A hybrid metaheuristic approach to the university course timetabling problem

This paper describes the development of a novel metaheuristic that combines an electromagnetic-like mechanism (EM) and the great deluge algorithm (GD) for the University course timetabling problem. This well-known timetabling problem assigns lectures to specific numbers of timeslots and rooms maximizing the overall quality of the timetable while taking various constraints into account. EM is a population-based stochastic global optimization algorithm that is based on the theory of physics, simulating attraction and repulsion of sample points in moving toward optimality. GD is a local search procedure that allows worse solutions to be accepted based on some given upper boundary or ‘level’. In this paper, the dynamic force calculated from the attraction-repulsion mechanism is used as a decreasing rate to update the ‘level’ within the search process. The proposed method has been applied to a range of benchmark university course timetabling test problems from the literature. Moreover, the viability of the method has been tested by comparing its results with other reported results from the literature, demonstrating that the method is able to produce improved solutions to those currently published. We believe this is due to the combination of both approaches and the ability of the resultant algorithm to converge all solutions at every search process.

Threshold effects in the Teaching Space Allocation Problem with Splitting

Universities aim for good “Space Management” so as to use the teaching space efficiently. Part of this task is to assign rooms and time-slots to teaching activities with limited numbers and capacities of lecture theaters, seminar rooms, etc. It is also common that some teaching activities require splitting into multiple events. For example, lectures can be too large to fit in one room or good teaching practice requires that seminars/tutorials are taught in small groups. Then, space management involves decisions on splitting as well as the assignments to rooms and time-slots. These decisions must be made whilst satisfying the pedagogic requirements of the institution and constraints on space resources. The efficiency of such management can be measured by the “utilisation”: the percentage of available seat-hours actually used. In many institutions, the observed utilisation is unacceptably low, and this provides our underlying motivation: to study the factors that affect teaching space utilisation, with the goal of improving it. We give a brief introduction to our work in this area, and then introduce a specific model for splitting. We present experimental results that show threshold phenomena and associated easy-hard-easy patterns of computational difficulty. We discuss why such behaviour is of importance for space management.

Pretreatment Effect on Pt/CeO2 Catalyst in the Selective Hydrodechlorination of Trichloroethylene

Pt-ceria catalysts present different surface chemistries depending on the preparation method and the pretreatment. The catalytic behavior of Pt/CeO2 catalysts in the hydrodechlorination of trichloroethylene (TCE) to ethylene was examined as a function of the pretreatment conditions and the noble metal precursor salts. Using FTIR and X-ray photoelectron spectroscopy, significant differences were observed in the surface properties of Pt/CeO2 prepared from the H2PtCl6 precursor after different pretreatment procedures (i.e.. reduction or oxidation-reduction). These surface changes are related to chloride residues from the synthesis. Strong changes were observed in the selectivity of the catalysts to ethylene depending on the pretreatment conditions. The 0.5%Pt/CeO2 catalyst showed a 13% selectivity toward ethylene after reduction, whereas alter oxidation, followed by reduction, the selectivity increased up to 85% at the same conversion level. This effect was only observed when a chloride-containing precursor was used in the preparation. In this way, it is demonstrated that the use of a Cl-containing Pt precursor and an air treatment prior to reduction strongly improves the ethylene selectivity of Pt-CeO2 dechlorination catalysts. This can be explained by formation or a CeOCl phase during the synthesis that decomposes upon air tempering, producing oxygen vacancies on the ceria support. We propose that these oxygen vacancies are active for cleaving off Cl from the TCE. Pt then supplies II to clean-off Cl as HCl. Reaction of TCE on Pt produces rather ethane, so Pt may be partly Cl-poisoned for the hydrodechlorination reaction but not for II, dissociation or CO adsorption.

The assimilation and chronic effects of sub-lethal concentrations of Endosulfan on condition and spawning in the common mussel Mytilus edulis

The rate of uptake of Endosulfan by Mytilus edulis L. exposed to pesticide concentrations of 0.1, 0.5, and 1.0 mg/l, and its subsequent elution on removal to clean sea water, was investigated. Higher residue levels were recorded for mussels exposed to higher concentrations of the pesticide, but concentration factors were reduced. There was a rapid initial fall in tissue residue levels on transfer to clean sea water due, it is suggested, to elution of Endosulfan adsorbed on particulate matter assimilated in the gut. The spawning period was prolonged at higher concentrations and, at 1.0 mg/l, the onset of spawning was delayed, possibly due to interference with gamonic action. At 0.1 mg/l, the minor protraction of the spawning period may reflect the effect of experimental tank conditions. No seasonal trend was obvious, and there was an exaggeration of the expected fall in condition in mussels exposed to higher concentrations of Endosulfan. In controls, the expected seasonal trend was reduced.

