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Sealing
Terms modified by Sealing Selected AbstractsInvestigations into the Sealing of Heat Damaged Areas by Applying Polymer Powders During Laser Cutting of Carbon Fiber Reinforced Composites,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Peter Jaeschke Endless carbon fiber reinforced plastics are recognized as having the greatest lightweight construction potential of all materials. Fully automated process chains for the manufacturing of composite structures are needed in order to achieve production rates and cycle times required in many industrial sectors. In this paper, a new technique, based on the in situ sealing of the kerf during high power laser cutting by application of polymer powder is presented. The degree of sealing is analyzed as a function of powder mass flow as well as carrying gas flow and it is shown that moisture uptake can be reduced compared to unsealed laser cut specimens. [source] Pulsatile Ventricular Assist Device with Pericardial Inner LiningARTIFICIAL ORGANS, Issue 11 2001Adolfo A. Leirner Abstract: Preserved pericardium in contact with blood is not thrombogenic, therefore avoiding the use of anticoagulants, and has excellent mechanical properties. Our objective is to take advantage of these characteristics and build a pulsatile ventricular assist device (VAD) with pericardium used as the inner lining of the blood chamber. A mold is used for the tanning of the pericardium, rendering it with an exact shape. A flexible polymeric structure is designed to serve as a base for the pericardium, guiding it and limiting its rate of strain. It consists of two halves, which when outfitted with the interior pericardium lining and connected to each other, form the blood chamber. This assembly is housed in rigid polyvinyl chloride (PVC) shells making up the air chamber for the pneumatic activation. Valves are likewise made of pericardium. Sealing of the chambers was tested statically up to 300 mm Hg with no air or fluid leakage. The device was tested for 60 continuous days in a mock loop, demonstrating hydrodynamic performance adequate for ventricular assist. Micrographs (confocal laser and scanning electron microscopy) were obtained of several pericardium areas, especially on the flexing regions that are a transition between the wet and dry regions. No sign of damage to the pericardium was observed either with the naked eye or at the microscopic level. From the hydraulic performance and materials viewpoints, a completely pericardium-lined pulsatile VAD displaying a polymeric structure that avoids unpredictable bending and limits strain is feasible. The results warrant further studies regarding biocompatibility and strength advantages. [source] Die neue Anwendungsnorm DIN V 18197 "Abdichten von Fugen in Beton mit Fugenbändern": Fugenbänder fachgerecht geplant, ausgewählt und eingebautBETON- UND STAHLBETONBAU, Issue 11 2005Rainer Hohmann Prof. Dr.-Ing. Fugenbänder werden seit Jahrzehnten erfolgreich zur Abdichtung von Bewegungs- und Arbeitsfugen in wasserundurchlässigen Bauwerken aus Beton eingesetzt. Mit der DIN V 18197 "Abdichten von Fugen in Beton mit Fugenbändern" wird nun sowohl dem Planer als auch dem Ausführenden ein Regelwerk zur Verfügung gestellt, in dem neben relevanten Hinweisen für die Planung und eine fachgerechte Handhabung von Fugenbändern auf der Baustelle auch Auswahldiagramme zu finden sind, mit denen der Planer in Abhängigkeit von der Beanspruchung auf einfache Art Fugenbänder auswählen kann. Dieser Beitrag geht auf die wesentlichen die Fugenabdichtung mit Fugenbändern betreffenden Regeln ein und zeigt an ausgewählten Beispielen, wie der Planer das auf seine Belastungen abgestimmte Fugenband mit Hilfe der Auswahldiagramme der DIN V 18197 auswählen kann. The new German Standard DIN V 18197 "Sealing of joints in concrete with waterstops" , waterstops correctly designed, dimensioned and used For decades, waterstops are successfully used for the waterproofing of movement and construction joints in watertight concrete structures. The DIN V 18197 "Sealing of joints in concrete with waterstops", provides a set of rules for both, the planner and the contractor. In addition to relevant details for the design and the professional handling of waterstops on the construction site, selection diagrams are included which, in a simple way, allows the planner to select waterstops in dependence of the loads. This article addresses to the essential rules concerning the joint waterproofing with waterstop and explains by means of several examples and the DIN V 18197 selection diagrams, how the planner can specify a waterstop complying with the loads. [source] Fugenausbildung und -abdichtung bei wasserundurchlässigen Bauwerken aus Beton: Neue Regelwerke setzen MaßstäbeBETON- UND STAHLBETONBAU, Issue 12 2004Rainer Hohmann Prof. Dr.-Ing. Fugen stellen bei wasserundurchlässigen Bauwerken aus Beton häufig eine Schwachstelle dar. Sie erfordern die besondere Beachtung des Planers und der Ausführenden. Eine fachgerechte Handhabung sowohl durch den Planer als auch durch den Ausführenden ist eine entscheidende Voraussetzung für eine funktionierende Abdichtung. Neue Regelwerke, wie die DAfStb-Richtlinie "Wasserundurchlässige Bauwerke aus Beton" und die DIN V 18197 "Abdichten von Fugen in Beton mit Fugenbändern" geben Hinweise, wie Abdichtungssysteme richtig einzusetzen und zu dimensionieren sind. In dem Beitrag wird auf die neuen Regelwerke und die wesentlichen Regelungen für die Abdichtung eingegangen. Joint Design and Joint Sealing in Waterproof Concrete Structures , New Regulations are setting New Sealing Standards In many cases joints in structures of waterproof concrete turn out to be a weak point. For this reason they demand the care and attention of the designer and the contractor. A professional application as well by the planner as by the contractor is a decisive precondition for an effective operation of the joint sealing. New regulations like DAfStb-code: "Waterproof concrete structures" and the German standard DIN V 18197: "Sealing of joints in concrete with waterstops" give details how the sealing systems should be used and dimensioned correctly. This article goes into the details of the new regulations and the basic rules for sealing. [source] A Quantitative Study of Fault Zone SealingACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010Yang LI Abstract: A fault is not simply a plane, but a zone consisting of a series of broken planes or lower faults. The greater the scale of faults, the wider and more complex the fault zone is. Fault-sealing