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Hard Surfaces (hard + surface)
Selected AbstractsDelayed Cardiac Perforation by Defibrillator Lead Placed in the Right Ventricular Outflow Tract Resulting in Massive Pericardial EffusionPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2008ERNEST W. LAU M.D. A 76-year-old man received a dual-chamber implantable cardioverter defibrillator (ICD), with the defibrillator lead positioned within the right ventricular outflow tract. The lead parameters at the time of implantation were satisfactory and the postprocedure chest X-ray showed the leads were in place. The patient was cardioverted from atrial fibrillation during defibrillation threshold testing and commenced on anticoagulation immediately. One month post implantation, he experienced multiple ventricular tachycardia episodes all successfully treated with antitachycardia pacing and shocks by his ICD, but he fell and hit his chest against a hard surface during one of these attacks. He developed a massive pericardial effusion and computed tomography confirmed cardiac perforation by the defibrillator lead. Pericardiocentesis was performed and the defibrillator lead replaced with a different model positioned at the right ventricular apex. The patient made an uneventful recovery. The management and avoidance of delayed cardiac perforation by transvenous leads were discussed. [source] A New Apparatus for Particle Impact TestsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2003Yevgeny Petukhov Abstract Breakage and chipping of particles due to collision with a hard surface is a common occurrence in many conveying and handling systems, such as pneumatic conveying and jet-mills. Studies of the breakage mechanism of particles due to impact and the effect of impact velocity and the number of impacts have been investigated in depth both experimentally and theoretically. In this paper, a new concept and apparatus are introduced for conducting particle impact tests. In most of the published test rigs, particles were accelerated towards a target. In our apparatus, the target moves and hits the particles. Using this concept, the machine can operate in a vacuum, which will reduce errors caused by air streams and turbulence. The performance of the new apparatus is analyzed and the breakage phenomenon is discussed, to some extent, for two materials. The results are presented in terms of the increase in the weight percentage of the feed broken and the decrease in the weight median size as the impact velocity or number of impacts increases. [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] Ultrasonic Nanofabrication with an AFMIMAGING & MICROSCOPY (ELECTRONIC), Issue 4 2007Nanomanipulation, Ultrasound Facilitates Nanolithography Abstract Ultrasonic AFM may improve fabrication technologies on the nanometer scale. In the presence of ultrasonic vibration, hard surfaces can be indented and scratched with the tip of a soft cantilever, due to its inertia. Ultrasound reduces or even eliminates friction, and hence modifies the tip-nanoparticle-surface interactions in AFM manipulation. The subsurface sensitivity of the technique makes feasible the purposed manipulation of subsurface nanoscale features by ultrasonic actuation. [source] How Nature Modulates a Fiber's Mechanical Properties: Mechanically Distinct Fibers Drawn from Natural Mesogenic Block Copolymer VariantsADVANCED MATERIALS, Issue 4 2009Matthew J. Harrington Mussel byssal threads are functionally graded biological fibers adapted for tethering the soft tissue of the organism (,1 MPa) to hard surfaces !(25 GPa) in the rocky seashore. A stiffness gradient mitigates contact deformation and is defined by an incrementally regulated distribution of two protein block copolymer variants with stiff and pliable domains, respectively. [source] Attachment to the substrate by soft coral fragments: desmocyte development, structure, and functionINVERTEBRATE BIOLOGY, Issue 2 2002Orit Barneah Abstract. Pieces cut from colonies of the soft coral Dendronephthya hemprichi exhibited rapid and effective attachment to hard surfaces. Attachment involved development of root-like processes (RLPs), which appeared at the basal part of the fragment 4 days after its removal from the colony. The fine structural changes and cascade of cellular events occurring in the RLP before and after attachment were studied using SEM, TEM, and LM. The epidermis of the RLPs is actively involved in the attachment process and several distinct phases are documented: appearance of numerous oval vesicles, extrusion of these vesicles resulting in the formation of an outer layer composed of extracellular organic matrix and organellar debris, which functions as an