PtRu/Ti anodes with varying Pt:Ru ratio prepared by electrodeposition for the direct methanol fuel cell

PtRu/Ti anodes with varying Pt : Ru ratio were prepared by electrodeposition of a thin PtRu catalyst layer onto Ti mesh for a direct methanol fuel cell (DMFC). The morphology and structure of the catalyst layers were analyzed by SEM, EDX and XRD. The catalyst coating layer shows an alloy character. The relative activities of the PtRu/Ti electrodes were assessed and compared in half cell and single DMFC experiments. The results show that these electrodes are very active for the methanol oxidation and that the optimum Ru surface coverage was ca. 9 at.% for DMFC operating at 20°C and 11 at.% at 60°C. The PtRu/Ti anode shows a performance comparable to that of the conventional carbon-based anode in a DMFC operating with 0.25 M or 0.5 M methanol solution and atmosphere oxygen gas at 90°C. © the Owner Societies 2006.

Determination of geographical origin of distillers dried grains and solubles using isotope ratio mass spectrometry

In recent years distillers dried grains and solubles (DDGS), co-products of the bio-ethanol and beverages industries, have become globally traded commodity for the animal feed sector. As such it is becoming increasingly important to be able to trace the geographical origin of commodities in case of a contamination incident or authenticity issue arise. In this study, 137 DDGS samples from a range of different geographical origins (China, USA, Canada and European Union) were collected and analyzed. Isotope ratio mass spectrometry (IRMS) was used to analyze the DDGS for ²H/¹H, ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O and ³⁴S/³²S isotope ratios which can vary depending on geographical origin and processing. Univariate and multivariate statistical techniques were employed to investigate the feasibility of using the IRMS data to determine botanical and geographical origin of the DDGS. The results indicated that this commodity could be differentiated according to their place of origin by the analysis of stable isotopes of hydrogen, carbon, nitrogen and oxygen but not with sulfur. By adding data to the models produced in this study, potentially an isotope databank could be set up for traceability procedures for DDGS, similar to the one established already for wine which will help in feed and food security issues arising worldwide.

The effect of variability in the powder/liquid ratio on the strength of zinc phosphate cement

Aim. To investigate (a) variability in powder/liquid proportioning and (b) effect of variability on diametral tensile strength (DTS), in a zinc phosphate cement. Statistical analyses (α = 0.05) were by Student's t-test in the case of powder/liquid ratio and one-way ANOVA and Tukey HSD for pair-wise comparisons of mean DTS. The Null hypotheses were that (a) the powder-liquid mixing ratios would not differ from the manufacturer's recommended ratio (b) DTS of the set cement samples using the extreme powder/liquid ratios would not differ from those made using the recommended ratio. 

Methodology. 34 dental students dispensed the components according to the manufacturer's instructions. The maximum and minimum powder/liquid ratios, together with the manufacturer's recommended ratio, were used to prepare samples for DTS testing. 

Results. Powder/liquid ratios ranged from 2.386 to 1.018. The mean ratio (1.644) was not significantly different from the recommended value of 1.718 (P = 0.189). DTS values for the maximum and minimum ratios were both significantly different from each other (P < 0.001) and from the mean value obtained from the recommended ratio (P < 0.001). 

Conclusions. Variability exists in powder/liquid ratio for hand dispensed zinc phosphate cement. This variability can affect the DTS of the set material.

Determinants and heritability of intraocular pressure and cup-to-disc ratio in a defined older population.

PURPOSE:

To investigate the heritability of intraocular pressure (IOP) and cup-to-disc ratio (CDR) in an older well-defined population.

DESIGN:

Family-based cohort study.

PARTICIPANTS:

Through the population-based Salisbury Eye Evaluation study, we recruited 726 siblings (mean age, 74.7 years) in 284 sibships.

METHODS:

Intraocular pressure and CDR were measured bilaterally for all participants. The presence or absence of glaucoma was determined by a glaucoma specialist for all probands on the basis of visual field, optic nerve appearance, and history. The heritability of IOP was calculated as twice the residual between-sibling correlation of IOP using linear regression and generalized estimating equations after adjusting for age, gender, mean arterial pressure, race, self-reported diabetes status, and history of systemic steroid use. The heritability of CDR was calculated using the same model and adjustments as above, while also adjusting for IOP.

