Spherical orbit closures in simple projective spaces and their normalizations

Let G be a simply connected semisimple algebraic group over an algebraically closed field k of characteristic 0 and let V be a rational simple G-module of finite dimension. If G/H \subset P(V) is a spherical orbit and if X is its closure, then we describe the orbits of X and those of its normalization. If moreover the wonderful completion of G/H is strict, then we give necessary and sufficient combinatorial conditions so that the normalization morphism is a homeomorphism. Such conditions are trivially fulfilled if G is simply laced or if H is a symmetric subgroup.Comment: 24 pages, LaTeX. v4: Final version, to appear in Transformation Groups. Simplified some proofs and corrected minor mistakes, added references. v3: major changes due to a mistake in previous version

Deterministic direct growth of WS2 on CVD graphene arrays

The combination of the exciting properties of graphene with those of monolayer tungsten disulfide (WS2) makes this heterostack of great interest for electronic, optoelectronic and spintronic applications. The scalable synthesis of graphene/WS2 heterostructures on technologically attractive substrates like SiO2 would greatly facilitate the implementation of novel two-dimensional (2D) devices. In this work, we report the direct growth of monolayer WS2 via chemical vapor deposition (CVD) on single-crystal graphene arrays on SiO2. Remarkably, spectroscopic and microscopic characterization reveals that WS2 grows only on top of the graphene crystals so that the vertical heterostack is selectively obtained in a bottom-up fashion. Spectroscopic characterization indicates that, after WS2 synthesis, graphene undergoes compressive strain and hole doping. Tailored experiments show that such hole doping is caused by the modification of the SiO2 stoichiometry at the graphene/SiO2 interface during the WS2 growth. Electrical transport measurements reveal that the heterostructure behaves like an electron-blocking layer at large positive gate voltage, which makes it a suitable candidate for the development of unipolar optoelectronic components

Phylogeny and biogeography of Ceiba Mill. (Malvaceae, Bombacoideae)

The Neotropics is the most species-rich area in the world, and the mechanisms that generated and maintain its biodiversity are still debated. This paper contributes to the debate by investigating the evolutionary and biogeographic history of the genus Ceiba Mill. (Malvaceae, Bombacoideae). Ceiba comprises 18 mostly Neotropical species, largely endemic to two major biomes, seasonally dry tropical forests (SDTFs) and rain forests. Its species are among the most characteristic elements of Neotropical SDTF, one of the most threatened biomes in the tropics. Phylogenetic analyses of DNA sequence data (from the nuclear ribosomal internal transcribed spacers [nrITS] for 30 accessions representing 14 species of Ceiba) recovered the genus as monophyletic. The phylogeny showed geographic and ecological structure in three main clades: (i) a rain forest lineage of nine accessions of C. pentandra sister to the remaining species; (ii) a highly supported clade composed of C. schottii and C. aesculifolia from Central American and Mexican SDTF, plus two accessions of C. samauma from semi-humid, inter Andean valleys in Peru; and (iii) a highly supported South American SDTF clade including 10 species showing little sequence variation. Within this South American SDTF clade, no species represented by multiple accessions were resolved as monophyletic. We demonstrate that the patterns of species age, monophyly, and geographic structure previously reported for SDTF species within the Leguminosae family are not shared by Ceiba, suggesting that further phylogenetic studies of unrelated groups are required to understand general patterns

Migraine mediates the influence of C677T MTHFR genotypes on ischemic stroke risk with a stroke-subtype effect.

BACKGROUND AND PURPOSE: The objective was to investigate the role of C677T MTHFR polymorphism in migraine pathogenesis and in the migraine-ischemic stroke pathway. METHODS: A first genotype-migraine association study was conducted on 100 patients with migraine with aura (MA), 106 with migraine without aura (MO), and 105 subjects without migraine, which provided evidence in favor of association of the TT677 MTHFR genotype with increased risk of MA compared with both control subjects (OR, 2.48; 95% CI, 1.11 to 5.58) and patients with MO (OR, 2.21; 95% CI, 1.01 to 4.82). Based on these findings, mediational models of the genotype-migraine-stroke pathway were fitted on a group of 106 patients with spontaneous cervical artery dissection, 227 young patients whose ischemic stroke was unrelated to a spontaneous cervical artery dissection (noncervical artery dissection), and 187 control subjects, and a genotype-migraine partial mediation model was selected. RESULTS: Both migraine and the TT genotype were more strongly associated to the subgroup of patients with spontaneous cervical artery dissection (OR, 4.06; 95% CI, 1.63 to 10.02 for MA; OR, 5.45; 95% CI, 3.03 to 9.79 for MO; OR, 2.87; 95% CI, 1.45 to 5.68 for TT genotype) than to the subgroup of patients with noncervical artery dissection ischemic stroke (OR, 2.22; 95% CI, 1.00 to 4.96 for MA; OR, 1.81; 95% CI, 1.02 to 3.22 for TT genotype) as compared with controls. CONCLUSIONS: Migraine may act as mediator in the methylenetetrahydrofolate reductase-ischemic stroke pathway with a more prominent effect in the subgroup of patients with spontaneous artery dissection

Connective tissue anomalies in patients with spontaneous cervical artery dissection.

