bluuebunny/crossref_metadata_2025 huggingface dataset:
Cutting Edge: Intravenous Ig Inhibits Invariant NKT Cell-Mediated Allergic Airway Inflammation through FcγRIIIA-Dependent Mechanisms
Authors: Araujo Luiza M. , Chauvineau Angélique , Zhu Ren , Diem Séverine , Bourgeois Elvire A. , Levescot Anaïs , Huerre Michel , Gombert Jean-Marc , Bayry Jagadeesh , Daëron Marc , Bruhns Pierre , Kaveri Srini V. , Herbelin André
Published: February 2011

Despite their increasing use in autoimmune, inflammatory, and allergic conditions, the mechanism of action of i.v. Igs (IVIg) is poorly understood. On the basis of the critical role of invariant NKT (iNKT) cells in allergic airway inflammation (AAI) and their constitutive expression of the low-affinity IgG receptor FcγRIIIA, we surmised that IVIg targets iNKT cells to exert their anti-inflammatory effect. We found that IVIg treatment significantly inhibited AAI in OVA-sensitized C57BL/6 mice and downregulated α-galactosylceramide–induced iNKT cell activation and cytokine production. Allergic responses were restored in iNKT cell-deficient mice by transferring iNKT cells from PBS- but not from IVIg-treated mice, suggesting that IVIg acts directly on activated iNKT cells that have a critical role in AAI. The inhibitory effects of IVIg on both iNKT cell activation/function and OVA-driven AAI were lost in FcγRIIIA−/− mice. Our data unravel an FcγRIIIA-dependent inhibitory effect of IVIg on activated iNKT cells that confers protection in AAI.
Recombinant Dimeric IgA Antibodies against the Epidermal Growth Factor Receptor Mediate Effective Tumor Cell Killing
Authors: Lohse Stefan , Derer Stefanie , Beyer Thomas , Klausz Katja , Peipp Matthias , Leusen Jeanette H. W. , van de Winkel Jan G. J. , Dechant Michael , Valerius Thomas
Published: February 2011

Dimeric IgA Abs contribute significantly to the humoral part of the mucosal immune system. However, their potential as immunotherapeutic agent has hardly been explored. In this article, we describe the production, purification, and functional evaluation of recombinant dimeric IgA against the epidermal growth factor receptor. Human joining chain-containing IgA was produced by nonadherent Chinese hamster ovarian (CHO)-K1 cells under serum-free conditions. Purification by anti-human κ and anti–His-tag affinity, as well as size exclusion chromatography, resulted in a homogenous preparation of highly pure IgA dimers. Functional studies demonstrated dimeric IgA to be at least as effective as monomeric IgA in triggering Ab-dependent cellular cytotoxicity by isolated monocytes or polymorphonuclear cell and in human whole-blood assays. Importantly, dimeric IgA was more effective in F(ab)-mediated killing mechanisms, such as inhibition of ligand binding, receptor downmodulation, and growth inhibition. Furthermore, only dimeric but not monomeric IgA or IgG was directionally transported by the polymeric Ig receptor through an epithelial cell monolayer. Together, these studies demonstrate that recombinant dimeric IgA Abs recruit a distinct repertoire of effector functions compared with monomeric IgA or IgG1 Abs.
A Barrier-Type Insulator Forms a Boundary between Active and Inactive Chromatin at the Murine TCRβ Locus
Authors: Carabana Juan , Watanabe Akiko , Hao Bingtao , Krangel Michael S.
Published: February 2011

In CD4−CD8− double-negative thymocytes, the murine Tcrb locus is composed of alternating blocks of active and inactive chromatin containing Tcrb gene segments and trypsinogen genes, respectively. Although chromatin structure is appreciated to be critical for regulated recombination and expression of Tcrb gene segments, the molecular mechanisms that maintain the integrity of these differentially regulated Tcrb locus chromatin domains are not understood. We localized a boundary between active and inactive chromatin by mapping chromatin modifications across the interval extending from Prss2 (the most 3′ trypsinogen gene) to Dβ1. This boundary, located 6 kb upstream of Dβ1, is characterized by a transition from repressive (histone H3 lysine 9 dimethylation [H3K9me2]) to active (histone H3 acetylation [H3ac]) chromatin and is marked by a peak of histone H3 lysine 4 dimethylation (H3K4me2) that colocalizes with a retroviral long terminal repeat (LTR). Histone H3 lysine 4 dimethylation is retained and histone H3 lysine 9 dimethylation fails to spread past the LTR even on alleles lacking the Tcrb enhancer (Eβ) suggesting that these features may be determined by the local DNA sequence. Notably, we found that LTR-containing DNA functions as a barrier-type insulator that can protect a transgene from negative chromosomal position effects. We propose that, in vivo, the LTR blocks the spread of heterochromatin, and thereby helps to maintain the integrity of the Eβ-regulated chromatin domain. We also identified low-abundance, Eβ-dependent transcripts that initiate at the border of the LTR and an adjacent long interspersed element. We speculate that this transcription, which extends across Dβ, Jβ and Cβ gene segments, may play an additional role promoting initial opening of the Eβ-regulated chromatin domain.
Highly Activated Cytotoxic CD8 T Cells Express Protective IL-10 at the Peak of Coronavirus-Induced Encephalitis
Authors: Trandem Kathryn , Zhao Jingxian , Fleming Erica , Perlman Stanley
Published: February 2011

