Hyper-heuristic decision tree induction

A hyper-heuristic is any algorithm that searches or operates in the space of heuristics as opposed to the space of solutions. Hyper-heuristics are increasingly used in function and combinatorial optimization. Rather than attempt to solve a problem using a fixed heuristic, a hyper-heuristic approach attempts to find a combination of heuristics that solve a problem (and in turn may be directly suitable for a class of problem instances). Hyper-heuristics have been little explored in data mining. This work presents novel hyper-heuristic approaches to data mining, by searching a space of attribute selection criteria for decision tree building algorithm. The search is conducted by a genetic algorithm. The result of the hyper-heuristic search in this case is a strategy for selecting attributes while building decision trees. Most hyper-heuristics work by trying to adapt the heuristic to the state of the problem being solved. Our hyper-heuristic is no different. It employs a strategy for adapting the heuristic used to build decision tree nodes according to some set of features of the training set it is working on. We introduce, explore and evaluate five different ways in which this problem state can be represented for a hyper-heuristic that operates within a decisiontree building algorithm. In each case, the hyper-heuristic is guided by a rule set that tries to map features of the data set to be split by the decision tree building algorithm to a heuristic to be used for splitting the same data set. We also explore and evaluate three different sets of low-level heuristics that could be employed by such a hyper-heuristic. This work also makes a distinction between specialist hyper-heuristics and generalist hyper-heuristics. The main difference between these two hyperheuristcs is the number of training sets used by the hyper-heuristic genetic algorithm. Specialist hyper-heuristics are created using a single data set from a particular domain for evolving the hyper-heurisic rule set. Such algorithms are expected to outperform standard algorithms on the kind of data set used by the hyper-heuristic genetic algorithm. Generalist hyper-heuristics are trained on multiple data sets from different domains and are expected to deliver a robust and competitive performance over these data sets when compared to standard algorithms. We evaluate both approaches for each kind of hyper-heuristic presented in this thesis. We use both real data sets as well as synthetic data sets. Our results suggest that none of the hyper-heuristics presented in this work are suited for specialization – in most cases, the hyper-heuristic’s performance on the data set it was specialized for was not significantly better than that of the best performing standard algorithm. On the other hand, the generalist hyper-heuristics delivered results that were very competitive to the best standard methods. In some cases we even achieved a significantly better overall performance than all of the standard methods

First record of Selene dorsalis (Osteichthyes : Carangidae) in the Mediterranean Sea, from coastal waters off the Maltese Islands

The first Mediterranean record of the African moonfish, Selene dorsalis, is reported, with the capture of a single female specimen by means of a trammel net from coastal waters off the Maltese Islands. The species is a non-indigenous one for the Mediterranean, being native of tropical and subtropical waters of the east Atlantic. The Mediterranean record of S. dorsalis could be indicative of a northward range expansion of the species, spurred in part by the recent warming trend observed in the Mediterranean Sea.peer-reviewe

Nested window management and task-oriented user interfaces

QDWM is an experimental window manager for X11 which distinguishes itself with the ability to run in a resizeable window managed by an existing X11 window manager, several times over. This abstract touches upon its implementation, related work and emerging opportunities for research.peer-reviewe

First record of Cassiopea andromeda (Scyphozoa : Rhizostomeae : Cassiopeidae) from the Central Mediterranean Sea

The occurrence of the scyphozoan Cassiopea andromeda is reported from the Maltese Islands, where a sizable aggregation was found in Marsamxett Harbour. This is the first record of this circumtropical species from the central Mediterranean Sea, hitherto known from the Levantine and Aegean basins. It is suggested that the most likely vector responsible for transporting this species to the Maltese Islands is shipping.peer-reviewe

New records of Lobotes surinamensis (Bloch, 1790) in Maltese coastal waters

Lobotes surinamensis is considered as a rare occurrence in the Mediterranean Sea, being mainly encountered in the eastern and central areas of the basin. The species was previously recorded only once from the Maltese Islands, from offshore waters 45 miles south of the islands. Numerous recent records of the species in Maltese nearshore waters suggest that the same species is becoming more common in such waters, possibly hinting at the geographical expansion of populations of this thermophilic fish species in the Mediterranean.peer-reviewe

Destination-Based Cash Flow Taxation

This paper presents, analyses, and further develops the idea of a destination-based cash-flow tax (DBCFT). Its purpose is expositional: to describe the DBCFT, how it might work, what its effects would be and some of the challenges that its implementation would face. The paper starts by introducing the basic mechanics of the DBCFT before evaluating it against five criteria: economic efficiency, robustness to avoidance and evasion, ease of administration, fairness and stability. It does so both for the case of universal adoption by all countries and the more plausible case of unilateral adoption. The paper then looks closely at the application of DBCFT treatment to the financial sector, which is a familiar problem under the VAT but has been little considered under the DBCFT. Finally, the paper sets out some core implementation issues, and how they might be addressed. It also compares the implementation of a DBCFT with the economically equivalent reform option that introduces a broad-based, uniform rate VAT (or achieves the same effect through an existing VAT), and reduces taxes on payroll by the same proportion