OBJECTIVE: To investigate the prevalence of connective tissue abnormalities in patients with spontaneous cervical artery dissections (sCeAD). METHODS: We systematically assessed clinically detectable signs of connective tissue aberration in a series of consecutive patients with sCeAD and of age- and sex-matched patients with ischemic stroke unrelated to CeAD (non-CeAD IS) by a standard examination protocol including 68 items, and performed extensive molecular investigation for hereditary connective tissue disorders in all patients with sCeAD. RESULTS: The study group included 84 patients with sCeAD (mean age, 44.5 ± 7.8 years; 66.7% men) and 84 patients with non-CeAD IS. None of the patients with sCeAD met clinical or molecular diagnostic criteria for established hereditary connective tissue disorder. Connective tissue abnormalities were detected more frequently in the group of patients with sCeAD than in the group of those with non-CeAD IS (mean number of pathologic findings, 4.5 ± 3.5 vs 1.9 ± 2.3; p < 0.001). Eighty-one patients (96.4%) in the sCeAD group had at least one detectable sign compared with 55 patients (66.7%) in the group with non-CeAD IS (p < 0.001). Skeletal, ocular, and skin abnormalities, as well as craniofacial dysmorphisms, were the clinical signs more strongly associated with sCeAD. Signs suggesting connective tissue abnormality were also more frequently represented in patients with sCeAD than in patients with traumatic CeAD (28.6%, p < 0.001; mean number of pathologic findings, 1.7 ± 3.7, p = 0.045). CONCLUSIONS: Connective tissue abnormalities are frequent in patients with sCeAD. This reinforces the hypothesis that systemic aberrations of the connective tissue might be implicated in the pathogenesis of the disease

High-order fractal states in graphene superlattices

Graphene superlattices were shown to exhibit high-temperature quantum oscillations due to periodic emergence of delocalized Bloch states in high magnetic fields such that unit fractions of the flux quantum pierce a superlattice unit cell. Under these conditions, semiclassical electron trajectories become straight again, similar to the case of zero magnetic field. Here, we report magnetotransport measurements that reveal second-, third-, and fourth-order magnetic Bloch states at high electron densities and temperatures above 100 K. The recurrence of these states creates a fractal pattern intimately related to the origin of Hofstadter butterflies. The hierarchy of the fractal states is determined by the width of magnetic minibands, in qualitative agreement with our band-structure calculations

Antithrombotic medications and the etiology of intracerebral hemorrhage: MUCH-Italy.

23noOBJECTIVE: To test the hypothesis that the effect of antithrombotic medications on the risk of intracerebral hemorrhage (ICH) varies according to the location of the hematoma. METHODS: Consecutive patients with ICH were enrolled as part of the Multicenter Study on Cerebral Hemorrhage in Italy (MUCH-Italy). Multivariable logistic regression models served to examine whether risk factors for ICH and location of the hematoma (deep vs lobar) predict treatment-specific ICH subgroups (antiplatelets-related ICH and oral anticoagulants [OACs]-related ICH). RESULTS: A total of 870 (313 lobar ICH, 557 deep ICH) subjects were included. Of these, 223 (25.6%) were taking antiplatelets and 77 (8.8%) OACs at the time of stroke. The odds of antiplatelet-related ICH increased with aging (odds ratio [OR] 1.05; 95% confidence interval [CI] 1.03-1.07) and hypertension (OR 1.86; 95% CI 1.22-2.85) but had no relation with the anatomical location of ICH. Conversely, lobar location of the hematoma was associated with the subgroup of OAC-related ICH (OR 1.70; 95% CI 1.03-2.81) when compared to the subgroup of patients taking no antithrombotic medications. Within the subgroup of patients taking OACs, international normalized ratio (INR) values were higher in those with lobar ICH as compared to those with deep ICH (2.8 ± 1.1 vs 2.2 ± 0.8; p = 0.011). The proportion of patients with lobar hematoma increased with increasing intensity of anticoagulation, with a ∼2-fold increased odds of lobar compared to deep ICH (odds 2.17; p = 0.03) in those exposed to overanticoagulation (INR values >3.0). CONCLUSIONS: OACs, as opposed to antiplatelets, predispose to lobar location of brain hematomas according to a dose-response relationship.openopenPezzini, A; Grassi, M; Paciaroni, M; Zini, A; Silvestrelli, G; Del Zotto, E; Caso, V; Dell'Acqua, Ml; Giossi, A; Volonghi, I; Simone, Am; Lanari, A; Costa, P; Poli, L; Morotti, A; De Giuli, V; Pepe, D; Gamba, M; Ciccone, A; Ritelli, M; Colombi, M; Agnelli, G; Padovani, APezzini, Alessandro; Grassi, M; Paciaroni, M; Zini, A; Silvestrelli, G; Del Zotto, E; Caso, V; Dell'Acqua, Ml; Giossi, A; Volonghi, I; Simone, Am; Lanari, A; Costa, P; Poli, L; Morotti, A; De Giuli, V; Pepe, D; Gamba, M; Ciccone, A; Ritelli, M; Colombi, Marina; Agnelli, G; Padovani, Alessandr

