Analysis of the vibrations due to thermal deflection of the drum in the coiling process

The modelling of the coiling process involves a mechanical model of the dynamic system that consists of the rotating coiling drum and the axially and transversally moving strip. Due to the coiling a change of mass in the system takes place. For such a variable mass system a control volume concept has to be introduced in order to get the equations of motion of the dynamic system with variable parameters. A Runge Kutta time integration algorithm is applied to compute the solution. It is assumed that the outer radius of the coiling drum increases linear with the rotation angle. The bending deflection of the shaft results from an inhomogeneous temperature distribution within the coiled material on the coiling drum. Two different boundary conditions of the moving strip have been considered and it is demonstrated that the thermal deflection of the drum has a high influence upon the fluctuation of the strip force. For a given geometry and strip speed we obtain a critical thermal deflection where the minimum strip tension force is zero. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Efficient Series Solutions for Shear Forces of Vibrating Thin Rectangular Plates on Elastic Foundation with Thermal Loads

Simply supported rectangular Kirchhoff-plates with two-parametric Pasternak-type foundation are studied under the action of a transient temperature moment, which is span-wise constant. In extension to a previous study it can be shown, that an excellent convergence of the series solutions of the static problem can be achieved by means of Kummer's transformation and Cesaro's generalized C₁-Summation. The convergence improvement of the other types of the solutions can be performed analogously. The dynamic solution for the deflection and shear forces is computed using the derived efficient solution for the quasi-static case with fast convergent Fourier series. Modal expansion is applied for the computation of the vibrations about this quasi-static part. The results of he analytical solution for defined parameters of the foundation are shown for some characteristic points of the plate and compared to the FE computation results . (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Formation of mixed monolayers of silsesquioxanes and alkylsilanes on gold

The formation of mixed monolayers of hydridospherosilsesquioxane clusters (H(8)Si(8)O(12)) and alkylsilanes (H(2n+1)C(n)SiH(3)) on Au has been investigated using X-ray photoelectron and reflection-absorption infrared spectroscopies and scanning tunneling microscopy. All of the techniques indicate the displacement of the majority of the siloxane clusters from the surface in favor of the alkylsilane.     

HPLC analysis of functionalized poly(amidoamine) dendrimers and the interaction between a folate-dendrimer conjugate and folate binding protein

Poly(amidoamine) (PAMAM) dendrimers of different generations with carboxyl, acetyl, and hydroxyl terminal groups and a folic acid (FA)-dendrimer conjugate were separated and analyzed using reverse-phase high performance liquid chromatography (HPLC). Analysis of both the individual PAMAM derivatives and the separation of mixed generations can be achieved using a linear gradient 0-50% acetonitrile (ACN) (balance water) within 40 min. We also show that PAMAMs with defined acetylation and carboxylation degrees can be analyzed using HPLC. Furthermore, a generation 5 dendrimer-FA conjugate (G5.75Ac-FA4; Ac denotes acetyl) was analyzed and its specific binding with a bovine folic acid binding protein (FBP) was monitored. The HPLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results indicate the formation of three complexes after the binding of G5.75Ac-FA4 with FBP. Dendrimers with FA moieties show much higher specific binding capability with FBP than those without FA moieties. Findings from this study indicate that HPLC is an effective technique not only for characterization and separation of functionalized PAMAM dendrimers and conjugates but also for investigation of the interaction between dendrimers and biomolecules.     

Effects of the alternating backbone configuration on the secondary structure and self-assembly of beta-peptides

Heterochiral homo-oligomers with alternating backbone configurations were constructed by using the different enantiomers of the cis- and trans-2-aminocyclopentanecarboxylic acid (ACPC) monomers. Molecular modeling and the spectroscopic techniques (NMR, ECD, and VCD) unequivocally proved that the alternating heterochiral cis-ACPC sequences form an H10/12 helix, where extra stabilization can be achieved via the cyclic side chains. The ECD and TEM measurements, together with molecular modeling, revealed that the alternating heterochiral trans-ACPC oligomers tend to attain a polar-strand secondary structure in solution, which can self-assemble into nanostructured fibrils. The observations indicate that coverage of all the possible secondary structures (various helix types and strand-mimicking conformations) can be attained with the help of cyclic beta-amino acid diastereomers. A relationship has been established between the backbone chirality pattern and the prevailing secondary structure, which underlines the role of stereochemical control in the beta-peptide secondary structure design and may contribute to future biological applications.     

Front Cover: Can Nanoplastics Alter Cell Membranes? (ChemPhysChem 1/2020)

Whilst the formation of plastic nanoparticles (nanoplastics) from plastic wastes has been unequivocally evidenced, little is known about the effects of these materials on living organisms at the subcellular or molecular levels. In the present contribution we show through molecular dynamics simulations that polyethylene nanoparticles dissolve in the hydrophobic core of lipid bilayers into a network of disentangled, single polymeric chains. The thereby induced structural and dynamic changes in the bilayer alter vital functions of the cell membrane, which if lacking a mechanism to decompose the polymer chains may result in the death of the cell.     

Analysis of deprenyl metabolites in some body compartments of rats using GC-MSD

Summary Deprenyl metabolites were analyzed in various organs of rats after chronic oral treatment. The investigation was carried out by gas chromatography combined with MSD after derivatization of the metabolites. When (−)-deprenyl (selegiline) was administered to rats higher ratios of methamphetamine to amphetamine were found in the kidney, and the heart at 1 and 5 h after treatment, than after (+)-deprenyl administration. Both deprenyl and its demethylated metabolite were also detected; however, their level was generally lower than that of either methamphetamine or amphetamine. Coadministration of verapamil with selegiline did not essentially alter the major metabolic pathway of deprenyl metabolism.     

Distribution of water-soluble and surface-active low-molecular-weight species in acrylic latex films

Monodisperse core-shell latices were synthesized, differing in the acrylic acid (AA) content in the particle shell (1 or 4 wt%) and the Tg of the acrylic core (around -40 or 10 degrees C). In a first step, the drying mechanisms of the dialyzed latices were studied by confocal Raman spectroscopy. It was shown that, besides some unexpected features (briefly described in the article), drying occurred in a rather classical way, i.e., simultaneously from top to bottom and from edge to center. Then, the distributions of sulfate ion (SO4) (from sodium sulfate) and sodium dodecyl sulfate (SDS) in the dry latex films were established by confocal Raman spectroscopy and attenuated total reflectance (ATR). The two techniques were complementary. SO4 and SDS distributions were quite different, although presenting some common characteristics. In both cases, repartition of the low-molecular-weight species in the film was even less homogeneous when the AA content was lower and the particle core softer. However, SO4 showed enrichment at the film-substrate interface and depletion at the air side, whereas SDS showed concentration maxima at both interfaces. Interpretations stress the importance of desorption from the particle-water interface, transport by water, size effects, and diffusion.     

Insertion of SO2 into a sulfide-bridged M-Ge bond: synthesis, characterization, and reactivity of the O-germyl-S-sulfoxylate

Addition of SO(2) to [formula: see text](1) results in the insertion of SO(2) into the Pd-Ge bond to give the O-germyl-S-sulfoxylate insertion isomer (Et3P)2Pd(mu-S)S(O)OGe[N(SiMe3)2]2 (2). Heating solutions of 2 results in the formation of (Et3P)Pd(SGe[N(SiMe3)2]2OSOGe[N(SiMe3)2]2S) (3) and a LnPd(0) fragment. X-ray crystal structures of 2 and 3 are reported.