111 research outputs found
Applying a Change-Point Detection Method on Frequency-Magnitude Distributions
A method based on nonparametric statistics (hereafter called "Median-Based Analysis of the Segment Slope,(MBASS)) is applied for the detection of change-points in Frequency Magnitude Distributions (FMD). The determination of the lowest magnitude for which the Gutenberg-Richter relation still applies is a key point for the computation of reliable b-values. The change-point detection method presented here is used to determine automatically this threshold magnitude (called m0 in this study) for large subsets extracted from four seismic catalogues. Results are successfully compared to those of a previous benchmark study from other authors. Moreover, the MBASS procedure is able to detect a magnitude artifact in the FMD of a regional catalogue. The results of the MBASS procedure confirm that a break in slope in a cumulative frequency distribution may be misleading when FMDs are analyzed by eye
High-resolution resonant inelastic soft X-ray scattering as a probe of the crystal electrical field in lanthanides demonstrated for the case of CeRh2Si2
The magnetic properties of rare earth compounds are usually well captured by
assuming a fully localized f shell and only considering the Hund's rule ground
state multiplet split by a crystal electrical field (CEF). Currently, the
standard technique for probing CEF excitations in lanthanides is inelastic
neutron scattering. Here we show that with the recent leap in energy
resolution, resonant inelastic soft X-ray scattering has become a serious
alternative for looking at CEF excitations with some distinct advantages
compared to INS. As an example we study the CEF scheme in CeRh2Si2, a system
that has been intensely studied for more than two decades now but for which no
consensus has been reached yet as to its CEF scheme. We used two new features
that have only become available very recently in RIXS, high energy resolution
of about 30 meV as well as polarization analysis in the scattered beam, to find
a unique CEF description for CeRh2Si2. The result agrees well with previous INS
and magnetic susceptibility measurements. Due to its strong resonant character,
RIXS is applicable to very small samples, presents very high cross sections for
all lanthanides, and further benefits from the very weak coupling to phonon
excitation. The rapid progress in energy resolution of RIXS spectrometers is
making this technique increasingly attractive for the investigation of the CEF
scheme in lanthanides
Factors predicting survival in patients with locally advanced pancreatic cancer undergoing pancreatectomy with arterial resection
Pancreatectomy with arterial resection is a treatment option in selected patients with locally advanced pancreatic cancer. This study aimed to identify factors predicting cancer-specific survival in this patient population. A single-Institution prospective database was used. Pre-operative prognostic factors were identified and used to develop a prognostic score. Matching with pathologic parameters was used for internal validation. In a patient population with a median Ca 19.9 level of 19.8 U/mL(IQR: 7.1–77), cancer-specific survival was predicted by: metabolic deterioration of diabetes (OR = 0.22, p = 0.0012), platelet count (OR = 1.00; p = 0.0013), serum level of Ca 15.3 (OR = 1.01, p = 0.0018) and Ca 125 (OR = 1.02, p = 0.00000137), neutrophils-to-lymphocytes ratio (OR = 1.16; p = 0.00015), lymphocytes-to-monocytes ratio (OR = 0.88; p = 0.00233), platelets-to-lymphocytes ratio (OR = 0.99; p = 0.00118), and FOLFIRINOX neoadjuvant chemotherapy (OR = 0.57; p = 0.00144). A prognostic score was developed and three risk groups were identified. Harrell’s C-Index was 0.74. Median cancer-specific survival was 16.0 months (IQR: 12.3–28.2) for the high-risk group, 24.7 months (IQR: 17.6–33.4) for the intermediate-risk group, and 39.0 months (IQR: 22.7–NA) for the low-risk group (p = 0.0003). Matching the three risk groups against pathology parameters, N2 rate was 61.9, 42.1, and 23.8% (p = 0.04), median value of lymph-node ratio was 0.07 (IQR: 0.05–0.14), 0.04 (IQR:0.02–0.07), and 0.03 (IQR: 0.01–0.04) (p = 0.008), and mean value of logarithm odds of positive nodes was − 1.07 ± 0.5, − 1.3 ± 0.4, and − 1.4 ± 0.4 (p = 0.03), in the high-risk, intermediate-risk, and low-risk groups, respectively. An online calculator is available at www.survivalcalculator-lapdac-arterialresection.org. The prognostic factors identified in this study predict cancer-specific survival in patients with locally advanced pancreatic cancer and low Ca 19.9 levels undergoing pancreatectomy with arterial resection
Influence of apical oxygen on the extent of in-plane exchange interaction in cuprate superconductors
In high Tc superconductors the magnetic and electronic properties are
determined by the probability that valence electrons virtually jump from site
to site in the CuO2 planes, a mechanism opposed by on-site Coulomb repulsion
and favored by hopping integrals. The spatial extent of the latter is related
to transport properties, including superconductivity, and to the dispersion
relation of spin excitations (magnons). Here, for three antiferromagnetic
parent compounds (single-layer Bi2Sr0.99La1.1CuO6+delta, double-layer
Nd1.2Ba1.8Cu3O6 and infinite-layer CaCuO2) differing by the number of apical
atoms, we compare the magnetic spectra measured by resonant inelastic x-ray
scattering over a significant portion of the reciprocal space and with
unprecedented accuracy. We observe that the absence of apical oxygens increases
the in-plane hopping range and, in CaCuO2, it leads to a genuine 3D
exchange-bond network. These results establish a corresponding relation between
the exchange interactions and the crystal structure, and provide fresh insight
into the materials dependence of the superconducting transition temperature.Comment: 9 pages, 4 figures, 1 Table, 42 reference
Kondo quasiparticle dynamics observed by resonant inelastic x-ray scattering
Effective models focused on pertinent low-energy degrees of freedom have
substantially contributed to our qualitative understanding of quantum
materials. An iconic example, the Kondo model, was key to demonstrating that
the rich phase diagrams of correlated metals originate from the interplay of
localized and itinerant electrons. Modern electronic structure calculations
suggest that to achieve quantitative material-specific models, accurate
consideration of the crystal field and spin-orbit interactions is imperative.
