Hyun-Suk Lee

Identification of Arabidopsis BAK1-Associating Receptor-Like Kinase 1 (BARK1) and Characterization of its Gene Expression and Brassinosteroid-Regulated Root Phenotypes

Brassinosteroids (BRs) activate the BRI1 and BAK1/SERK3 membrane receptor complex, which leads to a wide range of changes in gene expression, plant growth and development. As an initial step to elucidate additional roles of BAK1, we cloned a BAK1-binding protein, BAK1-Associating Receptor-Like Kinase 1 (BARK1), and characterized its gene expression and root phenotypes. BARK1 is a putative membrane LRR-RLK (leucine-rich repeat receptor-like kinase) protein that specifically binds to BAK1 and its homologs. Careful examination of BARK1 expression using transgenic plants expressing a green fluorescent protein (GFP) reporter under the control of the native BARK1 promoter (BARK1p::GFP) revealed that this gene is ubiquitously expressed in most plant tissues, and shows especially strong expression in the xylem vasculature of primary and lateral roots as well as in mature pollen. Interestingly, the expression of the BARK1 gene was increased in the BR biosynthetic loss-of-function mutant, det2, and a loss-of-function mutant of BR signaling, bak1-3. In contrast, this gene was down-regulated in the bzr1-1D plant, which is a BR signal gain-of-function mutant. BARK1-overexpressing transgenic plants clearly enhanced primary root growth in a dose-dependent manner, and their roots were hypersensitive to BR-induced root growth inhibition. In addition, both the number and density of lateral roots were dramatically increased in the BARK1 transgenic plants in a dose-dependent manner. Together with observations that ARF (AUXIN RESPONSE FACTOR) genes are up-regulated in the BARK1 overexpressor, we suggest that the BARK1 overexpressor phenotype with more lateral roots is partly due to the increased expression of ARF genes in this genetic background. In conclusion, BAK1-interacting BARK1 protein may be involved in BR-mediated plant growth and development such as in lateral roots via auxin regulation.

Characterizing X-ray detectors for prototype digital breast tomosynthesis systems

The digital breast tomosynthesis (DBT) system is a newly developed 3-D imaging technique that overcomes the tissue superposition problems of conventional mammography. Therefore, it produces fewer false positives. In DBT system, several parameters are involved in image acquisition, including geometric components. A series of projections should be acquired at low exposure. This makes the system strongly dependent on the detectors characteristic performance. This study compares two types of x-ray detectors developed by the Korea Electrotechnology Research Institute (KERI). The first prototype DBT system has a CsI (Tl) scintillator/CMOS based flat panel digital detector (2923 MAM, Dexela Ltd.), with a pixel size of 0.0748 mm. The second uses a-Se based direct conversion full field detector (AXS 2430, analogic) with a pixel size of 0.085 mm. The geometry of both systems is same, with a focal spot 665.8 mm from the detector, and a center of rotation 33 mm above the detector surface. The systems were compared with regard to modulation transfer function (MTF), normalized noise power spectrum (NNPS), detective quantum efficiency (DQE) and a new metric, the relative object detectability (ROD). The ROD quantifies the relative performance of each detector at detecting specified objects. The system response function demonstrated excellent linearity (R2>0.99). The CMOS-based detector had a high sensitivity, while the Anrad detector had a large dynamic range. The higher MTF and noise power spectrum (NPS) values were measured using an Anrad detector. The maximum DQE value of the Dexela detector was higher than that of the Anrad detector with a low exposure level, considering one projection exposure for tomosynthesis. Overall, the Dexela detector performed better than did the Anrad detector with regard to the simulated Al wires, spheres, test objects of ROD with low exposure level. In this study, we compared the newly developed prototype DBT system with two different types of x-ray detectors for commercial DBT systems. Our findings suggest that the Dexela detector can be applied to the DBT system with regard to its high imaging performance.

A feasibility study for anatomical noise reduction in dual-energy chest digital tomosynthesis

