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McDowell S.A.C.,The University of the West Indies, Cave Hill Campus
Chemical Physics Letters | Year: 2017

An MP2 computational study of model hydrogen-bonded pyrrole⋯YZ (YZ = NH3, NCH, BF, CO, N2, OC, FB) complexes was undertaken in order to examine the variation of the N[sbnd]H bond length change and its associated vibrational frequency shift. The chemical hardness of Y, as well as the YZ dipole moment, were found to be important parameters in modifying the bond length change/frequency shift. The basis set effect on the computed properties was also assessed. A perturbative model, which accurately reproduced the ab initio N[sbnd]H bond length changes and frequency shifts, was useful in rationalizing the observed trends. © 2017 Elsevier B.V.


Mohapatra B.R.,The University of the West Indies, Cave Hill Campus
International Journal of Biological Macromolecules | Year: 2017

In an effort to screen out the alginolytic and cellulolytic bacteria from the putrefying invasive seaweed Sargassum species accumulated off Barbados’ coast, a potent bacterial strain was isolated. This bacterium, which simultaneously produced alginate lyase and cellulase, was identified as Exiguobacterium sp. Alg-S5 via the phylogenetic approach targeting the 16S rRNA gene. The co-produced alginate lyase and cellulase exhibited maximal enzymatic activity at pH 7.5 and at 40 °C and 45 °C, respectively. The Km and Vmax values recorded as 0.91 mg/mL and 21.8 U/mg-protein, respectively, for alginate lyase, and 10.9 mg/mL and 74.6 U/mg-protein, respectively, for cellulase. First order kinetic analysis of the thermal denaturation of the co-produced alginate lyase and cellulase in the temperature range from 40 °C to 55 °C revealed that both the enzymes were thermodynamically efficient by displaying higher activation energy and enthalpy of denaturation. These enzymatic properties indicate the potential industrial importance of this bacterium in algal biomass conversion. This appears to be the first report on assessing the efficacy of a bacterium for the co-production of alginate lyase and cellulase. © 2017 Elsevier B.V.


Harris T.,The University of the West Indies, Cave Hill Campus
Expert Systems with Applications | Year: 2013

This paper compares support vector machine (SVM) based credit-scoring models built using Broad (less than 90 days past due) and Narrow (greater than 90 days past due) default definitions. When contrasting these two types of models, it was shown that models built using a Broad definition of default can outperform models developed using a Narrow default definition. In addition, this paper sought to create accurate credit-scoring models for a Barbados based credit union. Here, the results of empirical testing reveal that credit risk evaluation at the Barbados based institution can be improved if quantitative credit risk models are used as opposed to the current judgmental approach. © 2013 Elsevier Ltd. All rights reserved.


McDowell S.A.C.,The University of the West Indies, Cave Hill Campus | Joseph J.A.,The University of the West Indies, Cave Hill Campus
Physical Chemistry Chemical Physics | Year: 2014

A computational study of ionic X⋯AH3-Y complexes (X = F-, Cl-, Br-, Li+, Be2+; A = C, Si, Ge; Y = F, Cl, Br) predicted optimized structures which are held together by a combination of attractive forces, including ion-dipole and ion-σ-hole electrostatic interactions, and polarization forces. The trends (with variation in the halogen Y) for selected properties were rationalized by considering the electron density shifts due to the ion's electric field. Although it has been found previously that the trends for binding energies in neutral complexes follow the sigma-hole strength, the present study found that the dependence on the dipole polarizability of the A-Y bond can explain the trends for binding energies in these more strongly bound ionic complexes. This journal is © the Partner Organisations 2014.


Rogers T.,The University of the West Indies, Cave Hill Campus
Energy for Sustainable Development | Year: 2016

Most small island states are under economic pressure to transition from energy systems dominated by imported oil, into systems based on clean energy technologies, which are often already economically viable due to local high energy prices. Guidance on transforming energy systems is limited with few examples available to policy makers. This paper applies a technological innovation system approach to recording the development of the much-lauded Barbados solar water heating industry and applies Bergek et al.'s (2008) functional analysis approach to put forward reasons for its successful adoption. The research concludes that the Barbados solar water heater industry actually appears to be in a state of market stagnation (at around 35% penetration) and using functional analysis identifies barriers and opportunities for future growth in the local and regional solar hot water heater market, as well as proposing the key actor networks necessary for success in sustainable energy technology based innovation system for small island states. © 2016 International Energy Initiative.


