996 research outputs found
Eucomic acid methanol monosolvate
In the crystal structure of the title compound [systematic name: 2-hyÂdroxy-2-(4-hyÂdroxyÂbenzÂyl)butaneÂdioic acid methanol monosolvate], C11H12O6·CH3OH, the dihedral angles between the planes of the carboxyl groups and the benzene ring are 51.23 (9) and 87.97 (9)°. InterÂmolecular O—H⋯O hydrogen-bonding interÂactions involving the hyÂdroxy and carbÂoxyÂlic acid groups and the methanol solvent molÂecule give a three-dimensional structure
(2R,4R)-1-(tert-ButÂoxyÂcarbonÂyl)-4-methÂoxyÂpyrrolidine-2-carbÂoxyÂlic acid
In the title compound, C11H19NO5, the five-membered pyrrolidine ring adopts an envelope conformation. The dihedral angles between the carboxyl group plane, the pyrrolidine ring and the methÂoxy group are 59.50 (3) and 62.02 (1)°, respectively. In the crystal, interÂmolecular O—H⋯O hydrogen bonds link the molÂecules into chains along [100]. The absolute configuration is assigned in accord with that of (2R,4R)-1-(tert-butÂoxyÂcarbonÂyl)-4-hyÂdroxyÂpyrrolidine-2-carbÂoxyÂlic acid, which was the starting material in the synthesis
N′-(4-MethoxyÂbenzylÂidene)-4-nitroÂbenzoÂhydrazide methanol solvate
The title compound, C15H13N3O4·CH4O, was synthesized from the reaction of 4-methoxyÂbenzaldehyde with 4-nitroÂbenzohydrazide in methanol. The benzene rings of the Schiff base molÂecule are nearly coplanar, making a dihedral angle of 7.0 (3)°. The methanol solvent molÂecules are linked to the Schiff base molÂecules by N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds, forming chains running parallel to the b axis
Superconductivity at 41.0 K in the F-doped LaFeAsO1-xFx
Here we report the superconductivity in the LaFeAsO1-xFx system prepared by
high pressure synthesis. The highest onset superconducting transition
temperature (Tc) in this La-based system is 41.0 K with the nominal composition
of LaFeAsO1-xFx (x = 0.6), which is higher than that reported previously by
ambient pressure synthesis. The increase of Tc can be attributed to the further
shrinkage of crystal lattice that causes the stronger chemical pressure on the
Fe-As plane, which is induced by the increased F-doping level under high
pressure synthesis
Surrogate models based on machine learning methods for parameter estimation of left ventricular myocardium
A long-standing problem at the frontier of biomechanical studies is to develop fast methods capable of estimating material properties from clinical data. In this paper, we have studied three surrogate models based on machine learning (ML) methods for fast parameter estimation of left ventricular (LV) myocardium. We use three ML methods named K-nearest neighbour (KNN), XGBoost and multi-layer perceptron (MLP) to emulate the relationships between pressure and volume strains during the diastolic filling. Firstly, to train the surrogate models, a forward finite-element simulator of LV diastolic filling is used. Then the training data are projected in a low-dimensional parametrized space. Next, three ML models are trained to learn the relationships of pressure–volume and pressure–strain. Finally, an inverse parameter estimation problem is formulated by using those trained surrogate models. Our results show that the three ML models can learn the relationships of pressure–volume and pressure–strain very well, and the parameter inference using the surrogate models can be carried out in minutes. Estimated parameters from both the XGBoost and MLP models have much less uncertainties compared with the KNN model. Our results further suggest that the XGBoost model is better for predicting the LV diastolic dynamics and estimating passive parameters than other two surrogate models. Further studies are warranted to investigate how XGBoost can be used for emulating cardiac pump function in a multi-physics and multi-scale framework
Unconventional superconductivity of NdFeAsO0.82F0.18 indicated by the low temperature dependence of the lower critical field Hc1
We measured the initial M-H curves for a sample of the newly discovered
superconductor NdFeAsO0.82Fe0.18, which had a critical temperature, Tc, of 51
K, and was fabricated at the high pressure of 6 GPa. The lower critical field,
Hc1, was extracted from the deviation point of the Meissner linearity in the
M-H curves, which show linear temperature dependence in the low temperature
region down to 5 K. The Hc1(T) indicates no s-wave superconductivity, but
rather an unconventional superconductivity with a nodal gap structure.
Furthermore, the linearity of Hc1 at low temperature does not hold at high
temperature, but shows other characteristics, indicating that this
superconductor might have multi-gap features. Based on the low temperature
nodal gap structure, we estimate that the maximum gap magnitude delta 0 =
(1.6+- 0.2) kBTc.Comment: 8 pages, 3 figure
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