SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Adhesive

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Fabricated adhesives are demonstrated to support high loads while maintaining easy release on a variety of “real world” surfaces. These adhesives consist of simple elastomers and fabrics without nano or micron scale features, yet they surpass the adhesive force capacity of live Tokay geckos and can be scaled to large sizes.

Concepts: 2002 albums, Gecko, Polyurethane, Elastomer, Universe, Adhesion, Adhesive, Tokay gecko

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For the first time, we report the remarkable ability of the terrestrial leaf beetle Gastrophysa viridula to walk on solid substrates under water. These beetles have adhesive setae on their feet that produce a secretory fluid having a crucial role in adhesion on land. In air, adhesion is produced by capillary forces between the fluid-covered setae and the substrate. In general, capillary forces do not contribute to adhesion under water. However, our observations showed that these beetles may use air bubbles trapped between their adhesive setae to walk on flooded, inclined substrata or even under water. Beetle adhesion to hydrophilic surfaces under water was lower than that in air, whereas adhesion to hydrophobic surfaces under water was comparable to that in air. Oil-covered hairy pads had a pinning effect, retaining the air bubbles on their feet. Bubbles in contact with the hydrophobic substrate de-wetted the substrate and produced capillary adhesion. Additional capillary forces are generated by the pad’s liquid bridges between the foot and the substrate. Inspired by this idea, we designed an artificial silicone polymer structure with underwater adhesive properties.

Concepts: Enzyme substrate, Water, Foot, Polymer, Liquid, Beetle, Substrate, Adhesive

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Cyanoacrylate has been used as a commercial tissue adhesive. Recently, ethyl 2-cyanoacrylate has been suggested for the fixation of onlay autogenous bone graft. However, ethyl 2-cyanoacrylate must be biocompatible with bone tissue. This study evaluated the cytotoxicity of cyanoacrylate adhesives using a direct contact assay on human oral osteoblast cells.

Concepts: Bone, Cell, Cytotoxicity, Bone morphogenetic protein, Adhesive, Bone grafting, Adhesives, Cyanoacrylate

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BACKGROUND: Pilonidal sinus is a common condition often managed with invasive surgery associated with a significant morbidity and often a prolonged recovery time. Fibrin glue has been used in our institution as an alternative to conventional surgery. The purpose of this study was to perform a service evaluation of patient satisfaction and recovery following fibrin glue treatment for pilonidal sinus. METHODS: All pilonidal glue procedures for a single surgeon were identified from theatre and consultant diary records from March 2007 to September 2011. A questionnaire was sent by post to all patients. Patient satisfaction, time to return to normal activities, the need for further procedures and whether they would recommend a glue procedure to a friend were evaluated. RESULTS: Ninety-three patients were identified, accounting for a total of 119 glue procedures and 57/93 responses were received (61 %). The median age of respondents was 26 (17-70) years. Seventy-nine per cent (n = 45) were satisfied, pleased or very pleased with the result of their procedure. Fifty-four per cent (n = 31) were back to normal activities within a week with a further 17 % (n = 10) back to normal activities within 2 weeks. Seventy-four per cent (n = 42) required no further treatment. Of the 15 patients requiring a further procedure, 3 went on to have a repeat glue treatment which resulted in complete healing. Eighty-two per cent (n = 47) would recommend a glue procedure to a friend. CONCLUSIONS: Fibrin gluing for pilonidal sinus should be considered as first-line treatment for most pilonidal sinuses. It has a high level of patient satisfaction and allows a rapid return to normal activities in this group of patients of working age.

Concepts: Patient, Hospital, Surgery, Physician, Pilonidal cyst, Adhesive, Integers, Adhesives

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Among a myriad of spider web geometries, the orb web presents a fascinating, exquisite example in architecture and evolution. Orb webs can be divided into two categories according to the capture silk used in construction: cribellate orb webs (composed of pseudoflagelliform silk) coated with dry cribellate threads and ecribellate orb webs (composed of flagelliform silk fibres) coated by adhesive glue droplets. Cribellate capture silk is generally stronger but less-extensible than viscid capture silk, and a body of phylogenic evidence suggests that cribellate capture silk is more closely related to the ancestral form of capture spiral silk. Here, we use a coarse-grained web model to investigate how the mechanical properties of spiral capture silk affect the behaviour of the whole web, illustrating that more elastic capture spiral silk yields a decrease in web system energy absorption, suggesting that the function of the capture spiral shifted from prey capture to other structural roles. Additionally, we observe that in webs with more extensible capture silk, the effect of thread strength on web performance is reduced, indicating that thread elasticity is a dominant driving factor in web diversification.