Sex-related differences in risk factors, type of treatment received and outcomes in patients with atrial fibrillation and acute stroke: Results from the RAF-study (Early Recurrence and Cerebral Bleeding in Patients with Acute Ischemic Stroke and Atrial Fibrillation)

Introduction: Atrial fibrillation is an independent risk factor of thromboembolism. Women with atrial fibrillation are at a higher overall risk for stroke compared to men with atrial fibrillation. The aim of this study was to evaluate for sex differences in patients with acute stroke and atrial fibrillation, regarding risk factors, treatments received and outcomes. Methods Data were analyzed from the “Recurrence and Cerebral Bleeding in Patients with Acute Ischemic Stroke and Atrial Fibrillation” (RAF-study), a prospective, multicenter, international study including only patients with acute stroke and atrial fibrillation. Patients were followed up for 90 days. Disability was measured by the modified Rankin Scale (0–2 favorable outcome, 3–6 unfavorable outcome). Results: Of the 1029 patients enrolled, 561 were women (54.5%) (p &lt; 0.001) and younger (p &lt; 0.001) compared to men. In patients with known atrial fibrillation, women were less likely to receive oral anticoagulants before index stroke (p = 0.026) and were less likely to receive anticoagulants after stroke (71.3% versus 78.4%, p = 0.01). There was no observed sex difference regarding the time of starting anticoagulant therapy between the two groups (6.4 ± 11.7 days for men versus 6.5 ± 12.4 days for women, p = 0.902). Men presented with more severe strokes at onset (mean NIHSS 9.2 ± 6.9 versus 8.1 ± 7.5, p &lt; 0.001). Within 90 days, 46 (8.2%) recurrent ischemic events (stroke/TIA/systemic embolism) and 19 (3.4%) symptomatic cerebral bleedings were found in women compared to 30 (6.4%) and 18 (3.8%) in men (p = 0.28 and p = 0.74). At 90 days, 57.7% of women were disabled or deceased, compared to 41.1% of the men (p &lt; 0.001). Multivariate analysis did not confirm this significance. Conclusions: Women with atrial fibrillation were less likely to receive oral anticoagulants prior to and after stroke compared to men with atrial fibrillation, and when stroke occurred, regardless of the fact that in our study women were younger and with less severe stroke, outcomes did not differ between the sexes

Ultrafast, Zero-Bias, Graphene Photodetectors with Polymeric Gate Dielectric on Passive Photonic Waveguides.

We report compact, scalable, high-performance, waveguide integrated graphene-based photodetectors (GPDs) for telecom and datacom applications, not affected by dark current. To exploit the photothermoelectric (PTE) effect, our devices rely on a graphene/polymer/graphene stack with static top split gates. The polymeric dielectric, poly(vinyl alcohol) (PVA), allows us to preserve graphene quality and to generate a controllable p-n junction. Both graphene layers are fabricated using aligned single-crystal graphene arrays grown by chemical vapor deposition. The use of PVA yields a low charge inhomogeneity ∼8 × 1010 cm-2 at the charge neutrality point, and a large Seebeck coefficient ∼140 μV K-1, enhancing the PTE effect. Our devices are the fastest GPDs operating with zero dark current, showing a flat frequency response up to 67 GHz without roll-off. This performance is achieved on a passive, low-cost, photonic platform, and does not rely on nanoscale plasmonic structures. This, combined with scalability and ease of integration, makes our GPDs a promising building block for next-generation optical communication devices