A Fully Coupled Solver for Incompressible Navier–Stokes Equations using Operator Splitting

The steady incompressible Navier–Stokes equations are coupled by a Poisson equation for the pressure from which the continuity equation is subtracted. The equivalence to the original N–S problem is proved. Fictitious time is added and vectorial operator-splitting is employed leaving the system coupled at each fractional-time step which allows satisfaction of the boundary conditions without introducing artificial conditions for the pressure. Conservative second-order approximations for the convective terms are employed on a staggered grid. The splitting algorithm for the 3D case is verified through an analytic solution test. The stability of the method at high values of Reynolds number is illustrated by accurate numerical solutions for the flow in a lid-driven rectangular cavity with aspect ratio 1 and 2, as well as for the flow after a back-facing step.     

Charge Radii of Argon Isotopes in the f7/2 Shell and Radii Systematics in the Ca-Region

Changes in mean square (ms) nuclear charge radii of Ar isotopes across the 1f_7/2 shell are studied by fast-beam collinear laser spectroscopy using an ultra-sensitive detection method based on optical pumping and state-selective collisional ionization. The new data set on Ar, in combination with the known charge radii of K, Ca and Ti in the ν1f_7/2 shell, offers an opportunity to obtain a more complete overview of nuclear radii trends around the proton shell closure Z = 20 and between the neutron shell closures N = 20 and N = 28.     

Optical and holographic properties of Fe+Mn co-doped Bi4Ge3O12 crystals

The effect of iron and manganese co-doping on the light-induced, dark- and photoconductivity and holographic properties of Bi₄Ge₃O₁₂ crystals in comparison with Fe- and Mn-single doping is studied. Fe+Mn co-doped crystals exhibited strong photochromic effect at room temperature, the photochromic effect being fully reversible by thermal annealing. The observed light-induced absorption changes and non-linear dependence of photoconductivity on light intensities indicate deep and shallow photoactive levels contribution to the charge transport mechanism of Fe+Mn co-doped BGO. Holographic gratings are successfully recorded at different wavelengths and a possibility to extend the photorefractive sensitivity into the red spectral range is demonstrated. It is found furthermore that Fe+Mn-doping combination leads to faster response time during holographic recording, especially after a preliminary exposure with ultraviolet light, in comparison with Fe- and Mn-single doping.     

Nuclear charge radii changes of uranium and hafnium isotopes determined by laser spectroscopy

The present work reports measurements of isotope shifts and hyperfine structure in the optical spectra of two high-Z elements: Hf and U. The experiments are based on the observation of the resonance fluorescence in a well collimated atomic beam, excited by a tunable dye laser. The chains of the stable Hf isotopes and of^{233–236, 238}U have been investigated and changes in ms nuclear charge radii have been deduced. The results have been discussed from the point of view of nuclear structure in the investigated regions.     

Atomic Absorption Assessment of Mineral Iron Quantity in Ferritin

ABSTRACT

The goal of this work is to study the possibilities for quantitative determination of the number of iron atoms in the mineral core of ferritin by atomic absorption spectroscopy (AAS). Distinctive AAS measurements show iron content between 1000 and 4500 atoms per molecule ferritin.^[ 1-6 McKnight , J. ; White , N. ; Moore , G. R. Effect of copper(II) on the aerobic oxidative uptake of iron(II) by horse spleen ferritin . J. Chem. Soc. 1997 , 21 , 4043 – 4045 . Kyung , S. K. ; Mun , H. R. ; Lee , J. H. Iron cores of tadpole ferritin: Native, reconstituted and recombinant H-chain ferritins . Inorg. Chim. Acta 2000 , 298 , 107 – 111 . Beard , J. L. ; Burton , J. W. ; Theil , E. C. Purified ferritin and soybean meal can be sources of iron for treating iron deficiency in rats . J. Nutr. 1996 , 126 , 154 – 160 . Chasteen , N. D. ; Theil , E. C. Iron binding by horse spleen apoferritin. A vanadyl(IV) EPR spin probe study . J. Biochem. 1982 , 257 , 7672 – 7677 . Treffry , A. ; Harrison , P. M. Incorporation and release of inorganic phosphate in horse spleen ferritin . Biochem. J. 1978 , 171 , 313 – 320 . Harrison , P. M. Ferritin: An iron-storage molecule . Semin. Hematol. 1977 , 14 , 55 – 70 .  ^] This motivated us to investigate the amount of iron in the horse spleen ferritin with atomic absorption spectroscopy under application of the Bulgarian standard BDS EN 14082/2003 Foodstuffs—Determination of Trace Elements—Determination of Lead, Cadmium, Zinc, Copper, Iron and Chromium by Atomic Absorption Spectrometry (AAS) after Dry Ashing.^{[ 7} BDS EN 14082/2003 Foodstuffs—Determination of Trace Elements—Determination of Lead, Cadmium, Zinc, Copper, Iron and Chromium by Atomic Absorption Spectrometry (AAS) after Dry Ashing. www.bds–bds.org . [Google Scholar] ^]

We have obtained as a result 1792 atoms in one ferritin molecule. This result is in accordance with previous results, published by leading researchers.^{[ 4} Chasteen , N. D. ; Theil , E. C. Iron binding by horse spleen apoferritin. A vanadyl(IV) EPR spin probe study . J. Biochem. 1982 , 257 , 7672 – 7677 . [Google Scholar] ^{, 5} Treffry , A. ; Harrison , P. M. Incorporation and release of inorganic phosphate in horse spleen ferritin . Biochem. J. 1978 , 171 , 313 – 320 . [Google Scholar] ^] The investigation of the iron content with AAS under the use of the Bulgarian standard can be a good opportunity to study many other objects of biological interest.     

W1{infty}-convergence of the discrete free boundary for obstacle problems

We examine the discrete free boundaries arising from a finiteelement discretization of a variational inequality. We giveL error bounds for the Hausdorff distance of the discrete andtrue free boundary, as well as for the normals. The theoreticalresults are confirmed by numerical experiments in two and threedimensions.     

Optical isotope shifts and changes in nuclear charge radii of stable Ti isotopes

Isotope shifts and hyperfine structures in three optical transitions of TiI have been investigated by using laser induced resonance fluorescence in a collimated atomic beam. From the isotope shifts data, changes of the mean square charge radii of the stable titanium isotopes have been determined for the first time. Using a combined analysis with muonic atom data on root mean square nuclear charge radii, improved model independent r ^21/2 values for the odd-even Ti isotopes have been obtained.     

Hyperfine splitting constants in the optical transition \boldsymbol{{4{f}^{7}} {6{s}^{2}} \;{^{8}{\rm S}_{7/2}} \to {4{f}^{7}} {6{s}6{p}}\; {^{6}{\rm P}_{5/2}} \ {\rm of} \ {^{151-155}{\rm Eu}}} isotopes and hyperfine anomaly

Using the method of laser-induced fluorescence in an atomic beam we have measured the hyperfine splitting constants, A and B, of the ground and excited states of the optical transition 4f ⁷6s ^{2 8}S $_{1/2}\to 4f^{7}$ 6s6p ⁶P_5/2 (564.58 nm) for ^151???155Eu isotopes. For all isotopes, the magnetic dipole constants of the ⁶P_5/2 atomic level are determined to a precision better than 0.04%. The A and B constants for the ground state ⁸S_7/2 of the radioactive ^152,154,155Eu were obtained for the first time with a precision better than 0.5%. Our data along with previous ground state hyperfine structure measurements for the stable europium isotopes allow us to determine the hyperfine anomaly for mentioned Eu isotopes.