the medication is interrupted before surgery. We carried out a prospective study of 124 endarterectomies in 119 patients in which aspirin or clopidogrel was stopped and a bridge-therapy with enoxaparin was administered preoperatively. There was no case of stroke during the period of the bridge-therapy. One patient developed cervical clot (0.8%) in the fifth postoperative day. Mortality rate in this series was 0.8%. There was no complication directly related to the use of enoxaparin. Bridge-therapy with low molecular weight heparin is a safe strategy for patients elected for endarterectomy

Characterization of Sol and Gel in Hevea Natural Rubber

1997 ◽  
Vol 70 (5) ◽  
pp. 707-713 ◽  
Author(s):  
Jitladda Tangpakdee ◽  
Yasukuki Tanaka
Keyword(s):  
Molecular Weight ◽  
Weight Fraction ◽  
Toluene Solution ◽  
Low Molecular Weight ◽  
Branch Points ◽  
Gel Content ◽  
High Ammonia ◽  
Linear Molecules ◽  
Cis And Trans

Abstract The gel content of rubber from high-ammonia latex (HA-latex) decreased significantly after deproteinization with proteolytic enzyme. The addition of 1–2% ethanol in toluene solution reduced the gel content of rubbers from HA-latex, deproteinized HA-latex (HA-DP) and pale crepe. Transesterification of the rubber in toluene solution with sodium methoxide dissolved the gel fraction. The gel fractions solubilized after transesterification showed molecular weight distribution rich in low molecular-weight fraction. The Huggins k′ constant of the fractionated rubbers from solubilized-gels was in the range of 0.42–0.45, lower than that of the fractionated HA-DP of 0.5–0.8. This indicates that all the branch-points were decomposed by transesterification to form linear molecules. The Mn values of rubber chains assembling the gel was 5.5−8.3×105 by 13C-NMR measurements of the ratio between cis- and trans-isoprene units, which were comparable to the molecular weight between crosslinks, Mc, of 7−11×105 by swelling measurements. These findings suggest that the branching and crosslinks are composed of two types of branch-points, i. e. one by association or aggregation of proteins or oligopeptides at the initiating end and the other by ester linkages including phosphoric ester at the terminal end.

In Vitro Characterization Of Low Molecular Weight Fractions Of Heparin

1981 ◽  
Author(s):  
Jawed Fareed ◽  
Harry L Messmore ◽  
Daniel A Walz ◽  
Jean Choay ◽  
J C Lormeau
Keyword(s):  
Molecular Weight ◽  
The Other ◽  
Low Molecular Weight ◽  
In Vitro Test ◽  
Thrombin Time ◽  
Specific Test ◽  
Platelet Factor ◽  
At Iii ◽  
Heparin Fractions

Numerous extraction, chromatographic (ion exchange, gel, and affinity), chemical and enzymatic degradation methods have been employed to obtain heparin fractions. The present assays to evaluate potency (e.g. pharmacopeial and coagulant) do not truly reflect the antithrombotic properties of these fractions. In addition, the synthetic peptide substrate based assays to measure the anti Xa activity do not correlate with the coagulant anti Xa assays. We have developed an in vitro test battery to evaluate low molecular weight heparin fractions. Porcine mucosal heparin fractions are assayed for anti Xa activity in coagulant and amidolytic assays and the results are expressed as a ratio. The effect of these fractions on coagulant assays such as prothrombin time (PT), partial thromboplastin time (PTT), thrombin time (TT), Stypven time (ST) on freshly prepared normal human plasma (NHP) is determined The retention characteristics of these fractions on platelet factor 4 and AT-III bound sepharose columns were also determined. We have compared the extracted and chemically depolymerized heparin fractions and found that the anti Xa activity doesn’t always correlate with the other parameters studied. The extracted fractions were slightly stronger in the USP assays and showed a biphasic retention on the PF-4 column whereas the chemically depolymerized product showed only one peak. On the other hand, on the AT-III column both fractions showed similar elution patterns. Our studies suggest that heparin and its fractions exhibit differential behavior on various assays and a specific test may not be used as an index of the potency of their antithrombotic effects. Furthermore, the potency of these fractions should be stated on a weight basis when evaluated in the in vivo animal models rather than in terms of a specific test (e.g. anti Xa activity and US Pharmacopeial assays).