MAIN OUTCOME MEASURES:

Heritability and determinants of IOP and CDR, and impact of siblings' glaucoma status on IOP and CDR.

RESULTS:

We estimated the heritability to be 0.29 (95% confidence interval [CI], 0.12-0.46) for IOP and 0.56 (95% CI, 0.35-0.76) for CDR in this population. Mean IOP in siblings of glaucomatous probands was statistically significantly higher than in siblings of normal probands (mean difference, 1.02 mmHg; P = 0.017). The mean CDR in siblings of glaucomatous probands was 0.07 (or 19%) larger than in siblings of glaucoma suspect referrals (P = 0.045) and siblings of normal probands (P = 0.004).

CONCLUSIONS:

In this elderly population, we found CDR to be highly heritable and IOP to be moderately heritable. On average, siblings of glaucoma patients had higher IOPs and larger CDRs than siblings of nonglaucomatous probands.

Spatial variation in adult sex ratio across multiple scales in the invasive golden apple snail, Pomacea canaliculata

Adult sex ratio (ASR) has critical effects on behavior and life history and has implications for population demography, including the invasiveness of introduced species. ASR exhibits immense variation in nature, yet the scale dependence of this variation is rarely analyzed. In this study, using the generalized multilevel models, we investigated the variation in ASR across multiple nested spatial scales and analyzed the underlying causes for an invasive species, the golden apple snail Pomacea canaliculata. We partitioned the variance in ASR to describe the variations at different scales and then included the explanatory variables at the individual and group levels to analyze the potential causes driving the variation in ASR. We firstly determined there is a significant female-biased ASR for this species when accounting for the spatial and temporal autocorrelations of sampling. We found that, counter to nearly equal distributed variation at plot, habitat and region levels, ASR showed little variation at the town level. Temperature and precipitation at the region level were significantly positively associated with ASR, whereas the individual weight, the density characteristic, and sampling time were not significant factors influencing ASR. Our study suggests that offspring sex ratio of this species may shape the general pattern of ASR in the population level while the environmental variables at the region level translate the unbiased offspring sex ratio to the female-biased ASR. Future research should consider the implications of climate warming on the female-biased ASR of this invasive species and thus on invasion pattern.

Non-equilibrium modeling of the FE XVII 3C/3D Line Ratio in an Intense X-ray Free-electron Laser Excited Plasma

Recent measurements using an X-ray Free Electron Laser (XFEL) and an Electron Beam Ion Trap at the Linac Coherent Light Source facility highlighted large discrepancies between the observed and theoretical values for the Fe XVII 3C/3D line intensity ratio. This result raised the question of whether the theoretical oscillator strengths may be significantly in error, due to insufficiencies in the atomic structure calculations. We present time-dependent spectral modeling of this experiment and show that non-equilibrium effects can dramatically reduce the predicted 3C/3D line intensity ratio, compared with that obtained by simply taking the ratio of oscillator strengths. Once these non-equilibrium effects are accounted for, the measured line intensity ratio can be used to determine a revised value for the 3C/3D oscillator strength ratio, giving a range from 3.0 to 3.5. We also provide a framework to narrow this range further, if more precise information about the pulse parameters can be determined. We discuss the implications of the new results for the use of Fe XVII spectral features as astrophysical diagnostics and investigate the importance of time-dependent effects in interpreting XFEL-excited plasmas.

Line ratio diagnostics in helium and helium seeded argon plasmas

We investigate the potential use of line ratio diagnostics to evaluate electron temperature in either helium or helium seeded argon plasmas. Plasmas are produced in a helicon plasma source. A rf compensated Langmuir probe is used to measure both the electron temperature and plasma density while a spectrometer is used to measure He I line intensities from the plasma. For all plasma densities where the electron temperature remains at 5 ± 1 eV, three He line ratios are measured. Each experimental ratio is compared with the prediction of three different collisional radiative models. One of these models makes uses of recent R-matrix with pseudo-states calculations for collisional rate coefficients. A discussion related to the different observations and model predictions is presented.

