Anatomical and functional evaluation of tympanoplasty using a transitory natural latex biomembrane implant from the rubber tree Hevea brasiliensis

PURPOSE: To compare the role of transitory latex and sylastic (R) implants in tympanoplasty on the closure of tympanic perforations. METHODS: A randomized double-blind prospective study was conducted on 107 patients with chronic otitis media submitted to underlay tympanoplasty and divided at random into three groups: control with no transitory implant, latex membrane group, and sylastic (R) membrane group. RESULTS: Greater graft vascularization occurred in the latex membrane group (p<0.05). Good biocompatibility was obtained with the use of the latex and silicone implants, with no effect on the occurrence of infection, otorrhea or otorragy. CONCLUSION: The use of a transitory latex implant induced greater graft vascularization, with a biocompatible interaction with the tissue of the human tympanic membrane.

Understanding the mechanical and biodegradation behaviour of poly(hydroxybutyrate)/rubber blends in relation to their morphology

In this work poly(hydroxybutyrate/poly(vinyl butyral)- co-(vinyl alcohol)-co(vinyl acetate) (or ethylene propylene diene monomer rubber) blends were prepared by conventional processing techniques (extrusion and injection moulding). A droplet type morphology was obtained for P(3HB)/PVB blends whereas P(3HB)/EPDM blends presented some extent of co-continuous morphology. In addition, rubbery domains were much smaller in the case of PVB. These differences in morphology are discussed taking into account solubility parameters and rheological behaviours of each component. For both blends, the increase of elastomer ratio led to a decrease of Young's modulus but an increase in elongation at break and impact strength. The latter increased more in the case of P(3HB)/EPDM blends although the rubbery domains were larger. These results are explained in the light of the glass transition of the rubber and the presence of plasticizer in the case of PVB. The addition of elastomer also resulted in an increase of P(3HB) biodegradation rate, especially in the case of EPDM. It is assumed that, in this case, the size and morphology of the rubbery domains induce a geometrical modification of the erosion front which leads to an increase of the interface between P(3HB) phase and the degradation medium and consequently to an apparently faster biodegradation kinetics of PHB/rubber blends. Copyright (C) 2011 Society of Chemical Industry

Natural rubber latex LbL films: Characterization and growth of fibroblasts

The recent biomedical applications of natural rubber (NR) latex, mostly in dry membranes, have motivated research into novel, more noble uses of this low-cost biomaterial. In this article, we provide the first report on the fabrication of layer-by-layer (LbL) films of NR alternated with the polyelectrolytes polyethylenimine (PEI) and polyallylamine hydrochloride (PAH). Stable (PAH/NR)n and (PEI/NR)n LbL films displayed similar physicochemical properties, but differed in terms of film morphology according to atomic force microscopy (AFM) and scanning electron microscopy (SEM) data. Most significantly, (PEI/NR)5 LbL films were made of smaller and flattened particles, which were not efficient for the growth and proliferation of normal human fibroblasts (NHF). In contrast, efficient NHF proliferation could be obtained with (PAH/NR)n LbL films, with the fibroblasts exhibiting the expected elongated morphology. Furthermore, cell growth did not occur for cast films of NR, thus demonstrating the suitability of the LbL method for this biologically related application. The differences between the two polyelectrolytes illustrate the importance of the film architecture and morphology, which open the way for exploiting the molecular control inherent in the LbL technique for further applications of NR-containing films. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Preparation and Structural Characterization of Vulcanized Natural Rubber Nanocomposites Containing Nickel-Zinc Ferrite Nanopowders

Single-phase polycrystalline mixed nickel-zinc ferrites belonging to Ni0.5Zn0.5Fe2O4 were prepared on a nanometric scale (mean crystallite size equal to 14.7 nm) by chemical synthesis named the modified poliol method. Ferrite nanopowder was then incorporated into a natural rubber matrix producing nanocomposites. The samples were investigated by means of infrared spectroscopy, X-ray diffraction, scanning electron microscopy and magnetic measurements. The obtained results suggest that the base concentration of nickel-zinc ferrite nanoparticles inside the polymer matrix volume greatly influences the magnetic properties of nanoconnposites. A small quantity of nanoparticles, less than 10 phr, in the nanocomposite is sufficient to produce a small alteration in the semi-crystallinity of nanocomposites observed by X-ray diffraction analysis and it produces a flexible magnetic composite material with a saturation magnetization, a coercivity field and an initial magnetic permeability equal to 3.08 emu/g, 99.22 Oe and 9.42 X 10(-5) respectively.

