• Korean Chemical Engineering Research
• /
• v.61 no.3
• /
• pp.394-400
• /
• 2023

In this study, the tuning phenomena, gas storage capacity, and thermal expansion behaviors of binary (cyclopentylamine + CH₄) and (cyclopropylamine + CH₄) clathrate hydrates were investigated for the potential applications of clathrate hydrates to gas storage. To understand the tuning behaviors of binary (cyclopentylamine + CH₄) and (cyclopropylamine + CH₄) clathrate hydrates, ¹³C solid-state NMR spectroscopy was used, and the results confirmed that maximum tuning factors for the binary (cyclopentylamine + CH₄) and (cyclopropylamine + CH₄) clathrate hydrates were achieved at 0.5 mol% and 1.0 mol% of guest concentration, respectively. The gas storage capacity of binary (cyclopentylamine + CH₄) and (cyclopropylamine + CH₄) clathrate hydrates were also checked, and the results showed the CH₄ capacity of our hydrate systems was superior to that of binary (tetrahydrofuran + CH₄) and (cyclopentane + CH₄) clathrate hydrates. The synchrotron diffraction patterns of these hydrates collected at 100, 150, 200, and 250 K confirmed the formation of a cubic Fd-3m hydrate. In addition, the lattice constant of clathrate hydrates with cyclopentylamine and methane were larger than that with cyclopropylamine and methane due to the effects of molecular size and shape.

• Korean Journal of Legislative Studies
• /
• v.25 no.3
• /
• pp.69-96
• /
• 2019

This paper is written to suggest several recommendations for South Korea to deter and defend North Korean nuclear threat, when North Korea does not seem to give up its nuclear weapons and the US's extended deterrence including the nuclear umbrella could remain uncertain. For this purpose, it explains key options regarding nuclear deterrence and defense by non-nuclear weapon state. It evaluates the current status of South Korean non-nuclear preparedness against North Korean nuclear threat and provides some recommendations to improve the preparedness. As a result, this paper concluded that South Korean non-nuclear preparedness against North Korean nuclear threat was not that reliable. The preparedness has weakened since the South Korean effort to denuclearize North Korea through negotiations in 2018. In this sense, South Korea could have serious problems in protecting its people from North Korean nuclear threat if the US promise of extended deterrence is not implemented. South Korea should focus on its decapitation operation to North Korean highest leaders in case of North Korean nuclear attack based on a minimal deterrence concept. It should be prepared to conduct preventive strikes instead of preemptive strikes due to North Korea's development of solid fuel ballistic missiles. It should integrate its Ballistic Missile Defense with that of the US forces in Korea. South Korea should make a sincere effort for nuclear civil defense including construction of nuclear shelters.

• Journal of the Korean Electrochemical Society
• /
• v.26 no.4
• /
• pp.43-55
• /
• 2023

Mass transport through nanoporous structures such as nanopores or nanochannels has fundamental electrochemical implications and many potential applications as well. These structures can be particularly useful for water treatment, energy conversion, biosensing, and controlled delivery of substances. Earlier research focused on creating nanopores with diameters ranging from tens to hundreds of nanometers that can selectively transport cationic or anionic charged species. However, recent studies have shown that nanopores with diameters of a few nanometers or even less can achieve more complex and versatile transport control. For example, nanopores that mimic biological channels can be functionalized with specific receptors to detect viruses, small molecules, and even ions, or can be made hydrophobic and responsive to external stimuli, such as light and electric field, to act as efficient valves. This review summarizes the latest developments in nanopore-based systems that can control mass transport based on the size of the nanopores (e.g., length, diameter, and shape) and the physical/chemical properties of their inner surfaces. It also provides some examples of practical applications of these systems.

