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Littérature scientifique sur le sujet « Nuclear magnetic resonance. Chemistry, Physical and theoretical »

Auteur : Grafiati
Publié le 4 juin 2021
Mis à jour le 11 février 2022

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Articles de revues sur le sujet "Nuclear magnetic resonance. Chemistry, Physical and theoretical"

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V.S.D. « Studies in Physical and Theoretical Chemistry, Vol 72, Nuclear Magnetic Resonance : principles and theory »,. Journal of Molecular Structure 245, no 3-4 (mai 1991) : 403–4. http://dx.doi.org/10.1016/0022-2860(91)87115-x.

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Pfeifer, Harry. « Principles of Nuclear Magnetic Resonance Microscopy ». Zeitschrift für Physikalische Chemie 176, Part_1 (janvier 1992) : 132. http://dx.doi.org/10.1524/zpch.1992.176.part_1.132.

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A. Jones, Jonathan. « Quantum computing and nuclear magnetic resonance ». PhysChemComm 4, no 11 (2001) : 49. http://dx.doi.org/10.1039/b103231n.

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Yamasaki, Akira. « Cobalt-59 Nuclear Magnetic Resonance Spectroscopy in Coordination Chemistry ». Journal of Coordination Chemistry 24, no 3 (octobre 1991) : 211–60. http://dx.doi.org/10.1080/00958979109407886.

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Khitrin, Anatoly K., Vladimir L. Ermakov et B. M. Fung. « Nuclear magnetic resonance molecular photography ». Journal of Chemical Physics 117, no 15 (15 octobre 2002) : 6903–6. http://dx.doi.org/10.1063/1.1513310.

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Wu, Chin H., et Stanley J. Opella. « Shiftless nuclear magnetic resonance spectroscopy ». Journal of Chemical Physics 128, no 5 (7 février 2008) : 052312. http://dx.doi.org/10.1063/1.2816786.

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Warren, William W. « Nuclear Magnetic Resonance in Expanded Fluid Metals ». Zeitschrift für Physikalische Chemie 217, no 7 (1 juillet 2003) : 775–82. http://dx.doi.org/10.1524/zpch.217.7.775.20389.

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AbstractAdaptation of the internally-heated autoclave technique to nuclear magnetic resonance (NMR) has permitted NMR measurements of electronically-conducting fluids at high temperatures and pressures. The history of NMR experiments on mercury, selenium, and cesium is reviewed briefly with reference to subsequent relevant research on these materials.
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Bilalbegović, G. « Nuclear Magnetic Resonance Parameters of Water Hexamers ». Journal of Physical Chemistry A 114, no 2 (21 janvier 2010) : 715–20. http://dx.doi.org/10.1021/jp9075614.

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Pennanen, Teemu S., Perttu Lantto, Mikko Hakala et Juha Vaara. « Nuclear magnetic resonance parameters in water dimer ». Theoretical Chemistry Accounts 129, no 3-5 (15 août 2010) : 313–24. http://dx.doi.org/10.1007/s00214-010-0782-y.

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Lee, Y. K. « Spin-1 nuclear quadrupole resonance theory with comparisons to nuclear magnetic resonance ». Concepts in Magnetic Resonance 14, no 3 (2002) : 155–71. http://dx.doi.org/10.1002/cmr.10023.

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Thèses sur le sujet "Nuclear magnetic resonance. Chemistry, Physical and theoretical"

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Jones, Jonathan A. « Nuclear magnetic resonance data processing methods ». Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:7df97c9a-4e65-4c10-83eb-dfaccfdccefe.

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This thesis describes the application of a wide variety of data processing methods, in particular the Maximum Entropy Method (MEM), to data from Nuclear Magnetic Resonance (NMR) experiments. Chapter 1 provides a brief introduction to NMR and to data processing, which is developed in chapter 2. NMR is described in terms of the classical model due to Bloch, and the principles of conventional (Fourier transform) data processing developed. This is followed by a description of less conventional techniques. The MEM is derived on several grounds, and related to both Bayesian reasoning and Shannon information theory. Chapter 3 describes several methods of evaluating the quality of NMR spectra obtained by a variety of data processing techniques; the simple criterion of spectral appearance is shown to be completely unsatisfactory. A Monte Carlo method is described which allows several different techniques to be compared, and the relative advantages of Fourier transformation and the MEM are assessed. Chapter 4 describes in vivo NMR, particularly the application of the MEM to data from Phase Modulated Rotating Frame Imaging (PMRFI) experiments. In this case the conventional data processing is highly unsatisfactory, and MEM processing results in much clearer spectra. Chapter 5 describes the application of a range of techniques to the estimation and removal of splittings from NMR spectra. The various techniques are discussed using simple examples, and then applied to data from the amino acid iso-leucine. The thesis ends with five appendices which contain historical and philosophical notes, detailed calculations pertaining to PMRFI spectra, and a listing of the MEM computer program.
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Holmes, William Matthew. « An investigation of fluid transport in porous solids using nuclear magnetic resonance ». Thesis, University of Nottingham, 2001. http://eprints.nottingham.ac.uk/43467/.

