Uniform nucleation and epitaxy of bilayer molybdenum disulfide on sapphire.

Two-dimensional transition-metal dichalcogenides (TMDs) are of interest for beyond-silicon electronics1,2. It has been suggested that bilayer TMDs, which combine good electrostatic control, smaller bandgap and higher mobility than monolayers, could potentially provide improvements in the energy-delay product of transistors3-5. However, despite advances in the growth of monolayer TMDs6-14, the controlled epitaxial growth of multilayers remains a challenge15. Here we report the uniform nucleation (>99%) of bilayer molybdenum disulfide (MoS2) on c-plane sapphire. In particular, we engineer the atomic terrace height on c-plane sapphire to enable an edge-nucleation mechanism and the coalescence of MoS2 domains into continuous, centimetre-scale films. Fabricated field-effect transistor (FET) devices based on bilayer MoS2 channels show substantial improvements in mobility (up to 122.6 cm2 V-1 s-1) and variation compared with FETs based on monolayer films. Furthermore, short-channel FETs exhibit an on-state current of 1.27 mA µm-1, which exceeds the 2028 roadmap target for high-performance FETs16.

Tuning Piezoelectricity via Thermal Annealing at a Freestanding Ferroelectric Membrane.

Tuning the ferroelectric domain structure by a combination of elastic and electrostatic engineering provides an effective route for enhanced piezoelectricity. However, for epitaxial thin films, the clamping effect imposed by the substrate does not allow aftergrowth tuning and also limits the electromechanical response. In contrast, freestanding membranes, which are free of substrate constraints, enable the tuning of a subtle balance between elastic and electrostatic energies, giving new platforms for enhanced and tunable functionalities. Here, highly tunable piezoelectricity is demonstrated in freestanding PbTiO3 membranes, by varying the ferroelectric domain structures from c-dominated to c/a and a domains via aftergrowth thermal treatment. Significantly, the piezoelectric coefficient of the c/a domain structure is enhanced by a factor of 2.5 compared with typical c domain PbTiO3. This work presents a new strategy to manipulate the piezoelectricity in ferroelectric membranes, highlighting their great potential for nano actuators, transducers, sensors and other NEMS device applications.

Ultralow-pressure-driven polarization switching in ferroelectric membranes.

Van der Waals integration of freestanding perovskite-oxide membranes with two-dimensional semiconductors has emerged as a promising strategy for developing high-performance electronics, such as field-effect transistors. In these innovative field-effect transistors, the oxide membranes have primarily functioned as dielectric layers, yet their great potential for structural tunability remains largely untapped. Free of epitaxial constraints by the substrate, these freestanding membranes exhibit remarkable structural tunability, providing a unique material system to achieve huge strain gradients and pronounced flexoelectric effects. Here, by harnessing the excellent structural tunability of PbTiO3 membranes and modulating the underlying substrate's elasticity, we demonstrate the tip-pressure-induced polarization switching with an ultralow pressure (down to 0.06 GPa). Moreover, as an application demonstration, we develop a prototype non-volatile ferroelectric field-effect transistor integrated on silicon that can be operated mechanically and electrically. Our findings underscore the great potential of oxide membranes for utilization in advanced non-volatile electronics and highly sensitive pressure sensors.

[Effects of acupuncture combined general anesthesia on endorphin and hemodynamics of laparoscopic cholecystectomy patients in the perioperative phase].

