Self-consistent Data Research Articles

ASTROMETRIC MONITORING OF THE HR 8799 PLANETS: ORBIT CONSTRAINTS FROM SELF-CONSISTENT MEASUREMENTS

ABSTRACT We present new astrometric measurements from our ongoing monitoring campaign of the HR 8799 directly imaged planetary system. These new data points were obtained with NIRC2 on the W.M. Keck II 10 m telescope between 2009 and 2014. In addition, we present updated astrometry from previously published observations in 2007 and 2008. All data were reduced using the SOSIE algorithm, which accounts for systematic biases present in previously published observations. This allows us to construct a self-consistent data set derived entirely from NIRC2 data alone. From this data set, we detect acceleration for two of the planets (HR 8799b and e) at >3σ. We also assess possible orbital parameters for each of the four planets independently. We find no statistically significant difference in the allowed inclinations of the planets. Fitting the astrometry while forcing coplanarity also returns χ 2 consistent to within 1σ of the best fit values, suggesting that if inclination offsets of ≲20° are present, they are not detectable with current data. Our orbital fits also favor low eccentricities, consistent with predictions from dynamical modeling. We also find period distributions consistent to within 1σ with a 1:2:4:8 resonance between all planets. This analysis demonstrates the importance of minimizing astrometric systematics when fitting for solutions to highly undersampled orbits.

Thermodynamic description of the Ni–Yb and Ni–Eu binary systems

Thermodynamic descriptions of the Ni–Yb and Ni–Eu binary systems have been performed by means of the CALculation of PHAse Diagrams approach on the basis of the experimental data including the phase equilibria and thermodynamic properties. The Gibbs free energies of the liquid and the terminal solid solutions (fcc_A1, bcc_A2 and hcp_A3) are described by the subregular solution model with the Redlich–Kister formalism, and those of the intermetallic compounds αNiYb=NiYb_LT, βNiYb=NiYb_HT, Ni2Yb, Ni3Yb, Ni5Yb and Nil7Yb2 in the Ni–Yb system and NiEu, Ni2Eu, Ni5Eu and Ni17Eu2 in the Ni–Eu system were described as strict stoichiometric compounds. As a result, two self-consistent thermodynamic data sets for describing the Ni–Yb and Ni–Eu binary systems have been obtained, and the calculated results show a satisfactory agreement with the corresponding experimental data.

Workshop 5 – Cross Section, Nuclear Data, and Uncertainties

The Cross Section, Nuclear Data, and Uncertainties Workshop met with 30 participants. There was a lively discussion that covered several different topics. Some of the topics had resonance with topics brought up in other workshop at this symposium. One major issue was how to assign an a priori uncertainty to the trial spectrum used in spectrum adjustment techniques, or, more specifically, the need for a more rigorous and automated coupling of uncertainties into the radiation transport codes that are used to generate the a priori (trial) spectrum that is used in neutron spectrum adjustment approaches. Approaches based on discrete ordinate transport provide a means of generating sensitivity coefficients for specific variations, but fall short of the required task. While some Monte Carlo-based radiation transport codes permit the user to vary the cross sections for specific reactions or to vary material densities, a more universal and automated variation of all relevant inputs to the radiation transport code is required. One approach mentioned was a Total Monte Carlo (TMC) approach provided by a coupling into radiation transport codes of the recently generated statistical sample of random ENDF nuclear data evaluations produced by the TALYS code and incorporated into the TENDL library (for some isotopes). This would provide a set of self-consistent nuclear data files that can be sampled in a transport calculation. This variation of nuclear data would need to be coupled with a variation in material composition, density, and spatial dimensions. Another discussion topic was the need for the community to revisit the consistency of current approaches to spectrum unfolds/adjustment, i.e. a new round of the older REAL-84 and REAL-88 exercises to assess our status. While the dosimetry community has made great strides with the IRDFF library in establishing an international community consensus for dosimetry cross sections and associated nuclear data, the differences within the community in the treatment of the uncertainty in the trial spectrum and the availability of new spectrum adjustment techniques, such as Maximum Entropy codes like MAXED and the use of genetic algorithms, warrant a revisit of these international exercises to assess the current consistency (within stated uncertainty bonds) of approaches within the community to the characterization of neutron spectra and towards expressing the uncertainty in integral metrics based on these spectrum uncertainties. Since the IAEA/NDS has done such a good job in coordinating an international consensus in dosimetry cross sections and nuclear data, and since they coordinated the older REAL-8X exercises, we look to them to coordinate a new international assessment of our consistency in treating spectrum adjustments and characterizing the resulting uncertainties.

