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Various Materials (various + material)
Selected AbstractsRepair of the trigeminal nerve: a reviewAUSTRALIAN DENTAL JOURNAL, Issue 2 2010RHB Jones Abstract Nerve surgery in the maxillofacial region is confined to the trigeminal and facial nerves and their branches. The trigeminal nerve can be damaged as a result of trauma, local anaesthesia, tumour removal and implant placement but the most common cause relates to the removal of teeth, particularly the inferior alveolar and lingual nerves following third molar surgery. The timing of nerve repair is controversial but it is generally accepted that primary repair at the time of injury is the best time to repair the nerve but it is often a closed injury and the operator does not know the nerve is injured until after the operation. Early secondary repair at about three months after injury is the most accepted time frame for repair. However, it is also thought that a reasonable result can be obtained at a later time. It is also generally accepted that the best results will be obtained with a direct anastamosis of the two ends of the nerve to be repaired. However, if there is a gap between the two ends, a nerve graft will be required to bridge the gap as the two ends of the nerve will not be approximated without tension and a passive repair is important for the regenerating axons to grow down the appropriate perineural tubes. Various materials have been used for grafting and include autologous grafts, such as the sural and greater auricular nerves, vein grafts, which act as a conduit for the axons to grow down, and allografts such as Neurotube, which is made of polyglycolic acid (PGA) and will resorb over a period of time. [source] New and experimental approaches to treatment of diabetic foot ulcers: a comprehensive review of emerging treatment strategiesDIABETIC MEDICINE, Issue 11 2004R. Eldor Abstract Diabetic foot ulcers occur in up to 15% of all diabetic patients and are a leading cause of nontraumatic amputation worldwide. Neuropathy, abnormal foot biomechanics, peripheral vascular disease and external trauma are the major contributors to the development of a foot ulcer in the diabetic patient. Therapy today includes repeated debridement, offloading, and dressings, for lower grade ulcers, and broad spectrum antibiotics and occasionally limited or complete amputation for higher grades, requiring a team effort of health care workers from various specialties. The large population affected by diabetic foot ulcers and the high rates of failure ending with amputation even with the best therapeutic regimens, have resulted in the development of new therapies and are the focus of this review. These include new off loading techniques, dressings from various materials, methods to promote wound closure using artificial skin grafts, different growth factors or wound bed modulators and methods of debridement. These new techniques are promising but still mostly unproven and traditional approaches cannot be replaced. New and generally more expensive therapies should be seen as adding to traditional approaches. [source] Oral bacterial adhesion forces to biomaterial surfaces constituting the bracket,adhesive,enamel junction in orthodontic treatmentEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2009Li Mei Bacterial adhesion to biomaterial surfaces constituting the bracket,adhesive,enamel junction represents a growing problem in orthodontics, because bacteria can adversely affect treatment by causing demineralization of the enamel surface around the brackets. It is important to know the forces with which bacteria adhere to the surfaces of these junction materials, as the strength of these forces will determine how easy it will be to remove the bacteria. We compared the adhesion forces of five initially colonizing and four cariogenic strains of bacteria to an orthodontic adhesive, stainless steel, and enamel, with and without a salivary conditioning film. Adhesion forces were determined using atomic force microscopy and a bacterial probe. In the absence of a salivary conditioning film, the strongest bacterial adhesion forces occurred to the adhesive surface (,2.9 to ,6.9 nN), while adhesion forces to the enamel surfaces were lowest (,0.8 to ,2.7 nN). In the presence of a salivary conditioning film, adhesion forces were reduced strongly, to less than 1 nN, and the differences between the various materials were reduced. Generally, however, initial colonizers of dental hard surfaces presented stronger adhesion forces to the different materials (,4.7 and ,0.6 nN in the absence and presence of a salivary conditioning film, respectively) than cariogenic strains (,1.8 and ,0.5 nN). [source] Non-propagation conditions for fatigue cracks and fatigue in the very high-cycle regimeFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 8-9 2002R. PIPPAN ABSTRACT The propagation and non-propagation conditions of cracks with crack closure and without crack closure are investigated in various materials. It was found that there exist lower limits for the crack-driving force at which cracks do not propagate (da/dN is smaller than 10,10 mm cycle,1) for constant and variable amplitude loading. Finally, possible reasons for the growth of cracks below such limits, which may occur in the very high-cycle regime, are discussed. [source] Zeolite Catalysts with Tunable