Micromotion Analysis Research Articles

Solitary-wave description of condensate micromotion in a time-averaged orbiting potential trap

We present a detailed theoretical analysis of micro-motion in a time-averaged orbiting potential trap. Our treatment is based on the Gross-Pitaevskii equation, with the full time dependent behaviour of the trap systematically approximated to reduce the trapping potential to its dominant terms. We show that within some well specified approximations, the dynamic trap has solitary-wave solutions, and we identify a moving frame of reference which provides the most natural description of the system. In that frame eigenstates of the time-averaged orbiting potential trap can be found, all of which must be solitary-wave solutions with identical, circular centre of mass motion in the lab frame. The validity regime for our treatment is carefully defined, and is shown to be satisfied by existing experimental systems.

On using flexure‐hinge five‐bar linkages to develop novel walking mechanisms and small‐scale grippers for microrobots

AbstractThis paper presents the micromotion analysis of five‐bar linkages and demonstrates the approximate linearity of motion transmission of five‐bar mechanisms within a micromotion range. A novel walking mechanism used for a microrobot and a small‐scale gripper with a high transmission ratio are introduced, based on the flexure‐hinge five‐bar mechanism analysis. Results of numerical simulation show the validity of design and analysis on the introduced mechanisms and the feasibility of corresponding thoughts. The presented micromotion‐based robot mechanisms are devoid of friction and fitting errors, and particularly suitable for microrobot applications. © 2004 Wiley Periodicals, Inc.

Biomechanical Analysis of Design of Total Knee Joint Prosthesis. The Influence of Viscoelastic Property of the Bone on Micromotion after Impact Loading.

In the case of severely destroyed knee joint, TKA (Total Knee Arthroplasty) is indicated as surgical treatment. An ideal design of a prosthesis will provide (1) good initial and permanent fixation, (2) improvement of range of motion, and (3) excellentsurvivorship. The purpose of this study was to analyze the influence of viscoelastic property of the bone on micromotion with different tibial prostheses in TKA. The interface of the bone and a prosthesis was considered as debonded and relative displacement between prosthesis and bone was regarded as micromotion. Viscoelaastic property of the bone showed significant influence on the analysis of micromotion. The tibial prosthesis with a central stem of 60 mm length was found to exhibit less micromotion with differnt conditions. It was found to cause prosthetic loosening with less incidence.

Assessment of Rapid Morphological Changes Associated with Elevated cAMP Levels in Human Orbital Fibroblasts

Orbital fibroblasts exhibit a phenotype distinct from that of other types of fibroblasts. Addition of prostaglandin E2(PGE2) to culture medium elicits a dramatic change in orbital fibroblast morphology. That response is mediated through the generation of cAMP. Orbital fibroblasts can generate high levels of PGE2through induction by proinflammatory cytokines of prostaglandin endoperoxide H synthase-2 (PGHS-2). Here we compare the influence on fibroblast morphology of exogenous PGE2, forskolin, and 8-br-cAMP to that mediated through PGHS-2 induction by a lymphocyte-derived cytokine. Within a few hours, orbital fibroblasts treated with any of these test compounds appear under phase-contrast microscopy to exhibit a stellate morphology. When these changes were assessed quantitatively by electric cell–substrate impedance sensing (ECIS), it became evident that 8-br-cAMP, forskolin, and PGE2initiated shape changes within 30 min of addition to the culture medium, while effects of the cytokine were first evident after approximately 3.5 h. Dermal fibroblasts failed to respond to any of these compounds with regard to changes in cellular morphology. Analysis of micromotion, manifested as small impedance fluctuations, revealed that orbital fibroblasts treated with 8-br-cAMP exhibit less motion than did untreated cells. These results suggest that orbital fibroblast shape can be altered by several compounds known to alter intracellular cAMP levels. They demonstrate the utility of ECIS in the assessment of very rapid and dynamic cellular events associated with changes in cell morphology.

Cell–substrate impedance analysis of epithelial cell shape and micromotion upon challenge with bacterial proteins that perturb extracellular matrix and cytoskeleton

Research into the nature of host cell–microbial cross-talk needs more sensitive methods to analyze real time cellular reactions to infection or to toxic factors from infecting agents. Here, we introduce novel analytical applications of electrical cell–substrate impedance sensing (ECIS) to quantify changes in cell morphology and micromotion in response to bacterial challenge. Epithelial monolayers were challenged with an outer membrane (OM) extract of Treponema denticola, its purified 95 kDa chymotrypsin, and major surface protein (Msp). Impedance changes were analyzed and discriminated through model calculation as either junctional resistance ( R b) or average cell–substrate separation ( h). Fluctuations in impedance and the normalized variance ratio were used to quantify micromotion. The OM and the 95 kDa protease caused a rapid drop in impedance. Msp had no effect on R b and h, but contributed to the reduction in micromotion. These new analytical applications of ECIS can be used to study toxigenic activities of any pathogen that affects cell junctions, cytoskeletal integrity, cell shape, or contact with extracellular matrix.

