1,3-Dipolar Cycloaddition (Part II): Three-Component Cu(I) Catalysed Click Reactions

Cu(I) kataliziranim reakcijama sulfonil- odnosno fosforil-azida i terminalnih alkina nastaje intermedijar ketenimin koji reagira s nukleofilima kao što su voda, alkoholi, amini, piroli ili indoli, pri čemu nastaju odgovarajući amidi, imidati, amidini i supstituirani heterocikli, u jednom reakcijskom koraku. Te selektivne reakcije zbivaju se pri blagim reakcijskim uvjetima (sobna temperatura, prisustvo zraka i vode), bez steričkog i elektronskog utjecaja supstituenata na ishod reakcije.The Cu(I) catalysed reaction of sulfonyl or phosphoryl azide and terminal alkyne obtains a ketenimine intermediate that reacts with nucleophiles like water, alcohols, amines, imines, pyrroles or indoles producing corresponding amides, imidates, amidines and substituted heterocycles, in one reaction step. These selective reactions are characterised by mild reaction conditions (room temperature, presence of air and water), without steric or electron influence of substituents on the reaction outcome

Novel symmetric bis-benzimidazoles: Synthesis, DNA/RNA binding and antitrypanosomal activity.

The novel benzimidazol-2-yl-fur-5-yl-(1,2,3)-triazolyl dimeric series with aliphatic and aromatic central linkers was successfully prepared with the aim of assessing binding affinity to DNA/RNA and antitrypanosomal activity. UV-Visible spectroscopy, thermal denaturation showed interaction of heterocyclic bis-amidines with ctDNA. Circular dichroism studies indicated uniform orientation of heterocyclic bis-amidines along the chiral double helix axis, revealing minor groove binding as the dominant binding mode. The amidino fragment and 1,4-bis(oxymethylene)phenyl spacer were the main determinants of activity against Trypanosoma brucei. The bis-benzimidazole imidazoline 15c, which had antitrypanosomal potency in the submicromolar range and DNA interacting properties, emerged as a candidate for further structural optimization to obtain more effective agents to combat trypanosome infections

Calorimetric study of geopolymer binders based on natural pozzolan

This paper investigates the kinetics of geopolymerisation in an inorganic polymeric binder based on a natural pozzolan. The heat released by the exothermic geopolymerisation reaction process is monitored under isothermal temperature conditions, maintained in a differential scanning calorimeter using a water circulation cell. Calorimetric data are obtained isothermally at 65, 75, and 85 °C with various Na2O/Al2O3 and SiO2/Na2O molar ratios and in the presence and absence of small amounts of calcium aluminate cement (used as an efflorescence control admixture in these binder systems). The first stage of reaction, which is rapid and strongly exothermic, is shortened as the temperature increases. The total heat of reaction increases in the mixes containing calcium aluminate cement, but the apparent activation energy calculated using a pseudo-first-order reaction model is lower than without added calcium aluminate cement. At a constant overall SiO2/Na2O molar ratio, the apparent activation energy is decreased as the Na2O/Al2O3 molar ratio increases. Calcium aluminate cement, therefore, reduces the minimum energy required to initiate geopolymerisation reactions of this natural pozzolan and facilitates the progress of the reactions which lead to formation of a cementitious product

Thermographic Analysis of Stress Distribution in Welded Joints

The fatigue life prediction of welded joints based on S-N curves in conjunction with nominal stresses generally is not reliable. Stress distribution in welded area affected by geometrical inhomogeneity, irregular welded surface and weld toe radius is quite complex, so the local (structural) stress concept is accepted in recent papers. The aim of this paper is to determine the stress distribution in plate type aluminum welded joints, to analyze the reliability of TSA (Thermal Stress Analysis) in this kind of investigations, and to obtain numerical values for stress concentration factors for practical use. Stress distribution in aluminum butt and fillet welded joints is determined by using the three different methods: strain gauges measurement, thermal stress analysis and FEM. Obtained results show good agreement - the TSA mutually confirmed the FEM model and stresses measured by strain gauges. According to obtained results, it may be stated that TSA, as a relatively new measurement technique may in the future become a standard tool for the experimental investigation of stress concentration and fatigue in welded joints that can help to develop more accurate numerical tools for fatigue life prediction