Lung cancer is the leading cause of cancer death worldwide. Thus, early diagnosis is of considerable importance. For early screening of lung cancer, computed tomography (CT) has been used as the gold standard. Chest digital tomosynthesis (CDT) is a recently introduced modality for lung cancer screening with a relatively low radiation dose compared to CT. The dual energy material decomposition method has been proposed for better detection of pulmonary nodules by means of reducing anatomical noise. In this study, the possibility of material decomposition in CDT was tested by both a simulation study and an experimental study using a CDT prototype. The Geant4 application for tomographic emission (GATE) v6 and tungsten anode spectral model using interpolating polynomials (TASMIP) codes were used for the simulation study to create simulated phantom shapes consisting of five inner cylinders filled with different densities of bone and airequivalent materials. Furthermore, the CDT prototype system and human phantom chest were used for the experimental study. CDT scan in both the simulation and experimental studies was performed with linear movement and 21 projection images were obtained over a 30 degree angular range with a 1.5 degree angular interval. To obtain materialselective images, a projectionbased energy subtraction technique was applied to high and low energy images. The resultant simulation images showed that dual-energy reconstruction could achieve an approximately 32% higher contrast to noise ratio (CNR) in images and the difference in CNR value according to bone density was significant compared to single energy CDT. Additionally, image artifacts were effectively corrected in dual energy CDT simulation studies. Likewise the experimental study with dual energy produced clear images of lung fields and bone structure by removing unnecessary anatomical structures. Dual energy tomosynthesis is a new technique; therefore, there is little guidance regarding its integration into clinical practice and this study can be used to improve the diagnostic efficiency of lung field and spinal bone screening using CDT.

A Redescription of Pseudogonia rufifrons (Wiedemann) (Diptera: Tachinidae): The First Recording of the Genus and Species in Korea

Abstract This report describes the initial discovery of the genus Pseudogonia of the tribe Goniini (Diptera: Tachinidae) in Korea. This Old World genus currently includes seven nominal species. In the process of revising Korean Goniini, we were able to collect Korean representatives of the type species (P. rufifrons), and hereby provide the descriptions and illustrations of both sexes.

Quantitative evaluation of anatomical noise in chest digital tomosynthesis, digital radiography, and computed tomography

Lung cancer is currently the worldwide leading cause of death from cancer. Thus, detection of lung cancer at its early stages is critical for improving the survival rate of patients. Chest digital tomosynthesis (CDT) is a recently developed imaging modality, combining many advantages of digital radiography (DR) and computed tomography (CT). This method has the potential to be widely used in the clinical setting. In this study, we introduce a developed CDT R/F system and compare its image quality with those of DR and CT, especially with respect to anatomical noise and lung nodule conspicuity, for LUNGMAN phantoms. The developed CDT R/F system consists of a CsI scintillator flat panel detector, X-ray tube, and tomosynthesis data acquisition geometry. For CDT R/F imaging, 41 projections were acquired at different angles, over the ± 20° angular range, in a linear translation geometry. To evaluate the clinical effectiveness of the CDT R/F system, the acquired images were compared with CT (Philips brilliance CT 64, Philips healthcare, U.S.) and DR (ADR-M, LISTEM, Korea) phantom images in terms of the anatomical noise power spectrum (aNPS). DR images exhibited low conspicuity for a small-size lung nodule, while CDT R/F and CT exhibited relatively high sensitivity for all lung nodule sizes. The aNPS of the CDT R/F system was better than that of DR, by resolving anatomical overlapping problems. In conclusion, the developed CDT R/F system is likely to contribute to early diagnosis of lung cancer, while requiring a relatively low patient dose, compared with CT.

Improvement of material decomposition and image quality in dual-energy radiography by reducing image noise

Although digital radiography has been widely used for screening human anatomical structures in clinical situations, it has several limitations due to anatomical overlapping. To resolve this problem, dual-energy imaging techniques, which provide a method for decomposing overlying anatomical structures, have been suggested as alternative imaging techniques. Previous studies have reported several dual-energy techniques, each resulting in different image qualities. In this study, we compared three dual-energy techniques: simple log subtraction (SLS), simple smoothing of a high-energy image (SSH), and anti-correlated noise reduction (ACNR) with respect to material thickness quantification and image quality. To evaluate dual-energy radiography, we conducted Monte Carlo simulation and experimental phantom studies. The Geant 4 Application for Tomographic Emission (GATE) v 6.0 and tungsten anode spectral model using interpolation polynomials (TASMIP) codes were used for simulation studies and digital radiography, and human chest phantoms were used for experimental studies. The results of the simulation study showed improved image contrast-to-noise ratio (CNR) and coefficient of variation (COV) values and bone thickness estimation accuracy by applying the ACNR and SSH methods. Furthermore, the chest phantom images showed better image quality with the SSH and ACNR methods compared to the SLS method. In particular, the bone texture characteristics were well-described by applying the SSH and ACNR methods. In conclusion, the SSH and ACNR methods improved the accuracy of material quantification and image quality in dual-energy radiography compared to SLS. Our results can contribute to better diagnostic capabilities of dual-energy images and accurate material quantification in various clinical situations.

