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Regional and strain-level prevalence of nitrogen-fixing Bradyrhizobium with potential N2O reduction in South Korea
Get PDFAgricultural practices are the largest anthropogenic source of nitrous oxide (N2O), a potent greenhouse gas contributing to global climate change. Applying symbiotic microbial inoculants capable of complete denitrification offers a promising strategy to mitigate N2O emissions from agricultural fields. This study reports the strain-level diversity and geographical distribution of soybean symbiont bacteria Bradyrhizobium species carrying the nosZ gene, which encodes nitrous oxide reductase. Of 227 indigenous Bradyrhizobium isolates from soybean root nodules across South Korea, 162 were found to possess the nosZ gene, indicating their potential for N2O reduction. The majority of the most prevalent species, Bradyrhizobium diazoefficiens, harbor the nosZ gene, contributing to the overall high frequency of nosZ-positive genotypes nationwide. In contrast, no evidence of the nosZ gene was detected in the second most abundant species, Bradyrhizobium elkanii, which was predominantly isolated from the southwestern regions, raising the possibility of elevated N2O emissions in these areas. The presence of the nosZ gene varies substantially even within the same species, highlighting the importance of understanding strain-level genetic and functional diversity to develop Bradyrhizobium inoculants optimized for both nitrogen fixation and denitrification.TRUEsciescopuskc
Serum multi-biomarkers for predicting relapse in patients with depressive disorders under psychopharmacotherapy
No full textBackground: Effective predictive biomarkers for depression relapse remain elusive. This study examined the association of a multi-modal serum biomarker panel with relapse among outpatients with depressive disorders under psychopharmacotherapy, utilizing a naturalistic 24-month prospective design. Methods: atients were recruited from a University hospital in South Korea between March 2012 and April 2017. At baseline, 14 serum biomarkers along with socio-demographic and clinical characteristics were assessed in 1094 patients. Following initial antidepressant monotherapy, patients who responded (Hamilton Depression Rating Scale [HAMD] ≤ 14) at the 12-week mark (N = 823) were monitored for relapse (HAMD >14) every three months up to 24 months (N = 710). Logistic regression models, adjusted for relevant covariates, were used to evaluate predictive biomarkers of relapse. Results: The combined scores of four serum biomarkers (cortisol, high-sensitivity C-reactive protein, tumor necrosis factor-alpha, and brain-derived neurotrophic factor) showed a significant and graded association with depression relapse (P-value <0.001), even after adjustments. Conclusions: The application of a combined multi-serum biomarker panel could significantly enhance the predictability of depression relapse. Further validation of these biomarkers in diverse populations and settings is warranted to confirm their utility in clinical practice. © 2025 Elsevier Inc.FALSEsciescopu
Nanoscale Au-Si eutectic mixtures formed by dewetting of a Au-Ni film on Si3N4
No full textFormation of a eutectic AuSi compound was observed during the solid state dewetting and agglomeration in a Ni-Au bilayer thin film grown on a Si3N4 substrate using coherent X-ray diffractive imaging, X-ray diffraction, and scanning electron microscopy. During rapid thermal annealing at 850 degrees C in vacuum, AuNi films first separate into islands that are composed of a mixture of Au-rich and Ni-rich phases. As the dewetting proceeds, Si and nitrogen dissociate due to the catalytic action of Ni, which resulted in the formation of NiN, NiSi, and AuSi. With increasing time of the annealing process, nitrogen atoms in NiN are gradually evaporated by forming N2. The eutectic phenomenon in AuSi alloys results in the migration of Au atoms to form Au5Si2 with a composition near the eutectic point, 18.6 at% of Si. Our findings indicate that nucleation of the Au5Si2 alloy formation does not primarily occur through bulk interdiffusion, but instead initiates through grain boundary diffusion of Au atoms.TRUEsciescopu
Optimizing toe joint stiffness to improve human-like walking
