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Terms modified by Cantilever Selected AbstractsFive-year results of fixed implant-supported rehabilitations with distal cantilevers for the edentulous mandibleCLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2009German O. Gallucci Abstract Objectives: The purpose of this study was to evaluate the survival rate, success rate and primary complications associated with mandibular fixed implant-supported rehabilitations with distal cantilevers over 5 years of function. Material and methods: In this prospective multi-center trial, 45 fully edentulous patients were treated with implant-supported mandibular hybrid prostheses with distal extension cantilevers. Data were collected at numerous time points, including but not limited to: implant placement, abutment placement, final prosthesis delivery, 3 months and 5 years post-loading. Biological, implant and prosthetic parameters defining survival and success were evaluated for each implant including: sulcus bleeding ndex (SBI) at four sites per implant, width of facial and lingual keratinized gingiva (mm), peri-implant mucosal level (mid-facial from the top of the implant collar, measured in mm), modified plaque index (MPI) at four sites per implant, mobility and peri-implant radiolucency. Survival was defined as implants or prostheses that did not need to be replaced. Success rate was defined as meeting well-established criteria that were chosen to indicate healthy peri-implant mucosa osseointegration, prostheses success and complications. Results: A total of 237 implants in 45 completely edentulous patients were included in the study. In each patient, four to six implants were placed to support hybrid prostheses with distal cantilevers. Cantilevers ranged in length from 6 to 21 mm, with an average length of 15.6 mm. The ages of the patients ranged from 34 to 78 with a mean age of 59.5 years. The survival rate of implants was 100% (237/237) and for prostheses 95.5% (43/45). The overall treatment success rate was calculated as 86.7% (39/45). Of the six patients that have not met the criteria for success, two patients required replacement of the entire prosthesis and four patients presented >four complications events. Conclusion: Fixed implant-supported rehabilitation with distal cantilever resulted in a reliable treatment modality over the 5-year observation period. Although biological parameters of MPI, SBI, keratinized tissue and peri-implant mucosal levels showed statistically significant differences over time, the mean values for each patient remained within the normal limits of oral health. Complications were categorized as biological or technical. The majority of complications were technical complications (54/79) and of these most involved fracture of the acrylic teeth and base (20/54). While the survival rate was 100% for implants and 95.5% for prostheses, the application of strict criteria for treatment success resulted in an overall treatment success rate of 86.7%. [source] Effects of wet meadow riparian vegetation on streambank erosion.EARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2002Abstract We measured the effect of wet meadow vegetation on the bank strength and failure mechanics of a meandering montane meadow stream, the South Fork of the Kern River at Monache Meadow, in California's Sierra Nevada. Streambanks colonized by ,wet' graminoid meadow vegetation were on average five times stronger than those colonized by ,dry' xeric meadow and scrub vegetation. Our measurements show that strength is correlated with vegetation density indicators, including stem counts, standing biomass per unit area, and the ratio of root mass to soil mass. Rushes appear better than sedges at stabilizing coarse bar surfaces, while sedges are far more effective at stabilizing actively eroding cut banks. Wet meadow floodplain vegetation creates a composite cut bank configuration (a cohesive layer overlying cohesionless materials) that erodes via cantilever failure. Field measurements and a geotechnical model of cantilever stability show that by increasing bank strength, wet meadow vegetation increases the thickness, width, and cohesiveness of a bank cantilever, which, in turn, increases the amount of time required to undermine, detach, and remove bank failure blocks. At Monache Meadow, it takes approximately four years to produce and remove a 1 m wide wet meadow bank block. Wet meadow vegetation limits bank migration rates by increasing bank strength, altering bank failure modes, and reducing bank failure frequency. Copyright © 2002 John Wiley & Sons, Ltd. [source] From Molecular Machines to Microscale Motility of Objects: Application as "Smart Materials", Sensors, and NanodevicesADVANCED FUNCTIONAL MATERIALS, Issue 5 2007I. Willner Abstract Machinelike operations are common functions in biological systems, and substantial recent research efforts are directed to mimic such processes at the molecular or nanoscale dimensions. The present Feature Article presents three complementary approaches to design machinelike operations: by the signal-triggered mechanical shuttling of molecular components; by the signal-triggering of chemical processes on surfaces, resulting in mechanical motion of micro/nanoscale objects; and by the fuel-triggered motility of biomolecule,metal nanowire hybrid systems. The shuttling of molecular components on molecular wires assembled on surfaces in semirotaxane configurations using electrical or optical triggering signals is described. The control of the hydrophilic/hydrophobic surface properties through molecular shuttling or by molecular bending/stretching processes is presented. Stress generated on microelements, such as cantilevers, results in the mechanical deflection of the cantilever. The