Publications by authors named "Young Ki Kim"

86 Publications

Asbestos Exposure Level and the Carcinogenic Risk Due to Corrugated Asbestos-Cement Slate Roofs in Korea.

Int J Environ Res Public Health 2021 Jun 28;18(13). Epub 2021 Jun 28.

Department of Occupational and Environmental Medicine, Pusan National University Yangsan Hospital, Yangsan 50612, Korea.

Asbestos-cement slate roofs are one of the most common environmental causes of asbestos exposure. However, few studies have examined residential asbestos-cement slate-related exposure and its effects on human health. This study was performed to evaluate cumulative asbestos exposure levels and to calculate the Excess Lifetime Cancer Risk (ELCR) of residents of asbestos-cement slate-roofed houses. We reviewed previous Korean literature to estimate the concentration of airborne asbestos from asbestos-cement slate roofed buildings. Finally, eight studies were selected, and a pooled analysis was performed. The results derived from the pooled analysis were combined with the data from a health impact survey conducted from 2009 to 2016 at the Environmental Health Center for Asbestos (EHCA) of the Yangsan Pusan National University Hospital, and a carcinogenic risk assessment was performed. As a result, the representative value of the indoor exposure concentration related to asbestos-cement slate was found to be 0.0032 f/cc on average, and the representative value of the exposure related to occupational asbestos-cement slate dismantling and demolition was found to be 0.0034 f/cc. In addition, the ELCR of asbestos-cement slate related indoor exposure and occupational dismantling and demolition was found to be of medium risk, and the ELCR of residential dismantling and demolition of asbestos-cement slate was less than 10, indicating that the risk was low. Since there is no threshold for carcinogenicity related to asbestos, this should not be ignored even if the risk appears low, and it would be reasonable to calculate the carcinogenic risk based on total lifetime exposure. More studies on asbestos exposure scenarios and the scope of similar exposure groups through additional data collection and further analysis of risk are needed.
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http://dx.doi.org/10.3390/ijerph18136925DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8297172PMC
June 2021

Holographic metasurface gas sensors for instantaneous visual alarms.

Sci Adv 2021 Apr 7;7(15). Epub 2021 Apr 7.

Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.

The rapid detection of biological and chemical substances in real time is particularly important for public health and environmental monitoring and in the military sector. If the process of substance detection to visual reporting can be implemented into a single miniaturized sensor, there could be a profound impact on practical applications. Here, we propose a compact sensor platform that integrates liquid crystals (LCs) and holographic metasurfaces to autonomously sense the existence of a volatile gas and provide an immediate visual holographic alarm. By combining the advantage of the rapid responses to gases realized by LCs with the compactness of holographic metasurfaces, we develop ultracompact gas sensors without additional complex instruments or machinery to report the visual information of gas detection. To prove the applicability of the compact sensors, we demonstrate a metasurface-integrated gas sensor on safety goggles via a one-step nanocasting process that is attachable to flat, curved, and flexible surfaces.
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http://dx.doi.org/10.1126/sciadv.abe9943DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8026120PMC
April 2021

Efficient perovskite solar cells via improved carrier management.

Nature 2021 02 24;590(7847):587-593. Epub 2021 Feb 24.

Division of Advanced Materials, Korea Research Institute of Chemical Technology, Daejeon, Republic of Korea.

Metal halide perovskite solar cells (PSCs) are an emerging photovoltaic technology with the potential to disrupt the mature silicon solar cell market. Great improvements in device performance over the past few years, thanks to the development of fabrication protocols, chemical compositions and phase stabilization methods, have made PSCs one of the most efficient and low-cost solution-processable photovoltaic technologies. However, the light-harvesting performance of these devices is still limited by excessive charge carrier recombination. Despite much effort, the performance of the best-performing PSCs is capped by relatively low fill factors and high open-circuit voltage deficits (the radiative open-circuit voltage limit minus the high open-circuit voltage). Improvements in charge carrier management, which is closely tied to the fill factor and the open-circuit voltage, thus provide a path towards increasing the device performance of PSCs, and reaching their theoretical efficiency limit. Here we report a holistic approach to improving the performance of PSCs through enhanced charge carrier management. First, we develop an electron transport layer with an ideal film coverage, thickness and composition by tuning the chemical bath deposition of tin dioxide (SnO). Second, we decouple the passivation strategy between the bulk and the interface, leading to improved properties, while minimizing the bandgap penalty. In forward bias, our devices exhibit an electroluminescence external quantum efficiency of up to 17.2 per cent and an electroluminescence energy conversion efficiency of up to 21.6 per cent. As solar cells, they achieve a certified power conversion efficiency of 25.2 per cent, corresponding to 80.5 per cent of the thermodynamic limit of its bandgap.
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http://dx.doi.org/10.1038/s41586-021-03285-wDOI Listing
February 2021

Relationship Between Job Training and Subjective Well-being In Accordance With Work Creativity, Task Variety, and Occupation.

Saf Health Work 2020 Dec 1;11(4):466-478. Epub 2020 Sep 1.

Department of Occupational and Environment Medicine, Pusan National University Yangsan Hospital, Yangsan, Gyongnam, Republic of Korea.

Background: Job training influences the overall working environment and worker's well-being. The purpose of this study is to find the relationship between job training and subjective well-being in accordance with occupations and understand the influence of task characteristics-work creativity and task variety (WCTV)-on the effect of training.

Methods: A cross-sectional study based on the Fifth Korean Working Conditions Survey was conducted on 50,205 workers in the Republic of Korea. The World Health Oorganization-5 well-being index was used to measure their subjective well-being. The relationship between job training and subjective well-being was divided in accordance with the level of WCTV.

Results: Training paid for by employer showed a negative effect on subjective well-being when received for more than 3 days (OR 0.88, 0.01) in the last 12 months. Training paid for by oneself showed a positive linkage with well-being when the level of training was 1-3 days (Odds ratio = 1.55, 0.001). This result showed different aspects in accordance with the level of WCTV. For the high WCTV group, the aforementioned results were reaffirmed, but for the group with low WCTV, job training did not show a statistically significant result on well-being. On-the-job training was not related to subjective well-being regardless of the level of WCTV.