High performance staged event-driven middleware

In this paper, we investigate the design of highly efficient and scalable staged event-driven middleware for shared memory multi- processors. Various scheduler designs are considered and evaluated, including shared run queue and multiple run queue arrangements. Techniques to maximise cache locality while improving load balancing are studied. Moreover, we consider a variety of access control mechanisms applied to shared data structures such as the run queue, including coarse grained locking, fine grained locking and non-blocking algorithms. User- level memory management techniques are applied to enhance memory allocation performance, particularly in situations where non-blocking algorithms are used. The paper concludes with a comparative analysis of the various configurations of our middleware, in an effort to identify their performance characteristics under a variety of conditions.peer-reviewe

30 Year Patterns of Mortality in Tobago, West Indies, 1976-2005: Impact of Glucose Intolerance and Alcohol Intake

OBJECTIVES: To determine the main predictors of all-cause and cardiovascular (CV) mortality in a rural West Indian population in Plymouth, Tobago over 30 years. METHODS: Questionnaire survey for CV risk factors and alcohol consumption patterns administered at baseline in 1976 with 92.5% response rate. 831/832 patients were followed up until 2005 or death. RESULTS: Hypertension (>140/90 mm Hg) was prevalent in 48% of men and 44% of women, and 21% of men and 17% of women had diabetes. Evidence showed most predictors for all cause and cardiovascular mortality having the main effects at ages 160/95 mm Hg (HR 1.68, 95% CI 1.09-2.60), diabetes (HR 3.28, 95% CI 1.89-5.69), and BMI (HR 1.04, 95% CI 1.00-1.07). The main predictors of cardiovascular mortality were similar in the fully adjusted model: high sessional alcohol intake (HR 2.47 95% CI 1.10-5.57), severe hypertension (HR 2.78 95% CI 1.56-4.95), diabetes (HR 3.68 95% CI 1.77-7.67) and additionally LVH, (HR 5.54 95% CI 1.38-22.26), however BMI did not show independent effects. For men, high sessional alcohol intake explains 27% of all cause mortality, and 40% of cardiovascular mortality at age <60 yrs. In adults aged <60 years, the attributable risk fraction for IGT/Diabetes and all cause mortality and cardiovascular mortality is 28% in women vs. 11% in men, and 22% in women vs. 6% in men respectively. CONCLUSIONS: In this Afro-Caribbean population we found that a major proportion of deaths are attributable to high sessional alcohol intake (in males), diabetes, and hypertension and these risk factors primarily operate in those below 60 years

The first record of the Sargocentron genus from the Maltese Islands (Central Mediterranean) - who will unravel the current conundrum?

The squirrelfish genus, Sargocentron, is reported for the first time from Maltese coastal waters within the Central Mediterranean. The record is based on two individuals caught at two different coastal locations in the Maltese Islands within the space of a few days of each other, through the same fishing technique (trammel nets). In view of the impossibility to collect meristic, morphometric and molecular data from the recorded individuals, and due to the close similarity between a number of Sargocentron congeners, the exact taxonomic identity of the captured individuals could not be conclusively confirmed, although the livery on the two caught individuals resulted to be consistent with that of S. rubrum and S. hastatum.peer-reviewe

An exploration of hydration practices in Maltese residential care homes for older people

Background: The integral relationship between adequate hydration and good health is widely recognised. Older people with complex needs and frailty can struggle to maintain adequate hydration, with residents in care home settings being at an increased risk of dehydration. Aims: To explore current hydration practices in residential care homes in Malta. Methods: An exploratory qualitative approach was adopted to explore staff’s views and approaches in supporting resident’s hydration. Data was collected via semi-structured, individual and small group interviews with 2 care homes from the central and southern region of Malta. A process of open coding, followed by axial coding were used to analyse the data. Peer debriefing was performed throughout, until agreement was reached amongst the research team about the final themes and sub-themes. Findings: Three themes emerged from the data: culture of promoting fluid intake; challenges in supporting older people to achieve optimum hydration; hydration practices and approaches. Conclusion: A hydration promotion culture was demonstrated through various practices adopted in the care homes. The strong focus on water intake, in response to concerns about consuming sugary beverages, has implications on the promotion of a person-centred approach to hydration care. Inconsistencies in monitoring of fluids and daily recommended targets, highlights the importance of policies or guidelines to guide hydration practice. Challenges related to refusal of fluids and language barriers amongst non-native staff were evident and justifies further research is this area