bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epigenetic Changes at Il12rb2 and Tbx21 in Relation to Plasticity Behavior of Th17 Cells
Authors: Bending David , Newland Stephen , Krejčí Alena , Phillips Jenny M. , Bray Sarah , Cooke Anne 
Published: February 2011

Abstract
Plasticity within Th cell populations may play a role in enabling site-specific immune responses to infections while limiting tissue destruction. Epigenetic processes are fundamental to such plasticity; however, to date, most investigations have focused on in vitro-generated T cells. In this study, we have examined the molecular mechanisms underpinning murine Th17 plasticity in vivo by assessing H3K4 and H3K27 trimethylation marks at Tbx21, Rorc, Il17a, Ifng, and Il12rb2 loci in purified ex vivo-isolated and in vitro-generated Th17 cells. Although both populations had largely comparable epigenetic signatures, including bivalent marks at Tbx21, freshly isolated ex vivo Th17 cells displayed restricted expression from Il12rb2 due to the presence of repressive chromatin modifications. This receptor, however, could be upregulated on isolated ex vivo Th17 cells after in vitro activation or by in vivo immunization and was augmented by the presence of IFN-γ. Such activated cells could then be deviated toward a Th1-like profile. We show that IL-12 stimulation removes H3K27 trimethylation modifications at Tbx21/T-bet leading to enhanced T-bet expression with in vitro Th17 cells. Our study reveals important potential phenotypic differences between ex vivo- and in vitro-generated Th17 cells and provides mechanistic insight into Th17 cell plasticity.
Cutting Edge: CD8+ T Cell Priming in the Absence of NK Cells Leads to Enhanced Memory Responses
Authors: Soderquest Katrina , Walzer Thierry , Zafirova Biljana , Klavinskis Linda S. , Polić Bojan , Vivier Eric , Lord Graham M. , Martín-Fontecha Alfonso 
Published: February 2011

Abstract
It is uncertain whether NK cells modulate T cell memory differentiation. By using a genetic model that allows the selective depletion of NK cells, we show in this study that NK cells shape CD8+ T cell fate by killing recently activated CD8+ T cells in an NKG2D- and perforin-dependent manner. In the absence of NK cells, the differentiation of CD8+ T cells is strongly biased toward a central memory T cell phenotype. Although, on a per-cell basis, memory CD8+ T cells generated in the presence or the absence of NK cells have similar functional features and recall capabilities, NK cell deletion resulted in a significantly higher number of memory Ag-specific CD8+ T cells, leading to more effective control of tumors carrying model Ags. The enhanced memory responses induced by the transient deletion of NK cells may provide a rational basis for the design of new vaccination strategies.
Oxidation of Vulcanized Rubber. Effect of Temperature, State of Cure, and Thickness
Authors: Kemp A. R. , Ingmanson J. H. , Mueller G. S. 
Published: February 2011

Abstract
1. A previous investigation of the rate of oxidation of rubber over the temperature range of 60° to 80° C. has been extended to 90°, 100° and 110° C. 2. The rate of oxidation over the range which accounts for substantial deterioration of tensile strength appears to be a straight-line function of the time of aging from 60° up to an including 90° C. The rate of oxidation at 100° C. appears to diverge somewhat from a straight-line function of time decreasing as oxidation proceeds. 3. The rate of oxidation increases with increased temperature. Over the range of 60° to 110° C, the rate is doubled for each 7.5° increase in temperature, corresponding to a temperature coefficient of oxidation of 2.5. 4. Tensile strength decreases as a straight-line function of the time of aging and of the quantity of oxygen absorbed. 5. The quantity of absorbed oxygen, determined by weight gain corresponding to a 50 per cent decrease in tensile strength, varies with the temperature of oxidation. At 60° C. the oxygen requirement for 50 per cent deterioration is about 1.30 per cent, and at 110° C. about 0.65 per cent on the rubber hydrocarbon content. 6. Tensile strength increases, probably due to a mild curing effect, when specimens of the compound are heated in an atmosphere where the oxygen is replaced with carbon dioxide for the same periods of time at 80° and 110° C, were required to cause a 50 per cent deterioration in tensile strength in an oxygen atmosphere. 7. With increased time of vulcanization, the rate of oxidation increases. Oxidation appears to be autocatalytic in the case of overvulcanized rubber. 8. As time of vulcanization increases, there is a decrease in the quantity of oxygen required to cause a given decrease in tensile strength. 9. Thickness variations of 0.43 to 1.90 mm. in test-specimens of a compound containing an antioxidant do not affect quantity of oxygen absorbed or degree of tensile strength deterioration when aging is conducted at 80° C. and 3.5 kg. per sq. cm. oxygen pressure. 10. When tetramethylthiuram disulfide is used for vulcanization in place of sulfur, there appears to be no change in the mechanism of oxidation, but the rate of oxidation is reduced.
Experiments on the Determination of the Activity of Carbon Black by Its Power of Adsorbing Carbon Tetrachloride Vapor
Authors: Patryn T. 
Published: February 2011