This poses the question of how local high-energy degrees of freedom become
incorporated into a collective electronic state. Here, we use resonant
inelastic x-ray scattering (RIXS) on CePd to clarify the fate of all
relevant energy scales. We find that even spin-orbit excited states acquire
pronounced momentum-dependence at low temperature - the telltale sign of
hybridization with the underlying metallic state. Our results demonstrate how
localized electronic degrees of freedom endow correlated metals with new
properties, which is critical for a microscopic understanding of
superconducting, electronic nematic, and topological states
Kondo quasiparticle dynamics observed by resonant inelastic x-ray scattering
Effective models focused on pertinent low-energy degrees of freedom have substantially contributed to our qualitative understanding of quantum materials. An iconic example, the Kondo model, was key to demonstrating that the rich phase diagrams of correlated metals originate from the interplay of localized and itinerant electrons. Modern electronic structure calculations suggest that to achieve quantitative material-specific models, accurate consideration of the crystal field and spin-orbit interactions is imperative. This poses the question of how local high-energy degrees of freedom become incorporated into a collective electronic state. Here, we use resonant inelastic x-ray scattering (RIXS) on CePd to clarify the fate of all relevant energy scales. We find that even spin-orbit excited states acquire pronounced momentum-dependence at low temperature—the telltale sign of hybridization with the underlying metallic state. Our results demonstrate how localized electronic degrees of freedom endow correlated metals with new properties, which is critical for a microscopic understanding of superconducting, electronic nematic, and topological states
Imprint of charge and oxygen orders on Dy ions in DyBa2Cu3O6 x thin films probed by resonant x ray scattering
We used resonant x ray scattering at the Cu L3 and Dy M5 edges to investigate charge order in thin films of underdoped DyBa2Cu3O6 x DyBCO epitaxially grown on NdGaO3 110 substrates. The films show an orthorhombic crystal structure with short range ortho II oxygen order in the charge reservoir layers. At the Dy M5 edge we observe diffraction peaks with the same planar wave vectors as those of the two dimensional charge density wave in the CuO2 planes and of the ortho II oxygen order, indicating the formation of induced ordered states on the rare earth sublattice. The intensity of the resonant diffraction peaks exhibits a nonmonotonic dependence on an external magnetic field. Model calculations on the modulation of the crystalline electric field at the Dy sites by charge and oxygen order capture the salient features of the magnetic field, temperature, and photon energy dependence of the scattering intensit
Induced in Vivo Knockdown of the Brca1 Gene in Skeletal Muscle Results in Skeletal Muscle Weakness
4f excitations in Ce Kondo lattices studied by resonant inelastic x-ray scattering
The potential of resonant inelastic soft x-ray scattering to measure 4f crystal electric-field excitation spectra in Ce Kondo lattices has been examined. Spectra have been obtained for several Ce systems and show a well-defined structure determined by crystal-field, spin-orbit, and charge-transfer excitations only. The spectral shapes of the excitation spectra can be well understood in the framework of atomic multiplet calculations. For CeCu2Si2 we found notable disagreement between the inelastic x-ray-scattering spectra and theoretical calculations when using the crystal-field scheme proposed from inelastic neutron scattering. Modified sets of crystal-field parameters yield better agreement. Our results also show that, with the very recent improvements of soft x-ray spectrometers in resolution to below 30 meV at the Ce M4,5 edges, resonant inelastic x-ray scattering could be an ideal tool to determine the crystal-field scheme in Ce Kondo lattices and other rare-earth compounds
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