On the hierarchy of partially invariant submodels of differential equations

It is noticed, that partially invariant solution (PIS) of differential equations in many cases can be represented as an invariant reduction of some PIS of the higher rank. This introduce a hierarchic structure in the set of all PISs of a given system of differential equations. By using this structure one can significantly decrease an amount of calculations required in enumeration of all PISs for a given system of partially differential equations. An equivalence of the two-step and the direct ways of construction of PISs is proved. In this framework the complete classification of regular partially invariant solutions of ideal MHD equations is given

Invariants of differential equations defined by vector fields

We determine the most general group of equivalence transformations for a family of differential equations defined by an arbitrary vector field on a manifold. We also find all invariants and differential invariants for this group up to the second order. A result on the characterization of classes of these equations by the invariant functions is also given.Comment: 13 page

Classification of conservation laws of compressible isentropic fluid flow in n>1 spatial dimensions

For the Euler equations governing compressible isentropic fluid flow with a barotropic equation of state (where pressure is a function only of the density), local conservation laws in $n>1$ spatial dimensions are fully classified in two primary cases of physical and analytical interest: (1) kinematic conserved densities that depend only on the fluid density and velocity, in addition to the time and space coordinates; (2) vorticity conserved densities that have an essential dependence on the curl of the fluid velocity. A main result of the classification in the kinematic case is that the only equation of state found to be distinguished by admitting extra $n$-dimensional conserved integrals, apart from mass, momentum, energy, angular momentum and Galilean momentum (which are admitted for all equations of state), is the well-known polytropic equation of state with dimension-dependent exponent $\gamma=1+2/n$. In the vorticity case, no distinguished equations of state are found to arise, and here the main result of the classification is that, in all even dimensions $n\geq 2$, a generalized version of Kelvin's two-dimensional circulation theorem is obtained for a general equation of state.Comment: 24 pages; published version with misprints correcte

Electronic and magnetic structure of epitaxial NiO/Fe3_3O4_4(001) heterostructures grown on MgO(001) and Nb-doped SrTiO3_3(001)

We study the underlying chemical, electronic and magnetic properties of a number of magnetite based thin films. The main focus is placed onto NiO/Fe$_3$O$_4$(001) bilayers grown on MgO(001) and Nb-SrTiO$_3$(001) substrates. We compare the results with those obtained on pure Fe$_3$O$_4$(001) thin films. It is found that the magnetite layers are oxidized and Fe$^{3+}$ dominates at the surfaces due to maghemite ($\gamma$-Fe$_2$O$_3$) formation, which decreases with increasing magnetite layer thickness. From a layer thickness of around 20 nm on the cationic distribution is close to that of stoichiometric Fe$_3$O$_4$. At the interface between NiO and Fe$_3$O$_4$ we find the Ni to be in a divalent valence state, with unambiguous spectral features in the Ni 2p core level x-ray photoelectron spectra typical for NiO. The formation of a significant NiFe$_2$O$_4$ interlayer can be excluded by means of XMCD. Magneto optical Kerr effect measurements reveal significant higher coercive fields compared to magnetite thin films grown on MgO(001), and a 45$^{\circ}$ rotated magnetic easy axis. We discuss the spin magnetic moments of the magnetite layers and find that the moment increases with increasing thin film thickness. At low thickness the NiO/Fe$_3$O$_4$ films grown on Nb-SrTiO$_3$ exhibits a significantly decreased spin magnetic moments. A thickness of 20 nm or above leads to spin magnetic moments close to that of bulk magnetite

Observation of the second harmonic in superconducting current-phase relation of Nb/Au/(001)YBa2Cu3Ox heterojunctions

The superconducting current-phase relation (CPR) of Nb/Au/(001)YBa2Cu3Ox heterojunctions prepared on epitaxial c-axis oriented YBa2Cu3Ox thin films has been measured in a single-junction interferometer. For the first time, the second harmonic of the CPR of such junctions has been observed. The appearance of the second harmonic and the relative sign of the first and second harmonics of the CPR can be explained assuming, that the macroscopic pairing symmetry of our YBa2Cu3Ox thin films is of the d+s typeComment: 11 pages, 4 figure

Polaron physics and crossover transition in magnetite probed by pressure-dependent infrared spectroscopy

