Variable metric bundle methods: From conceptual to implementable forms

To minimize a convex function, we combine Moreau-Yosida regularizations, quasi-Newton matrices and bundling mechanisms. First we develop conceptual forms using “reversal” quasi-Newton formulae and we state their global and local convergence. Then, to produce implementable versions, we incorporate a bundle strategy together with a “curve-search”. No convergence results are given for the implementable versions; however some numerical illustrations show their good behaviour even for large-scale problems.     

Direct angle resolved photoemission spectroscopy and superconductivity of strained high-T c films

Since 1997 we systematically perform direct angle resolved photoemission spectroscopy (ARPES) on in-situ grown thin (<30 nm) cuprate films. Specifically, we probe low-energy electronic structure and properties of high-T _c superconductors (HTSC) under different degrees of epitaxial (compressive vs. tensile) strain. In overdoped and underdoped in-plane compressed (the strain is induced by the choice of substrate) ≈15 nm thin La_{2 − x} Sr _x CuO₄ (LSCO) films we almost double T _c to 40 K, from 20 K and 24 K, respectively. Yet the Fermi surface (FS) remains essentially two-dimensional. In contrast, ARPES data under tensile strain exhibit the dispersion that is three-dimensional, yet T _c drastically decreases. It seems that the in-plane compressive strain tends to push the apical oxygen far away from the CuO₂ plane, enhances the two-dimensional character of the dispersion and increases T _c, while the tensile strain acts in the opposite direction and the resulting dispersion is three-dimensional. We have established the shape of the FS for both cases, and all our data are consistent with other ongoing studies, like EXAFS. As the actual lattice of cuprates is like a ‘Napoleon-cake’, i.e. rigid CuO₂ planes alternating with softer ‘reservoir’, that distort differently under strain, our data rule out all oversimplified two-dimensional (rigid lattice) mean field models. The work is still in progress on optimized La-doped Bi-2201 films with enhanced T _c.      

High strength,acid-resistant composites from canola,sunflower, or linseed oils: Influence of triglyceride unsaturation on material properties

Here are reported composites made by crosslinking unsaturated units in canola, sunflower, or linseed oil with sulfur to yield CanS , SunS , and LinS , respectively. These plant oils were selected because the average number of crosslinkable unsaturated units per triglyceride vary from 1.3 for canola to 1.5 for sunflower and 1.8 for linseed oil. The remeltable composites show compressive strengths that increase with increasing unsaturation number from CanS (9.3 MPa) to SunS (17.9 MPa) to LinS (22.9 MPa). These values for SunS and LinS are competitive when compared with the value of 17 MPa required for residential building using traditional Portland cement. The plant oil composites are recyclable over many cycles and can retain up to 100% of strength after 24 hr in oxidizing acid under conditions where Portland cement is dissolved in under 30 min. Infusion of the composites into premade cement blocks affords them with significantly improved acid resistance as well. This work thus provides a simple, nearly 100% atom economical route to convert plant oils and waste sulfur to composites having enhanced performance over commercial structural materials.     

Structural investigation of group 10 metal complexes with thiosemicarbazone: crystal structure,mass spectrometry,Hirshfeld surface and in vitro antitumor activity

Structural Chemistry - The current work reports the synthesis and structural investigation of three novel complexes with 2-acetyl-pyridine-N(4)-phenylthiosemicarbazone (HL1), [Ni(L1)Cl] (1),...     

Thermal analysis: an effective characterization method of polyvinyl acetate films applied in corrosion inhibition field

Journal of Thermal Analysis and Calorimetry - To prepare a commercial product with economic and technical relevance, polyvinyl acetate (PVAc) was synthesized, under our laboratory conditions,...     

Metaheuristics for the team orienteering problem

The Team Orienteering Problem (TOP) is the generalization to the case of multiple tours of the Orienteering Problem, known also as Selective Traveling Salesman Problem. A set of potential customers is available and a profit is collected from the visit to each customer. A fleet of vehicles is available to visit the customers, within a given time limit. The profit of a customer can be collected by one vehicle at most. The objective is to identify the customers which maximize the total collected profit while satisfying the given time limit for each vehicle. We propose two variants of a generalized tabu search algorithm and a variable neighborhood search algorithm for the solution of the TOP and show that each of these algorithms beats the already known heuristics. Computational experiments are made on standard instances.     

Pseudo-Differential Operators in Algebras of Generalized Functions and Global Hypoellipticity

The aim of this work is to develop a global calculus for pseudo-differential operators acting on suitable algebras of generalized functions. In particular, a condition of global hypoellipticity of the symbols gives a result of regularity for the corresponding pseudo-differential equations. This calculus and this frame are proposed as tools for the study in Colombeau algebras of partial differential equations globally defined on R ⁿ .     

Weighted Best Local Approximation

In this survey, the notion of a balanced best multipoint local approximation is fully exposed since they were treated in the Lpspaces and recent results in Orlicz spaces. The notion of balanced point, which was introduced by Chui et al. in 1984 are extensively used.     

Characterisation of ancient Roman wall-painting fragments using non-destructive IBA and MA-XRF techniques

Scientific investigation is very important in studies addressing issues of archaeological and historical objects. Ion beam analysis (IBA) and macro X-ray fluorescence (MA-XRF) spectroscopy are remarkable tools to obtain information about elemental composition and imaging of historical artefacts with a non-invasive character. These investigation techniques were employed in the framework of a project aimed at supporting the characterization of materials and techniques related with the Roman wall painting. The archaeological excavations at Villa della Piscina in Rome have revealed a luxury building with a large pool (about 50 m long) and thermal baths and numerous fragments of plaster, coming from intentional demolitions referable to two distinct architectural contexts of the Villa during the imperial age, have been found. This work deals with studying the interesting wall pictorial apparatus of great cultural value of the heritage inherited from the Roman age in the area of the ancient city of Rome. The colour palette of the pigments investigated, in particular, by MA-XRF and particle-induced X-ray emission (PIXE) and has revealed Fe, Cu, Pb, Si and Hg as main elements. Traces of other constituents uncover the choice of the different colours chosen by the artists who had embellished the rooms of the Villa.