Conclusion: Job training had different effects on subjective well-being depending on the type and frequency of training, as well as the WCTV. It is imperative to comprehensively apply different types of job training in accordance with the characteristics of occupations to uplift workers' well-being.
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http://dx.doi.org/10.1016/j.shaw.2020.08.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7728823PMC
December 2020

Stimuli-Responsive Dynamic Metaholographic Displays with Designer Liquid Crystal Modulators.

Adv Mater 2020 Dec 10;32(50):e2004664. Epub 2020 Nov 10.

Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea.

Flat optics, realized by the artificially created 2D material platform called optical metasurfaces, is currently undergoing a science-to-technology transition. However, "real-time" active operations of such flat optical devices remain yet unresolved. Here, liquid crystals (LCs)-integrated metaholograms for ultracompact dynamic holographic displays are proposed. The anisotropic nature of the LCs allows facile and repeatable manipulation of the polarization of light. Specifically designed ("designer") LCs and efficient helicity-encoded metaholograms are combined to realize stimuli-responsive dynamic displays. The designer LC modulators are used as switches that enable a variety of external stimuli (e.g., electric field, heat, surface pressure) to operate holographic images in real-time. Such a dynamic metaholographic platform will provide a path to external stimuli-driven "smart" sensing and display applications such as hologram labels for temperature/pressure/touch monitoring and interactive holographic displays with haptic motion recognition.
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http://dx.doi.org/10.1002/adma.202004664DOI Listing
December 2020

Comparison of Biochemical Constituents and Contents in Floral Nectar of spp.

Molecules 2020 Sep 15;25(18). Epub 2020 Sep 15.

Department of Life Sciences & Convergence Research Center for Insect Vectors, Incheon National University, 199 Academy-ro, Incheon 22012, Korea.

Pollination is essential for efficient reproduction in pollinator-dependent crops that rely on the attraction of pollinators to flowers. Especially, floral nectar is considered to be an important factor attracting pollinator like honey bees, but differences among major chestnut species (, , , and ) are still little explored. This study aims to evaluate the value of honey source by analyzing floral nectar characteristics and comparing the composition of volatile organic compounds (VOCs) that mediate plant-pollinator interaction. In this study, we analyzed nectar samples obtained from male flowers using HPLC and HS-SPME/GC-MS. The five chestnuts showed significant differences between the volume of secreted nectar, free sugar composition, amino acid content and VOCs composition. Furthermore, (Japanese cultivar 'Ungi') was revealed to emit the highest total amounts of VOCs and high levels of benzenoid compounds that are generally associated with flower-visiting insects. The sugar content per catkin, which is used to determine the honey yield, was the highest in , suggesting that 'Ungi' can be highly valued as a honey tree. Therefore, a better understanding of the relationship between pollinator and nectar characteristics of could contribute to a prospective honey plant.
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http://dx.doi.org/10.3390/molecules25184225DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7570523PMC
September 2020

Structural and Optical Response of Polymer-Stabilized Blue Phase Liquid Crystal Films to Volatile Organic Compounds.

ACS Appl Mater Interfaces 2020 Sep 8;12(37):42099-42108. Epub 2020 Sep 8.

Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States.

Engineering useful mechanical properties into stimuli-responsive soft materials without compromising their responsiveness is, in many cases, an unresolved challenge. For example, polymer networks formed within blue-phase liquid crystals (BPs) have been shown to form mechanically robust films, but the impact of polymer networks on the response of these soft materials to chemical stimuli has not been explored. Here, we report on the response of polymer-stabilized BPs (PSBPs) to volatile organic compounds (VOCs, using toluene as a model compound) and compare the response to BPs without polymer stabilization and to polymerized nematic and cholesteric phases. We find that PSBPs generate an optical response to toluene vapor (change in reflection intensity under crossed polars) that is sixfold greater in sensitivity than the polymerized nematic or cholesteric phases and with a limit of detection (140 ± 10 ppm at 25 °C) that is relevant to the measurement of permissible exposure limits for humans. Additionally, when compared to BPs that have not been polymerized, PSBPs respond to a broader range of toluene vapor concentrations (5000 vs <1000 ppm) over a wider temperature interval (25-45 vs 45-53 °C). We place these experimental observations into the context of a simple thermodynamic model to explore how the PSBP response reflects the effect of toluene on competing contributions of double-twisted LC cylinders, disclinations, and polymer network to the free energy that controls the PSBP lattice spacing. Overall, we conclude that the mechanical and thermal stability of PSBPs, when combined with their optical responsiveness to toluene, make this class of self-supporting LCs a promising one as the basis of passive and compact (e.g., wearable) sensors for VOCs.
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http://dx.doi.org/10.1021/acsami.0c11138DOI Listing
September 2020

Characterization of surface anchoring energy of nematic liquid crystals via electrohydrodynamic instability.

Phys Rev E 2020 Jun;101(6-1):062703

Department of Physics, Yeungnam University, 280 Daehak-Ro, Gyeongsan 38541, Republic of Korea.

Herein, a method is proposed to determine the azimuthal anchoring energies of surface liquid crystals (LCs), as they gradually change orientation from a vertical to a horizontal state owing to an increase in the voltage applied to each LC cell. The LC cells are characterized using the direction of the Williams roll pattern related to the midplane LC director of the conduction regime of the electrohydrodynamic convection patterns of LCs. The application of the midplane LC directions, obtained from the direction of the roll patterns, to the Ericksen-Leslie equation produces the precise values of the surface anchoring strength. The hybrid type 90°-twisted nematic LC cell, composed of homeotropic and homogeneous LC alignment layers on the top and bottom substrates, respectively, was used to find the azimuthal anchoring energy of the surface LCs, indicated by voltages at the initially vertically aligned LC state. It was observed that the surface azimuthal anchoring energy on the homeotropic layer increased with an increase in voltage. We expect that the proposed technique may be excellent in terms of ease of use, simplicity, and accuracy because the azimuthal anchoring energy can be visually evaluated through the roll pattern.
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http://dx.doi.org/10.1103/PhysRevE.101.062703DOI Listing
June 2020

Antioxidant and Antibacterial Properties of Hovenia () Monofloral Honey Produced in South Korea.

