10,277 research outputs found
On magnetic leaf-wise intersections
In this article we introduce the notion of a magnetic leaf-wise intersection
point which is a generalization of the leaf-wise intersection point with
magnetic effects. We also prove the existence of magnetic leaf-wise
intersection points under certain topological assumptions.Comment: 43 page
Developing an efficient process for the production of retinal progenitor cells (RPCs) from human pluripotent stem cells using lowered oxygen tension
The efficient differentiation of retinal cells from human pluripotent stem
cells remains a major challenge for the development of successful and cost-effective
cellular therapies for various forms of blindness. Current differentiation strategies
rely upon exposing pluripotent stem cells to soluble growth factors which play key
roles during early development (such as DKK-1, Noggin and IGF-1) at 20% oxygen
(O2). This O2 tension is however, considerably higher than O2 levels during
organogenesis and may impair the differentiation process. In this study, we examined
the effect of mimicking the physiological O2 tension (2%) on the generation of
retinal progenitor cells (RPCs) from human induced pluripotent stem cells (iPSCs)
and human embryonic stem cells (hESCs). Both cell types were induced to
differentiate into RPCs at 20% and 2% O2. After three days in suspension culture as
embryoid bodies (EBs), 2% O2 caused the activation of hypoxia inducible factor
(HIF) responsive genes VEGF and LDHA and was accompanied by elevated
expression levels of the early eye field genes Six3 and Lhx2. 21 days after plating
EBs in an adherent culture, we observed more RPCs co-expressing Pax6 and Chx10
at 2% O2. qPCR analysis confirmed that lowering O2 tension had caused a rise in the
expression of both genes compared to 20% O₂. Our results indicate that mimicking physiological O2 is a favorable condition for the efficient generation of RPCs from
both hiPSCs and hESCs
Quantification of Thickness Effects for Circumferential Through-Wall Cracked Pipe Bend with Un-Uniform Thickness under In-Plane Opening Bending
AbstractAn Elbow is one of the major component that make up the piping system of a nuclear power plant and chemical plant facilities. In general, the elbow is made by welding a straight pipe and bend part. So, periodic welding inspection is required due to the potential defects in weld zone. Recently, the application of induction heating pipe bend is increasing in order to reduce this problem. Pipe bend made by induction heating band is not necessary welding process because it is made by bending a straight pipe but the intrados thickness and the extrados thickness are different. On the other hand, J-integral is widely used to evaluate a structural integrity (to check crack stability) but the J estimation of pipe bend with un-uniform thickness is very difficult because of the thickness differences in each locations.This paper proposes a reference stress based J estimation scheme of circumferential through-wall cracked pipe bend with un-uniform thickness under in-plane opening bending loading condition. The pipe bend with un-uniform thickness is assumed to have different thickness between intrados and extrados and the crack to be located in the entre of the pipe bend, either at the intrados or extrados
Structural approximations to positive maps and entanglement breaking channels
Structural approximations to positive, but not completely positive maps are
approximate physical realizations of these non-physical maps. They find
applications in the design of direct entanglement detection methods. We show
that many of these approximations, in the relevant case of optimal positive
maps, define an entanglement breaking channel and, consequently, can be
implemented via a measurement and state-preparation protocol. We also show how
our findings can be useful for the design of better and simpler direct
entanglement detection methods.Comment: 18 pages, 3 figure
Facile one-pot synthesis of dual-cation incorporated titanosilicate and its deposition to membrane surfaces for simultaneous removal of Cs⁺ and Sr²⁺
Selective removal of 137Cs and 90Sr from aqueous environments is essential for the volume reduction and ultimate safe storage of nuclear waste. This study introduces a facile one-pot hydrothermal synthesis of Dual-cation form of TitanoSilicate (DTS, M3HTi4O4(SiO4)3, M = Na+ and K+) for the effective and simultaneous removal of Cs+ and Sr2+. DTS showed enhanced adsorption capacities (469 mg/g for Cs+ and 179 mg/g for Sr2+) and the adsorption kinetics were extremely fast with around 98% and >99% removal achieved within 1 min from a dilute Cs+ and Sr2+ solution, respectively. Moreover, DTS indicated the superior selectivity for both Cs+ and Sr2+ due to the dual-cation incorporation in the structure. In groundwater, the distribution coefficients (Kd at V/m = 1000 mL/g) for DTS were high for both Cs+ (1 ppm, 2.9 × 105 mL/g) and Sr2+ (1 ppm, 1.0 × 105 mL/g), and even in seawater DTS maintained a Cs+ (1 ppm) Kd value as high as 4.9 × 104 mL/g. Remarkably, DTS is synthesized as a membrane with graphene oxide for continuous removal of the radionuclides, which is extremely beneficial to purifying a large volume of contaminated water
How confined lubricants diffuse during shear
The translational diffusion of a fluorescent dye embedded at a dilute concentration in a confined fluid was compared at rest and during shear. The fluid, octamethylcyclotetrasiloxane (OMCTS), was confined between step-free muscovite mica to thickness 3-4 layers. Fluorescence correlation spectroscopy showed that the time scales of intensity-intensity autocorrelation functions were essentially the same during shear and at rest, except they were faster during shear by a factor of 2 to 5. This dynamical probe of how liquids order in molecularly thin films fails to support the hypothesis that shear produced a melting transition.open242
Electron affinity of Li: A state-selective measurement
We have investigated the threshold of photodetachment of Li^- leading to the
formation of the residual Li atom in the state. The excited residual
atom was selectively photoionized via an intermediate Rydberg state and the
resulting Li^+ ion was detected. A collinear laser-ion beam geometry enabled
both high resolution and sensitivity to be attained. We have demonstrated the
potential of this state selective photodetachment spectroscopic method by
improving the accuracy of Li electron affinity measurements an order of
magnitude. From a fit to the Wigner law in the threshold region, we obtained a
Li electron affinity of 0.618 049(20) eV.Comment: 5 pages,6 figures,22 reference
Non-Markovian Exciton-Phonon Interactions in Core-Shell Colloidal Quantum Dots at Femtosecond Timescales
CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOWe perform two-dimensional coherent spectroscopy on CdSe/CdZnS core-shell colloidal quantum dots at cryogenic temperatures. In the two-dimensional spectra, sidebands due to electronic coupling with CdSe lattice LO-phonon modes are observed to have evolutions deviating from the exponential dephasing expected from Markovian spectral diffusion, which is instantaneous and memoryless. Comparison to simulations provides evidence that LO-phonon coupling induces energy-gap fluctuations on the finite timescales of nuclear motion. The femtosecond resolution of our technique probes exciton dynamics directly on the timescales of phonon coupling in nanocrystals.123516CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOSem informação2013/16911-22016/50011-7This work was supported by the Department of Energy Grant No. DE-SC0015782. D. B. A. acknowledges support by a fellowship from the Brazilian National Council for Scientific and Technological Development (CNPq). L. A. P. acknowledges support from FAPESP (Projects No. 2013/16911-2 and No. 2016/50011-7)
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