Intermolecular interactions and formation of the hydration sphere in phosphonic acid model systems as an approach to the description of vinyl phosphonic acid based polymers

Molecular model systems based on propyl phosphonic acid (ppa) were studied by means of density functional theory calculations in order to describe the acid-acid interaction and the formation of the hydration sphere. The formation of ppa dimers is reported and the energetic difference between two dimer structures is presented. The hydration sphere of ppa was represented by model systems ppa(H₂O)_n, for which the system with n=4 formed the first hydration sphere (h¹), while n=7 can be considered a good approximation to the complete inner hydration sphere around the phosphonic acid group. The study of the ppa-H⁺ (H₂O)_n model systems showed an interesting structural behavior comparatively to the ppa(H₂O)_n systems. The protonated acids exhibited equivalent phosphorous-oxygen bonds and a general molecular structure is proposed to represent these protonated species.     

Squalenoyl nanomedicines as potential therapeutics

Nucleoside analogues display significant anticancer or antiviral activity by interfering with DNA synthesis. However, there are some serious restrictions to their use, including their rapid metabolism and the induction of resistance. We have discovered that the linkage of nucleoside analogues to squalene leads to amphiphilic molecules that self-organize in water as nanoassemblies of 100-300 nm, irrespective of the nucleoside analogue used. The squalenoyl gemcitabine exhibited superior anticancer activity in vitro in human cancer cells and gemcitabine-resistant murine leukemia cells, and in vivo in experimental leukemia both after intravenous and oral administration. The squalenoylation of other antiretroviral nucleosides also led to more potent drugs when tested in primary cultures of HIV-infected lymphocytes. Thus, the squalenoylation is an original technology platform for generating more potent anticancer and antiviral nanomedicines.     

Impact of bleaching pine fibre on the fibre/cement interface

The goal of this article was to evaluate the surface characteristics of the pine fibres and its impact on the performance of fibre–cement composites. Lower polar contribution of the surface energy indicates that unbleached fibres have less hydrophilic nature than the bleached fibres. Bleaching the pulp makes the fibres less stronger, more fibrillated and permeable to liquids due to removal the amorphous lignin and its extraction from the fibre surface. Atomic force microscopy reveals these changes occurring on the fibre surface and contributes to understanding the mechanism of adhesion of the resulting fibre to cement interface. Scanning electron microscopy shows that pulp bleaching increased fibre/cement interfacial bonding, whilst unbleached fibres were less susceptible to cement precipitation into the fibre cavities (lumens) in the prepared composites. Consequently, bleached fibre-reinforced composites had lower ductility due to the high interfacial adhesion between the fibre and the cement and elevated rates of fibre mineralization.     

Hybrid organic–inorganic materials based on polypyrrole and 1,3-dithiole-2-thione-4,5-dithiolate (DMIT) containing dianions

The synthesis of hybrid materials by electropolymerization of pyrrole and inorganic complexes based on the DMIT ligand (1,3-dithiole-2-thione-4,5-dithiolate), e.g. [NEt₄]₂[M(DMIT) _n ] (M = Ni, Pd or Pd, n = 2; M = Sn, n = 3], in acetonitrile solution is reported. Spectroscopic data showed that DMIT-containing anions, [M(DMIT) _n ]²⁻, were inserted into the polypyrrole framework without chemical modification during the electropolymerization process. Cyclic voltammetry showed that materials obtained were electroactive, undergoing redox processes related to both the conducting polymer and the counteranions. The electrochemical results also suggest that, in the case of the transition metal containing films, the counteranions are not trapped in the PPy matrix but undergo anion exchange during the redox cycle of PPy. However, an opposite behaviour was observed with the film with [M(DMIT) _n ]²⁻. The films exhibit good thermal stabilities and have conductivity values expected for semiconductors. This study of these hybrid materials highlights the importance of targeting specific materials for specific applications.

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Robust design using a hybrid-cellular-evolutionary and interval-arithmetic approach: a reliability application

Sensitivity analysis is a technique by which one can determine, with good approximation, whether a system will work within the specification limits when the input vary between their limits.Although this type of analysis, from input to output, can provide useful information to the decision-maker, we present an approach based on the use of Cellular Evolutionary Strategies and Interval Arithmetic in which the inverse problem can be solved. That is, we move from output to input: starting with output range specifications, we infer the maximum uncertainty or variability that can be exhibited by the input parameters. The approach used is an indirect method based on optimisation instead of a direct method based on mapping from the output into the input space. The proposed approach is illustrated by computational examples applied to a reliability complex system. Results are compared with those obtained using a general non-linear optimisation package.     

Resistance.

This article reviews extant literature on how patient resistance has been defined and its effects on psychotherapy. Resistance has been considered as both a patient-in-treatment state and as an enduring trait. In either form, patient resistance seems to interfere with treatment outcome. Resistance also functions as a moderating variable in determining the effectiveness of different levels of therapist directiveness. The evidence that patients who enter treatment with high levels of trait like resistance will benefit most from nondirective interventions is moderately strong. Conversely, those who enter treatment with low levels of trait like resistance benefit most from therapist directed interventions. Therapeutic practices associated with the research evidence are advanced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cellulose modified fibres in cement based composites

The objective of the present work is to evaluate the effect of surface modification of cellulose pulp fibres on the mechanical and microstructure of fibre–cement composites. Surface modification of the cellulose pulps was performed with Methacryloxypropyltri-methoxysilane (MPTS) and Aminopropyltri-ethoxysilane (APTS) in an attempt to improve their durability into fibre–cement composites. The surface modification showed significant influence on the microstructure of the composites on the fibre–matrix interface and in the mineralization of the fibre lumen as seen by scanning electron microscopy (SEM) with back-scattered electron (BSE) detector. Accelerated ageing cycles decreased modulus of rupture (MOR) and toughness (TE) of the composites. Composites reinforced with MPTS-modified fibres presented fibres free from cement hydration products, while APTS-modified fibres presented accelerated mineralization. Higher mineralization of the fibres led to higher embrittlement of the composite after accelerated ageing cycles. These observations are therefore very useful for understanding the mechanisms of degradation of fibre–cement composites.     

One Dimensional Inverse Dielectric Profiling of Embedded Slabs by a Quadratic Approximation

In this paper the inverse problem of the determination of the dielectric profile of a slab embedded into a homogeneous half space starting from the knowledge of the scattered field for different illumination angles is considered. A comparison between the features of a linear and a quadratic distorted approximation of the scattering problem is carried out, in order to determine the kind of profiles that can be reconstructed. In particular, the investigation of the direct problem reveals that, under the linear approximation, only a limited number of Fourier harmonics of the profile give contribution to the scattered field. The use of the quadratic approximation allows to change the number and order of the harmonic that can be imaged. The dependence of the results on the dielectric permittivity of the host medium is also highlighted. Numerical examples support the theoretical considerations.