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.     

Ortho effect in the Bergman cyclization: electronic and steric effects in hydrogen abstraction by 1-substituted naphthalene 5,8-diradicals

We present a detailed theoretical study of geometries, electronic structure, and energies of transition states and intermediates completing the full Bergman cycloaromatization pathway of ortho-substituted enediynes with a focus on polar and steric contributions to the kinetics and thermodynamics of hydrogen abstraction. This study provides a rare unambiguous example of remote substitution that affects reactivity of a neutral reactive intermediate through an sigma framework.     

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.     

In search of efficient 5-endo-dig cyclization of a carbon-centered radical: 40 years from a prediction to another success for the Baldwin rules

Despite being predicted to be stereoelectronically favorable by the Baldwin rules, efficient formation of a C-C bond through a 5-endo-dig radical cyclization remained unknown for more than 40 years. This work reports a remarkable increase in the efficiency of this process upon beta-Ts substitution, which led to the development of an expedient approach to densely functionalized cyclic 1,3-dienes. Good qualitative agreement between the increased efficiency and stereoselectivity for the 5-endo-dig cyclization of Ts-substituted vinyl radicals and the results of density functional theory analysis further confirms the utility of computational methods in the design of new radical processes. Although reactions of Br atoms generated through photochemical Ts-Br bond homolysis lead to the formation of cyclic dibromide side products, the yields of target bromosulfones in the photochemically induced reactions can be increased by recycling the dibromide byproduct into the target bromosulfones through a sequence of addition/elimination reactions at the exocyclic double bond. Discovery of a relatively efficient radical 5-endo-dig closure, accompanied by a C-C bond formation, provides further support to stereoelectronic considerations at the heart of the Baldwin rules and fills one of the last remaining gaps in the arsenal of radical cyclizations.     

Green synthesis of silver nanoparticles using Solanum indicum L. and their antibacterial,splenocyte cytotoxic potentials

Research on Chemical Intermediates - Green synthesis of silver nanoparticles was carried out using Solanum indicum L. plant extract as a reducing agent. The morphology of the AgNPs was determined...     

Synthesis and Characterization of a Novel Heterocyclic Schiff Base and Development of a Fluorescent Sensor for Vitamin B12

Journal of Fluorescence - A heterocyclic Schiff base (MPDPI)was synthesized by the condensation reaction of 1-phenylisatin with 4,5-dimethylphenylene diamine. It was characterized by using...