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A commercially available NMR spectrometer has been used to investigate fluid transport within porous solids. Two water-wet porous solids were investigated. The first was a sample of Fontainebleau sandstone, and the second was an idealised porous solid made from a random packing of glass beads. The samples were saturated with two immiscible phases, i.e. an oil and water phase. Pulsed field gradient (PFG) NMR measurements of one- and two-dimensional displacement probability distributions are reported, for steady-state flow and diffusion, within two phase saturated porous solids. Measurements were made with the porous solids prepare in different steady-state saturations. NMR relaxation measurements are also reported. Using the NMR data it was possible to evaluate the physical importance of parameters such as wettability and phase saturation on transport phenomena in two phase saturated porous solids. Various computer simulations were developed to model the experimental data.
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Oprea, Corneliu I. « Density Functional Response Theory with Applications to Electron and Nuclear Magnetic Resonance ». Doctoral thesis, Stockholm, : Bioteknologi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4367.

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Edwards, Luke J. « Highly efficient quantum spin dynamics simulation algorithms ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:3eec480e-5a3a-4197-a786-e6d42988d4a5.

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Spin dynamics simulations are used to gain insight into important magnetic resonance experiments in the fields of chemistry, biochemistry, and physics. Presented in this thesis are investigations into how to accelerate these simulations by making them more efficient. Chapter 1 gives a brief introduction to the methods of spin dynamics simulation used in the rest of the thesis. The `exponential scaling problem' that formally limits the size of spin system that can be simulated is described. Chapter 2 provides a summary of methods that have been developed to overcome the exponential scaling problem in liquid state magnetic resonance. The possibility of utilizing the multiple processors prevalent in modern computers to accelerate spin dynamics simulations provides the impetus for the investigation found in Chapter 3. A number of different methods of parallelization leading to acceleration of spin dynamics simulations are derived and discussed. It is often the case that the parameters defining a spin system are time-dependent. This complicates the simulation of the spin dynamics of the system. Chapter 4 presents a method of simplifying such simulations by mapping the spin dynamics into a larger state space. This method is applied to simulations incorporating mechanical spinning of the sample with powder averaging. In Chapter 5, implementations of several magnetic resonance experiments are detailed. In so doing, use of techniques developed in Chapters 2 and 3 are exemplified. Further, specific details of these experiments are utilized to increase the efficiency of their simulation.
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Green, Timothy Frederick Goldie. « Prediction of NMR J-coupling in condensed matter ». Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:39ee4a7c-58f9-49fa-b14c-16bc03141e53.

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Nuclear magnetic resonance (NMR) is a popular spectroscopic method and has widespread use in many fields. Recent developments in solid-state NMR have increased interest in experiment and, alongside simultaneous developments in computational theory, have led to the field dubbed 'NMR crystallography.' This is a suite of methodologies, complementing the capabilities of other crystallographic methods in the determination of atomic structure, especially when large crystals cannot be made and when exploring materials with phenomena such as compositional, positional and dynamic disorder. NMR J-coupling is the indirect coupling between nuclear spins, which, when measured, can reveal a wealth of information about structure and bonding. This thesis develops and applies the method of Joyce for the prediction of NMR J-coupling in condensed matter systems using plane-wave pseudopotential density-functional theory, an important requirement for efficient treatment of finite and infinite periodic systems. It describes the first-ever method for the use of ultrasoft pseudopotentials and inclusion of special relativistic effects in J-coupling prediction, allowing for the treatment of a wider range of materials systems and overall greater user friendliness, thus making the method more accessible and attractive to the wider scientific community.
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Lynch, Charlotte Isabella. « First-principles calculations of NMR parameters for materials applications ». Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:f44b9122-1826-410e-990d-a88dc3bb1432.

