Effect of Complexing/Buffering Agents on Morphological Properties of CuInSe<SUB>2</SUB> Layers Prepared by Single-Bath Electrodeposition

Hana Lee,Wonjoo Lee,Kyungwon Seo,Doh-Kwon Lee,Honggon Kim 한국태양광발전학회 2013 Current Photovoltaic Research Vol.1 No.1

For preparing a device-quality CuInSe2 (CISe) light-absorbing layer by single-bath electrodeposition for a superstrate-type CISe cell, morphological properties of the CISe layers were investigated by varying concentrations of sulfamic acid and potassium biphthalate, complexing/buffering agents. CISe films were grown on an In2Se3 film by applying a constant voltage of -0.5V versus Ag/AgCl for 90 min in a solution with precursors of CuCl2, InCl3, and SeO2, and a KCl electrolyte. A dense and smooth layer of CISe could be obtained with a solution containing both sulfamic acid and potassium biphthalate in a narrow concentration range of combination. A CISe layer prepared on the In2Se3 film with proper concentrations of complexing/buffering agents exhibited thickness of 1.6~1.8 μm with few undesirable secondary phases. On the other hand, when the bath solution did not contain either sulfamic acid or potassium biphthalate, a CISe film appeared to contain undesirable flake?shape Cu2-xSe phases or sparse pores in the upper part of film.

LTE-R 송수신기를 활용한 테스트베드 커버리지 성능 분석

서하나(Hana Seo),김주엽(Juyeop Kim),박성수(Sungsoo Park),양효선(Hyosun Yang) 한국통신학회 2016 한국통신학회 학술대회논문집 Vol.2016 No.6

Effect of Complexing/Buffering Agents on Morphological Properties of CuInSe₂ Layers Prepared by Single-Bath Electrodeposition

Lee, Hana,Lee, Wonjoo,Seo, Kyungwon,Lee, Doh-Kwon,Kim, Honggon Korea Photovoltaic Society 2013 Current Photovoltaic Research Vol.1 No.1

For preparing a device-quality $CuInSe_2$ (CISe) light-absorbing layer by single-bath electrodeposition for a superstrate-type CISe cell, morphological properties of the CISe layers were investigated by varying concentrations of sulfamic acid and potassium biphthalate, complexing/buffering agents. CISe films were grown on an $In_2Se_3$ film by applying a constant voltage of -0.5V versus Ag/AgCl for 90 min in a solution with precursors of $CuCl_2$, $InCl_3$, and $SeO_2$, and a KCl electrolyte. A dense and smooth layer of CISe could be obtained with a solution containing both sulfamic acid and potassium biphthalate in a narrow concentration range of combination. A CISe layer prepared on the $In_2Se_3$ film with proper concentrations of complexing/buffering agents exhibited thickness of $1.6{\sim}1.8{\mu}m$ with few undesirable secondary phases. On the other hand, when the bath solution did not contain either sulfamic acid or potassium biphthalate, a CISe film appeared to contain undesirable flake-shape $Cu_{2-x}Se$ phases or sparse pores in the upper part of film.

Repetitive Transcranial Magnetic Stimulation Enhances Recovery in Central Cord Syndrome Patients

Hana Choi,Kyung Cheon Seo,Tae Uk Kim,Seong Jae Lee,Jung Keun Hyun 대한재활의학회 2019 Annals of Rehabilitation Medicine Vol.43 No.1

Objective To investigate the effect of repetitive transcranial magnetic stimulation (rTMS) on neurological and functional recovery in patients with central cord syndrome (CCS) involving the upper extremities between the treated and non-treated sides of the treated group and whether the outcomes are comparable to that of the untreated control group. Methods Nineteen CCS patients were treated with high-frequency (20 Hz) rTMS over the motor cortex for 5 days. The stimulation side was randomly selected, and all the subjects received conventional occupational therapy during the rTMS-treatment period. Twenty CCS patients who did not receive rTMS were considered as controls. Clinical assessments, including those by the International Standard for Neurological Classification of Spinal Cord Injury, the Jebsen-Taylor Hand Function Test, and the O'Connor Finger Dexterity Test were performed initially and followed up for 1 month after rTMS treatment or 5 weeks after initial assessments. Results The motor scores for upper extremities were increased and the number of improved cases was greater for the treated side in rTMS-treated patients than for the non-treated side in rTMS-treated patients or controls. The improved cases for writing time and score measured on the Jebsen-Taylor Hand Function Test were also significantly greater in number on the rTMS-treated side compared with the non-treated side and controls. There were no adverse effects during rTMS therapy or the follow-up period. Conclusion The results of the application of high-frequency rTMS treatment to CCS patients suggest that rTMS can enhance the motor recovery and functional fine motor task performance of the upper extremities in such individuals.

