Multidomain Symmetric Galerkin BEM for non-linear analysis of masonries in-plane loaded

The preservation of the historical and monumental buildings, but also of the considerable heritage of old constructions made by traditional techniques, is one of the actual problems of the structural mechanics. The level of knowledge of their structural behavior in presence of external actions is made through calculus methods and simple procedures in order to allow a reading of the material suffering degree and as a consequence of the related safety. In this paper an elastic analysis of walls, also in presence of geometrical nonlinearity consisting in the contact/detachment phenomenon among stone blocks. The wall having any shape and zone-wise variable physical characteristics is loaded in its plane. For these structures some interventions of structural strengthening have as aim to improve the wall behavior by reducing the stress concentration, so to have a better safety in comparison with its initial value

A symmetric BEM approach to strain gradient elasticity for 2D static boundary-value problems

The symmetric Galerkin Boundary Element Method is used to address a class of strain gradient elastic materials featured by a free energy function of the (classical) strain and of its (first) gradient. With respect to the classical elasticity, additional response variables intervene, such as the normal derivative of the displacements on the boundary, and the work-coniugate double tractions. The fundamental solutions - featuring a fourth order partial differential equations (PDEs) system - exhibit singularities which in 2D may be of the order 4 1/ r . New techniques are developed, which allow the elimination of most of the latter singularities. The present paper has to be intended as a research communication wherein a part of the results, being elaborated within a more general paper are reported

Strain energy evaluation in structures having zone-wise physical-mechanical quantities

Among the possible aims of structural analysis inside some engineering spheres it can be useful to know the strain energy stored in all or in a part of the structure caused by assigned external actions, like the boundary and domain quantities. This serves to evaluate globally whether an assigned portion of structure undergoes an excessive store of energy able to compromise the stability of all the structure. This evaluation can be carried out through boundary work obtained using appropriate boundary generalized quantities connected to the results of the analysis on the whole structure. The advantage consists in using a very restricted number of quantities which, because of the characteristics of the method, are only evaluated on the boundary. Some strategies used to evaluate the error made are introduced through the computation of the external direct work and of the reciprocal works involving quantities only connected to the boundary of the complementary domain and quantities connected to either the real boundary of the structure or the boundary of its complementary domain. A reduction of this error is suggested

Elastoplastic analysis by active macro-zones with linear kinematic hardening and von Mises materials

In this paper a strategy to perform elastoplastic analysis with linear kinematic hardening for von Mises materials under plane strain conditions is shown. The proposed approach works with the Symmetric Galerkin Boundary Element Method applied to multidomain problems using a mixed variables approach, to obtain a more stringent solution. The elastoplastic analysis is carried out as the response to the loads and the plastic strains, the latter evaluated through the self-equilibrium stress matrix. This matrix is used both, in the predictor phase, for trial stress evaluation and, in the corrector phase, for solving a nonlinear global system which provides the elastoplastic solution of the active macro-zones, i.e. those zones collecting bem-elements where the plastic consistency condition has been violated. The simultaneous use of active macro-zones gives rise to a nonlocal approach which is characterized by a large decrease in the plastic iteration number, although the proposed strategy requires the inversion and updating of Jacobian operators generally of big dimensions. A strategy developed in order to reduce the computational efforts due to the use of this matrix, in a recursive process, is shown

Strain gradient elasticity within the symmetric BEM formulation

The symmetric Galerkin Boundary Element Method is used to address a class of strain gradient elastic materials featured by a free energy function of the (classical) strain and of its (first) gradient. With respect to the classical elasticity, additional response variables intervene, such as the normal derivative of the displacements on the boundary, and the work-coniugate double tractions. The fundamental solutions - featuring a fourth order partial differential equations (PDEs) system - exhibit singularities which in 2D may be of the order 1/ r 4 . New techniques are developed, which allow the elimination of most of the latter singularities. The present paper has to be intended as a research communication wherein some results, being elaborated within a more general paper [1], are reported

Characterization of the terminal column of TRIGA Mark II reactor of Mainz through of alanine pellets.

We have studied the ESR response of alanine pellets with and without gadolinium exposed to the thermal column of the TRIGA Mark II research reactor at the University of Mainz (Germany). The choice of Gd as additive nucleus is due to its very high capture cross section to thermal neutrons and to the possibility for secondary particles produced after interaction with thermal neutrons of releasing their energy in the neighborhood of the reaction site. In particular, it was found that low concentration (5% by weight) of Gd brings about a neutron sensitivity enhancement of more than 10 times without heavily reducing tissue equivalence. Monte Carlo (MC) simulations of both response of alanine and Gd-alanine pellets with FLUKA code were performed and the results were compared with the experimental values

Dosimetry to Electron Spin Resonance (ESR) using organic compounds (alanine and ammonium tartrate) for mixed neutron-gamma fields