Hierarchy Factor by Pore-Growth ModeratorsADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Javier Pérez-Ramírez Abstract The design of hierarchical zeolite catalysts is attempted through the maximization of the hierarchy factor (HF); that is, by enhancing the mesopore surface area without severe penalization of the micropore volume. For this purpose, a novel desilication variant involving NaOH treatment of ZSM-5 in the presence of quaternary ammonium cations is developed. The organic cation (TPA+ or TBA+) acts as a pore-growth moderator in the crystal by OH, -assisted silicon extraction, largely protecting the zeolite crystal during the demetallation process. The protective effect is not seen when using cations that are able to enter the micropores, such as TMA+ Engineering the pore structure at the micro- and mesolevel is essential to optimize transport properties and catalytic performance, as demonstrated in the benzene alkylation with ethylene, a representative mass-transfer limited reaction. The hierarchy factor is an appropriate tool to classify hierarchically structured materials. The latter point is of wide interest to the scientific community as it not only embraces mesoporous zeolites obtained by desilication methods but it also enables to quantitatively compare and correlate various materials obtained by different synthetic methodologies. [source] Formation of Thick Porous Anodic Alumina Films and Nanowire Arrays on Silicon Wafers and Glass,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2003O. Rabin Abstract A method for the fabrication of thick films of porous anodic alumina on rigid substrates is described. The anodic alumina film was generated by the anodization of an aluminum film evaporated on the substrate. The morphology of the barrier layer between the porous film and the substrate was different from that of anodic films grown on aluminum substrates. The removal of the barrier layer and the electrochemical growth of nanowires within the ordered pores were accomplished without the need to remove the anodic film from the substrate. We fabricated porous anodic alumina samples over large areas (up to 70 cm2), and deposited in them nanowire arrays of various materials. Long nanowires were obtained with lengths of at least 9 ,m and aspect ratios as high as 300. Due to their mechanical robustness and the built-in contact between the conducting substrate and the nanowires, the structures were useful for electrical transport measurements on the arrays. The method was also demonstrated on patterned and non-planar substrates, further expanding the range of applications of these porous alumina and nanowire assemblies. [source] New approach to twin interfaces of modulated martensiteJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2010Zongbin Li In Ni,Mn,Ga ferromagnetic shape memory alloys, the crystallographic nature of martensitic variant interfaces is one of the key factors governing the variant reorientation through field-induced interface motion and hence the shape memory performance. So far, the crystal structure studies of these materials , conducted by means of transmission electron microscopy , have suffered from uncertainties in determining the number of unit cells of modulated superstructure, and consequently improper interpretations of orientation correlations of martensitic variants. In this paper a new approach is presented for comprehensive analysis of crystallographic and morphological information of modulated martensite, using automated electron backscatter diffraction. As a first attempt, it has been applied for the unambiguous determination of the orientation relationships of adjacent martensitic variants and their twin interface characters in an incommensurate 7M modulated Ni,Mn,Ga alloy, from which a clear and full-featured image of the crystallographic nature of constituent twin interfaces is built up. Certainly, this new approach will make it feasible not only to generalize the statistical analysis of martensitic variant distributions for various materials with modulated superstructure, but also to give insight into the crystallographic characteristics of martensitic variant interfaces and the variant reorientation mechanism of new advanced materials for interface engineering. [source] Do pipits use experimentally supplemented rich sources of calcium more often in an acidified area?JOURNAL OF AVIAN BIOLOGY, Issue 2 2001S. Bure How birds respond to the recent phenomenon of calcium deficiency in acidified areas is still poorly known. This study, carried out in the Jeseníky Mountains (heavily polluted, acidified area in the Czech Republic), in alpine ecosystems of central Norway, and in the limestone part of the Malá Fatra Mountains (Slovak Republic), provides the first experimental evidence that birds select and bring supplemented calcium-rich items to their nestlings more often in an acidified area. Meadow Pipits Anthus pratensis and Water Pipits A. spinoletta selected calcium-rich items (mainly snail shells) from various materials placed near their nests and this selectivity did not differ between areas or species. Thinning of egg shells (8% at blunt pole, 5% at egg side) suggests that Meadow Pipits in the Jeseníky Mountains were negatively influenced by the low calcium availability, in spite of their ability to adjust foraging behaviour. [source] A perspective on MALDI alternatives,total