3,720 research outputs found
Large enhancement of the thermopower in NaCoO at high Na doping
Research on the oxide perovskites has uncovered electronic properties that
are strikingly enhanced compared with those in conventional metals. Examples
are the high critical temperatures of the cuprate superconductors and the
colossal magnetoresistance in the manganites. The conducting layered cobaltate
displays several interesting electronic phases as is varied
including water-induced superconductivity and an insulating state that is
destroyed by field. Initial measurements showed that, in the as-grown
composition, displays moderately large thermopower and
conductivity . However, the prospects for thermoelectric cooling
applications faded when the figure of merit was found to be small at this
composition (0.60.7). Here we report that, in the poorly-explored
high-doping region 0.75, undergoes an even steeper enhancement. At the
critical doping 0.85, (at 80 K) reaches values 40 times
larger than in the as-grown crystals. We discuss prospects for low-temperature
thermoelectric applications.Comment: 6 pages, 7 figure
An improved constraint satisfaction adaptive neural network for job-shop scheduling
Copyright @ Springer Science + Business Media, LLC 2009This paper presents an improved constraint satisfaction adaptive neural network for job-shop scheduling problems. The neural network is constructed based on the constraint conditions of a job-shop scheduling problem. Its structure and neuron connections can change adaptively according to the real-time constraint satisfaction situations that arise during the solving process. Several heuristics are also integrated within the neural network to enhance its convergence, accelerate its convergence, and improve the quality of the solutions produced. An experimental study based on a set of benchmark job-shop scheduling problems shows that the improved constraint satisfaction adaptive neural network outperforms the original constraint satisfaction adaptive neural network in terms of computational time and the quality of schedules it produces. The neural network approach is also experimentally validated to outperform three classical heuristic algorithms that are widely used as the basis of many state-of-the-art scheduling systems. Hence, it may also be used to construct advanced job-shop scheduling systems.This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/01 and in part by the National Nature Science Fundation of China under Grant 60821063 and National Basic Research Program of China under Grant 2009CB320601
Transport and Magnetic Studies on the Spin State Transition of Pr1-xCaxCoO3 up to High Pressure
Transport and magnetic measurements and structural and NMR studies have been
carried out on (Pr1-yR'y)1-xAxCoO3 {R'=(rare earth elements and Y); A=(Ca, Ba
and Sr)} at ambient pressure or under high pressure. The system exhibits a
phase transition from a nearly metallic to an insulating state with decreasing
temperature T, where the low spin (LS) state of Co3+ is suddenly stabilized.
For y=0, we have constructed a T-x phase diagram at various values of the
external pressure p. It shows that the (T, x) region of the low temperature
phase, which is confined to a very narrow region around x=0.5 at ambient
pressure, expands as p increases, suggesting that the transition is not due to
an order-disorder type one. For the occurrence of the transition, both the Pr
and Ca atoms seem to be necessary. The intimate relationship between the local
structure around the Co ions and the electronic (or spin) state of Co3+ ions is
discussed: For the smaller unit cell volume or the smaller volume of the CoO6
octahedra and for the larger tilting angle of the octahedra, the temperature of
the transition becomes higher. The role of the carriers introduced by the
doping of the A atoms, is also discussed. By analyzing the data of 59Co-NMR
spectra and magnetic susceptibilities of Pr1-xCaxCoO3 the energy separations
among the different spin states of Co3+ and Co4+ are roughly estimated.Comment: 15 pages, 15 figures, 2 tables, submitted to J. Phys. Soc. Jp
Effect of Condensed Tannin in Lotus Corniculatus and Lotus Pedunculatus on Digestion of Rubisco in the Rumen
The in vitro precipitation of ribulose-1,5-bisphosphate carboxylase (Rubisco) by condensed tannin (CT) extracted from Lotus corniculatus and Lotus pedunculatus and the effect of these CT on the in vitro rumen degradation of Rubisco was used to compare the reactivity of these CT. The chemical structure of CT from Lotus corniculatus was homogenous with epicatechin stereochemistry and mostly procyanidin units. The CT from Lotus pedunculatus was heterogenous with mostly prodelphinidin units. The amount of CT required to precipitate all the Rubisco when total soluble leaf protein was incubated with CT from Lotus corniculatus and Lotus pedunculatus was similar. Although CT from both species were able to reduce the in vitro degradation of Rubisco, CT from Lotus corniculatus was less effective than CT from Lotus pedunculatus at reducing this degradation
Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy
We present an angle-resolved photoemission study of Na0.7CoO2, the host
cobaltate of the NaxCoO2.yH2O series. Our results show a large hexagonal-like
hole-type Fermi surface, an extremely narrow strongly renormalized
quasiparticle band and a small Fermi velocity. Along the Gamma to M high
symmetry line, the quasiparticle band crosses the Fermi level from M toward
Gamma consistent with a negative sign of effective single-particle hopping (t
): t is estimated to be about 8 meV which is on the order of exchange coupling
J in this system. This suggests that t ~ J ~ 10 meV is an important energy
scale in the system. Quasiparticles are well defined only in the T-linear
resistivity regime. Small single particle hopping and unconventional
quasiparticle dynamics may have implications for understanding the unusual
behavior of this new class of compounds.Comment: Revised text, Added Figs, Submitted to PR
Genome‐wide CRISPR screen identifies ZIC2 as an essential gene that controls the cell fate of early mesodermal precursors to human heart progenitors
Cardiac progenitor formation is one of the earliest committed steps of human cardiogenesis
and requires the cooperation of multiple gene sets governed by developmental
signaling cascades. To determine the key regulators for cardiac progenitor
formation, we have developed a two-stage genome-wide CRISPR-knockout screen.