properties are influenced by the fault zone itself, whose fault displacement, depth, net-to-gross-ratio of mudstone, fault plane angle, and fault mechanical properties play important controlling roles. The sealing of hydrocarbon by the fault zone depends on whether the fault zone can form a continuous sealing zone and if the pore throats connecting those fault zones are small enough. The concept of fault zone-sealing potential is proposed here, and a quantitative formula is established by using a great amount of practical statistical data as well as the fuzzy comprehensive evaluation method, which is a comprehensive characterization parameter to judge whether or not fault zones could seal oil hydrocarbon. The greater the value of the fault zone-sealing potential, the better sealed the fault is. For example, with increasing depth, the sealing degree of the Xin 68 Fault in the Dongxin 1 oilfield changes greatly, reflecting the complexity of fault-sealing properties. [source] Rationale for esthetic tissue preservation of a fresh extraction socket by an implant treatment concept simulating a tooth replantationDENTAL TRAUMATOLOGY, Issue 1 2010Georgia Trimpou A soft-tissue recession must be avoided, whether it is due to a compression of the peri-implant soft-tissue caused by an over-dimensioned restoration in the cervical collar of the provisional crown or to a too small dimensioned sulcus former. A simulation of the exact dimension of the lost tooth , especially on the cervical part of the new provisional restoration , is expected to preserve all relevant information and allows the design of a naturally looking emergence profile. Based on theoretical considerations and a case report, the authors intend to demonstrate that a near-naturally dimensioned sealing of the dento-gingival soft-tissue collar may initiate a tissue-maintaining healing process, similar to a tooth replantation. The natural dental crown, connected to an implant instead of the root, is applied for a tight sealing of the wound. If due to traumatic impact the tooth is no longer available, a naturally dimensioned crown restoration will serve as an alternative wound sealant. [source] Survival of mammalian B104 cells following neurite transection at different locations depends on somal Ca2+ concentrationDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2004Soonmoon Yoo Abstract We report that cell survival after neurite transection in a mammalian neuronal model (cultured B104 cells) critically depends on somal [Ca2+]i, a novel result that reconciles separate long-standing observations that somal survival decreases with more-proximal axonal transections and that increased somal Ca2+ is cytotoxic. Using fluorescence microscopy, we demonstrate that extracellular Ca2+ at the site of plasmalemmal transection is necessary to form a plasmalemmal barrier, and that other divalent ions (Ba2+, Mg2+) do not play a major role. We also show that extracellular Ca2+, rather than injury per se, initiates the formation of a plasmalemmal barrier and that a transient increase in somal [Ca2+]i significantly decreases the percentage of cells that survive neurite transection. Furthermore, we show that the increased somal [Ca2+]i and decreased cell survival following proximal transections are not due to less frequent or slower plasmalemmal sealing or Ca2+ entry through plasmalemmal Na+ and Ca2+ channels. Rather, the increased somal [Ca2+]i and lethality of proximal neurite injuries may be due to the decreased path length/increased diameter for Ca2+ entering the transection site to reach the soma. A ryanodine block of Ca2+ release from internal stores before transection has no effect on cell survival; however, a ryanodine- or thapsigargin-induced buildup of somal [Ca2+]i before transection markedly reduces cell survival, suggesting a minor involvement of Ca2+ -induced release from internal stores. Finally, we show that cell survival following proximal injuries can be enhanced by increasing intracellular Ca2+ buffering capacity with BAPTA to prevent the increase in somal [Ca2+]i. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 137,153, 2004 [source] Initial stages of neural regeneration in Helisoma trivolvis are dependent upon PLA2 activityDEVELOPMENTAL NEUROBIOLOGY, Issue 4 2003Matthew S. Geddis Abstract Neuronal regeneration after damage to an axon tract requires the rapid sealing of the injured plasma membrane and the subsequent formation of growth cones that can lead regenerating processes to their appropriate target. Membrane sealing and growth cone formation are Ca2+ -dependent processes, but the signaling pathways activated by Ca2+ to bring about these effects remain poorly understood. An in vitro injury model was employed in which neurites from identified snail neurons (Helisoma trivolvis) were transected with a glass microknife, and the formation of new growth cones from the distal portions of transected neurites was recorded at defined times after transection. This study presents three main results. First, phospholipase A2 (PLA2), a calcium-activated enzyme, is necessary for membrane sealing in vitro. Second, PLA2 activity is also required for the formation of a new growth cone after the membrane has sealed successfully. Thus, PLA2 plays a dual role by affecting both growth cone formation and membrane sealing. Third, the injury-induced activation of PLA2 by Ca2+ controls growth cone formation through the production of leukotrienes, secondary metabolites of PLA2 activity. Taken together, these results suggest that the injury-induced Ca2+ influx acts via PLA2 and leukotriene production to assure growth cone formation. These findings indicate that events that cause an inhibition of PLA2 or lipoxygenases, enzymes that produce leukotrienes, could result in the inability of neurites to regenerate. © 2003 Wiley Periodicals, Inc. J Neurobiol 54: 555,565, 2003 [source] Nonoperative treatment of four esophageal perforations with hemostatic clipsDISEASES OF THE ESOPHAGUS, Issue 5 2007A. Fischer SUMMARY., Spontaneous or iatrogenic esophageal perforations are despite advances of modern surgery and intensive care medicine still potentially life-threatening events with a considerable mortality rate. Recently, encouraging results on the sealing of esophageal perforations by placement of endoluminal prostheses were reported. However, if the perforation is very proximal (close to the larynx) or very distal (involving the cardia), the situation is to our experience unsuitable for stent therapy. In these special cases non-operative treatment is still possible by application of hemostatic metal