title: FTNMR and aspects of germanium chemistry

authors: Watkinson, Philip John

abstract: Experimentally determined baseline parameters were obtained for the NMR observation of 32 isotopes, notably including ⁷³Ge. 
Extensive ⁷³Ge studies were performed, despite the technical difficulties from a low NMR receptivity, and a low observation frequency. The majority of germanium compounds studied gave ⁷³Ge resonances.
Germanium-73 chemical shifts, linewidths, and germanium proton coupling constants have been obtained, doubling the total number of compounds studied directly by ⁷³Ge NMR. Sample concentrations must be typically at least 0.1 M to avoid using excessive instrument time ( > 5 hours).
The larger spectral dispersion of ⁷³Ge NMR than ¹H or ¹³C NMR often makes it a better tool for characterization. Trends in ⁷³Ge chemical shifts and coupling constants are surveyed and their use in characterizing hydrides and organogermanes are illustrated. Germanium-73 NMR gave more spectral information on redistributions in the GeY₄:SiX₄, GeX₄:SnY₄, and GeX₄:HgC1₂ systems than did ²⁹Si, ¹¹⁹Sn, or ¹⁹⁹Hg NMR, revealing a slower redistribution than in MX₄:MY₄ systems (M = Ge or Sn; X, Y = Cl or Br).
Nuclear relaxation studies on ⁷³Ge have been greatly extended, increasing the total number of compounds studied three-fold. Values of T₁ from inversion-recovery experiments ranged from 13 to 1300 ms near RT. The dominance of the quadrupolar relaxation mechanism has been established, and the non-existence of signals from compounds with germanium in an asymmetric environment is attributed to rapid relaxation. Estimates of activation energies for molecular reorientation, and nuclear quadrupole coupling constants (2.3-17 MHz) using ¹³C correlation times have been obtained.
Proton PT to ⁷³Ge via the sequence INEPT was established and its value demonstrated both for sensitivity enhancement and for help in spectral assignment. Observations imply that all compounds with ¹J(Ge,H) or ²J(Ge,C,H) coupling give proton PT. Large enhancements (2-20 fold) were obtained, although long proton T₁ values reduced instrument time savings to 3-100 fold, with the addition of a relaxant in some cases. The loss of signal during the sequence via nuclear relaxation is smaller for INEPT than for another multinuclear PT sequence, UPT, and this difference is maximized for a nucleus with a large spin, like ⁷³Ge. 
Preliminary work on ⁷⁷Se INEPT and multinuclear studies on transition metal carbonyls are presented.

text: FTNMR and aspects of germanium chemistry Experimentally determined baseline parameters were obtained for the NMR observation of 32 isotopes, notably including ⁷³Ge. 
Extensive ⁷³Ge studies were performed, despite the technical difficulties from a low NMR receptivity, and a low observation frequency. The majority of germanium compounds studied gave ⁷³Ge resonances.
Germanium-73 chemical shifts, linewidths, and germanium proton coupling constants have been obtained, doubling the total number of compounds studied directly by ⁷³Ge NMR. Sample concentrations must be typically at least 0.1 M to avoid using excessive instrument time ( > 5 hours).
The larger spectral dispersion of ⁷³Ge NMR than ¹H or ¹³C NMR often makes it a better tool for characterization. Trends in ⁷³Ge chemical shifts and coupling constants are surveyed and their use in characterizing hydrides and organogermanes are illustrated. Germanium-73 NMR gave more spectral information on redistributions in the GeY₄:SiX₄, GeX₄:SnY₄, and GeX₄:HgC1₂ systems than did ²⁹Si, ¹¹⁹Sn, or ¹⁹⁹Hg NMR, revealing a slower redistribution than in MX₄:MY₄ systems (M = Ge or Sn; X, Y = Cl or Br).
Nuclear relaxation studies on ⁷³Ge have been greatly extended, increasing the total number of compounds studied three-fold. Values of T₁ from inversion-recovery experiments ranged from 13 to 1300 ms near RT. The dominance of the quadrupolar relaxation mechanism has been established, and the non-existence of signals from compounds with germanium in an asymmetric environment is attributed to rapid relaxation. Estimates of activation energies for molecular reorientation, and nuclear quadrupole coupling constants (2.3-17 MHz) using ¹³C correlation times have been obtained.
Proton PT to ⁷³Ge via the sequence INEPT was established and its value demonstrated both for sensitivity enhancement and for help in spectral assignment. Observations imply that all compounds with ¹J(Ge,H) or ²J(Ge,C,H) coupling give proton PT. Large enhancements (2-20 fold) were obtained, although long proton T₁ values reduced instrument time savings to 3-100 fold, with the addition of a relaxant in some cases. The loss of signal during the sequence via nuclear relaxation is smaller for INEPT than for another multinuclear PT sequence, UPT, and this difference is maximized for a nucleus with a large spin, like ⁷³Ge. 
Preliminary work on ⁷⁷Se INEPT and multinuclear studies on transition metal carbonyls are presented.

