bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inducible Adeno-Associated Virus-Mediated IL-2 Gene Therapy Prevents Autoimmune Diabetes
Authors: Goudy Kevin S. , Johnson Mark C. , Garland Alaina , Li Chengwen , Samulski R. Jude , Wang Bo , Tisch Roland 
Published: February 2011

AbstractIL-2 and TGF-β1 play key roles in the immunobiology of Foxp3-expressing CD25+CD4+ T cells (Foxp3+Treg). Administration of these cytokines offers an appealing approach to manipulate the Foxp3+Treg pool and treat T cell-mediated autoimmunity such as type 1 diabetes. However, efficacy of cytokine treatment is dependent on the mode of application, and the potent pleiotropic effects of cytokines like IL-2 may lead to severe side effects. In the current study, we used a gene therapy-based approach to assess the efficacy of recombinant adeno-associated virus vectors expressing inducible IL-2 or TGF-β1 transgenes to suppress ongoing β cell autoimmunity in NOD mice. Intramuscular vaccination of recombinant adeno-associated virus to 10-wk-old NOD female mice and a subsequent 3 wk induction of IL-2 was sufficient to prevent diabetes and block the progression of insulitis. Protection correlated with an increased frequency of Foxp3+Treg in the periphery as well as in the draining pancreatic lymph nodes and islets. IL-2 induced a shift in the ratio favoring Foxp3+Treg versus IFN-γ–expressing T cells infiltrating the islets. Induction of IL-2 had no systemic effect on the frequency or activational status of T cells and NK cells. Induction of TGF-β1 had no effect on the Foxp3+Treg pool or the progression of β cell autoimmunity despite induced systemic levels of activated TGF-β1 that were comparable to IL-2. These results demonstrate that inducible IL-2 gene therapy is an effective and safe approach to manipulate Foxp3+Treg and suppress T cell-mediated autoimmunity and that under the conditions employed, IL-2 is more potent than TGF-β1.
Recurrence Relations for Strongly q-Log-Convex Polynomials
Authors: Chen William Y. C. , Wang Larry X. W. , Yang Arthur L. B. 
Published: February 2011

AbstractWe consider a class of strongly q-log-convex polynomials based on a triangular recurrence relation with linear coefficients, and we show that the Bell polynomials, the Bessel polynomials, the Ramanujan polynomials and the Dowling polynomials are strongly q-log-convex. We also prove that the Bessel transformation preserves log-convexity.
The Resultant of Chebyshev Polynomials
Authors: Jacobs David P. , Rayes Mohamed O. , Trevisan Vilmar 
Published: February 2011

AbstractLet Tn denote the n-th Chebyshev polynomial of the first kind, and let Un denote the n-th Chebyshev polynomial of the second kind. We give an explicit formula for the resultant res(Tm, Tn). Similarly, we give a formula for res(Um, Un).
The Saddle-Point Method and the Li Coefficients
Authors: Mazhouda Kamel 
Published: February 2011

AbstractIn this paper, we apply the saddle-point method in conjunction with the theory of the Nörlund–Rice integrals to derive precise asymptotic formula for the generalized Li coefficients established by Omar and Mazhouda. Actually, for any functionFin the Selberg classand under the Generalized Riemann Hypothesis, we havewithwhere γ is the Euler's constant and the notation is as below.
The Effect of Pile Bombardment on Uncured Elastomers
Authors: Davidson W. L. , Geib I. G. 
Published: February 2011

