Shock wave propagation in vibrofluidized granular materials

Shock wave formation and propagation in two-dimensional granular materials under vertical vibration are studied by digital high speed photography. The steepen density and temperature wave fronts form near the plate as granular layer collides with vibrating plate and propagate upward through the layer. The temperature front is always in the transition region between the upward and downward granular flows. The effects of driving parameters and particle number on the shock are also explored.Comment: 9 pages, 4 figures, submitted to PR

Distribution of Non-uniform Demagnetization Fields in Paramagnetic Bulk Solids

A general calculation for the distribution of non-uniform demagnetization fields in paramagnetic bulk solids is described and the fields for various sample geometries are calculated. Cones, ellipsoids, paraboloids and hyperboloids with similar sample aspect ratios are considered. Significant differences in their demagnetization fields are observed. The calculation shows that the demagnetization field magnitudes decrease along the axis of symmetry (along $z$) where an externally applied magnetic field is aligned, and increase in the vicinity of the lateral surfaces with the largest field values found in the cone and the narrowest field distributions found in the hyperboloid. Application is made to the theoretical modeling of the $^{1}$H-NMR spectra of a single crystal of field-induced superconductor $\lambda$-(BETS)$_{2}$FeCl$_{4}$ with a rectangular sample geometry, providing a good fit to the measured NMR spectra. This calculation is also applicable to diamagnetic or ferromagnetic materials in general.Comment: 7 pages, 7 figures, submitted to Physical Review B (Corresponding author: [email protected]

Formation and transportation of sand-heap in an inclined and vertically vibrated container

We report the experimental findings of formation and motion of heap in granular materials in an inclined and vertically vibrated container. We show experimentally how the transport velocity of heap up container is related to the driving acceleration as well as the driving frequency of exciter. An analogous experiment was performed with a heap-shaped Plexiglas block. We propose that cohesion force resulted from pressure gradient in ambient gas plays a crucial role in enhancing and maintaining a heap, and ratchet effect causes the movement of the heap. An equation which governs the transport velocity of the heap is presented.Comment: 9 pages, 5 figures, submitted to PR

Measurement of the Band-to-Band Registration of the SNPP VIIRS Imaging System from On-Orbit Data

No abstract availabl

Examining Road Traffic Mortality Status in China: A Simulation Study

Background Data from the Chinese police service suggest substantial reductions in road traffic injuries since 2002, but critics have questioned the accuracy of those data, especially considering conflicting data reported by the health department. Methods To address the gap between police and health department data and to determine which may be more accurate, we conducted a simulation study based on the modified Smeed equation, which delineates a non-linear relation between road traffic mortality and the level of motorization in a country or region. Our goal was to simulate trends in road traffic mortality in China and compare performances in road traffic safety management between China and 13 other countries. Results Chinese police data indicate a peak in road traffic mortalities in 2002 and a significant and a gradual decrease in population-based road traffic mortality since 2002. Health department data show the road traffic mortality peaked in 2012. In addition, police data suggest China’s road traffic mortality peaked at a much lower motorization level (0.061 motor vehicles per person) in 2002, followed by a reduction in mortality to a level comparable to that of developed countries. Simulation results based on health department data suggest high road traffic mortality, with a mortality peak in 2012 at a moderate motorization level (0.174 motor vehicles per person). Comparisons to the other 13 countries suggest the health data from China may be more valid than the police data. Conclusion Our simulation data indicate China is still at a stage of high road traffic mortality, as suggested by health data, rather than a stage of low road traffic mortality, as suggested by police data. More efforts are needed to integrate safety into road design, improve road traffic management, improve data quality, and alter unsafe behaviors of pedestrians, drivers and passengers in China

On-Orbit Measurement of the Focal Length of the SNPP VIIRS Instrument

The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument is a whiskbroom system with 22 spectral bands split between 16 moderate resolution bands (M-bands), five imagery resolution bands (I-bands) and a panchromatic day-night band. Latitude and Longitude geolocation data are generated for each pixel at the M-band, I-band and day-night band spatial resolutions based upon various instrument parameters including focal length. In this study we measure the focal length of the VIIRS instrument from on-orbit data. This is achieved by simulating VIIRS band I2 using Landsat 8 OLI band 5 utilizing the VIIRS instrument system point spread function (PSF) and geolocation data generated with varying values of focal length. The focal length value that produces the highest spatial correlation between the original and simulated VIIRS data is taken to be the measured instrument focal length

