Temporal trends and controlling factors for polychlorinated biphenyls in the UK atmosphere (1991-2008)

Long-term air monitoring data sets are needed for persistent organic pollutants (POPs), to assess the effectiveness of source abatement measures and the factors controlling ambient levels. The Toxic Organic Micro-Pollutants (TOMPS) program in the United Kingdom started in 1991, generating a data set for polychlorinated biphenyls (PCBs). The history and volumes of production, usage, and subsequent restrictions on PCBs in the UK are well-characterized relative to many countries, providing a valuable case study on the effectiveness of controls and the factors influencing ambient levels and trends of these "model POPs". PCB air concentrations (congeners PCB 28, 52, 90/101, 118, 138, 153, and 180) from six rural and urban monitoring sites are presented. Most show a statistically significant decrease in PCBs levels over time, consistent with estimates of emissions, helping to validate emissions inventories. Times for a 50% decline in concentrations (sometimes called clearance rates) averaged 4.7 ± 1.6 years for all congeners at all sites. The trends at different sites and for different congeners were not statistically different from each other. Concentration differences between sites are correlated with local population density (i.e., the degree of urbanization), which supports approaches to modeling of primary emissions on the national and regional scale. The data set indicates that ambient levels and underlying trends of PCBs continue to reflect the controlling influence of diffuse primary sources from the ongoing stock of PCBs in urban environments. Production and use restrictions came into force in the UK over 40 years ago; trends since monitoring began in the early 1990s should be seen as part of a continuing decline in ambient levels since that time.     

SREBP-1c Deficiency Affects Hippocampal Micromorphometry and Hippocampus-Dependent Memory Ability in Mice

Changes in structural and functional neuroplasticity have been implicated in various neurological disorders. Sterol regulatory element-binding protein (SREBP)-1c is a critical regulatory molecule of lipid homeostasis in the brain. Recently, our findings have shown the potential involvement of SREBP-1c deficiency in the alteration of novel modulatory molecules in the hippocampus and occurrence of schizophrenia-like behaviors in mice. However, the possible underlying mechanisms, related to neuronal plasticity in the hippocampus, are yet to be elucidated. In this study, we investigated the hippocampus-dependent memory function and neuronal architecture of hippocampal neurons in SREBP-1c knockout (KO) mice. During the passive avoidance test, SREBP-1c KO mice showed memory impairment. Based on Golgi staining, the dendritic complexity, length, and branch points were significantly decreased in the apical cornu ammonis (CA) 1, CA3, and dentate gyrus (DG) subregions of the hippocampi of SREBP-1c KO mice, compared with those of wild-type (WT) mice. Additionally, significant decreases in the dendritic diameters were detected in the CA3 and DG subregions, and spine density was also significantly decreased in the apical CA3 subregion of the hippocampi of KO mice, compared with that of WT mice. Alterations in the proportions of stubby and thin-shaped dendritic spines were observed in the apical subcompartments of CA1 and CA3 in the hippocampi of KO mice. Furthermore, the corresponding differential decreases in the levels of SREBP-1 expression in the hippocampal subregions (particularly, a significant decrease in the level in the CA3) were detected by immunofluorescence. This study suggests that the contributions of SREBP-1c to the structural plasticity of the mouse hippocampus may have underlain the behavioral alterations. These findings offer insights into the critical role of SREBP-1c in hippocampal functioning in mice.     

Improved trapped field performance of single grain Y-Ba-Cu-O bulk superconductors containing artificial holes

The intrinsic mechanical properties of single-grain RE-Ba-Cu-O bulk high-temperature superconductors can be improved by employing a thin-wall geometry. This is where the samples are melt-processed with a predefined network of artificial holes to decrease the effective wall thickness. In this study, the tensile strengths of thin-wall YBCO disks were determined using the Brazilian test at room temperature. Compared with conventional single grain YBCO disks, the thin-wall YBCO disks displayed an average tensile strength that is 93% higher when the holes were filled with Stycast epoxy resin. This implies a thin-wall sample should, in theory, be able to sustain a trapped field that is 39% higher without exceeding the mechanical limit of the sample. High-field magnetization experiments were performed by applying magnetization fields of up to 11.5 T, specifically to break the samples in order to verify the effect of increased mechanical strength (and improved cooling) on the ability of bulk (RE)BCO to trap field successfully. The standard YBCO sample failed when it was magnetized with a field of 10 T at 35 K, suffering permanent damage. As a result, the standard sample could only trap a maximum surface field of 7.6 T without failure. On the other hand, the thin-wall YBCO sample survived all magnetization cycles, including a maximum magnetization field of 11.5 T at 35 K, demonstrating a greater intrinsic ability to withstand significantly higher electromagnetic stresses. By subsequently field-cooling the thin-wall sample with 11 T at 30 K, a surface field of 8.8 T was trapped successfully without requiring any external ring reinforcement.     

