A new approach to the modeling of SHS reactions: Combustion synthesis of transition metal aluminides

A recently developed numerical simulation of self-propagating high-temperature synthesis (SHS) using an approach based on microscopic reaction mechanisms and utilizing appropriate physical parameters is applied to the SHS of a fairly large group of transition metal aluminides. The model was utilized to analyze temperature profiles and wave instability and the results were interpreted in terms of chemical and thermal effects. The effect of the particle size of the transition metal, the porosity of the reactant mixtures, and the dilution was iinvestigated. The results are in good agreement with available experimental data

Ignition and reaction mechanism of Co-Al and Nb-Al intermetallic compounds prepared by combustion synthesis

The ignition and propagation mechanism of the self-propagating high-temperature synthesis of several cobalt and niobium aluminides was investigated. Two propagation mechanisms were identified depending on the stoichiometry of the starting mixture. Al-rich compositions propagate through a dissolution-precipitation mechanism while Al-poor mixtures require solid state diffusion. The ignition temperatures were measured by means of microthermocouples in quasi-adiabatic conditions through experiments carried out in thermal explosion mode. Ignition temperatures were found to be characteristic of each system and to depend strongly on reactants particle size. Ignition energies for all compositions were evaluated through a mathematical model

from eto to mass customization a two horizon eto enabling process

During the past few years, many companies are playing in their respective market managing one batch of their commercial offer as mass customizer and another as a pure Engineer-to-Order (ETO) company. This newly created business model generates new needs and issues both in the internal organization approaches, and in the supporting IT systems. The competitive advantage of successful firms relies on the effective management of their purely customized orders, with the aim of including relevant knowledge and information in the standard space of action. Therefore, this study aims at conceptualizing this new business reality, presenting an innovative underlying scheme for the ETO enabling process in which the central focus is on the design phase. Furthermore, a set of success practices are represented, discriminated between long and short term horizons. In this context, both technological and organizational aspects have been explored. Lastly, applicability of the proposed framework has been empirically validated through case studies

Nanoscale effects on the ionic conductivity of highly doped bulk nanometric cerium oxide

Nanometric ceria powders doped with 30 mol % samaria are consolidated by a high-pressure spark plasma sintering (HP-SPS) method to form > 99 % dense samples with a crystallite size as small as 16.5 nm. A conductivity dependence on grain size was noted: when the grain size was less than 20 nm, only one semicircle in the AC impedance spectra was observed and was attributed to bulk conductivity. In contrast to previous observations on pure ceria, the disappearance of the grain-boundary blocking effect is not associated with mixed conductivity. With annealing and concomitant grain growth, the samples show the presence of a grain-boundary effect

Neuroanatomical substrates for recurrent epileptic limbic seizures

Epilepsy is a neurological disorder characterized by the recurrence of spontaneous, unprovoked epileptic seizures. Mesial temporal lobe epilepsy (more briefly, MTLE) is a very common form of epilepsy which is featured by the occurrence of focal limbic seizures, and associated to a specific neuropathological alteration, the so-called Ammon’s horn sclerosis, whose main features are a selective loss of the CA1 and CA3/4 section of the Ammon’s horn (CA, from Latin Cornu Ammonis, abbreviated as CA), a selective cell loss of inhibitory interneurons in the hilus of the dentate gyrus (DG), and the abnormal sprouting of granule cells mossy fibers (the so called mossy fiber sprouting, MFS). The onset of spontaneous seizures (SRS) is the hallmark of a good model of epilepsy. For temporal lobe epilepsy (TLE), the most used models consist in administering systemically chemoconvulsants inducing limbic status epilepticus (i.e. seizures lasting for more than 30’, SE) and evaluating the occurrence of SRS. However, in these models, the widespread involvement of different structures which complicates the interpretation of experimental findings: limbic seizures and status epilepticus (SE) can be triggered by focal infusion of chemoconvulsants within anterior piriform cortex (abbreviated as APC) This brain region is densely innervated by noradrenergic fibers arising from the locus coeruleus (LC), and we recently showed that a lesion of LC (induced by a selective neurotoxin, DSP-4, i.p.), induces SE. LC plays a critical role in modulating several models of seizures, and it plays a critical role in plastic mechanisms and neuroprotection in the brain. Thus, we compared the group DSP-4+bicuculline and cyclothiazide+bicuculline, to evaluate whether the focal SE evoked from the APC is capable of inducing SRS and AHS, and whether LC plays a significant role in this phenomena. We found that: the loss of LC induced: (i)a higher incidence of SRS; (ii) cell loss in the hippocampal DG hilus and CA3 (iii)the loss of parvalbumin-positive neurons. In conclusion, our study confirms that focal induction of SE from the APC represents a good model of TLE, and that NE released from the fibers originating from the LC plays a significant role both in the hippocampal damage occurring after SE, and in the incidence of SRS

Encoding many channels in the same frequency through radio vorticity: first experimental test

We have shown experimentally that it is possible to propagate and use the properties of twisted non-monochromatic incoherent radio waves to simultaneously transmit to infinity more radio channels on the same frequency band by encoding them in different orbital angular momentum states. This novel radio technique allows the implementation of, at least in principle, an infinite number of channels on one and the same frequency, even without using polarization or dense coding techniques. An optimal combination of all these physical properties and techniques represents a solution for the problem of radio band congestion. Our experimental findings show that the vorticity of each twisted electromagnetic wave is preserved after the propagation, paving the way for entirely new paradigms in radio communication protocols.Comment: 17 pages, 6 figures, with a public experiment, three audio files in mp3 forma

ARIANNA: A research environment for neuroimaging studies in autism spectrum disorders

The complexity and heterogeneity of Autism Spectrum Disorders (ASD) require the implementation of dedicated analysis techniques to obtain the maximum from the interrelationship among many variables that describe affected individuals, spanning from clinical phenotypic characterization and genetic profile to structural and functional brain images. The ARIANNA project has developed a collaborative interdisciplinary research environment that is easily accessible to the community of researchers working on ASD (https://arianna.pi.infn.it). The main goals of the project are: to analyze neuroimaging data acquired in multiple sites with multivariate approaches based on machine learning; to detect structural and functional brain characteristics that allow the distinguishing of individuals with ASD from control subjects; to identify neuroimaging-based criteria to stratify the population with ASD to support the future development of personalized treatments. Secure data handling and storage are guaranteed within the project, as well as the access to fast grid/cloud-based computational resources. This paper outlines the web-based architecture, the computing infrastructure and the collaborative analysis workflows at the basis of the ARIANNA interdisciplinary working environment. It also demonstrates the full functionality of the research platform. The availability of this innovative working environment for analyzing clinical and neuroimaging information of individuals with ASD is expected to support researchers in disentangling complex data thus facilitating their interpretation