Abstract
Previous work on the effects of ionizing radiations on hydrocarbons has established that four competitive processes are usually operative: (1) dehydrogenation, (2) condensation or polymerization, (3) hydrogenation (action of nascent hydrogen on any unsaturated matter present), (4) decomposition (C—C cleavage). The chain reacting nuclear pile offers an ideal means for subjecting relatively thick samples of matter (such as rubber) to uniformly high concentrations of radiation. Such studies on natural rubber, Butyl rubber, and polyisobutylene allow one to draw the following conclusions. 1. Uncured natural rubber undergoes a slight curing action when exposed to pile radiations. 2. Polyisobutylene samples are appreciably degraded by pile radiations. 3. The same effects as noted in (1) and (2) are greatly enhanced by secondary alpha particles, produced by an (n, α) reaction on boron (milled into the elastomer). However, even a 2-hour bombardment of natural rubber yields a product greatly inferior to sulfur vulcanizates. 4. Pile bombardment does not introduce measurable unsaturation in polyisobutylene and decreases the unsaturation in natural rubber but slightly. 5. A typical Butyl rubber stock is permanently degraded by pile irradiation, showing on cure reduced tensile strength compared to that of a control sample. 6. Natural rubber shows a weak but measurable radioactivity days after bombardment, probably because of its mineral content. Polyisobutylene is not appreciably active.
Strain Test for Evaluation of Rubber Compounds
Authors: Roth Frank L. , Stiehler Robert D. 
Published: February 2011

Abstract
Measurements of elongation of rubber vulcanizates at a fixed stress have been made with a precision much greater than can be obtained in the usual measurements of stress at a specified elongation. Such measurements form the basis of a strain test developed to characterize rubber vulcanizates in control and research testing. Statistical analyses show that the errors introduced in the actual strain measurements are negligible compared to those introduced by variations during compounding and curing, whereas the errors introduced by the usual measurements of stress at a specified elongation are of the same order of magnitude as those for compounding and curing. The high precision of strain testing has been used to detect variations within a single sheet of vulcanized rubber and variations among sheets cured from the same compounded batch. It has been possible also to determine with a single sheet its change in stiffness or modulus with age. The uniform treatment of specimens in the strain test makes them particularly useful for precise measurements of set. Further, it has been found that the decrease in elongation with time of cure apparently follows the laws of a second-order chemical reaction; consequently it is possible to represent the data by an equation involving three vulcanization parameters.
Determination of Resistance to Abrasive Wear. VIII. Influence of Softeners in Tests with the Akron-Croydon and Du Pont Machines
Authors: Morley J. F. 
Published: February 2011

Abstract
These experiments indicate that softeners can influence abrasion resistance, as measured by laboratory machines, in some manner other than by altering the stress-strain properties of the rubber. One possible explanation is that the softener acts as a lubricant to the abrasive surface. Since this surface, in laboratory abrasion-testing machines, is relatively small, and comes repeatedly into contact with the rubber under test, it seems possible that it may become coated with a thin layer of softener that reduces its abrasive power. It would be interesting in this connection to try an abrasive machine in which a long continuous strip of abrasive material was used, no part of it being used more than once, so as to eliminate or minimize this lubricating effect. The fact that the effect of the softener is more pronounced on the du Pont than on the Akron-Croydon machine lends support to the lubrication hypothesis, because on the former machine the rate of wear per unit area of abrasive is much greater. Thus in the present tests the volume of rubber abraded per hr. per sq. cm. of abrasive surface ranges from 0.03 to 0.11 cc. on the du Pont machine and from 0.0035 to 0.0045 cc. on the Akron-Croydon machine. On the other hand, if the softener acts as a lubricant, it would be expected to reduce considerably the friction between the abrasive and the rubber and hence the energy used in dragging the rubber over the abrasive surface. The energy figures given in the right-hand columns of Tables 1 and 3, however, show that there is relatively little variation between the different rubbers. As a test of the lubrication hypothesis, it would be of interest to vary the conditions of test so that approximately the same amount of rubber per unit area of abrasive is abraded in a given time on both machines; this should show whether the phenomena observed under the present test conditions are due solely to the difference in rate of wear or to an inherent difference in the type of wear on the two machines. This could most conveniently be done by considerably reducing the load on the du Pont machine. In the original work on this machine the load was standardized at 8 pounds, but no figures are quoted to show how abrasion loss varies with the load. As an addition to the present investigation, it is proposed to examine the effect of this variation with special reference to rubbers containing various amounts and types of softener. Published data on the influence of softeners on the road wear of tire rubbers do not indicate anything like such large effects as are shown by the du Pont machine. This throws some doubt on the value of this machine for testing tire tread rubbers, a conclusion which is confirmed by information obtained from other workers.
Sulfur Linkage in Vulcanized Rubber. Acetone Extraction of Vulcanizates
Authors: Selker M. L. , Kemp A. R. 
Published: February 2011

