2,527 research outputs found
Unmasked: The Author of Narrative of a Voyage to the Spanish Main in the Ship Two Friends
No full textIn 1819 John Miller of Burlington Arcade, Piccadilly, London, published the Narrative of a Voyage to the Spanish Main in the Ship Two Friends for an anonymous author, a young Englishman.1 The author, calling himself the Narrator, recounted his earlier voyage to Madeira Island, the Dutch island of St. Thomas, and Spanish East Florida. The Narrative paints a revealing portrait of northeast Florida during the waning years of the Second Spanish Period. In his introduction to the 1978 republication of the Narrative John W. Griffin posed two candidates, both named John Miller, for authorship; however, he concluded [w]ithal the author ... remains anonymous. 2 The Narrator\u27s anonymity has persisted, but overlooked sources render his identification possible
Motion of Knots in DNA Stretched by Elongational Fields
No full textKnots in DNA occur in biological systems, serve as a model system for polymer entanglement, and affect the efficacy of modern genomics technologies. We study the motion of complex knots in DNA by stretching molecules with a divergent electric field that provides an elongational force. We demonstrate that the motion of knots is nonisotropic and driven towards the closest end of the molecule. We show for the first time experimentally that knots can go from a mobile to a jammed state by varying an applied strain rate, and that this jamming is reversible. We measure the mobility of knots as a function of strain rate, demonstrating the conditions under which knots can be driven towards the ends of the molecule and untied
Dynamic simulations of colloidal dispersions: sticky and polarizable particles as building blocks for novel materials
No full textThe development of new materials is important for societal well being. There has been a great deal of effort recently to integrate experiments, theory, and simulation to accelerate materials discovery, and this broad effort is what motivates this thesis. While there are many different types of materials that are suited for particular applications, one class of materials with a high degree of custamizability is soft materials composed of colloidal particles. These dispersions can be fabricated to respond to a variety of stimuli, including external fields. There have been decades of work using both experiments and theory to investigate the microstructure and material properties of single-component colloidal dispersions. However, composite systems offer an even greater set of possible new materials, especially if the different interactions at play can be controlled and well understood. While there has been more work recently in the area of composite colloidal dispersions and their applications, there has been little focus on the use of processing to achieve different structures. In this thesis, we use Brownian dynamics (BD) simulations to efficiently explore a novel composite colloidal system and two processing schemes that lead to interesting colloidal materials.
Computation can only help to accelerate materials design if simulations include accurate models at modest computational expense. This thesis involves the development of an expression and numerical scheme for calculation of the stress in dispersions of spherical colloidal particles. We show that the quantity we compute differs significantly from that computed using a simpler model, and we also show that the virial stress is incorrect, as one should expect for long-ranged interactions. These results can be used as another tool in the efforts of the simulation community to more accurately investigate polarizable particles via simulations.
The next part of the thesis involves two different simulation studies of a composite colloidal system consisting of polarizable and attractive particles. Control of both attraction strength and applied field strength can be used to dictate particle interactions, and furthermore the role of processing has several different routes. We explore two different promising processing routes, and depending on the processing scheme, different anisotropic gel structures can be formed, and their microstructure further tuned based on the strength of competing interactions. These results highlight the use of simulations to investigate composite colloidal materials formed via specific processing conditions.
Professor Patrick S. Doyle has certified this thesis on behalf of James W. Swan, who passed away in November 2021. I would like to thank Professor Doyle for advising me in 2022-2023 and for certifying this thesis.Ph.D
'Business, Liberalism and dissent in Norwich, 1900-1930'
No full textIn much of the literature on the decline of the Liberal party, there is an implicit
assumption that the bulk of the party's middle-elass support, and in particular its
business support, had defected to the Conservatives by the early 1920s.2 This
literature also assumes that only two real issues separated the middle-elass in the
pre-war period - religion and free trade.3 Thus, when the war brought an end to
free trade and quickened the decline of organized religion in Britain, the middle
class united in a property-owning, anti-socialist alliance under Conservative
leadership.4 This article will challenge some of these assumptions by showing that
significant sections of the Norwich business and dissenting communities continued
to support Liberalism right down to 1930, and that chapel culture, in particular, was
of considerable importance in maintaining the Liberal party after 1919.
