Objective determination of feature resolution in two sea surface temperature analyses

Considerable effort is presently being devoted to producing high-resolution sea surface temperature (SST) analyses with a goal of spatial grid resolutions as low as 1 km. Because grid resolution is not the same as feature resolution, a method is needed to objectively determine the resolution capability and accuracy of SST analysis products. Ocean model SST fields are used in this study as simulated “true” SST data and subsampled based on actual infrared and microwave satellite data coverage. The subsampled data are used to simulate sampling errors due to missing data. Two different SST analyses are considered and run using both the full and the subsampled model SST fields, with and without additional noise. The results are compared as a function of spatial scales of variability using wavenumber auto- and cross-spectral analysis. The spectral variance at high wavenumbers (smallest wavelengths) is shown to be attenuated relative to the true SST because of smoothing that is inherent to both analysis procedures. Comparisons of the two analyses (both having grid sizes of roughly ) show important differences. One analysis tends to reproduce small-scale features more accurately when the high-resolution data coverage is good but produces more spurious small-scale noise when the high-resolution data coverage is poor. Analysis procedures can thus generate small-scale features with and without data, but the small-scale features in an SST analysis may be just noise when high-resolution data are sparse. Users must therefore be skeptical of high-resolution SST products, especially in regions where high-resolution (~5 km) infrared satellite data are limited because of cloud cover.

Automated determination of auroral breakup during the substorm expansion phase using all sky imager data

This technique paper describes a novel method for quantitatively and routinely identifying auroral breakup following substorm onset using the Time History of Events and Macroscale Interactions During Substorms (THEMIS) all-sky imagers (ASIs). Substorm onset is characterised by a brightening of the aurora that is followed by auroral poleward expansion and auroral breakup. This breakup can be identified by a sharp increase in the auroral intensity i(t) and the time derivative of auroral intensity i'(t). Utilising both i(t) and i'(t) we have developed an algorithm for identifying the time interval and spatial location of auroral breakup during the substorm expansion phase within the field of view of ASI data based solely on quantifiable characteristics of the optical auroral emissions. We compare the time interval determined by the algorithm to independently identified auroral onset times from three previously published studies. In each case the time interval determined by the algorithm is within error of the onset independently identified by the prior studies. We further show the utility of the algorithm by comparing the breakup intervals determined using the automated algorithm to an independent list of substorm onset times. We demonstrate that up to 50% of the breakup intervals characterised by the algorithm are within the uncertainty of the times identified in the independent list. The quantitative description and routine identification of an interval of auroral brightening during the substorm expansion phase provides a foundation for unbiased statistical analysis of the aurora to probe the physics of the auroral substorm as a new scientific tool for aiding the identification of the processes leading to auroral substorm onset.

Dayside ionospheric convection changes in response to long-period interplanetary Magnetic field oscillations: Determination of the ionospheric phase velocity

Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-hour interval in question IMF Bz oscillates between ±7 nT with about a 1-hour period. Corresponding variations in the ground magnetic disturbance are observed which we infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5° magnetic latitude, but separated by ∼2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector (∼10 MLT) and then spread outward toward dawn and dusk with a phase speed of ∼5 km s−1 over the longitude range ∼8 to 12 MLT, slowing to ∼2 km s−1 outside this range. Cross correlating the data from these ground stations with IMP 8 IMF Bz records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds. We interpret these observations in terms of the ionospheric response to the onset, expansion and decay of magnetic reconnection at the dayside magnetopause.

