Prevailing Synoptic Patterns for Persistent Positive Temperature Anomaly Episodes in the United States

Jongnam Choi(최종남),Gwangyong Choi(최광용),Thomas Williams 대한지리학회 2008 대한지리학회지 Vol.43 No.5

본 연구는 미국 지역을 사례로 겨울철 및 여름철에 장기간 지속되는 이상고온기 발생에 유리한 종관 규모의 매커니즘을 밝힌다. 여름철 이상고온기는 주로 미국의 남중부 지역에서 발생하는 반면, 겨울철 이상고온기는 미서부 지역에서 발생한다. 지상 및 상층 기압장 자료 분석 결과, 이러한 이상고온기는 태평양과 대서양의 아열대 고기압들의 활동과 밀접하게 관련되어있다. 장기간 지속되는 여름철 이상고온기는 중층 및 상층 블러킹 고기압의 활동에 의해 형성되는 매우 안정된 대기 조건하에서 주로 발생한다. 또한 이 시기에는 지표강제력으로 상대적으로 높은 보웬비(Bowen ratio)가 나타나지만, 따뜻한 공기의 이류의 영향은 크지 않다. 반면, 장기간 지속되는 겨울철 이상고온기는 블러킹 고기압에 의한 단열 기온 상승뿐만 아니라 따뜻한 공기의 이류의 복합적인 작용에 의해 나타난다. 그러나 이 시기의 지표 강제력의 영향은 약하다. This study examines the prevailing synoptic-scale mechanisms favorable for long-lived summer Persistent Positive Temperature Anomalies (PPTAs) as well as winter PPTAs in the United States. Such long-lived PPTAs usually occur in the south-central region of the United States in summer, but in the southwestern part of the United States in winter. Composite analyses of surface and pressure level data demonstrate that the formation of both winter and summer PPTAs is closely related to the movement of subtropical high pressure systems in the Pacific Ocean and Atlantic Ocean, respectively. The occurrence of long-lived summer PPTAs usually coincides with an extremely stable atmospheric condition caused by persistent blocking by mid- to upper-tropospheric anticyclones. Significant surface forcing is also easily identified through relatively high Bowen ratios at the surface. Warm air advection is, however, weak and appears to be an insignificant element in the formation of long-lived summer PPTAs. On the other hand, synergistic warming effects associated with adiabatic heating under an anticyclonic blocking system as well as significant warm air advection characterize the favorable synoptic environments for long-lived winter PPTAs. However, the impact of surface forcing mechanisms on winter PPTAs is insignificant.

Universal Gas-Uptake Behavior of a Zeolitic Imidazolate Framework ZIF-8 at High Pressure

Choi, Jinhyuk,Im, Junhyuck,Noh, Kyungkyou,Kim, Jaheon,Vogt, Thomas,Lee, Yongjae American Chemical Society 2019 The Journal of Physical Chemistry Part C Vol.123 No.42

<P>We report the pressure-induced insertion (PII) of gases in a zeolitic imidazolate framework (ZIF) at high pressure. ZIF-8 crystals were compressed in the presence of nonpolar CO<SUB>2</SUB> and SF<SUB>6</SUB> as well as polar CHClF<SUB>2</SUB> (<I>aka</I> R22) up to 4.07, 0.81, and 2.06 GPa, respectively, in a diamond anvil cell, and their X-ray powder diffraction data were analyzed by Rietveld methods. ZIF-8 showed pressure-induced amorphization in SF<SUB>6</SUB> but maintained its crystallinity in the presence of other gases. In general, the unit cell volume of ZIF-8 expanded via PII of CO<SUB>2</SUB> or R22 up to ca. 0.5 GPa and contracted linearly after completion of the PII processes. The total volumes of the inserted guest molecules, which were estimated from the residual electron densities, indicated that the inserted guest molecules fully occupy the pores of ZIF-8. The relationship between the total occupied volumes by guests and applied pressures was best represented with an asymptotic logarithmic curve regardless of the type of molecules. These results reveal the universal gas-uptake behavior of ZIF-8 at high pressure, which requires only the penetration of molecules into the pores of the framework of ZIF-8.</P> [FIG OMISSION]</BR>

Ground Beef High in Total Fat and Saturated Fatty Acids Decreases X Receptor Signaling Targets in Peripheral Blood Mononuclear Cells of Men and Women

Choi, Seong H.,Gharahmany, Ghazal,Walzem, Rosemary L.,Meade, Thomas H.,Smith, Stephen B. Wiley (John WileySons) 2018 Lipids Vol.53 No.3