STUDIES ON THE ISOLATION AND NATURE OF THE 'TERREGENS FACTOR'

1954 ◽  
Vol 32 (1) ◽  
pp. 400-406 ◽  
Author(s):  
M. O. Burton ◽  
F. J. Sowden ◽  
A. G. Lochhead
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Ferric Iron ◽  
Test Organism ◽  
The Other ◽  
Inorganic Salts ◽  
Low Molecular Weight ◽  
Straight Chain ◽  
Heat Stable ◽  
Growth Promoting

A procedure is described for the production and concentration of the 'terregens factor' (TF), a bacterial growth promoting substance synthesized by Arthrobacter pascens and essential for the growth of Arthrobacter terregens. From culture filtrates of A. pascens cultivated in a medium of inorganic salts and sucrose, concentrates of TF may be obtained that are active at 0.001 μgm. Per ml., heat stable and contain about 12.7% nitrogen. Acid hydrolysis yielded a number of amino acids, including glutamic acid, glycine, α–alanine, valine, leucine, proline, lysine, and arginine, as well as some unidentified compounds; however, TF does not appear to be a low molecular weight straight chain peptide.Although TF contains no iron, it combines readily with ferrous or ferric iron to form reddish-brown complexes with this metal. Activity for A. terregens is shown by certain iron containing complexes as hemin, coprogen, and ferrichrome. On the other hand none is shown by cytochrome or pulcherrimin; however, aspergillic acid, structurally related to the latter, possesses some growth promoting activity for the test organism.

scholarly journals Viscoelastic Properties of Unentangled Multicyclic Polystyrenes

Polymers ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 973 ◽  
Author(s):  
Zhi-Chao Yan ◽  
Md. Hossain ◽  
Michael Monteiro ◽  
Dimitris Vlassopoulos
Keyword(s):  
Molecular Weight ◽  
Shear Viscosity ◽  
Viscoelastic Properties ◽  
Dilution Effect ◽  
The Other ◽  
Low Molecular Weight ◽  
Zero Shear Viscosity ◽  
Rouse Model ◽  
Loop Size ◽  
Linear Chains

We report on the viscoelastic properties of linear, monocyclic, and multicyclic polystyrenes with the same low molecular weight. All polymers investigated were found to exhibit unentangled dynamics. For monocyclic polymers without inner loops, a cyclic-Rouse model complemented by the contribution of unlinked chains (whose fraction was determined experimentally) captured the observed rheological response. On the other hand, multicyclic polymers with inner loops were shown to follow a hierarchical cyclic-Rouse relaxation with the outer loops relaxing first, followed by the inner loop relaxation. The influence of unlinked linear chains was less significant in multicyclic polymers with inner loops. The isofrictional zero-shear viscosity decreased with increasing number of constrained segments on the coupling sites, which was attributed to the decreasing loop size and the dilution effect due to the hierarchical relaxation.

Fractionation of the Color of Pure Maple and Other Sirups by Gel Filtration

1965 ◽  
Vol 48 (3) ◽  
pp. 493-497
Author(s):  
E E Stinson ◽  
C O Willits
Keyword(s):  
Molecular Weight ◽  
Gel Filtration ◽  
Cane Sugar ◽  
The Other ◽  
Low Molecular Weight ◽  
Brown Sugar ◽  
Maple Sugar ◽  
Molecular Weight Fractions ◽  
Color Fraction

Abstract The colorants of pure maple, cane and maple, refined cane sugar, and light brown sugar sirups were separated into two fractions, one of high- and the other of lowmolecular weights, by means of gel filtration. The ratio of the amounts of high- to the low-molecular weight fractions of pure maple was the lowest of the four sirups and serves as a means of differentiation from these sirups. The color fraction ratio was highest for blended cane-maple sugar sirup. Many maple sirups are also distinguished by a pink band formed on the gel filtration column.