Food Sci Anim Resour 2020 Mar 1;40(2):221-230. Epub 2020 Mar 1.

Department of Nano-Bioengineering, Incheon National University, Incheon 22012, Korea.

The aim of this study was to evaluate the antioxidant and antibacterial activity of Hovenia () monofloral honey produced in Korea. To produce Hovenia monofloral honey, Hovenia trees were surrounded by a net house, and honeybees were breed there over a 20-day period. Hovenia monofloral honey contained more than 95% of Hovenia pollen and showed physicochemical properties in agreement with the international honey standard (Codex). The total phenolic and flavonoid contents of Hovenia monofloral honey ranged from a 24.82-27.00 mg gallic acid equivalent/100 g honey and a 0.41-0.46 mg quercetin equivalent/100 g honey, respectively. In addition, to evaluate the functional properties of Hovenia monofloral honey, the antioxidant activity of Hovenia monofloral honey was estimated by using the 1,1-diphenyl-2-picrylhydrazyl radical and the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assay. Furthermore, Hovenia monofloral honey showed an antibacterial activity against foodborne gram positive ( and ) and gram negative bacteria ( Typhimurium and O157:H7).
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http://dx.doi.org/10.5851/kosfa.2020.e6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7057034PMC
March 2020

Optical "Blinking" Triggered by Collisions of Single Supramolecular Assemblies of Amphiphilic Molecules with Interfaces of Liquid Crystals.

J Am Chem Soc 2020 04 18;142(13):6139-6148. Epub 2020 Mar 18.

Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States.

We report that incubation of aqueous dispersions of supramolecular assemblies formed by synthetic alkyl triazole-based amphiphiles against interfaces of thermotropic liquid crystals (LCs; 4-cyano-4'-pentylbiphenyl) triggers spatially localized (micrometer-scale) and transient (subsecond) flashes of light to be transmitted through the LC. Analysis of the spatiotemporal response of the LC supports our proposal that each optical "blinking" event results from collision of a single supramolecular assembly with the LC interface. Particle tracking at the LC interface confirmed that collision and subsequent spreading of amphiphiles at the interface generates a surface pressure-driven interfacial flow (Marangoni flow) that causes transient reorientation of LC and generation of a bright optical flash between crossed polarizers. We also found that dispersions of phospholipid vesicles cause "blinks". When using vesicles formed from 1,2-dilauroyl--glycero-3-phosphocholine (DLPC), we measured the frequency of blinking to decrease proportionally with the number density of vesicles in the aqueous phase, consistent with single vesicle events, with the lifetime of each blink dependent on vesicle size (800 ± 80 nm to 150 ± 30 nm). For 100 μM of DLPC, we measured vesicles with a diameter of 940 ± 290 nm to generate 47 ± 9 blinks min mm, revealing that the fraction of vesicle collisions resulting in fusion with the LC interface is ∼10. Overall, the results in this paper unmask new nonequilibrium behaviors of amphiphiles at LC interfaces, and provide fresh approaches for exploring the dynamic interactions of supramolecular assemblies of amphiphiles with fluid interfaces at the single-event level.
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http://dx.doi.org/10.1021/jacs.9b13360DOI Listing
April 2020

A New Strategy for Reporting Specific Protein Binding Events at Aqueous-Liquid Crystal Interfaces in the Presence of Non-Specific Proteins.

ACS Appl Mater Interfaces 2020 Feb 7;12(7):7869-7878. Epub 2020 Feb 7.

Smith School of Chemical and Biomolecular Engineering , Cornell University , Ithaca , New York 14853 , United States.

Aqueous-liquid crystal (LC) interfaces offer promise as responsive interfaces at which biomolecular recognition events can be amplified into macroscopic signals. However, the design of LC interfaces that distinguish between specific and non-specific protein interactions remains an unresolved challenge. Herein, we report the synthesis of amphiphilic monomers, dimers, and trimers conjugated to sulfonamide ligands via triazole rings, their assembly at aqueous-LC interfaces, and the orientational response of LCs to the interactions of carbonic anhydrase II (CAII) and serum albumin with the oligomer-decorated LC interfaces. Of six oligomers synthesized, only dimers without amide methylation were found to assemble at aqueous interfaces of nematic 4-cyano-4'-pentylbiphenyl (5CB) to induce perpendicular LC orientations. At dimer-decorated LC interfaces, we found that concentrations of CAII less than 4 μM did not measurably perturb the LC but prevented non-specific adsorption and penetration of serum albumin into the dimer-decorated interface that otherwise triggered bright, globular LC optical domains. These experiments and others (including competitive adsorption of CAII, BSA, and lysozyme) support our hypothesis that specific binding of CAII to the dimer prevents LC anchoring transitions triggered by non-specific adsorption of serum albumin. We illustrate the utility of the approach by reporting (i) the relative activity of two small-molecule inhibitors (6-ethoxy-2-benzothiazolesulfonamide and benzenesulfonamide) of CAII to sulfonamide and (ii) proteolytic digestion of a protein (CAII) by thermolysin. Overall, the results in this paper provide new insight into the interactions of proteins at aqueous-LC interfaces and fresh ideas for either blocking non-specific interactions of proteins at surfaces or reporting specific binding events at LC interfaces in the presence of non-specific proteins.
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http://dx.doi.org/10.1021/acsami.9b16867DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7368459PMC
February 2020

Distribution of age, gender, and occupation among individuals with carpal tunnel syndrome based on the National Health Insurance data and National Employment Insurance data.

Ann Occup Environ Med 2019 7;31:e31. Epub 2019 Nov 7.

Department of Health Sciences, Hanyang University Graduate School, Seoul, Korea.

Background: The present study aimed to investigate the basic characteristics of carpal tunnel syndrome (CTS) and its differences between occupations using Korea's National Health Insurance (NHI) and National Employment Insurance (NEI).

