Rotator cuff (RC) muscle insertion was previously thought to consist of singular, individual tendons inserting onto predefined areas on the greater and lesser tuberosities. However, more recent publications describe the RC muscle tendons as forming a singular insertion across the tuberosities, consisting of both tendinous and capsular portions. Orthopaedic surgeons are now considering these two layers in their surgical approach and treatment plans; therefore this study aimed to test and compare the elastic modulus and maximum load to failure for both tendinous and capsular layers taken from supraspinatus (SS), infraspinatus (IS) and subscapularis (SC). Fourteen (n = 14) fresh/frozen arms were used in this study. Each RC muscle was reverse dissected and trimmed to a 2 x 2cm strip, which was separated into its two layers, still attached to the humerus. An Instron 1342 with a 1kN load cell was used to place the samples under tensile testing till failure (Newtons/N). Accompanying Integrated Design Tools (IDT) NX8-S2 cameras captured images for full-field strain measurements with the Image Systems TEMA software package through digital image correlation (DIC). SS, IS, and SC tendinous layers yielded higher average elastic moduli readings (72.34 MPa, 67.04 MPa, and 59.61 MPa respectively) compared to their capsular components (27.38 MPa, 32.45 MPa, and 41.49 MPa respectively). Likewise, the tendinous layers for SS, IS and SC all showed higher average loads to failure (252.74 N, 356.27 N and 385.94 N, respectively) when compared to the capsular layers (211.21 N, 168.54 N and 281.74 N, respectively). These biomechanical differences need to be taken into account during surgical repair owing to the fact that, should these layers be repaired as one singular structure, it may place the weaker less elastic, capsular layer under more strain, possibly leading to either re-tear complications or reduced postoperative healing and functionality. Thus, based on the results, it is recommended that surgeons consider and repair each layer independently for better postoperative biomechanical integrity. / Dissertation (MSc)--University of Pretoria, 2019. / Anatomy / MSc / Unrestricted

Kenaf fiber is increasingly getting the attention of the industries due to its excellent mechanical properties, feasibility, growth rate, and ease of cultivation. On the other hand, cellulose nanofibril is one of the important building blocks of all the bast fibers which significantly contributes to their mechanical properties. However, most of the studies in the literature have estimated the value of axial elastic modulus for fiber-bundles which has some unavoidable issues resulting in incorrect modulus. Moreover, the transverse elastic modulus is another important parameter that also needs to be studied. Hence, to compensate for the gap in the literature, a single unit of both kenaf microfiber and cellulose nanofibril have been subjected to nanomechanical characterization to analyze their surface morphology and determine their elastic modulus in the axial and transverse direction. The experiments also pave to a protocol to characterize micro and nanofibrils nanomechanically and determine their elastic moduli.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18164号 / 医博第3884号 / 新制||医||1003(附属図書館) / 31022 / 京都大学大学院医学研究科医学専攻 / (主査)教授 戸口田 淳也, 教授 妻木 範行, 教授 開 祐司 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Soil cement has been used as a means of stabilizing highway pavement layers, airport pavement layers, embankments, and foundations for decades. The technology uses a compacted mixture of soil, cement, and water to form a hardened material layer that has specific strength and durability properties. Even after decades of utilization, however, design of soil cement pavement layers has room for enhancement. This thesis investigates factors that influence the design and performance of cement stabilized pavement layers in Mississippi. A survey was conducted to collect information about soil cement design procedures from across the U.S. The factors examined in the laboratory investigation are strength gain with time, unconfined compressive strength variability, elastic modulus, and wheel tracking. More than 1,100 specimens were tested to determine the influence of these factors on the design and performance of soil cement pavement layers.

