1,663 research outputs found

    Spine preparation: factors affecting optimum linkage of paper and adhesive in adhesive bookbinding

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    Adhesive bookbinding, a method of holding trimmed pages together in a book using hotmelt glue, offers rapid binding and curing time, but has the disadvantage of poor glue penetration into the paper edges. A weak binding will result unless good linkage can be made between paper and glue, which is the objective of spine-roughening treatments. Eight spine-roughening treatments from three manufacturers were compared on an uncoated and a coated paper stock, against a control treatment of trimmed paper. Treatments were studied by light- and scanning electron microscopic examination of paper edges and by measurement of the mean page-pull values based on samples of 30 or more page-pulls. The results were compared with four hypotheses concerning bookbinding strength. First, when 95 percent confidence intervals were compared, different spine-roughening treatments were found to produce different bookbinding strengths, as measured by mean page-pull value. Specifically, almost all of the treatments produced higher page-pull values than the control, showing that these roughening treatments increased book strength. Some treatments produced significantly higher page-pull values than others, indicating that some roughening treatments were better than others for binding the two papers studied. The results of these tests are summarized in the table at the top of the next page. Secondly, comparing mean page-pull values ranked on the uncoated stock with those of the coated stock, the relatively low correlation of 0.66 indicated that a spine-roughening treatment appropriate for one kind of paper may not be suitable for another kind of paper. One treatment produced the highest page-pull value on both papers, however, indicating that its edge geometry produced a strong bond in both papers studied. Table of Spine-Roughening Treatments with Page-Pull Values and Duncan Groupings. Ranked by Uncoated Paper: (Treatment, Mean Page-Pull Value, Duncan1 Groupings): ((Control) #1, 2.12 lb/in, F), (#48, 2.36, F E), (#2, 2.62, D E), (#16, 2.88, D C), (#24, 3.14, B C), (#20, 3.26, B), (#3, 3.34, B), (#30, 3.42, B), (#10 3.74 A). Ranked by Coated Paper: (Treatment, Mean Page-Pull Value, Duncan1 Groupings): ((Control) #1, 0.74, E), (#2, 0.78, E), (#30, 0.95, D), (#48, 1.09, D C), (#3, 1.16, C), (#20, 1.20, C), (#16, 1.36, B), (#24, 1.43, B), (#10, 1.61, A). 1 Duncan groupings indicate means which are not significantly different. Thirdly, two page-pull testers commonly used to measure page pull were compared using the Mandrell Sensitivity Analysis, which considers sensitivity to the measured attribute along with consistency of measurement. The Martini Tester was shown to be approximately 1 .5 times, or barely significantly, more sensitive than the Moffett Tester. Fourthly, three spine-roughening treatments were compared for book strength vs. production speed. Some treatments-those in which the edge-weakening effect of pattern undercutting was apparent produced higher page-pull values as production speed increase

    Development and application of methods for the biomechanical characterization of spine ligaments and intervertebral discs

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    The spine is one of the major organs subject to trauma or genetic problems. Today 30% of people suffer from back pain and every day a large number of surgical interventions on the spine are performed to treat those patients with severe spinal deformities (i.e. scoliosis or kyphosis). From a statistical analysis, the percentage of failures for this type of interventions is around 25-30%. The aim of my PhD thesis was the improvement of the knowledge of the strain distribution on biological tissues, in particular on ligaments and intervertebral discs of the human spine. The first part of this thesis aimed at improvement of the methodologies used to measure the strain distribution, simultaneously on hard (vertebrae) and soft tissues (ligaments and intervertebral discs), using Digital Image Correlation. The second part of my research studied the biomechanical behaviour of the intervertebral discs and of the different ligaments. The disc acts as a shock absorber for the spine, reducing shocks and impacts. The anterior longitudinal ligament (ALL), supraspinous and interspinous ligaments were studied analysing how they were deformed under different loading conditions. These ligaments limit the movement of the spine during flexion reducing the overload on the intervertebral disc. The ALL does not offer great mechanical strength during lateral bending and axial torsion. Summarizing, the study underlines the necessity of having a full-field strain analysis tool to enhance the knowledge of the biomechanics of the spine and the interaction between different types of tissue. Furthermore, the results reported in this thesis could be useful also to build better multibody spine models and to include more realistic properties in finite element models. These results could be a starting point for future works in which the effect of different surgical procedures and the use of new surgical devices could be investigated

    Control of the Mechanical Properties of the Synthetic Anterior Longitudinal Ligament and its Effect on the Mechanical Analogue Lumbar Spine Model

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    The development and validation of an anatomically correct mechanical analogue spine model would serve as a valuable tool in helping researchers and implant designers understand and alleviate low back pain. Advanced composite ligaments were designed to mimic the tensile mechanical properties of human spinal ligaments. By changing the composite properties, the stiffness and deformation at toe were controlled in a repeatable manner. Five analogue spine models, with three different Anterior Longitudinal Ligament (ALL) stiffness configurations, were tested in bending and compression using displacement control in a MTS load frame. The bending stiffness and kinematic ranges of motion of the spines were compared for each ALL stiffness configuration. The ALL stiffness had a significant effect on the stiffness and peak moment in extension of the overall spine model. The study demonstrated that a change in the synthetic ligament properties successfully controls the biomechanics of the analogue spine model and the model effectively mimics the human cadaveric biomechanical response

