Mercury Levels in Sediment, Shellfish and Fish of a Water Body in the Niger Delta

The concentrations of mercury in sediment and the muscle tissues of shellfish and fish of Bonny River and creeks around Okrika were determined in order to identify possible sources and indicator species that can be used to monitor pollution of the ecosystem, as well as assess possible health risk. Sediment samples were taken from ten (10) locations including the refinery effluent discharge channel, while shellfish and fish were randomly taken within the studied area. All samples were prepared and analysed by the cold vapour technique. The mean level of detectable values (ppm) in the sediment was 0.273±0.016. Those of shellfish were: P. aurita (0.016±0.012) and G. rhizophorea (0.018±0.026), while for fish we have: P. koelreuteri (0.014±0.019), M. cephalus (0.011±0.010), S. marderensis (0.008±0.011) and T. guineensis (0.026±0.032). The sediment results reveal largely anthropogenic enrichments mainly from refinery effluent. The pattern of accumulation by both fish types was both physiologically and ecologically characterized an indication that it is only the dissolved forms of metals that are effectively available to fish for bioaccumulation. The remarkable bioaccumulation factor (130.00) was associated with T. guineensis, which appeared to be the most efficient accumulator, and therefore a good bioindicator to monitor mercury pollution of the system. Mercury levels in all sample types were however generally low and do not portend serious danger with respect to human health. Nevertheless, the continued discharge of industrial effluents without regular monitoring may have imminent detrimental effect on the flora and fauna, since the metal is detectable in all the samples at sub-lethal concentrations. KEYWORDS: concentrations, shellfish, fish, mercury, indicator species, Bonny Rive

Naimark-Sacker Bifurcations in Linearly Coupled Quadratic Maps

We report exact analytical expressions locating the $0\to1$, $1\to2$ and $2\to4$ bifurcation curves for a prototypical system of two linearly coupled quadratic maps. Of interest is the precise location of the parameter sets where Naimark-Sacker bifurcations occur, starting from a non-diagonal period-2 orbit. This result is the key to understand the onset of synchronization in networks of quadratic maps.Comment: 6 pages, 3 figures (1 in color), submitted to Physica

Quantum Chaos in Open versus Closed Quantum Dots: Signatures of Interacting Particles

This paper reviews recent studies of mesoscopic fluctuations in transport through ballistic quantum dots, emphasizing differences between conduction through open dots and tunneling through nearly isolated dots. Both the open dots and the tunnel-contacted dots show random, repeatable conductance fluctuations with universal statistical proper-ties that are accurately characterized by a variety of theoretical models including random matrix theory, semiclassical methods and nonlinear sigma model calculations. We apply these results in open dots to extract the dephasing rate of electrons within the dot. In the tunneling regime, electron interaction dominates transport since the tunneling of a single electron onto a small dot may be sufficiently energetically costly (due to the small capacitance) that conduction is suppressed altogether. How interactions combine with quantum interference are best seen in this regime.Comment: 15 pages, 11 figures, PDF 2.1 format, to appear in "Chaos, Solitons & Fractals

Book Reviews

Book Review 1Book Title: Megaherbivores: the influence of very large body size on ecologyBook Author: R.N. Owen-SmithCambridge University Press, Cambridge, 1988. 369 pages.Book Review 2Book Title: Comparative Physiology of the Vertebrate KidneyBook Author: W.H. Dantzler Springer-Verlag 1989.198 pp. (Hardcover).Book Review 3Book Title: Atlas on the Biology of Soil ArthropodsBook Authors: G. Esenbeis & W. Wichard Springer-Verlag, Berlin 1987. 437 pp.Book Review 4Book Title: Primate Vocal CommunicationBook Authors: Edited by D. Todt, P. Goedeking & D. SymmesSpringer Verlag, Berlin (1988)Book Review 5Book Title: The Honey BeeBook Authors: J.L. Gould & C. G. GouldScientific American Ubrary, W.H.Freeman, New York. 239 pp.Book Review 6Book Title: Insect Development Photoperiodic and Temperature ControlBook Author: Victor A. ZaslavskiSpringer-Verlag, Berlin. 187 pp.Book Review 7Book Title: OrganellesBook Author: Mark CarrollMacmillan 1989. 202 pp.Book Review 8Book Title: Comparative Protozoology Ecology, Physiology, Life HistoryBook Author: O. Roger AndersonSpringer-Verlag, Berlin, 1988. 482pp.Book Review 9Book Title: Ecotoxicology: Problems and ApproachesBook Authors: Edited by S.A. Levin, M.A. Harwell, J.R. Kelly & K.D. KimballSpringer Verlag, New York. 547 pp