Influence of intraoperative femoral fractures and cerclage wiring on bone ingrowth into canine porous-coated femoral components

Intraoperative femoral fractures occur more frequently with cementless than with cemented components. In this study, the influence of controlled femoral fractures fixed with cerclage wires on rotational stability and bone ingrowth into porous-coated canine femoral components was evaluated. These data were compared with results of previous studies on unrecognized femoral fractures (not stabilized) and on the intact canine femur. Micromotion analysis revealed a significant increase in rotational instability in fractures not stabilized with cerclage wires ( P < .05) compared with the intact femur. Experimentally created femoral fractures had a significantly deleterious effect on bone ingrowth even after cerclage wiring. This appears to be caused by a lack of bone ingrowth deep to the fracture and an increase in femoral component micromotion. In clinical practice, femoral fractures occurring during cementless total hip arthroplasty are a serious problem, and use of a cemented prosthesis is recommended if rotational stability of the stem cannot be ensured.

Micromotion analysis of the fixation of total knee tibial component

Immediate post-operative stability is critical for the long-term success of biological implant fixations. Excessive motion at the bone-prosthesis interface is known to inhibit bone ingrowth and thereby cause failure of the fixation. In the present study, relative displacements between the host bone and the tibial component of total knee implants were evaluated, and the effect of the method on the immediate post-operative fixation was assessed using a three-dimensional friction-contact finite element model of the tibia-prosthesis unit and ADINA. Three types of fixations were considered: (1) close-fit; (2) press-fit; and (3) screw fixation. For the validation of the model, the predictions were compared with measurements in four human cadaveric specimens. The results of the study showed that, (i) friction affects significantly the magnitude of the interface relative displacement, (ii) the relative displacements are similar for close-fit and press-fit fixations, and (iii) the relative displacements are significantly less in comparison of those for press-fit fixation. Therefore, use of screws for immediate post-surgical fixation is likely to result in enhanced bone ingrowth.

Objective performance analysis of artificial hands towards improvements of function.

Micromotion analysis of the performance of below-elbow amputees is introduced. This procedure served as an objective method of evaluating amputees performance abilities, while using a standard body-powered hook device. Based on the results of such evaluation, it was possible to define which part of motion patterns should be considered for improving the design of a prosthetic device. Biomechanical and design considerations, derived from performance time measurements, indicate criteria for the improved design. A new configuration of body-powered hook is suggested.

Analyzing the Effectiveness of Child Resistant Closures by Studying Attempted Entry Behavior

The Poison Prevention Packaging Act of 1970 was the culmination of an effort lasting over a decade. The purpose of this act was “to protect children from serious personal injury or serious illness…” as the result of gaining access to hazardous household substances. The purpose of the investigation reported in this paper was to analyze three commonly available safety caps (plug-key), arrow line-up, and push-turn types), comparing them with one another and with standard types (snap and twist off) for a large group of children (99) aged 2, 3, 4, and 5 years, male and female. Testing procedures resembling those required under the federal standard were employed with two important exceptions: (1) children were not shown how to gain entry to the containers and (2) the period of attempted entry was reduced to two minutes. Incentives were placed in the containers to stimulate interest. Analysis of successful and unsuccessful entries was conducted with respect to container type, age, and sex. Several significant effects were noted. The push-turn type of safety cap proved most effective, followed by the arrow line-up and slot-key types. The percentage of successful entries was directly related to age. The statistics also revealed evidence questioning the effectiveness of some caps in meeting the federal standard. A detailed motion analysis was conducted on all subjects to study their investigative behaviors in attempting to gain entry to the containers. In testing subjects, all data were recorded on reel-to-reel video tape, permitting instant replay and micromotion analysis using slow motion and stop action viewing. A taxonomy and a frequency chart for these motions were then constructed.

Acceleration Accuracy: Analyses of High-Speed Camera Film

Acceleration due to gravity, g, was experimentally determined using the technique of micromotion analysis of high-speed motion-picture film taken of a steel sphere in free fall. Three methods of film analysis were compared with an independently calculated value of g. The analyses used and the error they produced were as follows: graphical, 6%; graphical-analytical, 1%; and analytical, 2%. For all of these experiments, a Bausch & Lomb Contour Measuring Projector was used