• Korean Journal of Radiology
• /
• v.22 no.5
• /
• pp.770-781
• /
• 2021

Objective: Chemical exchange-dependent saturation transfer (CEST) MRI is sensitive for detecting solid-like proteins and may detect changes in the levels of mobile proteins and peptides in tissues. The objective of this study was to evaluate the characteristics of chemical exchange proton pools using the CEST MRI technique in patients with dementia. Materials and Methods: Our institutional review board approved this cross-sectional prospective study and informed consent was obtained from all participants. This study included 41 subjects (19 with dementia and 22 without dementia). Complete CEST data of the brain were obtained using a three-dimensional gradient and spin-echo sequence to map CEST indices, such as amide, amine, hydroxyl, and magnetization transfer ratio asymmetry (MTR_asym) values, using six-pool Lorentzian fitting. Statistical analyses of CEST indices were performed to evaluate group comparisons, their correlations with gray matter volume (GMV) and Mini-Mental State Examination (MMSE) scores, and receiver operating characteristic (ROC) curves. Results: Amine signals (0.029 for non-dementia, 0.046 for dementia, p = 0.011 at hippocampus) and MTR_asym values at 3 ppm (0.748 for non-dementia, 1.138 for dementia, p = 0.022 at hippocampus), and 3.5 ppm (0.463 for non-dementia, 0.875 for dementia, p = 0.029 at hippocampus) were significantly higher in the dementia group than in the non-dementia group. Most CEST indices were not significantly correlated with GMV; however, except amide, most indices were significantly correlated with the MMSE scores. The classification power of most CEST indices was lower than that of GMV but adding one of the CEST indices in GMV improved the classification between the subject groups. The largest improvement was seen in the MTR_asym values at 2 ppm in the anterior cingulate (area under the ROC curve = 0.981), with a sensitivity of 100 and a specificity of 90.91. Conclusion: CEST MRI potentially allows noninvasive image alterations in the Alzheimer's disease brain without injecting isotopes for monitoring different disease states and may provide a new imaging biomarker in the future.

• Journal of Life Science
• /
• v.34 no.6
• /
• pp.418-425
• /
• 2024

Solid tumors are heterogeneous populations of multiple cell types. While the majority of the cells that comprise cancer are unable to divide, cancer stem cells have self-renewal and differentiation properties. Normal stem cell pathways that control self-renewal are overactivated in cancer stem cells, making cancer stem cells important for cancer cell expansion and progression. Dick first proposed the definition of cancer stem cells in acute myeloid leukemia, according to which cancer stem cells can be classified based on the expression of cell surface markers. Cancer stem cells maintain their potential in the tumor microenvironment. Multiple cell types in the tumor microenvironment maintain quiescent cancer stem cells and serve as regulators of cancer growth. Since current cancer treatments target proliferative cells, quiescent state cancer stem cells that are resistant to treatment increase the risk of recurrence or metastasis. Various signals of the tumor microenvironment induce changes to become a tumor-supportive environment by remodeling the vasculature and extracellular matrix. To effectively treat cancer, cancer stem cells and the tumor microenvironment must be targeted. Therefore, it is important to understand how the tumor microenvironment induces reprogramming of the immune response to promote cancer growth, immune resistance, and metastasis. In this review, we discuss the cellular and molecular mechanisms that can enhance immunosuppression in the tumor microenvironment.

• Journal of Powder Materials
• /
• v.31 no.1
• /
• pp.16-22
• /
• 2024

Composite-based piezoelectric devices are extensively studied to develop sustainable power supply and self-powered devices owing to their excellent mechanical durability and output performance. In this study, we design a lead-free piezoelectric nanocomposite utilizing (Ba_0.85 Ca_0.15)(Ti_0.9Zr_0.1)O₃ (BCTZ) nanomaterials for realizing highly flexible energy harvesters. To improve the output performance of the devices, we incorporate porous BCTZ nanowires (NWs) into the nanoparticle (NP)-based piezoelectric nanocomposite. BCTZ NPs and NWs are synthesized through the solid-state reaction and sol-gel-based electrospinning, respectively; subsequently, they are dispersed inside a polyimide matrix. The output performance of the energy harvesters is measured using an optimized measurement system during repetitive mechanical deformation by varying the composition of the NPs and NWs. A nanocomposite-based energy harvester with 4:1 weight ratio generates the maximum open-circuit voltage and short-circuit current of 0.83 V and 0.28 ㎂, respectively. In this study, self-powered devices are constructed with enhanced output performance by using piezoelectric energy harvesting for application in flexible and wearable devices.

• Animal Bioscience
• /
• v.37 no.7
• /
• pp.1168-1176
• /
• 2024

Objective: As a charismatic species, cashmere goats have rich genetic resources. In the Inner Mongolia Autonomous Region, there are three cashmere goat varieties named and approved by the state. These goats are renowned for their high cashmere production and superior cashmere quality. Therefore, it is vitally important to protect their genetic resources as they will serve as breeding material for developing new varieties in the future. Methods: Three breeds including Inner Mongolia cashmere goats (IMCG), Hanshan White cashmere goats (HS), and Ujimqin white cashmere goats (WZMQ) were studied. IMCG were of three types: Aerbas (AEBS), Erlangshan (ELS), and Alashan (ALS). Nine DNA samples were collected for each population, and they were genomically re-sequenced to obtain high-depth data. The genetic diversity parameters of each population were estimated to determine selection intensity. Principal component analysis, phylogenetic tree construction and genetic differentiation parameter estimation were performed to determine genetic relationships among populations. Results: Samples from the 45 individuals from the five goat populations were sequenced, and 30,601,671 raw single nucleotide polymorphisms (SNPs) obtained. Then, variant calling was conducted using the reference genome, and 17,214,526 SNPs were retained after quality control. Individual sequencing depth of individuals ranged from 21.13× to 46.18×, with an average of 28.5×. In the AEBS, locus polymorphism (79.28) and expected heterozygosity (0.2554) proportions were the lowest, and the homologous consistency ratio (0.1021) and average inbreeding coefficient (0.1348) were the highest, indicating that this population had strong selection intensity. Conversely, ALS and WZMQ selection intensity was relatively low. Genetic distance between HS and the other four populations was relatively high, and genetic exchange existed among the other four populations. Conclusion: The Inner Mongolia cashmere goat (AEBS type) population has a relatively high selection intensity and a low genetic diversity. The IMCG (ALS type) and WZMQ populations had relatively low selection intensity and high genetic diversity. The genetic distance between HS and the other four populations was relatively high, with a moderate degree of differentiation. Overall, these genetic variations provide a solid foundation for resource identification of Inner Mongolia Autonomous Region cashmere goats in the future.

