Modified Technogenic Asphaltenes as Enhancers of the Thermal Conductivity of Paraffin.

The low thermal conductivity of paraffin and other organic phase change materials limits their use in thermal energy storage devices. The introduction of components with a high thermal conductivity such as graphene into these materials leads to an increase in their thermal conductivity. In this work, we studied the use of inexpensive carbon fillers containing a polycyclic aromatic core, due to them having a structural similarity with graphene, to increase the thermal conductivity of paraffin. As such fillers, technogenic asphaltenes isolated from ethylene tar and their modified derivatives were used. It is shown that the optimal concentration of carbon fillers in the paraffin composite, which contributes to the formation of a structural framework and resistance to sedimentation, is 5 and 30 wt. %, while intermediate concentrations are ineffective, apparently due to the formation of large aggregates, the concentration of which is insufficient to form a strong framework. It has been found that the addition of asphaltenes modified with ammonium persulfate in acetic acid significantly increases the thermal conductivity of paraffin by up to 72%.

Study of the molecular-structural composition of alcoholic extracts of radio-induced potato tubers by mass spectrometry and EPR.

This article presents data on electron paramagnetic resonance (EPR) and mass spectrometric analysis of potato tubers, irradiated with gamma rays, in order to examine and identify changes in the molecular composition of organic matter following radiation exposure. The products of the Maillard reaction were compared with the products of intramolecular radiolysis of organic constituents of potatoes. The presence of free radicals was verified using EPR. DDPM (2,3-dihydro-3,5-dihydroxy-6-methyl-4 (H) -pyran-4-one) was among the radiolysis products detected via mass spectrometry, which points to the intramolecular dehydration of potato carbohydrates. EPR signals indicate single-electron transitions of the semidione radical anionic molecular compounds. It has been shown that irradiation with gamma rays significantly destroys the carbohydrate, lipid, keto-carotene and amino acid molecules of potatoes.

Intravenous Tranexamic Acid Bolus plus Infusion Is Not More Effective than a Single Bolus in Primary Hip Arthroplasty: A Randomized Controlled Trial.

BACKGROUND: Preoperative administration of the antifibrinolytic agent tranexamic acid reduces bleeding in patients undergoing hip arthroplasty. Increased fibrinolytic activity is maintained throughout the first day postoperation. The objective of the study was to determine whether additional perioperative administration of tranexamic acid would further reduce blood loss. METHODS: This prospective, double-blind, parallel-arm, randomized, superiority study was conducted in 168 patients undergoing unilateral primary hip arthroplasty. Patients received a preoperative intravenous bolus of 1 g of tranexamic acid followed by a continuous infusion of either tranexamic acid 1 g (bolus-plus-infusion group) or placebo (bolus group) for 8 h. The primary outcome was calculated perioperative blood loss up to day 5. Erythrocyte transfusion was implemented according to a restrictive transfusion trigger strategy. RESULTS: The mean perioperative blood loss was 919 ± 338 ml in the bolus-plus-infusion group (84 patients analyzed) and 888 ± 366 ml in the bolus group (83 patients analyzed); mean difference, 30 ml (95% CI, -77 to 137; P = 0.58). Within 6 weeks postsurgery, three patients in each group (3.6%) underwent erythrocyte transfusion and two patients in the bolus group experienced distal deep-vein thrombosis. A meta-analysis combining data from this study with those of five other trials showed no incremental efficacy of additional perioperative administration of tranexamic acid. CONCLUSIONS: A preoperative bolus of tranexamic acid, associated with a restrictive transfusion trigger strategy, resulted in low erythrocyte transfusion rates in patients undergoing hip arthroplasty. Supplementary perioperative administration of tranexamic acid did not achieve any further reduction in blood loss.

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products.

The present review describes the current status of synthetic five and six-membered cyclic peroxides such as 1,2-dioxolanes, 1,2,4-trioxolanes (ozonides), 1,2-dioxanes, 1,2-dioxenes, 1,2,4-trioxanes, and 1,2,4,5-tetraoxanes. The literature from 2000 onwards is surveyed to provide an update on synthesis of cyclic peroxides. The indicated period of time is, on the whole, characterized by the development of new efficient and scale-up methods for the preparation of these cyclic compounds. It was shown that cyclic peroxides remain unchanged throughout the course of a wide range of fundamental organic reactions. Due to these properties, the molecular structures can be greatly modified to give peroxide ring-retaining products. The chemistry of cyclic peroxides has attracted considerable attention, because these compounds are used in medicine for the design of antimalarial, antihelminthic, and antitumor agents.

Synthesis of asymmetric peroxides: transition metal (Cu, Fe, Mn, Co) catalyzed peroxidation of beta-dicarbonyl compounds with tert-butyl hydroperoxide.

The transition metal (Cu, Fe, Mn, Co) catalyzed peroxidation of beta-dicarbonyl compounds at the alpha position by tert-butyl hydroperoxide was discovered. A selective, experimentally convenient, and gram-scale method was developed for the synthesis of alpha-peroxidated derivatives of beta-diketones, beta-keto esters, and diethyl malonate. Virtually stoichiometric (2-3/1) molar ratios of tert-butyl hydroperoxide and a dicarbonyl compound were used in the reactions with beta-diketones and beta-keto esters. The target compounds were synthesized in the highest yields from beta-keto esters (45-90%) and in somewhat lower yields from beta-diketones (46-75%) and malonates (37-67%).

Facile and selective procedure for the synthesis of bridged 1,2,4,5-tetraoxanes; strong acids as cosolvents and catalysts for addition of hydrogen peroxide to beta-diketones.

A facile, experimentally simple, and selective method was developed for the synthesis of bridged 1,2,4,5-tetraoxanes based on the reaction of hydrogen peroxide with beta-diketones catalyzed by strong acids (H(2)SO(4), HClO(4), HBF(4), or BF(3)). The yields of the target products vary from 44% to 77%. 1,2,4,5-Tetraoxanes can easily be separated from other reaction products by column chromatography. A high concentration of a strong acid is a key factor determining the selectivity of formation and the yield of 1,2,4,5-tetraoxanes. Unlike many compounds containing the O-O bond, which undergo rearrangements in acidic media, the resulting cyclic peroxides are quite stable under these conditions.