Acute viral encephalitis requires rapid pathogen elimination without significant bystander tissue damage. In this article, we show that IL-10, a potent anti-inflammatory cytokine, is produced transiently at the peak of infection by CD8 T cells in the brains of coronavirus-infected mice. IL-10+CD8 and IL-10−CD8 T cells interconvert during acute disease, possibly based on recent Ag exposure. Strikingly, IL-10+CD8 T cells were more highly activated and cytolytic than IL-10−CD8 T cells, expressing greater levels of proinflammatory cytokines and chemokines, as well as cytotoxic proteins. Even though these cells are highly proinflammatory, IL-10 expressed by these cells was functional. Furthermore, IL-10 produced by CD8 T cells diminished disease severity in mice with coronavirus-induced acute encephalitis, suggesting a self-regulatory mechanism that minimizes immunopathological changes.
Multiscale Computational Modeling Reveals a Critical Role for TNF-α Receptor 1 Dynamics in Tuberculosis Granuloma Formation
Authors: Fallahi-Sichani Mohammad , El-Kebir Mohammed , Marino Simeone , Kirschner Denise E. , Linderman Jennifer J.
Published: February 2011

Multiple immune factors control host responses to Mycobacterium tuberculosis infection, including the formation of granulomas, which are aggregates of immune cells whose function may reflect success or failure of the host to contain infection. One such factor is TNF-α. TNF-α has been experimentally characterized to have the following activities in M. tuberculosis infection: macrophage activation, apoptosis, and chemokine and cytokine production. Availability of TNF-α within a granuloma has been proposed to play a critical role in immunity to M. tuberculosis. However, in vivo measurement of a TNF-α concentration gradient and activities within a granuloma are not experimentally feasible. Further, processes that control TNF-α concentration and activities in a granuloma remain unknown. We developed a multiscale computational model that includes molecular, cellular, and tissue scale events that occur during granuloma formation and maintenance in lung. We use our model to identify processes that regulate TNF-α concentration and cellular behaviors and thus influence the outcome of infection within a granuloma. Our model predicts that TNF-αR1 internalization kinetics play a critical role in infection control within a granuloma, controlling whether there is clearance of bacteria, excessive inflammation, containment of bacteria within a stable granuloma, or uncontrolled growth of bacteria. Our results suggest that there is an interplay between TNF-α and bacterial levels in a granuloma that is controlled by the combined effects of both molecular and cellular scale processes. Finally, our model elucidates processes involved in immunity to M. tuberculosis that may be new targets for therapy.
Cutting Edge: Distinct Glycolytic and Lipid Oxidative Metabolic Programs Are Essential for Effector and Regulatory CD4+ T Cell Subsets
Authors: Michalek Ryan D. , Gerriets Valerie A. , Jacobs Sarah R. , Macintyre Andrew N. , MacIver Nancie J. , Mason Emily F. , Sullivan Sarah A. , Nichols Amanda G. , Rathmell Jeffrey C.
Published: February 2011

Stimulated CD4+ T lymphocytes can differentiate into effector T cell (Teff) or inducible regulatory T cell (Treg) subsets with specific immunological roles. We show that Teff and Treg require distinct metabolic programs to support these functions. Th1, Th2, and Th17 cells expressed high surface levels of the glucose transporter Glut1 and were highly glycolytic. Treg, in contrast, expressed low levels of Glut1 and had high lipid oxidation rates. Consistent with glycolysis and lipid oxidation promoting Teff and Treg, respectively, Teff were selectively increased in Glut1 transgenic mice and reliant on glucose metabolism, whereas Treg had activated AMP-activated protein kinase and were dependent on lipid oxidation. Importantly, AMP-activated protein kinase stimulation was sufficient to decrease Glut1 and increase Treg generation in an asthma model. These data demonstrate that CD4+ T cell subsets require distinct metabolic programs that can be manipulated in vivo to control Treg and Teff development in inflammatory diseases.
Simian Immunodeficiency Virus-Induced Changes in T Cell Cytokine Responses in Cynomolgus Macaques with Latent Mycobacterium tuberculosis Infection Are Associated with Timing of Reactivation
Authors: Mattila Joshua T. , Diedrich Collin R. , Lin Philana Ling , Phuah Jiayao , Flynn JoAnne L.
Published: February 2011

