Accelerators in Hard Rubber

1935 ◽  
Vol 8 (1) ◽  
pp. 75-85
Author(s):  
B. L. Davies
Keyword(s):  
Progressive Increase ◽  
Time Axis ◽  
Sulfur Concentration ◽  
Minimum Concentration ◽  
Maximum Slope ◽  
Consecutive Reactions ◽  
Straight Line ◽  
Constant Quantity ◽  
Mineral Fillers ◽  
Reaction Speed

Abstract 1. The curve relating the hardness to the time of heating of a high-sulfur stock indicated the presence of two consecutive reactions. The second half of the curve was mainly linear, and its slope might be used as a measure of the second (hard rubber) reaction speed. 2. The straight line when produced downwards passed through or near to the origin. Its position was altered only slightly by normal variations in processing. 3. The straight line may be represented by the equation H=rt+ƒ where H = per cent hardness by Shore's Durometer, t = time of heating in minutes, r = rate of hard rubber formation represented by the tangent of the angle between the curve and the time axis, and ƒ = the intercept along the hardness axis. 4. Influences which are known to increase the speed of chemical reactions increased the slope of the line. Thus, increase of sulfur concentration, rise of vulcanizing temperature, and the presence of catalysts increased the value of r, yielding a “fan” of lines all passing through a point near to or coincident with the origin. 5. The organic accelerators of vulcanization in general were found to act as true accelerators if present in small amounts. With increasing concentration they increased the speed of hardening at 150° C. up to a definite maximum, which appears to be approximately the same for many accelerators. 6. From an investigation of the minimum concentration of accelerator which produced the maximum slope, numbers representing the efficiency of the accelerators have been found. 7. Further addition of accelerator produced no further change in r, but a definite and progressive increase in the value of ƒ. This effect was also produced by the addition of mineral fillers. 8. If the value of H be taken as 100 per cent hardness, the equation H=rt+ƒ may be used for determining the time of cure. r is the rate of cure, dependent upon the nature of the accelerator, and the nature and amount of filler determine the magnitude of ƒ. Values of ƒ referring to some commonly used fillers have been determined. 9. The effect of increasing the temperature of vulcanization on the rate of hardening was examined. It was found that the temperature coefficient of hard rubber formation was not a constant quantity for accelerated hard rubber stocks. In many cases its magnitude increased to a maximum within the temperature range 140–150° C., and then fell at still higher temperatures.

scholarly journals A New Method for the Evaluation of Well Rehabilitation from the Early Portion of a Pumping Test

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 744
Author(s):  
Daniel Kahuda ◽  
Pavel Pech
Keyword(s):  
Skin Effect ◽  
Pumping Test ◽  
Real Space ◽  
New Method ◽  
Maximum Slope ◽  
Skin Factor ◽  
Wellbore Storage ◽  
Straight Line ◽  
Early Portion ◽  
Well Rehabilitation

This study analyzes the unsteady groundwater flow to a real well (with wellbore storage and the skin effect) that fully penetrates the confined aquifer. The well is located within an infinite system, so the effect of boundaries is not considered. The Laplace-domain solution for a partial differential equation is used to describe the unsteady radial flow to a well. The real space solution is obtained by means of the numerical inversion of the Laplace transform using the Stehfest algorithm 368. When wellbore storage and the skin effect dominate pumping test data and testing is conducted for long enough, two semilogarithmic straight lines are normally obtained. The first straight line can be identified readily as the line of the maximum slope. The correlation of the dimensionless drawdown for the intersection time of this first straight line, with the log time axis as a function of the dimensionless wellbore storage and the skin factor, is shown. This paper presents a new method for evaluating the skin factor from the early portion of a pumping test. This method can be used to evaluate the skin factor when the well-known Cooper–Jacob semilogarithmic method cannot be used due to the second straight line not being achieved in the semilogarithmic graph drawdown vs. the log time. A field example is presented to evaluate the well rehabilitation in Veselí nad Lužnicí by means of the new correlation.

scholarly journals THEORY AND MEASUREMENT OF VISUAL MECHANISMS

1944 ◽  
Vol 27 (5) ◽  
pp. 401-432 ◽  
Author(s):  
W. J. Crozier ◽  
Ernst Wolf
Keyword(s):  
Visual Angle ◽  
Wave Length ◽  
Progressive Increase ◽  
Probability Summation ◽  
Neural Organization ◽  
Moving Contact ◽  
Constant Quantity ◽  
Image Area ◽  
Temporal Side ◽  
Image Pattern

