Index k saddles and dividing surfaces in phase space, with applications to isomerization dynamics

In this paper we continue our studies of the phase space geometry and dynamics associated with index k saddles (k > 1) of the potential energy surface. Using normal form theory, we give an explicit formula for a "dividing surface" in phase space, i.e. a co-dimension one surface (within the energy shell) through which all trajectories that "cross" the region of the index k saddle must pass. With a generic non-resonance assumption, the normal form provides k (approximate) integrals that describe the saddle dynamics in a neighborhood of the index k saddle. These integrals provide a symbolic description of all trajectories that pass through a neighborhood of the saddle. We give a parametrization of the dividing surface which is used as the basis for a numerical method to sample the dividing surface. Our techniques are applied to isomerization dynamics on a potential energy surface having 4 minima; two symmetry related pairs of minima are connected by low energy index one saddles, with the pairs themselves connected via higher energy index one saddles and an index two saddle at the origin. We compute and sample the dividing surface and show that our approach enables us to distinguish between concerted crossing ("hilltop crossing") isomerizing trajectories and those trajectories that are not concerted crossing (potentially sequentially isomerizing trajectories). We then consider the effect of additional "bath modes" on the dynamics, which is a four degree-of-freedom system. For this system we show that the normal form and dividing surface can be realized and sampled and that, using the approximate integrals of motion and our symbolic description of trajectories, we are able to choose initial conditions corresponding to concerted crossing isomerizing trajectories and (potentially) sequentially isomerizing trajectories.Comment: 49 pages, 12 figure

Asymmetric CuH-catalyzed Reductive Coupling of Allenamides with Carbonyl and Imine Electrophiles

The carbon scaffold of many drugs and natural products contain multiple stereogenic centers bearing heteroatoms. As a result of this, chemists have long sought methods to efficiently install these multi-heteroatom functionalities. Reductive coupling reactions have been extensively studied over the past decades, and the allylation of carbonyls via the reductive coupling approach has been a key method for generating chiral allylic alcohols. This work utilizes inexpensive Cu for the asymmetric reductive coupling of allenamides with carbonyls or imines to simultaneously install two heteroatoms (either oxygen and nitrogen or nitrogen and nitrogen, respectively) onto the product. These molecules have a polarity profile that makes them difficult to make using traditional methods. Herein, we report a method for the asymmetric reductive coupling reactions. Chapter 1 describes the development of a regio- and diastereoselective CuH-catalyzed reductive coupling of N-based allenes and imines, where stereoselectivity is controlled by a chiral auxiliary. This protocol provides access to branched products bearing the 1,2-diamine motif. Chemical transformations were performed on one of the branched products to furnish an aminopiperidine derivative that is a valuable intermediate to a major fragment of the potent NK-1 inhibitor compounds CP-99,994 and CP-122,721. Chapter 2 details the development of an asymmetric enantioselective aminoallylation of ketones, which builds on work previously published by our laboratory. This new protocol massively increases the enantiocontrol over this transformation by preventing an on-cycle carbamate migration that eroded enantioselectivity in the previous work and used allenamide protecting groups that were easier to cleave. This protocol provides an atom-economical approach for the synthesis of 1,2-aminoalcohols. Chapter 3 describes ongoing attempts to develop an asymmetric enantioselective aminoallylation of aldimines. This protocol would provide the same branched 1,2-diamine motif, as stated previously, but in a manner that would be more atom economical due to the chirality being provided by the catalyst instead of a chiral auxiliary

Playwriting and postcolonialism : identifying the key factors in the development and diminution of playwriting in Ghana 1916-2007

The focus of this thesis is playwriting in Ghana from the colonial era to the in 2007 and the Ghana@50 celebrations which marked fifty years of independence from Britain. Through the analysis of key playtexts produced in this period, which I use as a collective document of Ghana’s cultural history, I seek to uncover the major factors that contributed to the flourishing of playwriting directly post independence and its recent dramatic diminution. Over this time period only a few dozen Ghanaian plays were published and of those only a handful have become known to an international audience. However, collectively they document an intricate relationship between politics and culture within a colonial and then postcolonial society. The story that is revealed by the analysis of that relationship unveils a fascinating trajectory in the development of playwriting in Ghana, and highlights a complex, often over-lapping, interplay between theatre and politics. For this research I have drawn significantly on original interviews with artists and academics. The importance of Ghana as a choice of study lies both in analysing why the current situation exists and how, through that analysis, Ghana’s postcolonial experience speaks to, and questions, dominant trends in postcolonial theory. Through an analysis of the work of colonial and postcolonial playwrights I interrogate the claim of the politician and playwright Mohammed ben-Abdallah that his plays fit within Fanon’s ‘third phase’ of postcolonial artistic expression, and suggest that Ghana’s actual position in terms of postcolonial theory (and the effect of the postcolonial experience on playwrights) is far more nuanced. The findings of this research point towards the historic success of playwriting in Ghana being contingent upon the political promotion of a unitary sense of national identity, a situation that occurred both directly post independence and in the 1980s after a series of military coups. Playwrights’ synchronicity with politics during these periods (compounded by the establishment of institutions and the publishing of play texts as icons of Ghanaian culture) enabled political agendas to shape and influence the creative and performative codes of Ghanaian theatre. This led to the promotion of a strict model of legitimating criteria that simultaneously delegitimised alternative or pluralist voices. I argue that this process problematised playwriting and ultimately contributed to a situation where Ghana boasts strong theatrical institutions, but very few new published plays

Abstinence Only vs. Comprehensive Sex Education: What are the Arguments? What is the Evidence?

