Insertion Heuristics for Central Cycle Problems

A central cycle problem requires a cycle that is reasonably short and keeps a the maximum distance from any node not on the cycle to its nearest node on the cycle reasonably low. The objective may be to minimise maximumdistance or cycle length and the solution may have further constraints. Most classes of central cycle problems are NP-hard. This paper investigates insertion heuristics for central cycle problems, drawing on insertion heuristics for p-centres [7] and travelling salesman tours [21]. It shows that a modified farthest insertion heuristic has reasonable worstcase bounds for a particular class of problem. It then compares the performance of two farthest insertion heuristics against each other and against bounds (where available) obtained by integer programming on a range of problems from TSPLIB [20]. It shows that a simple farthest insertion heuristic is fast, performs well in practice and so is likely to be useful for a general problems or as the basis for more complex heuristics for specific problems

The Subtour Centre Problem

The subtour centre problem is the problem of finding a closed trail S of bounded length on a connected simple graph G that minimises the maximum distance from S to any vertex ofG. It is a central location problem related to the cycle centre and cycle median problems (Foulds et al., 2004; Labbé et al., 2005) and the covering tour problem (Current and Schilling, 1989). Two related heuristics and an integer linear programme are formulated for it. These are compared numerically using a range of problems derived from tsplib (Reinelt, 1995). The heuristics usually perform substantially better then the integer linear programme and there is some evidence that the simpler heuristics perform better on the less dense graphs that may be more typical of applications

Data Envelopment Analysis Models of Investment Funds

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Integration effects of pylon geometry on a high-wing transport airplane

An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine the installation effects of a series of pylons that had differing cross-sectional shapes on the pressure distributions and aerodynamic characteristics of a 1/24-scale high wing transport. The tests were conducted at Mach numbers at 0.70 and 0.80 at angles of attack from -3 degrees to 4 degrees with the pylons tested at various toe angles between 5 degrees inboard and 5 degrees outboard. Results of this study indicate that the installed drag was lowest for the pylons with a compression pylon type design which kept the flow under the wing in the pylon/wing junction comparable to the clean wing velocities

Characterizing the modulation of mGluR5 in a 6-OHDA-induced rat model of Parkinson's disease

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008.Includes bibliographical references (leaves 26-27).MicroPET imaging studies were conducted to investigate the role of metabotropic glutamate subtype-5 receptors (mGluR5) in Parkinson's disease (PD). Four analogical PET ligands were used to characterize modulation of mGluR5 function in a 6hydroxydopamine (6-OHDA) induced rat model of PD. Unilateral 6-OHDA lesions were made in the right medial forebrain bundle, and severity of these lesions was determined with [¹¹]CFT. The binding characteristics of the PET ligands were analyzed using a modified distribution volume method of the Logan reference region model. Binding potential values were calculated on the striatum, hippocampus, and cortex, using the cerebellum as a reference tissue. On the right (with lesion) side of the striatum, ["C]CFT binding decreased. Three of the four investigated mGluR5 ligands ([¹¹C]MPEP, [¹¹C]M-PEPy, and [¹¹C]MMPEP) also showed enhanced binding characteristics on the same side of the brain. The right hippocampus and cortex showed similar results. The mGluR5s' enhanced binding characteristics on the right side of the brain suggest a complementary and compensatory role of metabotropic glutamate receptors in the dopaminergic neurodegeneration of Parkinson's disease.by Peter Lamb.S.B

Examining the Impact of California\u27s Medical Marijuana Program on Public Health

The debate surrounding marijuana legalization has increased its popularity in recent years, as the state of California seriously considers the complete legalization of the substance for those ages 21 and over. This would make California the first government in recorded history to regulate the cultivation and sale of marijuana on a commercial level. Advocates back the economic positives concerning high tax revenues, but those opposed argue that the dangers associated with public health greatly outweigh any monetary gain. The present study attempts to reveal the possible public health concerns, even potential benefits, caused by marijuana use and its distribution. Specifically, measures of California’s Medical Marijuana Program will be assessed on the total number of drug treatment admissions in each county, taking into account treatment type and which type of drug is primarily responsible for said admissions. Findings reveal influences by both gateway and substitution effects, creating both positive and negative correlations throughout the field of public health. The influences of intangible variables, like that of the black market, make the results difficult to generalize. However, significant correlations can be found among specific health factors, like Heroin use, Crack/Cocaine use, and Residential Treatment

Irus and his jovial crew : representations of beggars in Vincent Bourne and other eighteenth-century writers of Latin verse

Alastair Fowler has written, with reference to the time of Milton, of ‘Latin's special role in a bilingual culture’, and this was still true in the early eighteenth century. The education of the elite placed great emphasis on the art of writing Latin verse and modern, as well as ancient, writers of Latin continued to be widely read. Collections of Latin verse, by individual writers such as Vincent Bourne (c. 1694–1747) or by groups such as Westminster schoolboys or bachelors of Christ Church, Oxford, could run into multiple editions, and included poems on a wide range of contemporary topics, as well as reworkings of classical themes. This paper examines a number of eighteenth-century Latin poems dealing with beggars, several of which are here translated for the first time. Particular attention is paid to the way in which the Latin poems recycled well-worn tropes about beggary which were often at variance with the experience of real-life beggars, and to how the specificities of Latin verse might heighten negative representations of beggars in a genre which, as a manifestation of elite culture, appealed to the very class which was politically and legally responsible for controlling them