Methods: The study participants were obtained from the NEI and NHI data from 2008 to 2015, with a diagnosis code of G560 (CTS) as the main or sub-diagnosis. Data about gender, age, diabetes mellitus, smoking, drinking, and length of employment, information about type of occupation, and number of employees according to age and occupation were obtained from NHI and NEI data. In total, 240 occupations were classified into blue-collar (BC) and white-collar (WC) work. In addition, each occupation was classified as high-risk and low-risk groups depending on the degree of wrist usage.

Results: The number of patients with CTS per 100,000 individuals increased with advancing age, and it was higher in women (4,572.2) than in men (1,798.5). Furthermore, the number was higher in BC workers (3,247.5) than in WC workers (1,824.1) as well as in the high-risk group than in the low-risk group in both BC workers (3,527.8 vs. 1,908.2) and WC workers (1,829.9 vs. 1,754.4). The number of patients with CTS was higher in the high-risk group than in the low-risk group among male and female BC workers and female WC workers. However, the number was higher in the low-risk group among male WC workers. In the BC category, the number of patients with CTS was highest among food processing-related workers (19,984.5). In the WC category, the number of patients with CTS was highest among social workers and counselors (7,444.1).

Conclusions: The results of this study are expected to help identify occupational differences in patterns of CTS. High number of patients with CTS was seen in new jobs, as well as in previous studies.
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http://dx.doi.org/10.35371/aoem.2019.31.e31DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6850790PMC
November 2019

Reconfigurable Multicompartment Emulsion Drops Formed by Nematic Liquid Crystals and Immiscible Perfluorocarbon Oils.

Langmuir 2019 Dec 25;35(49):16312-16323. Epub 2019 Nov 25.

Smith School of Chemical and Biomolecular Engineering , Cornell University , Ithaca , New York 14850 , United States.

Liquid crystalline (LC) oils offer the basis of stimuli-responsive LC-in-water emulsions. Although past studies have explored the properties of single-phase LC emulsions, few studies have focused on complex multicompartment emulsions containing co-existing isotropic and LC domains. In this paper, we report a study of multiphase emulsions using LCs and immiscible perfluoroalkanes dispersed in water or glycerol (the latter continuous phase is used to enable characterization). We found that the nematogen 4'-pentyl-4-biphenylcarbonitrile (5CB) anchors homeotropically (perpendicularly) and weakly at liquid perfluorononane (F9) interfaces, consistent with the smectic layering of 5CB molecules. The proposed role of smectic layering is supported by experiments performed with 4-(trans-4-pentylcyclohexyl)benzonitrile, a nematogen that possesses a cyclohexyl group that frustrates the smectic packing and leads to tilted orientations at the F9 interface. By employing perfluorocarbon and hydrocarbon surfactants in combination with multiphase 5CB and F9 emulsion droplets dispersed in a continuous water or glycerol phase, we observe a range of emulsion droplet morphologies to form, including core-shell and Janus structures, with internal organizations that reflect an interplay of interfacial (anchoring energies; F9 and glycerol) and elastic energies within the confines of the geometry of the emulsion droplet. By comparing experimental observations to simulations of the LC-perfluorocarbon droplets based on a Landau-de Gennes model of the free energy, we place bounds on the orientation-dependent interfacial energies that underlie the internal ordering of these complex emulsions. Additionally, by forming core-shells emulsion droplets from 5CB (shell) and perfluoroheptane (cores), we demonstrate how a liquid-to-vapor phase transition in the perfluorocarbon core can be used to actuate the droplet and rapidly thin the nematic shell. Overall, the results reported in this paper demonstrate that multiphase LC emulsions formed from mixtures of perfluoroalkanes and LCs provide new opportunities to engineer hierarchical and stimuli-responsive emulsion systems.
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http://dx.doi.org/10.1021/acs.langmuir.9b02864DOI Listing
December 2019

Soft matter from liquid crystals.

Soft Matter 2019 Sep 23;15(35):6913-6929. Epub 2019 Aug 23.

Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, 113 Ho Plaza, Ithaca, New York 14853, USA.

Liquid crystals (LCs) are fluids within which molecules exhibit long-range orientational order, leading to anisotropic properties such as optical birefringence and curvature elasticity. Because the ordering of molecules within LCs can be altered by weak external stimuli, LCs have been widely used to create soft matter systems that respond optically to electric fields (LC display), temperature (LC thermometer) or molecular adsorbates (LC chemical sensor). More recent studies, however, have moved beyond investigations of optical responses of LCs to explore the design of complex LC-based soft matter systems that offer the potential to realize more sophisticated functions (e.g., autonomous, self-regulating chemical responses to mechanical stimuli) by directing the interactions of small molecules, synthetic colloids and living cells dispersed within the bulk of LCs or at their interfaces. These studies are also increasingly focusing on LC systems driven beyond equilibrium states. This review presents one perspective on these advances, with an emphasis on the discovery of fundamental phenomena that may enable new technologies. Three areas of progress are highlighted; (i) directed assembly of amphiphilic molecules either within topological defects of LCs or at aqueous interfaces of LCs, (ii) templated polymerization in LCs via chemical vapor deposition, an approach that overcomes fundamental challenges related to control of LC phase behavior during polymerization, and (iii) studies of colloids in LCs, including chiral colloids, soft colloids that are strained by LCs, and active colloids that are driven into organized states by dissipation of energy (e.g. bacteria). These examples, and key unresolved issues discussed at the end of this perspective, serve to convey the message that soft matter systems that integrate ideas from LC, surfactant, polymer and colloid sciences define fertile territory for fundamental studies and creation of future transformative technologies.
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http://dx.doi.org/10.1039/c9sm01424aDOI Listing
September 2019

Oxygen Vacancy Diffusion and Condensation in Lithium-Ion Battery Cathode Materials.

Angew Chem Int Ed Engl 2019 Jul 24;58(31):10478-10485. Epub 2019 Jun 24.

Department of Energy Engineering and School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea.

