A Braking System for Tests with a Prescribed Deceleration Pulse

Tests with a prescribed deceleration pulse are fundamental to the development and certification of crashworthy structures. At the Politecnico di Milano Laboratory for the Safety of Transports these tests are carried out using a horizontal impact-sled facility. Test articles are mounted on a trolley which is launched down a rail and then arrested by means of a braking system that allows prescribed deceleration pulses to be obtained. The oleo-pneumatic braking system customarily used in these tests is difficult to use and user-defined time-histories of the deceleration pulse cannot be obtained. In an effort to overcome these limits, a new braking system was developed. The idea was to arrest the trolley by means of a number of beams that varied in length and that were positioned at variable distances from each other. Experimental tests and numerical simulations were carried out in parallel to verify the feasibility of the new system and improve on the initial design. A mathematical model and genetic algorithm were also developed and used as part of a method to find the test set-up that allowed user-defined deceleration pulses to be obtained. A full-scale test with the deceleration pulse prescribed for small airplane seat certification was carried out to assess the performance of the braking system. The test revealed a weakness of the braking system that was then further developed before being put into full operational service.     

Quantification of drug amorphous fraction by DSC

The processes of production of drugs and dosage forms in the solid state often cause unwanted transformation of portions of the substances into amorphous state, with significant changes of properties such as stability and bio-availability. When this amorphous fraction is of the order of a few percent, it usually goes unnoticed, but it should be accurately determined within a quality control system. In this work, we consider a model drug, perphenazine, where partial amorphisation may be induced by standard mechanical treatments. We show that Differential Scanning Calorimetry (DSC) leads to consistent estimations of the amorphous fractions induced by the treatment. Furthermore, DSC also yields the expected amounts of amorphous perphenazine when analysing known mixtures of perfectly crystalline samples (untreated) and partially amorphous samples (treated). We show that even amorphous fractions of the order of 1% are accurately estimated by our method.     

Thermal stability and spectroscopic properties of erbium-doped niobic-tungsten–tellurite glasses for laser and amplifier devices

Er³⁺ doped niobic-tungsten–tellurite glasses doped with concentration of Er³⁺ ion up to 3 wt% were fabricated. The effect of Er³⁺ doping concentration on thermal stability and optical properties was investigated in order to obtain the most suitable rare earth content for developing 1.5 μm compact fiber amplifier pumped with a commercial telecom 980 nm laser diode. The maximum doping concentration allowed was found to be around 1.77×10²⁰ ions/cm³, for which a broad 1.5 μm emission spectra of 65 nm FWHM and a lifetime of 3.4 ms for the ⁴I_13/2 level was measured.     

CO2 Separation by Imide/Imine Organic Cages

Two novel imide/imine-based organic cages have been prepared and studied as materials for the selective separation of CO₂ from N₂ and CH₄ under vacuum swing adsorption conditions. Gas adsorption on the new compounds showed selectivity for CO₂ over N₂ and CH₄. The cages were also tested as fillers in mixed-matrix membranes for gas separation. Dense and robust membranes were obtained by loading the cages in either Matrimid® or PEEK-WC polymers. Improved gas-transport properties and selectivity for CO₂ were achieved compared to the neat polymer membranes.     

Computation of local radius of information in SM-IBC identification of nonlinear systems

System identification consists in finding a model of an unknown system starting from a finite set of noise-corrupted data. A fundamental problem in this context is to asses the accuracy of the identified model. In this paper, the problem is investigated for the case of nonlinear systems within the Set Membership—Information Based Complexity framework of [M. Milanese, C. Novara, Set membership identification of nonlinear systems, Automatica 40(6) (2004) 957–975]. In that paper, a (locally) optimal algorithm has been derived, giving (locally) optimal models in nonlinear regression form. The corresponding (local) radius of information, providing the worst-case identification error, can be consequently used to measure the quality of the identified model. In the present paper, two algorithms are proposed for the computation of the local radius of information: The first provides the exact value but requires a computational complexity exponential in the dimension of the regressor space. The second is approximate but involves a polynomial (quadratic) complexity.     

