Sogang University

Octamer-binding transcription factor 4 (Oct-4) is essential for maintenance and pluripotency of embryonic stem (ES) cells. Despite the structural similarities between Oct-4 and its homologs (Oct-1, Oct-2, and Oct-6), these homologs cannot serve as substitutes for Oct-4 when generating stem cell colonies. While nuclear receptor subfamily 5, group A, member 2 (Nr5a2) can temporarily serve as a substitute for Oct-4 during cellular reprogramming, it is insufficient to maintain these functions in ES cells. The EWS-Oct-4 fusion protein, which was identified in human tumors, is a viable alternative that can potentially sustain and enhance ES cell functions. This study used ZHBTc4 ES cells, which have tetracycline-regulated Oct-4 expression, to explore the capabilities of EWS-Oct-4. It employed a variety of assays, including western blotting, immunocytochemistry, RT-PCR, luciferase reporter assays, flow cytometry, and teratoma formation assays. EWS-Oct-4 preserved the self-renewal capacity of Oct-4-null ES cells, as demonstrated by their undifferentiated morphology and increased expression of pluripotency markers such as Sox2, Nanog, and SSEA-1. It also boosted cell proliferation and influenced cell cycle dynamics by downregulating p21 and upregulating Oct-4 target genes, including Rex-1 and fibroblast growth factor-4. Epithelial markers were upregulated and mesenchymal markers were downregulated, suggesting a shift toward an epithelial phenotype. Prominent teratoma formation further confirmed the functionality of EWS-Oct-4 in vivo. The integrity and specific functional domains of EWS-Oct-4 were critical for these effects. Finally, comparative transcriptomic analysis revealed that ES cells expressing EWS-Oct-4 and those expressing Oct-4 had highly similar global gene expression profiles, with distinct variations in differentially expressed genes. These findings indicate that EWS-Oct-4 can effectively replace Oct-4, which has significant implications for advancements in stem cell research and regenerative medicine.

Birefringence, a vital property of anisotropic crystals, is indispensable for advanced optical technologies. Quasi‐1D structures, with their inherent structural anisotropy, offer fertile ground for discovering materials with exceptional optical anisotropy. In this work, we report four metal‐free quasi‐1D crystals—(C5H6NO)⁺(NO3)‐(4HPN), (C5H6NO)⁺(HC2O4)‐(4HPO), (C4N3H6)⁺(NO3)‐(2APMN), and (C4N3H6)⁺(HC2O4)‐·H2O (2APMO)—designed to feature pseudo‐chain structures and grown as centimeter‐scale crystals via a facile aqueous‐solution method. These crystals display wide bandgaps (3.40–4.48 eV) and exceptional birefringence, with calculated values up to 0.555@546 nm and an experimental maximum of 0.597@546 nm for 4HPN. The giant birefringence stems from their quasi‐1D architectures, high‐spatial density, and optimal arrangement of the birefringence‐active groups (BAGs). This study highlights the promise of metal‐free quasi‐1D materials for next‐generation miniaturized polarization optics and laser‐driven applications.

Quasi‐solid‐state batteries (QSSBs) are attracting considerable interest as a promising approach to enhance battery safety and electrochemical performance. However, QSSBs utilizing high‐capacity active materials with substantial volume fluctuations, such as Si microparticle (SiMP) anodes and Ni‐rich cathodes (NCM811), suffer from unstable interfaces due to contact loss during cycling. Herein, an in situ interlocking electrode–electrolyte (IEE) system is introduced, leveraging covalent crosslinking between acrylate‐functionalized interlocking binders on active materials and crosslinkers within the quasi‐solid‐state electrolyte (QSSE) to establish a robust, interconnected network that maintains stable electrode–electrolyte contact. This IEE system addresses the limitations of liquid electrolyte and QSSE configurations, evidenced by low voltage hysteresis in (de)lithiation peaks over 200 cycles, stable interfacial resistance throughout cycling, and the absence of void formation. A pressure‐detecting cell kit further confirms that the IEE system exhibits lower pressure changes during cycling without any voltage fluctuations from contact loss. Moreover, the SiMP||NCM811 full cell with the IEE system demonstrates superior electrochemical performance, and a bi‐layer pouch cell configuration achieves an impressive energy density of 403.7 Wh kg⁻¹/1300 Wh L⁻¹, withstanding mechanical abuse tests such as folding and cutting, providing new insights into high‐energy‐density QSSBs.

