The effects of pharmaceuticals on the regeneration of the cnidarian, Hydra attenuata

The Hydra attenuata regeneration assay was used to identify the teratogenic potential of 10 pharmaceuticals identified in effluent from a large city wastewater treatment plant (WWTP). Three types of solvents were used to solubilise the pharmaceuticals (DMSO, acetone and ethanol), at concentrations determined to have no significant effect on measured endpoints. On the one hand, regeneration was significantly inhibited at (nominal) concentrations of 1, 5 and 1 mg/L for gemfibrozil, ibuprofen and naproxen respectively and at the higher concentration of 50 mg/L for bezafibrate and trimethoprim. On the other hand, carbamazepine and the antibiotics sulfapyridine, oxytetracycline and novobiocin significantly increased regeneration at 25, 5, 50 and 50 mg/L respectively. Relatively high IC50 values of 0.9, 3.84, 4.9 and 22.5 mg/L were calculated for gemfibrozil, ibuprofen, naproxen and bezafibrate, respectively. However when subjected to tier two toxicity assessment under EU regulatory guidance using environmentally relevant concentrations a MEC/PNEC value>1 was calculated for gemfibrozil, ibuprofen and naproxen indicating teratogenic potential and the necessity for further tier three assessment. A toxicity index (TI) was also calculated using three different techniques, with TI values>3 (indicating teratogenic potential) found for gemfibrozil, ibuprofen, naproxen and bezafibrate and >1 (indicating a weak teratogenic potential) found for carbamazepine. These results are discussed in the context of their environmental relevance and toxic potential.     

Endocrine alteration and other biochemical responses in juvenile turbot exposed to the Prestige fuel oil

Juvenile turbot (Scophthalmus maximus) were exposed to different concentrations of the Prestige fuel oil through the diet. The effects on hepatic biotransformation enzymes, namely, 7-ethoxyresorufin O-deethylase (EROD), catalase, and phase II activities - UDP-glucuronosyltransferases (UGT) and cytosolic sulfotransferases (SULT) -, were monitored after 42-day exposure. Additionally, potential alterations on the endocrine system of juvenile turbot were assessed by measuring circulating levels of testosterone and 17beta-estradiol in plasma, together with gonadal P450 aromatase activity and the glucuronidation of testosterone by liver microsomal fractions. Fluorescent aromatic compounds (FACs) in bile were determined as an indicator of exposure to polycyclic aromatic hydrocarbons (PAHs). EROD activity increased in a dose dependent manner, and a positive correlation between levels of FACs in bile and EROD activity was observed. A significant increase in UGT activity was observed in fish exposed to medium and high fuel doses, whereas SULT cytosolic activity was not responsive to exposure. Exposure to the Prestige fuel oil sharply reduced circulating levels of testosterone in plasma. The obtained results suggest the ability of the Prestige fuel oil to alter hepatic biotransformation enzymes and to disrupt endogenous hormone levels in juvenile turbot, with unknown consequences in terms of sexual differentiation and reproduction.     

Charge transport in disordered graphene-based low dimensional materials

Two-dimensional graphene, carbon nanotubes, and graphene nanoribbons represent a novel class of low dimensional materials that could serve as building blocks for future carbon-based nanoelectronics. Although these systems share a similar underlying electronic structure, whose exact details depend on confinement effects, crucial differences emerge when disorder comes into play. In this review, we consider the transport properties of these materials, with particular emphasis on the case of graphene nanoribbons. After summarizing the electronic and transport properties of defect-free systems, we focus on the effects of a model disorder potential (Anderson-type), and illustrate how transport properties are sensitive to the underlying symmetry. We provide analytical expressions for the elastic mean free path of carbon nanotubes and graphene nanoribbons, and discuss the onset of weak and strong localization regimes, which are genuinely dependent on the transport dimensionality. We also consider the effects of edge disorder and roughness for graphene nanoribbons in relation to their armchair or zigzag orientation. This article is published with open access at Springerlink.com     

Physical processes within a 2D granular layer during an impact

In this paper, the impact of a block on a coarse granular soil corresponding to rockfall events is investigated using the Discrete Element Method. Different impacting particle and medium characteristics (impact point, impacting particle size and shape, sample height, etc.) are considered. The numerical results first exhibit the physical phenomena involved in the interaction between the impacting particle and the granular medium. The impact process starts with the partial energy exchange from the impacting particle to the soil. This phase is followed by the propagation of a shockwave from the impact point and a wave reflection on the bottom wall of the sample. A second energy exchange from soil particles to the impacting particle can occur if the reflected wave reaches the soil surface before the end of the impact. Based on these investigations, the impacting particle bouncing occurrence diagram is defined for various impacting particle sizes, incident kinematic parameters and sample heights. The bouncing occurrence diagram brings out three impact regimes. For a small impacting particle, the impact is mainly determined by the first interaction between the impacting particle and the soil, whereas for an intermediate-sized impacting particle, the shockwave propagation through the sample is the leading phenomenon. For a large impacting particle, bouncing is associated with the formation of a compact layer below the impacting particle.     

