scholarly journals The effect of temperature on the viscosity of air

1926 ◽  
Vol 113 (763) ◽  
pp. 233-237 ◽  
Keyword(s):  
Present Author ◽  
Effect Of Temperature ◽  
Appreciable Change ◽  
Temperature Range ◽  
Higher Temperature ◽  
The Difference ◽  
Experimental Values ◽  
Coefficient Of Viscosity ◽  
Slight Alteration

In a recent paper Prof. A. 0. Rankine has put forward a number of criticisms of the results obtained from, and the experimental method employed in, the determination of the temperature coefficient of viscosity of air by the present author. In the first place, a comparison is drawn between the author’s results and those of other observers in the lower part of the temperature range, and the conclusion is drawn therefrom that there is a possibility of an error of 3 percent, in the author’s measurements throughout the whole range of temperature used. This inference is reached from the figures quoted in Table II of Rankine’s paper, in which the temperature range from 15° to 183° C. is considered. That some difference exists between the author’s results and those of other observers in the lower part of the temperature range is clear, but it must again be emphasised that the values given for low temperatures are not experimental values, but were obtained by an extension of the graph (fig. 2) for higher temperature measurements to the value of the viscosity as given by Millikanj for room temperatures. A slight alteration of the curvature of this extension would make an appreciable change in the ratios η100/η15 and η183/η15 , but this would not be sufficient to account for the curvature at B in fig. 3 of the original paper. If the values of T ⅜ /η for Breitenbach’s results at 182° C. and 302° C. are plotted on this curve, they lie above the present results and on a curve which would intersect AB at about 600° C. That part of the difference is due to this cause seems to be indicated by the fact that the difference diminishes as the temperature rises. Thus at 300° C. the following values of η300/η15 are obtained by Breitenbach, the only other worker at this temperature, and the author. The figures used are those given by Rankine.

The Perchloric Method for the Determination of Sulfur in Rubber

1934 ◽  
Vol 7 (4) ◽  
pp. 730-735
Author(s):  
Ernest Kahane
Keyword(s):  
Nitric Acid ◽  
Perchloric Acid ◽  
Organic Substance ◽  
Present Author ◽  
General Idea ◽  
Organic Substances ◽  
Gutta Percha ◽  
Higher Temperature ◽  
As If

Abstract The problem of the determination of sulfur in rubber has been dealt with extensively in the literature, and it seems as if discussions and descriptions of new technic are nowhere nearly ended yet. The determination is so essential, and its rapid and precise execution is of such importance in industrial technic, that efforts in this direction should not be regarded as wasted. In 1926 and in 1927 Le Caoutchouc et La Gutta-Percha contained two articles in which the present author discussed the conditions of the determination of sulfur in rubber and then proposed the use of a new oxidizing mixture, not mentioned previous to that time, which involved the destruction of organic substances by perchloric acid. This method consisted simply in the attack on a 1-gram sample of rubber by 10 cc. of nitric acid (d. 1.39) and 5 cc. of perchloric acid (d. 1.61). Upon heating, attack by the nitric acid takes place, and this is followed by evaporation of the excess nitric acid, then at a little higher temperature there is an attack by the perchloric acid, which oxidizes the rest of the organic substance completely. This publication was concerned much more, in the determination of sulfur by the perchloric method, with the general idea of the destruction of organic substances than it was with the precise details of carrying it out. The technic had been studied somewhat superficially, as is shown by the text of the article itself.

The influence of temperature on the tension developed in an isometric twitch

1951 ◽  
Vol 138 (892) ◽  
pp. 349-354 ◽  
Keyword(s):  
Early Stage ◽  
Muscular Contraction ◽  
Effect Of Temperature ◽  
Maximum Tension ◽  
Velocity Of Shortening ◽  
Influence Of Temperature On ◽  
Higher Temperature ◽  
The Difference ◽  
Isometric Twitch ◽  
The One

In muscular contraction the development of tension requires that the contractile component should shorten and stretch the series elastic component. In an isometric twitch the maximum tension is reached as a balance between two opposing processes, internal shortening on the one hand and decay of the active state (relaxation) on the other. The fact that the maximum tension in a twitch is considerably less than in a tetanus has been attributed to oncoming relaxation allowing insufficient time for internal shortening to be completed. The maximum tension in a twitch is considerably reduced by a rise of temperature, while that in a tetanus is somewhat increased. This would require that the temperature coefficient of the velocity of shortening should be substantially less than that of the decay of activity. Evidence for this exists. On this view the effect of a quick stretch, applied during the early stage of a twitch, in increasing the tension ratio, stretch/isometric, should be much greater at a higher temperature. This expectation is confirmed on frogs’ muscles over the range 0 to 20°C. The effect of temperature, therefore, on the size of a twitch can be attributed to the difference between the temperature coefficients of velocity of shortening and rate of relaxation.

