bluuebunny/crossref_metadata_2025 huggingface dataset:
USDL
Authors: Kona Srividya , Bansal Ajay , Simon Luke , Mallya Ajay , Gupta Gopal
Published: February 2011

Web services and Service-Oriented Computing is being widely adopted. In order to effectively reuse existing services, we need an infrastructure that allows users and applications to discover, deploy, compose, and synthesize services automatically. This automation can take place only if a formal description of the Web services is available. In this article we present an infrastructure using USDL (Universal Service-Semantics Description Language), a language for formally describing the semantics of Web services. USDL is based on the Web Ontology Language (OWL) and employs WordNet as a common basis for understanding the meaning of services. USDL can be regarded as formal service documentation that will allow sophisticated conceptual modeling and searching of available Web services, automated service composition, and other forms of automated service integration. A theory of service substitution using USDL is presented. The rationale behind the design of USDL along with its formal specification in OWL is presented with examples. We also compare USDL with other approaches like OWL-S, WSDL-S, and WSML and show that USDL is complementary to these approaches.
A Framework and Protocols for Service Contract Agreements Based on International Contract Law
Authors: Parkin Michael , Kuo Dean , Brooke John
Published: February 2011

Current protocols to agree to Web/Grid service usage do not have the capability to form negotiated agreements, nor do they take into account the legal requirements of the agreement process. This article presents a framework and a domain-independent negotiation protocol for creating legally binding contracts for service usage in a distributed, asynchronous service-oriented architecture. The negotiation protocol, which builds on a simple agreement protocol to form a multiround “symmetric” negotiation protocol, is based on an internationally recognized contract law convention. By basing our protocol on this convention and taking into account the limitations of an asynchronous messaging environment, we can form contracts between autonomous services across national and juridical boundaries, necessary in a loosely coupled, widely geographically distributed environment such as the Grid.
The DeltaGrid Service Composition and Recovery Model
Authors: Xiao Yang , Urban Susan D.
Published: February 2011

This research has defined an abstract execution model for establishing user-defined correctness and recovery in a service composition environment. The service composition model defines a flexible, hierarchical service composition structure, where a service is composed of atomic and/or composite groups. The model provides multi-level protection against service execution failure by using compensation and contingency at different composition granularity levels, thus maximizing the potential for forward recovery of a process when failure occurs. The recovery procedures also include rollback as a recovery option, where incremental data changes known as deltas are extracted from service executions and externalized by streaming data changes to a Process History Capture System. Deltas can then be used to backward recover an operation through a process known as Delta-Enabled Rollback. This article defines the semantics of the service composition model and the manner in which compensation, contingency, and Delta-Enabled-rollback are used together to recover process execution. The authors also present a case study and describe a simulation and evaluation framework for demonstrating the functionality of the recovery algorithm and for evaluating the performance of the recovery command generation process.
The MACE Approach for Caching Mashups
Authors: Hassan Osama Al-Haj , Ramaswamy Lakshmish , Miller John
Published: February 2011

In recent years, Web 2.0 applications have experienced tremendous growth in popularity. Mashups are a key category of Web 2.0 applications, which empower end-users with a highly personalized mechanism to aggregate and manipulate data from multiple sources distributed across the Web. Surprisingly
On Utilizing Web Service Equivalence for Supporting the Composition Life Cycle
Authors: Rinderle-Ma Stefanie , Reichert Manfred , Jurisch Martin
Published: February 2011

Deciding on Web service equivalence in process-aware service compositions is a crucial challenge throughout the composition life cycle. However, restricting such decisions to (activity) label equivalence is not sufficient for many practical applications: if two activities and Web services respectively have equivalent labels, does this necessarily mean they are equivalent as well? In many scenarios (e.g., evolution of a composition schema or mining of completed composition instances), other factors also play an important role. Examples include context information (e.g., input and output messages) and information on the position of Web services within compositions. In this paper, the authors introduce the whole composition life cycle and discuss specific requirements for Web service equivalence along its different phases. The authors define adequate equivalence notions for the design, execution, analysis, and evolution of service compositions. This paper focuses on attribute and position equivalence and contributes a new understanding and treatment of equivalence notions in service compositions.
Lipid-Mediated Oxidative Stress and Inflammation in the Pathogenesis of Parkinson's Disease
Authors: Farooqui Tahira , Farooqui Akhlaq A.
Published: February 2011

