• Journal of Life Science
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• v.15 no.5 s.72
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• pp.679-684
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• 2005

The objective of this study was investigate the characteristic of biosurfactant produced from the iso-lated strain. The strain was isolated from soli samples of Duck-Yu Mountain and it was identified as Bacillus atrophaeus DYL-130 by 16S rDNA and gyrA gene nucleotide sequence analysis. The surface ten-sion of culture filtrate of Bacillus atrophaeus DYL-130 decreased to 28 mN/m and its biosurfactant con-centration was determined by diluting the culture filtrate until the critical micelle concentration (CMC). The emulsifying activity and stability of crude biosurfactant was measured by using water-immiscible hydrocarbons and oils as substrate. The biosurfactant was purified by affinity chromatography and the surface activity of purified biosurfactant was measured by drop-collapsing method and it could be effectively emulsify toluene.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.504-509
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• 2004

The reaction of Cu metal with mixed alkali metal polyselenide flux ($KNaSe_x$) produced large plate-like crystals of $KCu_4Se_3$. The structure of $KCu_4Se_3$, determined with X-ray single crystal diffraction techniques, is tetragonal (P4/mmm, a=4.013(1))${\AA}$, c=9.712(1))${\AA}$, z=1, R=6.7%). The structure is composed $[Cu_4Se_3]_n^{n-}$double layers which are made of fused anti PbO-type Cu2Se2 layers. Temperature variable resistivity measurement on single crystal of $KCu_4Se_3$ shows metallic behavior ranging from $1.8{\times}10^{-4}{\Omega}{\cdot}cm$ (at 300 K) to $1.0{\times}10^{-6}{\Omega}{\cdot}cm$ (at 20 K).

• Investigative Magnetic Resonance Imaging
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• v.16 no.2
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• pp.152-158
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• 2012

Purpose : To compare the arterial and venous detection sites of triggering methods in contrast-enhanced-MR-venography (CE-MRV) for the evaluation of intracranial venous system. Materials and Methods: 41 healthy patients underwent CE-MRV with autotriggering at either the cavernous segment of internal carotid artery with an inserted time-delay of 6 seconds (n = 20) or the superior sagittal sinus without any timedelay (n = 21). 0.1 mmol/kg gadolinium-based contrast material ($Magnevist^{(R)}$, Schering, Germany) was intravenously injected by hand injection. A sagittal fast-spoiled-gradient-echo-sequence ranging from one ear to the other was performed (TR/TE5.2/1.5, Matrix $310{\times}310$, 124 sections in the 15-cm-thick volume). 17 predefined venous structures were evaluated on all venograms by two neuroradiologists and defined as completely visible, partially visible, or none visible. Results: The rate of completely visible structures were 272 out of 323 (84%) in the arterial triggering CE-MRV and 310 out of 340 (91%) in the venous triggering CE-MRV. The venous triggering CE-MRV demonstrated an overall superior visualization of the cerebral veins than the arterial triggering CE-MRV (Fisher exact test, p < 0.006). Conclusion: CE-MRV using venous autotriggering method provides higher-quality images of the intracranial venous structures compared to that of arterial.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.542-547
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• 2010

n-Paraffin and saturated fatty acid methyl esters in the diesel and bio-diesel fuel crystallize at low temperature. Many articles have addressed various solutions for the low temperature crystallization problem and one of them is the use of methacrylate copolymers. In this work, we synthesized a series of copolymers in the reaction condition of 70 : 30 molar ratio of lauryl methacrylate (LMA) (or stearyl methacrylate (SMA)) and alkyl methacrylates. The structures of the copolymers were characterized by $^1H$-NMR and FT-IR spectroscopy, and the molecular weight of copolymers were obtained from Gel Permeation Chromatography (GPC) method. The concentrations of additives were 500~1000 ppm and 1000~10000 ppm in diesel fuels and bio-diesel fuel (BD5 and BD20), respectively. The addition of copolymers changes the many properties of fuel such as the pour point (PP), cloud point (CP) and cold filtering plugging point (CFPP). For example, the low temperature properties of the copolymers containing SMA ($PSMAmR_2n$) were excellently improved about 15, 7, and $10^{\circ}C$ for PP, CP and CFPP, respectively.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.10-13
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• 2007

Single crystalline, $LuFe_2O_4$, was grown by the floating zone method. The crystal structure was a two-dimensional layered-type rhombohedral($R\={3}mh$) structure, with an $a_0=3.440(2)\;{\AA}\;and\;a\;c_0=25.263(2)\;{\AA}$. The magnetic $N\'{e}el$ temperature($T_N$) was determined to be 250 K. The $M\"{o}ssbauer$ spectrum at 12 K was fitted with four sextet sets which was resulted from the crystal structure. The spectrm at room temperature consisted of three singlets and a doublet with the electric quadrupole splitting. The isomer shift($\delta$) value of the singlet was $0.20{\pm}0.01mm/s$ relative to the Fe metal indicating the $Fe^{3+}$ valence state, and the value of the doublet was $0.70{\pm}0.01mm/s$ indicating $Fe^{2+}$. The $M\"{o}ssbauer$ absorption area ratio between $Fe^{3+}$ and $Fe^{2+}$ at room temperature was 1:1. The doublet phase of spectra gradually disappears by up to 360 K. At 360 K, the spectrum shows the singlet phase. We suggested that the spontaneous polarization effect of $LuFe_2O_4$ was caused by the change of iron behavior.

