• Journal of Life Science
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• v.28 no.10
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• pp.1244-1253
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• 2018

Rumen microbiome consists of a wide variety of microorganisms, such as bacteria, archaea, protozoa, fungi, and viruses, that are in a symbiotic relationship in a strict anaerobic environment in the rumen. These rumen microbiome, a vital maker, play a significant role in feed fermentation within the rumen and produce different volatile fatty acids (VFAs). VFAs are essential for energy metabolism and protein synthesis of the host animal, even though emission of methane gas after feed fermentation is considered a negative indicator of loss of dietary energy of the host animal. To improve rumen microbial efficiency, a variety of approaches, such as feed formulation, the addition of natural feed additives, dietary feed-microbes, etc., have taken to increase ruminant performance. Recently with the application of high-throughput sequencing or next-generation sequencing technologies, especially for metagenomics and metatranscriptomics of rumen microbiomes, our understanding of rumen microbial diversity and function has significantly increased. The metaproteome and metabolome provide deeper insights into the complicated microbial network of the rumen ecosystem and its response to different ruminant diets to improve efficiency in animal production. This review summarized some recent advances of rumen microbiome techniques, especially "meta-omics," viz. metagenomic, metatranscriptomic, metaproteomic, and metabolomic techniques to increase feed fermentation and utilization in ruminants.

• Membrane Journal
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• v.30 no.4
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• pp.252-259
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• 2020

Olefins are industrially important materials used for the synthesis of various petrochemicals. During the polymerization process, unreacted olefin monomers are discharged together with a large amount of nitrogen. For economic benefits, these olefin gases should be efficiently separated from nitrogen. In this study, a poly(glycidyl methacrylate-co-methyl methacrylate) (PGM) comb-like copolymer was synthesized and 4,4'-diaminoazobenzene (DAAB) was introduced to the copolymer to prepare a cross-linked membrane for C₃H₆/N₂ separation. PGM and DAAB were readily reacted at room temperature through an epoxide-amine reaction without additional thermal treatment. PGM-based membrane, which is a glassy polymer, showed a faster permeation of N₂ compared to C₃H₆. The pristine PGM membrane exhibited the N₂ permeability of 0.12 barrer and the high N₂/C₃H₆ selectivity of 32.4. As DAAB was introduced as a cross-linker, the thermal stability of the membrane was significantly improved, which was confirmed by TGA result. The N₂/C₃H₆ selectivity was decreased at 1 wt% of DAAB content, but the N₂ permeability increased by approximately 4.7 times. We analyzed N₂/C₃H₆ gas separation properties through a glassy polymer-based membrane, which has not been widely studied. Also, we proposed that thermal stability of the membrane can be greatly improved by the cross-linking method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.4
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• pp.292-296
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• 2000

Mechenochemical reaction by planetary type ball mill is applied to prepare $Sm_2$$Fe_{17}$$N_{x}$ permanent magnet powders. Starting from pure samarium and iron powders, the formation process of hard magnetic $Sm_2$$Fe_{17}$$N_{x}$ phase by ball milling and a subsequent solid state reaction were studied. At as-milled stage powders were found to consist of amorphous Sm-Fe and $\alpha$-Fe phases in all composition of $Sm_2$$Fe_{100-x}$(x = 11, 13, 15). The dependence of starting composition of elemental powder on the formation of Sm-Fe intermetallic compound was investigated by heat treatment of as-milled powders. When Sm concentration was 15 at%, heat-treated powder consists of mostly $Sm_2$$Fe_{17}$$N_{x}$single phase. For synthesizing of hard magnetic $Sm_2$$Fe_{17}$$N_{x}$ compound, additional nitriding treatment was carried out under $N_2$gas atmosphere at $450^{\circ}C$. The increase in the coercivity and remanence was parallel to the nitrogen content which increased drastically at first and then gradually as the nitriding time was extended. The ball-milled Sm-Fe-N powders were expected to be prospective materials for synthesizing of permanent magnet with high performance.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.5
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• pp.181-187
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• 2016

