Well-posedness and long-time behaviour for a singular phase field system of conserved type

In this paper, we study the well-posedness of a singular non-linearpartial differential equation system and the long-time behaviourof its solutions. Namely, an equation ruling the evolution ofthe absolute temperature of the system (recently introducedin BONETTI, E., COLLI, P., FABRIZIO, M. & GILARDI, G. (2006)Modelling and long-time behaviour for phase transitions withentropy balance and thermal memory conductivity. Discrete Contin.Dyn. Syst. Ser. B, 6, 1001–1026 (electronic) and BONETTI,E., COLLI, P., FABRIZIO, M. & GILARDI, G. (2007) Globalsolution to a singular integrodifferential system related tothe entropy balance. Nonlinear Anal., 66, 1949–1979) iscoupled with a generalization of the well-known Cahn–Hilliardequation for the order parameter . In particular, under suitableassumptions on the non-linearities involved, we prove that theelements of the -limit set (i.e. the cluster points) of thetrajectories solve the steady-state system that is naturallyassociated to the evolution problem.     

Micellization of lithium perfluoroheptanoate and its aggregation on poly(ethylene glycol) oligomers in water

The interaction of lithium perfluoroheptanoate (LiPFHep) with poly(ethylene glycol) (PEG) of different molecular weights (300 < MW < 20 000 Da) was investigated in water at 298.15 and 308.15 K by the isothermal titration calorimetry (ITC). Density and sound velocity measurements were also performed at 288.15, 298.15, and 308.15 K, while viscosity and conductivity data were only collected at 298.15 K. The aggregation process of this surfactant on the PEG polymeric chain was found to be very similar to the process exhibited by the two homologous perfluorooctanoate and perfluorononanoate. Viscosity and ITC data indicated that the formation of polymer-surfactant complexes between PEG and LiPFHep also leads to a conformational change in the polymer. The aggregation of micelles of the lithium perfluoro surfactants on the PEG polymeric chain is characterized by a comparable thermodynamic stability, which results from a balance of enthalpy and entropy contributions, which both increase with the length of the surfactant hydrophobic chain.     

A density functional study of the SERS spectra of pyridine adsorbed on silver clusters

The effect of binding pyridine to silver clusters has been studied by density functional calculations by adopting a hybrid functional. The calculations allow proposing an explanation for the different SERS spectra of the ligand observed on Ag colloids in the presence and in the absence of coadsorbed chloride anions. In the latter case, a better agreement is obtained modeling the system by adsorption of pyridine on a surface cluster.     

An ESPI experimental study on the phenomenon of fracture in glass. Is it brittle or plastic?

The crack opening displacement (COD) in annealed soda-lime (float) glass has been measured with an electronic speckle pattern interferometry (ESPI) apparatus using coherent laser light. Specimens, naturally pre-cracked with a particular technique, were loaded under strain-driven bending until crack propagated; at regular intervals loading was paused to let the crack reach subcritical equilibrium and the COD measured. By using a post-processing algorithm comparing four images lighted with phase-shifted laser beams, surface displacements could be measured at a resolution of .Glass transparency has allowed to see through that the propagating crack front is not sharp but curved, jagged and merged in an opaque neighborhood. Numerical simulations show that the measured CODs cannot be reproduced if cohesive surface forces à la Barenblatt-Dugdale bridge the crack lips; instead a plastic-like region must form in a bulk neighborhood of the tip, where inelastic strains are associated with volume increase rather than deviatoric distortion. For this, a Gurson-Tvergaard model of porous plasticity, accounting for the formation of microvoids/microcracks, has been found more efficient than classical von Mises plasticity. This study confirms the formation at the crack tip of a process zone, whose occurrence in brittle materials like glass is still a subject of controversy.     

On the Motive Power of Chemical Transformations in?Open Systems

The classical basic concepts of cyclic processes and the efficiency of heat engines are used here to conjecture about the laws of thermodynamics for open systems that can exchange matter with a surrounding environment. An ideal chemomechanical elastic bar is envisioned that changes its stiffness while undergoing a chemical transformation which is, in turn, influenced by the axial strain of the bar. Stable equilibrium states are identified as minimizers of the total energy, which is assumed to be nonconvex in type. If the bar is loaded and then alternatively placed in environments at chemical potentials either ?? _i or ?? _s >?? _i , a reversible cycle analogous to the classical Carnot cycle may be traced. In this case, the environmental ??chemical potential?? plays the role of the temperature and the ??chemical work?? the role of heat. For the system, the main form of interaction with the exterior, other than mechanical work, is the exchange of mass of a component at different environmental chemical potentials. It is then possible to obtain an elementary theory of chemical engines in which efficiency estimates (in terms of environmental chemical potentials) and related pertinent issues can be discussed. This model may serve as a basis for analyzing coupled chemo-mechanical processes occurring in materials such as ionized gels for possible applications as actuators, and to interpret complex phenomena in biological systems, such as the chemical kinetics of smooth muscles.     