Responding to the continuing health threats of HIV, STIs and unplanned pregnancy among young people, the widely respected Institute of Medicine of the National Academy of Sciences recently recommended eliminating congressional, federal, state and local "requirements that public funds be used for abstinence-only education." And surveys consistently show that the public wants schools to deliver strong abstinence messages alongside information about self-protection for young people who find themselves in sexual situations. The vast majority of parents support sex education in the schools, including the provision of information about contraceptive and condom use.Unfortunately, federal policy is grossly out of step with the wishes of most parents and students, as well as the scientific research. Since the early 1980s, Congress has devoted significant resources to abstinence-only programming. Partly as a result of federal policy and funding changes, public schools are increasingly supporting abstinence-only curricula that are less likely to include information about birth control, STD prevention and sexual orientation. The evidence tells us that these trends represent a dangerous disservice to America's younger generation

The Currency of Art: a collaboration between the Baring Archive and the Graduate School of CCW.

This publication arises from a collaborative project undertaken by The Baring Archive and the Graduate School of CCW (Camberwell College of Arts, Chelsea College of Art and Design and Wimbledon College of Art, three of the constituent colleges of University of the Arts London). In 1995, ING acquired the business of Barings plc, after Barings became insolvent as a result of unauthorized trading. Along with the acquisition of the company came a collection of archival material relating to the long history of Barings, whose origins stretch back to 1717 when John Baring of Bremen settled in Exeter and set up business as a merchant and manufacturer. In 1762, his three sons established the London merchant house of John & Francis Baring & Co., later known as Baring Brothers and, by the nineteenth century, the firm had expanded to become a leading financier for overseas governments and businesses. Documentation and objects relating to the illustrious history of the bank were augmented by portraits – eighteenth and nineteenth century paintings of the Baring family by leading practitioners of the period, such as Thomas Lawrence, Benjamin West, John Linnell, Ambrose McEvoy and William Orpen. From the 1970s onwards, a distinguished collection of water-colours was added to the historical archive, containing works by artists such as Paul Sandby, Francis Towne and David Cox, and Barings, with great discernment, had also accrued an impressive group of modern British artworks to hang on its office walls.Prunella Clough, L.S. Lowry, Paul Nash, Matthew Smith, Stanley Spencer, Keith Vaughan and Carel Weight are just a few of the artists represented. The Currency of Art is one outcome of a collaboration initiated with ING seven years ago. Staff and students from Wimbledon College of Art, and pupils from three of its neighbouring secondary schools, were invited to create new works in response to the painting collection which now hangs in ING’s offices at 60 London Wall. The staff, students and schoolchildren – diverse communities in themselves – brought fresh perspectives, distinct from those of financial historians or more traditional academics, to the collection. Residencies, symposia and workshops generated responses to the paintings, culminating in two exhibitions hosted by ING, re:MAKING and re:INVENTING, whereby the newly created works were hung alongside the originals that had inspired them. This represented an unusual opportunity, given the problems associated with conservation and stewardship that often inhibit such a combination

De Camptown Races

[Verse 1]De camptown ladies sing dis songDoo-dah! Doo-dah!De camptown racetrack five miles longOh! Doo-dah day.I come down here wid my hat caved inDoo-dah! Doo-dah!I go back home wid ma pocket full of tinOh! Doo-dah day. [Chorus]Gwine to run all night, gwine to run all dayI bet my money on a bobtail nag, somebody bet on de bay. [Verse 2]De longtail filly an’ de big black hossDoo-dah! Doo-dah!Dey fly de track an’ dey both cut acrossOh! Doo-dah day.De blind hoss stuck in a big mud holeDoo-dah! Doo-dah!Can’t touch bottom wid a ten foot poleOh! Doo-dah day. [Chorus] [Verse 3]Old mully cow come on to de trackDoo-dah! Doo-dah!De bobtail flung her o’er his backOh! Doo-dah day.Den fly along like a railroad carDoo-dah! Doo-dah!Running a race wid a shooting starOh! Doo-dah day. [Chorus

Neural Attractors and Phonological Grammar

This volume collects three articles which constitute the bulk of my PhD research. The overarching theme of the volume is the role of attractors - a concept from dynamical systems theory – in the neural realization of phonological grammar. The motivation for this line of inquiry begins with the claim that the study of language should provide some insight into the workings of the human mind/brain. Indeed this is one of few mantras shared by linguists of the seemingly irreconcilable “Generative” and “Cognitive” schools (e.g. Chomsky 2002; Lakoff 1988). Given this apparent consensus then, it is perhaps surprising that no breakthrough in our understanding of the brain can yet be attributed to some insight from the study of language. An analysis and critique of this state of affairs is given by Poeppel & Embick (2005), who identify (amongst other things) that we currently have no way of relating the ontologies of linguistics and neuroscience. This Ontological Incommensurability Problem (OIP) can be resolved, they argue, by the use of a Linking Hypothesis, which spells out linguistic computations at the relevant level of algorithmic abstraction, such that the neuroscientist need only find the exact implementations of those algorithms in the brain. If such a hypothesis were sufficiently complete then it could, in principle, predict the kinds of neural configurations required for natural language processing, using linguistic theories as their starting point. In this way, we could finally realize the long sought-after goal of cashing in theories of language for understanding of the human brain. Simultaneously, a Linking Hypothesis also has the potential to unearth lower-level explanations for linguistic phenomena, for example where those explanations might depend on purely neurobiological notions (e.g. neuronal morphology, synaptic density, metabolic efficiency, etc.)