Effect of Temperature on Ozone Cracking of Butyl Rubbers

1968 ◽  
Vol 41 (5) ◽  
pp. 1294-1299 ◽  
Author(s):  
A. N. Gent ◽  
H. Hirakawa
Keyword(s):  
Crack Growth ◽  
Ozone Concentration ◽  
Effect Of Temperature ◽  
Segmental Mobility ◽  
Temperature Range ◽  
Styrene Copolymers ◽  
The Difference ◽  
Rates Of Growth ◽  
Rate Controlling Step ◽  
Butadiene Styrene

Abstract Rates of growth of single ozone cracks have been measured for vulcanizates of two butyl rubbers over the temperature range of 20-160° C. Over most of this range the rates are quantitatively related to the segmental mobility of the polymer and depend upon temperature in accord with the appropriate form of the WLF relation. The rates are also proportional to the concentration of ozone. It is therefore concluded that diffusion of ozone into the polymer before reaction is the rate-controlling step. This is contrasted with the behavior of butadiene styrene copolymers, for which rates of crack growth are also quantitatively related to the segmental mobility, but the rates are somewhat larger at equivalent mobilities and the dependence upon ozone concentration is smaller. The difference is attributed to different penetration distances before reaction in polymers containing low and high densities of reactive sites.

scholarly journals The effect of temperature on the viscosity of air

1926 ◽  
Vol 110 (753) ◽  
pp. 141-167 ◽  
Keyword(s):  
Kinetic Theory ◽  
Temperature Coefficient ◽  
Effect Of Temperature ◽  
Kinetic Theory Of Gases ◽  
Molecular Models ◽  
Large Measure ◽  
Viscosity Coefficients ◽  
Molecular Forces ◽  
Coefficient Of Viscosity

The Kinetic Theory of Gases leads to a number of relations between the diffusion, conductivity and viscosity coefficients of gases, and the large measure of confirmation of these has been the greatest triumph of that theory. Most of these relations have been shown by S. Chapman and Enskog to be independent of any particular model of the molecule. In the case of the dependence of viscosity upon temperature, however, the theory gives different results for different molecular models, and the determination of the temperature coefficient of viscosity can therefore be of service in the elucidation of molecular forces.

scholarly journals Evaluation of Methods to Correct the Effect of Temperature on Electrical Conductivity of Mortar

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Milena Rangelov ◽  
Somayeh Nassiri
Keyword(s):  
Electrical Conductivity ◽  
Cementitious Materials ◽  
Temperature Correction ◽  
Supplementary Cementitious Materials ◽  
Embedded Sensors ◽  
Degree Of Saturation ◽  
Effect Of Temperature ◽  
Temperature Range ◽  
Durability Assessment ◽  
Higher Temperature

Nondestructive methods to obtain the electrical conductivity (σ) or resistivity (ρ) of concrete are gaining popularity for durability evaluation. However, these methods are susceptible to the effects of curing and conditioning, primarily temperature and degree of saturation. Before σ of concrete at varied temperatures can be used for durability assessment, appropriate corrections must be made to account for the effect of temperature (T). In this study, two existing and one new temperature correction methods were evaluated for 12 mortar mixtures varying in water-to-cementitious material ratio (w/cm) and the content and types of supplementary cementitious materials (SCM). Mortar specimens instrumented with embedded sensors were cured in sealed conditions for 11–13 months. After this period, the sealed specimens were subjected to stepwise temperature change in 5–50°C range while σ was recorded using the embedded sensors. Linear, bilinear, and Arrhenius temperature correction (LTC, BLTC, and ATC, respectively) were fitted to the obtained σ-T datasets and were evaluated for fitness. LTC provided an acceptable fit to the σ-T data (R2 > 0.81) but was found the most suitable in 5–30°C temperature range. BLTC was defined as a combination of two distinct LTC below and above the reference temperature at 23°C and had a better fit to the data (R2 > 0.96). Lastly, ATC showed the best fit among the tested methods (R2 > 0.98) and was found applicable for the full tested temperature range. Comparison of correction coefficients among the mixtures indicated that increase in w/cm results in less sensitivity of σ to temperature. Mixtures with SCM generally exhibit higher temperature sensitivity compared to the corresponding plain mixture. Since the variations in correction coefficients were not substantial (less 18% variation among 10 of 12 mixtures), a single value of activation energy of conduction (Ec) at 32 kJ/mol was identified as the general recommendation for all the tested mixtures.