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Nuclear magnetic resonance (NMR) is a powerful experimental technique for probing the local environment of nuclei in materials. However, it can be difficult to separate the large number of interactions that are recorded in the resulting spectra. First-principles calculations based on quantum mechanics therefore provide much-needed support for interpreting experimental spectra. In this way, the underlying mechanisms recorded in experimental spectra can be investigated on an atomic level, and trends can be noted with which to guide the direction of future experiments. This thesis presents two cases in which first-principles calculations do just that. The first is an investigation of the perovskite structures of NaNbO3, KNbO3, LiNbO3 and the related solid solutions of NaxK1-xNbO3, KxNa1-xNbO3 and LixNa1-xNbO3 in order to study how structural disorder affects their NMR parameters. The second investigation involves the calculation of the Knight shift in platinum, palladium and rhodium---in their elemental bulk forms and in a set of surface structures. The Knight shift is a systematic shift in the NMR frequencies of metallic systems. It arises from the hyperfine interaction between the nuclear spins and the spins of the unpaired conduction electrons. When calculating the Knight shift, it is found that the Brillouin zone must be very finely sampled. A discussion of core polarisation is also presented. This is the polarisation of core electrons as a result of their interaction with valence electrons. In the case of Curie paramagnets, core polarisation can have a significant effect on the calculation of hyperfine parameters.
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Broadhurst, R. William. « Flash photolysis nuclear magnetic resonance ». Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257654.

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Raven, C. I. « Nuclear magnetic resonance studies of surfactant systems ». Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235350.

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Loffredo, William Michael. « Synthesis and physical studies of thiophospholipids using nuclear magnetic resonance / ». The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487596807823338.

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Tse, Tak Yan. « Deuteron nuclear magnetic resonance studies of molecular motion in solids ». W&M ScholarWorks, 1994. https://scholarworks.wm.edu/etd/1539623862.

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$\sp2$H-NMR is a powerful spectroscopic technique for investigating dynamics in solids. to extend the range of motional rates that can be quantitatively investigated, a new approach for measuring the quadrupolar spin-lattice relaxation time $T\sb{1Q}$ was developed. This uses a Broadband Jeener-Broekaert (BBJB) sequence with echo-detection, which avoids the frequency-discriminated excitation profile and spectral baseline distortion intrinsic to the conventional Jeener-Broekaert (JB) experiment. By combining the BBJB experiment with an Inversion-Recovery sequence with Quadrupole-Echo detection (IRQE), two independent longitudinal relaxation times, $T\sb{1Q}$ and $T\sb{1Z}$, can be measured. Spectral densities of motion $J\sb1(\omega\sb{o}$) and $J\sb2(2\omega\sb{o}$) are extracted from these relaxation times. The new approach was demonstrated on a nematic liquid crystal binary mixture of 4-methyl-4$\sp\prime$-cyanobiphenyl-d$\sb{11}$ (1CB) and 4-n-pentyl-4$\sp\prime$-cyanobiphenyl-d$\sb6$ (5CB). Measurements on mixtures containing 10 and 25 mol% 1CB revealed that rotational motion can be described by the third rate model and the correlation times and activation energies of 1CB and 5CB are concentration independent. In hexamethylbenzene, it was demonstrated that the orientation dependence of spectral densities provides geometric and kinetic information. This technique works well for motions which are in the fast regime ($k\ge10\sp7 s\sp{-1}$) and contribute to relaxation. at ambient temperature, the experimental data were fit by a simulation which included simultaneous threefold and sixfold rotations, with geometric distortions of the electric field gradient tensors of the methyl group. The best-fit jump rates for threefold methyl rotation was $k\sb3 = 5.0\times10\sp{11} s\sp{-1}$ and sixfold aromatic rotation was $k\sb6 = 3.85\times10\sp8 s\sp{-1}$, with out-of-plane and in-plane distortions of 2.5$\sp\circ$ and 1.2$\sp\circ$ respectively. Relaxation times of the bisphenol-A polycarbonate (BPA-PC) and its monomer (BPA) were measured between 250K to 400K. The data were fit to several dynamic models. Simple threefold methyl rotation accounts for the spectral density anisotropies of BPA but not those of the polymer BPA-PC. Inclusion of a semilogarithmic distribution of jump rates, $k\sb3$, improved the agreement qualitatively but not quantitatively. Modulation of threefold methyl jumps by libration of the $C\sb{3V}$ axis was treated with the Stochastic Liouville formalism. Best agreement is found if the two motions are correlated. Activation energies for methyl group rotation are 19.2 $\pm$ 2.0 kJ/mol and 13.0 $\pm$ 0.8 kJ/mol in monomer and polymer respectively.
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Livres sur le sujet "Nuclear magnetic resonance. Chemistry, Physical and theoretical"

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Vashman, Andreĭ Aleksandrovich. I͡A︡dernai͡a︡ magnitnai͡a︡ relaksat͡s︡ionnai͡a︡ spektroskopii͡a︡. Moskva : Ėnergoatomizdat, 1986.

