Syndiospecific oligomerization and polymerization of norbornene with titanium catalysts

Norbornene (NB) has been polymerized with TiCl₄-AlR₂Cl (R = Et, Me, iBu) at various NB/TiCl₄ molar ratio. The products obtained at low ratio (from ca. 5 to 12, depending on the mode of catalyst preparation) are a mixture of oligomers, from which it has been possible to isolate a crystalline heptamer having a 2,3-exo-disyndiotactic structure by single crystal X-ray analysis. The products obtained at higher NB/TiCl₄ ratio have a higher molecular weight (up to ca. 5000 for the soluble products) and consist of amorphous and crystalline polymers. The crystalline polymers, characterized by X-ray and ¹³C NMR, are a new type of stereoregular polynorbornene (PNB), having a 2,3-exo-disyndiotactic structure. Mechanistic aspects are examined and a precise assignment of some resonances in the ¹³C NMR spectrum of vinyl-type PNBs is reported.     

Natural antioxidants and volatile compounds of virgin olive oils obtained by two or three‐phases centrifugal decanters

Research has been carried out to ascertain the influence of different centrifugal decanters employed in olive process on oil yields and qualitative characteristics and composition of volatile compounds of virgin olive oil. Tests were performed in an olive oil mill equipped with centrifugal decanters at two or three‐phases. Results show that oil yields were similar and oils extracted from good‐quality olives do not differ in free fatty acids, peroxide value, UV absorptions and organoleptic assessment. Total phenols and o‐diphenols content as well as induction time values are higher in oils obtained by the centrifugal decanter at two‐phases, because it requires less quantity of water added to olive paste in comparison to the three‐phases centrifugal decanter. The amount of water added determines the dilution of the aqueous phase and lowers the concentration of the phenolic substances more soluble in vegetable waste water. Due to the partition equilibrium law the concentration of the same substances consequently diminishes in the oil. In this research, the coefficient of the partition equilibrium of total phenols between oil and vegetable water has been calculated and discussed. No significant difference occurred, due to the different decanters employed, in the average values of the volatile components of the head‐space of oils.     

Silicon Application Increases Biomass Yield in Sunflower by Improving the Photosynthesizing Leaf Area

Silicon - Sunflower is an oilseed plant important for food and biodiesel production. One cheap way to increase sunflower production is by the application of silicon (Si), which has shown to be...     

Silver nanoparticles as selective ionization probes for analysis of olefins by mass spectrometry

Laser desorption/ionization (LDI) using silver nanoparticles (AgNPs) is shown to selectively ionize olefinic compounds, e.g., cholesterol, 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC), and carotenoids. Selective AgNP LDI can be carried out from complex mixtures without the addition of an organic matrix, sample cleanup, or prefractionation. Results presented in this report are the first to demonstrate the selective ionization of specific compounds from a complex mixture using metal nanoparticles.     

The distinction between beliefs legitimizing aggression and deviant processing of social cues: Testing measurement validity and the hypothesis that biased processing mediates the effects of beliefs on aggression.

In 2 studies the authors examined knowledge and social information-processing mechanisms as 2 distinct sources of influence on child aggression. Data were collected from 387 boys and girls of diverse ethnicity in 3 successive years. In Study 1, confirmatory factor analyses demonstrated the discriminant validity of the knowledge construct of aggression beliefs and the processing constructs of hostile intent attributions, accessing of aggressive responses, and positive evaluation of aggressive outcomes. In Study 2, structural equation modeling analyses were used to test the mediation hypothesis that aggression beliefs would influence child aggression through the effects of deviant processing. A stronger belief that aggressive retaliation is acceptable predicted more deviant processing 1 year later and more aggression 2 years later. However, this latter effect was substantially accounted for by the intervening effects of deviant processing on aggression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Combining pixel domain and compressed domain index for sketch based image retrieval

Sketch-based image retrieval (SBIR) lets one express a precise visual query with simple and widespread means. In the SBIR approaches, the challenge consists in representing the image dataset features in a structure that allows one to efficiently and effectively retrieve images in a scalable system. We put forward a sketch-based image retrieval solution where sketches and natural image contours are represented and compared, in both, the compressed-domain of wavelet and in the pixel domain. The query is efficiently performed in the wavelet domain, while effectiveness refinements are achieved using the pixel domain to verify the spatial consistency between the sketch strokes and the natural image contours. Also, we present an efficient scheme of inverted lists for sketch-based image retrieval using the compressed-domain of wavelets. Our proposal of indexing presents two main advantages, the amount of the data to compute the query is smaller than the traditional method while it presents a better effectiveness.     

Fuzzy Modeling for Function Points Analysis

Function Point Analysis (FPA) is a largely used technique to estimate the size of development project, enhancement project or applications already installed. During the point counting process that represents the dimension of a project or an application, each function is classified according to its relative functional complexity. Several studies resulted in FPA extensions, and most of them are mainly aimed at achieving greater precision in the point assessment of systems of greater algorithmic complexity. This work proposes the use of concepts and properties from fuzzy set theory to extend FPA into FFPA (Fuzzy Function Point Analysis). Fuzzy theory seeks to build a formal quantitative structure capable of emulating the imprecision of human knowledge. With the function points generated by FFPA, the functionality of the project is better represented than it was through FPA. Thus, derived values such as costs and terms of development can be more precisely determined.     

On finite semigroups of matrices

Finite semigroups of n by n matrices over the naturals are characterized both by algebraic and combinatorial methods. Next we show that the cardinality of a finite semigroup S of n by n matrices over a field is bounded by a function depending only on n, the number of generators of S and the maximum cardinality of its subgroups. As a consequence, given n and k, there exist, up to isomorphism, only a finite number of finite semigroups of n by n matrices over the rationals, generated by at most k elements. Among other applications to Automaton Theory, we show that it is decidable whether the behavior of a given N – Σ automaton is bounded.