Altitudinal variation in parental energy expenditure by white-crowned sparrows

2002 ◽  
Vol 205 (18) ◽  
pp. 2915-2924 ◽  
Author(s):  
Wesley W. Weathers ◽  
Charisse L. Davidson ◽  
Christopher R. Olson ◽  
Martin L. Morton ◽  
Nadav Nur ◽  
...  
Keyword(s):  
Energy Expenditure ◽  
Sea Level ◽  
Thermal Environment ◽  
Level Population ◽  
Interindividual Variation ◽  
Effect Of Temperature ◽  
Operative Temperature ◽  
Physiological Capacity ◽  
Higher Temperature ◽  
The Difference

SUMMARY We used the doubly labeled water technique to measure daily energy expenditure (DEE) during the incubation and feeding nestling stages in two populations of white-crowned sparrows (Zonotrichia leucophrys)— one montane and migratory, the other coastal and sedentary —that differ in thermal environment and clutch size. We assessed the birds'thermal environment by continuously monitoring (among other variables)operative temperature and wind speed both in the open and within bushes and willow thickets occupied by sparrows. From these measurements, we derived several estimates of the birds' thermal environment, including standard operative temperature (Tes). Shade air temperature and Tes averaged 6.6 and 10.3°C lower, respectively, at the montane study site during DEE measurements. The montane population's DEE averaged 24% higher than that of the sea-level population (103.6±12.2 versus 83.7±9.6 kJ day-1; means ± S.D., N=31 and 22, respectively), reflecting both its larger brood size(3.7 versus 2.9) and the colder environment. The DEE:BMR ratio was lowest in the sea-level population (2.1 versus 2.6), but neither population worked to their physiological capacity to produce young. DEE was significantly correlated with temperature across populations, with Tes explaining 42% of the variation in DEE. Statistically removing the effect of temperature by adjusting DEE to a common temperature reduced the difference in DEE between populations by 34% to 87.7 and 100.8 kJ day-1, respectively, for sea-level and montane populations. Basal and resting metabolic rates were similar in both populations, implying that greater activity in the montane population accounted for its higher temperature-adjusted DEE. Our results indicate that the thermal context within which behavior occurs can significantly affect interindividual variation in DEE. Attempts to assess reproductive effort by measuring DEE should therefore account explicitly for the effect of temperature.

How temperature influences muscle and cuttlebone growth in juvenile cuttlefish (Sepia elliptica) (Mollusca: Cephalopoda) under conditions of food stress

2000 ◽  
Vol 78 (10) ◽  
pp. 1855-1861 ◽  
Author(s):  
Pilar Martínez ◽  
Vera Bettencourt ◽  
Ángel Guerra ◽  
Natalie A Moltschaniwskyj
Keyword(s):  
Somatic Growth ◽  
Growth Index ◽  
Effect Of Temperature ◽  
Food Ration ◽  
Feeding Regime ◽  
Food Stress ◽  
Food Concentrations ◽  
Two Temperatures ◽  
Higher Temperature

Environmental factors influencing growth during the first stages of an animal's life cycle are determinative. External factors have often been implicated in the determination of rates of development of teleost larvae; however, the first stages of development of cephalopods remain poorly studied. In view of the fact that previous studies had shown that temperature is an important factor affecting cephalopod growth, particularly at high food concentrations, in this study the effect of temperature under conditions of non-satiation were investigated. A food-stress experiment was carried out for 75 days on 80 juvenile cuttlefish (Sepia elliptica) reared under two temperatures (25 and 30°C) and two food rations of glass shrimps Acetes sibogae australis at high and low proportions (2:1, respectively). We examined the effect of temperature and feeding regime on the growth of the whole animal, cuttlebone, and muscle tissue. Mantle-muscle blocks were 15% larger at 30°C than at 25°C, with the greatest difference in the middle mantle region (21% more at 30°C), whereas cuttlebone and somatic growth varied when the combination that included either the higher temperature or the higher food ration was used. Thus, at 30°C under the low feeding regime, final dorsal mantle length (DML) and cuttlebone growth index (CGI) were higher; however, at 25°C, final DML, CGI, and survivorship increased under the higher feeding regime. It was concluded that food scarcity may exaggerate the effect of small temperature differences. The results are discussed in the light of previous findings on the growth of other cuttlefish species, cephalopods, and teleosts.