No full textThe human metatarsophalangeal joint-often referred to as the "toe joint"-plays a vital role in gait by supporting body weight during mid-stance, enabling smooth rollover from heel to toe, and facilitating effective push-off in terminal stance. However, identifying its optimal stiffness remains challenging despite its relevance to both biological and robotic locomotion. In this study, we used a simulation-based trajectory optimization approach to investigate toe joint stiffness in a bipedal model. The results revealed that lower stiffness facilitated rollover while higher stiffness enhanced push-off. Because continuously varying stiffness is impractical in most passive devices, we extracted a single representative value (0.98 Nm/deg) by averaging the time-varying stiffness during the push-off phase. We then conducted a human walking experiment using adjustable toe joint boots across multiple stiffness conditions. The 0.98 Nm/deg condition yielded the highest subjective satisfaction and favorable spatiotemporal outcomes, especially among participants with anthropometry similar to the simulation model. Although direct numerical comparison between simulation and experiment was not performed due to modeling simplifications, key qualitative trends-such as toe joint moment progression and heel-off timing-were consistent. These findings highlight the potential of toe joint stiffness tuning to improve walking performance and user experience.TRUEsciescopu
Engineered surface oxidation of porous metal substrate for simultaneous enhancement of kinetics and durability in electrochemical hydrogen evolution reaction
No full textThis study presents an effective approach to enhancing the catalytic performance, long-term stability, and surface hydrophilicity of porous nickel (Ni) substrates for the hydrogen evolution reaction (HER) via controlled surface oxidation without additional catalysts. In this study, the Ni tape-cast substrate (Ni-TCS), fabricated through a tape-casting method followed by oxidation and reduction treatments, exhibited a large surface area and fine porosity, resulting in a significantly improved catalytic activity compared to conventional Ni foam. Through partial oxidation at temperatures ranging from 300 degrees C to 450 degrees C, a catalytically favorable nickel oxide (NiO) nano layer was produced directly on the Ni-TCS surface, enhancing the HER activity and stabilizing the NiO/Ni interface for durability. Additionally, the NiO nano layer rendered the electrode surface hydrophilic as confirmed through contact angle measurements, facilitating effective electrolyte contact and improving mass transport. The Ni-TCS electrode oxidized at 400 degrees C (Ni-TCS400) demonstrated the highest HER activity, sustaining excellent stability at 500 mA cm-2 over 500 h. Ni-TCS400 exhibited lower kinetic and mass-transfer overpotentials than those of the Ni-TCS in an alkaline water electrolyzer (AWE) system, while a voltage of 1.81 V was required to achieve a current density of 0.4 A cm-2. Overall, the partial oxidation strategy circumvents the use of binders or precursors, while enabling improved stability, simplified fabrication, and high catalytic activity, making it a promising approach for the development of durable, efficient AWE electrodes.FALSEsciescopu
Screening of genes involved in Lipid Droplet morphology and inheritance in Saccharomyces cerevisiae
No full textLipid droplets (LDs) are conserved organelles that store neutral lipids and are essential for energy metabolism, lipid homeostasis, and stress responses. Although their formation and metabolic regulation have been extensively studied, the mechanisms that govern their inheritance and morphological integrity during cell division are poorly understood. To identify non-essential genes involved in LD inheritance and morphology, I conducted a fluorescence microscopy-based screen using Saccharomyces cerevisiae, examining 400 single gene deletion strains. LDs were visualized by BODIPY 493/503 staining, and their phenotypes were classified as inheritance defects based on LD presence in daughter cells, or as morphological abnormalities based on changes in droplet number, size, or shape. Among the screened strains, deletion of LDB16, a component of the seipin complex, resulted in a clear LD inheritance defect and an increase in LD size. In this mutant strain, 52% of daughter cells failed to receive LDs from mother cells, in contrast to 14% in the daughter cells of the wild-type strain. In addition, a number of mutant strains exhibited diverse abnormalities in LD morphology. LDs with ring-like morphology were observed in spo7Δ and nem1Δ mutants, while enlarged LDs were seen in tgl3Δ. Several mutants, including loa1Δ, arv1Δ, srx1Δ, cla4Δ, cnm67Δ, sla2Δ, sto1Δ, and chc1Δ, showed increases in LD number. These findings provide important insights into the genetic regulation of lipid droplet behavior.