deposition of a redox-active polyaniline film on a cantilever allows the reversible electrochemically induced deflection and retraction of the cantilever by the electrochemical oxidation or reduction of the polymer film, respectively. A micro-robot consisting of the polypyrrole (PPy) polymer deposited on a multi-addressable configuration of electrodes is described. Au magnetic core/shell nanoparticles are incorporated into a polyaniline film, and the conductivity of the composite polymer is controlled by an external magnet. Finally, the synthesis of a hybrid nanostructure consisting of two actin filaments tethered to the two ends of a Au nanowire is described. The adenosine triphosphate (ATP)-fueled motility of the hybrid nanostructure on a myosin monolayer associated with a solid support is demonstrated. [source] Fabrication of Microcantilever Sensors Actuated by Piezoelectric Pb(Zr0.52Ti0.48)O3 Thick Films and Determination of Their Electromechanical Characteristics,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2005H. Park Abstract The integration and the device realization of Pb(Zr,,Ti)O3 (PZT) thick films on Si substrates are known to be extremely difficult because the processing temperature of the PZT thick film is close to the melting point of Si. However, PZT thick-film devices on Si warrant attention as they are appropriate for biological transducers; they generate large actuating forces and have a relatively high sensitivity for mass detection, especially in liquids. In this study, Pb(Zr0.52Ti0.48)O3 thick-film cantilever devices are successfully fabricated on a Pt/TiO2/SiNx/Si substrate using a screen-printing method and microelectromechanical systems (MEMS) process. Elastic and electromechanical properties such as the Young's modulus and transverse piezoelectric coefficient are determined from microstructural and electrical analyses for further mechanical study. The calculated Young's modulus of the thick film, 53.9,±,3.85,GPa, corresponds to the resonant frequency obtained from the measured harmonic oscillation response. The transverse piezoelectric constant, d31, of ,20.7 to ,18.8,pC,N,1 is comparable to that of a dense thin film. These values promise the possibility of determining the resonance properties of a thick-film cantilever by designing its structure and then simulating the harmonic oscillation response. Using the PZT thick-film cantilever, a strong harmonic oscillation with a quality (Q) factor of about 23 is demonstrated in water. The observation of strong harmonic oscillation in liquid implies the feasibility of precise real-time recognition of biomolecules using PZT thick-film cantilevers. [source] Scanning Probe Parallel Nanolithography with Multiprobe Cantilever Array Fabricated by Bulk Silicon MicromachiningIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2008Hensy Gandjar Non-member Abstract This work describes a scanning probe parallel nanolithography (SPNL) technique for high throughput in nanometric patterning on single-crystal silicon (SCS) substrates. Two types of multiprobe cantilever arrays used for SPNL were fabricated by conventional micromachining. All the probes mounted on the free end of each cantilever were made of quasitrihedral pyramidal shape composed of (311) and (411) planes using the originally designed mask. Negative and positive types of nanolithography were performed on the basis of field-enhanced anodization and self-assembled monolayer mask techniques, respectively, and they succeeded in drawing a number of nanometric patterns of silicon dioxide (SiO2) on SCS substrates. After anisotropic wet etching of the SCS substrates using the SiO2 films as the mask material, we were also able to fabricate nanowires and nanogrooves. The effects of the applied voltage and scan time of cantilever arrays on wire and groove dimensions were systematically examined by atomic force microscopy (AFM) observations. An optimum condition for the parallel SPNL is proposed on the basis of this research. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [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] All-Oxide Crystalline Microelectromechanical Systems: Bending the Functionalities of Transition-Metal Oxide Thin FilmsADVANCED MATERIALS, Issue 23 2009Luca Pellegrino A crystalline all-oxide microelectromechanical system is presented. A suspended SrTiO3(001) cantilever is employed as flexible substrate for the deposition of epitaxial transition-metal oxide films. A strain generator device for oxide films is thus demonstrated, changing the conductivity of an overgrown epitaxial (La,Sr-)-MnO3 film by bending downward the SrTiO3 element with an AFM tip or a gate voltage bias. [source] On optimization of bio-probesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2004N. L. Pedersen Abstract The present paper deals with the modelling and optimization of small bio-probes that can be used for biological sensing; the bio-probes can be classified as MicroElectroMechnical Systems (MEMS). The objective is to optimize the structure of the bio-probes in order to maximize the sensing sensitivity. A biological coating results in a prestress on the sensing cantilever when certain molecules are present in the surrounding medium. The mechanical deformation due to the biological material is modelled by applying a prestress in the top layer of the bio-probes. Topology optimization is used to improve the design. In the present work it is necessary to use an interpolation scheme different from the SIMP (power law) approach which is usually used in topology optimization. In calculating the sensitivities, needed for the optimization, complications due to the prestress occur, but also due to the coupling between the elastic field and the electric field which both must be used in an integrated