Isoprene and Rubber. Part 47. The Decomposition of Rubber by Acids

1937 ◽  
Vol 10 (3) ◽  
pp. 445-450
Author(s):  
H. P. Mojen
Keyword(s):  
Atmospheric Carbon Dioxide ◽  
Atmospheric Oxygen ◽  
Free Play ◽  
Destructive Effect ◽  
Organic Bases ◽  
Inorganic Acids ◽  
Close Relationship ◽  
Rubber Part ◽  
Long Time ◽  
Effect Of Oxygen

Abstract The phenomena observed in the experiments which have been described can be explained in the following way. As already mentioned, raw rubber contains certain antioxygens which protect the rubber molecules from attack by oxygen. Very little is known about the nature of these antioxygens, but it is probably correct to assume that these substances are of a basic nature, like commercial antioxygens, which for the most part are complex organic bases. The activity of these anti-catalysts is stopped by the addition of organic or inorganic acids. As a result there is no longer any obstacle to an attack by oxygen, and decomposition can proceed under these conditions much more rapidly and much more extensively. The antioxygens are destroyed by the acids, even when oxygen is excluded during the experiments, but demolition of the fiber molecules does not then take place. The intense destructive effect of oxygen on rubber does not therefore depend on the action of acids on the fiber molecules of rubber, but is to be attributed solely to the fact that antioxygens which inhibit decomposition by oxygen are destroyed; destruction of the rubber itself is caused only by oxygen. It is not impossible that these phenomena bear a close relationship to the stickiness acquired by rubber. Rubber which has become sticky is composed of extensively decomposed rubber molecules. This phenomenon is noticeable at times in rubber goods which have been stored for a long time, and may be explained by the fact that atmospheric carbon dioxide destroys the natural antioxygens in the rubber. With their destruction, atmospheric oxygen then has free play to attack the rubber molecules. The acidic substances which are formed in this oxidation then destroy any remaining antioxygens, so that oxygen can destroy all of the rubber. Grateful acknowledgment is due Professor Staudinger, at whose instigation this work was carried out, who offered advice in various ways, and who took an active part in the investigation.

The Action of Copper Salts on Raw Rubber

1934 ◽  
Vol 7 (4) ◽  
pp. 618-631 ◽  
Author(s):  
B. V. Buizov ◽  
V. S. Molodenskii ◽  
N. I. Mikhailov
Keyword(s):  
Atmospheric Oxygen ◽  
Good Reason ◽  
Copper Salt ◽  
Copper Salts ◽  
Destructive Effect ◽  
Initial Stage ◽  
Destructive Action ◽  
Long Time ◽  
Effect Of Copper ◽  
Short Time

Abstract 1. An examination of the literature makes open to doubt the view of many investigators that copper salts exert a destructive action on rubber by functioning as catalysts which start the autoöxidation of rubber and then promote this autooxidation. The literature available indicates with just as good reason that there is another explanation of the effect of copper salts, viz., that the destructive action of these salts is characterized in its initial stage by a disaggregation of the. rubber. As a result of this disaggregation there is an increased surface of rubber micelles with an accumulation of double bonds. The rubber is then more readily susceptible to oxidation by atmospheric oxygen. 2. The detailed study in the present work of the action of copper salts on rubber solutions has shown that the complicated process as a whole can be divided into separate partial processes, i. e., into a desolvation, a micellar disaggregation, and a molecular disaggregation. 3. Observations of changes in weight and of the properties of rubber films proved conclusively that copper salts first bring about a desolvation of the rubber micelles and then a disaggregation. The latter proceeds without any accompanying oxidation of the rubber. Following this there is an oxidation of the irreversibly degenerated rubber. 4. The influence of oxygen on the appearance of stickiness is very slight, in fact tackiness appears both in the presence and the absence of oxygen. 5. The stickiness of rubber samples to which a copper salt has been added is always to be found in the interior of the samples, while a brittleness appears on the surfaces. 6. These facts lead to the conclusion that the stickiness of raw rubber appears as a result of disaggregation, whereas brittleness is the result of oxidation. 7. The destructive effect of copper salts depends to a large extent upon the state of dispersion of the copper salt in the rubber; the more finely dispersed is the salt in the rubber, the greater is its effect. 8. Copper salts accelerate vulcanization, without however increasing the proportion of combined sulfur. Upon standing a long time, rubber containing a copper salt loses completely its power of vulcanization. This latter phenomenon can be explained by the fact that copper compounds bring about in a relatively short time the disaggregation which is necessary to vulcanization, whereas after a longer time they destroy the rubber completely.