Understanding the early immunologic events accompanying reactivated tuberculosis (TB) in HIV-infected individuals may yield insight into causes of reactivation and improve treatment modalities. We used the cynomolgus macaque (Macaca fascicularis) model of HIV–Mycobacterium tuberculosis coinfection to investigate the dynamics of multifunctional T cell responses and granuloma T cell phenotypes in reactivated TB. CD4+ and CD8+ T cells expressing Th1 cytokines (IFN-γ, IL-2, TNF) and Th2 cytokines (IL-4 and IL-10) were followed from latent M. tuberculosis infection to reactivation after coinfection with a pathogenic SIV. Coinfected animals experienced increased Th1 cytokine responses to M. tuberculosis Ags above the latent-response baseline 3–5 wk post-SIV infection that corresponded with peak plasma viremia. Th2 cytokine expression was not Ag specific, but strong, transient IL-4 expression was noted 4–7 wk post-SIV infection. Animals reactivating <17 wk post-SIV infection had significantly more multifunctional CD4+ T cells 3–5 wk post-SIV infection and more Th2-polarized and fewer Th0-, Th1-polarized CD8+ T cells during weeks 1–10 post-SIV infection than animals reactivating >26 wk post-SIV infection. Granuloma T cells included Th0-, Th1-, and Th2-polarized phenotypes but were particularly rich in cytolytic (CD107+) T cells. When combined with the changes in peripheral blood T cells, these factors indicate that events during acute HIV infection are likely to include distortions in proinflammatory and anti-inflammatory T cell responses within the granuloma that have significant effects on reactivation of latent TB. Moreover, it appears that mycobacteria-specific multifunctional T cells are better correlates of Ag load (i.e., disease status) than of protection.
Surficial geology, Bluegoose River (south), Baffin Island, Nunavut
Authors: Vickers K J , Ward B C , Utting D J
Published: February 2011

This map was produced as part of the Southwest Baffin Integrated Geoscience Project (SWBIG), a joint effort between the Canada-Nunavut Geoscience Office and the Geological Survey of Canada. This map represents the first surficial geology map published for the
area. Earlier Quaternary geology research was conducted on Foxe Peninsula by Blake (1966), including an unpublished glacial landforms map of the region. Initial ice flow interpretations were presented by Utting et al. (2007) and results from a till geochemistry survey are given by Utting and Brown
(2007).
The Chemistry of Atmosphere-Forest Exchange (CAFE) Model – Part 2: Application to BEARPEX-2007 observations
Authors: Wolfe G. M. , Thornton J. A. , Bouvier-Brown N. C. , Goldstein A. H. , Park J.-H. , McKay M. , Matross D. M. , Mao J. , Brune W. H. , LaFranchi B. W. , Browne E. C. , Min K.-E. , Wooldridge P. J. , Cohen R. C. , Crounse J. D. , Faloona I. C. , Gilman J. B. , Kuster W. C. , de Gouw J. A. , Huisman A. , Keutsch F. N.
Published: February 2011

Abstract. In a companion paper, we introduced the Chemistry of Atmosphere-Forest Exchange (CAFE) model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. Here, we apply CAFE to noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007). In this work we evaluate the CAFE modeling approach, demonstrate the significance of in-canopy chemistry for forest-atmosphere exchange and identify key shortcomings in the current understanding of intra-canopy processes. CAFE generally reproduces BEARPEX-2007 observations but requires an enhanced radical recycling mechanism to overcome a factor of 6 underestimate of hydroxyl (OH) concentrations observed during a warm (~29 °C) period. Modeled fluxes of acyl peroxy nitrates (APN) are quite sensitive to gradients in chemical production and loss, demonstrating that chemistry may perturb forest-atmosphere exchange even when the chemical timescale is long relative to the canopy mixing timescale. The model underestimates peroxy acetyl nitrate (PAN) fluxes by 50% and the exchange velocity by nearly a factor of three under warmer conditions, suggesting that near-surface APN sinks are underestimated relative to the sources. Nitric acid typically dominates gross dry N deposition at this site, though other reactive nitrogen (NOy) species can comprise up to 28% of the N deposition budget under cooler conditions. Upward NO2 fluxes cause the net above-canopy NOy flux to be ~30% lower than the gross depositional flux. CAFE under-predicts ozone fluxes and exchange velocities by ~20%. Large uncertainty in the parameterization of cuticular and ground deposition precludes conclusive attribution of non-stomatal fluxes to chemistry or surface uptake. Model-measurement comparisons of vertical concentration gradients for several emitted species suggests that the lower canopy airspace may be only weakly coupled with the upper canopy. Future efforts to model forest-atmosphere exchange will require a more mechanistic understanding of non-stomatal deposition and a more thorough characterization of in-canopy mixing processes.
Determination of time- and height-resolved volcanic ash emissions for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption
Authors: Stohl A. , Prata A. J. , Eckhardt S. , Clarisse L. , Durant A. , Henne S. , Kristiansen N. I. , Minikin A. , Schumann U. , Seibert P. , Stebel K. , Thomas H. E. , Thorsteinsson T. , Tørseth K. , Weinzierl B.
Published: February 2011

Abstract. The April–May 2010 volcanic eruptions of Eyjafjallajökull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that dramatic improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3 ± 4.2 Tg for particles in the size range of 2.8–28 μm diameter and extrapolate this to a total ash emission of 11.9 ± 5.9 Tg for the size range of 0.25–250 μm. We evaluate the results of our a posteriori model using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "normal" flying zone in up to 14% (6–16%), 2% (1–3%) and 7% (4–11%), respectively, of the European area. For a limit of 2 mg m−3 only two episodes with fractions of 1.5% (0.2–2.8%) and 0.9% (0.1–1.6%) occurred, while the current "no-fly" zone criterion of 4 mg m−3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.
Underestimated effects of low temperature during early growing season on carbon sequestration of a subtropical coniferous plantation
Authors: Zhang W.-J. , Wang H.-M. , Yang F.-T. , Yi Y.-H. , Wen X.-F. , Yu G.-R. , Wang Y.-D. , Ning J.-C.
Published: February 2011