model. These complications are dealt with and analytically obtained sensitivities are presented. Copyright © 2004 John Wiley & Sons, Ltd. [source] Accessing Time,Varying Forces on the Vibrating Tip of the Dynamic Atomic Force Microscope to Map Material CompositionISRAEL JOURNAL OF CHEMISTRY, Issue 2 2008Ozgur Sahin In dynamic atomic force microscopes the primary physical quantities being measured are the amplitude/phase or amplitude/frequency of the vibrating force probe. Topographic images with spatial resolutions down to the atomic scale can be obtained by mapping these measurements across the sample surface under feedback control. During the imaging process the vibrating tip is observing tip,sample interaction potentials (force,distance relationships) at every point on the surface. The interaction potential is a superposition of short- and long,distance interactions of various origins determined by the material compositions of the tip, sample, and the medium of imaging. In principle, measurement of tip,sample interaction potential should allow determination and mapping of material composition of the sample. However, a single measurement of amplitude/phase or amplitude/frequency in dynamic atomic force microscopes is not enough to characterize a complicated tip,sample interaction potential. Recent developments in the understanding of dynamics of the vibrating force probe (cantilever), together with specially designed cantilevers that utilize torsional vibrations in addition to conventional vertical vibrations, enable the recovery of tip,sample interaction potentials at a timescale less than a millisecond. Here, with theory and experiments, we discuss how these cantilevers recover the information about the tip,sample interaction forces and give an example of compositional mapping on a polymeric material system. [source] Improved lateral force calibration based on the angle conversion factor in atomic force microscopyJOURNAL OF MICROSCOPY, Issue 2 2007DUKHYUN CHOI Summary A novel calibration method is proposed for determining lateral forces in atomic force microscopy (AFM), by introducing an angle conversion factor, which is defined as the ratio of the twist angle of a cantilever to the corresponding lateral signal. This factor greatly simplifies the calibration procedures. Once the angle conversion factor is determined in AFM, the lateral force calibration factors of any rectangular cantilever can be obtained by simple computation without further experiments. To determine the angle conversion factor, this study focuses on the determination of the twist angle of a cantilever during lateral force calibration in AFM. Since the twist angle of a cantilever cannot be directly measured in AFM, the angles are obtained by means of the moment balance equations between a rectangular AFM cantilever and a simple commercially available step grating. To eliminate the effect of the adhesive force, the gradients of the lateral signals and the twist angles as a function of normal force are used in calculating the angle conversion factor. To verify reliability and reproducibility of the method, two step gratings with different heights and two different rectangular cantilevers were used in lateral force calibration in AFM. The results showed good agreement, to within 10%. This method was validated by comparing the coefficient of friction of mica so determined with values in the literature. [source] Treatment planning for replacing missing teeth in UK general dental practice: current trendsJOURNAL OF ORAL REHABILITATION, Issue 7 2010P. M. PATEL Summary, The aim of this study was to examine the confidence, barriers and attitudes towards the replacement of missing teeth by general dental practitioners (GDPs). The perceived impact of the recently introduced National Health Service (NHS) contract on the provision of prosthodontic treatments was also considered. Pre-piloted postal questionnaires were mailed to 500 GDPs in Wales. Open- and closed-ended questions were utilised to establish confidence, adequacy of training and attitudes towards treatments for replacing missing teeth. Two hundred and seventeen completed questionnaires were received (response rate = 43·4%). Many respondents described themselves as ,confident' or ,very confident' in the provision of removable partial dentures (RPDs) (acrylic = 100%, metal based = 99·5%), cantilever resin-bonded bridges (94·4%) and conventional bridgework (98·6%). GDPs were ,not confident' providing fixed-fixed resin-bonded bridges (21·1%) or implants (81·4%). Financial barriers were identified to the provision of prosthodontic treatments, including comments such as "the new [National Health Service] contract does limit the treatments available". Privately funded patients were more likely to be offered a fixed bridge or implant replacement of a missing upper first molar, whereas non-privately funded patients were more likely to be offered no treatment (P < 0·01). Most respondents reported confidence at providing more routine forms of prosthodontic care such as RPDs and bridges. It appears that funding arrangements may have an impact on treatments offered to replace missing teeth, particularly under the current NHS contract. [source] A retrospective study of pre-fabricated carbon fibre root canal postsJOURNAL OF ORAL REHABILITATION, Issue 10 2003S.