1,566 research outputs found
Discovering new two-dimensional topological insulators from computational screening
We have performed a computational screening of topological two-dimensional
(2D) materials from the Computational 2D Materials Database (C2DB) employing
density functional theory. A full \textit{ab initio} scheme for calculating
hybrid Wannier functions directly from the Kohn-Sham orbitals has been
implemented and the method was used to extract indices, Chern
numbers and Mirror Chern numbers of 3331 2D systems including both
experimentally known and hypothetical 2D materials. We have found a total of 46
quantum spin Hall insulators, 7 quantum anomalous Hall insulators and 9
crystalline topological insulators that are all predicted to be dynamically
stable. Roughly one third of these were known prior to the screening. The most
interesting of the novel topological insulators are investigated in more
detail. We show that the calculated topological indices of the quantum
anomalous Hall insulators are highly sensitive to the approximation used for
the exchange-correlation functional and reliable predictions of the topological
properties of these materials thus require methods beyond density functional
theory. We also performed calculations, which yield a gap of 0.65 eV for
the quantum spin Hall insulator PdSe in the MoS crystal structure. This
is significantly higher than any known 2D topological insulator and three times
larger than the Kohn-Sham gap.Comment: 12 page
Transgenic Overexpression of LARGE Induces alpha-Dystroglycan Hyperglycosylation in Skeletal and Cardiac Muscle
Background: LARGE is one of seven putative or demonstrated glycosyltransferase enzymes defective in a common group of muscular dystrophies with reduced glycosylation of alpha-dystroglycan. Overexpression of LARGE induces hyperglycosylation of alpha-dystroglycan in both wild type and in cells from dystroglycanopathy patients, irrespective of their primary gene defect, restoring functional glycosylation. Viral delivery of LARGE to skeletal muscle in animal models of dystroglycanopathy has identical effects in vivo, suggesting that the restoration of functional glycosylation could have therapeutic applications in these disorders. Pharmacological strategies to upregulate Large expression are also being explored.Methodology/Principal Findings: In order to asses the safety and efficacy of long term LARGE over-expression in vivo, we have generated four mouse lines expressing a human LARGE transgene. On observation, LARGE transgenic mice were indistinguishable from the wild type littermates. Tissue analysis from young mice of all four lines showed a variable pattern of transgene expression: highest in skeletal and cardiac muscles, and lower in brain, kidney and liver. Transgene expression in striated muscles correlated with alpha-dystroglycan hyperglycosylation, as determined by immunoreactivity to antibody IIH6 and increased laminin binding on an overlay assay. Other components of the dystroglycan complex and extracellular matrix ligands were normally expressed, and general muscle histology was indistinguishable from wild type controls. Further detailed muscle physiological analysis demonstrated a loss of force in response to eccentric exercise in the older, but not in the younger mice, suggesting this deficit developed over time. However this remained a subclinical feature as no pathology was observed in older mice in any muscles including the diaphragm, which is sensitive to mechanical load-induced damage.Conclusions/Significance: This work shows that potential therapies in the dystroglycanopathies based on LARGE upregulation and alpha-dystroglycan hyperglycosylation in muscle should be safe
High throughput computational screening for 2D ferromagnetic materials: the critical role of anisotropy and local correlations
The recent observation of ferromagnetic order in two-dimensional (2D)
materials has initiated a booming interest in the subject of 2D magnetism. In
contrast to bulk materials, 2D materials can only exhibit magnetic order in the
presence of magnetic anisotropy. In the present work we have used the
Computational 2D Materials Database (C2DB) to search for new ferromagnetic 2D
materials using the spinwave gap as a simple descriptor that accounts for the
role of magnetic anisotropy. In addition to known compounds we find 12 novel
insulating materials that exhibit magnetic order at finite temperatures. For
these we evaluate the critical temperatures from classical Monte Carlo
simulations of a Heisenberg model with exchange and anisotropy parameters
obtained from first principles. Starting from 150 stable ferromagnetic 2D
materials we find five candidates that are predicted to have critical
temperatures exceeding that of CrI3. We also study the effect of Hubbard
corrections in the framework of DFT+U and find that the value of U can have a
crucial influence on the prediction of magnetic properties. Our work provides
new insight into 2D magnetism and identifies a new set of promising monolayers
for experimental investigation.Comment: Version 2. Updated Table 1 with corrected values of exchange coupling
constant
High throughput computational screening for 2D ferromagnetic materials: the critical role of anisotropy and local correlations
The recent observation of ferromagnetic order in two-dimensional (2D)
materials has initiated a booming interest in the subject of 2D magnetism. In
contrast to bulk materials, 2D materials can only exhibit magnetic order in the
presence of magnetic anisotropy. In the present work we have used the
Computational 2D Materials Database (C2DB) to search for new ferromagnetic 2D
