Effect of aluminum on the hyperfine field and crystallization behaviour of NANOPERM alloy

The effect of Al on the hyperfine fields and crystallization of NANOPERM alloy has been studied by introducing 2% Al for Fe in Fe₈₈Zr₇B₄Cu₁. Al is found to enhance the nucleation rate in these alloys. Mössbauer spectroscopic technique has been used to trace the effect of Al on the hyperfine interactions in the amorphous and nanocrystalline state of these alloys. The hyperfine field clearly shows the presence of Al both in the amorphous and the nanocrystalline phase. Magnetic measurements using VSM and also XRD, TEM and DSC studies have been used to support the conclusions derived using Mössbauer spectroscopy.     

Measurements of magnetic susceptibilities,their anisotropies and crystal field investigations of monoclinic single crystals of Ho2GeO5

Monoclinic single crystals of Ho₂GeO₅ were grown by a flux technique. The molar principal susceptibilities (χ₁ and χ₃) have been measured in the temperature range 300–13.5 K. The principal magnetic anisotropies (χ₁–χ_2,χ₂–χ₃ and χ₁–χ₃) are obtained from the measured anisotropies in different modes of suspensions (b-axis vertical, c-axis vertical and (1 0 0) plane horizontal) of the crystal. The molar principal susceptibility (χ₂) is obtained from the observed values of the principal anisotropies. The observed principal susceptibilities together with their anisotropies are explained by invoking the crystal field interaction of the Ho³⁺ ion with its diamagnetic neighbors in non-axial symmetry. The molar susceptibilities are correlated to the ionic values by finding out the proper orientation of the principal molar susceptibilities, i.e., crystal susceptibilities with respect to that of the ionic susceptibilities (K_x, K_y and K_z). The electronic heat capacities are calculated from the crystal field analysis showing Schottky type anomalies.     

Interferometry of direct photons in central 208Pb + 208Pb collisions at 158A GeV

Two-particle correlations of direct photons were measured in central 208Pb+208Pb collisions at 158A GeV. The invariant interferometric radii were extracted for 100相似文献   

Paradox of enrichment: A fractional differential approach with memory

The paradox of enrichment (PoE) proposed by Rosenzweig [M. Rosenzweig, The paradox of enrichment, Science 171 (1971) 385–387] is still a fundamental problem in ecology. Most of the solutions have been proposed at an individual species level of organization and solutions at community level are lacking. Knowledge of how learning and memory modify behavioral responses to species is a key factor in making a crucial link between species and community levels. PoE resolution via these two organizational levels can be interpreted as a microscopic- and macroscopic-level solution. Fractional derivatives provide an excellent tool for describing this memory and the hereditary properties of various materials and processes. The derivatives can be physically interpreted via two time scales that are considered simultaneously: the ideal, equably flowing homogeneous local time, and the cosmic (inhomogeneous) non-local time. Several mechanisms and theories have been proposed to resolve the PoE problem, but a universally accepted theory is still lacking because most studies have focused on local effects and ignored non-local effects, which capture memory. Here we formulate the fractional counterpart of the Rosenzweig model and analyze the stability behavior of a system. We conclude that there is a threshold for the memory effect parameter beyond which the Rosenzweig model is stable and may be used as a potential agent to resolve PoE from a new perspective via fractional differential equations.     

Magnetic, thermal and hyperfine behaviours of Tm3+ in TmPO4, YPO4 and LuPO4: a comparative study