Collagen type I is an extracellular matrix (ECM) protein that affords tensile strength and biological scaffolding to numerous vertebrate and invertebrate tissues. This strength has been attributed to the triple-helical structure of the collagen type I molecules, their organization into fibrils, and the presence of inter-molecular, covalent, enzymatic crosslinks. There are several different types of these crosslinks; their composition is tissue-specific and dependent upon factors such as age and health. Furthermore, these enzymatic crosslinks tend to form specifically at amino/N- and carboxy/C-terminal crosslinking sites. The mechanical behavior of collagen type I has been investigated, via experiment and theory, at the level of the molecule, microfibril, fibril, and fiber. However, the influence of different enzymatic crosslinks and their location (e.g., N- vs. C-site) on the mechanics of collagen type I has not been investigated in the literature. We employed molecular dynamics to model the mechanical behavior of uncrosslinked and crosslinked ~23-nm-long molecular segments and ~65-nm-long microfibril units of collagen type I. We then used these molecular simulations to construct a model of a single collagen type I fibril by considering the ~65-nm-long microfibril units arranged in series and then in parallel. When a uniaxial deformation was applied along the long axis of the molecular models, N-crosslinks aligned rapidly at lower strains followed by C-crosslinks more gradually at higher strains, leading to a two-stage crosslink recruitment. Then when comparing the influence of different enzymatic crosslinks, significant differences were observed for the high-strain elastic moduli of our microfibril unit models, namely and in increasing order, uncrosslinked, immature crosslinked (HLKNL and deH-HLNL), mature HHL-crosslinked, and mature PYD-crosslinked. At the fibril level, our low- and high-strain elastic moduli were in good agreement with some literature data, but in over-estimation of several other literature reports. Future work will seek to address simplifications and limitations in our modeling approach. A model such as this, accounting for different enzymatic crosslink types, may allow for the prediction of the mechanics of collagen fibrils and collagenous tissues, in representation of healthy and diseased states. / Ph. D.

The movement and control of the vocal folds within the laryngeal cavity enables three crucial physiological functions: 1) allowing respiration by opening, 2) aiding in airway protection by closing, and 3) regulating sound production during phonation. Although treatment options have improved, many of the estimated 7.5 million individuals in the United States who are annually affected by voice-related disorders still face serious challenges related to dysphonia and dysphagia. The need for improved voice-disorder treatments has motivated the work presented in this dissertation which focuses on modeling and manufacturing the vocal folds and aims to answer three main questions: 1) what are the mechanical properties of the vocal folds and how do they change across the full vocal range? 2) how do those properties influence the dynamic behavior of the tissue? and 3) can we manufacture a synthetic vocal fold model that exhibits a desired and controllable dynamic behavior? First, the elastic properties of sixteen porcine vocal folds were evaluated through uniaxial tensile tests on a custom built experimental setup. Stress-strain data was analyzed using an optimization method to yield continuous model parameters which described the linear and nonlinear elastic regions as well as transition points between those regions. Next, the impact of the vocal fold elastic properties on the frequencies of vibration was evaluated through dynamic tests on excised porcine larynges. Sound data was analyzed via a spectrogram and through the use of fast Fourier transforms to study changes in the frequency of vibration while the vocal folds were stretched. Additionally, a mathematical aeroelastic model of phonation was implemented to further evaluate the changing elastic properties on vocal fold dynamics. Next, eight synthetic vocal fold models were created, each with varying mechanical properties and a geometry based on reported anatomical measurements of porcine vocal folds. The synthetic models were then dynamically tested to further study the impact of changes in mechanical properties on the dynamic behavior of the synthetic vocal folds. / Doctor of Philosophy / The movement and control of the vocal folds within the voice-box enables three crucial physiological functions: 1) allowing respiration by opening, 2) aiding in airway protection and swallowing by closing, and 3) regulating sound production during vocalization. Although treatment options have improved, many of the estimated 7.5 million individuals in the United States who are annually affected by voice-related disorders still face serious challenges related to speech production and swallowing which often results in significant detrimental impacts to quality of life. The need for improved treatments is most easily observed in the evaluation of treatment options following a total laryngectomy, which is a procedure where the entire voice-box is removed often due to cancer. Following a laryngectomy, all three of the vital functions of the vocal folds are immediately impacted as patients adjust to breathing through and protecting a redirected airway and are forced to use alternative methods of speech production which often result in monotone or robotic-sounding speech. The need for improved voice-disorder treatments has motivated the work presented in this dissertation which focuses on modeling and manufacturing the vocal folds and aims to answer three main questions: 1) what are the mechanical properties of the vocal folds? 2) how do those properties influence the dynamic behavior of the tissue during sound production? and 3) can we manufacture synthetic vocal folds that produce a desired and controllable dynamic behavior? Sixteen porcine vocal fold samples were mechanical tested to evaluate the elastic properties of the tissue. Next, porcine voice-box samples were experimentally tested in a way that simulated sound production by subjecting the samples to a heated and humidified air flow, similar to the air flow conditions coming out of the lungs. In this way, the relationship between the tissue properties and the frequencies of sound was investigated. Lastly, the synthetic vocal fold samples were evaluated using a similar experimental protocol to further investigate the impact of changing structural properties on the dynamics of the vocal folds during sound production.

