A study of the relationships between the mechanical response of the tympanic membrane and the electrophysiological indicators of hearing in the bullfrog (Rana catesbeiana)

Mechanical response of frog membrane to stimulating frequencies and electrophysiologically determined hearing area

Experiments with hypersonic turbulent boundary layers on flat plates and delta wings

Hypersonic turbulent boundary layers on flat plates and delta wing

Modelling fixed plant and algal dynamics in rivers: an application to the River Frome

The development of eutrophication in river systems is poorly understood given the complex relationship between fixed plants, algae, hydrodynamics, water chemistry and solar radiation. However there is a pressing need to understand the relationship between the ecological status of rivers and the controlling environmental factors to help the reasoned implementation of the Water Framework Directive and Catchment Sensitive Farming in the UK. This research aims to create a dynamic, process-based, mathematical in-stream model to simulate the growth and competition of different vegetation types (macrophytes, phytoplankton and benthic algae) in rivers. The model, applied to the River Frome (Dorset, UK), captured well the seasonality of simulated vegetation types (suspended algae, macrophytes, epiphytes, sediment biofilm). Macrophyte results showed that local knowledge is important for explaining unusual changes in biomass. Fixed algae simulations indicated the need for the more detailed representation of various herbivorous grazer groups, however this would increase the model complexity, the number of model parameters and the required observation data to better define the model. The model results also highlighted that simulating only phytoplankton is insufficient in river systems, because the majority of the suspended algae have benthic origin in short retention time rivers. Therefore, there is a need for modelling tools that link the benthic and free-floating habitats

Measurements and comparison of primary biological aerosol above and below a tropical forest canopy using a dual channel fluorescence spectrometer

Original article can be found at: http://www.atmos-chem-phys.net/10/issue10.html Copyright - the authors. Authors grant any third party the right to use the article freely as long as its original authors and citation details are identified. The article and any associated published material is distributed under the Creative Commons Attribution 3.0 License.Aerosol particle size distributions were measured below and above a tropical rainforest canopy in Borneo, Malaysia, in June/July 2008 using the WIBS-3: a single particle dual channel fluorescence spectrometer. Material in the size range 0.8–20 μm was characterized according to optical equivalent diameter (DP), morphology and fluorescence at 310–400 nm and 400–600 nm following excitation at 280 nm and 370 nm respectively. Particles fluorescent after both excitations are likely to be fluorescent primary biological aerosol particles (FBAP). Measured FBAP number concentration (NFBAP) at both sites exhibited clear diurnal cycles. The largest variability was observed in the understorey, where NFBAP reached a minimum of 50–100 L−1 in late morning. In mid afternoon it exhibited strong transient fluctuations as large as 4000 L−1 that were followed by sustained concentrations of 1000–2500 L−1 that reduced steadily between midnight and sunrise. Above the canopy FBAP number ranged from 50–100 L−1 during the daytime to 200–400 L−1 at night but did not exhibit the transient enhancements seen in the understorey. The strong FBAP fluctuations were attributed to the release of fungal spores below the canopy and appeared to be linked to elevated relative humidity. The mean FBAP number fraction in the size range 0.8 μm<DP<20 μm was 55% in the understorey and 28% above canopy. A size mode at 2 μm<DP<4 μm appears at both sites and is primarily FBAP, which dominated the coarse (DP≥2.5 μm) number concentration at both sites, accounting for 75% in the understorey and 57% above the canopy. In contrast, the concentration of non-fluorescent particles (NNON) at both sites was typically 200–500 L−1, the majority of which occupied a size mode at 0.8<DP<1.5 μm. Enhanced understorey NNON was observed daily in mid-afternoon and also at midday on three occasions: the former coincided with the FBAP enhancements and measured approximately 10% of their magnitude; the latter occurred independently of the NFBAP diurnal cycle and comprised particles smaller than 2 μm. Particle diameter of 3–5 μm is consistent with smaller fungal spores, though absolute identification of biological species is not possible with the UV-LIF technique. Based on the measured FBAP and non-fluorescent particle abundances and their observed recovery times following rain showers, FBAP originated beneath the canopy while the non-fluorescent material was transported from further away. It is concluded that these separate sources contributed the majority of the aerosol measured by the WIBS-3 at both sites.Peer reviewe

Using historical lesion volume data in the design of a new phase II clinical trial in acute stroke

