Analytical approach in torsional multi-mass discrete-continuous systems with variable inertia

In the paper the systems torsionally deformed consisting of an arbitrary number of elastic elements connected by rigid bodies using the perturbation approach are investigated. The first rigid body represents a motor working with a constant speed, and the last one has a mass moment of inertia depending on the angular displacement. The problem is nonlinear and it is linearized after appropriate transformations. Exemplary numerical results for angular displacements for a two-mass and a three-mass systems are presented.     

Effects of addition of polar organic solvents on micellization

Micellization of several surfactants in water-organic solvent mixtures has been investigated. Only solvents localized mainly in the bulk phase of the micellar solutions (they do not incorporate into the micelles) were studied, with either higher or lower permittivity than that of pure water. Results show that the influence of organic solvent addition on the aggregation process can be approximately accounted for by considering the changes in the bulk phase cohesive energy density, described by the Gordon parameter, G. To our knowledge, this is the first time that, for a given surfactant, the Gibbs energies of micellization, Delta G M degrees , obtained in several water-organic solvent mixtures have been fitted together. It is worth noting that data from different research groups have been considered. The Delta G M degrees versus G correlation will permit the estimation of the variations in the Gibbs energy of micellization upon addition of known quantities of a given polar organic solvent. Speaking in a general way, organic solvent addition results in the bulk phase becoming a better solvent for the surfactant molecules. This would make the hydrophobic tail transfer from the bulk phase into the micelles less favorable and, as a consequence, Delta G M degrees increases (becomes less negative), making the aggregation process less spontaneous.     

Spirocyclic Amide Acetal Synthesis by [CpRu]-Catalyzed Condensations of α-Diazo-β-Ketoesters with γ-Lactams

The synthesis of spirocyclic amide acetals (33–93 %) has been achieved through Ru(II)-catalyzed condensations of N-carbamate protected pyrrolidinones with metal carbenes derived from α-diazo-β-ketoesters. Thanks to the mildness of the diazo decomposition conditions induced by a 1 : 1 combination of [CpRu(MeCN)₃][BAr_F] and 1,10-phenanthroline, the formation of the sensitive products is possible. Full characterization of this carbonyl-ylide mediated process is provided by DFT calculations.     

Towards improved gene delivery: Flip of cationic lipids in highly polarized liposomes

Hyperpolarization of cationic liposomes improves their stability in the presence of human serum albumin.     

Strain maps obtained by phase-shifting interferometry: An uncertainty analysis

We used Moiré interferometry to evaluate the strains induced on a specimen subjected to a steady tensile load. The strains were evaluated by differentiating the whole-field phase values obtained by a phase-shifting algorithm. Because the direct differentiation of even slightly noisy data may lead to unacceptable derivative errors, the strain evaluation procedure included the application of a low-pass filter, which allowed us to smooth out local fluctuations in the phase data. In addition to the noise, the strain values were also affected by systematic errors in the phase values rendered by the phase-shifting algorithm as well as uncertainties in the determination of both the interferometer sensitivity and the magnification of the imaging system. In this paper, the influence of these error sources was assessed by applying a Monte Carlo-based uncertainty propagation technique; the strain uncertainty evaluation was based on simulating a large number of times, both the phase-shifting procedure and the post-image processing (which included the filter application). We found that the strain uncertainty strongly depends on the low-pass filter used to counteract the noise effect. Although we obtained the phase data from a Moiré pattern, the procedure presented to evaluate the strain uncertainty is valid independently of the techniques used to generate the fringe pattern or the algorithm applied to exploit the phase-shifting procedure.     

Selection by rank in K‐dimensional binary search trees

In this work we show how to augment general purpose multidimensional data structures, such as K‐d trees, to efficiently support search by rank (that is, to locate the i‐th smallest element along the j‐th coordinate, for given i and j) and to find the rank of a given item along a given coordinate. To do so, we introduce two simple, practical and very flexible algorithms – Select‐by‐Rank and Find‐Rank – with very little overhead. Both algorithms can be easily implemented and adapted to several spatial indexes, although their analysis is far from trivial. We are able to show that for random K‐d trees of size n the expected number of nodes visited by Find‐Rank is for or , and for (with ), where depends on the dimension K and the variant of K‐d tree under consideration. We also show that Select‐by‐Rank visits nodes on average, where is the given rank and the exponent α is as above. We give the explicit form of the functions and , both are bounded in [0, 1] and they depend on K, on the variant of K‐d tree under consideration, and, eventually, on the specific coordinate j for which we execute our algorithms. As a byproduct of the analysis of our algorithms, but no less important, we give the average‐case analysis of a partial match search in random K‐d trees when the query is not random. © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 45, 14–37, 2014     

Salt effects upon reactions of different charge type reactants: Peroxodisulphate Oxidations of Fe(CN)4(bpy)2−, cis-Fe(CN)2(bpy)2 and Fe(bpy)32+ and Iron(II) Oxidation by Co(NH3)5Cl2+

Salt effects on the oxidation of the iron(II) complexes Fe(CN)₄(bpy)^2?, cis-(CN)₂(bpy)₂ and Fe(bpy)₃²⁺ by S₂O₈^2? as well as on the reaction Fe²⁺ + Co(NH₃)₅Cl²⁺ have been studied in concentrated electrolyte solutions at 298.2 K. We have gone from anion–anion to cation–cation reaction with the intermediate cases of anion–neutral and cation–anion reactions. Results show that the main cause of the kinetic salt effects observed is the interaction between supporting electrolytes and the solvent. © 1994 John Wiley & Sons, Inc.     

