The methoxymalonyl-acyl carrier protein biosynthesis locus and the nearby gene with the β-ketoacyl synthase domain are involved in the biosynthesis of galbonolides in Streptomyces galbus, but these loci are separate from the modular polyketide synthase

Karki, Suman,Kwon, So-Yeon,Yoo, Hye-Gyeong,Suh, Joo-Won,Park, Si-Hyung,Kwon, Hyung-Jin Oxford University Press 2010 FEMS microbiology letters Vol.310 No.1

Determination of Mo- and Ca-isotope ratios in ^{Ca 100} _{MoO 4} crystal for AMoRE-I experiment

Karki, S.,Aryal, P.,Kim, H.J.,Kim, Y.D.,Park, H.K. Elsevier 2018 Nuclear Instruments & Methods in Physics Research. Vol.877 No.-

<P><B>Abstract</B></P> <P>The first phase of the AMoRE (Advanced Mo-based Rare process Experiment) is to search for neutrinoless double-beta decay of <SUP>100</SUP>Mo with calcium molybdate ( <SUP> Ca 100 </SUP> <SUB> MoO 4 </SUB> ) crystals enriched in <SUP>100</SUP>Mo and depleted in <SUP>48</SUP>Ca using a cryogenic technique at Yangyang underground laboratory in Korea. It is important to know <SUP>100</SUP>Mo- and <SUP>48</SUP>Ca-isotope ratios in <SUP> Ca 100 </SUP> <SUB> MoO 4 </SUB> crystal to estimate half-life of <SUP>100</SUP>Mo decays and to 2 ν β β background from <SUP>48</SUP>Ca. We employed the ICP-MS (Inductive Coupled Plasma Mass Spectrometer) to measure <SUP>100</SUP>Mo- and <SUP>48</SUP>Ca-isotope ratios in <SUP> Ca 100 </SUP> <SUB> MoO 4 </SUB> crystal. The measured results for <SUP>100</SUP>Mo- and <SUP>48</SUP>Ca-isotope ratios in the crystal are ( 94 . 6 ± 2 . 8 ) % and ( 0 . 00211 ± 0 . 00006 ) %, respectively, where errors are included both statistical and systematic uncertainties.</P>

Three-dimensional nanoporous polyacrylonitrile-based carbon scaffold for effective separation of oil from oil/water emulsion

Karki, Hem Prakash,Kafle, Laxmi,Ojha, Devi Prasad,Song, Jun Hee,Kim, Han Joo Elsevier 2018 Polymer Vol.153 No.-

<P><B>Abstract</B></P> <P>The hydrophobic nature of the substances has served as important tools for governing the spatial behaviors of various fibrous substances depending on their affinities to oils or organic liquids. Herein, electrospun two-dimensional (2D) polyacrylonitrile (PAN) fiber mat was converted into three-dimensional (3D) mesh by hydrogen gas foaming technique using aqueous sodium borohydride (NaBH<SUB>4</SUB>) solution, which on heating at high temperature under a nitrogen atmosphere produced ultra-light, low density, hydrophobic 3D carbon scaffold with distinct affinities to oil phases. The fibrous materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectra. Specific surface area and porosity of the fiber were analyzed by the Brunauer-Emmett-Teller (BET) technique. The carbon scaffold exhibit dominance as absorbents for selectively separating oils such as diesel, canola oil, xylene, and n-hexane with absorption capacity from 68.71 g g<SUP>−1</SUP> to 131.33 g g<SUP>−1</SUP>. More interestingly, the absorbed oils were readily collected by simple mechanical squeezing and the recovered 3D carbon scaffold could be reused for the successive absorptions. This carbon scaffold could be a versatile platform to offer a kind of efficient and selective absorbent material for absorption of oils or organic liquids from the water.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrospinning technique was employed to fabricate 2D PAN fiber mat. </LI> <LI> 3D PAN fiber mesh was obtained from the 2D mat by neutral gas foaming technique. </LI> <LI> The pyrolysis of 3D fiber mesh was performed to get hydrophobic 3D PAN-based carbonized fiber. </LI> <LI> 3D carbon fiber scaffold was exploited for the successful sorption of oils from oil/water emulsion. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Hydroxychalcones as Potential Anti-Angiogenic Agent