&lt;p&gt;&lt;b&gt;Background and Purpose:&lt;/b&gt; Clinical research into the treatment of acute stroke is complicated, is costly, and has often been unsuccessful. Developments in imaging technology based on computed tomography and magnetic resonance imaging scans offer opportunities for screening experimental therapies during phase II testing so as to deliver only the most promising interventions to phase III. We discuss the design and the appropriate sample size for phase II studies in stroke based on lesion volume.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methods:&lt;/b&gt; Determination of the relation between analyses of lesion volumes and of neurologic outcomes is illustrated using data from placebo trial patients from the Virtual International Stroke Trials Archive. The size of an effect on lesion volume that would lead to a clinically relevant treatment effect in terms of a measure, such as modified Rankin score (mRS), is found. The sample size to detect that magnitude of effect on lesion volume is then calculated. Simulation is used to evaluate different criteria for proceeding from phase II to phase III.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Results:&lt;/b&gt; The odds ratios for mRS correspond roughly to the square root of odds ratios for lesion volume, implying that for equivalent power specifications, sample sizes based on lesion volumes should be about one fourth of those based on mRS. Relaxation of power requirements, appropriate for phase II, lead to further sample size reductions. For example, a phase III trial comparing a novel treatment with placebo with a total sample size of 1518 patients might be motivated from a phase II trial of 126 patients comparing the same 2 treatment arms.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Discussion:&lt;/b&gt; Definitive phase III trials in stroke should aim to demonstrate significant effects of treatment on clinical outcomes. However, more direct outcomes such as lesion volume can be useful in phase II for determining whether such phase III trials should be undertaken in the first place.&lt;/p&gt

The electronic structure and localized molecular orbitals in S<SUB>4</SUB>N<SUB>4</SUB> by the CNDO/BW theory

The energies calculated for tetranitrogen tetrasulfide, S4N4, by the CNDO/BW theory favor a structure with coplanar nitrogen atoms and not a structure with coplanar sulfur atoms. Both structures have been proposed from experimental studies. Localized molecular orbitals are calculated for S4N4 and used to choose the appropriate Lewis structure for the molecule. The hybridization at the nitrogen and sulfur atoms is discussed. There is electron delocalization in the molecule, the S-N bond is a bent bond involving pure p-orbitals on the sulfur and nitrogen atoms and there is a pure p-bent bond between the sulfur atoms on the same side of the coplanar nitrogen atoms. There is no N-N bond in S4N4

Polycyclic aromatic hydrocarbons in residential dust: sources of variability.

BackgroundThere is interest in using residential dust to estimate human exposure to environmental contaminants.ObjectivesWe aimed to characterize the sources of variability for polycyclic aromatic hydrocarbons (PAHs) in residential dust and provide guidance for investigators who plan to use residential dust to assess exposure to PAHs.MethodsWe collected repeat dust samples from 293 households in the Northern California Childhood Leukemia Study during two sampling rounds (from 2001 through 2007 and during 2010) using household vacuum cleaners, and measured 12 PAHs using gas chromatography-mass spectrometry. We used a random- and a mixed-effects model for each PAH to apportion observed variance into four components and to identify sources of variability.ResultsMedian concentrations for individual PAHs ranged from 10 to 190 ng/g of dust. For each PAH, total variance was apportioned into regional variability (1-9%), intraregional between-household variability (24-48%), within-household variability over time (41-57%), and within-sample analytical variability (2-33%). Regional differences in PAH dust levels were associated with estimated ambient air concentrations of PAH. Intraregional differences between households were associated with the residential construction date and the smoking habits of residents. For some PAHs, a decreasing time trend explained a modest fraction of the within-household variability; however, most of the within-household variability was unaccounted for by our mixed-effects models. Within-household differences between sampling rounds were largest when the interval between dust sample collections was at least 6 years in duration.ConclusionsOur findings indicate that it may be feasible to use residential dust for retrospective assessment of PAH exposures in studies of health effects

One-Centre-Expansion Self-Consistent-Field Calculations on HCl. Part I.

The 71-or.bital OCE-SCF calculation re.ported by Moccia8 has been repeated with electron repulsion integrals stored to greater precision: for the energy, effective field gradient, viirial theorem, dipole moment, molecrular quadrupole moment etc. the results are considerably altered and generally improved. A series of OCE bases for HCl has been constructed by adding STO\u27s to a basis proposed by Gilbert and Wahl for Cl2 33 • In ithe largest basis, 29-orbitals, the total energy -460.068938 au art the equilibrium internuclear distance is lower than that in the 71- -orbital basis, -460.052595 au. The two bases are compared with experiment and with the results from Two-Centre-Expansion theory, in order to assess their relative validity and usefulness

One-Centre-Expansion Self-Consistent-Field Calculations on HCl. Part I.

The 71-or.bital OCE-SCF calculation re.ported by Moccia8 has been repeated with electron repulsion integrals stored to greater precision: for the energy, effective field gradient, viirial theorem, dipole moment, molecrular quadrupole moment etc. the results are considerably altered and generally improved. A series of OCE bases for HCl has been constructed by adding STO\u27s to a basis proposed by Gilbert and Wahl for Cl2 33 • In ithe largest basis, 29-orbitals, the total energy -460.068938 au art the equilibrium internuclear distance is lower than that in the 71- -orbital basis, -460.052595 au. The two bases are compared with experiment and with the results from Two-Centre-Expansion theory, in order to assess their relative validity and usefulness