Implementation of a new atomic basis for the He i equilibrium line ratio technique for electron temperature and density diagnostic in the SOL for H-mode plasmas in DIII-D

Evaluating the ratio of selected helium lines allows for measurement of electron densities and temperatures. This technique is applied for L-mode plasmas at TEXTOR (O. Schmitz et al., Plasma Phys. Control. Fusion 50 (2008) 115004). We report our first efforts to extend it to H-mode plasma diagnostics in DIII-D. This technique depends on the accuracy of the atomic data used in the collisional radiative model (CRM). We present predictions for the electron temperatures and densities by using recently calculated R-Matrix With Pseudostates (RMPS) and Convergent Close-Coupling (CCC) electron-impact excitation and ionization data. We include contributions from higher Rydberg states by means of the projection matrix. These effects become significant for high electron density conditions, which are typical in H-mode. We apply a non-equilibrium model for the time propagation of the ionization balance to predict line emission profiles from experimental H-mode data from DIII-D. © 2010 Elsevier B.V. All rights reserved.

Hybrid time dependent/independent solution for the He i line ratio temperature and density diagnostic for a thermal helium beam with applications in the scrape-off layer-edge regions in tokamaks

Spectroscopic studies of line emission intensities and ratios offer an attractive option in the\r\ndevelopment of non-invasive plasma diagnostics. Evaluating ratios of selected He I line\r\nemission profiles from the singlet and triplet neutral helium spin systems allows for simultaneous\r\nmeasurement of electron density (ne) and temperature (Te) profiles. Typically, this powerful\r\ndiagnostic tool is limited by the relatively long relaxation times of the 3S metastable term of helium\r\nthat populates the triplet spin system, and on which electron temperature sensitive lines are based.\r\nBy developing a time dependent analytical solution, we model the time evolution of the two spin\r\nsystems. We present a hybrid time dependent/independent line ratio solution that improves the\r\nrange of application of this diagnostic technique in the scrape-off layer (SOL) and edge plasma\r\nregions when comparing it against the current equilibrium line ratio helium model used at\r\nTEXTOR.

Helium line intensity ratio in microwave-generated plasmas

The line intensity ratio method provides a nonintrusive diagnostic for the measurement of electron temperature in microwave-generated plasmas. For optically thin plasmas of low density, a line intensity method using He I lines can often be used, and is based on the fact that the electron impact excitation rate coefficients for helium singlet and triplet states are insensitive to electron density but differ as a function of the electron temperature. Line intensity measurements are presented from microwave-generated helium plasmas. Both steady-state corona and collision-radiative theoretical models are used to evaluate the ground and excited state populations. The line ratio versus electron temperature obtained from both of these methods are compared with the results from measurements. However, it is not possible to diagnose the electron temperature from the line ratios alone due to the presence of significant opacity and nonnegligible 1s2s S-3 metastable fraction in the plasma. (C) 2004 American Institute of Physics.

Conflit sexuel et polyandrie de la commodité chez une espèce polygynandre: les effets combinés des processus pré- et post- copulatoires sur le succès reproducteur de "Gerris buenoi"

Chez les patineurs, des processus postcopulatoires sont documentés et un conflit sexuel sur le taux d’accouplement est démontré. Cependant, leurs effets combinés sur le succès reproducteur ont rarement été investigués. Cette étude joint une analyse de filiation génétique à des observations comportementales pour évaluer l’effet des processus pré- et post- copulatoires sur le succès reproducteur de Gerris buenoi. Nos résultats montrent la nature antagoniste des combats précopulatoires et un niveau de résistance optimal intermédiaire pour les femelles. Cependant, le taux d’accouplement n’a eu aucune influence sur le succès reproducteur des deux sexes. Un taux d’accouplement élevé permettant à des processus postcopulatoires de se mettre en place ainsi que plusieurs copulations superflues ont vraisemblablement masqué les effets attendus du taux d’accouplement. Notre étude confirme l’idée que des précisions peuvent être apportées sur les forces de sélection sexuelle en jeu lorsque l’on considère tous les épisodes d’un cycle d’accouplement chez les animaux polygynandres.