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Kazanʹ, Russia) Vserossiĭskiĭ seminar Novye dostizhenii︠a︡ I︠A︡MR v. strukturnykh issledovanii︠a︡kh (2nd 1995. II Vserossiĭskiĭ seminar Novye dostizhenii︠a︡ I︠A︡MR v strukturnykh issledovanii︠a︡kh : S uchastiem zarubezhnykh uchenykh : Kazanʹ, 5-7 apreli︠a︡ 1995 goda : materialy seminara. Kazanʹ : Kazanskiĭ gos. universitet, 1995.

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Lenk, R. Fluctuations, diffusion, and spin relaxation. Amsterdam : Elsevier, 1986.

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Vladislav, Orekhov, et SpringerLink (Online service), dir. Novel Sampling Approaches in Higher Dimensional NMR. Berlin, Heidelberg : Springer Berlin Heidelberg, 2012.

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Marshall, Alan G. Fourier transforms in NMR, optical, and mass spectrometry : A user's handbook. Amsterdam : Elsevier, 1990.

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Spectroscopic techniques and hindered molecular motion. Boca Raton : CRC Press, 2012.

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Rudin, M. In-Vivo Magnetic Resonance Spectroscopy II : Localization and Spectral Editing. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992.

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Rudin, M. In-Vivo Magnetic Resonance Spectroscopy III : In-Vivo MR Spectroscopy : Potential and Limitations. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992.

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Fleischer, U. Deuterium and Shift Calculation. Berlin, Heidelberg : Springer Berlin Heidelberg, 1991.

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Alfred, Benzon Symposium (26th 1987 Copenhagen Denmark). NMR spectroscopy in drug research : Proceedings of the Alfred Benzon Symposium 26, held at the premises of the Royal Danish Academy of Sciences and Letters, Copenhagen 16-20 August 1987. Copenhagen : Munksgaard, 1988.

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Chapitres de livres sur le sujet "Nuclear magnetic resonance. Chemistry, Physical and theoretical"

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Jameson, Cynthia J., et Angel C. De Dios. « Theoretical and physical aspects of nuclear shielding ». Dans Nuclear Magnetic Resonance, 46–75. Cambridge : Royal Society of Chemistry, 2015. http://dx.doi.org/10.1039/9781782622758-00046.

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« Essentials of Nuclear Magnetic Resonance ». Dans Essentials of Physical Chemistry, 459–84. CRC Press, 2011. http://dx.doi.org/10.1201/b12869-25.

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Knicker, Heike, et Mark A. Nanny. « Introduction Nuclear Magnetic Resonance Spectroscopy : Basic Theory and Background ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0004.

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Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful experimental methods available for atomic and molecular level structure elucidation. It is a powerful technique in that it is a noninvasive probe that can be used to identify individual compounds, aid in determining structures of large macromolecules, such as proteins, and examine the kinetics of certain reactions. NMR spectroscopy takes advantage of the magnetic properties of the observed nucleus that are influenced not only by its chemical environment, but also by physical interactions with its environment. Both can be examined by measuring specific NMR parameters such as coupling constants, relaxation times, or changes in chemical shifts. As NMR techniques and instrumentation advance, NMR spectroscopy is becoming more important in the environmental sciences, tackling problems and questions that previously were difficult to answer. For example, sensitivity enhancement techniques increase the ability to examine a sample without chemical or physical pretreatment. A sample examined in this manner is in its original state and is unaffected by chemical or physical reactions caused by the pretreatment procedure. Despite its increasing popularity and numerous advantages, NMR spectroscopy can be a mysterious, and at times daunting, technique. The purpose of this chapter is to provide an overview of basic NMR theory and background for the uninitiated. It is hoped that it will provide enough information to those unfamiliar with NMR and its terminology for them to find the remaining chapters understandable and interesting. Those who desire a greater understanding are referred to the many textbooks on solution-state NMR, solid-state NMR, and the application of NMR to geochemistry, soil chemistry, oils and coals, and carbonaceous solids. The advance that led to NMR spectroscopy came in 1939 with resonance experiments by Rabi and coworkers, who demonstrated the property of nuclear spin. In 1945, the research groups of Bloch and Purcell independently obtained the first nuclear resonance signals. For this they won the 1952 Nobel prize. The first application of NMR spectroscopy in the field of humic substance research was 1H NMR of liquids. González-Vila et al. were the first to apply 13C solution-state NMR to natural humic acids.
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Nanny, Mark A. « Sorption Processes in the Environment : Nuclear Magnetic Resonance Spectroscopy as a New Analytical Method ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0006.