solvent-free analysis and electron transfer dissociation of highly charged ions by laserspray ionizationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2010Sarah Trimpin Abstract Progress in research is hindered by analytical limitations, especially in biological areas in which sensitivity and dynamic range are critical to success. Inherent difficulties of characterization associated with complexity arising from heterogeneity of various materials including topologies (isomeric composition) and insolubility also limit progress. For this reason, we are developing methods for total solvent-free analysis by mass spectrometry consisting of solvent-free ionization followed by solvent-free gas-phase separation. We also recently constructed a novel matrix-assisted laser desorption ionization (MALDI) source that provides a simple, practical and sensitive way of producing highly charged ions by laserspray ionization (LSI) or singly charged ions commonly observed with MALDI by choice of matrix or matrix preparation. This is the first ionization source with such freedom,an extremely powerful analytical ,switch'. Multiply charged LSI ions allow molecules exceeding the mass-to-charge range of the instrument to be observed and permit for the first time electron transfer dissociation fragment ion analysis. Copyright © 2010 John Wiley & Sons, Ltd. [source] Water sorption, glass transition, and protein-stabilizing behavior of an amorphous sucrose matrix combined with various materialsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2010Koreyoshi Imamura Abstract The effects of various additives on the physical properties of an amorphous sugar matrix were compared. Amorphous, sugar,additive mixtures were prepared by freeze-drying and then rehumidified at given RHs. Sucrose and eighteen types of substances were used as the sugar and the additive, respectively, and water sorption, glass-to-rubber transition, and protein stabilization during freeze-drying for the various sucrose,additive mixtures were examined. The additives were categorized into two groups according to their effects on Tg and water sorption. Presence of polysaccharides, cyclodextrins, and polymers (large-sized additives) resulted in a decrease in equilibrium water content from the ideal value calculated from individual water contents for sucrose and additive, and in contrast, low MW substances containing ionizable groups (small-ionized additives) resulted in an increase. The increase in Tg by the addition of large-sized additives was significant at the additive contents >50,wt.% whereas the Tg was markedly increased in the lower additive content by the addition of small-ionized additives. The addition of small-ionized additives enhanced the decrease in Tg with increasing water content. The protein stabilizing effect was decreased with increasing additive content in the cases of the both groups of the additives. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:4669,4677, 2010 [source] Differential effect of materials for surface hemostasis on red blood cell morphologyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 10 2008Carr J. Smith Abstract The design of devices for surface (topical) hemostasis has been based on maximizing activation of platelets and accelerating coagulation pathways. The studies reported herein examine another aspect of blood contact with topical hemostasis materials, i.e., surface binding of red blood cells (RBCs) and related alterations in RBC morphology. Whole blood was allowed to contact poly- N -acetyl glucosamine (pGlcNAc) containing materials: pGlcNAc nanofibers with parallel polymer alignment (,-pGlcNAc), chitin, and chitosan. The effect on RBC morphology and function via contact with the artificial surfaces on the cell's morphology was examined with scanning and transmission electron microscopy (TEM). ,-pGlcNAc was found to densely bind RBCs and induce a stomatocytic-like morphology. Chitin and chitosan also bound RBCs, but with approximately 10-fold lower levels and with less distinct general morphologies. ,-pGlcNAc is thus unique in the nature of its interaction with RBCs. These studies indicate that the differential ability of various materials to bind and alter the morphology of RBCs at the artificial surface interface with blood is an important consideration in the design of devices for surface hemostasis. Microsc. Res. Tech., 2008. © 2008 Wiley-Liss, Inc. [source] Hemispheric brain volume replacement with free latissimus dorsi flap as first step in skull reconstructionMICROSURGERY, Issue 4 2005Anton H. Schwabegger M.D. Large skull defects lead to progressive depression deformities, with resulting neurological deficits. Thus, cranioplasty with various materials is considered the first choice in therapy to restore cerebral function. A 31-year-old female presented with a massive left-sided hemispheric substance defect involving bone and brain tissue. Computed tomography showed a substantial convex defect involving the absence of calvarial bone as well as more than half of the left hemisphere of the brain, with a profound midline shift and a compression of the ventricular system. There was a severe problem due to multiple deep-skin ulcerations at the depression margin, prone to skin perforation with a probability of intracranial infection. In a first step, a free myocutaneous latissimus dorsi flap was transplanted for volume replacement of the