Investigation on Breakdown Characteristics of Various Surface Terminal Structures for GaN-Based Vertical P-i-N Diodes

GaN-based vertical P-i-N diode with mesa edge terminal structure due to electric field crowding effect, the breakdown voltage of the device is significantly reduced. This work investigates three terminal structures, including deeply etched, bevel, and stepped-mesas terminal structures, to suppress electric field crowding effects at the device and junction edges. Deeply-etched mesa terminal yields a breakdown voltage of 1205 V, i.e., 89% of the ideal voltage. The bevel-mesa terminal achieves about 89% of the ideal breakdown voltage, while the step-mesa terminal is less effective in mitigating electric field crowding, at about 32% of the ideal voltage. This work can provide an important reference for the design of high-power, high-voltage GaN-based P-i-N power devices, finding a terminal protection structure suitable for GaNPiN diodes to further enhance the breakdown performance of the device and to unleash the full potential of GaN semiconductor materials.

Design and Simulation of Improved SOI SiGe Hetero-Junction Bipolar Transistor Architecture with Strain Engineering

In order to improve the electrical and frequency characteristics of SiGe heterojunction bipolar transistors (HBTs), a novel structure of SOI SiGe heterojunction bipolar transistor is designed in this work. Compared with traditional SOI SiGe HBT, the proposed device structure has smaller window widths of emitter and collector areas. Under the act of additional uniaxial stress induced by Si0.85Ge0.15, all the collector region, base region and emitter region are strained, which is beneficial to improve the performance of SiGe HBTs. Employing the SILVACOⓇTCAD tools, the numerical simulation results show that the maximum current gain βmax, the Earley voltage VA are achieved for 1062 and 186 V, respectively, the product of β and VA, i.e., β ×VA, is 1.975 × 105 V and, the peak cutoff frequency fT is 419 GHz when the Ge component in the base has configured to be a trapezoidal distribution. The proposed SOI SiGe HBT architecture has a 52.9% improvement in cutoff frequency fT compared to the conventional SOI SiGe HBTs.

Modelling and Calculation of Silicon Conduction Band Structure and Parameters with Arbitrary Uniaxial Stress

Using the k·p theory, the coupling effect between the Δ1 and Δ2’ bands on the energy band structure of different energy valleys is studied. The analytical model of the energy-dispersion relationship applicable to uniaxial stress for arbitrary crystal plane and orientation as well as different energy valleys is established. For typical crystal orientations, the main parameters of energy band structure such as band edge level, splitting energy, density-of-state (DOS) effective mass and conductivity effective mass are calculated. The calculated results are in good agreement with the data reported in related literature. Finally, the relationship between the DOS effective mass, conductivity effective mass and the change of stress and orientation of different crystal planes is given. The proposed model and calculation results can provide a theoretical reference for the design of nano-electronic devices and TCAD simulation.

L3SN: A Level-Based, Large-Scale, Longevous Sensor Network System for Agriculture Information Monitoring

We developed L3SN, a scalable, longevous, adaptive, and internet accessible wireless sensor network system for agriculture information monitoring, which is meticulously designed to meet the requirement of thousands hectares coverage, years of time monitoring and the adverse environment. The system architecture, the agriculture sensor device, the mesh protocol, and the web-based information processing platform are introduced. We also presented some implementation experience. The mesh protocol (LayerMesh) is highlighted, in which “stair scheduling” and “distributed dynamic load-balancing” are proposed to response the scalability, longevity and adaptivity requirements. We believe the design of L3SN is useful to many other large-scale, longevous applications such as hydrologic monitoring, geological monitoring etc.

Synergistic realization of high efficiency solar desalination and carbon dioxide reduction

Methods of seawater desalination and carbon dioxide(CO_(2))reduction using clean and renewable energy have attracted much attention withing the reducing fresh water and growing CO_(2)concentration.Here,we propose a synergistic method for solardriven desalination and CO_(2)reduction at the surface of sea using a three-dimensional titanium oxide-gold semiconductor/metal(TiO_(2)-Au NW/NPs(NW:nanowire,NP:nanoparticle))photothermal conversion membrane that can efficiently harvest a broad solar spectrum(200 to 2500 nm,94%)to undertake the conversion of light-to-heat and light-to-electricity.The TiO_(2)-Au NW/NPs membrane demonstrated a high solar vapor conversion efficiency of~90%,CO_(2)reduction yields of 0.066μmol·cm^(-2)CH_(4)and 0.015μmol·cm^(-2)CO within 5 h.In addition,the membrane efficiently evaporated seawater with different salt concentrations to produce drinking water which meet World Health Organization(WHO)and US Environmental Protection Agency(EPA)standards.This work provides an integrated solution for solar desalination and CO_(2)reduction at the surface of sea to reduce the harm to marine life caused by ocean acidification while producing pure water.

