A study of pulse propagation of electromagnetic signals through the solar corona

Solar probe to measure radial variation of electron density in solar coron

Polarizations and Nullcone of Representations of Reductive Groups

The paper starts with the following simple observation. Let V be a representation of a reductive group G, and let f_1,f_2,...,f_n be homogeneous invariant functions. Then the polarizations of f_1,f_2,...,f_n define the nullcone of k 0} h(t) x = 0 for all x in L. This is then applied to many examples. A surprising result is about the group SL(2,C) where almost all representations V have the property that all linear subspaces of the nullcone are annihilated. Again, this has interesting applications to the invariants on several copies. Another result concerns the n-qubits which appear in quantum computing. This is the representation of a product of n copies of $SL_2$ on the n-fold tensor product C^2 otimes C^2 otimes ... otimes C^2. Here we show just the opposite, namely that the polarizations never define the nullcone of several copies if n <= 3. (An earlier version of this paper, distributed in 2002, was split into two parts; the first part with the title ``On the nullcone of representations of reductive groups'' is published in Pacific J. Math. {bf 224} (2006), 119--140.

The decomposition of level-1 irreducible highest weight modules with respect to the level-0 actions of the quantum affine algebra Uq′(sl^n)U'_q(\hat{sl}_n)

We decompose the level-1 irreducible highest weight modules of the quantum affine algebra $U_q(\hat{sl}_n)$ with respect to the level-0 $U'_q (\hat{sl}_n)$--action defined in q-alg/9702024. The decomposition is parameterized by the skew Young diagrams of the border strip type.Comment: 22 pages, AMSLaTe

Field-induced incommensurate-to-commensurate transition in Ba_2CuGe_2O_7

We report an observation of a commensurate-incommensurate phase transition in the Dzyaloshinskii-Moriya spiral antiferromagnet Ba_2 Cu Ge_2 O_7. The transition is induced by an external magnetic field applied along the c-axis of the tetragonal structure, i. e., in the plane of spin rotation. Bulk magnetic measurements and neutron diffraction experiments show that the transition occurs in a critical field Hc=2.1T. Experimental results for the period of the magnetic structure and magnetization as functions of magnetic field are in quantitative agreement with our exact analytical solution for Dzyaloshinskii's model of commensurate-incommensurate transitions in spiral magnets.Comment: 11 double column pages, 9 figures, submitted to PR

In Situ Surface Studies of Site-Isolated Hydrogenation Catalysts – The Intermetallic Compound PdGa

Selective acetylene hydrogenation is an important method for removing traces of acetylene in the ethylene feed for the production of polyethylene. Typical catalysts, like Pd dispersed on metal oxides are widely used for this reaction and show a limited selectivity and long-term stability. This can be attributed to the presence of active-sites ensembles on the catalyst surface. This drawback can be overcome by using the intermetallic compound PdGa which possesses palladium atoms in the crystal structure well isolated from each other by a gallium shell. PdGa shows higher selectivity and increased long-term stability compared to the commercial catalysts, including PdAg alloys. In the present work the surface of the intermetallic compound PdGa was probed by in situ XPS as well as CO adsorption using FTIR spectroscopy. The XPS investigation before hydrogenation revealed a significant modification of the Pd electronic state in the intermetallic compound compared to Pd metal: the Pd3d5/2 peak is shifted by 1 eV to higher binding energy. In situ XPS measurements, performed at ~1 mbar pressure, showed a high stability of the Pd surface states without appearance of any additional components or significant shifts of the Pd3d5/2 peak when applying the reactive atmosphere and temperature (1.0 mbar of H2 + 0.1 mbar of C2H2 at 120 ºC). This is in contrast to Pd metal for which the formation of an additional Pd component during alkyne hydrogenation was detected. Investigation of carbon and palladium depth profiles for PdGa indicates the absence of a subsurface carbon-containing phase, distinguishing this material decidedly from metallic palladium catalysts. The adsorption of CO on the PdGa compound at room temperature results in the appearance of only one band with a maximum at 2047 cm-1, which corresponds to linear Pd–CO carbonyls. It should be mentioned that the observed band (2047 cm–1) is shifted to lower wavenumbers compared to the respective CO (on-top) species forming upon adsorption on metallic palladium (2100-2080 cm–1), which is an indication for the modification of the Pd electronic states by covalent bonding in the investigated intermetallic compound. The absence of bands due to bridged carbonyls in the observed spectra and the fact that the observed band is not coverage dependent indicated that the active sites in PdGa are really isolated. Characterization of PdGa by FTIR and in situ XPS revealed high surface stability during the reaction of acetylene hydrogenation and confirms the isolation of the active Pd site on the surface. In combination with modified electronic Pd states due to covalent bonding in the intermetallic compound it leads to superior catalytic properties like high selectivity and long-term stability during the partial hydrogenation of acetylene

In Situ Studies of Site-Isolated Hydrogenation Catalysts – The Intermetallic Compound PdGa