Karki, Radha,Kang, You-Ra,Kim, Chul-Hoon,Kwak, Kyung-Sook,Kim, Jung-Ae,Lee, Eung-Seok Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.9

Synthesis, Topoisomerase I and II Inhibitory Activities, and Cytotoxicity of 4,6-Diaryl-2,4'-bipyridine Derivatives

Karki, Radha,Thapa, Pritam,Kwon, Young-Joo,Lee, Eung-Seok Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.6

Effective reduction of <i>p</i>-nitrophenol by silver nanoparticle loaded on magnetic Fe₃O₄/ATO nano-composite

Karki, Hem Prakash,Ojha, Devi Prashad,Joshi, Mahesh Kumar,Kim, Han Joo Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.435 No.-

<P><B>Abstract</B></P> <P>A silver loaded hematite (Fe<SUB>3</SUB>O<SUB>4</SUB>) and antimony doped tin oxide (ATO) magnetic nano-composite (Ag-Fe<SUB>3</SUB>O<SUB>4</SUB>/ATO) was successfully synthesized by in situ one pot green and facile hydrothermal process. The formation of nano-composite, its structure, morphology, and stability were characterized by field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), electron diffraction spectroscopy (EDS), elemental mapping by high resolution scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red spectroscopy (FTIR). UV–vis spectroscopy was used to monitor the catalytic reduction of <I>p</I>-nitrophenol (PNP) into p-aminophenol (PAP) in presence of Ag-Fe<SUB>3</SUB>O<SUB>4</SUB>/ATO nano-composite with excess of sodium borohydride (NaBH<SUB>4</SUB>). The pseudo-first order kinetic equation could describe the reduction of <I>p</I>-nitrophenol with excess of NaBH<SUB>4</SUB>. For the first time, ATO surface was used for hydrothermal growth of silver and iron oxide magnetic nanoparticles. The in situ growth of these nanoparticles provided an effective bonding of components of the nano-composite over the surface of ATO nanoparticles. This nano-composite exhibited easy synthesis, high stability, cost effective and rapid separation using external magnet. The excellent catalytic and anti-bacterial activity of as-synthesized silver nano-composite makes it potential nano-catalyst for waste water treatment as well as biomedical application.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag-Fe<SUB>3</SUB>O<SUB>4</SUB>/ATO nano-catalyst is synthesized via facile one pot hydrothermal process. </LI> <LI> The common organic water pollutant PNP was reduced into PAP. </LI> <LI> Nano-composite exhibited superior catalytic and anti-bacterial activities. </LI> <LI> Easy separation from reaction system using an external magnet for successive use. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of Sowing Time on Germination and Early Seedling Growth of Quercus floribunda Lindl.

Karki, Himani,Bargali, Kiran,Bargali, SS Institute of Forest Science 2018 Journal of Forest Science Vol.34 No.3

Quercus floribunda (Tilonj oak) is among the five species of Quercus and an evergreen tree found in Kumaun Himalayan region. Timing of germination is a crucial event determining the success of seedling establishment and survival. The aims of the study were to investigate the effect of sowing date on the germination and morphological responses of Tilonj oak (Quercus floribunda), cultivated during the month of August-September, with supplementary irrigation. The experiment was conducted by sowing seeds at two dates with one month interval in glass house conditions at DSB Campus, Nainital, Uttarakhand, India. Present study revealed that higher germination percentage (46.67 %) was recorded at sowing time $S_2$ as compared to the sowing time $S_1$ (32.86 %). Germination percentage as well as seedling growth were affected by sowing date though the differences were insignificant. At both the sowing dates, highest germination percentage was recorded for large seeds (32.86-46.67 %) followed by medium (31.43-33.33 %) and lowest germination (6.67-7.14 %) was recorded for small size seeds. In all parameters assessed, sowing time $S_2$ had the best performance in combination with large seed size. Thus, September is suitable month for best germination, growth and seedling vigour and large seed size is recommended to silviculturists and tree planters. The information on seed germination and seedling growth is vital both for conservation and rehabilitation of degraded lands.