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The transport and fate of chemicals in the environment comprise one of the most pertinent issues in environmental chemistry. Physical and chemical interactions between the chemical of interest (sorbate) and the various components present in soil, water, and sediment (sorbent) can dramatically influence the transport and fate of the chemical. For example, organic material such as humic acids or surfactants, when bound to the surface of soil, sediment, and clay particles, can enhance sorption of chemicals to the particle surface, immobilizing the chemicals and possibly protecting them from degradation. The term “sorption,” as used in this chapter, refers to any physical or chemical association between the sorbate and sorbent. Thus, this definition includes molecular associations ranging from hydrophobic partitioning processes to covalent binding. It has also been observed that sorbents can act as a “buffer system” for the sorbate by taking up the sorbate when it is present at high concentrations and then slowly releasing it back into solution during periods of low or zero sorbate concentration. This type of behavior is important when the environmental presence of the chemical is episodic, such as in seasonal application of pesticides and herbicides. A dramatic example of this is presented by Steinberg et al., who detected the volatile, soil fumigant 1,2-dibromoethane in agricultural topsoils up to 19 years after the last application. On the other hand, soluble organic matter such as dissolved humic and fulvic acids can dramatically increase the apparent solubility of many hydrophobic chemicals in soil and sediment pore water. In this manner, the mobility of the chemical is increased. Thus, the nature and presence of organic material can strongly influence the transport properties of many chemicals in the environment. It is well known that sorption processes are a function of numerous parameters: the chemical characteristics of the sorbate (e.g., hydrophobicity, polarity), and the identity and chemical characteristics of the mineral phase and its organic coating. Other parameters important to sorption processes are the porosity of the sorbent particles, the presence of dissolved organic matter, and the solution pH and ionic strength.
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Leenheer, Jerry A., et Gary E. Maciel. « Preparation of Low-Carbon Sediments from the Mississippi River and Certain Tributaries for Solid-state CPMAS 13C NMR Analysis ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0024.

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The nature of organic carbon in aquatic sediments and soils with low carbon contents and significant contents of paramagnetic elements such as iron and manganese is difficult to assess by solid-state, cross-polarization magic angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectrometry because of the inherent low sensitivity of 13C NMR analyses, and band broadening and sensitivity losses caused by paramagnetic elements. Other investigators have addressed this problem in the analysis of soils by enriching the organic carbon content by flotation, by magnetic separation of paramagnetic minerals, and by chemical reduction of iron by stannous chloride and sodium dithionite. In this study, they found that satisfactory 13C NMR spectra could be obtained if the C/Fe ratio was greater than 1 wt%. Each of the physical and chemical treatments used to increase the C/Fe ratio resulted in losses of organic matter and changes in the nature of organic matter through physical fractionation and chemical alteration. Suspended stream sediments frequently have equivalent contents of organic carbon and sesquioxide coatings with which the organic matter is associated. These sesquioxide coatings consist predominantly of iron and manganese oxyhydroxides that cause problems with NMR analyses. In this chapter we describe a method to enrich organic matter and remove iron and manganese from low-carbon sediments sampled from the Mississippi, Illinois, and Ohio Rivers with minimal loss and alteration of the organic matter. The second objective is to characterize the sedimentary organic matter by 13C NMR using recent advances that increase instrument sensitivity. Suspended and bed sediments were collected during a sampling cruise on the Mississippi River during May–June 1990. Fine bed sediments were collected in depositional regions of the river or tributaries with a pipe dredge. Suspended silts were collected using a continuous-flow centrifuge operated on board the Research Vessel Acadiana. Both bed sediments and suspended silts were freeze-dried prior to additional treatment procedures and NMR analyses. A flow chart of selective mineral dissolution procedures is presented in Figure 17.1. The acid pyrophosphate treatment6 was placed first in the sequence to remove calcium and magnesium minerals that would form insoluble oxalates in the following extraction.
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Minear, Roger A., et Mark A. Nanny. « Solution and Condensed Phase Characterization ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0012.