-O. Hedlund summary, Although pre-fabricated carbon fibre posts have been used during the past decade clinical evaluations of the technique are still few. Using dental records and radiographs the clinical performance of 65 pre-fabricated carbon fibre posts (Composipost and Endopost) placed in 48 patients who regularly visited a general practice were evaluated in the present study. After an average time of 2.3 ± 0·8 years (median 2·1 years, range 1,4·9 years) of clinical service the failure rate was 3%. Failure occurred in one tooth with a single crown restoration and in one tooth that was part of a cantilever fixed partial denture. Although the failure rate is lower than those mostly reported for metallic posts and cores more clinical studies are necessary to assess the suitability of pre-fabricated carbon fibre posts for routine use as an alternative to individually cast posts. [source] Intrinsic adhesion force of lubricants to steel surfaceJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2004Jonghwi Lee Abstract The intrinsic adhesion forces of lubricants and other pharmaceutical materials to a steel surface were quantitatively compared using Atomic Force Microscopy (AFM). A steel sphere was attached to the tip of an AFM cantilever, and its adhesion forces to the substrate surfaces of magnesium stearate, sodium stearyl fumarate, lactose, 4-acetamidophenol, and naproxen were measured. Surface roughness varied by an order of magnitude among the materials. However, the results clearly showed that the two lubricants had about half the intrinsic adhesion force as lactose, 4-acetamidophenol, and naproxen. Differences in the intrinsic adhesion forces of the two lubricants were insignificant. The lubricant molecules were unable to cover the steel surface during AFM measurements. Intrinsic adhesion force can slightly be modified by surface treatment and compaction, and its tip-to-tip variation was not greater than its difference between lubricants and other pharmaceutical particles. This study provides a quantitative fundamental basis for understanding adhesion related issues. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:2310,2318, 2004 [source] THE STRUCTURE AND NANOMECHANICAL PROPERTIES OF THE ADHESIVE MUCILAGE THAT MEDIATES DIATOM-SUBSTRATUM ADHESION AND MOTILITY,JOURNAL OF PHYCOLOGY, Issue 6 2003Michael J. Higgins We investigated the adhesive mucilage and mechanism of cell-substratum adhesion of two benthic raphid diatoms, the marine species Craspedostauros australis E. J. Cox and the freshwater species Pinnularia viridis (Nitzsch) Ehrenberg. SEM images of P. viridis and C. australis cells revealed the presence of multistranded tethers that appear to arise along the raphe openings and extend for a considerable distance from the cell before forming a "holdfast-like" attachment with the substratum. We propose that the tethers result from the elongation/stretching of composite adhesive mucilage strands secreted from raphes during the onset of cell adhesion and reorientation. Atomic force microscopy (AFM) force measurements reveal that the adhesive strands originating from the nondriving raphe of live C. australis and P. viridis are highly extensible and accumulate to form tethers. During force measurements tethers can be chemically stained and are seen to extend between the cantilever tip and a cell during elongation and relaxation. In most cases, AFM force measurements recorded an interaction with a number of adhesive strands that are secreted from the raphe. The force curves of C. australis and P. viridis revealed a sawtooth pattern, suggesting the successive unbinding of modular domains when the adhesive strands were placed under stress. In addition, we applied the "fly-fishing" technique that allowed the cantilever, suspended a distance above the cell, to interact with single adhesive strands protruding from the raphe. These force curves revealed sawtooth patterns, although the binding forces recorded were in the range for single molecule interactions. [source] STIFFNESS OF COMPRESSION TESTING MACHINESJOURNAL OF TEXTURE STUDIES, Issue 2 2000HARALD ROHM ABSTRACT A ring test with six participating laboratories and rubber stoppers as reference material was performed to monitor the performance of commercial compression testing instruments. Testing conditions were chosen to be in the range of regular compression testing. Small, single screw instruments with a cantilever exhibited a significant deviation in the force/deformation-response compared with double-screw instruments with a crosshead. Additional tests made with an external device for displacement recording revealed that these differences have to be attributed to insufficient stiffness and some compliance in the cantilever of the tested single-screw instruments. Some consequences of the test results for experiments on soft, semi-soft and rigid food materials are discussed and an equation is developed to correct for the flexing of the cantilever beam in the single screw machine. [source] Silicon Nitride Colloidal Probe Measurements: Interparticle Forces and the Role of Surface-Segment Interactions in Poly(acrylic acid) Adsorption from Aqueous SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001Eric Laarz Direct measurements of forces between silicon nitride surfaces in the presence of poly(acrylic acid) (PAA) are presented. The force-distance curves were obtained at pH > pHiep with an atomic force microscopy (AFM) colloidal-probe technique using a novel spherical silicon nitride probe attached to the AFM cantilever. We found that PAA adsorbs onto the negatively charged silicon nitride surface, which results in an increased repulsive surface potential. The steric contribution to the interparticle repulsion is small and the layer conformation remains flat even at high surface potentials or high ionic strength. The general features of the stabilization of ceramic powders with PAA are discussed; we suggest that PAA adsorbs onto silicon nitride by sequential adsorption of neighboring segments ("zipping"), which results in a flat conformation. In contrast, the long-range steric force found in the ZrO2/PAA system at pH > pHiep arises because the stretched equilibrium bulk conformation of the highly charged