Evolutionary History and Phylodynamics of Influenza A and B Neuraminidase (NA) Genes Inferred from Large- Scale Sequence Analyses

Background: Influenza neuraminidase (NA) is an important surface glycoprotein and plays a vital role in viral replication and drug development. The NA is found in influenza A and B viruses, with nine subtypes classified in influenza A. The complete knowledge of influenza NA evolutionary history and phylodynamics, although critical for the prevention and control of influenza epidemics and pandemics, remains lacking. Methodology/Principal findings: Evolutionary and phylogenetic analyses of influenza NA sequences using Maximum Likelihood and Bayesian MCMC methods demonstrated that the divergence of influenza viruses into types A and B occurred earlier than the divergence of influenza A NA subtypes. Twenty-three lineages were identified within influenza A, two lineages were classified within influenza B, and most lineages were specific to host, subtype or geographical location. Interestingly, evolutionary rates vary not only among lineages but also among branches within lineages. The estimated tMRCAs of influenza lineages suggest that the viruses of different lineages emerge several months or even years before their initial detection. The dN/dS ratios ranged from 0.062 to 0.313 for influenza A lineages, and 0.257 to 0.259 for influenza B lineages. Structural analyses revealed that all positively selected sites are at the surface of the NA protein, with a number of sites found to be important for host antibody and drug binding. Conclusions/Significance: The divergence into influenza type A and B from a putative ancestral NA was followed by the divergence of type A into nine NA subtypes, of which 23 lineages subsequently diverged. This study provides a better understanding of influenza NA lineages and their evolutionary dynamics, which may facilitate early detection of newly emerging influenza viruses and thus improve influenza surveillance

1^{1}H-NMR spin-echo measurements of the static and dynamic spin properties in λ\lambda-(BETS)2_{2}FeCl4_{4}

$^{1}$H-NMR spin-echo measurements of the spin-echo decay $M(2\tau)$ with a decay rate 1/$T_{2}$ and the frequency shift $\Delta\nu/\nu_{0}$ under applied magnetic field $\mathbf{B}$$_{0}$ = 9 T along the a-axis over a temperature range 2.0$-$180 K are reported for a single crystal of the organic conductor $\lambda$-(BETS)$_{2}$FeCl$_{4}$. It provides the spin dynamic and static properties in the paramagnetic metal (PM) and antiferromagnetic insulator (AFI) states as well as across the PM$-$AFI phase transition. A large slow beat structure in the spin-echo decay is observed with a typical beat frequency of $f$ $\sim$ 7 kHz and it varies across the spectrum. Its origin is attributed to the $^{1}$H$-$$^{1}$H dipole interactions rather than to the much larger dipolar field contribution from the Fe$^{3+}$ electrons (spin $S$ = 5/2). A simple phenomenological model provides an excellent fit to the data. The dominant $^{1}$H-NMR frequency shift comes from the dipolar field from the 3d Fe$^{3+}$ ions, and the Fe$^{3+}$ $-$ Fe$^{3+}$ exchange interactions ($J_{0}$) ($J_{0}$ includes the d$-$d exchange interactions through the $\pi-$electrons) have a substantial effect to the local field at the proton sites expecially at low temperatures. A good fit is obtained with $J_{0}$ = - 1.7 K. The data of the spin-echo decay rate 1/$T_{2}$ indicates that there is a significant change in the slow fluctuations of the local magnetic field at the $^{1}$H-sites on traversing the PM to AFI phase. This evidence supports earlier reports that the PM$-$AFI phase transition in $\lambda$-(BETS)$_{2}$FeCl$_{4}$ is driven magnetically and first order.Comment: 9 pages, 10 figures, resubmitted to Phys. Rev. B in response to comments of Editor and reviewers on March 23, 200