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At least 325 records · Page 18Linked to original sources
PubMed2006

Bacterial endocarditis following rubber band ligation in a patient with a ventricular septal defect: report of a case and guideline analysis.

Rubber band ligation is a common option used to treat symptomatic internal hemorrhoids. Severe complications such as pelvic sepsis are a rare occurrence. We report a case of endocarditis leading to septic pulmonary and renal emboli following single-quadrant rubber band ligation. The patient had a known ventricular septal defect and developed low back pain and fever after ligation of a right anterior internal hemorrhoid. He was found to have septic pulmonary emboli, a renal wedge septic infarct, and a large vegetation on his membranous ventricular septal defect requiring operative intervention. Before this report, rubber band ligation has not been associated with endocarditis. According to several guidelines, this patient did not require antibiotic prophylaxis. It is unclear whether prophylaxis could have prevented this complication. Surgeons utilizing rubber band ligation need to be familiar with all potential complications.

Endocarditis, Bacterial↗
PubMed2004

Rhinolithiasis: a very late complication after dacryocystorhinostomy with rubber-gum and polyethylene stenting.

PURPOSE: To describe a rare case of rhinolith formation 21 years after dacryocystorhinostomy (DCR) with rubber gum and polyethylene tubing surgery. DESIGN: Interventional case report. METHODS: A 23-year-old-woman underwent uneventful left DCR with rubber gum and polyethylene tubing for chronic dacryocystitis. Twenty-one years later, she presented with purulent rhinorrhea, nasal obstruction, and facial pain. Computed tomography revealed a radiopaque density in the left nasal cavity. RESULTS: A rubber gum foreign body embedded with granulation tissue and a huge rhinolith was removed endoscopically through the anterior nares. After surgery, the patient reported immediate and complete relief of symptoms. CONCLUSION: Rhinoliths can develop progressively several years after DCR as a result of foreign body reaction to rubber gum or polyethylene tubing. This rare complication should be ruled out in patients complaining of purulent rhinorrhea who underwent DCR with tubing before the early 1980s.

Adult↗
PubMed2006

A follow-up study of women in the synthetic rubber industry: study methods.

BACKGROUND: Concerns about the possible toxic effects of workplace exposures in the synthetic rubber industry have centered on 1,3-butadiene (BD), styrene and dimethyldithiocarbamate (DMDTC). Our previous mortality studies of over 17,000 male synthetic rubber workers found an excess of leukemia that may be due to BD or BD plus other chemicals. Experimental studies have shown that BD produces mammary tumors in female mice and rats and ovarian tumors in female mice. AIM: This paper presents the methods of a follow-up study that evaluates the mortality experience of women employed in the North American synthetic rubber industry. METHODS: Women employed for at least 1 day at any of eight North American styrene-butadiene rubber plants were followed up from 1943 to 2002. Identifying and work history information were obtained from personnel records. Estimated quantitative exposure to BD, styrene and DMDTC, developed for our previous study of men, were used in this study. External analyses use the standardized mortality ratios (SMRs) to compare the cohort's cause-specific mortality rates to the rates of the female general population of the states or the province where the plants are located. Internal analyses use the Poisson regression and Cox proportional hazards models to examine specific cancer mortality rates in relation to BD, styrene and DMDTC exposure, by comparing an exposed cohort subgroup with the rate of unexposed cohort members.

Animals↗
PubMed2005

Formation of calcium crystallites in dry natural rubber particles.

In this paper, the effects of drying and aging of natural rubber particles of Hevea brasiliensis are studied. The evolutions of the particle morphology and of the elemental distribution are investigated using electron-energy-loss spectroscopy imaging in a low-energy transmission electron microscope (ESI-TEM). It is found that when the sample is aged, calcium salt crystallites are formed around the particles. Fusion of these crystallites with time to form larger crystals shows evidence of ion mobility in the dry rubber matrix. Electron diffraction patterns and elemental mapping analysis indicate the crystals to be calcium sulfate. These crystallites are closely associated with membrane materials of the rubber particle and are surprisingly compatible with the hydrocarbon matrix of the rubber particle. It is proposed that polar sites on the membrane materials provide nucleation sites for the crystallization of calcium and sulfate ions from the latex serum.