Real-Time Measurement of SO2, H2S, and CS2 Mixed Gases Using Ultraviolet Spectroscopy and a Least Squares Algorithm

2020 ◽  
pp. 000370282097322
Author(s):  
Zhaolun Cui ◽  
Xiaoxing Zhang ◽  
Dachang Chen ◽  
Yi Li ◽  
Yufei Wang ◽  
...  
Keyword(s):  
Hydrogen Sulfide ◽  
Sulfur Dioxide ◽  
Least Squares ◽  
Carbon Disulfide ◽  
Sulfur Hexafluoride ◽  
Quantitative Detection ◽  
Quantitative Calculation ◽  
Efficient Detection ◽  
High Concentrations ◽  
Mixed Gases

Sulfur dioxide, carbon disulfide, and hydrogen sulfide are important decomposition products of insulating gas sulfur hexafluoride, and their types and contents are of great significance for the fault diagnosis of SF6 insulated equipment. In this paper, a method of combining ultraviolet absorption spectroscopy and least squares fitting is proposed for the quantitative calculation of sulfur dioxide, carbon disulfide, and hydrogen sulfide mixed gases. All three gases have absorption peaks in the ultraviolet band and they overlap with each other which makes it hard to determinate the concentrations of the three gases directly. During the experiment, we found that high concentrations of sulfur dioxide and carbon disulfide interfered with the hydrogen sulfide calculation and the magnitude of this interference was positively correlated with these two gas concentrations. Therefore, we found a modified equation for the correction of hydrogen sulfide. Combined with this equation, accurate quantitative detection of three gases can be achieved. The detection ranges are 0.5–10 parts per million for sulfur dioxide and hydrogen sulfide, and 10–300 parts per billion for carbon disulfide. This paper provides a simple and efficient detection method, which is convenient for integration into detection equipment and it provides a support method for the diagnosis of sulfur hexafluoride decomposition gases.

Butyl Networks Containing Unattached Polyisobutylene Chains: Part II, Correlation of Tear, Tensile, and Hysteretic Properties

1986 ◽  
Vol 59 (2) ◽  
pp. 347-360 ◽  
Author(s):  
G. R. Hamed ◽  
F. Ogbimi
Keyword(s):  
Molecular Weight ◽  
Crack Tip ◽  
The Other ◽  
Low Molecular Weight ◽  
Load Bearing ◽  
Tear Strength ◽  
Tearing Energy ◽  
High Molecular Weight Polyisobutylene ◽  
Hysteretic Properties ◽  
Crack Tip Blunting

Abstract Butyl networks containing either unattached polyisobutylene chains or a low-molecular-weight plasticizer have been made by crosslinking butyl rubber in the presence of one of these diluents. With dodecane as a plasticizer, tear strength is reduced both because of a decrease in the density of load-bearing chains and diminished hysteresis. On the other hand, when the diluent is a high-molecular-weight polyisobutylene, tear strength is enhanced if the test rate is sufficiently high. In this case, the polyisobutylene chains are load bearing (at least initially) before slipping at higher strains to relieve local crack-tip stresses and blunt the propagating tear. This hysteretic mechanism delays the onset of crack propagation, thereby enhancing the fracture energy. However, at low tear rates, in which there is adequate time for the unattached chains to relax such that they bear little load and hysteresis is minimized, tear strength decreases with increasing free-chain content—much the same as occurs with a low-molecular-weight diluent. Finally, under conditions in which the average propagating tearing energy is enhanced for the butyl-polyisobutylene system, the initiation tearing energy is increased only moderately. This suggests that crack-tip blunting during steady-state tearing is at least partially responsible for increases in strength in the presence of free chains.

Solution Autoxidation of EPDM and Termonomers

1972 ◽  
Vol 45 (4) ◽  
pp. 1125-1135
Author(s):  
H. Schnecko ◽  
J. S. Walker
Keyword(s):  
Activation Energy ◽  
Molecular Weight ◽  
Oxygen Uptake ◽  
The Other ◽  
Low Molecular Weight ◽  
Kinetic Behavior ◽  
Ethylene Propylene ◽  
Very High

Abstract Oxygen uptake of 3 low molecular weight ethylene-propylene terpolymers (EPDM) and their respective bicyclic diolefin termonomers (dicyclopentadiene, ethylidene norbornene, and methyl endomethylene hexahydronaphthalene) has been measured at ⩽70°. From the kinetic behavior and from the activation energy, it has been concluded that ethylidene norbornene reacts differently from the other two monomers; its autoxidation is much slower. In all cases, conversion is not very high due to formation of an unidentified inhibitor.

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