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Improvements in nuclear magnetic resonance (NMR) instrumentation, magnetic field strength, pulse sequences, and computer technology and software have increased the range of applications and specific elements available for study by NMR. The five chapters in this Part clearly indicate the benefits of these advances, especially regarding studies of aquatic, environmental significance. Each of the studies focuses on environmentally significant issues. For example, chlorination is widely used to disinfect drinking waters, a method that can produce undesirable disinfection by-products. This was first recognized in 1974 with the discovery of trihalomethanes in most finished drinking waters where hypochlorite was used for disinfection. Chapter 7 examines the chlorination of alanine and relates it to the chlorination reactions of acetaldehyde and ammonia, a topic of importance with respect to drinking water disinfection. Aluminum is also widely used in drinking water treatment, and understanding its hydrolysis chemistry and complexation behavior is of great importance to aquatic chemistry. In addition, the aquatic chemistry of aluminum is important because acid rain can release soluble aluminum ions from clay into soil water, possibly damaging terrestrial plant life. Aluminum may eventually reach and accumulate in hydrological systems where it can be toxic to aquatic life. Chapters 8 and 9 focus on 27Al NMR in defining aqueous aluminum speciation in a mildly acidic solution or in the presence of complexing organic compounds. Furthermore, aluminum is of environmental and geochemical significance since it is an integral component of clays, another ubiquitous constituent of natural waters (surface and ground). Interaction between clays, cations, and internal water molecules can be significant in understanding the fate and transport of chemicals through the environment. Since colloidal suspensions of clay materials frequently represent challenges to water and wastewater treatment, understanding of physical and chemical processes are of tantamount importance to the environmental scientist and engineer. Chapter 10 explores cation behavior in clay matrices by using “uncommon” nuclei such as 7Li, 23Na, and 133Cs as probes. This is unique in that many NMR studies of complexation in clay have focused primarily upon the nuclei 27A1 and 29Si.
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Bortiatynski, Jacqueline M., et Patrick G. Hatcher. « The Development of 13C Labeling and 13C NMR Spectroscopy Techniques to Study the Interaction of Pollutants with Humic Substances ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0007.

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Modern agricultural practices have contributed to the accumulation of herbicides, pesticides and their decomposition products in the soil. These pollutants are known to interact with soil organic matter to form covalent and/or noncovalent bonding associations. The covalent bonds are thought to result from addition or oxidative coupling reactions, some of which may be catalyzed by oxidoreductive enzymes. Noncovalent associations include such interactions as ion exchange, hydrogen bonding, protonation, charge transfer, ligand exchange, coordination through metal ions, van der Waals forces, and hydrophobic bonding. The association of pollutants with soil organic matter is an area of study that is of extreme interest for two reasons. First, dissolved organic matter present in lakes and streams is known to enhance the solubility of pollutants, which poses a real threat to the quality of fresh water supplies. Therefore, if we are to predict the movement of pollutants in the water table we need to have a mechanistic understanding of their interactions with dissolved humic materials. Second, early studies had indicated that some pollutants chemically bind to humic materials, thus reducing the risk of further transport and dispersion. If this chemical binding of the pollutants is irreversible, then this process may serve as a natural means for their detoxification. Regardless of the type of association, the first task in any mechanistic study is to characterize the reaction products structurally. In the case of noncovalent binding mechanisms, studies have focused on the physical characteristics of the process and not on the structure of the associated pollutant. Association studies are used to determine the sorption kinetics and transport of pollutants as well as their association constants. These types of studies utilize various techniques such as batch sorption, gas-purge desorption, column adsorption, and miscible displacement. All of these techniques are only capable of providing quantitative information on the amount of pollutant sorbed by a substrate. The study of the covalent binding of pollutants to humic substances has utilized 14C labeling in addition to various spectrometric techniques such as ultraviolet (UV) difference, fluorescence polarization and infrared (IR) spectroscopy.
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Netzel, Daniel A., et Francis P. Miknis. « Adsorption Isotherms and 13C Solid-state NMR Study of Hazardous Organic Compounds Sorbed on Coal Fly Ash ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0010.