Abstract
On the basis that a material like carbon black must, because of its very high ratio of surface area to volume, possess very high adsorptive capacity, several investigators have attempted to establish the relationship between the adsorptive capacity of carbon black and its activity in rubber. Spear and Moore used aqueous solutions of malachite green, Victoria blue and hexamethylenetetramine; Beaver and Keller used iodine in aqueous potassium iodide; Goodwin and Park used iodine in carbon tetrachloride and also an aqueous solution of methylene blue; Carson and Sebrell used iodine, benzoic acid, mercaptobenzothiazole and diphenylguanidine. All these workers tested various types of carbon black. If one examines critically the data of these several investigators from the point of view of the relation between the adsorptive capacity of a carbon black and its activity in rubber, it will be evident that the investigations do not lead to any reliable method whereby the behavior of carbon black in rubber can be judged by its adsorptive capacity.
Dilatometer Studies of Pigment-Rubber Systems
Authors: Jones H. C. , Yiengst H. A. 
Published: February 2011

Abstract
A number of years ago Schippel observed that, when certain pigmented rubber stocks were stretched, there was a reduction in specific gravity of the compound. This he attributed to the separation of the rubber from the pigment, resulting in vacuole formation. Green confirmed Schippel's explanation with the aid of a microscope. He prepared photomicrographs of stretched rubber films showing the formation of vacuoles at coarse pigment particles and undispersed pigment acting as single large particles. These vacuoles were conical in shape, and extended from one or both sides of the particles in the direction of elongation. Depew and Easley reported microscopic results relating particle surface and particle size and shape to the formation of vacuoles in stretched rubber. Several years ago Holt and McPherson designed a dilatometer to measure the volume change of rubber compounds under tension. In stretching gum-rubber bands, they noted a decrease in volume, which they ascribed to the fibering of the rubber, and an increase in volume of pigmented rubber bands, which they explained by the formation of vacuoles around the pigment particles. Furthermore these investigators pointed out that the decrease in volume of rubber on stretching is influenced by the same considerations as the x-ray diffraction, since it is observed only above a certain critical elongation and is greater the higher the elongation, the lower the temperature, and the longer the time the sample is kept stretched. Holt and McPherson dealt almost entirely with gum stocks except that they included measurements on a whiting and a carbon black stock. The object of this investigation was to extend the work of Holt and McPherson to a more complete study of pigmented stocks, with particular reference to those compounded with zinc oxide.
Investigation of the Fine Structure of High-Molecular Substances with the Universal Electron Microscope. Part II. The Morphology of Rubber and Buna
Authors: Von Ardenne M. , Beischer D. 
Published: February 2011

Abstract
In the last twenty years scientific methods and research have contributed to an ever increasing extent to the improvement of technical processes and to better control of these processes. In the production of crude rubber, for example, the personal skill of experienced experts, which formerly was the only controlling factor, has now been supplemented by a knowledge of how to carry out the process with rigid physico-chemical control. In addition to this, the development of rubber-like materials, such as Buna, has brought to the field of highly elastic materials new accomplishments and methods of investigation of fundamental importance. Since the structural units of rubber and of rubber-like materials lie within the range of colloidal dimensions, the various methods of colloid research have been the chief means of investigation of these materials in the past. Recently the electron microscope has become a new aid to colloid research, and has made possible the direct determination and measurement of the form and size of structural units and their mutual spatial arrangement. In view of this, it was but natural to undertake an electron microscopic investigation of the morphology of rubber and Buna. Even the first broad approach to this problem, which is described in the present communication, makes it evident that the electron microscope technique offers an easy means of gaining an insight into the structure of these systems in various fields of rubber technology.
Transparent Rubber Compounds. The Effect of Chemical Composition of Magnesium Carbonate Fillers
Authors: Bixby Willard F. , Cramer Howard I. 
Published: February 2011

