2,630 research outputs found
Investigation of element-specific and bulk magnetism, electronic and crystal structures of La{0.70}Ca{0.30}Mn{1-x}Cr{x}O{3}
The magnetic interactions in La{0.70}Ca{0.30}Mn{1-x}Cr{x}O{3} (x = 0.15, 0.50
and 0.70) are investigated by x-ray absorption spectroscopy (XAS), x-ray
magnetic circular dichroism (XMCD), high-resolution x-ray powder diffraction,
and bulk magnetization measurements. XAS in the Mn and Cr L{2,3} edges support
stable single valent Cr{3+} ions and a varying Mn valence state with x, while
the O K edge XAS spectrum reveals local maxima in the O 2p density of states
close to the Fermi level due to mixing with Mn and Cr 3d states. A robust
antiferromagnetic state is found for x=0.70 below TN = 258 K. For x=0.15,
combined XMCD and bulk magnetization measurements indicate a fully polarized
ferrimagnetic state for the Mn and Cr spins below Tc=224 K. For x=0.50, a
reduced ferrimagnetic component dominated by Mn spins is present below Tc=154
K. No evidence of lattice anomalies due to cooperative charge and orbital
orderings is found by x-ray diffraction for all samples. The magnetic
properties of this system are rationalized in terms of a competition of
ferromagnetic Mn-Mn double exchange and antiferromagnetic Cr-Cr and Cr-Mn
superexchange interactions.Comment: 25 pages, 9 figure
Investing in Indonesia's education : allocation, equity, and efficiency of public expenditures
What are the current trends and main characteristics of public education spending in Indonesia? Is education spending insufficient? Are expenditures in education efficient and equitable? This study reports the first account of Indonesia's aggregated (national and sub-national) spending on education, as well as the economic composition of education spending and its breakdown by programs. It presents estimations of the expected (average) level of education spending for a country with its economic and social characteristics. This analysis sheds light on the efficiency and equity of education spending by presenting social rates of return by level of education, by assessing the adequacy of current teacher earnings relative to other paid workers and the distribution of teachers across urban, rural, and remote regions, and by identifying the main determinants of education enrollment. It concludes that the current challenges in Indonesia are no longer defined by the need of additional spending, but rather the need to improve the quality of education services, and to improve the efficiency of education expenditures by re-allocating teachers to undersupplied regions and re-adjusting the spending mix within and between education programs for future additional spending in the sector. The study finds that poverty and student-aged labor are also significant constraints to education enrollment, stressing the importance of policies aimed at addressing demand-side factors.Education For All,Primary Education,Tertiary Education,Teaching and Learning,
Computer-Assisted Segmentation of Videocapsule Images Using Alpha-Divergence-Based Active Contour in the Framework of Intestinal Pathologies Detection
Visualization of the entire length of the gastrointestinal tract through natural orifices is a challenge for endoscopists. Videoendoscopy is currently the “gold standard” technique for diagnosis of different pathologies of the intestinal tract. Wireless Capsule Endoscopy (WCE) has been developed in the 1990's as an alternative to videoendoscopy to allow direct examination of the gastrointestinal tract without any need for sedation. Nevertheless, the systematic post-examination by the specialist of the 50,000 (for the small bowel) to 150,000 images (for the colon) of a complete acquisition using WCE remains time-consuming and challenging due to the poor quality of WCE images. In this article, a semiautomatic segmentation for analysis of WCE images is proposed. Based on active contour segmentation, the proposed method introduces alpha-divergences, a flexible statistical similarity measure that gives a real flexibility to different types of gastrointestinal pathologies. Results of segmentation using the proposed approach are shown on different types of real-case examinations, from (multi-) polyp(s) segmentation, to radiation enteritis delineation
Implementing the Gribov-Zwanziger framework in N=1 Super Yang-Mills in the Landau gauge
The Gribov-Zwanziger framework accounting for the existence of Gribov copies
is extended to N=1 Super Yang--Mills theories quantized in the Landau gauge. We
show that the restriction of the domain of integration in the Euclidean
functional integral to the first Gribov horizon can be implemented in a way to
recover non-perturbative features of N=1 Super Yang--Mills theories, namely:
the existence of the gluino condensate as well as the vanishing of the vacuum
energy.Comment: 19 pages, no figure
Spin-Electron-Phonon Excitation in Re-based Half-Metallic Double Perovskites
A remarkable hardening (~ 30 cm-1) of the normal mode of vibration associated
with the symmetric stretching of the oxygen octahedra for the Ba2FeReO6 and
Sr2CrReO6 double perovskites is observed below the corresponding magnetic
ordering temperatures. The very large magnitude of this effect and its absence
for the anti-symmetric stretching mode provide evidence against a conventional
spin-phonon coupling mechanism. Our observations are consistent with a
collective excitation formed by the combination of the vibrational mode with
oscillations of local Fe or Cr 3d and Re 5d occupations and spin magnitudes.Comment: 12 pages, 4 figure
Renormalization aspects of N=1 Super Yang-Mills theory in the Wess-Zumino gauge
The renormalization of N=1 Super Yang-Mills theory is analysed in the
Wess-Zumino gauge, employing the Landau condition. An all orders proof of the
renormalizability of the theory is given by means of the Algebraic
Renormalization procedure. Only three renormalization constants are needed,
which can be identified with the coupling constant, gauge field and gluino
renormalization. The non-renormalization theorem of the gluon-ghost-antighost
vertex in the Landau gauge is shown to remain valid in N=1 Super Yang-Mills.
Moreover, due to the non-linear realization of the supersymmetry in the
Wess-Zumino gauge, the renormalization factor of the gauge field turns out to
be different from that of the gluino. These features are explicitly checked
through a three loop calculation.Comment: 15 pages, minor text improvements, references added. Version accepted
for publication in the EPJ
H
This paper presents necessary and sufficient conditions for the existence of a quadratically stabilizing output feedback controller which also assures H2
guaranteed cost performance on a discrete linear uncertain system where the uncertainty is of the norm bounded type. The conditions are presented as a collection of linear matrix inequalities.The solution, however requires a search over a scalar parameter space
Observational - relation for Sct stars using eclipsing binaries and space photometry
Delta Scuti ( Sct) stars are intermediate-mass pulsators, whose
intrinsic oscillations have been studied for decades. However, modelling their
pulsations remains a real theoretical challenge, thereby even hampering the
precise determination of global stellar parameters. In this work, we used space
photometry observations of eclipsing binaries with a Sct component to
obtain reliable physical parameters and oscillation frequencies. Using that
information, we derived an observational scaling relation between the stellar
mean density and a frequency pattern in the oscillation spectrum. This pattern
is analogous to the solar-like large separation but in the low order regime. We
also show that this relation is independent of the rotation rate. These
findings open the possibility of accurately characterizing this type of
pulsator and validate the frequency pattern as a new observable for
Sct stars.Comment: 11 pages, including 2 pages of appendix, 2 figures, 2 tables,
accepted for publication in ApJ
- …