On the determination of ion temperature in the auroral F-region ionosphere

Assessment is made of the effect of the assumed form for the ion velocity distribution function on estimates of three-dimensional ion temperature from one-dimensional observations. Incoherent scatter observations by the EISCAT radar at a variety of aspect angles are used to demonstrate features of ion temperature determination and to study the ion velocity distribution function. One form of the distribution function which has recently been widely used In the interpretation of EISCAT measurements, is found to be consistent with the data presented here, in that no deviation from a Maxwellian can be detected for observations along the magnetic field line and that the ion temperature and its anisotropy are accurately predicted. It is shown that theoretical predictions of the anisotropy by Monte Carlo computations are very accurate, the observed value being greater by only a few percent. It is also demonstrated for the case studied that errors of up to 93% are introduced into the ion temperature estimate if the anisotropy is neglected. Observations at an aspect angle of 54.7°, which are not subject to this error, have a much smaller uncertainty (less than 1%) due to the adopted form of the distribution of line-of-sight velocity.

Determination of the absolute accuracy of UK chamber facilities used in measuring methane emissions from livestock

Respiration chambers are one of the primary sources of data on methane emissions from livestock. This paper describes the results from a coordinated set of chamber validation experiments which establishes the absolute accuracy of the methane emission rates measured by the chambers, and for the first time provides metrological traceability to international standards, assesses the impact of both analyser and chamber response times on measurement uncertainty and establishes direct comparability between measurements made across different facilities with a wide range of chamber designs. As a result of the validation exercise the estimated combined uncertainty associated with the overall capability across all facilities reduced from 25.7% (k = 2, 95% confidence) before the validation to 2.1% (k = 2, 95% confidence) when the validation results are applied to the facilities’ data.

Determination of the embedded thermo-optical expansion coefficients of PbTe and ZnSe thin film infrared multilayers

This paper reports the first derived thermo-optical properties for vacuum deposited infrared thin films embedded in multilayers. These properties were extracted from the temperature-dependence of manufactured narrow bandpass filters across the 4-17 µm mid-infrared wavelength region. Using a repository of spaceflight multi-cavity bandpass filters, the thermo-optical expansion coefficients of PbTe and ZnSe were determined across an elevated temperature range 20-160 ºC. Embedded ZnSe films showed thermo-optical properties similar to reported bulk values, whilst the embedded PbTe films of lower optical density, deviate from reference literature sources. Detailed knowledge of derived coefficients is essential to the multilayer design of temperature-invariant narrow bandpass filters for use in non-cooled infrared detection systems. We further present manufacture of the first reported temperature-invariant multi-cavity narrow bandpass filter utilizing PbS chalcogenide layer material.

Towards a unified approach for the determination of the bioaccessibility of organic pollutants

Bioaccessibility studies have been widely used as a research tool to determine the potential human exposure to ingested contaminants. More recently they have been practically applied for soil borne toxic elements. This paper reviews the application of bioaccessibility tests across a range of organic pollutants and contaminated matrices. Important factors are reported to be: the physiological relevance of the test, the components in the gut media, the size fraction chosen for the test and whether it contains a sorptive sink. The bioaccessibility is also a function of the composition of the matrix (e.g. organic carbon content of soils) and the physico-chemical characteristics of the pollutant under test. Despite the widespread use of these tests, there are a large number of formats used and very few validation studies with animal models. We propose a unified format for a bioaccessibility test for organic pollutants. The robustness of this test should first be confirmed through inter laboratory comparison, then tested in-vivo.

Suitability of bronopol preservative treated milk for fatty acid determination

This work aimed to test if milk preserved with bronopol can be reliably used for fatty acid determination. Dairy production and milk quality are often monitored regularly to assess performance and contribute to selection indices. With evidence that fat composition can be influenced by selective breeding, there might be an interest in using samples collected in routine testing to evaluate individual cow fatty acid profiles, contributing to breeding indices. However, most recording services use a preservative such as bronopol and there is no published record if this influences subsequent fatty acid analysis. This study used milk from an oil seed supplementation trial, generating a wide range of milk fatty acid profiles, to test if the concentration of 31 individual fatty acids determined by GC were influenced by bronopol. Provided preserved samples are subsequently frozen, milk treated with bronopol can reliably be used to evaluate fatty acid composition in most cases; however bronopol might influence a few long-chain fatty acids present in relatively low concentrations. This is one small step towards simplifying milk compositional analysis but it could ultimately streamline the inclusion of milk fat quality into breeding indices, either with a view to 'healthier' milk or potentially reducing methane output and the environmental impact of dairy production.

