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Analysis of coupled transport phenomena in concrete at elevated temperatures  [PDF]
Michal Bene?,Radek ?tefan,Jan Zeman
Mathematics , 2010,
Abstract: In this paper, we study a non-linear numerical scheme arising from the implicit time discretization of the Ba\v{z}ant-Thonguthai model for hygro-thermal behavior of concrete at high temperatures. Existence and uniqueness of the time-discrete solution in two dimensions is established using the theory of pseudomonotone operators in Banach spaces. Next, the spatial discretization is accomplished by the conforming finite element method. An illustrative numerical example shows that the numerical model reproduces well the rapid increase of pore pressure in wet concrete due to extreme heating. Such phenomenon is of particular interest for the safety assessment of concrete structures prone to thermally-induced spalling.
Elevated Bile Acids in Newborns with Biliary Atresia (BA)  [PDF]
Kejun Zhou, Na Lin, Yongtao Xiao, Yang Wang, Jie Wen, Gang-Ming Zou, XueFan Gu, Wei Cai
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049270
Abstract: Biliary Atresia (BA), a result from inflammatory destruction of the intrahepatic and extrahepatic bile ducts, is a severe hepatobiliary disorder unique to infancy. Early diagnosis and Kasai operation greatly improve the outcome of BA patients, which encourages the development of early screening methods. Using HPLC coupled tandem mass spectrometry, we detected primary bile acids content in dried blood spots obtained from 8 BA infants, 17 neonatal jaundice and 292 comparison infants at 3–4 days of life. Taurocholate (TC) was significantly elevated in biliary atresia infants (0.98±0.62 μmol/L) compared to neonatal jaundice (0.47±0.30 μmol/L) and comparison infants (0.43±0.40 μmol/L), with p = 0.0231 and p = 0.0016 respectively. The area under receiver operating characteristic (ROC) curve for TC to discriminate BA and comparison infants was 0.82 (95% confidence interval: 0.72–0.92). A cutoff of 0.63 μmol/L produced a sensitivity of 79.1% and specificity of 62.5%. The concentrations of total bile acids were also raised significantly in BA compared to comparison infants (6.62±3.89 μmol/L vs 3.81±3.06 μmol/L, p = 0.0162), with the area under ROC curve of 0.75 (95% confidence interval: 0.61–0.89). No significant difference was found between the bile acids of neonatal jaundice and that of comparison infants. The early increase of bile acids indicates the presentation of BA in the immediate newborn period and the possibility of TC as newborn screening marker.
Modeling electrical dispersion phenomena in Earth materials  [cached]
D. Patella
Annals of Geophysics , 2008, DOI: 10.4401/ag-3041
Abstract: It is illustrated that IP phenomena in rocks can be described using conductivity dispersion models deduced as solutions to a 2nd-order linear differential equation describing the motion of a charged particle immersed in an external electrical field. Five dispersion laws are discussed, namely: the non-resonant positive IP model, which leads to the classical Debye-type dispersion law and by extension to the Cole-Cole model, largely used in current practice; the non-resonant negative IP model, which allows negative chargeability values, known in metals at high frequencies, to be explained as an intrinsic physical property of earth materials in specific field cases; the resonant flat, positive or negative IP models, which can explain the presence of peak effects at specific frequencies superimposed on flat, positive or negative dispersion spectra.
Theory of Electron Differentiation, Flat Dispersion and Pseudogap Phenomena  [PDF]
Masatoshi Imada,Shigeki Onoda
Physics , 2000, DOI: 10.1016/S0022-3697(00)00099-8
Abstract: Aspects of electron critical differentiation are clarified in the proximity of the Mott insulator. The flattening of the quasiparticle dispersion appears around momenta $(\pi,0)$ and $(0,\pi)$ on square lattices and determines the criticality of the metal-insulator transition with the suppressed coherence in that momentum region of quasiparticles. Such coherence suppression at the same time causes an instability to the superconducting state if a proper incoherent process is retained. The d-wave pairing interaction is generated from such retained processes without disturbance from the coherent single-particle excitations. Pseudogap phenomena widely observed in the underdoped cuprates are then naturally understood from the mode-mode coupling of d-wave superconducting(dSC) fluctuations with antiferromagnetic ones. When we assume the existence of a strong d-wave pairing force repulsively competing with antiferromagnetic(AFM) fluctuations under the formation of flat and damped single-particle dispersion, we reproduce basic properties of the pseudogap seen in the magnetic resonance, neutron scattering, angle resolved photoemission and tunneling measurements in the cuprates.