Abstract
1. For the soft rubber stock SB1A, there is no evidence for the change: polysulfide → free sulfur on acetone extraction. 2. Evidence for the change: polysulfide → other sulfur links on acetone extraction is indicated by increased reactivity of extracted SB1A to methyl iodide. 3. Natural and GR-S ebonites lose about one-third of their combined sulfur on reaction with methyl idode at 24° C. Trimethylsulfonium iodide is found in large quantities. 4. Neither extraction experiments nor methyl iodide reactions offer evidence for occurrence of polysulfides in 32 per cent sulfur natural ebonite.
The Interaction between Rubber and Liquids. X. Some New Experimental Tests of a Statistical Thermodynamic Theory of Rubber-Liquid Systems
Authors: Gee Geoffrey 
Published: February 2011

Abstract
Experimental data are reported on the effects of vulcanization, extension, and temperature on the swelling of rubber. Although in qualitative agreement with a simple equation derived from a statistical theory of polymer solutions, these reveal quantitative discrepancies which are important in discussions of two-phase equilibria.
The Dynamic Characteristics of Neoprene Vulcanizates
Authors: Catton N. L. , Krismann E. H. , Keen W. N. 
Published: February 2011

Abstract
The utilization of the elastomeric spring goes back at least to the days of solid rubber carriage tires. The use of such materials to dampen vibration or absorb shock expanded rapidly despite the lack of engineering data and the inadequacy of testing methods for proper evaluation. Within the last twenty years these materials have been used in many dynamic applications, even though no appropriate means existed for the measurement of dynamic properties to determine their suitability for the particular service. Coincident with the practical application of rubber parts to vibration problems, engineers developed considerable data on the use of natural rubber in springs. Marked differences in performance were encountered when engineers were obliged to replace natural rubber with synthetic rubber in spring applications. Some engineers redesigned the rubber part used and obtained workable, although not entirely acceptable, performance. Design alone was not a complete solution to the problem, and it was necessary to call on the rubber technologist to produce vulcanizates having properties especially suitable for dynamic service.
Electrically Conducting Rubber
Authors: Lane K. A. , Gardner E. R. 
Published: February 2011

Abstract
In recent years the dangers and inconveniences arising from the presence of static electrical charges on rubber conveyor belts, rubber flooring, rubber-tired vehicles and the like, have aroused interest in the use of electrically conducting rubber as a means of minimizing the accumulation of static electricity. Conventional rubber compounds, which have electrical resistivities normally above 107 ohm-cm, and as high as 1014–1016 ohm-cm. for nonblack compositions, favor the accumulation of static charges. By using high loadings of channel black, the resistivity can be reduced considerably. If special types of carbon black are employed the resistivity can be reduced to a very low value ; in fact, the development of a compound with a resistivity of 1 ohm-cm. has been reported. A compound with a resistivity of about 10 ohm-cm., processible on ordinary factory-size rubber machinery, is described later in this paper. Rubber compounds with resistivities less than 107 ohm-cm. are generally grouped under the generic title of “electrically conducting rubbers”. The conduction of electricity through rubber-carbon black compositions is attributed to the ability of the carbon black to form chains of particles through the rubber. The formation of these chains depends on the particle size, crystal structure, and degree of dispersion of the black. The special types of black referred to above, termed conducting blacks, possess this ability for chain formation to an advanced degree. The work described below deals with the compounding of conducting rubbers, their application, and the methods used for testing. It appears under three main headings: measurement of resistivity; development of highly conducting rubber ; and development and testing of antistatic tires.
Properties of Ebonite. XXXV. Further Experiments on the Influence of Sulfur Ratio
Authors: Scott J. R. 
Published: February 2011