In this study, new composition of orange color pigment was developed by replacing formerly used lead and chromium with environment-friendly elements. $TiO_2-SnO-ZnO$ composite was synthesized using the solid state reaction under the reducing atmosphere with the LPG and air mixture gas. The synthesized pigments were characterized by spectrophotometer, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The colorimetric analysis of pigments exhibited color values ranging from yellow to orange-red. Five different crystalline phases were formed after the heat treatment for 4 and 6 hours. The color of pigments was strongly influenced by the crystalline structure of $SnO_2$, having either cubic or tetragonal structure. The oxidation state study of elements revealed that the color of pigment is getting close to rYR with the increase of $Sn^{4+}$ ratio.

• Membrane Journal
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• v.27 no.6
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• pp.487-498
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• 2017

In this study, pervaporation performances of water/methanol and water/butanol mixture were evaluated using zeolite 4A membranes manufacutred by FINETECH by experimental works and numerical modeling. Permeation and separation characteristics, such as flux and separation factor, were analyzed by gas chromatography (TCD) and liquid nitrogen traps. Experiments have shown that water is selectively separated from a mixture of water and methanol (separation factor up to approximately 250) and water and butanol (separation factor up to approximately 1,500). Generalized Maxwell Stefan (GMS) theory was implemented to predict pervaporation behaviors of water/alcohol mixtures and diffusional coefficients of zeolite layer were obtained through parameter estimation using $MATLAB^{(R)}$ optimization toolbox. Since the pore size of zeolite 4A are much larger than kinetic diameter of water molecules and smaller than those of methanol and butanol, zeolite 4A membranes can be applied to in situ water removal process such as membrane reactors or hybrid reaction-dehydration process.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.358-363
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• 2013

Lithium-ammonia (Li-$NH_3$) solutions are possible to be successfully made under the vacuum condition but there still remains a problem of undergoing stable and reliable decomposition in vacuum for high-efficiency thermoelectric power generation. This paper describes a new method for improving the thermoelectric conversion efficiency of Li-$NH_3$ solutions in vacuum. The proposed method uses a 'U'-shaped Pyrex vacuum tube for the preparation and decomposition of pure fluid Li-$NH_3$ solutions. The tube is shaped so that a gas passageway ('U') connecting both legs of the 'U' helps to balance pressure inside both ends of the tube (due to $NH_3$ gasification) during decomposition on the hot side. Thermoelectric experimental results show that solution reaction in the 'U'-shaped tube proceeds more stably and efficiently than in the 'U'-shaped tube, and consequently, thermoelectric conversion efficiency is improved. It is also proved that the proposed method can provide a reversible reaction, which can rotate between synthesis and decomposition in the tube, for deriving the long-time, high-efficiency thermoelectric power.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.289-289
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• 2013

While there are plenty of studies on synthesizing semiconducting germanium nanowires (Ge NWs) by vapor-liquid-solid (VLS) process, it is difficult to inject dopants into them with uniform dopants distribution due to vapor-solid (VS) deposition. In particular, as precursors and dopants such as germane ($GeH_4$), phosphine ($PH_3$) or diborane ($B_2H_6$) incorporate through sidewall of nanowire, it is hard to obtain the structural and electrical uniformity of Ge NWs. Moreover, the drastic tapered structure of Ge NWs is observed when it is synthesized at high temperature over $400^{\circ}C$ because of excessive VS deposition. In 2006, Emanuel Tutuc et al. demonstrated Ge NW pn junction using p-type shell as depleted layer. However, it could not be prevented from undesirable VS deposition and it still kept the tapered structures of Ge NWs as a result. Herein, we adopt $C_2H_2$ gas in order to passivate Ge NWs with carbon sheath, which makes the entire Ge NWs uniform at even higher temperature over $450^{\circ}C$. We can also synthesize non-tapered and uniformly doped Ge NWs, restricting incorporation of excess germanium on the surface. The Ge NWs with carbon sheath are grown via VLS process on a $Si/SiO_2$ substrate coated 2 nm Au film. Thin Au film is thermally evaporated on a $Si/SiO_2$ substrate. The NW is grown flowing $GeH_4$, HCl, $C_2H_2$ and PH3 for n-type, $B_2H_6$ for p-type at a total pressure of 15 Torr and temperatures of $480{\sim}500^{\circ}C$. Scanning electron microscopy (SEM) reveals clear surface of the Ge NWs synthesized at $500^{\circ}C$. Raman spectroscopy peaked at about ~300 $cm^{-1}$ indicates it is comprised of single crystalline germanium in the core of Ge NWs and it is proved to be covered by thin amorphous carbon by two peaks of 1330 $cm^{-1}$ (D-band) and 1590 $cm^{-1}$ (G-band). Furthermore, the electrical performances of Ge NWs doped with boron and phosphorus are measured by field effect transistor (FET) and they shows typical curves of p-type and n-type FET. It is expected to have general potentials for development of logic devices and solar cells using p-type and n-type Ge NWs with carbon sheath.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.257-261
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• 2005

