Variation of magnetic properties with different annealed temperatures in the Ni_3[Fe(CN)_6]_2ㆍXH_2O

M. Liu,X.F. Bian,Y.F. Xia,Z. Bao,H.S. Wu,M.X. Xu 한국물리학회 2011 Current Applied Physics Vol.11 No.3

Molecular magnet nickel(II) hexacyanoferrate(III) powder Ni_3[Fe(CN)_6]_2ㆍXH_2O was prepared by coprecipitation method. The coprecipitated powder was annealed in vacuum at different temperatures of 140,and 160 ℃. Water molecules contained in Prussian blue analogues were removed by heating. The annealing of Ni^II ferricyanide induced an inner charge transfer from Ni^II towards Fe^III to form the mixed valence system Ni(II) Ni(III) ferri-ferro-cyanide. Variation of magnetic properties with different annealed temperatures was studied by elemental analysis, powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared, and Mössbauer and magnetization measurements. The differences in magnetic phase transition temperature, coercivity, remanence and effective magnetization are studied. Differences in magnetic properties may be attributed to a partial charge transfer from Ni^II to Fe^III.

여대생의 인유두종 바이러스 및 인유두종 바이러스 백신 관련 지식과 예방접종 실태와의 상관관계

Xu, Meiling,김현지,이희수,이윤지,한동연,박소영,엄효윤,최정민,홍서진,홍예림,이경은,이혜림 이화여자대학교 간호과학대학 2017 이화간호학회지 Vol.- No.51

Purpose: Human Papillomavirus (HPV) vaccination is readily available, but immunization rate is minimal. Lack of knowledge concerning the HPV infection and vaccine is expected as the primary reason. The correlation between knowledge levels and vaccination will provide applicable guidelines for successful interventions. Method: 309 female university students have completed surveys September 2016, reporting of HPV infection knowledge, HPV vaccine knowledge, source of knowledge, and attitudes concerning vaccination. Result: HPV infection and vaccine knowledge levels were both suboptimal(9.57±1.84, 7.59±1.58), and the Internet(16.2%) was recognized as the most generally used means of obtaining information on the HPV vaccine. However, vaccination rates were reported to be low(28.2%), with lack of information(46.6%) hindering immunization. Correlations were found between HPV infection knowledge and cervical cancer insight, but the correlations between knowledge levels and vaccination rates were insignificant. Conclusion: Prior information on cervical cancer had an effect on the knowledge levels of HPV infection, but other factors were insignificant. Lack of information on the HPV vaccine was speculated, thus programs should focus on accessibility and effectiveness.

High-efficiency p–i–n organic light-emitting diodes with a novel n-doping electron transport layer

Wei Xu,M.A. Khan,Yu Bai,X.Y. Jiang,Z.L. Zhang,W.Q. Zhu 한국물리학회 2009 Current Applied Physics Vol.9 No.4

We demonstrate p–i–n organic light-emitting diodes (OLEDs) incorporating an n-doping transport layer which comprises 8-hydroxy-quinolinato lithium (Liq) doped into 4'7-diphyenyl-1,10-phenanthroline (Bphen) as ETL and a p-doping transport layer which includes tetrafluro-tetracyano-quinodimethane (F4-TCNQ) doped into 4,4',4''-tris(3-methylphenylphenylamono) triphenylamine (m-MTDATA). In order to examine the improvement in the conductivity of transport layers, hole-only and electron-only devices are fabricated. The current and power efficiency of organic light-emitting diodes have been improved significantly after introducing a novel n-doping (Bphen: 33 wt% Liq) layer as an electron transport layer (ETL) and a p-doping layer composed of m-MTDATA and F4-TCNQ as a hole transport layer (HTL). Compared with the control device (without doping), the current efficiency and power efficiency of Device C (most efficient) is enhanced by approximately 51% and 89%, respectively, while driving voltage is reduced by 29%. This improvement is attributed to the improved conductivity of the transport layers that leads to the efficient charge balance in the emission zone. We demonstrate p–i–n organic light-emitting diodes (OLEDs) incorporating an n-doping transport layer which comprises 8-hydroxy-quinolinato lithium (Liq) doped into 4'7-diphyenyl-1,10-phenanthroline (Bphen) as ETL and a p-doping transport layer which includes tetrafluro-tetracyano-quinodimethane (F4-TCNQ) doped into 4,4',4''-tris(3-methylphenylphenylamono) triphenylamine (m-MTDATA). In order to examine the improvement in the conductivity of transport layers, hole-only and electron-only devices are fabricated. The current and power efficiency of organic light-emitting diodes have been improved significantly after introducing a novel n-doping (Bphen: 33 wt% Liq) layer as an electron transport layer (ETL) and a p-doping layer composed of m-MTDATA and F4-TCNQ as a hole transport layer (HTL). Compared with the control device (without doping), the current efficiency and power efficiency of Device C (most efficient) is enhanced by approximately 51% and 89%, respectively, while driving voltage is reduced by 29%. This improvement is attributed to the improved conductivity of the transport layers that leads to the efficient charge balance in the emission zone.