    Swimming versus voluntary running exercise on bone health in ovariectomized retired breeder rats

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    Physical activity may increase long bone calcium (Ca) content to preserve bone strength in postmenopausal women. This study determined the effect of compulsory swimming and voluntary running exercise on bone mineral density, bone Ca and phosphorus (P) content, and femoral neck and tibia strength in ovariectomized (OVX) retired breeder rats, as a model for postmenopausal women. Thirty-seven nine-month old Sprague Dawley rats were assigned randomly into one of four treatment groups for the nine-week study: OVX + running (OR; n=9); OVX + swimming (OS; n=10); OVX + no exercise (O; n=9); sham-surgery + no exercise (Sh; n=9). OR rats had free access to running wheels; OS rats were trained over one week to swim for one hour, five days a week. At sacrifice, femurs, tibias, humeri, and vertebrae were removed. Bone mineral density was analyzed using pDEXA, and bone Ca and P content were analyzed using atomic absorption spectrometry and colormetric assay, respectively. Femur and tibia strength was determined by Q-tester. Bone mineral density was significantly higher for all bones measured in the exercise groups compared to the sedentary groups. Mean grams (g) of Ca per dry femur weight for OS rats were higher than O rats (p=0.019). Tibias of the OR and OS rats were able to absorb significantly more energy to break load than the O rats (p=0.000; p=0.001, respectively), and energy absorption was significantly higher for the OR compared to Sh tibia (p=0.022). No other significant differences in parameters were observed among the four groups. Results of this study suggest that both types of exercise improve bone mineral density, that swim exercise may be beneficial in preserving femur Ca content, and that swim exercise and voluntary running may be beneficial in improving tibia strength in OVX rats

    Interfibrillar stiffening of echinoderm mutable collagenous tissue demonstrated at the nanoscale

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    The mutable collagenous tissue (MCT) of echinoderms (e.g., sea cucumbers and starfish) is a remarkable example of a biological material that has the unique attribute, among collagenous tissues, of being able to rapidly change its stiffness and extensibility under neural control. However, the mechanisms of MCT have not been characterized at the nanoscale. Using synchrotron small-angle X-ray diffraction to probe time-dependent changes in fibrillar structure during in situ tensile testing of sea cucumber dermis, we investigate the ultrastructural mechanics of MCT by measuring fibril strain at different chemically induced mechanical states. By measuring a variable interfibrillar stiffness (E(IF)), the mechanism of mutability at the nanoscale can be demonstrated directly. A model of stiffness modulation via enhanced fibrillar recruitment is developed to explain the biophysical mechanisms of MCT. Understanding the mechanisms of MCT quantitatively may have applications in development of new types of mechanically tunable biomaterials

    A reliability study of a new back strain monitor based on clinical trials

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    Movements of the lower back are a contributing factor for developing low back pain. Various techniques have been developed and tested for the measurement of lower back movement but most have been too expensive, too cumbersome and have been unable to measure movements over a prolonged period. The thesis investigates the development, the reliability and the validity of a new device (the Back Strain Monitor) to be used to measure lower back movement during a day’s activity. After a review of potential devices, three transducers to measure back movement were selected for laboratory testing. The first transducer, the conductive silicone polymer, performed poorly displaying an electrical drift as the polymer underwent repeated stretching. The second, the inductive coil technique, performed well in the laboratory trials with a CV of 0.54% for maximum linear stretch measurements. However, issues relating to electrical drift and electrical lag led to large variation of the baseline readings (CV = 82%). The third transducer, the accelerometer method, performed very well during the laboratory trials displaying a CV of 0.12% for the range of movement. Two of the three sensors (the inductive coil and the accelerometer method) were developed to the level of stand-alone prototypes, capable of being tested within a clinical trial setting. The first clinical trial involved three testers applying the inductive coil prototype to 15 subjects to assess its measurement properties. The inductive coil performed with moderate inter tester reliability (ICC (2,1) = 0.65). There was limited evidence of validity for the inductive coil technique as it showed poor to average correlation with the three comparator techniques (ICC (2,1) values from 0.47 to 0.75). The second clinical trial applied the accelerometer method to 23 subjects with three testers. There was very good inter tester reliability (ICC (2,1) ≥ 0.86) and test re-test reliability (ICC (2,1) ≥ 0.89). The accelerometer method also displayed a high level of agreement (ICC (2,1) ≥ 0.88) with the main recognized comparator technique (the double inclinometer) providing evidence of criterion validity. The accelerometer method provided a reliable option for measuring movements of the lower back. There was evidence of criterion validity and a preliminary case study demonstrated that the movement data collected over 8 hours was able to alter back postures via biofeedback. The accelerometer method displays advantages over other methods in that there is the potential to measure three dimensional movement at a high sampling rate and for extended periods of time. The device may provide a new management tool to assist health practitioners in the treatment of low back pain

    Delivery Optimization and Evaluation of Biomechanics of an Injectable Nucleus Pulposus Replacement Device