Parkinson's disease (PD) is a neurodegenerative movement disorder of unknown etiology. PD is characterized by the progressive loss of dopaminergic neurons in the substantia nigra, depletion of dopamine in the striatum, abnormal mitochondrial and proteasomal functions, and accumulation ofα-synuclein that may be closely associated with pathological and clinical abnormalities. Increasing evidence indicates that both oxidative stress and inflammation may play a fundamental role in the pathogenesis of PD. Oxidative stress is characterized by increase in reactive oxygen species (ROS) and depletion of glutathione. Lipid mediators for oxidative stress include 4-hydroxynonenal, isoprostanes, isofurans, isoketals, neuroprostanes, and neurofurans. Neuroinflammation is characterized by activated microglial cells that generate proinflammatory cytokines, such as TNF-αand IL-1β. Proinflammatory lipid mediators include prostaglandins and platelet activating factor, together with cytokines may play a prominent role in mediating the progressive neurodegeneration in PD.
Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China
Authors: Fang Y. T. , Koba K. , Wang X. M. , Wen D. Z. , Li J. , Takebayashi Y. , Liu X. Y. , Yoh M.
Published: February 2011

Abstract. Nitric acid (HNO3) or nitrate (NO3−) is the dominant sink for reactive nitrogen oxides (NOx = NO + NO2) in the atmosphere. In many Chinese cities, HNO3 is becoming a significant contributor to acid deposition. In the present study, we measured nitrogen (N) and oxygen (O) isotopic composition of NO3− in 113 precipitation samples collected from Guangzhou City in southern China over a two-year period (2008 and 2009). We attempted to better understand the spatial and seasonal variability of atmospheric NOx sources and the NO3− formation pathways in this N-polluted city in the Pearl River Delta region. The δ15N values of NO3− (versus air N2) ranged from −4.9 to +10.1‰, and averaged +3.9‰ in 2008 and +3.3‰ in 2009. Positive δ15N values were observed throughout the year, indicating the anthropogenic contribution of NOx emissions, particularly from coal combustion. Different seasonal patterns of δ15N-NO3− were observed between 2008 and 2009, which might reflect different human activities associated with the global financial crisis and the intensive preparations for the 16th Asian Games. Nitrate δ18O values (versus Vienna Standard Mean Ocean Water) varied from +33.4 to +86.5‰ (average +65.0‰ and +67.0‰ in 2008 and 2009, respectively), a range being lower than those reported for high latitude and polar areas. Sixteen percent of δ18O values was observed lower than the expected minimum of +55‰ at our study site. This was likely caused by the reaction of NO with peroxy radicals; peroxy radicals can compete with O3 to convert NO to NO2, thereby donate O atoms with much lower δ18O value than that of O3 to atmospheric NO3−. Our results highlight that the influence of human activities on atmospheric chemistry can be recorded by the N and O isotopic composition of atmospheric NO3− in a N-polluted city.
Characterisation of individual aerosol particles collected during a haze episode in Incheon, Korea using the quantitative ED-EPMA technique
Authors: Geng H. , Ryu J. Y. , Maskey S. , Jung H.-J. , Ro C.-U.
Published: February 2011

Abstract. A quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), called low-Z particle EPMA, was used to analyse individual aerosol particles collected in Incheon, Korea on 13–18 October 2008 (a typical haze episode occurred from 15 to 18 October). Overall 3600 individual particles in PM2.5-10 and PM1.0-2.5 fractions from 12 aerosol samples collected on haze and non-haze days were analysed. The analysed particles were classified, based on their X-ray spectral data together with their secondary electron images. The major particle types included organic carbon (OC), elemental carbon (EC), sea-salt, mineral dust (such as aluminosilicate, SiO2, CaCO3/CaMgCO3, etc.), (NH4)2SO4/NH4HSO4-containing, K-containing, Fe-rich and fly ash particles. Their relative number abundance results showed that OC particles were significantly increased while sea-salts and mineral dust particles were significantly decreased (especially in PM1.0-2.5 fraction) when haze occurred. For the other particle types (except Fe-rich particles in PM2.5-10 fraction), there were no significant differences in their relative abundances between haze and non-haze samples. On non-haze days, the nitrate-containing reacted sea-salt and mineral dust particles in PM1.0-2.5 fraction significantly outnumbered the sulfate-containing ones, whereas it was the reverse on haze days, implying that on haze days there were special sources or formation mechanisms for fine aerosol particles (≤2.5 μm in aerodynamic diameter). The emission of air pollutants from motor vehicles and stagnant meteorological conditions, such as low wind speed and high relative humidity, might be responsible for the elevated level of OC particles on haze days.
The influence of semi-volatile and reactive primary emissions on the abundance and properties of global organic aerosol
Authors: Jathar S. H. , Farina S. C. , Robinson A. L. , Adams P. J.
Published: February 2011

