Nonlinear Oscillations of a Nonresonant Cable under In-Plane Excitation with a Longitudinal Control

The nonlinear oscillations of a controlled suspended elastic cable under in-plane excitation are considered. Active control realized by longitudinal displacement of one support is introduced in order to reduce the transverse in-plane and out-of-plane vibrations. Linear and quadratic enhanced velocity feedback control laws are chosen and their effects on the cable motion are investigated using a two degree-of-freedom model. Perturbation analysis is performed to determine the in-plane steady-state solutions and their stability under an out-of-plane disturbance. The analysis is extended to the bifurcated two-mode steady-state oscillations in the region of parametric excitation. The dependence of the control effectiveness on the system parameters is investigated in the case of the first symmetric mode and the range of oscillation amplitudes in which the proposed control ensures a dissipation of energy is determined. Although control based only on in-plane response quantities is effective in reducing oscillations with a prevailing in-plane component, addition of out-of-plane measures has to be considered when the motion is characterized by two comparable components.     

Growth mechanisms involved in the synthesis of smooth and microtextured films by acetylene magnetron discharges

The growth of hydrogenated amorphous carbons (a-C:H) produced by continuous or pulsed discharges of acetylene (C(2)H(2)) in an unbalanced magnetron setup was investigated. At 5 × 10(-3) Torr, only smooth films are obtained, whereas at 5 × 10(-1) Torr using a pulsed discharge some microtextured films are formed if the duty cycle is low. The morphology of these microtextured films consists of nanoparticles, filamentary particles, and particular agglomerates ("microflowers"). This paper presents a study of acetylene gas phase polymerization by mass spectrometry, and a detailed analysis of bulk structure of films by combining three techniques which include IR spectroscopy, Raman spectroscopy, and laser desorption/ionization Fourier transform mass spectrometry (LDI-FTMS). Finally, based on the study of gas phase and film structure, we propose a model for the growth of both smooth and microtextured films.     

Evaluation of the separation mechanism of electrokinetic chromatography with a microemulsion and cyclodextrins using NMR and molecular modeling

Electrokinetic chromatography (EKC) allows the separation of closely related substances by the detection of fine effects in analyte-separation system interactions. With the goal of understanding the fine effects involved in separation using a dual cyclodextrin-microemulsion EKC system, an integrated study of NMR and molecular modeling was carried out. The above dual cyclodextrin-microemulsion system was previously used in the separation of clemastine and its related substances and was prepared by the addition of methyl-β-cyclodextrin (MβCD) and heptakis(2,6-di-O-methyl)-β-cyclodextrin (DMβCD) to an oil-in-water microemulsion. The use of DMβCD was shown to be essential in the separation of clemastine from one of its related substance (I(B) ). A molecular modeling study allowed the different affinities of clemastine and I(B) for the two cyclodextrins to be explained. Furthermore, rotating-frame Overhauser effect spectroscopy NMR experiments clearly indicated that besides the primary pseudostationary phase, namely the ionic microemulsion, cyclodextrins acted as a secondary pseudostationary phase. In addition, it was shown that inclusion complexation of sodium dodecyl sulfate (SDS) monomers into the cyclodextrins cavity occurs; differently, the oil (n-heptane) used in the preparation of microemulsion system resulted to be not included into the macrocycle cavity. These experimental results were supported by molecular modeling, which highlighted the preferential inclusion of SDS into DMβCD. On the basis of these results, it was confirmed that, besides its primary role as the ionic carrier in EKC, SDS is involved in inclusion equilibria toward CDs, which can be effective in increasing the system selectivity.     

Water-soluble peptide-coated nanoparticles: control of the helix structure and enhanced differential binding to immune cells

The stabilizing action of C(α)-tetrasubstituted α-amino acids inserted into a sequence of short peptides allowed for the first time the preparation of water-soluble nanoparticles of different materials coated with a helix-structured undecapeptide. This peptide coating strongly favors nanoparticle uptake by human immune system cells.     

A general framework for inhibitor resistance in protein kinases

Protein kinases control virtually every aspect of normal and pathological cell physiology and are considered ideal targets for drug discovery. Most kinase inhibitors target the ATP binding site and interact with residue of a hinge loop connecting the small and large lobes of the kinase scaffold. Resistance to kinase inhibitors emerges during clinical treatment or as a result of in vitro selection approaches. Mutations conferring resistance to ATP site inhibitors often affect residues that line the ATP binding site and therefore contribute to selective inhibitor binding. Here, we show that mutations at two specific positions in the hinge loop, distinct from the previously characterized "gatekeeper," have general adverse effects on inhibitor sensitivity in six distantly related kinases, usually without consequences on kinase activity. Our results uncover a unifying mechanism of inhibitor resistance of protein kinases that might have widespread significance for drug target validation and clinical practice.     

Hysteresis loops for para–ferromagnetic phase transitions

In this paper, by an extension of the Ginzburg–Landau theory, we propose a mathematical model describing hard magnets within which we are able to explore the para–ferromagnetic transition and by using the Landau–Lifshitz–Gilbert equation, to study the 3D evolution of magnetic field. Finally, the hysteresis loops are obtained and represented by numerical implementations.     

Efficient organic monoliths prepared by γ-radiation induced polymerization in the evaluation of histone deacetylase inhibitors by capillary(nano)-high performance liquid chromatography and ion trap mass spectrometry

New monolithic HPLC columns were prepared by γ-radiation-triggered polymerization of hexyl methacrylate and ethylene glycol dimethacrylate monomers in the presence of porogenic solvents. Polymerization was carried out directly within capillary (250-200 μm I.D.) and nano (100-75 μm I.D.) fused-silica tubes yielding highly efficient columns for cap(nano)-LC applications. The columns were applied in the complete separation of core (H2A, H2B, H3, and H4) and linker (H1) histones under gradient elution with UV and/or electrospray ionization (ESI) ion trap mass spectrometry (MS) detections. Large selectivity towards H1, H2A-1, H2A-2, H2B, H3-1, H3-2 and H4 histones and complete separation were obtained within 8 min time windows, using fast gradients and very high linear flow velocities, up to 11 mm/s for high throughput applications. The method developed was the basis of a simple and efficient protocol for the evaluation of post-translational modifications (PTMs) of histones from NCI-H460 human non-small-cell lung cancer (NSCLC) and HCT-116 human colorectal carcinoma cells. The study was extended to monitoring the level of histone acetylation after inhibition of Histone DeACetylase (HDAC) enzymes with suberoylanilide hydroxamic acid (SAHA), the first HDAC inhibitor approved by the FDA for cancer therapy. Attractive features of our cap(nano)-LC/MS approach are the short analysis time, the minute amount of sample required to complete the whole procedure and the stability of the polymethacrylate-based columns. A lab-made software package ClustMass was ad hoc developed and used to elaborate deconvoluted mass spectral data (aligning, averaging, clustering) and calculate the potency of HDAC inhibitors, expressed through a Relative half maximal Inhibitory Concentration parameter, namely R_IC(50) and an averaged acetylation degree.