Oxygen vacancies (OV) are native defects in transition metal (TM) oxides and their presence has a critical effect on the physicochemical properties of the oxide. Metal oxides are commonly used in lithium-ion battery (LIB) cathodes and there is still a lack of understanding of the role of OVs in LIB research field. Here, we report on the behavior of OVs in a single-crystal LIB cathode during the non-equilibrium states of charge and discharge. We found that microcrack evolution in a single crystal occurs due to OV condensation in specific crystallographic orientations generated by the continuous migration of OVs and TM ions. Moreover, understanding the effects of the presence and diffusion of OVs in metal oxides enables the elucidation of most of the conventional mechanisms of capacity fading in LIBs and provides new insights for new electrochemical applications.
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http://dx.doi.org/10.1002/anie.201904469DOI Listing
July 2019

Thermally reconfigurable Janus droplets with nematic liquid crystalline and isotropic perfluorocarbon oil compartments.

Soft Matter 2019 Mar;15(12):2580-2590

Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.

We report that mixtures of perfluorocarbon oils and hydrocarbon mesogens can be used to prepare multi-compartment (Janus) emulsion drops comprising coexisting nematic liquid crystalline (LC) and isotropic oil phases. The droplets exhibit stable spherical shapes with internal Janus-type morphologies that can be tuned widely through changes in temperature or adsorbates. In particular, we observe evidence of preferential adsorption of hydrocarbon or fluorocarbon surfactants on the interfaces of nematic versus isotropic domains, respectively, providing added control over the droplet structure. Comparisons of experiments and numerical simulations using a Landau-de Gennes continuum model provide insight into the relative importance of the LC elasticity and orientational-dependent interfacial energies on droplet morphologies and properties. We show that the hierarchical organization of the LC compartments generates optical properties and responsiveness not found in emulsions of isotropic oils.
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http://dx.doi.org/10.1039/c8sm02600aDOI Listing
March 2019

Successful Conservative Management of Hepatic Portal Venous Gas due to Anastomosis Leakage After a Sigmoidectomy.

Ann Coloproctol 2019 Jan 25:282-284. Epub 2019 Jan 25.

Department of Surgery, Inje University Seoul Paik Hospital, Seoul, Korea.

In past decades, hepatic portal venous gas (HPVG) has rarely been reported, and the mortality rate has been very high. In most cases, surgical intervention was needed. Presently, abdominal computed tomography can be conveniently used to diagnose HPVG, which has various underlying causes and benign courses. We present the case of a patient with HPVG due to anastomosis leakage after a sigmoidectomy for diverticulitis; the patient was cured with conservative management.
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http://dx.doi.org/10.3393/ac.2018.03.23.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6863010PMC
January 2019

Templated nanofiber synthesis via chemical vapor polymerization into liquid crystalline films.

Science 2018 11;362(6416):804-808

Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA.

Extrusion, electrospinning, and microdrawing are widely used to create fibrous polymer mats, but these approaches offer limited access to oriented arrays of nanometer-scale fibers with controlled size, shape, and lateral organization. We show that chemical vapor polymerization can be performed on surfaces coated with thin films of liquid crystals to synthesize organized assemblies of end-attached polymer nanofibers. The process uses low concentrations of radical monomers formed initially in the vapor phase and then diffused into the liquid-crystal template. This minimizes monomer-induced changes to the liquid-crystal phase and enables access to nanofiber arrays with complex yet precisely defined structures and compositions. The nanofiber arrays permit tailoring of a wide range of functional properties, including adhesion that depends on nanofiber chirality.
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http://dx.doi.org/10.1126/science.aar8449DOI Listing
November 2018

A Study on Prevalence and Risk Factors for Varicose Veins in Nurses at a University Hospital.

Saf Health Work 2018 Mar 24;9(1):79-83. Epub 2017 Aug 24.

Department of Occupational & Environmental Medicine, Pusan National University Yangsan Hospital, Yangsan, Republic of Korea.

Background: Lower-limb varicose veins (VVs) are common and known to have a higher prevalence among people who work in occupations requiring prolonged standing. In the Republic of Korea, however, VV-related occupational factors have seldom been examined. This study was conducted to assess the prevalence of VVs among nurses, an occupational group considered to be at high risk of VVs, and determine the occupational risk factors of prolonged standing.

Methods: Between March and August 2014, a questionnaire survey coupled with Doppler ultrasonography was conducted on the nurses working at a university hospital.

Results: A total of 414 nurses participated in the survey and diagnostic testing. From the survey analysis and test results, the prevalence of VVs in nurses was estimated to be 16.18%. Significant factors for venous reflux were age [odds ratio (OR) = 1.06, 95% confidence interval (CI) = 1.03-1.10], pregnancy (OR = 2.15, 95% CI = 1.17-3.94), and delivery (OR = 2.02, 95% CI = 1.08-3.78). The statistical significance of these factors was verified after risk adjustment for sociodemographic factors (OR = 3.40, 95% CI = 1.27-9.09).

Conclusion: Factors significantly associated with venous reflux were increasing age and prolonged working hours (≥ 4 hours) in a standing position (OR = 2.80, 95% CI = 1.08-7.25), even after risk adjustment for sociodemographic factors. This study is significant in that an objective diagnosis of VVs preceded the analysis of the risk factors for VV incidence, thus verifying objectively that VVs are associated with occupations requiring prolonged hours of working in a standing position.
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http://dx.doi.org/10.1016/j.shaw.2017.08.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6111140PMC
March 2018

Amphiphile-Induced Phase Transition of Liquid Crystals at Aqueous Interfaces.

ACS Appl Mater Interfaces 2018 Oct 22;10(43):37618-37624. Epub 2018 Oct 22.

Argonne National Laboratory , Argonne , Illinois 60439 , United States.

Monolayer assemblies of amphiphiles at planar interfaces between thermotropic liquid crystals (LCs) and an aqueous phase can give rise to configurational transitions of the underlying LCs. A common assumption has been that a reconfiguration of the LC phase is caused by an interdigitation of the hydrophobic tails of amphiphiles with the molecules of the LC at the interface. A different mechanism is discovered here, whereby reorientation of the LC systems is shown to occur through lowering of the orientation-dependent surface energy of the LC due to formation of a thin isotropic layer at the aqueous interface. Using a combination of atomistic molecular dynamics simulations and experiments, we demonstrate that a monolayer of specific amphiphiles at an aqueous interface can cause a local nematic-to-isotropic phase transition of the LC by disturbing the antiparallel configuration of the LC molecules. These results provide new insights into the interfacial, molecular-level organization of LCs that can be exploited for rational design of biological sensors and responsive systems.
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http://dx.doi.org/10.1021/acsami.8b09639DOI Listing
October 2018

Differences in the Incidence of Symptomatic Cervical and Lumbar Disc Herniation According to Age, Sex and National Health Insurance Eligibility: A Pilot Study on the Disease's Association with Work.

