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The proposed electro-responsive hydrogel has great benefit for transdermal drug delivery system (TDDS) applications. To improve the physical or chemical properties of hydrogels, a number of researchers have previously studied the mixing efficiencies of the blended hydrogels. However, few studies have focused on improving the electrical conductivity and drug delivery of the hydrogels. We developed a conductive blended hydrogel by mixing alginate with gelatin methacrylate (GelMA) and silver nanowire (AgNW). We demonstrated that and the tensile strength of blended hydrogels were increased by a factor of 1.8 by blending GelMA and the electrical conductivity was enhanced by a factor of 18 by the addition of AgNW. Furthermore, the GelMA-alginate-AgNW (Gel-Alg-AgNW) blended hydrogel patch enabled on-off controllable drug release, indicating 57% doxorubicin release in response to electrical stimulation (ES) application. Therefore, this electro-responsive blended hydrogel patch could be useful for smart drug delivery applications.

The precise manipulation of the neural stem cell (NSC)-derived neural differentiation is still challenging, and there is a technological barrier to regulate the axonal regeneration in a controlled manner. Here, we developed a microfluidic chip integrated with a microelectrode array as an axonal guidance platform. The microfluidic electrode array chip consisted of two compartments and a bridge microchannel that could isolate and guide the axons. We demonstrated that the NSCs were largely differentiated into neural cells as the electric field was applied to the microfluidic electrode array chip. We also confirmed the synergistic effects of the electrical stimulation (ES) and neurotrophic factor (NF) on axonal outgrowth. This microfluidic electrode array chip can serve as a central nervous system (CNS) model for axonal injury and regeneration. Therefore, it could be a potentially powerful tool for an

Radiation-based imaging systems comprise multiple radiation sensors that are assembled with coupled Si PIN (positive — intrinsic — negative) photodetectors and scintillators. This paper describes the fabrication and characterization of a four-channel array Si PIN photodetector for security inspection systems. The Si PIN photodetector was fabricated using conventional (CMOS) processes at the Radiation Equipment Fab. The junction depth, passivation, and anti-reflection layer of the photodetector were controlled to maximize the light detection efficiency and the signal-to-noise ratio. The spectral responsivity obtained was 0.28 A/W for the cadmium tungstate (CWO) emission at a wavelength of 475 nm. Finally, a line pattern image was acquired using the fabricated Si PIN sensor and a self-developed readout and data acquisition system. The significance of this study is it confirms the feasibility of using the developed array-type Si PIN photodetectors in radiation-based imaging systems.

We investigated the algorithm analysis of the bubble generation in a microfluidic device to study the effect of the surface tension and the flow rate on the microbubble size. For the analysis of the surface tension, five different solutions were used: 3.5% brine, mineral oil, 1% polyethylene glycol (PEG) 400, 1% tween 80, and 1% triton X-100. The various flow rates were also employed: 5~15 µL/min for the liquid and 100~200 mL/min for the gas phase. The size of the bubble was measured via the algorithm analysis and the bubble defect was also detected by c chart. We observed that the microbubble size was affected by the flow rates of solution and the gas. Hence, we developed an equation to estimate the size through the flow rate ratio between the solution and gas phase, showing that the microbubble size could be controlled by the liquid properties or the flow rates. Therefore, this algorithm-based microfluidic device could be a powerful tool for generating gas micro-bubbles in a controlled manner.

Electrical stimuli play an important role in regulating the delivery of plasmonic nanomaterials with cancer targeting peptides. Here, we developed an electro-responsive hydrogel-based microfluidic actuator platform for brain tumor targeting and photothermal therapy (PTT) applications. The electro-responsive hydrogels consisted of highly conductive silver nanowires (AgNWs) and biocompatible collagen I gels. We confirmed that an electrically conductive hydrogel could be used as an effective actuator by applying an electrical signal in the microfluidic platform. Furthermore, we successfully demonstrated PTT efficacy for brain tumor cells using targetable Arg-Gly-Asp (RGD) peptide-conjugated gold nanorods (GNRs). Therefore, our electro-responsive hydrogel-based microfluidic actuator platform could be useful for electro-responsive intelligent nanomaterial delivery and PTT applications.