Abstract. Semi-volatile and reactive primary organic aerosols are modeled on a global scale using the GISS GCM II' "unified" climate model. We employ the volatility basis set framework to simulate emissions, chemical reactions and phase partitioning of primary and secondary organic aerosol (POA and SOA). The model also incorporates the emissions and reactions of intermediate volatility organic compounds (IVOCs) as a source of OA, one that has been missing in most prior work. Model predictions are evaluated against a broad set of observational constraints including mass concentrations, degree of oxygenation, volatility and isotopic composition. A traditional model that treats POA as non-volatile and non-reactive is also compared to the same set of observations to highlight the progress made in this effort. The revised model predicts a global dominance of SOA and brings the POA/SOA split into better agreement with ambient measurements. This change is due to traditionally defined POA evaporating and the evaporated vapors oxidizing to form non-traditional SOA. IVOCs (traditionally not included in chemical transport models) oxidize to form condensable products that account for a third of total OA, suggesting that global models have been missing a large source of OA. Predictions of the revised model for the oxygenated OA (OOA) fraction at 17 different locations and OA volatility at 3 different locations compared much better to observations than predictions from the traditional model. When compared against monthly averaged OA mass concentrations measured by the IMPROVE network, model predictions lied within a factor of two in summer and mostly within a factor of five during winter. A sensitivity analysis indicates that the winter comparison can be improved either by increasing POA emissions or lowering the volatility of those emissions. Model predictions of the isotopic composition of OA are compared against those computed via a radiocarbon isotope analysis of field samples. The contemporary fraction, on average, is slightly under-predicted (20%) during the summer months but is a factor of two lower during the winter months. We hypothesize that the large wintertime under-prediction of surface OA mass concentrations and the contemporary fraction is due to an under-representation of biofuel (particularly, residential wood burning) emissions in the emission inventory. Overall, the model evaluation highlights the importance of treating POA as semi-volatile and reactive in order to predict accurately the sources, composition and properties of ambient OA.
Laboratory evaluation of the effect of nitric acid uptake on frost point hygrometer performance
Authors: Thornberry T. , Gierczak T. , Gao R. S. , Vömel H. , Watts L. A. , Burkholder J. B. , Fahey D. W.
Published: February 2011

Abstract. Chilled mirror hygrometers (CMH) are widely used to measure water vapour in the troposphere and lower stratosphere from balloon-borne sondes. Systematic discrepancies among in situ water vapour instruments have been observed at low water vapour mixing ratios (<5 ppm) in the upper troposphere and lower stratosphere (UT/LS). Understanding the source of the measurement discrepancies is important for a more accurate and reliable determination of water vapour abundance in this region. We have conducted a laboratory study to investigate the potential interference of gas-phase nitric acid (HNO3) with the measurement of frost point temperature, and consequently the water vapour mixing ratio, determined by CMH under conditions representative of operation in the UT/LS. No detectable interference in the measured frost point temperature was found for HNO3 mixing ratios of up to 4 ppb for exposure times up to 150 min. HNO3 was observed to co-condense on the mirror frost, with the adsorbed mass increasing linearly with time at constant exposure levels. Over the duration of a typical balloon sonde ascent (90–120 min), the maximum accumulated HNO3 amounts were comparable to monolayer coverage of the geometric mirror surface area, which corresponds to only a small fraction of the actual frost layer surface area. This small amount of co-condensed HNO3 is consistent with the observed lack of HNO3 interference in the frost point measurement because the CMH utilizes significant reductions (>10%) in surface reflectivity by the condensate to determine H2O.
A brief review on the presentation of cycle 24, the first integrated solar cycle in the new millennium
Authors: Li K. J. , Feng W. , Liang H. F. , Zhan L. S. , Gao P. X.
Published: February 2011

Abstract. The status of the extended solar activity minimum, since the second half of 2007, has been briefly instructed to the solar-terrestrial community. Cycle 24 has the most spotless days since cycle 16, and probably even since the modern cycles, latitudes of high-latitude (>35°) sunspots belonging to a new cycle around the minimum time of the cycle are statistically the lowest at present, compared with those of cycle 12 onwards, and there is only one or no sunspots in a month appearing at high latitudes (>20°) for 58 months (from November 2003 to September 2008), which is observed for the first time since cycle 12 onwards. The solar wind velocity and pressure, 10.7 cm solar radio flux, the polar solar magnetic field, solar total irradiance, and so on reach their minima during the 23–24 cycle minimum time. In order to explain the present extreme low activity, we introduced here one possible mechanism using helio-seismology observations. Viewing, from the long-term running of the time scales of both the Gleissberg period and millenniums, the extended solar activity minimum becomes logical. According to the present observations, the cycle 24 should start in November 2008. Solar activity is predicted at being about 30% lower in cycle 24 than in cycle 23, synthesizing the typical predictions of solar activity, including those given by NASA and NOAA. The 24th solar cycle is sluggishly coming and it should be an opportune moment for studying solar physics and solar-terrestrial physics.
Ground-level ozone concentration over Spain: an application of Kalman Filter post-processing to reduce model uncertainties
Authors: Sicardi V. , Ortiz J. , Rincón A. , Jorba O. , Pay M. T. , Gassó S. , Baldasano J. M.
Published: February 2011

