Altered condylar morphology associated with disc displacement in TMJ dysfunction: observations by MRI

Magnetic resonance images of 276 TM joints in 138 symptomatic patients were analyzed in a retrospective study to determine the condylar shape and size and to correlate it with internal derangement. Internal derangement by MRI was noted in 66% of the TM joints. Our study demonstrates that the regressive condylar changes in TM joints with internal derangement were more common (61%) than proliferative bony changes (39%). On the converse, none of the TM joints with regressive condyles revealed normal disc. The altered bony morphology also correlated with the severity of internal derangement, i.e. bony changes in TM joints with anterior closed lock were noted in 64% compared to 45% with reducible disc. The cause and effect relationship of the regressive condylar remodeling and disc abnormality is not clear and needs further study.     

NDDO MO calculations: isotropic hyperfine coupling constants and nuclear spin-spin coupling constants

The nonempirical NDDO MO method in its unrestricted form has been used to evaluate isotropic hyperfine coupling constants and nuclear spin-spin coupling constants. Satisfactory agreement with INDO and experimental results is obtained.     

NDDO MO calculations

Three valence-only schemes based on the Roby version of NDDO MO theory, which differ only in the core-valence treatment and the choice of the basis set, have been applied to the study of molecules containing first-row atoms. Orbital energies, charge distribution, dipole moments, field gradients, and a few other one-electron molecular properties are calculated to satisfactory accuracy. The schemes appear unreliable in the prediction of barriers to internal rotation in molecules, presumably due to errors in the core contribution to the total energy. An alternative treatment is suggested.     

Magneto-resistance above 300 K in nano-crystalline Co–Ag metastable solid solutions

A series of nano-crystalline Co_xAg_100−x solid solutions have been prepared by NaBH₄ reduction of the corresponding metal salts at room temperature in Ar gas flow. Alloys heat-treated at 600 °C in Ar/H₂ (5%) show the evolution of metastable fcc Co precipitates in Ag. Magnetic studies indicate that all the compositions are ferromagnetic with Curie temperatures >400 K. For a nominal composition of Co₆₀Ag₄₀, heat-treated at 600 °C, an effective negative magneto-resistance (MR) ratio of the order of ∼21% at 350 K, at 2 T is observed. This could arise from the influence of magnetic field on the electron–phonon scattering effects near to T_c and to the spin-mixing scattering by magnons.     

Crystal and molecular structure ofN-methylphenazinium bis(maleodinitriledithiolato)nickelate(III), [NMP]+ [Ni(mnt)2]−

The crystal and molecular structure of the title compound, C₂₁H₁₁N₆S₄Ni, is reported. The crystals are triclinic:P¯1 (No. 2),Z=4,a=8.768(1),b=11.817(3),c=22.131(3) Å,=97.44(1),=91.90(1), and =94.04(1)°. The structure was solved by the heavy-atom method, and refined by full-matrix least squares toR=0.039 for 3213 unique reflections. The Ni atoms of both anions in the asymmetric unit have an approximately square-planar configuration. Anions and cations form segregated stacks alonga. The stacking of the anions along this direction is dimeric, with alternating Ni-Ni distances 4.111(2) and 7.593(2) Å for molecule I and 4.208(1) and 8.155(2) Å for molecule II. Static susceptibility measurements show strong antiferromagnetic coupling (2J=-241 cm^–1) between the two anions of the dimers.     

Exchange interactions in some low-dimensional metal dithiolene complexes

Low-dimensional systems are formed by planar metal dithiolene complexes which stack as columnar structures in the solid state. Stronger interactions among units within a chain leads to highly anisotropic magnetic properties. The magnetic effects are a manifestation of exchange interaction,J and can be studied through detailedepr techniques in conjunction with magnetic susceptibility and x-ray crystal structure. A brief review of such studies carried out mostly in our laboratory is presented along with the relevant background materials.     

Lefschetz fixed point theory on fibrations

For a fibre preserving map ϕ: E → E on a fibration (E, π, B), we construct a grading preserving map T(ϕ, π) between H*(E) and H*(B) that generalizes the Lefschetz number. If T(ϕ, π) is an isomorphism between H ⁰(E) and H ⁰(B), then π restricts to a surjective local diffeomorphism on each connected component of the fixed point set of ϕ under a transversality condition. This yields a characterization for the bundle H → G → G/H to be trivial when π ₁ (G/H) = 0.     

Exchange interactions in bis(diethyldithiocarbamato)copper(II), Cu(detc)2

The exchange coupling constant J in bis(diethyldithiocarbamato)copper(II) has been derived through analysis of the EPR g values and linewidth as a function of orientation, frequency and temperature. The single line in the ac* plane is due to the averaging of the fine-structure splitting by interdimer exchange for which a lower limit of 0.02 cm^?1 has been obtained. Analysis of the spectra in the bc plane gives an estimate of 0.008 cm^?1 for the intersite exchange.