Despite their simplicity, monolayer cell cultures are not able to accurately predict drug behavior in vivo due to their inability to accurately mimic cell-cell and cell-matrix interactions. In contrast, cell spheroids are able to reproduce these interactions and thus would be a viable tool for testing drug behavior. However, the generation of homogenous and reproducible cell spheroids on a large scale is a labor intensive and slow process compared to monolayer cell cultures. Here, we present a droplet-based microfluidic device for the automated, large-scale generation of homogenous cell spheroids in a uniform manner. Using the microfluidic system, the size of the spheroids can be tuned to between 100 and 130 μm with generation frequencies of 70 Hz. We demonstrated the photothermal therapy (PTT) application of brain tumor spheroids generated by the microfluidic device using a reduced graphene oxide-branched polyethyleneimine-polyethylene glycol (rGO-BPEI-PEG) nanocomposite as the PTT agent. Furthermore, we generated uniformly sized neural stem cell (NSC)-derived neurospheres in the droplet-based microfluidic device. We also confirmed that the neurites were regulated by neurotoxins. Therefore, this droplet-based microfluidic device could be a powerful tool for photothermal therapy and drug screening applications. A microfluidic device for the efficient production of three-dimensional ‘spheroid’ cell cultures could accelerate the discovery and testing of therapeutic agents. These small clumps of cells can better recapitulate the physiology of the tissue environment than two-dimensional cultures, but are challenging to produce in a high-throughput fashion. Researchers led by Prof. Bong Geun Chung of Sogang University, Seoul, Korea have now developed a system that can generate 42,000 spheroids/h with minimal user intervention. As an initial demonstration, they produce brain tumor-derived spheroids, and use these to test the cancer-killing efficacy of a therapy based on heated graphene-based nanoparticles. Prof. Chung and colleagues subsequently employ their device to assess the detrimental effects of the neurotoxin thapsigargin on neural stem cell-derived spheroids, highlighting the potential value of this platform for high-throughput cell screening assays.

Flavonoids, including maackiain (Maac) from Sophora flavescens Aiton roots, have many pharmacological properties, such as antitumor, antimicrobial, and antifungal activities. This research aimed to develop an in vitro plant and callus culture system for S. flavescens for the purpose of generating an alternative production system for enhancing Maac production, as Maac is usually present in very small amounts in S. flavescens&rsquo, roots. We arranged the optimal conditions of different tissues of S. flavescens and supplemented the medium with various plant growth regulators (PGRs). The highest induction and proliferation rates of callus was shown in combination treatments of all concentrations of thidiazuron (TDZ) and picloram. In addition, calli induced with leaf explants cultured on 2.0 mg/L picloram and 0.5 mg/L 6-benzyladenine (BA) in Murashige and Skoog (MS) medium had the highest accumulation of the active metabolite Maac. In vitro shoots were regenerated on medium containing combinations of TDZ and &alpha, Naphthalene acetic acid (NAA). A reliable protocol for the mass production of secondary metabolites using a callus culture of S. flavescens was successfully established.

We developed the microfluidic co-culture platform to study photothermal therapy applications. We conjugated folic acid (FA) to target breast cancer cells using reduced graphene oxide (rGO)-based functional nanomaterials. To characterize the structure of rGO-based nanomaterials, we analyzed the molecular spectrum using UV–visible and Fourier-transform infrared spectroscopy (FT-IR). We demonstrated the effect of rGO-FA-based nanomaterials on photothermal therapy of breast cancer cells in the microfluidic co-culture platform. From the microfluidic co-culture platform with breast cancer cells and human umbilical vein endothelial cells (HUVECs), we observed that the viability of breast cancer cells treated with rGO-FA-based functional nanomaterials was significantly decreased after near-infrared (NIR) laser irradiation. Therefore, this microfluidic co-culture platform could be a potentially powerful tool for studying cancer cell targeting and photothermal therapy.

Microwell arrays are widely used for the analysis of fluorescent-labelled biomaterials. For rapid detection and automated analysis of microwell arrays, the computational image analysis is required. Support Vector Machines (SVM) can be used for this task. Here, we present a SVM-based approach for the analysis of microwell arrays consisting of three distinct steps: labeling, training for feature selection, and classification into three classes. The three classes are filled, partially filled, and unfilled microwells. Next, the partially filled wells are analyzed by SVM and their tendency towards filled or unfilled tested through applying a Gaussian filter. Through this, all microwells can be categorized as either filled or unfilled by our algorithm. Therefore, this SVM-based computational image analysis allows for an accurate and simple classification of microwell arrays.

We developed a three-dimensional (3D) simple multi-layer microfluidic gradient generator to create molecular gradients on the centimeter scale with a wide range of flow rates. To create the concentration gradients, a main channel (MC) was orthogonally intersected with vertical side microchannel (SC) in a 3D multi-layer microfluidic device. Through sequential dilution from the SC, a spatial gradient was generated in the MC. Two theoretical models were created to assist in the design of the 3D multi-layer microfluidic gradient generator and to compare its performance against a two-dimensional equivalent. A first mass balance model was used to predict the steady-state concentrations reached, while a second computational fluid dynamic model was employed to predict spatial development of the gradient by considering convective as well as diffusive mass transport. Furthermore, the theoretical simulations were verified through experiments to create molecular gradients in a 3D multi-layer microfluidic gradient generator.

An analog pre-filter circuit for digital pulse processing is designed and optimized for X-ray fluorescence (XRF) applications to replace traditional analog shaping amplifiers. To optimize the pre-filter performance, we characterized noise electrons as a function of the input pulse rise time and decay time of the output pulse by using the full width at half maximum. In addition, gamma-ray energy measurements at room temperature showed that the commercially available CdTe Schottky-type radiation detector with our newly designed and optimized pre-filter circuit exhibited full widths at half maxima of 4.97 (Ba-133, at 53 keV) and 5.56 keV (Am-241, at 59.5 keV), respectively.