McDowell S.A.C.,The University of the West Indies, Cave Hill Campus | Yarde H.K.,The University of the West Indies, Cave Hill Campus
Physical Chemistry Chemical Physics | Year: 2012

A comparative computational study of the cooperative effect of hydrogen-, lithium- and halogen-bonding on model F-H and F-Li complexes with H 2O was undertaken at the MP2/6-311++G(d,p) level of theory. The general trend of increased attraction or a positive cooperative effect on introduction of a third molecule to the F-H/Li...;OH 2 dimer shows that lithium bonding has the greatest effect, followed by hydrogen bonding and then halogen bonding. The computed three-body nonadditive energy has a more substantial contribution to the interaction energy of the cyclic trimers than to the open linear trimer clusters. © 2012 the Owner Societies.


McDowell S.A.C.,The University of the West Indies, Cave Hill Campus | Marcellin R.C.,The University of the West Indies, Cave Hill Campus
Journal of Chemical Physics | Year: 2010

A computational study of hydrogen-bonded complexes of F3 CH and C1H and of lithium-bonded complexes of F3 CLi and CILi, with small molecules such as N2 and H2 O was undertaken at the MP2/6-311++G (d,p) level of theory. Bond extensions and redshifts were obtained for the ClH bond in the ClH complexes, while bond contractions and blueshifts were obtained for the CH bond in the F3 CH complexes. By contrast, bond extensions and blueshifts were obtained for all of the lithium-bonded species. These results were rationalized using a model derived from perturbation theory. © 2010 American Institute of Physics.


McDowell S.A.C.,The University of the West Indies, Cave Hill Campus
Journal of Chemical Physics | Year: 2010

A computational study predicts a number of stable, unusual halogen- and hydrogen-bonded complexes involving FBr, NCH, and FH. Starting from the linear halogen-bonded FBr ⋯ NCH dimer, increasingly more stable complexes are obtained by the successive hydrogen bonding of one to three FH molecules to the lone pairs on the Br atom of FBr to form a trimer, tetramer, and pentamer. A hexamer is obtained from the pentamer by the bonding of FH to the F atom of FBr. The combined halogen and hydrogen bonding gives rise to a large computed zero-point corrected binding energy of 98 kJ/mol for the hexamer at the MP 2/6-31++G (d,p) level of theory. © 2010 American Institute of Physics.


Peter Adams O.,The University of the West Indies, Cave Hill Campus
Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy | Year: 2013

Background: Moderate-intensity exercise improves blood glucose (BG), but most people fail to achieve the required exercise volume. High-intensity exercise (HIE) protocols vary. Maximal cycle ergometer sprint interval training typically requires only 2.5 minutes of HIE and a total training time commitment (including rest and warm up) of 25 minutes per session. The effect of brief high-intensity exercise on blood glucose levels of people with and without diabetes is reviewed. Methods: HIE (≥80% maximal oxygen uptake, VO2max) studies with ≤15 minutes HIE per session were reviewed. Results: Six studies of nondiabetics (51 males, 14 females) requiring 7.5 to 20 minutes/week of HIE are reviewed. Two weeks of sprint interval training increased insulin sensitivity up to 3 days postintervention. Twelve weeks near maximal interval running (total exercise time 40 minutes/week) improved BG to a similar extent as running at 65% VO2max for 150 minutes/ week. Eight studies of diabetics (41 type 1 and 22 type 2 subjects) were reviewed. Six were of a single exercise session with 44 seconds to 13 minutes of HIE, and the others were 2 and 7 weeks duration with 20 and 2 minutes/week HIE, respectively. With type 1 and 2 diabetes, BG was generally higher during and up to 2 hours after HIE compared to controls. With type 1 diabetics, BG decreased from midnight to 6 AM following HIE the previous morning. With type 2 diabetes, a single session improved postprandial BG for 24 hours, while a 2-week program reduced the average BG by 13% at 48 to 72 hours after exercise and also increased GLUT4 by 369%. Conclusion: Very brief HIE improves BG 1 to 3 days postexercise in both diabetics and non diabetics. HIE is unlikely to cause hypoglycemia during and immediately after exercise. Larger and longer randomized studies are needed to determine the safety, acceptability, long-term efficacy, and optimal exercise intensity and duration. © 2013 Adams, publisher and licensee Dove Medical Press Ltd.


McDowell S.A.C.,The University of the West Indies, Cave Hill Campus
Chemical Physics Letters | Year: 2014

A computational study of anionic complexes of general formula [FX⋯CH3⋯YF]- (X, Y = Cl, Br) predicted minimum energy structures with unusual bonding features. The two F atoms, the halogens X and Y and the central C atom all lie on the same straight line, with the three H atoms forming covalent CH bonds perpendicular to this straight line. The bonding analysis suggests that the extra negative charge is localized on the central C atom and interacts favourably with the sigma-holes originating from the adjacent FX and YF molecular subunits. This unusual cooperative bonding results in energetically stable complexes. © 2014 Elsevier B.V. All rights reserved.

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