Spectral clustering with more than K eigenvectors

Spectral clustering techniques are heuristic algorithms aiming to find approximate solutions to difficult graph-cutting problems, usually NP-complete, which are useful to clustering. A fundamental working hypothesis of these techniques is that the optimal partition of K classes can be obtained from the first K eigenvectors of the graph normalized Laplacian matrix L_N if the gap between the K-th and the K+1-th eigenvalue of L_N is sufficiently large. If the gap is small a perturbation may swap the corresponding eigenvectors and the results can be very different from the optimal ones.In this paper we suggest a weaker working hypothesis: the optimal partition of K classes can be obtained from a K-dimensional subspace of the first M>K eigenvectors, where M is a parameter chosen by the user. We show that the validity of this hypothesis can be confirmed by the gap size between the K-th and the M+1-th eigenvalue of L_N. Finally we present and analyse a simple probabilistic algorithm that generalizes current spectral techniques in this extended framework. This algorithm gives results on real world graphs that are close to the state of the art by selecting correct K-dimensional subspaces of the linear span of the first M eigenvectors, robust to small changes of the eigenvalues.     

Parametric investigations of target normal sheath acceleration experiments

One of the most important challenges related to laser-driven ion acceleration research is to actively control some important ion beam features. This is a peculiar topic in the light of future possible technological applications. In the present work we make use of one theoretical model for target normal sheath acceleration in order to reproduce recent experimental parametric studies about maximum ion energy dependencies on laser parameters. The key role played by pulse energy and intensity is enlightened. Finally the effective dependence of maximum ion energy on intensity is evaluated using a combined theoretical approach, obtained by means of an analytical and a particle-in-cell numerical investigation.     

Waste grape skins: evaluation of safety aspects for the production of functional powders and extracts for the food sector

Skin powders and aqueous alcohol extracts were obtained from waste marcs from different grape varieties (Barbera, Nebbiolo, Pinot Noir, Chardonnay, Moscato and Müller-Thurgau). Both skins and extracts were analysed for the content of chemical contaminants: ochratoxin A (OTA), biogenic amines (BIAs), pesticides and metals. OTA was detected in low concentrations in Barbera, Moscato and Nebbiolo skins, but only in Barbera and Moscato extracts. Cadaverine, putrescine, ethanolamine and ethylamine were found in extracts at very low levels, while potential allergenic amines, tyramine and histamine, were never detected. Different pesticides were present in both skins and extracts. Pb and Cd were found in trace only in the powders, and K, Ca and Mg were the most abundant elements in both skin powders and extracts. Concentrations of the different contaminants were related to fibre content or total phenolics content of powders and extracts, respectively, in order to evaluate their use in the food sector.     

Dietary citrus pulp improves protein stability in lamb meat stored under aerobic conditions

The antioxidant effects of dried citrus pulp on proteins in lamb meat, when used as a replacement of concentrate in the feed, was studied using meat from 26 male Comisana lambs. The lambs of age 90 days had been grouped randomly to receive one of the three dietary treatments: (1) commercial concentrate with 60% barley (Control, n = 8), (2) concentrate with 35% barley and 24% citrus pulp (Cp24, n = 9), or (3) concentrate with 23% barley and 35% citrus pulp (Cp35, n = 9). Slices from the longissimus thoracis et lomborum muscle were packed aerobically and stored for up to 6 days at 4°C in the dark. The citrus pulp groups, Cp24 and Cp35, significantly decreased protein radicals and carbonyls, and preserved more thiols within six days of storage compared to the Control group. The citrus pulp groups significantly slowed down the rate of protein oxidation, indicating that dietary citrus pulp reduced oxidative changes in meat proteins.     

How does the search for knowledge drive firms’ eco-innovation? Evidence from the wine industry

The importance of eco-innovations to food manufacturing has risen exponentially in recent years. In this paper we investigate the drivers of different types of eco-innovation in the Italian wine industry, a particularly relevant sector both in terms of its economic performance and its use of natural resources. We focus on the internal knowledge sourcing of firms and on the ‘breadth’ and ‘depth’ of their engagement with external agents when performing eco-innovation activity. We test our research hypotheses in the context of cleaner processes, end-of-pipe technologies and the use of organic input factors. The empirical evidence is based on a questionnaire survey administered to 334 Italian wine producers. The econometric exercise provides mixed results: both internal R&D and engagement with external agents have a significant effect on eco-innovations depending on the type of eco-innovation taken into account. Moreover, we find a non-linear relationship between external knowledge sourcing and eco-innovation activity.     

A new software architecture for developing and testing algorithms for space exploration missions

In recent years, planet exploration has received an increasing interest due to the possibility of exploiting planet resources and assuring a human–robotic colonized presence on suitable planetary surfaces. These goals can be reached through the development of smart robots, which are able to work on their own and without requiring a constant human supervision but, at the same time, assuring a great level of safety and reliability. To this aim, the development of effective architectures, concerning both software and hardware issues, could represent a great improvement toward this ambitious objective. This paper presents a novel modular architecture called Test Bench for Robotics and Autonomy (TBRA), the main objective of which is to create a test bench for rover autonomy missions where different implementations of a particular subsystem can be easily tested, while keeping the rest of the system unchanged. Thus, it allows the developers to be able to compare the results of tests and understand which version works better. Such architecture has been built on top of the Workframe, a generic middleware for real-time robotics. This two-layered approach allows the final user to deal only with the TBRA interface, which is designed to be extremely simple to use and takes care of most real-time programming problems, while allowing flexibility in the development, maintenance and future extension of the TBRA itself.