Abstract. The CALIOPE air quality modelling system, namely WRF-ARW/HERMES-EMEP/CMAQ/BSC-DREAM8b, has been used to perform the simulation of ground level O3 concentration for the year 2004, over the Iberian Peninsula. We use this system to study the daily ground-level O3 maximum. We investigate the use of a post-processing such as the Kalman Filter bias-adjustment technique to improve the simulated O3 maximum. The Kalman Filter bias-adjustment technique is a recursive algorithm to optimally estimate bias-adjustment terms from previous measurements and model results. The bias-adjustment technique is found to improve the simulated O3 maximum for the entire year and the whole domain. The corrected simulation presents improvements in statistical indicators such as correlation, root mean square error, mean bias, standard deviation, and gross error. After the post-processing the exceedances of O3 concentration limits, as established by the European Directive 2008/50/CE, are better reproduced and the uncertainty of the modelling system is reduced from 20% to 7.5%. Such uncertainty in the model results is under the established EU limit of the 50%. Significant improvements in the O3 average daily cycle and in its amplitude are also observed after the post-processing. The systematic improvements in the O3 maximum simulations suggest that the Kalman Filter post-processing method is a suitable technique to reproduce accurate estimate of ground-level O3 concentration.
Some Results Obtained in a Study of the Development of Stickiness by Vulcanized Rubber
Authors: Toullec Lucien
Published: February 2011

The experiments described in the present paper show the possibility of reproducing artificially the stickiness which appears during natural aging, and the results show the experimental conditions which are most favorable to a study of the phenomenon. The indications are that it is best to use an oxygen bomb of small capacity, at a temperature of 60–70° C, and with a pressure of 1–4 kg. per sq. cm. of oxygen. The factor which under no conditions must be disregarded if almost certain failure is to be avoided is unquestionably the problem of ventilation. The Geer oven does not seem to be of any service in such experimentation. The appearance of stickiness during aging is not indicative of an advanced stage of deterioration, but is a manifestation of one form or type of aging rather than the consequence of an extreme state of deterioration. Finally, the influence of certain factors has been established. As far as factors inherent to the rubber mixtures themselves are concerned, the accelerator-vulcanizing agent system plays a determinant part. The character of the phenomenon depends on the aging conditions, particularly on the rate of oxidation. The tendency of a vulcanizate to become sticky on aging is particularly great when the temperature is relatively low and the pressure of oxygen is likewise low.
A Chemical Study of Accelerators of the Plasticization of Rubber
Authors: Montu Michel
Published: February 2011

Substances which peptize rubber, of which the most active fall within the class of aromatic thiols such as 2-naphthalenethiol and xylenethiol, are also accelerators of plasticization. Their action, which differs from that of “plasticizers”, is of a chemical nature, and it can be modified by certain agents, such as metalloids of the sulfur family. The use of plasticization accelerators requires certain precautions. A study of the oxidizability of rubber in the presence of plasticization accelerators has shown that these substances make rubber more sensitive to oxygen, whose part in the plasticization of rubber is already well known. At the beginning of the reaction, oxygen is absorbed rapidly under the catalytic influence of the thiol, which is simultaneously transformed into the corresponding disulfide. By means of ultraviolet spectrography, this transformation of thiols while playing the part of catalytic agents can be followed.
Some Effects of Solid Fillers in Rubbers
Authors: Williams Ira
Published: February 2011

The presence of pigments in rubber compounds produces physical properties which are of importance both before and after vulcanization. The ability of the unvulcanized mixture to calender or extrude smoothly with minimum swelling and to maintain shape during air cures, and the tensile strength, tear resistence, and abrasion resistance of vulcanized stocks all are affected. The methods by which these changes are brought about have been considered by many investigators and have been summarized by Parkinson1 and by Shepard, Street, and Park. Since carbon black is the most generally useful reinforcing pigment, it is natural that investigations have been directed particularly to this product. However, while it is recognized that differences exist in the final properties imparted by different pigments, all solid compounding ingredients have something in common. This point can be illustrated by the tear resistance imparted by such a variety of pigments as carbon black, zinc oxide, whiting, and clay. The effect of volume loading on the tear resistance of vulcanized stocks containing these materials, determined by the method of Zimmerman is shown in Figure 1. The effect of solid compounding ingredients can be studied only by considering the compound as a whole, since the properties are determined very largely by the relation between the solid particle and the matrix which surrounds it. Since the introduction of the many types of synthetic rubbers, the complexity of the problem has been greatly increased by the different states of polymerization, which affect the ability of the rubber to conform to the shape of the pigment particle and by the differences in polar nature which affect the type and the degree of adhesion between filler and matrix.
Apparatus for the Measurement of the Dynamic Shear Modulus and Hysteresis of Rubber at Low Frequencies
Authors: Fletcher W. P. , Gent A. N.
Published: February 2011

An apparatus is described which subjects a rubber test-piece to a force in simple shear, varying sinusoidally with time in the frequency range of 0.0017– 17 c/s, the instantaneous values of force and displacement being measured by photoelectric pickups. From the display on the screen of a cathode-ray tube of the mechanical hysteresis loop described by the vibrating rubber, measurements are made which make possible calculation of the dynamic shear modulus and hysteresis. Typical results are given.
Wear Resistance of Vulcanized Elastomers
Authors: Burns J. C. , Storey E. B.
Published: February 2011