year: 1984

title: Quantitative characterization of the multiscale mechanical properties of low-permeability sandstone roofs of coal seams based on nanoindentation and triaxial tests and its implications for CO2 geological sequestration

authors: Cao, F

abstract: Microstructural heterogeneity of low-permeability sandstone roofs of deep unmineable coal seams due to diagenesis significantly affects rock mechanical behavior, greatly impacting the sealing potential of in situ CO2 sequestration and the structural stability of the geological formation. However, little is known about how the microstructure of different mineral groups influences the multiscale mechanical behavior of deep sandstone. This study proposes a new method for quantitatively characterizing the multiscale mechanical properties of low-permeability sandstone and shows the mechanisms responsible for mechanical failure at the micro-, meso-, and macroscale. Triaxial compression tests and targeted nanoindentation tests were conducted to assess the micro- and macroscale mechanical properties of different types of sandstone. The micro- and macroscale experiments were coupled with numerical simulations of compression using a unified cohesive model based on Voronoi polygons to clarify the multiscale mechanical behavior. The results indicate that quartz, the primary mineral component of the sandstones examined, exhibits the strongest micromechanical properties, followed by feldspar, calcite, and clay minerals. Compared to polycrystalline quartz, monocrystalline quartz has a more stable microstructure and is mechanically stronger. The macro-mechanical properties of tight sandstone samples are weakened by increased microstructural inhomogeneity and larger grain size. This leads to a higher likelihood of splitting damage, characterized by a high degree of discrete and weak stress sensitivity. The major conclusion is that the positive rhythm lithofacies of medium-grained sandstone to siltstone are the most favorable for efficient CO2 sequestration in deep unmineable coal seams.

text: Quantitative characterization of the multiscale mechanical properties of low-permeability sandstone roofs of coal seams based on nanoindentation and triaxial tests and its implications for CO2 geological sequestration Microstructural heterogeneity of low-permeability sandstone roofs of deep unmineable coal seams due to diagenesis significantly affects rock mechanical behavior, greatly impacting the sealing potential of in situ CO2 sequestration and the structural stability of the geological formation. However, little is known about how the microstructure of different mineral groups influences the multiscale mechanical behavior of deep sandstone. This study proposes a new method for quantitatively characterizing the multiscale mechanical properties of low-permeability sandstone and shows the mechanisms responsible for mechanical failure at the micro-, meso-, and macroscale. Triaxial compression tests and targeted nanoindentation tests were conducted to assess the micro- and macroscale mechanical properties of different types of sandstone. The micro- and macroscale experiments were coupled with numerical simulations of compression using a unified cohesive model based on Voronoi polygons to clarify the multiscale mechanical behavior. The results indicate that quartz, the primary mineral component of the sandstones examined, exhibits the strongest micromechanical properties, followed by feldspar, calcite, and clay minerals. Compared to polycrystalline quartz, monocrystalline quartz has a more stable microstructure and is mechanically stronger. The macro-mechanical properties of tight sandstone samples are weakened by increased microstructural inhomogeneity and larger grain size. This leads to a higher likelihood of splitting damage, characterized by a high degree of discrete and weak stress sensitivity. The major conclusion is that the positive rhythm lithofacies of medium-grained sandstone to siltstone are the most favorable for efficient CO2 sequestration in deep unmineable coal seams.

year: 2025

title: Association of Single Nucleotide Polymorphisms in Surfactant Protein A and D with Otitis Media.

authors: Barnett, Catherine Margaret Eleanor

subjects: otitis media

abstract: Otitis Media is one of the most common childhood diseases. Recurrent acute otitis media RAOM is characterized by repeated episodes of inflammation of the middle ear in conjunction with middle ear fluid, and often with an inflamed or bulging eardrum. Defective clearance by the Eustachian tube results in mucus build-up and is characteristic of otitis media with effusion (OME). Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, respiratory syncytial virus, and rhinovirus are the most common contributors to otitis media pathogenesis. In New Zealand, OME has been implicated with conductive hearing loss in childhood and has been shown to significantly impact on speech and language development. New Zealand Māori and Polynesian children have displayed significantly higher hearing test failure rates than European-Caucasian children.

The collectins, Surfactant Protein (SP)-A and -D are encoded by three genes (SP-A1, SP-A2, and SP-D) and are host defense proteins present in the middle ear and Eustachian tube. Single nucleotide polymorphisms (SNPs) in SP-A1 and SP-A2 have been associated with increased or decreased susceptibility to otitis media, meningococcal disease, and range of respiratory diseases. Using allele-specific primers and real-time PCR with SYBR  Green I melting curve analysis, four groups of individuals were genotyped for eleven SP-A1, SP-A2, and SP-D SNPs: European-Caucasian individuals with RAOM/OME; New Zealand Māori/Polynesian individuals with RAOM/OME; individuals with meningococcal disease; and a control group. The computer program, Haploview, was employed to perform χ2 analyses and identify statistically significant associations of alleles/haplotypes with RAOM/OME or meningococcal disease.