polymer is preserved via the formation of strong, irreversible surface-segment bonds on adsorption. [source] Molecular dynamics simulation of the contact process in AFM surface observationsLUBRICATION SCIENCE, Issue 2 2002J. Shimizu Abstract In the present work, several molecular dynamics simulations have been performed to clarify dynamically the contact mechanism between the specimen surface and probe tip in surface observations by an atomic force microscope (SFM) or friction force microscope (FFM). In the simulation, a three-dimensional model is proposed where the specimen and the probe are assumed to consist of monocrystalline copper and rigid diamond or a carbon atom, respectively. The effect of the cantilever stiffness of the AFM/FFM is also taken into consideration. The surface observation process is simulated on a well-defined Cu{100} surface. From the simulation results it has been verified that the surface images and the two-dimensional atomic-scale stick-slip phenomenon, just as is the case for real AFM/FFM surface observations, can be detected from the spring force acting on the cantilever. From the evaluation of the behaviour of specimen surface atoms, the importance of the specimen stiffness in deciding the cantilever properties can also be understood. The influence of the probe tip shape on the force images is also evaluated. From the results it can be verified that the behaviour of the specimen surface atoms as well as the solid surface images in AFM/FFM surface observations can be understood using the molecular dynamics simulation of the model presented. [source] Mechanical Properties of a Single Electrospun Fiber and Its StructuresMACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2005Shu-Ying Gu Abstract Summary: A method to measure the Young's modulus of a single electrospun polyacrylonitrile (PAN) fiber is reported. The Young's modulus can be calculated from the force-displacement curves obtained by the bending of a single fiber attached to an atomic force microscopy (AFM) cantilever. It is suggested that the high modulus of electrospun fibers is caused by the orientation of molecular chains, which is confirmed by wide-angle X-ray diffraction (WAXD) measurements. The communication will provide a basic understanding of the relationship between mechanical properties and structures of electrospun fibers. A PAN fiber was attached to a contact mode cantilever to facilitate the measurement of force-displacement curves and Young's modulus. [source] Physical attachment of fluorescent protein particles to atomic force microscopy probes in aqueous media: Implications for surface pH, fluorescence, and mechanical properties studiesMICROSCOPY RESEARCH AND TECHNIQUE, Issue 8 2010Susana Moreno-Flores Abstract Transfer of a fluorescently labeled protein particle from a surface to a microsized scanning probe has been induced by repetitive scanning in aqueous medium. The so-attached particle can in turn act as a probing tool to study particle,substrate and particle,particle interactions. Attachment of the fluorescent particle occurs at the apical region of an atomic force microscope (AFM) cantilever tip and it endures repetitive loading,unloading cycles against the sample surface. Fluorescence microscopy has been used to address the exact location of the attached particle in the cantilever and to identify the moment when the particle contacts the sample. Moreover, we have observed that fluorescence intensity at the contact point is lower when the probing particle contacts another fluorescent particle than when it contacts the nonfluorescent substrate. The change in fluorescence is attributed to local changes of pH and interparticle-quenching of fluorophores in the contact region. These findings are promising since they constitute a chemical-free way to attach bioparticles to AFM probes under fisiological conditions. The atomic force microscopy combined with fluorescence microscopy provides a straight forward method to study particle/particle and particle/substrate interactions, as well as to investigate mechanical properties of biocolloids. Microsc. Res. Tech. 73:746,751, 2010. © 2009 Wiley-Liss, Inc. [source] Mechanically detected field-induced Mn spin rotation in GaMnAsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Koji Onomitsu Abstract To study the magnetization properties of a micron-sized GnMnAs film, we characterize the mechanical properties of a micro-cantilever integrating a GaMnAs Hall bar. The magnetic field dependence of its mechanical resonance frequency below the Curie temperature is remarkably different from that above the Curie temperature. The frequency shift, which reflects the field-induced Mn spin rotation, is mainly caused by the magnetoelastic coupling. This result demonstrates that a micromechanical cantilever is a powerful tool for investigating the magnetic properties of micrometer-sized ferromagnetic materials. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic-Field Induced Strains in Ferromagnetic Shape Memory Alloy Ni55Mn23Ga22 Deposited by RF-Magnetron SputteringPLASMA PROCESSES AND POLYMERS, Issue S1 2009Florent Bernard Abstract 1.5,µm,Ni55Mn23Ga22 ferromagnetic thin films were deposited onto silicon substrates and silicon single beam cantilever using radio-frequency magnetron sputtering. As-deposited sample and heat-treated thin films were studied on their silicon substrates and peeled off to determine the influence of the stress. Post-heat treatment process allows at the films to achieve the shape memory effect (SME). Vibrating sample magnetometer (VSM) and deflection measurement of the sample annealed at 873,K during 36,ks exhibit ferromagnetic martensitic structure with a typical SME response to the magnetic field induced strains which match the values of the bulk