Comparative Analysis of Torrefaction Characteristics of Sewage Sludge using Fluidized and Downdraft Fixed Bed Reactors

Karki Sujeeta,Ja hyung Choi,Jeeban Poudel,Sea Cheon Oh 한국폐기물자원순환학회 2018 한국폐기물자원순환학회 학술대회 Vol.2018 No.05

The aim of this project was to explore the potential of the torrefaction treatment for upgrading sewage sludge into valuable product. An ancillary investigation on the cold fluidization and the behavior of sewage sludge was analyzed. The effects of the main torrefaction variables, temperature and residence time, on the performance parameters such as fixed carbon, calorific value; molar ratios, ultimate and proximate analysis, chemical exergy etc. were investigated for torrefied sewage sludge. Results for both the reactors showed that the thermochemical transformations that sewage sludge underwent, as a results of the release of volatile matter due to thermal decomposition of its organic constituents, resulted in significant improvement of their chemical and physical properties. Results obtained from this study showed that despite the leverage that fluidized bed offers (heat and mass transfer) fixed bed configuration was more pronounced for torrefaction of sewage sludge. However, a decisive conclusion cannot be made at this stage as more detail study would be required to draw a definitive conclusion over the preference of reactor for torrefaction.

1P-628 Thermal Pre-treatment of Sewage Sludge in Fluidized Bed for Enhancing its Solid Fuel Properties

( Karki Sujeeta ),( Poudel Jeeban ),오세천 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

In the present work, fluidization of sewage sludge, a non-lignocellulosic biomass, was studied using a bench scale fluidized bed. The influence of torrefaction temperature ranging from 200 - 350°C and residence time of 0 - 50 minutes on the physical and chemical properties of sewage sludge was investigated. The properties of torrefied product were analyzed on the basis of degree of torrefaction, ultimate and proximate analysis, gas analysis and chemical exergy. The degree of torrefaction and chemical exergy showed positive influence on increasing the torrefaction temperature. The effect of torrefaction temperature and residence time was studied on elemental variation of sewage sludge which exhibited a decrease of H/C and O/C ratios. The product gas emitted during torrefaction was analyzed to study the pathway of hydrocarbons and oxygen containing compounds. Torrefaction using fluidized bed improved the overall physiochemical properties of sewage sludge.

Evaluation of seismic strengthening techniques for non-ductile soft-story RC frame

Karki, Prajwol,Oinam, Romanbabu M.,Sahoo, Dipti Ranjan Techno-Press 2020 Advances in concrete construction Vol.9 No.4

Open ground story (OGS) reinforced concrete (RC) buildings are vulnerable to the complete collapse or severe damages under seismic actions. This study investigates the effectiveness of four different strengthening techniques representing the local and global modifications to improve the seismic performance of a non-ductile RC OGS frame. Steel caging and concrete jacketing methods of column strengthening are considered as the local modification techniques, whereas steel bracing and RC shear wall systems are selected as the global strengthening techniques in this study. Performance-based plastic design (PBPD) approach relying on energy-balance concept has been adopted to determine the required design force demand on the strengthening elements. Nonlinear static and dynamic analyses are carried out on the numerical models of study frames to assess the effectiveness of selected strengthening techniques in improving the seismic performance of OGS frame.. Strengthening techniques based on steel braces and RC shear wall significantly reduced the peak interstory drift response of the OGS frame. However, the peak floor acceleration of these strengthened frames is amplified by more than 2.5 times as compared to that of unstrengthened frame. Steel caging technique of column strengthening resulted in a reasonable reduction in the peak interstory drift response without substantial amplification in peak floor acceleration of the OSG frame.