OBJECTIVE: To observe the effects of different anesthesia ways on endorphin and hemodynamics of laparoscopic cholecystectomy patients in the perioperative phase. METHODS: A total of 90 laparoscopic cholecystectomy patients, 29 to 80 years old, were randomly assigned to Group A (treated with electroacupuncture at acupoints combined general anesthesia), Group B (treated with electroacupuncture at non-acupoints combined general anesthesia), and Group C (treated with general anesthesia) according to American Society of Anesthesiologists (ASA) I-II, 30 cases in each group. All patients were induced by 3 microg/kg Fentanyl (Fen), 2 mg/kg Propofol (Pro), and 0.1 mg/kg Vecuronium (Vcr). Bispectral index (BIS), being 40 -65, indicated the state of general anesthesia. The anesthesia was maintained by intravenous injecting Pro, interruptedly intravenous injecting Fen and Vcr. Each patient received patient controlled intravenous analgesia (PCIA) after operation. On these bases, patients in Group A received electrical acupuncture at bilateral Hegu (LI4), Neiguan (PC6), Quchi (Ll11), Zusanli (ST36), and Yanglingquan (GB34). Patients in Group B received electrical acupuncture at the points beside acupoints. The electroacupuncture was lasted from 15 -30 min before anesthesia induction to the end of the operation in Group A and B. The heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), cardiac output (CO), systemic vascular resistance index (SVRI), and acceleration index (ACI) were recorded before anesthesia induction, immediate before pneumoperitoneum, 5 min after pneumoperitoneum, excision of gallbladder, and at the end of operation. The time consumption from discontinuation to spontaneously breathing recovery, analeptic, and extubation were recorded. The blood samples (3 mL each time) were collected from the peripheral vein before anesthesia induction, 2 h after operation, the 1st day after operation, and the 3rd day after operation to detect the beta-endorphin (beta-EP) level. The visual analogue scale (VAS) were observed and recorded in the 3 groups at post-operative 4, 6, 8, 24, and 44 h, respectively. RESULTS: (1) Compared with before anesthesia induction in the same group, the CI, CO, ACI of all patients decreased significantly at 5 min after pneumoperitoneum and at excision of gallbladder (P < 0.01, P < 0.05). The HR, MAP, SVRI obviously increased in Group B and Group C at each time point (P < 0.05, P < 0.01). Less change happened in Group A. Compared with Group C, the increment of MAP was less in Group A at 5 min after pneumoperitoneum, showing statistical difference (P < 0.05). (2) The time consumption from discontinuation to analeptic and extubation was obviously shorter in Group A than in Group B and Group C (P < 0.05, P < 0.01). (3) The level of beta-EP on the 1st day of operation was significantly lower in Group A than in Group B (P < 0.05) and Group C (P < 0.01). (4) The VAS score at post-operative 44 h was significantly lower in Group A than in Group B and Group C (P < 0.05). CONCLUSIONS: Electroacupuncture at acupoints combined general anesthesia could maintain the stabilization of haemodynamics, and relieve the stress reaction after pneumoperitoneum and operation, and prolong it to early post-operative period, and strengthen the effects of post-operative analgesia. The post-operative recovery was fast, safe, and reliable.

Pt/CNT Micro-Nanorobots Driven by Glucose Catalytic Decomposition.

Swimming micro-nanorobots have attracted researchers' interest in potential medical applications on target therapy, biosensor, drug carrier, and others. At present, the experimental setting of the swimming micro-nanorobots was mainly studied in pure water or H2O2 solution. This paper presents a micro-nanorobot that applied glucose in human body fluid as driving fuel. Based on the catalytic properties of the anode and cathode materials of the glucose fuel cell, platinum (Pt) and carbon nanotube (CNT) were selected as the anode and cathode materials, respectively, for the micro-nanorobot. The innovative design adopted the method of template electrochemical and chemical vapor deposition to manufacture the Pt/CNT micro-nanorobot structure. Both the scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to observe the morphology of the sample, and its elements were analyzed by energy-dispersive X-ray spectroscopy (EDX). Through a large number of experiments in a glucose solution and according to Stoker's law of viscous force and Newton's second law, we calculated the driving force of the fabricated micro-nanorobot. It was concluded that the structure of the Pt/CNT micro-nanorobot satisfied the required characteristics of both biocompatibility and motion.

Rewritable High-Mobility Electrons in Oxide Heterostructure of Layered Perovskite/Perovskite.

