286 research outputs found
Enhancing shock wave energy dissipation in metallosupramolecular polymer by tuning metal-imidazole coordination interactions
No full textThe development of materials capable of shock wave energy dissipation (SWED) is critical for modern protective applications. In this study, metallosupramolecular poly(dimethylsiloxane) (PDMS) networks cross-linked with Zn2+, Cu2+, and Ni2+ ions and imidazole ligands were designed to enhance SWED by leveraging the dynamic nature of metal-ligand coordination bonds. A laser-induced shock wave technique revealed that Cu2+ cross-linked PDMS exhibited superior SWED performance, likely due to coordination rearrangement dynamics occurring within a relevant timescale for shock wave dissipation. Time-temperature superposition (TTS) analysis indicated that while associative ligand exchange may assist in shock attenuation, metal-ligand bond dissociation plays a more dominant role under extreme shock conditions. DFT calculations further demonstrated that coordination geometry significantly influences SWED performance, with Cu2+ in square planar (trans) coordination exhibiting greater rupture susceptibility. These findings highlight the tunability of metal-ligand interactions as an effective strategy for optimizing energy dissipation in metallosupramolecular polymers. Additionally, they provide a comprehensive SWED mechanism analysis by synergistically integrating a laser-induced shock wave test and DFT calculations.
Formyl peptide receptors in the mucosal immune system
No full textFormyl peptide receptors: Receptors in the mucosal immune system Key receptors in defense against bacteria may also be attractive targets for diseases of the mucosa, the tissue that lines and protects areas such as the airways and gastrointestinal tract. Formyl peptide receptors (FPRs) detect substances produced by bacteria and host cells triggering immune or wound-healing responsesYoe-Sik Bae and Yu Sun Jeong at Sungkyunkwan University, Suwon, South Korea, have reviewed how FPRs in the mucosa mediate the immune response. They report that FPRs play many roles, promoting wound closure, enhancing fibrosis of tissues, and promoting or suppressing inflammation in various tissues. FPRs may also be involved in conditions such as Crohn’s disease and asthma. Further study may reveal opportunities for development of FPRs as therapeutic targets in mucosal diseases
Thermomechanical Behavior of Intramolecular Cross-linked Thermoplastics
No full textPolymers are materials composed of a large number of macromolecular chains, exhibiting a broad range of thermomechanical properties. Polymer properties are determined by interactions between chains and interactions between monomers within individual chains. Since these two different types of interactions, intermolecular and intramolecular, can be tuned, polymers exhibit a broad range of properties. For example, poly(methylmethacrylate) and poly(urethane) have different monomers and exhibit different properties. These interactions are dependent on the conformation of chains as well as monomer chemistry, molecular weight, etc. Creating covalent cross-links between different macromolecular chains changes the configuration of chains and inter- and intramolecular interactions. However, intermolecular cross-linking changes material processability as well as its underlying structure. Intermolecular cross-linking results in thermosets, polymers that are not thermally processable or reprocessable. In contrast to intermolecular cross-linking, intramolecular cross-linking literally creates a cross-link within a single macromolecular chain. While this intramolecular cross-linking has been widely studied on single macromolecular chains because of its precise control of chain morphology and ability to generate small polymer nanoparticles, the effects of intramolecular cross-linking in bulk polymers in the solid state have attracted little attention. In this dissertation we characterize the structure-dependent properties of polymers assembled solely from intramolecular cross-linked macromolecular chains. We adopt intramolecular cross-linking as a means of changing the underlying structure of polymers while keeping the polymers as thermoplastics. This class of polymeric materials are investigated by molecular modeling and simulations and synthesis and experiments. Firstly, we study the effects of intramolecular cross-linking on individual, independent macromolecular chains by using a molecular dynamics (MD) model. MD models of different cross-linking degrees are generated and used to study the effects of intramolecular cross-linking on size, shape, chain mobility/dynamics, and mechanics of individual, independent intramolecular cross-linked chains in vacuum. Our simulations demonstrate that the higher the CL degree, the less mobile the monomers of single cross-linked chains, and the stiffer and more rigid the chains. Individual, independent cross-linked chains are studied