Flicker contours for a square image of 3° visual angle, centered 6° on the temporal side of the fovea, the light sectored at a focus, are strikingly modified if the same illuminated area is arranged in four squares separated by a narrow opaque cross. The "cone" curves are made much steeper, and their abscissae of inflection (τ' are at higher intensities; Fmax. is not greatly changed, but alters less with change of light-time fraction in the flash cycle (tL). This modification is accompanied by a great enlargement of the scotopic segment of the duplex curves, consistent with the theory of the integrative relations of neural effects in the two groups of units involved. The changes are not consistent with the view that flicker end-points are determined by the activation of retinal cells with a fixed spatial distribution of invariable thresholds. At tL = 0.50 the 3° subdivided area gives very nearly the same contour as does a square 6° x 6°, with the same total perimeter of light-dark separation; the "edge effect" thus suggested is complicated by differences in the dependence of Fmax. and τ' upon tL. When an image pattern is produced by a grid of light bars separated by equally broad opaque spaces (10° x 10° over-all, centered at the fovea), the photopic flicker contours are made very steep and their midpoints are situated at quite low intensities, while the "rod" contribution tends to be more completely fused with the "cone" than is found for fields not subdivided. However, instead of a progressive increase of τ' with tL the curves for tL = 0.75 and 0.90 lie respectively below that for tL = 0.25 and 0.50 for a field of four broader stripes (1.43°) and both are below tL = 0.25 for a field of seven narrower stripes (0.77°). These latter changes are discussed in terms of the participation of subsidiary phenomena involving so called "γ movement." It is pointed out that since in these data σ1/Im is for each set of conditions a statistically constant quantity with a characteristic breadth of scatter σσ, it is possible to calculate a "coefficient of internal correlation" r which is a function of the conditions (as: image area, location, wave length of light, structure of image, light-time fraction) and which describes a property of any entire contour. The changes in r, as a function of the conditions of flicker excitation, reflect changes in the neural organization responsible for the liminal discrimination of flicker. It is shown that as consequence of simple changes in the image field, three parameters, as of the probability summation, are required for the description of a simplex flicker contour—since each of these is independently modifiable as to its magnitude and in its dependence on the light-time fraction. Subdivision of the image, with light sectored at a focus, produces in part only the changes in the flicker contour which we have earlier labelled the "pecten effect." In the latter, with light not sectored at a focus but with bar images moving across a field with inclined fixed opaque bars, the "cone" slope (dF/d log I) is sharply increased for tL > 0.50, but not below tL = 0.50, and the value of τ' is much less than it "should be." Consequently, the change in contrast brought about by the moving contact of light/dark borders is the significant factor in the "pecten effect," not simply pulsatile interruption of the light.

scholarly journals THE INFLUENCE OF NATURAL HUMIDITY UPON THE INDEX OF THE COMPRESSION OF LIMNOGLACIAL CLAY/NATŪRALIOJO DRĖGNIO ĮTAKA LIMNOGLACIALINIO MOLIO KOMPRESIJOS KOEFICIENTUI

2001 ◽  
Vol 7 (1) ◽  
pp. 34-37
Author(s):  
Antanas Alikonis
Keyword(s):  
Water Mass ◽  
Water Saturation ◽  
Soil Layer ◽  
Solid Particles ◽  
Natural Soil ◽  
Straight Line ◽  
Compressibility Index ◽  
Different Types ◽  
Constant Quantity ◽  
Solid Soil

The coefficients of soil porosity and compressibility are not the only indices showing links between loading and squeezability. The index of compressibility is sometimes inconvenient for practical use. The graph of soil compressibility in the system of semi-logarithmic co-ordinations is a straight line, that's why the index of compressibility which is determined by it is a constant quantity and can be applied for a big interval of loading. The index of compressibility is very often defined as the interval the beginning of which is relictic pressure and is used to calculate the deformations of the soil layer when the loadings are bigger [2, 3]. The index of compressibility is different not only for different types of soil but for the same type of soil too, depending on the indices of its condition, its mineral composition and the peculiarities of its formation. The author of this article has investigated the influence of natural and fluid humidity upon the compression coefficient of Lithuanian limnoglacial clays. The natural soil humidity was defined according to the standard method as the ratio of water mass which is in soil and the mass of solid particles. Lithuanian limnoglacial clay from Jūros-Šešupės, Kauno-Kaišiadorių, Mūšos and Dysnos main basins was used for investigations. The plasticity index of solid soils was bigger than 17, water saturation level was 0.8–1. Hydro-mica (average 65–75%) and kaolin (average 10–20%) composed the mineral structure of limnoglacial clay. The index of compressibility was calculated by working up the results of investigations. Most often the calculable interval was between the tensions σ=0.2Mpa and σ=0.4 Mpa. The calculated index of compressibility Cc is connected with the natural humidity W of that soil. The values of coefficient k were calculated according to humidity and the compressibility index. A formula to calculate the index of compressibility was obtained. The values of natural humidity W of solid soil varied from 10 up to 39%, the values of the calculated index of compressibility Cc from 0.13 up to 0.24, and the values of coefficient k varied from 0.0033 up to 0.0066.

