Characterization of a Multi-Laminate Angle-Ply AF Patch for Annulus Fibrosus Repair

Annually, over 5.7 million Americans are diagnosed with two IVD-associated pathologies: IVD herniation (IVDH- a mechanical disruption of the concentric fibrous layers of the annulus fibrosus (AF))) and degeneration (IVDD- a multifactorial process which initiates within the inner gelatinous core (NP), and results in a biochemical degradation of NP tissue), with over 2.7 million requiring surgical inteventions.1,2 Although both underlying pathologies are different, quite often they both lead to a decrease in IVD height, impaired mechanical function, and increased pain and disability. These pain symptoms affect approximately 80% of the adult population during their lifetime with estimated expenditures exceeding $85.9 billion.3,4 Current surgical procedures for IVDH and IVDD are palliative and suffer from drawbacks. While they are performed to address patient symptoms, they fail to address the underlying pathology of a defect remaining within the subsequent layers of the AF. An effective AF closure/repair device in conjunction with a less aggressive discectomy for IVDH and/or NP arthroplasty for IVDD, may result in improved patient outcomes, decreased pain, and provide fewer revision surgeries via lower re-herniation and expulsion rates.5,6 Therefore, an intact AF must be re-established to prevent implant expulsion or re-herniation, thus addressing the two major spinal pathologies directly associated with an IVD. Currently within the medical device market, no tissue engineering biomaterials are available for AF closure/repair. Current market AF closure devices (Intrinsic Barricaid, Anulex X-Close Tissue Repair System, and Anulex Inclose Surgical Mesh System) are synthetic materials focused solely on preserving and reinforcing the native tissue and lack efficient strategies for implantation, fixation, and regeneration. Therefore, there has been an increase in tissue engineering and regenerative therapeutic approaches aiming for structural and biological AF repair investigated over the last decade using in vivo and in vitro experimentation. It is proposed that the optimum AF tissue engineering scaffold should reproduce the architecture, and the mechanical properties of the native human AF tissue.7 Recent articles illustrate several novel suture, seal, and barrier techniques currently under development, resulting in an increasing attention at scientific workshops and conferences.8-15 To develop a tissue engineering biomaterial that is suitable for AF closure it must meet the following criteria: (1) mimic the structural angle-ply architecture of the native AF, (2) withstand static and dynamic mechanical properties mimicking the native functional characteristics, and (3) express cytocompatibility while promoting tissue regeneration. Current biomaterials growing attention in the tissue engineering academic field, electrospinning, polymers, glue, silk scaffolds, and honeycomb-scaffolds, require complex manufacturing procedures and typically work to address two of the three criteria (mimicking the biological and structural characteristics).5 Although the mechanical advantage of closing annular defects to retain NP material seems intuitive, only recently have AF closure devices begun to examined in human cadaveric or animal tissues for their ability to withstand in situ IDP or flexibility testing.16 Therefore, the use of decellularized tissue from a xenogeneic source is ideal due to its advantage of maintaining native extracellular matrix (ECM) while also removing all potential harmful xenogeneic factors. We propose to address all three criteria with the development of a biomimetic angle-ply annulus fibrosus patch comprised of decellularized porcine pericardium. Porcine pericardium was chosen due to its native type I collagen content, mechanical strength, and cytocompatibility. The objectives of this research were to investigate the development of a biomimetic patch, consisting of decellularized porcine pericardium, to biologically augment AF repair by (1) characterizing the micro-architecture of the multi-laminate angle-ply AF patch, (2) evaluating the mechanical properties through static and dynamic tensile loading and impact resistance of IDP, and (3) evaluating the cytocompatibility of the patch using a healthy alternative cell source for AF tissue regeneration

The LifeV library: engineering mathematics beyond the proof of concept

LifeV is a library for the finite element (FE) solution of partial differential equations in one, two, and three dimensions. It is written in C++ and designed to run on diverse parallel architectures, including cloud and high performance computing facilities. In spite of its academic research nature, meaning a library for the development and testing of new methods, one distinguishing feature of LifeV is its use on real world problems and it is intended to provide a tool for many engineering applications. It has been actually used in computational hemodynamics, including cardiac mechanics and fluid-structure interaction problems, in porous media, ice sheets dynamics for both forward and inverse problems. In this paper we give a short overview of the features of LifeV and its coding paradigms on simple problems. The main focus is on the parallel environment which is mainly driven by domain decomposition methods and based on external libraries such as MPI, the Trilinos project, HDF5 and ParMetis. Dedicated to the memory of Fausto Saleri.Comment: Review of the LifeV Finite Element librar

