A simple continuous-flow toxicity test system for microscopic life stages of aquatic organisms

This paper describes a flow-through toxicity testing system utilizing a new exposure chamber designed for microscopic organisms. Typically, flow-through testing is conducted with either a serial or proportional diluting system. While generally relying on gravity to drive water flow, as different amounts of toxicant and diluent are combined in glass or plexiglass mixing cells, they are almost always open to the surrounding atmosphere. In contrast, the system described here is based on a simple exposure design utilizing premixed stocks representing each exposure concentration. While the system is entirely closed to the surrounding atmosphere, for testing of volatile organic mixtures in addition to nonvolatile inorganic toxicants, the delivery manifold may be aerated for toxicants of low volatility and high BOD. The system incorporates flexible Teflon gas sampling bags for stock preparation and storage (thus avoiding need for a headspace), and digital unified-drive peristaltic pumps for controlled toxicant delivery. To reduce surface partitioning of toxicants, all system components are constructed of chemically inert materials (Teflon, glass and silicone).     

High-gain, V-band, low-noise MMIC amplifiers usingpseudomorphic MODFETs

State-of-the-art, 60-GHz, low-noise MMICs based on pseudomorphic modulation-doped FETs, with 0.25-μm×60-μm gates offset 0.3 μm from the source ohmic, are discussed. Single-state low-noise amplifiers (LNAs) exhibited minimum noise figures of 2.90 dB with 4.1 dB of associated gain at 59.25 GHz. Dual-state MMICs had minimum noise figures of 3.5 dB and 10.8 dB of associated gain at 58.50 GHz. Cascaded four-stage LNAs (two dual-stage MMICs) had minimum noise figures of 3.7 dB and over 20.7 dB of associated gain at 58.0 GHz. Finally, when biased for maximum gain, the four-stage amplifier exhibited over 30.4 dB of gain at 60.0 GHz     

Modelling of speech using primarily prosodic parameters

Hidden Markov Models are used in an experiment to investigate how state occupancy corresponds to prosodic parameters and spectral balance. In order to define separate sub-classes in the data using a maximum likelihood approach, modelling was performed using a single model where individual states correspond to different categories without assuming the structure of the data, rather than manually segmenting the data and modelling each predefined category separately.The results indicate a significant content of segmental information in the prosodic parameters, but the results based on the time-alignment of the model states with the feature vectors are in a form which is not directly usable in a recognition environment. The classification of various phonetic categories is particularly consistent for vowels and nasals and is generally better for voiced than unvoiced speech. The classification is also robust to influences of segmental effects on the data, with consistent alignments with segments regardless of the type of neighbouring phenemes.     

Strategies of text retrieval: A criterion shift account.

This study scrutinized people's ability to apply different strategies to randomly intermixed immediate and delayed test items. In three experiments a total of 221 participants first read one set of stories. Later, they read more stories, and after each one, answered intermixed questions about that story and one of the earlier ones. The experiments cumulatively manipulated amount of delay, test probe plausibility, probe relation (explicit, paraphrase, inference), and testing procedure (mixed versus uniform delay). Using signal detection response criterion as the index of strategy, the authors contrasted the single criterion hypothesis, according to which one text retrieval criterion is applied to all test items and a multiple-criterion hypothesis. The results consistently favoured the multiple-criterion hypothesis. The results also indicated that the presence of immediate and delayed probes mutually influence one another less extreme signal detection criteria were adopted under mixed than uniform testing. It was concluded that text retrieval strategy is continually calibrated with reference to the quality of the test probes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gyrators Application in Power Processing Circuits

The gyrator is a lossless two-port network which transforms one-port networks into its dual with respect to its gyration conductance. For example, capacitance at the gyrator output is viewed as inductance at the input and a voltage source is transformed to a current source.     

Study of an annular laser beam based axially-fed powder cladding process

An annular laser beam based powder cladding head, which enables an axial powder feeding and variation of the laser beam intensity distribution (LBID) on the workpiece surface is presented. The influence of typical LBIDs, including Ring, Tophat(?), Tophat(+), and Gaussian-like, on a cladding process has been characterized based on the process and melt pool visualization, powder catchment efficiency, clad layer geometry, and porosity. The results showed that the most stable process without plasma formation but with low dilution and porosity of the clad layer can be achieved within the range from a Ring to a Tophat(?) LBID. Additionally, axial powder feeding results in a high powder catchment efficiency above 80%.     

Significance of urban and agricultural land use for biocide and pesticide dynamics in surface waters

Biocides and pesticides are designed to control the occurrence of unwanted organisms. From their point of application, these substances can be mobilized and transported to surface waters posing a threat to the aquatic environment. Historically, agricultural pesticides have received substantially more attention than biocidal compounds from urban use, despite being used in similar quantities.This study aims at improving our understanding of the influence of mixed urban and agricultural land use on the overall concentration dynamics of biocides and pesticides during rain events throughout the year. A comprehensive field study was conducted in a catchment within the Swiss plateau (25 km²). Four surface water sampling sites represented varying combinations of urban and agricultural sources. Additionally, the urban drainage system was studied by sampling the only wastewater treatment plant (WWTP) in the catchment, a combined sewer overflow (CSO), and a storm sewer (SS). High temporal resolution sampling was carried out during rain events from March to November 2007.The results, based on more than 600 samples analyzed for 23 substances, revealed distinct and complex concentration patterns for different compounds and sources. Five types of concentration patterns can be distinguished: a) compounds that showed elevated background concentrations throughout the year (e.g. diazinon >50 ng L⁻¹), indicating a constant household source; b) compounds that showed elevated concentrations driven by rain events throughout the year (e.g. diuron 100-300 ng L⁻¹), indicating a constant urban outdoor source such as facades; c) compounds with seasonal peak concentrations driven by rain events from urban and agricultural areas (e.g. mecoprop 1600 ng L⁻¹ and atrazine 2500 ng L⁻¹ respectively); d) compounds that showed unpredictably sharp peaks (e.g. atrazine 10,000 ng L⁻¹, diazinon 2500 ng L⁻¹), which were most probably due to improper handling or even disposal of products; and finally, e) compounds that were used in high amounts but were not detected in surface waters (e.g. isothiazolinones).It can be safely concluded that in catchments of mixed land use, the contributions of biocide and pesticide inputs into surface waters from urban areas are at least as important as those from agricultural areas.