Abstract
From this investigation the following conclusions may be drawn. 1. The x-ray results of Bixby and Hauser have been substantiated by chemical analysis and by microscopic examination. The magnesium carbonate productive of highest light transmitting properties is of the type: 5MgO.4CO2.xH2O. The normal carbonate, MgCO3, gives very low transmissions. 2. The best Japanese carbonate studied (sample No. 3) is pure 5MgO.4CO2.xH2O. 3. A domestic carbonate (sample No. 20), which is also pure 5MgO.4CO2.xH2O, is commercially available and produces transparency in rubber compounds equal to that obtained with the Japanese product. 4. Domestic carbonates in general contain more carbon dioxide than is required by a 5MgO.4CO2.xH2O carbonate, and are probably mixtures of this material and of the normal carbonate, MgCO3. 5. Light transmitting properties fall rapidly as the proportion of normal carbonate, MgCO3, rises. 6. Carbonates containing less than enough carbon dioxide to provide a 5MgO.4CO2.xH2O carbonate are probably mixtures of this material and hydrated magnesium oxide, MgO.H2O. 7. In preparing basic carbonates for use in producing high light-transmitting rubber, it is better to produce a material with slightly less carbon dioxide than necessary for a 5MgO.4CO2.xH2O carbonate, rather than more. 8. Particle size is an important factor influencing light transmission, especially when the normal carbonate, MgCO3, is present. Generally speaking, especially in the size ranges encountered in these carbonates, a finely divided MgCO3 will offer greater hindrance to the passage of light than will a larger size material.
Factors Influencing the T-50 Value
Authors: Gardner E. R. 
Published: February 2011

Abstract
The paramount importance of producing the correct state of cure in a rubber article is too well known to need further emphasis. In the light of this, statement, the necessity of possessing a convenient and accurate method of assessing the state of cure is obvious. Before the advent of the T-50 test, the state of cure was measured mainly by a determination of the quantity of sulfur combined with the rubber, of stress-strain properties, or of optimum resistance to aging. The determination of combined sulfur has a disadvantage which is immediately apparent; it is laborious. Also, the figure obtained includes the amount of sulfur combined with metallic oxides used as activators, and to get an accurate measure of the quantity of sulfur combined with the rubber, a second analysis must be undertaken. There is yet another disadvantage, namely, that sulfur-containing substances added to the rubber mix interfere with the determination. The determination of tensile strength, modulus, or resistance to aging cannot be regarded as suitable for giving an accurate measure of cure, and are probably best looked on as complementary to the sulfur determination. With this state of affairs existing, it was only to be expected that, on the introduction of an entirely new and independent method of testing the state of cure, far-reaching claims should have been made, and also that the discovery should have been hailed as the elixir for all cure-testing ills. The present work was undertaken with a view to testing the validity of the claims put forward and to investigating, prior to the introduction of the T-50 as a routine test, the effect of variables likely to be encountered.
Infra-Red Spectra of Rubber and High Polymers
Authors: Sears W. C. 
Published: February 2011