• Clean Technology
• /
• v.30 no.1
• /
• pp.1-12
• /
• 2024

Nanoplastics (NP) exhibit distinct material properties compared to microplastics (MP), necessitating their separate recognition. Review of research outcomes and policy documents on NP reveals that most policy frameworks predominantly define MPs as solid synthetic polymer materials measuring 5 mm or less, but do not distinguish them from NP. However, recent revisions in regulations by the EU classify NPs as particles that range in size from 1 to 1,000 nm, as confirmed by some academic studies. Research on NPs often relies on experimental investigations centered around water systems, with a focus on high-concentration experimental conditions using spherical polystyrene-based NPs in behavior and impact studies. Notably, the environmental behavior characteristics of NP show differences in influence depending on the NP type, emphasizing the need for field simulation research. These challenges are mirrored in Korean society, so it is necessary to redefine NP to be distinct from MP in both research and policy. This study aimed to assess the current state of NP management globally and domestically and highlight policy considerations and issues in the existing response to NP. Upon comprehensive review, it becomes apparent that reaching an international agreement on MP faces methodological limitations, which could potentially burden efforts to precisely define NP size. Therefore, referencing the EU's recent regulatory revisions is crucial in domestic policy. Specific adjustments should commence from the MP concept through insights from the domestic industry, guidance from the academic community, and thorough discussions to ensure social acceptance.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.34 no.4
• /
• pp.125-130
• /
• 2024

Preparation of ferromagnetic powders for the mixture of hematite and pure Mg powders by ball milling has been investigated. Also, consolidation of the ball-milled powders was performed in a spark plasma sintering machine at 800-1,000℃. It is found that a ferromagnetic Fe-MgO composite powders are obtained by ball milling of hematite and pure Mg powders before 1 hour. The magnetization and coercivity of ball-milled samples change at the results of the solid state reaction of hematite by pure Mg during ball milling. The saturation magnetization of ball-milled samples increases with increasing ball milling time and reaches to a maximum value of 93.4 emu/g after 5 hours of ball milling. Shrinkage change after sintering of ball-milled sample for 5 hours was significant above 300℃ and gradually increased with increasing temperature up to 800℃. X-ray diffraction result shows that the average grain size of Fe in Fe-MgO bulk sample sintered at 900℃ is 50 nm. It can be also seen that the coercivity of bulk sample sintered at 900℃ is still high value of 90 Oe, indicating that the grain growth of magnetic Fe phase during sintering process tend to be suppressed.

• Therapeutic Science for Rehabilitation
• /
• v.13 no.3
• /
• pp.69-83
• /
• 2024

Objective : This study investigated the prevalence of dysphagia in older adults in Gangwon Special Self-Governing Province and its impact on Quality of Life (QoL) and educational needs. Methods : A cross-sectional survey was conducted from August 1 to 15, 2023, with 207 cognitively normal older adults from three senior welfare centers. Data included general characteristics, Korean-version of the Eating Assessment Tool (K-EAT-10), Swallowing-QoL, and educational needs related to swallowing disorders. Dysphagia was defined by a K-EAT-10 score of 3 or higher. Participants were divided into normal and risk groups for analysis using chi-square and Independent t-test. Results : The prevalence of dysphagia risk (K-EAT-10 score of 3 or higher) was 41.5% (86 individuals). Among the 92 individuals reporting dysphagia symptoms, 64 (69.6%) were at risk. QoL was significantly lower in the risk group, especially among those living alone or with denture discomfort. The most preferred educational need was training in eating solid foods (Mean = 4.27), with higher needs in the dysphagia risk group. Conclusion : This study underscores the prevalence of dysphagia, its impact on QoL, and the need for educational programs. Emphasizing prevention, public awareness, and early detection, along with the role of dysphagia rehabilitation experts and community collaboration, is essential for supporting healthy aging.