“Driving While Black”: A Theory for Interethnic Integration and Evolution of Prejudice

This paper studies the evolution of interethnic attitudes, the integration or segregation dynamics of ethnic minorities and the conditions for the rising of ethnic-based social hierarchies. By means of a cultural evolution framework, a dynamics of interethnic attitudes is provided and conditions for their convergence derived. Steady states implying a constant role of racism and no role for racism are identified. Deriving sufficient conditions for convergence, we find that the way in which Oblique Socialization Schemes (the way children react to out-of-family stimuli when forming their cultural values) are defined and modelled becomes crucial for the structure of the derived long run equilibria. In particular, we find that Steady States implying an Ethnic-based social ranking or full integration of ethnicities may be reached depending on whether or not agents use Reciprocity and/or Ethnocentrism in their interethnic attitudes formation schemes. Allowing different groups for asymmetric use of reciprocity and Ethnocentrism, we explain why different ethnic minorities may show different integration patterns, and what are the different roles (Cultural bridge, cultural hub) an ethnic group may play in the integration process. Moreover, in this way, we explain why attitudes of some groups towards others converge to the same values, while other groups seems to be excluded from this process. At last, we provide the first steps for the endogeneization of socialization structures.Cultural transmission, Minority integration, Evolution of preferences

System archetypes underlying formal-informal urban water supply dynamics

Contrary to developed countries, developing countries have been observed to have an increased reliance on a diversity of water supply options to meet their daily demands, where formal supply systems are incapable of fulfilling the daily needs of consumers. In filling a demand-supply gap, informal supply systems are increasingly being associated with issues of long-term sustainability, higher consumer cost, and inequity. Emerging formal-informal dynamics in developing countries require a thorough understanding of complex human-water interactions for policy direction, in order to best support the advancement of urban water sustainability. Accordingly, system archetypes offer a platform to explain the behaviors of complex systems. This paper identifies common system archetypes that define urban waterscapes in the developing world. In this way, Causal Loop Diagrams (CLDs) are used to present relationships and identify common archetypes that define the complexity of urban water supply systems in Hyderabad, Pakistan. These archetypes include ‘fixes that fail’, ‘shifting the burden’, ‘limits to growth/success’ and ‘growth and underinvestment’. These archetypes demonstrate that increases in formal infrastructure capacity and the number of informal suppliers to increase supply reliability are symptomatic solutions, restrained by financial and technical resources, and thus have unintended consequences. Further, a number of policy instruments are discussed as leverage points to achieve financial sustainability of formal systems. This paper emphasizes the need of a policy framework for informal supply system in national and regional water policies to ensure its service reliability as a short to medium term solution

NMR struture determination and MD simultations of membrane peptides and proteins : a peptide derived from H+-V-ATPase subunit alpha, and MscL

H+-V-ATPase est une protéine responsable de la translocation des protons. Les propriétés structurales d'un peptide dérivé de la sous-unité a de H+-V-ATPase, ont été étudiées. La structure dans des micelles de SDS a été déterminée par RMN. Il a été démontré par dichroisme circulaire que le peptide est structuré en feuillet beta dans l'octylglucoside à haut pH, tandis qu'il présente 60\% d'hélice alpha dans le SDS. Ces observations ont été expliquées par des simulations de dynamique moléculaire, qui ont démontré que le peptide est inseré dans la micelle de SDS à haut pH, alors qu'en présence d'octylglucoside il est en interaction avec la surface de la micelle. La structure RMN en combinaison avec les simulations nous a permis d'identifier les residues participant au canal périplasmique. Dans la deuxième partie de la thèse, des essais de préparation d'échantillons du canal mécanosensible de haute conductance (MscL) dans des bicouches orientées de lipides ont été réalisés afin d'étudier cette protéine par RMN du solideThe structural properties of a peptide derived from the proton translocating H+-V-ATPase subunit a were studied. An NMR structure was obtained in SDS micelles. Circular dichroism measurements indicated that the peptide formed a beta-sheet at high pH in octylglucoside, while it was 60% alpha-helical in SDS. These findings were explained using molecular dynamics simulations, which indicated that at high pH the peptide took a transmembrane position in SDS but was located in the interface region in octylglucoside. The combination of the NMR structure and the MD simulations allowed us to identify the residues that line the lumenal proton channe