Lamellar microdomain orientation and phase transition of polystyrene-<i>b</i>-poly(methyl methacrylate) films by controlled interfacial interactions

Choi, Seunghoon,Kim, Eunhye,Ahn, Hyungju,Naidu, Sudhakar,Lee, Yonghoon,Ryu, Du Yeol,Hawker, Craig J.,Russell, Thomas P. The Royal Society of Chemistry 2012 Soft matter Vol.8 No.12

<P>The orientation of lamellar microdomains and phase transition for the thin films of a symmetric polystyrene-<I>b</I>-poly(methyl methacrylate) (PS-<I>b</I>-PMMA) on random copolymer-grafted substrates were investigated by transmission electron microscopy (TEM) and grazing-incidence small-angle X-ray scattering (GISAXS). The styrene mole fraction (<I>X</I><SUB>S</SUB>) in random copolymers of P(S-<I>r</I>-MMA) was controlled to tune the interfacial interactions at the substrates from PS-selective to PMMA-selective. Except in the case of a neutral substrate with <I>X</I><SUB>S</SUB> = 0.55, all the films showed the parallel orientations of lamellar microdomains, which were validated by the TEM images. However, the GISAXS analysis of PS-<I>b</I>-PMMA films indicated that the intensity ratio of the <I>out-of-plane</I> scattering to the <I>in-plane</I> scattering can be a sensitive indicator for evaluating the degree of orientation of lamellar microdomains or surface neutrality at the substrates. The orientation of lamellar microdomains on a neutral substrate was influenced by the film thickness and molecular weight of PS-<I>b</I>-PMMA, which results from predominantly the entropic contribution to the free energy in competition between the chain-end effect and nematic term. Intriguingly, the order-to-disorder temperature (ODT) of PS-<I>b</I>-PMMA films on a series of the substrates shows a minimum at <I>X</I><SUB>S</SUB> = 0.55. The ODT measurements, a new approach to evaluating the interfacial interactions at substrates, confirm that a neutral substrate induces surface compatibility between the PS and PMMA blocks at the substrate.</P> <P>Graphic Abstract</P><P>A new approach to evaluating the interfacial interactions at substrates confirms that a neutral substrate induces surface compatibility between the PS and PMMA blocks. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2sm07297a'> </P>

Impact of robot‐assisted radical prostatectomy on health‐related quality of life in patients with lower urinary tract symptoms

Choi, Eun Yong,Jeong, Jeongyun,Kang, Dong Il,Johnson, Kelly,Ercolani, Matt,Jang, Thomas,Lee, Dong Hyeon,Kim, Wun‐,Jae,Kim, Isaac Yi Blackwell Publishing Asia 2011 International journal of urology Vol.18 No.4

<P><B>Objective: </B> Lower urinary tract symptoms (LUTS) are a common complaint in patients with prostate cancer. We attempted to elucidate the effect of robot‐assisted radical prostatectomy (RARP) on patients having different preoperative LUTS severity through analysis of postoperative health‐related quality of life.</P><P><B>Methods: </B> From 1/2006 to 9/2009, over 500 patients underwent RARP at our institution. Preoperative American Urologic Association Symptom Score (AUA‐SS), preoperative Sexual Health Inventory for Men, and postoperative Expanded Prostate Cancer Index Composite were available in 183 of them. These patients were divided into three subgroups based on their AUA‐SS as follows: mild AUA‐SS (score 0–7) group, moderate AUA‐SS (8–19) group, and severe AUA‐SS (20–35) group.</P><P><B>Results: </B> Of the 183 men, 94 (51.4%), 70 (38.2%), and 19 (10.4%) were in the mild, moderate, and severe group, respectively. In the comparison of Expanded Prostate Cancer Index Composite domain subscales with mean score, only urinary domain had significant differences among subgroups. Patients with high preoperative LUTS persistently showed a statistical trend for decreased urinary function (<I>P</I> = 0.056) and suffered more from urinary bother postoperatively (<I>P</I> < 0.01). In the analysis of urinary bother items, all items except “bleeding with urination” showed statistically significant differences among the subgroups (<I>P</I> < 0.05).</P><P><B>Conclusions: </B> Even after RARP, patients with severe preoperative LUTS continue to have significant symptoms postoperatively. In analyzing urinary bother items, all LUTS items, including dysuria, storage symptoms, and postmicturition or voiding symptoms, were higher in patients with high preoperative AUA‐SS.</P>

GOCI Yonsei Aerosol Retrieval (YAER) algorithm and validation during the DRAGON-NE Asia 2012 campaign