• Membrane Journal
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• v.12 no.1
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• pp.8-20
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• 2002

In this study using $N_2$-back flushing, which wwas not the general back-flushing method of membranes, the discharged wastewater from a paper plant was filtrated by 4 kinds of tubular carbon ceramic ultrafiltration membranes. We could in vestigate effects of $N_2$-back flushing period, transmembrane pressure (TMP)and flow rate and find optimal operating conditions. The $N_2$-back flushing time (BT) was fixed at 40 sec, filtration times (FT) were changed in 4~32 min, TNP in $1.0~3.0kg_f/cm^2$ the flow celocities in 0.53~1.09cm/s. The optimal conditions were discussed in the viewpoints of dimensionless permeate flux ($J/J_0$), toal permeate volume ($V_T$) and resistance of membrane fouling ($R_f$). Optimal back-flushing period was BT/FT=0.167 (FT=8 min ), in which more $V_T$ was obtained than that in BT/FT=0.083 (FT=4 min) which was the most friquent back-flushing condition. Then rising TMP should increase the driving force, and more $V_T$ could be accumulated. And rising flow rate should decrease membrane fouling increase permeate flux, and more $V_T$could be produced. Average rejection rates of pollutants were higher than 95% for turbidity and 45~83% for $COD_{Cr}$, but rejection rates of total dissolved solid (TDS) were lower than 10%.

• The Korean Journal of Nuclear Medicine
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• v.36 no.4
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• pp.261-270
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• 2002

Purpose: Nicotinic acetylcholine receptors (nAChRs), which mediate excitatory neurotransmission, are known to participate in various neurophysiological functions. Severe losses of nAChRs have been noted in Alzheimer's and Parkinson's diseases. Therefore, noninvasive and quantitative imaging of nAChRs would offer a better understanding on the function of these receptors. In this study, $2-[^{18}F]fluoro-A85380\;([^{18}F]1)$, an ${\alpha}_4{\beta}_2$ nAChRs radioligand, was prepared using one HPLC purification and evaluated in mouse brain, and the results were compared with those in the literature. Materials and Methods: $[^{18}F]1$ was prepared by $[^{18}F]$fluorination of the iodo precursor followed by acidic deprotection and then purified by HPLC. Tissue distribution studies were performed in mouse brain at the indicated time points and the result was expressed as %ID/g. Inhibition studies were also carried out with pretreatment of various ligands. Results: One HPLC purification method gave the desired product in 15-20% radiochemical yield and with high specific activity ($38-55GBq/{\mu}mol$). Tissue distribution studies showed that $[^{18}F]1$ specifically labeled nAChRs in mouse brain with a high thalamus to cerebellum uptake ratio (13.8 at 90 min). Inhibition studios demonstrated selective binding of $[^{18}F]1$ to nAChRs, blocking the uptake of the $[^{18}F]1$ in nAChR-rich legions by selective ligands such as cytisine and nicotine which are well-known nAChRs agonists. Conclusion: This study demonstrated that the $[^{18}F]1$ produced by the method using one HPLC purification gave the results similar to those reported in the literature. Therefore, this synthetic method can be readily applied to the routine preparation of $[^{18}F]1$, a PET radioligand for ${\alpha}_4{\beta}_2$ nAChRs imaging.

• Journal of Chest Surgery
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• v.33 no.4
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• pp.290-300
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• 2000