The Effect of Ultrasonic Power in Aluminum Wire Bonding Hardness Profiles

Ultrasonic wire bonding is a critical process used widely across the microelectronics industry. Despite its ubiquity, there is a breadth of literature and ongoing active research into the basic principles of wire bonding. In particular, the effects of ultrasonic bonding on material properties are not fully understood. This thesis presents the effects of different ultrasonic bond powers on material properties. The changes in mechanical properties were measured by collecting Vickers microhardness data and nanoindentation data. The hardness in the bonded wire varied with two parameters: the distance from the bond interface, and the applied ultrasonic power. The hardness varied 5 HV across the profile of a bond and a 5 HV difference was also measured due to change in bond power. In addition, the measured hardness of the bonds was lower by up to 10 HV than calculated hardness values based on strain hardening only. These trends were found with the microhardness data and corroborated by nanoindentation results. This work provides a method to further study the effects of additional bonding parameters on mechanical properties

A cooperative framework for molecular biology database integration using image object selection

The theme and the concept of 'Molecular Biology Database Integration' and the problems associated with this concept initiated the idea for this Ph.D research. The available technologies facilitate to analyse the data independently and discretely but it fails to integrate the data resources for more meaningful information. This along with the integration issues created the scope for this Ph.D research. The research has reviewed the 'database interoperability' problems and it has suggested a framework for integrating the molecular biology databases. The framework has proposed to develop a cooperative environment to share information on the basis of common purpose for the molecular biology databases. The research has also reviewed other implementation and interoperability issues for laboratory based, dedicated and target specific database. The research has addressed the following issues: diversity of molecular biology databases schemas, schema constructs and schema implementation multi-database query using image object keying, database integration technologies using context graph, automated navigation among these databases. This thesis has introduced a new approach for database implementation. It has introduced an interoperable component database concept to initiate multidatabase query on gene mutation data. A number of data models have been proposed for gene mutation data which is the basis for integrating the target specific component database to be integrated with the federated information system. The proposed data models are: data models for genetic trait analysis, classification of gene mutation data, pathological lesion data and laboratory data. The main feature of this component database is non-overlapping attributes and it will follow non-redundant integration approach as explained in the thesis. This will be achieved by storing attributes which will not have the union or intersection of any attributes that exist in public domain molecular biology databases. Unlike data warehousing technique, this feature is quite unique and novel. The component database will be integrated with other biological data sources for sharing information in a cooperative environment. This involves developing new tools. The thesis explains the role of these new tools which are: meta data extractor, mapping linker, query generator and result interpreter. These tools are used for a transparent integration without creating any global schema of the participating databases. The thesis has also established the concept of image object keying for multidatabase query and it has proposed a relevant algorithm for matching protein spot in gel electrophoresis image. An object spot in gel electrophoresis image will initiate the query when it is selected by the user. It matches the selected spot with other similar spots in other resource databases. This image object keying method is an alternative to conventional multidatabase query which requires writing complex SQL scripts. This method also resolve the semantic conflicts that exist among molecular biology databases. The research has proposed a new framework based on the context of the web data for interactions with different biological data resources. A formal description of the resource context is described in the thesis. The implementation of the context into Resource Document Framework (RDF) will be able to increase the interoperability by providing the description of the resources and the navigation plan for accessing the web based databases. A higher level construct is developed (has, provide and access) to implement the context into RDF for web interactions. The interactions within the resources are achieved by utilising an integration domain to extract the required information with a single instance and without writing any query scripts. The integration domain allows to navigate and to execute the query plan within the resource databases. An extractor module collects elements from different target webs and unify them as a whole object in a single page. The proposed framework is tested to find specific information e.g., information on Alzheimer's disease, from public domain biology resources, such as, Protein Data Bank, Genome Data Bank, Online Mendalian Inheritance in Man and local database. Finally, the thesis proposes further propositions and plans for future work