Effect of Temperature on Rate of Oxidation of Rubber. Nature of Resultant Deterioration

1954 ◽  
Vol 27 (1) ◽  
pp. 120-133 ◽  
Author(s):  
J. Reid Shelton ◽  
Fred J. Wherley ◽  
William L. Cox
Keyword(s):  
Quantitative Measure ◽  
Chain Scission ◽  
Absolute Temperature ◽  
Rate Of Change ◽  
Effect Of Temperature ◽  
Oxygen Absorption ◽  
Short Term ◽  
Degradation Reactions ◽  
Lower Temperature ◽  
Time Required

Abstract The same reaction appears to be rate-controlling in the oxidation of natural rubber and GR-S stocks at all temperatures in the range studied, 50° to 110° C. This is apparent from the linear relationship established between rate of oxygen absorption and the reciprocal of the absolute temperature. Presumably this would also be true for a reasonable extrapolation to lower or higher temperatures. Thus it is possible to determine the probable rate of oxygen absorption at room temperature on the basis of data obtained in short-term tests at higher temperatures, provided data are available at several temperatures. The effect on properties which accompanies the absorption of a given amount of oxygen varies with the temperature. For example, aging at higher temperatures produces a softer stock with lower modulus and higher elongation than is obtained by the absorption of the same amount of oxygen at a lower temperature. Thus chain scission predominates at higher temperatures, while cross-linking becomes of greater relative importance at lower temperatures. These facts, together with the observation that the same reaction is rate-controlling at all temperatures studied, indicate that the degradation reactions must be secondary reactions which are not rate-controlling. One cannot predict the aging characteristics of a stock by the use of an accelerated test at only one temperature. It is possible, however, to establish a quantitative measure of the rate of change in a given property (per unit amount of oxygen absorbed) as a function of temperature by means of tests at more than one temperature. Thus it is now possible to utilize short-term oxygen-absorption measurements at, say, three temperatures to establish the relationships, and then to extrapolate the data to lower temperatures and predict the time required to absorb a given amount of oxygen and the degradation of properties to be expected under comparable conditions at the lower temperature. If a change from oxygen to air is also involved, the effect of the changes in oxygen concentration must also be taken into account.

Volumetric Oxygen-Absorption Test for Rubber Aging

1951 ◽  
Vol 24 (4) ◽  
pp. 981-998
Author(s):  
J. Reid Shelton ◽  
William L. Cox
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Chain Scission ◽  
Rate Of Change ◽  
Oxygen Absorption ◽  
Absorption Test ◽  
Absorption Data ◽  
Direct Function ◽  
Oxygen Bomb ◽  
Early Stages

Abstract A volumetric oxygen-absorption test for aging of rubber has been investigated from the point of view of the effect of cure and the effect of mercapto-benzimidazole on the aging behavior. The test has also been evaluated by comparison with conventional air oven and oxygen bomb aging. A compounded but uncured Hevea black stock is more resistant to oxidation than the vulcanized material, but after a reasonable cure is obtained, further heating produces only a small change in the rate of oxygen absorption. The change in physical properties corresponding to a given amount of oxygen absorbed varies somewhat with time of cure in the initial stages, but after the absorption of 4 or 5 cc. of oxygen per gram of rubber, the changes in most physical properties are a direct function of the amount of oxygen absorbed. Neither time of cure nor the presence or absence of inhibitor has any significant effect on the subsequent rate of change in such properties as tensile strength and ultimate elongation for a given amount of oxygen absorbed. Oven aging data on identical time cures confirm the reported superiority of a combination of mercaptobenzimidazole with a conventional type of anti-oxidant. Oxygen absorption data reveal, however, that mercaptobenzimidazole causes a significant decrease in the rate of oxidation of a Hevea black stock, and thus it clearly functions at least in part as an antioxidant in the usually accepted sense. The deterioration of properties is, in general, proportional to the oxygen absorbed, except in the early stages of oxidation where the mercaptobenzimidazole stocks change somewhat less than the controls for a given amount of oxygen absorbed. When the cures are selected to give comparable initial properties, however, the change in tensile strength of the mercaptobenzimidazole stocks with amount of oxygen absorbed is essentially the same as for the controls, even in the initial stages. These data suggest that the observed protection imparted by mercaptobenzimidazole results from a combination of two factors: (1) the normal antioxidant activity of mercaptobenzimidazole, which reduces the amount of oxygen absorbed; and (2) an effect on the nature of the cure attained when mercaptobenzimidazole is present, such that the absorption of a given amount of oxygen in the early stages is not accompanied by as great a change in properties. Thus, it appears that the deactivating effect may be the result of the effect of this material on the vulcanization process rather than a direct effect on the oxidation process. A comparison of the effect of oxygen absorption, air oven, and oxygen bomb aging methods on changes in physical properties of Hevea black stocks shows that the results obtained by oxygen absorption and air oven methods (both at 100° C) are similar, but that the higher oxygen concentration of the oxygen bomb test (70° C and 300 pounds per square inch) apparently results in a higher proportion of chain scission when compared to cross-linking of the polymer chains.