scholarly journals Plans d’eau glaciaires et isostasie dans les bassins de la haute Ware et de la rivière Otter, Massachusetts (2e partie)

2005 ◽  
Vol 17 (41) ◽  
pp. 251-264
Author(s):  
Gilbert Cestre
Keyword(s):  
New England ◽  
Eastern Canada ◽  
Low Area ◽  
Proglacial Lakes ◽  
Close Relationship ◽  
Long Time ◽  
History Of ◽  
Connecticut Valley ◽  
The City ◽  
Detailed Work

The present study is one of the unpublished research projects which are known to have been conducted in New England and in Eastern Canada under the guidance of the late Richard J. LOUGEE, long-time professor of Geomorphology at Clark University. Over a number of years, this writer has worked in close relationship with Lougee and much evidence in the field was studied together. It is believed that here has been recorded a most detailed work of surveying, and this undoubtedly accounts for the somewhat exceptional results that will be presented. The area selected for this study (about 80% of it is woodland) is located in the highlands of Central Massachusetts in Worcester County, about twenty miles (32 kilo-meters) northwest of the city of Worcester. It consists of the valley of the Otter River draining north, and of a small portion of the East Branch of the Ware River draining south. Since completion of this study, parts of the low area which held the ancient glacial lakes have been flooded to become water reservoirs. That proglacial lakes, though temporary they may have been, once submerged much of the area under study, is shown by an abundance of deltas, kames, eskers and deltaic kames terraces. It is believed that all of these were built under water in such lakes. Other features, such as kettle-holes and glacial outlets, especially ice-marginal channels cut diagonally down the slope, have also been studied. By plotting on a profile of the most characteristic elevations (often carefully surveyed), it is possible to find the water planes of ancient proglacial lakes. To this must be added experiments conducted in a sedimentation tank as also measurements of both the imbrication of cobbles in eskers and the « smoothness indexes » of such stones and pebbles, using A. Cailleux' methods. Thus were obtained results which tend to show that : 1- the area under study probably was in a deep interlobate space created between the Connecticut Valley lobe to the west and the Boston Basin lobe to the east ; 2— ice-marginal channels are an indication of the existence of a thick, fast-retreating ice border ; 3- an isostatic balance restored itself by sometimes quick and strong adjustments of the crust of the earth ; 4— an early upwarping, made up of various zones of tilting articulated on hinge lines, has been referred to as Hubbard Uplift and is the earliest known in the post-Glacial history of New England.

ASSESSMENT OF THE RISK OF OCCUPATIONAL PATHOLOGY IN WORKERS OF NOISE-HAZARDOUS PROFESSIONS OF METALLURGICAL PRODUCTION

2021 ◽  
Author(s):  
E.F. Chernikova ◽  
◽  
I.V. Fedotova ◽  
M.M. Nekrasova
Keyword(s):  
Hearing Loss ◽  
Cognitive Dissonance ◽  
Working Conditions ◽  
Work Experience ◽  
Risk Group ◽  
Production Factors ◽  
Joint Influence ◽  
Close Relationship ◽  
Long Time ◽  
The Impact

Abstract: Working conditions at metallurgical enterprises are characterized by the impact of a complex of harmful production factors that do not correspond to the normalized levels, which causes the risk of developing professional and professionally conditioned pathology. Trained workers who are exposed for a long time to industrial noise that exceeds the permissible values by 10 dB or more are considered as a risk group for the development of aural (sensorineural hearing loss, SHT) and extraaural (high blood pressure, HBP) pathology. Hearing loss is an important medical and social problem, as it turns into a cognitive dissonance and a violation of verbal communication for the employee. Working conditions at one of the modern metallurgical plants were evaluated according to the data of sanitary and hygienic characteristics of working conditions. The study of the prevalence of SHT and HBP was carried out based on the materials of a medical examination and a questionnaire survey of workers (n=73, male, aged 36-75 years (57.32±0.89), with work experience of 8-58 years (34.29±1.16)). To assess the joint influence of age and seniority, an original scoring system was used, which allowed us to distinguish 3 observation groups. The severity of SHT and HBP was also assessed in points. The study showed a significant increase in the prevalence and severity of hearing loss and HBP with an increase in the duration of exposure and the age of employees. The presence of a close relationship between the analyzed pathology and working conditions is illustrated by the value of the odds ratio in groups 1-3 (ORSHT = 3.75-4.71; ORHBP = 2.0-5.0). Thus, the studied professional group of trained qualified metallurgists needs to develop health-improving measures to preserve labor longevity.