The label free DNA sensor using a silicon nanowire array

Kulkarni, A.,Xu, Y.,Ahn, C.,Amin, R.,Park, S.H.,Kim, T.,Lee, M. Elsevier Science Publishers 2012 Journal of biotechnology Vol.160 No.3

Biosensors based on silicon nanowire (Si-NW) promise highly sensitive dynamic label free electrical detection of various biological molecules. Here we report Si-NW array electronic devices that function as sensitive and selective detectors of as synthesized 2D DNA lattices with biotins. The Si-NW array was fabricated using top-down approach consists of 250 nanowires of 20μm in length, equally spaced with an interval of 3.2μm. Measurements of photoresistivity of the Si-NW array device with streptavidin (SA) attached on biotinylated DNA lattices at different concentration were observed and analyzed.. The conductivity in the DNA lattices with protein SA shows significant change in the photoresistivity of Si-NW array device. This Si-NW based DNA sensor would be one of very efficient devices for direct, label free DNA detection and could provide a pathway to immunological assays, DNA forensics and toxin detection in modern biotechnology.

Biosynthesis and Recycling of Nicotinamide Cofactors in<i>Mycobacterium tuberculosis</i> : <i>AN ESSENTIAL ROLE FOR NAD IN NONREPLICATING BACILLI</i>

Boshoff, Helena I. M.,Xu, Xia,Tahlan, Kapil,Dowd, Cynthia S.,Pethe, Kevin,Camacho, Luis R.,Park, Tae-Ho,Yun, Chang-Soo,Schnappinger, Dirk,Ehrt, Sabine,Williams, Kerstin J.,Barry III, Clifton E. American Society for Biochemistry and Molecular Bi 2008 The Journal of biological chemistry Vol.283 No.28

<P>Despite the presence of genes that apparently encode NAD salvage-specific enzymes in its genome, it has been previously thought that Mycobacterium tuberculosis can only synthesize NAD de novo. Transcriptional analysis of the de novo synthesis and putative salvage pathway genes revealed an up-regulation of the salvage pathway genes in vivo and in vitro under conditions of hypoxia. [14C]Nicotinamide incorporation assays in M. tuberculosis isolated directly from the lungs of infected mice or from infected macrophages revealed that incorporation of exogenous nicotinamide was very efficient in in vivo-adapted cells, in contrast to cells grown aerobically in vitro. Two putative nicotinic acid phosphoribosyltransferases, PncB1 (Rv1330c) and PncB2 (Rv0573c), were examined by a combination of in vitro enzymatic activity assays and allelic exchange studies. These studies revealed that both play a role in cofactor salvage. Mutants in the de novo pathway died upon removal of exogenous nicotinamide during active replication in vitro. Cell death is induced by both cofactor starvation and disruption of cellular redox homeostasis as electron transport is impaired by limiting NAD. Inhibitors of NAD synthetase, an essential enzyme common to both recycling and de novo synthesis pathways, displayed the same bactericidal effect as sudden NAD starvation of the de novo pathway mutant in both actively growing and nonreplicating M. tuberculosis. These studies demonstrate the plasticity of the organism in maintaining NAD levels and establish that the two enzymes of the universal pathway are attractive chemotherapeutic targets for active as well as latent tuberculosis.</P>

Highly Sensitive and Selective Detection of Dopamine at Poly(chromotrope 2B)-Modified Glassy Carbon Electrode in the Presence of Uric Acid and Ascorbic Acid

Li, X.B.,Rahman, Md.M.,Xu, G.R.,Lee, J.J. Pergamon Press 2015 ELECTROCHIMICA ACTA Vol.173 No.-