Abstract
1. As the percentage of sulfur in a rubber-sulfur ebonite is progressively increased, the yield temperature rises to a maximum and then falls again. There is thus an optimum proportion of sulfur for producing a heat-resistant ebonite. The cause of the reversion on exceeding this optimum has not yet been studied ; it is suggested, though without proof, that it may be due to the large amount of sulfur left uncombined. The swelling time (period required for the swelling in benzene to reach a given fraction of its maximum) likewise passes through a maximum at about the same sulfur ratio, and possibly for the same reason. 2. During prolonged vulcanization ebonite may become much harder and more heat-resistant, with little increase in combined sulfur. 3. Plastic yield temperature, hardness (as measured by Young's modulus), and absorption of petroleum hydrocarbons (petroleum ether, paraffin, transformer oil) are not determined solely by the combined sulfur content of the ebonite, but depend on how this has been attained, i.e. on the proportion of sulfur in the mix and the period of vulcanization. Increase of combined sulfur by prolonging vulcanization is more effective in producing the characteristic properties of ebonite (high yield temperature, hardness, resistance to petroleum hydrocarbons) than the same increase brought about by adding more sulfur. 4. In attempting to improve the heat-resistance of unloaded rubber-sulfur ebonites it is useless to increase the proportion of sulfur beyond the maximum now generally used, i.e. about 35 per cent of the mix, even when an accelerator is used to promote its combination with the rubber. The fact that ebonite can be made more heat-resistant without increase of combined sulfur, suggests a line along which improvement may be sought. 5. The results confirm the previous observation that well vulcanized ebonite is practically unaffected by oils of the petroleum (aliphatic) type, even at 90°– 100° C. The swelling action of such liquids, however, increases rapidly when the degree of vulcanization of the ebonite is reduced. The proportion of combined sulfur needed to confer good swelling resistance varies with the nature of the liquid, but can be deduced from the data recorded. There should be no difficulty in making an ebonite to give satisfactory service, so far as swelling resistance is concerned, in contact with oils, provided these consist of aliphatic hydrocarbons. As, however, aromatic hydrocarbons, e.g. benzene, toluene, xylene, have a strong swelling action, equally good resistance cannot be expected towards oils of appreciable aromatic content. Hydrocarbons of the cycloparaffin series (naphthenes) appear to be relatively innocuous.
Pyrolytic Depolymerization of Rubber into Isoprene
Authors: Boonstra B. B. S. T. , van Amerongen G. J. 
Published: February 2011

Abstract
The depolymerization of natural rubber into isoprene under the influence of high temperature was studied. Several methods, discontinuous and continuous, were tried on the principle of heating the rubber as rapidly as possible to cracking temperatures. The best method appeared to be the pressing of rubber by means of an extruder into a reaction tube of the desired temperature and pressure. After systematically varying the conditions for cracking, a yield of 58 per cent isoprene from crude rubber was obtained at a cracking temperature of about 750° C and a pressure of 10 mm. of mercury. Good isoprene yields were obtained in a rather wide range of temperatures between 675° and 800° C; however, the yield became rapidly less at higher pressures. At lower temperatures, e.g., 450° C, dipentene was the main cracking product. By studying the pyrolysis of isoprene itself in contrast to the pyrolysis of rubber, it became evident that low pressure has a twofold favorable influence—it causes quicker “evaporation” of rubber at lower temperature and shortens the contact time of pyrolysis products. When Hevea latex was dropped into a cracking tube, the yield of isoprene from the rubber it contained was about 52 per cent. Several synthetic rubbers and plastics were depolymerized under almost the same conditions as rubber.
Decomposition of Elastomers at High Temperatures
Authors: Skinner Glenn S. , McNeal James H. 
Published: February 2011