Background: To evaluate the diagnostic accuracy of EBT(Electron Beam Tomography) in the diagnosis of conotruncal anomaly and to determine whether it can be used as a substitute for cardiac angiography. Material and Method: 20 patients(11M & 9F) with TOF(n=7, pulmonary atresia 2), DORV(n=7), complete TGV(n=4), & corrected TGV(n=2) were included. The age ranged from 7 days to 26 years(median 60 days). We analyzed the sequential chamber localization, the main surgical concenrn in each disease category (PA size, LVED volume and coronary artery pattern for TOF & pulmonary atresia, the LV mass, LVOT obstruction, coronary artery pattern for complete TGV, and type of VSD and TV-PV distance for DORV, etc) and other associated anomalies(e.g., VSD, arch anomalies, tracheal stenosis, etc). Those were compared with the results of echocardiography(n=19), angiography (n=9), and surgery(n=11). The interval between EBT and echocardiography/angiography was within 20/11 days, respectively except for an angiography in a patient with corrected TGV (48 days). Result: EBT correctly diagnosed the basic components of conotruncal anomalies in all subjects, compared to echocardiography, angiography or surgery. These included the presence, type and size of VSD(n=20), pulmonic/LV outflow tract stenosis(n=15/2), relation of great arteries and the pattern of the proximal epicardial coronary arteries(16 out of 20). EBT proved to be accurate in quantitation of the intrapericardial and hilar pulmonary arterial dimension and showed high correlation and no difference compared with echocardiography, angiography, or surgery(p>0.05) except for left pulmonary arterial & ascending arterial dimension by echocardiography. LVED volume in seven TOF(no difference: p>0.05 & high correlation: r=0.996 with echocardiography), and LV mass in 4 complete TGV were obtained. Additionally, EBT enabled the cdiagnosis of subjlottic tracheal stenosis and tracheal bronchus in 1 respectively. Some peripheral PA stenosis were not detected by echocardiography, while echocardiography appeared to be slightly more accurate than EBT in detecing ASD or PDA. Conclusion: EBT can be a non-invasive and accurate modality of for the evaluation of most anatomical alteration including peripheral PS or interruption in patients with conotruncal anomalies. Combined with echocardiography, EBT study provides sufficient information for the palliative or total repair of anomalies.

• Corrosion Science and Technology
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• v.8 no.4
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• pp.162-169
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• 2009

Pure titanium and its alloys are drastically used in implant materials due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus than cortical bone. Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. For this reason, Ti-30Ta-xZr alloy systems have been studied in this study. The Ti-30Ta containing Zr(5, 10 and 15 wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24 hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and Ti coating and then coated with TiN, respectively, by using DC magnetron sputtering method. The analyses of coated surface were carried out by field emission scanning electron microscope(FE-SEM). The electrochemical characteristics were examined using potentiodynamic (- 1500 mV~+ 2000 mV) and AC impedance spectroscopy(100 kHz~10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The equiaxed structure was changed to needle-like structure with increasing Zr content. The surface defects and structures were covered with TiN/Ti coated layer. From the polarization behavior in 0.9% NaCl solution, The corrosion current density of Ti-30Ta-xZr alloys decreased as Zr content increased, whereas, the corrosion potential of Ti-30Ta-xZr alloys increased as Zr content increased. The corrosion resistance of TiN/Ti-coated Ti-30Ta-xZr alloys were higher than that of the TiN-coated Ti-30Ta-xZr alloys. From the AC impedance in 0.9% NaCl solution, polarization resistance($R_p$) value of TiN/Ti coated Ti-30Ta-xZr alloys showed higher than that of TiN-coated Ti-30Ta-xZr alloys.

• Journal of Veterinary Science
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• v.23 no.6
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• pp.12.01-12.10
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• 2022

Background: Staphylococcus aureus and Streptococcus agalactiae are the main cause of clinical mastitis in dairy cattle in Argentina, whereas coagulase-negative staphylococci (CNS) and environmental streptococci are the main cause of subclinical mastitis. Bacteria isolated from infected animals show increasing antimicrobial resistance. Objectives: This study aims to determine the antimicrobial resistance of staphylococci and streptococci isolated from milk with mastitis, and to genotypically characterize the methicillin-resistant (MR) staphylococci. Methods: Isolation was performed on blood agar and identification was based on biochemical reactions. Antimicrobial susceptibility was according to the Clinical and Laboratory Standards Institute guidelines. The antimicrobial resistance genes, SCCmec type and spa type were detected by the polymerase chain reaction method. Results: We isolated a total of 185 staphylococci and 28 streptococci from 148 milk samples. Among the staphylococcal isolates, 154 were identified as CNS and 31 as S. aureus. Among the 154 CNS, 24.6% (n = 38) were resistant to penicillin, 14.9% (n = 23) to erythromycin, 17.5% (n = 27) to clindamycin, 6.5% (n = 10) to cefoxitin and oxacillin. Among the S. aureus isolates, 16.1% (n = 5) were resistant to penicillin, 3.2% (n = 1) to cefoxitin and oxacillin (MRSA). Six MR isolates (5 CNS and 1 MRSA) were positive to the mecA gene, and presented the SCCmec IVa. The MRSA strain presented the sequence type 83 and the spa type 002. Among the 28 streptococcal isolates, 14.3% (n = 4) were resistant to penicillin, 10.7% (n = 3) to erythromycin and 14.3% (n = 4) to clindamycin. Conclusions: The present findings of this study indicate a development of antimicrobial resistance in main bacteria isolated from cows with mastitis in Argentina.