Perovskite oxide SrTiO3 can be electron-doped and exhibits high mobility by introducing oxygen vacancies or dopants such as Nb or La. A reversible after-growth tuning of high mobility carriers in SrTiO3 is highly desired for the applications in high-speed electronic devices. Here, we report the observation of tunable high-mobility electrons in layered perovskite/perovskite (Srn+1TinO3n+1/SrTiO3) heterostructure. By use of Srn+1TinO3n+1 as the oxygen diffusion barrier, the oxygen vacancy concentration near the interface can be reversibly engineered by high-temperature annealing or infrared laser heating. Because of the identical elemental compositions (Sr, Ti, and O) throughout the whole heterostructure, interfacial ionic intermixing is absent, giving rise to an extremely high mobility (exceeding 55000 cm2 V-1 s-1 at 2 K) in this type of oxide heterostructure. This layered perovskite/perovskite heterostructure provides a promising platform for reconfigurable high-speed electronic devices.

[Effect of acupuncture--general anesthesia on hemodynamics in perioperative period of patients undergoing cholecystectomy].

OBJECTIVE: To observe the effect of acupuncture-general anesthesia on hemodynamics in the perioperative period of patients undergoing laparoscopic cholecystectomy. METHODS: Sixty patients of ASA class I-II scheduled to receive laparoscopic cholecystectomy were randomly assigned to two groups equally, Group A, the control group, and Group B, the compound anesthesia group. The general anesthesia applied on them during operation was induced by combined midazolam, fentanyl, propofol and vecuronium bromide, but for those in Group B, 15 min of electric stimulation at bilateral Neiguan (PC6), Hegu (LI4) and Quchi (LI11) was given with an acupuncture anesthesia apparatus before the drug induction as acupuncture anesthesia induction, then the general anesthesia started and maintained the same as that in Group A. Changes of cardiac function and hemodynamics were monitored using thoracic electrical bio-impedance method at different time points of operation, i.e. the baseline before induction (T0), after induction when loss of consciousness (T1), during intubation (T2), beginning of operation (T3), ending of operation (T4), during extubation (T5) and 10 min after extubation (T6). RESULTS: No significant difference between the two groups was found in operation lasting time and anesthesia maintaining time (P > 0.05). The amount of vecuronium bromide consumed in an unit of time in Group B was significantly lower than that in Group A (P < 0.05). The mean arterial pressure (MAP), heart rate (HR), rate pressure product (RPP), cardiac output (CO), systemic vascular resistance (SVR), and blood flow acceleration index (ACI) in Group A at T1 were all significantly lower (P < 0.05 or P < 0.01), but became significantly higher at T2 and T5 as compared with those of baseline (P < 0.05 or P < 0.01), while no significant change of them was found in Group B. Moreover, MAP, RPP, SVR and ACI were significantly higher in Group A than those in Group B at T2 and T5 (P < 0.05 or P < 0.01). CONCLUSION: The acupuncture-general anesthesia shows a bi-directional effect for diminishing the fluctuation of hemodynamics and stabilizing the blood circulation, and also can reduce the consumption of narcotics during operation, so it has an extensive value in clinical practice.

Development of in situ optical-electrical MEMS platform for semiconductor characterization.

In situ transmission electron microscopy (TEM) technology has become one of the fastest growing areas in TEM research in recent years. This technique allows researchers to investigate the dynamic response of materials to external stimuli inside the microscope. Optoelectronic functional semiconducting materials play an irreplaceable role in several key fields such as clean energy, communications, and pollution disposal. The ability to observe the dynamic behavior of these materials under real working conditions using advanced TEM technologies would provide an in-depth understanding of their working mechanisms, enabling further improvement of their properties. In this work, we designed a microelectromechanical-system-chip-based system to illuminate a sample inside a transmission electron microscope. This system allows simultaneous in situ optical and electrical measurements, which are crucial for optoelectronic semiconductor characterization.

Direct observation of high spin polarization in Co2FeAl thin films.

