18,382 research outputs found
Compact conformally Kahler Einstein-Weyl manifolds
We give a classification of compact conformally Kahler Einstein-Weyl
manifolds whose Ricci tensor is hermitian.Comment: 11 page
Slow-light enhanced optical detection in liquid-infiltrated photonic crystals
Slow-light enhanced optical detection in liquid-infiltrated photonic crystals
is theoretically studied. Using a scattering-matrix approach and the
Wigner-Smith delay time concept, we show that optical absorbance benefits both
from slow-light phenomena as well as a high filling factor of the energy
residing in the liquid. Utilizing strongly dispersive photonic crystal
structures, we numerically demonstrate how liquid-infiltrated photonic crystals
facilitate enhanced light-matter interactions, by potentially up to an order of
magnitude. The proposed concept provides strong opportunities for improving
existing miniaturized absorbance cells for optical detection in lab-on-a-chip
systems.Comment: Paper accepted for the "Special Issue OWTNM 2007" edited by A.
Lavrinenko and P. J. Robert
Contributions of Mammalian Chimeras to Pluripotent Stem Cell Research.
Chimeras are widely acknowledged as the gold standard for assessing stem cell pluripotency, based on their capacity to test donor cell lineage potential in the context of an organized, normally developing tissue. Experimental chimeras provide key insights into mammalian developmental mechanisms and offer a resource for interrogating the fate potential of various pluripotent stem cell states. We highlight the applications and current limitations presented by intra- and inter-species chimeras and consider their future contribution to the stem cell field. Despite the technical and ethical demands of experimental chimeras, including human-interspecies chimeras, they are a provocative resource for achieving regenerative medicine goals.British Heart Foundation Centre of Regenerative Medicine, Wellcome Trust, Medical Research Council Cambridge Stem Cell Institute, Cambridge NIHR Biomedical Research CentreThis is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.stem.2016.07.01
Correlation-induced conductance suppression at level degeneracy in a quantum dot
The large, level-dependent g-factors in an InSb nanowire quantum dot allow
for the occurrence of a variety of level crossings in the dot. While we observe
the standard conductance enhancement in the Coulomb blockade region for aligned
levels with different spins due to the Kondo effect, a vanishing of the
conductance is found at the alignment of levels with equal spins. This
conductance suppression appears as a canyon cutting through the web of direct
tunneling lines and an enclosed Coulomb blockade region. In the center of the
Coulomb blockade region, we observe the predicted correlation-induced
resonance, which now turns out to be part of a larger scenario. Our findings
are supported by numerical and analytical calculations.Comment: 5 pages, 4 figure
Human-Mouse Chimerism Validates Human Stem Cell Pluripotency.
Pluripotent stem cells are defined by their capacity to differentiate into all three tissue layers that comprise the body. Chimera formation, generated by stem cell transplantation to the embryo, is a stringent assessment of stem cell pluripotency. However, the ability of human pluripotent stem cells (hPSCs) to form embryonic chimeras remains in question. Here we show using a stage-matching approach that human induced pluripotent stem cells (hiPSCs) and human embryonic stem cells (hESCs) have the capacity to participate in normal mouse development when transplanted into gastrula-stage embryos, providing in vivo functional validation of hPSC pluripotency. hiPSCs and hESCs form interspecies chimeras with high efficiency, colonize the embryo in a manner predicted from classical developmental fate mapping, and differentiate into each of the three primary tissue layers. This faithful recapitulation of tissue-specific fate post-transplantation underscores the functional potential of hPSCs and provides evidence that human-mouse interspecies developmental competency can occur.This work was supported by National Institutes of Health grant No. 1R21ID012228 (R.A.P.); Medical Research Council/British Heart Foundation grant No. G1000847 (R.A.P.); British Heart Foundation Ph.D. studentship (V.L.M.); British Heart Foundation Centre of Regenerative Medicine (Oxford grant RM/13/3/3015); core support from the Wellcome Trust – Medical Research Council Cambridge Stem Cell Institute; and the Cambridge NIHR Biomedical Research Centre.This is the final version of the article. It first appeared from Cell Press via http://dx.doi.org/10.1016/j.stem.2015.11.01
Antiferromagnetic noise correlations in optical lattices
We analyze how noise correlations probed by time-of-flight (TOF) experiments
reveal antiferromagnetic (AF) correlations of fermionic atoms in
two-dimensional (2D) and three-dimensional (3D) optical lattices. Combining
analytical and quantum Monte Carlo (QMC) calculations using experimentally
realistic parameters, we show that AF correlations can be detected for
temperatures above and below the critical temperature for AF ordering. It is
demonstrated that spin-resolved noise correlations yield important information
about the spin ordering. Finally, we show how to extract the spin correlation
length and the related critical exponent of the AF transition from the noise.Comment: 4 pages, 4 figure
Selected new developments in computational chemistry.
Molecular dynamics is a general technique for simulating the time-dependent properties of molecules and their environments. Quantum mechanics, as applied to molecules or clusters of molecules, provides a prescription for predicting properties exactly (in principle). It is reasonable to expect that both will have a profound effect on our understanding of environmental chemistry in the future. In this review, we consider several recent advances and applications in computational chemistry
Frequency response in surface-potential driven electro-hydrodynamics
Using a Fourier approach we offer a general solution to calculations of slip
velocity within the circuit description of the electro-hydrodynamics in a
binary electrolyte confined by a plane surface with a modulated surface
potential. We consider the case with a spatially constant intrinsic surface
capacitance where the net flow rate is in general zero while harmonic rolls as
well as time-averaged vortex-like components may exist depending on the spatial
symmetry and extension of the surface potential. In general the system displays
a resonance behavior at a frequency corresponding to the inverse RC time of the
system. Different surface potentials share the common feature that the
resonance frequency is inversely proportional to the characteristic length
scale of the surface potential. For the asymptotic frequency dependence above
resonance we find a 1/omega^2 power law for surface potentials with either an
even or an odd symmetry. Below resonance we also find a power law omega^alpha
with alpha being positive and dependent of the properties of the surface
potential. Comparing a tanh potential and a sech potential we qualitatively
find the same slip velocity, but for the below-resonance frequency response the
two potentials display different power law asymptotics with alpha=1 and
alpha~2, respectively.Comment: 4 pages including 1 figure. Accepted for PR
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