Reforming of olive mill wastewater through a Pd-membrane reactor

This work investigates the exploitation of olive mill wastewater (OMW) for producing hydrogen in a membrane reformer.     

Large-Area Direct Hetero-Epitaxial Growth of 1550-nm InGaAsP Multi-Quantum-Well Structures on Patterned Exact-Oriented (001) Silicon Substrates by Metal Organic Chemical Vapor Deposition

We employ a simple two-step growth technique to grow large-area 1550-nm laser structures by direct hetero-epitaxy of III–V compounds on patterned exact-oriented (001) silicon (Si) substrates by metal organic chemical vapor deposition. Densely-packed, highly uniform, flat and millimeter-long indium phosphide (InP) nanowires were grown from Si v-grooves separated by silicon dioxide (SiO₂) stripes with various widths and pitches. Following removal of the SiO₂ patterns, the InP nanowires were coalesced and, subsequently, 1550-nm laser structures were grown in a single overgrowth without performing any polishing for planarization. X-ray diffraction, photoluminescence, atomic force microscopy and transmission electron microscopy analyses were used to characterize the epitaxial material. PIN diodes were fabricated and diode-rectifying behavior was observed.     

A semantic approach to remove incoherent items from a user profile and improve the accuracy of a recommender system

Recommender systems usually suggest items by exploiting all the previous interactions of the users with a system (e.g., in order to decide the movies to recommend to a user, all the movies she previously purchased are considered). This canonical approach sometimes could lead to wrong results due to several factors, such as a change in user preferences over time, or the use of her account by third parties. This kind of incoherence in the user profiles defines a lower bound on the error the recommender systems may achieve when they generate suggestions for a user, an aspect known in literature as magic barrier. This paper proposes a novel dynamic coherence-based approach to define the user profile used in the recommendation process. The main aim is to identify and remove, from the previously evaluated items, those not semantically adherent to the others, in order to make a user profile as close as possible to the user’s real preferences, solving the aforementioned problems. Moreover, reshaping the user profile in such a way leads to great advantages in terms of computational complexity, since the number of items considered during the recommendation process is highly reduced. The performed experiments show the effectiveness of our approach to remove the incoherent items from a user profile, increasing the recommendation accuracy.     

On the nature and importance of the transition between molecules and nanocrystals: towards a chemistry of "nanoscale perfection"

This paper discusses the importance of the transition between molecular compounds and nanocrystals. The boundary between molecular and nanocrystals/nanoclusters can be defined by the emergence of the bulk phase; atoms in the core of the nanoclusters that are not bound to ligands. This transition in dimensions and structural organization is important because it overlaps with the boundary between atomically defined moieties (molecules can be isolated with increasing purity) and mixtures (nanocrystals have a distribution of sizes, shapes, and defects; they cannot be easily separated into batches of structurally identical species). Passing through this boundary, as the size of a structure increases beyond a few nanometres, the information about the position of each atom gradually disappears. This loss of structural information about a chemical structure fundamentally compromises our ability to use it as a part of a complex chemical system. If we are to engineer complex functions encoded in a chemical language, we will need pure batches of atomically defined (truly monodisperse) nanoscale compounds, and we will need to understand how to make them and preserve them over a broad range of length scales, compositions, and timeframes. In this review we survey most classes of monodisperse nanomaterials (mostly nanoclusters) and highlight the recent breakthroughs in this area which might be spearheading the development of a chemistry of "nanoscale perfection".     

Three-dimensional silicon inverse photonic quasicrystals for infrared wavelengths

Quasicrystals are a class of lattices characterized by a lack of translational symmetry. Nevertheless, the points of the lattice are deterministically arranged, obeying rotational symmetry. Thus, we expect properties that are different from both crystals and glasses. Indeed, naturally occurring electronic quasicrystals (for example, AlPdMn metal alloys) show peculiar electronic, vibrational and physico-chemical properties. Regarding artificial quasicrystals for electromagnetic waves, three-dimensional (3D) structures have recently been realized at GHz frequencies and 2D structures have been reported for the near-infrared region. Here, we report on the first fabrication and characterization of 3D quasicrystals for infrared frequencies. Using direct laser writing combined with a silicon inversion procedure, we achieve high-quality silicon inverse icosahedral structures. Both polymeric and silicon quasicrystals are characterized by means of electron microscopy and visible-light Laue diffraction. The diffraction patterns of structures with a local five-fold real-space symmetry axis reveal a ten-fold symmetry as required by theory for 3D structures.     

Comparative performance analysis of some extrapolative estimatorsof probability tails

In some applications, estimation of probabilities of the order of 10^-6 or lower is required. Extrapolative methods based on extreme value theory (EVT) and generalized extreme value theory (GEVT) are considered. They give a closed-form approximation of the probability tail in terms of two or three parameters, respectively. A Monte Carlo simulation study was carried out to assess EVT and GEVT estimators' performances with respect to several factors, such as estimation methods, initial distribution, sample size, and partition of the initial sample. It was found that the GEVT estimators are consistently more efficient, while achieving a substantial sample-size saving with respect to the conventional counting procedure. Some applications to estimation problems encountered in radar systems design are considered     

The LAST operation: techniques and results before and after the stabilization era

BACKGROUND: Left anterior descending artery stabilization allows performance of left internal mammary artery grafting via a left anterior small thoracotomy on a beating heart. Our surgical experience was reviewed to assess if surgical results have improved as result of specialized instrumentation. METHODS: Of 545 patients who had the left anterior small thoracotomy operation, 261 underwent this procedure for single left anterior descending artery disease. Two groups were considered, before and after the use of specialized instrumentation: group A (n = 93), operated on from November 21, 1994, to April 20, 1996; and group B (n = 168), operated on from April 21, 1996, to December 1997. RESULTS: Early mortality was similar in the two groups. The further revascularization (operation or percutaneous transluminal coronary angioplasty) and the rate of occlusion of the conduit were higher in group A, whereas anastomotic or conduit malfunction was not. Cumulating angiography and Doppler flow evaluation, 92.5% of the anastomoses in group A and 98.8% in group B (p = 0.026) were patent, and 90.3% in group A and 97.6% in group B (p = 0.031) were patent and not restrictive. At 19 months, survival was similar, but the event-free survival was higher in group B. CONCLUSIONS: Both left anterior descending artery stabilization and safer left internal mammary artery harvesting contributed to improve angiographic and clinical results after the left anterior small thoracotomy operation.     

Recycling of waste glasses into partially crystallized glass foams

Waste soda-lime glass, alone or mixed with wastes from the manufacturing of glass fibers, was successfully converted into partially crystallized glass foams by a particularly simple and economic processing, consisting of a direct heating of glass powders at temperatures from 900 to 1050 °C. The foaming operated by the oxidation of SiC, inserted as powder additive, was found to depend on a complex combination of processing temperature, soaking time, tendency of the investigated glasses toward devitrification, and amount of MnO₂, acting as oxidation promoter. Selected combinations led to foams with a good microstructural homogeneity and mechanical strength, suitable for application as aggregates in lightweight concrete.