Kinetics of xanthan gum production from whey by constructed strains of Xanthomonas campestris in batch fermentations

Two new constructed strains of X. campestris XLM1521 and XMT1, either alone or in mixed cultures were used for the production of xanthan gum in batch fermentations from whey. Fermentations were carried out at three different pH levels of 6.0, 7.0 and 8.0 and the results were compared with those previously reported for fermentations in Erlenmeyer flasks without controlling the pH. The kinetics of cultures of the strain X. campestris XLM1521 were studied in a batch reactor at constant pH values. A mathematical model, based on the Luedeking-Piret equation, was used and experimental design was employed in order to correlate model's parameters with pH variation. The highest xanthan gum concentration, 17.3 g/l, was observed at pH 8.0. This is the largest amount of xanthan gum reported so far.     

Robust sliding-mode control applied to a 5-link biped robot

In this paper the application of robust control to a 5-link biped robotic model is investigated through the sliding mode approach, and compared to pure computed torque control. The biped consists of five links, namely the torso and two links in each leg. These links are connected via four (two hip and two knee) rotating joints which are considered to be friction-free and driven by independent d.c. motors. The locomotion of the biped is assumed to be constrained on the sagittal plane. The paper provides a full derivation of the biped dynamic model (single-leg support phase, biped-in-the-air phase) and an outline of the computed torque and sliding mode control algorithms. The simulation results were derived with two sets of parameters (one of which corresponds to a human-sized biped) and several degrees of parametric uncertainty (from 10% to 200%). In all cases the results obtained through the sliding mode control were much better than those obtained with the computed torque control. This superiority was shown to become stronger as the degree of uncertainty and the size of the biped increases.     

User engagement with scholarly tweets of scientific papers: a large-scale and cross-disciplinary analysis

Scientometrics - This study investigates the extent to which scholarly tweets of scientific papers are engaged with by Twitter users through four types of user engagement behaviors, i.e., liking,...     

Preparation and characterization of lyophilised egg PC liposomes incorporating curcumin and evaluation of its activity against colorectal cancer cell lines

Curcumin has been associated with the treatment of various diseases in traditional medicine, among them cancer. The major problems that prevent its approval as therapeutic agent are its low water solubility and its relatively low in vivo bioavailability. Liposomes are considered as effective drug carriers because of their ability to solubilize hydrophobic compounds and to alter their pharmacokinetic properties. The purpose of this study was the development of lyophilised liposomal curcumin fully characterized in terms of its physical properties [(zeta-potential, size, size distribution and Polydispercity index (PI)], and to evaluate its in vitro cytotoxic against colorectal cancer cell lines in a short-term and in a long-term (clonogenic) assay. Curcumin was incorporated in egg-phosphatidylcholine (EPC) liposomes at a drug to lipid molar ratio 1:14 achieving high incorporation efficiency close to 85%. The liposomal curcumin was lyophilized preserving thus its stability. The reconstitution of the formulation resulted in the original liposomal suspension. The release in FBS showed a plateau near 14% at 96 hours of incubation. The in vitro studies against colorectal cancer cell lines have shown that liposomes improve the activity of curcumin especially in the long-term assay and the liposomal formulation found to be more potent against HCT116 and HCT15, cell lines which express the MDR phenotype. EPC liposomal curcumin in a molar ratio of curcumin/EPC 1:14 has shown improved cytotoxic activity versus free curcumin against colorectal cancer cell lines. In vivo studies based on the recent findings are in progress in our laboratory.     

An aggregate model for energy costs: National product interdependence

A small model is constructed which describes energy-economy interactions on an aggregate level. The model, based on a neo-classical approach, estimates the impact on net national product and energy demand of changes in the cost of domestic and imported energy if tax and tariff rates - as percentages of total price — are kept constant. A parametric analysis is carried out to investigate the role of structural parameters such as the price and income elasticities. Among others, a key parameter of primary importance in the energy-economy interaction is revealed to be the cost to output ratio of the energy sector. Through this parameter, we are able to analyse the interdependence of the tariff rates, the relative cost of imported to domestic energy and the energy import share, and thereafter assess their combined effect on the energy-economy interaction.     

From the web of data to a world of action

This paper takes as its premise that the web is a place of action, not just information, and that the purpose of global data is to serve human needs. The paper presents several component technologies, which together work towards a vision where many small micro-applications can be threaded together using automated assistance to enable a unified and rich interaction. These technologies include data detector technology to enable any text to become a start point of semantic interaction; annotations for web-based services so that they can link data to potential actions; spreading activation over personal ontologies, to allow modelling of context; algorithms for automatically inferring ‘typing’ of web-form input data based on previous user inputs; and early work on inferring task structures from action traces. Some of these have already been integrated within an experimental web-based (extended) bookmarking tool, Snip!t, and a prototype desktop application On Time, and the paper discusses how the components could be more fully, yet more openly, linked in terms of both architecture and interaction. As well as contributing to the goal of an action and activity-focused web, the work also exposes a number of broader issues, theoretical, practical, social and economic, for the Semantic Web.     

Tribological performance of hybrid organo-silicate coatings

Hybrid organo-silicate coatings (hybrid coatings) present many advantages and find use in many applications. However, their tribological performance has not been widely investigated due to the non-uniformity of the synthesized hybrid materials. In this work, nanoscratch tests have been employed for the investigation of wear mechanisms and organic–inorganic coatings adhesion. The tribological performance was investigated under low applied normal forces, in order to estimate the coefficient of friction (μ) values, the coatings resistance and the humidity effect when the synthesized coatings were submerged on a cell culture medium. Also, the performed plastic deformation was correlated with the experimental data and the surface images taken with a scanning probe microscope after the scratch tests. Furthermore, the experimental data were fitted and the relative coefficient of friction and cohesive force of each synthesized coating were calculated, since organic and hybrid materials do not conform with the classic tribology laws and are greatly affected by the adhesion forces observed between tip and sample's surface.