A Comparative Study of Gamma-Ray Irradiation-Induced Oxidation: Polyethylene, Poly (Vinylidene Fluoride), and Polytetrafluoroethylene.

Radiation techniques are used to modify the physical, chemical and biological properties of polymers. This induces crosslinking and degradation reactions of polymers by utilizing radicals generated through ionizing radiation. However, oxidation products (such as carbonyl) can be formed because oxidation occurs by chain scission in the presence of oxygen. Herein, we demonstrate the gamma-ray irradiation-induced oxidation with and without fluorine using polyethylene, polyvinylidene fluoride and polytetrafluoroethylene under the same conditions. In this study, changes in element-content and chemical-bond structures were analyzed before and after gamma-ray irradiation under air atmosphere. As a result, polytetrafluo-roethylene showed less oxidation and excellent thermal properties after the absorbed dose of 500 kGy. This can be attributed to the generation of stable perfluoroalkylperoxy radicals after gamma ray irradiation in the PTFE structure containing only CF2 groups, thereby hindering the oxidation reaction.

Accuracy-Power Controllable LiDAR Sensor System with 3D Object Recognition for Autonomous Vehicle.

Light detection and ranging (LiDAR) sensors help autonomous vehicles detect the surrounding environment and the exact distance to an object's position. Conventional LiDAR sensors require a certain amount of power consumption because they detect objects by transmitting lasers at a regular interval according to a horizontal angular resolution (HAR). However, because the LiDAR sensors, which continuously consume power inefficiently, have a fatal effect on autonomous and electric vehicles using battery power, power consumption efficiency needs to be improved. In this paper, we propose algorithms to improve the inefficient power consumption of conventional LiDAR sensors, and efficiently reduce power consumption in two ways: (a) controlling the HAR to vary the laser transmission period (TP) of a laser diode (LD) depending on the vehicle's speed and (b) reducing the static power consumption using a sleep mode, depending on the surrounding environment. The proposed LiDAR sensor with the HAR control algorithm reduces the power consumption of the LD by 6.92% to 32.43% depending on the vehicle's speed, compared to the maximum number of laser transmissions (Nx.max). The sleep mode with a surrounding environment-sensing algorithm reduces the power consumption by 61.09%. The algorithm of the proposed LiDAR sensor was tested on a commercial processor chip, and the integrated processor was designed as an IC using the Global Foundries 55 nm CMOS process.

Effect of Heat Budget After Capacitor Formation on the Leakage Current Characteristics of ZrO2-Based High-k Dielectrics for Next-Generation Dynamic Random-Access Memory Capacitors.

Successful development of 20 nm or smaller dynamic random-access memory (DRAM) requires reduction of the leakage current in capacitors with high-k dielectrics. To reduce the leakage current of the capacitor, we fabricated a ZrO2-based metal-insulator-metal (MIM) capacitor and investigated changes in leakage current characteristics associated with heat budget following capacitor formation. Leakage current characteristics were drastically degraded by applying an additional heat treatment to the MIM capacitor. Through detailed analysis of leakage versus bias voltage (I-V) characteristics, dielectric constants, and high-resolution transmission electron microscopy (HR-TEM) findings, we determined that the leakage current degradation was caused by an increase in Poole-Frenkel (P-F) emission due to an increase in defect density in the dielectrics and an increase in the dielectric constant due to enhancement of the crystallinity of ZrO2. Based on the experimental results, we propose a new, simple strategy to reduce leakage current without changing the capacitor structure or material used in the DRAM manufacturing process. This simple approach will not only enable mass production of 20 nm DRAM, but also contribute to the development of next-generation DRAMs by reducing the leakage current of the capacitor.

Single-Incision, Two-Port Laparoscopic Appendectomy as an Alternative to Transumbilical Single-Port Laparoscopic Appendectomy.

Purpose: We designed a modified technique to perform an advanced procedure using conventional instruments and did not employ specialized single-incision laparoscopic surgery (SILS) port equipment. We compared postoperative results for transumbilical, single-port laparoscopic appendectomy (TUSPLA) and single-incision, 2-port laparoscopic appendectomy (SITPLA). Methods: This retrospective study enrolled 77 patients who underwent TUSPLA or SITPLA to provide more minimally invasive surgery between May 2017 and April 2018. TUSPLA was performed in 39 patients and 38 underwent SITPLA. In the SITPLA group, two 5-mm trocars were inserted through the umbilicus and an extra puncture site was used for a left-handed instrument. Demographic characteristics, operative data, and postoperative outcomes were collected and compared between the groups. Results: The mean total operative time in the SITPLA group was shorter than in the TUSPLA group (p=0.003). The mean laparoscopic instrumental time was also shorter (p<0.001) in the SITPLA. The number of postoperative analgesics in the SITPLA group was less than in the TUSPLA group (p=0.002). The length of hospital day after surgery was shorter in the SITPLA group than in the TUSPLA group (p=0.008). There were no other significant differences between the groups. Conclusion: SITPLA had a shorter operative time, required less pain management, and had a similar cosmetic outcome when compared with TUSPLA.

