We explore the influence of local strain on the electronic structure of graphene. We show that strain can be easily tailored to generate electron beam collimation, 1D channels, surface states, and ...confinement. These can be seen as basic elements for all-graphene electronics which, by suitable engineering of local strain profiles, could be integrated on a single graphene sheet. In addition this proposal has the advantage that patterning can be made on substrates rather than on graphene, thereby protecting the integrity of the latter.
A condensate of excitons was theoretically conjectured in the 1960s but has been challenging to pinpoint experimentally. Evidence has now emerged that it could be the ground state of tungsten ...ditelluride, a rich topological material.
Two air-stable, isostructural, mononuclear six-coordinate manganese(II) and cobalt(II) oxamate complexes, M(4-HOpa)2(H2O)2 4-HOpa = N-4-hydroxyphenyloxamate; M= Mn2+ (1) or Co2+ (2), exhibit ...field-induced slow magnetic relaxation. A bottleneck process is observed throughout the temperature range of 2–20 K for 1, while for 2, it dominates only at low temperatures (2–4 K). Additionally, the Raman process n = 6.9(2) is responsible for an increase in the relaxation time at higher temperatures to 2.
Recent experiments suggest that excitonic degrees of freedom play an important role in precipitating the charge density wave (CDW) transition in 1T−TiSe2. Through systematic calculations of the ...electronic and phonon spectrum based on density functional perturbation theory, we show that the predicted critical doping of the CDW phase overshoots the experimental value by 1 order of magnitude. In contrast, an independent self-consistent many-body calculation of the excitonic order parameter and renormalized band structure is able to capture the experimental phase diagram in extremely good qualitative and quantitative agreement. This demonstrates that electron-electron interactions and the excitonic instability arising from direct electron-hole coupling are pivotal to accurately describe the nature of the CDW in this system. This has important implications to understand the emergence of superconductivity within the CDW phase of this and related systems.
The problem of electron-electron interactions in graphene is reviewed. Starting from the screening of long-range interactions in these systems, the existence of an emerging Dirac liquid of Lorentz ...invariant quasiparticles in the weak-coupling regime is discussed, as well as the formation of strongly correlated electronic states in the strong-coupling regime. The analogy and connections between the many-body problem and the Coulomb impurity problem are also analyzed. The problem of the magnetic instability and Kondo effect of impurities and/or adatoms in graphene is also discussed in analogy with classical models of many-body effects in ordinary metals. Lorentz invariance is shown to play a fundamental role and leads to effects that span the whole spectrum, from the ultraviolet to the infrared. The effect of an emerging Lorentz invariance is also discussed in the context of finite size and edge effects as well as mesoscopic physics. The effects of strong magnetic fields in single layers and some of the main aspects of the many-body problem in graphene bilayers are briefly reviewed. In addition to reviewing the fully understood aspects of the many-body problem in graphene, a plethora of interesting issues are shown to remain open, both theoretically and experimentally, and the field of graphene research is still exciting and vibrant.
The ability to switch magnetic elements by spin‐orbit‐induced torques has recently attracted much attention for a path toward high‐performance, nonvolatile memories with low power consumption. ...Realizing efficient spin‐orbit‐based switching requires the harnessing of both new materials and novel physics to obtain high charge‐to‐spin conversion efficiencies, thus making the choice of spin source crucial. Here, the observation of spin‐orbit torque switching in bilayers consisting of a semimetallic film of 1T′‐MoTe2 adjacent to permalloy is reported. Deterministic switching is achieved without external magnetic fields at room temperature, and the switching occurs with currents one order of magnitude smaller than those typical in devices using the best‐performing heavy metals. The thickness‐dependence can be understood if the interfacial spin‐orbit contribution is considered in addition to the bulk spin Hall effect. Further threefold reduction in the switching current is demonstrated with resort to dumbbell‐shaped magnetic elements. These findings foretell exciting prospects of using MoTe2 for low‐power semimetal‐material‐based spin devices.