Birefringent crystals are essential for polarized optical devices, yet achieving large birefringence through rational design remains challenging. The key lies in constructing birefringence‐active groups (BAGs) with giant polarization anisotropy and optimal spatial arrangements. Here, we report the successful construction of linear interhalogen BAGs, IX2‐ (X = Cl, Br), enabling giant polarization anisotropy. This was accomplished by simple halogenation of IO3‐ groups in an aqueous solution. Four novel birefringent crystals were synthesized: [H‐4AP][ICl2] (1, 4AP = 4‐aminopyridine), [HDMA]2[ICl2]·Cl (2, DMA = dimethylamine), [H‐4AP][IBr2] (3), and [HDMA]2[IBr2]·Br (4). In all these compounds, the linear IX2‐ BAG adopts parallel arrangements, effectively maximizing synergistic polarization anisotropy. As a result, compounds 1–4 exhibit giant birefringence values in both the visible (0.647, 0.585, 0.836, and 0.782 at 546 nm) and near‐infrared (NIR) regions (0.510, 0.356, 0.762, and 0.509 at 1064 nm), surpassing commercial birefringent crystals and many state‐of‐the‐art materials. Furthermore, these compounds achieve an optimal balance between giant birefringence and moderate bandgap among linear BAG‐based materials. Detailed theoretical calculations confirm that the IX2‐ BAGs play a dominant role in this exceptional birefringence. This study demonstrates the remarkable potential of linear interhalogen anions for developing high‐performance birefringent crystals.

Birefringent crystals are essential for polarized optical devices, yet achieving large birefringence through rational design remains challenging. The key lies in constructing birefringence‐active groups (BAGs) with giant polarization anisotropy and optimal spatial arrangements. Here, we report the successful construction of linear interhalogen BAGs, IX2‐ (X = Cl, Br), enabling giant polarization anisotropy. This was accomplished by simple halogenation of IO3‐ groups in an aqueous solution. Four novel birefringent crystals were synthesized: [H‐4AP][ICl2] (1, 4AP = 4‐aminopyridine), [HDMA]2[ICl2]·Cl (2, DMA = dimethylamine), [H‐4AP][IBr2] (3), and [HDMA]2[IBr2]·Br (4). In all these compounds, the linear IX2‐ BAG adopts parallel arrangements, effectively maximizing synergistic polarization anisotropy. As a result, compounds 1–4 exhibit giant birefringence values in both the visible (0.647, 0.585, 0.836, and 0.782 at 546 nm) and near‐infrared (NIR) regions (0.510, 0.356, 0.762, and 0.509 at 1064 nm), surpassing commercial birefringent crystals and many state‐of‐the‐art materials. Furthermore, these compounds achieve an optimal balance between giant birefringence and moderate bandgap among linear BAG‐based materials. Detailed theoretical calculations confirm that the IX2‐ BAGs play a dominant role in this exceptional birefringence. This study demonstrates the remarkable potential of linear interhalogen anions for developing high‐performance birefringent crystals.