Alongside with the development of Neutron Capture Therapy (NCT) and the use of thermal neutrons for radiotherapeutic purposes, many efforts have been devoted to the characterization of the beam in order to optimize therapy procedures. Reliable dose measurements should be able to determine the various (neutrons and photonic) components of the mixed beam usually employed for therapy. This paper studies the effect of additives such as Boric and Gadolinium nuclei on the sensitivity of neutron organic (alanine and ammonium tartrate) dosimeters analyzed through Electron Spin Resonance (ESR) technique. These dosimeters were exposed to a mixed (neutron-gamma) field mainly composed of thermal neutrons. The choice of 10B and 64Gd as nuclei additives is due to their very high capture cross section for thermal neutrons. Also, after the nuclear reaction with thermal neutrons are emitted particles, which in turn release their energy in the vicinity of the reaction site. The irradiation with mixed (neutron-gamma) field were performed within the thermal column of the TRIGA reactor, University of Pavia. Dosimeters readout was performed through the Electron Spin Resonance (ESR) spectrometer Bruker ECS106 located at the Laboratory of Dosimetry ESR / TL of the Department of Physics and Chemistry - University of Palermo. We found that the addition of Gadolinium allows to largely increase the sensitivity of the dosimeters for thermal neutrons. In particular, a low concentration (5% by weight) of gadolinium oxide leads to an improvement of the sensitivity of neutrons more than 10 times. In addition, for this low content of gadolinium the photon tissue equivalence is not heavily reduced. This experimental analyses are compared with computational analyses carried out by means of Monte Carlo simulations performed with the MCNP (Monte Carlo N-Particle) transport code. A good agreement was observed for alanine dosimeters

Atti del Workshop: Tecniche Speciali e Avanzate di Dosimetria e Radioprotezione

Atti del Workshop organizzato dall'Associazione Italiana di Radioprotezione (AIRP) in collaborazione con l'Università degli Studi di Palermo, dal titolo "Tecniche Speciali e Avanzate in Dosimetria e Radioprotezione" che si svolgerà venerdì 24 Giugno a Palermo presso l'Aula Magna del Dipartimento di Fisica e Chimica, Viale delle Scienze Edificio 18. L'evento rientra tra i 210 Eventi organizzati per i 210 anni dalla fondazione dell'Ateneo palermitano su iniziativa del Magnifico Rettore, Prof. Fabrizio Micari. L’evento prevede la discussione di 4 tematiche in ambito della dosimetria e della radioprotezione in campo sanitario ed ambientale (Dosimetria Clinica, Dosimetria Ambientale, Dosimetria Retrospettiva e Tecniche Dosimetriche avanzate in Radioprotezione) ciascuna delle quali ha una relazione generale ad invito e alcune brevi comunicazioni orali. Le sessioni sono moderate da Dirigenti Fisici medici di due delle più importanti Aziende Ospedaliere Siciliane, Dirigenti dell’Istituto Superiore di Sanità e l’ex Rettore dell’Ateneo e membro del CdA del CNR, il Prof. Roberto Lagalla. Interverranno il magnifico Rettore dell’Università di Palermo, l’Assessore alla Sanità della Regione Sicilia, il Direttore dell’Istituto Zooprofilattico Sperimentale di Sicilia, il Direttore Generale dell’Agenzia per la Protezione dell’Ambiente Sicilia, il Direttore del Dipartimento di Fisica e Chimica, il Direttore di ATeN Center (Advanced Technologies Network), Dirigenti Fisici dell’Istituto Superiore di Sanità e dell’Istituto Europeo Oncologico di Milano. Hanno contribuito alla parte organizzativa e scientifica Dirigenti dell’ARPA Sicilia, Dirigenti dell’ARNAS Civico di Palermo, Docenti dell’Università di Palermo e di Milano, Ricercatori del CNR e Specializzandi UniPa. Questo evento è di grande rilevanza nazionale in termini di divulgazione scientifica vista la presenza dei relatori e moderatori invitati che ne danno lustro e rilevanza. Sarà un'occasione di confronto e di analisi retrospettiva a quarant'anni della giornata di studio “Problemi e prospettive della Fisica Sanitaria nel settore medico” organizzata dalla Prof.ssa Maria Brai

1,3,4-Oxadiazole and 1,3,4-Thiadiazole Nortopsentin Derivatives against Pancreatic Ductal Adenocarcinoma: Synthesis, Cytotoxic Activity, and Inhibition of CDK1

A new series of nortopsentin analogs, in which the central imidazole ring of the natural lead was replaced by a 1,3,4-oxadiazole or 1,3,4-thiadiazole moiety, was efficiently synthesized. The antiproliferative activity of all synthesized derivatives was evaluated against five pancreatic ductal adenocarcinoma (PDAC) cell lines, a primary culture and a gemcitabine-resistant variant. The five more potent compounds elicited EC50 values in the submicromolar-micromolar range, associated with a significant reduction in cell migration. Moreover, flow cytometric analysis after propidium iodide staining revealed an increase in the G2-M and a decrease in G1-phase, indicating cell cycle arrest, while a specific ELISA demonstrated the inhibition of CDK1 activity, a crucial regulator of cell cycle progression and cancer cell proliferation

Characterization of phenolic pellets for ESR dosimetry in photon beam radiotherapy.

We report a study of the dosimetric features of phenolic compounds for applications in radiation therapy dosimetry of clinical photon beams by using ESR spectroscopy. After the optimization of the ESR readout parameters, basic dosimetric properties (such as intra-batch reproducibility, dose-response, sensitivity, linearity, dose rate dependence, tissue-equivalence and signal stability) of laboratory-made phenolic dosimeters in form of pellets were investigated. Furthermore, these dosimeters were tested for measuring the depth dose profile of a 6 MV clinical photon beam. The results reported show that these dosimeters are promising materials for ESR dosimetric applications in radiation therapy