Ammonia↗
PubMed2005

Ultrasound facilitates and improves removal of Cd(II) from aqueous solution by the discarded tire rubber.

Some of the heavy metal ions such as cadmium are toxic and represent as hazardous pollutants due to their persistence in the environment. In this study the ground discarded tire rubber was used for the sorption of cadmium from aqueous solution. The batch sorption tests were conducted to investigate the sorption of Cd(II) by discarded tire rubber in the presence and absence of ultrasound. To assess the capability of sorbent, research parameters such as ultrasonic waves, solution temperature, particle size of ground tire and others were investigated. The experimental data were fitted in Langmuir model better than Freundlich one. Therefore, the former model was applied to the sorption equilibrium in order to determine the maximum metal sorption capacity in the presence and absence of ultrasound. The Langmuir constants were also obtained from the isotherms under different conditions. In the presence of ultrasound the tire rubber was a more efficient sorbent for this pollutant than its absence. According to the results, the internal porous and film diffusions were both effective in the sorption process. The porous and film diffusion coefficients of the ground tire rubber were, respectively, about 1.8 and 2.7 times more in the presence of ultrasound than its absence. The effect of ultrasound on the sorption process could be explained by the thermal and non-thermal properties of ultrasonic field.

Biodegradation, Environmental↗
PubMed2002

High frequency testing of rubber mounts.

Rubber and fluid-filled rubber engine mounts are commonly used in automotive and aerospace applications to provide reduced cabin noise and vibration, and/or motion accommodations. In certain applications, the rubber mount may operate at frequencies as high as 5000 Hz. Therefore, dynamic stiffness of the mount needs to be known in this frequency range. Commercial high frequency test machines are practically nonexistent, and the best high frequency test machine on the market is only capable of frequencies as high as 1000 Hz. In this paper, a high frequency test machine is described that allows test engineers to study the high frequency performance of rubber mounts at frequencies up to 5000 Hz.

Aircraft↗
PubMed2003

Activation and inhibition of rubber transferases by metal cofactors and pyrophosphate substrates.

Metal cofactors are necessary for the activity of alkylation by prenyl transfer in enzyme-catalyzed reactions. Rubber transferase (RuT, a cis-prenyl transferase) associated with purified rubber particles from Hevea brasiliensis, Parthenium argentatum and Ficus elastica can use magnesium and manganese interchangably to achieve maximum velocity. We define the concentration of activator required for maximum velocity as [A](max). The [A](max)(Mg2+) in F. elastica (100 mM) is 10 times the [A](max)(Mg2+) for either H. brasiliensis (10 mM) or P. argentatum (8 mM). The [A](max)(Mn2+) in F. elastica (11 mM), H. brasiliensis (3.8 mM) and P. argentatum (6.8 mM) and the [A](max)(Mg2+) in H. brasiliensis (10 mM) and P. argentatum (8 mM) are similar. The differences in [A](max)(Mg2+) correlate with the actual endogenous Mg(2+) concentrations in the latex of living plants. Extremely low Mn(2+) levels in vivo indicate that Mg(2+) is the RuT cofactor in living H. brasiliensis and F. elastica trees. Kinetic analyses demonstrate that FPP-Mg(2+) and FPP-Mn(2+) are active substrates for rubber molecule initiation, although free FPP and metal cations, Mg(2+) and Mn(2+), can interact independently at the active site with the following relative dissociation constants K(d)(FPP) <K(d)(FPP-Metal) <K(d)(E-Metal). Similarly, IPP-Mg(2+) and IPP-Mn(2+) are active substrates for rubber molecule polymerization. Although metal cations can interact independently at the active site with the relative dissociation constant K(d)(IPP-Metal) <K(d)(E-Metal), unlike FPP, IPP alone does not interact independently. All three RuTs have similar characteristics-indeterminate sized products, high K(m)(IPP), high metal [A](max), metal cofactor requirements, and are membrane-bound enzymes.