Metal-based antitumour drugs in the post-genomic era: what comes next?

In our Dalton Transactions Perspective article entitled, 'Metal-based antitumour drugs in the post genomic era', (Dalton Trans., 2006, 1929-1933) we discussed metal-based drugs in light of past decades of research. We concluded that the post-genomic era would dictate a change in the direction of the field with knowledge of the genome increasingly allowing protein targets to be identified and not simply assuming that DNA is the only relevant target of metal-based drugs. Since our article was published new insights into the mode of action of metal-based drugs have emerged making some older findings increasingly relevant to current drug design. In this article we discuss these developments in terms of what we believe should be the future direction for the field.     

Ruthenium anticancer compounds: myths and realities of the emerging metal-based drugs

Ruthenium anticancer drugs have attracted an increasing interest in the last 20 years and two of them have entered clinical trials. Compared to platinum drugs, the complexes based on ruthenium are often identified as less toxic and capable of overcoming the resistance induced by platinum drugs in cancer cells. These activities were attributed to the transportation to tumour cells by transferrin and to the selective activation to more reactive species by the reducing environment of solid tumours as compared to healthy tissues. Ruthenium anticancer drugs have been almost always designed to mimic platinum drugs, particularly for targeting DNA. Indeed, none of the above properties has never been clearly demonstrated even for the ruthenium drugs that entered clinical trials. The suggestion for the future is to change the perspective when designing new chemical entities, abandoning the philosophy that guided the actual panel of ruthenium drugs and to look further into the fine mechanism by which the most relevant ruthenium complexes available kill the target tumour cells, then focusing on targets selective of tumour cells and responsible for cell growth and malignancy.     

Organometallic ruthenium-based antitumor compounds with novel modes of action

Both metal complexes and organic molecules are widely used for the treatment of various diseases including cancer - in addition to surgery and radiotherapy. Recent years have witnessed a surge of interest in the application of organometallic compounds to treat cancer and other diseases. Indeed, the unique properties of organometallic compounds, intermediate between those of classical inorganic and organic materials provide new opportunities in medicinal chemistry. In this review, based on the award lecture at ICBOMC’10, we describe a class of ruthenium(II)-arene complexes that are weakly cytotoxic in vitro, but show selective antimetastatic activity in vivo. These compounds, [Ru(η⁶-p-arene)Cl₂(pta)] termed RAPTA, interact strongly with proteins, with the ability to discriminate binding to different proteins, but show a relatively low propensity to bind DNA, which is considered to be the main target of many metal-based drugs. The basic RAPTA structure is quite stable in physiological environments, and studies have shown that aquation of the chloride bonds occurs, it may not be an essential step for anticancer drug activity - direct substitution with biomolecular targets is also possible. Based on the favorable physicochemical properties of RAPTA compounds, combined with their highly promising pharmacological properties, the structure represents an ideal scaffold for rational drug design. Thus far, strategies to overcome drug resistance, by interference with critical enzymes responsible for drug deactivation, and tumor targeting, by tethering to human serum albumin via hydrolyzable linkers, have been demonstrated. However, many more approaches can be envisaged. In any case, the net result are a type of hybrid compounds, that occupy a niche somewhere between classical cisplatin-type anticancer agents that are widely applied to many tumor types and targeted therapies based on organic structures used to inhibit specific enzymes. As such, should these compounds prove themselves in the clinic it is not inconceivable that they could be rapidly refined to form personalized chemotherapies.     

Specificity in the Cu interactions with prion protein fragments and related His-rich peptides from mammals to fishes

The prion proteins may play a critical role in copper homeostasis and the antioxidant activity in the brain. This review presents the state of art in the studies on Cu²⁺ prion systems. The proteins discussed are from different species from mammals to fishes. All proteins are His-rich and the research discussed clearly indicates the basic role of imidazole side chains and the adjacent amide nitrogen atoms in metal ion binding. Prions represent the family of proteins with new mode of Cu²⁺ binding which includes the amide nitrogen coordination. The multi-imidazole coordination is also likely and it can play a critical role in the antioxidant activity of the copper–prion complexes. The combination of the imidazole and amide nitrogen atoms to Cu²⁺ ions could also be relevant in histidine-rich peptide antibiotics including demegen. The impact of peptide sequence and His positions on copper binding ability is also discussed.