scholarly journals Selection Response in Finite Populations

Genetics ◽  
1996 ◽  
Vol 144 (4) ◽  
pp. 1961-1974 ◽  
Author(s):  
Ming Wei ◽  
Armando Caballero ◽  
William G Hill
Keyword(s):  
Linkage Disequilibrium ◽  
Inbreeding Depression ◽  
Genetic Variance ◽  
Relative Rate ◽  
Selection Response ◽  
Rate Of Change ◽  
Effective Population ◽  
Short Term ◽  
Model Account

Formulae were derived to predict genetic response under various selection schemes assuming an infinitesimal model. Account was taken of genetic drift, gametic (linkage) disequilibrium (Bulmer effect), inbreeding depression, common environmental variance, and both initial segregating variance within families (σAW02) and mutational (σM2) variance. The cumulative response to selection until generation t(CRt) can be approximated asCRt≈R0[t−β(1−σAW∞2σAW02)t24Ne]−Dt2Ne,where Ne is the effective population size, σAW∞2=NeσM2 is the genetic variance within families at the steady state (or one-half the genic variance, which is unaffected by selection), and D is the inbreeding depression per unit of inbreeding. R  0 is the selection response at generation 0 assuming preselection so that the linkage disequilibrium effect has stabilized. β is the derivative of the logarithm of the asymptotic response with respect to the logarithm of the within-family genetic variance, i.e., their relative rate of change. R  0 is the major determinant of the short term selection response, but σM2, Ne and β are also important for the long term. A selection method of high accuracy using family information gives a small Ne and will lead to a larger response in the short term and a smaller response in the long term, utilizing mutation less efficiently.

scholarly journals Extended exposure to elevated temperature affects escape response behaviour in coral reef fishes

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3652 ◽  
Author(s):  
Donald T. Warren ◽  
Jennifer M. Donelson ◽  
Mark I. McCormick
Keyword(s):  
Elevated Temperature ◽  
Escape Response ◽  
Community Dynamics ◽  
Thermal Exposure ◽  
Reef Fishes ◽  
Effect Of Temperature ◽  
Short Term ◽  
Physical Ability ◽  
Pomacentrus Amboinensis ◽  
Extended Exposure

The threat of predation, and the prey’s response, are important drivers of community dynamics. Yet environmental temperature can have a significant effect on predation avoidance techniques such as fast-start performance observed in marine fishes. While it is known that temperature increases can influence performance and behaviour in the short-term, little is known about how species respond to extended exposure during development. We produced a startle response in two species of damselfish, the lemon damselPomacentrus moluccensis,and the Ambon damselfishPomacentrus amboinensis,by the repeated use of a drop stimulus. We show that the length of thermal exposure of juveniles to elevated temperature significantly affects this escape responses.Short-term (4d) exposure to warmer temperature affected directionality and responsiveness for both species. After long-term (90d) exposure, onlyP. moluccensisshowed beneficial plasticity, with directionality returning to control levels. Responsiveness also decreased in both species, possibly to compensate for higher temperatures. There was no effect of temperature or length of exposure on latency to react, maximum swimming speed, or escape distance suggesting that the physical ability to escape was maintained. Evidence suggests that elevated temperature may impact some fish species through its effect on the behavioural responses while under threat rather than having a direct influence on their physical ability to perform an effective escape response.

scholarly journals Animal size and seawater temperature, but not pH, influence a repeatable startle response behaviour in a wide-ranging marine mollusc

2020 ◽  
Author(s):  
Jeff Clements ◽  
Kirti Ramesh ◽  
Jacob Nysveen ◽  
Sam Dupont ◽  
Fredrik Jutfelt
Keyword(s):  
Startle Response ◽  
Marine Invertebrates ◽  
Seawater Temperature ◽  
Effect Of Temperature ◽  
Short Term ◽  
Blue Mussels ◽  
Marine Mollusc ◽  
Closure Duration ◽  
Ecosystem Level ◽  
Animal Size