Hybrid integral-differential simulator of EM force interactions/scenario-assessment tool with pre-computed influence matrix in applications to ITER

A necessity to address a wide spectrum of engineering problems in ITER determined the need for efficient tools for modeling of the magnetic environment and force interactions between the main components of the magnet system. The assessment of the operating window for the machine, determined by the electro-magnetic (EM) forces, and the check of feasibility of particular scenarios play an important role for ensuring the safety of exploitation. Such analysis-powered prevention of damages forms an element of the Machine Operations and Investment Protection strategy. The corresponding analysis is a necessary step in preparation of the commissioning, which finalizes the construction phase. It shall be supported by the development of the efficient and robust simulators and multi-physics/multi-system integration of models. The developed numerical model of interactions in the ITER magnetic system, based on the use of pre-computed influence matrices, facilitated immediate and complete assessment and systematic specification of EM loads on magnets in all foreseen operating regimes, their maximum values, envelopes and the most critical scenarios. The common principles of interaction in typical bilateral configurations have been generalized for asymmetry conditions, inspired by the plasma and by the hardware, including asymmetric plasma event and magnetic system fault cases. The specification of loads is supported by the technology of functional approximation of nodal and distributed data by continuous patterns/analytical interpolants. The global model of interactions together with the mesh-independent analytical format of output provides the source of self-consistent and transferable data on the spatial distribution of the system of forces for assessments of structural performance of the components, assemblies and supporting structures. The numerical model used is fully parametrized, which makes it very suitable for multi-variant and sensitivity studies (positioning, off-normal events, asymmetry, etc). The obtained results and matrices form a basis for a relatively simple and robust force processor as a specialized module of a global simulator for diagnostic, operational instrumentation, monitoring and control, as well as a scenario assessment tool. This paper gives an overview of the model, applied technique, assessed problems and obtained qualitative and quantitative results.

Turbulent Drag Reduction by Biopolymers in Large Scale Pipes

In this work, we describe drag reduction experiments performed in a large diameter pipe (i.d. 100 mm) using a semirigid biopolymer Xanthan Gum (XG). The objective is to build a self-consistent data base which can be used for validation purposes. To aim this, we ran a series of tests measuring friction factor at different XG concentrations (0.01, 0.05, 0.075, 0.1, and 0.2% w/w XG) and at different values of Reynolds number (from 758 to 297,000). For each concentration, we obtain also the rheological characterization of the test fluid. Our data is in excellent agreement with data collected in a different industrial scale test rig. The data is used to validate design equations available from the literature. Our data compare well with data gathered in small scale rigs and scaled up using empirically based design equations and with data collected for pipes having other than round cross section. Our data confirm the validity of a design equation inferred from direct numerical simulation (DNS) which was recently proposed to predict the friction factor. We show that scaling procedures based on this last equation can assist the design of piping systems in which polymer drag reduction can be exploited in a cost effective way.

An automated pipeline for constructing personalized virtual brains from multimodal neuroimaging data

