On Pillai’s problem with Pell numbers and powers of 2

In this paper, we find all integers c having at least two representations as a difference between a Pell number and a power of 2

Surface-Modified Bacterial Cellulose with Mercaptosilane as a Multifunctional Platform

Cellulose synthesized by bacteria has unique properties such as high water retention capacity, biocompatibility, biodegradability and flexibility. Nevertheless, modification of this biomaterial is required in order to obtain multifunctional materials, which may be applied in several high-value added products, as catalytic and cell culture platforms. The surface of bacterial cellulose (BC) can be modified by several approaches, namely: (i) physical treatment by plasma, (ii) adsorption of molecules onto BC surface, and (iii) chemical modification. In this sense, the aim of this study was to modify the BC surface by silanization reaction at room temperature using a mixture of ethanol and water, using two different protocols. Thus, BC membranes synthesized by Komagataeibacter xylinus were modified by adding the thiol (SH) functional group with (3-mercaptopropyl)trimethoxysilane under mild conditions. The produced materials were analyzed by elemental analysis, ATR-FTIR, TGA and SEM, and the successful modification was proven by elemental analysis and SEM.

Taxonomias e consideraçóes metodológicas sobre testes de usabilidade em sistemas interativos multimídia

In this work we present a study that comes to contribute with concepts and taxonornies for the development of a methodology of structuring, implantation and application of Usability Testing on interactive multimedia systems in distance education. The used case study is the » Metodología GIM para la formación a distancia» pro ject developed by the “Grup de Recerca Escola Multimedia UPC”. Previous works such as the selection of bibliographic references and a study about modelling, evaluation and improvement of the software process of this pro ject, were used as support material. The principal discoveries of our research include (1) the proposed taxonomy, and (2) the rnethodological considerations for the proceedings of Usability Testing application in the interactive multimedia systems used in distance education. We comment on the conclusions obtained from analysing the result of this research and we put forward sorne suggestions for future works.Neste artigo apresentarnos um estudo que contribui corn conceitos e taxonomias para o desenvolvimento de urna metodologia de estruturaçdo, irnplantaçdo e aplica çao de Testes de Usabilidade ern sisternas interativos multimídia para a forma çdo a distáncia. O estudo de caso utilizado em nosso trabaiho do pro jeto »Metodología GIM para la formación a distancia» desenvolvido pelo “Grup de Recerca Escola Multimedia UPC’ Trabaihos anteriores como a seleçdo de referéncias bibliográficas e urn estudo sobre modelagem, ayaliaçJo e melhora do processo de software do citado pro jeto, forarn utilizados corno material de apoio. Os principais resultados da nossa pes quisa incluern (1) a taxonornia proposta e (2) as considera çóes metodológicas para os procedirnentos de aplicaçáo dos Testes de Usabilidade ern sistemas interativos multirnídia para a formaçáo a distáncia. Comentamos as conclusóes obtidas através desta pesquisa e as propostas para trabalhos futuros

Bacterial Cellulose as a Raw Material for Food and Food Packaging Applications

Bacterial cellulose (BC) has been produced for a number of applications, mainly focused on the biomedical area. Although there is a variety of interesting applications of BC for food and food packaging, only a few have been explored to the moment, since the high cost of BC production is usually considered as a limiting factor. On the other hand, several cost-effective culture media have been proposed, contributing to reduce BC production costs. This article overviews the bioprocess conditions that affects BC production and the main possible applications of BC for food and food packaging purposes

On Pillai's problem with Pell numbers and powers of 2

In this paper, we find all integers c having at least two representations as a difference between a Pell number and a power of 2