material. [source] Investigation into the Chemical Reactivity of Plasma-Deposited Perfluorophenyl Methacrylate Using Infrared Reflection Absorption Spectroscopy and Microcantilever StudiesPLASMA PROCESSES AND POLYMERS, Issue S1 2007Nuria Queralto Abstract Perfluorophenyl methacrylate (pp-PFM) was plasma-polymerized using low duty cycle conditions to yield a surface rich in active ester groups. The reactivity of this surface towards different primary amines was investigated using infrared reflection absorption spectroscopy (IRRAS) and micromechanical cantilever (MC) sensors. While IRRAS provided information on the chemistry, the MC sensors technique gave insights into volume changes induced by the reactions of the polymer film. We found that the volume change upon reaction was different for each of the amines studied and correlated this to the ability of the amines to diffuse into the polymer matrix. The changes observed can be related to reactions occurring either at the liquid,solid interface or to reactions occurring within the matrix of the polymer and appear to be related to the chemical structure of the amines. [source] Ionic polymer-metal composites as multifunctional materialsPOLYMER COMPOSITES, Issue 1 2003Mohsen Shahinpoor This paper presents a description and a set of experimental results on Ionic Polymer-Metal Composites (IPMC's) as dynamic sensors, transducers, and actuators. Strips of IPMC can exhibit large dynamic deformation if placed in a time-varying electric field of the order of 10's of volts/mm. Conversely, dynamic deformation and flexing of such ionic polymers produces dynamic electric fields that closely follow the form of the electric signal. The underlying principle of such a mechanoelectric effect in IPMC's can be explained by the linear irreversible thermodynamics in which ion and solvent transport are the fluxes and electric field and solvent pressure gradient are the forces. Important parameters include the material conductance and the solvent permeability. The dynamic sensing, transduction, and actuation responses of a strip of IPMC under an impact-type loading is also discussed. When a cantilever strip of IPMC is flipped, a damped oscillatory electric response is produced across a pair of electrodes placed at the cantilever of the strip, which is highly repeatable with a broad frequency range above 104 Hz. Such direct mechanoelectric responses of IMPC's are related to the endo-ionic mobility due to stresses imposed. Imposition of a finite solvent flux without allowing a current flux causes the material to create a certain conjugate electric field that can be dynamically monitored and measured. IPMC's are shown to be highly capacitive at low frequencies while they are highly resistive under high frequency excitations. IN a sending mode, IPMC strips can also sense chemical environments and humidity. These types of sensors/transducers/actuators conceivably can replace piezoresistive and piezoelectric sensors with just one sensor for broad ranges of frequencies. [source] Identification, control and hysteresis compensation of a 3 DOF metrological AFMASIAN JOURNAL OF CONTROL, Issue 2 2009Roel Merry Abstract Atomic Force Microscopes (AFMs) are widely used for the investigation of samples at the nanometer scale. The metrological AFM used in this work uses a 3 degrees-of-freedom (DOFs) stage, driven by piezo-stack actuators, for sample manipulation in combination with a fixed cantilever. The piezo-stack actuators suffer from hysteresis, which acts as a nonlinear disturbance on the system and/or can change the system dynamics. The contributions of this paper are the application of feedback control to all 3 DOFs of the metrological AFM and the design and application of a hysteresis feedforward for the asymmetric hysteresis present in the system. The amount of coupling between the DOFs is assessed by a non-parametric multiple-input-multiple-output (MIMO) identification. Since the dynamics appear to be decoupled in the frequency range of interest, feedback controllers are designed for each DOF separately. For the modeling of the asymmetric hysteresis an extended Coleman-Hodgdon model is proposed. This model is used for feedforward compensation of the hysteresis. The combination of feedback control for all DOFs and the asymmetric hysteresis feedforward enables the AFM to track scanning profiles within the sensor bound of 5,nm. Real-time imaging of the sample is possible with an accuracy of 2,nm. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] Mechanical Response Analysis and Power Generation by Single-Cell StretchingCHEMPHYSCHEM, Issue 4 2005Alexandre Micoulet Dr. Abstract To harvest useful information about cell response due to mechanical perturbations under physiological conditions, a cantilever-based technique was designed, which allowed precise application of arbitrary forces or deformation histories on a single cell in vitro. Essential requirements for these investigations are a mechanism for applying an automated cell force and an induced-deformation detection system based on fiber-optical force sensing and closed loop control. The required mechanical stability of the setup can persist for several hours since mechanical drifts due to thermal gradients can be eliminated sufficiently (these gradients are caused by local heating of the cell observation chamber to 37,°C). During mechanical characterization, the cell is visualized with an optical microscope, which enables the simultaneous observation of cell shape and intracellular morphological changes. Either the cell elongation is observed as a reaction against a constant load or the cell force is measured as a response to constant deformation. Passive viscoelastic deformation and active cell response can be discriminated. The active power