Treatment of estrogens and androgens in dairy wastewater by a constructed wetland system.

Constructed wetland systems (CWS) have been used as a low cost bio-filtration system to treat farm wastewater. While studies have shown that CWS are efficient in removing organic compounds and pathogens, there is limited data on the presence of hormones in this type of treatment system. The objective of this study was to evaluate the ability of the CWS to reduce estrogenic and androgenic hormone concentration in dairy wastewater. This was achieved through a year long study on dairy wastewater samples obtained froma surface flow CWS. Analysis of hormonal levels was performed using a solid phase extraction (SPE) sample clean-up method, combined with reporter gene assays (RGAs) which incorporate relevant receptors capable of measuring total estrogenic or androgenic concentrations as low as 0.24 ng L1 and 6.9 ng L1 respectively. Monthly analysis showed a mean removal efficiency for estrogens of 95.2%, corresponding to an average residual concentration of 3.2 ng L1 17b-estradiol equivalent (EEQ), below the proposed lowest observable effect concentration (LOEC) of 10 ng L1. However, for one month a peak EEQ concentration of 115 ng L1 was only reduced to 18.8 ng L1. The mean androgenic activity peaked at 360 ng L1 and a removal efficiency of 92.1% left an average residual concentration of 32.3 ng L1 testosterone equivalent (TEQ). The results obtained demonstrate that this type of CWS is an efficient system for the treatment of hormones in dairy wastewater. However, additional design improvements may be required to further enhance removal efficiency of peak hormone concentrations.

A comparative study of qualitative immunochemical screening assays for the combined measurement of T-2/HT-2 in cereals and cereal-based products

Many different immunochemical platforms exist for the screening of naturally occurring contaminants in food from the low cost enzyme linked immunosorbent assays (ELISA) to the expensive instruments such as optical biosensors based on the phenomenon of surface plasmon resonance (SPR). The primary aim of this study was to evaluate and compare a number of these platforms to assess their accuracy and precision when applied to naturally contaminated samples containing HT-2/T-2 mycotoxins. Other important factors considered were the speed of analysis, ease of use (sample preparation techniques and use of the equipment) and ultimately the cost implications. The three screening procedures compared included an SPR biosensor assay, a commercially available ELISA and an enzyme-linked immunomagnetic electrochemical array (ELIME array). The qualitative data for all methods demonstrated very good overall agreements with each other, however on comparison with mass spectrometry confirmatory results, the ELISA and SPR assay performed slightly better than the ELIME array, exhibiting an overall agreement of 95.8% compared to 91.7%. Currently, SPR is more costly than the other two platforms and can only be used in the laboratory whereas in theory both the ELISA and ELIME array are portable and can be used in the field, but ultimately this is dependent on the sample preparation techniques employed. Sample preparative techniques varied for all methods evaluated, the ELISA was the most simple to perform followed by that of the SPR method. The ELIME array involved an additional clean-up step thereby increasing both the time and cost of analysis. Therefore in the current format, field use would not be an option for the ELIME array. In relation to speed of analysis, the ELISA outperformed the other methods.

Benzimidazole carbamate residues in milk: Detection by Surface Plasmon Resonance-biosensor, using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method for extraction

A surface plasmon resonance (SPR) biosensor screening assay was developed and validated to detect 11 benzimidazole carbamate (BZT) veterinary drug residues in milk. The polyclonal antibody used was raised in sheep against a methyl 5(6)-[(carboxypentyl)-thio]-2-benzimidazole carbamate protein conjugate. A sample preparation procedure was developed using a modified QuEChERS method. BZT residues were extracted from milk using liquid extraction/partition with a dispersive solid phase extraction clean-up step. The assay was validated in accordance with the performance criteria described in 2002/657/EC. The limit of detection of the assay was calculated from the analysis of 20 known negative milk samples to be 2.7 mu g kg(-1). The detection capability (CC beta) of the assay was determined to be 5 mu g kg(-1) for 11 benzimidazole residues and the mean recovery of analytes was in the range 81-116%. A comparison was made between the SPR-biosensor and UPLC-MS/MS analyses of milk samples (n = 26) taken from cows treated different benzimidazole products, demonstrating the SPR-biosensor assay to be fit for purpose. (C) 2009 Elsevier B.V. All rights reserved.