Insight into silicate-glass corrosion mechanisms

The remarkable chemical durability of silicate glass makes it suitable for a wide range of applications. The slowdown of the aqueous glass corrosion kinetics that is frequently observed at long time is generally attributed to chemical affinity effects (saturation of the solution with respect to silica). Here, we demonstrate a new mechanism and highlight the impact of morphological transformations in the alteration layer on the leaching kinetics. A direct correlation between structure and reactivity is revealed by coupling the results of several structure-sensitive experiments with numerical simulations at mesoscopic scale. The sharp drop in the corrosion rate is shown to arise from densification of the outer layers of the alteration film, leading to pore closure. The presence of insoluble elements in the glass can inhibit the film restructuring responsible for this effect. This mechanism may be more broadly applicable to silicate minerals.     

Materials nanoarchitectonics: a conspectus for polymer scientists

Materials nanoarchitectonics has led to important innovations in the design and construction of nanosystems for electronics, nanomachine systems and energy conversion. In this perspective, we define the key features of materials nanoarchitectonics and examine how they can be combined with the concepts of polymer science to address some of the current and future challenges of soft matter nanoassemblies. Copyright © 2013 Society of Chemical Industry     

Model updating of a rotating machine using the self-adaptive differential evolution algorithm

Despite the good accuracy of finite element (FE) models to represent the dynamic behaviour of mechanical systems, practical applications show significant discrepancies between analytical predictions and experimental results, which are mostly due to uncertainties on the geometry configuration, imprecise material parameters and vague boundary conditions. Thereby, different approaches have been proposed to solve the inverse problems associated with the updating of FE models. Among them, the techniques based on minimization processes have shown to be some of the most promising ones. In this paper, a self-adaptive heuristic optimization method, namely the self-adaptive differential evolution (SADE), is evaluated. Differently from the canonical differential evolution (DE) algorithm, the SADE strategy is able to update dynamically the required parameters such as population size, crossover parameter and perturbation rate. This is done by considering a defined convergence rate on the evolution process of the algorithm in order to reduce the number of evaluations of the objective function. For illustration purposes, the SADE strategy is applied to the solution of typical mathematical functions. Additionally, the strategy is equally used to update the FE model of a rotating machine composed by a horizontal flexible shaft, two rigid discs and two unsymmetrical bearings. For comparison purposes, the canonical DE is also used. The results indicate that the SADE algorithm is a recommended technique for dealing with this kind of inverse problem.     

An SVD-Aided Efficient Bit-Loading Algorithm for MIMO Transmission Over Spatially Correlated Channels

This paper proposes an efficient bit-loading algorithm for Multiple-Input-Multiple-Output transmission over spatially correlated channels with perfect Channel State Information at both link ends. Based on water-filling principle, the algorithm does not assume the well-known gap approximation and accounts for the spatial correlation effects through the initial bit allocation. The result is the optimal distribution of bits and power over the eigenmodes for multiple antenna systems. We report the performance evaluations in the presence of spatial correlation in order to illustrate the efficiency and the robustness of our bit-loading algorithm in realistic environments. The simulation results demonstrate that our algorithm leads to significant improvements. In addition, these results show that our algorithm achieves the maximal diversity order, as well as exhibiting a high extra coding gain.     

Reassessing the value of resources for cross-lingual transfer of POS tagging models

When linguistically annotated data is scarce, as is the case for many under-resourced languages, one has to resort to less complete forms of annotations obtained from crawled dictionaries and/or through cross-lingual transfer. Several recent works have shown that learning from such partially supervised data can be effective in many practical situations. In this work, we review two existing proposals for learning with ambiguous labels which extend conventional learners to the weakly supervised setting: a history-based model using a variant of the perceptron, on the one hand; an extension of the Conditional Random Fields model on the other hand. Focusing on the part-of-speech tagging task, but considering a large set of ten languages, we show (a) that good performance can be achieved even in the presence of ambiguity, provided however that both monolingual and bilingual resources are available; (b) that our two learners exploit different characteristics of the training set, and are successful in different situations; (c) that in addition to the choice of an adequate learning algorithm, many other factors are critical for achieving good performance in a cross-lingual transfer setting.     

Hydrothermal Synthesis of Ferroelectric Mixed Potassium Niobate–Lead Titanate Nanoparticles

Potassium niobate–lead titanate solid‐solution nanoparticles have been synthesized using a new hydrothermal method. The key step is an in situ acid–base exothermic reaction with a large excess of KOH, generating an amorphous precipitated gel. This gel, when crystallized in an autoclave for 2 h at 190°C, produces a mixed perovskite solid solution with [KNbO₃]_0.8–[PbTiO₃]_0.2 (KNPT) composition, and parallelepiped particles rang in size from a few tens to a few hundreds of nanometer in length. This study proves that the pure perovskite phase can be obtained in spite of the different solubilities of the reactive cations in an ethanol–water solution. Dielectric measurements show that KNPT ceramic with a grain size of 50 nm is ferroelectric at room temperature. In addition, ceramics sintered at 950°C have an average grain size of 500 nm, and exhibit a maximum permittivity of 2100 at 1 kHz near T_C = 510 K and a remanent polarization P_r = 12 μC/cm²