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Fly ash is a by-product from the combustion of coal. The 1985 annual US production was estimated to be about 1 x 108 metric tons. The utilization of fly ash during the 1980s remained stable at about 25% per year. Because of its pozzolanic properties, nearly 50% of the utilized fly ash is consumed in the production of cement and concrete. The vast quantity of fly ash that is not being used and its availability throughout the country and worldwide have motivated research for new uses in commerce and industry. Little is known of the organic adsorbent properties of fly ash. However, if they are found to be favorable, the potential commercial applications of the adsorptive characteristics of fly ash could include its use as an adsorbent sandwich for organics in combination with landfill or other dump-site liners, in traps for organics in waste waters, in filters for organics in process air streams, and as a stabilizer for organic wastes in drums. Variables that may affect the adsorbability of the fly ash towards organics in water include temperature; solution pH; and interactions between solute molecules and fly ash, and between solvent molecules and fly ash. Thus, there is an essential need to characterize each coal fly ash type to enable potential correlation between coal fly ash structural properties and the effectiveness of the adsorption characteristics of coal fly ash for immobilizing organic hazardous waste compounds. The composition and properties of pulverized fly ash depend on the type of coal burned and the nature of the combustion process. Thus, fly ashes from different origins may have significantly different sorption properties towards organic compounds of environmental interest. Eastern and western coal fly ashes differ significantly in their physical and chemical properties. The major minerals found in coal fly ash are α-quartz (SiO2), mullite (3A12O3 ·2SiO2), hematite (Fe2O3), magnetite (Fe3O4), lime (CaO), and gypsum (CaSO4·2H2O). Little is known of the coordination state and distribution of siliceous and aluminous material in coal fly ashes. Most siliceous and aluminous materials in fly ash are amorphous and thus are not detected or quantified by X-ray techniques.
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« Research Needs for Environmental NMR ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry, sous la direction de Mark A. Nanny, Roger A. Minear et Jerry A. Leenheer. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0025.

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This chapter is the result of a panel discussion held at the end of the symposium “NMR Spectroscopy in Environmental Science and Technology” that was presented at the ACS National Meeting in Denver, Colorado, March 28–April 2, 1993. The intention of the panel discussion was to examine and make recommendations for the future of environmental NMR research. This chapter is a general synopsis of the answers and comments from the panelists and members of the audience to three posed questions. The six panelists were: . . . Dr. Roger A. Minear (Moderator), University of Illinois, Urbana, IL Dr. H.-D. Lüdemann, Institut für Biophysik & Physikalische Biochemie, Regensburg, Germany Dr. Robert Wershaw, United States Geological Survey, Denver, CO Dr. Jerry A. Leenheer, United States Geological Survey, Denver, CO Dr. Gary Maciel, Colorado State University, Fort Collins, CO Dr. Leo Condron, Lincoln University, Canterbury, New Zealand . . . It was generally agreed that the area in which environmental NMR research will be the most influential is the examination of chemical and physical interactions between contaminants and the environmental matrix, especially for heterogeneous and complex matrices. This is because NMR can be used as an in-situ and non-invasive probe. One advantage of NMR for environmental studies is that it can specifically follow the chemistry occurring in complex environments and matrices. In addition, the wide range of NMR-accessible nuclei creates significant potential for research in this area. A specific area where NMR could be useful is the examination of chemicals and their transformation in soils and sediments, both biotic and abiotic, without having to use extraction methods. This could provide information regarding precursors, reaction products, and changes occurring in soils, without jeopardizing sample integrity by extraction methods. Tracking reactions and reaction by-products in such matrices can be carried one step further by labeling compounds with NMR-sensitive nuclei and following the concurrent reactions. It will also be useful to use NMR in this fashion to examine the influence of the biota upon the reaction and the reaction products, which will in turn advance studies examining bioavailability and bioremediation processes.
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Nanny, Mark A., et Roger A. Minear. « 31P FT-NMR of Concentrated Lake Water Samples ». Dans Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0020.

