1H-N.M.R. and Theoretical Studies of the Conformation of the Antibiotic Lincomycin

1990 ◽  
Vol 43 (3) ◽  
pp. 535 ◽  
Author(s):  
GP Moloney ◽  
DJ Craik ◽  
MN Iskander ◽  
SLA Munro
Keyword(s):  
Chemical Shift ◽  
Potential Energy ◽  
Resolution Enhancement ◽  
Side Chain ◽  
Theoretical Studies ◽  
Two Dimensional ◽  
Coupling Constant ◽  
Theoretical Conformational Analysis ◽  
One Dimensional ◽  
Sugar Moiety

One- and two-dimensional 1H n.m.r. spectra of the amino glycoside antibiotic lincomycin have been measured and analysed. One-dimensional n.m.r. techniques applied included selective decoupling, resolution enhancement, and n.O.e. difference experiments. Two-dimensional n.m.r. techniques included chemical shift correlated spectroscopy (COSY) and n.O.e. spectroscopy (NOESY) experiments. A theoretical conformational analysis of the side chain of the sugar moiety has also been done by using a simplified potential energy program. Together, the theoretical and experimental (coupling constant and n.O.e.) data have allowed the conformation of lincomycin to be determined.

A two-dimensional technique for chemical-shift resolution in one-dimensional NMR images

1991 ◽  
Vol 93 (1) ◽  
pp. 181-183
Author(s):  
Douglas C McCain ◽  
William M Westler ◽  
John L Markley
Keyword(s):  
Chemical Shift ◽  
Two Dimensional ◽  
One Dimensional

Nonreciprocal Wave Transmission in Metastable Modular Metastructures Utilizing Asymmetric Dual-Threshold Snap-Through

2019 ◽  
Author(s):  
Xiang Liu ◽  
Guoping Cai ◽  
K. W. Wang
Keyword(s):  
Potential Energy ◽  
Excitation Frequency ◽  
Excitation Amplitude ◽  
Wave Transmission ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
One Dimensional ◽  
Threshold Phenomenon ◽  
Energy Equilibrium ◽  
Nonreciprocal Transmission

Abstract In this research, the nonreciprocal wave transmission features in one-dimensional and two-dimensional metastable modular metastructures are studied. Unlike previous work, in which the nonreciprocal transmission in metastable metastructures is realized by utilizing the supratransmission phenomenon when the excitation frequency is inside the linearized bandgap, a new approach is explored to achieve nonreciprocal wave transmission exploiting metastability and asymmetric dual-threshold snap-through. It is found that because of the asymmetry of potential energy wells of the equilibria, there will be two excitation amplitude thresholds for a metastable component when it is initially at the high-potential-energy equilibrium with excitation frequency within the passband. When the excitation amplitude increases and exceeds the first threshold, the metastable component will snap to the low-potential-energy equilibrium and maintain intrawell motion around this stable point, which will cause a significant decrease of the wave transmission. And when the excitation amplitude exceeds the second threshold, the metastable component will start to perform interwell motion, and now the wave transmission will increase suddenly. By using this “dual-threshold” phenomenon, nonreciprocal wave transmission in a one-dimensional structure is realized by connecting a metastable chain with a linear periodic part. Because of the wave attenuation effect of the linear part of the system, the excitation amplitude thresholds on different sides of the one-dimensional structure will be discrepant. Therefore, nonreciprocal wave transmission can be developed when the excitation amplitude is within certain ranges. It is interesting to note that the direction of nonreciprocal wave transmission can be changed by setting the excitation amplitude to different values. By changing the configuration of the metastable chain, the operation frequency and excitation amplitude ranges of the nonreciprocal transmission can be tuned. For a two-dimensional metastable metastructure, nonreciprocal wave transmission can be realized by adjusting the parameters of some metastable modules in the metastructure in the manner that the potential energy and energy thresholds of the adjusted modules and the unadjusted modules are different, but the passbands of the adjusted modules and the unadjusted modules will overlap in some frequency regions. Numerical studies provide clear insight of the proposed nonreciprocal wave transmission approach.

scholarly journals Cross-Peaks in Simple 2D NMR Experiments from Chemical Exchange of Transverse Magnetization

2019 ◽  
Author(s):  
Chris Waudby ◽  
Tom Frenkiel ◽  
John Christodoulou
Keyword(s):  
Chemical Shift ◽  
Chemical Exchange ◽  
Exchange Process ◽  
2D Nmr ◽  
Two Dimensional ◽  
One Dimensional ◽  
Exchange Processes ◽  
Rich Information ◽  
Multiple Chemical

Two-dimensional correlation measurements such as COSY, NOESY, HMQC and HSQC experiments are central to small molecule and biomolecular NMR spectroscopy, and commonly form the basis of more complex experiments designed to study chemical exchange occurring during additional mixing periods. However, exchange occurring during chemical shift evolution periods can also influence the appearance of such spectra. While this is often exploited through one-dimensional lineshape analysis ('dynamic NMR'), the analysis of exchange across multiple chemical shift evolution periods has received less attention. Here we report that chemical exchange-induced cross-peaks can arise in even the simplest two-dimensional NMR experiments. These cross-peaks can have highly distorted phases that contain rich information about the underlying exchange process. The quantitative analysis of such peaks, from a single 2D spectrum, can provide a highly accurate characterization of underlying exchange processes.