In yeast, Sey1p is the primary mediator of homotypic ER membrane fusion, whereas Dnm1p is well known for its role in mitochondrial and peroxisomal fission. However, the potential interplay between these machineries in ER network maintenance remains unclear. Here, I investigated the relationship between Dnm1p and Sey1p in Saccharomyces cerevisiae. Co-immunoprecipitation experiments demonstrated a physical association between Dnm1p and Sey1p, suggesting a possible connection between ER fusion and fission processes. Functional assays revealed that deletion of DNM1 resulted in inconsistent effects on in vitro ER microsome fusion activity, with both increased and decreased fusion observed in different experiments. Furthermore, in Sey1p-dependent proteoliposome fusion assays, the addition of Dnm1-MBP, as well as all control conditions—including boiled Dnm1-MBP, MBP alone, and TEV protease—led to a marked reduction in fusion compared to Sey1p alone, indicating non-specific inhibition rather than a direct regulatory effect of Dnm1p. These findings highlight the complexity of ER network regulation and indicate that while Dnm1p and Sey1p physically interact, Dnm1p does not play a considerable role in regulating Sey1p-mediated ER membrane fusion in vitro. To fully elucidate the functional significance of the Dnm1p-Sey1p interaction, future studies should employ optimized in vitro fusion assays and in vivo approaches to dissect the molecular mechanisms underlying ER dynamics.MasterI. Introduction 1
II. Materials and Methods 3
II-1. Yeast strains 3
II-2. Microscopy 3
II-3. Lipid droplet quantification 4
III. Results 5
III-1. Microscopy-based screening and classification of lipid droplet phenotypes in yeast 5
III-2. Identification of the mutant with lipid droplet inheritance and morphology defects 5
III-3. Identification of mutants with abnormal lipid droplet morphology 6
III-4. Identification of the mutant with enlarged lipid droplet 6
III-5. Identification of mutants with increased lipid droplet number 7
IV. Discussion 20
V. Abstract in Korean 22
Chapter Ⅱ Study on Regulation of ER Tubular Network Formation by the Dynamin-related GTPase DNM 1 24
I. Abstract 24
II. Introduction 25
III. Materials and Methods
II-1. Yeast strains and strain construction 26
II-2. DNA constructs and plasmids 26
II-3. Preparation of ER microsomes 27
II-4. In vitro ER microsome fusion assay 27
II-5. Preparation of recombinant proteins 28
II-6. Proteoliposome reconstitution and lipid-mixing assay 28
II-7. Coimmunoprecipitation 29
IV. Results 30
III-1. Dnm1p-Sey1p Co-Immunoprecipitation (Co-IP) Analysis 30
III-2. Effects of DNM1 deletion on ER microsome fusion 30
III-3. Effects of Dnm1p on proteoliposome lipid mixing 31
V. Discussion 40
VI. Abstract in Korean 42
References 43
Acknowledgement 4
A Study of Planar-to-Waveguide Transition for Wideband Millimeter-Wave Signal Coupling Co-advisor: Professor Jae-Hyung Jang
No full textMillimeter-wave communication systems demand high-speed data transmission, minimal signal loss, and broadband signal coupling to support the performance requirements of next-generation applications. However, the integration of planar circuits and waveguide structures remains a significant challenge due to their differing guiding mechanisms, characteristic impedances, and field distributions. Efficient energy transfer between microstrip lines and rectangular waveguides is particularly difficult and often constrained by radiation leakage, fabrication complexity, and alignment sensitivity.
This dissertation addresses these challenges by proposing and analyzing two novel planar-to-waveguide transition structures, focusing on broadband performance, ease of manufacturing, and high integration capability with planar and multilayer circuit platforms.
