\u3ci\u3eMyxosoma funduli\u3c/i\u3e Kudo 1918 (Protozoa: Myxosporida) in \u3ci\u3eFundulus kansae\u3c/i\u3e: Summer Epizootiology

The occurrence and distribution of the myxosporidan Myxosoma funduli on the gills of the plains killifish (Fundulus kansae) were investigated; Fundulus kansae is reported as a new host. Host samples from various sites on the South Platte River, Nebraska, were collected during the summer months of 1975 and 1976. The protozoan parasite population was shown to be overdispersed within the host population, and this distribution was similar to that described by the negative binomial equation. Demographic characteristics of the infected fish subpopulation were virtually identical to those of the whole fish population. Infection intensity was independent of gill bar number or side. The frequency of bilateral infections was 0.54, of left only infections was 0.23, and of right only infections was 0.22. Distribution of immature and mature plasmodia indicated that a pre-existing infection did not preclude a new infection, and suggested a prepatent period of less than two months

Star Routing: Between Vehicle Routing and Vertex Cover

We consider an optimization problem posed by an actual newspaper company, which consists of computing a minimum length route for a delivery truck, such that the driver only stops at street crossings, each time delivering copies to all customers adjacent to the crossing. This can be modeled as an abstract problem that takes an unweighted simple graph $G = (V, E)$ and a subset of edges $X$ and asks for a shortest cycle, not necessarily simple, such that every edge of $X$ has an endpoint in the cycle. We show that the decision version of the problem is strongly NP-complete, even if $G$ is a grid graph. Regarding approximate solutions, we show that the general case of the problem is APX-hard, and thus no PTAS is possible unless P $=$ NP. Despite the hardness of approximation, we show that given any $\alpha$-approximation algorithm for metric TSP, we can build a $3\alpha$-approximation algorithm for our optimization problem, yielding a concrete $9/2$-approximation algorithm. The grid case is of particular importance, because it models a city map or some part of it. A usual scenario is having some neighborhood full of customers, which translates as an instance of the abstract problem where almost every edge of $G$ is in $X$. We model this property as $|E - X| = o(|E|)$, and for these instances we give a $(3/2 + \varepsilon)$-approximation algorithm, for any $\varepsilon > 0$, provided that the grid is sufficiently big.Comment: Accepted to the 12th Annual International Conference on Combinatorial Optimization and Applications (COCOA'18

Hybrid Meta-heuristics with VNS and Exact Methods: Application to Large Unconditional and Conditional Vertex p-Centre Problems

Large-scale unconditional and conditional vertex p-centre problems are solved using two meta-heuristics. One is based on a three-stage approach whereas the other relies on a guided multi-start principle. Both methods incorporate Variable Neighbourhood Search, exact method, and aggregation techniques. The methods are assessed on the TSP dataset which consist of up to 71,009 demand points with p varying from 5 to 100. To the best of our knowledge, these are the largest instances solved for unconditional and conditional vertex p-centre problems. The two proposed meta-heuristics yield competitive results for both classes of problems

Solving Large p-median Problems by a Multistage Hybrid Approach Using Demand Points Aggregation and Variable Neighbourhood Search

A hybridisation of a clustering-based technique and of a variable neighbourhood search (VNS) is designed to solve large-scale p-median problems. The approach is based on a multi-stage methodology where learning from previous stages is taken into account when tackling the next stage. Each stage is made up of several subproblems that are solved by a fast procedure to produce good feasible solutions. Within each stage, the solutions returned are put together to make up a new promising subset of potential facilities. This augmented p-median problem is then solved by VNS. As these problems used aggregation, a cost evaluation based on the original demand points instead of aggregation is computed for each of the ‘aggregation’-based solution. The one yielding the least cost is then selected and its chosen facilities included into the next stages. This multi-stage process is repeated several times until a certain criterion is met. This approach is enhanced by an efficient way to aggregate the data and a neighbourhood reduction scheme when allocating demand points to their nearest facilities. The proposed approach is tested, using various values of p, on the largest data sets from the literature with up to 89,600 demand points with encouraging results

Ultrastructure of Interlamellar \u3ci\u3eHenneguya exilis\u3c/i\u3e in the Channel Catfish

Ultrastructural aspects of interlamellar Henneguya exilis infections in channel catfish are reported. The plasmodium wall of this form differs from that of other species in that it is composed of two outer unit membranes which give rise to a zone of numerous pinocytic canals. Single-membraned canals appeared to be a stable feature of the wall while double-membraned canals are interpreted as those actively carrying out pinocytosis. Evidence suggests that host cellular cytoplasm as well as interstitial material is taken in by plasmodia. Plasmodium wall integrity, aggregation of parasite ectoplasmic components, numbers of pinocytic canals, and number of mitochondria proximal to the wall vary among different plasmodium profiles and may be related to plasmodium maturity. The parasite causes extensive hyperplasia of basal cells, which in turn replaces most other cell types found in noninfected gill filaments. Cytoarchitectural differences between basal cells of noninfected filaments and basal cells adjacent to plasmodia include significantly shorter microfilament bundles in the latter

\u3ci\u3eMyxosoma funduli\u3c/i\u3e Kudo 1918 (Protozoa: Myxosporida) in \u3ci\u3eFundulus kansae\u3c/i\u3e (Pisces: Cyprinodontidae): Annual Prevalence and Geographic Distribution

The occurrence and distribution of the myxosporidan, Myxosoma funduli, in the Plains killifish (Fundulus kansae) were investigated. Samples from sites on the South Platte and Platte River drainages in Nebraska were collected by seining during various months of 1976, 1977, and 1978. At a number of the localities no F. kansae were found; the remainder of the collecting sites showed the host population to be abundant, but the M. funduli infections to vary in prevalence. The protozoan parasite population in F. kansae, upstream from the Nebraska Tri-County Diversion Dam and Canal, at North Platte, Nebraska, demonstrated year-long distributions and intensities similar to those reported for the summer months of 1975 and 1976 (Knight et al., 1977). However, downstream from the diversion dam, prevalence of M. funduli in F. kansae was considerably lower than that observed upstream. The demographic characteristics of the infected fish subpopulation were identical to those of the whole fish population upstream from the diversion, whereas those infected fish downstream from the diversion were too few to establish conclusive demographic results

Dynamic Height and Seawater Transport Across the Louisiana-Texas Shelf Break. Final Report

45 pgs.Our study quantifies time dependent, highly vertically resolved geostrophic transport of waters from the Gulf of Mexico across the Louisiana-Texas continental shelf break, and provides a first order picture of the spatial and temporal variability of shelf break exchange processes. Cross-shelf transport is large, and consistent with the findings of Bender and Reid. The annual volume of water transported off the shelf across the shelf break is approximately equal to the total volume of water on the shelf.... The present study begins with the determination of orthogonal patters of pressure anomaly that are characteristic of geostrophic flow, computed from LATEX-A field hydrography and assumed dynamics of the system. Shelf break mooring data then is projected onto these patterns of variability, which are called dynamic vertical structure functions or dynamic modes (Kundu et al. 1975; Flierl 1978; SAIC 1989; Arango and Reid 1990; Current 1993). Estimates of time varying pressure anomaly profiles and dynamic height are produced by the summation of weighted dynamic modes, and estimation of cross-shelf geostrophic transport follows from these profiles by invoking geostrophic balance.http://gbic.tamug.edu/request.ht

Dynamic Height and Seawater Transport across the Louisiana-Texas Shelf Break: Final Report

The final report of a study focused on understanding and quantifying the horizontal transportation of seawater across the Louisiana-Texas continental shelf break