Microstructural, optical and electrical properties of Cl-doped CdTe crystals grown by the low pressure Bridgman (LPB) method were investigated for four different doping concentrations (unintentionally doped, 4.97 × 1019 cm−3, 9.94 × 1019 cm−3 and 1.99 × 1020 cm−3) and three different locations within the ingots (namely, samples from top, middle and bottom positions in the order of the distance from the tip of the ingot). It was shown that Cl dopant suppressed the unwanted secondary (5 1 1) crystalline orientation. Also, the average size and surface coverage of Te inclusions decreased with an increase in Cl doping concentration. Spectroscopic ellipsometry measurements showed that the optical quality of the Cl-doped CdTe single crystals was enhanced. The resistivity of the CdTe sample doped with Cl at the 1.99 × 1020 cm−3 was above 1010 Ω.cm.

We examined the temperature-dependent magnetic and structural properties of α-HgI 2 in the temperature range of 300–400 K using temperature-dependent DC-magnetization, x-ray diffraction (XRD), and x-ray absorption fine structure (XAFS) measurements. DC-magnetization measurements of α-HgI 2 single crystals show a sudden reduction of diamagnetic susceptibility for T > 350 K. XRD measurements with Rietveld refinements reveal a small but substantial amount of decrease in disorder in both Hg and I sites above 350 K, with neither a structural transition nor vacancies in the temperature range. XAFS demonstrates a shift of the I K edge for T > 350 K but no changes at the Hg L 3 edge. A stronger bonding of Hg-I pairs above 350 K likely affects the electrons in the outermost shells of iodine atoms and enhances the intrinsic paramagnetic properties, thereby producing a reduction in diamagnetism.

The Korea Atomic Energy Research Institute (KAERI) has been developing a Container Inspection System (CIS) by using a dual-energy (9/6 MeV) S-band (= 2856 MHz) electron linear accelerator. The key components of the CIS are the electron linear accelerator (including an electron gun, an accelerating structure, an RF power source, cooling chillers, vacuum pumps, magnet power supplies, and two solenoid magnets with beam focusing and shielding functions), a tungsten target for X-ray generation, an X-ray collimator, a detector array, and a container moving system. Generally, in accelerators, beam focusing is mainly done by solenoids operating in the region of a few MeV to keep the shape of transverse beam symmetrically round so as to reduce the loss of electrons, which increases the beam current and the beam power. In addition, a specially-designed component is needed to protect against the radiation due to the lost electrons. In this paper, we describe the design, fabrication, and optimization of two specially- designed solenoids with focusing and radiation shielding functions for a dual-energy S-band electron linear accelerator for a CIS.

Background: For positron emission tomography (PET) application, cadmium zinc telluride (CZT) has been investigated by several institutes to replace detectors from a conventional system using photomultipliers or Silicon-photomultipliers (SiPMs). The spatial and energy resolution in using CZT can be superior to current scintillator-based state-of-the-art PET detectors. CZT has been under development for several years at the Korea Atomic Energy Research Institute (KAERI) to provide a high performance gamma ray detection, which needs a single crystallinity, a good uniformity, a high stopping power, and a wide band gap. Materials and Methods: Before applying our own grown CZT detectors in the prototype PET system, we investigated preliminary research with a developed discrete type data acquisition (DAQ) system for coincident events at 128 anode pixels and two common cathodes of two CZT detectors from Redlen. Each detector has a 19.4×19.4×6 mm3 volume size with a 2.2 mm anode pixel pitch. Discrete amplifiers consist of a preamplifier with a gain of 8 mV·fC-1 and noise of 55 equivalent noise charge (ENC), a CR-RC4 shaping amplifier with a 5 μs peak time, and an analog-to-digital converter (ADC) driver. The DAQ system has 65 mega-sample per second flash ADC, a self and external trigger, and a USB 3.0 interface. Results and Discussion: Characteristics such as the current-to-voltage curve, energy resolution, and electron mobility life-time products for CZT detectors are investigated. In addition, preliminary results of gamma ray imaging using 511 keV of a 22Na gamma ray source were obtained. Conclusion: In this study, the DAQ system with a CZT radiation sensor was successfully developed and a PET image was acquired by two sets of the developed DAQ system.

Background: TlBr is of considerable technological importance for radiation detection applications where detecting high-energy photons such as X-rays and γ-rays are of prime importance. However, there were few reports on investigating optical properties of TlBr itself for deeper understandings of this material and for making better radiation detection devices. Thus, in this paper, we report on the optical characterizations of TlBr single crystals. Spectroscopic ellipsometry (SE) and photoluminescence (PL) measurements at RT were performed for this work. Materials and Methods: A 2-inch TlBr single crystalline ingot was grown by using the vertical Bridgman furnace. SE measurements were performed at RT within the photon energy range from 1.1 to 6.5 eV. PL measurements were performed at RT by using a home-made PL system equipped with a 266 nm-laser and a spectrometer. Results and Discussion: Dielectric responses from SE analysis were shown to be slightly different among the different samples possibly due to the different structural/optical properties. Also from the PL measurements, it was observed that the peak intensities of the middle samples were significantly higher than those of the other two samples. With the given values for permittivity of free space (e0 = 8.854x10-12 F·m-1), thickness (d = 1 mm), and area (A = 10x10 mm2) of the TlBr sample, capacitances of TlBr were 6.9 pF (at hν = 3 eV) and 4.4 pF (at hν = 6 eV), respectively. Conclusion: SE and PL measurement and analysis were performed to characterize TlBr samples from the optical perspective. It was observed that dielectric responses of different TlBr samples were slightly different due to the different material properties. PL measurements showed that the middle sample exhibited much stronger PL emission peaks due to the better material quality. From the SE analysis, optical, dielectric constants were extracted, and calculated capacitances were in the few pF range.

