Comparison of alternative N-staging models in patients with oral cancer. Is nodal yield or burden the most critical parameter?

Background: There is increasing evidence in the literature that alternative N-classification systems offer a simpler and more precise risk stratification than the current N- classification in patients with oral squamous cell carcinoma. The purpose of this study is to compare three broadly proposed models incorporating lymph node ratio, log odds of positive lymph nodes and number of positive lymph nodes regarding disease-free and overall survival.

Methods: This is a retrospective study of patients treated in a single center between 2013 and 2019.

Vibrational spectra and gas-phase structure of N-methyl-S,S-bis(trifluoromethyl)sulfimide, CH3N=S(CF3)2.

The molecular structure of N-methyl-S,S-bis(trifluoromethyl)sulfimide, CH3N=S(CF3)2, was determined by gas electron diffraction and quantum chemical calculations [B3LYP and MP2 with 6-31+G(2df,p) basis sets]. Furthermore, vibrational spectra, IR (gas) and Raman (liquid), were recorded. These spectra were assigned by comparison with analogous molecules and with calculated frequencies and intensities (HF, B3LYP, and MP2 with 6-311G basis sets).

Fluoroformyl trifluoroacetyl disulfide, FC(O)SSC(O)CF3: synthesis, structure in solid and gaseous states, and conformational properties.

Fluoroformyl trifluoroacetyl disulfide, FC(O)SSC(O)CF3, is prepared by quantitative reaction between FC(O)SCl and CF(3)C(O)SH. The conformational properties and geometric structure of the gaseous molecule have been studied by vibrational spectroscopy (IR(gas), Raman(liquid), IR(matrix)), gas electron diffraction (GED), and quantum chemical calculations (B3LYP and MP2 methods). The disulfide bond length derived from the GED analysis amounts 2.

Perfluoromethyl fluorocarbonyl peroxide, CF3OOC(O)F: structure, conformations, and vibrational spectra studied by experimental and theoretical methods.

The conformational properties and the geometric structure of perfluoromethyl fluorocarbonyl peroxide, CF(3)OOC(O)F, have been studied by matrix IR spectroscopy, gas electron diffraction, and quantum chemical calculations (HF, B3LYP, and MP2 methods with 6-311G* basis sets). Matrix IR spectra imply a mixture of syn and anti conformers (orientation of the C=O bond relative to the O-O bond) with DeltaH degrees = H(anti) degrees - H(syn) degrees = 2.16(22) kcal/mol.

Gas phase structure of O-nitrobis(trifluoromethyl)hydroxylamine, (CF3)2NONO2: an extremely long O-N bond.

The gas phase structure of O-nitrobis(trifluoromethyl)hydroxylamine, (CF(3))(2)NONO(2), has been determined with gas electron diffraction and quantum chemical calculations (HF, MP2, and B3LYP with 6-31G basis sets). The calculations predict a structure with C(s) overall symmetry, a planar NONO(2) skeleton, and the NO(2) group oriented anti with respect to the CNC plane. The electron diffraction intensities are reproduced very well with such a model.