Risk factors for re-bleeding of aneurysmal subarachnoid hemorrhage: Meta-analysis of observational studies

Objective The mortality of re-bleeding following aneurysmal subarachnoid hemorrhage is high, and surviving patients often have poor clinical condition and worse outcome than patients with a single bleed. In this study, we performed an updated systematic review and meta-analysis to determine the most common risk factors for re-bleeding in this patient population, with the goal of providing neurologists, neurosurgeons, neuro-interventionalists with a simple and fast method to evaluate the re-bleeding risk for aneurysmal subarachnoid hemorrhage. Method We conducted a thorough meta-analysis of the risk factors associated with re-bleeding or re-rupture of intracranial aneurysms in cases published between 2000 and 2013. Pooled mean difference was calculated for the continuous variables (age), and pooled odds ratio (OR) was calculated for categorical factors. If heterogeneity was significant (p<0.05), a random effect model was applied; otherwise, a fixed model was used. Testing for pooled effects and statistical significance for each potential risk factor were analyzed using Review Manager software. Results Our literature search identified 174 articles. Of these, only seven retrospective studies met the inclusion criteria. These seven studies consisted of 2470 patients, 283 of which had aneurysmal re-bleeding, resulting in a weighted average rate of re-bleeding of 11.3% with 95% confidence interval [CI]: 10.1–12.6. In this population, sex (OR 1.46; 95% CI: 1.11–1.92), high systolic blood pressure [SBP] (OR 2.52; 95% CI: 1.40–4.53), aneurysm size (OR 3.00; 95% CI: 2.06–4.37), clinical condition (Hunt & Hess) (OR 4.94; 95% CI: 2.29,10.68), and Fisher grade (OR 2.29; 95% CI: 1.45, 3.61) were statistically significant risk factors for re-bleeding. Conclusion Sex, high SBP, high Fisher grade, aneurysm size larger than 10mm, and poor clinical condition were independent risk factors for aneurysmal re-bleeding. The importance of early aneurysm intervention and careful consideration of patient risk factors should be emphasized to eliminate the risk of re-bleeding and poor outcome

Optical Signatures of Dirac Nodal-lines in NbAs2_2

Using polarized optical and magneto-optical spectroscopy, we have demonstrated universal aspects of electrodynamics associated with Dirac nodal-lines. We investigated anisotropic electrodynamics of NbAs$_2$ where the spin-orbit interaction triggers energy gaps along the nodal-lines, which manifest as sharp steps in the optical conductivity spectra. We show experimentally and theoretically that shifted 2D Dirac nodal-lines feature linear scaling $\sigma_1 (\omega)\sim\omega$, similar to 3D nodal-points. Massive Dirac nature of the nodal-lines are confirmed by magneto-optical data, which may also be indicative of theoretically predicted surface states. Optical data also offer a natural explanation for the giant magneto-resistance in NbAs$_2$

Swashplateless-elevon Actuation for a Dual-rotor Tail-sitter VTOL UAV

In this paper, we propose a novel swashplateless-elevon actuation (SEA) for dual-rotor tail-sitter vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs). In contrast to the conventional elevon actuation (CEA) which controls both pitch and yaw using elevons, the SEA adopts swashplateless mechanisms to generate an extra moment through motor speed modulation to control pitch and uses elevons solely for controlling yaw, without requiring additional actuators. This decoupled control strategy mitigates the saturation of elevons' deflection needed for large pitch and yaw control actions, thus improving the UAV's control performance on trajectory tracking and disturbance rejection performance in the presence of large external disturbances. Furthermore, the SEA overcomes the actuation degradation issues experienced by the CEA when the UAV is in close proximity to the ground, leading to a smoother and more stable take-off process. We validate and compare the performances of the SEA and the CEA in various real-world flight conditions, including take-off, trajectory tracking, and hover flight and position steps under external disturbance. Experimental results demonstrate that the SEA has better performances than the CEA. Moreover, we verify the SEA's feasibility in the attitude transition process and fixed-wing-mode flight of the VTOL UAV. The results indicate that the SEA can accurately control pitch in the presence of high-speed incoming airflow and maintain a stable attitude during fixed-wing mode flight. Video of all experiments can be found in youtube.com/watch?v=Sx9Rk4Zf7sQComment: 8 pages, 13 figure

Computation Efficiency Optimization for Millimeter-Wave Mobile Edge Computing Networks with NOMA

In this paper, by improving the computation efficiency (CE) and ensuring the fairness among users, we study the CE optimization for millimeter-wave mobile edge computing (mmWave-MEC) Networks with NOMA, where both the analog beamforming (ABF) and hybrid beamforming (HBF) architectures under the partial offloading mode are considered. Firstly, according to the max-min fairness criterion, the CE maximization problem is formulated to jointly optimize the ABF and the local resource allocation of each user. An efficient CE optimization algorithm based on the penalized successive convex approximation is proposed to solve this non-convex problem. Then, the max-min CE optimization problem in mmWave-MEC with HBF is studied, where the joint design of the HBF and the local resource allocation of each user is carried out. By using the penalty function and the inexact block coordinate descent method, a feasible CE optimization algorithm is developed to tackle this challenging problem. Simulation results verify the convergence of the proposed algorithms and show that the proposed computation-efficient resource allocation schemes can improve the CE effectively, and mmWave-MEC with HBF can obtain higher CE than that with ABF. Besides, the NOMA scheme exhibits superior performance over the conventional orthogonal multiple access scheme in terms of CE

Surface Versus Bulk Dirac States Tuning in a Three-Dimensional Topological Dirac Semimetal

Recently, crystalline-symmetry-protected three-dimensional (3D) bulk Dirac semimetal phase has been experimentally identified in a stoichiometric high-mobility compound, Cd3As2. The Dirac state observed in Cd3As2 has been attributed to originate mostly from the bulk state while calculations show that the bulk and surface states overlap over the entire Dirac dispersion energy range. In this study, we unambiguously reveal doping induced evolution of the ground state of surface and bulk electron dynamics in a 3D Dirac semimetal. We develop a systematic technique to isolate the surface and bulk states in Cd3As2, by simultaneously utilizing angle-resolved photoemission spectroscopy (ARPES) and in-situ surface deposition. Our experimental results provide a method for tuning the chemical potential as well as to observe surface states degenerate with bulk states, which will be useful for future applications of 3D Dirac semimetal.Comment: 5 pages, 4 figure

Momentum space imaging of Cooper pairing in a half-Dirac-gas topological superconductor (a helical 2D topological superconductor)

Superconductivity in Dirac electrons has recently been proposed as a new platform between novel concepts in high-energy and condensed matter physics. It has been proposed that supersymmetry and exotic quasiparticles, both of which remain elusive in particle physics, may be realized as emergent particles in superconducting Dirac electron systems. Using artificially fabricated topological insulator-superconductor heterostructures, we present direct spectroscopic evidence for the existence of Cooper pairing in a half Dirac gas 2D topological superconductor. Our studies reveal that superconductivity in a helical Dirac gas is distinctly different from that of in an ordinary two-dimensional superconductor while considering the spin degrees of freedom of electrons. We further show that the pairing of Dirac electrons can be suppressed by time-reversal symmetry breaking impurities removing the distinction. Our demonstration and momentum-space imaging of Cooper pairing in a half Dirac gas and its magnetic behavior taken together serve as a critically important 2D topological superconductor platform for future testing of novel fundamental physics predictions such as emergent supersymmetry and quantum criticality in topological systems.Comment: Submitted June'14; Accepted to NaturePhysics, to appear AOP (2014