Ionic strength effects in binary aqueous mixtures: Study of the reaction between Co(en)2(2-pzCO2)2+ and Fe(CN)5H2O3−

The reaction between Co(en)₂(2?pzCO₂)²⁺ (bis-ethylenediamine (2-pyrazinecarboxylato)cobalt(III)) and Fe(CN)₅H₂O^3? (aquopentacyanoferrate(II)) to form the binuclear complex [(en)₂Co( μ-pzCO₂)Fe(CN)₅]^? has been studied in several isodielectric binary mixtures at 298.2 K (cosolvents: methanol, ethanol, tertbutyl alcohol, ethyleneglycol, and glycerol). Results were rationalized by using a free energy relationship. The importance of correcting the rate constants obtained in the different mixtures from the ionic strength influence has been shown. © 1995 John Wiley & Sons, Inc.     

Overcrowded 1,8-diazafluorenylidene-chalcoxanthenes. Introducing nitrogens at the fjord regions of bistricyclic aromatic enes

The effects of introducing nitrogen atoms in the fjord regions and chalcogen bridges on the conformations of overcrowded bistricyclic aromatic enes (1, X not equal to Y) (BAEs) were studied. 9-(9'H-1',8'-Diazafluoren-9'-ylidene)-9H-thioxanthene (12), 9-(9H-1',8'-diazafluoren-9'-ylidene)-9H-selenoxanthene (13), 9-(9'H-1',8'-diazafluoren-9'-ylidene)-9H-telluroxanthene (14), 9-(9' H-1',8'-fluoren-9-ylidene)-9H-xanthene (15) and 9-(9' H-1',8'-fluoren-9'-ylidene)-9H-fluorene (16) were synthesized by two-fold extrusion coupling reactions of 1,8-diaza-9H-fluoren-9-one (19)/chalcoxanthenthiones (24-27) (or /9H-fluorene-9-thione (30)). The 1',8'-diazafluoren-9-ylidene-chalcoxanthenes (11) were compared with the respective fluoren-9-ylidene-chalcoxanthenes (10). The structures of 12-16 were established by 1H, 13C, 77Se, and 125Te NMR spectroscopies. The crystal and molecular structures of 12-14 were determined by X-ray analysis. The yellow molecules of 12-14 adopted mono-folded conformations with folding dihedrals in the chalocoxanthylidene moieties of 62.7 degrees (12), 62.4 degrees (13) and 59.9 degrees (14). The folding dihedrals in the respective 1',8'-diazafluorenylidene moieties were very small, ca. 2 degrees, compared with 10.2/8.0 degrees in (9'H-fluoren-9'-ylidene)-9H-selenoxanthene (7). A 5 degree pure twist of C9=C9' in 14 is noted. The degrees of overcrowding in the fjord regions of 12-14 (intramolecular non-bonding distances) were relatively small. The degrees of pyramidalization of C9 and C9' were 17.0/3.0 degrees (12), 17.4/2.4 degrees (13) and 2.2/2.2 degrees (14). These high values in 12 and 13 stem from the resistance of the 1.8-diazafluorenylidene moiety to fold and from the limits in the degrees of folding of the thioxanthylidene and selenoxanthylidene moieties (due to shorter S10-C4a/S10-C10a and Se10-C4a/Se10-C10a bonds, as compared with the respective Te-C bonds in 14). The molecules of 15 and 16 adopt twisted conformations, a conclusion drawn from the 1H NMR chemical shifts of the fjord regions protons (H1 and H8) at 8.70 (15) and 9.00 ppm (16) and from their colors and UV/VIS spectra: 15 is purple (lambdamax = 521 nm) and 16 is orange-red. A comparison of the NMR spectra of 11 and 10 (deltadelta = delta(11) -delta(10)) showed substantial downfield shifts of 0.56-0.62 ppm of the fjord regions protons of twisted 15 and 16: deltadelta (C9) were negative (upfield): -4.0 (12), -3.7 (13), -3.4 (14), -7.1 (15), -5.0 ppm (16), while deltadelta (C9') were positive (downfield) = +6.8 (12), +6.5 (13), +5.8 (14), + 11.7 (15), +7.7 ppm (16). In 15, deltadelta (C9) - deltadelta (C9') = + 18.8 ppm, attributed to a push-pull character and significant contributions of zwitterionic structures in the twisted conformation. The 77Se and 125Te NMR signals of 13 and 14 were shifted upfield relative to the respective fluorenylidene-chalcoxanthene derivatives: deltadelta77Se = 17.2 ppm and deltadelta125Te = 22.0 ppm. The presence of the nitrogen atoms (N1' and N8') in 13 and 14 causes shielding of the selenium and tellurium nuclei.