Fabrication of Spin-Transfer Nano-Oscillator by Colloidal Lithography

We fabricate nanoscale spin-transfer oscillators (STOs) by utilizing colloidal nanoparticles as a lithographic mask. By this approach, high quality STO devices can be fabricated, and as an example the fabricated STO devices using MgO magnetic tunnel junction as the basic cell exhibit current-induced microwave emission with a large frequency tunability of 0.22 GHz/mA. Compared to the conventional approaches that involve a step of defining nanoscale elements by means of electron beam lithography, which is not readily available for many groups, our strategy for STO fabrication does not require the sophisticated equipment (~ million dollars per unit) and expensive lithography resist, while being cost-effective and easy to use in laboratory level. This will accelerate efforts to implement STO into on-chip integrated high-radio frequency applications

Fabrication and characteristics of flexible normally-off AlGaN/GaN HEMTs

In this paper, we present a method for removing a high electron mobility transistor (HEMT) silicon substrate using mechanical grinding and deep silicon etching technology and successfully transferred the epitaxial wafer to a PET substrate to achieve the flexible normally-off HEMT. By testing the output characteristics and transfer characteristics of the Si-substrate HEMT and PET-substrate HEMT, we have demonstrated that the PET-substrate HEMT has excellent performance and successfully achieved the mechanical flexibility. Furthermore, we analyzed the physical mechanisms of the change in PET-substrate and Si-substrate HEMT characteristics, as well as flexible HEMT performance under bent and flattened states. The flexible HEMT array demonstrates significant potential in integration with other flexible devices, such as GaN-based micro-LED arrays

Ultralow-current-density and bias-field-free spin-transfer nano-oscillator

The spin-transfer nano-oscillator (STNO) offers the possibility of using the transfer of spin angular momentum via spin-polarized currents to generate microwave signals. However, at present STNO microwave emission mainly relies on both large drive currents and external magnetic fields. These issues hinder the implementation of STNOs for practical applications in terms of power dissipation and size. Here, we report microwave measurements on STNOs built with MgO-based magnetic tunnel junctions having a planar polarizer and a perpendicular free layer, where microwave emission with large output power, excited at ultralow current densities, and in the absence of any bias magnetic fields is observed. The measured critical current density is over one order of magnitude smaller than previously reported. These results suggest the possibility of improved integration of STNOs with complementary metal-oxide-semiconductor technology, and could represent a new route for the development of the next-generation of on-chip oscillators.Comment: 18 pages, 4 figure

Mean Platelet Volume and Platelet Distribution Width as Markers in the Diagnosis of Acute Gangrenous Appendicitis

Introduction. Acute gangrenous appendicitis (AGA) is a common medical condition; however, the grade of appendicitis usually cannot be established preoperatively. We have attempted to identify some indicators, such as the mean platelet volume (MPV) and the platelet distribution width (PDW), to diagnose AGA. Aims. To evaluate whether or not the MPV and PDW are suitable markers to diagnose AGA. Methods. A retrospective study of 160 patients with AGA and 160 healthy patients was undertaken. Disease diagnosis was confirmed based on the pathologic examination of surgical specimens. Patient white blood cell (WBC) count, neutrophil ratio (NR), platelet (PLT) count, MPV, PDW, and hematocrit (HCT) were analyzed. Receiver operating characteristic (ROC) curves were used to evaluate the sensitivity and specificity of these indices in AGA. Results. There were no significant differences between the AGA and control groups in age and gender. Compared to the control group, the WBC count, NR, and PDW were significantly higher ( < 0.001, resp.) and the MPV and HCT were significantly lower ( < 0.001, resp.) in the AGA group. The diagnostic specificities of the WBC count, NR, PLT count, MPV, PDW, and HCT were 86.3%, 92.5%, 58.1%, 81.7%, 83.9%, and 66.3%, respectively. Therefore, the NR had the highest diagnostic specificity for the diagnosis of AGA. Conclusions. This is the first study to assess the MPV and PDW in patients with AGA. Our present study showed that the MPV is reduced and the PDW is increased in patients with AGA; the sensitivity of PDW was superior to the MPV. A decreased MPV value and an increased PDW could serve as two markers to diagnose AGA. The NR had the highest specificity for the diagnosis of AGA

The role of provincial government spending composition in growth and convergence in China

China’s development policy since 1978 has differed across regions. With rapid aggregate growth has come widening regional inequality. The fiscal decentralisation reforms in 1994 shifted political pressure onto provincial officials to boost local growth through local public investments. These investments affect regional convergence by counteracting regulatory frictions in factor accumulation, and can also determine steady-state growth. However, the effect of public spending allocations across physical and human capital on growth and convergence processes is empirically unexplored for Chinese provinces. We take provincial time-series data on public spending by category, finding local public spending and its components augment convergence rates differently across regions. Spending on education and health contributes significantly more to growth and convergence than capital spending, confirming that the public capital-spending bias is not a local growth-optimising strategy. We suggest a policy of aligning local government promotion incentives to human capital targets to correct local resource misallocation

Ginsenoside Rb1 Prevents H2O2-Induced HUVEC Senescence by Stimulating Sirtuin-1 Pathway

We have previously reported that Ginsenoside Rb1 may effectively prevent HUVECs from senescence, however, the detailed mechanism has not demonstrated up to now. Recent studies have shown that sirtuin-1 (Sirt1) plays an important role in the development of endothelial senescence. The purpose of this study was to explore whether Sirt1 is involved in the action of Ginsenoside Rb1 regarding protection against H2O2-induced HUVEC Senescence.Senescence induced by hydrogen peroxide (H2O2) in human umbilical vein endothelial cells (HUVECs) was examined by analyzing plasminogen activator inhibitor-1 (PAI-1) expression, cell morphology, and senescence-associated beta-galactosidase (SA-β-gal) activity. The results revealed that 42% of control-treated HUVECs were SA-β-gal positive after treatment by 60 µmol/L H2O2, however, this particular effect of H2O2 was decreased more than 2-fold (19%) in the HUVECs when pretreated with Rb1 (20 µmol/L) for 30 min. Additionally, Rb1 decreased eNOS acetylation, as well as promoted more NO production that was accompanied by an increase in Sirt1 expression. Furthermore, upon knocking down Sirt1, the effect of Rb1 on HUVEC senescence was blunted.The present study indicated that Ginsenoside Rb1 acts through stimulating Sirt1 in order to protect against endothelial senescence and dysfunction. As such, Sirt1 appears to be of particular importance in maintaining endothelial functions and delaying vascular aging

The Study on Dynamic Characteristics of Twin-Screw Compressor Rotor

In the working process of twin-screw compressor, the rotors are subjected to multiple physical effects of the gas temperature, pressure and force, and presents a periodic change. In this paper, three-dimensional Computational Fluid Dynamics (CFD) simulation of screw compressor is carried out, and the characteristics of temperature distribution, pressure distribution and gas force distribution on the rotors’ surface are studied. Firstly, the rotor domain, suction and exhaust face grids are generated by TwinMesh, and then they are imported into the CFX calculation model. Through the fluid-structure interaction analysis and calculation, the strain shape of the screw rotor under the multiple alternating physical action of gas temperature, pressure and force is analyzed, and the deformation of the rotor structure caused by the pressure and temperature in the working process is obtained, which plays a good guiding role in the design of the screw rotor and the improvement of the performance of the compressor