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The use of phosphorus-31 Fourier Transform nuclear magnetic resonance (31P FT-NMR) spectroscopy for the study of dissolved organic phosphorus (DOP) in fresh water has been recently established by Nanny and Minear. The fact that NMR is an element-specific technique, is nondestructive, and has the ability to differentiate between similar phosphorus compounds makes it invaluable for the identification and characterization of DOP. Such information regarding DOP is required in order to understand aquatic nutrient cycling. The difficulty with using 31P FT-NMR spectroscopy for such studies is the extremely low DOP concentration; usually ranging from < 1 μg P/L in oligotrophic lakes to approximately 100 μg P/L for eutrophic systems. Nanny and Minear raised the DOP concentration into the NMR detection range, which is on the order of milligrams of phosphorus/liter, by concentrating large volumes of lake water with ultrafiltration (UF) and reverse osmosis (RO) membranes. Volume concentration factors of several ten thousand fold provided DOP concentrations of up to 60 mg P/L. Other DOP concentration methods such as anion exchange, lanthanum hydroxide precipitation, and lyophilization require severe chemical and/or physical transformations of the sample and/or they need long processing times, all of which increase the risk of DOP hydrolysis. Sample concentration with UF and RO membranes does not require the sample to undergo these major changes and is also a relatively rapid concentration method. In addition to these concentration capabilities, the use of ultrafiltration and reverse osmosis membranes permitted fractionation of the DOP samples according to molecular size. Nanny and Minear used three membranes in series with decreasing pore size: 30kDa (kilodaltons), 1 kDa, and RO (95% NaCl rejection) to separate the high-molecular-weight, intermediate-molecular-weight, and low-molecular-weight DOP species. In the intermediate-molecular-weight fraction, Nanny and Minear observed the presence of monoester and diester phosphates. Spectra from ten samples collected over a year typically consisted of a large broad signal in the monoester phosphate region spanning from a chemical shift of 2.00 ppm to −0.50 ppm. The maximum of this signal was usually in the range of 1.00 to 1.50 ppm. This broad signal had a shoulder in the diester phosphate region which sometimes was intense enough to appear as an individual signal.
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Actes de conférences sur le sujet "Nuclear magnetic resonance. Chemistry, Physical and theoretical"

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Park, Jiyong, Byungnam Kahng et Wonmuk Hwang. « Supramolecular Structure and Stability of the GNNQQNY β-Sheet Bilayer Filament : A Computational Study ». Dans ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-175588.

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Self-assembly of β-sheet forming peptides into filaments has drawn great interests in biomedical applications [1,2]; Hydrogels formed by filaments self-assembled from de novo designed peptides possess potential applications for cell culture scaffolds [3]. On the other hand, peptides derived from amyloidogenic proteins in neurodegenerative diseases such as Alzheimer’s and Parkinson’s also form similar β-sheet filaments in vitro. They share little sequence homology, yet filaments formed by these self-assembling peptides commonly have the cross-β structure, the key signature of the amyloid fibril. Detailed structural information of the self-assembled β-sheet filaments has been limited partly due to the difficulty in preparing ordered filament samples, and it has been only recently that solid-state nuclear magnetic resonance and x-ray techniques have revealed their molecular structure at the atomic level [4,5]. Although molecular structures of amyloid fibrils are becoming available, physical principles governing their self-assembly and the properties of the filaments are not well-understood, for which computational as well as theoretical approaches are desirable [6].
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Hon, Vai Yee, Ismail Mohd Saaid, Ching Hsia Ivy Chai, Noor 'Aliaa M. Fauzi, Estelle Deguillard, Jan van Male et Jan-Willem Handgraaf. « Digital Oil Model Development and Verification ». Dans International Petroleum Technology Conference. IPTC, 2021. http://dx.doi.org/10.2523/iptc-21305-ms.

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Abstract Advances in digital technologies have the potential to enhance model predictive capability and redefine its boundaries at various scale. Digital oil with accurate representation of atomistic components is a powerful tool to analyze both macroscopic properties and microscopic phenomena of crude oil under any thermodynamic conditions. Digital oil model presented in this paper is the key input in molecular chemistry modeling for designing chemical enhanced oil recovery formulation. Hence, it is constructed based on a fit-for purpose strategy focusing in oil components that have large contribution to microemulsion stability. Complete crude oil composition could comprise over 100,000 components. Lengthy simulation time is required to simulate all crude oil components which is impratical, despite the challenges to identify all crude oil components experimentally. Therefore, we established a practical experimental strategy to identify key crude oil components and constructed the digital oil model based on surrogate components. The surrogate components are representative molecules of the volatiles, saturates, aromatics and resins. Two-dimensional digital oil model, with aromaticity on one axis, and the size of the molecules on the other axis was constructed. We developed algorithm to integrate nuclear magnetic resonance response with architecture of the molecular structure. A group contribution method was implemented to ensure reliable representation of the molecular structure. We constructed the digital oil models for a field in Malaysia Basin. We validated the physical properties of the digital oil model with properties measured from experiment, predicted from molecular dynamics simulation and calculated from quantitative property-property relationship method. Good agreement was obtained from the validation, with less than 5% and 13% variance in crude density and Equivalent Alkane Carbon Number respectively, indicating that the molecular characteristic of the digital oil model was captured correctly. We adopted the digital oil model in molecular chemistry modeling to gain insights into microemulsion formation in chemical enhanced oil recovery formulation design. Digital oil is a robust tool to make predictions when information cannot be extracted from experimental data alone. It can be extended for engineering applications involving processing, safety, hazard, and environmental considerations.
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