Continuous quality improvement program and its results of Korean Society for Cytopathology.

BACKGROUND: Since 1995, the Korean Society for Cytopathology has overseen the Continuous Quality Improvement program for cytopathology laboratories. The Committee of Quality Improvement has carried out an annual survey of cytology data for each laboratory and set standards for proficiency tests. METHODS: Evaluations were conducted four times per year from 2008 to 2018 and comprised statistics regarding cytology diagnoses of previous years, proficiency tests using cytology slides provided by the committee, assessment of adequacy of gynecology (GYN) cytology slides, and submission of cytology slides for proficiency tests. RESULTS: A total of 206 institutes participated in 2017, and the results were as follows. The number of cytology tests increased from year to year. The ratio of liquid-based cytology in GYN gradually decreased, as most of the GYN cytology had been performed at commercial laboratories. The distribution of GYN diagnoses demonstrated nearly 3.0% as atypical squamous cells. The rate for squamous cell carcinoma was less than 0.02%. The atypical squamous cell/squamous intraepithelial lesion ratio was about 3:1 and showed an upward trend. The major discordant rate of cytology-histology in GYN cytology was less than 1%. The proficiency test maintained a major discordant rate less than 2%. The rate of inappropriate specimens for GYN cytology slides gradually decreased. CONCLUSIONS: The Continuous Quality Improvement program should be included in quality assurance programs. Moreover, these data can contribute to development of national cancer examination guidelines and facilitate cancer prevention and treatment.

Highly Sensitive H2S Sensor Based on the Metal-Catalyzed SnO2 Nanocolumns Fabricated by Glancing Angle Deposition.

As highly sensitive H2S gas sensors, Au- and Ag-catalyzed SnO2 thin films with morphology-controlled nanostructures were fabricated by using e-beam evaporation in combination with the glancing angle deposition (GAD) technique. After annealing at 500 °C for 40 h, the sensors showed a polycrystalline phase with a porous, tilted columnar nanostructure. The gas sensitivities (S = Rgas/Rair) of Au and Ag-catalyzed SnO2 sensors fabricated by the GAD process were 0.009 and 0.015, respectively, under 5 ppm H2S at 300 °C, and the 90% response time was approximately 5 s. These sensors showed excellent sensitivities compared with the SnO2 thin film sensors that were deposited normally (glancing angle = 0°, S = 0.48).

Giant Electroresistive Ferroelectric Diode on 2DEG.

Manipulation of electrons in a solid through transmitting, storing, and switching is the fundamental basis for the microelectronic devices. Recently, the electroresistance effect in the ferroelectric capacitors has provided a novel way to modulate the electron transport by polarization reversal. Here, we demonstrate a giant electroresistive ferroelectric diode integrating a ferroelectric capacitor into two-dimensional electron gas (2DEG) at oxide interface. As a model system, we fabricate an epitaxial Au/Pb(Zr(0.2)Ti(0.8))O3/LaAlO3/SrTiO3 heterostructure, where 2DEG is formed at LaAlO3/SrTiO3 interface. This device functions as a two-terminal, non-volatile memory of 1 diode-1 resistor with a large I+/I- ratio (>10(8) at ± 6 V) and I(on)/I(off) ratio (>10(7)). This is attributed to not only Schottky barrier modulation at metal/ferroelectric interface by polarization reversal but also the field-effect metal-insulator transition of 2DEG. Moreover, using this heterostructure, we can demonstrate a memristive behavior for an artificial synapse memory, where the resistance can be continuously tuned by partial polarization switching, and the electrons are only unidirectionally transmitted. Beyond non-volatile memory and logic devices, our results will provide new opportunities to emerging electronic devices such as multifunctional nanoelectronics and neuromorphic electronics.

Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays.

Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures.

High output piezo/triboelectric hybrid generator.

Recently, piezoelectric and triboelectric energy harvesting devices have been developed to convert mechanical energy into electrical energy. Especially, it is well known that triboelectric nanogenerators have a simple structure and a high output voltage. However, whereas nanostructures improve the output of triboelectric generators, its fabrication process is still complicated and unfavorable in term of the large scale and long-time durability of the device. Here, we demonstrate a hybrid generator which does not use nanostructure but generates much higher output power by a small mechanical force and integrates piezoelectric generator into triboelectric generator, derived from the simultaneous use of piezoelectric and triboelectric mechanisms in one press-and-release cycle. This hybrid generator combines high piezoelectric output current and triboelectric output voltage, which produces peak output voltage of ~370 V, current density of ~12 µA · cm(-2), and average power density of ~4.44 mW · cm(-2). The output power successfully lit up 600 LED bulbs by the application of a 0.2 N mechanical force and it charged a 10 µF capacitor to 10 V in 25 s. Beyond energy harvesting, this work will provide new opportunities for developing a small, built-in power source in self-powered electronics such as mobile electronics.