Choi, Myungje,Kim, Jhoon,Lee, Jaehwa,Kim, Mijin,Park, Young-Je,Jeong, Ukkyo,Kim, Woogyung,Hong, Hyunkee,Holben, Brent,Eck, Thomas F.,Song, Chul H.,Lim, Jae-Hyun,Song, Chang-Keun Copernicus GmbH 2016 Atmospheric measurement techniques Vol.9 No.3

<P><p><strong>Abstract.</strong> The Geostationary Ocean Color Imager (GOCI) onboard the Communication, Ocean, and Meteorological Satellite (COMS) is the first multi-channel ocean color imager in geostationary orbit. Hourly GOCI top-of-atmosphere radiance has been available for the retrieval of aerosol optical properties over East Asia since March 2011. This study presents improvements made to the GOCI Yonsei Aerosol Retrieval (YAER) algorithm together with validation results during the Distributed Regional Aerosol Gridded Observation Networks &amp;ndash; Northeast Asia 2012 campaign (DRAGON-NE Asia 2012 campaign). The evaluation during the spring season over East Asia is important because of high aerosol concentrations and diverse types of Asian dust and haze. Optical properties of aerosol are retrieved from the GOCI YAER algorithm including aerosol optical depth (AOD) at 550<span class='thinspace'></span>nm, fine-mode fraction (FMF) at 550<span class='thinspace'></span>nm, single-scattering albedo (SSA) at 440<span class='thinspace'></span>nm, Ångström exponent (AE) between 440 and 860<span class='thinspace'></span>nm, and aerosol type. The aerosol models are created based on a global analysis of the Aerosol Robotic Networks (AERONET) inversion data, and covers a broad range of size distribution and absorptivity, including nonspherical dust properties. The Cox-Munk ocean bidirectional reflectance distribution function (BRDF) model is used over ocean, and an improved minimum reflectance technique is used over land. Because turbid water is persistent over the Yellow Sea, the land algorithm is used for such cases. The aerosol products are evaluated against AERONET observations and MODIS Collection 6 aerosol products retrieved from Dark Target (DT) and Deep Blue (DB) algorithms during the DRAGON-NE Asia 2012 campaign conducted from March to May 2012. Comparison of AOD from GOCI and AERONET resulted in a Pearson correlation coefficient of 0.881 and a linear regression equation with GOCI AOD<span class='thinspace'></span> = <span class='thinspace'></span>1.083<span class='thinspace'></span> × <span class='thinspace'></span>AERONET AOD<span class='thinspace'></span>&amp;minus;<span class='thinspace'></span>0.042. The correlation between GOCI and MODIS AODs is higher over ocean than land. GOCI AOD shows better agreement with MODIS DB than MODIS DT. The other GOCI YAER products (AE, FMF, and SSA) show lower correlation with AERONET than AOD, but still show some skills for qualitative use.</p> </P>

Molecular Simulations for Anti-amyloidogenic Effect of Flavonoid Myricetin Exerted against Alzheimer’s β-Amyloid Fibrils Formation

Choi, Young-Jin,Kim, Thomas Donghyun,Paik, Seung R.,Jeong, Karp-Joo,Jung, Seun-Ho Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.8

Comparative molecular simulations were performed to establish molecular interaction and inhibitory effect of flavonoid myricetin on formation of amyloid fibris. For computational comparison, the conformational stability of myricetin with amyloid $\beta$ -peptide (A$\beta$ ) and $\beta$ -amyloid fibrils (fA$\beta$) were traced with multiple molecular dynamics simulations (MD) using the CHARMM program from Monte Carlo docked structures. Simulations showed that the inhibition by myricetin involves binding of the flavonoid to fA$\beta$ rather than A$\beta$ . Even in MD simulations over 5 ns at 300 K, myricetin/fA$\beta$ complex remained stable in compact conformation for multiple trajectories. In contrast, myricetin/A$\beta$ complex mostly turned into the dissociated conformation during the MD simulations at 300 K. These multiple MD simulations provide a theoretical basis for the higher inhibitory effect of myricetin on fibrillogenesis of fA$\beta$ relative to A$\beta$ . Significant binding between myricetin and fA$\beta$ observed from the computational simulations clearly reflects the previous experimental results in which only fA$\beta$ had bound to the myricetin molecules.

