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At least 1,135 records · Page 63Linked to original sources
PubMed2006

89Y magic-angle spinning NMR of Y2Ti2-xSnxO7 pyrochlores.

The yttrium local environment in the series of pyrochlores Y2Ti2-xSnxO7 was studied using 89Y NMR. Oxides with the pyrochlore structure exhibit a range of interesting physical and chemical properties, resulting in many technological applications, including the encapsulation of lanthanide- and actinide-bearing radioactive waste. The use of the nonradioactive Y3+ cation provides a sensitive probe for any changes in the local structure and ordering with solid solution composition, through 89Y (I = 1/2) NMR. We confirm that a single pyrochlore phase is formed over the entire compositional range, with Y found only on the eight-coordinated A site. A significant (approximately 15 ppm) chemical shift is observed for each Sn substituted into the Y second neighbor coordination environment. The spectral signal intensities of the possible combinations of Sn/Ti neighbors match those predicted statistically assuming a random distribution of Sn4+/Ti4+ on the six-coordinated pyrochlore B site.

Journal Article↗
PubMed2006

Magic structures of h-passivated 110 silicon nanowires.

We report a genetic algorithm approach combined with ab initio calculations to determine the structure of hydrogenated 110 Si nanowires. As the number of atoms per length increases, we find that the cross section of the nanowire evolves from chains of six-atom rings to fused pairs of such chains to hexagons bounded by {001} and {111} facets. Our calculations predict that hexagonal wires become stable starting at about 1.2 nm diameter, which is consistent with recent experimental reports of nanowires with diameters of about 3 nm.

Hydrogen↗
PubMed2000

The magical age of 10.

Developmental processes of "puberty" and their cultural contexts in understanding the emergence of sexual subjectivity, especially sexual attraction, prior to gonadarche are critically examined. In particular, we consider the hypothesis that "sexual attraction" follows the onset of adrenal puberty, termed adrenarche, precipitating the development of stable and memorable attraction toward others approximately by the age of 10. In a prior study, the authors suggested that adrenarche is a significant source of this developmental change in sexuality (McClintock, M., and Herdt, G., 1996). The inferential evidence from New Guinea is compared with recent studies from the United States, including clinical findings on "precocious puberty." We conclude with the question of whether the age of 10 is a human universal in the development of attraction and sexuality.

Child↗
PubMed2000

Might and magic, lust and language--the eye as a metaphor in literature. Notes on the hierarchy of the senses.

The special anatomy and physiology of the eye predestine it to function as the primary mediator between the world within us and the world without. The way we respond to and reflect on our world is strongly associated with our eyesight. Since antiquity literature, the most important medium for propagating knowledge, has abounded with symbols for the motif 'eye,' symbolizing the responsibility, independence and significance of the visual sense. Today the mechanisms of the modern information media engulf us with new and permanent stimuli. If we surrender ourselves uncritically to this profusion of images, we risk 'overstraining' our sense of sight and losing the connection between perception and cognition. In the following a few references to the international non-medical literature may explain and illustrate the functions of the eye as a metaphor for the mind and describe the past and the prospects of visual perception.

Eye↗
PubMed1999

Resonance assignment of 13C/15N labeled solid proteins by two- and three-dimensional magic-angle-spinning NMR.

The comprehensive structure determination of isotopically labeled proteins by solid-state NMR requires sequence-specific assignment of 13C and 15N spectra. We describe several 2D and 3D MAS correlation techniques for resonance assignment and apply them, at 7.0 Tesla, to 13C and 15N labeled ubiquitin to examine the extent of resonance assignments in the solid state. Both interresidue and intraresidue assignments of the 13C and 15N resonances are addressed. The interresidue assignment was carried out by an N(CO)CA technique, which yields Ni-C alpha i-1 connectivities in protein backbones via two steps of dipolar-mediated coherence transfer. The intraresidue connectivities were obtained from a new 3D NCACB technique, which utilizes the well resolved C beta chemical shift to distinguish the different amino acids. Additional amino acid type assignment was provided by a 13C spin diffusion experiment, which exhibits 13C spin pairs as off-diagonal intensities in the 2D spectrum. To better resolve carbons with similar chemical shifts, we also performed a dipolar-mediated INADEQUATE experiment. By cross-referencing these spectra and exploiting the selective and extensive 13C labeling approach, we assigned 25% of the amino acids in ubiquitin sequence-specifically and 47% of the residues to the amino acid types. The sensitivity and resolution of these experiments are evaluated, especially in the context of the selective and extensive 13C labeling approach.

Amino Acid Sequence↗
PubMed2000

Three-dimensional structure determination of a uniformly labeled molecule by frequency-selective dipolar recoupling under magic-angle spinning.

The complete three-dimensional (3D) structure of a glycylisoleucine (Gly-Ile) molecule was determined by individually measuring six dihedral angles with a frequency-selective homonuclear dipolar recoupling method, R2TR (rotational resonance in the tilted rotating frame), using a powder sample of diluted uniformly 13C,15N-labeled Gly-Ile. Each dihedral angle was obtained by recoupling a dipolar interaction between three or four bonds distant spins concerned or observing a dipolar correlation 2D powder pattern. The 3D structure of a Gly-Ile molecule was also determined by X-ray crystallography, and a good agreement with the NMR result was obtained. The results demonstrate that the R2TR method in a uniformly labeled powder sample can provide the 3D structure without the need to prepare a lot of selectively labeled samples.

Carbon Isotopes↗
PubMed2001

Ordinary magic. Resilience processes in development.

The study of resilience in development has overturned many negative assumptions and deficit-focused models about children growing up under the threat of disadvantage and adversity. The most surprising conclusion emerging from studies of these children is the ordinariness of resilience. An examination of converging findings from variable-focused and person-focused investigations of these phenomena suggests that resilience is common and that it usually arises from the normative functions of human adaptational systems, with the greatest threats to human development being those that compromise these protective systems. The conclusion that resilience is made of ordinary rather than extraordinary processes offers a more positive outlook on human development and adaptation, as well as direction for policy and practice aimed at enhancing the development of children at risk for problems and psychopathology.

Adaptation, Psychological↗
PubMed1996

The magical number .7 +/- .2: meta-meta-analysis of the probability of superior outcome in comparisons involving therapy, placebo, and control.

The "probability of superiority estimate" (PS) estimates the probability that a randomly sampled client from a population given a treatment will have an outcome that is superior to that of a randomly sampled client from a population given another treatment. The meta-analytic clinical outcome literature was examined to calculate mean PS (PS) for comparisons involving therapy versus control, therapy versus placebo, therapy versus therapy, and placebo versus control. The range of PS was found to be approximately .7 +/- .2, with median PS greatest when therapy and control are compared (Mdn PSTC = .70, where T = therapy and C = control) and least when 2 therapies are compared (Mdn PSTT = .56). Results suggested that there is more to therapeutic success than placebo effects (Mdn PSTP = .66, where T = therapy and P = placebo) and that placebo is typically better than do-nothing control conditions (Mdn PSPC = .62). The present exceptionally large study, controlling for dependencies and confounding variables, may put to rest the question of the superiority of therapy to placebo. It also appears that the strength of effect of therapy is typically at least average among the effects of independent variables in psychology.

Adult↗
PubMed1977

Muck is magic.

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Agriculture↗