The first transition introduces a partially covered back-short design in the microstrip-to-waveguide transition (MWT) to achieve wideband operation and low insertion loss without relying on a shorted waveguide cavity or additional matching structures. Implemented using a printed circuit board with three copper layers and two dielectric layers, the transition features a via fence and a partially covered microstrip line to suppress radiation leakage. It leverages multiple resonances to achieve broadband signal coupling while maintaining structural simplicity and cost-effectiveness. Back-to-back measurements validate its performance, demonstrating a return loss greater than 10 dB over the 41–63 GHz band, corresponding to a 42% operating bandwidth.
The second transition focuses on enhancing manufacturability and misalignment tolerance in waveguide-to-microstrip interfaces. A wedge-waveguide to microstrip transition (WMT) is proposed, employing three key innovations. First, it utilizes broadside aperture coupling, which contrasts with conventional end-wall aperture methods, offering greater coupling area and improved misalignment tolerance. Second, it avoids the high losses and complexity associated with probe-insert broadside couplings by enabling robust inline coupling through a wedge-waveguide structure. Third, it eliminates the need for complex tapers or ridges, reducing both volume and fabrication difficulty. The design supports seamless MMIC integration and requires no waveguide splitting. It achieves a fractional bandwidth of 44% and a back-to-back insertion loss of 8.5 dB, including 5.5 dB from a 1-meter-long waveguide path, while tolerating ±250 µm vertical and ±300 µm horizontal misalignments with negligible performance degradation. Together, these transition architectures offer scalable, low-loss, and fabrication-friendly solutions that enable efficient planar-to-waveguide coupling for advanced millimeter-wave systems.DoctorAbstract i
Contents iii
List of Figures v
List of Tables vii
Chapter 1 Introduction 1
1.1 Background 1
1.2 Microstrip-to-Waveguide Transitions 2
1.3 Problem Statement and Motivation 4
1.4 Objectives and Contributions 4
1.5 Thesis Organization 5
Chapter 2 Literature Review 7
2.1 Historical Context and Evolution of Microstrip-to-Waveguide Transitions- 7
2.2 Theoretical Considerations and Electromagnetic Insights 7
2.3 Overview of Transition Design Strategies 8
2.3.1 Vertical Transitions 9
2.3.2 Inline Transitions 10
2.4 Comparative Performance Summary 12
2.5 Recent Advances and Emerging Applications 13
Chapter 3 Design Methodology for Microstrip-to-Waveguide Transitions 16
3.1 Introduction 16
3.2 Design Workflow 16
3.3 Design Methodology 18
3.3.1 Ensure dominant mode of propagation 18
3.3.2 Impedance Matching Between Microstrip Line and Waveguide 20
3.3.3 Targeted Insertion Loss 20
3.3.4 Additional Design Guidelines 22
Chapter 4 Transition Design and Simulation Results 23
4.1 Introduction 23
4.2 Design and Simulation of the MWT 23
4.2.1 Design & Working Principle 24
4.2.2 Transition Performance 24
4.2.3 Broadband Performance Realization 26
4.2.4 Radiation Suppression Mechanism 28
4.3 Design and Simulation of the WMT 29
4.3.1 Operating Principle 29
4.3.2 Structure and Configuration 30
4.3.3 Transition Performance 33
4.3.4 Sensitivity to Misalignment in E-Plane and H-Plane 35
4.3.5 Comparison with State-of-Art Transitions 35
4.4 Summary 36
Chapter 5 Experimental and Simulation Validation of Microstrip-to-Waveguide Transitions- 38 -
5.1 Experimental Setup 38
5.2 Ansys HFSS Simulation Model 39
5.3 Fabrication Process 40
5.3.1 PCB Substrate and Materials 42
5.3.2 Waveguide Connecter 42
5.4 Fabrication of Transition Board Panels 44
5.4.1 Panel Details: 44
5.4.2 Panel Configuration 45
5.5 Experimental Results and Discussions of MWT 47
5.5.1 Back-to-back Measurement Setup 47
5.5.2 Procedure to Estimate Loss: 49
5.6 Impact of Misalignment Tolerance and Manufacturing Errors on MWT 50
5.6.1 Manufacturing Errors 50
5.6.2 Misalignment tolerance in the E-plane and H-plane of the waveguides 49
5.6.3 Comparison with State-of-Art Vertical Transitions 53
5.7 Experimental Results and Discussions of WMT 54
5.7.1 Back-to-Back Transition Results 55
5.7.2 Waveguide Loss Extraction: 55