The use of a stainless steel wire screen on the National Bureau of Standards abrader will produce a wearing action on a vulcanized elastomer and 41° and 122° F GR-S vulcanizates exhibit the same relative order of wear resistance that has been observed in road tests. The wear resistance determined on this surface is sensitive to the state of cure of the vulcanizate, and a maximum value is obtained at a cure slightly longer than the optimum tensile cure. The method is very sensitive to the type and quantity of carbon black and softener loading in the vulcanizate. These factors are ranked also in the same order as observed in road tests. The method may be applied to footwear compounds as well as to tread vulcanizates of synthetic elastomers. The use of a metal screen offers a uniform and reproducible test surface for determining wear resistance; it suffers little change during continued use; and the material is not affected by minor changes in the ambient temperature or relative humidity. The reproducible nature of the wire screen greatly reduces the need for a reference standard, and comparisons may be made between tests conducted at relatively long intervals of time on either the same or a duplicate screen.
Mooney Viscosity Changes in Freshly Prepared Raw Natural Rubber
Authors: Wood R. I.
Published: February 2011

In the course of investigations carried out in connection with the technical classification of natural rubber, large permanent increases in Mooney viscosity of the order of 30 to 40 units have been observed when freshly prepared raw or masticated rubber is stored under conditions of low relative humidity. The rate of change and the extent of the increase are both affected by the relative humidity of storage, the effects being most marked in the region below about 30 per cent relative humidity. Rate of change in dry air increases with decreasing sample thickness and with increasing temperature, although the effects are masked somewhat by oxidative breakdown on prolonged storage at temperatures higher than about 30° C. Mooney values continue to increase long after the rubber has reached constant weight on drying; the removal of acetone soluble and nitrogenous non-rubber components and of oxygen does not prevent the changes taking place. The effects are only partially reversed by subsequent storage at high relative humidity, and there is evidence to suggest that the hardening is associated with the development of a cross-linked benzene-insoluble gel structure throughout the rubber. The rate of mill-breakdown of dry stored rubber is greater than for fresh rubber, but in comparisons using a fixed breakdown procedure, the hardened rubber still has a higher Mooney value after mastication. Rubbers hardened by dry air storage exhibit slightly improved vulcanized properties in a pure-gum mix even after the additional breakdown required to reach normal stock viscosity levels. Fluctuation of temperature and humidity in commercial smokehouses and drying sheds may well account for part of the variability of natural rubber as measured by Mooney viscosity determinations on the freshly prepared product, and different conditions of storage will add a further contribution to the total hardness variation experienced by the consumer.
A Study of the Stage of Dispersion of Synthetic Latexes by the Intensity of Light Scattering
Authors: Yurzhenko A. I. , Gusyakov V. P.
Published: February 2011

1. Light scattering in synthetic latexes of varying dilutions was studied as a function of the conditions under which the latexes were prepared. When the polymer concentration is increased, the intensity of light scattering reaches a maximum; this is related to the absorption of scattered light in the latex itself. 2. When the polymer concentration is less than 1×10−2 per cent, the turbidity-concentration relation is linear. Calculation of the radius of polymer particles for this region of concentration by Rayleigh's equation gives results approximating those obtained by ultramicroscopy, but tending to be slightly lower. A similar picture is observed in the application of Debye's equation. 3. When the conversion is increased, the size of the latex particles increases. Accumulation of the polymer in the aqueous phase of the emulsion is largely the result of an increase of volume of the polymer particles, and not of their number.
Classifying Butyl Rubber with Respect to Modulus. A Chemical Method
Authors: Currie L. L.
Published: February 2011

The stress-strain method of determining the modulus of Butyl rubber possesses severe shortcomings when applied to plant control, the most serious being the time lag in reporting reliable results. A chemical method is described which is less time-consuming and at the same time is more reproducible. The basic iodine-mercuric acetate method for Butyl unsaturation has been improved by the standardization of reaction conditions, and a correlation between unsaturation and stress strain values in the National Bureau of Standards formula has been developed. This comprehensive study has covered commercial grades of Butyl rubber over an 18-month period. The application of the method to plant control is described, and improved product uniformity is indicated. Reliable results suitable for control purposes are available in 3 to 4 hours.
Physical Aspects of GR-S and Alfin Polymer Modifications
Authors: Dinsmore R. P.
Published: February 2011

It seems that the possibilities of this development, both as a lead to improved rubbers and as a spur to the explanation of rubber behavior, are exceptionally stimulating. Far from being a completed work, this is more likely to be the first and exciting chapter of a series yet to be unfolded. It is a distinct possibility that useful improvements to natural rubber, as well as to synthetic, may result from further investigation of the field. It is perhaps unnecessary to caution that the quantitative relationships developed are not sacrosanct and may be altered by more extensive data. The importance of the results, however, is not entirely dependent on their numerical values.
Changes of Fatigue Resistance of Vulcanized Natural Rubbers during Swelling
Authors: Gul V. E. , Dorokhina T. V. , Dogadkin B. A.
Published: February 2011

