N M R Studies of Coal

<p>Carbon-13 CP/MAS NMR was used to study a selection of fifty-seven New Zealand coals and ten Australian coals. The coal rank varied from lignite to semianthracite. A qualitative survey of the plant origins of NMR signals was followed by an EPR study of the unpaired spin-species in coal. The quantitative reliability of the NMR response of coal was analysed in relaxation and "visibility" studies. Different approaches to the problem of accounting for intensity in spinning-side-band (SSB) signals were assessed. The most successful approach was found to be the complete computer simulation of the spectrum from combinations of SSB intensity patterns broadened by a mixture of Lorentzian and Gaussian lineshapes. This method of analysis produced oxygen contents that showed a good correlation with oxygen contents (by difference) from Ultimate analysis. The resultant carbon, hydrogen and oxygen functional group analyses allowed considerable insight into the depositional influences on, and alteration of, the coal structure with increasing degree of coalification.</p>

N M R Studies of Coal

<p>Carbon-13 CP/MAS NMR was used to study a selection of fifty-seven New Zealand coals and ten Australian coals. The coal rank varied from lignite to semianthracite. A qualitative survey of the plant origins of NMR signals was followed by an EPR study of the unpaired spin-species in coal. The quantitative reliability of the NMR response of coal was analysed in relaxation and "visibility" studies. Different approaches to the problem of accounting for intensity in spinning-side-band (SSB) signals were assessed. The most successful approach was found to be the complete computer simulation of the spectrum from combinations of SSB intensity patterns broadened by a mixture of Lorentzian and Gaussian lineshapes. This method of analysis produced oxygen contents that showed a good correlation with oxygen contents (by difference) from Ultimate analysis. The resultant carbon, hydrogen and oxygen functional group analyses allowed considerable insight into the depositional influences on, and alteration of, the coal structure with increasing degree of coalification.</p>

N M R Studies of Coal

<p>Carbon-13 CP/MAS NMR was used to study a selection of fifty-seven New Zealand coals and ten Australian coals. The coal rank varied from lignite to semianthracite. A qualitative survey of the plant origins of NMR signals was followed by an EPR study of the unpaired spin-species in coal. The quantitative reliability of the NMR response of coal was analysed in relaxation and "visibility" studies. Different approaches to the problem of accounting for intensity in spinning-side-band (SSB) signals were assessed. The most successful approach was found to be the complete computer simulation of the spectrum from combinations of SSB intensity patterns broadened by a mixture of Lorentzian and Gaussian lineshapes. This method of analysis produced oxygen contents that showed a good correlation with oxygen contents (by difference) from Ultimate analysis. The resultant carbon, hydrogen and oxygen functional group analyses allowed considerable insight into the depositional influences on, and alteration of, the coal structure with increasing degree of coalification.</p>

N M R Studies of Coal

<p>Carbon-13 CP/MAS NMR was used to study a selection of fifty-seven New Zealand coals and ten Australian coals. The coal rank varied from lignite to semianthracite. A qualitative survey of the plant origins of NMR signals was followed by an EPR study of the unpaired spin-species in coal. The quantitative reliability of the NMR response of coal was analysed in relaxation and "visibility" studies. Different approaches to the problem of accounting for intensity in spinning-side-band (SSB) signals were assessed. The most successful approach was found to be the complete computer simulation of the spectrum from combinations of SSB intensity patterns broadened by a mixture of Lorentzian and Gaussian lineshapes. This method of analysis produced oxygen contents that showed a good correlation with oxygen contents (by difference) from Ultimate analysis. The resultant carbon, hydrogen and oxygen functional group analyses allowed considerable insight into the depositional influences on, and alteration of, the coal structure with increasing degree of coalification.</p>

The importance of Asn52 in the structure–function relationship of human cytochrome c

Naturally occurring N52S human cytochrome c adopts a small fraction of high-spin species and exhibits an enhanced peroxidase activity.

Structural Insights into the Two-Step Spin-Crossover Compound Fe(3,4-dimethyl-pyridine)2[Ag(CN)2]2

The crystal structure of the polymeric spin crossover compound Fe(3,4-dimethyl-pyridine)2[Ag(CN)2]2 has been solved and its temperature dependence followed by means of single-crystal and powder X-ray diffraction. This compound presents a two-step spin transition with relatively abrupt steps centred at ca. 170 K and 145 K and a plateau at around 155 K. The origin of the two-step transition is discussed in light of these structural studies. The observations are compatible with a mostly disordered state between the two steps, consisting of mixing of high-spin and low-spin species, while weak substructure reflections in the mixed phase could indicate some degree of long-range order of the high-spin and low-spin sites.

A new limit of the 129Xenon Electric Dipole Moment

We report on the first preliminary result of our 129Xe EDM measurement performed by the MIXed collaboration. The aim of this report is to demonstrate the feasibility of a new method to set limits on nuclear EDMs by investigating the EDM of the diamagnetic 129Xe atoms. In our setup, hyperpolarized 3He serves as a comagnetometer needed to suppress magnetic field fluctuations. The free induction decay of the two polarized spin species is directly measured by low noise DC SQUIDs, and the weighted phase difference extracted from these measurements is used to determine a preliminary upper limit on the 129Xe EDM.

Magnetic Defects in Transitional Metal Di-Chalcogenide Semiconducting Layers

ABSTRACTIn this work, we report on the electron spin resonance (ESR) studies performed on few-layered nanocrystalline (NCs) MoS2, WS2, and TiS2 prepared using hydrothermal and vapor transport methods. From the temperature dependent ESR spectra collected from MoS2 NCs, we have identified adsorbed oxygen species, sulphur vacancies, thio- and oxo-Mo5+ related paramagnetic defect centers. WS2 NCs have exhibited W+3 and oxo-W+5 paramagnetic defect spin species. TiS2 NCs showed defects such as Fe3+ (unwanted), oxygen and sulfur vacancies. This work demonstrates the usage of spin-sensitive spectroscopy such as ESR in unravelling the defects which contain unpaired electron spin centers in layered NCs two-dimensional materials.

An iron(II) complex tripodally chelated with 1,1,1-tris(pyridin-2-yl)ethane showing room-temperature spin-crossover behaviour

The spin-crossover phenomenon is a reversible low- and high-spin transition caused by external stimuli such as heat. In the novel iron(II) complex salt tetraphenylphosphonium tris(thiocyanato-κN)[1,1,1-tris(pyridin-2-yl)ethane-κ3N,N′,N′′]ferrate(II), (C24H20P)[Fe(NCS)3(C17H15N3)], the Fe—N bond lengths are in the range 2.027 (2)–2.089 (2) Å, indicating that the specimen consists of comparable molar fractions of the low- and high-spin species at 296 K. A magnetic study confirmed that spin-crossover takes place at around 290 K.