Growth and energy generation by Enterococcus faecium FAIR-E 198 during citrate metabolism

Citrate metabolism by Enterococcus faecium FAIR-E 198, isolated from Greek Feta cheese, was studied in various growth media containing citrate either in the presence of glucose, or as the sole carbon source, both under aerobic and anaerobic conditions. In de Man-Rogosa-Sharpe (MRS) broth with increasing citrate concentrations, cometabolism of citrate and glucose took place. Glucose was stoichiometrically converted into lactate, while citrate into acetate. Glucose consumption and biomass yield were enhanced with increasing initial citrate concentrations, even though maximum specific growth rate was not. When citrate was used as the sole carbon source in increasing initial concentrations, the main end product was acetate. Small amounts of lactate, formate, ethanol, and acetoin were also produced. In all cases, no significant differences were observed between aerobic and anaerobic conditions. However, when citrate was used as sole carbon source, formate production was favored in the absence of oxygen. The present work shows that E. faecium is able to utilize citrate in synthetic media, either in the presence of glucose or as the sole carbon source, resulting in energy production and the formation of aroma compounds.     

Coalitional tracking

We propose a novel tracking method that uses a network of independent particle filter trackers whose interactions are modeled using coalitional game theory. Our tracking method is general, it maintains pixel level accuracy, and can negotiate surface deformations and occlusions. We tested our method on a substantial video set featuring non-trivial motion from over 40 objects in both the infrared and visual spectra. The coalitional tracker demonstrated fault tolerant behavior that exceeds by far the performance of single particle filter trackers. Our method represents a shift from the typical tracking paradigms and may find application in demanding imaging problems across the electromagnetic spectrum.     

An effective and efficient parallel approach for random graph generation over GPUs

The widespread usage of random graphs   has been highlighted in the context of database applications for several years. This because such data structures turn out to be very useful in a large family of database applications ranging from simulation to sampling, from analysis of complex networks to study of randomized algorithms, and so forth. Amongst others, Erd?s–Rényi _Γv,p${\Gamma }_{v,p}$ is the most popular model to obtain and manipulate random graphs. Unfortunately, it has been demonstrated that classical algorithms for generating Erd?s–Rényi based random graphs do not scale well in large instances and, in addition to this, fail to make use of the parallel processing capabilities of modern hardware. Inspired by this main motivation, in this paper we propose and experimentally assess a novel parallel algorithm for generating random graphs under the Erd?s–Rényi model that is designed and implemented in a Graphics Processing Unit (GPU), called PPreZER. We demonstrate the nice amenities due to our solution via a succession of several intermediary algorithms, both sequential and parallel, which show the limitations of classical approaches and the benefits due to the PPreZER algorithm. Finally, our comprehensive experimental assessment and analysis brings to light a relevant average speedup gain of PPreZER over baseline algorithms.     

Modeling users on the World Wide Web based on cognitive factors,navigation behavior and clustering techniques

This paper focuses on modeling users’ cognitive styles based on a set of Web usage mining techniques on user navigation patterns and clickstream data. Main aim is to investigate whether specific clustering techniques can group users of particular cognitive style using measures obtained from psychometric tests and content navigation behavior. Three navigation metrics are proposed and utilized to find identifiable groups of users that have similar navigation patterns in relation to their cognitive style. The proposed work has been evaluated with two user studies which entail a psychometric-based survey for extracting the users’ cognitive styles, combined with a real usage scenario of users navigating in a controlled Web 2.0 environment. A total of 106 participants of age between 17 and 25 participated in the study providing interesting insights with respect to cognitive styles and navigation behavior of users. Studies like the reported one can be useful for modeling users and assist adaptive Web 2.0 environments to organize and present information and functionalities in an adaptive format to diverse user groups.     

Stability analysis of LPV time-delayed systems

This work provides one of the first attempts to derive computationally tractable criteria for analysing the stability of linear parameter varying (LPV) time-delayed systems. We present both delay-independent and delay-dependent stability conditions, which are derived using appropriately selected Lyapunov-Krasovskii functionals. According to the system parameter dependence, these functionals can be selected to obtain increasingly non-conservative results. Gridding techniques may be used to cast these tests as linear matrix inequalities (LMIs). In cases when the system matrices depend affinely or quadratically on the parameter, gridding may be avoided. These LMIs can be solved efficiently using available software. A numerical example of a time-delayed system motivated by a metal removal process is used to demonstrate the theoretical results.     

