on the occasion of his 80th birthday A normal coordinate analysis of the vibration spectrum of crystalline V20, is carried out in the assumption of a Urey-Bradley force field. The calculated frequencies are adjusted to 29 experimental infrared and Raman frequencies by an automatic force constant refinemeat program. Analysis of the potential energy distribution and the atomic displacements allows the classification of the modes into nine types of oxygen vibrations and three types of chain modes. A discussion is given of effective charges and infrared intensities. An assignment of the infrared spectrum of polycrystalline V,O, is added. The inErared (IR) spectrum of V,O,, and to a lesser extent the Raman spectrum, have been the subject of several papers [l to 111. Due to the complicated lattice structure and the high number of fundamentals, the assignment of experimental frequencies without normal-mode calculations has necessarily been restricted t o a few bands in the higher-frequency range. A thorough understanding of the vibration spectrum is however of both academic and practical importance. The latter is illustrated by the frequent use of the TR spectrum of V,O, catalysts as a monitor for bond changes which occur a t different stages of the reaction.Some years ago, Gilson et al. [8] have published an extended list of IR and Raman frequencies of V,O,, together with calculated frequencies and bond assignments. As we have already shown in a previous paper [lo], the experimental frequencies as determined by Gilson et al. deviate substantially from the correct values. We have therefore carried out new normal-mode calculations starting from our own IR and Raman data. The calculated frequencies are fitted to the experimental ones by adjusting the force constants in an automatic least-squares fitting program. We found that a simple valence force field is inadequate for a reasonable fit to some of the important bands. The fit was markedly improved by allowance for repulsive action between non-bonded atoms (UB force field).
The objective of this study was to evaluate the appearance of localized giant cell tumour of the tendon sheath (GCTTS) on unenhanced and Gd-enhanced MR images. MR images of 13 histologically proven cases of localized GCTTS were evaluated for mean size, location, homogeneity and signal intensity (SI) on both T1- and T2-weighted images, and enhancement pattern. All lesions except 1 affected young adults. On T1- and T2-weighted images, lesions showed predominantly low SI equal to or slightly higher than skeletal muscle. On Gd-enhanced T1-weighted images, strong homogeneous enhancement was seen. These findings reflect the underlying histological composition of the lesion; haemosiderin deposition in xanthoma cells, shortening T2-relaxation time, and abundant collagenous proliferation are responsible for low SI on T1- and T2-weighted images. Strong homogeneous enhancement originates from numerous proliferative capillaries in the collagenous stroma. We conclude that these characteristic MR features, together with clinical information, are a valuable diagnostic tool in offering a correct preoperative diagnosis.
The aim of this study was to investigate, in 114 stroke patients, the frequency of occurrence of a largely unknown neurological disorder, characterized by a postural imbalance due to a 'pushing away' reaction of the body towards the contralesional side of space, in function of hemispheric lesion localization and gender. The study also investigate the relation of this contraversive pushing with active movement, somatosensory perception deficits and, in particular, inattention of contralesional hemispace and body. The similarity of the presence of contraversive pushing and the syndrome of spatial hemineglect together with a gender-related differentiation suggest the existence of a "pusher syndrome", in which the pathophysiology points in the direction of a spatial higher-order processing deficit, related to spatial inattention, underlying the higher frequency and severity of contraversive pushing after right brain lesions.
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