Chaparral growth-ring analysis as an indicator of stand biomass development

2016 ◽  
Vol 25 (10) ◽  
pp. 1086 ◽  
Author(s):  
Kellie A. Uyeda ◽  
Douglas A. Stow ◽  
John F. O'Leary ◽  
Christina Tague ◽  
Philip J. Riggan
Keyword(s):  
Growth Ring ◽  
Basal Area ◽  
Biomass Accumulation ◽  
Field Measurements ◽  
Solar Irradiation ◽  
Annual Precipitation ◽  
Total Biomass ◽  
Growth Rings ◽  
Close Relationship ◽  
Long Time

Chaparral wildfires typically create even-aged stands of vegetation that grow quickly in the first 2 decades following a fire. Patterns of this growth are important for understanding ecosystem productivity and re-establishment success, but are logistically challenging to measure over long time periods. We tested the utility of a novel method of using shrub growth rings to estimate stand-level biomass accumulation at an annual time scale in southern California chaparral. We examined how temporal variation in precipitation and spatial variation in solar irradiation influence that accumulation. Using field measurements and a relationship between stem basal area and aboveground biomass, we estimated current biomass levels in an 11-year-old chaparral stand, and used growth-ring diameters to estimate growth in each year from age 4 to 11 years. We found that annual growth as measured by shrub growth rings tracked closely with patterns of annual precipitation, but not with time since fire. Solar irradiation was not found to be a significant covariate with total biomass by plot, possibly due to sampling area limitations. The close relationship of annual biomass accumulation with annual precipitation indicates that shrub growth-ring measurements can provide a useful metric of stand-level recovery.

scholarly journals Evgeniy Dobrzhinsky (1864-1938). The Outstanding Talent of Librarian

2014 ◽  
pp. 68-75
Author(s):  
E. V. Dementieva ◽  
A. Yu. Ivanova
Keyword(s):  
Active Member ◽  
Crucial Point ◽  
Library Education ◽  
Library Community ◽  
Close Relationship ◽  
Long Time ◽  
History Of ◽  
Universal Decimal Classification ◽  
Relationship Of ◽  
Decimal Classification

E.N. Dobrzhinsky (1864-938) stood at the origins of library education in Russia; he developed the system of implementation of the Universal Decimal Classification in the library practice, and he was an active member of the First All-Russian Congress of Libraries. Numerous works of E.N. Dobrzhinsky on establishing the librarianship for a long time were the main guidance for the majority of library institutions in our country. There are considered the circumstances contributed to discover the talents of one of the brightest representatives of the library community at the crucial point in the Russian history. On January 21 we celebrate the 150th anniversary of the birth of E.N. Dobrzhinsky. The article shows the close relationship of the life of the first director of the Fundamental Library of the St. Petersburg State Polytechnic Institute with the history of this institution (nowadays - St. Petersburg State Polytechnic University).

scholarly journals PCR based detection and evaluation of fermenting capability of local strains of Saccharomyces cerevisiae

2019 ◽  
Vol 2 (2) ◽  
pp. 23-26
Author(s):  
GUL GHUTAI ABDULLAH ◽  
Naseer Ahmed ◽  
Arsalan Ahmed Shah ◽  
Abdul samad ◽  
Tauseef M Asmat
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Reference Strain ◽  
Raw Materials ◽  
Molecular Techniques ◽  
Alcoholic Beverages ◽  
Fruit Samples ◽  
Reaction Test ◽  
Close Relationship ◽  
Long Time ◽  
Growth Shape

On Earth there are several organisms that share close relationship with humankind and Saccharomyces cerevisiae is one of them. Saccharomyces cerevisiae is also known as the brewer´s or baker´s yeast and has been used for fermentation and production of bread and alcoholic beverages since long time. The purpose of this study was to evaluate the fermentation capability of Saccharomyces cerevisiae local isolates. For this purpose 100 fruit samples (mango, sugarcane, orange, honey melon, grapes) were collected from local fruit markets and subjected to identification by standard microbiology tests and advance molecular techniques like Polymerase reaction test (PCR). The results revealed the typical growth, shape and color of S. cerevisiae on YPD media. The growth culture subjected to microscopy showed the budding characteristic of S. cerevisiae.  The initial identified strains by virtue of YPD selective media and microscopy were subjected to PCR. The PCR results revealed the presence of S. cerevisiae in 28 samples among all analyzed samples. Importantly, the presence of S. cerevisiae was detected 30% in oranges, in mango 27.77%, in sugarcane 35% while in honey melon and grapes it was 13.63%, 31.81% respectively. This study concludes that S. cerevisiae was more abundant in sugarcane and grapes analyzed samples. The collected strains of present study may be further used in future studies like ethanol production from raw materials and also used as reference strain when working with samples of unknown nature

