G. Albertini

An efficient solver for nearshore flows based on the WAF method

Abstract We describe an efficient and robust flow solver for the integration of the classic Nonlinear Shallow Water Equations (NSWE) on a beach of arbitrary topography. On the basis of the ‘shock capturing’ Weighted Average Flux (WAF) method, a numerical code is implemented which employs a space-splitting technique to integrate the NSWE over a horizontally two-dimensional domain (2DH). Special care is put in handling the moving shoreline and a new, efficient formulation of the shoreline boundary conditions is presented. This is based on the hydrodynamic equivalent of the cavitation condition used in gas dynamics. Model capabilities are illustrated by means of a number of tests (both 1DH and 2DH). These reveal that, though primarily conceived for modelling nearshore hydrodynamics, the solver can be successfully adopted even for studying the run-up of large tsunami waves.

Thermodynamic and structural effects of propranolol on DPPC liposomes

Some thermodynamic and structural aspects of propranolol-DPPC liposomes interaction were investigated by DSC and X-ray diffraction: the lamellar arrangement of the lipid matrix remains intact even at high concentrations of the drug (until 1:1 drug/lipid molar ratio). However, the bilayer thickness increases significantly and the chains become perpendicular to the lamellar planes, for increasing drug content. At still higher propranolol concentrations a hexagonal phase occurs followed by a lamellar phase, in which the liposomes are destroyed. Moreover, the presence of propranolol has been found to impart fluidity to the lipid matrix.

Determination of residual stresses in materials and industrial components by neutron diffraction

We present a review of the determination of residual stresses in materials and components of industrial interest by using the non-destructive technique of neutron diffraction. The fundamental aspects are discussed, together with a brief description of the experimental facilities. Several experimental results are then reported, particularly concerning applications to materials and components for power plants (CrMo steel, AISI304 stainless steel and 2.25Cr1Mo ferritic steel), aerospace and automotive technology (Al alloys, metal matrix composites, nickel superalloy gas-turbine components) and fusion-reactor technology (AISI316L for the first wall). A few thermomechanical treatments are considered, such as welding, cold-expanded holes, thermoelastic coupling and thermal and mechanical fatigue. Moreover, a few applications to general industrial problems are shown, namely brazed ceramic-steel components, coatings and fatigue-cracked samples. In some cases, experimental results are compared with numerical models or results from x-ray diffraction measurements.

Organization of Extracellular Matrix Fibers Within Polyglycolic Acid–Polylactic Acid Scaffolds Analyzed Using X-Ray Synchrotron-Radiation Phase-Contrast Micro Computed Tomography

Spatiotemporal organized patterns of cell surface-associated and extracellular matrix (ECM)-embedded molecules play important roles in the development and functioning of tissues. ECM proteins interact with the surface of bioscaffold polymers and influence material-driven control of cell differentiation., Using X-ray phase-contrast micro computed tomography (microCT), we visualized the three-dimensional (3D) image of ECM organization after in vitro seeding of bone marrow-derived human and murine mesenchymal stem cells (MSCs) induced to myogenic differentiation, labelled with iron oxide nanoparticles, and seeded onto polyglycolic acid-polylactic acid scaffolds. X-ray microCT enabled us to detect with high spatial resolution the 3D structural organization of ECM within the bioscaffold and how the presence of cells modified the construct arrangement. Species-specific differences between the matrix produced by human and murine cells were observed. In conclusion, X-ray synchrotron radiation microCT analysis appeared to be a useful tool to identify the spatiotemporal pattern of organization of ECM fibers within a bioscaffold.

Interaction of the herbicide atrazine with model membranes I: physico-chemical studies on dipalmitoyl phosphatidylcholine liposomes

Atrazine (2-chloro-4 ethylamino-6-(isopropylamino)-s-triazine) is one of the most widely used herbicides. Fourier transform infrared spectroscopy, differential scanning calorimetry and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and of its derivative 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) were used to study the interaction of atrazine with dipalmitoyl phosphatidylcholine liposomes used as a model for biological membranes. The results show that atrazine does not perturb the hydrophobic core of the lipid bilayer and suggest that the herbicide localizes near the glycerol backbone of the lipid.