hemispheric brain defect, and 4 months later, artificial bone substitute was implanted in order to prevent progressive vault depression deformity. Healing was uneventful, and the patient showed definite neurological improvement postoperatively. Free tissue transfer can be a valuable option in addition to cranioplasty in the treatment of large bony defects of the skull. Besides providing stable coverage for the reconstructed bone or its substitute, it can also serve as a volume replacement. © 2005 Wiley-Liss, Inc. Microsurgery 25:325,328, 2005. [source] Surface plasmon enhanced light emission from semiconductor materialsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Koichi Okamoto Abstract Surface plasmon (SP) coupling technique was used to enhance light emissions from semiconductor nanocrystals with evaporated metal layers. We found that the SP coupling can increase the internal quantum efficiencies (IQE) of emission from CdSe-based nanocrystals regardless of the initial efficiencies. This suggests that this technique should be much effective for various materials that suffer from low quantum efficiencies. We also obtained 70-fold enhancement of emission from silicon nanocrystals in silicon dioxide. Obtained IQE value is 38%, which is as large as that of a compound semiconductor with direct transition. The SP coupling technique would bring a great improvement to silicon photonics. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] PI3D processing of DLC coatings for different applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2008S. A. Nikiforov Abstract DLC (a -C:H) and Si-DLC coatings have been deposited on various materials (steel, aluminium, silicon, glass, polymers) using a 1-m3 interior-antenna ICP PI3D facility with HMDSO and toluene as precursors. For conformal treatment of 3-D workpiececs, a low-voltage (0.5 - 1) kV, high repetition rate (up to 70 kHz) pulsing was applied. However, DLC formation on dielectric substrates was performed at higher (2 - 10) kV voltage using short (1 - 1.5) ,s pulses to minimize surface charging. Coating adhesion was achieved by formation of multi layer structure comprising Si-containing buffer layer, transient layer, DLC layer with gradually increasing hardness, and top hard DLC. Film hardness was (5 - 20) GPa, and the deposition rate (4 - 0.5) ,m/h. DLC surface roughness was (0.7 - 60) nm and water contact angle 70° - 110° depending on process parameters which implies various applications. Batch processing of sliding parts, cutting tools, glass moulds was performed. Double-side DLC coating on polymer web eliminated its rolling up due to the coating stress. With novel ICP antenna the DLC processing is promising for large-scale nano pattern transfer technology. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] On the Thermodynamic Stability of Liquid Capillary BridgesTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2007Janet Aw Elliott Abstract Capillary condensation is important in the behaviour of various materials encountered in nature and in industrial processes. The behaviour of liquid capillary bridges has mostly been investigated from a mechanical perspective, with an emphasis on computing the relevant adhesion forces. In the present paper, a thermodynamic approach is used, computing the free energy of such systems (based on numerically constructed shapes of liquid bridges) in order to determine the nature and properties of their equilibrium states. The dependence of the thermodynamic equilibrium configurations on the geometry of the system is investigated, and comparisons are made with experimental findings reported in the literature. La condensation capillaire est importante dans le comportement de divers matériaux rencontrés dans la nature et dans les procédés industriels. Le comportement des ponts capillaires liquides a surtout été étudié d'un point de vue mécanique, l'accent étant mis sur le calcul par ordinateur des forces d'adhésion pertinentes. Dans le présent article, on utilise une approche thermodynamique utilisant le calcul par ordinateur de l'énergie libre de tels systèmes (d'après les formes numériquement construites des ponts liquides), dans le but de déterminer la nature et les propriétés de leurs états d'équilibre. La dépendance des configurations d'équilibre thermodynamique sur la géométrie du système est étudiée, et des comparaisons sont faites avec les résultats expérimentaux présentés dans la littérature scientifique. [source] Material wear of polymeric tracheostomy tubes: A six-month study,THE LARYNGOSCOPE, Issue 4 2009Sara Backman MSc Abstract Objectives: The objectives were to study long-term material wear of tracheostomy tubes made of silicone (Si), polyvinyl chloride (PVC), and polyurethane (PU) after 3 and 6 months of clinical use. Study Design: The study has a prospective and comparative design. Methods: Nineteen patients with long-term tracheostomy, attending the National Respiratory Center in Sweden, were included, n = 6 with Si tubes, n = 8 with PVC tubes, and n = 5 with PU tubes. The tubes were exposed to the local environment in the trachea for 3 and 6 months and analyzed by scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and differential scanning calorimetry. Results: All tubes revealed severe surface changes. No significant differences were established after 3 or 6 months of exposure between the various materials. The changes