A method of fatiguing swollen vulcanizates of natural rubber while maintaining a minimum deforming load, independent of the change of modulus of elasticity of the experimental specimens, was devised. The effect of swelling vulcanized natural rubber in petrolatum and in dibutyl phthalate on fatigue resistance was studied. With increase of swelling of a vulcanizate in dibutyl phthalate and in petrolatum, an initial increase of fatigue resistance was observed up to 1.8 times the fatigue resistance of the unswollen vulcanizate. Following this, a decrease of fatigue resistance was observed. The equation obtained for the change of fatigue resistance as a function of the degree of swelling is explained by two simultaneous processes: (1) increase of fatigue resistance because of decrease of energy loss in the destructionof intermolecular bonds, and (2) initiation of chemical processes leading to destruction, and a smaller difference between the deformation and the relative elongation at rupture. The effect of the character of the solvent used for swelling on the nature of the fatigue resistance-swelling relation is shown.
Studies of the Mechanism of Mastication of Rubber. V. The Viscosity Lowering of Rubber Solutions by Phenyl Disulfide Derivatives
Authors: Imoto Minoru , Kiriyama Shigeru
Published: February 2011

Nine derivatives of phenyl disulfide having substituents in the o- or p-position, were synthesized, and the lowering of the viscosity of toluene solutions of rubber by means of these derivatives was measured. Compounds substituted in o-position were more effective than were compounds substituted in p-position, and the effects of the substituents were in the order : C6H5CONH > CH3CONH > NH2. These conclusions are in agreement with electronic interpretations.
The Meaning of Terms Related to Curing
Authors: Schade J. W.
Published: February 2011

Anyone unfamiliar with rubber technology would naturally assume that the terms used in describing vulcanization convey the same concepts to all technologists in the industry. This is not the case. For example, the term optimum cure is variously defined, and compounders utilize a variety of methods for selecting optimum cures. Some technologists rely mainly on the shape of the modulus-time curve; others include tensile strength values in their analysis; still others depend on sensory indications, such as resistance to tearing by hand, before choosing an optimum. That there is no common basis for selecting optimum cures from moduli, tensile strengths, and ultimate elongations of a series of five cures ranging from 30 to 150 minutes was clearly demonstrated some years ago. Data of this kind were obtained for specimens of GR-S supplied by the fifteen GR-S plants then operating. These data were presented to six technologists employed in the larger rubber companies and at the Government Laboratories, with a request that they select the optimum cures for the specimens. In one company the estimates of four technologists were averaged; in another company two estimates were considered. The differences in optimum cures selected by the technologists for the fifteen specimens varied from 15 to 45 minutes, with an average difference of 28 minutes. If the values selected for optimum cure of the fifteen specimens had been such as to indicate agreement on a common basis for selecting optimum cure, a great variation among the commercial GR-S produced by the fifteen plants at that time would have been evidenced. The values reported from identical data varied, however, for the different specimens over a range of 10 to 40 minuutes. These results show that the compounders could not have used a common method of selecting the optimum cures. The term optimum cure obviously meant different intervals to the technologists who analyzed the data. Furthermore, discussions at various meetings of technical men have disclosed that concepts of the meaning of rate of cure and of state of cure also differed materially. Therefore an attempt at logical definitions of terms seems desirable.
Stress Relaxation in Compression of Rubber and Synthetic Rubber Vulcanizates Immersed in Oil
Authors: Beatty J. R. , Juve A. E.
Published: February 2011

The practical implications of this study are that rubber compounds which swell in the presence of oil have a property which may be utilized in some applications where it may serve a useful purpose. Examples are O-ring seals and other types of gaskets, where the rubber is used in compression. In these cases the stress decays more slowly with time, and in some cases the force would increase, and the tendency to leakage would be minimized. In these experiments the sample was relatively unconfined except for the direction of loading with only low frictional forces which tended to prevent increase in volume. It was noted (Figures 4 and 6) that, with natural rubber and GR-S at 70° C the stress reached a maximum between 1000 and 10,000 hours, which is a result of the sample reaching equilibrium with respect to swelling by the oil, and the stress then decreases, depending on the oxidative scission of bonds in the same manner as found for tests conducted in air. However, according to Scott, the attack of swelling agents accelerates oxidation; so it is possible that this oxidative scission might be in addition to that normally measured in air.
Simultaneous Effects of Phenyl-β-Naphthylamine, Sulfur, and Vulcanization Accelerators on the Oxidation of Rubber
Authors: Kuzminskii˘ A. S. , Lezhnev N. N.
Published: February 2011