Large amounts of multimodal neuroimaging data are acquired every year worldwide. In order to extract high-dimensional information for computational neuroscience applications standardized data fusion and efficient reduction into integrative data structures are required. Such self-consistent multimodal data sets can be used for computational brain modeling to constrain models with individual measurable features of the brain, such as done with The Virtual Brain (TVB). TVB is a simulation platform that uses empirical structural and functional data to build full brain models of individual humans. For convenient model construction, we developed a processing pipeline for structural, functional and diffusion-weighted magnetic resonance imaging (MRI) and optionally electroencephalography (EEG) data. The pipeline combines several state-of-the-art neuroinformatics tools to generate subject-specific cortical and subcortical parcellations, surface-tessellations, structural and functional connectomes, lead field matrices, electrical source activity estimates and region-wise aggregated blood oxygen level dependent (BOLD) functional MRI (fMRI) time-series. The output files of the pipeline can be directly uploaded to TVB to create and simulate individualized large-scale network models that incorporate intra- and intercortical interaction on the basis of cortical surface triangulations and white matter tractograpy. We detail the pitfalls of the individual processing streams and discuss ways of validation. With the pipeline we also introduce novel ways of estimating the transmission strengths of fiber tracts in whole-brain structural connectivity (SC) networks and compare the outcomes of different tractography or parcellation approaches. We tested the functionality of the pipeline on 50 multimodal data sets. In order to quantify the robustness of the connectome extraction part of the pipeline we computed several metrics that quantify its rescan reliability and compared them to other tractography approaches. Together with the pipeline we present several principles to guide future efforts to standardize brain model construction. The code of the pipeline and the fully processed data sets are made available to the public via The Virtual Brain website (thevirtualbrain.org) and via github (https://github.com/BrainModes/TVB-empirical-data-pipeline). Furthermore, the pipeline can be directly used with High Performance Computing (HPC) resources on the Neuroscience Gateway Portal (http://www.nsgportal.org) through a convenient web-interface.

Transmittance and optical constants of Ca films in the 4-1000 eV spectral range.

The low expected absorption of Ca in the extreme ultraviolet (EUV) makes it an attractive material for multilayers and filters because most materials in nature strongly absorb the EUV. Few optical constant data had been reported for Ca. In this research, Ca films of various thicknesses were deposited on grid-supported C films and their transmittance measured in situ from the visible to the soft x-rays. The measurement range contains M2,3 and L2,3 absorption edges. Transmittance measurements were used to obtain the Ca extinction coefficient k. A minimum k of 0.017 was obtained at ∼23 eV, which makes Ca a promising low-absorption material for EUV coatings. A second spectral range of interest for its low absorption is below the Ca L3 edge at ∼343 eV. Measured k data and extrapolations were used to calculate the refractive index n using Kramers-Krönig relations. This is the first self-consistent data set on Ca covering a wide spectral range including the EUV.

Temperature dependence of self-consistent full matrix material constants of lead zirconate titanate ceramics.

Up to date, there are no self-consistent data in the literature on the temperature dependence of full matrix material properties for piezoelectric materials because they are extremely difficult to determine. Using only one sample, we have measured the temperature dependence of full matrix constants of lead zirconate titanate (PZT-4) from room temperature to 120 °C by resonant ultrasound spectroscopy. Self-consistency is guaranteed here because all data at different temperatures come from one sample. Such temperature dependence data would make it a reality to accurately predict device performance at high temperatures using computer simulations.