We investigate the influence of frequency noise on the beam pattern within a frequency diverse array (FDA) utilizing the Cramér-Rao Lower Bound (CRLB). FDA radar offers an ability to adjust the beam pattern with distance as well as angle. This technology has the potential to significantly enhance target detection capabilities by concentrating energy on a specific location. We focus on symmetrical FDA, where the frequency increment is symmetrically distributed across the array, to focus a beam on a specific region. To assess the effect of frequency noise on a FDA, we utilize the CRLB to estimate the variance of the energy-concentrated spot size. Simulations are conducted to model the size of energy spot based on the noise variance, and the CRLB is calculated. It is observed that as the standard deviation of frequency noise increases, the variation of beam size also increases. The resulting CRLB value can help establish a required noise level when implementing FDA hardware. On the other hand, it is also found that the frequency noise enhanced the capability of FDA on concentrating a beam, as the average size of the beam decreases with noise. This phenomenon can be harnessed to create a smaller energy spot in a specific region.

The conventional Oliver-Pharr method of estimating elastic modulus shows reasonably good accuracy, but errors occur due to inaccuracies in the actual contact area. To resolve this issue, this study proposed a new method to estimate the elastic modulus using two different indenters without additional equipment or complicated calibration. We aimed to estimate the elastic modulus using the theoretical indentation depth, without the consideration of sink-in / pile-up effect. A numerical indentation test was performed using Berkovich and spherical indenters, and the theoretical contact area and initial unloading slope of the indentation load-depth curve were calculated to derive c-ratio based on the correction factor c. Numerical validation using finite element analysis for various material properties of J2 and pressure-dependent hardening models showed that the method estimates the elastic modulus with R 2 = 98 %, outperforming the conventional method. Microindentation tests were conducted on copper, Al1050, SS304 specimens for experimental validation. The estimated elastic moduli with proposed method showed good agreement with those from tensile tests with an error of 7 %. This study proposed a new method for estimating elastic modulus that overcomes the limitations of the conventional method, which is difficult to accurately measure the actual contact area at maximum load, and has high applicability to various materials by using the correction factor c.

Threshold public good games with binary contributions and without rebates or refunds embody both the incentive to free-ride and the risks of non-provision and wasted contributions. We investigate the implications of heterogeneity in strategic sophistication in this context, focusing on the cognitive hierarchy model. We find that the contribution of the initial strategic level (i.e., level-1) is crucial for the provision of the public good. We furthermore demonstrate that a higher average sophistication among a group of players does not necessarily lead to a higher probability of provision. Finally, we find that it would be easier to provide the public good for larger groups if the average sophistication is lower.

In the absence of treatment, detection of pathogenic RNA viruses and quarantine of infected individuals are critical for controlling the infection spread. Conventional antibody‐based methods often lack the required accuracy and sensitivity, due to the need for a substantial amount of viral antigens. Similarly, traditional reverse transcription real‐time polymerase chain reaction methods face challenges in providing timely results due to their multiple thermal nucleic acid amplification steps. To overcome these limitations, a new method based on imaging of virus‐specific DNA markers is developed. This approach employs specially designed single‐stranded circular DNA probes that capture virus‐derived RNA fragments generated by RNase digestion of the viral genome. These fragments serve as primers for a subsequent single‐step DNA filling reaction, producing double‐stranded virus‐specific marker molecules. These individual markers are recognized through fluorescence imaging following linearization by enzyme cleavage and subsequent fluorescence staining. This method can detect viruses at a genome equivalent level of 14 within 40 min. In addition, the molecule‐level imaging‐based method effectively detects human immunodeficiency virus‐1 in clinical samples. This diagnostic approach does not require sophisticated thermal controls nor extensive nucleic acid amplifications, allowing for accurate, sensitive, and rapid detection without the need for large equipment, offering substantial potential for point‐of‐care applications.

