2,901 research outputs found
Experimental evidence for the role of paramagnetic oxygen concentration on the decay of long-lived nuclear spin order
No full textNuclear singlet lifetimes are often dependent on the quantity of paramagnetic oxygen species present in solution, although the extent to which quenching or removing molecular oxygen has on extending singlet lifetimes is typically an unknown factor. Here we investigate the behaviour of the singlet relaxation time constant as a function of the oxygen concentration in solution. An experimental demonstration is presented for a chemically inequivalent proton pair of the tripeptide alanine-glycine-glycine in solution. We introduce a simple methodology to ensure the solution is saturated with predetermined concentrations of oxygen gas prior to measurements of the singlet lifetime. Singlet lifetimes were measured by using the spin-lock induced crossing pulse sequence. We present a linear relationship between the amount of oxygen dissolved in solution and the singlet relaxation rate constant. Singlet relaxation was found to be ∼2.7 times less sensitive to relaxation induced by paramagnetic oxygen compared with longitudinal relaxation. The relaxation behaviour is described by using a model of correlated fluctuating fields. We additionally examine the extension of singlet lifetimes by doping solutions with the chelating agent sodium ascorbate, which scavenges oxygen radicals in solution.</p
Homonuclear ADAPT: A general preparation route to long-lived nuclear singlet order
No full textWe introduce a simple strategy to access and readout nuclear singlet order based on the alternate repetition of hard pulses and delays. We demonstrate the general applicability of the method by accessing nuclear singlet order in spin systems characterized by diverse coupling regimes. We show that the method is highly efficient in the strong-coupling and chemical equivalence regimes, and can overcome some limitations of other well-established and more elaborated pulse sequences. A simulation package is provided which allows the determination of pulse sequence parameters.</p
No. 617 Stuart Ruckman
No full textTranscript (12, 40 pages) of two interviews by Matt Driscoll with Stuart Ruckman on April 9, 2010, and July 7, 2011Ruckman (b. 1966) was born in Salt Lake City, Utah. Stuart shares how his family, particularly his father, played a significant role in introducing him to the outdoors. Some of his initial explorations included a hike to the top of Mount Olympus when he was five years old, backpacking trips in the Wasatch and Uinta Mountains, and a successful summit attempt on the Grand Teton when he was twelve. Stuart discovered technical rock climbing due to the influence of his older brother Bret, five years Stuart\u27s senior. Bret learned under Dennis Turville, a well-respected Salt Lake climbing instructor. Stuart shares his observations on the Salt Lake climbing community of the late 1970s and 1980s, noting the intimacy of the community, while also pointing out the significant influence of a handful of climbers, including Merrill Bitter, Les Ellison, and Brian Smoot. He briefly describes the proliferation of new-route development in the Wasatch during his first decade in climbing. In collaboration with his brother Bret, Stuart published comprehensive guidebooks on climbing in the Wasatch Mountains. Stuart\u27s contributions as a first-ascensionist and co-author of Rock Climbing the Wasatch Range attest to his lasting impact on Utah climbing. Interview is part of the Outdoor Recreation History Project. Interviewer: Matt Driscol
Henry J. Kaiser's visit to Purdue
No full textHenry J. Kaiser's visit to Purdue 11-30-1944, Purdue Memorial Union. L to R: Carl F. Boester, Commander Hugh J. Bartley, Col. D.M. Beere, Henry W. Marshall, Henry J. Kaiser, F.C. Hockema, Pres. Elliott, Allison E. Stuart, T.R. Johnston, H.J. Reed, G. Stanley Meikle, Grove Webster. Photograph by J.C. Allen and Son; E.C. Elliott paper
Aplicação dos fractais ao mercado de capitais utilizando-se as Elliott Waves
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.Esta pesquisa apresenta o método Elliott Waves de previsão dos próximos movimentos de preços no mercado financeiro sob o enfoque da teoria do caos e da complexidade, novas áreas da ciência que procuram entender o que a física newtoniana ainda não conseguiu explicar: o comportamento dos sistemas complexos. A possibilidade de conexão entre os mercados de capitais e as teorias do caos e da complexidade foi motivada pela descoberta do comportamento fractal das séries temporais de preços por Benoit Mandelbrot (1997) e pelos registros de repetições quase perfeitas de padrões fractais nos gráficos históricos de ações e mercadorias referentes à bolsa de valores Nova York e à bolsa de mercadorias de Chicago, feitos por Ralph Nelson Elliott e relatados por Robert Prechter (2000) e Glenn Neely (1990). Como alternativa à tradicional Hipótese dos Mercados Eficientes (HME), que está para a Economia assim como a mecânica de Newton está para a Física, a modelagem matemática através dos fractais produz resultados que acompanham as mudanças reais nos preços de uma maneira mais precisa e explicam o comportamento do mercado nos momentos de maior volatilidade. Enquanto os fractais Elliott baseiam-se em dados históricos para se prever acontecimentos futuros, a HME tem como uma de suas premissas a inexistência de memória nos mercados, ou seja, os preços variam aleatoriamente (distribuição de Gauss) e unicamente em função dos novos eventos econômicos, já que os eventos passados já foram totalmente assimilados pelo mercado e descontados nos preços atuais. A HME não corresponde à realidade dos mercados financeiros, o que foi comprovado por esta dissertação
