Bicontinuous extensions of invertible combinatorial functions

We discuss and solve the problem of constructing a diffeomorphic componentwise extension for an arbitrary invertible combinatorial function. Interpreted in physical terms, our solution constitutes a proof of the physical realizability of general computing mechanisms based onreversible primitives.This research was supported by Grant N00014-75-C-0661, Office of Naval Research, funded by DARPA.     

Collinear stress effect on the crack branching phenomenon

The importance of the non-singular terms of the series representation for the stresses in the crack tip region has been underlined in recent papers. In the present work it is recognized that the stress-intensity factors K_I and K_II are no longer sufficient to define fracture crisis for the plane problem. Some fracture criteria are applied introducing the third parameter λ, which is connected with the stress collinear to the crack's line. The respective fracture loci in the K_I−K_II−λ space are discussed; they depend on the distance from the crack tip at which the crisis conditions are checked. Finally an application of the above mentioned loci to the uniaxial loading condition is shown.

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Résumé Le problème de la mécanique de la rupture a été étudie jusqu'ici en considérant, dans la solution élastique, valable autour des extrémités de fissure, le seul premier terme du développement en autofonctions de Williams. Ce terme de la série qui représente le champ de contrainte est inversement proportionnel à la racine carrée de la distance radiale de l'extrémité de l'axe de fissuration. Cependant, dans cette étude, on considère aussi le deuxième terme de cette série, indépendant de la distance radiale. L'omission du deuxième terme, comme on le souligne dans des travaux assez récents, équivaut à négliger l'effet des tensions normales colinéaires à l'axe de fissuration. Si l'on considère aussi le terme non singulier, on admet que la rupture dépend d'un paramètre ultérieur lié à la contriante normale colinéaire à l'axe de fissuration. Par conséquent, les facteurs d'intensité de contrainte K_I et K_II, introduits par Irwin, ne suffisent plus à décrire la ramification de la fissure. Les endroits de rupture, comme on le montre dans cette étude, sont représentés par des surfaces dans l'espace tridimensionnel K_I−K_II−λ, et non plus par des courbes dans le plan K_I−K_II. Conformément à ces hypothèses, les surfaces varient en fonction de la distance radiale de l'extrémité de la fissure d'après laquelle on estime les conditions de crise (déterminant la rupture). Cette distance est caractéristique du matériau considéré, puisqu'elle est liée à la dimension de la zone plastique à l'extrémité de la fissure. Dans la partie finale de l'étude, on montre ensuite une application dans un cas de sollicitation sous charge monoaxiale en indiquant les résultats expérimentaux obtenus sur des plaques de plexiglass entaillées.

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Research sponsored by the C.N.R. (Consiglio Nazionale delle Ricerche, Italy)     

Fullerene‐Promoted Singlet‐Oxygen Photochemical Oxygenations in Glass‐Polymer Microstructured Reactors

In this paper we report the fabrication of thiolene‐based microstructured reactors (MRs) that have been specifically designed to include solid‐supported reagents within the microchannels network. We propose a convenient solution to realize reversible press‐fit, leak‐proof interconnects that greatly simplify the MR coupling to the external environment such as capillary tubing, sample reservoirs and pumps. The MRs have been used to carry out the oxidation of α‐terpinene and methionine using [60]fullerene, covalently linked to Tentagel^® and silica gel matrices, as a singlet oxygen sensitizer. High conversions have been observed for both substrates although, in the case of α‐terpinene, a partial photodegradation of the endo‐peroxide product was detected. Interestingly, in the case of methionine, a quantitative conversion to the corresponding sulfoxides was achieved in about 40 seconds, using low‐power, white LED illumination. The reaction time is considerably shorter when compared to the batch procedure that requires, for the same process, about one hour illumination and the use of a 300‐W tungsten halogen lamp.     

High performance size-exclusion chromatography analysis of polar compounds applied to refined, mild deodorized, extra virgin olive oils and their blends: An approach to their differentiation

An investigation was carried out to evaluate the use of High Performance Size-Exclusion Chromatography (HPSEC) of polar compounds of refined, mild deodorized, extra virgin olive oils as well as of their blends, in attempting to reveal significant differences in the amounts of the substance classes constituting polar compounds among these oils. Two sets of blends were prepared by mixing an extra virgin olive oil with both refined and mild deodorized olive oils in increasing amounts. The obtained data highlighted that the triacylglycerol oligopolymers were absent or present in traces in the extra virgin olive oil, while their mean amount was equal to 0.04 g/100 g and 0.72 g/100 g in mild deodorized and refined olive oils, respectively. Oxidized triacylglycerols and diacylglycerols were more abundant in mild deodorized oil and refined oil than in extra virgin olive oil. The Factorial Discriminant Analysis of the data showed that the HPSEC analysis could reveal the presence of refined/mild deodorized oils in extra virgin olive oils. In particular, the classification functions obtained allowed designation of mixtures containing at least 30 g/100 g of mild deodorized oil and all those containing refined olive oil as deodorized oil, therefore as oils subjected to at least a mild refining treatment.     