Photoreactive natural polymer for medical application

Hana Na,Yoshihiro Ito,Hyoungjae Lee,Shinhye Park,Siwoong Seo,Kwangil Kim,Taeil Son 한국당과학회 2011 한국당과학회 학술대회 Vol.2011 No.1

Mainly, chemical and physical methods have been used for immobilization of bioactive materials. However, there are some of drawbacks with those methods. For example, chemical method may produce potential toxic by-product and, in case of physical method, low efficiency of immobilized bioactive material is observed. To solve these problems, recently, the immobilization by photoreaction has been researched widely. The advantages of photo-immobilization are 1) high selectivity of chemical reactions or processes under mild conditions (ambient temperature of also much below), 2) typically no need for added catalysts or special solvents, 3) spatially addressable effects (2D and 3D structuring possible) and 4) applicable to very small and (relatively) large scales. To use for photo-immobilization, various natural polymers reacted by irradiation to ultra violet and visible light can be synthesized. It is considered that these photoreactive natural polymers can be applied for medical area to increase biocompatibility and functionality, for example, coating agent for bioinnert devices like stent and implant, anti-adhesive agent, wound dressing and bio-adhesive.

Composition-Tuned Co_<i>n</i>Si Nanowires: Location-Selective Simultaneous Growth along Temperature Gradient

Seo, Kwanyong,Lee, Sunghun,Yoon, Hana,In, Juneho,Varadwaj, Kumar S. K.,Jo, Younghun,Jung, Myung-Hwa,Kim, Jinhee,Kim, Bongsoo American Chemical Society 2009 ACS NANO Vol.3 No.5

<P>We report the simultaneous and selective synthesis of single-crystalline Co(n)Si NWs (n = 1-3) and their corresponding crystal structures--simple cubic (CoSi), orthorhombic (Co(2)Si), and face-centered cubic (Co(3)Si)--following a composition change. Co(n)Si NWs were synthesized by placing the sapphire substrates along a temperature gradient. The synthetic process is a successful demonstration of tuning the chemical composition in Co(n)Si NWs. The synthesis and detailed crystal structure of single-crystalline Co(2)Si and Co(3)Si are reported for the first time including the bulk and the nanostructure phases. The electrical and magnetic properties of Co(2)Si NWs are investigated and compared with those of CoSi NWs.</P>

Pressure-volume-temperature gauging method experiment using liquid nitrogen under microgravity condition of parabolic flight

Seo, Mansu,Park, Hana,Yoo, DonGyu,Jung, Youngsuk,Jeong, Sangkwon The Korea Institute of Applied Superconductivity a 2014 한국초전도저온공학회논문지 Vol.16 No.2

Measuring an exact amount of remaining cryogenic liquid propellant under microgravity condition is one of the important issues of rocket vehicle. A Pressure-Volume-Temperature (PVT) gauging method is attractive due to its minimal additional hardware and simple gauging process. In this paper, PVT gauging method using liquid nitrogen is investigated under microgravity condition with parabolic flight. A 9.2 litre metal cryogenic liquid storage tank containing approximately 30% of liquid nitrogen is pressurized by ambient temperature helium gas. During microgravity condition, the inside of the liquid tank becomes near-isothermal condition within 1 K difference indicated by 6 silicon diode sensors vertically distributed in the middle of the liquid tank. Helium injection with higher mass flow rate after 10 seconds of the waiting time results in successful measurements of helium partial pressure in the tank. Average liquid volume measurement error is within 11% of the whole liquid tank volume and standard deviation of errors is 11.9. As a result, the applicability of PVT gauging method to liquid propellant stored in space is proven with good measurement accuracy.