We mimicked the progenitor formation process by differentiating human pluripotent
stem cells (hPSCs) into cardiomyocytes, monitored by two distinct stage markers of
early cardiac mesodermal formation and commitment to a multipotent heart progenitor
cell fate: MESP1 and ISL1, respectively. From the screen output, we compiled a
list of 15 candidate genes. After validating seven of them, we identified ZIC2 as an
essential gene for cardiac progenitor formation. ZIC2 is known as a master regulator
of neurogenesis. hPSCs with ZIC2 mutated still express pluripotency markers. However,
their ability to differentiate into cardiomyocytes was greatly attenuated. RNASeq
profiling of the ZIC2-mutant cells revealed that the mutants switched their cell
fate alternatively to the noncardiac cell lineage. Further, single cell RNA-seq analysis
showed the ZIC2 mutants affected the apelin receptor-related signaling pathway during
mesoderm formation. Our results provide a new link between ZIC2 and human
cardiogenesis and document the potential power of a genome-wide unbiased
CRISPR-knockout screen to identify the key steps in human mesoderm precursor
cell- and heart progenitor cell-fate determination during in vitro hPSC cardiogenesis.Swedish Research Council for Health, Working Life and Welfare (Forte)Knut and Alice Wallenberg Foundation, KAW 2013.0028Swedish Research Council, 541-2013-8351, 539‐2013‐7002European Research Council Advanced Research Grant Award, AdG743225Publishe
Ultrasound diagnosis of serous surface papillary borderline ovarian tumor: A case series with a review of the literature
Serous surface papillary borderline ovarian tumors (SSPBOTs) are a rare morphologic variant of serous ovarian tumors that are typically confined to the ovarian surface, while the ovaries themselves tend to appear normal in size and shape. In this report, we describe the findings from five premenopausal women diagnosed with SSPBOTs, in whom ultrasound showed grossly normal ovaries that were partially or wholly covered with irregular solid tumors. In all five cases, histologic examination showed evidence of borderline serous tumors. These findings demonstrate that SSPBOTs can be diagnosed on a preoperative sonographic examination, which could facilitate conservative, fertility-sparing surgery in young women affected by this condition. © 2015 Wiley Periodicals, Inc. J Clin Ultrasound, 2015
Curie Temperatures for Three-Dimensional Binary Ising Ferromagnets
Using the Swendsen and Wang algorithm, high accuracy Monte Carlo simulations
were performed to study the concentration dependence of the Curie temperature
in binary, ferromagnetic Ising systems on the simple-cubic lattice. Our results
are in good agreement with known mean-field like approaches. Based on former
theoretical formulas we propose a new way of estimating the Curie temperature
of these systems.Comment: nr. of pages:13, LATEX. Version 2.09, Scientific Report :02/1994
(Univ. of Bergen, Norway), 7 figures upon reques
Phase segregation in NaxCoO2 for large Na contents
We have investigated a set of sodium cobaltates (NaxCoO2) samples with
various sodium content (0.67 \le x \le 0.75) using Nuclear Quadrupole Resonance
(NQR). The four different stable phases and an intermediate one have been
recognized. The NQR spectra of 59Co allowed us to clearly differentiate the
pure phase samples which could be easily distinguished from multi-phase
samples. Moreover, we have found that keeping samples at room temperature in
contact with humid air leads to destruction of the phase purity and loss of
sodium content. The high sodium content sample evolves progressively into a
mixture of the detected stable phases until it reaches the x=2/3 composition
which appears to be the most stable phase in this part of phase diagram.Comment: 5 pages, 4 figure
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