Effect of Amount of Aluminum on the Performance of Si-Al Codeposited Anodes for Lithium Batteries.

Silicon is considered one of the most promising anode materials for high-performance Li-ion batteries due to its 4000 mAh/g theoretical specific capacity, relative abundance, low cost, and environmental benignity. However, silicon experiences a dramatic volume change (-300%) during full charge/discharge cycling, leading to severe capacity decay and poor cycling stability. Here, we report Si-Al codeposited anode material for Li-ion batteries. The Si-Al thin films were deposited by co-deposition from Si and Al target on nickel substrate. The composition of Si and Al in the film is estimated by energy-dispersive spectroscopy. The XRD and SEM analysis revealed that the Si-Al thin films were amorphous in structure. The electrochemical performance of the Si-Al thin film as anode material for lithium ion battery was investigated by the charge/discharge tests. Galvanostatic half-cell electrochemical measurements were conducted in between 0 mV to 2 V using a Li counter electrode, demonstrating that the Al rich Si-Al thin film achieved a good cycleability up to 100 cycles with a high capacity retention. Si-Al sample having 11.04% Al shows capacity 825 mAh/g over the 100 cycles.

Enhanced Output Power of PZT Nanogenerator by Controlling Surface Morphology of Electrode.

Piezoelectric power generation using Pb(Zr,Ti)O3(PZT) nanowires grown on Nb-doped SrTiO3(nb:STO) substrate has been demonstrated. The epitaxial PZT nanowires prepared by a hydrothermal method, with a diameter and length of approximately 300 nm and 7 µm, respecively, were vertically aligned on the substrate. An embossed Au top electrode was applied to maximize the effective power generation area for non-uniform PZT nanowires. The PZT nanogenerator produced output power density of 0.56 µW/cm2 with a voltage of 0.9 V and current of 75 nA. This research suggests that the morphology control of top electrode can be useful to improve the efficiency of piezoelectric power generation.

Nonvolatile resistance switching on two-dimensional electron gas.

Two-dimensional electron gas (2DEG) at the complex oxide interfaces have brought about considerable interest for the application of the next-generation multifunctional oxide electronics due to the exotic properties that do not exist in the bulk. In this study, we report the integration of 2DEG into the nonvolatile resistance switching cell as a bottom electrode, where the metal-insulator transition of 2DEG by an external field serves to significantly reduce the OFF-state leakage current while enhancing the on/off ratio. Using the Pt/Ta2O5-y/Ta2O5-x/SrTiO3 heterostructure as a model system, we demonstrate the nonvolatile resistance switching memory cell with a large on/off ratio (>10(6)) and a low leakage current at the OFF state (∼10(-13) A). Beyond exploring nonvolatile memory, our work also provides an excellent framework for exploring the fundamental understanding of novel physics in which electronic and ionic processes are coupled in the complex heterostructures.

Highly stretchable piezoelectric-pyroelectric hybrid nanogenerator.

A highly stretchable hybrid nanogenerator has been developed using a micro-patterned piezoelectric polymer P(VDF-TrFE), PDMS-CNT composite, and graphene nanosheets. Mechanical and thermal energies are simultaneously harvested from a single cell of the device. The hybrid nanogenerator exhibits high robustness behavior even after 30% stretching and generates very stable piezoelectric and pyroelectric power outputs due to micro-pattern designing.

Extremely sensitive and selective NO probe based on villi-like WO3 nanostructures for application to exhaled breath analyzers.

Self-assembled WO3 thin film nanostructures with 1-dimensional villi-like nanofingers (VLNF) have been synthesized on the SiO2/Si substrate with Pt interdigitated electrodes using glancing angle deposition (GAD). Room-temperature deposition of WO3 by GAD resulted in anisotropic nanostructures with large aspect ratio and porosity having a relative surface area, which is about 32 times larger than that of a plain WO3 film. A WO3 VLNF sensor shows extremely high response to nitric oxide (NO) at 200 °C in 80% of relative humidity atmosphere, while responses of the sensor to ethanol, acetone, ammonia, and carbon monoxide are negligible. Such high sensitivity and selectivity to NO are attributed to the highly efficient modualtion of potential barriers at narrow necks between individual WO3 VLNF and the intrinsically high sensitivity of WO3 to NO. The theoretical detection limit of the sensor for NO is expected to be as low as 88 parts per trillion (ppt). Since NO is an approved biomarker of chronic airway inflammation in asthma, unprecedentedly high response and selectivity, and ppt-level detection limit to NO under highly humid environment demonstrate the great potential of the WO3 VLNF for use in high performance breath analyzers.

Non-volatile control of 2DEG conductivity at oxide interfaces.