Anthocyanin profiles of major red grape (Vitis vinifera L.) varieties cultivated in Greece and their relationship with in vitro antioxidant characteristics

A range of fourty‐six red grape (Vitis vinifera spp.) samples, originating from six widely cultivated varieties and covering major parts of the Hellenic vineyard, were assayed for their content in six principal anthocyanin pigments. Representative in vitro antioxidant parameters were also determined, including antiradical activity (A_AR), reducing power (P_R) and hydroxyl free radical scavenging activity (SA_HFR). Quantitative determination using high performance liquid chromatography showed that the prevalent pigment was malvidin 3‐O‐glucoside (average content 82.53 mg per 100 g fresh berry weight), followed by its coumarate derivative (29.26 mg per 100 g), paeonidin 3‐O‐glucoside (10.84 mg per 100 g), petunidin 3‐O‐glucoside (7.80 mg per 100 g) cyanidin 3‐O‐glucoside (5.67 mg per 100 g) and delphinidin 3‐O‐glucoside (1.28 mg per 100 g). The richest variety was Syrah, with total average anthocyanin content of 186.02 mg per 100 g, whereas the Hellenic native variety Xinomavro had the lowest average anthocyanin level (38.70 mg per 100 g). The establishment of correlations of individual and total anthocyanin contents with the values from the antioxidant test was accomplished with linear regression. The links of total anthocyanins were significant with all antioxidant parameters (P < 0.001), but more importantly with SA_HFR (R² = 0.740). Malvidin 3‐O‐glucoside content had the higher correlation with SA_HFR compared with all other anthocyanins (R² = 0.698, P < 0.001).     

The influence of alteration on the engineering properties of dolerites: The examples from the Pindos and Vourinos ophiolites (northern Greece)

The influence of alteration on the physico-mechanical properties of dolerites from the Pindos and Vourinos ophiolites, northern Greece, is investigated. Quantitative petrographic analysis shows that the samples display various percentages of secondary minerals. Two new micropetrographic indices are calculated from the results of petrographic modal analysis for the engineering assessment of dolerites: the micropetrographic strength index I_ps and the replacement index I_rep. The samples are also tested to determine water absorption, apparent density, total porosity, sand equivalent, uniaxial compressive strength, Los Angeles abrasion value, aggregate impact value, aggregate abrasion value and polished stone value. The influence of alteration on the rock quality and especially the relationships between the proposed micropetrographic indices and the engineering parameters are determined using regression analysis and the derived equations were verified by the t-test and the F-test. The relationships between the I_ps and I_rep indices and the engineering properties show that alteration products generally result in mechanically weaker rocks. However, the results of the physico-mechanical tests indicate that dolerites retain their strength and durability due to the low proportions of soft minerals and microcracks, along with the preservation of their igneous textures. The polishing resistance is the only engineering parameter that is positively affected by alteration processes, as expressed by the I_ps index. Particularly, the replacement of the primary mafic minerals by secondary minerals, expressed by the I_rep index, can enhance the polishing resistance of dolerites when used in the wearing surface of a road. The results also indicate strong positive correlations between the chlorite content and the water absorption and total porosity values.     

Implementation of response surface methodology to optimise extraction of onion (Allium cepa) solid waste phenolics

An experimental setup based on a 2³-full factorial, central composite design was implemented with the aim to optimising recovery of polyphenols from onion solid wastes (OSW). In order to allow for the establishment of a sustainable process, reusable and non-toxic solutions composed of water/ethanol/citric acid were employed as extracting media. The factors considered were (i) the pH of the medium, (ii) the extraction time and (iii) the ethanol concentration. The model obtained produced a satisfactory fitting of the experimental data with regard to total polyphenol extraction (R² = 0.97, p = 0.0025) and the reducing power of the extracts (R² = 0.97, p = 0.0033), but not with the antiradical activity (R² = 0.89, p = 0.0592). The 2nd order polynomial equations obtained after elaboration of the experimental data indicated that all parameters considered were significant in respect with the efficiency of total polyphenol recovery. The highest total polyphenol yield was theoretically predicted to be 9342 ± 1435 mg gallic acid equivalents per 100 g dry weight, under optimal conditions (60% EtOH, pH 2 and 4.2 h). Liquid chromatography-electrospray ionisation mass spectrometry of the optimally obtained extract revealed that the principal phytochemicals recovered were quercetin 3,4′-diglucoside, quercetin 4′-glucoside and quercetin. Simple linear regression analysis between the total polyphenol and the antiradical activity of the OSW extracts showed that there was no correlation in a statistically significant manner, as opposed to reducing power.Industrial relevanceThe recovery of value-added substances from agri-food industrial wastes is an issue with importance pertaining to both the reduction of the waste load released to the environment, and the development of novel, natural food additives with functional properties. Up to date, the examinations pertaining to the clarification of factors that can affect extractability were based on rather unilateral assessment, while it is generally accepted that the retrieval depends on several parameters, which render the phenomenon a particular complexity. In this view, the implementation of factorial design with respect to investigating in parallel several factors pertaining to efficient polyphenol recovery becomes imminent. Thus the establishment of models on such a sound experimental basis is expected to provide a reliable background for more costand resource-effective processes, with a potential direct industrial applicability.     

Model for Understanding, Preventing, and Resolving Project Disputes

Based on the comparative analysis of 24 construction disputes, this paper presents a process model that explains the development of disputes. The model examines the combined effect of project uncertainty, contract, working relations, and problem solving effectiveness on the development of disputes. The model develops a classification of problem situations, and identifies the problem-solving requirements and the potential for dispute in each situation. The model indicates that the prevention of complex, high cost disputes depends more on the planning and problem solving ability of the project organization, and less on the contractual terms. The paper identifies the following actions that can reduce the number and severity of claims: reduction of project uncertainty, reduction of contractual problems, reduction of opportunistic behavior, increased the project organization's problem-solving ability, and use of alternative dispute resolution methods to reduce resolution costs.