clips. We present four cases unsuitable for stent therapy where the perforation was sealed by endoscopic clip application. All patients had an uneventful recovery. Non-operative treatment of esophageal perforations with hemostatic metal clips is feasible and safe in cases not treatable with self-expanding metal stents. [source] Interrill erosion on cultivated Greek soils: modelling sediment deliveryEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2006D. Dimoyiannis Abstract For interrill erosion, raindrop-induced detachment and transport of sediment by rainfall-disturbed sheet flow are the predominant processes, while detachment by sheet flow and transport by raindrop impact are negligible. In general, interrill subprocesses are inter-actively affected by rainfall, soil and surface properties. The objective of this work was to study the relationships among interrill runoff and sediment loss and some selected para-meters, for cultivated soils in central Greece, and also the development of a formula for predicting single storm sediment delivery. Runoff and soil loss measurement field experiments have been conducted for a 3·5-year period, under natural storms. The soils studied were developed on Tertiary calcareous materials and Quaternary alluvial deposits and were textured from sandy loam to clay. The second group of soils showed greater susceptibility to sealing and erosion than the first group. Single storm sediment loss was mainly affected by rain and runoff erosivity, being significantly correlated with rain kinetic energy (r = 0·64***), its maximum 30-minute intensity (r = 0·64***) and runoff amount (r = 0·56***). Runoff had the greatest correlation with rain kinetic energy (r = 0·64***). A complementary effect on soil loss was detected between rain kinetic energy and its maximum 30-minute intensity. The same was true for rain kinetic energy and topsoil aggregate instability, on surface seal formation and thus on infiltration characteristics and overland flow rate. Empirical analysis showed that the following formula can be used for the successful prediction of sediment delivery (Di): Di = 0·638,EI30tan(,) (R2 = 0·893***), where , is a topsoil aggregate instability index, E the rain kinetic energy, I30 the maximum 30-minute rain intensity and , the slope angle. It describes soil erodibility using a topsoil aggregate instability index, which can be determined easily by a simple laboratory technique, and runoff through the product of this index and rain kinetic energy. Copyright © 2006 John Wiley & Sons, Ltd. [source] Investigations into the Sealing of Heat Damaged Areas by Applying Polymer Powders During Laser Cutting of Carbon Fiber Reinforced Composites,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Peter Jaeschke Endless carbon fiber reinforced plastics are recognized as having the greatest lightweight construction potential of all materials. Fully automated process chains for the manufacturing of composite structures are needed in order to achieve production rates and cycle times required in many industrial sectors. In this paper, a new technique, based on the in situ sealing of the kerf during high power laser cutting by application of polymer powder is presented. The degree of sealing is analyzed as a function of powder mass flow as well as carrying gas flow and it is shown that moisture uptake can be reduced compared to unsealed laser cut specimens. [source] Dentine sealing provided by smear layer/smear plugs vs. adhesive resins/resin tagsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2007Marcela R. Carrilho The aim of this study was to evaluate the ability of five experimental resins, which ranged from hydrophobic to hydrophilic blends, to seal acid-etched dentine saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents (100% resin) or as solutions solvated with absolute ethanol (70% resin/30% ethanol). Fluid conductance was measured at 20 cm H2O hydrostatic pressure after sound dentine surfaces were: (i) covered with a smear layer; (ii) acid-etched; or (iii) bonded with neat or solvated resins, which were applied to acid-etched dentine saturated with water or ethanol. In general, the fluid conductance of resin-bonded dentine was significantly higher than that of smear layer-covered dentine. However, when the most hydrophobic neat resins (R1 and R2) were applied to acid-etched dentine saturated with ethanol, the fluid conductance was as low as that produced by smear layers. The fluid conductance of resin-bonded dentine saturated with ethanol was significantly lower than for resin bonded to water-saturated dentine, except for resin R4. Application of more hydrophobic resins may provide better sealing of acid-etched dentine if the substrate is saturated with ethanol instead of with water. [source] Reliability Aspects of Microsystems for Automotive Applications,ADVANCED ENGINEERING MATERIALS, Issue 4 2009Roland Müller-Fiedler Abstract The implementation of microsystems in automotive applications is certainly one of the driving forces for the success of MEMS as an industrial technology on mass production level. In many cases, automotive systems based on microsensors are critical to safety. Consequently, microsystems have to assure an accurate, reliable, and failsafe operation during the entire lifetime of the vehicle. Since, the car represents a harsh environment for electronic or mechanical systems and components, reliability issues of MEMS have moved more and more into the focus of research and development. In particular, reliability aspects related to packaging and assembly have become a key issue in lifetime investigations. The packaging of microsystems comprises a variety of materials and material combinations, that directly affect the stability of MEMS components. Therefore, sophisticated characterization methods are needed to extract the reliability-relevant material parameters. This paper gives an introduction into investigations of the stability assessment of glass frit bonding as well as new bonding technologies based on metallic sealing of MEMS devices. [source] Fabrication of Flexible Binary Amplitude Masks for Patterning on Highly Curved SurfacesADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Audrey M. Bowen Abstract This paper describes soft lithography methods that expand current fabrication capabilities by enabling high-throughput patterning on nonplanar substrates. These techniques exploit optically dense elastomeric mask elements embedded in a transparent poly(dimethylsiloxane) (PDMS) matrix by vacuum-assisted microfluidic patterning, UV,ozone-mediated irreversible