TlBr single crystals grown using the vertical Bridgman-Stockbarger method were characterized for semiconductor based radiation detector applications. It has been shown that the vertical Bridgman-Stockbarger method is effective to grow high-quality single crystalline ingots of TlBr. The TlBr single crystalline sample, which was located 6 cm from the tip of the ingot, exhibited lower impurity concentration, higher crystalline quality, high enough bandgap (>2.7 eV), and higher resistivity (2.5 × 1011Ω·cm) which enables using the fabricated samples from the middle part of the TlBr ingot for fabricating high performance semiconductor radiation detectors.

The radiation equipment research division of Korea Atomic Energy Research Institute has developed a Container Inspection System (CIS) using a Radio Frequency (RF) electron linear accelerator for port security. The primary purpose of the CIS is to detect nuclear materials and explosives, as well country-specific prohibited substances, e.g., smuggled. The CIS consists of a 9/6 MeV dualenergy electron linear accelerator for distinguishing between organic and inorganic materials. The accelerator consists of an electron gun, an RF accelerating structure, an RF driver, a modulator, electromagnets, a cooling system, a X-ray generating target, X-ray collimator, a detector, and a container moving system. The RF driver is an important part of the configuration because it is the RF power source: it supplies the RF power to the accelerating structure. A unique aspect of the RF driver is that it generates dual RF power to generate dual energy (9/6 MeV). The advantage of this RF driver is that it can allow the pulse width to vary and can be used to obtain a wide range of energy output, and pulse repetition rates up to 300 Hz. For this reason, 140 W (5 MW − 9 MeV) and 37 W (3.4 MW − 6 MeV) power outputs are available independently. A high power test for 20 minutes demonstrate that stable dual output powers can be generated. Moreover, the dual power can be applied to the accelerator which has stable accelerator operation. In this paper, the design, fabrication and high power test of the RF driver for the RF electron linear accelerator (linac) are presented.

The soilborne fungus Fusarium oxysporum f. sp. lilii (Fol) is a serious threat to all lily cultivars, especially infecting bulbs and flowers. It has become increasingly important to develop varieties resistant against the bulb rot disease. Genetic diversity of cultivars and reliable screening methods are required for this purpose. Here, an efficient in vitro screening system for evaluating resistance to Fol in 38 in vitro-grown lily plants was investigated. Various factors including culture conditions of Fol, inoculum density, appropriate plant materials, inoculation method and duration, and incubation period of plant materials after inoculation were combined to optimize the screening method. As a result, we suggest optimal conditions for an in vitro screening system for the selection of Fol-resistant lily cultivars as follows. Fol was grown on potato dextrose agar (PDA) medium for 6 days at 25°C in darkness and used as working inoculation. Spore suspensions were prepared (inoculum density: 1.0 × 10 4 spores‧mL -1 ), and then leaf segments 1.5 × 2.0 cm 2 were inoculated by dipping for 22 hours at 25°C in dark. Later, leaves were cultured on 0.6% agar plates at 25°C and 50% humidity with a photoperiod of 16 hours light/8 hours dark (fluence rate of 40 μmol・m -2 ・s -1 ) to examine the progress of bulb rot. After 7 days, disease levels were classified into indices 1 (no symptom) to 6 (serious bulb rot). Soil inoculation of Fol carried out with resistant or susceptible lily cultivars that had been selected through in vitro screening confirmed the reproducibility of results. Therefore, the in vitro screening method established in this study is efficient and reliable for selection of lily cultivars resistant against bulb rot disease. Additional key words: bulb rot, disease index, disease resistance, Lillium spp. *Corresponding author: hyuns@kribb.re.kr ※ Received 15 May 2015; Revised 6 July 2015; Accepted 16 July 2015. 본 연구는 농림축산식품부・해양수산부・농촌진흥청・산림청 Golden Seed 프로젝트 원예종자사업단의 지원에 의해 이루어진 것임. C 2015 Korean Society for Horticultural Science 서 언 우리나라의 백합은 2013년 통계 기준 전년 대비 7.3% 재 배면적이 감소하였으나 절화 수출액의 32.5%를 차지하는 등 화훼 수출산업에 있어서 중요한 위치를 차지하고 있다 (MAFRA, 2014). 주로 비닐하우스나 온실에서 재배되는 백 합은 그 재배환경으로 인해 뿌리나 구근의 부패병에 많이 노출되어 과다한 농약사용이 문제시되고 있는 것이 현실이 다(Lebiush-Mordechai et al., 2014). 구근으로 번식하는 백 합은 꽃 재배기간뿐만 아니라 구근의 증식, 보관 기간에도 Penicillium sp.와 Fusarium oxysporum f. sp. lilii(Fol)균에 인한 감염으로 절화나 종구의 생산량과 품질에 치명적인 저 하가 발생한다(Loffler and Rumine, 1991). 이 구근부패병은 주로 종구나 지하부 줄기에서 감염이 일어나는데, 연작지 사질토에서 발생이 심하고 주로 토양으로부터 전염이 된다. 구근표면에 갈색 부정형 병반이 생기며, 심하면 구근 전체 Korean J. Hortic. Sci. Technol. 33(6), December 2015 884 가 갈색으로 변하여 썩고, 계속 진전되면 인편이 탈락하게 된다(Komada, 1975). 외관상으로는 아랫잎부터 점차 떨어 져버리고 포기 전체가 죽어가기도 한다. 고사한 줄기의 지 제부위에는 병원체의 균사가 하얗거나 붉은색으로 자라나 있는 것을 볼 수 있다. 주로 정식 전에 토양해충방제를 철저 히 하고 작업 중에 상하지 않도록 하여 상처부위를 통한 침 입을 예방하는 등의 방법으로 피해 정도를 최소화하고 있다. 그러나 이러한 방법보다도 더욱 효율적으로 구근부패병을 방제하기 위해서는 구근부패병에 대한 저항성이 있는 품종 을 선별하여 재배하는 것이 중요하며, 이를 위하여 각 품종 의 구근부패병 저항성 정도를 진단하기 위한 간편하고 민감