Abstract
All of the elastomer compositions tested from natural rubber, GR-S, butadiene-acrylonitrile copolymer, and Neoprene undergo an exothermic decomposition when rapidly heated. Increase in the heating rate enhances the abruptness and magnitude of the exothermic rise. Long heating at 190–200° C eliminates exothermic action. The rapid action also takes place in an atmosphere of nitrogen. Various compounding agents may modify this behavior, but they do not eliminate it. The exothermic action is therefore characteristic of the elastomers in the stocks. The only known structural characteristic common to all these elastomers is the residual double bond. The exothermic activity is, therefore, ascribed primarily to this source. This interpretation is further supported by the work of Midgley and Henne, which showed that the C—C bond in the 1–3 position to the residual double bond in crepe rubber is most readily cleaved. It is rendered still more probable by the evolution of products from the gum stocks tested, which require active hydrogen atoms for their formation. Very little hydrogen chloride is evolved before rapid action begins, and the rate of evolution increases sharply at the peak of exothermic action. Similarly, the butadiene-acrylonitrile copolymer yields hydrogen cyanide, and natural rubber yields saturated gaseous hydrocarbons. The evolution of smoke does not necessarily parallel the exothermic action. Smoke densities sufficient to cause 50 per cent extinction are always obtained before the beginning of the rapid rise in temperature. Complete extinction of the light in the apparatus occurs at a point between the beginning and the peak of the exothermic action. The smoke just above the sample of some stocks may clear completely during the exothermic action. Stocks containing zinc and magnesium oxides give colored smokes of a greatly increased order of density during the exothermic action. Phosgene cannot be detected in the smoke from Neoprene stocks. The outside heating temperatures at which the smoke and volatile gases flash are very similar for the four elastomers in the gum stocks. The initial flash occurs at the beginning of the exothermic rise. The smoke from Neoprene extinguishes the pilot light, while the other samples are ignited and continue to burn.
Frictional Properties of Tread-Type Compounds on ICE
Authors: Conant F. S. , Dum J. L. , Cox C. M. 
Published: February 2011

Abstract
The laboratory test method described is capable of indicating with a fair degree of accuracy the tractive ability of a tire tread compound on ice. Coefficients of both dynamic and static friction are important in determining the resistance to slide of a tire. The base polymer in a tread compound is the principal factor affecting the coefficients of friction. Among compounds based on different polymers, the coefficients of friction on ice are not closely related to either the stiffness or hardness of the stock or to its hysteresis. The coefficients of friction of stocks based on a single polymer, however, are greatly influenced by the type and amount of softener and by the type and amount of black.
The Structure of Neoprene. II. Determination of End Groups by Means of Radiosulfur
Authors: Mochel W. E. , Peterson J. H. 
Published: February 2011

Abstract
By use of radioactive sulfur it has been shown that sulfur-modified Neoprene, i.e., Neoprene Type GN, is essentially a copolymer of chloroprene and sulfur in the approximate ratio of 100 chloroprene units per sulfur atom. The sulfur units, possibly disulfides, are cleaved by an alkaline emulsion of tetraethylthiuram disulfide, so that a gel polymer containing combined sulfur can thus be converted to a soluble, plastic product. The mechanism of this cleavage reaction has not been completely elucidated as yet. Potassium persulfate, used as initiator for the polymerization of Neoprene, appears to be combined with the polymer in Neoprene Type GN in amounts equivalent to 8–17 polymer molecules formed for each sulfur-cpntaining initiator fragment. However, when dodecanethiol is used as modifier, a large proportion of the polymer molecules contain essentially no combined sulfur from the persulfate, and it appears that the true initiator is the RS free radical formed by reaction of the thiol with potassium persulfate. Dodecanethiol used as a polymerization modifier or chain transfer agent is combined in a greater amount than the one thiol per polymer molecule expected on the basis of simple chain transfer. High molecular-weight fractions contained 3–4 thiol sulfur atoms per polymer molecule and the results suggest that thiol addition to the double bonds of the polymer had occurred.
Modern Views on the Chemistry of Vulcanization Changes. III. Reaction of Sulfur with Squalene and with Rubber
Authors: Bloomfield George F. 
Published: February 2011

Abstract
The hexaisoprene, squalene (C30H50), is a promising hydrocarbon for inclusion in a comprehensive survey of sulfur-olefin reactivity and the mechanism of rubber vulcanization, since its molecular complexity is such as to render it more closely comparable with long-chain polyisoprenes than is the diisoprene dihydromyrcene, while its molecular weight is still sufficiently low to enable molecular distillation of the sulfurated reaction product to be accomplished without recourse to unduly elevated temperatures. It has been shown elsewhere that the behavior of squalene toward halogens resembles more closely that of rubber than does the behavior of dihydromyrcene. It is now found that the reaction of squalene with sulfur at the ordinary vulcanization temperature pursues a course very similar to that of dihydromyrcene while at the same time showing a close resemblance to rubber-sulfur vulcanization.