had progressed significantly after this period, compared to previously reported changes after 30 days of exposure. The results from all analyzing techniques correlated well. Conclusions: All tubes, exposed in the trachea for 3,6 months, revealed major degradation and changes in the surface of the material. Polymeric tracheostomy tubes should be changed before the end of 3 months of clinical use. Laryngoscope, 2009 [source] Tissue reaction of the rabbit urinary bladder to tension-free vaginal tape and porcine small intestinal submucosaBJU INTERNATIONAL, Issue 6 2002D.M. Rabah Objectives ,To compare the histological tissue reactions of urinary bladder in close contact with polypropylene mesh tension-free vaginal tape (TVT) or porcine small intestinal submucosal (SIS) grafts, as the commercial availability of various materials has considerably simplified sling procedures for treating urinary incontinence, but erosion and infection after using artificial sling materials remain an important concern. Materials and methods ,Thirty female New Zealand rabbits were randomized to three groups, i.e. group A (TVT, 12 animals), group B (SIS, 12) and group C (surgical control, six). Through a laparotomy under anaesthesia and an aseptic technique, the bladder was approached at its dome, where a 0.5 × 1 cm piece of TVT or SIS was fixed in direct contact with the bladder wall. The control group underwent only bladder manipulation with no material applied. Half the animals in each group were killed after 6 weeks and the other half after 12 weeks. The urinary bladder was harvested and examined histologically. Results ,The grafts in both groups were characterized by dense foreign-body type reactions and were mostly attached loosely to the bladder wall by a thin layer of fibrovascular tissue. More importantly, the bladder wall reactions showed no inflammation in all 12 animals in group A (TVT) but three of them had various grades of fibrosis. There was severe transmural inflammation in one animal in group B (SIS); one rabbit had grade I and two had grade II fibrosis. The controls, as expected, showed no bladder wall reactions. Conclusion ,In this descriptive analysis of reaction types elicited on the urinary bladder by these grafts, both materials appeared to be safe. Although TVT elicited fewer and less severe adverse reactions, no statistical conclusions can be drawn. The clinical significance of these findings should emerge from long-term clinical data when they become available. [source] 4237: New biomaterials for keratoprosthesesACTA OPHTHALMOLOGICA, Issue 2010AW LLOYD Purpose Although a wide range of keratoprostheses have been developed from various materials over the last 30 years there has been limited optimisation of material properties to enhance clinical performance and minimise tissue incompatibility within the ocular environment. The development of our understanding of the biological interactions between materials and corneal tissues, the failure of existing keratoprostheses, the advances in the design and synthesis of materials of controlled molecular architectures and the advancements in composite biomaterials in recent years provides an opportunity to design enhanced biomaterials for the fabrication of the next generation of keratoprosthetic with improved clinical performance. Methods This paper will review studies undertaken by our group which have enhanced our understanding of the biological interactions of existing keratoprosthetic materials in the ocular environment and the development of novel approaches to new materials for the fabrication of keratoprosthetic based on the utilisation of biomimetic and composite systems and recent advances in the polymeric biomaterials. Results The paper will review data relating to the biological degradation of biomimetic materials and approaches to optimising these processes to provide materials with enhanced tissue integration and reduced inflammatory response. The in vitro biological evaluation of some of these materials indicates that material engineering may improve the clinical performance of biomaterials in the corneal environment. Conclusion The development of novel materials for the fabrication of keratoprostheses relies on improving our understanding of the mechanisms of failure of existing devices and how biomaterials can be engineered to overcome these challenges [source] Bone resorption after alloplastic augmentation of the mandibleCLINICAL OTOLARYNGOLOGY, Issue 2 2002H.A. SALEH Augmentation mentoplasty is a commonly performed operation especially in conjunction with rhinoplasty. While various materials have previously been used for this procedure, silastic has been the implant of choice for the last three decades. Concerns have been raised due to the occurrence of bone resorption beneath these implants. Controversy prevails as to the cause and the long-term effects of the resorption. It has been suggested by some that the resorption is self-limiting although this has not been confirmed in clinical studies. In total, 40 patients with silastic implants, who had a mean follow-up of 20 months (8,60 months), were studied radiologically. In 21 of them (52%), a degree of resorption from 0.5 to 2 mm was observed. Spearman's rank correlation showed a statistically significant relationship between the degree of resorption and the time lapse since surgery (P = 0.048). [source] | ||||||||||||||||