Inhibition of the decrease of volatile esters and terpenes during storage of a white wine and a model wine medium by glutathione and N-acetylcysteine

Glutathione and N‐acetylcysteine, each at 20 mg L^?1, were tested as inhibitors of the decrease of volatile esters and terpenes during storage of Debina white wine. Moreover, the inhibition of the decrease of isoamyl acetate, ethyl hexanoate and linalool in a model wine medium by glutathione and N‐acetylcysteine, each at 0–20 mg L^?1, was also tested. Several volatiles, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate and linalool, decreased during wine storage. Glutathione or N‐acetylcysteine significantly restricted the decrease of these volatiles. In the model medium, each thiol inhibited the decrease of the three volatiles in a dose‐dependent manner. N‐acetylcysteine inhibited the decrease of all three volatiles at 2.5 mg L^?1 while glutathione at 2.5 or 5.0 mg L^?1. The present results indicate that glutathione and N‐acetylcysteine may be taken into account as potent inhibitors of the disappearance of aromatic esters and terpenes in wines.     

The clinical value of solid marker transit studies in childhood constipation and soiling

Assessment of constipation in childhood is difficult, particularly when the presenting symptom is spurious diarrhoea or faecal incontinence. We have therefore assessed the clinical usefulness, reliability and acceptability of a solid marker transit technique in 52 patients with constipation (median age 8.0 years; range 2-13.5 years) at two referral centres. Median duration of symptoms was 60 months. Soiling was a prominent feature in 43 children (83%). Ten, 3 mm pieces of 6FG radio-opaque Silastic tubing were given orally at 9am on days 1, 2 and 3 and a plain abdominal film taken on day 5. Laxative treatment was not interrupted. Each film was divided into right colon, left colon and rectosigmoid areas, using bony landmarks, and the marker content of each area counted. The coefficient of variation of intra and inter-observer errors was 3.1% and 2.1% respectively. By day 5, 7% (group median) of markers were still in the right colon, 17% in the left colon and 42% in the rectosigmoid. Twenty-one patients (40%) had normal transit, 4 (8%) mild delay, 9 (17%) moderate and 18 (35%) severe transit delay. Marker distribution indicated slow pan-colonic transit in 29% and slow segmental transit in 10%. In 21%, clustering of markers in the rectosigmoid suggested outlet obstruction. A significant correlation was found between both transit delay and marker distribution and the severity of clinical symptoms of constipation and soiling. Repeat studies in six children following colonic evacuation revealed significant improvement (P < 0.05) in marker transit.(ABSTRACT TRUNCATED AT 250 WORDS)     

Symposium on Operations Research 1995 Jahrestagung der DGOR, GM?OR und ?GOR (SOR '95) Universit?t Passau, 13. September –15. September, 1995

Jahrestagung der DGOR, GMÖOR und ÖGOR (SOR '95) Universität Passau, 13. September –15. September, 1995     

The Hausdorff Voronoi Diagram of Point Clusters in the Plane

We study the Hausdorff Voronoi diagram of point clusters in the plane, a generalization ofVoronoi diagrams based on the Hausdorff distance function. We derive a tight combinatorial bound on the structural complexity of this diagram and present a plane sweep algorithm for its construction. In particular, we show that the size of the Hausdorff Voronoi diagram is (n + m), where n is the number of points on the convex hulls of the given clusters, and m is the number of crucial supporting segments between pairs of crossing clusters. The plane sweep algorithm generalizes the standard plane sweep paradigm for the construction of Voronoi diagrams with the ability to handle disconnected Hausdorff Voronoi regions. The Hausdorff Voronoi diagram finds direct application in the problem of computing the critical area of a VLSI layout, a measure reflecting the sensitivity of the VLSI design to spot defects during manufacturing.     

Systems dynamics modelling of a manufacturing supply chain system

Supply chains are multifaceted structures focusing on the integration of all the factors involved in the overall process of production and distribution of end products to the customers. Growing interest in supply chain systems has highlighted the need to adopt appropriate approaches that can ensure the efficient management of their complexity, enormity and broadness of scope. With the main aim of supply chain management being to optimise the performance of supply chains, attention is mainly drawn to the development of modelling frameworks that can be utilised to analyse and comprehend the dynamic behaviour of supply chains. While there have been only a few supply chain modelling attempts reported in the literature, this paper proposes a modelling framework that is used to simulate the operation of a supply chain network of moderate complexity. The proposed model comprises four echelons and is build around a central medium-sized manufacturing company operating as a typical Make-to-Order (MTO) system. The developed model was built using a systems dynamics (SD) approach. The operations performed within a supply chain are a function of a great number of key variables which often seem to have strong interrelationships. The ability of understanding the network as a whole, analysing the interactions between the various components of the integrated system and eventually supplying feedback without de-composing it make systems dynamics an ideal methodology for modelling supply chain networks. The objective of the paper is to model the operation of the supply chain network under study and obtain a true reflection of its behaviour. The modelling framework is also used to study the performance of the system under the initial conditions considered and compare it with that obtained by running the system under eight different scenarios concerning commonly addressed real-life operational conditions. The modelling effort has focused on measuring the supply chain system performance in terms of key metrics such as inventory, WIP levels, backlogged orders and customer satisfaction at all four echelons. The study concludes with the analysis of the obtained results and the conclusions drawn from contrasting the system’s performance under each investigated scenario to that of the benchmark model.     

Enhancement of hybrid renewable energy systems control with neural networks applied to weather forecasting: the case of Olvio

In this paper, an intelligent forecasting model, a recurrent neural network (RNN) with nonlinear autoregressive architecture, for daily and hourly solar radiation and wind speed prediction is proposed for the enhancement of the power management strategies (PMSs) of hybrid renewable energy systems (HYRES). The presented model (RNN) is applicable to an autonomous HYRES, where its estimations can be used by a central control unit in order to create in real time the proper PMSs for the efficient subsystems’ utilization and overall process optimization. For this purpose, a flexible network-based design of the HYRES is used and, moreover, applied to a specific system located on Olvio, near Xanthi, Greece, as part of Systems Sunlight S.A. facilities. The simulation results indicated that RNN is capable of assimilating the given information and delivering some satisfactory future estimation achieving regression coefficient from 0.93 up to 0.99 that can be used to safely calculate the available green energy. Moreover, it has some sufficient for the specific problem computational power, as it can deliver the final results in just a few seconds. As a result, the RNN framework, trained with local meteorological data, successfully manages to enhance and optimize the PMS based on the provided solar radiation and wind speed prediction and make the specific HYRES suitable for use as a stand-alone remote energy plant.     

A flexible and adaptable planning and control system for an MTO supply chain system

Evolving consumer demand has led to the emergence of a new business era where change plays a dominant role. This new era has in turn posed a number of competences that supply chain systems need to posses so as to survive and prosper under change and uncertainty. The main aim of this work is to model the performance of an make-to-order (MTO) production environment that operates as part of a wider supply chain network under various control policies and identify the best performing ones. A simulation model has been created and used as a tool to help quantify the effects of three control policies on this MTO system. A number of performance metrics such as Work-in-process (WIP), tardiness, responsiveness and mean flow time have been considered to provide further insight into the impact of these three localised control policies. The three control policies implemented were push, and two modes of pull control, which are, CONWIP and tight pull.