Use of synchrotron tomographic techniques in the assessment of diffusion parameters for solute transport in groundwater flow

This technical note describes the use of time-resolved synchrotron radiation tomographic energy dispersive diffraction imaging (TEDDI) and tomographic X-ray fluorescence (TXRF) for examining ion diffusion in porous media. The technique is capable of tracking the diffusion of several ion species simultaneously. This is illustrated by results which compare the movement of Cs+, Ba2+ and La3+ ions from solution into a typical sample of English chalk. The results exhibited somewhat anomalous (non-Fickian) behaviour and revealed heterogeneities (in 1D) on the scale of a few millimetres

Resonance Contributions to η\eta Photoproduction on Protons Found Using Dispersion Relations and an Isobar Model

The contributions of the resonances $D_{13}(1520)$, $S_{11}(1535)$, $S_{11}(1650)$, $D_{15}(1675)$, $F_{15}(1680)$, $D_{13}(1700)$, $P_{11}(1710)$, $P_{13}(1720)$ to $\gamma p\to \eta p$ are found from the data on cross sections, beam and target asymmetries using two approaches: fixed-t dispersion relations and an isobar model. Utilization of the two approaches and comparison of the results obtained with different parametrizations of the resonance contributions allowed us to make conclusions about the model-dependence of these contributions. We conclude that the results for the contributions of the resonances $D_{13}(1520)$, $S_{11}(1535)$, $F_{15}(1680)$ to corresponding multipole amplitudes are stable. With this the results for $D_{13}(1520)$ and $F_{15}(1680)$, combined with their PDG photoexcitation helicity amplitudes, allowed us to find the branching ratios $Br (D_{13}(1520)\to \eta N)=0.05\pm 0.02$, $Br (F_{15}(1680)\to \eta N)=0.16\pm0.04$ which have significantly better accuracy than the PDG data. The total Breit-Wigner width of the $S_{11}(1535)$ is model-dependent, we have obtained $\Gamma (S_{11}(1520))=142 MeV$ and $195 MeV$ using dispersion relations and the isobar model, respectively. The results for the $S_{11}(1650)$, $D_{15}(1675)$, $P_{11}(1710)$, $P_{13}(1720)$ are model dependent, only the signs and orders of magnitude of their contributions to multipole amplitudes are determined. The results for the $D_{13}(1700)$ are strongly model-dependent.Comment: 26 pages, 6 figure

Cavity cooling a single charged nanoparticle

The development of laser cooling coupled with the ability to trap atoms and ions in electromagnetic fields, has revolutionised atomic and optical physics, leading to the development of atomic clocks, high-resolution spectroscopy and applications in quantum simulation and processing. However, complex systems, such as large molecules and nanoparticles, lack the simple internal resonances required for laser cooling. Here we report on a hybrid scheme that uses the external resonance of an optical cavity, combined with radio frequency (RF) fields, to trap and cool a single charged nanoparticle. An RF Paul trap allows confinement in vacuum, avoiding instabilities that arise from optical fields alone, and crucially actively participates in the cooling process. This system offers great promise for cooling and trapping a wide range of complex charged particles with applications in precision force sensing, mass spectrometry, exploration of quantum mechanics at large mass scales and the possibility of creating large quantum superpositions.Comment: 8 pages, 5 figures Updated version includes additional references, new title, and supplementary information include

The 8^8B Neutrino Spectrum

Knowledge of the energy spectrum of $^8$B neutrinos is an important ingredient for interpreting experiments that detect energetic neutrinos from the Sun. The neutrino spectrum deviates from the allowed approximation because of the broad alpha-unstable $^8$Be final state and recoil order corrections to the beta decay. We have measured the total energy of the alpha particles emitted following the beta decay of $^8$B. The measured spectrum is inconsistent with some previous measurements, in particular with a recent experiment of comparable precision. The beta decay strength function for the transition from $^8$B to the accessible excitation energies in $^8$Be is fit to the alpha energy spectrum using the R-matrix approach. Both the positron and neutrino energy spectra, corrected for recoil order effects, are constructed from the strength function. The positron spectrum is in good agreement with a previous direct measurement. The neutrino spectrum disagrees with previous experiments, particularly for neutrino energies above 12 MeV.Comment: 15 pages, 13 figures, 4 tables, submitted to Phys. Rev. C, typos correcte