Most rubber mixtures contain, besides antioxidants, sulfur and vulcanization accelerators, and these latter have a substantial influence on the oxidation process. Consequently a study of the action of these substances when present simultaneously with antioxidants is important, particularly since there have been no reports concerning this question in the scientific literature. In an earlier article we showed that sulfur, when dissolved in purified sodium-butadiene rubber, is a negative catalyst of oxidation. Above 70° C, the inhibitory effect of sulfur is only slight, and is manifest in a retardation of the autocatalytic process. This retarding effect is much more characteristic of sulfur than of ordinary rubber antioxidants. For example, when added to purified rubber, phenyl-β-naphthylamine prolongs the induction period, but has little influence on the rate of the final auto-accelerated reaction. This behavior of phenyl-β-naphthylamine can be explained by its great inhibitory activity. It acts as a true inhibitor, even in the smallest concentrations'. Consequently, the autocatalytic reaction commences only when almost no phenyl-β-naphthylamine is present, whereas the period of partial retardation of this reaction in the case of an ordinary inhibitor is negligible.
Stability of the Vulcanized Cross-Link in Butyl Rubber: Theory and Application
Authors: Zapp R. L. , Ford F. P.
Published: February 2011

When rubberlike polymers are vulcanized with sulfur, the process involves two competing phenomena. The competing reactions are cross-linking and degradative in nature, and the conditions of vulcanization, as well as the extent, govern the rate at which these actions take place. At lower temperatures (110 to 150° C) vulcanizate degradation is held at a minimum, while higher temperatures usually accelerate the reversion process. A recent stoichiometric study of sulfur addition during Butyl rubber vulcanization revealed that the cross-link was composed of two atoms of sulfur. Calculations from analytical data placed the number of atoms at 1.7 to 2.2 per cross-link. This degree of constancy was maintained, regardless of the extent of vulcanization, until the onset of reversion. Reversion is the degradative process opposite to cross-linking. It can be pictured as the breakdown of the sulfur bridges between polymer molecules, and in Butyl it is evident at vulcanization temperature above 350° F. in 20 minutes. The type of rubber plays an important part in the relative way the two competing reactions occur. In addition, the whole process of cross-linking and reversion may be complicated by oxidative phenomena in predominantly diene type polymers. For example, when the vulcanization of natural rubber is prolonged, softening of the structure is followed by a hardening of the network, attributed to oxidation or cyclization. With Buna type rubbers, the softening action is barely evident before continued heating leads to a harder less extensible material As shown by Andrews, Tobolsky, and Hanson, the stress of a GR-S vulcanizate under intermittent strain increased on aging at 130° C. The stress of a Butyl sample remained essentially unchanged under the same conditions for about 10 hours, whereupon noticeable stress relaxation ensued. The use of an elastomer with a chemical unsaturation of 1 to 2 mole per cent of that found in polyisoprene reduces the opportunities for cyclization reactions. Observations on the stability of the sulfur cross-link can be made with less interference.
The Addition of Thio Compounds to Olefins. III. Reactions of Tri- and Hexamethylenedithiols, and of Bisthioladipic and Bisthiolsebacic Acids
Authors: Cuneen J. I.
Published: February 2011

Certain thiols and bisthiol acids react with natural rubber and with some related olefins in a manner analogous to the corresponding monofunctional compounds. The physical characteristics of the vulcanizates obtained from natural rubber and bisthioladipic acid are described.
The Structure of Chlorinated Rubbers
Authors: Allirot René , Orsini Léon
Published: February 2011

Natural rubber chlorinated to the maximum degree is a homogeneous product in chemical composition and likewise in chemical structure. It is a chemically saturated compound, with a chain structure having the cyclohexane group, C10HxCl7, as the base unit. Such a structure is conceivable only if x has a value of 11, which cannot be determined precisely by any of the methods of organic analysis.
Determination of Volatile Fatty Acids in Natural Rubber Latex
Authors: Philpott M. W. , Sekar K. C.
Published: February 2011

The want of a chemical method to determine incipient decomposition in preserved latex has been long felt by producers and consumers of latex. A method often used is to neutralize the ammonia in latex with boric acid or sulfuric acid, and to judge the extent of decomposition from the intensity of putrefactive odors. This method, besides having limitations common to all subjective tests, is insufficiently sensitive to detect the early stages of putrefaction. Another way of assessing deterioration in latex is to determine the total concentration of acidic substances by KOH titration. Though it is widely used in industry, the method has several disadvantages, both as a test for decomposition and as an index of processing behavior. First, acids are estimated which titrate up to pH 11.2, thus failing to discriminate between stabilizing (i.e. soap forming) and destabilizing (e.g. formic, acetic) acids. Second, conjugate acids of bases, basic groups of zwitterions from amino acids, etc., are included. Third, it fails with latexes to which soaps or fixed alkalies have been added. Following observations made in 1941 by the late W. S. Davey at the Rubber Research Institute of Malaya, we have now shown that a substantial proportion of the acids formed in latex as a result of natural degradation processes can be distilled in steam, and that these volatile acids consist mainly of acetic acid, with some formic and propionic acids. It is considered that a test of spoilage based on the estimation of these acids would be free from the disadvantages that are inherent in the KOH titration, and methods of determining quantitatively the volatile fatty acids in latex have accordingly been worked out.
Electron Microscopy of Rubber Globules in Hevea Latex
Authors: van den Tempel M.
Published: February 2011