Startle response behaviours are important in predator avoidance and escape for a wide array of animals. For many marine invertebrates, however, startle response behaviours are understudied, and the effects of global change stressors on these responses are unknown. We exposed two size classes of blue mussels (Mytilus edulis × trossulus) to different combinations of temperature (15 and 19 °C) and pH (8.2 and 7.5 pHT) for three months and subsequently measured individual time to open following a tactile predator cue (i.e., startle response time) over a series of four consecutive trials. Time to open was highly repeatable on the short-term and decreased linearly across the four trials. Individuals from the larger size class had a shorter time to open than their smaller-sized counterparts. High temperature increased time to open compared to low temperature, while pH had no effect. These results suggest that bivalve time to open is repeatable, related to relative vulnerability to predation, and affected by temperature. Given that increased closure times impact feeding and respiration, the effect of temperature on closure duration may play a role in the sensitivity to ocean warming in this species and contribute to ecosystem-level effects.

EFFECT OF TEMPERATURE ON THE PATHOGENESIS OF BACILLUS THURINGIENSIS BERLINER IN LARVAE OF THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA CLEM. (LEPIDOPTERA: TORTRICIDAE)

1994 ◽  
Vol 126 (4) ◽  
pp. 1061-1065 ◽  
Author(s):  
Kees van Frankenhuyzen
Keyword(s):  
Bacillus Thuringiensis ◽  
Bacterial Growth ◽  
Choristoneura Fumiferana ◽  
Larval Mortality ◽  
Lethal Dose ◽  
Spruce Budworm ◽  
Effect Of Temperature ◽  
Vegetative Cells ◽  
Time Required ◽  
Peak Abundance

AbstractThe relationship between temperature and pathogenesis of Bacillus thuringiensis Berliner var. kurstaki in infected larvae of the eastern spruce budworm, Choristoneura fumiferana Clem., was investigated to determine if more rapid death of larvae with an increase in temperature could be accounted for by enhanced bacterial growth. Cumulative mortality of larvae force-fed with a lethal dose of HD-1-S-1980 peaked within 2 days at 25 °C, 3 days at 19 °C, 7 days at 16 °C, and 21 days at 13 °C. The progress of bacterial growth in the larvae was followed from spore germination to cell lysis, and was completed within 4 days at 25 °C, 6 days at 22 °C, 12 days at 19 °C, 14 days at 16 °C, and > 28 days at 13 °C. Peak abundance of vegetative cells in the larvae was observed after 1 day at 25 °C, 2 days at 22 °C, 3 days at 19 °C, 7 days at 16 °C, and 21 days at 13 °C, and thus coincided almost exactly with the time required for maximum larval mortality. This correlation suggests that the observed effect of temperature on progression of larval mortality was due to its effect on the proliferation of vegetative cells in the infected larvae, and that bacterial septicemia makes an important contribution to death.

Description of an In Vitro Platelet Function Analyzer-PFA-100™

1995 ◽  
Vol 21 (S 02) ◽  
pp. 106-112 ◽  
Author(s):  
Sourav Kundu ◽  
Eric Heilmann ◽  
Reynaldo Sio ◽  
Carmen Garcia ◽  
Rosa Davidson ◽  
...  
Keyword(s):  
Platelet Function ◽  
Quantitative Measure ◽  
Biologically Active ◽  
High Shear Rates ◽  
Function Analyzer ◽  
Potential Applications ◽  
Time Required ◽  
Platelet Function Analyzer ◽  
Von Willebrand

A new in vitro system for the detection of platelet dysfunction, PFA-100™* has been developed. It provides a quantitative measure of platelet function in anticoagulated whole blood. The system comprises a microprocessor-controlled instrument and a disposable test cartridge containing a biologically active membrane. The instrument aspirates a blood sample under constant vacuum from the sample reservoir through a capillary and a microscopic aperture cut into the membrane. The membrane is coated with collagen and epinephrine or adenosine 5’-diphosphate. The presence of these biochemical stimuli, and the high shear rates generated under the standardized flow conditions, result in platelet attachment, activation, and aggregation, slowly building a stable platelet plug at the aperture. The time required to obtain full occlusion of the aperture is reported as the m“closure time.” We have found that impairment of von Willebrand factor, or inhibition of platelet receptors glycoprotein Ib or IIblIIIa with monoclonal antibodies or peptides, resulted in abnormal closure times. An antifibrinogen antibody, in contrast, failed to show any effect. The test appears to be sensitive to platelet adherence and aggregation abnormalities. The PFA-100™ system has potential applications in routine evaluation of platelet function in the clinical setting because of its accuracy, ease of operation, and rapid turnaround of results. * Under evaluation

