Application of Mathematical Programming to a Large-scale Agricultural Production and Distribution System

This paper addresses an actual production planning problem for a large seed corn production company. Various scenarios are included in different mathematical programming models in order to help the management make production decisions. A linear programming package and a mixed-integer programming package are combined by a designed heuristic program to solve the problem. The solutions obtained and an accompanying sensitivity analysis provide the management with insight into the system's operation and potentials of cost savings.     

Simulation Model of a Multi-Shuttle System

Journal of the Operational Research Society - This paper reports on a study of modelling a shuttle transportation system. There were three objectives, the first was to consider alternative ways of...     

Characterization of Pathogen Airborne Inoculum Density by Information Theoretic Analysis of Spore Trap Time Series Data

In a previous study, air sampling using vortex air samplers combined with species-specific amplification of pathogen DNA was carried out over two years in four or five locations in the Salinas Valley of California. The resulting time series data for the abundance of pathogen DNA trapped per day displayed complex dynamics with features of both deterministic (chaotic) and stochastic uncertainty. Methods of nonlinear time series analysis developed for the reconstruction of low dimensional attractors provided new insights into the complexity of pathogen abundance data. In particular, the analyses suggested that the length of time series data that it is practical or cost-effective to collect may limit the ability to definitively classify the uncertainty in the data. Over the two years of the study, five location/year combinations were classified as having stochastic linear dynamics and four were not. Calculation of entropy values for either the number of pathogen DNA copies or for a binary string indicating whether the pathogen abundance data were increasing revealed (1) some robust differences in the dynamics between seasons that were not obvious in the time series data themselves and (2) that the series were almost all at their theoretical maximum entropy value when considered from the simple perspective of whether instantaneous change along the sequence was positive.     

Discrimination of non-native consonant contrasts varying in perceptual assimilation to the listener's native phonological system

Classic non-native speech perception findings suggested that adults have difficulty discriminating segmental distinctions that are not employed contrastively in their own language. However, recent reports indicate a gradient of performance across non-native contrasts, ranging from near-chance to near-ceiling. Current theoretical models argue that such variations reflect systematic effects of experience with phonetic properties of native speech. The present research addressed predictions from Best's perceptual assimilation model (PAM), which incorporates both contrastive phonological and noncontrastive phonetic influences from the native language in its predictions about discrimination levels for diverse types of non-native contrasts. We evaluated the PAM hypotheses that discrimination of a non-native contrast should be near-ceiling if perceived as phonologically equivalent to a native contrast, lower though still quite good if perceived as a phonetic distinction between good versus poor exemplars of a single native consonant, and much lower if both non-native segments are phonetically equivalent in goodness of fit to a single native consonant. Two experiments assessed native English speakers' perception of Zulu and Tigrinya contrasts expected to fit those criteria. Findings supported the PAM predictions, and provided evidence for some perceptual differentiation of phonological, phonetic, and nonlinguistic information in perception of non-native speech. Theoretical implications for non-native speech perception are discussed, and suggestions are made for further research.     

Enzyme-catalysed synthesis and reactions of benzene oxide/oxepine derivatives of methyl benzoates

A series of twelve benzoate esters was metabolised, by species of the Phellinus genus of wood-rotting fungi, to yield the corresponding benzyl alcohol derivatives and eight salicylates. The isolation of a stable oxepine metabolite, from methyl benzoate, allied to evidence of the migration and retention of a carbomethoxy group (the NIH Shift), during enzyme-catalysed ortho-hydroxylation of alkyl benzoates to form salicylates, is consistent with a mechanism involving an initial arene epoxidation step. This mechanism was confirmed by the isolation of a remarkably stable, optically active, substituted benzene oxide metabolite of methyl 2-(trifluoromethyl)benzoate, which slowly converted into the racemic form. The arene oxide was found to undergo a cycloaddition reaction with 4-phenyl-1,2,4-triazoline-3,5-dione to yield a crystalline cycloadduct whose structure and racemic nature was established by X-ray crystallography. The metabolite was also found to undergo some novel benzene oxide reactions, including epoxidation to give an anti-diepoxide, base-catalysed hydrolysis to form a trans-dihydrodiol and acid-catalysed aromatisation to yield a salicylate derivative via the NIH Shift of a carbomethoxy group.     