Abstract. The impact of air temperature in early months on the carbon sequestration of a subtropical coniferous plantation was discussed by analyzing the eddy flux observations at Qianyanzhou (QYZ) site located in southern China from 2003 to 2008. This site experienced two cold early growing seasons (with temperature anomalies of 2–5° C) in 2005 and 2008, and also a severe summer drought in 2003. Results indicated that the low air temperature from January to March was the major factor controlling the inter-annual variations in net carbon uptake at this site, rather than the previously thought summer drought. The accumulative air temperature from January to February showed high correlation (R2 = 0.970, p < 0.001) with the annual net ecosystem production (NEP). This was due to the controls of early-months temperature on the plant phenology developing and the growing season length at this subtropical site. The cold spring greatly shortened the growing season length and therefore reduced the carbon uptake period. The eddy flux observations showed a carbon loss of 4.04 g C m−2 per growing-season day at this coniferous forest site. On the other hand, the summer drought also reduced the net carbon uptake strength because the photosynthesis was more sensitive to water deficit stress than the ecosystem respiration. However, the impact of summer drought occurred within a relatively shorter period and the carbon sequestration went back to the normal level once the drought was relieved.
Future flood risk estimates along the river Rhine
Authors: te Linde A. H. , Bubeck P. , Dekkers J. E. C. , de Moel H. , Aerts J. C. J. H.
Published: February 2011

Abstract. In Europe, water management is moving from flood defence to a risk management approach, which takes both the probability and the potential consequences of flooding into account. It is expected that climate change and socio-economic development will lead to an increase in flood risk in the Rhine basin. To optimize spatial planning and flood management measures, studies are needed that quantify future flood risks and estimate their uncertainties. In this paper, we estimated the current and future fluvial flood risk in 2030 for the entire Rhine basin in a scenario study. The change in value at risk is based on two land-use projections derived from a land-use model representing two different socio-economic scenarios. Potential damage was calculated by a damage model, and changes in flood probabilities were derived from two climate scenarios and hydrological modeling. We aggregated the results into seven sections along the Rhine. It was found that the annual expected damage in the Rhine basin may increase by between 54% and 230%, of which the major part (~ three-quarters) can be accounted for by climate change. The highest current potential damage can be found in the Netherlands (110 billion €), compared with the second (80 billion €) and third (62 billion €) highest values in two areas in Germany. Results further show that the area with the highest fluvial flood risk is located in the Lower Rhine in Nordrhein-Westfalen in Germany, and not in the Netherlands, as is often perceived. This is mainly due to the higher flood protection standards in the Netherlands as compared to Germany.
Singular value decomposition (SVD) for extraction of gravity anomaly associated with gold mineralization in Tongshi gold field, Western Shandong Uplifted Block, Eastern China
Authors: Zhao B. B. , Chen Y. Q.
Published: February 2011

Abstract. A singular value decomposition (SVD) program on MATLAB platform was effectively used to handle gravity signals for the Tongshi gold field. Firstly, the gravity signals were decomposed into different eigenimages with the help of singular value decomposition method (SVD). Secondly, the thresholds between the eigenvalues reflecting different layers of ore-controlling factors were established by multi-fractal method. Finally images reflecting different layers of ore-controlling factors were rebuilt. This yielded two layers of two-dimensional singular value images that depict regional and local ore-controlling factors, respectively. 1. The regional ore-controlling factor is a saddle valley with the gravity anomaly values varying from −55 to 51 μm s−2 on the NW trending swell with the gravity anomaly values varying from −55 to 567 μm s−2 on the SW side of the Mesozoic volcanic sedimentary basin with the gravity anomaly values varying from −56 to −974 μm s−2. The saddle valley might be tectonically an extensional area where the Tongshi complex pluton and all gold deposits are located and thus this area is favorable for gold deposits. 2. The local ore-controlling factor is the Tongshi complex pluton with a negative circular gravity anomaly varying from −339 to −11 μm s−2 and the ring contact metasomatic mineralization zone around the Tongshi complex with the positive gravity anomaly varying from 37 to 345 μm s−2. The skarn and porphyry types of gold deposits are located within the complex pluton and the Carlin and cryptobreccia types of gold deposits are located within the contact metasomatic mineralization zone. Thus both of them are potential areas for gold deposits. 3. The Tongshi gold field exhibits a typical complexity with multi-layers of ore-controlling factors.
“Ten steps for the maternal breastfeeding success” compliance in “baby-friendly hospitals” in Recife, Pernambuco, Brazil
Authors: Albuquerque Karla Alexsandra de , Osório Monica Maria
Published: February 2011