We have studied the Co2FeAl thin films with different thicknesses epitaxially grown on GaAs (001) by molecular beam epitaxy. The magnetic properties and spin polarization of the films were investigated by in-situ magneto-optic Kerr effect (MOKE) measurement and spin-resolved angle-resolved photoemission spectroscopy (spin-ARPES) at 300 K, respectively. High spin polarization of 58% (±7%) was observed for the film with thickness of 21 unit cells (uc), for the first time. However, when the thickness decreases to 2.5 uc, the spin polarization falls to 29% (±2%) only. This change is also accompanied by a magnetic transition at 4 uc characterized by the MOKE intensity. Above it, the film's magnetization reaches the bulk value of 1000 emu/cm3. Our findings set a lower limit on the thickness of Co2FeAl films, which possesses both high spin polarization and large magnetization.

[Effects of different anesthesia methods on the T lymphocyte subsets and hemodynamics of patients with abdominal tumor in peri-operational period].

OBJECTIVE: To explore the effects of different anesthesia Methods on the cellular immune function and mean arterial pressure, heart rate in patients with abdominal tumor in the peri-operational period. METHODS: Patients were anesthetized by general anesthesia (GA), combined acupuncture-general anesthesia (AGA), combined epidural-general anesthesia (EGA), and combined acupuncture-epidural-general anesthesia (AEA), respectively. Changes of T lymphocyte subsets and hemodynamics were observed at different time points before and after treatment. RESULTS: Patients' cellular immune function after GA was lowered, which could be alleviated by combination of GA with acupuncture anesthesia (AA) or with epidural anesthesia. Combined acupuncture-drug anesthesia showed a stabilizing effect on hemodynamics in peri-operational period to some extent. CONCLUSION: EGA and AGA are good anesthesia choice in clinical practice, which would be favorable for early recovery of immune function in patients with abdominal tumor after operation.

[Effects of laparoscopic cholecystectomy under different anesthetic methods on T-lymphocyte immune function and postoperative analgesia].

OBJECTIVE: To compare the differences in the effect of laparoscopic cholecystectomy (LC) with different anesthetic methods on T-lymphocyte immune function and postoperative analgesia as well as validate the specificity of meridian points. METHODS: Ninety cases of LC were randomized into three groups, named group A (compound general anesthesia group with meridian points involved), group B (compound general anesthesia group with placebo points involved) and group C (general anesthesia group). In group A, electroacupuncture was applied at first for 15 to 30 min to bilateral Hegu (LI 4), Neiguan (PC 6), Zusanli (ST 36), Yanglingquan (GB 34) and Quchi (LI 11). Afterwards, the general anesthesia was conducted and electric stimulation lasted till the end of operation. In group B, the points adopted were the midpoints between the meridians in which the acupoints were selected in group A and the adjacent meridians on the lateral side, at the level of selected meridian points correspondingly. The method and time of electroacupuncture were same as those in group A. In group C, the general anesthesia was adopted simply. The changes of T-lymphocyte subgroup were detected before anesthesia, in 2 h, 1 day and 3 days after operation separately; and the dose of narcotic in operation as well as the dose of analgesia pumper in 4 h, 6 h, 8 h, 24 h and 44 h after operation separately. RESULTS: (1) In comparison between the result 2 h after operation and that before operation, the levels of CD3+, CD4+ and CD8+ in all of three groups were lower than those before operation. Except that the change in CD4+ in group A did not present significant statistical difference as compared with that before operation (P > 0.05), all of the other differences in T-lymphocyte subgroup indicated statistical significance (all P < 0.05). The ratio of CD4+/CD8+ in three groups was higher than that before operation, but the difference in group A was significant statistically (P < 0.05). In 3 days after operation, the levels of CD3+, CD4+ and CD4+/CD8+ were all higher than those before operation, indicating significant statistical differences (all P < 0.05) except CD4+/CD8+ in group B (P > 0.05). (2) In group A, during operation, the dose of narcotic reduced apparently (P < 0.05). (3) Separately, in 4, 6 and 8 h after operation, the dose of analgesia pumper reduced significantly in group A (all P < 0.05). CONCLUSION: Compound general anesthesia with meridian points involved can increase pain threshold of human body, reduce the dose of narcotic during operation, alleviate the suppression in body immune regulation due to stress reaction of general anesthesia and operation, prolong the time-effect of postoperative analgesia and explain the specificity of meridian points.