Single crystals of thulium phosphates (TmPO₄) are grown and the principal magnetic susceptibility perpendicular to the symmetry axis ‘c’ of the crystal $$\left( {{\text{ $ \chi $ }}_ \bot } \right)$$ and the magnetic anisotropy $$\Delta {\text{ $ \chi $ }}\left( {{\text{ = $ \chi $ }}_\parallel - {\text{ $ \chi $ }}_ \bot } \right)$$ are measured in the temperature range 300–13.5 K and 300–80 K, respectively. Though $${\text{ $ \chi $ }}_ \bot $$ increases rapidly with the decrease of temperature, $${\text{ $ \chi $ }}_\parallel $$ increases very slowly with the lowering of temperature. The tetragonal crystal structure of TmPO₄ is similar to that of Tm³⁺ in YPO₄ and LuPO₄ and in all the cases the non-Kramers Tm³⁺ ion occupies a site of D_2d symmetry. Our observed magnetic data on TmPO₄ are analyzed using crystal field analysis where the Hamiltonian includes the atomic free ion and crystal field (one-electron) interaction term. The computed and measured paramagnetic susceptibilities of TmPO₄ agree very well in the temperature range of our study. The magnetic behaviours of Tm³⁺ in YPO₄ and LuPO₄ are also studied and the results are compared with that of TmPO₄. In all the cases the natures of thermal variations of average susceptibilities and magnetic anisotropies are mostly governed by the perpendicular susceptibilities as their values are higher and rapidly increase with the lowering of temperature compared to parallel susceptibilities. The computed nuclear quadruple splittings, electronic heat capacities of Tm³⁺ in three different hosts give some interesting results.     

Midrapidity antiproton-to-proton ratio from Au+Au collisions at sqrt [s(NN)]=130 GeV

We report results on the ratio of midrapidity antiproton-to-proton yields in Au+Au collisions at sqrt[s(NN)] = 130 GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of /y/<0.5 and 0.4相似文献   

Thermodynamic stability of the γ-Co1−x Se phase by CaF2 electrolyte galvanic cell method

The partial molar free enthalpy of cobalt, , and the molar free enthalpy of formation of Co _x Se alloy phase, G _f ⁰ (Co _x Se) at 873K, were determined by the solid CaF₂ electrolyte galvanic cell method forx=0.725 to 0.956. was observed to be a monotonic function of the mole fractionX _Co in the composition region of the investigation with an inflexion point atX _Co=0.455. The measurements were extended down to a temperature of 710 K and a partial Co–Se phase diagram was evaluated from the resultant data.

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Untersuchung der thermodynamischen Stabilität der -Co-_1–x Se Phase mittels galvanischer Zelle mit CaF₂ Elektrolyt

Zusammenfassung Die partiellen molaren freien Enthalpien von Kobalt ( ) und die molaren freien Bildungsenthalpien der Co _x Se Legierungsphase [G f/0 (Co _x Se) bei 873 K] wurden mittels galvanischer Zelle (CaF₂ Fest-Elektrolyt) fürx=0,725–0,956 bestimmt. wurde im untersuchten Bereich als monotone Funktion vom MolenbruchX _Co, mit einer Inflexion beiX=0,455, gefunden. Die Messungen wurden bis zu einer Temperatur von 710 K ausgedehnt und die Daten wurden zur Erstellung eines partiellen Co–Se-Phasendiagramms ausgewertet.

     

Optimal use of instrumental neutron and photon activation analyses for multielement determinations in sewage sludges

A combination of instrumental neutron activation analysis (INAA) and instrumental photon activation analysis (IPAA) methods has been developed for multielement determinations in a variety of sludges and fertilizers. The precision and accuracy of both the methods have been evaluated by analyzing replicate samples, NBS standard reference materials, and an interlaboratory intercomparison sewage sludge sample. The concentration rages of up to 50 elements in raw and chemical sludges, sludge-based fertilizers, and other organic and inorganic fertilizers are reported here. The advantages and limitations of the INAA and IPAA methods are also discussed here.     

A model for spherical SH wave propagation in self-reinforced linearly elastic media

We study a spherical wave propagating in the radial and latitude directions and oscillating in the longitude direction in the case of fibre-reinforced linearly elastic material. A function system solving Euler's equation of motion in this case and depending on certain Bessel and associated Legendre functions is derived.