Novel polyurethane dispersions based on renewable raw materials—Stability studies by variations of DMPA content and degree of neutralisation

Renewable resources, especially natural oils, have received increasing attention as raw materials for polymers. The synthesis and characterisation of novel aqueous polyurethane dispersions derived from rapeseed oil are investigated. The applied renewable polyol is high-hydrophobic due to the triglyceride backbone. Dimethylolpropionic acid (DMPA) as internal emulsifier was used to incorporate hydrophilic groups into the polymer chain to achieve stable self-emulsifying dispersions. By neutralisation of the carboxyl groups with triethylamine a predominately electrostatic stabilisation was generated. A weak steric stabilisation by pending chain ends exists beside the predominant electrostatic stabilisation. Outgoing from a DMPA content of 5.6 wt% related to the polymer, the content was decreased successively with the objective being to analyse the influence of ionic concentration and stability. Furthermore, the influence of the degree of neutralisation with respect to the stabilisation of these novel dispersions was investigated.     

Differentiation of human mesenchymal stem cells on plasma-treated polyetheretherketone

Polyetheretherketone (PEEK) generally exhibits physical and chemical characteristics that prevent osseointegration. To activate the PEEK surface, we applied oxygen and ammonia plasma treatments. These treatments resulted in surface modifications, leading to changes in nanostructure, contact angle, electrochemical properties and protein adhesion in a plasma power and process gas dependent way. To evaluate the effect of the plasma-induced PEEK modifications on stem cell adhesion and differentiation, adipose tissue-derived mesenchymal stem cells (adMSC) were seeded on PEEK specimens. We demonstrated an increased adhesion, proliferation, and osteogenic differentiation of adMSC in contact to plasma-treated PEEK. In dependency on the process gas (oxygen or ammonia) and plasma power (between 10 and 200 W for 5 min), varying degrees of osteogenic differentiation were induced. When adMSC were grown on 10 and 50 W oxygen and ammonia plasma-treated PEEK substrates they exhibited a doubled mineralization degree relative to the original PEEK. Thus plasma treatment of PEEK specimens induced changes in surface chemistry and topography and supported osteogenic differentiation of adMSC in vitro. Therefore plasma treated PEEK holds perspective for contributing to osseointegration of dental and orthopedic load-bearing PEEK implants in vivo.     

Evaluation of magnetic nanoparticles performance as photocatalyst for the catalytic treatment of direct red 28 dye in synthetic and real water effluents

Integrated water resources management practice is gaining popularity as an alternative water source due to the limited supply of freshwater. The present study was carried out on the photocatalytic degradation of Direct red 28 (DR-28) dye using magnetic nanoparticles (MNPs; Fe₃O₄) as a photocatalyst. The study was conducted on the photocatalytic degradation of DR-28 dye in synthetic dye effluent water, to understand the effects of different photoreaction parameters on the degradation kinetics. The influence of different parameters such as time, amount of photocatalyst, concentration of H₂O₂ and pH was investigated. At the optimum dosage of MNPs (0.6?g/L) with 4?mmol/L of H₂O₂, significant photocatalytic degradation of DR-28 dye (93.2%) was observed. The kinetic study revealed that the photocatalytic degradation followed pseudo-first-order kinetics. The degradation performance of Fe₃O₄ nanoparticles as a photocatalyst for DR-28 dye was compared with titanium dioxide (TiO₂) and it was found that the performance of Fe₃O₄ as a photocatalyst is superior to TiO₂ photocatalyst. The real dye effluent was also degraded at optimum conditions and promising results were achieved.     

Efficient procedures for the optimization of defects in photonic crystal structures

Seven different stochastic binary optimizers--based on the concepts of genetic algorithms and evolutionary strategies--are developed, applied to determine defect locations in several photonic crystal structures that serve as test cases, and compared by extensive statistical analysis. In addition to the stochastic optimizers, a quasi-deterministic optimizer based on an algorithm inspired by hill-climbing algorithms was implemented. The test cases include the prominent 90 degrees photonic crystal waveguide bend and a photonic crystal power divider. The analysis of the results shows that many different photonic crystal structures with high transmission may be found for any operating frequency. All of the eight optimizers outperform standard codes-because they maintain an incomplete fitness table-and find the global optima with a high probability even when the number of fitness evaluations is much smaller than the number of potential solutions contained in the discrete search space. Based on the incomplete fitness table, an algorithm to estimate bit-fitness values is presented. The bit-fitness values are then used to improve the performance of some algorithms. The four best algorithms-an extended microgenetic algorithm, two mutation-based algorithms, and the quasi-deterministic algorithm inspired by hill-climbing algorithms-are considered to be of high value for the optimization of defects in photonic crystals and for similar binary optimization problems.     

Observer-based control for high order delayed systems with an unstable pole and a pole at the origin

Time delays in dynamical systems are challenging when trying to control them. One of the most common techniques consists in estimating one or more signals of interest before they are delayed, in order to use them in the control stage. In this work, an observer-based control strategy for unstable linear systems with a pole at the origin and delay is suggested. Also, the proposed observer is extended to be used in the case of a high order unstable delayed system. Likewise, the conditions to ensure the existence of the proposed observer-predictor are presented. A methodology is introduced to obtain the observer parameters. The proposed observer scheme makes use of a Proportional-Integral-Derivative control that makes it possible to ensure the tracking of step-type references and the rejection of disturbances of the same type in the closed-loop system.