Anti-proliferative activity of CGK012 against multiple myeloma cells via Wnt/ß-catenin signaling attenuation.

The aberrant activation of Wnt/ß-catenin signaling is involved in the development of multiple myeloma; thus, this signaling pathway is a potential target for the development of therapeutics for this malignancy. Here, we performed cell-based chemical screening and found that CGK012, a pyranocoumarin compound, suppressed the Wnt3a-CM-mediated activation of ß-catenin response transcription. CGK012 induced ß-catenin phosphorylation at Ser33/Ser37/Thr41, leading to proteasomal degradation and reducing the level of intracellular ß-catenin. Furthermore, CGK012 consistently decreased the amount of ß-catenin and repressed the expression of cyclin D1, c-myc, and axin-2 (downstream target genes of ß-catenin) in RPMI-8226 multiple myeloma cells. In addition, CGK012 inhibited the proliferation of RPMI-8226 cells and promoted apoptosis, as indicated by the increase in the population of Annexin V-FITC-stained cells and caspase-3/7 activity. These findings suggest that CGK012 could exert antiproliferative activity against multiple myeloma cells by attenuating the Wnt/ß-catenin pathway; thus, it may have potential as a therapeutic agent for multiple myeloma treatment.

Real-time dynamics of carbon nanotube porins in supported lipid membranes visualized by high-speed atomic force microscopy.

In-plane mobility of proteins in lipid membranes is one of the fundamental mechanisms supporting biological functionality. Here we use high-speed atomic force microscopy (HS-AFM) to show that a novel type of biomimetic channel-carbon nanotube porins (CNTPs)-is also laterally mobile in supported lipid membranes, mimicking biological protein behaviour. HS-AFM can capture real-time dynamics of CNTP motion in the supported lipid bilayer membrane, build long-term trajectories of the CNTP motion and determine the diffusion coefficients associated with this motion. Our analysis shows that diffusion coefficients of CNTPs fall into the same range as those of proteins in supported lipid membranes. CNTPs in HS-AFM experiments often exhibit 'directed' diffusion behaviour, which is common for proteins in live cell membranes.This article is part of the themed issue 'Membrane pores: from structure and assembly, to medicine and technology'.

Defect visualization of Cu(InGa)(SeS)2 thin films using DLTS measurement.

Defect depth profiles of Cu (In1-x,Gax)(Se1-ySy)2 (CIGSS) were measured as functions of pulse width and voltage via deep-level transient spectroscopy (DLTS). Four defects were observed, i.e., electron traps of ~0.2 eV at 140 K (E1 trap) and 0.47 eV at 300 K (E2 trap) and hole traps of ~0.1 eV at 100 K (H1 trap) and ~0.4 eV at 250 K (H2 trap). The open circuit voltage (VOC) deteriorated when the trap densities of E2 were increased. The energy band diagrams of CIGSS were also obtained using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and DLTS data. These results showed that the valence band was lowered at higher S content. In addition, it was found that the E2 defect influenced the VOC and could be interpreted as an extended defect. Defect depth profile images provided clear insight into the identification of defect state and density as a function of depth around the space charge region.

Electrical Properties of Solution Processed In-Ga-ZnO Thin Film Transistors with Multi-Stacked Active Layer.

In this study, we prepared solution-based In-Ga-ZnO thin film transistors (IGZO TFTs) having a multistacked active layer. The solution was prepared using an In:Zn = 1:1 mole ratio with variation in Ga content, and the TFTs were fabricated by stacking layers from the prepared solutions. After we measured the mobility of each stacked layer, the saturation mobility showed values of 0.8, 0.6 and 0.4 (cm2/Vs), with an overall decrease in electrical properties. The interface formed between the each layers affected the current path, resulting in reduced electrical performance. However, when the gate bias VG = 10 V was applied for 1500 s, the threshold voltage shift decreased in the stack. The uniformity of the active layer was improved in the stacked active layer by filling the hole formed during pre-baking, resulting in improved device stability. Also, the indium ratio was increased to enhance the mobility from 0.86 to 3.47. These results suggest high mobility and high stability devices can be produced with multistacked active layers.