Objective determination of the extratropical transition of tropical cyclones in the Northern Hemisphere

Extratropical transition (ET) has eluded objective identification since the realisation of its existence in the 1970s. Recent advances in numerical, computational models have provided data of higher resolution than previously available. In conjunction with this, an objective characterisation of the structure of a storm has now become widely accepted in the literature. Here we present a method of combining these two advances to provide an objective method for defining ET. The approach involves applying K-means clustering to isolate different life-cycle stages of cyclones and then analysing the progression through these stages. This methodology is then tested by applying it to five recent years from the European Centre of Medium-Range Weather Forecasting operational analyses. It is found that this method is able to determine the general characteristics for ET in the Northern Hemisphere. Between 2008 and 2012, 54% (±7, 32 of 59) of Northern Hemisphere tropical storms are estimated to undergo ET. There is great variability across basins and time of year. To fully capture all the instances of ET is necessary to introduce and characterise multiple pathways through transition. Only one of the three transition types needed has been previously well-studied. A brief description of the alternate types of transitions is given, along with illustrative storms, to assist with further study

Ex vivo evaluation of the accuracy of two electronic apex locators during root canal length determination in primary teeth

Aim To evaluate ex vivo the accuracy of two electronic apex locators during root canal length determination in primary incisor and molar teeth with different stages of physiological root resorption. Methodology One calibrated examiner determined the root canal length in 17 primary incisors and 16 primary molars (total of 57 root canals) with different stages of root resorption based on the actual canal length and using two electronic apex locators. Root canal length was measured both visually, with the placement of a K-file 1 mm short of the apical foramen or the apical resorption bevel, and electronically using two electronic apex locators (Root ZX II - J. Morita Corp. and Mini Apex Locator - SybronEndo) according to the manufacturers` instructions. Data were analysed statistically using the intraclass correlation (ICC) test. Results Comparison of the actual root canal length and the electronic root canal length measurements revealed high correlation (ICC = 0.99), regardless of the tooth type (single-rooted and multi-rooted teeth) or the presence/absence of physiological root resorption. Conclusions Root ZX II and Mini Apex Locator proved useful and accurate for apex foramen location during root canal length measurement in primary incisors and molars.

Electronic working length determination in primary teeth by Propex and Digital Signal Processing

The purpose of this study was to evaluate the accuracy of electronic apex locators Digital Signal Processing (DSP) and ProPex, for root canal length determination in primary teeth. Fifteen primary molars (a total of 34 root canals) were divided into two groups: Group I - without physiological resorption (n = 16); and Group II - with physiological resorption (n = 18). The length of each canal was measured by introducing a file until its tip was visible and then it was retracted 1 mm. For electronic measurement, the devices were set to 1 mm short of the apical resorption. The data were analysed statistically using the intraclass correlation coefficient (ICC). Results showed that the ICC was high for both electronic apex locators in all situations - with (ICC: DSP = 0.82 and Propex = 0.89) or without resorption (ICC: DSP = 0.92 and Propex = 0.90). Both apex locators were extremely accurate in determining the working length in primary teeth, both with or without physiological resorption.

Determination of volatile organic compounds in recycled polyethylene terephthalate and high-density polyethylene by headspace solid phase microextraction gas chromatography mass spectrometry to evaluate the efficiency of recycling processes

A method for the determination of volatile organic compounds (VOCs) in recycled polyethylene terephthalate and high-density polyethylene using headspace sampling by solid-phase microextraction and gas chromatography coupled to mass spectrometry detection is presented. This method was used to evaluate the efficiency of cleaning processes for VOC removal from recycled PET. In addition, the method was also employed to evaluate the level of VOC contamination in multilayer packaging material containing recycled HDPE material. The optimisation of the extraction procedure for volatile compounds was performed and the best extraction conditions were found using a 75 mu m carboxen-polydimethylsiloxane (CAR-PDMS) fibre for 20 min at 60 degrees C. The validation parameters for the established method were linear range, linearity, sensitivity, precision (repeatability), accuracy (recovery) and detection and quantification limits. The results indicated that the method could easily be used in quality control for the production of recycled PET and HDPE. (C) 2011 Elsevier B.V. All rights reserved.