generated during contraction is in the range of Pmax=10,16Watts, which corresponds to 2500 ATP molecules,s,1at 10 kBT/molecule. The ratio of contractive to dissipative power is estimated to be in the range of 10,2. The highest forces supported by the cell suggest that about 104molecular motors must be involved in contraction. This indicates an energy-conversion efficiency of approximately 0.5. Our findings propose that, in addition to the recruitment of cell-contractile elements upon mechanical stimulation, the cell cytoskeleton becomes increasingly crosslinked in response to a mechanical pull. Quantitative stress,strain data, such as those presented here, may be employed to test physical models that describe cellular responses to mechanical stimuli. [source] Scanning Force Microscopy Based Rapid Force Curve Acquisition on Supported Lipid Bilayers: Experiments and Simulations Using Pulsed Force ModeCHEMPHYSCHEM, Issue 7 2004Stephanie Krüger Dr. Abstract In situ pulsed force mode scanning force microscopy (PFM,SFM) images of phase separated solid-supported lipid bilayers are discussed with the help of computer simulations. Simultaneous imaging of material properties and topography in a liquid environment by means of PFM,SFM is severely hampered by hydrodynamic damping of the cantilever. Stiffness and adhesion images of solid-supported membranes consisting of cholesterol, sphingomyelin, and 1,2-dioleyl-phosphatidylcholine obtained in aqueous solution exhibit contrast inversion of adhesion and stiffness images depending on parameters such as driving frequency, amplitude, and trigger setting. Simulations using a simple harmonic oscillator model explain experimental findings and give a deeper insight into the way PFM,SFM experiments have to be performed in order to obtain interpretable results and hence pave the way for reliable material contrast imaging at high speed. [source] Implant-supported fixed cantilever prosthesis in partially edentulous jaws: a cohort prospective studyCLINICAL ORAL IMPLANTS RESEARCH, Issue 11 2009Eugenio Romeo Abstract: Background: Reconstructive procedures present a higher rate of biological costs due to the necessity of bone harvest and grafts, use of semipermeable barriers etc. On the hand, implant supported cantilever prostheses could allow a simpler rehabilitation procedure. Aims: The aim of the present study was to assess the clinical outcome of patients treated with implant-supported fixed partial dentures (FPD) with cantilever after a mean follow-up time of 8 years. Material and methods: The study included 45 consecutive partially edentulous patients treated between January 1994 and August 2006 with 59 partial cantilever fixed prostheses supported by 116 ITI® implants. The primary outcome variable considered was the presence of complications at the subject and bridge level; the secondary outcome variable was marginal bone loss (MBL). The frequency of complications was analyzed according to cantilever location and opposite dentition and tested by Fisher's exact test. A multilevel regression model was constructed to analyze the factors influencing MBL with three levels: subject as the highest, and then implant and site. During the follow-up period, 11 implants showed a bone loss exceeding the limit for success, out of which two implants showed an infection of the peri-implant tissue. Results: After an average observation of 8.2 years of cantilever prostheses loading, the implant success and survival rates were 90.5% and 100%, respectively. Besides, the prosthetic success and survival rate were 57.7% and 100%, respectively. Discussion: None of the predictors included in the multilevel model presented a significant impact on the bone loss between baseline and the follow-up examination. Conclusions: The authors concluded that the prognosis of implant-supported FPDs and marginal bone loss at implants were not influenced by the position or the length of the cantilever, the location of the bridge and type of opposite dentition. Implant-supported fixed cantilever prosthesis can be considered a suitable treatment choice. [source] Five-year results of fixed implant-supported rehabilitations with distal cantilevers for the edentulous mandibleCLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2009German O. Gallucci Abstract Objectives: The purpose of this study was to evaluate the survival rate, success rate and primary complications associated with mandibular fixed implant-supported rehabilitations with distal cantilevers over 5 years of function. Material and methods: In this prospective multi-center trial, 45 fully edentulous patients were treated with implant-supported mandibular hybrid prostheses with distal extension cantilevers. Data were collected at numerous time points, including but not limited to: implant placement, abutment placement, final prosthesis delivery, 3 months and 5 years post-loading. Biological, implant and prosthetic parameters defining survival and success were evaluated for each implant including: sulcus bleeding ndex (SBI) at four sites per implant, width of facial and lingual keratinized gingiva (mm), peri-implant mucosal level (mid-facial from the top of the implant collar, measured in mm), modified plaque index (MPI) at four sites per implant, mobility and peri-implant radiolucency. Survival was defined as implants or prostheses that did not need to be replaced. Success rate was defined as meeting well-established criteria that were chosen to indicate healthy peri-implant mucosa osseointegration, prostheses success and complications. Results: A total of 237 implants in 45 completely edentulous patients were included in the study. In each patient, four to six implants were placed to support hybrid prostheses with distal cantilevers. Cantilevers ranged in length