Constructing subject-specific virtual brains from multimodal neuroimaging data

Event Abstract Back to Event Constructing subject-specific virtual brains from multimodal neuroimaging data Michael Schirner1, 2, Simon Rothmeier1, 2 and Petra Ritter1, 2* 1 Charité Berlin, Germany 2 Bernstein Center for Computational Neuroscience, Bernstein Focus State Dependencies of Learning, Germany Large amounts of multimodal neuroimaging data are acquired every year worldwide. In order to extract high dimensional information for computational neuroscience applications standardized data fusion and efficient reduction into integrative data structures are required. Such self-consistent multimodal data sets can be used for computational brain modeling to constrain models with individual measurable features of the brain, such as done with The Virtual Brain (TVB). TVB is a simulation platform that uses empirical structural and functional data to build full brain models of individual humans. For convenient model construction, we developed a shell scripted processing pipeline for structural, functional and diffusion-weighted magnetic resonance imaging (MRI) and optionally electroencephalography (EEG) data. The pipeline combines several state-of-the-art neuroinformatics tools to generate subject-specific cortical and subcortical parcellations, surface-tessellations, structural and functional connectomes, lead field matrices, electrical source activity estimates and region-wise aggregated blood oxygen level dependent (BOLD) functional MRI (fMRI) time-series. The output files of the pipeline can be directly uploaded to TVB to create and simulate individualized large-scale network models. We detail the pitfalls of the individual processing streams and discuss ways of validation. With the pipeline we also introduce novel ways of estimating the transmission strengths of fiber tracts in whole-brain structural connectivity (SC) networks and compare the outcomes of different tractography or parcellation approaches. We tested the functionality of the pipeline on 50 multimodal data sets. In order to quantify the robustness of the connectome extraction part of the pipeline we computed several metrics that quantify its rescan reliability and compared them to other tractography approaches. Together with the pipeline we present several principles to guide future efforts to standardize brain model construction. The code of the pipeline and the fully processed data sets are made available to the public via The Virtual Brain website (thevirtualbrain.org) and via Github (https://github.com/BrainModes/TVB-empirical-data-pipeline). Furthermore, the pipeline can be directly used with High Performance Computing (HPC) resources on the Neuroscience Gateway Portal (http://www.nsgportal.org) through a convenient web-interface. References Michael Schirner, Simon Rothmeier, Viktor K. Jirsa, Anthony Randal McIntosh, Petra Ritter, An automated pipeline for constructing personalized virtual brains from multimodal neuroimaging data, NeuroImage, Available online 31 March 2015, ISSN 1053-8119, http://dx.doi.org/10.1016/j.neuroimage.2015.03.055 Keywords: multi modal data, the virtual brain, connectome, tractography, computational modeling Conference: Neuroinformatics 2015, Cairns, Australia, 20 Aug - 22 Aug, 2015. Presentation Type: Poster, to be considered for oral presentation Topic: Computational neuroscience Citation: Schirner M, Rothmeier S and Ritter P (2015). Constructing subject-specific virtual brains from multimodal neuroimaging data. Front. Neurosci. Conference Abstract: Neuroinformatics 2015. doi: 10.3389/conf.fnins.2015.91.00005 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 29 May 2015; Published Online: 05 Aug 2015. * Correspondence: Dr. Petra Ritter, Charité Berlin, Berlin, Germany, petra.ritter@charite.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Michael Schirner Simon Rothmeier Petra Ritter Google Michael Schirner Simon Rothmeier Petra Ritter Google Scholar Michael Schirner Simon Rothmeier Petra Ritter PubMed Michael Schirner Simon Rothmeier Petra Ritter Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Species-dependent adaptation of the cardiac Na+/K+ pump kinetics to the intracellular Na+ concentration.

The Na(+)/K(+) ATPase (NKA) plays a critical role in maintaining ionic homeostasis and dynamic function in cardiac myocytes, within both the in vivo cell and in silico models. Physiological conditions differ significantly between mammalian species. However, most existing formulations of NKA used to simulate cardiac function in computational models are derived from a broad range of experimental sources spanning many animal species. The resultant inability of these models to discern species-specific features is a significant obstacle to achieving a detailed quantitative and comparative understanding of physiological behaviour in different biological contexts. Here we present a framework for characterising the steady-state NKA current using a biophysical mechanistic model specifically designed to provide a mechanistic explanation of the NKA flux supported by self-consistent species-specific data. We thus compared NKA kinetics specific to guinea- pig and rat ventricular myocytes. We observe that the apparent binding affinity for sodium in the rat is significantly lower, whereas the overall pump cycle rate is doubled, in comparison to the guinea pig. This sensitivity of NKA to its regulatory substrates compensates for the differences in Na(+) concentrations between the cell types. NKA is thereby maintained within its dynamic range over a wide range of pacing frequencies in these two species, despite significant disparities in sodium concentration. Hence, by replacing a conventional generic NKA model with our rat-specific NKA formula into a whole-cell simulation, we have, for the first time, been able to accurately reproduce the action potential duration and the steady-state sodium concentration as functions of pacing frequency.

Characterization of blood flow rate in dental pulp by speckle patterns of backscattered light from an in vivo tooth.

