Reactively Curable Rubbers—I: Diene Elastomers with Pendant Isocyanate and/or Hydroxyl Functionality

Abstract In conclusion, we have demonstrated that modified diene elastomers containing active hydrogens and/or blocked-isocyanate derivatives can be crosslinked (cured) by three distinct methods. These methods include: 1. reaction of polymer-bound active hydrogens with monomeric polyisocyanates (Type I), 2. reaction of polymer-bound isocyanates with compounds containing two or more active hydrogens (Type II), and 3. reaction between polymer segments that contain both polymer-bound isocyanates and active hydrogens (Type III). Additionally, we have shown that the new polymerizable blocked-isocyanate derivatives (Type II and III systems) can be readily incorporated into SBR and NBR elastomers by standard emulsion-polymerization techniques. The degree and distribution of these monomers within the elastomer matrix were shown to be controlled by knowledge of their reactivity ratios. Furthermore, we have shown that the processing and properties of these systems can be readily controlled by the proper combination of isocyanate blocking group, active-hydrogen component, and catalyst. In many cases, these modified elastomers can be coagulated, dried, compounded, and cured using methods common to the rubber industry. Although not optimized, we have also shown that useful vulcanizates can be produced from extremely simple recipes. Conventional acceleration systems e.g., sulfur, accelerator, zinc oxide, are eliminated. The resulting urethane or urea crosslinks are remarkably durable under both thermal and hydrolytic conditions. Obviously, the possibilities for these uniquely reactive elastomers have not been exhausted. Many other intriguing applications of this technology are currently being explored. These applications will be the subject of future publications.

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The amino acid sequence of component 7c, a type II intermediate-filament protein from wool

Biochemical Journal ◽

10.1042/bj2611015 ◽

1989 ◽

Vol 261 (3) ◽

pp. 1015-1022 ◽

Cited By ~ 26

Author(s):

L G Sparrow ◽

C P Robinson ◽

D T W McMahon ◽

M R Rubira

Keyword(s):

Amino Acid ◽

Amino Acid Sequence ◽

Intermediate Filament ◽

Coiled Coil ◽

British Library ◽

Intermediate Filament Protein ◽

Type I ◽

Type Ii ◽

Blocking Group ◽

Intermediate Filament Proteins

Component 7c is one of the four homologous type II intermediate-filament proteins that, by association with the complementary type I proteins, form the microfibrils or intermediate filaments in wool. Component 7c was isolated as the S-carboxymethyl derivative from Merino wool and its amino acid sequence was determined by manual and automatic sequencing of peptides produced by chemical and enzymic cleavage reactions. It is an N-terminally blocked molecule of 491 residues and Mr (not including the blocking group) of 55,600; the nature of the blocking group has not been determined. The predicted secondary structure shows that component 7c conforms to the now accepted pattern for intermediate-filament proteins in having a central rod-like region of approximately 310 residues of coiled-coil alpha-helix flanked by non-helical N-and C-terminal regions. The central region is divided by three non-coiled-coil linking segments into four helical segments 1A, 1B, 2A and 2B. The N-and C-terminal non-helical segments are 109 and 71 residues respectively and are rich in cysteine. Details of procedures use in determining the sequence of component 7c have been deposited as a Supplementary Publication SUP 50152 (65 pages) at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1989) 257,5. The information comprises: (1) details of chemical and enzymic methods used for cleavage of component 7c, peptides CN1, CN2 and CN3, and various other peptides, (2) details of the procedures used for the fractionation and purification of peptides from (1), including Figures showing the elution profiles from the chromatographic steps used, (3) details of methods used to determine the C-terminal sequence of peptide CN3, and (4) detailed evidence to justify a number of corrections to the previously published sequence.

