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The load response, energy absorption, different damage mechanisms and failure modes of sandwich panels subjected to complete perforation by quasi-static indentation and the insights gleaned are presented in this paper. The experimental campaign was carried out on samples made of different type of facesheets: Aluminium, glass fibre-reinforced plastic and metal-composite hybrid (combined aluminium and GFRP) with two different core heights. Reliable numerical models were developed with appropriate constitutive material and damage model for facesheets and honeycomb core to complement the experimental observations. Good agreement between experimental results and numerical predictions in terms of force-displacement response and perforation damage ensure the fidelity of the developed numerical model. Effects of facesheet type, core height, energy absorbed by the constituent layers, damage evolution history are briefly discussed. It was observed that the energy absorption of sandwich panels and peak indentation force resisted by the top and bottom facesheet are strongly dependent on its metal-volume fraction, whilst unaffected with the height of the core. Recommendations for developing computationally efficient numerical models were provided.

Nowadays, laminated composites are widely used in the aerospace sector. All laminates have interply/interlaminar interfaces even if they are made using automated processes. The interfaces act as the areas of weaknesses and the potential crack initiation regions. Hence, any enhancement in the crack initiation and propagation resistance is always sought after. Usage of polymeric thin films is one of the promising and viable ways to achieve this. It is also easy to incorporate micro-thin films into any automation process. In the present study, different customized thin films that are compatible with Glass/BMI composites are fabricated. Fracture toughness tests in Mode I (opening mode), Mode II (sliding mode) and Mixed Mode I/II are conducted respectively using Double Cantilever Beam (DCB), End Notch Flexure (ENF) and Mixed Mode Bending (MMB) test specimens. This paper discusses the manufacturing of compatible micro-thin films. The various challenges faced during the manufacturing and incorporation of thin films are presented. The results of the various fracture toughness tests are examined. Mechanisms through which the different films help in resisting the crack initiation and propagation are deliberated and discussed. The incorporation of this technique in Automated Fiber Placement (AFP) is also discussed.

Even with small infinitesimal increase in load, change of equilibrium configuration of completely different character is highly possible for thin shell structures and that could eventually result the whole structure become unstable. This article presents numerical investigation on buckling and post-buckling characteristics of laminated composite circular cylindrical/conical shell subjected to torsional, thermal and combined loads. Using commercial finite element software ABAQUS, both linear and non-linear buckling response of composite shells are simulated. Linear critical buckling load due to uncoupled torsional and thermal loads is determined using eigen value buckling analysis. Non-linear post-buckling response of shell is simulated using Riks arc length method. Un-coupled and coupled influence of thermal-torsional influence to critical buckling load is estimated. Mode shape associated with linear Eigen value analysis are used as initial geometric imperfection for non-linear analysis. Thermo-mechanical coupling found reduces the buckling load resistance of cylindrical shell by maximum of 47%. It was observed that the generation of additional axial compressive reaction force due to thermal expansion restrain on axial constrained shell edges could be the major influential factor. Except a small radial expansion of cylindrical surface, deformation shape predicted from non-linear post buckling analysis resembles rather similar irrespective of any proportion of thermal-torsional coupling.

The present paper gives details of the structural response of titanium-based fiber metal laminates (TFML) subjected to high velocity impact. Dynamic perforation behavior of two different sample configurations, TFML-2/1 and 3/2 are presented. The behavior of the metal and composite layer is defined using two independent appropriate constitutive material models. Both experimental and numerically predicted residual velocity follows the Recht-Ipson model variation with impact velocity. Being larger in thickness, residual velocity, peak contact force and total energy absorbed were found to be larger for TFML-3/2 than 2/1. However, the contact duration was rather insignificantly affected. Having similar metal volume fraction (MVF), energy dissipated by means of plastic deformation of metal layers was found to be constant for both TFML configurations that were considered. The axisymmetric loading, boundary conditions and having balanced material property distribution along the principle axes resulted in doubly symmetric damage surfaces, both layer-wise and overall. The developed finite element (FE) model adequately simulated the contact behavior and all of the experimentally realized damage modes in the metal and composite layers and confirmed its reliability. Having limited experimental information, the obtained numerical information allows one to briefly understand the dynamic perforation behavior of TFML laminates.

This article discusses the impact behavioral responses of opaque bi-layered metal bonded hybrid composites from geometrically equivalent transparent plastic specimens. Low velocity drop weight impact experiments were conducted on bi-material laminated plates made of brittle acrylic sheet adhesively bonded with ductile polycarbonate layer by a compatible room temperature cure epoxy. Depending on the nature of impact face (brittle or ductile) battered by the impactor, the induced impact damage are characterized either as partial or complete interface failure that leads to formation of radial cracks or spalling fracture in the acrylic layer. The influence of relative constituent thickness towards impact damage resistance and the resultant structural integrity are extensively discussed. The obtained results from similitude study made it possible to understand the behavior of geometrically equivalent bi-layered fibre metal laminates under similar impact conditions. In addition through numerical simulations, the energy dissipated via plastic work by the ductile layers was found to be dominant and the only source that create significant difference in energy absorption between hard and soft side impact samples.