sealing, and chemical etching. These protocols provide highly flexible photomasks exhibiting either positive- or negative-image contrasts, which serve as amplitude masks for large-area photolithographic patterning on a variety of curved (and planar) surfaces. When patterning on cylindrical surfaces, the developed masks do not experience significant pattern distortions. For substrates with 3D curvatures/geometries, however, the PDMS mask must undergo relatively large strains in order to make conformal contact. The new methods described in this report provide planar masks that can be patterned to compliantly compensate for both the displacements and distortions of features that result from stretching the mask to span the 3D geometry. To demonstrate this, a distortion-corrected grid pattern mask was fabricated and used in conjunction with a homemade inflation device to pattern an electrode mesh on a glass hemisphere with predictable registration and distortion compensation. The showcased mask fabrication processes are compatible with a broad range of substrates, illustrating the potential for development of complex lithographic patterns for a variety of applications in the realm of curved electronics (i.e., synthetic retinal implants and curved LED arrays) and wide field-of-view optics. [source] Geomechanical simulation to predict open subsurface fracturesGEOPHYSICAL PROSPECTING, Issue 2 2009Helen Lewis ABSTRACT Geomechanical simulation of the evolution of a geological structure can play an important role in predicting open fracture development for all stages in that structure's development. In this work, three such geomechanical simulations are used to predict the evolving stress and strain fields, including dilational and compactional changes in the rock fabric in developing fault and fold systems. Their consequences for open fracture development and flow are addressed. These simulated stress and strain fields show considerable spatial and temporal heterogeneity that is consistent with deformation patterns observed in both natural examples and in laboratory-deformed analogues. But the stress and strain states that develop are neither co-axial nor do they bear a simple relationship to one another. The dilational and compactional strains, manifest as open fracturing or sealing, represent some significantly increased or significantly decreased flow rates. However, open-fracture predictions based on such geomechanical simulations are extremely difficult to validate with any degree of confidence as there is little direct evidence of sub-surface fracture distributions. In this context we also discuss possible integration of seismic anisotropy measurements, as an independent measure of open fracture alignment, to support the geomechanically derived fracture predictions. The focus of this work is on volumetric strains in fault zone evolution, though folding is also addressed. [source] Current techniques of liver transectionHPB, Issue 3 2007RONNIE T.P. POON The operative mortality rate of liver resection has decreased from 10% to 20% before the 1980s to <5% in most specialized hepatobiliary centers nowadays. The most important factor for better outcome is reduced blood loss due to improvement in surgical techniques. Liver transection is the most challenging part of liver resection, associated with a risk of massive hemorrhage. Understanding the segmental anatomy of the liver and delineation of the proper transection plane using intraoperative ultrasound are prerequisites to safe liver transection. Clamp crushing and ultrasonic dissection are the two most widely used transection techniques. In recent years, new instruments using different types of energy for coagulation or sealing of vessels have been developed for liver transection. These include radiofrequency devices, Harmonic Scalpel, Ligasure and TissueLink dissecting sealer. Whether these new instruments, used alone or in combination with clamp crushing or ultrasonic dissection, improve the safety of liver transection has not been clearly demonstrated. The use of the vascular stapler for transection of major intrahepatic vascular trunks is also gaining popularity. These new instruments are particularly useful in liver transection during laparoscopic liver resection. Adjunctive measures such as intermittent Pringle maneuver and low central venous pressure anesthesia are also useful measures to reduce the risk of hemorrhage. This article reviews the safety and efficacy of different techniques of liver transection, with particular attention to evidence from randomized controlled trials available in the literature. [source] An in vitro comparison of adhesive systems to seal pulp chamber wallsINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2004B. Ozturk Abstract Aim, To compare in vitro the sealing properties of five different dentine adhesive materials (Prime&Bond NT (PBNT); Prompt L-Pop (PLP); Clearfil SE Bond (CSEB); Scotchbond Multi Purpose Plus (SMPP); EBS-Multi (EBSM)) inside the pulp chamber. Methodology, Seventy-five recently extracted human molar teeth were used. The roof of the pulp chambers and roots were removed under water cooling. Pulp tissue was removed, and the canal orifices were sealed. The pulp chambers were then treated with 5% sodium hypochlorite (NaOCl) for 1 min. The teeth were randomly divided into five groups of 15 teeth each. Adhesive systems were applied to the pulp chamber walls according to the manufacturers' instructions. The samples were connected to Plexiglass plates, and a fluid filtration method was used for quantitative evaluation of leakage. Measurements of fluid movement were made at 2-min intervals for 8 min. The quality of seal of each specimen was measured immediately, after 24 h, 1 week and 1 month. The data were statistically analysed by repeated-measurements multivariate anova, Friedman test, Wilcoxon signed rank test, Kruskal,Wallis of one-way anova and Mann,Whitney U -tests. The pulp chamber wall with and without NaOCl and resin,dentine interfaces of specimens were observed under a scanning electron microscope (SEM). Results, The leakage values of the materials were significantly different at different measurement periods. In all groups, leakage values decreased with time (P < 0.05). PBNT and PLP had the least leakage during immediate measurements (P < 0.05). After 1 month, leakage of all adhesive systems was not significantly different (P < 0.05). SEM observation of pulp chamber walls demonstrated that the irregular dentine surface without smear layer was present in the nontreated group. However, NaOCl application removed the collagen