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    Lower back pain effects up to 80% of people at some point in their life, a majority of cases being the result of degenerative disc disease. Treatment options for degenerative disc disease are limited, jumping from physical therapy to major spinal fusion and total disc replacement surgery with little to no approaches in between. Furthermore, surgical treatments have not shown to be more effective than conservative treatments and reducing pain and disability over the long term. Hydrogels have shown promise as a potential nucleus pulposus replacement device. Their properties are controllable and can be implanted into the body through minimally evasive routes. In order to successful act as a minimally invasive nucleus pulposus replacement device, the hydrogel must demonstrate an ability to be easily injectable, cure within the body, and restore mechanics once in place.One potential formulation to complete this task is HYDRAFILTM. HYDRAFILTM is a PVA/PEG based hydrogel designed as a nucleus pulposus replacement device. HYDRAFILTM demonstrates thermosetting properties that can be controlled through the use of thermal cycling and holding the material at elevated temperatures until injection. Through various mechanical tests and thermal analyses, HYDRAFILTM demonstrated the ability to cure within the disc and act as a solid implant. After curing HYDRAFILTM exhibits substantial mechanical strength and desired hydration properties

    The Development and Application of a Custom Robotic Biomechanical Testing Platform Employing Real-time Load-control to Compare Spinal Biomechanical Testing Protocols: Pure Moment, Ideal Follower Load, and a Novel Trunk Weight Protocol

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    The human lumbar spine has been the subject of biomechanical study for many decades owing to the numerous medical cases resulting in the development of various corrective surgical procedures and medical devices intended to relieve patient discomfort. Spinal biomechanics is a broad field containing but not limited to the in vitro study of cadaveric tissue utilizing testing platforms used to apply motion- or load-profiles to tissue in the investigation of the various kinetic or kinematic responses, respectively. The particular arena field of this research concerns the field of robotics as it applies to testing platforms and how they are applied to lumbar spine biomechanical testing. The in vivo spine is subject to six degrees of freedom (DOF) of motion as a consequence of the applied loads of surrounding musculature which apply component loads in 6 DOF. However current in vitro standard protocols apply isolated loads primarily in the anatomical planes. Although the primary goal of in vitro testing may not be the simulation of in vivo circumstances, the accurate recreation of the in vivo loading environment would reveal much regarding the passive biomechanics of the spine. To accomplish such a goal, it would be ideal to utilize a platform capable of providing 6 DOF of controlled mobility as well as capable of apply controlled load in those 6 DOF. The Musculoskeletal Research Laboratory has developed such a system. The system’s load-control capabilities were validated by simulating two standard biomechanical protocols, the pure moment and the ideal follower load on 6 L4-L5 single motion segment units. The robotic performance of the system was evaluated by measuring the tracking errors during testing, or the difference between experimental forces being applied and the forces commanded by the custom motion programs executed during protocol simulation. The biomechanical data that was recorded and compared to the literature for validation was rotational range of motion in the sagittal plane and anatomical point translation. Translation data proved to be difficult to compare effectively to the literature due to the sparseness of comparable numbers. There was also interest in the platform’s ability to control protocols. To test this hypothesis, three different biomechanical protocols were simulated and there biomechanical results were compared: pure moment, ideal follower load, and trunk weight. The system provided stable, good load-control in during combined motions involving all 6 DOF. The tracking errors observed were low compared to other published robotic biomechanical platforms. The mean combined flexion-extension rotational range of motion in the sagittal plane for the pure moment protocol, the ideal follower load, and the trunk weight protocols were 8.2°(±2.5°), 7.6°(±2.9°), and 7.4°(±2.8°), respectively. There were statistically significant differences in the absolute translational data across the protocols but when comparing relative changes due to flexion and extension only, there are no significant differences across protocols. In conclusion to this research the platform developed and validated in the current study adequately provides the capabilities of 6 DOF coordinated motion and 5 DOF coordinated load-control. It is sufficient to simulate the standard spine biomechanical test protocols of pure moment and ideal follower load on single segments. It is also a good tool for comparing the effects of particular protocols on the passive biomechanics of human cadaveric tissue. To the author’s knowledge, this is the first publication of a fully robotic system adequately controlling a non-zero dynamic force vector while a bending protocol was being applied to a human spinal segment. This research is limited to the sagittal plane and single lumbar spine motion segment units

    AFM-based mechanical characterization of single nanofibres

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    Nanofibres are found in a broad variety of hierarchical biological systems as fundamental structural units, and nanofibrillar components are playing an increasing role in the development of advanced functional materials. Accurate determination of the mechanical properties of single nanofibres is thus of great interest, yet measurement of these properties is challenging due to the intricate specimen handling and the exceptional force and deformation resolution that is required. The atomic force microscope (AFM) has emerged as an effective, reliable tool in the investigation of nanofibrillar mechanics, with the three most popular approaches—AFM-based tensile testing, three-point deformation testing, and nanoindentation—proving preferable to conventional tensile testing in many (but not all) cases. Here, we review the capabilities and limitations of each of these methods and give a comprehensive overview of the recent advances in this field
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