A mass-extended 't Hooft-Nobbenhuis complex transformations and their consequences

We have extended the 't Hooft-Nobbenhuis complex transformations to include mass. Under these new transformations, Schrodinger, Dirac, Klein-Gordon and Einstein general relativity equations are invariant. The non invariance of the cosmological constant in Einstein field equations dictates it to vanish thus solving the longstanding cosmological constant problem.Comment: 6 LateX pages, no figure

On the generalized continuity equation

A generalized continuity equation extending the ordinary continuity equation has been found using quanternions. It is shown to be compatible with Dirac, Schrodinger, Klein-Gordon and diffusion equations. This generalized equation is Lorentz invariant. The transport properties of electrons are found to be governed by Schrodinger-like equation and not by the diffusion equation.Comment: 9 Latex pages, no figure

The influence of mechanical milling and subsequent calcination on the formation of lithium ferrites

The influence of ball milling and subsequent calcination of a 2.5:1 molar mixture of alpha-Fe2O3 and Li2CO3 on the formation of lithium ferrites has been investigated. Premilling was found to considerably lower the temperature at which the lithium ferrites LiFeO2 and LiFe5O8 are formed. A beta-to-alpha-phase transition in LiFe5O8 was found to take place on cooling from ca. 1000degreesC depending on the milling history and cooling regime. (C) 2002 Elsevier Science (USA)

Prediction of defect structure in lithiated tin- and titanium-doped alpha-Fe2O3 using atomistic simulation

The defect structure of lithiated tin- and titanium-doped alpha-Fe2O3 has been assessed using interatomic potential calculations. Of the models considered for lithiation, a model in which Li+ occupies an interstitial site balanced by the reduction of Fe3+ to Fe2+ on an Fe3+ site was found to be more favourable than the substitution of Li+ on an Fe3+ octahedral site balanced by an O2- vacancy. Insertion of lithium into the interstitial site between adjacent M4+ ions was particularly favourable. The calculated lattice parameters decrease on lithiation as has been observed experimentally

Synthesis, structural, and magnetic characterisation of magnesium-doped lithium ferrite of composition Li0.5Fe2.5O4

Spinel-related magnesium-doped Li0.5Fe2.5O4 has been synthesised at a lower than normal temperature. The Mg2+ ions substitute for Fe3+ ions on the tetrahedral sites whilst Li+ions are located on octahedral sites. Magnetic measurements are consistent with this structural model

Tin-, titanium-, and magnesium-doped alpha-Cr2O3: characterisation and rationalisation of the structures

Tin- and titanium-doped α-Cr2O3 have been prepared by the calcination of precipitates. Rietveld structure refinement of the X-ray powder diffraction patterns shows that the dopant metals occupy interstitial sites and partially substitute on octahedral chromium sites in the corundum-related α-Cr2O3 structure. Interatomic potential calculations show that such defects are energetically more favourable than the exclusive substitution of chromium or the occupation by the dopant of interstitial sites in α-Cr2O3 with charge balance being achieved by an appropriate number of cation vacancies. However, the attempted incorporation of magnesium within α-Cr2O3 results in the formation of spinel-related MgCr2O4. The observation is rationalised in terms of the greater thermodynamic stability of the spinel-related structure

pH Controlled Nanostructure and Optical Properties of ZnO and Al-Doped ZnO Nanorod Arrays Grown by Microwave-Assisted Hydrothermal Method

The low-temperature microwave-assisted hydrothermal method was used to successfully grow pure and Al-doped ZnO (AZO) nanorod (NR) arrays on glass substrates. The combined effects of doping and pH on the structural properties, surface chemistry, and optical properties of all samples were investigated. Thermodynamic-based simulations of the growth solution were performed and a growth mechanism, that considers the effects of both the pH and Al-doping, is proposed, and discussed. Tuning the solution pH is key parameter to grow well-aligned, single crystal, highly packed, and high aspect ratio nanorod arrays. Moreover, the optical absorption in the visible range is enhanced by controlling the pH value. The PL spectra reveal a shift of the main radiative emission from the band-to-band into a transition involving deep defect levels of Zinc interstitial Zni. This shift is caused by an enhancement of the non-radiative components (phonon relaxation) at high pH values. The production of well-ordered ZnO and AZO nanorod arrays with visible-active absorption/emission centers would increase their potential use in various applications

Mössbauer Study of Weathered H-meteorite from the Desert of Oman

A number of meteorites from the desert of Oman, classified as H-chondrites, with known and unknown ages, were studied by using 57Fe Mössbauer spectroscopy to determine their Fe3+-bearing compositions. Mössbauer spectra measured at 78 K were composed of paramagnetic doublets superimposed on magnetic sextets. The doublets are assigned to the silicate minerals olivine and pyroxene and Fe3+ phases. The magnetic sextets in most samples showed the presence of at least three magnetic phases, namely troilite, magnetite and kamacite, which commonly exist in most ordinary chondrites. The relative amounts (area %) of Fe3+ in the known-age meteorites, determined from the Mössbauer spectra, were plotted against their terrestrial ages. The plot was used to estimate the terrestrial ages of meteorites with unknown terrestrial age