Development and validation of a method for the confirmation of halofuginone in chicken liver and eggs using electrospray tandem mass spectrometry

A method is described for the quantitative confirmation of halofuginone (HFG) residues in chicken liver and eggs. This method is based on LC coupled to positive ion electrospray MS-MS of the tissue extracts, prepared by trypsin digestion of the tissues followed by liquid-liquid extraction and final clean-up using Solid Phase Extraction (SPE). The [M+H](+) ion at m/z 416 is monitored along with four transitions at m/z 398, 138, 120 and 100. The method has been validated according to the draft EU criteria for the analysis of veterinary drug residues at 15, 30 and 45 mug kg (-1) in liver and 5, 15 and 50 mug kg (-1) in eggs. The new analytical limits, CCalpha and CCbeta were calculated for liver and were 35.4 and 43.6 mug kg (-1), respectively. (C) 2003 Elsevier Science B.V. All rights reserved.

Screening and confirmatory determination of ractopamine residues in calves treated with growth promoting doses of the beta-agonist

Ractopamine (RCT) is a phenethanolamine member of the family of beta-adrenergic agonists (beta-agonists), This class of compounds have become notable for their properties of enhancing the growth rates of farm animal species but are not licensed for use in Europe. An ELISA procedure employing a polyclonal antibody raised in a goat was developed to detect RCT residues in bovine urine samples, The assay had a high sensitivity (calibration curve mid-point of 22 pg per well), allowing the analysis of urine samples without the need for sample clean-up. In addition, an LC-MS-MS confirmatory procedure was developed which was able to act as a confirmatory procedure for the ELISA results. Four calves were orally treated with RCT (0.1 mg kg(-1) body mass for 17 d) and urine samples collected were assayed by both analytical procedures. It was observed that RCT residues were excreted mainly in the form of glucuronides and deconjugation could be achieved using two different sources of the enzyme beta-glucuronidase (Helix pomatia and Escherichia coli), High concentrations of RCT residues were found throughout the medication period (44-473 ng ml(-1); LC-MS-MS data) and remained present for several days following removal of the drug from the diet, RCT residues were no longer detectable 2 weeks after withdrawal, Good agreement (r(2) = 0.73) was achieved between the ELISA and LC-MS-MS results, especially when sample deconjugation was applied to the urine samples for both sets of analyses, The results show that an effective screening and confirmatory system was devised to detect RCT residues in urine samples taken during treatment and close to withdrawal, However, alternative matrices may have to be selected to allow the illegal use of the substance to be detected following prolonged withdrawal times.

LIQUID-CHROMATOGRAPHY THERMOSPRAY MASS-SPECTROMETRIC ASSAY FOR TRENBOLONE IN BOVINE BILE AND FECES

A liquid chromatography-thermospray mass spectrometric assay was developed and validated to confirm the presence of illegal residues of the synthetic androgenic growth promoter, trenbolone acetate, in cattle. The assay was specific for 17alpha-trenbolone, the major bovine metabolite of trenbolone acetate. Methods were developed for the determination of 17alpha-trenbolone in both bile and faeces, the most appropriate matrices for the control of trenbolone acetate abuse. The clean-up.procedure developed relied on enzymatic hydrolysis, followed by sequential liquid-liquid and liquid-solid extraction. The extracts were then subjected to immunoaffinity chromatography. 17alpha-Trenbolone was detected by selected ion monitoring at m/z 271 using positive ion thermospray ionisation. The limit of detection was approximately 0.5 ng/g in faeces and 0.5 ng/ml in bile.

Creating a spontaneous conversational speech corpus

Speech recognition and language analysis of spontaneous speech arising in naturally spoken conversations are becoming the subject of much research. However, there is a shortage of spontaneous speech corpora that are freely available for academics. We therefore undertook the building of a natural conversation speech database, recording over 200 hours of conversations in English by over 600 local university students. With few exceptions, the students used their own cell phones from their own rooms or homes to speak to one another, and they were permitted to speak on any topic they chose. Although they knew that they were being recorded and that they would receive a small payment, their conversations in the corpus are probably very close to being natural and spontaneous. This paper describes a detailed case study of the problems we faced and the methods we used to make the recordings and control the collection of these social science data on a limited budget.