Mercury accumulation in fishes from tropical aquatic ecosystems in the Niger Delta, Nigeria

Fishes are important biomarkers of trace elements in aquatic ecosystems, and are used to evaluate the status of water pollution by mercury in tropical aquatic ecosystems in Nigeria. Common fishes, Chrysichthys nigrodigitatus,Brycinus nurse, Hemichromis fasciatus, Lutianus ava, Oreochromis nilotica, Pomadasys jubelini, Stellifer stellifer and Tilapia guineensis were analysed for Hg accumulation using the cold vapour atomic absorption spectrophotometry technique. The results showed that Hg concentration in P. jubelini was relatively the highest, with a mean concentration of 0.063 ± 0.03 mg kg–1. Other concentration values were 0.044 ± 0.031 mg kg–1 for O. nilotica, 0.026 ± 0.013 mg kg–1 for B. nurse, 0.034 ± 0.034 mg kg–1 for H. fasciatus, 0.023 ± 0.020 mg kg–1 for C. nigrodigitatus and 0.33 ± 0.016 mg kg–1 for L. ava. Concentrations of Hg accumulated by the fishes were low and within internationally accepted limit, not likely to cause mercury poisoning. Because of the high Hg accumulating potential of P. jubelini, it is recommended as a biomarker for assessment of Hg toxicity in a tropical aquatic environment

Continuous phase amplification with a Sagnac interferometer

We describe a weak value inspired phase amplification technique in a Sagnac interferometer. We monitor the relative phase between two paths of a slightly misaligned interferometer by measuring the average position of a split-Gaussian mode in the dark port. Although we monitor only the dark port, we show that the signal varies linearly with phase and that we can obtain similar sensitivity to balanced homodyne detection. We derive the source of the amplification both with classical wave optics and as an inverse weak value.Comment: 5 pages, 4 figures, previously submitted for publicatio

Reliability assessment of a digital electronic board assembly using the physics-of-failure approach: a case study

An independent study has been carried out to assess the extent to which the physics-of-failure (PoF) technique can help in reliability enhancement and assessment of electronic assemblies. In particular, a specific case study has been conducted on a real, digital electronic board assembly with known failure modes. Results from the study include the simulation of substrate and component temperatures based on the knowledge of component power dissipation, board assembly materials and cooling methods of the board assembly. The fundamental frequencies and dynamic displacements of the board were computed from the vibration models. The thermal and vibration results were then used to model the damage accumulation at solder joints of the components to accurately predict failure trends and failure sites. These results are compared with field failure data and results from other computer aided engineering (CAE) tools

The genetic organisation of prokaryotic two-component system signalling pathways

BACKGROUND: Two-component systems (TCSs) are modular and diverse signalling pathways, involving a stimulus-responsive transfer of phosphoryl groups from transmitter to partner receiver domains. TCS gene and domain organisation are both potentially informative regarding biological function, interaction partnerships and molecular mechanisms. However, there is currently little understanding of the relationships between domain architecture, gene organisation and TCS pathway structure. RESULTS: Here we classify the gene and domain organisation of TCS gene loci from 1405 prokaryotic replicons (>40,000 TCS proteins). We find that 200 bp is the most appropriate distance cut-off for defining whether two TCS genes are functionally linked. More than 90% of all TCS gene loci encode just one or two transmitter and/or receiver domains, however numerous other geometries exist, often with large numbers of encoded TCS domains. Such information provides insights into the distribution of TCS domains between genes, and within genes. As expected, the organisation of TCS genes and domains is affected by phylogeny, and plasmid-encoded TCS exhibit differences in organisation from their chromosomally-encoded counterparts. CONCLUSIONS: We provide here an overview of the genomic and genetic organisation of TCS domains, as a resource for further research. We also propose novel metrics that build upon TCS gene/domain organisation data and allow comparisons between genomic complements of TCSs. In particular, 'percentage orphaned TCS genes' (or 'Dissemination') and 'percentage of complex loci' (or 'Sophistication') appear to be useful discriminators, and to reflect mechanistic aspects of TCS organisation not captured by existing metrics

Resolving the Surfaces of Extrasolar Planets With Secondary Eclipse Light Curves

We present a method that employs the secondary eclipse light curves of transiting extrasolar planets to probe the spatial variation of their thermal emission. This technique permits an observer to resolve the surface of the planet without the need to spatially resolve its central star. We evaluate the feasibility of this technique for the HD 209458 system [..]. We consider two representations of the planetary thermal emission; a simple model parameterized by a sinusoidal dependence on longitude and latitude, as well as the results of a three-dimensional dynamical simulation of the planetary atmosphere previously published by Cooper & Showman. We find that observations of the secondary eclipse light curve are most sensitive to a longitudinal offset in the geometric and photometric centroids of the hemisphere of the planet visible near opposition. To quantify this signal, we define a new parameter, the ``uniform time offset,'' which measures the time lag between the observed secondary eclipse and that predicted by a planet with a uniform surface flux distribution. We compare the predicted amplitude of this parameter for HD 209458 with the precision with which it could be measured with IRAC. We find that IRAC observations at 3.6um a single secondary eclipse should permit sufficient precision to confirm or reject the Cooper & Showman model of the surface flux distribution for this planet. We quantify the signal-to-noise ratio for this offset in the remaining IRAC bands (4.5um, 5.8um, and 8.0um), and find that a modest improvement in photometric precision (as might be realized through observations of several eclipse events) should permit a similarly robust detection.Comment: AASTeX 5.2, 24 pages, 5 figures, accepted for publication in ApJ; v2: clarifications, updated to version accepted by ApJ; v3: try to reduce spacin

Anti-growth properties of BAY 41-2272 in vascular smooth muscle cells

Vascular smooth muscle (VSM) growth is integral in the pathophysiology of blood vessel diseases, and identifying approaches that have capacity to regulate VSM growth is critically essential. Cyclic nucleotide signaling has been generally considered protective in cardiac and vascular tissues and has been the target of numerous basic science and clinical studies. In this project, the influence of BAY 41-2272 (BAY), a recently described soluble guanylate cyclase (sGC) stimulator and inducer of cyclic guanosine monophosphate (cGMP) synthesis, on VSM cell growth was analyzed. In rat A7R5 VSM cells BAY significantly reduced proliferation in dose- and time-dependent fashion. BAY activated cGMP and cyclic adenosine monophosphate (cAMP) signaling evidenced through elevated cGMP and cAMP content, increased expression of cyclic nucleotide-dependent protein kinases, and differential vasodilator-stimulated phosphoprotein (VASP) phosphorylation. BAY significantly elevated cyclin E expression, decreased expression of the regulatory cyclin-dependent kinases (Cdk)-2 and -6, increased expression of cell cycle inhibitory p21WAF1/Cip1 and p27Kip1, and reduced expression of phosphorylated focal adhesion kinase (FAK). These comprehensive findings provide first evidence for the anti-growth, cell cycle-regulatory properties of the neoteric agent BAY 41-2272 in VSM and lend support for its continued study in the clinical and basic cardiovascular sciences. Originally published Journal of Cardiovascular Pharmacology, Vol. 53, No. 2, Feb 200

Can community volunteers work to trace patients defaulting from scheduled psychiatric clinic appointments?

Reproduced with permission of the publisher