Dephasing in Open Quantum Dots

Shape-averaged magnetoconductance (weak localization) is used for the first time to obtain the electron phase coherence time $\tau_{\phi}$ in open ballistic GaAs quantum dots. Values for $\tau_{\phi}$ in the range of temperature T from 0.335 to 4 K are found to be independent of dot area, and are not consistent with the $\tau_{\phi} \propto T^{-2}$ behavior expected for isolated dots. Surprisingly, $\tau_{\phi}(T)$ agrees quantitatively with the predicted dephasing time for disordered two-dimensional electron systems.Comment: 9 pages, 4 figure

Septal ablation in hypertrophic obstructive cardiomyopathy improves systolic myocardial function in the lateral (free wall): a follow-up study using CMR tissue tagging and 3D strain analysis

Aims: Alcohol septal ablation (ASA) has been successful in the treatment of symptomatic hypertrophic obstructive cardiomyopathy (HOCM). The aim of this study is to evaluate the effects of ethanol-induced myocardial infarcts on regional myocardial function using cardiac magnetic resonance (CMR) tissue tagging and 3-dimensional (3D) strain analysis. Methods and results: In nine patients (age 52±15 years) who underwent ASA, CMR was performed prior to and 6 months after the procedure. Regional myocardial mass was evaluated using cine imaging. Myocardial tagging was used to calculate systolic 3D myocardial strain values. These strain values were used to calculate the shortening index (SI), a robust parameter for myocardial contraction. Maximum end-systolic (ES) SI and systolic SI rate were quantified in three circumferential segments: septum, adjacent, and remote (lateral) myocardium. Compared with baseline, septal and non-septal mass decreased at follow-up (from 72±27 to 59±21 g; P=0.008 and from 131±34 to 109±30 g; P=0.008, respectively). In the septum, maximum ES SI and SI rate remained unchanged after ASA. In adjacent myocardium, ES SI remained unchanged, whereas SI rate improved (from -56.5±21.1 to -70.0±16.7%/s; P=0.02). Both ES SI and SI rate improved significantly in remote myocardium (from -16.9±2.8 to -18.8±3.2%; P=0.02 and from -70.3±9.2 to -86.1±15.0%/s; P=0.01, respectively). Conclusion: Reduction of left ventricular (LV) outflow tract obstruction in symptomatic HOCM is associated with a significant reduction in myocardial mass and improvement of intramural systolic function in the lateral (remote) wall, indicating reversed LV remodelling. © The European Society of Cardiology 2006. All rights reserved

The Histone Variant MacroH2A1 Regulates Key Genes for Myogenic Cell Fusion in a Splice-Isoform Dependent Manner

Altres ajuts: This research project was supported by the Fundació La Marató de TV3 257/C/2019 (to MB). Research at the IJC is supported by the 'La Caixa' Foundation, the Fundació Internacional Josep Carreras, Celgene Spain.MacroH2A histone variants have functions in differentiation, somatic cell reprogramming and cancer. However, at present, it is not clear how macroH2As affect gene regulation to exert these functions. We have parted from the initial observation that loss of total macroH2A1 led to a change in the morphology of murine myotubes differentiated ex vivo. The fusion of myoblasts to myotubes is a key process in embryonic myogenesis and highly relevant for muscle regeneration after acute or chronic injury. We have focused on this physiological process, to investigate the functions of the two splice isoforms of macroH2A1. Individual perturbation of the two isoforms in myotubes forming in vitro from myogenic C2C12 cells showed an opposing phenotype, with macroH2A1.1 enhancing, and macroH2A1.2 reducing, fusion. Differential regulation of a subset of fusion-related genes encoding components of the extracellular matrix and cell surface receptors for adhesion correlated with these phenotypes. We describe, for the first time, splice isoform-specific phenotypes for the histone variant macroH2A1 in a physiologic process and provide evidence for a novel underlying molecular mechanism of gene regulation

A systematic review of physical activity promotion strategies

This article was first published in:British Journal of Sports Medicine:1996:30:84-89We have reviewed randomised controlled trials of physical activity promotion to provide recent and reliable information on the effectiveness of physical activity promotion. Computerised databases and references of references were searched. Experts were contacted and asked for information about existing work. Studies assessed were randomised controlled trials of healthy, free living, adult subjects, where exercise behaviour was the dependent variable. Eleven trials were identified. No United Kingdom based studies were found. Interventions that encourage walking and do not require attendance at a facility are most likely to lead to sustainable increases in overall physical activity. Brisk walking has the greatest potential for increasing overall activity levels of a sedentary population and meeting current public health recommendations. The small number of trials limits the strength of any conclusions and highlights the need for more research