[Effect of different anesthesia methods on immune function in patients of laparoscopic cholecystectomy in peri-operational period].

OBJECTIVE: To compare the influence of acupuncture combine with general anesthesia (ACGA) and general anesthesia (GA) on immune function in patients of laparoscopic cholecystectomy (LC) in peri-operational period. METHODS: Thirty-nine cases undergoing LC were randomly divided into an ACGA group and a GA group. The ACGA group was treated with electroacupuncture at Hegu (LI 4), Zusanli (ST 36) and Yanglingquan (GB 34) for 15-30 minutes and subsequently with the general anesthesia followed by continuous electroacupuncture stimulation till the operation finished. The GA group was treated with simple general anesthesia. Changes of T cell subset, tumor necrosis factor-apha (TNF-alpha) and interleukin-6 (IL-6) were observed at time points of before anesthesia induction, 2 hours after operation, 1 and 3 days after operation and the occurrence of adverse reaction after operation was recorded. RESULTS: The percentages of CD3+ and CD8+ in both groups at 2 hours after operation were significant lower than that before anesthesia induction (all P < 0.05), and the percentage of CD4+ in the GA group decreased significantly at that time point (P < 0.05), while there was no significant difference in the ACGA group and CD4+/CD8+ increased significantly (P < 0.05). The level of TNF-alpha in the ACGA group decreased significantly at 3 days after operation as compared with that of before anesthesia induction (P < 0.05). There were significantly less cases nauseated after operation in the ACGA group than that in the GA group (P < 0.05). CONCLUSION: Acupuncture combine with general anesthesia has very little effect on immune function in patients of LC with less adverse reactions.

[Influence of acupuncture at acupoints and non-acupoints on the perioperative analgesic effect in patients with laparoscopic cholecystectomy].

OBJECTIVE: To explore the effect of general anesthesia, acupuncture at acupoints compound general anesthesia and acupuncture at non-acupoints compound general anesthesia on the perioperative analgesic effect in patients with laparoscopic cholecystectomy. METHODS: Ninety patients scheduled to undergo laparoscopic cholecystectomy were randomly divided into a general anesthesia group (group A), an acupuncture at acupoints compound general anesthesia group (group B) and an acupuncture at non-acupoints compound general anesthesia group (group C), 30 cases in each group. General anesthesias were all induced by Fentanyl, Propofol and Vecuronium Bromide. The bilateral Hegu (LI 4), Neiguan (PC 6), Zusanli (ST 36) and Yanglingquan (GB 34) were selected in the group B, and the middle points of the line connecting the meridians where every acupoint mentioned above belonged and their lateral neighbor meridians selected in the group C. The dosage of anesthetics, the time of goggle and the time of evulsion cannulation and direction location in all the patients were compared, and the dosage of analgesia pump within 4, 6, 8, 24 and 44 hours and Visual Analogue Scale (VAS) of pain were recorded after surgery. RESULTS: The dosage of Fentanyl in the group B was obviously lower than that in both the group A and the group C (both P<0.05), and the dosages of Propofol and Vecuronium Bromide in the group B were obviously lower than those in the group A (P<0.05, P<0.01). The time of goggle, evulsion cannulation and direction location in the group B were significantly shorter than those in the other groups (all P<0.01). After surgery, the dosage of analgesia pump in the group B was significantly fewer than that in the group C within 4 and 6 hours (both P<0.05), and it was significantly fewer than that in the group A within 4, 6, 8 hours (all P<0.05). The scores of VAS of pain at 44th hour after surgery in the group B were obviously lower than those in the other groups (both P<0.05). CONCLUSION: Acupuncture at acupoints can enhance the anesthetic effect of compound general anesthesia and prolong the analgesia period. Acupuncture at non-points has a certain effect, but their effectiveness is less than that of acupoints. Thus, the acupoint has the specificity and accurate acupoint selection is the key factor affecting analgesia effect.