In vitro stalk cell differentiation in wild-type and ‘slugger’ mutants of Dictyostelium discoideum

Development ◽  
1993 ◽  
Vol 118 (2) ◽  
pp. 523-526 ◽  
Author(s):  
K. Inouye ◽  
J. Gross
Keyword(s):  
Dictyostelium Discoideum ◽  
Fruiting Body ◽  
Cell Maturation ◽  
Stalk Cell ◽  
Wild Type ◽  
Fruiting Body Formation ◽  
Body Formation ◽  
Close Relationship ◽  
Long Time

In ‘slugger’ mutants of Dictyostelium discoideum, aggregates of cells remain for an abnormally long time in the migratory phase under conditions where wild-type aggregates form fruiting bodies. In the present work, we have examined the relationship between the defect in fruiting body formation in these mutants and their ability to form mature stalk cells. We dissociated anterior cells from slugs of the mutants and their parents and tested their ability to form stalk cells when incubated at low density in the presence of (1) the stalk cell morphogen Differentiation Inducing Factor-1 (DIF-1) together with cyclic AMP, or (2) 8-Br-cAMP, which is believed to penetrate cell membrane and activate cAMP- dependent protein kinase (PKA). Most of the mutants were markedly defective in forming stalk cells in response to DIF-1 plus cAMP, confirming a close relationship between fruiting body formation and stalk cell maturation. On the other hand, many of these same mutants formed stalk cells efficiently in response to 8-Br-cAMP. This supports evidence for an essential role of PKA in stalk cell maturation and fruiting body formation. It also indicates that many of the mutants owe their slugger phenotype to defects in functions required for optimal adenylyl cyclase activity.

scholarly journals Atmospheric oxygen and carbon dioxide observations from two European coastal stations 2000–2005: continental influence, trend changes and APO climatology

2010 ◽  
Vol 10 (4) ◽  
pp. 1599-1615 ◽  
Author(s):  
C. Sirignano ◽  
R. E. M. Neubert ◽  
C. Rödenbeck ◽  
H. A. J. Meijer
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
Atmospheric Oxygen ◽  
Co2 Production ◽  
Monitoring Networks ◽  
Co2 Concentrations ◽  
Anthropogenic Co2 ◽  
The Difference ◽  
Carbon Dioxide Co2 ◽  
Atmospheric Co2 Concentrations

Abstract. Seeking for baseline conditions has biased the atmospheric carbon dioxide (CO2) and later on also oxygen (O2) monitoring networks towards remote marine stations, missing part of the variability that is due to regional anthropogenic as well as land biotic activity. We present here a five-year record of atmospheric CO2 concentrations and oxygen/nitrogen (O2/N2) ratio measurements from the coastal stations Lutjewad (LUT), The Netherlands and Mace Head (MHD), Ireland, derived from flask samples. O2/N2 ratios, a proxy for O2 concentrations, concurrently measured with CO2 concentrations, help determine regional CO2 fluxes by separating land fluxes from sea fluxes. Mace Head is the closest marine baseline station to Lutjewad, located at the same latitude, and therefore is taken as a reference. During the studied period, from 2000 until 2005, we observed an average increase of CO2 in the atmosphere of (1.7±0.2) ppm y−1, and a change of the O2/N2 ratio of (−20±1) per meg y−1. The difference between the CO2 summer minimum and the winter maximum is 14.4 ppm and 16.1 ppm at Mace Head and Lutjewad, respectively, while the paraphase variation in the O2 signal equals 113 per meg and 153 per meg, respectively. We also studied the atmospheric potential oxygen (APO) tracer at both stations. By this analysis, evidence has been found that we need to be careful when using APO close to anthropogenic CO2 sources. It could be biased by combustion-derived CO2, and models need to take into account daily and seasonal variations in the anthropogenic CO2 production in order to be able to simulate APO over the continents.

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