Pozzolanic behavior of bamboo leaf ash: Characterization and determination of the kinetic parameters

The paper presents a characterization and study of the pozzolanic behavior between calcium hydroxide (CH) and bamboo leaf ash (BLAsh), which was obtained by calcining bamboo leaves at 600 degrees C for 2 h in a laboratory electric furnace. To evaluate the pozzolanic behavior the conductometric method was used, which is based on the measurement of the electrical conductivity in a BLAsh/CH solution with the reaction time. Later, the kinetic parameters are quantified by applying a kinetic-diffusive model. The kinetic parameters that characterize the process (in particular, the reaction rate constant and free energy of activation) were determined with relative accuracy in the fitting process of the model. The pozzolanic activity is quantitatively evaluated according to the values obtained of the kinetic parameters. Other experimental techniques, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), were also employed. The results show that this kind of ash is formed by silica with a completely amorphous nature and a high pozzolanic activity. The correlation between the values of free energy of activation (Delta G(#)) and the reaction rate constants (K) are in correspondence with the theoretical studies about the rate processes reported in the literature. (C) 2010 Elsevier Ltd. All rights reserved.

Reactive oxygen and nitrogen species balance in the determination of thyroid hormones-induced cardiac hypertrophy mediated by renin-angiotensin system

Role of reactive oxygen species (ROS)/nitric oxide (NO) balance and renin-angiotensin system in mediating cardiac hypertrophy in hyperthyroidism was evaluated in an in vivo and in vitro experimental model. Male Wistar rats were divided into four groups: control, thyroid hormone, vitamin E (or Trolox, its hydrosoluble analogue), thyroid hormone + vitamin E. Angiotensin II receptor (AT1/AT2) gene expression, immunocontent of AT1/AT2 receptors, angiotensinogen, NADPH oxidase (Nox2), and nitric oxide synthase isoforms, as well as ROS concentration (hydrogen peroxide and superoxide anion) were quantified in myocardium. Thyroid hormone increased ROS and NO metabolites, iNOS, nNOS and eNOS isoforms and it was accompanied by cardiac hypertrophy. AT1/AT2 expression and the immunocontent of angiotensinogen and Nox2 were enhanced by thyroid hormone. Antioxidants reduced ROS levels, Nox2, AT1/AT2, NOS isoforms and cardiac hypertrophy. In conclusion, ROS/NO balance may play a role in the control of thyroid hormone-induced cardiac hypertrophy mediated by renin-angiotensin system. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Determination of dental decay rates with optical coherence tomography

We report the use of optical coherence tomography (OCT) to detect and quantify demineralization process induced by S. mutans biofilm in third molars human teeth. Artificial lesions were induced by a S. mutans microbiological culture and the samples (N = 50) were divided into groups according to the demineralization time: 3, 5, 7, 9, and 11days. The OCT system was implemented using a light source delivering an average power of 96 mu W in the sample arm, and spectral characteristics allowing 23 mu m of axial resolution. The images were produced with lateral scans step of 10 pan and analyzed individually. As a result of the evaluation of theses images, lesion depth was calculated as function of demineralization time. The depth of the lesion in the root dentine increased from 70 pm to 230,urn (corrected by the enamel refraction index, 1.62 @ 856 nm), depending of exposure time. The lesion depth in root dentine was correlated to demineralization time, showing that it follows a geometrical progression like a bacteria growth law. [GRAPHICS] Progression of lesion depth in root dentine as function of exposure time, showing that it follows a geometrical progression like a bacteria growth law(C) 2009 by Astro Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA