[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

From the Publisher: 
The accessible presentation of this book gives both a general view of the entire computer vision enterprise and also offers sufficient detail to be able to build useful applications. Users learn techniques that have proven to be useful by first-hand experience and a wide range of mathematical methods. A CD-ROM with every copy of the text contains source code for programming practice, color images, and illustrative movies. Comprehensive and up-to-date, this book includes essential topics that either reflect practical significance or are of theoretical importance. Topics are discussed in substantial and increasing depth. Application surveys describe numerous important application areas such as image based rendering and digital libraries. Many important algorithms broken down and illustrated in pseudo code. Appropriate for use by engineers as a comprehensive reference to the computer vision enterprise.

Computer vision : a modern approach = 计算机视觉 : 一种现代的方法

A paradigm shift is taking place in medicine from using synthetic implants and tissue grafts to a tissue engineering approach that uses degradable porous material scaffolds integrated with biological cells or molecules to regenerate tissues. This new paradigm requires scaffolds that balance temporary mechanical function with mass transport to aid biological delivery and tissue regeneration. Little is known quantitatively about this balance as early scaffolds were not fabricated with precise porous architecture. Recent advances in both computational topology design (CTD) and solid free-form fabrication (SFF) have made it possible to create scaffolds with controlled architecture. This paper reviews the integration of CTD with SFF to build designer tissue-engineering scaffolds. It also details the mechanical properties and tissue regeneration achieved using designer scaffolds. Finally, future directions are suggested for using designer scaffolds with in vivo experimentation to optimize tissue-engineering treatments, and coupling designer scaffolds with cell printing to create designer material/biofactor hybrids.

/pdf/porous-scaffold-design-for-tissue-engineering-2a1maztjuj.pdf

Porous scaffold design for tissue engineering

In this paper we develop a new constitutive law for the description of the (passive) mechanical response of arterial tissue. The artery is modeled as a thick-walled nonlinearly elastic circular cylindrical tube consisting of two layers corresponding to the media and adventitia (the solid mechanically relevant layers in healthy tissue). Each layer is treated as a fiber-reinforced material with the fibers corresponding to the collagenous component of the material and symmetrically disposed with respect to the cylinder axis. The resulting constitutive law is orthotropic in each layer. Fiber orientations obtained from a statistical analysis of histological sections from each arterial layer are used. A specific form of the law, which requires only three material parameters for each layer, is used to study the response of an artery under combined axial extension, inflation and torsion. The characteristic and very important residual stress in an artery in vitro is accounted for by assuming that the natural (unstressed and unstrained) configuration of the material corresponds to an open sector of a tube, which is then closed by an initial bending to form a load-free, but stressed, circular cylindrical configuration prior to application of the extension, inflation and torsion. The effect of residual stress on the stress distribution through the deformed arterial wall in the physiological state is examined. The model is fitted to available data on arteries and its predictions are assessed for the considered combined loadings. It is explained how the new model is designed to avoid certain mechanical, mathematical and computational deficiencies evident in currently available phenomenological models. A critical review of these models is provided by way of background to the development of the new model.

https://hal.archives-ouvertes.fr/hal-01297725/document

A new constitutive framework for arterial wall mechanics and a comparative study of material models

Constitutive relations are fundamental to the solution of problems in continuum mechanics, and are required in the study of, for example, mechanically dominated clinical interventions involving soft biological tissues. Structural continuum constitutive models of arterial layers integrate information about the tissue morphology and therefore allow investigation of the interrelation between structure and function in response to mechanical loading. Collagen fibres are key ingredients in the structure of arteries. In the media (the middle layer of the artery wall) they are arranged in two helically distributed families with a small pitch and very little dispersion in their orientation (i.e. they are aligned quite close to the circumferential direction). By contrast, in the adventitial and intimal layers, the orientation of the collagen fibres is dispersed, as shown by polarized light microscopy of stained arterial tissue. As a result, continuum models that do not account for the dispersion are not able to capture accurately the stress–strain response of these layers. The purpose of this paper, therefore, is to develop a structural continuum framework that is able to represent the dispersion of the collagen fibre orientation. This then allows the development of a new hyperelastic free-energy function that is particularly suited for representing the anisotropic elastic properties of adventitial and intimal layers of arterial walls, and is a generalization of the fibre-reinforced structural model introduced by Holzapfel & Gasser (Holzapfel & Gasser 2001 Comput. Meth. Appl. Mech. Eng. 190, 4379–4403) and Holzapfel et al. (Holzapfel et al. 2000 J. Elast. 61, 1–48). The model incorporates an additional scalar structure parameter that characterizes the dispersed collagen orientation. An efficient finite element implementation of the model is then presented and numerical examples show that the dispersion of the orientation of collagen fibres in the adventitia of human iliac arteries has a significant effect on their mechanical response.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2005.0073

Hyperelastic modelling of arterial layers with distributed collagen fibre orientations

Multiaxial mechanical properties and constitutive modeling of human adipose tissue

Loris Nagler: Simulation of Sound Transmission through Poroeleastic Plate-like Structures

Mechanical stress in abdominal aneurysm: influence of geometry and material

Changes in the mechanical environment of lesions due to stent-artery interaction - A computational analysis

Introduction The ability of tendons to withstand stress generally decreases with age, often resulting in increased tissue degeneration and decreased regeneration capacity. However, the underlying molecular and cellular mechanisms of tendon senescence remain poorly characterized. Therefore, the aim of the current study was to identify genes showing an age-dependent altered expression profile in tendons. Materials and Methods A suppression-subtractive-hybridization (SSH) screen comparing cDNA libraries generated from Achilles tendons of mature-adult (3 months) and old (18 months) female C57BL/6 mice was conducted. Subsequently, the differential expression of the identified genes was validated by RT-qPCR and selected genes were then further analysed by immunohistochemistry and Western blot. To investigate age-related structural alterations in the collagenous extracellular matrix we applied SHG-microscopy and TEM. In vitro experiments with young and old tendon derived stem/progenitor cells (TDSCs) involved wounding assays, tendon-like constructs as well as collagen gel contraction assays. Results Among 168 identified genes, several ECM genes showed a differential expression, including Col1a1, Col3a1, fibronectin, fibromodulin, thrombospondin-1, decorin, biglycan, lysyl oxidase, and Sparc. As evidenced by RT-qPCR the mRNA levels of these genes were down-regulated in old tendons and in old TDSCs. Additionally, protein content of SPARC and Lysyl oxidase was diminished in vitro in cellular extracts from old TDSCs. The impact of Sparc on tendon ageing was further analysed in young and old Sparc−/− C57BL/6 as well as in age-matched wildtype mice. Tendons of Sparc−/− mice are generally thinner and TEM revealed thinner collagen fibrils and a larger interfibrillar area. Further, TDSCs of old and Sparc−/− tendons formed thinner in vitro tendon constructs, showed a higher collagen gel contraction capacity, and display altered cell-ECM adhesion and cell migration properties when compared to young wildtype cells. Employing SHG-microscopy we further observed age-related changes in the collagenous structure of Achilles tendons. Discussion The decreased expression of ECM proteins and modulators thereof in old tendons in combination with structural changes is potentially associated with an increased risk of tendon injury in the elderly, since structure and composition of the tendon are directly related to its function.

Gerhard Holzapfel

Papers

Multiaxial mechanical properties and constitutive modeling of human adipose tissue

Loris Nagler: Simulation of Sound Transmission through Poroeleastic Plate-like Structures

Mechanical stress in abdominal aneurysm: influence of geometry and material

Changes in the mechanical environment of lesions due to stent-artery interaction - A computational analysis

Age matters: molecular mechanisms contributing to tendon senescence