Pressure-induced enhancement of optoelectronic properties in PtS2

PtS2, which is one of the group-10 transition metal dichalcogenides, attracts increasing attention due to its extraordinary properties under external modulations as predicted by theory, such as tunable bandgap and indirect-to-direct gap transition under strain; however, these properties have not been verified experimentally. Here we report the first experimental exploration of its optoelectronic properties under external pressure. We find that the photocurrent is weakly pressuredependent below 3 GPa but increases significantly in the pressure range of 3 GPa–4 GPa, with a maximum ～ 6 times higher than that at ambient pressure. X-ray diffraction data shows that no structural phase transition can be observed up to26.8 GPa, which indicates a stable lattice structure of PtS2 under high pressure. This is further supported by our Raman measurements with an observation of linear blue-shifts of the two Raman-active modes to 6.4 GPa. The pressure-enhanced photocurrent is related to the indirect-to-direct/quasi-direct bandgap transition under pressure, resembling the gap behavior under compression strain as predicted theoretically.

Watt-level,green-pumped optical parametric oscillator based on periodically poled potassium titanyl phosphate with high extraction efficiency

We report a compact,efficient optical parametric oscillator(OPO)based on a periodically poled potassium titanyl phosphate(PPKTP)crystal pumped by a 532 nm laser,which generated 1.51 W of average power at the signal wavelength of 709 nm with the pulse duration of~1.0 ns.The extraction efficiency was up to 59%.To the best of our knowledge,this is the first report on Watt-level green-pumped PPKTP-based singly resonant oscillator OPO(SRO-OPO).The precise build-up time of OPO was determined to be 1.6 ns benefitting from the characteristic of twin-peak pulse profile of pump beam.The spectrum width of the idler was also measured to be 4.2 nm with the central wavelength of 2134 nm at 0.2 nm spectral resolution of optical spectrum analyzer.In addition,the beam quality of M^(2)<1.9 of generated signal exhibits a good consistency with M^(2)<1.5 for the pump source.

Multimodal image fusion-assisted endoscopic evacuation of spontaneous intracerebral hemorrhage

Purpose:Although traditional craniotomy(TC)surgery has failed to show benefits for the functional outcome of intracerebral hemorrhage(ICH).However,a minimally invasive hematoma removal plan to avoid white matter fiber damage may be a safer and more feasible surgical approach,which may improve the prognosis of ICH.We conducted a historical cohort study on the use of multimodal image fusion-assisted neuroendoscopic surgery(MINS)for the treatment of ICH,and compared its safety and effectiveness with traditional methods.Methods:This is a historical cohort study involving 241 patients with cerebral hemorrhage.Divided into MINS group and TC group based on surgical methods.Multimodal images(CT skull,CT angiography,and white matter fiber of MRI diffusion-tensor imaging)were fused into 3 dimensional images for preoperative planning and intraoperative guidance of endoscopic hematoma removal in the MINS group.Clinical features,operative efficiency,perioperative complications,and prognoses between 2 groups were compared.Normally distributed data were analyzed usingt-test of 2 independent samples,Nonnormally distributed data were compared using the Kruskal-Wallis test.Meanwhile categorical data were analyzed via the Chi-square test or Fisher’s exact test.All statistical tests were two-sided,andp<0.05 was considered statistically significant.Results:A total of 42 patients with ICH were enrolled,who underwent TC surgery or MINS.Patients who underwent MINS had shorter operative time(p<0.001),less blood loss(p<0.001),better hematoma evacuation(p=0.003),and a shorter stay in the intensive care unit(p=0.002)than patients who underwent TC.Based on clinical characteristics and analysis of perioperative complications,there is no significant difference between the 2 surgical methods.Modified Rankin scale scores at 180 days were better in the MINS than in the TC group(p=0.014).Conclusions:Compared with TC for the treatment of ICH,MINS is safer and more efficient in cleaning ICH,which improved the prognosis of the patients.In the future,a larger sample size clinical trial will be needed to evaluate its efficacy.

Existence and Multiplicity of Solutions for Nonlocal Systems with Kirchhoff Type

Firstly,we use Nehari manifold and Mountain Pass Lemma to prove an existence result of positive solutions for a class of nonlocal elliptic system with Kirchhoff type.Then a multiplicity result is established by cohomological index of Fadell and Rabinowitz.We also consider the critical case and prove existence of positive least energy solution when the parameter β is sufficiently large.

Existence of Positive Solutions for a General Nonlinear Eigenvalue Problem

Let Ω R n be a bounded domain, H = L 2 （Ω）, L ： D（L） H → H be an unbounded linear operator, f ∈ C（ × R, R） and λ∈ R. The paper is concerned with the existence of positive solutions for the following nonlinear eigenvalue problem Lu = λf （x, u）, u ∈ D（L）, which is the general form of nonlinear eigenvalue problems for differential equations. We obtain the global structure of positive solutions, then we apply the results to some nonlinear eigenvalue problems for a second-order ordinary differential equation and a fourth-order beam equation, respectively. The discussion is based on the fixed point index theory in cones.