5,583 research outputs found
Sc substitution for Mg in MgB2: effects on Tc and Kohn anomaly
Here we report synthesis and characterization of Mg_{1-x}Sc_{x}B_{2}
(0.12T_{c}>6 K.
We find that the Sc doping moves the chemical potential through the 2D/3D
electronic topological transition (ETT) in the sigma band where the ``shape
resonance" of interband pairing occurs. In the 3D regime beyond the ETT we
observe a hardening of the E_{2g} Raman mode with a significant line-width
narrowing due to suppression of the Kohn anomaly over the range 0<q<2k_{F}.Comment: 8 pages, 4 EPS figures, to be published in Phys. Rev.
Avaliação das características morfológicas do sistema radicular de linhagens recombinantes endogâmicas de sorgo em solução nutritiva sob estresse de fósforo.
Semi-regular sequences and other random systems of equations
The security of multivariate cryptosystems and digital signature schemes
relies on the hardness of solving a system of polynomial equations over a
finite field. Polynomial system solving is also currently a bottleneck of
index-calculus algorithms to solve the elliptic and hyperelliptic curve
discrete logarithm problem. The complexity of solving a system of polynomial
equations is closely related to the cost of computing Groebner bases, since
computing the solutions of a polynomial system can be reduced to finding a
lexicographic Groebner basis for the ideal generated by the equations. Several
algorithms for computing such bases exist: We consider those based on repeated
Gaussian elimination of Macaulay matrices. In this paper, we analyze the case
of random systems, where random systems means either semi-regular systems, or
quadratic systems in n variables which contain a regular sequence of n
polynomials. We provide explicit formulae for bounds on the solving degree of
semi-regular systems with m > n equations in n variables, for equations of
arbitrary degrees for m = n+1, and for any m for systems of quadratic or cubic
polynomials. In the appendix, we provide a table of bounds for the solving
degree of semi-regular systems of m = n + k quadratic equations in n variables
for 2 <= k; n <= 100 and online we provide the values of the bounds for 2 <= k;
n <= 500. For quadratic systems which contain a regular sequence of n
polynomials, we argue that the Eisenbud-Green-Harris Conjecture, if true,
provides a sharp bound for their solving degree, which we compute explicitly.Comment: 27 pages, 4 table
No measure for culture? Value in the new economy
This paper explores articulations of the value of investment in culture and the arts through a critical discourse analysis of policy documents, reports and academic commentary since 1997. It argues that in this period, discourses around the value of culture have moved from a focus on the direct economic contributions of the culture industries to their indirect economic benefits. These indirect benefits are discussed here under three main headings: creativity and innovation, employability, and social inclusion. These are in turn analysed in terms of three forms of capital: human, social and cultural. The paper concludes with an analysis of this discursive shift through the lens of autonomist Marxist concerns with the labour of social reproduction. It is our argument that, in contemporary policy discourses on culture and the arts, the government in the UK is increasingly concerned with the use of culture to form the social in the image of capital. As such, we must turn our attention beyond the walls of the factory in order to understand the contemporary capitalist production of value and resistance to it. </jats:p
Phase equilibria in the La-Mg-Ge system at 500 °c and crystal structure of the new ternary compounds La11Mg2Ge7 and LaMg3-xGe2
The whole 500 \ub0C isothermal section of the La-Mg-Ge ternary system was constructed. The existence and crystal structure of three ternary compounds were confirmed: La2+xMg1-xGe2 (\u3c42, P4/mbm, tP10-Mo2FeB2, 0 64x 640.25), La 4Mg5Ge6 (\u3c43, Cmc21, oS60-Gd4Zn5Ge6) and La4Mg 7Ge6 (\u3c44, C2/m, mS34, own structure type). Five novel compounds were identified and structurally characterized: La 11Mg2Ge7 (\u3c41, P4 2/ncm, tP88-8, own structure type, a=1.21338(5), c=1.57802(6) nm), LaMg3-xGe2 (\u3c45, P 3\u3041c, hP34-0.44, own structure type, x=0.407(5), a=0.78408(4), c=1.45257(7) nm), La 6Mg23Ge (\u3c46, Fm3\u304m, cF120-Zr 6Zn23Si, a=1.46694(6) nm), La4MgGe 10-x (\u3c47, x=0.37(1), C2/m, mS60-1.46, own structure type, a=0.88403(8), b=0.86756(8), c=1.7709(2) nm, \u3b2=97.16\ub0(1) and La2MgGe6 (\u3c48, Cmce, oS72-Ce 2(Ga0.1Ge0.9)7, a=0.8989(2), b=0.8517(2), c=2.1064(3) nm). Disordering phenomena were revealed in several La-Mg-Ge phases in terms of partially occupied sites. The crystal structures of La11Mg2Ge7 and LaMg3-xGe2 are discussed in details. The latter is a 1a3a
7 1a3a
72c superstructure of the LaLi3Sb2 structure type; the symmetry reduction scheme is shown in the B\ue4rnighausen formalism terms. \ua9 2014 Elsevier Inc
A new glance on R2MGe6 (R = rare earth metal, M = another metal) compounds. An experimental and theoretical study of R2PdGe6germanides
The R2PdGe6series (R = rare earth metal) was structurally characterized, and the results achieved were extended for a comprehensive study on R2MGe6(M = another metal) compounds, employing symmetry-based structural rationalization and energy calculations. Directly synthesized R2PdGe6exists for almost all R-components (R = Y, La-Nd, Sm and Gd-Lu) and even if with La is probably metastable. Several single crystal X-ray analyses (R = Y, Ce, Pr, Nd, Er and Lu) indicated oS72-Ce2(Ga0.1Ge0.9)7as the correct structure. The alternative In-flux method, once optimized, produced three good quality R2PdGe6single crystals: La2PdGe6and Pr2PdGe6turned out to be mS36-La2AlGe6-type non-merohedrally twinned crystals and Yb2PdGe6is of oS72-Ce2(Ga0.1Ge0.9)7-type. The vacancy ordering phenomenon was considered as a possible cause of the symmetry reduction relations connecting the most frequently reported 2:1:6 structural models (oS18, oS72 and mS36) with the oS20-SmNiGe3aristotype. The detected twin formation is consistent with the symmetry relations, which are discussed even considering the validity of the different structural models. DFT total energy calculations were performed for R2PdGe6(R = Y and La) in the three abovementioned structural models, and for La2MGe6(M = Pt, Cu, Ag and Au) in the oS18 and oS72 modifications. The results indicate that the oS18-Ce2CuGe6structure, prevalently proposed in the literature, is associated with the highest energy and thus it is not likely to be realized in these series. The oS72 and mS36 polytypes are energetically equivalent, and small changes in the synthetic conditions could easily stabilize any of them, in agreement with experimental results obtained by direct and flux syntheses
Root traits analysis of recombinant inbred lines underlying phosphorus acquisition efficiency in maize.
Cloning and characterization of the gene expression profiles of maize phosphorus-starvation tolerance 1 genes.
- …