The functionalization of two-dimensional electron gas (2DEG) at oxide interfaces can be realized integrating 2DEG with multifunctional oxide overlayers by epitaxial growth. Using a ferroelectric Pb(Zr0.2 Ti0.8 )O3 overlayer on 2DEG (LaAlO3 /SrTiO3 ), we demonstrate a model system of the functionalized 2DEG, where electrical conductivity of 2DEG can be reversibly controlled with a large on/off ratio (>1000) in a non-volatile way by ferroelectric polarization switching.

Electrochemical properties of Sn-substituted LiMn2O4 thin films prepared by radio-frequency magnetron sputtering.

The LiMn2O4 and LiSn0.0125Mn1975O4 thin films were grown on Pt/Ti/SiO2/Si (100) substrate by RF magnetron sputtering. To obtain the structural stability and good cycle performance, deposition parameters, namely working pressure, sputtering gas ratio of Ar and O2, post-annealing temperature were established. The structure and surface morphology of thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electrochemical properties were estimated by two electrode half-cell test with WBCS 3000 (Wonatech, Korea) at constant current rate of 1 C-rate. The Sn substituted LiMn2O4 thin film deposited at 10 mtorr with mixture of argon and oxygen (Ar/O2 = 3/1) and then annealed at 500 degrees C in O2 atmosphere showed good cycle performance. The Sn substituted LiMn2O4 thin films showed larger capacity of -30 microAh/microm-cm2 and higher cyclability than LiMn2O4 thin films.

Structural and electrical properties of NASICON type solid electrolyte nanoscaled glass-ceramic powder by mechanical milling for thin film batteries.

During last two decades, lithium-based glasses have been studied extensively as electrolytes for solid-state secondary batteries. For practical use, solid electrolyte must have high ionic conductivity as well as chemical, thermal and electrochemical stability. Recent progresses have focused on glass electrolytes due to advantages over crystalline solid. Glass electrolytes are generally classified into two types oxide glass and sulfide glass. Oxide glasses do not react with electrode materials and this chemical inertness is advantageous for cycle performances of battery. In this study, major effort has been focused on the improvement of the ion conductivity of nanosized LiAlTi(PO4)3 oxide electrolyte prepared by mechanical milling (MM) method. After heating at 1000 degrees C the material shows good crystallinity and ionic conductivity with low electronic conductivity. In LiTi2(PO4)3, Ti4+ ions are partially substituted by Al3+ ions by heat-treatment of Li20-Al2O3-TiO2-P2O5 glasses at 1000 degrees C for 10 h. The conductivity of this material is 1.09 x 10(-3) S/cm at room temp. The glass-ceramics show fast ion conduction and low E(a) value. It is suggested that high conductivity, easy fabrication and low cost make this glass-ceramics promising to be used as inorganic solid electrolyte for all-solid-state Li rechargeable batteries.

Sensitivity enhancement of nanostructured SnO2 gas sensors fabricated using the glancing angle deposition method.

0.5 wt.% Pd-catalyzed SnO2 thin-film gas sensors with microstructures controlled on a nanometer scale were fabricated by an e-beam evaporator using the glancing angle deposition (GAD) method. After annealing at 500 degrees C for 1 h, the sensors produced were polycrystalline with a nanoporous, tilted columnar microstructure. The gas-sensing properties of these SnO2 sensors were measured in the concentration range of 1 to 5 ppm NO2 at 250 degrees C and of 10 to 50 ppm C2H5OH at 400 degrees C, respectively. The sensors fabricated by e-beam evaporation in combination with the GAD method showed much higher sensitivities than normally prepared sensors and exhibited rapid response times. The gas sensitivity (S = R(gas)/R(air)) of the SnO2 sensor using the GAD method was 43.4 for 5 ppm NO2 and 0.08 for 10 ppm C2H5OH, respectively. These sensors showed excellent sensitivities compared to the normal thin film sensors (S = 2 for 5 ppm NO2 and 0.92 for 10 ppm C2H5OH). We consider that the nanostructured sensors produced using the GAD process could be used to detect various gases emitted by automobiles and industrial installations.

A near single crystalline TiO2 nanohelix array: enhanced gas sensing performance and its application as a monolithically integrated electronic nose.

We present high performance gas sensors based on an array of near single crystalline TiO(2) nanohelices fabricated by rotating oblique angle deposition (OAD). The combination of large surface-to-volume ratio, extremely small size (<30 nm) comparable to the Debye length, a near single crystallinity of TiO(2) nanohelices, together with the unique top-and-bottom electrode configuration hugely improves the H(2)-sensing performance, including ∼10 times higher response at 50 ppm, approximately a factor of 5 lower detection limit, and much faster response time than the conventional TiO(2) thin film devices. Beyond such remarkable performance enhancement, the excellent compatibility of the OAD method compared with the conventional micro-fabrication technology opens a new avenue for monolithic integration of high-performance chemoresistive sensors to fabricate a simple, low cost, reliable, yet fully functional electronic nose and multi-functional smart chips for in situ environmental monitoring.