PHYSICAL PROCESSES IN THE SPREAD OF OIL ON A WATER SURFACE

1971 ◽  
Vol 1971 (1) ◽  
pp. 463-467 ◽  
Author(s):  
James A. Fay
Keyword(s):  
Water Surface ◽  
Theoretical Studies ◽  
Field Observations ◽  
Two Dimensional ◽  
Physical Processes ◽  
One Dimensional ◽  
Rate Of Spread ◽  
Spreading Rates

ABSTRACT Formulae are recommended for calculating the extent of the spread of oil slicks on water as a function of time. They are based on empirical measurements of spreading rates and analytical and theoretical studies of the physical processes which accelerate or retard the spread of a film Both one-dimensional and two-dimensional (axisymmetric) slicks are treated. Comparisons of the recommended formulae are made with the limited number of field observations, both for the rate of spread and the maximum slick size.

scholarly journals Cross-Peaks in Simple 2D NMR Experiments from Chemical Exchange of Transverse Magnetization

2019 ◽  
Author(s):  
Chris Waudby ◽  
Tom Frenkiel ◽  
John Christodoulou
Keyword(s):  
Chemical Shift ◽  
Chemical Exchange ◽  
Exchange Process ◽  
2D Nmr ◽  
Two Dimensional ◽  
One Dimensional ◽  
Exchange Processes ◽  
Rich Information ◽  
Multiple Chemical

Two-dimensional correlation measurements such as COSY, NOESY, HMQC and HSQC experiments are central to small molecule and biomolecular NMR spectroscopy, and commonly form the basis of more complex experiments designed to study chemical exchange occurring during additional mixing periods. However, exchange occurring during chemical shift evolution periods can also influence the appearance of such spectra. While this is often exploited through one-dimensional lineshape analysis ('dynamic NMR'), the analysis of exchange across multiple chemical shift evolution periods has received less attention. Here we report that chemical exchange-induced cross-peaks can arise in even the simplest two-dimensional NMR experiments. These cross-peaks can have highly distorted phases that contain rich information about the underlying exchange process. The quantitative analysis of such peaks, from a single 2D spectrum, can provide a highly accurate characterization of underlying exchange processes.

scholarly journals A unidimensionalização da linguagem e a fragilização teórica do campo investigativo educacional: desafios para a pesquisa em educação 

2021 ◽  
Vol 34 (71) ◽  
pp. 965-987
Author(s):  
Vivian Baroni
Keyword(s):  
Educational Research ◽  
Theoretical Studies ◽  
Two Dimensional ◽  
One Dimensional ◽  
Present Essay ◽  
Palabras Clave ◽  
Research In Education

Resumo: Tendo por base o conceito marcuseano de linguagem unidimensional, o presente ensaio pretende problematizar esse tema com relação às suas implicações no campo da pesquisa educacional. A não utilização do conceito e do excesso de significado que a linguagem bidimensional traz em si, resulta na fragilidade teórica fortemente sentida no campo da pesquisa educacional, que resulta, em última instância, na dificuldade de validação do seu conhecimento. Nesse sentido, defendemos a importância da retomada dos estudos de caráter teórico, assim como do trabalho adequado do conceito e dos universais, como instrumentos conceituais imprescindíveis na pesquisa que deseja considerar toda a complexidade do campo da educação. Palavras chave: linguagem unidimensional; pesquisa educacional; teoria; empiria; formação. The unidimensionalization of language and the theoretical fragilization of the educational investigative field: challenges for research in education  Abstract: Based on the Marcusean concept of unidimensional language, the present essay intends to problematize this theme in relation to its implications in the field of educational research. The non-use of the concept and the excess of meaning that the two-dimensional language brings in itself results in the theoretical fragility strongly felt in the field of educational research, which results, in the last instance, the difficulty of validating its knowledge. In this sense, we defend the importance of resuming theoretical studies, as well as the adequate work of the concept and the universals, as essential conceptual instruments in the research that wishes to consider all the complexity of the field of education.  Keywords: one-dimensional language; educational research; theory; empiria; formation. Unidimensionalización del lenguaje y fragilización teórica del campo de investigación educativa: desafíos para la investigación educativa  Resumen: Basado en el concepto marcusiano de lenguaje unidimensional, el presente ensayo pretende problematizar este tema en relación con sus implicaciones en el campo de la investigación educativa. La falta de uso del concepto y el exceso de significado que el lenguaje bidimensional trae consigo resulta en la debilidad teórica que se siente fuertemente en el campo de la investigación educativa, lo que en última instancia resulta la dificultad de validar su conocimiento. En este sentido, defendemos la importancia de la reanudación de los estudios teóricos, así como el trabajo adecuado del concepto y los universales, como instrumentos conceptuales indispensables en la investigación que desea considerar toda la complejidad del campo de la educación.  Palabras clave: lenguaje unidimensional; investigación educativa; teoría empirismo formación. Apoio/Financiamento: PROSUC/CAPES Data de registro: 31/07/2019 Data de aceite: 30/10/2019

A one-dimensional self-gravitating stellar gas

1966 ◽  
Vol 25 ◽  
pp. 46-48 ◽  
Author(s):  
M. Lecar
Keyword(s):  
Gravitational Field ◽  
Phase Space ◽  
Motion Picture ◽  
Space Distribution ◽  
Two Dimensional ◽  
One Dimensional ◽  
Phase Space Distribution ◽  
Dimensional Phase Space ◽  
The Mean

“Dynamical mixing”, i.e. relaxation of a stellar phase space distribution through interaction with the mean gravitational field, is numerically investigated for a one-dimensional self-gravitating stellar gas. Qualitative results are presented in the form of a motion picture of the flow of phase points (representing homogeneous slabs of stars) in two-dimensional phase space.

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