adhesive device leading to initial attachment. The latter phase was followed by the formation of desmocytes, which develop in the RLP epidermis and function as anchoring devices, mediating the firm attachment of the fragment to the substrate. This is the first evidence among anthozoans that desmocytes play an active role in anchoring tissue to substrate and thus extends the range of functions exhibited by desmocytes among anthozoans. [source] The intra-oral translocation of periodontopathogens jeopardises the outcome of periodontal therapyJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 6 2001A review of the literature Abstract Background: Although periodontitis has a multi-factorial aetiology, the success of its therapy mainly focuses on the eradication/reduction of the exogenous/endogenous periodontopathogens. Most of the species colonise several niches within the oral cavity (e.g. the mucosae, the tongue, the saliva, the periodontal pockets and all intra-oral hard surfaces) and even in the oro-pharyngeal area (e.g., the sinus and the tonsils). Methods: This review article discusses the intra-oral transmission of periodontopathogens between these niches and analyses clinical studies that support the idea and importance of such an intra-oral translocation. Results and conclusions: Based on the literature, the oro-pharyngeal area should indeed be considered as a microbiological entity. Because untreated pockets jeopardise the healing of recently instrumented sites, the treatment of periodontitis should involve "a one stage approach" of all pathologic pockets (1-stage full-mouth disinfection) or should at least consider the use of antiseptics during the intervals between consecutive instrumentations, in order to prevent a microbial translocation of periodontopathogens during the healing period. For the same reason, regeneration procedures or the local application of antibiotics should be postponed until a maximal improvement has been obtained in the remaining dentition. This more global approach offers significant additional clinical and microbiological benefits. Zusammenfassung Grundlagen: Obwohl die Parodontitis eine multifaktorielle Ätiologie hat, konzentriert sich der Erfolg ihrer Therapie hauptsächlich auf die Eliminierung/Reduktion der exogenen/endogenen Parodontalpathogene. Die meisten dieser Spezies kolonisieren verschiedene Nischen innerhalb der Mundhöhle (z.B. die Schleimhäute, die Zunge, den Speichel, die parodontalen Taschen und alle intraoralen Hartgewebe) und sogar den oro-pharyngealen Bereich (z.B. die Nebenhöhlen und die Tonsillen). Methoden: Dieser Übersichtartikel diskutiert die intraorale Übertragung von Parodontalpathogenen zwischen diesen Nischen und analysiert klinische Studien, die die Idee und Wichtigkeit dieser intraoralen Übertragung unterstützen. Ergebnisse und Schlussfolgerung: Auf der Grundlage der Literatur sollte der oro-pharyngeale Bereich in der Tat als eine mikrobiologische Einheit angesehen werden. Weil unbehandelte Taschen die Heilung von kürzlich instrumentierten Stellen gefährden, sollte die Behandlung der Parodontitis ein einzeitiges Vorgehen bei allen pathogenen Taschen beinhalten (einzeitige vollständige Mundhöhlen-Desinfektion). Oder es sollten wenigsten die Verwendung von antiseptischen Mitteln während der Intervalle zwischen aufeinanderfolgenden Instrumentierungen erwogen werden, um die mikrobielle Übertragung von Parodontalpathogenen während der Heilungsphase zu verhindern. Aus dem gleichen Grunde sollten regenerative Maßnahmen oder die lokale Applikation von Antibiotika so lange verschoben werden, bis eine maximale Verbesserung im restlichen Gebiss erzielt wurde. Dieser globalere Ansatz liefert zusätzliche signifikante klinische und mikrobiologische Vorteile. Résumé Origine: Bien que la parodontite ait une étiologie multifactorielle, le succès de son traitement repose principalement sur l'éradication/réduction des bactéries parodontopathogènes exogènes/endogènes. La plupart des espèces colonisent plusieurs niches au sein de la cavité buccale (par exemple, les muqueuses, la langue la salive, les poches parodontales et toutes les surfaces dures intraorales), et même dans la zone oro-pharyngée (par example, les sinus et les amygdales). Méthodes: Cette revue critique discute la transmission intra-buccale des pathogènes parodontaux entre ces niches et analyse les études clinique qui soutiennent l'idée et l'importance d'une telle translocation intra-buccale. Résultats et conclusions: D'après la littérature, la zone oro-pharyngée peut vraiment être considérée comme une entité microbiologique. Puisque les poches non traitées compromettent la cicatrisation des sites récemment instrumentés, le traitement de la parodontite