Finite element method for the stress analysis of isotropic cylindrical helical spring

This paper presents an efficient two nodes finite element with six degrees of freedom per node, capable to model the total behaviour of a helical spring. The formulation, which includes the shear deformation effects, is based on the assumed forces hybrid approach. The resultant forces approximation verifies exactly the resultant equilibrium equations. The developed model proves its accuracy compared with other elements. This element permits to get the distribution of different stresses along the spring and through the wire surface by only one element.     

Crystal Structure,Dielectric Characteristics and Conduction Mechanism of a New Hybrid Material,Tetra(Phenylpiperazinium) Decachlorotriplumbate(II)

Monocrystalline (C₁₀H₁₅N₂)₄Pb₃Cl₁₀ was obtained via an aqueous solution reaction and characterized by single-crystal X-ray diffraction technique, elemental analyses, IR spectroscopy, UV–Vis spectrum, photoluminescence properties and thermal analysis. Structural characterization reveals that the title compound is built from [Pb₃Cl₁₀]^4? units sharing Cl2 atom to form 2-D [Pb₃Cl₁₀] _n ^4n? layers, these anions are linked to the organic cations via N–H···Cl and C–H···Cl hydrogen bonding. Moreover, dielectric relaxation spectroscopy has also been determined to show different molecular motions. Measurements of AC conductivity as a function of frequency at different temperatures indicated the hopping conduction mechanism.     

Crystal packing,vibrational studies,DFT calculations of a new hybrid nickel (II)‐complex and its application in Heck and Sonogashira cross‐ coupling reactions

We particularly investigate a new material [Ni(C₁₂H₁₂N₂)(H₂O)₄]SO₄ that it was hydrothermally synthesized by reaction of 5,5’‐dimethyl‐2,2’‐bipyridne, denoted (dmbpy), metal salt and sulfuric acid. The large crystals are characterized by X‐ray single crystal diffraction, infrared, Raman spectroscopy and DFT calculation. The thermogravimetric analysis indicated that the dehydration occurs in two steps, leading to an anhydrous compound. At room temperature, the complex crystallises in the centrosymmetric space group P2₁/c with the following parameters a = 9.492 (7) Å, b = 9.539 (7) Å, c = 18.411 (1) Å, β =102.616 (1)°, V = 1626.8 (2) ų and Z = 4. The asymmetric unit contains one free SO₄^2‐counter‐ion and [Ni(dmbpy)(H₂O)₄]²⁺ complex cation. The crystal structure of the complex is built up from infinite parallel two‐dimensional planes, containing all the components of the structure and perpendicular to the axis b. The aqua ligands are connected to the sulfate anion via O‐H…O hydrogen bonds that stabilize the three‐dimensional network. The catalytic activity of the complex was examined in the coupling reactions of Heck and Sonogashira in the presence of different bases in various organic solvents under ultrasonic irradiation. The obtained results show that this type of complex can be considered as an effective catalyst for these coupling reactions. The ultrasonic activation results the encouraging yields for a short period of time: 30‐45 min.     

Synthesis,structural characterization,Hirshfeld surface analysis,spectroscopic and ferroelectric properties studies of 4-methylbenzylammonium sulfate

Single crystals of 4-methylbenzylammonium sulfate were grown in an aqueous solution at room temperature. The grown compound is characterized by spectroscopic, thermal, and dielectric studies and its structure was determined by single-crystal X-ray diffraction analysis. Its crystal structure is described as a three-dimensional network where the sulfate anions (HSO₄^?) are interconnected through H-bonds to form anionic layers between which the 4-methylbenzylammonium cations are located. The hydrogen bonding network connecting the different components is given. Hirshfeld surface analysis was performed to visualize, explore and quantify intermolecular interactions in the crystal lattice. This analysis revealed the presence of H…C/H…C, C…O/O…C intermolecular interactions and O…O, H…H short contacts in the crystal. X-ray, structural and electrical results are correlated. The kind of the observed conduction is protonic by translocation. Differential scanning calorimetry (DSC) shows that this material presents a reversible phase transition at 390 K, confirmed by the dielectric permittivity study.     

Catalytic and biological valorization of a supramolecular mononuclear copper complex based 4‐aminopyridine

Hydrothermal reaction of copper bromide with 4‐aminopyridine in DMF solution yields a new mononuclear copper complex [Cu(C₅H₆N₂)₄]2Br.2(C₃H₇NO) abbreviated Cu‐4AP‐Br . The product was characterized, structurally, by single‐crystal X‐ray diffraction analysis and, thermally, by DSC‐ATG measurement. The inorganic–organic hybrid compound Cu‐4AP‐Br crystallizes in the centrosymmetric space group Pbcn, exhibiting a supramolecular network. Simultaneous DSC‐ATG analysis shows that this compound remains stable up to 100 °C and then performs a successive decompositions accompanied with endothermic peaks. The complex Cu‐4AP‐Br was applied as a catalyst in the Heck coupling reaction under ultrasonic irradiation in various reaction conditions. The yields, obtained for a short period of time, allow us to consider this complex, generating selectivity on the external position of styrene with a preference of the trans form over cis, as an excellent catalyst for this type of reaction. Interestingly, Cu‐4AP‐Br displayed important antibacterial (Gram‐positive and Gram‐negative) and antioxidant activities (β‐carotene bleaching inhibition, scavenging effect on DPPH free radical, and reducing power).     

Comparison of MALDI‐TOF mass spectra with microsatellite length polymorphisms in Candida albicans

Candida albicans is the most frequent yeast involved in human infections. Its population structure can be divided into several genetic clades, some of which have been associated with antifungal susceptibility. Therefore, detecting and monitoring fungal clones in a routine laboratory setting would be a major epidemiological advance. Matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra results are now widely used as bar codes to identify microorganisms in clinical microbiology laboratories. This study aimed at testing MALDI‐TOF mass spectra bar codes to identify clades among a set of C. albicans isolates. Accordingly, 102 clinical strains were genotyped using 10 microsatellite markers and analyzed via MALDI‐TOF mass spectrometry. The mass spectra were compared with a reference spectral library including 33 well‐characterized collection strains, using a Microflex^TM system and Biotyper^TM software, to test the capacity of the spectrum of a given isolate to match with the reference mass spectrum of an isolate from the same genetic clade. Despite high confidence species identification, the spectra failed to significantly match with the corresponding clade (p = 0.74). This was confirmed with the MALDI‐TOF spectra similarity dendrogram, in which the strains were dispersed irrespective of their genetic clade. Various attempts to improve intra‐clade spectra recognition were unsuccessful. In conclusion, MALDI‐TOF mass spectra bar code analysis failed to reliably recognize genetically related C. albicans isolates. Further studies are warranted to develop alternative MALDI‐TOF mass spectra analytical approaches to identify and monitor C. albicans clades in the routine clinical laboratory. Copyright © 2015 John Wiley & Sons, Ltd.