Marcel\u27s Bedroom

Senior Project submitted to The Division of Arts of Bard College

W.G. Sebald: On a Cliff\u27s Edge

Senior Project submitted to The Division of Languages and Literature of Bard College

The computation and measurement of residual stresses in laser deposited layers

Laser metal forming is an attractive process for rapid prototyping or the rebuilding of worn parts. However, large tensile stress may arise in layers deposited by laser melting of powder. A potential solution is to preheat the substrate before and during deposition of layers to introduce sufficient contraction during cooling in the substrate to modify the residual stress distribution in the deposited layers. To demonstrate the value of this approach, specimens were prepared by depositing stellite F on a stainless steel substrate with and without preheating. Residual stresses were computed by numerical simulation and measured using the crack compliance method. For non-preheated specimens simulation and experiment agreed well and showed that extremely high residual tensile stresses were present in the laser melted material. By contrast, pre-heated specimens show high compressive stresses in the clad material. However, in this case the numerical simulation and experimental measurement showed very different stress distribution. This is attributed to out of plane deformation due to the high compressive stresses which are not permitted in the numerical simulation. A ‘‘strength of materials’’ analysis of the effect of out of plane deformation was used to correct the simulation, Agreement with experimental results was then satisfactory

Enhancing accuracy and precision of transparent synthetic soil modelling

Over recent years non-intrusive modelling techniques have been developed to investigate soil-structure interaction problems of increasingly complex geometry. This paper concerns the development of a small-scale, 1 g, modelling technique using a transparent analogue for soil with particle image velocimetry for internal displacement measurement. Larger model geometry achieved in this research using fine-grained transparent synthetic soils has led to an increased need for rigorous photogrammetric correction techniques. A correction framework, based upon a modified version of the pinhole camera model, is presented that corrects for lens and camera movement induced errors as well as scaling from image space to object space. An additional statistical approach is also developed to enhance the system precision, by minimising the impact of increased non-coplanarity between the photogrammetry control plane and the target plane. The enhanced data correction and statistical precision is demonstrated using a case study examining the failure mechanism around a double helical screw pile installed in transparent synthetic soil representative of a soft clay

Optimized polydopamine coating and DNA conjugation onto gold nanorods for single nanoparticle bioaffinity measurements

Gold nanorods (NRs) have attracted a great deal of interest for a variety of biomedical and sensing applications. However, developing robust methods for biofunctionalizing NRs has continued to be challenging, especially for NR–DNA conjugates. This is due to the presence of cetyltrimethylammonium bromide (CTAB), which plays an essential role in controlling the anisotropic particle growth. In this article, we systematically explore the growth of a polydopamine (PDA) layer on a range of NR surfaces, comparing different polyelectrolyte and alkanethiol coatings as well as direct CTAB displacement. This revealed that the PDA layer thickness and growth rate is strongly dependent on the underlying nanorod functionalization chemistry and allowed us to establish a preferred route for the creation of stable, non-aggregated suspensions of PDA-coated NRs. The utility of this platform was then demonstrated by self-assembling packed monolayers of single-stranded DNA on the outer surface. Both the surface attachment and bioactivity of the resulting NR–DNA conjugates was then demonstrated by performing bulk solution and single nanoparticle imaging fluorescence measurements

Clostridium perfringens epsilon toxin mutant Y30A-Y196A as a recombinant vaccine candidate against enterotoxemia

Epsilon toxin (Etx) is a β-pore-forming toxin produced by Clostridium perfringens toxinotypes B and D and plays a key role in the pathogenesis of enterotoxemia, a severe, often fatal disease of ruminants that causes significant economic losses to the farming industry worldwide. This study aimed to determine the potential of a site-directed mutant of Etx (Y30A-Y196A) to be exploited as a recombinant vaccine against enterotoxemia. Replacement of Y30 and Y196 with alanine generated a stable variant of Etx with significantly reduced cell binding and cytotoxic activities in MDCK.2 cells relative to wild type toxin (>430-fold increase in CT50) and Y30A-Y196A was inactive in mice after intraperitoneal administration of trypsin activated toxin at 1000× the expected LD50 dose of trypsin activated wild type toxin. Moreover, polyclonal antibody raised in rabbits against Y30A-Y196A provided protection against wild type toxin in an in vitro neutralisation assay. These data suggest that Y30A-Y196A mutant could form the basis of an improved recombinant vaccine against enterotoxemia