Stretchable displays, characterized by their flexibility and deformability, are gaining attention as next‐generation display technologies. While various studies have been conducted on hardware aspects of stretchable displays, the software aspects have received comparatively less focus. When displays are stretched, empty pixels inevitably lead to a decrease in overall luminance, which significantly degrades visual quality and user experience. To address this issue from a software aspect, we propose a novel luminance compensation method that leverages deep learning through a Learned Perceptual Image Patch Similarity (LPIPS)‐based pre‐optimization technique combined with Gaussian‐weighted kernels. The proposed method applies relatively higher values to areas near empty pixels, where luminance loss is most significant while preserving the original luminance in unaffected areas. This design minimizes color distortion and enhances brightness effectively. Specifically, the optimal brightness increase rates (BIRs) are pre‐optimized using an LPIPS‐based loss function, tailored to various stretching scenarios, such as stretching types, directions, and rates. Based on the optimized BIRs, Gaussian‐weighted kernels are generated for efficient luminance adjustment. Our method flexibly supports diverse stretching conditions, including linear/non‐linear stretching and uni‐directional/bi‐directional stretching, with stretching ratios ranging from 10% to 30%. Through simulations, we qualitatively and quantitatively compared the proposed method with existing approaches, demonstrating superior performance across a wide range of scenarios.

Objectives We examine how parenthood shapes pro‐environmental attitudes. In particular, we discuss the dual pressure of legacy motivations and childcare burdens, gender disparities in caregiving responsibilities, and financial constraints on parents’ capacity to engage with environmental concerns. Methods We utilize the Cooperative Congressional Election Study (CCES) from 2016, 2018, and 2020. The dependent variable is the pro‐environmental attitude score, and the key independent variables include parenthood, the number of children, gender, and income. The ordinary least squares (OLS) regressions are fitted to examine the main effects as well as the interactive effects. Results Our analysis shows that the effect of the number of children on pro‐environmental attitudes is conditional upon gender and income. Fathers and high‐income parents initially show greater support for pro‐environmental policies when they have fewer children as compared to when they have no children. However, as family size grows, their support for pro‐environmental policies declines. On the other hand, mothers and low‐income parents experience monotonically decreasing support for pro‐environmental policies as they have more children. Conclusions Our analysis suggests that legacy motivations prevail at first, helping parents to have higher pro‐environmental support. But, as childcare burdens intensify, they dominate legacy motivations and lower pro‐environmental support.

The sixth‐generation (6G) communication technology is expected to provide the seamless and ubiquitous wireless access for future cellular networks. Due to the rise of network demands and the limited communication resource, the multiband network (MBN) system is needed to satisfy the stringent communication requirements. This trend triggers to utilize millimeter wave and THz frequency bands, in addition to traditional radio frequency band. In this paper, we divide the MBN control problem into two subproblems: the base station (BS) association problem and spectrum allocation problem. To jointly optimize these problems, we mainly focus on the cooperative game theory. According to the coalition formation game, each device considers the characteristics of different spectrum bands and forms its BS association for communication services. And then, a new control paradigm, called Max‐min Multicriteria Bargaining Solution (MMBS), is introduced to solve the MBN spectrum allocation problem. By considering multiple criteria, the main concept of MMBS is the max–min–max optimization method based on the Nash product. By using the interactive relationship between BSs and individual devices, our joint control approach can effectively handle the MBN technology to ensure mutual advantages. Finally, simulation results show the efficiency and the effectiveness of our cooperative game approach. Compared with the existing MBN protocols, analytical results demonstrate the superior performance of the proposed solution.

We fabricated GaN/BN double heterostructure light-emitting diodes (LEDs) where the BN layer exhibited an amorphous-like short-range order and facilitated the in-situ epitaxial lateral overgrowth (ELOG) of GaN films. Using an identical metal-organic chemical vapor deposition, the BN layer was reliably formed on the GaN film and then served as a growth mask during the high-temperature growth of the GaN overlayer. The BN layers were well dispersed over the entire surface with a partial coverage of 40–60% and a thickness of a few nm. The laterally overgrown GaN was epitaxially related to the initial GaN film exhibiting single crystallinity with flat and smooth surface morphology. Meanwhile, the in-situ-formed BN layer effectively blocked the threading dislocations where its density reductions were comparable to those of typical ex-situ ELOG processes. Furthermore, the BN-assisted ELOG reduced the mosaic of the practical single crystalline GaN grains and drastically improved crystallographic alignment and internal quantum efficiency. More importantly, the BN-assisted ELOG yielded high device performance of the GaN LEDs demonstrating that the benefits of ELOG were fully achieved with the fast and instant fabrication process.