Performance evaluation of low environmental impact asphalt concretes using the mechanistic empirical design method based on laboratory fatigue and permanent deformation models

The "sustainability" concept relates to the prolonging of human economic systems with as little detrimental impact on ecological systems as possible. Construction that exhibits good environmental stewardship and practices that conserve resources in a manner that allow growth and development to be sustained for the long-term without degrading the environment are indispensable in a developed society. Past, current and future advancements in asphalt as an environmentally sustainable paving material are especially important because the quantities of asphalt used annually in Europe as well as in the U.S. are large. The asphalt industry is still developing technological improvements that will reduce the environmental impact without affecting the final mechanical performance. Warm mix asphalt (WMA) is a type of asphalt mix requiring lower production temperatures compared to hot mix asphalt (HMA), while aiming to maintain the desired post construction properties of traditional HMA. Lowering the production temperature reduce the fuel usage and the production of emissions therefore and that improve conditions for workers and supports the sustainable development. Even the crumb-rubber modifier (CRM), with shredded automobile tires and used in the United States since the mid 1980s, has proven to be an environmentally friendly alternative to conventional asphalt pavement. Furthermore, the use of waste tires is not only relevant in an environmental aspect but also for the engineering properties of asphalt [Pennisi E., 1992]. This research project is aimed to demonstrate the dual value of these Asphalt Mixes in regards to the environmental and mechanical performance and to suggest a low environmental impact design procedure. In fact, the use of eco-friendly materials is the first phase towards an eco-compatible design but it cannot be the only step. The eco-compatible approach should be extended also to the design method and material characterization because only with these phases is it possible to exploit the maximum potential properties of the used materials. Appropriate asphalt concrete characterization is essential and vital for realistic performance prediction of asphalt concrete pavements. Volumetric (Mix design) and mechanical (Permanent deformation and Fatigue performance) properties are important factors to consider. Moreover, an advanced and efficient design method is necessary in order to correctly use the material. A design method such as a Mechanistic-Empirical approach, consisting of a structural model capable of predicting the state of stresses and strains within the pavement structure under the different traffic and environmental conditions, was the application of choice. In particular this study focus on the CalME and its Incremental-Recursive (I-R) procedure, based on damage models for fatigue and permanent shear strain related to the surface cracking and to the rutting respectively. It works in increments of time and, using the output from one increment, recursively, as input to the next increment, predicts the pavement conditions in terms of layer moduli, fatigue cracking, rutting and roughness. This software procedure was adopted in order to verify the mechanical properties of the study mixes and the reciprocal relationship between surface layer and pavement structure in terms of fatigue and permanent deformation with defined traffic and environmental conditions. The asphalt mixes studied were used in a pavement structure as surface layer of 60 mm thickness. The performance of the pavement was compared to the performance of the same pavement structure where different kinds of asphalt concrete were used as surface layer. In comparison to a conventional asphalt concrete, three eco-friendly materials, two warm mix asphalt and a rubberized asphalt concrete, were analyzed. The First Two Chapters summarize the necessary steps aimed to satisfy the sustainable pavement design procedure. In Chapter I the problem of asphalt pavement eco-compatible design was introduced. The low environmental impact materials such as the Warm Mix Asphalt and the Rubberized Asphalt Concrete were described in detail. In addition the value of a rational asphalt pavement design method was discussed. Chapter II underlines the importance of a deep laboratory characterization based on appropriate materials selection and performance evaluation. In Chapter III, CalME is introduced trough a specific explanation of the different equipped design approaches and specifically explaining the I-R procedure. In Chapter IV, the experimental program is presented with a explanation of test laboratory devices adopted. The Fatigue and Rutting performances of the study mixes are shown respectively in Chapter V and VI. Through these laboratory test data the CalME I-R models parameters for Master Curve, fatigue damage and permanent shear strain were evaluated. Lastly, in Chapter VII, the results of the asphalt pavement structures simulations with different surface layers were reported. For each pavement structure, the total surface cracking, the total rutting, the fatigue damage and the rutting depth in each bound layer were analyzed.