A highly sensitive and selective electrochemical method based on a poly(chromotrope 2B)-modified anodized glassy carbon electrode (PCHAGCE) was developed for the determination of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA). The PCHAGCE sensor exhibited excellent electron-mediating behavior towards the oxidation of DA in 0.1M phosphate buffer solution (PBS) (pH7.0). It was found that the electrocatalytic activity was significantly dependent on the charge status and molecular structure of the target molecules. Differential pulse voltammetry (DPV) measurements revealed oxidation signals for DA, UA, and AA that were well-resolved into three distinct peaks with AA-DA, DA-UA, and AA-UA peak potential separations (ΔE<SUB>p</SUB>) of 172, 132, and 304mV, respectively. A detection limit of 0.04+/-0.001μM (S/N=3) and a quantification limit (S/N=10) of 0.149+/-0.03μM were obtained for DA sensing in a linear range of 1 to 40μM in PBS (pH7.0) with a very high sensitivity of 1.522+/-0.032μA.μM<SUP>-1</SUP>. The DA concentrations in human urine samples were also successfully determined with recoveries of 94.0-98.0%. This approach provides a simple, easy, sensitive, and selective method to detect DA in the presence of AA and UA.

Numerical Study in 2D-UVAC Mixed with EDM by Varying of Discharged Pulsed Frequency of Gaussian Heat Flux

T. J. Ko(고태조),R. Kurniawan(쿠르니아완 렌디),G. C. Park(박건철),M. R. Xu(쉬모란),P. W. Han(한필완),I. J. Yoon(윤인준) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월

This manuscript studies about preliminary numerical study in the 2D-UVAC (Two-dimensional Ultrasonic Vibration Assisted Cutting) mixed with the EDM (Electrical Discharged Machining) method. The commercial finite element analysis of ABAQUS 6.4 solver has been used in this research problem. The 2D-UVAC has been carried out with variation vibration frequency of 40-60 kHz, vibration amplitude for both directions about 10 μm, the constant cutting speed of 2 m/s, and constant cutting depth of 100 μm. Meanwhile, the EDM was assumed as a single Gaussian distribution heat flux with different pulsated frequency about 100 to 300 kHz with constant discharged voltage of 220 V, and discharged current of 1 A. According to numerical solution, the EDM maximum temperature can achieve about 1,200°C. By increasing pulsated frequency increases average EDM temperature thus it could decrease the average shear stress during cutting in 2D-UVAC. Therefore, the EDM brings benefit such as decreasing von-Mises stress during cutting in 2D-UVAC.

Source signatures from combined isotopic analyses of PM_2.5 carbonaceous and nitrogen aerosols at the peri-urban Taehwa Research Forest, South Korea in summer and fall

Lim, Saehee,Lee, Meehye,Czimczik, Claudia I.,Joo, Taekyu,Holden, Sandra,Mouteva, Gergana,Santos, Guaciara M.,Xu, Xiaomei,Walker, Jennifer,Kim, Saewung,Kim, Hyun Seok,Kim, Soyoung,Lee, Sanguk Elsevier 2019 Science of the Total Environment Vol.655 No.-

<P><B>Abstract</B></P> <P>Isotopes are essential tools to apportion major sources of aerosols. We measured the radiocarbon, stable carbon, and stable nitrogen isotopic composition of PM<SUB>2.5</SUB> at Taehwa Research Forest (TRF) near Seoul Metropolitan Area (SMA) during August–October 2014. PM<SUB>2.5</SUB>, TC, and TN concentrations were 19.4 ± 10.1 μg m<SUP>−3</SUP>, 2.6 ± 0.8 μg C m<SUP>−3</SUP>, and 1.4 ± 1.4 μg N m<SUP>−3</SUP>, respectively. The δ<SUP>13</SUP>C of TC and the δ<SUP>15</SUP>N of TN were − 25.4 ± 0.7‰ and 14.6 ± 3.8‰, respectively. EC was dominated by fossil-fuel sources with F<SUB>ff</SUB> (EC) of 78 ± 7%. In contrast, contemporary sources were dominant for TC with F<SUB>c</SUB> (TC) of 76 ± 7%, revealing the significant contribution of contemporary sources to OC during the growing season. The isotopic signature carries more detailed information on sources depending on air mass trajectories. The urban influence was dominant under stagnant condition, which was in reasonable agreement with the estimated δ<SUP>15</SUP>N of NH<SUB>4</SUB> <SUP>+</SUP>. The low δ<SUP>15</SUP>N (7.0 ± 0.2‰) with high TN concentration was apparent in air masses from Shandong province, indicating fossil fuel combustion as major emission source. In contrast, the high δ<SUP>15</SUP>N (16.1 ± 3.2‰) with enhanced TC/TN ratio reveals the impact of biomass burning in the air transported from the far eastern border region of China and Russia. Our findings highlight that the multi-isotopic composition is a useful tool to identify emission sources and to trace regional sources of carbonaceous and nitrogen aerosols.</P> <P><B>Highlights</B></P> <P> <UL> <LI> For PM<SUB>2.5</SUB>, the average δ<SUP>13</SUP>C of TC and δ<SUP>15</SUP>N of TN were −25.4 ± 0.7‰ and 14.6 ± 3.8‰respectively. </LI> <LI> EC and TC were dominated by fossil-fuel (78 ± 7%) and contemporary (76 ± 7%) sources, respectively. </LI> <LI> Low δ<SUP>15</SUP>N (7.0 ± 0.2‰) with high TN concentration was evident in air masses from Shandong province. </LI> <LI> Multi-isotopic composition is useful to trace regional sources of PM<SUB>2.5</SUB> aerosol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>δ<SUP>13</SUP>C of TC versus f<SUB>M</SUB> (EC) for different levels of δ<SUP>15</SUP>N of TN observed at Taehwa Research Forest (TRF) and Gosan Climate Observatory (GCO). TRF samples were classified into groups according to air mass origin.</P> <P>[DISPLAY OMISSION]</P>