Experimental data on the hemodynamics of dental pulp at different stages of caries treatment are given. Observations of speckle patterns in backscattered laser light are used as a measurement method to qualitatively characterize changes in blood flow rate through the dental pulp. The measurements were made by the author-designed experimental setup. Theoretical estimations showed that stationary reflected light from an in vivo tooth contains a negligibly small information body on changes in the pulpal blood flow due to the shadowing of the pulp by optically thick enamel and dentin. Therefore, the temporal variations in the speckle patterns are the only possible way that can provide monitoring of blood conditions in the pulp by using backscattered light. Various statistical characteristics of the random reflected light fields are studied as indicators of blood flow rate changes. There were selected five statistical parameters of backscattered speckle images that give self-consistent data on these changes. The parameters include four combinations of integrals of the Fourier transforms of the observed temporal variations as well as the speckle image contrast. The selected parameters are shown to qualitatively agree with general considerations on the effects of reduced or increased blood flow rates on the selected integral quantities.

Structure, stability and geochemical role of palladium chloride complexes in hydrothermal fluids

In situ X-ray absorption spectroscopy (XANES and EXAFS) was applied to study palladium speciation in model (Na,Li)Cl–HCl–HNO3–HClO4–H2O solutions and to measure the solubility of PdO(s) and PdS(s) in NaCl–HCl–H2O solutions up to 450°C and 600bar. In HNO3 and HClO4 solutions, the square planar Pd(H2O)42+ cation with an average Pd–O distance of 2.00±0.01Å is the dominant form at 30–100°C. At T>100°C, this cation undergoes hydrolysis resulting in Pd precipitation. In (Na,Li)Cl–HCl solutions Pd forms square planar PdCln(H2O)4−n2−n complexes with Pd–O and Pd–Cl distances of 2.00–2.10 and 2.26–2.31Å, respectively. At 30–250°C our data are consistent with a mixture of PdCl(H2O)3+, PdCl2(H2O)20(aq), PdCl3(H2O)−, and PdCl42−, but at T>250°C PdCl3(H2O)− and PdCl42− become dominant over a wide range of chloride concentration, from ∼0.03 to at least 9mol/kgH2O. XANES and EXAFS analyses of these species distribution allowed derivation of the stability constant of the reaction PdCl3−+Cl−=PdCl42− from 300 to 450°C and 600bar. These results, coupled with in situ PdO(s) and PdS(s) solubility measurements of this study and a revision of thermodynamic data for these solid phases, allowed generation of a self-consistent thermodynamic data set of the system PdS(s)–PdO(s)–PdCl3−–PdCl42−. Our data indicate that Pd can be significantly mobilized as chloride complexes only in sulfide-free oxidizing geological settings (e.g., Chudnoe deposits in Russia, Waterberg deposits in South Africa, Jacutinga-type deposits in Brazil). By contrast, at typical pH (4–8), chlorinity (<10–15wt% NaCl) and H2S contents (0.001–0.1wt%) of most hydrothermal fluids, the absolute concentration of Pd–Cl complexes is too low to explain Pd enrichment in volcanogenic massive sulfide, modern seafloor sulfide, and porphyry Cu–Au–Mo deposits. Complexes with S-bearing ligands, very likely other than H2S/HS−, such as S3− and other polysulfide anions, are required to account for Pd hydrothermal mobility in these geological settings.

Determination of full set material constants of [011]c poled 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystal from one sample.

0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystals poled along [011]c have macroscopic orthorhombic mm2 symmetry. There are total 17 independent material coefficients for this symmetry so that the determination of self-consistent full matrix data is extremely difficult because many samples are needed and there is a large property variation from sample to sample. To overcome this self-consistency difficulty, we have developed a combined ultrasonic pulse-echo and impedance spectroscopy method, which can extract all coefficients from only one small sample. This method is especially useful for piezoelectric materials whose properties are strongly dependent on geometry and for crystals with only limited size available.

