183 research outputs found
Visualizing topological edge states of single and double bilayer Bi supported on multibilayer Bi(111) films
Freestanding single-bilayer Bi(111) is a two-dimensional topological
insulator with edge states propagating along its perimeter. Given the
interlayer coupling experimentally, the topological nature of Bi(111) thin
films and the impact of the supporting substrate on the topmost Bi bilayer are
still under debate. Here, combined with scanning tunneling microscopy and
first-principles calculations, we systematically study the electronic
properties of Bi(111) thin films grown on a NbSe2 substrate. Two types of
non-magnetic edge structures, i.e., a conventional zigzag edge and a 2x1
reconstructed edge, coexist alternately at the boundaries of single bilayer
islands, the topological edge states of which exhibit remarkably different
energy and spatial distributions. Prominent edge states are persistently
visualized at the edges of both single and double bilayer Bi islands,
regardless of the underlying thickness of Bi(111) thin films. We provide an
explanation for the topological origin of the observed edge states that is
verified with first-principles calculations. Our paper clarifies the
long-standing controversy regarding the topology of Bi(111) thin films and
reveals the tunability of topological edge states via edge modifications.Comment: 36 pages, 10 figure
Aharonov-Bohm interference in topological insulator nanoribbons
Topological insulators represent novel phases of quantum matter with an
insulating bulk gap and gapless edges or surface states. The two-dimensional
topological insulator phase was predicted in HgTe quantum wells and confirmed
by transport measurements. Recently, Bi2Se3 and related materials have been
proposed as three-dimensional topological insulators with a single Dirac cone
on the surface and verified by angle-resolved photoemission spectroscopy
experiments. Here, we show unambiguous transport evidence of topological
surface states through periodic quantum interference effects in layered
single-crystalline Bi2Se3 nanoribbons. Pronounced Aharonov-Bohm oscillations in
the magnetoresistance clearly demonstrate the coverage of two-dimensional
electrons on the entire surface, as expected from the topological nature of the
surface states. The dominance of the primary h/e oscillation and its
temperature dependence demonstrate the robustness of these electronic states.
Our results suggest that topological insulator nanoribbons afford novel
promising materials for future spintronic devices at room temperature.Comment: 5 pages, 4 figures, RevTex forma
Вихретоковый анизотропный термоэлектрический первичный преобразователь лучистого потока
Представлена оригинальная конструкция первичного преобразователя лучистого потока, который может служить основой для создания приемника неселективного излучения с повышенной чувствительностью
Effects of alirocumab on types of myocardial infarction: insights from the ODYSSEY OUTCOMES trial
Aims The third Universal Definition of Myocardial Infarction (MI) Task Force classified MIs into five types: Type 1, spontaneous; Type 2, related to oxygen supply/demand imbalance; Type 3, fatal without ascertainment of cardiac biomarkers; Type 4, related to percutaneous coronary intervention; and Type 5, related to coronary artery bypass surgery. Low-density lipoprotein cholesterol (LDL-C) reduction with statins and proprotein convertase subtilisin–kexin Type 9 (PCSK9) inhibitors reduces risk of MI, but less is known about effects on types of MI. ODYSSEY OUTCOMES compared the PCSK9 inhibitor alirocumab with placebo in 18 924 patients with recent acute coronary syndrome (ACS) and elevated LDL-C (≥1.8 mmol/L) despite intensive statin therapy. In a pre-specified analysis, we assessed the effects of alirocumab on types of MI. Methods and results Median follow-up was 2.8 years. Myocardial infarction types were prospectively adjudicated and classified. Of 1860 total MIs, 1223 (65.8%) were adjudicated as Type 1, 386 (20.8%) as Type 2, and 244 (13.1%) as Type 4. Few events were Type 3 (n = 2) or Type 5 (n = 5). Alirocumab reduced first MIs [hazard ratio (HR) 0.85, 95% confidence interval (CI) 0.77–0.95; P = 0.003], with reductions in both Type 1 (HR 0.87, 95% CI 0.77–0.99; P = 0.032) and Type 2 (0.77, 0.61–0.97; P = 0.025), but not Type 4 MI. Conclusion After ACS, alirocumab added to intensive statin therapy favourably impacted on Type 1 and 2 MIs. The data indicate for the first time that a lipid-lowering therapy can attenuate the risk of Type 2 MI. Low-density lipoprotein cholesterol reduction below levels achievable with statins is an effective preventive strategy for both MI types.For complete list of authors see http://dx.doi.org/10.1093/eurheartj/ehz299</p
Enhancing Abiotic Stress Tolerance in Cereals Through Breeding and Transgenic Interventions
The success of plant breeding in the 20th century led to new cultivars that, to date, have provided enough food for an increasing world population (Conway and Toenniessen 1999; Mifflin 2000). The results of the Green Revolution-led in the 1960s by Henry M. Beachell andNormanE. Dotlaug—resulted in a dramatic increase in rice and wheal grain yields (Milford and Runge 2007; Ortiz et al. 2007). However, abiotic stresses and climate change are becoming increasingly serious threats to crop production worldwide at a time when food staple supply will need to be significantly higher to meet the demand of the growing human population. Water scarcity (Rockstrom et al. 2007], salinity (Rengasamy 2006). and low soil fertility (Sanchez and Swaminathan 2005) rank among the moat important abiotic stresses worldwide. Similarly, increased climatic disturbances due to global warming are causing the major stresses that necessitate crop improvements to safeguard grain supply, particularly in the developing world (Kumar 2006). Hence, genetic enhancement of cereal crops with respect to abiotic stress tolerance will be essential far ensuring grain yields in water-limited, increasingly hotter agricultural zones, particularly If these conditions combine with poor and saline soils, conditions that prevail in parts of the developing world. Crop breeding for adaptation to abiotic stress-prone environments remains a challenging task, not least because of the complexity of the stress-adaptive mechanisms in plants and particularly cereal crops, which are the staple of most of the world's population (Reynolds et al. 2005}
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