Il polverino di gomma nel riciclaggio a freddo: metodo sperimentale

In questo lavoro sono state studiate diverse miscele di conglomerato bituminoso riciclato a freddo, nelle quali si è inserito polverino di gomma proveniente da riciclaggio di pneumatici dismessi. Lo scopo è stato quello di valutare l’effetto del polverino di gomma all’interno di miscele, contenenti il 100% di fresato, confezionate a freddo con emulsione di bitume e cemento, analizzandone gli effetti sulla lavorabilità, sulla resistenza a trazione indiretta, sui moduli di rigidezza e sulle resistenze a fatica. Nel capitolo primo è introdotto il concetto di sviluppo sostenibile con particolare attenzione al campo delle pavimentazioni stradali. Sono analizzati i più recenti dati riguardanti la produzione di rifiuti di demolizione e ricostruzione in Europa e in Italia. Segue una descrizione del materiale di risulta da scarifica delle pavimentazioni stradali, dei pneumatici e delle modalità di recupero degli stessi. Nel capitolo secondo sono riportati i principali riferimenti legislativi a livello comunitario, nazionale e locale riguardanti le attività coinvolte nel processo di riciclaggio dei rifiuti per la loro utilizzazione nella costruzione di opere stradali, accompagnati dai principali documenti ausiliari, quali sentenze e disposizioni applicative a completamento del suddetto quadro normativo. Nel capitolo terzo vengono descritte le principali tecniche di riciclaggio del fresato. Particolare attenzione viene posta nella descrizione delle procedure operative e dei macchinari adottati nelle operazioni di riciclaggio in sito. Infine vengono valutati i pregi e i difetti delle tecniche di riciclaggio a freddo analizzando i vantaggi economici ed ambientali rispetto a quelle tradizionali a caldo. Nel capitolo quarto sono analizzate le singole costituenti della miscela: Emulsione Bituminosa, Cemento, Aggregati, Polverino di Gomma e Acqua, definendone per ciascuna il ruolo e le caratteristiche meccaniche e fisiche che le contraddistinguono. Nel capitolo quinto, viene sviluppato il programma sperimentale, sono definiti gli obbiettivi e descritte in modo approfondito le cinque fasi nelle quali si articola. Nella fase uno, vengono introdotte le miscele che dovranno essere studiate. Segue una caratterizzazione dei principali costituenti alla base di tali miscele: fresato , polverino di gomma, cemento, filler,emulsione bituminosa. Nella fase due avviene il confezionamento dei provini mediante compattazione con pressa giratoria. Al termine della realizzazione dei campioni, vengono descritte e analizzate le proprietà volumetriche del materiale quali il grado di addensamento, la densità, la lavorabilità. Nelle fasi tre, quattro e cinque, vengono eseguiti in successione test per la valutazione delle resistenze a trazione indiretta ITS, test per la determinazione dei moduli di rigidezza ITSM ed infine test per la valutazione delle durate dei materiali a fatica ITFT. Per ognuno dei test, sono descritte le procedure operative sulla base delle normative di riferimento vigenti. Segue l’analisi dei risultati di ciascuna prova e la valutazione dell’effetto che i singoli costituenti hanno sulle caratteristiche meccaniche della miscela.