fibrils leaving the dentine surface smooth. At resin,dentine interfaces of specimens, no hybridization zone was observed. Conclusions, None of the materials had created a perfect seal to the pulp chamber walls. PBNT and PLP had better sealing over the short term, but over the long term, there were no differences between the materials. [source] Fluoropassivation and gelatin sealing of polyester arterial prostheses to skip preclotting and constrain the chronic inflammatory responseJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2010Xingyi Xie Abstract Fluoropassivation and gelatin coating have been applied to polyethylene terephthalate (PET) vascular prosthesis to combine the advantages of both polytetrafluoroethylene (PTFE) and PET materials, and to eliminate the preclotting procedure. The morphological, chemical, physical, and mechanical properties of such prostheses were investigated and compared with its original model. Fluoropassivation introduced OCF3, CF3, and CFCF2 structures onto the surface of the polyester fibers. However, the surface fluorine content was only 28,32% compared to the 66% in expanded PTFE (ePTFE) grafts. The fluoropassivation decreased the hydrophilicity, slightly increased the water permeability, and marginally lowered the melting point and the crystallinity of the PET fibers. After gelatin coating, the fluoropassivated and nonfluoropassivated prostheses showed similar surface morphology and chemistry. While gelatin coating eliminated preclotting, it also renders the prostheses slightly stiffer. The original prosthesis had the highest bursting strength (275 N), with the fluoropassivated and gelatin-sealed devices showing similar bursting strength between 210 and 230 N. Fluoropassivation and gelatin coating lowered the retention strength by 23 and 30% on average, respectively. In vitro enzymatic incubation had only marginal effect on the surface fluorine content of the nongelatin-sealed prostheses. However, the gelatin-sealed ones significantly lost their surface fluorine after in vitro enzymatic incubation (by 69,85%) or in vivo 6-month implantation (by 51,60%), showing the lability of the fluoropolymer layer under the hostile biological environment. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [source] A new force field for simulating phosphatidylcholine bilayersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2010David Poger Abstract A new force field for the simulation of dipalmitoylphosphatidylcholine (DPPC) in the liquid-crystalline, fluid phase at zero surface tension is presented. The structure of the bilayer with the area per lipid (0.629 nm2; experiment 0.629,0.64 nm2), the volume per lipid (1.226 nm3; experiment 1.229,1.232 nm3), and the ordering of the palmitoyl chains (order parameters) are all in very good agreement with experiment. Experimental electron density profiles are well reproduced in particular with regard to the penetration of water into the bilayer. The force field was further validated by simulating the spontaneous assembly of DPPC into a bilayer in water. Notably, the timescale on which membrane sealing was observed using this model appears closer to the timescales for membrane resealing suggested by electroporation experiments than previous simulations using existing models. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] CLINICAL CONSIDERATIONS FOR RESTORING MANDIBULAR INCISORS WITH PORCELAIN LAMINATE VENEERSJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 4 2008Robert D. Walter DDS Authors Porcelain laminate veneers have been proven to be a successful treatment modality for maxillary incisors in clinical practice and in controlled clinical studies. However, the data in clinical studies on the success of veneers for restoring mandibular incisors are limited. Clinically, the successful restoration of mandibular incisors with porcelain laminate veneers is one of the more challenging procedures in all of esthetic restorative dentistry. Limited coronal dimensions, the small amount of enamel available for bonding (particularly in the cervical areas), materials and techniques for the bonding procedures, and the response of the tooth,veneer complex to forces generated during the incisal loading in both functional as well as parafunctional contacts must be considered as potential sources of success or failure. This Critical Appraisal reviews three recent scientific articles to shed some light on these issues and, as in all research endeavors, leads the reader to identify additional areas of concern that might stimulate further scientific inquiry. The first publication studied predictors for enamel thickness for mandibular incisors. The second examined bonding protocols for exposed dentin and suggested immediate dentin sealing. The third paper addressed fracture behavior of mandibular incisors restored with porcelain laminate veneers in vitro. [source] Endoscopic fibrin sealing of gastrocutaneous fistulas after sleeve gastrectomy and biliopancreatic diversion with duodenal switchJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 12 2008Theodossis S Papavramidis Abstract Background and Aim:, Gastrocutaneous fistulas (GCF) are uncommon complications accounting for 0.5,3.9% of gastric operations. When their management is not effective, the mortality rate is high. This study reports the conservative treatment of GCF in morbidly obese patients who underwent biliopancreatic diversion with duodenal switch. Methods:, Ninety-six morbidly obese patients were treated in our department with biliopancreatic diversion with duodenal switch (Marceau technique) and, in six of them, a high-output GCF developed. A general protocol was applied to all patients presenting a GCF. Everyone was treated by total parenteral nutrition (TPN) and somatostatin for at least 7 days after the appearance of the leak. If the leak continued, then fibrin glue was used as a tissue adhesive. Endoscopic application of the sealant was accomplished under direct vision via a double-lumen catheter passed through a forward-viewing gastroscope. Results:, All patients were treated successfully with conservative treatment (either solely with TPN and somatostatin, or with endoscopic fibrin sealing sessions). No evidence of fistula was observed at gastroscopy 3 and 24 months after therapy. Conclusion:, The conservative treatment of GCF following biliopancreatic diversion with duodenal switch is highly effective. All patients should enter a protocol that includes TPN and somatostatin. When the GCF persist, endoscopic sealing glue should be considered before operation because it is