5.7.3 Comparison with State-of-Art Transitions 56
5.8 Summary 56
Chapter 6 Conclusion & Future Work 57
6.1 Summary of Findings 57
6.2 Future Directions 57
References 59
Acknowledgment 66
Appendix A: Curriculum Vitae 6
A distributed framework for the minimum cost problem based on graph decomposition☆
No full textControlling a system is a fundamental challenge in real-world applications. Efficient control requires determining the optimal placement of inputs to ensure effective system performance. The Minimum Cost Problem (MCP) aims to minimize control costs by selecting the most effective input locations. However, existing centralized optimization methods for solving the MCP, which rely on global information, face significant challenges, including high computational complexity in large-scale networks and non-convex cost functions that often lead to undesirable local minima. This paper introduces distributed frameworks based on graph decomposition, enabling the application of existing optimization methods in a distributed manner. These frameworks significantly reduce computational complexity and improve scalability. Simulation results on real-world networks demonstrate that the proposed framework significantly outperforms centralized methods in terms of both computational efficiency and energy minimization.FALSEsciescopu
Design, Synthesis and Biological Evaluation of Pyrazolopyrimidine Derivatives as Aryl Hydrocarbon Receptor Antagonists for Colorectal Cancer Immunotherapy
No full textBackground: Aryl hydrocarbon receptor (AhR) is a transcription factor that is involved in the regulation of immunity. AhR inhibits T cell activation in tumors, which induces immune suppression in the blood and solid tumors. We identified effective small-molecule AhR antagonists for cancer immunotherapy. Methods: A new series of pyrazolopyrimidine derivatives was synthesized and evaluated for AhR antagonistic activity. Results: Compound 7k exhibited significant antagonistic activity against AhR in a transgenic zebrafish model. In addition, 7k exhibited good AhR antagonist activity, with a half-maximal inhibitory concentration (IC50) of 13.72 nM. Compound 7k showed a good pharmacokinetic profile with an oral bioavailability of 71.0% and a reasonable half-life of 3.77 h. Compound 7k selectively exerted anti-proliferative effects on colorectal cancer cells without affecting normal cells, concurrently suppressing the expression of AhR-related genes and the PD-1/PD-L1 signaling pathway. Compound 7k exhibited potent antitumor activity in syngeneic colorectal cancer models. Importantly, the combination of anti-PD1 and compound 7k enhanced antitumor immunity by augmenting cytotoxic T lymphocyte (CTL)-mediated activity. Conclusions: Collectively, a new pyrazolopyrimidine derivative, 7k, shows promise as a potential therapeutic agent for treating colorectal cancer.TRUEsciescopu
Quasi-ordered plasmonic metasurfaces with unclonable stochastic scattering for secure authentication
No full textQuasi-order in structural coloration, as observed in nature, offers intrinsic, unclonable near-field stochastic fingerprints while preserving far-field uniform colors. However, replicating this balance in artificial photonic metasurfaces remains a major challenge. Here, we present plasmonic metasurfaces that achieve this balance through electrostatic self-assembly of quasi-ordered gold nanoparticles onto a dielectric-spaced metallic mirror. These metasurfaces enable precise tuning of far-field reflective colors across the visible spectrum by adjusting the dielectric gap thickness, while simultaneously generating stochastic near-field scattering patterns that serve as unique physically unclonable functions (PUFs). The resulting scattering PUF keys exhibit uniform bit uniformity (average: 0.501), high uniqueness (inter-Hamming distance: 0.496) and large capacity (similar to 10(260)), with strong environmental stability and resistance to unauthorized cloning. We further demonstrate the practical applications of these plasmonic metasurfaces in security and authentication, including information camouflage and the integration of hidden PUF keys into identification cards and quick-response codes.TRUEsciescopu