In the European-Caucasian population, two SP-A1 alleles, one SP-A2 allele, and four haplotypes (CGAGC, 1A3, 1A9, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). Conversely, haplotypes 6A2 and 1A2 were found to be protective against susceptibility to RAOM/OME (P lt; 0.05). In New Zealand Māori and Polynesian individuals, two SP-A1 alleles, three SP-A2 alleles, one SP-D allele, and four haplotypes (6A8, 6A10, 1A3, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). An additional four haplotypes (6A2, 1A0, 1A2, and TA) were determined to be protective against susceptibility to RAOM/OME (P lt; 0.05). However, protective SPA1/SPA2/SPD haplotype 6A2-1A0-TA was significantly under-represented in the New Zealand Māori and Polynesian population (P lt; 0.05). A single allele and haplotype were associated with increased risk of meningococcal disease (P lt; 0.05).

The findings of this study confirm that specific genetic variants of SP-A and SP-D are associated with either increased or decreased risk of developing RAOM and/or OME. Furthermore, it was demonstrated that New Zealand Māori and Polynesian individuals appear to exhibit more haplotypes susceptible to RAOM/OME. This may provide a partial explanation for the higher RAOM/OME-related failure rates of hearing tests in New Zealand Māori and Polynesian children. However, there are numerous socio-economic and environmental factors that also contribute to otitis media pathogenesis which were not considered in this study. The effects of the SP-A1, SP-A2, and SP-D alleles and haplotypes on the bacterial/viral binding efficiencies of SP-A and SP-D need to be investigated by further research, using a large population, to confirm the association with susceptibility or resistance with RAOM/OME.

text: Association of Single Nucleotide Polymorphisms in Surfactant Protein A and D with Otitis Media. Otitis Media is one of the most common childhood diseases. Recurrent acute otitis media RAOM is characterized by repeated episodes of inflammation of the middle ear in conjunction with middle ear fluid, and often with an inflamed or bulging eardrum. Defective clearance by the Eustachian tube results in mucus build-up and is characteristic of otitis media with effusion (OME). Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, respiratory syncytial virus, and rhinovirus are the most common contributors to otitis media pathogenesis. In New Zealand, OME has been implicated with conductive hearing loss in childhood and has been shown to significantly impact on speech and language development. New Zealand Māori and Polynesian children have displayed significantly higher hearing test failure rates than European-Caucasian children.

The collectins, Surfactant Protein (SP)-A and -D are encoded by three genes (SP-A1, SP-A2, and SP-D) and are host defense proteins present in the middle ear and Eustachian tube. Single nucleotide polymorphisms (SNPs) in SP-A1 and SP-A2 have been associated with increased or decreased susceptibility to otitis media, meningococcal disease, and range of respiratory diseases. Using allele-specific primers and real-time PCR with SYBR  Green I melting curve analysis, four groups of individuals were genotyped for eleven SP-A1, SP-A2, and SP-D SNPs: European-Caucasian individuals with RAOM/OME; New Zealand Māori/Polynesian individuals with RAOM/OME; individuals with meningococcal disease; and a control group. The computer program, Haploview, was employed to perform χ2 analyses and identify statistically significant associations of alleles/haplotypes with RAOM/OME or meningococcal disease.

In the European-Caucasian population, two SP-A1 alleles, one SP-A2 allele, and four haplotypes (CGAGC, 1A3, 1A9, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). Conversely, haplotypes 6A2 and 1A2 were found to be protective against susceptibility to RAOM/OME (P lt; 0.05). In New Zealand Māori and Polynesian individuals, two SP-A1 alleles, three SP-A2 alleles, one SP-D allele, and four haplotypes (6A8, 6A10, 1A3, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). An additional four haplotypes (6A2, 1A0, 1A2, and TA) were determined to be protective against susceptibility to RAOM/OME (P lt; 0.05). However, protective SPA1/SPA2/SPD haplotype 6A2-1A0-TA was significantly under-represented in the New Zealand Māori and Polynesian population (P lt; 0.05). A single allele and haplotype were associated with increased risk of meningococcal disease (P lt; 0.05).

The findings of this study confirm that specific genetic variants of SP-A and SP-D are associated with either increased or decreased risk of developing RAOM and/or OME. Furthermore, it was demonstrated that New Zealand Māori and Polynesian individuals appear to exhibit more haplotypes susceptible to RAOM/OME. This may provide a partial explanation for the higher RAOM/OME-related failure rates of hearing tests in New Zealand Māori and Polynesian children. However, there are numerous socio-economic and environmental factors that also contribute to otitis media pathogenesis which were not considered in this study. The effects of the SP-A1, SP-A2, and SP-D alleles and haplotypes on the bacterial/viral binding efficiencies of SP-A and SP-D need to be investigated by further research, using a large population, to confirm the association with susceptibility or resistance with RAOM/OME.

year: 2007