Cancer genome sequencing has implicated the cytosine deaminase activity of apolipoprotein B mRNA editing enzyme catalytic polypeptide-like (APOBEC) genes as an important source of mutations in diverse cancers, with APOBEC3B (A3B) expression especially correlated with such cancer mutations. To better understand the processes directing A3B over-expression in cancer, and possible therapeutic avenues for targeting A3B, we have investigated the regulation of A3B gene expression. Here, we show that A3B expression is inversely related to p53 status in different cancer types and demonstrate that this is due to a direct and pivotal role for p53 in repressing A3B expression. This occurs through the induction of p21 (CDKN1A) and the recruitment of the repressive DREAM complex to the A3B gene promoter, such that loss of p53 through mutation, or human papilloma virus-mediated inhibition, prevents recruitment of the complex, thereby causing elevated A3B expression and cytosine deaminase activity in cancer cells. As p53 is frequently mutated in cancer, our findings provide a mechanism by which p53 loss can promote cancer mutagenesis.

The present thesis covers detailed investigation on the quasi-static indentation and low-velocity impact response of Fibre Metal Laminates (FML) using experimental and finite element simulation study. The FML panels investigated were made from balanced woven GFRP fabric composite layer bonded with aluminium alloy Al 2024-O metal sheet. Indentation and low velocity impact experiments were conducted on FML panels of 1/1, 2/1, 3/2 and 4/3 configurations using hemispherical ended indenter/impactor. Static indentation test allows one to correlate the characteristic load-displacement curve with distinct failure stages of the respective material layer in the FML panel. It also provides corresponding energy magnitude required to induce particular failure mode in FML panel. Using these energy levels, impact velocities for impact tests were derived. Along with experimental observations, a robust and reliable finite element model was developed using ABAQUS, a commercially available finite element software. Adhesive bonding between metal and composite layers of FML was modelled using special purpose cohesive element. Three non-interactive material models were defined to simulate the behaviour of metal, composite and cohesive interface in finite element model. The damage response was defined using continuum damage mechanics (CDM) based damage model constituting 1) Johnson-cook (JC) failure criteria for metal layer 2) Interactive mode based failure model for composite layer and 3) Quadratic nominal stress based failure criteria for cohesive layer in progression with fracture mechanics based damage evolution formulation. High fidelity solutions were obtained through these robust finite element models. Variable parameters having interrelated influencing factors were studied to understand the role of the material layers to indentation and impact response of FML. The influence of initial contact surface (geometry related), impact velocity (event related) and metal composite interface (MCI) bonding (material related) were considered for the investigation. Both experiment and numerical results showed that the considered geometry and the material related parameters have strong influence on the threshold force to cause damage initiation in FML whereas the threshold influence of event related parameter is constant for all investigated FML configurations. From the absorbed energy perspective, FML panels absorb ~90% of impact energy in average through different dissipation modes; ~60% by plastic deformation of the metal layer, ~20% by residual elastic energy and ~10% by forming new damage surface. Finally, the influence of the clustering level of metal and composite layers towards the structural integrity of FML panel was analysed. Load carrying capability, plastic flow of metal layers and extent of damage in each material layers were found strongly dependent on level of clustering for a given FML panel thickness and metal volume fraction (MVF). Doctor of Philosophy (MAE)

This paper presents an extensive study on the experimental and numerical investigation of metal layered interply hybrid composites subjected to low velocity impact. In an effort to understand the contribution of individual layer to energy absorption and subsequent failure in fibre-metal laminates, the test specimens were fabricated with a layer of metal bonded to a layer of composite. The mechanical response of each specimen to low velocity impact load is compartmentalized through two test cases: (i) specimen impacted on the ductile metal layer and (ii) specimen impacted on the brittle composite layer. For a detailed insight into the response of individual layers, a numerical study was carried out using commercially available software called ABAQUS with elastic–plastic model for metal layer and a user defined constitutive model via a VUMAT subroutine for composite layer. The level of correlation between experimental and numerical results is comparable. Being stiff in nature, with small impact energy absorption, exhibit less concentrated damage, brittle side impact samples are found to provide excellent impact resistance than ductile side impact samples.

Plants still represent untapped sources of novel compounds with potential therapeutic effects. Hence, the present investigation was carried out to study the in vitro evaluation of antimicrobial potential and to assess the bioactive constituents of the aerial parts of Vitis setosa Wall. The powdered aerial material was extracted with different solvents and examined for antimicrobial activity against Escherichia coli, Salmonella typhi, Bacillus subtilis, Streptococcus pyogenes, Candida albicans, Fusarium solani and Trichophyton rubrum using well diffusion method. An ethanol extract of V. setosa showed significant antimicrobial activity against all the tested pathogens. The fresh aerial parts contained eight primary metabolites (chlorophylls, carotenoids, total soluble sugars, total soluble proteins, total free amino acids, total phenol, hydroxyl phenols and lipids) and alkaloids, tannins, saponins, triterpenoids and phenolic compounds. Gas chromatography-mass spectrometry (GC-MS) results also showed 26 bioactive compounds including n-hexadecanoic acid, 9,12,15-octadecatrienoic acid (z,z,z)- and τ-tocopherol. In conclusion, the aerial parts of V. setosa are a promising source of antimicrobial bioactive compounds. Key words: Bioactive constituents, Vitis setosa, GC-MS analysis, ethanolic extract, antimicrobial activity, folk medicine.

