Precision engineering of the chicken genome for disease control

The thesis examines the application of precision genome engineering technology to improve the disease resistance in chicken model

Effect of the Sliding of Stacked Live Loads on the Seismic Response of Structures

Dynamic interaction between sliding live loads and the structure they act on is significant in the seismic analysis and design of the structure. The problem becomes more complex when the live loads are in the form of stacks. This paper presents a numerical model to simulate the dynamic interaction between a primary structure (PS) and a set of stacked bodies lying on it. Individual bodies in the stack were termed as secondary bodies (SBs) in this study. The lowest SB in the stack interacts with the structure through friction. Similar frictional forces also exist between different levels of the stack. This numerical model was verified with a Finite Element model. A parametric study was performed on the seismic response by varying the dynamic properties of the structure and SBs. The energy dissipation is found to be significant due to sliding within the stack. A novel methodology is proposed to calculate a modified structural period (Tnew) of the structure to use in its design. It was found that the Tnew varies significantly with the structural period, mass ratios, and coefficients of friction. Finally, design equations are proposed to calculate the Tnew . Two Indian seismic hazard levels were considered for this study

Finite Element Analysis Of Modified Conebolt Under Static And Dynamic Loadings

Axisymmetric finite element models are developed to simulate static pull test and dynamic drop test of MCB33 (modified conebolt with full dedonding) using ABAQUS. Results from the numerical models are in reasonable agreement with the test results. A parametric study is performed considering various variables (i.e. friction, cone angle, material strength, etc.) to analyze the performance of MCB33. The results demonstrate that friction between the steel and resin, cone angle, and the Poisson’s ratio of the resin affect the static and dynamic behaviors of the rockbolt. These parameters can be modified to improve the current design and enhance the overall performance of the rockbolt

Effects Of Unit-Cell Boundary Type On The Electromechanical Properties Of Randomly Distributed Multifunctional Composite Structures

The unit-cell composition of three-dimensional finite element models for 3-0 and 3-1 type polymer (PVDF) - ceramic (BaTiO3) and ceramic (PZT-7A) - ceramic (BaTiO3) structures are compared to determine the effects of fiber interaction at the surface of the unit-cell on the effective elastic, piezoelectric and dielectric properties of the multifunctional composite systems. The first unit-cell type examined has enclosed fibers that are completely contained within its boundaries, the second type has fibers that are contained within the sides of the unit-cell but can be cut at the top and bottom surfaces, and the third type has fibers that can be cut on the top, bottom and side surfaces of the unit-cell. All cut fibers are matched on opposing surfaces for continuity. Randomly distributed and aligned circular fibers, randomly distributed and randomly oriented circular fibers, and one central enclosed fiber with varying volume fractions and aspect ratios are compared with these three unit-cell structures. Results show that fiber models display greater or equal values of C"" when compared to aligned or randomly oriented fibers for all cases except aspect ratio 1 polymer-ceramic structures. The third type of unit-cell shows the highest e""values for single, aligned and randomly oriented fiber structures, except for the aspect ratio 10 polymerceramic case where the second type of unit-cell has greater results for aligned and single fibers. Finally, it can generally be seen that randomly oriented fibers have smaller values than similar aligned and single fiber structures with the exception being C"" of the ceramic-ceramic structures

Genome editing in poultry - opportunities and impacts

Poultry products (meat and eggs) are a major source of animal protein on which the world is increasingly reliant to feed a rapidly growing population. Improved breeds and advances in farm management practices have had a large impact on the poultry industry. For example, using current genetic stock and production practices, broiler chickens can weigh 2 kg in about 34 days. Forty-five years ago it would have typically taken over 60 days. These impressive advances have been made using traditional selective breeding methods and more recently by using genomics. Now, with the availability of precision genome engineering tools there are new opportunities to improve poultry production above and beyond those achievable by traditional means. One major opportunity is disease resilience, particularly for viral diseases such as avian influenza that has devastating impacts on the poultry industry. Resilience to specific diseases can be a notoriously difficult trait to select for using traditional breeding and the latest technologies that precisely edit the genome have created new ways to address this challenge

The effect of density and feature size on mechanical properties of isostructural metaffic foams produced by additive manufacturing