Asteraceae↗
PubMed2002

The leaching of inorganic species from activated carbons produced from waste tyre rubber.

Waste tyre rubber can be used as a precursor for the production of high quality activated carbons. However, there is concern that inorganic impurities present in the rubber feed may restrict their use in liquid phase applications with high purity requirements. This paper presents an investigation of the presence and the leaching of inorganic species from activated carbons derived from waste tyre rubber. For the purpose of this work, a number of carbons were produced, characterised for their BET surface area and analysed for their inorganic composition. Subsequently, a number of tests were performed to evaluate the leaching of different inorganic species into solution at various pH values and carbon doses. Results showed that rubber-derived carbons contained elevated concentrations of sulphur and zinc, as well as traces of other metals such as lead, cadmium, chromium and molybdenum. Inorganic levels were significantly affected by production conditions, particularly degree of carbon activation and the nature of the gasification agent. However, leaching tests showed that the availability of these species in neutral pH conditions was very limited. Results demonstrated that, when using carbons doses comparable to those employed in water treatment works, only sulphur levels exceeded, in some occasions, health based quality standards proposed for drinking water.

Carbon↗
PubMed2003

Syringes with rubber-coated plungers and inactivation of surfactant.

Injectable drugs are generally administered to newborns with 1 mL syringes. During in-vitro measurements of surface tension with a pulsating bubble surfactometer, we noticed that surfactant was inactivated after repeated aspiration into a 1 mL syringe with a rubber-coated plunger. Inactivation did not take place, however, when we used rubber-free two-part syringes with polyethylene pistons. Results of further studies showed that the silicone fluid used to lubricate the rubber surface of the syringe was inactivating the surfactant. Our findings suggest that contact with rubber surfaces should be avoided in the handling of surfactant material for biophysical assessment or clinical use.

Equipment Design↗
PubMed1986

Effect of rubbers and their constituents on proliferation of Legionella pneumophila in naturally contaminated hot water.

The proliferation of Legionella pneumophila serogroups 1, 9, and 10 in naturally contaminated hot potable water was measured after the addition of various rubbers and their constituents. When compared with controls 9/14 rubbers and 15/30 constituents shortened lag time for growth of L pneumophila at 37 degrees C and, produced a 10-100 000 fold increase in the number of L pneumophila organisms. In most experiments this increase was due mainly to the growth of L pneumophila serogroup 10, which predominated in all fresh water samples (47-53 degrees C); in others a shift in predominance from serogroup 10 to serogroup 1 occurred. Rubbers containing thiuram did not enhance the growth of L pneumophila, while the addition of thiuram alone inhibited growth. Therefore thiuram-containing rubbers should be used in water systems.

Equipment Contamination↗
PubMed1999

Natural rubber base matrix containing Calendula officinalis plant as a source of molluscicdal saponin.

Natural rubber (NR) has been used as a binding matrix for Calendula officinalis, where it is used as a vulcanizate. Various doses of the plant covering the range from 100 up to 200 parts per 100 of rubber (phr) were found suitable for processing conditions using conventional rubber mixing equipment. The release rate of saponin was extended to over 4 months. Incorporation of fillers, such as HAF and Hisil, in the compounded rubber decreased the release of saponin; especially in the first period of immersion. The amount of saponin released was affected by the environmental temperature and the type of fillers present in the formulations. The scanning electron micrographs illustrate the presence of a tortuous pass and pore structure that formed after soaking in water and leaching process occurred.

Animals↗
PubMed1998

Latex: a cause of allergic contact eczema in users of natural rubber gloves.