Abstract
The rubber industry is interested in all methods for studying the structure of highly polymerized substances. Infra-red spectroscopy has been recognized by recent workers as a possible means for determining the valence forces in long chain molecules. Accordingly, the infra-red spectra of rubber and related compounds have been measured by several workers. An investigation of rubber, gutta percha, indene, polyindene, styrene, polystyrene, polyvinylacetate and polyvinylchloracetate has been carried out by Stair and Coblentz. Later Williams measured natural and vulcanized rubber, rubber hydrochloride, isoprene, styrene and polymerized butadiene in the region between 2.5µ and 9µ, but his spectra of rubber did not agree with that of Stair and Coblentz. Williams and Taschek reported that the bands in rubber become broader with increasing stretch. Recently a rough survey of the infra-red transmission of rubber, Pliofilm, Vinylite XYSG, Shawinigan V-15, polystyrene, methyl methacrylate polymer and Cellophane has been made by Wells. The Raman data of rubber obtained by Gehman and Osterhof are in fair agreement with the infra-red results of Stair and Coblentz.
Elastic and Thermoelastic Properties of Rubberlike Materials. A Statistical Theory
Authors: Guth Eugene , James Hubert M. 
Published: February 2011

Abstract
A statistical theory of the elasticity of rubber and similar high-molecular compounds was proposed by one of the authors several years ago, and an extended form of the theory was presented recently. The theory is applied here to vulcanizates, and shows the dependence of stress on both temperature and deformation for both extension and compression. The foundations of the theory will be stated precisely, inasmuch as some recent articles dealing with it are likely to lead to misunderstandings concerning the assumption of free rotation and structure of long-chain compounds, such as vulcanized rubber. The possible ro^le of kinetic effects for the rubber type of elasticity has been discussed qualitatively by Wöhlisch, Busse, Karrer, Meyer, Susich and Valkó, and Shacklock. The first quantitative theory was developed by one of the authors in 1934 and published later, partly in collaboration with Mark. In the statistical theory, the main assumption is that of quasi-free rotation in a rubber molecule around a single carbon-carbon bond. An important consequence of this free rotation is that the molecules are coiled in the unstretched state. The contraction of stretched rubber is due mainly to the tendency of the stretched chain to change from a less probable stretched form back to the most probable coiled form. This happens in accordance with the statistical interpretation of the second law of thermodynamics, and is not caused by forces. Our theory, then, is that the kinetic motion of freely rotating groups in the rubber molecule is the main cause of contraction.
Report of the Crude Rubber Committee. Presented at the Semi-Annual Meeting of the Division of Rubber Chemistry—April 11, 1941 Concluding Remarks
Authors: Sackett G. A. , McColm E. M. , Nellen A. H. , Oldham E. W. , Parrish W. D. , Schatzel R. A. , Walton J. C. 
Published: February 2011

Abstract
The Crude Rubber Committee has not given up the possibility of working out a test for determining the age-resistance properties of crude rubber. Much laboratory work remains to be done on this problem before reaching any decision, and such an investigation will be considerably delayed by the present need for work for national defense. The Committee is giving serious consideration to the problem of sampling crude rubber. The drawing of a representative sample presents more of a practical statistical problem than one of rubber technology, and the adoption of a standard method must be based on a statistical study. It is hoped that a paper on this subject can be presented before the Division of Rubber Chemistry at an early date.
The Autoöxidizability of the Alkyl Groups in Xylene
Authors: Farmer Ernest Harold , Narracott Eric S. 
Published: February 2011

Abstract
In the course of early experiments on the oxidation of rubber, it was observed that its solutions in commercial xylene, when exposed at 75° to a stream of oxygen, in presence of acetic anhydride (added to accelerate reaction) and a cobalt catalyst, gave m- and p-toluic acid, together with neutral liquids which were clearly not derived from the rubber. For instance, when a solution of 675 g. of rubber in 6075 g. of xylene was mixed with 844 cc. of acetic anhydride and 42 g. of cobalt naphthenate, and the mixture (in 4 batches) was treated at 75° for 2 days with a stream of oxygen, there were obtained, respectively, (1) by extraction of the xylene solution with 10% caustic alkali and (2) by subsequent distillation at approximately 1 mm. pressure of the volatile product from the residual xylene liquor, about 10 g. of crystalline acid and 80 g. of volatile neutral oxidation products. The acid was toluic acid (found: C, 70.6; H, 6.1; equiv., 135; calculated for C8H8O2: C, 70.55; H, 5.95%; equiv. 136), from which samples of both the m- and the p-isomeride (m. p. 110° and 176°, respectively) were isolated by fractional crystallization.
Vulcanization of Latex. Differences in the Behavior of Fresh, Old, and Purified Latex
Authors: Dalfsen J. W. Van 
Published: February 2011