scholarly journals Modelling of Average Pore Size and Porosity of Porous Polycaprolactone/Hydroxyapatite (PCL/HA) Composite Blends

2019 ◽  
Vol 9 (1) ◽  
pp. 5791-5797
Keyword(s):  
Pore Size ◽  
Average Pore Size ◽  
Effect Of Temperature ◽  
Coefficient Of Determination ◽  
Average Pore ◽  
Foaming Process ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Predicted Values ◽  
Experimental Values

The objective of this paper is to develop mathematical relationship between average pore size and porosity of porous polycaprolactone/hydroxyapatite (PCL/HA) composite and investigate the combined effect of temperature and pressure of foaming process and presence of HA. Porous PCL/HA composite was prepared using supercritical carbon dioxide (ScCO2) solid state foaming process. Three different temperatures and pressures of foaming process were varied at 35°C, 40°C, 45°C and 10MPa, 20MPa, 30MPa respectively. Meanwhile weight of HA was varied at 10, 20, 30 and 40 wt%. The result from analysis of variance (ANOVA) using Microsoft Excel found that average pore size is reduced with higher pressure and content of HA presence does not significantly affect the average pore size due to poor distribution of HA. Meanwhile for porosity, higher temperature is more dominant in increasing of porosity compared to the HA content. In addition, both designed models have low values of Average Absolute Relative Deviation (%AARD) and high value of coefficient of determination (R2 ) which reflects a good and satisfying result between the experimental values and model predicted values.

scholarly journals Effect of temperature on the production of cellulases, xylanases and lytic enzymes by selected Trichoderma reesei mutants

2014 ◽  
Vol 30 (2) ◽  
pp. 255-264 ◽  
Author(s):  
Piotr Janas ◽  
Zdzisław Targoński
Keyword(s):  
Trichoderma Reesei ◽  
Effect Of Temperature ◽  
Cellulolytic Enzymes ◽  
Lytic Enzymes ◽  
Complex Composition ◽  
Temperature Range ◽  
Mutant Strains ◽  
Higher Temperature ◽  
C 30 ◽  
Xylanolytic Enzymes

The effect of temperature in the rangę of 26-38°C on the production of cellulases, xylanases and lytic enzymes by four mutant strains of <i>Trichoderma reesei</i> was analysed. On the basis of these investigations three thermosensitive strains (M-7. RUT C 30 and VTT-D-78085) which showed reduced excretion of the above mentioned enzymes as well as protein and a thermoresistant mutant (VTT-D-79I24) which grew within a temperature range of 26-34°C were characterized. Higher temperature caused an increase in the level of xylanolytic enzymes produced by the four mutants. In addition. it effected the complex composition of cellulolytic enzymes secreted by VTT-D-79l 24 (i.c. increased and reduced excertion of (β-glucosidase and β-1,4-endoglucanase respectively).

scholarly journals The effect of temperature on the viscosity of neon

1928 ◽  
Vol 119 (783) ◽  
pp. 578-590 ◽  
Keyword(s):  
Low Temperatures ◽  
Large Range ◽  
Effect Of Temperature ◽  
Theoretical Formula ◽  
Lennard Jones ◽  
Two Temperatures ◽  
The Difference ◽  
First Time ◽  
Crucial Test

The experiments described in this paper have been carried out to obtain accurate data with respect to the variation of the viscosity of neon with temperature, over a range of several hundred degrees Centigrade. This has been rendered more desirable in view of the recent publication of a new theoretical formula for the variation of viscosity of a gas with temperature by J. E. Lennard-Jones, which he has applied with conspicuous success to various gases. In the case of neon, however, it was not possible to make a test of the formula as the experimental data are so sparse, only one observer, A. O. Rankine, having made measurements upon its viscosity, and then at only two temperatures. Accordingly, as neon should provide a crucial test between Lennard-Jones’ formula and that of Sutherland, the method already applied by the author J to the case of air was suitably modified for use with a gas of which the quantity available was strictly limited and values of the viscosity obtained from 444-5° C. downwards. Owing, however, to the increase in the quantity of neon required as the temperature was reduced, it was not found possible to take observations at a temperature lower than — 78-4° C. Unfortunately, it is only at low temperatures that the difference between the two formulæ becomes marked, and hence the results obtained have not been sufficient to provide a really crucial test between them. The determination of the viscosity over a large range does, however, for the first time, provide sufficient data for a reliable comparison to be made of the molecular properties of neon, as determined from its viscosity with the values of the same properties deduced from other sources.

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