Simulation of Atmospheric Dispersion of Elevated Releases from Point Sources in Mississippi Gulf Coast with Different Meteorological Data  [PDF]
Anjaneyulu Yerramilli,Challa Venkata Srinivas,Hari Prasad Dasari,Francis Tuluri,Loren D. White,Julius Baham,John H. Young,Robert Hughes,Chuck Patrick,Mark G. Hardy,Shelton J. Swanier
International Journal of Environmental Research and Public Health , 2009, DOI: 10.3390/ijerph6031055
Abstract: Atmospheric dispersion calculations are made using the HYSPLIT Particle Dispersion Model for studying the transport and dispersion of air-borne releases from point elevated sources in the Mississippi Gulf coastal region. Simulations are performed separately with three meteorological data sets having different spatial and temporal resolution for a typical summer period in 1-3 June 2006 representing a weak synoptic condition. The first two data are the NCEP global and regional analyses (FNL, EDAS) while the third is a meso-scale simulation generated using the Weather Research and Forecasting model with nested domains at a fine resolution of 4 km. The meso-scale model results show significant temporal and spatial variations in the meteorological fields as a result of the combined influences of the land-sea breeze circulation, the large scale flow field and diurnal alteration in the mixing depth across the coast. The model predicted SO2 concentrations showed that the trajectory and the concentration distribution varied in the three cases of input data. While calculations with FNL data show an overall higher correlation, there is a significant positive bias during daytime and negative bias during night time. Calculations with EDAS fields are significantly below the observations during both daytime and night time though plume behavior follows the coastal circulation. The diurnal plume behavior and its distribution are better simulated using the mesoscale WRF meteorological fields in the coastal environment suggesting its suitability for pollution dispersion impact assessment in the local scale. Results of different cases of simulation, comparison with observations, correlation and bias in each case are presented.
Simulating the Charge Dispersion Phenomena in Micro Pattern Gas Detectors with a Resistive Anode  [PDF]
M. S. Dixit,A. Rankin
Physics , 2006, DOI: 10.1016/j.nima.2006.06.050
Abstract: The TPC for the International Linear Collider (ILC) will need to measure about 200 track points with a transverse resolution close to 100 microns. The resolution goal is beyond the capability of the conventional proportional wire/cathode pad TPC and Micro-Pattern Gas Detectors (MPGD) are being developed to meet the challenge. The standard MPGD readout techniques will, however, have difficulty in achieving the ILC-TPC resolution goal with the 2 mm x 6 mm pads as was initially envisioned. Proposals for smaller width pads will improve the resolution but will require a larger number of readout channels and increase the TPC detector cost and complexity. The new MPGD readout concept of charge dispersion has the potential to achieve the ILC-TPC resolution goal without resorting to narrower pads. This was recently demonstrated in cosmic ray tests of a small prototype TPC read out with MPGDs using the charge dispersion technique. Here we describe the simulation of the charge dispersion phenomena for the MPGD-TPC. The detailed simulation includes initial ionization clustering, electron drift, diffusion effects, the intrinsic detector pulse-shape and electronics effects. The simulation is in excellent agreement with the experimental data and can be used to optimize the MPGD charge dispersion readout for the TPC.
Dispersion of the superconducting spin resonance in underdoped and antiferromagnetic Ba(Fe1-xCox)2As2  [PDF]
D. K. Pratt,A. Kreyssig,S. Nandi,N. Ni,A. Thaler,M. D. Lumsden,W. Tian,J. L. Zarestky,S. L. Bud'ko,P. C. Canfield,A. I. Goldman,R. J. McQueeney
Physics , 2010, DOI: 10.1103/PhysRevB.81.140510
Abstract: Inelastic neutron scattering measurements have been performed on underdoped Ba(Fe1-xCox)2As2 (x = 4.7%) where superconductivity and long-range antiferromagnetic (AFM) order coexist. The broad magnetic spectrum found in the normal state develops into a magnetic resonance feature below TC that has appreciable dispersion along c-axis with a bandwidth of 3-4 meV. This is in contrast to the optimally doped x = 8.0% composition, with no long-range AFM order, where the resonance exhibits a much weaker dispersion [see Lumsden et al. Phys. Rev. Lett. 102, 107005 (2009)]. The results suggest that the resonance dispersion arises from interlayer spin correlations present in the AFM ordered state.
