HPLC confirmatory method development for the determination of seven quinolones in salmon tissue (Salmo salar L.) validated according to the European Union Decision 2002/657/EC

A confirmatory high pressure liquid chromatographic method for the determination of seven quinolone antibiotics in tissue of Atlantic salmon (Salmo salar L.) was developed. Ciprofloxacin (CIP), danofloxacin (DAN), enrofloxacin (ENR), sarafloxacin (SAR), oxolinic acid (OXO), nalidixic acid (NAL) and flumequine (FLU) were separated on a Perfectsil ODS-2 120 (250 mm × 4 mm, 5 μm) column by gradient elution with a mobile phase consisting of 0.1% trifluoroacetic acid (pH = 1), acetonitrile and methanol at 25 °C within 22 min. Analytes were monitored at 255 nm (for the determination of OXO, NAL and FLU) and 275 nm (for CIP, DAN, ENR and SAR) by means of photodiode array detector. Examined quinolones were isolated from salmon tissue by extraction with citrate buffer solution (pH = 4.7) and purified by solid phase extraction using Oasis HLB (200 mg/6 mL) cartridges. The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability and sensitivity according to the European Union Decision 2002/657/EC. The accuracy of the method was additionally proved by its application to certified reference material of salmon tissue (BCR® 725).     

Partial purification and characterization of peroxidase from olives (<Emphasis Type="Italic">Olea europaea</Emphasis> cv. Koroneiki)

The enzyme peroxidase (POD) activity was extracted from olives (Olea europaea cv. Koroneiki) and was partially purified by ammonium sulfate fractionation and gel permeation chromatography (Sephacryl S 300). Further characterization of the POD was performed using the ammonium sulfate purified fraction. POD showed a molecular mass of 44 ± 2 kDa and it expressed catalytic activity with 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS), N,N-dimethyl-p-phenylenediamine (DMPD) and some olive fruit phenols. However, the enzyme was found ineffective as regards the oxidation of oleuropein, the major polyphenol of olives, as well as with coumaric, ferulic, ascorbic and p-hydroxy benzoic acids. pH optimum of the peroxidase-catalyzed oxidation depended on the substrate used and it varied from 4.0 to 6.0. Olive peroxidase shows high thermal stability. Oleuropein, the major polyphenol of olives, drastically inhibited ABTS peroxidation by the POD preparation with an IC₅₀ value of 47 μM. The presence of POD enzyme activity in virgin olive oil samples was also confirmed.     

YmalDB: exploring relational databases via result-driven recommendations

The typical user interaction with a database system is through queries. However, many times users do not have a clear understanding of their information needs or the exact content of the database. In this paper, we propose assisting users in database exploration by recommending to them additional items, called Ymal (“You May Also Like”) results, that, although not part of the result of their original query, appear to be highly related to it. Such items are computed based on the most interesting sets of attribute values, called faSets, that appear in the result of the original query. The interestingness of a faSet is defined based on its frequency in the query result and in the database. Database frequency estimations rely on a novel approach of maintaining a set of representative rare faSets. We have implemented our approach and report results regarding both its performance and its usefulness.     

Polycyanurate networks modified by polyoxytetramethylene glycol

Summary We report results obtained within a collaborative project dealing with the preparation of hybrid polycyanurate/polyoxytetramethylene glycol (PCN/PTMG) networks and the investigation of their structure-property relationships by a variety of experimental techniques. The hybrids were prepared from PCN and PTMG (molar mass 1.000 g/mol) with 10, 20, 30 and 40 wt% PTMG. The degree of incorporation of PTMG into the PCN network was determined by gel fraction measurements. WAXS and SAXS studies had indicated that the materials under investigation are amorphous and exhibit nanostructural heterogeneity, which increases with increasing amount of PTMG. Stress-strain measurements show improvement of the mechanical properties for PTMG contents of 30 and 40%. The focus in this paper is on the detailed investigation of the α relaxation associated with the glass transition in wide ranges of frequency and temperature by dielectric techniques. A single α relaxation was observed in all the compositions shifting systematically to lower temperatures/higher frequencies with increasing PTMG content. The results were systematically analyzed in terms of time scale and relaxation strength of the response and are discussed in terms of plasticization, presence of nanostructural heterogeneities and hybridization. Co-operativity of the α relaxation, quantified in terms of fragility, was found to decrease with increasing amount of PTMG, in correlation with increasing level of nanoheterogenity.     

Sequential group recommendations based on satisfaction and disagreement scores

Journal of Intelligent Information Systems - Recently, group recommendations have gained much attention. Nevertheless, most approaches consider only one round of recommendations. However, in a...     

Managing contextual preferences

To handle the overwhelming amount of information currently available, personalization systems allow users to specify through preferences which pieces of data interest them. Most often, users have different preferences depending on context. In this paper, we introduce a model for expressing such contextual preferences. Context is modeled using a set of hierarchical attributes, thus allowing context specification at various levels of detail. We formulate the context resolution problem as the problem of selecting appropriate preferences based on context for personalizing a query. We also propose algorithms for context resolution based on data structures that index preferences by exploiting the hierarchical nature of the context attributes. Finally, we evaluate our approach from two perspectives: usability and performance. Usability evaluates the overheads imposed on users for specifying context-dependent preferences, as well as their satisfaction from the quality of the results. Our performance results focus on the context resolution using the proposed indexes.     

Providing Database Interoperability through Object-Oriented Language Constructs

Seamless access to resources and services provided by distributed, autonomous, and heterogeneous systems is central to many advanced applications. Building an integrated system to provide such uniform access and cooperation among underlying heterogeneous systems is both an increasing necessity and a formidable challenge. An important component of such a complex integrated system is a unified language that serves both as a data definition and as a data manipulation tool. Special requirements are posed in the instance of an integrated system which includes database systems among its components. In this paper, we introduce the necessary constructs that an object-oriented programming language should provide for being adopted as the language of the integrated system in such a setting. We adopt a modular, object-based approach to integration. Each component system that joins the integration provides a set of basic classes and pre-defined basic methods. We show how the class hierarchy of the system can be used to provide a uniform way of mapping database resources to basic classes and associative queries to basic methods. A view mechanism is introduced that supports the integration of the basic classes and provides a means of expressing relationships among them and resolving any potential conflicts. The view mechanism is implemented by extending the standard class constructors of an object-oriented language to support the definition of virtual classes. The language provides workflow constructs for defining the structure of programs and for attaining synchronization among concurrently executing programs. Furthermore, atomicity and concurrency control information is included in the form of consistency assertions as part of the interface of each basic method.