EVIDENCE OF ALPHA EMISSION FROM COMPRESSED STEEL BARS

Four cylindrical steel bars of 2 cm diameter and 20 cm height were subjected to compression cycles each of them consisting of a loading phase at fixed stress rate followed by a rapid stress release. Different compression rates were used for the same sample. The area surrounding the loaded samples was monitored in order to check whether ionizing particles were emitted. To this aim, three ZnS(Ag) detectors, a Geiger counter, and some polycarbonate CR39 detectors of alpha particles were used. An 3He proportional detector of neutrons was also used. The whole set of results is discussed and proposed as an evidence of alpha particles emission from the bars during the compression cycles.

Lipid-aminoacid interactions: a study of tryptophan effects on dipalmitoyl-phosphatidylcholine multilamellar liposomes

Abstract Experimental evidence of tryptophan incorporation inside dipalmitoyl-lecithin liposomes is reported. The thermodynamic and structural changes induced in the model membranes by tryptophan were investigated by using electron spin resonance (ESR), X-ray diffraction, calorimetry and fluorescence techniques. The amino acid interacts with the polar region of the membrane at low tryptophan concentrations, and with the hydrophobic interior of the membrane at the higher concentrations. The liposomes-tryptophan reciprocal effects are discussed as an example of perturbation induced by an exogenous molecule that penetrates the lipid bilayer. Moreover, they are relevant in relation to the study of lipid-protein interactions and for the possible use of liposomes as amino acid carriers.

DEFORMED SPACE-TIME OF THE PIEZONUCLEAR EMISSIONS

In this paper, an experimental verification of the relationship between the deformed Minkowsky space-time and the piezonuclear emission has been obtained by testing several cylindrical steel bars cyclically loaded in a mechanical fatigue machine. During the compression cycles, α-particles have been both detected by a ZnS(Ag) scintillator and a Geiger counter. Taking into account the theory of the deformed special relativity, we report that the emission only occurs after a specific value of energy is overcome. This value is strictly related to the weak and strong nuclear interactions, which in turn define the regions of Minkowsky and non-Minkowsky space-time.

Neutron diffraction measurements for the determination of heat treatment effectiveness in generating compressive residual stress in an automotive crown gear

Abstract Thermal austenitizing and tempering treatments are being developed in automotive industry to prevent crack initiation and propagation, especially in components where stress intensity factors influence the stress field and ultimately the fatigue life of the component. This is the case of crown gears, where the tooth root typically undergoes impulsive and very high loads which frequently cause cracking if tensile residual stresses are present at the surface. The sign reversal of these stresses is the aim of austenitizing and tempering treatments. In this work neutron diffraction measurements of residual stress (RS) on a UNI55Cr3 steel crown gear, carried out at HMI-BENSC 1 , are presented. The sample was submitted to a new multi-frequency induction technique whose effectiveness was checked. Comparisons with X-ray measurements are shown, and RS measured by X-rays on a similar shot-peened sample are also mentioned.

Lipid-drug interaction: A structural analysis of pindolol effects on model membranes

The ternary system constituted by distearoylphosphatidylcholine, pindolol (a vasodilator drug) and water has been investigated by using X-ray diffraction and calorimetric techniques. The structural modifications induced by the drug have been determined and a possible interaction model has been derived. In particular, the pindolol content-temperature dependent phase diagram shows the occurrence of two new phases: the first is an interdigitated gel, and the second is a lamellar structure presenting an unusual mixed disordered-ordered conformation of the hydrocarbon chains (L alpha beta). The comparative analysis of electron density profiles relative to the L alpha beta phase, reveals significant modifications in the paraffinic region of the lipid layer. In agreement with thermodynamic results, the structural data suggest that the drug induces a stiffening and a tightening of the hydrocarbon chains. Moreover, the hydrophilic properties of the membrane (particularly in P beta, and L alpha beta phases) present an evident dependence with the drug concentration.