Highly temperature responsive core-shell magnetic particles: synthesis, characterization and colloidal properties

Three new dimeric cholesterol-based compounds of A(LS)(2) type, where A stands for aromatic component, S steroid moiety, and L a linker connecting the two units, have been designed and prepared. Gelation test in 30 solvents demonstrated that the compounds can gel some of the solvents and form 37 gels, of which 16 form spontaneously at room temperature (~25 °C). These gels possess smart thixotropic properties as revealed by rheological studies. FTIR and (1)H NMR measurements revealed that hydrogen bonding is an important driving force for the formation of the gel networks. XRD analysis demonstrated that unlike commonly found layered structures adopted by dimeric cholesterol-based low-molecular mass gelators (LMMGs), one of the gelators created in this study adopts a hexagonal packing structure in its benzene gel.     

Monodispersed Gold Nanoparticles Decorated Carbon Nanotubes as an Enhanced Sensing Platform for Nanomolar Detection of Tramadol

A promising composite‐modified glassy carbon electrode is fabricated by electrodeposition of mono‐dispersed gold nanoparticles onto carbon nanotubes (AuNPs/CNTs/GCE). The electroanalysis of Tramadol (TRA) was achieved by different electrochemical techniques. The effect of different parameters including pH, concentration and potential scan on the oxidation current signal of TRA was investigated. Large excess of ascorbic acid (AA) and uric acid (UA) with a maximum molar ratio of 1/1000 and 1/100, respectively, did not interfere with the response of TRA. The detection limit with high sensitivity is 68 nM. TRA was successfully determined in pharmaceutical dosage forms, without any pretreatment of the samples.     

A mixed breadth-depth first strategy for the branch and bound tree of Euclidean k-center problems

The k-center problem arises in many applications such as facility location and data clustering. Typically, it is solved using a branch and bound tree traversed using the depth first strategy. The reason is its linear space requirement compared to the exponential space requirement of the breadth first strategy. Although the depth first strategy gains useful information fast by reaching some leaves early and therefore assists in pruning the tree, it may lead to exploring too many subtrees before reaching the optimal solution, resulting in a large search cost. To speed up the arrival to the optimal solution, a mixed breadth-depth traversing strategy is proposed. The main idea is to cycle through the nodes of the same level and recursively explore along their first promising paths until reaching their leaf nodes (solutions). Thus many solutions with diverse structures are obtained and a good upper bound of the optimal solution can be achieved by selecting the minimum among them. In addition, we employ inexpensive lower and upper bounds of the enclosing balls, and this often relieves us from calling the computationally expensive exact minimum enclosing ball algorithm. Experimental work shows that the proposed strategy is significantly faster than the naked branch and bound approach, especially as the number of centers and/or the required accuracy increases.     

Synthesis and anti-arrhythmic activity of some piperidine-based 1,3-thiazole, 1,3,4-thiadiazole, and 1,3-thiazolo[2,3-c]-1,2,4-triazole derivatives

Abstract  The reaction of 1-[4-(piperidin-1-yl)benzylidene]thiosemicarbazide with hydrazonoyl chlorides afforded 1,3-thiazole derivatives. Cyclization of two compounds of the latter 1,3-thiazole by means of bromine in the presence of sodium acetate at room temperature gave 1,3-thiazolo[2,3-c]-1,2,4-triazole derivatives. The reaction of 2-cyano-3-(4-piperidin-1-ylphenyl)prop-2-enethioamide with hydrazonoyl chlorides under reflux in ethanol in the presence of triethylamine yielded 1,3-thiazoles. Treatment of 3-oxo-3-(piperidin-1-yl)propanenitrile with phenyl isothiocyanate in DMF, in the presence of KOH, at ambient temperature, resulted in the formation of 3-anilino-3-mercapto-2-(piperidin-1-ylcarbonyl)acrylonitrile which was reacted with hydrazonoyl chlorides to yield the corresponding 1,3,4-thiadiazole derivatives. Some of the newly synthesized compounds had significant anti-arrhythmic activity. Graphical Abstract        

Synthesis and Application of Some Azo and Azomethine Dyes Containing Pyrazolone Moiety

3-Amino-1-phenyl-4,5-dihydro-1H-pyrazol-5-one (1) was used as starting material for the synthesis of a number of azo compounds 3a—3c and azomethine derivative 4. The deblocking of 3a—3c and 4 gave rise to 5a—5c and 6 in which a free amino was revealed. The diazonium salts of 5a—5c and 6 were coupled with several phenols to produce a number of bis azo compounds 7a—7c and 8a—8c with azomethine in position 4 and azoic group in position 3. The prepared dyes were structurally confirmed by elemental analysis, spectral methods and applied to different fibers (wool, polyester and blend of wool/polyester) as disperse dyes and their fastness properties were measured.     

Analysis of the influence of cooling hole arrangement on the protection of a gas turbine combustor liner

Numerical investigations of an industrial gas turbine combustor were conducted in this paper. The studied combustion chamber has a high degree of geometrical complexity related to the injection system as well as the cooling system which consists of thousands of small holes (about 3390 holes) bored on the liner walls. The main aim of this study was to propose modifications into the liner cooling system that can enhance the protection of this critical component. The calculations were carried out using the industrial CFD code fluent 6.3. It was shown that the addition of rows of cooling holes in the primary zone of the liner leads to a reduction of the maximum liner metal temperature of 33%. Nevertheless, this modification causes an increase of the maximum gas temperature at the outlet of the combustion chamber of 12% which could be harmful to the turbine vanes. It was also shown that this increase can be controlled by the suppression of rows of cooling holes in the dilution zone.     

Non-Lifshitz Tails at the Spectral Bottom of Some Random Operators

In this paper we continue with the investigation of the behavior of the integrated density of states of random operators of the form H _ω =−∇ ρ _ω ∇. In the present work we are interested in its behavior at 0, the bottom of the spectrum of H _ω . We prove that it converges exponentially fast to the integrated density of states of some periodic operator . Being periodic, cannot exhibit a Lifshitz behaviour. This result relates to the result of S.M. Kozlov (Russ. Math. Surv. 34(4):168–169, 1979) and improves it. Research partially supported by the Research Unity 01/UR/ 15-01 projects.     

Topological defects in the left-right symmetric model and their relevance to cosmology

It is shown that the minimal left-right symmetric model admits cosmic string and domain wall solutions.