11B nuclear magnetic resonance study of boron nitride nanotubes prepared by mechano-thermal method

We reported ¹¹B nuclear magnetic resonance studies of boron nitride (BN) nanotubes prepared by mechano-thermal route. The NMR lineshape obtained at 192.493 MHz (14.7 T) was fitted with two Gaussian functions, and the ¹¹B nuclear magnetization relaxations were satisfied with the stretched–exponential function, exp[-(tlT₁)^(D+1)/6] (D: space dimension) at all temperatures. In addition, the temperature dependence of spin–lattice relaxation rates was well described by T_i^-1 = aT (a: constant, T: temperature) and could be understood in terms of direct phonon process. All the 11BNMR results were explained by considering the inhomogeneous distribution of the paramagnetic metal catalysts, such as α-Fe, Fe–N, and Fe₂ B, that were incorporated during the process of high-energy ball milling of boron powder and be synthesized during subsequent thermal annealing. X-ray powder diffraction as well as electron paramagnetic resonance (EPR) on BN nanotubes were also conducted and the results obtained supported these conclusions.

Studies on the mechanism of the peroxyoxalate chemiluminescence reaction : part 2, further identification of intermediates using 2D EXSY 13C nuclear magnetic resonance spectroscopy

Further consideration has been given to the reaction pathway of a model peroxyoxalate chemiluminescence system. Again utilising doubly labelled oxalyl chloride and anhydrous hydrogen peroxide, 2D EXSY ¹³C nuclear magnetic resonance (NMR) spectroscopy experiments allowed for the characterisation of unknown products and key intermediate species on the dark side of the peroxyoxalate chemiluminescence reaction. Exchange spectroscopy afforded elucidation of a scheme comprised of two distinct mechanistic pathways, one of which contributes to chemiluminescence. ¹³C NMR experiments carried out at varied reagent molar ratios demonstrated that excess amounts of hydrogen peroxide favoured formation of 1,2-dioxetanedione: the intermediate that, upon thermolysis, has been long thought to interact with a fluorophore to produce light.

Phylogenetic relationships among nine scallop species (Bivalvia : Pectinidae) inferred from nucleotide sequences of one mitochondrial and three nuclear gene regions

Current knowledge of the evolutionary relationships among scallop species (Mollusca: Bivalvia: Pectinidae) in the Indo-Pacific region is rather scanty. To enhance the understanding of the relationships within this group, phylogenies of nine species of scallops with the majority from coastal regions of Thailand, were reconstructed by maximum parsimony, maximum likelihood, and Bayesian methods using sequences of the 16S rRNA of the mitochondrial genome, and a fragment containing the ITS1, 5.8S and ITS2 genes of the nuclear DNA. The trees that resulted from the three methods of analysis were topologically identical, however, gained different levels of support at some nodes. Nine species were clustered into two major clades, corresponding to two subfamilies (Pectininae and Chlamydinae) of the three currently recognized subfamilies within Pectinidae. Overall, the relationships reported herein are mostly in accordance with the previous molecular studies that used sequences of the mtDNA cytochrome oxidase subunit I, and the classification system based on microsculpture of shell features and morphological characteristics of juveniles. Levels of divergences were different among genes (i.e., the 5.8S gene showed the lowest levels of nucleotide divergence at all levels, whereas the 16S rRNA showed the highest level of variation within species, and ITS2 gene revealed the highest level of divergence at higher levels).

Nuclear rivalry in South Asia : an examination of post Cold War nuclear arms control initiatives