only by MD modeling and simulations. Next, we extend our research to studying the effects of intramolecular cross-linking on the thermomechanical properties of bulk polymers. We build MD models representative of bulk polymers made from the assembly of intramolecular cross-linked chains by using MD models of single intramolecular cross-linked chains as building blocks. These MD models, representative of bulk polymers, are studied in terms of chain topology and thermomechanical properties. In addition to modeling and simulation, we mechanically characterize by experiments the same class of materials, synthesized by collaborating chemists. These materials are analyzed by uniaxial tensile tests and cyclic tests. We find from simulations and experiments that the higher the CL degree, the less unfolded and entangled the macromolecular chains are in bulk polymers. These differences in the underlying structure due to intramolecular cross-linking result in tailored thermomechanical properties. We find that the material becomes stiffer, stronger, and more brittle at the glassy state, and stiffer, stronger, and more stretchable at the rubbery state with increasing CL degree. Our simulation results are vital in explaining the mechanisms underlying these enhanced mechanical properties
Laboratory and pilot-scale field experiments for application of iron oxide nanoparticle-loaded chitosan composites to phosphate removal from natural water
No full textThe aim of this study was to apply iron oxide nanoparticle-chitosan (ION-chitosan) composites to phosphate removal from natural water collected from the Seoho Stream in Suwon, Republic of Korea. Laboratory batch experiments showed that phosphate removal by the ION-chitosan composites was not sensitive to pH changes between pH values of 5.0 and 9.0. During six cycles of adsorption–desorption, the composites could be successfully regenerated with 5 mM NaOH solution and reused for phosphate removal. Laboratory fixed-bed column experiments (column height = 10 and 20 cm, inner diameter = 2.5 cm, flow rate = 8.18 and 16.36 mL/min) demonstrated that the composites could be successfully applied for phosphate removal under dynamic flow conditions. A pilot-scale field experiment was performed in a pilot plant, which was mainly composed of chemical reactor/dissolved air flotation and an adsorption tower, built nearby the Seoho Stream. The natural water was pumped from the Seoho Stream into the pilot plant, passed through the chemical reactor/dissolved air flotation process, and then introduced into the adsorption tower (height = 100 cm, inner diameter = 45 cm, flow rate = 7.05 ± 0.18 L/min) for phosphate removal via the composites (composite volume = 80 L, composite weight = 85.74 kg). During monitoring of the adsorption tower (33 days), the influent total phosphorus (T-P) concentration was in the range of 0.020–0.046 mgP/L, whereas the effluent T-P concentration was in the range of 0.010–0.028 mgP/L. The percent removal of T-P in the adsorption tower was 52.3% with a phosphate removal capacity of 0.059 mgP/g. © 2017 Informa UK Limited, trading as Taylor & Francis GroupOAIID:RECH_ACHV_DSTSH_NO:T201815714RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A075960CITE_RATE:1.666DEPT_NM:조경·지역시스템공학부EMAIL:[email protected]_YN:YN
Immobilization of layered double hydroxide in poly(vinylidene fluoride)/poly(vinyl alcohol) polymer matrices to synthesize bead-type adsorbents for phosphate removal from natural water
No full textLayered double hydroxide (LDH) has been widely used as an adsorbent to remove contaminants from aqueous solutions. However, LDH in powder form might not be suitable in water and wastewater treatment systems due to low hydraulic conductivity and sludge production. Therefore, it is necessary to synthesize bead-type adsorbents for application in treatment systems. In this study, LDH beads were prepared through immobilization of powdered Mg-Fe LDH in polymer matrices, composed of poly(vinylidene fluoride) and poly(vinyl alcohol). The LDH beads had an average size of 2.4 +/- 0.6 mm with a Brunauer-Emmett-Teller (BET) specific surface area of 30.41 m(2)/g and total pore volume of 0.12 cm(3)/g. Batch experiments were conducted on the use of the LDH beads for phosphate sorption in stream water (pH = 6.9, ionic strength = 613 mu S/cm) collected from the Seoho stream located in Suwon, Korea. Fourier-transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS) were used to analyze the chemical characteristics of the LDH beads before and after phosphate sorption. Phosphate sorption to the LDH beads remained relatively constant at initial pH values of 5-9. The LDH beads could be used repeatedly for phosphate sorption through desorption with a NaOH solution. The equilibrium time for the phosphate sorption was 3 h, whereas the maximum sorption capacity was 2.050 mgP/g. In addition, the phosphate sorption increased with a rise in temperature from 15 to 45 degrees C. Under dynamic flow conditions (flow rate = 4.9 and 9.8 mL/min; bed depth = 10, 20, and 30 cm; inner diameter of column = 2.5 cm), fixed-bed column experiments were performed to test the applicability of the LDH beads in the phosphate removal from the stream water. The phosphate sorption capacity of the column was quantified to be 1.175 mgP/g at given experimental conditions (bed depth = 30 cm; flow rate = 4.9 mL/min). The performance of fixed-bed columns was quantified by analyzing phosphate breakthrough curves with fixed-bed kinetic sorption models (Bohart-Adams and modified dose-response models). This study demonstrated that the LDH beads could be successfully applied as adsorbents for phosphate removal from natural water.N