Three-dimensional (3D) tumor spheroid models closely mimic in vivo tumor environment and play a vital role in studying oncological research. Despite their significance, the existing methods for analyzing 3D tumor spheroids often suffer from limitations, including low throughput, high cost, and insufficient resolution. To address these challenges, we developed a portable imaging system for the real-time sensing and quantitative analysis of the 3D tumor spheroids. The system integrated the seamless workflow of spheroid generation, cell morphology tracking, and drug screening. The spheroid generation was successfully characterized using MCF-7 breast cancer cells by optimizing cell concentration (5–20 × 106 cells/mL), incubation time (24–96 h) and microwell diameter (400–600 μm). A custom-written algorithm was developed for automated analysis of spheroids, exhibiting high sensitivity (98.99%) and specificity (98.21%). Confusion matrices and receiver operating characteristic curve analysis further confirmed the robustness of the algorithm with an area under the curve value of 93.75% and an equal error rate of 0.79%. Following the characterization, the real-time sensing of spheroid generation and the response of spheroids to drug treatment were successfully demonstrated. Furthermore, the live/dead assays with chemotherapy provided a detailed insight into the efficacy and cytotoxic effects of the drug, demonstrating a significant dose-dependent decrease in a spheroid viability. Therefore, our system offers considerable potential for enhancing drug development processes and personalized treatment strategies, thereby contributing to more effective cancer therapies.

The present study explored the potential of categorical frequency judgments as effective ensemble judgments, motivated by the observation that most studies on ensemble judgments have focused on univariate statistics, such as mean and variance. However, these univariate statistics may not fully capture the complexity of real-world tasks that require judgments on complex object features. In such cases, categorical statistics like mode (the most frequent instance in a set) and diversity (the number of different instances in a set) may provide more relevant information. For instance, when a speaker enters an auditorium and scans her audience, relative frequencies of different emotional expressions could be more useful than the representation of the average face with a potentially faint expression. Study 1 examined the relationship between mode judgment and diversity comparison in facial identities, while Study 2 extended the examination of mode judgments across different object categories (faces and blobs). The results indicate that categorical frequency judgments share behavioral variability across tasks and object categories, supporting their potential as effective ensemble judgments. Future research may explore how these categorical frequency judgments interact with univariate statistical judgments to enhance our understanding of ensemble judgments.

A drift from a cooling tower is an important research topic in both academic and practical perspectives due to a similarity to the jet in crossflow and possible relationship to Legionella transmission. The dynamic and thermal characteristics of a drift under crossflow are investigated numerically using an Eulerian–Lagrangian approach and droplet phase change model, focusing on the near-field development under varying Grashof numbers and velocity ratios. Large eddy simulations are performed for the base, low atmospheric temperature, and low velocity ratio (LVR) cases. The development of counter-rotating vortex pair (CVP) in a LVR range shows the opposite trend to that in a high velocity ratio range. Unlike the jet centerline, the droplet trajectory shows higher sensitivity to the Grashof number and distinctive double inflection points in the LVR case. A modified semi-empirical formula for the drift radius is presented with improved prediction accuracy. Time evolution of a two-dimensional probability density function (PDF) on the Lagrangian droplet phase presents two distinctive temperature regimes based on the droplet ejection location and explains the mechanisms driving a branch shape in the PDF. The histograms of the droplet mass show higher sensitivity of smaller droplets to the phase change and increased Grashof number. The LVR case shows distinct droplet evolution mechanism due to the compact and strong CVP collecting hot and small droplets inside. The higher intensity CVP increases the mass of smaller droplets via increased condensation, while stronger crossflow momentum decreases the mass of larger droplets via mixing.