simple, safe, effective and, in some cases, life-saving. Therefore, conservative treatment should be employed as a therapeutic option in GCF developing after bariatric surgery. [source] Evaluation of different sealing methods for anodized aluminum-silicon carbide (Al/SiC) composites using EIS and SEM techniquesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2007H. Herrera-Hernandez Electrochemical impedance spectroscopy (EIS) and the scanning electron microscope (SEM) have been used in an investigation of the effectiveness of various sealing methods that can be used to improve the corrosion resistance of an anodized aluminum-silicon carbide (Al/SiC) composite. Anodic oxide films were grown on Al7075-T6 and the Al/SiC composite by sulfuric acid anodizing and sealing in a cold saturated solution of nickel acetate. Other samples were sealed using the traditional method of boiling water or hot nickel acetate for comparison. The results revealed a uniform anodized layer on Al7075-T6 that resisted pitting corrosion for more than 2,weeks exposure to NaCl, whereas a cracked oxide film with variations in thickness was observed on the composite material. Pit initiation occurred in less than 5,days on the anodized Al/SiC that was sealed in the hot solutions. This study suggests that the traditional hot sealing methods did not provide sufficient corrosion protection for aluminum metal,matrix composites (MMCs) because the reinforcing SiC particles deteriorated the surface film structure. However, this defective film can be repaired by nickel hydrate precipitation during cold sealing or by applying a thick polyurethane coating. [source] Intracellular membrane trafficking in bone resorbing osteoclastsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2003Mika Mulari Abstract There is ample evidence now that the two major events in bone resorption, namely dissolution of hydroxyapatite and degradation of the organic matrix, are performed by osteoclasts. The resorption cycle involves several specific cellular activities, where intracellular vesicular trafficking plays a crucial role. Although details of these processes started to open up only recently, it is clear that vesicular trafficking is needed in several specific steps of osteoclast functioning. Several plasma membrane domains are formed during the polarization of the resorbing cells. Multinucleated osteoclasts create a tight sealing to the extracellular matrix as a first indicator of their resorption activity. Initial steps of the sealing zone formation are ,v,3 -integrin mediated, but the final molecular interaction(s) between the plasma membrane and mineralized bone matrix is still unknown. A large number of acidic intracellular vesicles then fuse with the bone-facing plasma membrane to form a ruffled border membrane, which is the actual resorbing organelle. The formation of a ruffled border is regulated by a small GTP-binding protein, rab7, which indicates the late endosomal character of the ruffled border membrane. Details of specific membrane transport processes in the osteoclasts, e.g., the formation of the sealing zone and transcytosis of bone degradation products from the resorption lacuna to the functional secretory domain remain to be clarified. It is tempting to speculate that specific features of vesicular trafficking may offer several potential new targets for drug therapy of bone diseases. Microsc. Res. Tech. 61:496,503, 2003. © 2003 Wiley-Liss, Inc. [source] Characterization for water vapour barrier and heat sealability properties of heat-treated paperboard/polylactide structurePACKAGING TECHNOLOGY AND SCIENCE, Issue 8 2009Kimmo Lahtinen Abstract The moisture barrier and heat sealability properties of polylactide (PLA) extrusion-coated paperboard were investigated. The first part of the study focused on the influences of coating weight and surroundings temperature and relative humidity on the water vapour transmission rate (WVTR) of the structure. The outcome arising from this part was a simple and practical equation that allows calculating the WVTR as a function of PLA coating weight under specific thermo-hygrometric conditions. The second part of the study investigated the effect of heat treatments between 100 and 150°C on the WVTR and heat sealability of a 20,g/m2 PLA-coated paperboard. According to the results, the lowest WVTR values achieved were about 2.5 times lower than the WVTR of the untreated structure. Presumably, the PLA coating experienced two types of reordering mechanisms: crystalline growth and packing of the amorphous structure. The greatest barrier improvement was achieved when both of these mechanisms were accumulated effectively. This was observed from the samples after a 40,min treatment at 130°C. Ultimately, the crystalline growth was experienced by PLA at 100,130°C temperatures. The packing of the amorphous section, which was also accumulated at higher temperatures, was suggested to be the decisive factor influencing WVTR. According to the heat sealing results, the heat treatments causing crystalline growth resulted in considerably increased sealing temperatures and reduced applicability of the material in high-speed packaging applications. The treatments at 140,150°C caused only a slight increase in the sealing temperature and maintained the sealing performance of PLA. Copyright © 2009 John Wiley & Sons, Ltd. [source] Seal bond characterization of laminated plastic food cups by scanning electron and optic microscopesPACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2004Zehra Ayhan Abstract Heat seals of laminated semi-rigid food cups were evaluated to characterize the seal bond. Laminated lidding material was sealed at temperatures of 160,180°C to thermoformed cups. Various seal regions of the cups with different ultrasonic signal strengths (%) were sectioned at the rim and examined using optical and scanning electron microscopes (SEM). Ultrasonic signals were able to pinpoint seal defects; however, the magnitude of the signals did not relate to the actual seal condition or seal quality affected by the sealing process. This was attributed to the very short seal width and non-parallel surface of the heat seal, which possibly resulted in signal loss by reflection and scattering from the seal surface. C-scan of ultrasound, SEM and optical microscopic images provided the information that the heat-sealing process was unstable, due to insufficient and non-uniform heat-seal temperature or pressure, misalignment of the sealing jaws or non-parallel sealing or cutting unit configuration. Copyright © 2004 John Wiley & Sons, Ltd. [source] Heat penetration characteristics and shelf-life studies of mushrooms in brine processed in retort pouchesPACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2004V. Chandrasekar Abstract White button mushrooms were washed, blanched and cut longitudinally into two halves. 