A digital microfluidic method for dried blood spot analysis

Blood samples stored as dried blood spots (DBSs) are emerging as a useful sampling and storage vehicle for a wide range of applications. Unfortunately, the surging popularity of DBS samples has not yet been accompanied by an improvement in automated techniques for extraction and analysis. As a first step towards overcoming this challenge, we have developed a prototype microfluidic system for quantification of amino acids in dried blood spots, in which analytes are extracted, mixed with internal standards, derivatized, and reconstituted for analysis by (off-line and in-line) tandem mass spectrometry. The new method is fast, robust, precise, and most importantly, compatible with automation. We propose that the new method can potentially contribute to a new generation of analytical techniques for quantifying analytes in DBS samples for a wide range of applications.     

Dioxygenase-catalysed cis-dihydroxylation of meta-substituted phenols to yield cyclohexenone cis-diol and derived enantiopure cis-triol metabolites

cis-Dihydroxylation of meta-substituted phenol (m-phenol) substrates, to yield the corresponding cyclohexenone cis-diol metabolites, was catalysed by arene dioxygenases present in mutant and recombinant bacterial strains. The presence of cyclohexenone cis-diol metabolites and several of their cyclohexene and cyclohexane cis-triol derivatives was detected by LC-TOFMS analysis and confirmed by NMR spectroscopy. Structural and stereochemical analyses of chiral ketodiol bioproducts, was carried out using NMR and CD spectroscopy and stereochemical correlation methods. The formation of enantiopure cyclohexenone cis-diol metabolites is discussed in the context of postulated binding interactions of the m-phenol substrates at the active site of toluene dioxygenase (TDO).     

Bacterial dioxygenase- and monooxygenase-catalysed sulfoxidation of benzo[b]thiophenes

Asymmetric heteroatom oxidation of benzo[b]thiophenes to yield the corresponding sulfoxides was catalysed by toluene dioxygenase (TDO), naphthalene dioxygenase (NDO) and styrene monooxygenase (SMO) enzymes present in P. putida mutant and E. coli recombinant whole cells. TDO-catalysed oxidation yielded the relatively unstable benzo[b]thiophene sulfoxide; its dimerization, followed by dehydrogenation, resulted in the isolation of stable tetracyclic sulfoxides as minor products with cis-dihydrodiols being the dominant metabolites. SMO mainly catalysed the formation of enantioenriched benzo[b]thiophene sulfoxide and 2-methyl benzo[b]thiophene sulfoxides which racemized at ambient temperature. The barriers to pyramidal sulfur inversion of 2- and 3-methyl benzo[b]thiophene sulfoxide metabolites, obtained using TDO and NDO as biocatalysts, were found to be ca.: 25-27 kcal mol(-1). The absolute configurations of the benzo[b]thiophene sulfoxides were determined by ECD spectroscopy, X-ray crystallography and stereochemical correlation. A site-directed mutant E. coli strain containing an engineered form of NDO, was found to change the regioselectivity toward preferential oxidation of the thiophene ring rather than the benzene ring.     

Isolation of lipid and 2-alkylcyclobutanones from irradiated foods by supercritical fluid extraction.

The 2-alkylcyclobutanone method was adopted as a European Standard (EN1785) and MAFF Validated Method (MAFF V37) in 1996 for the detection of irradiated food containing fat. As the method requires a relatively long period (ca 2 days) of time for extraction of the 2-alkylcyclobutanones from a foodstuff, a means was sought to increase the speed at which these irradiation markers could be isolated while at the same time decreasing the amount of organic solvents required. Thus, the technique of supercritical fluid extraction (SFE) was investigated. Results showed that SFE can be used for the rapid extraction (60 min) of lipid from irradiated foods such as chicken, pork, liquid whole egg, ground beef, and from the seeds of irradiated mango and papaya with only 10 mL n-hexane being necessary for collection of the extracted sample. A method was also developed whereby the 2-alkylcyclobutanones can be selectively extracted from irradiated foods without prior extraction of the lipid. The sample extract, in 10 mL n-hexane, is purified through a Florisil SPE cartridge which is washed with 10 mL n-hexane and the 2-alkylcyclobutanones eluted with 10 mL 2% diethyl ether in n-hexane before analysis by gas chromatography/mass spectrometry. 2-Dodecylcyclobutanone and 2-tetradecylcyclobutanone were selectively extracted from irradiated chicken meat, liquid whole egg, ground beef, and mango as well as from beef burgers and baked products containing irradiated ground beef and liquid whole egg, respectively. Using this method, samples can be analyzed for irradiation treatment within 6 h as opposed to the 2-day period required for the EN1785/MAFF V37 validated method.