Roughening of close-packed singular surfaces

An upper bound to the roughening temperature of a close-packed singular surface, fcc Al (111), is obtained via free energy calculations based on thermodynamic integration using the embedded-atom interaction model. Roughening of Al (111) is predicted to occur at around 890 K, well below bulk melting (933 K), and it should therefore be observable, save for possible kinetic hindering.Comment: RevTeX 4 pages, embedded figure

Studio di complessi di rame (II) e platino (II) con proprietà antitumorali

Cisplatin is one of the most active drugs in anticancer therapy, and it is currently used for the treatment of a wide range of cancers, in particular advanced ones. After its introduction in clinical therapy, the research in this field has focused on the preparation of new metal complexes with increased activity and lower side-effects. Besides, the use of drug combinations with synergistic effect, i.e. an effect greater than the sum of the effects of the single drugs, has been introduced. This thesis is focused on the preparation of Cu(II) and Pt(II) complexes and on the study of their cytotoxic properties, alone or in combination with cisplatin. Cu(II) complexes with 1,10-phenantroline (phen), 1,10-phenantrolin-5,6-dione and 1,10- phenantrolin-5,6-diol, with 1:1 or 1:2 metal:ligand stoichiometry, have been synthesized. In addition, mixed Cu(II) complexes with phen and thiophene derivatives of general formula [Cu(phen)2(T)](ClO4)2 (T=1-methylthio-thiophene-2-carboxylic acid, 2- methylthio-thiophene-1-carboxylic acid, 2-thiophenecarboxamide, 2- thiophenecarboxylate) have been prepared. A family of Pt(II) complexes of general formula [Pt(P)(D)2](ClO4)2, being P a derivative of phen and D a derivative of imidazolidin-2-thione, has been synthesized. In order to find the species present in solution in conditions similar to the physiological ones (37 °C and NaCl 0.1 M), the formation constants of the complexes have been determined through potentiometric titrations. The dipole moments of the platinum complexes have been determined through quantum mechanical calculations. The in vitro cytotoxic activity of ligands and metal complexes has been evaluated against a panel of human tumour cell lines, and it has been correlated to their structures. Finally, a new method, based on experimental design and artificial neural networks, has been proposed for the evaluation of the synergy in mixtures of two or more drugs. Exploiting this method, the cytotoxic activity of mixture of cisplatin and three Cu(II) complexes ([Cu(phen)(H2O)2(ClO4)2], [Cu(phen)2(H2O)](ClO4)2 e [Cu(phen)2(imidazolidin-2-thione)](ClO4)2) has been studied, and the combination with higher synergistic effect have been identified

Computational Modeling of Open Framework Silicates: Probing Straight Bond Angles in Ferrierite Reveals Intriguing Links Between Mineralogy, Nanomaterial Science and Technological Applications

For several decades, zeolites have acted as a porous bridge intimately connecting mineralogy to advanced technology through industrial applications. Such a key linkage between mineral and material science has been reinvigorated by the numerous successes of computational modeling. The intriguingrelationships between synthetic zeolites and their natural counterparts unveiled by theoretical studies have greatly contributed to improve the properties and practical applications of zeolite-based materials in various technological areas ranging from industrial catalysis, to environmental protection, up toadvanced optics, electronics, and solar energy harvesting. To pinpoint the key role of modeling in zeolite science, we focus herein on a simple yet instructive example of computational-driven problemsolving: can tetrahedral frameworks sustain straight (i.e. 180°) Si-O-Si bond angles? Indeed, the true crystal symmetry of zeolite ferrierite, especially in its all-silica form, has been intensely debated for 30 years before being solved in the Pmnn space group. Yet there are indications that an Immm structure, featuring energetically unfavourable flat (180°) Si-O-Si angles, could be formed at high temperature. To provide insight on this issue, we perform density functional theory optimizations and frequency calculations of all-silica ferrierite in both the Pmnn and Immm space groups. Our results indicate that Pmnn is more stable than Immm, in line with experiments. While the Pmnn structure is a true minimum in the free energy profile of ferrierite, the Immm structure has four imaginary frequency vibrations, two of which are localized on the 180° Si-O-Si angles. This suggest that ferrierites with Immm symmetry may be classified as metastable phases. Such a designation is also supported by firstprinciples molecular dynamics on Immm FER, evidencing that the average value of 180° actually results from Si-O-Si angle inversion. An exciting implication of this study with interesting geological and technological consequences is the possible association of flat Si-O-Si angles experimentally detected in open-framework silicates to metastable structures characterized by pore openings more circular than in the corresponding equilibrium structures. Such a lower channel ellipticity might play an important role in sorption phenomena, which are ubiquitous in geological processes and industrial applications alike. More in general, this work underlines how highly complex processes involving zeolite materials can be understood and accurately captured using theoretical techniques.</div

Computer modeling of apparently straight bond angles: The intriguing case of all-silica ferrierite