Olive oil traceability by means of chemical and sensory analyses: A comparison with SSR biomolecular profiles

The relationship between genetic diversity and phenotype in olive, instrumental to improve the efficacy of olive clonal selection, is still far from being fully understood. This work reports on a comparison made between plant SSR genetic data and quality of monovarietal olive oils. Nine monovarietal oils produced by selected genotypes were characterised under chemical and sensory profiles. Fatty acid compositions were determined to evaluate quantitative differences among oils; some fatty acids are actually highly correlated with the genetic matrix, and PCA of fatty acids composition explains 85.53% variability. Moreover some oils characterised by high levels of oleic acid appeared interesting from a nutritional standpoint. Organoleptic profiles evidenced differences especially for the attributes defined as “pleasant flavours”; oils obtained by different genetic matrices were characterised by different flavour intensities of tomato or artichoke, almond or aromatic herbs, correspondence analysis among sensory pleasant attributes and olive oil samples explaining 91.68% variability.     

Piezoelectricity in Monolayer Hexagonal Boron Nitride

2D hexagonal boron nitride (hBN) is a wide-bandgap van der Waals crystal with a unique combination of properties, including exceptional strength, large oxidation resistance at high temperatures, and optical functionalities. Furthermore, in recent years hBN crystals have become the material of choice for encapsulating other 2D crystals in a variety of technological applications, from optoelectronic and tunneling devices to composites. Monolayer hBN, which has no center of symmetry, is predicted to exhibit piezoelectric properties, yet experimental evidence is lacking. Here, by using electrostatic force microscopy, this effect is observed as a strain-induced change in the local electric field around bubbles and creases, in agreement with theoretical calculations. No piezoelectricity is found in bilayer and bulk hBN, where the center of symmetry is restored. These results add piezoelectricity to the known properties of monolayer hBN, which makes it a desirable candidate for novel electromechanical and stretchable optoelectronic devices, and pave a way to control the local electric field and carrier concentration in van der Waals heterostructures via strain. The experimental approach used here also shows a way to investigate the piezoelectric properties of other materials on the nanoscale by using electrostatic scanning probe techniques.     

Broad-Spectrum Flavivirus Inhibitors: a Medicinal Chemistry Point of View

Infections by flaviviruses, such as Dengue, West Nile, Yellow Fever and Zika viruses, represent a growing risk for global health. There are vaccines only for few flaviviruses while no effective treatments are available. Flaviviruses share epidemiological, structural, and ecologic features and often different viruses can co-infect the same host. Therefore, the identification of broad-spectrum inhibitors is highly desirable either for known flaviviruses or for viruses that likely will emerge in the future. Strategies targeting both virus and host factors have been pursued to identify broad-spectrum antiflaviviral agents. In this review, we describe the most promising and best characterized targets and their relative broad-spectrum inhibitors, identified by drug repurposing/libraries screenings and by focused medicinal chemistry campaigns. Finally, we discuss about future strategies to identify new broad-spectrum antiflavivirus agents.     

Social information use and the evolution of unresponsiveness in collective systems

Animal groups in nature often display an enhanced collective information-processing capacity. It has been speculated that natural selection will tune this response to be optimal, ensuring that the group is reactive while also being robust to noise. Here, we show that this is unlikely to be the case. By using a simple model of decision-making in a dynamic environment, we find that when individuals behave rationally and are subject to selection based on their accuracy, optimality of collective decision-making is not attained. Instead, individuals overly rely on social information and evolve to be too readily influenced by their neighbours. This is due to a classic evolutionary conflict between individual and collective interest. The result is a sub-optimal system that is poised on the cusp of total unresponsiveness. Individuals in the evolved group exhibit delayed reactions to changes in the environment, before responding with rapid, socially reinforced transitions, reminiscent of familiar human and animal social systems (markets, stampedes, fashions, etc.). Our results demonstrate that behaviour of this type may not be pathological, but instead could represent an evolutionary attractor for such collective systems.     

When agility meets open innovation: two approaches to manage inbound projects

Open Innovation is a leading paradigm in the current landscape, and scholars have been highly focused on defining the characteristics and capabilities that firms need to implement it successfully. This research aims to understand how organizations may implement inbound OI projects. Relying on a multiple case study approach and based on primary and secondary sources, this research highlights two main approaches: team‐centred and individual‐centred. The two approaches are discussed according to previous studies, highlighting how the first one is particularly coherent with previous research on Open Innovation, while the second one offers great insights from an Agile Project Management perspective. In particular, this research suggests how the Open Innovation literature can be enriched by considering the recent advancements in the Agile literature, valuing the individual and its autonomy to embrace external ideas from an OI perspective.