Thermal regimes in the Chukchi Sea from 1941 to 2008

The summer (June–October) temperature observations in the surface (0m) and subsurface (20m-bottom) Chukchi Sea layers collected from 1941 to 2008 have been analyzed using the self-consistent data recovery procedure based on correlation analysis and iterative empirical orthogonal function (EOF) decomposition. The analysis of the surface and subsurface EOFs identified “cold”, “normal”, and “warm” thermal states with variability of 2–3 years, and also 4–7 years. We found that the Chukchi Sea water temperature has gradually increased since 1941. Warming in the surface layer since 1941 has been minimal in the Bering Strait (0.012°Cyr−1, total 0.8°C) and maximal in Long Strait (0.030–0.036°Cyr−1, total 2.0–2.4°C). In the subsurface layer, temperatures have increased about half as much; minimal (0.0030–0.0075°Cyr−1, total 0.2–0.5°C) in Long Strait and rather uniform (0.010–0.015°Cyr−1, total 0.7–1.0°C) for the remaining Chukchi Sea. Analysis of the satellite sea-surface height anomaly data shows that during the “warm” periods there is a stronger flow through the Bering Strait and intensification of the northwestward currents in the central Chukchi Sea. Extensive correlation analysis shows that the thermal state of the Chukchi Sea agrees well with the flow of Pacific water through the Bering Strait and by an increase of the global atmospheric temperature. In addition, typical circulation during “warm” and “cold” periods was reconstructed using four-dimensional variational (4Dvar) data assimilation into the ocean model, and estimates of volume and heat fluxes in the Chukchi Sea during “cold” and “warm” periods were derived which are consistent with EOF and correlation analyses.

Gas-Phase Enthalpies of Formation and Enthalpies of Sublimation of Amino Acids Based on Isodesmic Reaction Calculations

Accurate gas-phase enthalpies of formation (ΔfH298°) of 20 common α-amino acids, seven uncommon amino acids, and three small peptides were calculated by combining G4 theory calculations with an isodesmic reaction approach. The internal consistency over a set of ΔfH298°(g) values was achieved by sequential adjustment of their values through the isodesmic reactions. Four amino acids, alanine, β-alanine, sarcosine, and glycine, with reliable internally self-consistent experimental data, were chosen as the key reference compounds. These amino acids together with about 100 compounds with reliable experimental data (their accuracy was supported by G4 calculations) were used to estimate the enthalpies of formation of remaining amino acids. All of the amino acids with the previously established enthalpies of formation were later used as the reference species in the isodesmic reactions for the other amino acids. A systematic comparison was made of 14 experimentally determined enthalpies of formation with the results of calculations. The experimental enthalpies of formation for 10 amino acids were reproduced with good accuracy, but the experimental and calculated values for 4 compounds differed by 11–21 kJ/mol. For these species, the theoretical ΔfH298°(g) values were suggested as more reliable than the experimental values. On the basis of theoretical results, the recommended values for the gas-phase enthalpies of formation were also provided for amino acids for which the experimental ΔfH298°(g) were not available. The enthalpies of sublimation were evaluated for all compounds by taking into account the literature data on the solid-phase enthalpies of formation and the ΔfH298°(g) values recommended in our work. A special attention was paid to the accurate prediction of enthalpies of formation of amino acids from the atomization reactions. The problems associated with conformational flexibility of these compounds and harmonic treatment of low frequency torsional modes were discussed. The surprisingly good agreement between the ΔfH298°(g) values calculated from the atomization and isodesmic reactions is largely the result of a fortuitous mutual compensation of various corrections used in the atomization reaction procedure.

A self-consistent evaluation of 242Cm alpha and gamma emission intensities

As a rule the evaluated decay data and their uncertainties reflect the current level of consistency of the experimental data as well as its shortage. However, if we assume a priori that the structure of the decay scheme is precisely established, the inclusion of the exact balance relationships in the evaluation procedure leads to lower uncertainties of the recommended data and strong correlations between some of the evaluated parameters. Such a self-consistent decay data evaluation was carried out using the 242Cm alpha decay as an example.

Optical constants and spatial uniformity of thermally grown oxide layer of custom, induced-junction, silicon photodiodes for a predictable quantum efficient detector

We have investigated the optical properties of self-induced inversion-layer silicon photodiodes using spectroscopic ellipsometric measurement techniques. We report a self-consistent data set and dispersion relation for the optical constants of the thermally grown oxide layer. The oxide layer thickness and spatial uniformity of a series of custom manufactured 22 mm × 11 mm rectangular diodes are evaluated. These photodiodes are used in a light trapping arrangement and exhibit predictable quantum efficiency and thus, predictable spectral responsivity. For comparison, we report measurements of the absolute spatial uniformity of the oxide layer on commercial “S6337” and “S1337” radiometric quality photodiodes.