Singlet-triplet dispersion reveals additional frustration in the triangular dimer compound Ba$_3$Mn$_2$O$_8$  [PDF]
M. B. Stone,M. D. Lumsden,S. Chang,E. C. Samulon,C. D. Batista,I. R. Fisher
Physics , 2008, DOI: 10.1103/PhysRevLett.100.237201
Abstract: We present single crystal inelastic neutron scattering measurements of the S=1 dimerized quasi-two-dimensional antiferromagnet Ba$_3$Mn$_2$O$_8$. The singlet-triplet dispersion reveals nearest-neighbor and next-nearest-neighbor ferromagnetic interactions between adjacent bilayers that compete against each other. Although the inter-bilayer exchange is comparable to the intra-bilayer exchange, this additional frustration reduces the effective coupling along the c-axis and leads to a quasi-two dimensional behavior. In addition, the obtained exchange values are able to reproduce the four critical fields in the phase diagram.
Exploratory Analysis of Sediment Geochemistry to Determine the Source and Dispersion of Ba, Fe, Mn, Pb and Cu and in Chihuahua, Northern Mexico  [cached]
Melida Gutierrez,Victor M. Reyes Gomez,Ma. Teresa Alarcon Herrera,Daniel Nu?ez Lopez
Journal of Geography and Geology , 2012, DOI: 10.5539/jgg.v4n4p26
Abstract: Exploratory Data Analysis (EDA) was applied to asediment geochemistry data set (N = 2,584) within the Chihuahuan Desert in northern Mexico. Each data point contained information on the location, concentration of 19 elements, and lithology. A Box Plot analysis was applied to the data to determine mild and extreme anomaly thresholds. Anomaly maps revealed areas of concentration of anomalies as well as dispersion patterns for each element; Ba was the most mobile of the five elements and Pb the least. Specific potential sources of contamination were identified visually after superimposing anomalies with map layers of mines, urban centers and/or hydrology. The patterns revealed that mining was an important source of Pb, Fe, Mn and Ba contamination, while copper instead was associated to the presence of Tertiary volcanic rocks that abound in the western edge of the study area. Multi-element exploratory techniques yielded four principal components that accounted for 74% of total variance, exposing a strong association among Fe, Mn, P and Mg in PC1, Ca and Sr in PC2, Co, Cu, Cr, and Ni in PC3 and Pb in PC4. By identifying potential contaminant sources, EDA shed some light into the nature of the contamination, if natural or anthropogenic, a critical piece of information to impact assessment studies and best management plans.
Dispersion-like phenomena in Jovian decametric S-bursts: Tabooed Facts  [PDF]
Oleksiy V. Arkhypov,Helmut O. Rucker
Physics , 2014,
Abstract: The dominant viewpoint on Jovian decametric S-burst emission neglects the time delay of the radiation, although its base theory of electron cyclotron maser instability allows a significant decreasing of X-mode group velocity near the cutoff frequency at the bottom of source region. We searched for effects of the frequency-related delay of radiation in broadband Jovian radio storms consisting of periodic S-bursts (S-burst trains) at 16 to 30 MHz. It was found that up to 1% of bursts in a train are of distorted meandering shape in dynamic spectrum, where the emission from one radio source was observed at several frequencies simultaneously. It is difficult to explain such spectra in terms of radio waves beaming or causality without significant frequency-related delay of radio emission. We found experimentally that the frequency drift rate of middle lines of such events coincides with the drift rate of disturbances in common S-bursts. This indicates a general distortion of the dynamic spectrum of S-bursts. As a result, the correlation method for the measurement of the spectral distortion is proposed. Using this method, we found the approximation coefficients for the distortion in 32 spectra of 8 Io-B storms. The corrected spectra formally show that S-burst trains do not move mainly outward from Jupiter, as it is usually assumed, but fly in the opposite direction. Our simulation confirms that the dispersion is capable in principle to reproduce the found spectral distortion. Hence, the dispersion-like phenomena in Jovian S-bursts deserve discussion because they have no satisfactory explanations in terms of traditional approach.
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