The droplet-generating microfluidics has become an important technique for a variety of applications ranging from single cell analysis to nanoparticle synthesis. Although there are a large number of methods for generating and experimenting with droplets on microfluidic devices, the dispensing of droplets from these microfluidic devices is a challenge due to aggregation and merging of droplets at the interface of microfluidic devices. Here, we present a microfluidic dual-nozzle device for the generation and dispensing of uniform-sized droplets. The first nozzle of the microfluidic device is used for the generation of the droplets, while the second nozzle can accelerate the droplets and increase the spacing between them, allowing for facile dispensing of droplets. Computational fluid dynamic simulations were conducted to optimize the design parameters of the microfluidic device. Electronic supplementary material The online version of this article (10.1186/s40580-018-0145-2) contains supplementary material, which is available to authorized users.

Room-temperature semiconductor radiation detectors (RTSDs) such as cadmium zinc telluride (CZT) have been under development for several decades to provide a high performance for gamma ray detection, which needs a single crystallinity, a good uniformity, a high stopping power, and a wide band gap. However, the performance of CZT is limited in terms of the energy resolution by an incomplete charge collection owing to the slow mobility of the hole and polarization effects. To overcome such limitation, a virtual Frisch-grid CZT detector using a single polarity charge sensing method has been introduced. In this paper, we optimized the shielding electrode length of a virtual Frisch-grid to enhance the energy resolution and detection efficiency. In addition, the applied bias can be decreased by using the relatively thin (40 μm) encapsulate materials to reduce the system power consumption. The detector was fabricated using 5 × 5 × 14 mm3 CZT from Redlen, and the fabrication process used to make the virtual Frisch-grid CZT radiation detector is described. Characteristics such as the current-to-voltage curve, energy resolution, electron mobility life-time products, and intrinsic detection efficiency are compared by varying the shielding electrode lengths of the virtual Frisch-grid CZT detector. The results from these measurements will give us an optimal shielding electrode length and achieve a higher performance for a room-temperature radiation detector.

A single-polarity charge-sensing method was studied by using a CdZnTe Frisch collar grid detector grown by using a low-pressure Bridgeman furnace at the Korea Atomic Energy Research Institute (KAERI). The Frisch collar grid CdZnTe detector has an active volume of 5 × 5 × 10 mm3, and was fabricated from a single crystal, Teflon tape and copper tape used as a Frisch collar grid. A room-temperature energy resolution of 6% full width at half maximum (FWHM) was obtained for the 662keV peak of Cs-137 without any additional electrical corrections. The detector’s fabrication process is described, and its characteristics are discussed. Finally, the charge transport properties and gamma-ray energy resolution of the fabricated Frisch collar grid detector are compared with those of two other Frisch collar detectors grown by using different crystal growth methods and purchased from eV-products and Redlen technology.

Si PIN photodiode radiation detectors with three different active areas (3×3 mm2, 5×5 mm2, and 10×10 mm2) were designed and fabricated at the Korea Atomic Energy Research Institute (KAERI) for low energy X- and gamma-ray detection. In Si-based semiconductor radiation detectors, one of the noise sources is thermal noise, which degrades their energy resolution performance. In this study, the temperature effects on the energy resolution were investigated using a 3×3 mm2 active area PIN photodiode radiation detector using a Thermoelectric Module (TEM) from room temperature to −23 °C. Energy resolutions from 25 keV auger electrons to 81 keV gamma-ray from a Ba-133 calibration source were measured and compared at every 10 °C interval. At −23 °C, energy resolutions were improved by 15.6% at 25 keV, 4.0% at 31 keV, and 1.2% at 81 keV in comparison with resolutions at room temperature. CsI(Tl)/PIN photodiode radiation detectors were also fabricated for relatively high energy gamma-ray detection. Energy resolutions for Cs-137, Co-60, and Na-22 sources were measured and compared with the spectral responsivity.