A flow electrochemistry-enabled synthesis of 2-substituted <i>N</i>-(methyl-<i>d</i>)piperidines
No full textA synthesis of N-monodeuteriomethyl-2-substituted piperidines is described. An efficient and readily scalable anodic methoxylation of N-formylpiperidine in an undivided microfluidic electrolysis cell delivers methoxylated piperidine 3, which is a precursor to a N-formyliminium ion and enables C-nucleophiles to be introduced at the 2-position. The isotopically labelled N-deuteriomethyl group is installed using the Eschweiler-Clarke reaction with formic acid-d2 and unlabelled formaldehyde. Monodeuterated N-methyl groups in these molecular systems possess small isotropic proton chemical shift differences important in the investigation of molecules that are able to support long-lived nuclear spin states in solution nuclear magnetic resonance
An Examination of Factors Influencing Small Proton Chemical Shift Differences in Nitrogen-Substituted Monodeuterated Methyl Groups
No full textMonodeuterated methyl groups have previously been demonstrated to provide access to long-lived nuclear spin states. This is possible when the CH2D rotamers have sufficiently different populations and the local environment is chiral, which foments a non-negligible isotropic chemical shift difference between the two CH2D protons. In this article, the focus is on the N-CH2D group of N-CH2D-2-methylpiperidine and other suitable CH2D-piperidine derivatives. We used a combined experimental and computational approach to investigate how rotameric symmetry breaking leads to a 1H CH2D chemical shift difference that can subsequently be tuned by a variety of factors such as temperature, acidity and 2-substituted molecular groups.</jats:p
NMR lineshapes and scalar relaxation of the 17O-labelled water-endofullerene H2O@C60
No full textThe 17O isotopomer of the water-endofullerene H2O@C60 displays a remarkable proton NMR spectrum, with six well resolved peaks. These peaks are due to the J-coupling between the water protons and the 17O nucleus, which has spin-5/2. The resolution of these peaks is enabled by the suppression of water proton exchange by the fullerene cage. The six peaks display an unusual pattern of linewidths, which we model by a Liouville-space treatment of scalar relaxation due to quadrupolar relaxation of the 17O nuclei. The data are consistent with rotational diffusion of the water molecule on the sub-picosecond timescale
Steps toward a psychological calculus for game theory : application of a model of categorization to the repeated prisoner's dilemma
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Economics, 1992.Includes bibliographical references (p. 193-197).by Stuart W. Elliott.Ph.D
Redemption in the work of Francis Stuart
No full textThe idea of redemption is central to an understanding of the work
of Francis Stuart. Through an examination of its development and
expression, it is possible to demonstrate the integrity of his work and
its distinctive qualities. Such a demonstration is necessary because
Stuart's writing has been subjected to comparatively little scholarly
inquiry, although reviews of his work, especially that produced since
1949, suggest that it is impressive and important.
First, a general background to Stuart's work, a discussion of the
special problems associated with reading it, and a summary of his corpus
is provided. This indicates that the idea of redemption is important to
his earliest writing. The state of redemption is shown to be a
necessary apotheosis for Stuart's outcast heroes; it involves spiritual
suffering through which may be found a sense of reintegration and a
higher reality. This is expressed through interrelated themes such as
those of gambler, artist and ordinary man; mystic and criminal; sacred
and profane love; and spirituality and the mundane. The nature of the
redemptive experience is further elaborated by distinctive, complex
motifs, especially the hare, the ark and the woman-Christ. Their
recurrence provides an important element in the unity of Stuart's work.
Because Stuart's idea of the outcast raises important biographical
questions, an examination of the relationship between Stuart's life and
his work is made. Finally, the way in which the idea of redemption
exists in the language structures of Stuart's novels is examined, with
especial reference to his most recent work, The High Consistory. The
thesis shows that the development of the these of redemption
demonstrates the integrity of Stuart's work
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