ABSTRACTObjective: to evaluate the performance of the "Ten Steps to Successful Breastfeeding" in "Baby-Friendly Hospitals" in Recife, Pernambuco, Brazil. Method: a survey conducted by interviewing 419 mothers in five Baby-Friendly Hospitals, reference centers in the state. The sample was based on the number of deliveries performed in the 12 months prior to data collection. For inclusion of the mothers: prenatal care and deliveries in the research institution, the postpartum period> 6 hours, absence of clinical complications during childbirth and immediate postpartum, newborn low-risk. This study was approved by the Ethics Committee of Research of the hospitals. Results: steps 6, 7 and 9 were reported as completed by more than 80% of mothers. The Steps 3 and 5 are below the normalized (
Studies in the Dispersion of SRF Carbon Black in Butyl Rubber
Authors: Ford F. P. , Mottlau A. Y.
Published: February 2011

A simple method is described for producing different degrees of carbon black dispersion in elastomers under controlled laboratory conditions. Careful selection of milling conditions has made possible the preparation of stocks possessing variations in degree of dispersion, comparable to the wide differences noted in practice. A new technique is described for studying these carbon black dispersions in rubber by means of the electron microscope. Such studies show large differences in degree of agglomeration of carbon black in compounds made under simple variations of conditions. Representative electron micrographs are shown. Good correlation is obtained between these micrographs and light transmission measurements of dilute solutions of the compounds. Such photometric analysis provides a simple method for the measurement of carbon black dispersion in research or control work. The observed differences in degree of dispersion have an effect on the physical properties of the unvulcanized compounds. This effect was observed by means of the parallel-plate plastometer. The viscosity values obtained with this instrument show a direct correlation with electron micrographic observations. Some of the practical and theoretical implications of this study are discussed with reference to recent work in this field by other investigators.
Copolymerization Theory of the Vulcanization of Rubber. VI. Hydrogen Sulfide Effects and Some Self-Limiting Features
Authors: Craig David , Juve A. E. , Davidson W. L. , Semon W. L. , Hay D. C.
Published: February 2011

Vulcanization with sulfur is ascribed to the formation of sulfur radicals, which are believed to copolymerize with the double bonds of the rubber molecule. Hydrogen sulfide is proposed as necessary for chain initiation, but, when formed in sufficient amounts, it serves as a chain terminator. This is believed to lead to numerous self-limiting features, including ceiling temperatures, postvulcanization, and delayed-action effects. Initiation may result from the oxidation of H2S to sulfur radicals, and termination to the formation of HS radicals.
Cold Mastication of Rubber
Authors: Watson W. F.
Published: February 2011

The processes underlying the plasticizing of rubber by cold and hot mastication are of different chemical types. In hot mastication, plasticizing is caused by oxidative reactions. In cold mastication, plasticizing is due to a primary rupture of the long chain rubber molecules by the applied deformation forces, and a secondary consummation of this rupture by oxygen or other compounds reactive towards the ruptured chains. Alternative to consummation of rupture, certain compounds thereby initiate cross-linking. Experimental results are quoted in support of this interpretation of cold mastication processes and some practical conclusions are drawn.
Structure of Alkali Metal-Catalyzed Butadiene Polymers
Authors: Meyer A. W. , Hampton R. R. , Davison J. A.
Published: February 2011

The structures of various sodium and potassium-catalyzed butadiene polymers were determined from infrared absorption measurements. All of the polymers had a higher proportion of butadiene in the 1,2-configuration (45–80 per cent) than emulsion polybutadiene (18–23 per cent). Polybutadienes catalyzed by potassium had 15–20 per cent less butadiene in the 1,2-configuration than those in which sodium was the catalyst. When a mixture of sodium and potassium was used, the results were nearly the same as with the potassium catalyst alone. Polybutadienes made at 5° had 10 to 15 per cent more butadiene in the 1,2-configuration than those made at 45°. Diluent type had little or no effect on the structure of the polybutadienes. The butadiene portions of butadiene-styrene copolymers were found to have the same relative proportions of 1,2-, cis-1,4- and trans-1,4-configurations as the butadiene homopolymers. The second order transition temperature of sodium-catalyzed polybutadiene polymerized at 30° was −45°, whereas the 75° polybutadiene had a value of −64°.
Studies on the Yellow Fraction of Latex
Authors: van Gils G. E.
Published: February 2011

The investigations described in this paper are part of the studies of fresh latex carried out at the INIRO (Indonesian Rubber Research Institute). For readers not acquainted with the special subject, it may be useful to mention that Homans and van Gils have found that fresh Hevea latex is not solely a dispersion of rubber globules in an aqueous medium, the serum, but that there are also present large colloidal jellylike units or agglomerations of them, constituting a separate phase in the rubber dispersion. These bodies were called lutoids by the discoverers, because they contained the yellow coloring substances of the rubber. Under a microscope, however, these lutoids look like transparent islands against a darker background of rubber particles. After centrifugation, the lutoids are separated at the bottom of the tube and look like a viscous yellowish jellylike mass, containing a low percentage of rubber. It is also possible to separate this mass by other means. As a whole, these agglomerations of lutoids are called the yellow fraction. The remaining latex is called the white fraction. Investigations carried out at the Rubber Research Institutes in Indonesia and Malaya have shown that the lutoids are responsible for many phenomena occurring in fresh latex. Recent studies of Ruinen seem to indicate that the lutoids are also involved in the rubber formation in the tree.
Effect of Carbon Black on the Development of Oxidation Processes in Raw and Vulcanized Rubbers
Authors: Kuzmixskiĭ A. S. , Lyubchanskaya L. I. , Khitrova N. G. , Bass S. I.
Published: February 2011