Itinerant Helimagnetic Single-Crystalline MnSi Nanowires

Seo, Kwanyong,Yoon, Hana,Ryu, Seong-Wan,Lee, Sunghun,Jo, Younghun,Jung, Myung-Hwa,Kim, Jinhee,Choi, Yang-Kyu,Kim, Bongsoo American Chemical Society 2010 ACS NANO Vol.4 No.5

<P>We report the synthesis of free-standing MnSi nanowires <I>via</I> a vapor transport method with no catalyst and measurements of their electrical and magnetic properties for the first time. The single-crystalline MnSi nanowire ensemble with a simple cubic (B20) crystal structure shows itinerant helimagnetic properties with a <I>T</I><SUB>c</SUB> of about 30 K. A single MnSi nanowire device was fabricated by a new method using photolithography and a nanomanipulator that produces good ohmic contacts. The single-nanowire device measurements provide large (20%) negative magnetoresistance and very low electrical resistivity of 544 μΩcm for the MnSi nanowire.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-5/nn901653q/production/images/medium/nn-2009-01653q_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn901653q'>ACS Electronic Supporting Info</A></P>

Diffusion-Driven Crystal Structure Transformation: Synthesis of Heusler Alloy Fe₃Si Nanowires

Seo, Kwanyong,Bagkar, Nitin,Kim, Si-in,In, Juneho,Yoon, Hana,Jo, Younghun,Kim, Bongsoo American Chemical Society 2010 NANO LETTERS Vol.10 No.9

<P>We report fabrication of Heusler alloy Fe<SUB>3</SUB>Si nanowires by a diffusion-driven crystal structure transformation method from paramagnetic FeSi nanowires. Magnetic measurements of the Fe<SUB>3</SUB>Si nanowire ensemble show high-temperature ferromagnetic properties with <I>T</I><SUB>c</SUB> ≫ 370 K. This methodology is also successfully applied to Co<SUB>2</SUB>Si nanowires in order to obtain metal-rich nanowires (Co) as another evidence of the structural transformation process. Our newly developed nanowire crystal transformation method would be valuable as a general method to fabricate metal-rich silicide nanowires that are otherwise difficult to synthesize.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-9/nl102093e/production/images/medium/nl-2010-02093e_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl102093e'>ACS Electronic Supporting Info</A></P>

Elevated expression of exogenous RAD51 enhances the CRISPR/Cas9-mediated genome editing efficiency

Seo Jung Park,Seobin Yoon,Eui-Hwan Choi,Hana Hyeon,Kangseok Lee,김근필 생화학분자생물학회 2023 BMB Reports Vol.56 No.2

Genome editing using CRISPR-associated technology is widelyused to modify the genomes rapidly and efficiently on specificDNA double-strand breaks (DSBs) induced by Cas9 endonuclease. However, despite swift advance in Cas9 engineering,structural basis of Cas9-recognition and cleavage complex remainsunclear. Proper assembly of this complex correlates toeffective Cas9 activity, leading to high efficacy of genomeediting events. Here, we develop a CRISPR/Cas9-RAD51 plasmidconstitutively expressing RAD51, which can bind to singlestrandedDNA for DSB repair. We show that the efficiency ofCRISPR-mediated genome editing can be significantly improvedby expressing RAD51, responsible for DSB repair via homologousrecombination (HR), in both gene knock-out and knock-inprocesses. In cells with CRISPR/Cas9-RAD51 plasmid, expressionof the target genes (cohesin SMC3 and GAPDH) was reducedby more than 1.9-fold compared to the CRISPR/Cas9 plasmidfor knock-out of genes. Furthermore, CRISPR/Cas9-RAD51 enhancedthe knock-in efficiency of DsRed donor DNA. Thus, theCRISPR/Cas9-RAD51 system is useful for applications requiringprecise and efficient genome edits not accessible to HR-deficientcell genome editing and for developing CRISPR/Cas9-mediatedknockout technology.