This contribution hopes to give a comprehensive review of past and current research work published on the dynamic response of fibre-metal laminates subjected to low velocity impact. The historical development of fibre-metal laminates is first reviewed in details, and notable researchers and their contributions are chronologically tabulated and reviewed. Included are also reviews on published experimental, numerical and analytical work on the low velocity impact of fibre-metal laminates. Detailed discussions on the two main groups of parameters namely geometry and material based parameters that influenced the structural response of fibre metal laminates to low-velocity impact. The review concludes with detailed discussions on the future works needed for fibre-metal laminates subjected to low velocity impact loads.

Silica Aerogel composites are ultra-low density, highly porous foam-like materials that exhibit excellent thermal insulation and high strain recovery characteristics. In the present work, environment-friendly silica aerogel composites are fabricated using silica aerogel granules with bio based porcine-gelatin as the binding agent dissolved in water and by further drying the mix at sub-zero condition. This article focuses on improvement studies carried on the mold design and the manufacturing process to achieve better geometric compliance for the silica aerogel composites. It also presents contact angle measurements, compressive behavior under different cycles of loading, time dependent behavior and flexural response of the composites. The influence of additives, such as fumed silica and carbon nanotubes on mechanical properties of the composites is also deliberated. Water droplet contact angle experiments confirmed the ultra-hydrophobic nature of the composites. The mechanical properties were characterized under cyclic loading-unloading compression and three-point flexure tests. On successive compression in three consecutive load cycles, the strain and thickness recovery were found to decrease by around 30%. The flexural properties of the aerogel composites were investigated using it as the core covered by thin carbon composite face sheets. It was found that the flexural strength and the failure strain of this aerogel sandwich composites is approximately half of the conventional nomex honeycomb sandwich equivalent.

A%675$&7Fibre Metal Lam inate (FML), a metal sandwiche d hybrid composite material is well-known for its enhanced impact properties and better damage tolerance and it has been successfully implemented in diverse engineering applications in aviation industry. With heterogeneous constituents, the stacking sequence of FML is believe to play a cri tical role to govern its overall energy absorption capability by means of controlli ng delamination of metal composite interface and plastic deformation of metal layers. As a precursor, low velocity impact experiments were conducted on interply configured transparent plastic plates in orde r to extract the significance of stacking sequence and realize the characteristics of each layer through nake d eye which is not possible in FML due to opacity of metal layer. The stack configuration constitute hard acrylic (brittle) and soft polycarbonate (ductile) plates analogous to composite (brittle) and metal (ductile) layers on FML laminate and the impact ev ent is performed on either hard or soft facing sides separately. Hard side samples resemble more protective than soft side impact sample, with large peak resistant force and expose smaller damage growth in all experimented cases. Keywords: Transparent plastics, Fibre Metal Lamina te, Low velocity impact, Impact face 1. IntroductionIn engineering applications, structures made of heterogeneous composition fulfill majority of anticipation in terms of robustness, reliability and durability. The investigation of bi-material structure often provides a fundame ntal understanding of role played by the individual material constituents and also pave the way to enhance and optimize its influence. Wear resistant structures, coated substrates, sandwich panels, and laminated composites are some of the

Breast cancer is the most common cancer worldwide, with 1.38 million women diagnosed with the disease each year. Estrogens play a critical role in the development and progression of breast cancer, their action being mediated by the estrogen receptors (ER), ERα and ERß, which are the members of the nuclear receptor superfamily of transcription factors. This understanding has led to the development of endocrine therapies aimed at inhibiting ER action by competitive binding to the ER (anti-estrogens), or using inhibitors of estrogen biosynthesis (aromatase inhibitors). Determining the mechanisms by which ER regulate gene expression will aid our understanding of the role of ER in breast cancer progression, response and resistance to endocrine therapies. Upon binding estrogen, ER drives the expression of estrogen responsive genes through the orderly recruitment of co-regulators that act by remodelling and modifying chromatin, ultimately promoting RNA polymerase II recruitment and transcription initiation. Previous work from our laboratory has shown that the APOBEC3B cytosine deaminase acts as an ERα transcriptional coactivator in reporter gene assays. Here, I have developed these initial observations and demonstrate that APOBEC3B is important for the regulation of estrogen responsive genes and breast cancer cell growth. I show that APOBEC3B is recruited to the promoters of estrogen-responsive genes and interacts with ERα. Studies carried out to identify the molecular mechanisms by which APOBEC3B regulates the expression of estrogen-responsive genes included its potential role in DNA demethylation and identified a role for APOBEC3B in DNA strand break formation at the promoter of the estrogen regulated pS2 gene. Together, these studies identify APOBEC3B as an important new coregulator of ERα that is required for the regulation of gene expression by estrogen in breast cancer cells.