The Korea Atomic Energy Research Institute (KAERI) has fabricated Si-PIN radiation detectors with low leakage current, high resistivity (>11 kΩ cm) and low capacitance for high-energy physics and X-ray spectroscopy. Floating-zone (FZ) 6-in. diameter N-type silicon wafers, with 〈1 1 1〉 crystal orientation and 675 μm thick, were used in the detector fabrication. The active areas are 3 mm×3 mm, 5 mm×5 mm and 10 mm×10 mm. We used a double deep-diffused structure at the edge of the active area for protection from the surface leakage path. We also compared the electrical performance of the Si-PIN detector with anti-reflective coating (ARC). For a detector with an active area of 3 mm×3 mm, the leakage current is about 1.9 nA and 7.4 nA at a 100 V reverse bias voltage, and 4.6 pF and 4.4 pF capacitance for the detector with and without an ARC, respectively. In addition, to compare the energy resolution in terms of radiation hardness, we measured the energy spectra with 57 Co and 133 Ba before the irradiation. Using developed preamplifiers (KAERI-PA1) that have ultra-low noise and high sensitivity, and a 3 mm×3 mm Si-PIN radiation detector, we obtained energy resolutions with 122 keV of 57 Co and 81 keV of 133 Ba of 0.221 keV and 0.261 keV, respectively. After 10, 100, 10 3 , 10 4 and 10 5 Gy irradiation, we tested the characteristics of the radiation hardness on the Si-PIN radiation detectors in terms of electrical and energy spectra performance changes. The fabricated Si-PIN radiation detectors are working well under high dose irradiation conditions.

Double deep diffused structured Si PIN diode having ALD Al 2 O 3 anti-reflection and passivation layer were fabricated and characterized. Detailed device fabrication process is described at the experimental section and electrical, optical and radiation response characteristics were characterized.

We previously isolated Nicotiana benthamiana matrix metalloprotease 1 (NMMP1) from tobacco leaves. The NMMP1 gene encodes a highly conserved, Zn-containing catalytic protease domain that functions as a factor in the plant’s defense against bacterial pathogens. Expression of NMMP1 was strongly induced during interactions between tobacco and one of its pathogens, Phytophthora infestans. To elucidate the role of the NMMP1 in defense of N. benthamiana against fungal pathogens, we performed gain-of-function and loss-of-function studies. NMMP1-overexpressing plants had stronger resistance responses against P. infestans infections than control plants, while silencing of NMMP1 resulted in greater susceptibility of the plants to the pathogen. This greater susceptibility correlated with fewer NMMP1 transcripts than the non-silenced control. We also examined cell death as a measure of disease. The amount of cell death induced by the necrosis-inducing P. infestans protein 1, PiNPP1, was dependent on NMMP1 in N. benthamiana. Potato plants overexpressing NMMP1 also had enhanced disease resistance against P. infestans. RT-PCR analysis of these transgenic potato plants revealed constitutive up-regulation of the potato defense gene NbPR5. NMMP1-overexpressing potato plants were taller and produced heavier tubers than control plants. We suggest a role for NMMP1in pathogen defense and development.

Responding to the need for recombinant acidic fibroblast growth factor in the pharmaceutical and cosmetic industries, we established a scalable expression system for recombinant human aFGF using transient and a DNA replicon vector expression in Nicotiana benthamiana. Recombinant human-acidic fibroblast growth factor was recovered following Agrobacterium infiltration of N. benthamiana. The optimal time point at which to harvest recombinant human acidic fibroblast growth factor expressing leaves was found to be 4 days post-infiltration, before necrosis was evident. Commassie-stained SDS-PAGE gels of His-tag column eluates, concentrated using a 10 000 molecular weight cut-off column, showed an intense band at the expected molecular weight for recombinant human acidic fibroblast growth factor. An immunoblot confirmed that this band was recombinant human acidic fibroblast growth factor. Up to 10 µg recombinant human-acidic fibroblast growth factor/g of fresh leaves were achieved by a simple affinity purification protocol using protein extract from the leaves of agroinfiltrated N. benthamiana. The purified recombinant human acidic fibroblast growth factor improved the survival rate of UVB-irradiated HaCaT and CCD-986sk cells approximately 89 and 81 %, respectively. N. benthamiana-derived recombinant human acidic fibroblast growth factor showed similar effects on skin cell proliferation and UVB protection compared to those of Escherichia coli-derived recombinant human acidic fibroblast growth factor. Additionally, N. benthamiana-derived recombinant human acidic fibroblast growth factor increased type 1 procollagen synthesis up to 30 % as well as reduced UVB-induced intracellular reactive oxygen species generation in fibroblast (CCD-986sk) cells.UVB is a well-known factor that causes various types of skin damage and premature aging. Therefore, the present study demonstrated that N. benthamiana-derived recombinant human acidic fibroblast growth factor effectively protects skin cell from UVB, suggesting its potential use as a cosmetic or therapeutic agent against skin photoaging.