Realizing efficient spin‐orbit‐based switching requires the harnessing of both new materials and physics to obtain high charge‐to‐spin conversion efficiencies. The observation of spin‐orbit torque switching in bilayers consisting of a semimetallic film of 1T′‐MoTe2 adjacent to permalloy is reported. Deterministic switching is achieved without external magnetic fields at room temperature with currents one order of magnitude smaller than those using heavy metals.
Objective
Faster time from onset to recanalization (OTR) in acute ischemic stroke using endovascular therapy (ET) has been associated with better outcome. However, previous studies were based on ...less‐effective first‐generation devices, and analyzed only dichotomized disability outcomes, which may underestimate the full effect of treatment.
Methods
In the combined databases of the SWIFT and STAR trials, we identified patients treated with the Solitaire stent retriever with achievement of substantial reperfusion (Thrombolysis in Cerebral Infarction TICI 2b–3). Ordinal numbers needed to treat values were derived by populating joint outcome tables.
Results
Among 202 patients treated with ET with TICI 2b to 3 reperfusion, mean age was 68 (±13), 62% were female, and median National Institutes of Health Stroke Scale (NIHSS) score was 17 (interquartile range IQR: 14–20). Day 90 modified Rankin Scale (mRS) outcomes for OTR time intervals ranging from 180 to 480 minutes showed substantial time‐related reductions in disability across the entire outcome range. Shorter OTR was associated with improved mean 90‐day mRS (1.4 vs. 2.4 vs. 3.3, for OTR groups of 124‐240 vs. 241‐360 vs. 361‐660 minutes; p < 0.001). The number of patients identified as benefitting from therapy with shorter OTR were 3‐fold (range, 1.5–4.7) higher on ordinal, compared with dichotomized analysis. For every 15‐minute acceleration of OTR, 34 per 1,000 treated patients had improved disability outcome.
Interpretation
Analysis of disability over the entire outcome range demonstrates a marked effect of shorter time to reperfusion upon improved clinical outcome, substantially higher than binary metrics. For every 5‐minute delay in endovascular reperfusion, 1 of 100 patients has a worse disability outcome. Ann Neurol 2015;78:584–593
Among patients with acute ischemic stroke due to occlusions in the proximal anterior intracranial circulation, less than 40% regain functional independence when treated with intravenous tissue ...plasminogen activator (t-PA) alone. Thrombectomy with the use of a stent retriever, in addition to intravenous t-PA, increases reperfusion rates and may improve long-term functional outcome.
We randomly assigned eligible patients with stroke who were receiving or had received intravenous t-PA to continue with t-PA alone (control group) or to undergo endovascular thrombectomy with the use of a stent retriever within 6 hours after symptom onset (intervention group). Patients had confirmed occlusions in the proximal anterior intracranial circulation and an absence of large ischemic-core lesions. The primary outcome was the severity of global disability at 90 days, as assessed by means of the modified Rankin scale (with scores ranging from 0 no symptoms to 6 death).
The study was stopped early because of efficacy. At 39 centers, 196 patients underwent randomization (98 patients in each group). In the intervention group, the median time from qualifying imaging to groin puncture was 57 minutes, and the rate of substantial reperfusion at the end of the procedure was 88%. Thrombectomy with the stent retriever plus intravenous t-PA reduced disability at 90 days over the entire range of scores on the modified Rankin scale (P<0.001). The rate of functional independence (modified Rankin scale score, 0 to 2) was higher in the intervention group than in the control group (60% vs. 35%, P<0.001). There were no significant between-group differences in 90-day mortality (9% vs. 12%, P=0.50) or symptomatic intracranial hemorrhage (0% vs. 3%, P=0.12).
In patients receiving intravenous t-PA for acute ischemic stroke due to occlusions in the proximal anterior intracranial circulation, thrombectomy with a stent retriever within 6 hours after onset improved functional outcomes at 90 days. (Funded by Covidien; SWIFT PRIME ClinicalTrials.gov number, NCT01657461.).
Tight-binding approach to uniaxial strain in graphene Pereira, Vitor M.; Castro Neto, A. H.; Peres, N. M. R.
Physical review. B, Condensed matter and materials physics,
07/2009, Letnik:
80, Številka:
4
Journal Article
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