Effects of ATF cladding properties on PWR responses to an SBO accident: A sensitivity analysis
No full textTo investigate the effects of ATF cladding properties on the plant responses to severe accidents, shortterm station blackout simulations and sensitivity analyses on hypothetical cladding materials were performed using MAAP code. For sensitivity analyses, 7 hypothetical cladding materials were used. Hypo-0 was the reference cladding whose properties are anticipated to show the poorest fuel performance during an STSBO. The input property values for Hypo-1 through Hypo-6 were selected by changing each variable independently while keeping the others at their reference values. The onset times for core uncovery and cladding oxidation were similar for all the simulation cases, implying that single property cannot affect the event times. A main conclusion is that a large enthalpy of cladding can delay the increase in temperatures of fuel and cladding by playing a role as a heat sink after the core uncovery occurs, resulting in the delayed hot leg rupture. (c) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Impact of statins on risk of new onset diabetes mellitus: a population-based cohort study using the Korean National Health Insurance claims database
No full textJimin Lee,1 Yoojin Noh,1 Sooyoung Shin,1 Hong-Seok Lim,2 Rae Woong Park,3 Soo Kyung Bae,4 Euichaul Oh,4 Grace Juyun Kim,5 Ju Han Kim,5 Sukhyang Lee1 1Division of Clinical Pharmacy, College of Pharmacy, Ajou University, Suwon, South Korea; 2Department of Cardiology, School of Medicine, Ajou University, Suwon, South Korea; 3Department of Biomedical Informatics, School of Medicine, Ajou University, Suwon, South Korea; 4Division of Pharmaceutical Sciences, College of Pharmacy, The Catholic University of Korea, Bucheon, South Korea; 5Division of Biomedical Informatics, College of Medicine, Seoul National University, Seoul, South Korea Abstract: Statin therapy is beneficial in reducing cardiovascular events and mortalities in patients with atherosclerotic cardiovascular diseases. Yet, there have been concerns of increased risk of diabetes with statin use. This study was aimed to evaluate the association between statins and new onset diabetes mellitus (NODM) in patients with ischemic heart disease (IHD) utilizing the Korean Health Insurance Review and Assessment Service claims database. Among adult patients with preexisting IHD, new statin users and matched nonstatin users were identified on a 1:1 ratio using proportionate stratified random sampling by sex and age. They were subsequently propensity score matched further with age and comorbidities to reduce the selection bias. Overall incidence rates, cumulative rates and hazard ratios (HRs) between statin use and occurrence of NODM were estimated. The subgroup analyses were performed according to sex, age groups, and the individual agents and intensities of statins. A total of 156,360 patients (94,370 in the statin users and 61,990 in the nonstatin users) were included in the analysis. The incidence rates of NODM were 7.8% and 4.8% in the statin users and nonstatin users, respectively. The risk of NODM was higher among statin users (crude HR 2.01, 95% confidence interval [CI] 1.93–2.10; adjusted HR 1.84, 95% CI 1.63–2.09). Pravastatin had the lowest risk (adjusted HR 1.54, 95% CI 1.32–1.81) while those who were exposed to more than one statin were at the highest risk of NODM (adjusted HR 2.17, 95% CI 1.93–2.37). It has been concluded that all statins are associated with the risk of NODM in patients with IHD, and it is believed that our study would contribute to a better understanding of statin and NODM association by analyzing statin use in the real-world setting. Periodic screening and monitoring for diabetes are warranted during prolonged statin therapy in patients with IHD. Keywords: Atorvastatin, Fluvastatin, Lovastatin, Rosuvastatin, Pitavastatin, Pravastatin, Simvastatin, Ischemic heart disease, IHD, new onset diabetes mellitus, NOD
A hybrid machine learning approach to investigate the changing urban thermal environment by dynamic land cover transformation: A case study of Suwon, republic of Korea