Abnormal Threshold Voltage Shifts in P-Channel Low-Temperature Polycrystalline Silicon Thin Film Transistors Under Negative Bias Temperature Stress.

In this research, we have investigated the instability of P-channel low-temperature polycrystalline silicon (poly-Si) thin-film transistors (LTPS TFTs) with double-layer SiO2/SiNx dielectrics. A negative gate bias temperature instability (NBTI) stress was applied and a turn-around behavior phenomenon was observed in the Threshold Voltage Shift (Vth). A positive threshold voltage shift occurs in the first stage, resulting from the negative charge trapping at the SiNx/SiO2 dielectric interface being dominant over the positive charge trapping at dielectric/Poly-Si interface. Following a stress time of 7000 s, the Vth switches to the negative voltage direction, which is "turn-around" behavior. In the second stage, the Vth moves from -1.63 V to -2 V, overwhelming the NBTI effect that results in the trapping of positive charges at the dielectric/Poly-Si interface states and generating grain-boundary trap states and oxide traps.

Preparation and Characterization of P-Type and N-Type Doped Expanded Graphite Polymer Composites for Thermoelectric Applications.

In this work, we demonstrate that expanded graphite can be sufficiently dispersed in polymer solution to form suspensions. Thin composite films were prepared by casting and drying the suspensions. The thermoelectric properties of expanded graphite (ExG)-polymer composites were easily modified by chemical doping. Electrically and thermally insulating polymers of PC, PS, and PMMA served as matrix materials. ExG composite films in PC, PMMA, and PS were prepared using thionyl chloride as the p-type dopant and PEI as the n-type dopant. By comparing the electrical conductivity and Seebeck coefficient values of the composite films, we observed that use of an electron acceptor material (thionyl chloride) in composites enhanced electrical conductivity and reduced the value of the positive Seebeck coefficient, which are p-type doping effects. In contrast, when the donor material PEI was used, there was an increase in electrical conductivity and changes in the value and sign of the Seebeck coefficient from positive to negative, confirming n-type doping.

Temperature-dependent electrical characteristics of c-Si and CIGS solar cells.

We characterized the electrical behavior of crystalline silicon (c-Si) and Cu(In(1-x)Ga(x))Se2 (CIGS) solar cells by current-voltage (I-V) and capacitance-voltage (C-V) methods. We investigated the temperature-dependent carrier transport mechanism by determining the parameters of ideality factor (n) and activation energy (E(a)) deduced from I-V measurements. CLGS solar cells, as a function of temperature, showed drastic changes in n and E(a) in the space charge region (SCR) that forms near the ZnS/CIGS interface. Furthermore, by using a C-V measured substrate doping profiling method, we confirmed that the CIGS absorption layer had a graded band-gap structure from the end point of the SCR to the CIGS/Mo back contacts, while c-Si solar cells had a uniformly doped carrier concentration.

An FET-type charge sensor for highly sensitive detection of DNA sequence.

We have fabricated an field effect transistor (FET)-type DNA charge sensor based on 0.5 microm standard complementary metal oxide semiconductor (CMOS) technology which can detect the deoxyribonucleic acid (DNA) probe's immobilization and information on hybridization by sensing the variation of drain current due to DNA charge and investigated its electrical characteristics. FET-type charge sensor for detecting DNA sequence is a semiconductor sensor measuring the change of electric charge caused by DNA probe's immobilization on the gate metal, based on the field effect mechanism of MOSFET. It was fabricated in p-channel (P) MOSFET-type because the phosphate groups present in DNA have a negative charge and this charge determines the effective gate potential of PMOSFET. Gold (Au) which has a chemical affinity with thiol was used as the gate metal in order to immobilize DNA. The gate potential is determined by the electric charge which DNA possesses. Variation of the drain current versus time was measured. The drain current increased when thiol DNA and target DNA were injected into the solution, because of the field effect due to the electrical charge of DNA molecules. The experimental validity was verified by the results of mass changes detected using quartz crystal microbalance (QCM) under the same measurement condition. Therefore it is confirmed that DNA sequence can be detected by measuring the variation of the drain current due to the variation of DNA charge and the proposed FET-type DNA charge sensor might be useful in the development for DNA chips.