A parallel variable neighborhood search approach for the obnoxious p‐median problem

The obnoxious p‐median problem consists of selecting p locations, considered facilities, in a way that the sum of the distances from each nonfacility location, called customers, to its nearest facility is maximized. This is an ‐hard problem that can be formulated as an integer linear program. In this paper, we propose the application of a variable neighborhood search (VNS) method to effectively tackle this problem. First, we develop new and fast local search procedures to be integrated into the basic VNS methodology. Then, some parameters of the algorithm are tuned in order to improve its performance. The best VNS variant is parallelized and compared with the best previous methods, namely branch and cut, tabu search, and GRASP over a wide set of instances. Experimental results show that the proposed VNS outperforms previous methods in the state of the art. This fact is finally confirmed by conducting nonparametric statistical tests.     

Segmentation of weather radar image based on hazard severity using RDE: reconstructed mutation strategy for differential evolution algorithm

Weather describes the condition of our atmosphere during a specific period of time, and climate represents a composite of day to day weather over longer period of time. Climatology attempts to analyze and explain the impact of climate so that the society can plan accordingly. Climatology analysis is often done on radar images representing various climatic conditions. These images contain varying scale of severity for any specific climatic parameter of study. The climatologists often find it convenient to analyze climatic conditions if tools are available to segment the weather images based on the severity scale which is represented by different colors. Segmentation of the weather radar image is also used for automated analysis of weather conditions. Differential evolution (DE) approach instead is used for fast selection of optimal threshold. In present paper, we have applied DE with multilevel thresholding for weather image segmentation which results in minimum computational time and excellent image quality. A new mutation strategy for DE named reconstructed differential evolution (RDE) strategy is suggested for better performance over image segmentation. Using fuzzy entropy and RDE for multilevel thresholding provides better results in comparison with last suggested methods.

     

Influence of commercial sanitizers on lipopolysaccharide production by Salmonella Enteritidis ATCC 13076

The effect of typical sanitizers on the composition and toxicity of lipopolysaccharides (LPSs) produced by Salmonella Enteritidis ATCC 13076 was analyzed. Salmonella Enteritidis was propagated up to the late exponential phase in the presence of commercial sanitizing solutions. LPS was extracted and derivatized with trifluoroacetylation, and gas chromatography-mass spectrometry analysis and the chromogenic Limulus amoebocyte lysate assay were used to assess the ultrastructure and toxicity of the LPS. The viability and debris formation during growth were evaluated to verify the bactericidal and bacteriostatic effects of the sanitizers and to assess sanitizer effects on LPS formation. The LPSs produced were quantified at 1.7 x 10(4), 1.2 x 10(4), 3.6 x 10(3), and 9.6 x 10(4) [KDO] x OD(620nm)(-1) for the controls and the organisms grown in the presence of a chlorinated sanitizer, a heavy-duty alkaline cleaner, and a phenolic hand wash solution, respectively. In response to these treatments, the short-chain polysaccharide fractions of the LPSs in the Salmonella Enteritidis cells increased. This finding suggests that this organism increases the low-molecular-weight fraction of the LPS in relation to the high-molecular-weight fraction to survive these unfavorable conditions. The cumulative change in the LPS in response to the sanitizers influenced the toxicity of the LPS; however, this change could not be related to an individual compound within any of the assessed fractions.     

Comparison of chronic toxicity and carcinogenicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in 2-year bioassays in female Sprague-Dawley rats

The cancer bioassay for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) conducted by the Dow Chemical company in the mid 70s has been used extensively for conducting quantitative cancer risk assessments for human exposure to TCDD. More recently the National Toxicology Program (NTP) conducted a cancer bioassay of similar design as part of its evaluation of the dioxin toxic equivalency factor methodology. This report compares the design and the results of these two cancer bioassays. This comparison confirms, in most cases, previously published and widely used carcinogenic response characteristics with respect to dose, time course, organ selectivity, tumor type and maximum intensity of TCDD-induced carcinogenicity and toxicity in the Sprague-Dawley rat. Specifically, increases in the incidences of neoplasms were seen in both studies in the liver, lung and oral mucosa. The most notable difference was the significant increase in the incidence of cholangiocarcinoma of the liver seen in the NTP study but not in the Dow study. The experimental designs for the two studies are similar but some protocol parameters differed, such as vehicle, dosing schedule, diet and rat sub-strain utilized. Differences in the shapes of the dose response curves for several neoplasms were noted between the studies, with the NTP study showing non-linearity for all neoplasms. This may result from differences in the experimental protocols as well as divergence in the biological behavior of the different stocks of Sprague-Dawley rat strains used.     

