Impact of ramp-up on the optimal capacity-related reconfiguration policy

This paper presents an optimal solution, based on Markov decision theory, for the problem of optimal capacity-related reconfiguration of manufacturing systems, under stochastic market demand. Both capacity expansion and reduction are considered. The solution quantitatively takes into account the effect of the ramp-up phenomenon, following each reconfiguration, on the optimal policy. A closed-form solution is presented for when product demand is independently and generally distributed over time. A real case concerning a flexible manufacturing line in the automotive sector is shown, to prove that ignoring the ramp-up effect in the decision process can lead to significant increases in overall costs.     

The design and evaluation of a virtual distributed computing environment

Current advances in high-speed networks such as ATM and fiber-optics, and software technologies such as the JAVA programming language and WWW tools, have made network-based computing a cost-effective, high-performance distributed computing environment. Metacomputing, a special subset of network-based computing, is a well-integrated execution environment derived by combining diverse and distributed resources such as MPPs, workstations, mass storage, and databases that show a heterogeneous nature in terms of hardware, software, and organization. In this paper we present the Virtual Distributed Computing Environment (VDCE), a metacomputing environment currently being developed at Syracuse University. VDCE provides an efficient web-based approach for developing, evaluating, and visualizing large-scale distributed applications that are based on predefined task libraries on diverse platforms. The VDCE task libraries relieve end-users of tedious task implementations and also support reusability. The VDCE software architecture is described in terms of three modules: (a) the Application Editor, a user-friendly application development environment that generates the Application Flow Graph (AFG) of an application; (b) the Application Scheduler, which provides an efficient task-to-resource mapping of AFG; and (c) the VDCE Runtime System, which is responsible for running and managing application execution and for monitoring the VDCE resources. We present experimental results of an application execution on the VDCE prototype for evaluating the performance of different machine and network configurations. We also show how the VDCE can be used as a problem-solving environment on which large-scale, network-centric applications can be developed by a novice programmer rather than by an expert in low-level details of parallel programming languages. This revised version was published online in July 2006 with corrections to the Cover Date.     

Drosophilid Assemblages at Different Urbanization Levels in the City of Porto Alegre, State of Rio Grande do Sul, Southern Brazil

The present study analyzed the drosophilid assemblages in different levels of urbanization in the city of Porto Alegre, Rio Grande do Sul, Brazil. Collections were carried out in 2008 in three different environments: a highly urbanized area????Jardim Botanico,?? a forested area with intermediary urbanization????Parque Gabriel Knijnik,?? and in a relatively well-preserved forested area, although threatened by the urban growth????Morro Santana.?? In Jardim Botanico, 36 species belonging to four genera were found, with high abundance of exotic species as Drosophila simulans Sturtevant and Zaprionus indianus (Gupta). In Parque Gabriel Knijnik, 33 species that belonged to four genera were found, with higher abundances of native species belonging to the Drosophila tripunctata species group and Drosophila willistoni species subgroup, and lower abundance of exotic species. As for Morro Santana, 32 species and three genera were found, with higher abundances of native groups, low representativeness of exotic species, and absence of Zaprionus indianus. The analysis of the Jaccard index showed higher similarity in the species composition between samples collected in summer and autumn, and between samples collected in winter and spring. On the other hand, the Morisita index differentiated Jardim Botanico from the other two studied sites. Our results show that Morro Santana is an important area of native biodiversity, reinforcing, therefore, the inclusion of this area in the project for the creation of an ecological corridor as proposed by the Ministry of the Environment of Brazil.     

Directed optimization of biocatalytic transglycosylation processes by the integration of genetic algorithms and fermentative approaches into a kinetic model

Many biocatalysts exhibit strict stereospecificity and regioselectivity. However, their thermodynamically controlled equilibria often limit yields in industrial production processes. Herein, we describe the synthesis of fructooligosaccharides from sucrose by various fructansucrases. We previously demonstrated that transfructosylation to diverse acceptors yields d-glucose and the fructose-containing product along with diverse by-products. To streamline this reaction, we developed a procedure that allows the enhanced transfructosylation of diverse acceptors by different fructansucrases. By diverting the released glucose from the reaction via metabolism by living cells we limited the back reaction and forced the consumption of sucrose. The basic conditions for the resulting fermentation process were optimized by a genetic algorithm and integrated into a kinetic model. This strategy allows the prediction of optimal reaction parameters for the production of desired target compounds.     

The 1,4-naphthoquinone scaffold in the design of cysteine protease inhibitors

A series of 1,4-naphthoquinone derivatives diversely substituted at C-2, C-3, C-5 and C-8, prepared by reaction of amines, amino acids and alcohols with commercial 1,4-naphthoquinones, has been evaluated against papain and bovine spleen cathepsin B. These 1,4-naphthoquinone derivatives were found to be irreversible inhibitors for both cysteine proteases, with second-order rate constants, k(2), ranging from 0.67 to 35.4M(-1)s(-1) for papain, and from 0.54 to 8.03M(-1)s(-1) for cathepsin B. Some derivatives display a hyperbolic dependence of the first-order inactivation rate constant, k(obs), with the inhibitor concentration, indicative of a specific interaction process between enzyme and inhibitor. The chemical reactivity of the compounds towards cysteine as a model thiol is dependent on the naphthoquinone LUMO energy, whereas papain inactivation is not. The 1,4-naphthoquinone derivatives are inactive against the serine protease, porcine pancreatic elastase.     

Diversity of yeasts from bovine mastitis in Southern Brazil

Mastitis is one of the most serious problems in the dairy cattle farms. The great majority of the cases are caused by bacteria, but lately there have been an increasing number of reports about cases of mycotic etiology. The objective of this work was to characterize the yeasts and yeast-like fungi associated with milk of cows with mastitis. Milk samples (n = 248) from a dairy belt situated around the region of Passo Fundo, hinterland of the state of Rio Grande do Sul, Southern Brazil, were analyzed. Aliquots of 0.1 ml of milk were inoculated on yeast extract-malta agar with chloramphenicol. After a period of incubation of 3-5 days at 22-25 degrees C, the counting of the morphologically distinct colonies was performed, as well as the isolation and identification through phenotypical and physiological criteria. It was possible to isolate 68 yeast species from 43 (17.3%) of the samples. The most frequent genera were Candida (37.9%), Pichia (19.1%), Cryptococcus (10.3%) and Rhodotorula (10.3%).