The microbial cellulose is in a form of three dimensional net structures that consists of 20~50 nm fibrils. It possesses high crystallinity and orientation. It is difficult to synthesize large amount of fibrous carbon nanomaterials by the carbonization process using raw materials such as polyacrylonitrile (PAN), regenerated cellulose (Rayon) and pitch. However, it seems possible thru the application of microbial cellulose as raw material. The application of such cellulose can be further extended to the synthesis of highly oriented graphite fiber. Out of three different cellulose-producing strains, G. xylinus ATCC11142 was chosen as it has the highest productivity (0.066 g dried cellulose/15 mL medium). Tar is often produced during the carbonization of cellulose that limits the formation fibrous structure of the carbonized sample. In order to solve such a problem, pre-studied purification methods of carbon nanotube such as liquid phase oxidation, gas phase oxidation and filtration associated with ultrasonication were applied at the carbonized cellulose. In that case. only by filtration associated with ultrasonication, improved the formation of fiber structure of the carbonized cellulose.

• Korean Journal of Food Science and Technology
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• v.46 no.5
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• pp.630-635
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• 2014

Pine nut oil (PNO) is well known to impart beneficial effects in overweight individuals, but the mechanisms underlying PNO-mediated weight loss remain unclear. To investigate how PNO promotes weight loss, its composition was determined by gas chromatography coupled with mass spectrometry (GC-MS). In addition, the effects of PNO on cytotoxicity, lipid accumulation, expression of lipid metabolism-related biomarkers, and leptin secretion were assessed in 3T3-L1 cells. GC-MS analyses revealed that PNO contains several components, including linoleic acid, oleic acid, palmitic acid, and stearic acid. Moreover, PNO did not have a cytotoxic effect on 3T3-L1 cells. However, it inhibited the expression of peroxisome proliferator-activated receptor (PPAR) and adipocyte protein 2 (aP2). Finally, PNO significantly increased leptin secretion in a dose-dependent manner. Taken together, these results support the notion that PNO is useful for weight management in overweight individuals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5376-5383
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• 2011

The objective of this study is the development of carbon-recycle technology, that converts carbon dioxide captured from flue gas to carbon monoxide or carbon for reuse in industrial fields. It is difficult to decompose $CO_2$ because $CO_2$ is very stable molecule. And then metal oxide was used as an activation agent or catalyst for the decomposition of $CO_2$ at low temperature. Metal oxides, which converts $CO_2$ to CO or C, were prepared using Ni-ferrite by solid state method and hydrothermal synthesis in this study. TPR/TPO and TGA were used as an analysis method to analyze the decomposition characteristics of $CO_2$. As the results, the reduction area of $H_2$ was high value at 15 wt% of NiO and the decomposition area of $CO_2$ was superior capacity at 5 wt% of NiO. However, TGA data showed contrary results that reduction area of $H_2$ was 28.47wt% and oxidation area by $CO_2$ was 26.95wt% at 2.5 wt% of NiO, one of the Ni-ferrite powders synthesized using solid state method. $CO_2$ decomposition efficiency was 94.66% and it is excellent results in comparison with previous studies.