A new method of visualization of lone pairs is proposed using fluorine atoms in fluoroacetylene, trifluoroethylene, and fluoroform (sp, sp 2 , and sp 3 hybridized carbons) as an example. The space around fluorines was probed by a helium atom and at each point 3 He NMR chemical shift δ He and its Laplacian r 2 δ He were calculated. The r 2 δ He isosurfaces have symmetrical toroidal shapes along CF axes; the maximum values of r 2 δ He are reached at about 1.5 Å from fluorine atom center in the direction roughly coinciding with the lone pair localization. The absolute values of the r 2 δ He could be used to quantify the electron-rich regions of lone pairs. The results are compared with more common visualization methods-3D maps of the molecular electrostatic potential and the electron localization function. We show that a helium atom could be used for evaluation of fine features of molecular electronic shell, since 3 He NMR spectral characteristics remain sensitive at relatively large distances.

No abstract

In this work, we present the first results of outer electronic shell visualization by using a He atom as a probe particle. As model objects we have chosen F, FH, and FH species, as well as the hydrogen-bonded complex FH···F at various H···F distances (3.0, 2.5, 2.0, and 1.5 Å and equilibrium at ca. 1.14 Å). The interaction energy of investigated objects with helium atom (CCSD/aug-cc-pVTZ) and helium atom chemical shift (B3LYP/pcS-2) surfaces were calculated, and their topological analysis was performed. For comparison, the results of standard quantum mechanical approaches to electronic shell visualization were presented (ESP, ELF, ED, ∇ED). We show that the Laplacian of helium chemical shift, ∇δ, is sensitive to fluorine atom lone pair localization regions, and it can be used for the visualization of the outer electronic shell, which could be used to evaluate the proton accepting ability. The sensitivity of ∇δ to lone pairs is preserved at distances as large as 2.0-2.5 Å from the fluorine nucleus (in comparison with the distance to ESP minima, located at 1.0-1.5 Å or maxima of ELF, which are as close as 0.6 Å to the fluorine nucleus).

Primary cutaneous lymphomas are quite rare in children. Clinical and histopathological manifestations of these diseases in children differ significantly from those in adults. Due to their rarity and complex clinical presentation, diagnosis may take long time. Mycosis fungoides (MF) is the most commonly diagnosed form of primary cutaneous lymphomas in childhood. There are no clinical guidelines for the treatment of children. Literature data on MF variants in children are scarce; the largest study includes 34 patients who were diagnosed on average 4 years after the onset of the first symptoms. In the present article we describe a clinical case of MF in an 11-year-old child with an 8-year history of multiple lesions of the skin and scalp. The patient's parents gave their consent to the use of their child's data, including photographs, for research purposes and in publications.   The aim of our article is to demonstrate the problems in the diagnosis of the disease, especially at an early stage, because its symptoms may be similar to those of many common pediatric inflammatory skin conditions.