Caratterizzazione avanzata in laboratorio di materie prime secondarie rigenerate o stabilizzate con emulsione di bitume e leganti cementizi

Il recupero dei materiali di scarto è un aspetto di grande attualità in campo stradale, così come negli altri ambiti dell’ingegneria civile. L’attenzione della ricerca e degli esperti del settore è rivolta all’affinamento di tecniche di riciclaggio che riducano l’impatto ambientale senza compromettere le prestazioni meccaniche finali. Tali indagini cercano di far corrispondere le necessità di smaltimento dei rifiuti con quelle dell’industria infrastrutturale, legate al reperimento di materiali da costruzione tecnicamente idonei ed economicamente vantaggiosi. Attualmente sono già diversi i tipi di prodotti rigenerati e riutilizzati nella realizzazione delle pavimentazioni stradali e numerosi sono anche quelli di nuova introduzione in fase di sperimentazione. In particolare, accanto ai materiali derivanti dalle operazioni di recupero della rete viaria, è opportuno considerare anche quelli provenienti dall’esercizio delle attività di trasporto, il quale comporta ogni anno il raggiungimento della fine della vita utile per centinaia di migliaia di tonnellate di pneumatici di gomma. L’obiettivo della presente analisi sperimentale è quello di fornire indicazioni e informazioni in merito alla tecnica di riciclaggio a freddo con emulsione bituminosa e cemento, valutando la possibilità di applicazione di tale metodologia in combinazione con il polverino di gomma, ottenuto dal recupero degli pneumatici fuori uso (PFU). La ricerca si distingue per una duplice valenza: la prima è quella di promuovere ulteriormente la tecnica di riciclaggio a freddo, che si sta imponendo per i suoi numerosi vantaggi economici ed ambientali, legati soprattutto alla temperatura d’esercizio; la seconda è quella di sperimentare l’utilizzo del polverino di gomma, nelle due forme di granulazione tradizionale e criogenica, additivato a miscele costituite interamente da materiale proveniente da scarifica di pavimentazioni esistenti e stabilizzate con diverse percentuali di emulsione di bitume e di legante cementizio.

Influence of rubber dam on objective and subjective parameters of stress during dental treatment of children and adolescents - a randomized controlled clinical pilot study

BACKGROUND Rubber dam is recommended for isolating the working field during adhesive dentistry procedures; however, dentists often omit rubber dam, particularly in paediatric dentistry, supposing that it would stress the patient. AIM The aim of this study was to evaluate stress parameters during a standardized dental treatment procedure performed with or without rubber dam. The treatment time was measured as a secondary outcome variable. DESIGN This study was designed as a randomized, controlled, clinical study with 72 patients (6-16 years; mean age, 11.1). During standardized fissure sealing procedures, objective parameters of stress (e.g., skin resistance, breath rate) were recorded. The operator's stress level was measured by pulse rate. Subjective pain (patients) and stress perception (operator) were evaluated by an interview. RESULTS The breath rate was significantly (P<0.05) lower and the skin resistance level was significantly higher during treatment with rubber dam compared to the control group. Subjective pain perception was significantly lower for the test group. The treatment time needed for the fissure sealing procedure was 12.4% less in the test group. CONCLUSION Isolation with rubber dam caused less stress in children and adolescents compared to relative isolation with cotton rolls if applied by an experienced dentist.

Restoring tactile awareness through the rubber hand illusion in cervical spinal cord injury

BACKGROUND Bodily sensations are an important component of corporeal awareness. Spinal cord injury can leave affected body parts insentient and unmoving, leading to specific disturbances in the mental representation of one's own body and the sense of self. OBJECTIVE Here, we explored how illusions induced by multisensory stimulation influence immediate sensory signals and tactile awareness in patients with spinal cord injuries. METHODS The rubber hand illusion paradigm was applied to 2 patients with chronic and complete spinal cord injury of the sixth cervical spine, with severe somatosensory impairments in 2 of 5 fingers. RESULTS Both patients experienced a strong illusion of ownership of the rubber hand during synchronous, but not asynchronous, stroking. They also, spontaneously reported basic tactile sensations in their previously numb fingers. Tactile awareness from seeing the rubber hand was enhanced by progressively increasing the stimulation duration. CONCLUSIONS Multisensory illusions directly and specifically modulate the reemergence of sensory memories and enhance tactile sensation, despite (or as a result of) prior deafferentation. When sensory inputs are lost, and are later illusorily regained, the brain updates a coherent body image even several years after the body has become permanently unable to feel. This particular example of neural plasticity represents a significant opportunity to strengthen the sense of the self and the feelings of embodiment in patients with spinal cord injury.