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Chromosomal bacterial type II toxin–antitoxin systems

Canadian Journal of Microbiology ◽

10.1139/w2012-025 ◽

2012 ◽

Vol 58 (5) ◽

pp. 553-562 ◽

Cited By ~ 16

Author(s):

Mohammad Adnan Syed ◽

Céline M. Lévesque

Keyword(s):

De Novo ◽

Physiological Role ◽

Type I ◽

Type Ii ◽

Translation Process ◽

Bacterial Physiology ◽

The Subject ◽

Almost All ◽

Bacterial Type

Most prokaryotic chromosomes contain a number of toxin–antitoxin (TA) modules consisting of a pair of genes that encode 2 components, a stable toxin and its cognate labile antitoxin. TA systems are also known as addiction modules, since the cells become “addicted” to the short-lived antitoxin product (the unstable antitoxin is degraded faster than the more stable toxin) because its de novo synthesis is essential for their survival. While toxins are always proteins, antitoxins are either RNAs (type I, type III) or proteins (type II). Type II TA systems are widely distributed throughout the chromosomes of almost all free-living bacteria and archaea. The vast majority of type II toxins are mRNA-specific endonucleases arresting cell growth through the mechanism of RNA cleavage, thus preventing the translation process. The physiological role of chromosomal type II TA systems still remains the subject of debate. This review describes the currently known type II toxins and their characteristics. The different hypotheses that have been proposed to explain their role in bacterial physiology are also discussed.

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Mechanical behavior and electrical conductivity of zinc-oxide ceramics

Uspihi materialoznavstva ◽

10.15407/materials2020.01.046 ◽

2020 ◽

Vol 2020 (01) ◽

pp. 46-54

Author(s):

Y. M. Ostroverkh ◽

◽

I. O. Polishko ◽

D. M. Brodnikovskyi ◽

L. L. Kovalenko ◽

...

Keyword(s):

Activation Energy ◽

Electrical Conductivity ◽

Zinc Oxide ◽

Room Temperature ◽

Sintering Temperature ◽

Type I ◽

Type Ii ◽

Conductivity Activation Energy ◽

Zno Powder ◽

Zno Ceramics

Ceramics sintered from zinc oxide powders, which differ in crystal structure, particle size and amount and type of impurities, have been studied for their mechanical behavior (strength and micromechanisms of biaxial bending at room temperature) and electrical conductivity depending on the purity of ZnO powder (99,9% byweight — type I and 99,5% byweight — type II) and its sintering temperature in the interval from 800 to 1250 ºC for 2 hours. It is found that the maximum values of strength and electrical conductivity are achieved in ZnO-ceramics sintered at temperatures of 1100—1200 and 1000—1150 ºC, respectively, and their micromechanism of fracture is the cleavage only. ZnO-powder developed (type II), being twice as large as the purchased (type I), 300—350 nm instead of 150—200 nm, provides close to 100% density at 1100 °C, the type II powder is sintering at almost 100 °C lower temperature than the purchased one. Type I ceramics provide biaxial strength at room temperature of 150—170 MPa; type II — 120—160 MPa. ZnO-ceramics from powders of both types provide maximum electrical conductivities of 8,54 10-3S/ cm and 1,6·10-3 S / cm at temperatures of 265 and 600 ºC, respectively. The activation energy of the electrical conductivity of ZnO-ceramics is dependent significantly on the properties of the powder and, accordingly, the structure of the ceramics and the test temperature. Type I ZnO ceramics have a lower conductivity activation energy than type II, 0,2—0,3 eVand 0,3—0,5 eV, respectively. The mechanism of electrical conductivity of ZnO-ceramics type I is practically unchanged in all the interval of testing temperatures, from the room one to 600 °C. In ZnO-ceramics of the type II, it changes at least twice. Keywords: zinc oxide, ZnO ceramics, sintering temperature, porosity, grain size, micromechanism of fracture, bending strength, electrical conductivity, activation energy.

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STUDIES ON MENINGOCOCCUS INFECTION

Journal of Experimental Medicine ◽

10.1084/jem.58.3.341 ◽

1933 ◽

Vol 58 (3) ◽

pp. 341-360 ◽

Cited By ~ 9

Author(s):

Geoffrey Rake ◽

Henry W. Scherp

Keyword(s):

Chemical Analysis ◽

Type I ◽

Type Ii ◽

Type Iii ◽

Specific Substance ◽

The Subject ◽

Detailed Chemical

Three fractions have been isolated from autolysates of the meningococcus. Of these, one, the type-specific substance, has been described in detail. The same type-specific substance appears to be present in Type I and Type III organisms, but a substance differing at least serologically has been obtained from Type II strains. Detailed chemical analysis of both of the type-specific substances thus far isolated is being carried out and will be the subject of a later paper.

