1,016 research outputs found

    Looking at Vector Space and Language Models for IR using Density Matrices

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    In this work, we conduct a joint analysis of both Vector Space and Language Models for IR using the mathematical framework of Quantum Theory. We shed light on how both models allocate the space of density matrices. A density matrix is shown to be a general representational tool capable of leveraging capabilities of both VSM and LM representations thus paving the way for a new generation of retrieval models. We analyze the possible implications suggested by our findings.Comment: In Proceedings of Quantum Interaction 201

    Using the quantum probability ranking principle to rank interdependent documents

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    A known limitation of the Probability Ranking Principle (PRP) is that it does not cater for dependence between documents. Recently, the Quantum Probability Ranking Principle (QPRP) has been proposed, which implicitly captures dependencies between documents through “quantum interference”. This paper explores whether this new ranking principle leads to improved performance for subtopic retrieval, where novelty and diversity is required. In a thorough empirical investigation, models based on the PRP, as well as other recently proposed ranking strategies for subtopic retrieval (i.e. Maximal Marginal Relevance (MMR) and Portfolio Theory(PT)), are compared against the QPRP. On the given task, it is shown that the QPRP outperforms these other ranking strategies. And unlike MMR and PT, one of the main advantages of the QPRP is that no parameter estimation/tuning is required; making the QPRP both simple and effective. This research demonstrates that the application of quantum theory to problems within information retrieval can lead to significant improvements

    A time-temperature integrator based on fluorescent and polymorphic compounds

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    Despite the variety of functional properties of molecular materials, which make them of interest for a number of technologies, their tendency to form inhomogeneous aggregates in thin films and to self-organize in polymorphs are considered drawbacks for practical applications. Here, we report on the use of polymorphic molecular fluorescent thin films as time temperature integrators, a class of devices that monitor the thermal history of a product. The device is fabricated by patterning the fluorescent model compound thieno(bis)imide-oligothiophene. The fluorescence colour of the pattern changes as a consequence of an irreversible phase variation driven by temperature, and reveals the temperature at which the pattern was exposed. The experimental results are quantitatively analysed in the range 20–200°C and interpreted considering a polymorph recrystallization in the thin film. Noteworthy, the reported method is of general validity and can be extended to every compound featuring irreversible temperature-dependent change of fluorescence

    Phytochemicals Recovery from Grape Pomace: Extraction Improvement and Chemometric Study

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    In the last 20 years, an increased interest has been shown in the application of different types and combinations of enzymes to obtain phenolic extracts from grape pomace in order to maximize its valorization. Within this framework, the present study aims at improving the recovery of phenolic compounds from Merlot and Garganega pomace and at contributing to the scientific background of enzyme-assisted extraction. Five commercial cellulolytic enzymes were tested in different conditions. Phenolic compound extraction yields were analyzed via a Design of Experiments (DoE) methodology and a second extraction step with acetone was sequentially added. According to DoE, 2% w/w enzyme/substrate ratio was more effective than 1%, allowing a higher total phenol recovery, while the effect of incubation time (2 or 4 h) variation was more enzyme-dependent. Extracts were characterized via spectrophotometric and HPLC-DAD analyses. The results proved that enzymatic and acetone Merlot and Garganega pomace extracts were complex mixtures of compounds. The use of different cellulolytic enzymes led to different extract compositions, as demonstrated using PCA models. The enzyme effects were observed both in water enzymatic and in the subsequent acetone extracts, probably due to their specific grape cell wall degradation and leading to the recovery of different molecule arrays

    Rubbing induced reversible fluorescence switching in thiophene-based organic semiconductor films by mechanical amorphisation

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    Here, we applied rubbing on thiophene-basedorganic semiconductor thin films to induce a reversible mechanical amorphisation. Amorphisation is associated with fluorescence switching, which is regulated by the polymorphic nature of the film. Thermal annealing of rubbed films produces an opposite effect with respect to rubbing, inducing film crystallization. Notably, thermal crystallisation starts at a low temperature but generates the polymorph stable at a high temperature in the bulk. The mechanism of mechanical transformation is explained considering the mechanical properties of the material and demonstrated through combined X-ray diffraction, atomic force microscopy and photoluminescence at confocal microscopy. This journal i

    Surface Functionalization of 3C-SiC Nanowires

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    One dimensional nanostrucures have potential applications in nanoscale electronic, optoelectronic or sensing devices. Core-shell nanowire (NW) structures of SiO2/β-SiC and SiC-NWs are interesting for fundamental studies and technological applications: 3C-SiC is particularly appealing because of its good physical, chemical properties and biocompatibility, offering opportunities for nano-scale devices operating in biological environment. Moreover, functionalized 3C-SiC nanowires have the potential to act as highly sensitive detector elements in bio-chemical field. Here, we report on the preliminary results of the functionalization of 3C-SiC nanowires with an optically active, thiophene-based, π-conjugated oligomer (PyT4). Oligothiophenes are semiconducting and fluorescent materials, widely used in organic electronics and biodiagnostic. SiC/SiO2 core/shell NWs grown by a Chemical Vapour Deposition (CVD) process on n-type Si (001) substrates, using carbon monoxide (CO) as the carbon source and nickel nitrate as the catalyst. The synthesis, performed at temperatures between 1050-1100?C. 3C-SiC NWs were grown in a home-made Vapor Phase Epitaxy (VPE) reactor using propane and silane as precursors (both diluted 3% in hydrogen) and a few nm of Ni as catalyst, deposited on Si(100) substrate using e-beam system. The nickel-deposited substrate is preheated at 1100?C for 5 minutes before introducing reagents for the grow time of 10 minutes. SiC/SiO2 core/shell NWs were then reacted with the triethoxysilane terminated with PyT4 to yield the hybrid NWs. The covalent grafting of the fluorophores was confirmed by fluorescence microscopy. The nanowires were further characterised by X-ray diffraction, Scanning Electron Microscopy, Cathodoluminescence and Transmission Electron Microscopy

    Visible-Light Assisted Covalent Surface Functionalization of Reduced Graphene Oxide Nanosheets with Arylazo Sulfones

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    We present an environmentally benign methodology for the covalent functionalization (arylation) of reduced graphene oxide (rGO) nanosheets with arylazo sulfones. A variety of tagged aryl units were conveniently accommodated at the rGO surface via visible-light irradiation of suspensions of carbon nanostructured materials in aqueous media. Mild reaction conditions, absence of photosensitizers, functional group tolerance and high atomic fractions (XPS analysis) represent some of the salient features characterizing the present methodology. Control experiments for the mechanistic elucidation (Raman analysis) and chemical nanomanipulation of the tagged rGO surfaces are also reported

    Relationship between productive and reproductive parameters of dairy cows in different production systems

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    The majority of the milk producing systems in Argentina are based on the use of perennial and annual pastures plus supplementation with cereal grains and conserved forages. The genetic change that occurred in Argentine dairy cattle was due principally to the importation of semen from the USA and Canada. In those countries the Holstein breed was selected over many years for milk yield and body size under conditions of intensive management. It has been observed that upon increasing milk producing potential as a result of genetic selection, reproductive indexes deteriorate. Under grazing conditions it is impossible to control environmental conditions to the same or nearly the same degree as in intensive systems. Therefore, the use of animals originating from intensive systems under grazing conditions results in a mismatch between the requirements of the new genotype and those that the environment can provide. Thus the increase in individual production potential could be detrimental to the overall productivity of the grazing system, since this system cannot sustain those high levels of productio
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