Tissue-specific promoters for efficient expression of transgenes at specific times or in specific plant tissues can be applied to develop new transgenic plants. To exploit a promoter capable of driving strong expression in potato tubers, we isolated the promoter region of the laccase gene from potato (Solanum tuberosum L. cv. Desiree) and characterized its activity in transgenic Solanaceae plants, such as potato, tobacco and tomato. The ability of the laccase promoter to induce the β-glucuronidase (GUS) reporter was evaluated in independent transgenic potato lines and compared with that of the constitutive CaMV35S promoter. To determine the tissue specificity of expression in transgenic potato, GUS levels in shoot tips, leaves, stems, roots and tubers were measured by histochemical analysis. The laccase promoter conferred tuber-specific expression in transgenic potato regardless of the developmental stage, and there was no GUS reporter expression in leaves, stems or roots. Serial 5′ deletion analysis of the laccase promoter revealed that the tuber-specific regulatory elements might be scattered throughout the promoter. The laccase promoter responded weakly to salt stress, mannitol stress, and mechanical wounding but not to cold stress in the leaves and stems of transgenic potato. In transgenic tobacco, weak GUS expression driven by the laccase promoter was detected throughout the entire plant, whereas in transgenic tomato, GUS expression was detected only in the roots and seeds. Our data show that the laccase promoter represents a feasible candidate to drive high and preferential expression of genes in potato tubers.

An indium-doped (7 ppm) Cd0.9Zn0.1Te single crystal for use in room-temperature radiation detectors has been grown using a low-pressure Bridgman (LPB) furnace at the Korea Atomic Research Institute. The single crystal has a (111) orientation and a high resistivity of ∼1 × 1012 Ω·cm. In addition, the mobility-lifetime products of the electrons and hole are 4.2 × 10−4 cm2/V and 5 × 10−5 cm2/V, respectively. These values are simply derived by using a Hecht and a neural equation and 5 MeV alpha particles emitted from an 241Am alpha source. To characterize the Cd0.9Zn0.1Te grown by using the LPB method, we fabricated planar detectors with volume of 10 × 10 × 2.5 mm3 from a 2-inch-diameter Cd0.9Zn0.1Te ingot.

One of the noise sources of a semiconductor radiation detector is thermal noise, which degrades the performance, such as the energy resolution and unexpected random pulse signals. In this study, PIN photodiode radiation detectors, with different active areas were designed and fabricated for an experimental comparison of the energy resolutions for different temperatures and capacitances by using a Ba-133 calibration gamma-ray source. The experimental temperature was approximately in the range from −7 to 24 °C and was controlled by using a peltier device. The design considerations and the electrical characteristics, such as the I–V and the C–V characteristics, are also addressed.

The use of conventional radiation detectors in harsh environments is limited by radiation damage to detector materials and by temperature constraints. We fabricated a wide-band gap semiconductor radiation detector based on silicon carbide. All the detector components were considered for an application in a high temperature environment like a nuclear reactor core. The radiation response, especially to alpha particles, was measured using an (241)Am source at variable operating voltages at room temperature in the air. The temperature on detector was controlled from 30°C to 250°C. The alpha-particle spectra were measured at zero bias operation. Even though the detector is operated at high temperature, the energy resolution as a function of temperature is almost constant within 3.5% deviation.

We developed a three-dimensional (3D) simple multi-layer microfluidic gradient generator to create molecular gradients on the centimeter scale with a wide range of flow rates. To create the concentration gradients, a main channel (MC) was orthogonally intersected with vertical side microchannel (SC) in a 3D multi-layer microfluidic device. Through sequential dilution from the SC, a spatial gradient was generated in the MC. Two theoretical models were created to assist in the design of the 3D multi-layer microfluidic gradient generator and to compare its performance against a two-dimensional equivalent. A first mass balance model was used to predict the steady-state concentrations reached, while a second computational fluid dynamic model was employed to predict spatial development of the gradient by considering convective as well as diffusive mass transport. Furthermore, the theoretical simulations were verified through experiments to create molecular gradients in a 3D multi-layer microfluidic gradient generator.

Silicon carbide (SiC) is a promising material for neutron detection at harsh environments because of its capability to withstand strong radiation fields and high temperatures. Two PIN-type SiC semiconductor neutron detectors, which can be used for nuclear power plant (NPP) applications, such as in-core reactor neutron flux monitoring and measurement, were designed and fabricated. As a preliminary test, MCNPX simulations were performed to estimate reaction probabilities with respect to neutron energies. In the experiment, I-V curves were measured to confirm the diode characteristic of the detectors, and pulse height spectra were measured for neutron responses by using a neutron source at KRISS (Korea Research Institute of Standards and Science), and a Tandem accelerator at KIGAM (Korea Institute of Geoscience and Mineral Resources). The neutron counts of the detector were linearly increased as the incident neutron flux got larger.