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Heat-Etching with a Bullivant Type II Simple Freeze-Cleave Device

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100067522 ◽

1970 ◽

Vol 28 ◽

pp. 106-107 ◽

Cited By ~ 1

Author(s):

Ronald S. Weinstein ◽

N. Scott McNutt

Keyword(s):

New Zealand ◽

General Hospital ◽

Massachusetts General Hospital ◽

Type I ◽

Type Ii ◽

Collaborative Effort ◽

Temperature And Pressure ◽

The University

The Type I simple cold block device was described by Bullivant and Ames in 1966 and represented the product of the first successful effort to simplify the equipment required to do sophisticated freeze-cleave techniques. Bullivant, Weinstein and Someda described the Type II device which is a modification of the Type I device and was developed as a collaborative effort at the Massachusetts General Hospital and the University of Auckland, New Zealand. The modifications reduced specimen contamination and provided controlled specimen warming for heat-etching of fracture faces. We have now tested the Mass. General Hospital version of the Type II device (called the “Type II-MGH device”) on a wide variety of biological specimens and have established temperature and pressure curves for routine heat-etching with the device.

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Labelling of non-A, non-B hepatitis infected chimpanzee hepatocytes with nuclease-gold conjugates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111367 ◽

1984 ◽

Vol 42 ◽

pp. 250-251

Author(s):

G. D. Gagne ◽

M. F. Miller ◽

D. A. Peterson

Keyword(s):

Endoplasmic Reticulum ◽

Experimental Infection ◽

Uranyl Acetate ◽

Type I ◽

Cellular Injury ◽

Type Ii ◽

Tubular Structures ◽

Type Iii ◽

Type Iv ◽

Infected Chimpanzee

Experimental infection of chimpanzees with non-A, non-B hepatitis (NANB) or with delta agent hepatitis results in the appearance of characteristic cytoplasmic alterations in the hepatocytes. These alterations include spongelike inclusions (Type I), attached convoluted membranes (Type II), tubular structures (Type III), and microtubular aggregates (Type IV) (Fig. 1). Type I, II and III structures are, by association, believed to be derived from endoplasmic reticulum and may be morphogenetically related. Type IV structures are generally observed free in the cytoplasm but sometimes in the vicinity of type III structures. It is not known whether these structures are somehow involved in the replication and/or assembly of the putative NANB virus or whether they are simply nonspecific responses to cellular injury. When treated with uranyl acetate, type I, II and III structures stain intensely as if they might contain nucleic acids. If these structures do correspond to intermediates in the replication of a virus, one might expect them to contain DNA or RNA and the present study was undertaken to explore this possibility.

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Comparative surface and ultrastructural views of methylotrophic bacteria by TEM, STEM, SE, and freeze-etch electron microscopy.

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128274 ◽

1987 ◽

Vol 45 ◽

pp. 792-793

Author(s):

T.A. Fassel ◽

M.J. Schaller ◽

M.E. Lidstrom ◽

C.C. Remsen

Keyword(s):

Cytoplasmic Membrane ◽

Structural Features ◽

Methylotrophic Bacteria ◽

Type I ◽

Type Ii ◽

Membrane Complex ◽

Oxidation Of Methane ◽

Methane Oxidizing Bacteria ◽

Wall Structures ◽

Methylomonas Albus

Methylotrophic bacteria play an Important role in the environment in the oxidation of methane and methanol. Extensive intracytoplasmic membranes (ICM) have been associated with the oxidation processes in methylotrophs and chemolithotrophic bacteria. Classification on the basis of ICM arrangement distinguishes 2 types of methylotrophs. Bundles or vesicular stacks of ICM located away from the cytoplasmic membrane and extending into the cytoplasm are present in Type I methylotrophs. In Type II methylotrophs, the ICM form pairs of peripheral membranes located parallel to the cytoplasmic membrane. Complex cell wall structures of tightly packed cup-shaped subunits have been described in strains of marine and freshwater phototrophic sulfur bacteria and several strains of methane oxidizing bacteria. We examined the ultrastructure of the methylotrophs with particular view of the ICM and surface structural features, between representatives of the Type I Methylomonas albus (BG8), and Type II Methylosinus trichosporium (OB-36).

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