The Kinetics of Anodic Dissolution and Repassivation on 316L Stainless Steel in Borate Buffer Solution Studied by Abrading Electrode Technique

( H S Xu1 ),( D B Sun ),( H Y Yu ),( H M Meng ) 한국부식방식학회(구 한국부식학회) 2015 Corrosion Science and Technology Vol.14 No.6

The capacity of passive metal to repassivate after film damage determines the development of local corrosion and the resistance to corrosion failures. In this work, the repassivation kinetics of 316L stainless steel (316LSS) was investigated in borate buffer solution (pH 9. 1) using a novel abrading electrode technique. The repassivation kinetics was analyzed in terms of the current density flowing from freshly bare 316L SS surface as measured by a potentiostatic method. During the early phase of decay (t < 2 s), according to the Avrami kinetics-based film growth model, the transient current was separated into anodic dissolution (idiss) and film formation (ifilm) components and analyzed individually. The film reformation rate and thickness were compared according to applied potential. Anodic dissolution initially dominated the repassivation for a short time, and the amount of dissolution increased with increasing applied potential in the passive region. Film growth at higher potentials occurred more rapidly compared to at lower potentials. Increasing the applied potential from 0 VSCE to 0. 8 VSCE resulted in a thicker passive film (0. 12 to 0. 52 nm). If the oxide monolayer covered the entire bare surface (θ=1), the electric field strength through the thin passive film reached 1. 6 × 107 V/cm.

Witnessing a Large-scale Slipping Magnetic Reconnection along a Dimming Channel during a Solar Flare

Jing, Ju,Liu, Rui,Cheung, Mark C. M.,Lee, Jeongwoo,Xu, Yan,Liu, Chang,Zhu, Chunming,Wang, Haimin American Astronomical Society 2017 ASTROPHYSICAL JOURNAL LETTERS - Vol.842 No.2

<P>We report the intriguing large-scale dynamic phenomena associated with the M6.5 flare (SOL2015-06-22T18:23) in NOAA active region 12371, observed by RHESSI, Fermi, and the Atmospheric Image Assembly (AIA) and Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO). The most interesting feature of this event is a third ribbon (R3) arising in the decay phase, propagating along a dimming channel (seen in EUV passbands) toward a neighboring sunspot. The propagation of R3 occurs in the presence of hard X-ray footpoint emission and is broadly visible at temperatures from 0.6 MK to over 10 MK through the differential emission measure analysis. The coronal loops then undergo an apparent slipping motion following the same path of R3, after a similar to 80 minute delay. To understand the underlying physics, we investigate the magnetic configuration and the thermal structure of the flaring region. Our results are in favor of a slipping-type reconnection followed by the thermodynamic evolution of coronal loops. In comparison with those previously reported slipping reconnection events, this one proceeds across a particularly long distance (similar to 60 Mm) over a long period of time (similar to 50 minutes) and shows two clearly distinguished phases: the propagation of the footpoint brightening driven by nonthermal particle injection and the apparent slippage of loops governed by plasma heating and subsequent cooling.</P>