See paper for full list of authors; The Korea Rare Isotope Accelerator, currently referred to as KoRIA, is briefly presented. The KoRIA facility is aimed to enable cutting-edge sciences in a wide range of fields. It consists of a 70 kW isotope separator on-line (ISOL) facility driven by a 70 MeV, 1 mA proton cyclotron and a 400 kW in-flight fragmentation (IFF) facility. The ISOL facility uses a superconducting (SC) linac for post-acceleration of rare isotopes up to about 18 MeV/u, while the SC linac of IFF facility is capable of accelerating uranium beams up to 200 MeV/u, 8 pμA and proton beams up to 600 MeV, 660 μA. Overall features of the KoRIA facility are presented with a focus on the accelerator design.

A sensitivity analysis of the methods used to evaluate the transport properties of a CdZnTe detector was performed using two different radiations (α particle and gamma-ray) emitted from an 241 Am source. The mobility-lifetime products of the electron-hole pair in a planar CZT detector (5×5×2 ㎣) were determined by fitting the peak position as a function of biased voltage data to the Hecht equation. To verify the accuracy of these products derived from α particles and low-energy gamma-rays, an energy spectrum considering the transport property of the CZT detector was simulated through a combination of the deposited energy and the charge collection efficiency at a specific position. It was found that the shaping time of the amplifier module significantly affects the determination of the (μτ) products; the α particle method was stabilized with an increase in the shaping time and was less sensitive to this change compared to when the gamma-ray method was used. In the case of the simulated energy spectrum with transport properties evaluated by the α particle method, the peak position and tail were slightly different from the measured result, whereas the energy spectrum derived from the low-energy gamma-ray was in good agreement with the experimental results. From these results, it was confirmed that low-energy gamma-rays are more useful when seeking to obtain the transport properties of carriers than α particles because the methods that use gamma-rays are less influenced by the surface condition of the CZT detector. Furthermore, the analysis system employed in this study, which was configured by a combination of Monte Carlo simulation and the Hecht model, is expected to be highly applicable to the study of the characteristics of CZT detectors.

Wide-band-gap semiconductors such as SiC, AlN, and GaN are promising materials for harsh environment applications due to their high-temperature operation capability. Two types of PIN-type semiconductor neutron detectors based on SiC were designed and fabricated for nuclear power plant (NPP) applications such an in-core reactor neutron flux monitoring and safeguarding nuclear materials. One is for fast neutron detection and the other, which was evaporated with 6LiF, is for thermal neutron detection. In this study, preliminary tests, such as the determination of I-V and alpha responses, were performed. Reaction probabilities with respect to neutron energies were also calculated by using an MCNPX code for comparison with the experimental results. Responses of the neutrons were measured at the Ex-core Neutron irradiation Facility (ENF) of the High-flux Advanced Neutron Application Reactor (HANARO) research reactor at the Korea Atomic Energy Research Institute (KAERI). Pulse height spectra and count rates were...

Cadmium zinc telluride (CZT) has been shown to be suitable for use in high-resolution γ-ray energy spectroscopy and radiation imaging. A low-energy tail appears in the energy spectrum when the high-energy γ-ray energy spectrum is obtained with a CZT planar detector. This is due to the low charge transport in the crystal. In this study, a CZT detector with strip electrodes was fabricated to reduce the low-energy tail in the energy spectrum. CZT strip detectors with various electrode designs were fabricated, and their operation properties were determined and compared. The optimized detector had the following electrode design: an electrode pitch of 1.2 mm, an electrode width of 0.8 mm and a spacing between the electrodes of 0.4 mm. γ-ray energy spectra were measured for energies in the range of 60 – 660 keV. The low-energy tail in the spectrum was reduced significantly when the CZT strip detector was used.

By developing the special relation between the electron and the hole mobility-lifetime products ((µ )e and (µ )h), we propose a new approach to evaluate each parameter for gamma-rays instead of particles. We assumed that the incident gamma-ray was absorbed by only one reaction within the semiconductors because the cross-section of the photoelectric eect is much higher than there of other reactions at low energies. For the planar CZT detector manufactured by eV Products, the values of (µ )e = 1.44 ◊ 10 3 cm 2 /V and (µ )h = 7.56 ◊ 10 5 cm 2 /V were simply derived by using a modified single-parameter Hecht equation and 59.5 keV gamma-rays emitted from the 241 Am isotope.

High-pressure Xe (HPXe) ionization chamber is considered as an ideal detector for the Radiation Monitoring System (RMS) in nuclear power plants, since detector response has been shown to be uniform over large temperature ranges up to 170 �i C. By using the MCNPX simulation code, the energy spectra were calculated with respect to the thickness of the outer shell and the dependence on the incident direction of the radiation sources in the nuclear power plant. A cylindrical HPXe ionization chamber, which was configured with a shielding mesh to improve its energy resolution, was designed and fabricated. With the gas purification and injection system, Xe and 7% 4 He was purified and injected into the chamber and the performances of the chamber were evaluated. The leakage and saturation currents of the chamber were measured with an electrometer, respectively. Linearity against dose rates was also measured with 226 Ra (0.906 mCi) radiation source and the 0.994 of root-mean-square value was estimated. In a future work, energy spectra with the fabricated HPXe ionization chamber will be measured and compared with the simulated energy spectra.