GOCI Yonsei aerosol retrieval version 2 products: an improved algorithm and error analysis with uncertainty estimation from 5-year validation over East Asia

Choi, Myungje,Kim, Jhoon,Lee, Jaehwa,Kim, Mijin,Park, Young-Je,Holben, Brent,Eck, Thomas F.,Li, Zhengqiang,Song, Chul H. Copernicus GmbH 2018 Atmospheric measurement techniques Vol.11 No.1

<P><p><strong>Abstract.</strong> The Geostationary Ocean Color Imager (GOCI) Yonsei aerosol retrieval (YAER) version 1 algorithm was developed to retrieve hourly aerosol optical depth at 550&amp;thinsp;nm (AOD) and other subsidiary aerosol optical properties over East Asia. The GOCI YAER AOD had accuracy comparable to ground-based and other satellite-based observations but still had errors because of uncertainties in surface reflectance and simple cloud masking. In addition, near-real-time (NRT) processing was not possible because a monthly database for each year encompassing the day of retrieval was required for the determination of surface reflectance. This study describes the improved GOCI YAER algorithm version 2 (V2) for NRT processing with improved accuracy based on updates to the cloud-masking and surface-reflectance calculations using a multi-year Rayleigh-corrected reflectance and wind speed database, and inversion channels for surface conditions. The improved GOCI AOD <span class='inline-formula'><i>τ</i>_G</span> is closer to that of the Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) AOD than was the case for AOD from the YAER V1 algorithm. The V2 <span class='inline-formula'><i>τ</i>_G</span> has a lower median bias and higher ratio within the MODIS expected error range (0.60 for land and 0.71 for ocean) compared with V1 (0.49 for land and 0.62 for ocean) in a validation test against Aerosol Robotic Network (AERONET) AOD <span class='inline-formula'><i>τ</i>_A</span> from 2011 to 2016. A validation using the Sun-Sky Radiometer Observation Network (SONET) over China shows similar results. The bias of error (<span class='inline-formula'><i>τ</i>_G−<i>τ</i>_A)</span> is within <span class='inline-formula'>−</span>0.1 and 0.1, and it is a function of AERONET AOD and Ångström exponent (AE), scattering angle, normalized difference vegetation index (NDVI), cloud fraction and homogeneity of retrieved AOD, and observation time, month, and year. In addition, the diagnostic and prognostic expected error (PEE) of <span class='inline-formula'><i>τ</i>_G</span> are estimated. The estimated PEE of GOCI V2 AOD is well correlated with the actual error over East Asia, and the GOCI V2 AOD over South Korea has a higher ratio within PEE than that over China and Japan.</p> </P>

Design Considerations of Cryogenic Cooling System for High Field Magnets

Choi, Yeon-Suk,Kim, Dong-Lak,Lee, Byoung-Seob,Yang, Hyung-Suk,Yoo Jong-Shin,Painter Thomas A.,Miller John R. The Korean Society of Superconductivity and Cryoge 2006 한국초전도저온공학회논문지 Vol.8 No.4

Several crucial issues are discussed in the design of cryogenic cooling system for high field magnets. This study is mainly motivated by our ongoing program to develop a 21 T Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR MS). The magnets of this system will be built horizontally to accomplish the requirement of user friendliness and reliability, and the replenishment of cryogen will not be necessary by a closed-loop cooling concept. The initial cool-down and safety are basically considered in this paper. The effects of the helium II volume and the gap distance of the weight load relief valve (or safety valve) on the cool-down time and temperature rising during an off-normal state are discussed. The total amount of cryogenic cooling loads and the required helium flow rate during cool-down are also estimated by a relevant heat transfer analysis. The temperatures of cryogen-free radiation shield are finally determined from the refrigeration power of a cryocooler and the total cryogenic loads.

Nodal probabilistic production cost simulation considering transmission system unavailabilty

Choi, J.,Tran, T.,Kwon, J.,Thomas, R.,Mount, T.,Billinton, R. IET 2008 IET generation, transmission & distribution Vol.2 No.1

<P>A nodal probabilistic production cost simulation method is described for power system long-term expansion planning considering unavailability and delivery limitation constraints of the transmission system. This new nodal production cost simulation model includes capacity constraints and unavailabilities of generators as well as transmission lines. This simulation methodology comes from the nodal composite power system equivalent load duration curve (CMELDC), based on a new effective load model at load points developed by the authors. The nodal CMELDC can be obtained from convolution integral processing of the outage capacity probability distribution function of the fictitious generator and the original LDC. It is expected that the new simulation model based on the nodal CMELDC proposed here will provide solutions to many problems based on nodal and decentralised operation and control of electric power systems under a competition environment. The nodal CMELDC based on the new model at load points can extend application areas of nodal probabilistic production cost simulation, probabilistic congestion cost assessment, analytical outage cost assessment and nodal reliability evaluation and so on at load points. The characteristics and effectiveness of this new proposed methodology are illustrated by a small system case study using a network flow and enumeration method.</P>