Selective acetylene hydrogenation is an important method for removing traces of acetylene in the ethylene feed for the production of polyethylene. Typical catalysts show a limited selectivity and long-term stability. This can be attributed to the presence of active-site ensembles. This drawback can be overcome by using the intermetallic compound PdGa which possesses palladium atoms in the crystal structure well isolated by a gallium shell. PdGa shows higher selectivity and increased long-term stability compared to commercial catalysts. The XPS investigation before the reaction revealed a significant modification of the Pd electronic state in the intermetallic compound compared to Pd metal: the Pd3d5/2 peak is shifted by 1 eV to higher binding energy. In situ XPS measurements showed a high stability of the Pd surface states without appearance of any additional components or significant shifts of the Pd3d5/2 peak when applying the reactive atmosphere and temperature (1.0 mbar H2 0.1 mbar C2H2 at 120 ºC). This is in contrast to Pd metal for which the formation of an additional Pd component during alkyne hydrogenation was reported recently. The adsorption of CO on PdGa at room temperature results in the appearance of only one band with a maximum at 2047 cm-1, which should correspond to linearly bound CO (Pd–CO). It should be mentioned that the observed band (2047 cm–1) is shifted to lower wavenumbers compared to the respective CO (on-top) species forming upon adsorption on metallic palladium (2100-2080 cm–1), which may be an indication for the modification of the Pd electronic states by covalent bonding in the investigated intermetallic compound. The absence of bands due to bridged carbonyls in the spectra and the fact that the observed band is not coverage dependent indicates that the active sites in PdGa are really isolated. Characterization of PdGa revealed high surface stability during the hydrogenation of acetylene and confirms the isolation of the active Pd sites on the surface. In combination with the modified electronic Pd states – perhaps due to the covalent bonding – it leads to superior catalytic properties high selectivity and long-term stability

Field-induced Commensurate-Incommensurate phase transition in a Dzyaloshinskii-Moriya spiral antiferromagnet

We report an observation of a commensurate-incommensurate phase transition in a Dzyaloshinskii-Moriya spiral magnet Ba_2CuGe_2O_7. The transition is induced by applying a magnetic field in the plane of spin rotation. In this experiment we have direct control over the strength of the commensurate potential, while the preferred incommensurate period of the spin system remains unchanged. Experimental results for the period of the soliton lattice and bulk magnetization as a function of external magnetic field are in quantitative agreement with theory.Comment: 4 pages, 4 figures, submitted to PR

Pinning the catalytic centre: A new concept for catalysts development

A new concept for the development of catalysts is introduced. Utilizing ordered Pd-Ga intermetallic compounds high selectivity and long-term stability in the acetylene hydrogenation can be achieved. The high selectivity observed for all compounds (Pd3Ga7, PdGa, Pd2Ga) indicates that not only the surface geometric site isolation but also the suppression of hydride formation through a covalent bonding interaction absent in conventional Pd alloys are important for achieving superior catalytic properties. Our results demonstrate that structurally well-defined intermetallic compounds exhibit a high potential in heterogeneous catalysis and are promising candidates for industrial applications

Success Factors of Small and Medium-Sized International Enterprises in the Chinese Market from the Perspective of Polish Direct Investment (Cultural Approach)

Globalization has resulted in increasing transfer of firms operations, regardless of their size, to other countries. The recent dynamic emergence of China in the global economy, connecting with the vast inflows of foreign direct investment in their territory and common adjustments problems of many Western companies, has resulted in growing interest for best suitable business practices to this culturally and socially different environment. In this article, the key factors critical to the success of international companies in this region are introduced, with particular consideration to indigenous cultural elements and specific operation requirements of small and medium-sized enterprises in Business-to-Business sectors. The presented information are based on the broad literature review, five years of direct observation and thirty eight interviews conducted with Polish managers directly residing in China. In addition, some practical recommendations for managers and further research are given.Globalizacja wymusza na firmach, niezależnie od ich wielkości, coraz częstsze przenoszenie operacji do innych krajów. Dynamiczne pojawienie się Chin w światowej gospodarce i szeroki napł;yw zagranicznych inwestycji bezpośrednich na ich teren oraz problemy adaptacyjne wielu zachodnich przedsiębiorstw, spowodował;y zainteresowanie najlepszymi praktykami biznesowymi dostosowanymi do tego odmiennego kulturowo i społ;ecznie otocznia. W artykule zaprezentowane został;y najważniejsze czynnik mające wpł;yw na osiągnięcie sukcesu przez firmy międzynarodowe na tym obszarze, ze szczególnym uwzględnieniem aspektów kulturowych i specyfiki dział;ania mał;ych i średnich podmiotów na rynkach B2B. Prezentowane informacje są oparte na przeglądzie literatury, pięcioletnich obserwacjach bezpośrednich oraz trzydziestu ośmiu wywiadach przeprowadzonych z menadżerami polskich przedsiębiorstw odpowiedzialnymi za operacje w Chinach. Dodatkowo wskazano kilka praktycznych rekomendacji menadżerskich oraz możliwości dalszych badań