Publications by Rebinder, Ab, and Vei˘ler, Pisarenko and Rebinder, and Dogadkin, Pechkovskaya, and Chernikina have been devoted to an explanation of the mechanism of the accelerating action of carbon blacks. However, only fragmentary and contradictory information about the influence of carbon blacks on the development of oxidation processes is found in scientific literature. In the present article, several important laws regarding the role of channel carbon black in the oxidation of sodium-butadiene rubber are studied. Carbon black can be incorporated in rubber in high proportions (100–125 parts by weight to 100 parts of rubber). It is well known how great is the influence of the surface area of reaction vessels in which the rupture of chains takes place on the development of chain reactions. It is also known that the oxidation of any type of rubber is a chain process of decomposition, with formation of side chains. Therefore in the study of these processes in rubbers, it is necessary to take into account the highly developed surface of contact between the carbon black and rubber particles.
Creep, Recovery, and Permanent Set for GR-S and Hevea
Authors: Gehman S. D.
Published: February 2011

A study was made of creep, recovery, and permanent set of Hevea and GR-S over a 1000-hour period and a range of elongations at 35° C. Creep of GR-S is greater than that of Hevea. The stress of GR-S is considered to be supported to a greater extent by a relatively unstable secondary bond structure. This is consistent with the large creep values of GR-S at low elongations and the large ratio of primary or recoverable creep to permanent set. Hevea, in contrast, shows low creep at both high and low elongations and maximum creep at intermediate elongations for which the structure is heterogeneous, consisting of amorphous and crystalline phases. A procedure was worked out for determining the contribution of permanent set to the observed creep. The creep curves were concave to the strain axis when plotted against logarithmic time. After correction was made for permanent set, they were found to be approximately linear, thus extending the range of application of the Tobolsky-Eyring theory of creep. At the start of the creep test the flow appears to be due largely to the reversible yielding of relatively weak bonds which can reform under the action of the elastic network when the stress is removed. For longer periods of time, or for higher elongations, the flow involves more deep seated changes in structure. Larger units of structure are displaced or stronger bonds broken with resultant permanent molecular displacements upon removal of the stress. For Hevea at high elongations all of the flow was accounted for by permanent set.
Factors Influencing the Configuration of Carbon Particles in Rubber
Authors: Parkinson D. , Blanchard A. F.
Published: February 2011

The properties of rubber vulcanizates containing channel black can be modified either by heat treatment under certain conditions of the rubber-carbon stock or by addition to the stock of small quantities of certain chemical substances, including benzidine. The effects of heat treatment and benzidine are to some extent additive, and it is shown by electrical resistance measurements that they are associated with changes in the configuration of the carbon particles in the rubber. The resistivity of unvulcanized channel black-rubber stocks depends on the temperature and on any temporary stretching or flexing to which the rubber may have been subjected. Any change which causes increased carbon structure which may occur when the stock is heated is reversed when it is cooled and strained. Remilling of rubber-black stocks results in an increased electrical resistance, due to a breaking down (decatenation) of chains of carbon particles. This effect is enhanced by previous heating of the stock or by incorporation of benzidine. Once the structure is broken down in this way there is no evidence that it can be formed again. For these and other reasons the hypothesis that individual carbon particles flocculate in rubber by a mechanism such as Brownian movement of the particles is rejected. It is suggested that the increased resilience of carbon-rubber vulcanizates following heat or benzidine treatment of the unvulcanized stock results from an increase of the carbon-rubber attachments at the expense of the carbon-carbon attachments.
Study of the Reaction of Buna Rubbers with Aliphatic Thiols
Authors: Serniuk G. E. , Banes F. W. , Swaney M. W.
Published: February 2011

Thioglycolic acid added exothermally to butadiene polymers and copolymers in benzene solution under mild conditions to give apparent double-bond saturation values of 38 to 47 per cent. When the same polymers reacted with aliphatic thiols of C2 to C16 chain length, in mass or latex reactions, saturation values were obtained which were in accord with those found by thioglycolic acid addition. It is suggested that the double bonds in butadiene polymers and copolymers which were readily saturated by the above thiols are predominately those present in the polymer chains as vinyl side groups.
Steam and Radio-Frequency Curing of Natural Rubber
Authors: Sharbaugh A. H.
Published: February 2011

