Ultrafast Nonlinear Optical Response of Strongly Correlated Systems: Dynamics in the Quantum Hall Effect Regime

We present a theoretical formulation of the coherent ultrafast nonlinear optical response of a strongly correlated system and discuss an example where the Coulomb correlations dominate. We separate out the correlated contributions to the third-order nonlinear polarization, and identify non-Markovian dephasing effects coming from the non-instantaneous interactions and propagation in time of the collective excitations of the many-body system. We discuss the signatures, in the time and frequency dependence of the four-wave-mixing (FWM) spectrum, of the inter-Landau level magnetoplasmon (MP) excitations of the two-dimensional electron gas (2DEG) in a perpendicular magnetic field. We predict a resonant enhancement of the lowest Landau level (LL) FWM signal, a strong non-Markovian dephasing of the next LL magnetoexciton (X), a symmetric FWM temporal profile, and strong oscillations as function of time delay, of quantum kinetic origin. We show that the correlation effects can be controlled experimentally by tuning the central frequency of the optical excitation between the two lowest LLs.Comment: 21 pages, 10 figure

Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable. Funding: UK Medical Research Council and Health Technology Assessment Programme

Tahini consumption affects blood pressure and endothelial function in healthy males

Sesame (Sesamum indicum L.) is rich in polyunsaturated fatty acids, proteins, vitamin E, and lignans. Recent studies have highlighted the antioxidant, antihypertensive, hypolipidemic, and appetite-control properties of sesame seeds and sesame oil. However, there is a gap in the literature regarding the effect of tahini (sesame paste) consumption on human health. Thus, the aim is to investigate the postprandial effect of tahini consumption on blood pressure, endothelial function, and arterial stiffness. Twenty healthy men with mean age of 28 y and mean BMI of 25.81 kg/m(2) were included. After a 12-h fast, baseline blood was collected, participants consumed 50 g of tahini, and blood collection was repeated 4 h postprandially. Assessment of blood pressure, pulse rate, hemodynamic parameters, and endothelial function was performed at baseline and at the end of the trial. Blood samples were used for the quantification of intercellular cell-adhesion molecule-1, vascular cell-adhesion molecule-1, and E-selectin levels at baseline and 4 h postprandially. A statistically significant decrease in diastolic blood pressure (p = 0.010) and pulse rate (p = 0.002) was observed 4 h after tahini consumption. Significant increases in serum triglycerides (p < 0.001) and flow-mediated dilatation were observed (p = 0.022) 4 h postprandially. No changes were observed in other indices measured at the end of the intervention compared with baseline. This is the first study to report that tahini consumption can lower blood pressure and pulse rate and improve endothelial function, suggesting a healthy snack in place of others with a less desirable lipid profile