Acute and chronic pain in calves after different methods of rubber-ring castration

The goal of the present study was to evaluate the effect of different methods of rubber-ring castration on acute and chronic pain in calves. Sixty-three 4-6 week-old calves were randomly and sequentially allocated to one of five groups: Group RR (traditional rubber ring castration); group BRR (combination of one rubber ring with Burdizzo); group Rcut (one rubber ring applied with the scrotal tissue and rubber ring removed on day 9); group 3RR (three rubber rings placed one above the other around the scrotal neck); and group CO (controls; sham-castrated). All calves received 0.2 mL/kg bodyweight lidocaine 2%, injected into the spermatic cords and around the scrotal neck 15 min before castration. The presence of acute and chronic pain was assessed using plasma cortisol concentrations, response to palpation of scrotal area, time from castration until complete wound healing, and behavioural signs. Calves of group 3RR showed severe swelling and inflammation, and licking of the scrotal area occurred significantly more often than in groups Rcut and CO. Technique 3RR was discontinued for welfare reasons before the end of the study. All castration groups had significantly more pain upon palpation than calves of group CO, but palpation elicited markedly less pain in group Rcut than in the other castration groups. The most rapid healing time and shortest duration of chronic pain after castration was achieved in group Rcut. For welfare reasons, the Rcut technique should be considered as a valuable alternative to traditional rubber ring castration of calves at 4-6 weeks of age.

A MORTALITY STUDY OF BUTYL-CHLOROBUTYL RUBBER WORKERS

Worker populations are potentially exposed to multiple chemical substances simultaneously during the performance of routine tasks. The acute health effects from exposure to toxic concentrations of these substances are usually well-described. However, very little is known about the long-term health effects of chronic low dose exposure to all except a few chemical substances. A mortality study was performed on a population of workers employed at a butyl rubber manufacturing plant in Baton Rouge, Louisiana for the period 1943-1978, with special emphasis on potential exposure to methyl chloride.^ The study population was enumerated using company records. The mortality experience among the population was evaluated by comparing the number of observed deaths (total and cause-specific) to the expected number of deaths, based on the U.S. general age, race, sex specific rates. An internal comparison population was assembled to address the issue of lack of comparability when the U.S. rates are used to calculate expected deaths in an employed population.^ There were 18% fewer total observed deaths compared to the expected when the U.S. death rates were used to obtain the expected. Deaths from specific causes were also less than expected except when numbers of observed and expected deaths were small. Similar results were obtained when the population was characterized by intensity and duration of potential exposure to methyl chloride. When the internal comparison population was utilized to evaluate overall mortality of the study population, the relative risk was about 1.2.^ The study results were discussed and conclusions drawn in light of certain limitations of the methodology and study population size. ^

A simulation method to estimate closing forces in car-sealing rubber elements

The door-closing process can reinforce the impression of a solid, rock-proof, car body or of a rather cheap, flimsy vehicle. As there are no real prototypes during rubber profile bidding-out stages, engineers need to carry out non-linear numerical simulations that involve complex phenomena as well as static and dynamic loads for several profile candidates. This paper presents a structured virtual design tool based on FEM, including constitutive laws and incompressibility constraints allowing to predict more realistically the final closing forces and even to estimate sealing overpressure as an additional guarantee of noise insulation. Comparisons with results of physical tests are performed.

AFBC of coal with tyre rubber. Influence of the co-combustion variables on the mineral matter of solid by-products and on Zn lixiviation

The study focuses on the generation and distribution of mineral species in fly and bottom ashes. These were formed during a fluidised co-combustion of a fossil fuel (coal) and a non-fossil fuel (tyre rubber) in a small fluidised bed combustor (7cm x 70cm). The pilot plant had continuous fuel feed using varying ratios of coal and rubber. The study also focuses on the lixiviation behaviour of metallic elements with the assessement of zinc recovering.