Observations upon Lord Orrery's remarks on the life and writings of Dr. Jonathan Swift : containing several singular andecdotes relating to the ... celebrated Stella ... : to which are added two original pieces of the same author (excellent in their kind) never before publish'd
No full text[Patrick Delany]Verfasser gemäss Halket
Knots modify the coil–stretch transition in linear DNA polymers
No full textWe perform single-molecule DNA experiments to investigate the relaxation dynamics of knotted polymers and examine the steady-state behavior of knotted polymers in elongational fields. The occurrence of a knot reduces the relaxation time of a molecule and leads to a shift in the molecule's coil-stretch transition to larger strain rates. We measure chain extension and extension fluctuations as a function of strain rate for unknotted and knotted molecules. The curves for knotted molecules can be collapsed onto the unknotted curves by defining an effective Weissenberg number based on the measured knotted relaxation time in the low extension regime, or a relaxation time based on Rouse/Zimm scaling theories in the high extension regime. Because a knot reduces a molecule's relaxation time, we observe that knot untying near the coil-stretch transition can result in dramatic changes in the molecule's conformation. For example, a knotted molecule at a given strain rate can experience a stretch-coil transition, followed by a coil-stretch transition, after the knot partially or fully unties.National Science Foundation (U.S.) (Grant CBET-1602406
Coil−Stretch Transition of DNA Molecules in Slitlike Confinement
No full textWe experimentally investigate the influence of slitlike confinement on the coil−stretch transition of single DNA molecules in a homogeneous planar elongational electric field. We observe a more gradual coil−stretch transition characterized by two distinct critical strain rates for DNA in confinement, different from the unconfined case where a single critical strain rate exists. We postulate that the change in the coil−stretch transition is due to a modified spring law in confinement. We develop a dumbbell model to extract an effective spring law by following the relaxation of an initially stretched DNA. We then use this spring law and kinetic theory modeling to predict the extension and fluctuations of DNA in planar elongational fields. The model predicts that a two-stage coil−stretch transition emerges in confinement, in accord with experimental observations.Singapore–MIT Alliance for Research and Technology (SMART)National Science Foundation (U.S.) (Grant CBET-0852235)National Institute of Biomedical Imaging and Bioengineering (U.S.) (Award No. T32EB006348
Simulation of electrophoretic stretching of DNA in a microcontraction using an obstacle array for conformational preconditioning
No full textRecently our group has reported experiments using an obstacle array to precondition the conformations of DNA molecules to facilitate their stretch in a microcontraction. Based upon previous successes simulating electrophoretic stretching in microcontractions without obstacles, we use our simulation model to study the deformation of DNA chains in a microcontraction preceded by an array of cylindrical obstacles. We compare our data to the experimental results and find good qualitative, and even quantitative, agreement concerning the behavior of the chains in the array; however, the simulations overpredict the mean stretch of the chains as they leave the contraction. We examine the amount of stretch gained between leaving the array and reaching the end of the contraction and speculate that the differences seen are caused by nonlinear electrokinetic effects that become important in the contraction due to a combination of field gradients and high field strengths.Singapore-MIT AllianceNational Institute of Biomedical Imaging and Bioengineering (U.S.) (Award No. T32EB006348
Thermal processing of thermogelling nanoemulsions as a route to tune material properties
No full textMany soft matter systems have properties which depend on their processing history. It is generally accepted that material properties can be finely tuned by carefully directing self-assembly. However, for gelling colloidal systems, it is difficult to characterize such path-dependent effects since the colloidal attraction is often provided by adding another component to the system such as salts or depletants. Therefore, studies of and an understanding of the role of processing on the material properties of attractive colloidal systems are largely lacking. In this work, we systematically studied how processing greatly influences the properties and the microstructures of model attractive colloidal systems. We perform experiments using a thermogelling nanoemulsion as a model system where the isotropic attraction can be precisely tuned via the temperature. The effects of processing conditions on gel formation and properties is tested by performing well-designed sequential temperature jumps. By properly controlling the thermal history, we demonstrate that properties of colloidal gels can be beyond the limit set by direct quenching, which has been a major focus in literature, and that otherwise slow aging of the system associated with a decrease in elasticity can be prevented. Our results provide new experimental evidence of path-dependent rheology and associated microstructures in attractive colloidal systems and provide guidance to future applications in manufacturing complex colloid-based materials.National Science Foundation (U.S.) (DMR – 1419807)Think Global Education Trust (Taiwan) (scholarship
Measuring industry-science links through inventor-author relations: A profiling method
No full textIn this pilot study we examine the performance of text-based profiling in recovering a set of validated inventor-author links. In a first step we match patents and publications solely based on their similarity in content. Next, we compare inventor and author names on the highest ranked matches for the occurrence of name matches. Finally, we compare these candidate matches with the names listed in a validated set of inventor-author names. Our text-based profile methodology performs significantly better than a random matching of patents and publications, suggesting that text-based profiling is a valuable complementary tool to the name searches used in previous studies.innovation; industry-science links; text-based profiling;
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