No full textUrban thermal environment should be analyzed by considering the dynamic structural changes as cities grow both horizontally and vertically. Local Climate Zone (LCZ) scheme can describe built-up areas in detail, mainly based on density and height; however, the low overall accuracy of LCZ urban classes (OAurb) remains a notable limitation that requires improvement. This study proposes a hybrid analytical method considering bidirectional urban expansion and low OAurb. Temporal LCZ maps were constructed using a convolutional neural network to observe the dynamic urban growth between 2004 and 2021 in Suwon, South Korea. Unlike previous LCZ mapping studies, we utilized the additional information provided by deep learning through softmax-based probability maps. Random forest-based downscaling models were developed by combining various auxiliary variables related to the Land Surface Temperature (LST) to observe the detailed surface energy flux. A filtering method was then employed by eliminating areas where LCZs were identified with a low confidence level using extracted probability maps. Finally, thermal variability was investigated by overlaying the filtered LCZ maps and the corresponding LST. The produced LCZ maps and spatially downscaled LSTs accurately depicted dynamic urban form changes, with the LCZ maps exhibiting an average overall accuracy of approximately 90% and downscaled LSTs showing an average coefficient of determination of ∼ 0.9 and a root mean square error of 0.7 °C. Thermal variability occurring due to structural transitions varied in magnitude depending on the height and density of the buildings, while exhibiting a maximum and minimum value of 2.8 °C and − 2.2 °C, respectively. By selecting reliably classified areas, the proposed filtering method produced more rational results than the original non-filtering method, resulting in higher variability from − 0.4 °C to 0.6 °C
Metabolomic Analysis of Morus Cultivar Root Extracts and Their Ameliorative Effect on Testosterone-Induced Prostate Enlargement in Sprague-Dawley Rats
No full textWe investigated the metabolite changes of Morus roots (MRs) according to different cultivar families (Simheung, Daesim, Cheong-il, Sangchon, Daeseong, Suhong, Suwon, and Igsu) using ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC–QTOF-MS) to understand the relationship between different cultivars and metabolite changes. Data were analyzed by partial least squares discriminant analysis (PLS-DA), and samples were successfully separated in PLS-DA scores. Eight metabolites in the electrospray ionization (ESI)-positive mode and 16 metabolites in the ESI-negative mode contributed to the separation in PLS-DA. Our data suggest that comparative analysis of MR metabolites according to different cultivars is useful to better understand the relationship between the different cultivars and metabolite changes. Furthermore, we analyzed the MRs for their ability to improve benign prostatic hyperplasia (BPH). LNCaP cells were used to evaluate the prostate-specific antigen (PSA) inhibitory activity of MRs, and, amongst them, the extract with the highest activity was selected. Igsu demonstrated the highest inhibition effect of prostate-specific antigen (PSA) expression among the MR cultivars. Igsu was also evaluated by administration in a testosterone-induced benign prostatic hyperplasia model in Sprague-Dawley rats. Igsu was shown to ameliorate BPH as evidenced by the prostate index, expression of androgen receptor (AR) signaling-related protein, growth factors, cell proliferation-related proteins, apoptosis-related proteins, mitogen-activated protein kinase (MAPK) signaling proteins, and histological analysis. Hence, this study strongly suggests that Igsu may have a beneficial effect of on BPH
Chain Redistribution Stabilizes Coexistence Phases in Block Copolymer Blends
No full textThe nanoscale morphologies of block copolymer (BCP) thin
films
are determined by chain architecture. Experimental studies of thin
film blends of different BCP chain types have demonstrated that blending
can stabilize new motifs, such as coexistence phases. Here, we deploy
coarse-grained molecular dynamics (MD) simulations in order to better
understand the self-assembly behavior of BCP blend thin films. We
consider blends of lamella- and cylinder-forming BCP chains, studying
their morphological makeup, the chain distribution within the morphology,
and the underlying polymer chain conformations. Our simulations show
that there are local concentration deviations at the scale of the
morphological objects that dictate the local structure, and that BCP
chains redistribute within the morphology so as to stabilize the structure.
Underlying these effects are measurable distortions in the BCP chain
conformations. The conformational freedom afforded by BCP blending
stabilizes defects and allows coexistence phases to appear, while
also leading to kinetic trapping effects. These results highlight
the power of blending in designing the morphology that forms
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