Plasminogen Assay by Means of the Lysis Time Method

1965 ◽  
Vol 14 (01/02) ◽  
pp. 127-144 ◽  
Author(s):  
W Berg ◽  
K Korsan-Bengtsen ◽  
J Ygge
Keyword(s):  
Maximal Activity ◽  
Fibrin Clot ◽  
Order Reaction ◽  
Zero Order ◽  
Fibrinogen Concentration ◽  
Plasmin Activity ◽  
Consecutive Reactions ◽  
Lysis Time ◽  
Straight Line

SummaryThe lysis time method for the determination of plasminogen has been investigated using plasminogen-free thrombin and fibrinogen preparations.The experiments have shown that the lysis of a fibrin clot is the result of two consecutive reactions: the formation of fibrin which proceeds as a first order reaction and the degradation of fibrin which proceeds as a zero order reaction. Plasminogen is activated in a separate reaction. If the rate of the fibrin formation is much greater than the rate of degradation, the lysis of the fibrin clot is approximately of zero order in fibrin. The lysis time will then be inversely proportional to the plasmin concentration and proportional to the fibrinogen concentration. In a double logaritmic system the correlation between lysis time and plasmin activity is a straight line with a slope of 135°.Plasminogen is rapidly activated with streptokinase. Maximal activation is obtained only with a certain streptokinase concentration. Higher concentrations inactivate plasmin and with lower concentrations, the maximal activity is never reached. A spontaneous inactivation is seen after about 30 minutes. With urokinase, a higher maximal plasminogen activity is obtained than with streptokinase. Urokinase in higher concentrations does not inactivate plasmin.A standard assay for determination of plasminogen by the lysis time method has been worked out and is based on these results.

Microdensitometer—computer correlation analysis of ultrastructural periodicity

1978 ◽  
Vol 36 (2) ◽  
pp. 32-33
Author(s):  
D.R. Ensor ◽  
C.G. Jensen ◽  
J.A. Fillery ◽  
R.J.K. Baker
Keyword(s):  
Correlation Analysis ◽  
Background Noise ◽  
Computer Control ◽  
Optical Diffraction ◽  
Screw Thread ◽  
Straight Line ◽  
Computer Storage ◽  
Correlation Process ◽  
Electron Microscope Image ◽  
Fixed Beam

Because periodicity is a major indicator of structural organisation numerous methods have been devised to demonstrate periodicity masked by background “noise” in the electron microscope image (e.g. photographic image reinforcement, Markham et al, 1964; optical diffraction techniques, Horne, 1977; McIntosh,1974). Computer correlation analysis of a densitometer tracing provides another means of minimising "noise". The correlation process uncovers periodic information by cancelling random elements. The technique is easily executed, the results are readily interpreted and the computer removes tedium, lends accuracy and assists in impartiality.A scanning densitometer was adapted to allow computer control of the scan and to give direct computer storage of the data. A photographic transparency of the image to be scanned is mounted on a stage coupled directly to an accurate screw thread driven by a stepping motor. The stage is moved so that the fixed beam of the densitometer (which is directed normal to the transparency) traces a straight line along the structure of interest in the image.

Freeze fracture imaging and computer simulation of liposome structure: Membrane geometry and defects

1983 ◽  
Vol 41 ◽  
pp. 646-647
Author(s):  
Joseph A. Zasadzinski
Keyword(s):  
Liquid Crystalline ◽  
Freeze Fracture ◽  
Continuum Theory ◽  
Closed Surfaces ◽  
Straight Line ◽  
Low Weight ◽  
Concentric Spheres ◽  
Membrane Geometry ◽  
Dupin Cyclides ◽  
Limiting Case

At low weight fractions, many surfactant and biological amphiphiles form dispersions of lamellar liquid crystalline liposomes in water. Amphiphile molecules tend to align themselves in parallel bilayers which are free to bend. Bilayers must form closed surfaces to separate hydrophobic and hydrophilic domains completely. Continuum theory of liquid crystals requires that the constant spacing of bilayer surfaces be maintained except at singularities of no more than line extent. Maxwell demonstrated that only two types of closed surfaces can satisfy this constraint: concentric spheres and Dupin cyclides. Dupin cyclides (Figure 1) are parallel closed surfaces which have a conjugate ellipse (r1) and hyperbola (r2) as singularities in the bilayer spacing. Any straight line drawn from a point on the ellipse to a point on the hyperbola is normal to every surface it intersects (broken lines in Figure 1). A simple example, and limiting case, is a family of concentric tori (Figure 1b).To distinguish between the allowable arrangements, freeze fracture TEM micrographs of representative biological (L-α phosphotidylcholine: L-α PC) and surfactant (sodium heptylnonyl benzenesulfonate: SHBS)liposomes are compared to mathematically derived sections of Dupin cyclides and concentric spheres.

Human Enamel Replication

1976 ◽  
Vol 34 ◽  
pp. 180-181
Author(s):  
Norman L. Dockum ◽  
John G. Dockum
Keyword(s):  
Organic Matrix ◽  
Human Teeth ◽  
Human Enamel ◽  
Straight Line ◽  
Ultrastructural Characteristics

Ultrastructural characteristics of fractured human enamel and acid-etched enamel were compared using acetate replicas shadowed with platinum and palladium. Shadowed replications of acid-etched surfaces were also obtained by the same method.Enamel from human teeth has a rod structure within which there are crystals of hydroxyapatite contained within a structureless organic matrix composed of keratin. The rods which run at right angles from the dentino-enamel junction are considered to run in a straight line perpendicular to the perimeter of the enamel, however, in many areas these enamel rods overlap, interlacing and intertwining with one another.

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