Survival feeding of cattle during drought

TO obtain adequate returns from the grazing of developed land, which has involved considerable capital investment, farmers may carry stock at rates which, though normally satisfactory, are too high in exceptionally poor seasons. A look at some slternatives and their costs to maintaine the herd in drought

Optomechanical cooling of levitated spheres with doubly-resonant fields

Optomechanical cooling of levitated dielectric particles represents a promising new approach in the quest to cool small mechanical resonators towards their quantum ground state. We investigate two-mode cooling of levitated nanospheres in a self-trapping regime. We identify a rich structure of split sidebands (by a mechanism unrelated to usual strong-coupling effects) and strong cooling even when one mode is blue detuned. We show the best regimes occur when both optical fields cooperatively cool and trap the nanosphere, where cooling rates are over an order of magnitude faster compared to corresponding single-sideband cooling rates.Comment: 8 Pages, 7 figure

Studies of the superconducting properties of Sn1-xInxTe (x=0.38 to 0.45) using muon-spin spectroscopy

The superconducting properties of Sn1-xInxTe (x = 0.38 to 0.45) have been studied using magnetization and muon-spin rotation or relaxation (muSR) measurements. These measurements show that the superconducting critical temperature Tc of Sn1-xInxTe increases with increasing x, reaching a maximum at around 4.8 K for x = 0.45. Zero-field muSR results indicate that time-reversal symmetry is preserved in this material. Transverse-field muon-spin rotation has been used to study the temperature dependence of the magnetic penetration depth lambda(T) in the mixed state. For all the compositions studied, lambda(T) can be well described using a single-gap s-wave BCS model. The magnetic penetration depth at zero temperature lambda(0) ranges from 500 to 580 nm. Both the superconducting gap Delta(0) at 0 K and the gap ratio Delta(0)/kBTc indicate that Sn1-xInxTe (x = 0.38 to 0.45) should be considered as a superconductor with intermediate to strong coupling.Comment: 7 pages, 6 figures, 3 table

Source-filter Separation of Speech Signal in the Phase Domain

Deconvolution of the speech excitation (source) and vocal tract (filter) components through log-magnitude spectral processing is well-established and has led to the well-known cepstral features used in a multitude of speech processing tasks. This paper presents a novel source-filter decomposition based on processing in the phase domain. We show that separation between source and filter in the log-magnitude spectra is far from perfect, leading to loss of vital vocal tract information. It is demonstrated that the same task can be better performed by trend and fluctuation analysis of the phase spectrum of the minimum-phase component of speech, which can be computed via the Hilbert transform. Trend and fluctuation can be separated through low-pass filtering of the phase, using additivity of vocal tract and source in the phase domain. This results in separated signals which have a clear relation to the vocal tract and excitation components. The effectiveness of the method is put to test in a speech recognition task. The vocal tract component extracted in this way is used as the basis of a feature extraction algorithm for speech recognition on the Aurora-2 database. The recognition results shows upto 8.5% absolute improvement in comparison with MFCC features on average (0-20dB)

Nodeless superconductivity in the cage-type superconductor Sc5Ru6Sn18 with preserved time-reversal symmetry

We report the single-crystal synthesis and detailed investigations of the cage-type superconductor Sc5Ru6Sn18, using powder x-ray diffraction (XRD), magnetization, specific-heat and muon-spin relaxation (muSR) measurements. Sc5Ru6Sn18 crystallizes in a tetragonal structure (space group I41/acd) with the lattice parameters a = 1.387(3) nm and c = 2.641(5) nm. Both DC and AC magnetization measurements prove the type-II superconductivity in Sc5Ru6Sn18 with Tc = 3.5(1) K, a lower critical field H_c1 (0) = 157(9) Oe and an upper critical field, H_c2 (0) = 26(1) kOe. The zero-field electronic specific-heat data are well fitted using a single-gap BCS model, with superconducting gap = 0.64(1) meV. The Sommerfeld constant varies linearly with the applied magnetic field, indicating s-wave superconductivity in Sc5Ru6Sn18. Specific-heat and transverse-field (TF) muSR measurements reveal that Sc5Ru6Sn18 is a superconductor with strong electron-phonon coupling, with TF-muSR also suggesting the single-gap s-wave character of the superconductivity. Furthermore, zero-field muSR measurements do not detect spontaneous magnetic fields below Tc, hence implying that time-reversal symmetry is preserved in Sc5Ru6Sn18.Comment: 23 pages, 11 figure