Optimal controllers for spatially invariant systems with delayed communication requirements

We consider the problem of optimal design of semi-decentralized controllers for a special class of spatially distributed systems. This class includes spatially invariant and distributed discrete-time systems with an inherent temporal delay in the interaction of neighboring sites. We consider the problem of optimal design of distributed controllers that have the same information passing delay structure as the plant. We show how for stable plants, the YJBK parameterization of such stabilizing controllers yields a convex parameterization for this class. We then show how the optimal problem can be solved.     

Interplay between upsampling and regularization for provider fairness in recommender systems

User Modeling and User-Adapted Interaction - Considering the impact of recommendations on item providers is one of the duties of multi-sided recommender systems. Item providers are key stakeholders...     

Double Mutant Cycles as a Tool to Address Folding,Binding, and Allostery

Quantitative measurement of intramolecular and intermolecular interactions in protein structure is an elusive task, not easy to address experimentally. The phenomenon denoted ‘energetic coupling’ describes short- and long-range interactions between two residues in a protein system. A powerful method to identify and quantitatively characterize long-range interactions and allosteric networks in proteins or protein–ligand complexes is called double-mutant cycles analysis. In this review we describe the thermodynamic principles and basic equations that underlie the double mutant cycle methodology, its fields of application and latest employments, and caveats and pitfalls that the experimentalists must consider. In particular, we show how double mutant cycles can be a powerful tool to investigate allosteric mechanisms in protein binding reactions as well as elusive states in protein folding pathways.     

A genetic expectation-maximization method for unsupervised change detection in multitemporal SAR imagery

In this paper, we present a novel, automatic and unsupervised change-detection approach to the analysis of single-channel single-polarization multitemporal SAR images. The statistical parameters of the changed and unchanged classes, which are assumed to follow a generalized Gaussian (GG) distribution in the analysed log-ratio image, are explicitly estimated by the expectation-maximization (EM) algorithm initialized with a robust strategy based on genetic algorithms (GAs). In addition, the proposed approach integrates two further processing capabilities. The first one intends to cope with the problem of the automatic detection of multiple changes in the scene. This is carried out by modelling the log-ratio image histogram with a multimodal GG mixture whose number of components is estimated basing on the Bayesian information criterion (BIC). The second processing capability allows exploitation of spatial contextual information in the change detection process through a Markovian formulation. Results obtained on both simulated and real data are reported and discussed.     

Two-points-based receptance coupling method for tool-tip dynamics prediction

Tool-tip frequency response function (FRF) is essential to predict chatter vibration in milling. This key input can be acquired by experimental tests, but a new test has to be performed for every tool clamped on the machine. To avoid such time-consuming procedures, receptance coupling methods have been developed, allowing coupling of the experimental dynamic response of the machine to the numerical model of the tool. Such techniques require joint rotation response, which is hard to experimentally identify. Inversion of receptance coupling technique is usually performed on additional experimental measurements to overcome this issue. This procedure amplifies measurement uncertainties, reducing accuracy of the coupling approach. In this article, a novel receptance coupling technique is presented. Machine and toolkit are connected through two distinct points, eliminating the experimental phase and computation of rotational degrees of freedom (DOFs). Only translation responses are required, acquired by a single test setup. Proposed technique was experimentally validated on different case studies.     

Origin of Gas Porosity in Gold-Based Alloys Cast in Calcium Sulfate-Bonded Investment and Influence of Metal Oxide Acid–Base Properties on Calcium Sulfate Thermal Stability

The origin of gas-porosity in gold-based alloys produced via lost-wax casting in CaSO₄-bonded investment has been identified using a combination of microanalytical and thermal techniques. The occurrence of gas-porosity is related to the thermal decomposition of CaSO₄, which, with SiO₂, constitutes the investment material and decomposes at a temperature very close to the casting temperature of some typical gold alloys used for jewelry production. The thermal reaction generates SO₂, leading to gas-porosity and, therefore, to defective products. Furthermore, the results show the detrimental effect of thermal decomposition caused by the presence of ZnO, Cu₂O, CuO, NiO, and Ag₂O formed on the surface of the gold-based alloy during air melting or casting. Therefore, the solid-state thermal decomposition of CaSO₄ in the presence of other ceramic oxides has been investigated and found to be related to their surface acid–base properties, measured as isoelectric points on the solid surface.     

NADPH-dependent D-aldose reductases and xylose fermentation in Fusarium oxysporum

Two aldose (xylose) reductases (ARI and ARII) from Fusarium oxysporum were purified and characterized. The native ARI was a monomer with M(r) 41000, pI 5.2 and showed a 52-fold preference for NADPH over NADH, while ARII was homodimeric with a subunit of M(r) 37000, pI 3.6 and a 60-fold preference for NADPH over NADH. In this study, the influence of aeration and the response to the addition of electron acceptors on xylose fermentation by F. oxysporum were also studied. The batch cultivation of F. oxysporum on xylose was performed under aerobic, anaerobic and oxygen-limited conditions in stirred tank reactors. Oxygen limitation had considerable influence on xylose metabolism. Under anaerobic conditions (0 vvm), xylitol was the main product with a maximum yield of 0.34 mole of xylitol/mole of xylose while the maximum ethanol yield (1.02 moles of ethanol/mole of xylose) was obtained under aerobic conditions (0.3 vvm). When the artificial electron acceptor acetoin was added to an anaerobic batch fermentation of xylose by F. oxysporum, the ethanol yield increased while xylitol excretion was also decreased.     

Biotransformation of Waste Bile Acids: A New Possible Sustainable Approach to Anti-Fungal Molecules for Crop Plant Bioprotection?

Phytopathogenic fungi are among the main causes of productivity losses in agriculture. To date, synthetic chemical pesticides, such as hydroxyanilides, anilinopyrimidines and azole derivatives, represent the main treatment tools for crop plant defence. However, the large and uncontrolled use of these substances has evidenced several side effects, namely the resistance to treatments, environmental damage and human health risks. The general trend is to replace chemicals with natural molecules in order to reduce these side effects. Moreover, the valorisation of agri-food industry by-products through biotransformation processes represents a sustainable alternative to chemical synthesis in several sectors. This research is aimed at comparing the anti-phytopathogenic activity of waste bovine and porcine bile with secosteroids obtained by biotransformation of bile acids with Rhodococcus strains. The ultimate goal is to apply these natural products on food crops affected by phytopathogenic fungi.