Simple models describing the relationship between basic mechanical properties and the relative density of various types of porous metals (such as foams, sponges and lattice structures) are well established. Carefully evaluating these relationships experimentally is challenging, however, because of the stochastic structure of foams and the fact that it is difficult to systematically isolate density changes from variations in other factors, such as pore size and pore distribution. Here a new method for producing systematic sets of stochastic foams is employed based on electron beam melting (EBM) additive manufacturing (AM). To create idealised structures, structural blueprints were reverse-engineered by inverting X-ray computed tomographs of a randomly packed bed of glass beads. This three-dimensional structure was then modified by computer to create five foams of different relative density ρr, but otherwise consistent structure. Yield strength and Young’s modulus have been evaluated in compression tests and compared to existing models for foams. A power of 3 rather than a squared dependence of stiffness on relative density is found, which agrees with a recent model derived for replicated foams. A similar power of 3 relation was found for yield strength. Further analysis of the strength of nominally fully dense rods of different diameters built by EBM AM suggest that surface defects mean that the minimum size of features that can be created by EBM with similar strengths to machined samples is ∼1 mm

Electric field distribution in porous piezoelectric materials during polarization

High piezoelectric coupling coefficients enable the harvesting of more energy or increase the sensitivity of sensors which work using the principle of piezoelectricity. These coefficients depend on the material properties, but the manufacturing process can have a significant impact on the resulting overall coefficients. During the manufacturing process, one of the main steps is the process of polarization where a poling electric field aligns the ferroelectric domains in a similar direction in order to create a transversely isotropic material able to generate electric fields or deformations. The degree of polarization depends on multiple factors and it can strongly influence the final piezoelectric coefficients. In this paper, a study on the electric field distribution on the sensitivity of the main piezoelectric and dielectric coefficients to the polarization process is performed, focusing on porous piezoelectric materials. Different inclusion geometries are considered, namely spherical, ellipsoidal and spheres with cracks. The electric field distribution at the micro scale within a representative volume element is modelled to determine the material polarization level using the finite element method. The results show that the electric field distribution is highly dependent on the inclusion geometries and cracks and it has a noticeable impact on the equivalent piezoelectric coefficients. These results are compared with experimental measurements from published literature. Good agreement is found between the ellipsoidal model and the experimental data

Surrogate broodstock to enhance biotechnology research and applications in aquaculture

Aquaculture is playing an increasingly important role in meeting global demands for seafood, particularly in low and middle income countries. Genetic improvement of aquaculture species has major untapped potential to help achieve this, with selective breeding and genome editing offering exciting avenues to expedite this process. However, limitations to these breeding and editing approaches include long generation intervals of many fish species, alongside both technical and regulatory barriers to the application of genome editing in commercial production. Surrogate broodstock technology facilitates the production of donor-derived gametes in surrogate parents, and comprises transplantation of germ cells of donors into sterilised recipients. There are many successful examples of intra- and inter-species germ cell transfer and production of viable offspring in finfish, and this leads to new opportunities to address the aforementioned limitations. Firstly, surrogate broodstock technology raises the opportunity to improve genome editing via the use of cultured germ cells, to reduce mosaicism and potentially enable in vivo CRISPR screens in the progeny of surrogate parents. Secondly, the technology has pertinent applications in preservation of aquatic genetic resources, and in facilitating breeding of high-value species which are otherwise difficult to rear in captivity. Thirdly, it holds potential to drastically reduce the effective generation interval in aquaculture breeding programmes, expediting the rate of genetic gain. Finally, it provides new opportunities for dissemination of tailored, potentially genome edited, production animals of high genetic merit for farming. This review focuses on the state-of-the-art of surrogate broodstock technology, and discusses the next steps for its applications in research and production. The integration and synergy of genomics, genome editing, and reproductive technologies have exceptional potential to expedite genetic gain in aquaculture species in the coming decades

Virtual testing of advanced composites, cellular materials and biomaterials: A review

This paper documents the emergence of virtual testing frameworks for prediction of the constitutive responses of engineering materials. A detailed study is presented, of the philosophy underpinning virtual testing schemes: highlighting the structure, challenges and opportunities posed by a virtual testing strategy compared with traditional laboratory experiments. The virtual testing process has been discussed from atomistic to macrostructural length scales of analyses. Several implementations of virtual testing frameworks for diverse categories of materials are also presented, with particular emphasis on composites, cellular materials and biomaterials (collectively described as heterogeneous systems, in this context). The robustness of virtual frameworks for prediction of the constitutive behaviour of these materials is discussed. The paper also considers the current thinking on developing virtual laboratories in relation to availability of computational resources as well as the development of multi-scale material model algorithms. In conclusion, the paper highlights the challenges facing developments of future virtual testing frameworks. This review represents a comprehensive documentation of the state of knowledge on virtual testing from microscale to macroscale length scales for heterogeneous materials across constitutive responses from elastic to damage regimes