On the onset of fracture as a silicon-based polymer converts into the ceramic phase

Silicon-based polymers evolve into refractory ceramics when heated gradually up to ~1000°C. The conversion is accompanied by the loss of gaseous species, and by a two-fold increase in density. The shrinkage can produce microcracks if the heating rate is too high, or if the specimen is too thick. This communication builds on earlier work whereby the measurement of gas evolution, and its relationship with viscous flow, are related to the onset of fracture in disk-shaped green (polymer) samples. The onset is determined as a function of the thickness of the disks, and of the heating rate. The results are presented in the form of a processing map. The overlay with gas evolution, and strain-rate measurements, suggest that fracture initiates with the release of hydrogen and methane, starting at temperatures near 750°C.     

2-Phenyloxazole-4-carboxamide as a Scaffold for Selective Inhibition of Human Monoamine Oxidase B

A series of 2-phenyloxazoles bearing an amide group at position 4 were designed and synthesized for evaluation as potential inhibitors of human recombinant monoamine oxidases (hrMAOs). Results of kinetics experiments demonstrated that all compounds behave as competitive MAO inhibitors, with good selectivity toward the MAO-B isoform. The most potent and selective derivatives are characterized by inhibition constant (K_i) values in the sub-micromolar range and a good selectivity index (K_{i MAO-A}/K_{i MAO-B}>50). Some derivatives were also found to be able to inhibit MAO activity in nerve growth factor (NGF)-differentiated PC12 cells, taken as a model of neuronal cells. In particular, 2-(2-hydroxyphenyl)-N-phenyloxazole-4-carboxamide (compound 4 a ) may be a promising new scaffold, exerting the highest selectivity and inhibitory effect toward MAOs in NGF-differentiated PC12 cell lysates, without compromising cell viability. Molecular docking analysis allowed a rationalization of the experimentally observed binding affinity and selectivity.     

Anti-fingerprints fluorinated coating for anodized titanium avoiding color alteration

In this study amorphous fluorinated coatings applied to anodized titanium surface have been investigated. A copolymer between tetrafluoroethylene and perfluoro-4-trifluoromethoxy-1,3-dioxole (AD60) and two perfluoropolyether containing ammonium phosphate (F10) or triethoxysilane (S10) functionalities have been tested. To estimate the color alteration of the anodized titanium surfaces due to the application of the coatings, spectrophotometric analyses have been made. Water and n-dodecane contact angles as well as apparent surface energy have been evaluated. Ellipsometry and atomic force microscopy data have been used to measure the thickness of the fluorinated coatings. A tailored mechanical preliminary test has also been explored to evaluate the adhesion of the coatings on the anodized titanium surface. The resistance to surface soiling with castor oil was also preliminarily investigated. The fluorinated coating tested on anodized titanium showed a low apparent surface energy and high chromatic aspect conservation, this is particularly evident for the titanium anodized coated with triethoxysilane functionalities fluoropolymers S10.     

Time-resolved photoelectron spectroscopy to probe ultrafast charge transfer and electron dynamics in solid surface systems and at metal-molecule interfaces

Photoelectron spectroscopy (PES) is a versatile tool, which provides insight into electronic structure and dynamics in condensed matter, surfaces, interfaces and molecules. The history of PES is briefly outlined and illustrated by current developments in the field of time-resolved PES. Our group's research is mostly aimed at studying ultrafast processes and associated lifetimes related to electronic excitation at solid surfaces.     

The inverse type II β-turn on D-Trp-Phe, a pharmacophoric motif for MOR agonists

Herein we propose the D ‐Trp‐Phe sequence within an inverse type II β‐turn as a new kind of pharmacophoric motif for μ‐opioid receptor (MOR) cyclopeptide agonists. Initially, we observed that c[Tyr‐D ‐Pro‐D ‐Trp‐Phe‐Gly] ( 4 ), an analogue of endomorphin‐1 (H‐Tyr‐Pro‐Trp‐Phe‐NH₂) lacking the crucial protonatable amino group of Tyr 1, is a MOR agonist with 10^?8 M affinity. Molecular docking analysis suggested that the relevant interactions with the receptor involve D ‐Trp‐Phe. The bioactive conformation of this region was investigated by selected derivatives of 4 designed to adopt an inverse type II β‐turn. These efforts led to c[Tyr‐Gly‐D ‐Trp‐Phe‐Gly] ( 14 ) and to the cyclotetrapeptide c[D ‐Asp‐1‐amide‐β‐Ala‐D ‐Trp‐Phe] ( 15 ), showing improved nanomolar affinity. Both 14 and 15 selectively bind MOR, as they have negligible affinity for the κ‐ and δ‐opioid receptors. Both 14 and 15 behave as partial MOR agonists in functional assays. Conformational and docking analyses confirm the role of the inverse β‐turn in binding. These results indicate that the D ‐Trp‐Phe inverse β‐turn structure can be used for designing non‐endomorphin‐like peptidomimetic opioid agonists in general, characterized by an atypical mechanism of interaction between ligand and receptor.     