Single titanium-oxide species implanted in 2D g-CsN4 matrix as a highly efficient visible-light CO2 reduction photocatalyst

A visible-light-response, efficie nt and robust photo-catalyst for CO2 reduction is highly desirable. Herein, we demonstrate that single titanium-oxide species impla nted in two-dime nsion al (2D) graphitic carb on n itride (g-C3N4) matrix (2D TiO-CN) can efficie ntly photo-catalyze the reduction of CO2 to CO under the irradiation of visible light. The synergistic interaction between single titanium oxide species and g-C3N4 in 2D TiO-CN not only enhances the separation of photo-excited charges, but also results in visible light response of single titanium-oxide species, realizing high activity of CO2 photo-reduction with extremely high CO generation rate of 283.9 pmol·h^-1·g^-1, 5.7, 6.8 and 292.2 times larger than those of TQ2/CN hybrid material, CN and commercial TiO2, respectively. Time-resolved fluoresce nee and electron spin resonance spectroscopy revealed the catalytic mechanism of the fabricated 2D TiO-CN photocatalysts for CO2 reduction.

Targeting BMI-1-mediated epitheliale-mesenchymal transition to inhibit colorectal cancer liver metastasis

Liver is the most common metastatic site for colorectal cancer(CRC),there is no satisfied approach to treat CRC liver metastasis(CRCLM).Here,we investigated the role of a polycomb protein BMI-1 in CRCLM.Immunohistochemical analysis showed that BMI-1 expression in liver metastases was upregulated and associated with T4 stage,invasion depth and right-sided primary tumor.Knockdown BMI-1 in high metastatic HCT116 and LOVO cells repressed the migratory/invasive phenotype and reversed epithelialemesenchymal transition(EMT),while BMI-1 overexpression in low metastatic Ls174 T and DLD1 cells enhanced invasiveness and EMT.The effects of BMI-1 in CRC cells were related to upregulating snail via AKT/GSK-3βpathway.Furthermore,knockdown BMI-1 in HCT116 and LOVO cells reduced CRCLM using experimental liver metastasis mice model.Meanwhile,BMI-1 overexpression in Ls174 T and DLD1 significantly increased CRCLM.Moreover,sodium butyrate,a histone deacetylase and BMI-1 inhibitor,reduced HCT116 and LOVO liver metastasis in immunodeficient mice.Our results suggest that BMI-1 is a major regulator of CRCLM and provide a potent molecular target for CRCLM treatment.

SMAD7 and SERPINE1 as novel dynamic network biomarkers detect and regulate the tipping point of TGF-beta induced EMT

Epithelial–mesenchymal transition(EMT) is a complex nonlinear biological process that plays essential roles in fundamental biological processes such as embryogenesis, wounding healing, tissue regeneration,and cancer metastasis. A hallmark of EMT is the switch-like behavior during state transition, which is characteristic of phase transitions. Hence, detecting the tipping point just before mesenchymal state transition is critical for understanding molecular mechanism of EMT. Through dynamic network biomarkers(DNB) model, a DNB group with 37 genes was identified which can provide the early-warning signals of EMT. Particularly, we found that two DNB genes, i.e., SMAD7 and SERPINE1 promoted EMT by switching their regulatory network which was further validated by biological experiments. Survival analyses revealed that SMAD7 and SERPINE1 as DNB genes further acted as prognostic biomarkers for lung adenocarcinoma.

Global quantitative biology can illuminate ontological connections between diseases

Owing to its interdisciplinary nature, quantitative biology is playing ever-increasing roles in biological researches. To make quantitative biology even more powerful, it is important to develop a holistic perspective by integrating information from multiple biological levels and by considering related biocomplexity simultaneously. Using complex diseases as an example, I show in this paper how their ontological connections can be revealed by considering the diseases on a common ground. The obtained insights may be useful to the prediction and treatment of the diseases. Although the example involves only with cancer and diabetes, the approaches are applicable to the study of other diseases, or even to other biological problems.

Entanglement purification for memory nodes in a quantum network

The entanglement between quantum memory nodes is a prerequisite in a quantum network, and the diamond nitrogen-vacancy(NV) center is a promising candidate serving as a quantum memory node. Here, we investigate the possibility of achieving an entanglement purification protocol(EPP) for entangled NV centers in distant diamonds. To construct the EPP, we design a nondestructive parity-check detector(PCD) utilizing an auxiliary polarization-entangled photon pair, which makes our EPP less time consuming and insensitive to the phase fluctuation of the optical path length. The satisfied fidelity of an NV center pair after purification and efficiency of obtaining a purified NV center pair with our EPP can be obtained with current experimental techniques in the realistic condition. This EPP is useful for a quantum network in which NV centers are used as quantum memory nodes.

Testing the leanocentric locking-point theory by in silico partial lipectomy

Background:The lipostatic set-point theory,ascribing fat mass homeostasis to leptin mediated central feedback regulation targeting the body9s fat storage,has caused a variety of conundrums.We recently proposed a leanocentric locking-point theory and the corresponding mathematical model,which not only resolve these conundrums but also provide valuable insights into weight control and health assessment.This paper aims to further test the leanocentric theory.Methods:Partial lipectomy is a touchstone to test both the leanocentric and lipostatic theories.Here we perform in silico lipectomy by using a mathematical model embodying the leanocentric theory to simulate the long-term body fat change after removing some fat cells in the body.Results:The mathematical modeling uncovers a phenomenon called post-surgical fat loss,which was well-documented in real partial lipectomy surgeries;thus,the phenomenon can serve as an empirical support to the leanocentric theory.On the other hand,the leanocentric theory,but not the lipostatic theory,can well explain the post-surgical fat loss.Conclusions:The leanocentric locking-point theory is a promising theory and deserves further testing.Partial lipectomy surgeries are beneficial to obese patients for quite a long period.