The object of this investigation was to compare the resulting vulcanizates when natural rubber is cured in a conventional steam-heated mold and when it is cured by dielectric losses at radio frequencies under identical time-temperature conditions. In practice it is of course recognized that dielectric heating offers many advantages in speeding up heating processes through its inherent ability to heat uniformly throughout the mass, compared with relatively slower heating where heat is conducted in from hot surfaces. The purpose was, then, to determine if any appreciable difference in vulcanizates is obtained when identical conditions of time and temperature are artificially maintained by the two methods. One series of tests was made on samples with different curing times at a fixed curing temperature; another series was carried out with a fixed curing time, with the temperature the independent variable. Finally a comparison was made with samples which had a curing cycle consisting of a gradually rising temperature during a relatively short curing time—that is, the type of temperature variation normally encountered in a radio-frequency cure when a constant radio-frequency field is imposed on a rubber load. The vulcanizates were evaluated physically by measuring their stress-strain relationships and ultimate tensile properties, electrically by their dielectric constant and loss factor-frequency dependence, and chemically by the amount of sulfur of vulcanization. No significant differences were observed in the rubber products cured by the two methods.
Reclaiming Agents for Synthetic Rubber
Authors: Cook W. S. , Albert H. E. , Kilbourne F. L. , Smith G. E. P.
Published: February 2011

Some highly alkylated phenol sulfides have proved to be among the most active reclaiming agents for GR-S and other synthetic rubbers. A study has been made of the activities of these materials as related to molecular structure and to the fate of sulfur during the reclaiming process. The nature and mechanism of the chemical reactions taking place during the reclaiming of natural and synthetic rubbers have been discussed in the light of the results obtained.
Polymeric Unsaturation and Relative Rate of Cross-Linkage
Authors: Zapp R. L.
Published: February 2011

In conventional vulcanization reactions with sulfur and accelerator, the rate as well as the extent of cross-linking to form polymer networks depends on the concentration of chemical unsaturation. The purpose of this paper was to determine the relationships between polymeric unsaturation and the rate of vulcanization. The course of the cross-linking reaction was followed by volume swelling measurements converted to a relative cross-linked index; this index is shown to be directly related to extension modulus before the onset of crystallization. Experimental evidence with a system of polymer, zinc oxide, sulfur, and tetramethylthiuram disulfide closely approaches the hypothesis, based on the possible paths of cross-linkage between adjacent chains. The experimental equation, at constant relative cross-links of 18.2 at 1000 per cent volume increase in cyclohexane, is t=c/n1.8 when adjustments are applied. When a system utilizing benzothiazyl monocyclohexyl sulfenamide is studied, the time to a constant state of vulcanization is related to the reciprocal of the first power of the unsaturation, t=c/n. In both relations, t is time, n is the polymeric unsaturation, and c is a constant which depends on the temperature and state of cure. The difference in response to polymeric unsaturation by these two types of accelerators is reflected in the percentage of combined sulfur for a given concentration of cross-links (state of cure). The thiuram requires less combined sulfur for a given state of vulcanization than does the thiazole, whereas a nonaccelerated mixture requires still more combined sulfur for a given state of cure. In an attempt to rationalize the differences in accelerator behavior, four points are discussed which involve the concepts of active centers, carbon-carbon linkages, varying porportions of sulfur in a carbon-sulfur-carbon bridge, and consideration of inter- and intramolecular linkages.
Semiebonites
Authors: Rostler Fritz S.
Published: February 2011

To summarize the principal results of the present investigation, it was found that whereas natural rubber is a poor raw material for the manufacture of semiebonite, butadiene-styrene and butadiene-acrylonitrile rubbers are suitable raw materials, especially in combination with unsaturated hydrocarbon extenders of the Naftolen type. The superiority of GR-S to natural rubber in the form of semiebonite should be an interesting piece of information for every compounder conscientious about the importance of keeping up the use and the manufacture of GR-S. With natural rubber becoming more and more available, there exists, as we all know, the definite danger that GR-S will be pushed into the background. As a matter of fact, we are approaching the situation where the supply of rubber hydrocarbons, natural and synthetic, will exceed the demand by multiples if new uses for rubber in large volume are not found. The increased use of rubber products in the building and construction industry and in road surfacing might provide such an outlet for rubber. Semiebonite with good aging qualities might find many uses along these lines. It might lend itself to the manufacture of floor coverings, of waterproof wall insulation, etc. The possibilities of using semiebonites from GR-S for tire beads has been suggested in a previously published article, but no detailed study comparing various rubbers has been reported. The primary purpose of this report is to present these basic data, which can be used as starting points for compound development and to point out that we have in the semiebonite range a possibility of using GR-S to advantage. As to butadiene-acrylonitrile rubbers, with which, in distinction to GR-S, very useful semihard rubber products can be made with phenolic resins, the medium sulfur range opens the possibility of making semiebonites which are easier to process and cheaper than resin combinations. The use of plastics in the rubber industry was recently discussed and summarized by Winkelmann. The compounding of semiebonites with Naftolen-type products offers a means of regulating the plasticity of the uncured stock as well as the elongation of the vulcanizate. Aging and prevention of sulfur bloom appear also improved. In other words, it was found that the combined use of 15 to 20 parts of sulfur with 15 to 50 parts of a Naftolen-type hydrocarbon gives a satisfactory semiebonite with GR-S, as well as with Hycar, and both these rubbers appear superior to natural rubber in semiebonites.
Sulfur Linkage in Vulcanized Rubber. Reaction of Methyl Iodide with Sulfur Compounds
Authors: Selker M. L.
Published: February 2011