100,g mushroom halves was placed into each retort pouch and 90,ml hot brine (2% salt, 0.1% citric acid) was added. Retort pouches (105,µm thick) had an outer polyester layer (12.5,µm), a middle aluminium layer (12.5,µm) and an inner cast polypropylene layer (80,µm); pouch size was 20 × 16,cm, seal size 10,mm and lip size 4,mm. Pouches were fixed with thermocouples for recording the core temperature of the mushroom pieces, using a data recorder and a computer. After sealing and over-pressure retorting at F0 = 9.6, the pouches were stored at the ambient conditions. The heat penetration parameters were calculated. The heating curve obtained was logarithmic in nature. Sensory evaluation of mushroom curry prepared from the stored mushrooms showed that the product had high acceptability (7.9 on a scale of 10) which reduced very slightly (to 7.5) during storage for 12 months. No deformity, leakage or spoilage was noticed and the product remained sterile and acceptable even after 12 months of storage at the ambient conditions (20,30°C). Copyright © 2004 John Wiley & Sons, Ltd. [source] The potential efficiency of irrigation management and propargyl bromide in controlling three soil pests: Tylenchulus semipenetrans, Fusarium oxysporum and Echinochloa crus-galliPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2005Suzanne E Allaire Abstract Propargyl bromide (3-bromopropyne, 3BP) is a potential alternative for methyl bromide. Little information is available about its efficiency in controlling pests. The purpose of this paper is to estimate the 3BP dose required for killing three pests and to compare the efficiency of water management approaches to that of fumigation. The pests, Fusarium oxysporum Schlecht (fungus), Echinochloa crus-galli (L) Beauv (grass) and Tylenchulus semipenetrans Cobb (nematode) were exposed to different 3BP concentrations in a sandy loam at 30 °C in a closed system. The lethal dose for killing 90% of the population (LD90) was calculated from the total applied mass, and varied from 0.3 µg g,1 soil for the nematode, 3 µg g,1 for the grass, and 9 µg g,1 for the fungus. The concentration,time index for killing 90% of the population (CT90) was 11 µg g,1 h for the nematode, 112 µg g,1 h for the grass and 345 µg g,1 h for the fungus. 3BP seems as efficient as other fumigant alternatives in controlling these pests. Using an open system, it was shown that the volume of soil in which the pests were controlled varied for different irrigation managements. Even 96 h after fumigation (with a concentration 10 times higher than would potentially be applied in the field), more than 20% of the soil volume had not reached the fungus and grass CT90 of the non-irrigated soil. The soil underneath the furrow and the bed reached CT90 only slowly in all irrigated treatments even though techniques for increasing efficiency were used (tarping, surface sealing with water and high application rate). Copyright © 2005 Society of Chemical Industry [source] Nitric oxide, induced by wounding, mediates redox regulation in pelargonium leavesPLANT BIOLOGY, Issue 5 2009M. Arasimowicz Abstract The subject of this study was the participation of nitric oxide (NO) in plant responses to wounding, promoted by nicking of pelargonium (Pelargonium peltatum L.) leaves. Bio-imaging with the fluorochrome 4,5-diaminofluorescein diacetate (DAF-2DA) and electrochemical in situ measurement of NO showed early (within minutes) and transient (2 h) NO generation after wounding restricted to the site of injury. In order to clarify the functional role of NO in relation to modulation of the redox balance during wounding, a pharmacological approach was used. A positive correlation was found between NO generation and regulation of the redox state. NO caused a slight restriction of post-wounded O2, production, in contrast to the periodic and marked increase in H2O2 level. The observed changes were accompanied by time-dependent inhibition of catalase (CAT) and ascorbate peroxidase (APX) activity. The effect was specific to NO, since the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5 tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) reversed the inhibition of CAT and APX, as well as temporarily enhancing H2O2 synthesis. Finally, cooperation of NO/H2O2 restricted the depletion of the low-molecular weight antioxidant pool (i.e. ascorbic acid and thiols) was positively correlated with sealing and reconstruction changes in injured pelargonium leaves (i.e. lignin formation and callose deposition). The above results clearly suggest that NO may promote restoration of wounded tissue through stabilisation of the cell redox state and stimulation of the wound scarring processes. [source] Novel highly elastic magnetic materials for dampers and seals: part II.POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2007Material behavior in a magnetic field Abstract The combination of polymers with magnetic particles displays novel and often enhanced properties compared to the traditional materials. They can open up possibilities for new technological applications. The magnetic field sensitive elastomers represent a new type of composites consisting of small particles, usually from nanometer range to micron range, dispersed in a highly elastic polymeric matrix. In this paper, we show that in the presence of built-in magnetic particles it is possible to tune the elastic modulus by an external magnetic field. We propose a phenomenological equation to describe the effect of the external magnetic field on the elastic modulus. We demonstrate the engineering potential of new materials on the examples of two devices. The first one is a new type of seals fundamentally different from those used before. In the simplest case, the sealing assembly includes a magnetoelastic strip and a permanent magnet. They attract due to the magnetic forces. This ensures that due to high elasticity of the proposed composites and good adhesion properties, the strip of magnetoelastic will adopt the shape of the surface to be sealed, this fact leading to an excellent sealing. Another straightforward application of the magnetic composites is based on their magnetic field dependent elastic modulus. Namely, we demonstrate in this paper the possible application of these materials as adjustable vibration dampers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Latest