High-resolution and tandem mass spectrometry--the indispensable tools of the XXI century

Mass spectrometry-based qualitative and quantitative (bio)molecular analysis is a corner stone in the state-of-the-art pipelines in systems biology and environmental sciences. High-resolution and efficient tandem mass spectrometry methods and techniques are the essential analytical capabilities for the in-depth analysis of extremely complex mixtures of (bio)molecules of a very broad dynamic range of concentrations. Here, we briefly review the advantages and limitations of the current mass spectrometry with a focus on resolution, or resolving power, and methods of (bio)molecular fragmentation in the gas phase. We conclude with an outlook that considers possible avenues for further mass spectrometry-based method and technique development, indispensable for advancing the challenging real-life mass spectrometry applications in the XXI century.     

Predicting and rationalizing the effect of surface charge distribution and orientation on nano-wire based FET bio-sensors

A single charge screening model of surface charge sensors in liquids (De Vico et al., Nanoscale, 2011, 3, 706-717) is extended to multiple charges to model the effect of the charge distributions of analyte proteins on FET sensor response. With this model we show that counter-intuitive signal changes (e.g. a positive signal change due to a net positive protein binding to a p-type conductor) can occur for certain combinations of charge distributions and Debye lengths. The new method is applied to interpret published experimental data on Streptavidin (Ishikawa et al., ACS Nano, 2009, 3, 3969-3976) and Nucleocapsid protein (Ishikawa et al., ACS Nano, 2009, 3, 1219-1224).     

Limitations of quadrature-based moment methods for modeling inhomogeneous polydisperse fluidized powders

Computational fluid dynamics (CFD) is extensively used to investigate the behavior of dense fluidized suspensions. Often modelers assume that these are formed by few solid phases of particles with constant size. But real powders are continuously distributed over the particle size, and their distribution functions change continuously in time and space reflecting the physical and chemical phenomena occurring within the system. To account for this key feature, models have to include a population balance equation (PBE), which needs to be solved in place of or along with the customary fluid dynamic transport equations. The recently developed quadrature method of moments (QMOM) and direct quadrature method of moments (DQMOM) permit to solve PBEs in commercial CFD codes at relatively low computational cost. These methods, however, still need testing in the context of multiphase flows. Investigating a simple problem, namely the dynamics of two inert polydisperse fluidized suspensions initially segregated, we highlight an important limitation of these methods, which fail to properly model diffusion in real space. We explain where the problem originates and comment on a possible way to overcome it. To conclude the work, we discuss some simulations based on the original and revised formulations of the methods, describing how the code numerics affects the results.     

Thermal,thermo‐mechanical,and dynamic mechanical properties of polypropylene/cycloolefin copolymer blends

Interaction of the components and physical properties of the polypropylene (PP)/cycloolefin copolymer (COC) blends were studied by means of differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), Vicat softening temperature (VST), and measurements of the coefficient of linear thermal expansion (CLTE) and of the density. The attention was focused on the blends with 90–60% of PP by wt, where the COC minority component was present in the form of short fibers. DSC, DMTA, and density measurements concurrently prove the immiscibility of PP and COC. DSC measurements reveal that crystallinity and melting temperature of the PP component slightly decrease with the fraction of COC in blends, in the range of 56–47% and 164–161°C, respectively. Storage modulus and loss modulus of the blends are in a good accord with the model predictions based on (i) the equivalent box model (EBM) and on (ii) modified equations of the percolation theory. The dependence of the VST on the blend composition is in a good correlation with the previous morphological analysis. Measurements of the coefficient of thermal expansion provide useful data as the functions of temperature and blend composition. Density of the blends was found to obey the volume additivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.