The optical properties of magnetite at room temperature were studied by infrared reflectivity measurements as a function of pressure up to 8 GPa. The optical conductivity spectrum consists of a Drude term, two sharp phonon modes, a far-infrared band at around 600 cm$^{-1}$, and a pronounced mid-infrared absorption band. With increasing pressure both absorption bands shift to lower frequencies and the phonon modes harden in a linear fashion. Based on the shape of the MIR band, the temperature dependence of the dc transport data, and the occurrence of the far-infrared band in the optical conductivity spectrum the polaronic coupling strength in magnetite at room temperature should be classified as intermediate. For the lower-energy phonon mode an abrupt increase of the linear pressure coefficient occurs at around 6 GPa, which could be attributed to minor alterations of the charge distribution among the different Fe sites.Comment: 7 pages, 7 figure

Electronic properties and degradation upon VUV irradiation of sodium chloride on Ag 111 studied by photoelectron spectroscopy

The growth as well as vacuum ultraviolet VUV radiation induced degradation of sodium chloride NaCl on Ag 111 is investigated by ultraviolet and x ray photoelectron spectroscopy. In line with previous scanning tunneling microscopy studies, our results confirm that NaCl grows initially as a bilayer before island growth starts. Simple spectroscopic methods for calibrating the closure of the NaCl bilayer are further presented. In addition, the energy level alignment is studied as a function of NaCl film thickness and VUV light intensity. When measuring with ultra low photon flux, a sharp interface dipole lowers the sample work function by 0.65 eV upon adsorption of the first bilayer, which is followed by vacuum level alignment for subsequently deposited layers. In contrast, measurements performed with standard photon fluxes, such as those provided by commercial He discharge lamps, shows downward band bending like characteristics in the NaCl films. Upon extended exposure time to the standard VUV intensity, photoemission measurements further reveal that strong modifications of the electronic properties of the NaCl surface occur. These are likely correlated with halogen emission, eventually resulting in the formation of Na clusters promoting low work function of parts of the sample surface. This study provides general guidelines for obtaining reliable spectroscopic measurements on alkali halide thin films on metal

Molecular tectonics: Grid and porous coordination networks based on combinations of iron thiocyanate and pyridyl appended derivatives of tetrathiacalix[4]arene and tetramercaptotetrathiacalix[4]arene

© ISUCT Publishing. The combination of three pyridyl appended tetrathiacalix[4]arene (TCA) and tetramercaptotetrathiacalix[4]arene (TMTCA) derivatives in 1,3-alternate imposed conformation behaving as neutral tectons with octahedral FeII(NCS)2 complex as a metallatecton, leads to the formation of new coordination networks. Whereas the tecton 4, a tetrasubstituted TCA derivative (pyridyl in ortho position), leads to a 2D grid-like network, for the other two tectons 5 and 6, the formation of 3D diamond-like architectures is observed

Ethnography on Philippine Migration Labour : Case Studies on Ifugao Female Workers Overseas and Filipina Brides in Australia

この論文は、海外移住労働について民族誌的かつ記述的な研究を目差したものである。3セクションからなり、先ず、文献研究のセクションと、少数民族のイフガオ女性の労働状況についての記述、最後にオーストラリアのフィリピン花嫁の労働状況を記述したセクションである。第1セクションでは、統計資料からフィリピンの海外移住労働の現況を概括し、先行研究からフィリピン移民と海外移住労働の歴史や政策についてまとめた。次の節で、パレニャスによるローマとロスアンジェルスにおけるフィリピン移住労働者の比較研究を簡単に紹介し、その問題点を扱う。最後の節では、香港におけるフィリピン女性家事労働者についても、コンステーブルによる研究を要約し、問題点を取りあげた。第2セクションは、主に北部ルソン島におけるイフガオ女性の海外移住労働者とその家族についての事例と、香港とシンガポールでの労働状況について事例を記述した。同時に女性の海外移住労働が深刻な社会変化と文化変容を生じさせている現状を表した。第3セクションは、オーストラリアにおけるフィリピン花嫁の労働実態を中心に記述したが、その背後には家族呼びよせと不法就労者の実態が浮かび上がる。異なった視座から女性の移住労働者を捉えることで、各章と事例を総括することで結論とした。This paper aims to describe overseas Philippine migration labour. It consists of three sections. The first deals with statistical data and historical backgrounds on migration from the Philippines included national policies. There are two other parts in this section, which summarize Filipina workers in Rome and Los Angeles by Parenas and Filipina domestic helpers in Hong Kong by Constable, and point out some theoretical difficulties for better comprehension of Philippine society and culture. The second section treats ethnographic case studies on Ifugao female workers in Hong Kong and Singapore, and Ifugao families at home. The third section describes the working conditions and lives among Filipina brides and immigrant families in Australia