Site length for biological assessment of boatable rivers

There is increasing international interest by water resource management agencies worldwide in developing the capacity for quantitative bioassessments of boatable rivers. This interest stems from legal mandates requiring assessments, plus growing recognition of the threats to such systems from multiple and co‐varying stressors (e.g. chemical pollutants, physical habitat alterations, altered flow regimes, channel modifications and alien species). The elevated cost and inefficiencies of jurisdictionally‐ and taxonomically‐segregated assessments is widely recognized, as is the desire to obtain comparable data that can be easily shared among political jurisdictions and ecological regions. The objectives, sampling methods, indicators, site‐scale sampling designs and geographic extent of the resources being sampled differ among programmes, thereby limiting such data exchanges. Our objective in this paper is to review major biological assessment design alternatives for boatable rivers, with special attention given to the sample site length from which data are collected. We suggest that sufficient site length determinations should be based on the survey objectives, the relative heterogeneity of the habitat template, and the quality of data necessary for meeting programmatic data quality objectives. Future sampling effort studies should be designed to allow separate samples of several short sub‐sites at many diverse sites to generate multiple data points for each site. Data from those multiple sub‐sites should be analysed using randomization‐based data evaluation methods. We hope that our recommendations will be useful to the maximum number of institutions, including those with limited funds and a purely local focus, as well as those responsible for sampling at continental geographic extents. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimal algorithms for symmetry detection in two and three dimensions

Exact algorithms for detecting all rotational and involutional symmetries in point sets, polygons and polyhedra are described. The time complexities of the algorithms are shown to be (n) for polygons and (n logn) for two- and three-dimensional point sets. (n logn) time is also required for general polyhedra, but for polyhedra with connected, planar surface graphs (n) time can be achieved. All algorithms are optimal in time complexity, within constants.     

Dual resonance excitation system for the contact mode of atomic force microscopy

We propose an improved system that enables simultaneous excitation and measurements of at least two resonance frequency spectra of a vibrating atomic force microscopy (AFM) cantilever. With the dual resonance excitation system it is not only possible to excite the cantilever vibrations in different frequency ranges but also to control the excitation amplitude for the individual modes. This system can be used to excite the resonance frequencies of a cantilever that is either free of the tip-sample interactions or engaged in contact with the sample surface. The atomic force acoustic microscopy and principally similar methods utilize resonance frequencies of the AFM cantilever vibrating while in contact with the sample surface to determine its local elastic modulus. As such calculation demands values of at least two resonance frequencies, two or three subsequent measurements of the contact resonance spectra are necessary. Our approach shortens the measurement time by a factor of two and limits the influence of the AFM tip wear on the values of the tip-sample contact stiffness. In addition, it allows for in situ observation of processes transpiring within the AFM tip or the sample during non-elastic interaction, such as tip fracture.     

An examination of the surface characteristics of activated sludge in relation to bulking during the treatment of paper mill wastewater

The addition of mineral talc, Aquatal^®(Toulouse, France), to activated sludge treating paper mill effluents and its effect on settlement characteristics has been investigated. One laboratory study and a full‐scale investigation on a large waste water treatment plant (WWTP) with a capacity of 500.000 population equivalent (p.e.) have been carried out using this mineral. The sludge in the full‐scale plant was filamentous and had specific sludge volume index (SSVI) values in excess of 250. The talc dosing which was adapted to sludge settleability reduced SSVI values by 38%, improved the total suspended solids' concentrations by 86% and reduced the specific sludge load by 34%. In the laboratory‐scale plant, the sludge had SSVI values of 200–260 before treatment and was hydrophilic. The use of Aquatal^® at a dose of 0.7 g/g mixed liquor suspended solids (MLSS) took 2 weeks to reduce the SSVI to 78. It also increased the hydrophobicity to a balanced 50%. The use of mineral converted the somewhat diffuse flocs into a compact structure.     

Discrimination of facial appearance stimuli in body dysmorphic disorder.

Cognitive-behavioral models of body dysmorphic disorder (BDD) propose that information-processing biases--in particular, selective attention to a defect in one's appearance as well as improved aesthetical perception--might contribute to the development or maintenance of the disorder. In the present study, the authors tested the hypothesis that patients with BDD discriminate facial appearance stimuli more accurately than controls. Sixty female patients from a dermatological clinic participated in the study: 21 patients with BDD, 19 patients with disfiguring dermatological conditions, and 20 patients with nondisfiguring dermatological disorders. Participants rated dissimilarities between pictures of neutral faces that had been manipulated with regard to aesthetic characteristics. Manipulation ratings of participants with BDD were significantly more accurate than those of both control groups. Implications of these results for cognitive theories of BDD are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low-crosstalk penalty MZI space switch with a 0.64-mm phase shifterusing quantum-well electrorefraction

We investigate Mach-Zehnder interferometric (MZI) space switches with quantum-well phase shifters. We find that the minimum phase shifter length is limited by additional crosstalk due to electroabsorption-induced imbalance in the MZI. This criterion also provides an optimal detuning between the bandgap and the operating wavelength of the MZI. Finally, we present a novel MZI with an ultrashort 0.64-mm phase shifter     

Synthesis, properties and applications of inorganic–organic copolymers (ORMOCERs)

Hybrid inorganic-organic polymers based on organically modified heteropolysiloxanes have found widespread attention and application as materials with adjustable properties using tailor-made precursors. The chemical structures of monomers and their modified sol-gel processing method are described. An overview is given for the control of various properties (mechanical, electrical, optical) of the materials on a molecular scale. Successful material developments and industrial applications are described.     

Atomically Defined Rare‐Earth Scandate Crystal Surfaces

The fabrication of well‐defined, atomically sharp substrate surfaces over a wide range of lattice parameters is reported, which is crucial for atomically regulated epitaxial growth of complex oxide heterostructures. By applying a framework for controlled selective wet etching of complex oxides on the stable rare‐earth scandates (REScO₃), a_pseudocubic = 0.394 – 0.404 nm, the large chemical sensitivity of REScO₃ to basic solutions is exploited, which results in reproducible, single‐terminated surfaces. Time‐of‐flight mass‐spectroscopy measurements show that after wet etching the surfaces are predominantly ScO₂ ‐terminated. Moreover, the morphology study of SrRuO₃ thin‐film growth gives no evidence for mixed termination. Therefore, it is concluded that the REScO₃ surfaces are completely ScO₂ ‐terminated.