Energy or Traffic: Which One to Transfer

In this paper, we study joint topology management and energy cooperation in cellular networks. The topology management scheme transfers users (traffic) from one base station (BS) to another BS by adjusting the cell- size of the BSs, and the energy cooperation scheme transfers harvested energy from one BS to another BS. We first formulate a joint topology management and energy cooperation problem which aims at minimizing the total on-grid energy consumption while satisfying the quality-of-service (QoS) requirement of each user. Then, by solving the problem, we develop a joint topology management and energy cooperation scheme. Topology management and energy cooperation are different approaches to save the on-grid energy consumption, and each scheme is effective to save the on-grid energy consumption in different environments such as different traffic and weather conditions. Through the simulation results, we show which scheme is more effective to save the on-grid energy consumption considering various environments. In addition, we also show that our joint scheme is most effective to deal with the environment which changes dynamically.

Investigation of various reconstruction parameters for algebraic reconstruction technique in a newly developed chest digital tomosynthesis

Chest digital tomosynthesis (CDT) is a promising new modality that provides 3D information by reconstructing limited projection views. CDT systems have been developed to improve the limitations of conventional radiography such as image degradation and low sensitivity. However, the development of reconstruction methods is challenging because of the limited projection views within various angular ranges. Optimization of reconstruction parameters for various reconsturction methods in CDT system also is needed. The purpose of this study was to investigate the feasibility of algebraic reconstruction technique (ART) method, and to evaluate the effect of the reconstruction parameters for our newly developed CDT system. We designed ART method with 41 projection views over an angular range of ±20°. To investigate the effect of reconstruction parameters, we measured the contrast-to-noise ratio (CNR), artifact spread function (ASF), and quality factor (QF) using LUNGMAN phantom included tumors. We found that the proper choice of reconstruction parameters such as relaxation parameter, initial guess, and number of iterations improved the quality of reconstructed images from the same projection views. Optimal values of ART relaxation parameter with uniform (UI) and back-projection (BP) initial guesses were 0.4 and 0.6, respectively. BP initial guess improved image quality in comparison with UI initial guess, in terms of providing a higher CNR and QF values with a faster speed. CNR and QF values improved with increasing number of iteration. Particularly, ART method with BP initial guess (when β = 0.6) after 3-terations provide satisfactory reconstructed image. In conclusion, the use of ART method with proper reconstruction parameters provided better image quality than FBP method as well as conventional radiography. These results indicated that the ART method with optimal reconstruction parameters could improve image quality for nodule detection using the CDT system.

Nine Species of the Family Lauxaniidae (Diptera, Lauxanioidea) New to Korea

A total of 36 species and 11 genera of the fly family Lauxanidae have been previously recorded in Korean Peninsula. As a result of our ongoing study of this family, we here report the following nine species new to Korea: Homoneura albomarginata Czerny, 1932, Minettia filia (Becker), 1895, Pachycerina alutacea Shatalkin, 1998, Poecilolycia zherichini Shatalkin, 2000, Protrigonometopus sexlituris (Shatalkin), 1992, Salebrifacies czurkini Shatalkin, 1992, Sapromyza albiceps Fallen, 1820, Steganopsis dichroa Shatalkin, 1998, and Trigonometopus eborifacies Shatalkin, 1997. The genera Poecilolycia Shewell, 1986, Salebrifacies Shatalkin, 1992, and Steganopsis de Meijere, 1910 are recognized for the first time in this country. Therefore, 45 species in 14 genera are now officially recognized for the Korean lauxaniid fauna. In addition, we provide diagnoses and color photographs of adult external structures including male genitalia to aid their specific identification.

Crystallization of Borosilicate Glasses for High-Strength Bulletproof Materials

Borosilicate glass(GVB-Solutions in glass, 2mm, Germany) was prepared in the composition of 80.4SiO24.2Na2O-2.4Al2O3-13.0B2O3. The 2-step crystallization was performed around 584°C of glass transition temperature (Tg), and 774°C of crystallization temperature(Tc). The maximum nucleation rate was 8.8×10/mm·hr at 600°C and the maximum crystal growth rate was 3.5nm/min at 750°C. The maximum mechanical properties were observed at 22.8% of volume fraction, the strength, hardness and fracture toughness was 555MPa, 752kg/mm, 1.082MPa·mm. The crystal size of 177nm which has volume fraction of 22.8% showed maximum strength of 562MPa, it is about 157% higher than parent borosilicate glass. From these results, the crystallized borosilicate glass can be applied weight lighting of bullet proof materials.