BACKGROUND: Latex is a common cause of contact urticaria in glove users. We recently found that 1.2% of patients attending a contact dermatitis investigation unit had delayed type hypersensitivity to latex as a cause of eczema. OBJECTIVE: We reassessed the relevant contact allergens in users of natural rubber gloves with hand dermatitis. Particular emphasis was placed on allergens not included in the standard patch test series. METHODS: Consecutive natural rubber glove users with hand dermatitis were investigated for the presence of contact dermatitis and urticaria. RESULTS: One hundred seventeen consecutive patients were tested. The American standard series missed 34% and the European 40% of patients with positive patch test reactions to rubber related chemicals. Six percent of patients (20% of those with a positive reaction) demonstrated delayed type hypersensitivity to latex, often in the absence of other relevant contact allergens and contact urticaria to latex. CONCLUSION: Latex is a relatively common cause of allergic contact eczema in the absence of contact urticaria. Latex should be included in a rubber series for screening patients with hand dermatitis who are glove users.

Adolescent↗
PubMed2002

Removal of phenol from aqueous solution and resin manufacturing industry wastewater using an agricultural waste: rubber seed coat.

Activated carbon prepared from rubber seed coat (RSCC), an agricultural waste by-product, has been used for the adsorption of phenol from aqueous solution. In this work, adsorption of phenol on rubber seed coat activated carbon has been studied by using batch and column studies. The equilibrium adsorption level was determined to be a function of the solution pH, adsorbent dosage and contact time. The equilibrium adsorption capacity of rubber seed coat activated carbon for phenol removal was obtained by using linear Freundlich isotherm. The adsorption of phenol on rubber seed coat activated carbon follows first order reversible kinetics. The suitability of RSCC for treating phenol based resin manufacturing industry wastewater was also tested. A comparative study with a commercial activated carbon (CAC) showed that RSCC is 2.25 times more efficient compared to CAC based on column adsorption study for phenolic wastewater treatment.

Adsorption↗
PubMed2003

Environmental impact of highway construction and repair materials on surface and ground waters. Case study: crumb rubber asphalt concrete.

The practice of incorporating certain waste products into highway construction and repair materials (CRMs) has become more popular. These practices have prompted the National Academy of Science, National Cooperative Highway Research Program (NCHRP) to research the possible impacts of these CRMs on the quality of surface and ground waters. State department of transportations (DOTs) are currently experimenting with use of ground tire rubber ( crumb rubber) in bituminous construction and as a crack sealer. Crumb rubber asphalt concrete (CR-AC) leachates contain a mixture of organic and metallic contaminants. Benzothiazole and 2(3H)-benzothiazolone (organic compounds used in tire rubber manufacturing) and the metals mercury and aluminum were leached in potentially harmful concentrations (exceeding toxic concentrations for aquatic toxicity tests). CR-AC leachate exhibited moderate to high toxicity for algae ( Selenastrum capriconutum) and moderate toxicity for water fleas ( Daphnia magna). Benzothiazole was readily removed from CR-AC leachate by the environmental processes of soil sorption, volatilization, and biodegradation. Metals, which do not volatilize or photochemically or biologically degrade, were removed from the leachate by soil sorption. Contaminants from CR-AC leachates are thus degraded or retarded in their transport through nearby soils and ground waters.

Animals↗
PubMed2001

Bacterial degradation of natural and synthetic rubber.

The degradation of natural rubber (NR), synthetic poly(cis-1,4-isoprene) (SR), and cross-linked NR (latex gloves) by Gram-positive and Gram-negative bacteria was analyzed by weight loss, gel permeation chromatography, and determination of the protein content. Weight losses of 11-18% and an increase in protein up to 850 microg/mL after incubation of Nocardia sp. DSMZ43191, Streptomyces coelicolor, Streptomyces griseus, bacterial isolate 18a, Acinetobacter calcoaceticus, and Xanthomonas sp. with latex gloves as a carbon source indicated degradation of the polymer. An increase of protein up to 1250 microg/mL was obtained upon incubation of the bacteria with SR. No or only little weight losses and no increase in the protein content were found for nondegrading control strains such as Streptomyces lividans and Streptomyces exfoliatus and for mutants of degrading strains of S. coelicolor and S. griseus, which have been identified by their inability to produce clearing zones on opaque latex agar. Measurement of the average molecular weight of synthetic rubber before and after degradation showed a time-dependent shift to lower values for the degrading strains. Diketone derivates of oligo(cis-1,4-isoprene) were identified as metabolites of rubber degradation. An oxidative degradation pathway of poly(cis-1,4-isoprene) to acetyl-coenzymeA and propionyl-coenzymeA by beta-oxidation is suggested for bacterial degradation of isoprene rubber.