devrait impliquer une approche en une étape de toutes les poches pathologiques (désinfection de toute la bouche en une étape) ou devrait au moins considérer l'utilisation d'antiseptiques pendant les intervals entre deux instrumentations successives, de façon à prévenir une translocation bactérienne des pathogènes parodontaux pendant la période de cicatrisation. Pour la même raison, les procédures de régénération ou les applications locales d'antibiotiques devraient être remises jusqu'à ce qu'une amélioration maximale ait été obtenue sur le reste de la denture. Cette approche plus globale donne des bénéfices cliniques et microbiologiques supplémentaires significatifs. [source] Biofilms in the Edentulous Oral CavityJOURNAL OF PROSTHODONTICS, Issue 5 2008Amit Sachdeo BDS, DMSc Abstract Purpose: The oral cavity presents numerous surfaces for microbial colonization. These surfaces produce biofilms of differing complexities unique to each individual. Several studies have looked at biofilms in dentate patients. There has been limited research regarding biofilms on dentures or soft tissues of edentulous patients. The purpose of the present investigation was to provide meaningful data describing microbial ecological relationships in the oral cavity of edentulous patients and to evaluate the microbiota on hard and soft tissue surfaces and saliva in edentulous patients wearing complete dentures. Materials and Methods: Sixty-one edentulous subjects with complete maxillary and mandibular dentures were recruited. "Supragingival" biofilm samples were taken from 28 denture teeth for each subject. Biofilm samples were also taken from the dorsal, lateral, and ventral surfaces of the tongue, floor of mouth, buccal mucosa, hard palate, vestibule/lip, "attached gingiva," and saliva. Samples were individually analyzed for their content of 41 bacterial species using checkerboard DNA,DNA hybridization. Levels and proportions of each species were determined for every sample location. Results: Periodontal pathogens such as Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were clearly present in the samples from the edentulous subjects. Microbial profiles in samples from the soft tissue surfaces differed among site locations. Samples from the dorsum of the tongue exhibited the highest bacterial counts followed by the "attached gingiva" and the lateral surfaces of the tongue, while the lowest mean counts were found in samples from the buccal mucosa and labial vestibules. Using cluster analysis of the proportions of the test species, three clusters were formed. The first cluster comprised saliva, supragingival plaque, and the lateral and dorsal surfaces of the tongue. The second cluster comprised the other six soft tissue surfaces. Species on the denture palate formed a third cluster. Conclusions: One of the major findings in this study was the detection of periodontal pathogens, A. actinomycetemcomitans and P. gingivalis, in the edentulous subjects, as these species were thought to disappear after removal of all natural teeth. This finding has implications regarding future dental treatment and the general health of individuals. Distinct patterns of microbial colonization were seen on the different soft tissue surfaces. Thus, this investigation provided the first step in defining the organisms that are associated with edentulous patients on both soft (mucosa) and hard surfaces (denture). The study also provided meaningful data that described microbial ecological relationships in the oral cavity of edentulous subjects. The authors believe that this study is the first comprehensive assessment of the microbiota in the complete denture-wearing subject. [source] Analysis of circular waveguides with soft and hard surfaces realized by strip-loaded walls using asymptotic boundary conditionsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2001Ahmed A. Kishk Abstract Soft and hard walls are realized for a circular waveguide with walls coated by a uniform dielectric layer of appropriate thickness and loaded with conducting strips. The strips are oriented along the waveguide axis (z -axis) for hard surfaces or ,-directed for soft surfaces in a periodic form. The simple approximate asymptotic strip boundary condition (ASBC) is used to analyze the structure. For the dominant mode, when the waveguide walls are hard or soft, a linear field distribution across the waveguide cross section can be obtained. Then the waveguide can be used as an antenna with good linear polarization. The characteristics of such waveguides are presented with sample radiation patterns as compared with hollow waveguide radiation patterns. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 433,436, 2001. [source] | |||||||||||||