219 research outputs found
Development of a novel liquid/liquid extraction and ultra-performance liquid chromatography tandem mass spectrometry method for the assessment of thiols in South African Sauvignon Blanc wines
Background and Aims: The thiol compounds, 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA), are important, pleasant volatile thiols conferring fruity notes in wines. The analytical determination of these thiols in wine remains problematic due to their trace concentration and instability. The main aim of this study was to develop a liquid/liquid extraction and ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the determination of 3MH and 3MHA concentration in Sauvignon Blanc wines. Methods and Results: A novel sample preparation based on a liquid/liquid extraction was developed. Thiols were quantified by UPLC-MS/MS after derivatisation with o-phthaldialdehyde. Good results were obtained with the method in terms of limit of detection and of quantification, accuracy and repeatability. Average concentration of 3MH in 18 South African wines was 1320 and of 3MHA 313ng/L. Conclusions: The analytical method described enables the liquid/liquid extraction of 3MH and 3MHA from wine, separates them by liquid chromatography and detects them by MS/MS at a concentration lower than that of their sensory threshold. Significance of the Study: The determination of the concentration of 3MH and 3MHA in Sauvignon Blanc wines could enable wine producers to predict the sensory attributes of the wine
An evaluation of metal removal during wastewater treatment: The potential to achieve more stringent final effluent standards
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2011 Taylor & Francis.Metals are of particular importance in relation to water quality, and concern regarding the impact of these contaminants on biodiversity is being encapsulated within the latest water-related legislation such as the Water Framework Directive in Europe and criteria revisions to the Clean Water Act in the United States. This review undertakes an evaluation of the potential of 2-stage wastewater treatment consisting of primary sedimentation and biological treatment in the form of activated sludge processes, to meet more stringent discharge consents that are likely to be introduced as a consequence. The legislation, sources of metals, and mechanisms responsible for their removal are discussed, to elucidate possible pathways by which the performance of conventional processes may be optimized or enhanced. Improvements in effluent quality, achievable by reducing concentrations of suspended solids or biochemical oxygen demand, may also reduce metal concentrations although meeting possible requirements for the removal of copper my be challenging
Authentic leadership, followership, and psychological capital as antecedents of work engagement
The present study investigated authentic leadership, psychological capital, and followership behaviour influences on work
engagement of employees . Respondents were 901 South African employees within the healthcare industry organisation
(n = 647) and mining industry (n = 254) . The employees completed questionnaires on authentic leadership, psychological
capital, and followership behaviour, and work engagement . Results following structural equation modelling and mediation
analysis suggest work engagement to be explained by the psychological capital of the employee rather than by authentic
leadership qualities . Improving employee psychological capital has the potential to enhance the levels of work engagement
of employees
Magnetodielectric effect of Graphene-PVA Nanocomposites
Graphene-Polyvinyl alcohol (PVA) nanocomposite films with thickness were synthesized by solidification of PVA in a solution with dispersed
graphene nanosheets. Electrical conductivity data were explained as arising due
to hopping of carriers between localized states formed at the graphene-PVA
interface. Dielectric permittivity data as a function of frequency indicated
the occurrence of Debye-type relaxation mechanism. The nanocomposites showed a
magnetodielectric effect with the dielectric constant changing by 1.8% as the
magnetic field was increased to 1 Tesla. The effect was explained as arising
due to Maxwell-Wagner polarization as applied to an inhomogeneous
two-dimensional,two-component composite model. This type of nanocomposite may
be suitable for applications involving nanogenerators.Comment: 13 pages, 11 figure
Classical Simulation of Relativistic Quantum Mechanics in Periodic Optical Structures
Spatial and/or temporal propagation of light waves in periodic optical
structures offers a rather unique possibility to realize in a purely classical
setting the optical analogues of a wide variety of quantum phenomena rooted in
relativistic wave equations. In this work a brief overview of a few optical
analogues of relativistic quantum phenomena, based on either spatial light
transport in engineered photonic lattices or on temporal pulse propagation in
Bragg grating structures, is presented. Examples include spatial and temporal
photonic analogues of the Zitterbewegung of a relativistic electron, Klein
tunneling, vacuum decay and pair-production, the Dirac oscillator, the
relativistic Kronig-Penney model, and optical realizations of non-Hermitian
extensions of relativistic wave equations.Comment: review article (invited), 14 pages, 7 figures, 105 reference
Studies on Lake Erie's littoral algae; Host specificity and temporal periodicity of epiphytic diatoms
Substratum specificity and temporal periodicity of the attached diatom flora upon three aquatic vascular plants and an artificial substratum were examined in three Lake Erie marshes. No qualitative or quantitative specificity for substrata was observed. Variability of diatom assemblage structure within replicate samples of a particular substratum type was as great as, or greater than, variability between substrata. Diatom assemblages upon dowel rod displayed a mid to late summer density maximum. Variability of density maxima upon natural substrata was attributed to different growth rates of the host macrophytes. Diatom assemblages within each sampling site possessed a distinct temporal periodicity indicating that factors affecting diatom growth are heterogeneous in distribution throughout Lake Erie's littoral zone.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42923/1/10750_2004_Article_BF00013712.pd
Allergic diseases in the elderly
Demographic distribution of the population is progressively changing with the proportion of elderly persons increasing in most societies. This entails that there is a need to evaluate the impact of common diseases, such as asthma and other allergic conditions, in this age segment. Frailty, comorbidities and polymedication are some of the factors that condition management in geriatric patients. The objective of this review is to highlight the characteristics of allergic diseases in older age groups, from the influence of immunosenescence, to particular clinical implications and management issues, such as drug interactions or age-related side effects
The Making of a Monster: Postnatal Ontogenetic Changes in Craniomandibular Shape in the Great Sabercat Smilodon
Derived sabercats had craniomandibular morphologies that in many respects were highly different from those of extant felids, and this has often been interpreted functionally as adaptations for predation at extreme gape angles with hypertrophied upper canines. It is unknown how much of this was a result of intraspecific postnatal ontogeny, since juveniles of sabercats are rare and no quantitative study has been made of craniomandibular ontogeny. Postnatal ontogenetic craniomandibular shape changes in two morphologically derived sabercats, Smilodon fatalis and S. populator, were analysed using geometric morphometrics and compared to three species of extant pantherines, the jaguar, tiger, and Sunda clouded leopard. Ontogenetic shape changes in Smilodon usually involved the same areas of the cranium and mandible as in extant pantherines, and large-scale modularization was similar, suggesting that such may have been the case for all felids, since it followed the same trends previously observed in other mammals. However, in other respects Smilodon differed from extant pantherines. Their crania underwent much greater and more localised ontogenetic shape changes than did the mandibles, whereas crania and mandibles of extant pantherines underwent smaller, fewer and less localised shape changes. Ontogenetic shape changes in the two species of Smilodon are largely similar, but differences are also present, notably those which may be tied to the presence of larger upper canines in S. populator. Several of the specialized cranial characters differentiating adult Smilodon from extant felids in a functional context, which are usually regarded as evolutionary adaptations for achieving high gape angles, are ontogenetic, and in several instances ontogeny appears to recapitulate phylogeny to some extent. No such ontogenetic evolutionary adaptive changes were found in the extant pantherines. Evolution in morphologically derived sabercats involved greater cranial ontogenetic changes than among extant felids, resulting in greatly modified adult craniomandibular morphologies
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