The Effect of Temperature on the Growth and Respiration of Fish Embryos (Salmo Fario)

1932 ◽  
Vol 9 (3) ◽  
pp. 271-276
Author(s):  
A. H. WOOD
Keyword(s):  
Growth Rate ◽  
Oxygen Consumption ◽  
Relative Intensity ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Effect Of Temperature ◽  
Total Oxygen ◽  
Average Efficiency ◽  
Complete Development ◽  
Time Required

1. The rate of respiration (as expressed in c.c. O2 per gram embryo per hour) of the embryos of Salmo fario remains constant at any given temperature until the embryo has reached its maximum growth-rate, after this point it declines. It is suggested that the rate of respiration may be proportional to the amount of available yolk. 2. When incubated at 7° C. the time required to complete development after hatching was 58 days and the total oxygen consumed by an average embryo during this period was 20·31 c.c. (N.T.P.). At 12° the time required for the completion of development was reduced to 27 days, but the oxygen consumption remained practically unchanged at 20·71 c.c. At 3° C. the time required for development was 108 days and the oxygen consumption was 26·96 c.c. per embryo. 3. At 7 and 12° C. the efficiency of development was found to be identical with the value given by Gray for 11·5° C., viz. 63 per cent.; at 3°C. the average efficiency over the period considered was only 54 per cent. 4. It is suggested that, between the limits of temperature to which a trout egg is normally exposed, the effect of temperature on respiration is neither greater nor less than its effect on the growth-rate; possibly both processes are dependent on the same controlling factor. Above and below this range of temperature, the relative intensity of the respiratory processes (to those of growth) is increased, and a smaller embryo is the final result of incubation.

Learning from a Frozen Ocean: The Changing Face of Antarctic Ocean Ecology

2016 ◽  
Author(s):  
Hugh W. Ducklow
Keyword(s):  
Research Collaboration ◽  
Scientific Work ◽  
Principal Investigator ◽  
Rate Of Change ◽  
Short Term ◽  
Temporal Perspective ◽  
Ocean Science ◽  
Long Term Ecological Research ◽  
History Of ◽  
First Time

The temporal perspective provided by the Long-Term Ecological Research (LTER) program places individual, limited, short-term observations and experiments in a valuable context. Proper interpretation of short-term results may be incomplete without a longer-term perspective. This often makes me skeptical of individual studies. The remote location and harsh environment of Antarctica place special demands and constraints on research, collaboration, and education. Meeting these challenges is one of the most exhilarating aspects of our LTER project. Keeping the proper balance between maintaining continuity of observations and keeping the research program new and innovative is another key challenge for research in the LTER program. But rather than constraining them, the ongoing nature of the LTER program facilitates and enhances creative observations and innovation. In 2001, I joined the LTER network as lead principal investigator for the Palmer LTER project (PAL), one of two pelagic marine sites in the LTER network. That was my first formal exposure to the LTER program, about midway through my scientific career. After majoring in the history of science in college, I received my PhD in environmental engineering from Harvard in 1977. I was originally trained as an environmental microbiologist and gradually evolved into a biological oceanographer and ocean biogeochemist. Prior to joining PAL, I worked in other large, multidisciplinary, and interdisciplinary ocean science programs. In addition to leading PAL, I study the roles of ocean microbes in the biogeochemical cycling of carbon and other elements in the ice-influenced ocean surrounding Antarctica. As a principal investigator, I participate in planning and guiding the LTER network. Network participation has significantly broadened my perspective on my own personal scientific work. This participation has been one of my more interesting and fulfilling experiences as a scientist. Over the past 20 years, research has shown that the western Antarctic Peninsula is one of the most rapidly warming regions on earth, and we are gradually beginning to understand how the ecosystem is responding to this unprecedented rate of change. Joining PAL changed my life. (Actually, going to Antarctica for the first time changed my life, but the LTER program gave me the opportunity to go there every year.)

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