Abstract
Patents granted to Schidrowitz show that when latex is vulcanized and then dried at room temperature, the product has the properties of vulcanized rubber. Films produced in this way show tensile strengths and elasticity which correspond to those of latex films vulcanized in the dry state. It is apparent, however, that when fresh latex is vulcanized under certain definite conditions, the product has fair tensile strength and elasticity only at a relative humidity of zero, but which under ordinary atmospheric conditions is brittle, seems to be overcured, and is practically without tensile strength. This tensile strength, however, is increased by additional dry vulcanization, so there can be no question of overcure. Just as soon as vulcanization has proceeded to a point where brittle films without tensile strength are obtained, the latex, when treated with acid, does not coagulate, but merely flocculates. Nor can such vulcanized fresh latex at this stage be made to coagulate coherently by other means. This form of latex is not sticky. The flocculate referred to can be obtained only by vulcanizing fresh latex in the presence of zinc oxide, and under conditions such that hydrolysis of the nonrubber substances is a minimum. It is, therefore, desirable to have recourse to ultra-accelerators and to be sure that the vulcanization temperature is not too high. By keeping fresh latex alkaline, or by purifying it, it will not flocculate. Latex that has been purified or aged may occasionally, under similar conditions, give a brittle and incoherent coagulum, whereas in other cases a normally coherent but somewhat brittle coagulum results. The nature of the coagulum is governed by the degree of purification and hydrolysis of the nonrubber substances; hence all transition stages between a flocculate and a completely coherent coagulum may occur. By adding serum from fresh latex to purified latex, the behavior of such purified latex changes in the sense that it behaves more like fresh latex. In studying experimentally the difference in behavior of fresh latex and purified latex, the first thing considered was the combination of sulfur. It was found that sulfur first dissolves in the serum, after which it dissolves in the rubber itself. Only then does vulcanization take place. This became evident from the definite acceleration of the combination of sulfur in the latex stage, when before vulcanization, latex was heated with sulfur alone. By this preparatory treatment too, dry vulcanization at room temperature was accelerated, but there was no noticeable effect on dry vulcanization at 80° and 110° C. At 30° C, about 1 per cent of the sulfur dissolved in the rubber particles, in the form of free sulfur. From this it was concluded that it is not possible to remove by mechanical means (as by clarification) excess free sulfur from vulcanized latex. No essential difference could be found between the combined sulfur of fresh latex and that of purified old latex.
Electrodecantation for Concentrating and Purifying Latex
Authors: Murphy E. A. 
Published: February 2011

Abstract
The chief methods employed in the production of concentrated latex have been confined to the controlled evaporation of water from the latex by the application of heat, concentration by centrifuging, and separation of the latex into layers of different concentrations by the action of creaming agents. Recently, another process has been used commercially, which produces concentrates similar to those obtained by the centrifuging and creaming methods in that a substantial part of the serum constituents is removed during the concentration. The new method is based on phenomena observed by Pauli and his co-workers on the behavior of colloidal sols when subjected to electrodialysis. It was noted that in the purification of sols, such as silicic acid and serum albumen, by subjecting them to electrodialysis between vertical semipermeable membranes, separation was frequently obtained into superimposed layers containing different concentrations of the sol. The more concentrated layers were uppermost, or vice-versa, according to the relative densities of the sol and dispersing medium. This stratification is probably the result of the combined influence of the electrical potential and gravitational force under suitably chosen conditions. The colloidal particles migrate to one of the membranes under the influence of the electric field, with consequent concentration at the membrane surface. If the field strength is not too great, the particles become more under the influence of gravitational force than of the electrical force, tending to cause deposition on the membrane. The concentrated layer of particles tends, therefore, to move upwards or downwards along the surface of the membrane in accordance with its relative density with respect to that of the surrounding liquid. Conversely, there is a corresponding reduction in the concentration of the sol at the other membrane surface, which promotes a flow of more dilute dispersion in the opposite direction to that of the stream on the other membrane. If this action is allowed to continue, the dispersions of different concentrations spread out through the cell liquid in the form of horizontal layers which may be decanted.