Defending Against Cooperative Attacks in Cooperative Spectrum Sensing

Accurate spectrum sensing is important in cognitive radio networks. False sensing results in either waste of spectrum or harmful interference to primary users. To improve accuracy, cooperative spectrum sensing, in which a set of secondary users cooperatively sense the presence of the primary user, has emerged. This technique, however, opens a window for malicious users and attackers, who may remotely or physically capture the sensors and manipulate the sensing reports. In this paper, we consider the attack model whereby the attacker injects self-consistent false data simultaneously, and propose a modified COI (combinatorial optimization identification) algorithm to defend against such attacks. We also provide a theorem that detection uncertainty may exist in cooperative spectrum sensing. We intensively evaluate our algorithm with simulations, and the results show that our algorithm is a good technique to complement an existing algorithm, called IRIS.

Experimental Equilibrium Tested by Plagioclase Loop Widths

are solid and liquid, respectively, and An is the mole fraction (or per cent) An/(An þ Ab). It is measured from the plagioclase composition and an estimate of the liquid composition based on standard assumptions rooted in the norm recalculation routine. A survey of a large, new database allows study of the 1 atm experimental literature involving 819 experiments.The approach to equilibrium is tested empirically by the loop width and its transform, the linear partitioning function KD.This function is the exchange coefficient formed as the intercept at pure An S from the array over all X S of the partition coefficient D when defined as (X S /X L )w hereX is the mole fraction. D and KD are thus limited to lie between zero and 1·0. The results show a 1atm loop width ranging from 0· 2t o 68 mol %A n with associated KD ¼ 0·03^0·98. These extrema represent loops both far too small and far too large to represent stable equilibrium between plagioclase and liquid. Some of the higher values lie near the persodic limit because the An component of the liquid is scarce, and the liquid composition is Ab-rich. The loops from Ne-normative liquids span the range from 40 to 90 mol % An in the crystal with loops 2^50 mol % wide. A baseline for loop width is derived from the precise synthetic study of the system Di^An^Ab at 1atm and an array of high-pressure data that extrapolates to the same value of KD ¼ 0·26 at 1atm. Many of the 1atm experimental data fall far outside any reasonable uncertainty limits on the baseline. Causes of departure include crystal disequilibrium that can lead to errors in both directions, and compositional problems. Comparison of the values of KD with liquid compositions in silica, oxygen fugacity, temperature, kinetics, and sodium reveals the common presence of sodium deficiency. A crystallinity study shows a definite decrease in sodium content with liquid evolution, whereas the sodium content should increase or at least remain nearly constant with evolution of the melt. A selection of self-consistent 1atm data from a few laboratories shows a close correspondence to the standard distribution of loop widths and indeed most literature data lie within the limited range of KD ¼ 0·26^0·4. Experiments known to be hydrous show very low values of KD and corresponding large loop widths, as previously understood from literature data. When data limited to nearbaseline KD values are plotted against temperature, they yield expected thermal slopes and concave-up curves of temperature plotted against plagioclase composition. Literature data show a positive correlation of KD with dry pressure, and a separate database from 2 to 15 kbar shows that more than half the data comport with this pressure effect. A different group ranges down to KD as low as 0·2, with increasing loop widths. Some of these are alkalic and hence rich in the Ab component of the liquid. Others were obtained in Fe containers that control the oxygen fugacity to low values and convert the fayalite component of the liquid to iron, oxygen, and silica. This reaction increases the activity of silica and in turn the activity of Ab in the melt, thus widening the loop. Thermodynamic studies concerned with plagioclase^melt equilibria will profit from an awareness of these effects.

Equation of state and opacities for warm dense matter

This work presents recent developments in the calculation of opacity and equation of state tables suitable for including in the radiation hydrodynamic code ARWEN (1) to study processes like ICF or X-ray secondary sources. For these calculations we use the code bigbart to compute opacities in LTE conditions, with self-consistent data generated with the Flexible Atomic Code (FAC) (2). Non-LTE effects are approximately taken into account by means of the new RADIOM model developed in (3), which makes use of existing LTE data tables. We use the screened-hydrogenic model (4) to derive the Equation of State (EOS) using the population and energy of each level.