materials using the spinwave gap as a simple descriptor that accounts for the
role of magnetic anisotropy. In addition to known compounds we find 12 novel
insulating materials that exhibit magnetic order at finite temperatures. For
these we evaluate the critical temperatures from classical Monte Carlo
simulations of a Heisenberg model with exchange and anisotropy parameters
obtained from first principles. Starting from 150 stable ferromagnetic 2D
materials we find five candidates that are predicted to have critical
temperatures exceeding that of CrI3. We also study the effect of Hubbard
corrections in the framework of DFT+U and find that the value of U can have a
crucial influence on the prediction of magnetic properties. Our work provides
new insight into 2D magnetism and identifies a new set of promising monolayers
for experimental investigation.Comment: Version 2. Updated Table 1 with corrected values of exchange coupling
constant
Unconventional Metallic Magnetism in LaCrSb{3}
Neutron-diffraction measurements in LaCrSb{3} show a coexistence of
ferromagnetic and antiferromagnetic sublattices below Tc=126 K, with ordered
moments of 1.65(4) and 0.49(4) Bohr magnetons per formula unit, respectively
(T=10 K), and a spin reorientation transition at ~95 K. No clear peak or step
was observed in the specific heat at Tc. Coexisting localized and itinerant
spins are suggested.Comment: PRL, in pres
Detection of possible factors favouring the evolution of migraine without aura into chronic migraine
In a minority of cases, the natural history of migraine without aura (MO) is characterised over time by its evolution into a form of chronic migraine (CM). In order to detect the possible factors predicting this negative evolution of MO, we searched in our Headache Centre files for all clinical records that met the following criteria: (a) first visit between 1976 and 1998; (b) diagnosis of MO or of common migraine at the first observation, with or without association with other primary headache types; (c) <15 days per month of migraine at the first observation; and (d) at least one follow-up visit at least 10 years after the first visit. The patients thus identified were then divided into two groups based on a favourable/steady evolution (Group A: n = 243, 195 women and 48 men) or an unfavourable evolution (Group B: n = 72, 62 women and 10 men) of their migraine over time. In the two groups, we compared various clinical parameters that were present at the first observation or emerged at the subsequent follow-up visits. The parameters that were statistically significantly more frequent in Group B--and can therefore be considered possible negative prognostic factors--were: (a) ≥ 10 days per month of migraine at the first observation; (b) presence of depression at the first visit in males; and (c) onset of depression or arterial hypertension after the first observation but before transformation to CM in females. Based on these findings, in MO patients the high frequency of migraine attacks, comorbidity with depression, and the tendency to develop arterial hypertension should require particular attention and careful management to prevent evolution into CM
Barley beta-glucan promotes MnSOD expression and enhances angiogenesis under oxidative microenvironment
Manganese superoxide dismutase (MnSOD), a foremost antioxidant enzyme, plays a key role in angiogenesis. Barley-derived (1.3) β-d-glucan (β-d-glucan) is a natural water-soluble polysaccharide with antioxidant properties. To explore the effects of β-d-glucan on MnSOD-related angiogenesis under oxidative stress, we tested epigenetic mechanisms underlying modulation of MnSOD level in human umbilical vein endothelial cells (HUVECs) and angiogenesis in vitro and in vivo. Long-term treatment of HUVECs with 3% w/v β-d-glucan significantly increased the level of MnSOD by 200% ± 2% compared to control and by 50% ± 4% compared to untreated H2O2-stressed cells. β-d-glucan-treated HUVECs displayed greater angiogenic ability. In vivo, 24 hrs-treatment with 3% w/v β-d-glucan rescued vasculogenesis in Tg (kdrl: EGFP) s843Tg zebrafish embryos exposed to oxidative microenvironment. HUVECs overexpressing MnSOD demonstrated an increased activity of endothelial nitric oxide synthase (eNOS), reduced load of superoxide anion (O2-) and an increased survival under oxidative stress. In addition, β-d-glucan prevented the rise of hypoxia inducible factor (HIF)1-α under oxidative stress. The level of histone H4 acetylation was significantly increased by β-d-glucan. Increasing histone acetylation by sodium butyrate, an inhibitor of class I histone deacetylases (HDACs I), did not activate MnSOD-related angiogenesis and did not impair β-d-glucan effects. In conclusion, 3% w/v β-d-glucan activates endothelial expression of MnSOD independent of histone acetylation level, thereby leading to adequate removal of O2-, cell survival and angiogenic response to oxidative stress. The identification of dietary β-d-glucan as activator of MnSOD-related angiogenesis might lead to the development of nutritional approaches for the prevention of ischemic remodelling and heart failure
APE Results of Hadron Masses in Full QCD Simulations
We present numerical results obtained in full QCD with 2 flavors of Wilson
fermions. We discuss the relation between the phase of Polyakov loops and the
{\bf sea} quarks boundary conditions. We report preliminary results about the
HMC autocorrelation of the hadronic masses, on a lattice
volume, at with .Comment: 3 pages, compressed ps-file (uufiles), Contribution to Lattice 9
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