Tuning 2D Magnetism in Cobalt Monoxide Nanosheets Via In Situ Nickel-Doping.

Element doping has become an effective strategy to engineer the magnetic properties of two-dimensional (2D) materials and is widely explored in van der Waals layered transition metal dichalcogenides. However, the high-concentration substitution doping of 2D nonlayered metal oxides, which can preserve the original crystal texture and guarantee the homogeneity of doping distribution, is still a critical challenge due to the isotropic bonding of closed-packed structures. In this work, the synthesis of high-quality 2D nonlayered nickel-doped cobalt monoxide nanosheets via in situ atmospheric pressure chemical vapor deposition method is reported. High-resolution transmission electron microscopy confirmed that nickel atoms are doped at the intrinsic cobalt atom sites. The nickel doping concentration is stable at ≈15%, superior to most magnetic dopants doping in 2D materials and metal oxides. Magnetic measurements showed that pristine cobalt monoxide is nonferromagnetic, whereas nickel-doped cobalt monoxide exhibits robust ferromagnetic behavior with a Curie temperature of ≈180 K. Density functional theory calculations reveal that nickel atoms can improve the internal ferromagnetic correlation, giving rise to significant ferromagnetic performance of cobalt monoxide nanosheets. These results provide a valuable case for tuning the competing correlated states and magnetic ordering by substitution doping in 2D nonlayered oxide semiconductors.

Van der Waals Epitaxy Growth of 2D Single-Element Room-Temperature Ferromagnet.

2D single-element materials, which are pure and intrinsically homogeneous on the nanometer scale, can cut the time-consuming material-optimization process and circumvent the impure phase, bringing about opportunities to explore new physics and applications. Herein, for the first time, the synthesis of ultrathin cobalt single-crystalline nanosheets with a sub-millimeter scale via van der Waals epitaxy is demonstrated. The thickness can be as low as ≈6 nm. Theoretical calculations reveal their intrinsic ferromagnetic nature and epitaxial mechanism: that is, the synergistic effect between van der Waals interactions and surface energy minimization dominates the growth process. Cobalt nanosheets exhibit ultrahigh blocking temperatures above 710 K and in-plane magnetic anisotropy. Electrical transport measurements further reveal that cobalt nanosheets have significant magnetoresistance (MR) effect, and can realize a unique coexistence of positive MR and negative MR under different magnetic field configurations, which can be attributed to the competition and cooperation effect among ferromagnetic interaction, orbital scattering, and electronic correlation. These results provide a valuable case for synthesizing 2D elementary metal crystals with pure phase and room-temperature ferromagnetism and pave the way for investigating new physics and related applications in spintronics.

Enterprise Operational Resilience with Digitalization Approach amid the COVID-19 Era: An Empirical Assessment.

The development of the COVID-19 pandemic has had a devastating impact on one Chinese city that has depended heavily on tourism, which is the core focus of the current study. This article uses phenomenological research methods in qualitative research to conduct semistructured and in-depth interviews with travel agency managers in China Highlights. Through the application of tourism resilience theory in the tourism crisis management domain, this article investigates the performance of China Highlights, a local tourism enterprise in Guilin, China, to restore the functioning and growth of the tourism industry in the postpandemic period. The results show that China's tourism industry is in the early stages of the fast growth stage of economic recovery, and tourism enterprises are faced with a significant challenge in determining how to make sound business choices during the pandemic and after the crisis has passed. It proposes that the tourism resilient theory can serve as a modern crisis management model to facilitate tourism enterprises to revive their performance in times of hardship.

Aperture Ratio Improvement by Optimizing the Voltage Slope and Reverse Pulse in the Driving Waveform for Electrowetting Displays.