All-solution-processed flexible thin film piezoelectric nanogenerator.

An all-solution-processed flexible thin film piezoelectric nanogenerator is demonstrated using reactive zinc hydroxo-condensation and a screen-printing method. The highly elastic thin film allows the piezoelectric energy to be generated through the mechanical rolling and muscle stretching of the piezoelectric unit. This flexible all solution-processed nanogenerator is promising for use in future energy harvesters such as wearable human patches and mobile electronics.

Self-activated ultrahigh chemosensitivity of oxide thin film nanostructures for transparent sensors.

One of the top design priorities for semiconductor chemical sensors is developing simple, low-cost, sensitive and reliable sensors to be built in handheld devices. However, the need to implement heating elements in sensor devices, and the resulting high power consumption, remains a major obstacle for the realization of miniaturized and integrated chemoresistive thin film sensors based on metal oxides. Here we demonstrate structurally simple but extremely efficient all oxide chemoresistive sensors with ~90% transmittance at visible wavelengths. Highly effective self-activation in anisotropically self-assembled nanocolumnar tungsten oxide thin films on glass substrate with indium-tin oxide electrodes enables ultrahigh response to nitrogen dioxide and volatile organic compounds with detection limits down to parts per trillion levels and power consumption less than 0.2 microwatts. Beyond the sensing performance, high transparency at visible wavelengths creates opportunities for their use in transparent electronic circuitry and optoelectronic devices with avenues for further functional convergence.

Association of serum alanine aminotransferase and γ-glutamyltransferase levels within the reference range with metabolic syndrome and nonalcoholic fatty liver disease.

BACKGROUND/AIMS: Nonalcoholic fatty liver disease (NAFLD) has recently been found to be a novel component of metabolic syndrome (MS), which is one of the leading causes of chronic liver disease. The serum alanine aminotransferase (ALT) and ⟨-glutamyltransferase (GGT) levels are suggested to affect liver fat accumulation and insulin resistance. We assessed the associations of serum ALT and GGT concentrations within the reference ranges with MS and NAFLD. METHODS: In total, 1,069 subjects enrolled at the health promotion center of Wonkwang University Hospital were divided into 4 groups according to serum ALT and GGT concentrations levels within the reference ranges. We performed biochemical tests, including liver function tests and lipid profiles, and diagnosed fatty liver by ultrasonography. Associations of ALT and GGT concentrationgrading within the reference range with fatty liver and/or MS were investigated. RESULTS: The presence of MS, its components, and the number of metabolic abnormalities [except for high-density lipoprotein-cholesterol (HDL-C) and fasting blood glucose] increased with the ALT level, while the presence of MS, its components, and the number of metabolic abnormalities (except for HDL-C) increased with the GGT level. The odds ratios for fatty liver and MS increased with the ALT level (P⟨0.001 and P=0.049, respectively) and the GGT level (P=0.044 and P=0.039, respectively). CONCLUSIONS: Serum ALT and GGT concentrations within the reference ranges correlated with the incidence of NAFLD and MS in a dose-dependent manner. There associations need to be confirmed in large, prospective studies.

Dynamic properties of an omni-directional piezoelectric motor for precision position control.

A piezoelectric motor capable of omni-directional movements has been developed to apply for robot joints, eyes, and precision positioning stage. The piezoelectric actuator has a simple structure of a cone type consisting of two piezoelectric ring-typed ceramics with electrodes divided into four segments and stainless steel elastic bodies. Before manufacturing the piezoelectric motor, the admittance characteristics and displacements of the actuator as a function of frequency were simulated. Elliptical motions of the actuator were created at several frequencies between the longitudinal and transverse resonance frequencies. The actual motor with alumina ball exhibited nice performance using a driving circuit with two rotary encoders and a PID controller. The moving element was omni-directionally operated at a driving frequency of 53.8 kHz and an output voltage of 280 V(p-p). The developed motor enables the moving element to move to a desired position with a resolution of 1.2 degrees/pulse, an angular velocity of 4 rad/s, and a thrust force of 200 g.

Analysis of shaking beam actuator for piezoelectric linear ultrasonic motor.

In this paper, piezoelectric linear ultrasonic motors (PLUM) have been investigated on the elliptic trajectory of a contact point in shaking beam, which has been accomplished by two resonance vibration modes of the actuators. The actuators have generated the vibration modes, longitudinal and flexural, by two longitudinal mechanical vibrations with phase difference of pi/2. Modal and harmonic analysis of the shaking beam actuator were performed by the finite element method (FEM) to calculate a resonance frequency and a modal shape and to perform harmonic response. Experimental results proved that a contact point of the PLUM tends to move with an elliptic trajectory.