Statistical Model of Superconductivity in a 2D Binary Boson-Fermion Mixture

A two-dimensional (2D) assembly of noninteracting, temperature-dependent, composite-boson Cooper pairs (CPs) in chemical and thermal equilibrium with unpaired fermions is examined in a binary boson-fermion statistical model as the superconducting singularity temperature is approached from above. The model is derived from {\it first principles} for the BCS model interfermion interaction from three extrema of the system Helmholtz free energy (subject to constant pairable-fermion number) with respect to: a) the pairable-fermion distribution function; b) the number of excited (bosonic) CPs, i.e., with nonzero total momenta--usually ignored in BCS theory--and with the appropriate (linear, as opposed to quadratic) dispersion relation that arises from the Fermi sea; and c) the number of CPs with zero total momenta. Compared with the BCS theory condensate, higher singularity temperatures for the Bose-Einstein condensate are obtained in the binary boson-fermion mixture model which are in rough agreement with empirical critical temperatures for quasi-2D superconductorsComment: 16 pages and 4 figures. This is a improved versio

Instrumental Diagnostics and Treatment of Acute Adhesive Bowel Obstruction

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. Despite advances in medicine, acute adhesive bowel obstruction (AABO) continues to be one of the most difficult problems of emergency abdominal surgery. The study was based on the results of treatment of 150 patients with AABO from 2016 to 2018. Age of patients was from 16 to 96, Ме = 55 (38–70), men were 55 (36.6%), and women were 95 (63.3%). In the first 12 hours from the onset of the disease received 70 (46.7%) patients, from 12 to 24 hours – 30 (20%), in 50 cases (33.3%) patients were admitted a day or more after the onset of the disease. Patients had complex examination with clinical, laboratory, and radiological tests. According to the indications, CT scan and laparoscopy were performed. All patients had intra-abdominal pressure monitoring. Based on data obtained from information of ultrasound picture, the “enteral index” was offered by authors. It reflected the degree of structural and functional disorders in the small intestine. For more visual representation of the prevalence of the adhesive process, the authors during the US examination divided the anterior abdominal wall into 4 sectors (S). Early postoperative AABO were diagnosed at 9 (6%) patients. Sixty-three (42%) patients were operated. With a diffuse adhesive process, adhesiolysis was performed by laparotomy, with a local laparoscopy. Laparotomy was performed at 16 patients. Laparoscopy was performed at 47 cases, of which 43 (91.5%) patients had successful results of adhesiolysis. The new therapeutic and diagnostic algorithm allowed to reduce the duration of the diagnostic stage for adhesive bowel obstruction with strangulation up to 3 h (2.75–3.25), and it determined the indications for surgery in a timely manner. The rate of postoperative complications was 14.3%, postoperative mortality was 7.9%, and “good” long-term treatment results were obtained in 64.9% of patient

Crystal structure and Hirshfeld surface analysis of 6-Amino-8-phenyl-1,3,4,8-Tetra­hydro-2H-pyrido[1,2-A]pyrimidine-7,9-dicarbo­nitrile

In the title compound, C16H15N5, the 1,4-di­hydro­pyridine ring has a shallow boat conformation, while the 1,3-diazinane ring adopts an envelope conformation. In the crystal, pairwise N-H⋯N hydrogen bonds generate centrosymmetric dimers featuring R 2 2(12) motifs and C-H⋯N contacts connect these dimers to form double layers lying parallel to (001). Weak C-H⋯π and N-H⋯π inter­actions help to consolidate the double layers and van der Waals inter­actions occur between layers. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from H⋯H (38.5%), N⋯H/H⋯N (33.3%) and C⋯H/H⋯C (27.3%) contacts. © 2021

Crystal structure and Hirshfeld surface analysis of 6-Amino-8-(2,6-di­chloro­phen­yl)-1,3,4,8-Tetra­hydro-2H-pyrido[1,2-A]pyrimidine-7,9-dicarbo­nitrile

In the mol­ecular structure of the title compound, C16H13Cl2N5, the 1,4-di­hydro­pyridine ring of the 1,3,4,8-Tetra­hydro-2H-pyrido[1,2-A]pyrimidine ring system adopts a screw-boat conformation, while the 1,3-diazinane ring is puckered. In the crystal, inter­molecular N-H⋯N and C-H⋯N hydrogen bonds form mol­ecular sheets parallel to the (110) and ( 10) planes, crossing each other. Adjacent mol­ecules are further linked by C-H⋯π inter­actions, which form zigzag chains propagating parallel to [100]. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from N⋯H/H⋯N (28.4%), H⋯H (24.5%), C⋯H/H⋯C (21.4%) and Cl⋯H/H⋯Cl (16.1%) contacts. © 2021