news and product developmentsPRESCRIBER, Issue 6 2008Article first published online: 24 APR 200 Government responds to NICE report The Government has published its response to the Health Select Committee's report into NICE, broadly arguing that the Committee's recommendations are either already being dealt with or are not appropriate. The Committee recommended appraisals for all new drugs, shorter, rapid appraisals to coincide with their launch, and improved mechanisms for setting drug prices. The Government says its negotiations on the PPRS preclude a detailed response but suggests a rapid system may not be transparent or legally robust. It is exploring how high-cost drugs can be brought within the payment-by-results tariff. While defending NICE's reliance on QALYs, the Government accepts the need to explore how wider economic factors can be considered. As for the threshold cost per QALY by which NICE defines cost effectiveness, it says this is being validated scientifically and NICE will continue to determine the threshold. More topically, the Committee criticised the quality of clinical trial data available to NICE. The Government sees no need to compel pharmaceutical companies to disclose information and says NICE is already becoming more involved with research programmes. All clinical trials must be registered (confidentially) with the EU and the Government believes mandatory registration in the UK would be ineffective and illegal. Prescription charge up again from April The Government has raised the prescription charge by 25p to £7.10 per item with effect from 1 April. Prescription prepayment certificates will cost £27.85 for three months and £102.50 for 12 months. The increase, below the annual rate of inflation for the 10th successive year, will be levied on the 12 per cent of prescriptions that are liable for the charge: 5 per cent via prepayment certificates and 7 per cent from other prescriptions. The charge will generate £435 million in England in 2008/09; this excludes money from prescriptions written by dispensing doctors, which is retained by the PCT. Following criticism of the charge by the Health Select Committee, the Government says it has reviewed the charge and is now consulting on ,cost-neutral' options. MHRA safety update The MHRA warns of possible dose errors associated with Boots Medisure Domiciliary Dosage System in its latest issue of Drug Safety Update (2008;1:issue 8). One case has been reported in which incomplete sealing allowed tablets to mix between compartments. No other cases are known and the MHRA says no harm was reported but the risk is serious. The system should be carefully sealed and inspected visually and physically. The MHRA reaffirms its plans to reclassify all pseudoephedrine and ephedrine products to prescription-only status in 2009 if the new restrictions on sales do not reduce misuse. Other topics in this month's Update include revised indications for oral ketoconazole (Nizoral), restricting its use to selected conditions unresponsive to topical therapy; reformulation of the injectable antibiotic Tazocin (piperacillin plus tazobactum); the risk of peripheral neuropathy associated with pegylated interferon and telbivudine (Sebivo) in the treatment of hepatitis B; and serious adverse events associated with modafinil (Provigil). First oral anticoagulant since warfarin In January this year the EMEA issued a positive opinion to recommend marketing authorisation of the oral, fixed-dose, direct thrombin inhibitor dabigatran etexilate (Pradaxa) for the primary prevention of venous thromboembolism (VTE) in adult patients that have undergone elective knee or hip replacement surgery. Marketing authorisation for the EU (including the UK) is expected from the European Commission in the next few weeks, making dabigatran the first oral anticoagulant since warfarin was introduced in 1954. Dabigatran etexilate has been shown to be as safe and effective as enoxaparin (Clexane) with a similar adverse event profile in the noninferiority phase III RENOVATE (Lancet 2007;370: 949-56) and RE-MODEL (J Throm Haemost 2007;5:217885) trials, which investigated the efficacy and safety of dabigatran compared to enoxaparin in reducing the risk of VTE after total hip and knee surgery respectively. Dabigatran has the practical advantage over low-molecular-weight heparin of oral postoperative administration and no risk of heparin-induced thrombocytopenia and, unlike warfarin, does not require monitoring or dose titration. Risk scale predicts anticholinergic effects US investigators have developed a scale for predicting the risk of anticholinergic side-effects from older patients' medicines (Arch Intern Med 2008;168: 508-13). The scale assigns a score from 1 (low) to 3 (high) for the risk of anticholinergic effects such as dry mouth, constipation and dizziness associated with commonly prescribed medicines. Checking the scale retrospectively in older patients in residential care, a higher score was associated with a 30 per cent increased risk of side-effects after adjustment for age and number of medicines. When this was repeated prospectively in a primary-care cohort, the increased risk was 90 per cent. HRT cancer risk persists The latest analysis of the Women's Health Initiative (WHI) trial of HRT shows that the small increase in the risk of cancer persists for up to three years after stopping treatment (J Am Med Assoc 2008;299:1036-45). WHI was stopped after 5.6 years' follow-up when it became clear the risks of HRT outweighed its benefits. This follow-up after a further three years (mean 2.4) involved 15 730 women. The annual risk of cardiovascular events was similar for HRT (1.97 per cent) and placebo (1.91 per cent). Cancers were more common among women who had taken HRT (1.56 vs 1.26 per cent), in particular breast cancer (0.42 vs 0.33 per cent). All-cause mortality was higher, but not statistically significantly so, with HRT (1.20 vs 1.06 per cent). Tight glycaemic control may increase falls Maintaining HbA1C at or below 6 per cent with insulin is associated with an increased risk of falls, a US study suggests (Diabetes Care 2008;31:391-6). The Health, Aging and Composition study involved 446 older people with type 2 diabetes (mean age 74) followed up for approximately five years. The incidence of falls ranged from 22 to 30 per cent annually. Comparing subgroups with HbA1C of ,6 per cent and >8 per cent, an increased risk of falls was associated with insulin use (odds ratio 4.4) but not oral hypoglycaemic drugs. Copyright © 2008 Wiley Interface Ltd [source] | |||||||||||||||||||||||||