The work described here is an extension of the study of the reaction of methyl iodide with sulfur compounds originally begun with the purpose of using such data in determining the sulfur linkage in vulcanized rubber. A previous paper dealt with the reactions of methyl iodide with propanethiol, propyl sulfide, propyl disulfide, allyl sulfide, and thiophene. This article adds to the list, n-butyl methallyl sulfide, allyl disulfide, allyl tetrasulfide, n-propyl tetrasulfide, and trithiane. The removal of combined sulfur from vulcanized rubber as trimethylsulfonium iodide on treatment with methyl iodide at room temperature was persuasive evidence of the presence of sulfide sulfur linked to allylic type residues. The evidence offered, however, did not constitute exclusive proof because it was not known whether still other types of sulfur linkage would also yield trimethylsulfonium iodide. To shed more light on this question, the sulfur linkages most likely to occur in vulcanizates—the allyl-alkyl monosulfide, diallyl and dialkyl di- and polysulfide—were investigated. The trithiane reaction is of interest mostly from the point of view of the reaction of overcured stocks or secondary reaction products stemming from the original polysulfides. The reactions were carried out using the method described in a previous paper.
Strain Tester for Rubber
Authors: Holt W. L. , Knox E. O. , Roth F. L.
Published: February 2011

A tester for measuring the strain of rubber vulcanizates when subjected to a predetermined stress is described. The operation of the tester and a description of the apparatus for cutting and measuring the test specimens are presented. With this equipment routine determinations of a point on the stress-strain curve can be made with greater accuracy and precision than has hitherto been possible with the usual stress-strain equipment. This strain test also requires less labor than the customary stress tests.
Preparation of Dried Latex Films
Authors: Maron Samuel H. , Madow Benjamin
Published: February 2011

Various technical applications of latex call for the formation of a latex film and its drying by evaporation of the water in which the rubber is dispersed. The same problem is encountered also in the preparation of dried latex films, both uncompounded and compounded, for film testing for tensile, elongation, and other properties. Very frequently the preparation of such films is complicated by the development of surface cracks and ridges in the drying films, which mar the appearance of the films, detract from their strength, and make testing difficult and uncertain. These imperfections in the films generally arise from the formation of impervious surface skins on the drying latex. Such impervious skins lead to shrinkage and subsequent cracking of the films on the one hand, and to bubble formation on the other. The result is that the preparation of dried latex films by this method becomes a very slow process, which yields as a rule films of inferior appearance and quality. It was found in this laboratory that many of the difficulties encountered in the preparation of latex films by evaporation can be overcome by appropriate control of humidity in the initial drying stages, and the use of an agent which prevents formation of the impervious surface skins on the drying latex. The agent found to be most suitable with alkaline latexes for the latter purpose is carbon dioxide gas. By utilizing moisture and carbon dioxide in a definite technique, films can be prepared from various latexes which are smooth and uniform in thickness and possess improved appearance and properties. The purpose of this paper is to describe the technique developed for preparation of dried latex films by casting, and to give some results for tensile and elongation obtained on GR-S, Hycar, Neoprene, and natural latexes.
Properties of Ebonite. XXVIII. Influence of Light-Absorbent Pigments on Electrical Surface Deterioration during Exposure to Light
Authors: Fisher D. G. , Scott J. R.
Published: February 2011

The incorporation of gas black, ferric oxide, and lead titanate, which absorb actinic rays, into rubber-sulfur ebonites did not reduce the rate of electrical surface deterioration appreciably. It increased the final equilibrium resistivity, but not sufficiently for the increase to be of much practical value. This result confirms the conclusion from a study of the mechanism of surface deterioration that a light-absorbent pigment is unlikely to be effective in retarding deterioration because its particles are relatively large and far apart in comparison with the thickness of the surface layer responsible for the deterioration. The use of the mercury-vapor lamp causes a more rapid deterioration than daylight, but does not appear to alter the order in which the samples range themselves.
Properties of Ebonite. XXIX. The Absorption Spectrum of Ebonite
Authors: Dock E. H. , Porritt B. D. , Willott W. H.
Published: February 2011

The absorption spectrum of ebonite has some practical interest, because the absorption of light causes the surface to deteriorate. A knowledge of the absorption spectrum should help in discovering which are the harmful rays. Published information hitherto appears to be limited to radiation of long wave length, i.e., thermal or infrared. The present note describes experiments on rubber-sulfur (65:35 or 68:32) compositions vulcanized for about 5 hours at 155° C. Owing to the great opacity of ebonite, it is necessary to work with very thin specimens. Various methods of obtaining these suggest themselves: (1) grinding down a small thin sheet; (2) cutting thin shavings; (3) vulcanizing as of a thin film between glass or quartz plates; (4) vulcanizing a film of rubber, deposited on glass or quartz, by immersion in molten sulfur; (5) vulcanizing a deposited film of a rubber-sulfur mix by heating in an inert gas. Methods (1), (2) and (5) have so far been found the most satisfactory. In method (2) it is advantageous to soften the material by swelling, e.g., in nitrobenzene; the swelling liquid can then be removed by extraction with a volatile solvent. Methods (1) and (2) have the advantage of enabling specimens to be obtained from larger pieces that can be analyzed or submitted to other tests.