Concepts: World Wide Web, Web 2.0, Silk, Adhesive, Spider silk, Spider, Spider web, Spider anatomy

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Pressure-sensitive adhesives such as tapes become easily contaminated by dust particles. By contrast, animal adhesive pads are able to self-clean and can be reused millions of times over a lifetime with little reduction in adhesion. However, the detailed mechanisms underlying this ability are still unclear. Here we test in adhesive pads of stick insects (Carausius morosus) (1) whether self-cleaning is enhanced by the liquid pad secretion, and (2) whether alternating push-pull movements aid the removal of particles. We measured attachment forces of insect pads on glass after contamination with 10 µm polystyrene beads. While the amount of fluid present on the pad showed no effect on the pads' susceptibility to contamination, the recovery of adhesive forces after contamination was faster when higher fluid levels were present. However, this effect does not appear to be based on a faster rate of self-cleaning since the number of spheres deposited with each step did not increase with fluid level. Instead, the fluid may aid the recovery of adhesive forces by filling in the gaps between contaminating particles, similar to the fluid’s function on rough surfaces. Further, we found no evidence that an alternation of pushing and pulling movements, as found in natural steps, leads to a more efficient recovery of adhesion than repeated pulling slides.

Concepts: Insect, Liquid, Carausius morosus, Phasmatodea, Adhesion, Adhesive, Dust, A Lifetime

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ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Adhesives for the restoration of non-carious cervical lesions: a systematic review. Chee B, Rickman LJ, Satterthwaite JD. J Dent 2012;40(6):443-52. Epub 2012 Feb 18. REVIEWER: David G. Pendrys, DDS, PhD PURPOSE/QUESTION: The purpose of this systematic review was to assess the effectiveness of currently available resin-based adhesive systems SOURCE OF FUNDING: Information not available TYPE OF STUDY/DESIGN: Systematic review LEVEL OF EVIDENCE: Level 2: Limited-quality, patient-oriented evidence STRENGTH OF RECOMMENDATION GRADE: Grade B: Inconsistent or limited-quality patient-oriented evidence.

Concepts: Evaluation, Evidence-based medicine, Review, Accept, Book review, Adhesive, Bibliographic database, Adhesives

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Adhesives that are naturally produced by marine organisms are potential sources of inspiration in the search for medical adhesives. Investigations of barnacle adhesives are at an early stage but it is becoming obvious that barnacles utilize a unique adhesive system compared to other marine organisms. The current study examined the fine structure and chemistry of the glandular system that produces the adhesive of the barnacle Lepas anatifera. All components for the glue originated from large single-cell glands (70-180 μm). Staining (including immunostaining) showed that L-3,4-dihydroxyphenylalanine and phosphoserine were not present in the glue producing tissues, demonstrating that the molecular adhesion of barnacles differs from all other permanently gluing marine animals studied to date. The glandular tissue and adhesive secretion primarily consisted of slightly acidic proteins but also included some carbohydrate. Adhesive proteins were stored in cytoplasmic granules adjacent to an intracellular drainage canal (ICC); observations implicated both merocrine and apocrine mechanisms in the transport of the secretion from the cell cytoplasm to the ICC. Inside the ICC, the secretion was no longer contained within granules but was a flocculent material which became “clumped” as it traveled through the canal network. Hemocytes were not seen within the adhesive “apparatus” (comprising of the glue producing cells and drainage canals), nor was there any structural mechanism by which additions such as hemocytes could be made to the secretion. The unicellular adhesive gland in barnacles is distinct from multicellular adhesive systems observed in marine animals such as mussels and tubeworms. Because the various components are not physically separated in the apparatus, the barnacle adhesive system appears to utilize completely different and unknown mechanisms for maintaining the liquid state of the glue within the body, as well as unidentified mechanisms for the conversion of extruded glue into hard cement. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.

Concepts: Cell, Secretion, Cytoplasm, Liquid, Gland, Exocrine gland, Adhesive, Animal glue

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Mussel-mimetic, bioadhesive polymers are synthesized from plant-derived sources. The strong adhesive action is caused by interactions between the catechol groups at the end of the polymer terminal chains and the substrate surface. Here, we present a preliminary study of the adhesion properties and a discussion of the adhesion mechanism.

Concepts: Sociology, Adhesive

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The retreatability of recent calcium silicate or mineral trioxide aggregate (MTA) sealers has not yet been assessed. The aim of this study was to evaluate the removal of 2 MTA-based sealers (MTA Fillapex [Angelus Soluções Odontológicas, Londrina, PR, Brazil] and MTA Plus [Prevest-Denpro, Jammu City, India]) using a rotary retreatment system, considering an epoxy resin sealer (AH Plus [Dentsply Maillefer, Ballaigues, Switzerland]) as the standard for comparison.

Concepts: Magnesium, Endodontic therapy, Epoxy, Adhesive