The particle size distribution of the rubber globules in Hevea latex has been studied by means of electron microscopy. Most of the particles, even in concentrated latex, are less than 0.2 micron in diameter and are, consequently, not visible in the light microscope. These small particles have considerable influence on the specific interface, but they contain only a few per cent of the rubber present.
Chromatograpic Analysis of Vulcanized Rubbers. Some Rapid Methods for the Detection of Certain Accelerators and Antioxidants
Authors: Parker C. A. , Berriman Joyce M.
Published: February 2011

The chromatographic behavior on silica gel/Celite adsorbent, of thirty-two accelerators and antioxidants has been investigated. Adsorption series have been established with four binary solvent mixtures and, based on these results, some simple and rapid methods have been designed for the identification of the compounds. These depend on the application of various streak reagents to the extruded chromatographic column, and with many of the compounds they give an almost unambiguous identification, even when several compounds are present in admixture. The methods are discussed in relation to those previously available for the identification of accelerators and antioxidants. They offer some important advantages. The methods have been successfully applied to a number of rubbers of known composition. Accelerator transformation products have in some cases been detected or identified. No case of accelerator decomposition during chromatography has been observed, but decomposition of certain accelerators during acetone extraction of the rubber has been noted. The results obtained have been compared with previous work on accelerator transformation products.
Variables Controlling the Cross-Linking Reactions in Rubber
Authors: Barton Bernard C. , Hart Edwin J.
Published: February 2011

During vulcanization, sulfur reacts with rubber and compounding ingredients in various ways to give diversified reaction products. Only the sulfur that forms cross-links between rubber molecules contributes to the transformation of rubber from the plastic to the elastic state. Reactions of sulfur which lead to products other than intermolecular cross-links are considered side reactions of secondary importance to vulcanization. This study was initiated to determine in a relatively quantitative manner the effect of time, temperature, and concentration of reactants on the yield of intermolecular cross-links in the 2-mercaptobenzothiazole-accelerated sulfur-vulcanization of Hevea rubber. This investigation was considered a necessary step in a study of the over-all mechanism of the vulcanization reactions. When conditions necessary for the greatest yield of cross-links per unit of combined sulfur are followed, a linear relationship exists between stress at 200 per cent elongation (a measure of the relative number of cross-links) and combined sulfur. Under conditions that lead to a maximum yield of crosslinks, a linear relationship exists between retractive force and zinc sulfide.
Studies of the Vulcanization of Rubber. X. The Vulcanization of Natural Rubber with a Mixture of Sulfur Dioxide and Hydrogen Sulfide
Authors: Dogadkin B. A. , Keifetz F.
Published: February 2011

1. The dynamics of the changes of the properties of rubber during vulcanization by a mixture of sulfur dioxide and hydrogen sulfide, in distinction from conventional vulcanization by sulfur, is expressed by smooth curves. No vulcanization optimum is observed. 2. With multiple cycles of vulcanization, the increase of bound sulfur content above 3 per cent results in a decrease of tensile strength. 3. Changes of tensile strength of the vulcanizate dependent on changes of sulfur content are attributable to the influence of the density of the spatial network on the orientation processes during deformation.
Mechanism of the Action of Inhibitors of the Oxidation of Elastomers
Authors: Kuzminskii˘ A. S. , Angert L. G.
Published: February 2011

A number of works have been published in the recent scientific literature concerning the action of antioxidants in elastomers. Most of these works are of an empirical nature and are of purely practical value. In certain foreign works, unsuccessful attempts were made to relate the effectiveness of action of antioxidants with one of their specific properties, for example, with their oxidation-reduction potential. The mechanism of inhibited and of free oxidation of elastomers was studied in detail by one of the present authors. Based on a theory of chain reactions, Semenov concluded that the oxidation of rubber involves a chain degradation process, and he showed that the inhibitor, phenyl-β-naphthylamine, breaks the oxidation chains, reacting with the peroxidic radicals which are formed in the rubber molecules during oxidation. The inhibitor is consumed by union with the hydrocarbon molecule. Consumption of inhibitor during heat treatment of rubber is observed only in the presence of oxygen. In the light of our theories of the oxidation of rubber, and also on the basis of contemporary theories of the activity of radicals, according to which the more active molecules in the radical reactions form less active radicals, and vice versa, the mechanism of the action of inhibitors can be described as follows. The peroxide radicals of the rubber detach the more active or mobile hydrogen from the inhibitor molecule, and the radical formed as a result of this reacts with the rubber radicals, breaking the oxidation chains.