Yes / Liquid crystal is a new emerging biomaterial. The physical property of liquid crystal plays a role in supporting the adhesion of cells. Nano and microball indentation techniques were applied to determine the elastic modulus or viscoelasticity of the cholesteryl ester liquid crystals in the culture media. Nano-indentation results (108 ± 19.78 kPa, N = 20) agreed well with the microball indentation (110 ± 19.95 kPa, N = 60) for the liquid crystal samples incubated for 24 hours at 37o C, respectively. However, nanoindentation could not measure the modulus of the liquid crystal (LC) incubated more than 24 hours. This is due to the decreased viscosity of the liquid crystal after immersion in the cell culture media for more than 24 hours. Alternatively, microball indentation was used and the elastic modulus of the LC immersed for 48 hours was found to decrease to 55 ± 9.99 kPa (N = 60). The microball indentation indicated that the LC did not creep after 40 seconds of indentation. However, the elastic modulus of the LC was no longer measurable after 72 hours of incubation due to the lost of elasticity. Microball indentation seemed to be a reliable technique in determining the elastic moduli of the cholesteryl ester liquid crystals. / Science Fund Vot. No. S024 or Project No. 02- 01-13-SF0104 and FRGS Vot. No. 1482 awarded by Malaysia Ministry of Education

Neste trabalho determinamos o módulo elástico de filmes finos metálicos nanoestruturados. Os metais estudados, platina, ouro e paládio foram depositados utilizando a técnica de Metal Plasma Immersion Ion Implantation and Deposition. Um novo método foi utilizado para as medidas de módulo elástico, no qual cantiléveres de microscopia de força atômica são uniformemente recobertos com os filmes finos metálicos. Medidas das frequências de ressonância dos cantiléveres foram realizadas antes e depois dos recobrimentos com os filmes. Usando a teoria de vibração de barras, determinamos os valores dos módulos elásticos desses filmes. Obtivemos valores que estão entre 7 e 12% menores do que os respectivos módulos elásticos dos metais na forma de bulk. Um modelo simples em conta o caráter nanoestruturado dos materiais. Caracterizações complementares foram realizadas como : microscopia de tunelamento, difração de raios X e RBS (Rutherfor Backscattering Spectrometry). / In this work we have determined the elastic moduli of nanostructured metallic thin films. The analyzed metals, platinum, gold and palladium, have been deposited using the technique Metal Plasma Immersion Ion Implantation and Deposition. A new method was adopted to determine the elastic moduli, where cantilevers of atomic force microscopy were uniformly coated with thin films. The resonance frequencies of the cantilevers have been measured before and after the films coating. The elastic moduli were finally obtained using the vibration beam theory. The determined elastic constants are smaller than the respective bulk moduli: about 12% for Pt and Au and about 7% for Pd. A simple model is proposed to explain the softening of the elastic moduli taking into account the nanostructured character of the films. Additional characterizations have been done like: scanning tunneling microscopy, X-ray diffraction and RBS (Rutherford Backscattering Spectrometry).