Intensification of separation effects of nanoporous polymeric membranes in the gas separation processes

The purpose of the present work is the intensification of the separation effects of nanoporous polymeric membranes in the gas separation processes by the use of the membrane modules with feeding reservoir

X-ray study of the electric double layer at the n-hexane/nanocolloidal silica interface

The spatial structure of the transition region between an insulator and an electrolyte solution was studied with x-ray scattering.The electron density profile across the n-hexane/silica sol interface (solutions with 5-nm, 7-nm, and 12-nm colloidal particles) agrees with the theory of the electrical double layer and shows separation of positive and negative charges. The interface consists of three layers, i.e., a compact layer of Na+, a loose monolayer of nanocolloidal particles as part of a thick diffuse layer, and a low-density layer sandwiched between them. Its structure is described by a model in which the potential gradient at the interface reflects the difference in the potentials of "image forces" between the cationic Na+ and anionic nanoparticles and the specific adsorption of surface charge. The density of water in the large electric field (1-10 GV/m) of the transition region and the layering of silica in the diffuse layer is discussed.Comment: 9 pages, 9 figure

The Kinetics of the Adiabatic and Nonadiabatic Reactions at the Metal and Semiconductor Electrodes

The basic results of the correct quantum-mechanical calculqtions of the probability of the elementary act of adiabatic homogeneous reactions are summarized. The calculations are carried out for the model of the one-dimensional potential energy curves without using the perturbation theory. The adiabatic and nonadiabatic electrochemical reactions at the metal and semiconductor electrodes are considered. The physical picture of the process is discussed. The adiabatic electrochemical process is shown to be of the many-electron character. The expressions for the transition probability is derived for the metal and semiconductor electrodes. The redox reactions at the semiconductor are considered in the presence of the surface states

Ion-Size Effect at the Surface of a Silica Hydrosol

The author used synchrotron x-ray reflectivity to study the ion-size effect for alkali ions (Na$^+$, K$^+$, Rb$^+$, and Cs$^+$), with densities as high as $4 \times 10^{18}- 7 \times 10^{18}$ m$^{-2}$, suspended above the surface of a colloidal solution of silica nanoparticles in the field generated by the surface electric-double layer. According to the data, large alkali ions preferentially accumulate at the sol's surface replacing smaller ions, a finding that qualitatively agrees with the dependence of the Kharkats-Ulstrup single-ion electrostatic free energy on the ion's radius.Comment: 17 pages, 4 figure

Crystals of Na+ ions at the surface of a silica hydrosol

I used x-ray grazing incidence diffraction to measure the spatial correlations between sodium ions adsorbed with Bjerrum's density at the surface of a monodispersed 22-nm-particle colloidal silica solution stabilized by NaOH with a total bulk concentration mol/L. My findings show that the surface compact layer is in a two-dimensional crystalline state (symmetry p2), with four ions forming the unit cell and a ~30 Angstrom translational correlation length between sodium ions.Comment: 13 pages, 4 figure

Torsional fluctuations in columnar DNA assemblies

In columnar assemblies of helical bio-molecules the azimuthal degrees of freedom, i.e. rotations about the long axes of molecules, may be important in determining the structure of the assemblies especially when the interaction energy between neighbouring molecules explicitly depends on their relative azimuthal orientations. For DNA this leads to a rich variety of mesophases for columnar assemblies, each categorized by a specific azimuthal ordering. In a preceding paper [A. Wynveen, D. J. Lee, and A. A. Kornyshev, Eur. Phys. J. E, 16, 303 (2005)] a statistical mechanical theory was developed for the assemblies of torsionally rigid molecues in order to determine how thermal fluctuations influence the structure of these mesophases. Here we extend this theory by including torsional fluctuations of the molecules, where a DNA molecule may twist about its long axis at the cost of torsional elastic energy. Comparing this with the previous study, we find that inclusion of torsional fluctuations further increases the density at which the transition between the hexagonal structure and the predicted rhombic phase occurs and reduces the level of distortion in the rhombic phase. As X-ray diffraction may probe the 2-D lattice structure of such assemblies and provide information concerning the underlying interaction between molecules, we have also calculated correlation functions for the azimuthal ordering which are manifest in an x-ray scattering intensity profiles.Comment: 33 pages, 8 figure

Efficacy of regional analgesia techniques in abdominal surgery patients with obesity

