13,685 research outputs found
Control of effective free energy landscape in a frustrated magnet by a field pulse
Thermal fluctuations can lift the degeneracy of a ground state manifold,
producing a free energy landscape without accidentally degenerate minima. In a
process known as order by disorder, a subset of states incorporating
symmetry-breaking may be selected. Here, we show that such a free energy
landscape can be controlled in a non-equilibrium setting as the slow motion
within the ground state manifold is governed by the fast modes out of it. For
the paradigmatic case of the classical pyrochlore XY antiferromagnet, we show
that a uniform magnetic field pulse can excite these fast modes to generate a
tunable effective free energy landscape with minima at thermodynamically
unstable portions of the ground state manifold.Comment: 10 pages, 6 figures; minor revision
5-hydroxymethylcytosine is a key epigenetic regulator of keratinocyte stem cells during psoriasis pathogenesis
Epigenetic regulation is now known to play an important role in determining stem cell fate during normal tissue development and disease pathogenesis. In this study, we report loss of 5-hydroxymethylcytosine (5-hmC) mediated by ten-eleven translocation (TET) methylcytosine dioxygenases in keratinocyte stem cells (KSCs) and in their progenitor transit-amplifying (TA) cells of psoriatic lesions. We establish the DNA hydroxymethylation profile in both human psoriasis as well as in the imiquimod (IMQ)-induced mouse psoriasis model. Genome-wide mapping of 5-hmC in IMQ-treated mice epithelium revealed a loci-specific reduction of 5-hmC in genes associated with maintaining stem cell homeostasis including those involved in the RAR and Wnt/ÎČ-catenin signaling pathways. Restoration of TET expression in human KSC cultures via vitamin C treatment increased 5-hmC levels and induced more normal KSC differentiation. We found that by modulating 5-hmC levels in vitro, we could alter downstream expression of genes important in regulating stem cell homeostasis like nestin as well as IL-17R known to promote the psoriatic phenotype. Our findings demonstrate that loss of 5-hmC is a critical epigenomic phenomenon in KSCs and TA cells during psoriasis pathogenesis.2019-12-17T00:00:00
Can We Predict Vulnerability to Poverty?
There are alternative definitions of vulnerability to poverty. Most researchers prefer to define vulnerability as the probability of a household or individual falling into poverty in the future. Based on this definition and using household survey panel data from rural China, this paper attempt to assess the extent to which we can measure vulnerability to poverty. The assessment is based on comparisons between predicted vulnerability and actually observed poverty. We find that the precision of prediction, first, varies depending on the vulnerability line; our results suggest setting the line at 50 per cent in order to improve predictive power. Second, precision depends on how permanent income is estimated. Assuming log-normal distribution of income, it is preferable to use past weighted average income as an estimate of permanent income rather than using regressions to gage permanent income. And third, prediction precision depends on the chosen poverty line. More accurate measurement of vulnerability to poverty is obtained with a higher poverty line of US1.vulnerability, poverty, permanent income, transitory income
Competing electronic orders on Kagome lattices at van Hove filling
The electronic orders in Hubbard models on a Kagome lattice at van Hove
filling are of intense current interest and debate. We study this issue using
the singular-mode functional renormalization group theory. We discover a rich
variety of electronic instabilities under short range interactions. With
increasing on-site repulsion , the system develops successively
ferromagnetism, intra unit-cell antiferromagnetism, and charge bond order. With
nearest-neighbor Coulomb interaction alone (U=0), the system develops
intra-unit-cell charge density wave order for small , s-wave
superconductivity for moderate , and the charge density wave order appears
again for even larger . With both and , we also find spin bond order
and chiral superconductivity in some particular
regimes of the phase diagram. We find that the s-wave superconductivity is a
result of charge density wave fluctuations and the squared logarithmic
divergence in the pairing susceptibility. On the other hand, the d-wave
superconductivity follows from bond order fluctuations that avoid the matrix
element effect. The phase diagram is vastly different from that in honeycomb
lattices because of the geometrical frustration in the Kagome lattice.Comment: 8 pages with 9 color figure
Quantum dimer model for the spin-1/2 kagome Z2 spin liquid
We revisit the description of the low-energy singlet sector of the spin-1/2
Heisenberg antiferromagnet on kagome in terms of an effective quantum dimer
model. With the help of exact diagonalizations of appropriate finite-size
clusters, we show that the embedding of a given process in its kagome
environment leads to dramatic modifications of the amplitudes of the elementary
loop processes, an effect not accessible to the standard approach based on the
truncation of the Hamiltonian to the nearest-neighbour valence-bond basis. The
resulting parameters are consistent with a Z spin liquid rather than with a
valence-bond crystal, in agreement with the last density matrix renormalization
group results.Comment: Potential terms of the effective QDM include
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