Small plasma focus studied as a source of hard X-ray

An experimental study on hard X-ray pulses emitted by a small plasma focus is performed, regarding its application to biological radiographs in fast dynamic situations. It is found that the radiation intensity in a single shot is high enough to obtain fine resolution radiographs in very short exposures (about 10 ns). As an example, a radiograph on a live mouse is shown. It is found that the relation between responses of different detectors, i.e., thermoluminescence dosimeters and scintillator-photomultiplier, is linear     

Chemistry of cultural glasses: the early medieval glasses of Monselice's hill (Padova, Italy)

To investigate the mechanisms of deterioration of historical glasses, under natural evolution, some early medieval glasses from the archaeological site of the Monselice's hill have been analysed. By an archaeological approach, developed at the Dipartimento di Scienze dell'Antichità, University of Padova, the glasses were dated between the VI and the beginning of the VII century and they were ascribed to the same artist or school. By a geological approach, developed at the Dipartimento di Mineralogia e Petrologia, University of Padova, it was found that some pieces of glasses, from the same archaeological site, were made of silica, rich in sodium and calcium, with iron and manganese. The composition was analogous the one of glasses produced during Roman empire, using `natron' (Na<sub>2</sub>CO<sub>3</sub>·NaHCO<sub>3</sub>·2H<sub>2</sub>O) as melting agent and glasses produced during medieval age, in the Mediterranean basin, using plant ash like `Salsola Kali' as melting agent. It was also found that there was a surface layer, with a special lamellar structure, easy to remove. The surface layer was found poor in alkali and alkaline-earth elements. By surface and microscopic analyses (optical microscopy, SEM-EDS, microRaman, XPS, SIMS and Mössbauer) it has been found that all the samples have a composition rich in silica, sodium and calcium except one that, unexpectedly, was rich in potassium and poorer in sodium. This sample, as composition, seems just like medieval glasses produced north of the Alps, using plant ash like ferns as melting agent. In all the samples the surface layers have less alkaline elements and the depletion goes to ten μm of depth. The extreme consequence of this depletion is the formation, in some samples, of an alteration layer, easy to remove, that the XPS analyses tell us it is made of very hydrated silica. The surface layers show a little accumulation of calcium. The calcium ion is also present in some birefringent crystal aggregates immersed in the glass that, in some samples, are around one mm large. These aggregates have a circular shape, with a nucleation centre in them. By microRaman spectroscopy it was found that the crystal aggregates are made of vateritic and calcitic calcium carbonate. By Mössbauer spectroscopy it was found that in the flat yellow coloured glasses, richer in iron, the Fe(III) species predominates. Instead in the pale green ones, poorer in iron, the Fe(II) prevails.     

Febantel: looking for new polymorphs

The aim of this work was to search for new polymorphic forms of febantel, an anthelminthic drug of great present interest for the veterinary industry. Solvent-based recrystallization, thermal and mechanical treatments and spray drying were chosen to discover new solid forms. The solids obtained were physicochemically characterized by thermal techniques (DSC and TG), FTIR spectroscopy, laboratory and synchrotron X-ray powder diffraction and scanning electron microscopy. Our work leads to obtain a new solid form never described in the literature. In particular, the new polymorph was obtained by the anti-solvent method and the crystallization from isopropanol. The experimental conditions of crystallization favorable to the formation of the highest amount of the new solid phase were selected. The new phase shows a thermal, spectroscopic and diffractometric behavior unique. Furthermore, the preliminary structure investigation suggests two possible crystal systems: an orthorhombic or a monoclinic one, with really comparable lattice parameters and cell volume. Measurements put into evidence that the new phase is a metastable polymorph that is in monotropic relationship with the stable and known form.

     

Synthesis, characterization and antibacterial activity against Gram positive and Gram negative bacteria of biomimetically coated silver nanoparticles

In the present work, we describe a simple procedure to produce biomimetically coated silver nanoparticles (Ag NPs), based on the postfunctionalization and purification of colloidal silver stabilized by citrate. Two biological capping agents have been used (cysteine Cys and glutathione GSH). The composition of the capped colloids has been ascertained by different techniques and antibacterial tests on GSH-capped Ag NPs have been conducted under physiological conditions, obtaining values of Minimum Inhibitory Concentration (MIC) of 180 and 15 μg/mL for Staphylococcus aureus and Escherichia coli, respectively. The antibacterial activity of these GSH capped NPs can be ascribed to the direct action of metallic silver NPs, rather than to the bulk release of Ag(+).