Adverse effects of citrate/gold nanoparticles on human dermal fibroblasts

Nanoscale engineering is one of the most dynamically growing areas at the interface between electronics, physics, biology, and medicine. As there are no safety regulations yet, concerns about future health problems are rising. We investigated the effects of citrate/gold nanoparticles at different concentrations and exposure times on human dermal fibroblasts. We found that, as a result of intracellular nanoparticle presence, actin stress fibers disappeared, thereby inducing major adverse effects on cell viability. Thus, properties such as cell spreading and adhesion, cell growth, and protein synthesis to form the extracellular matrix were altered dramatically. These results suggest that the internal cell activities have been damaged.     

Self-organisation in urban spatial planning: evidence from the Greater Accra Metropolitan Area,Ghana

There is growing interest among spatial planners to see spontaneous civic initiatives supporting urban development. The occurrence of self-organisation in two informal settlements in Greater Accra Metropolitan Area, Ghana is considered. The system theories of self-organisation (dissipative structures, synegertics and autopoietic) and actor-network theory were used to analyse the two cases. The findings indicate that actors in these informal settlements are triggered by certain contextual factors to undertake initiatives for their own survival and sustenance. At the regional level, these settlements jointly form patterns relating to self-organisation. We conclude that since self-organisation is context specific, planning rules should be reconstructed to guide actions of the various actors in the urban system.     

Motivating blood donors to recruit new donors: Experimental evaluation of an evidence-based behavior change intervention.

Objective: A sustainable, evidence-based intervention to motivate current blood donors to recruit new donors was evaluated using a quasi-experimental, in-service trial at three donation centers. Design: Participating blood donors in three conditions (N = 734), received (1) an evidence-based leaflet designed to enhance recruitment motivation and five postcards facilitating recruitment and donor registration, (2) five postcards alone, or (3) no materials. Main Outcome Measures: Self-reported donor recruitment by donors was measured at 1-week and 6-week follow-up. Results: At 1-week and at 6-week follow-up, donors in both intervention conditions reported talking to more people about donation and asking more people to donate than control participants. Intervention participants also reported persuading more people to register as a donor than control participants. Results indicated that postcards plus leaflet was somewhat more effective than the postcards alone. Donors' intentions to recruit at 1-week follow-up mediated the behavioral effects at 6-week follow-up. Conclusion: Motivating and facilitating recruitment of new blood donors through existing donors has the potential to continually replenish the donor population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unitary Manufacturing Cell Design with Random Product Feedback Flow

This paper presents a capacity model that incorporates the influence of stochastic feedback flow on the productivity of a unitary manufacturing cell. A Unitary Manufacturing Cell is defined as an automated group of work stations served by a robot, and producing one single product at a time. Process control considerations and the need to rework a certain portion of produced items usually results in recirculation, or feedback flow. A statistical analysis of parts flow with recirculation is presented along with an illustration of the oscillatory characteristic of its total-cell-time probability density function.     

On the interconnection constants of Hopfield nets

Hopfield nets are a class of neural networks that are often applied to optimisation problems. The role played by certain constants appearing in the interconnections are crucial to the computations. A bad choice of constant values results in the convergence of the system to states that represent extraneous results. This paper examines a discrete model of the nets which allows a better characterisation of the constants. The formal approach followed in this paper allows the specification of values to the constants that ensure convergence of the system to states that represent results that are not extraneous. Using the Hopfield nets terminology, we have identified methods to remove extraneous energy minima in the discrete version of the system. Since any simulation study of Hopfield nets on real computers must use discretised approximations to analog values, the results are of interest in a practical domain as well.