from 6 to 21 mm, with an average length of 15.6 mm. The ages of the patients ranged from 34 to 78 with a mean age of 59.5 years. The survival rate of implants was 100% (237/237) and for prostheses 95.5% (43/45). The overall treatment success rate was calculated as 86.7% (39/45). Of the six patients that have not met the criteria for success, two patients required replacement of the entire prosthesis and four patients presented >four complications events. Conclusion: Fixed implant-supported rehabilitation with distal cantilever resulted in a reliable treatment modality over the 5-year observation period. Although biological parameters of MPI, SBI, keratinized tissue and peri-implant mucosal levels showed statistically significant differences over time, the mean values for each patient remained within the normal limits of oral health. Complications were categorized as biological or technical. The majority of complications were technical complications (54/79) and of these most involved fracture of the acrylic teeth and base (20/54). While the survival rate was 100% for implants and 95.5% for prostheses, the application of strict criteria for treatment success resulted in an overall treatment success rate of 86.7%. [source] A systematic review of the survival and complication rates of implant supported fixed dental prostheses with cantilever extensions after an observation period of at least 5 yearsCLINICAL ORAL IMPLANTS RESEARCH, Issue 5 2009Marco Aglietta Abstract Objective: The aim of this systematic review was to assess the survival rates of short-span implant-supported cantilever fixed dental prostheses (ICFDPs) and the incidence of technical and biological complications after an observation period of at least 5 years. Material and methods: An electronic MEDLINE search supplemented by manual searching was conducted to identify prospective or retrospective cohort studies reporting data of at least 5 years on ICFDPs. Five- and 10-year estimates for failure and complication rates were calculated using standard or random-effect Poisson regression analysis. Results: The five studies eligible for the meta-analysis yielded an estimated 5- and 10-year ICFDP cumulative survival rate of 94.3% [95 percent confidence interval (95% CI): 84.1,98%] and 88.9% (95% CI: 70.8,96.1%), respectively. Five-year estimates for peri-implantitis were 5.4% (95% CI: 2,14.2%) and 9.4% (95% CI: 3.3,25.4%) at implant and prosthesis levels, respectively. Veneer fracture (5-year estimate: 10.3%; 95% CI: 3.9,26.6%) and screw loosening (5-year estimate: 8.2%; 95% CI: 3.9,17%) represented the most common complications, followed by loss of retention (5-year estimate: 5.7%; 95% CI: 1.9,16.5%) and abutment/screw fracture (5-year estimate: 2.1%; 95% CI: 0.9,5.1%). Implant fracture was rare (5-year estimate: 1.3%; 95% CI: 0.2,8.3%); no framework fracture was reported. Radiographic bone level changes did not yield statistically significant differences either at the prosthesis or at the implant levels when comparing ICFDPs with short-span implant-supported end-abutment fixed dental prostheses. Conclusions: ICFDPs represent a valid treatment modality; no detrimental effects can be expected on bone levels due to the presence of a cantilever extension per se. [source] Bone level changes at implants supporting crowns or fixed partial dentures with or without cantileversCLINICAL ORAL IMPLANTS RESEARCH, Issue 10 2008Gian Andrea Hälg Abstract Objective: The aim of this study was to analyze whether or not a cantilever extension on a fixed dental prosthesis (FDP) supported by implants increased the amount of peri-implant bone loss or technical complications compared with reconstructions without cantilevers. Materials and Methods: Fifty-four partially dentate patients with a total of 54 FDPs supported by 78 implants were enrolled in the study. Twenty-seven FDPs were with cantilever and 27 FDPs were without cantilever (control group). All FDPs were supported by one or two implants and were located in the posterior maxilla or mandible. The primary outcome variable was change in peri-implant marginal bone level from the time of FDP placement to the last follow-up visit. FDPs were under functional loading for a period of 3 up to 12.7 years. Statistical analysis was carried out with Student's t -test. Regression analyses were carried out to evaluate the influence of confounding factors on the peri-implant bone level change. In addition, implant survival rates were calculated and technical complications assessed. Results: After a mean observation period of 5.3 years, the mean peri-implant bone loss for the FDPs with cantilevers was 0.23 mm (SD±0.63 mm) and 0.09 mm (SD±0.43 mm) for FDPs without cantilever. Concerning the bone level change at implants supporting FDPs with or without cantilevers no statistically significant differences were found. The regression analysis revealed that jaw of implant placement had a statistically significant influence on peri-implant bone loss. When the bone loss in the cantilever group and the control group were compared within the maxilla or mandible separately, no statistically significant difference was found. Implant survival rates reached 95.7% for implants supporting cantilever prostheses and 96.9% for implants of the control group. Five FDPs in the cantilever group showed minor technical complications, none were observed in the control group. Conclusion: Within the limitations of this study it was concluded that cantilever on FDPs did not lead to a higher implant failure rate and did not lead to more bone loss around supporting implants compared with implants supporting conventional FDPs. In contrast to these results more technical complications were observed in the group reconstructed with cantilever. [source] | ||||||||||||||||||||||