Acrylates↗
PubMedDate not supplied

Microbial scission of sulfide linkages in vulcanized natural rubber by a white rot basidiomycete, Ceriporiopsis subvermispora.

A white rot basidiomycete, Ceriporiopsis subvermispora, degraded vulcanized natural rubber (NR) sheets on a wood medium. The fungus decreased the total sulfur content of the rubber by 29% in 200 days, accompanied by the cleavage of sulfide bonds between polyisoprene chains. X-ray photoelectron spectroscopy (XPS) demonstrated that C. subvermispora reduced the frequency of S-C bonds by 69% with a concomitant formation of S-O bonds during the culture period. Dipolar decoupling/magic angle spinning (DD/MAS) solid state 13C NMR revealed that the fungus preferentially decomposed monosulfide bonds linked to a cis- and trans-1,4-isoprene backbone but the cleavage of polysulfide bonds was also observed. In contrast, no decrease in weight or devulcanization of rubber was observed in cultures of a white rot fungus, Dichomitus squalens. The oxidative cleavage of sulfide bonds by C. subvermispora demonstrates that ligninolytic basidiomycetes are potential microbes for the biological devulcanization of rubber products.

Biodegradation, Environmental↗
PubMedDate not supplied

Structural characterization of alpha-terminal group of natural rubber. 1. Decomposition of branch-points by lipase and phosphatase treatments.

Deproteinized natural rubber latex (DPNR-latex) was treated with lipase and phosphatase in order to analyze the structure of the chain-end group (alpha-terminal). The enzymatic treatment decreased the content of long-chain fatty acid ester groups in DPNR from about 6 to 2 mol per rubber molecule. The molecular weight and intrinsic viscosity were reduced to about one-third after treatment with lipase and phosphatase. The Huggins' k' constant of the enzyme-treated DPNR showed the formation of linear rubber molecules. The molecular weight distribution of DPNR changed apparently after treatment with lipase and phosphatase. (1)H NMR spectrum of rubber obtained from DPNR-latex showed small signals due to monophosphate, di-phosphate and phospholipids at the alpha-terminus. Treatment of DPNR-latex with lipase and phosphatase decreased the relative intensity of the (1)H NMR signals corresponding to phospholipids, whereas no change was observed for the signals due to mono- and diphosphates. The residual mono- and diphosphate signals as well as some phospholipid signals after lipase and phosphatase treatments indicate that mono- and diphosphate groups are directly linked at the alpha-terminus with the modified structure, expected by aggregation or linking with phospholipid molecules.

Hevea↗
PubMed2003

Potential application of recycled rubber in oil pollution control.

The abundance and indiscriminate disposal of scrap tyres in urban areas in Nigeria create serious health and environmental problems. The potential of using rubber recycled from scrap tyres as an absorbent in crude oil clean up was investigated. Rubber particles of mesh sizes within the range of 0.15 to 2.36 mm were used to absorb crude oil at different temperatures (5 to 40 degrees C). The rapid increase in oil absorption within the first 20 min was followed by a much slower rate, with the equilibrium absorption being attained after 30 min. The equilibrium absorption increased with decreasing particle size and decreasing temperature of absorption. At 30 degrees C, the oil absorption for the 0.15 mm rubber particles was more than twice that of the 2.36 mm particle size. When regenerated recycled rubber was used, the equilibrium absorption decreased by about 15-40%. The extent of reduction was higher for the larger particles and at lower temperature of absorption.

Conservation of Natural Resources↗