The relationships between synthetic zeolites and their natural counterparts that have been unveiled by theoretical studies have contributed to improving the properties and applications of zeolite-based materials in strategic areas such as industrial catalysis, environmental protection, and solar energy harvesting. To pinpoint the role of modeling in zeolite science, we discuss an example of computationally driven problem solving: can tetrahedral frameworks sustain straight (i.e., 180 degrees) Si-O-Si bond angles? The true crystal symmetry of zeolite ferrierite (FER), especially in its all-silica form, had been intensely debated for 30 years before being solved in the Pmnn space group. Yet there are indications that an Immm structure with energetically unfavorable linear Si-O-Si linkages could be formed at high temperature. To gather insight, we perform density functional theory (DFT) optimizations and frequency calculations of all-silica ferrierite in both the Pmnn and Immm space groups. Our results indicate that Pmnn is more stable than Immm, in line with experiments. While the Pmnn structure is a true minimum in the energy profile of ferrierite, the Immm structure has four imaginary frequency vibrations, three of which are localized on the 180 degrees Si-O-Si angles. This suggests that ferrierites with Immm symmetry may be classified as metastable phases. Such a designation is also supported by first-principles molecular dynamics on Immm FER, showing that the average value of 180 degrees actually results from Si-O-Si angle inversion. An implication of this study with interesting geological and technological consequences is the association of straight Si-O-Si angles experimentally detected in open-framework or low-density silicates to an angle-inversion process occurring at the femtosecond scale. Such flexibility of the apparently flat Si-O-Si linkages might play an important role in sorption phenomena, which are ubiquitous in geological processes and industrial applications alike.The relationships between synthetic zeolites and their natural counterparts that have been unveiled by theoretical studies have contributed to improving the properties and applications of zeolite-based materials in strategic areas such as industrial catalysis, environmental protection, and solar energy harvesting. To pinpoint the role of modeling in zeolite science, we discuss an example of computationally driven problem solving: can tetrahedral frameworks sustain straight (i.e., 180\ub0) Si-O-Si bond angles? The true crystal symmetry of zeolite ferrierite (FER), especially in its all-silica form, had been intensely debated for 30 years before being solved in the Pmnn space group. Yet there are indications that an Immm structure with energetically unfavorable linear Si-O-Si linkages could be formed at high temperature. To gather insight, we perform density functional theory (DFT) optimizations and frequency calculations of all-silica ferrierite in both the Pmnn and Immm space groups. Our results indicate that Pmnn is more stable than Immm, in line with experiments. While the Pmnn structure is a true minimum in the energy profile of ferrierite, the Immm structure has four imaginary frequency vibrations, three of which are localized on the 180\ub0 Si-O-Si angles. This suggests that ferrierites with Immm symmetry may be classified as metastable phases. Such a designation is also supported by first-principles molecular dynamics on Immm FER, showing that the average value of 180\ub0 actually results from Si-O-Si angle inversion. An implication of this study with interesting geological and technological consequences is the association of straight Si-O-Si angles experimentally detected in open-framework or low-density silicates to an angle-inversion process occurring at the femtosecond scale. Such flexibility of the apparently flat Si-O-Si linkages might play an important role in sorption phenomena, which are ubiquitous in geological processes and industrial applications alike

First principles studies on boron sites

Results of periodic first-principles calculations on boron containing zeolites are presented. The boron site trigonal-to-tetrahedral transition is studied in model B-SOD and B-FER. We show how boron acid sites in different frameworks respond differently to bases

Deepening the Knowledge of ROS1 Rearrangements in Non-Small Cell Lung Cancer: Diagnosis, Treatment, Resistance and Concomitant Alterations

ROS proto-oncogene 1 (ROS1) rearrangements are reported in about 1&ndash;2% of non-squamous non-small-cell lung cancer (NSCLC). After efficacy of crizotinib was demonstrated, identification of ROS1 translocations in advanced disease became fundamental to give patients the chance of specific and effective treatment. Different methods are available for detection of rearrangements, and probably the real prevalence of ROS1 rearrangements is higher than that reported in literature, as our capacity to detect gene rearrangements is improving. In particular, with next generation sequencing (NGS) techniques, we are currently able to assess multiple genes simultaneously with increasing sensitivity. This is leading to overcome the &ldquo;single oncogenic driver&rdquo; paradigm, and in the very near future, the co-existence of multiple drivers will probably emerge more frequently and represent a therapeutic issue. Since recently, crizotinib has been the only available therapy, but today, many other tyrosine kinase inhibitors (TKI) are emerging and seem promising both in first and subsequent lines of treatment. Indeed, novel inhibitors are also able to overcome resistance mutations to crizotinib, hypothesizing a possible sequential strategy also in ROS1-rearranged disease. In this review, we will focus on ROS1 rearrangements, dealing with diagnostic aspects, new therapeutic options, resistance issues and the coexistence of ROS1 translocations with other molecular alterations