Determining elemental strontium distribution in rat bones treated with strontium ranelate and strontium citrate using 2D micro-XRF and 3D dual energy K-edge subtraction synchrotron imaging

Strontium-based medications, such as strontium ranelate, have been suggested to have therapeutic effects in patients with osteoporosis. Strontium salts available off-shelf in stores across North America are assumed to provide similar effects as strontium ranelate and thus should lead to similar distributions of elemental strontium incorporated in bone. The objective of this study was to compare the spatial distribution of strontium in animal bones following the administration of strontium ranelate and strontium citrate. Seventeen-week-old Sprague–Dawley rats were split into three groups over 10 weeks and given 625 mg/kg/day of strontium ranelate and 676 mg/kg/day of strontium citrate; the control group received no additional supplementary strontium. The humeri were collected from all animals, and strontium distribution was mapped using 2D micro-XRF and 3D dual energy K-edge subtraction (KES) imaging. 2D and 3D elemental mapping methods demonstrated that strontium delivered during treatment by both salts had the same spatial distribution. 3D elemental strontium maps of treated animal bones showed that strontium was largely observed in the trabecular regions under the epiphyseal (growth) plate. The thickness of the strontium layers in both the strontium ranelate and strontium citrate sample was not significantly different (p = .9201). 2D micro-XRF and 3D dual-energy KES images effectively elucidated the spatial distribution of elemental strontium in calcified tissue. These methods provide a novel approach to evaluating the potential efficacy of strontium supplements in the treatment of osteoporosis.     

Regge oscillations in integral cross sections for proton impact on atomic hydrogen

The integral cross sections for elastic scattering and spin exchange for proton impact on atomic hydrogen show several oscillations in the energy range 0.01-1.0 eV that cannot be associated with resonances or the glory effect. A complex angular momentum analysis using computed Regge trajectories shows that each peak of the oscillatory structure is predominantly associated with at most three trajectories. In this way, the peaks are related to the L=0 bound states of H+ 2. The complex angular momentum theory for integral cross sections that we introduce shows that such oscillations are a general feature of potential scattering.     

Mechanism of hopping transport in disordered mott insulators

By using a combination of detailed experimental studies and simple theoretical arguments, we identify a novel mechanism characterizing the hopping transport in the Mott insulating phase of Ca2-xSrxRuO4 near the metal-insulator transition. The hopping exponent alpha shows a systematic evolution from a value of alpha=1/2 deeper in the insulator to the conventional Mott value alpha=1/3 closer to the transition. This behavior, which we argue to be a universal feature of disordered Mott systems close to the metal-insulator transition, is shown to reflect the gradual emergence of disorder-induced localized electronic states populating the Mott-Hubbard gap.     

Thermal collapse of spin polarization in half-metallic ferromagnets

We propose two novel approaches to study the temperature dependence of the magnetization and the spin polarization at the Fermi level in magnetic compounds, and apply them to half-metallic ferromagnets. We reveal a new mechanism, where the hybridization of states forming the half-metallic gap depends on thermal spin fluctuations and the polarization can drop abruptly at temperatures much lower than the Curie point. We verify this for NiMnSb by ab initio calculations. The thermal properties are studied by mapping ab initio results to an extended Heisenberg model which includes longitudinal fluctuations and is solved by a Monte Carlo method.     

Application of very weak formulation on homogenization of boundary value problems in porous media

Czechoslovak Mathematical Journal - The goal of this paper is to present a different approach to the homogenization of the Dirichlet boundary value problem in porous medium. Unlike the standard...     

Low latency localization of multiple sound sources in reverberant environments

Sound source localization algorithms determine the physical position of a sound source in respect to a listener. For practical applications, a localization algorithm design has to take into account real world conditions like multiple active sources, reverberation, and noise. The application can impose additional constraints on the algorithm, e.g., a requirement for low latency. This work defines the most important constraints for practical applications, introduces an algorithm, which tries to fulfill all requirements as good as possible, and compares it to state-of-the-art sound source localization approaches.     

Cauchy’s residue theorem for a class of real valued functions

Let [a, b] be an interval in ℝ Rand let F be a real valued function defined at the endpoints of [a, b] and with a certain number of discontinuities within [a, b]. Assuming F to be differentiable on a set [a, b] | E to the derivative f, where E is a subset of [a, b] at whose points F can take values ±∞ or not be defined at all, we adopt the convention that F and f are equal to 0 at all points of E and show that KH-vt ∝ _a ^b f = F(b) − F(a), where KH-vt denotes the total value of the Kurzweil-Henstock integral. The paper ends with a few examples that illustrate the theory.     

Production of heavy fragments in interactions of high-energy protons with silver

A silver target was exposed to 14, 18 and 23 GeV protons. The values of the cross-sections for production of events with two and three fragments have been determined by the use of a polycarbonate detector. The results obtained show that these events are due to fission as well as to fragmentation and spallation.     

NMR phase noise in bitter magnets

We have studied the temporal instability of a high field resistive Bitter magnet through nuclear magnetic resonance (NMR). This instability leads to transverse spin decoherence in repeated and accumulated NMR experiments as is normally performed during signal averaging. We demonstrate this effect via Hahn echo and Carr--Purcell--Meiboom--Gill (CPMG) transverse relaxation experiments in a 23-T resistive magnet. Quantitative analysis was found to be consistent with separate measurements of the magnetic field frequency fluctuation spectrum, as well as with independent NMR experiments performed in a magnetic field with a controlled instability. Finally, the CPMG sequence with short pulse delays is shown to be successful in recovering the intrinsic spin--spin relaxation even in the presence of magnetic field temporal instability.     

Effect of atmospheric pressure pulsed discharge spatial inhomogeneity on Ar I and H I lines: Electron number density study

The spatial inhomogeneity of pulsed atmospheric pressure discharge in argon is investigated using the electron number density N_e diagnostics procedure applied to asymmetrically broadened Ar I lines. A dedicated fitting procedure is used for describing Ar I 703.0 nm line shape recorded from argon gas discharge and H I (at 486.13 and 656.28 nm) lines recorded from Ar-H₂ gas mixture discharge. The results revealed the change in N_e in both axial and radial directions. The additional Ar I lines at 614.5, 710.7, 731.2, and 731.6 nm, recorded from integral spatial radiation, are analysed as well to confirm the results from the plasma column region. The possibility of using AlO (B²∑⁺–X²∑⁺) and CN (B²∑⁺–X²∑⁺) molecular bands for gas temperature T_g measurements in this type of gas discharge source is demonstrated and T_g used as an input parameter for the N_e diagnostics procedure. For the proper identification of molecular band spectral lines, the Fortrat parabolas are constructed. The results obtained from Ar I 703.0 nm line indicate three different N_e values, with N_e1 ≈ 0.6 × 10¹⁶ cm⁻³, N_e2 ≈ 3.6 × 10¹⁶ cm⁻³, and N_e3 ≈ 19 × 10¹⁶ cm⁻³ measured from the plasma column. These N_e values increase in the cathode and anode region.