Int J Environ Res Public Health 2018 09 25;15(10). Epub 2018 Sep 25.

Department of Occupational and Environmental Medicine, Pusan National University, Yangsan Hopspital, Yangsan, Mulgeum-eup, Bumeo-ri, Yangsan, Gyongnam 626-770, Korea.

The aim of this research was to identify the differences in the incidence of symptomatic cervical and lumbar disc herniation according to age, sex, and national health insurance eligibility. We evaluated the hospital documents of patients who received medical treatment for symptomatic cervical and lumbar disc herniation between 2004 and 2010 and excluded those who claimed to have expenses at oriental medical clinics or pharmacies. Furthermore, any duplicate documents from the labor force population aged 20⁻69 years were excluded from the analysis. The results showed that the number of individuals diagnosed with symptomatic cervical and lumbar disc herniation increased with age, and the incidence of these diseases was higher in women than in men. Additionally, the incidence differed depending on the subject's qualification for health insurance. The incidence of lumbar disc herniation showed differences depending on the degree of the lumbar burden. The present study findings may help determine whether lumbar disc herniation is associated with tasks performed at the patient's workplace. Further research is needed to classify the risk of lumbar disk herniation in the workplace into detailed categories such as types of business, types of occupation, and lumbar compression force.
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http://dx.doi.org/10.3390/ijerph15102094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6210730PMC
September 2018

Occupational Burden of Asbestos-Related Diseases in Korea, 1998-2013: Asbestosis, Mesothelioma, Lung Cancer, Laryngeal Cancer, and Ovarian Cancer.

J Korean Med Sci 2018 Aug 19;33(35):e226. Epub 2018 Jul 19.

Department of Occupational and Environmental Medicine, Pusan National University Yangsan Hospital, Yangsan, Korea.

Background: Asbestos exposure causes asbestos-related diseases (ARDs) including asbestosis, malignant mesothelioma, lung cancer, laryngeal cancer, and ovarian cancer. Although Korea used substantial amounts of asbestos in the past, no study has focused on its occupational burden of disease (OBD). Therefore, this study aimed to determine the OBDs of ARDs in Korea.

Methods: The CARcinogen Exposure (CAREX) database was used to determine the proportion of exposed population. Relative risks for lung cancer, laryngeal cancer, and ovarian cancer were used to determine the population-attributable fraction. Data for deaths caused by ARDs during 1998-2013 were obtained from the World Health Organization mortality database. The potential years of life lost (PYLL) and annual average PYLL (APYLL) indicated OBDs.

Results: In Korea, the number of ARD-attributable deaths and PYLL due to all ARDs during 1998-2013 were 4,492 and 71,763.7, respectively. The number of attributable deaths and PYLL due to asbestosis, malignant mesothelioma, lung cancer, laryngeal cancer, and ovarian cancer were 37 and 554.2, 808 and 15,877.0, 3,256 and 47,375.9, 120 and 1,605.5, and 271 and 6,331.1, respectively; additionally, the APYLL were 15.0, 19.7, 14.6, 13.4, and 23.4, respectively, and the average age at death was 70.4, 62.6, 69.1, 69.9, and 61.8, respectively. Our study showed that although the use of asbestos has ceased in Korea, the incidence of ARDs tends to increase.

Conclusion: Therefore, efforts to reduce future OBDs of ARDs, including early detection and proper management of ARDs, are needed in Korea.
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http://dx.doi.org/10.3346/jkms.2018.33.e226DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6105774PMC
August 2018

The roles of doctors, nurses, and industrial hygienists in the healthcare management services in Korea: a comparison of the opinions of specialized health management institutions and entrusted enterprises.

Ann Occup Environ Med 2018 7;30:50. Epub 2018 Aug 7.

4Occupational Safety & Health Research Institute, Korea Occupational Safety & Health Agency, 44429 400, Jongga-ro, Jung-gu, Ulsan, Republic of Korea.

Background: This study aimed to identify the difference of perception about the role of appointing health officers by comparing and analyzing the response of entrustment workplace (EW) and specialized health management institution (SI). This is considered an important aspect of an institutional assessment to improve the quality of health management services.

Methods: A survey questionnaire was mailed to 122 SIs and 319 EWs nationwide. The questionnaire survey was about the general characteristics of SIs and EWs and main occupations for each evaluation item. In total, 81 SIs (66.4%) and 30 EWs responded to the questionnaire. A logistic regression analysis was performed to compare the opinions of SI and EW.

Results: Based on the analysis, the items showing statistically significant differences were as follows. Doctors' main tasks survey: "Guidance on their wearing personal protective equipment (PPE)" (OR: 4.58), "Guidance of improvement of work environment (WE)" (OR: 3.33), etc.; Nurses' main tasks survey: "Guidance on their wearing PPE" (OR: 3.86), "Guidance for programs on health process in confined space (CS)" (OR: 0.36), "Guidance on the hearing conservation program (HCP)" (OR: 0.28), etc.; Industrial hygienist (IH)'s main tasks survey: "Guidance of work through inspection (WTI)" (OR: 0.15), "Guidance on the improvement of WE" (OR: 0.32), "Management confirmation of substances used by process and Material Safety Data Sheet (MSDS)" (OR: 0.08), "Guidance on posting or keeping of MSDS and warning signs" (OR: 0.03), "Prevention of dust-induced medical problems" (OR: 0.28), "Guidance for programs of health process in CS" (OR: 0.39), etc.