Abstract The use of regional anesthetic techniques in abdominal surgery is an essential component of the multimodal approach to perioperative analgesia, yet data on their use in obese patients remains limited. The aim of this study is to determine the effectiveness of the epidural analgesia (EA) and the transversus abdominis plane block (TAP-block) in laparoscopic obese patients, as well as to evaluate the possibility of using the rectus sheath block (RSB) as a “rescue” anesthetic technique after laparotomy in obese patients. Materials and methods. The data on the 102 obese patients operated on esophageal hiatal diaphramgmatic hernia, colon tumor, postoperative ventral hernia, morbid obesity and choledocholithiasis were analyzed. In laparoscopic surgery 20 patients received EA (EA group), 21 patients – TAP-block (TAP group), 21 patients – opioids and non-steroidal anti-inflammatory drugs (NSAIDs) without any regional anesthesia techniques (group TIVA1). In laparotomic surgery 16 patients received RSB (RSB group) and 24 patients – only opioids and NSAIDs (TIVA2 group). After the surgery the following was estimated: the time of extubation, the total dose of opioids, the level of pain according to the 10-point numeric range score (NRS), the incidence of dyspnea using the monitor Utas 300 (Ukraine), the incidence of postoperative nausea and vomiting (PONV), the time of active patient mobilization, and the level of satisfaction with analgetic regimen. For the RSB group, the complexity of the RSB and the mean time to achieve adequate analgesia (pain intensity ≤3 points per NRS) were determined additionally. The statistical analysis was performed using the Statistica for Windows version 6.0 software. Results. In the EA group, the intraoperative dose of fentanyl was twice lower, and patients were extubated two times faster than in the TAP, TIVA1, RSB, TIVA2 groups (P < 0.05). At the same time, none of the patients in the EA group required the restoration of neuromuscular conduction with neostigmine (P < 0.05). After the surgery, the pain level was 2–3 times higher in the TIVA1, RSB, and TIVA2 groups than in the EA and TAP groups (P < 0.05). “Rescue” analgesia in the RSB group was performed from the first attempt in all the patients in 5–10 minutes and provided an adequate effect in 3 (2–4) min. The complexity level of RSB was defined as “easy” in 12 (75 %) patients, as “average” in 4 (25 %) patients (P < 0.05). The incidence of dyspnea and opioid doses after surgery in the EA, TAP and RSB groups of patients were 2 times lower, and the incidence of PONV was 3 to 4 times lower than in the TIVA1 and TIVA2 patients’ groups (P < 0.05). In the EA and TAP groups, patients became mobile after 8–13 hours after surgery, in the group TIVA1 – after 16–22 hours, in the group RSB – after 18–36 hours, in the group TIVA2 – after 48–96 hours (P < 0.05). 100 % of the respondents from the EA, TAP and RSB groups were satisfied with the analgesic regimen at the “excellent – good” level. In the TIVA1 and TIVA2 groups, 20–25 % of respondents identified analgesic comfort as “good”, 60–65 % of respondents – as “satisfactorily”, about 15 % of respondents – as “unsatisfactorily” (P < 0.05). Conclusions. In laparoscopic surgery the use of EA or TAP-block in obese patients significantly reduces the level of postoperative pain, the need for opioids, the incidence of dyspnea and PONV, which leads to the possibility of patients’ mobilization within 8–13 hours after surgery. After laparotomic surgery in obese patients RSB effectively “rescues” from pain and prevents excessive use of opioids, which reduces the number of adverse reactions and increases satisfaction with the quality of analgesia

Palladium Nanoparticles–Polypyrrole Composite as Effective Catalyst for Fluoroalkylation of Alkenes

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Abstract: Palladium nanoparticles–polypyrrole composite (Pd/PPy) catalyzes the addition of perfluoroalkyl halides to olefins to produce a variety of products with good yields. An effective fluoroalkylation technique tested with various olefins, fluoroalkyl halides and Pd/PPy was developed. The reaction proceeds highly efficient under mild phosphine-free reaction conditions with different substrates, easy catalyst recycling and provides a general and straightforward access to fluoroalkylated products. Furthermore, we were able to control whether the addition of perfluoroalkyl occurs with various monomer (fluoroalkylated alkene or alkane with RF and OH moieties) or dimer formation (under electrochemical conditions). Graphical Abstract: [Figure not available: see fulltext.]