Electrowetting display (EWD) performance is severely affected by ink distribution and charge trapping in pixel cells. Therefore, a multi structural driving waveform is proposed for improving the aperture ratio of EWDs. In this paper, the hysteresis characteristic (capacitance-voltage, C-V) curve of the EWD pixel is tested and analyzed for obtaining the driving voltage value at the inflection point of the driving waveform. In the composition of driving waveform, a voltage slope is designed for preventing ink dispersion and a reverse pulse is designed for releasing the trapped charge which is caused by hysteresis characteristic. Finally, the frequency and the duty cycle of the driving waveform are optimized for the max aperture ratio by a series of testing. The experimental results show that the proposed driving waveform can improve the ink dispersion behavior, and the aperture ratio of the EWD is about 8% higher than the conventional driving waveform. At the same time, the response speed of the driving waveform can satisfy the dynamic display in EWDs, which provides a new idea for the design of the EWD driving scheme.

Efficacy and Safety of a Novel Catheter for Transradial Cerebral Angiography.

BACKGROUND: The goal of this study is to evaluate the safety and efficacy of a novel catheter for right radial artery approach cerebral angiography. METHODS: Patients from the Neurology Department of The Second Affiliated Hospital of Guangxi Traditional Chinese Medical University who underwent diagnostic cerebral angiography of either the left vertebral artery dominant type or balanced type were enrolled in this study. RESULTS: A total of 167 patients were treated between February 2016 and December 2017, of whom 44 were excluded based on study exclusion criteria and 123 were enrolled in the present analysis. Bilateral subclavian artery catheterization and bilateral common carotid artery catheterization were conducted successfully in all 123 patients. The success rate of selective catheterization of the left vertebral artery was 87.8% (108/123). The success rate of selective catheterization of the right vertebral artery using the novel catheter was 89.0% (73/82). The average fluoroscopy time was 6.5 ± 3.4 min, the average operation duration was 47 ± 3.7 (range 50-90) min, and the average dosage of contrast agent was 112.3 ± 8.1 mL. One patient exhibited an absence of pulse in the punctual radial artery after the removal of the arterial compression band, but there was no evidence of ischemia of the distal hand. One patient who was undergoing dual anti-platelet drug treatment suffered from bleeding at the puncture point when deflated for 2 hr after operation; this patient was re-pressurized and re-timed. CONCLUSIONS: This novel catheter improved the success rate of selective left vertebral artery catheterization, and allowed for simplification of the relevant surgical steps. The controllability of this novel catheter was satisfactory, and its associated surgical risk was found to be low.

The Effect of Vascular Morphology on Selective Left Vertebral Artery Catheterization in Right-sided Radial Artery Cerebral Angiography.

BACKGROUND: The aim of this study is to determine, via retrospective study, the effects of vascular morphology and related factors on the success of selective arterial catheterization of the left vertebral artery when approached via right-sided radial artery cerebral angiography. METHODS: Patients who had undergone diagnostic cerebral angiography were enrolled, and their medical history, catheter type, and vessel morphology were analyzed. RESULTS: A total of 205 patients were enrolled in this study from February 2014 to December 2015. After exclusion according to defined criteria, 161 patients were incorporated into the final analysis. Selective catheterization of the bilateral subclavian artery and the bilateral common carotid artery were conducted successfully in all patients, and the success rate of selective catheterization of the left vertebral artery was 82.0%. The success rate of the left vertebral artery catheterization was positively correlated with the angle between the left vertebral artery and the left subclavicular artery (P < 0.001), with 90° serving as a demarcation point, and this was higher in patients without innominate artery distortion (90.2-75.0%), although this finding was not statistically significant. However, the morphology of the aortic artery did not affect the success rate of selective catheterization of the left vertebral artery (P = 0.189), and there was no significant difference (P = 0.231) in the success rate of selective catheterization if the left vertebral artery was predominant (91.0%, 81/89) or balanced (84.7%, 61/72). A total of 0.9% (2/161) of the patients experienced surgery-related complications. Both these patients exhibited bleeding at the puncture point when they were deflated 2 hr after the operation. They were pressurized and depressurization was again conducted for an appropriate period of time. CONCLUSIONS: The angle between the left vertebral artery and the left subclavicular artery is the primary vessel-associated morphological factor affecting the success rate of selective catheterization of the left vertebral artery in the right-sided radial artery cerebral angiography, while innominate artery distortion also had some more limited impact on this success rate.