Conclusions: It is necessary to educate the EWs to recognize the need for physicians to perform tasks, such as wearing a PPE, and instruction to improve WE. As for nurses' tasks, such as education about the CS and the noise work, educating the nurses of the SI is regarded necessary as the demand of the EWs is considered. With respect to the unique tasks of IH, such as WE management and instructions for wearing PPE, among several other tasks of IH, training should be provided for improved IH recognition.
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http://dx.doi.org/10.1186/s40557-018-0261-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6081804PMC
August 2018

Relationships of Lower Lung Fibrosis, Pleural Disease, and Lung Mass with Occupational, Household, Neighborhood, and Slate Roof-Dense Area Residential Asbestos Exposure.

Int J Environ Res Public Health 2018 08 2;15(8). Epub 2018 Aug 2.

Preventive, Occupational and Environmental Medicine, School of Medicine, Pusan National University, Yangsan 50612, Korea.

This study aimed to evaluate the relationship between various asbestos exposure routes and asbestos-related disorders (ARDs). The study population comprised 11,186 residents of a metropolitan city who lived near asbestos factories, shipyards, or in slate roof-dense areas. ARDs were determined from chest X-rays indicating lower lung fibrosis (LFF), pleural disease (PD), and lung masses (LMs). Of the subjects, 11.2%, 10.4%, 67.2% and 8.3% were exposed to asbestos via occupational, household, neighborhood, and slate roof routes, respectively. The odds ratio (OR) of PD from household exposure (i.e., living with asbestos-producing workers) was 1.9 (95% confidence interval: 0.9⁻4.2), and those of LLF and PD from neighborhood exposure, or residing near asbestos factories) for <19 or >20 years, or near a mine, were 4.1 (2.8⁻5.8) and 4.8 (3.4⁻6.7), 8.3 (5.5⁻12.3) and 8.0 (5.5⁻11.6), and 4.8 (2.7⁻8.5) and 9.0 (5.6⁻14.4), respectively. The ORs of LLF, PD, and LM among those residing in slate-dense areas were 5.5 (3.3⁻9.0), 8.8 (5.6⁻13.8), and 20.5 (10.4⁻40.4), respectively. Substantial proportions of citizens residing in industrialized cities have potentially been exposed to asbestos, and various exposure routes are associated with the development of ARDs. Given the limitations of this study, including potential confounders such as socioeconomic status, further research is needed.
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http://dx.doi.org/10.3390/ijerph15081638DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6121390PMC
August 2018

Oligomers as Triggers for Responsive Liquid Crystals.

Langmuir 2018 08 20;34(34):10092-10101. Epub 2018 Aug 20.

Department of Chemical and Biological Engineering , University of Wisconsin-Madison , 1415 Engineering Drive , Madison , Wisconsin 53706 , United States.

We report an investigation of the influence of aqueous solutions of amphiphilic oligomers on the ordering of micrometer-thick films of thermotropic liquid crystals (LCs), thus addressing the gap in knowledge arising from previous studies of the interactions of monomeric and polymeric amphiphiles with LCs. Specifically, we synthesized amphiphilic oligomers (with decyl hydrophobic and pentaethylene glycol hydrophilic domains) in monomer, dimer, and trimer forms, and incubated aqueous solutions of the oligomers against nematic films of 4'-pentyl-4-biphenylcarbonitrile (5CB). All amphiphilic oligomers caused sequential surface-driven orientational (planar to homeotropic) and then bulk phase transitions (nematic to isotropic) with dynamics depending strongly on the degree of oligomerization. The dynamics of the orientational transitions accelerated from monomer to trimer, consistent with the effects of an increase in adsorption free energy. The mechanism underlying the orientational transition, however, involved a decrease in anchoring energy and not change in the easy axis of the LC. In contrast, the rate of the phase transition induced by absorption of oligomers into the LC decreased from monomer to trimer, suggesting that constraints on configurational degrees of freedom influence the absorption free energies of the oligomers. Interestingly, the oligomer-induced transition from the nematic to isotropic phase of 5CB was observed to nucleate at the aqueous-5CB interface, consistent with surface-induced disorder underlying the above-reported decrease in anchoring energy caused by the oligomers. Finally, we provided proof-of-concept experiments of the triggering of LCs using a trimeric amphiphile that is photocleaved by UV illumination into monomeric fragments. Overall, our results provide insight into the rational design of oligomers that can be used as triggers to create responsive LCs.
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http://dx.doi.org/10.1021/acs.langmuir.8b01944DOI Listing
August 2018

Monitoring and Simulating Environmental Asbestos Dispersion from a Textile Factory.

Int J Environ Res Public Health 2018 07 3;15(7). Epub 2018 Jul 3.

Preventive, Occupational and Environmental Medicine, School of Medicine, Pusan National University, Yangsan 50612, Korea.

Although workplace asbestos concentrations (AC) have been reported several times, the past environmental AC are relatively poorly studied. Due to the harmful effects of the asbestos industry, production has moved from early industrialized countries (Japan), to late industrialized countries (Korea), and finally to industrializing countries (Indonesia). The purpose of this study was to determine current occupational exposure levels and evaluate neighborhood environmental exposure levels in an Indonesian asbestos textile factory through collaboration among three generation of industrialized countries. Asbestos concentrations were measured inside and outside of the factory and compared with simulated data. ACs in the factory were similar to those of 1980s and 1990s levels in the Korean factory that transferred the machines. Environmental ACs were dispersed according to wind direction. There were no significant differences between monitored and simulated data, and correlation coefficients between downwind, upwind, and middle wind directions were high, with some statistical significance. This study can be used to estimate past environmental ACs to understand the causality of asbestos related diseases. Because of the small sample size and specific weather conditions, a large-scale study of various asbestos exposure sources, including asbestos cement factories, shipyards, and mines, and various atmospheric conditions is required.
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http://dx.doi.org/10.3390/ijerph15071398DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6068513PMC
July 2018

Age-Related Decrease in Stress Responsiveness and Proactive Coping in Male Mice.

Front Aging Neurosci 2018 7;10:128. Epub 2018 May 7.

Graduate School of East-West Medical Science, Kyung Hee University, Yongin, South Korea.