South Asia has emerged in the post-Cold War era as a region where ongoing nuclear rivalry has the potential to result in a nuclear exchange between India and Pakistan. The United States, together with the global community, is devoting considerable effort to prevent the further development and deployment of nuclear weapons by India and Pakistan. This thesis analyses the underlying reasons for the ongoing nuclear rivalry between India and Pakistan, details post-Cold War initiatives to end the nuclear rivalry and examines the prospect of United States efforts to cap, reduce and eventually eliminate the nuclear arsenals of India and Pakistan. The thesis finds that historical factors form the basis of the continuing hostility and animosity between the two nations. The two nations have been bitter rivals since the time of partition in 1947 and the disputed territory of Kashmir continues to be the manifestation of deep seated antagonism and hostility. Pakistan's geography leaves it extremely vulnerable to conventional Indian attack and possession of nuclear weapons is seen as a means to redress the imbalance. Strong domestic support together with fervent nationalism and international prestige will continue to drive the nuclear programs of each nation. This thesis concludes that the nuclear rivalry between India and Pakistan is regional in nature and the end of the Cold War has done little to improve the prospects for nuclear disarmament in the region. United States led efforts have failed to persuade India or Pakistan to either accede to the Non-Proliferation Treaty (NPT) or dismantle their nuclear weapons. The thesis also notes that the United States has failed to take account of China as a significant regional power and it's impact on the nuclear programs of India and Pakistan. A fresh approach (to include China) with more emphasis on regional dialogue is suggested as a first step to ending the nuclear rivalry.

Reduced glycogen availability is associated with increased AMPKα2 activity, nuclear AMPKα2 protein abundance, and GLUT4 mRNA expression in contracting human skeletal muscle

Glycogen availability can influence glucose transporter 4 (GLUT4) expression in skeletal muscle through unknown mechanisms. The multisubstrate enzyme AMP-activated protein kinase (AMPK) has also been shown to play an important role in the regulation of GLUT4 expression in skeletal muscle. During contraction, AMPK [alpha]2 translocates to the nucleus and the activity of this AMPK isoform is enhanced when skeletal muscle glycogen is low. In this study, we investigated if decreased pre-exercise muscle glycogen levels and increased AMPK [alpha]2 activity reduced the association of AMPK with glycogen and increased AMPK [alpha]2 translocation to the nucleus and GLUT4 mRNA expression following exercise. Seven males performed 60 min of exercise at ~70% [VO.sub.2] peak on 2 occasions: either with normal (control) or low (LG) carbohydrate pre-exercise muscle glycogen content. Muscle samples were obtained by needle biopsy before and after exercise. Low muscle glycogen was associated with elevated AMPK [alpha]2 activity and acetyl-CoA carboxylase [beta] phosphorylation, increased translocation of AMPK [alpha]2 to the nucleus, and increased GLUT4 mRNA. Transfection of primary human myotubes with a constitutively active AMPK adenovirus also stimulated GLUT4 mRNA, providing direct evidence of a role of AMPK in regulating GLUT4 expression. We suggest that increased activation of AMPK [alpha]2 under conditions of low muscle glycogen enhances AMPK [alpha]2 nuclear translocation and increases GLUT4 mRNA expression in response to exercise in human skeletal muscle.

Nuclear weapons and deterrence

Discusses deterrence theory in relation to the nuclear armed nations. Suggests the world may turn from the deterrence of war using nuclear weapons to deterring countries and other oganisations from their acquisition.

13C Nuclear magnetic resonance spectroscopic study of plasticization in solid polymer electrolytes

Preliminary results are presented on the correlation between enhanced solvent mobility and ionic conductivity in plasticized polyether–urethane solid polymer electrolytes using ¹³C nuclear magnetic resonance spectroscopic spin–lattice relaxation time measurements to probe polymer mobility.

Structural characterization of conducting polypyrrole using 13C cross-polarization/magic-angle spinning solid-state nuclear magnetic resonance spectroscopy

¹³C nuclear magnetic resonance (n.m.r.) has been used to study polypyrrole and N-substituted polypyrrole in the solid state. The extent of oxidation appears to be counterion-dependent; in particular, the quinoid structure appears favoured in the films prepared with dodecyl sulfate. Resonances associated with the quinoid unit are lost upon reduction of the polypyrrole film, which supports the idea that the quinoid structure is associated with the oxidized form of polypyrrole. N-substituted polypyrroles have a more distinct resonance at 110 ppm, which is linked to lower degrees of oxidation or charge delocalization in these systems. The decrease in conductivity of polypyrrole upon thermal ageing in air is associated with both the loss of counterion (‘thermal dedoping’) and the decomposition of the quinoid structure in the polymer backbone. There is no indication of carbonyl formation in the solid-state n.m.r. spectra obtained in the present study.