Coping is a strategic approach to dealing with stressful situations. Those who use proactive coping strategies tend to accept changes and act before changes are expected. In contrast, those who use reactive coping are less flexible and more likely to act in response to changes. However, little research has assessed how coping style changes with age. This study investigated age-related changes in coping strategies and stress responsiveness and the influence of age on the processing of conditioned fear memory in 2-, 12- and 23-month-old male mice. Coping strategy was measured by comparing the escape latency in an active avoidance test and by comparing responses to a shock prod. The results showed that proactivity in coping response gradually decreased with age. Stress responsiveness, measured by stress-induced concentration of corticosterone, was also highest in 2-month-old mice and decreased with age. Consolidation of fear memory was highest in 12-month-old mice and was negatively correlated with the degree of stress responsiveness and proactivity in coping. Fear extinction did not differ among age groups and was not correlated with stress responsiveness or the proactivity of coping. However, the maintenance of extinct fear memory, which was best in 2-month-old mice and worst in 12-month-old mice, was negatively correlated with stress responsiveness but not with coping style. Age-dependent changes in the expression of glucocorticoid receptor (GR) and its regulatory co-chaperones, which are accepted mechanisms for stress hormone stimulation, were measured in the hippocampus. The expression of GR was increased at 12 months compared to other age groups. There were no differences in Hsp70 and BAG1 expression by age. These results can be summarized as follows: (1) stress responsiveness and proactivity in coping decreased with age class; (2) consolidation of fear memory was negatively correlated with both stress responsiveness and proactivity; however, maintenance of extinct fear memory was negatively correlated with stress responsiveness only; and (3) consolidation and maintenance of extinct fear memory appeared to be more influenced by factors other than stress reactivity and proactivity in coping, such as the amount of hippocampal glucocorticoid expression.
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http://dx.doi.org/10.3389/fnagi.2018.00128DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5952218PMC
May 2018

Self-reporting and self-regulating liquid crystals.

Nature 2018 05 9;557(7706):539-544. Epub 2018 May 9.

Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI, USA.

Liquid crystals (LCs) are anisotropic fluids that combine the long-range order of crystals with the mobility of liquids. This combination of properties has been widely used to create reconfigurable materials that optically report information about their environment, such as changes in electric fields (smart-phone displays) , temperature (thermometers) or mechanical shear , and the arrival of chemical and biological stimuli (sensors). An unmet need exists, however, for responsive materials that not only report their environment but also transform it through self-regulated chemical interactions. Here we show that a range of stimuli can trigger pulsatile (transient) or continuous release of microcargo (aqueous microdroplets or solid microparticles and their chemical contents) that is trapped initially within LCs. The resulting LC materials self-report and self-regulate their chemical response to targeted physical, chemical and biological events in ways that can be preprogrammed through an interplay of elastic, electrical double-layer, buoyant and shear forces in diverse geometries (such as wells, films and emulsion droplets). These LC materials can carry out complex functions that go beyond the capabilities of conventional materials used for controlled microcargo release, such as optically reporting a stimulus (for example, mechanical shear stresses generated by motile bacteria) and then responding in a self-regulated manner via a feedback loop (for example, to release the minimum amount of biocidal agent required to cause bacterial cell death).
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http://dx.doi.org/10.1038/s41586-018-0098-yDOI Listing
May 2018

Multi-Scale Responses of Liquid Crystals Triggered by Interfacial Assemblies of Cleavable Homopolymers.

Chemphyschem 2018 08 16;19(16):2037-2045. Epub 2018 May 16.

Department of Chemical and Biological Engineering, University of Wisconsin-Madison Madison, Wisconsin, 53706, USA.

Liquid crystals (LCs) offer the basis of stimuli-responsive materials that can amplify targeted molecular events into macroscopic outputs. However, general and versatile design principles are needed to realize the full potential of these materials. To this end, we report the synthesis of two homopolymers with mesogenic side chains that can be cleaved upon exposure to either H O (polymer P1) or UV light (polymer P2). Optical measurements reveal that the polymers dissolve in bulk LC and spontaneously assemble at nematic LC-aqueous interfaces to impose a perpendicular orientation on the LCs. Subsequent addition of H O to the aqueous phase or exposure of the LC to UV was shown to trigger a surface-driven ordering transition to a planar orientation and an accompanying macroscopic optical output. Differences in the dynamics of the response to each stimulus are consistent with sequential processing of P1 at the LC-aqueous interface (H O ) and simultaneous transformation of P2 within the LC (UV). The versatility of the approach is demonstrated by creating stimuli-responsive LCs as films or microdroplets, and by dissolving mixtures of P1 and P2 into LCs to create LC materials that respond to two stimuli. Overall, our results validate a simple and generalizable approach to the rational design of polymers that can be used to program stimuli-responsiveness into LC materials.
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http://dx.doi.org/10.1002/cphc.201800106DOI Listing
August 2018

Iatrogenic Development of Cerebrospinal Fluid Leakage in Diagnosing Spontaneous Intracranial Hypotension.

Korean J Fam Med 2018 Mar 22;39(2):122-125. Epub 2018 Mar 22.

Department of Anesthesiology and Pain Medicine, Gangneung Asan Hospital, Gangneung, Korea.

A 34-year-old woman came to the emergency room complaining of a severe orthostatic headache. Results of a cerebrospinal fluid tap and brain computed tomography were normal. Based on her history and symptoms, she was found to have spontaneous intracranial hypotension. She was hospitalized and her symptoms improved with conservative treatment. On the next day, her headache suddenly worsened. Cisternography was performed to confirm the diagnosis and determine the spinal level of her cerebrospinal fluid leak. It revealed multiple cerebrospinal fluid leaks in the lumbar and upper thoracic regions. It was strongly believed that she had an iatrogenic cerebrospinal fluid leak in the lumbar region. An epidural blood patch was performed level by level on the lumbar and upper thoracic regions. Her symptoms resolved after the epidural blood patch and she was later discharged without any complications. In this case, an iatrogenic cerebrospinal fluid leak was caused by a dural puncture made while diagnosing spontaneous intracranial hypotension, which is always a risk and hampers the patient's progress. Therefore, in cases of spontaneous intracranial hypotension, an effort to minimize dural punctures is needed and a non-invasive test such as magnetic resonance imaging should be considered first.
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http://dx.doi.org/10.4082/kjfm.2018.39.2.122DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5876047PMC
March 2018
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