• Title/Summary/Keyword: oxygen level

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The Influence of CH3Cl on CH4/CH3Cl/O2/N2 Premixed Flames Under the O2 Enrichment (산소부화 조건인 CH4/CH3Cl/O2/N2 예혼합 화염에서 CH3Cl의 영향)

  • Shin Sung Su;Lee Ki Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.2 s.233
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    • pp.255-262
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    • 2005
  • A comprehensive experimental and numerical study has been conducted to understand the influence of $CH_{3}Cl$ addition on $CH_4/O_2/N_2$ premixed flames under the oxygen enrichment. The laminar flame speeds of $CH_4/CH_{3}Cl/O_2/N_2$ premixed flames at room temperature and atmospheric pressure are experimentally measured using Bunsen nozzle flame technique, varying the amount of $CH_{3}Cl$ in the fuel, the equivalence ratio of the unburned mixture, and the level of the oxygen enrichment. The flame speeds predicted by a detailed chemical kinetic mechanism employed are found to be in excellent agreement with those deduced from experiments. Even though the molar amount of $CH_{3}Cl$ in a methane flame is increased, temperature at the postflame is not significantly varied, but the calculated heat release rate and emission index of NO are largely decreased for the oxygen enhanced flame. The function of $CH_{3}Cl$ as inhibitor on hydrocarbon flames becomes weakened as the level of the oxygen enrichment is increased from 0.21 to 0.5.

Regulation of Metabolic Flux in Lactobacillus casei for Lactic Acid Production by Overexpressed ldhL Gene with Two-Stage Oxygen Supply Strategy

  • Ge, Xiang-Yang;Xu, Yan;Chen, Xiang;Zhang, Long-Yun
    • Journal of Microbiology and Biotechnology
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    • v.25 no.1
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    • pp.81-88
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    • 2015
  • This study describes a novel strategy to regulate the metabolic flux for lactic acid production in Lactobacillus casei. The ldhL gene encoding L-lactate dehydrogenase (L-LDH) was overexpressed in L. casei, and a two-stage oxygen supply strategy (TOS) that maintained a medium oxygen supply level during the early fermentation phase, and a low oxygen supply level in the later phase was carried out. As a consequence, a maximum L-LDH activity of 95.6 U/ml was obtained in the recombinant strain, which was over 4-fold higher than that of the initial strain. Under the TOS for L. casei (pMG-ldhL), the maximum lactic acid concentration of 159.6 g/l was obtained in 36 h, corresponding to a 62.8% increase. The results presented here provide a novel way to regulate the metabolic flux of L. casei for lactic acid production in different fermentation stages, which is available to enhance organic acid production in other strains.

The High Concentration Oxygen Therapy in Severe Head Injury Patients (중증 뇌손상 환자에서 고농도 산소치료법)

  • Park, Sung-Ho;Park, Han-Jun;Youn, Seung-Hwan;Cho, Joon;Moon, Chang-Taek;Chang, Sang-Jeun
    • Journal of Korean Neurosurgical Society
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    • v.30 no.sup1
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    • pp.37-43
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    • 2001
  • Object : The rapid and early oxygen delivery to brain tissue was a common therapeutic method in the treatment of severe head injury patients. The purpose of this study was to investigate the effect of increased fraction of inspired oxygen in early stage of severe head injury. Methods : The parameters of research were CSF(cerebral spinal fluid) oxygen pressure($PcsfO_2$), lactate, pH, temperature, and CSF carbon dioxide pressure($PcsfCO_2$). We selected 28 patients with head trauma whose the Glasgow Coma Scale(GCS) score was less than 8 point at admission. All patients were mechanically ventilated and monitored with the commercial ICP monitoring device. Each of parameters was compared as increased fraction of inspired oxygen. In experimental cohort of 14 patients, the mean $PcsfO_2$ level was increased to $314.93{\pm}259.15mmHg$ by raising the $FiO_2$ from 40% to 100% for nine hours(p<0.05). And the mean CSF lactate level was decreased to $2.96{\pm}1.98mmol/L$ on 100% $FiO_2$ as compared with $5.98{\pm}3.25mmol/L$ on 40% $FiO_2$ in control group(p<0.05). The only above two parameters were showed statistically meaningful outcome. Conclusions : Although this study was performed in small cohort and short period, these results supports that increased inspired oxygen therapy in severe head injuried patients was recommended as a modality of treatment in future through the continuous survey.

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The Effect of Highly Concentrated Oxygen Administration on Cerebrum Lateralization of Young Men during Visuospatial Task (고농도의 산소 공급이 공간지각 과제 수행 시 젊은 성인 남자의 대뇌 편측화에 미치는 영향)

  • 정순철;손진훈;김익현
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.8
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    • pp.180-187
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    • 2004
  • The present study attempted to investigate the effects of supply of highly concentrated (30%) oxygen on human ability of visuospatial cognition and cerebrum lateralization. compared to air of normal oxygen concentration (21%). The experiment consisted of two runs, one fur visuospatial cognition test with normal air (21% of oxygen) and for visuospatial cognition test with more oxygen in the air (30% of oxygen). Each run was composed of four blocks and each block included eight control tasks and five visuospatial tasks. Functional brain images were taken from 3T MRI using the single-shot EPI method. The result of task performance showed the accuracy increased at 30%'s concentration of oxygen rather than 21%'s. There were more activations observed at the left and right hemisphere, but there was decrease cerebrum lateralization with 30% oxygen administration. Thus, it is concluded that the positive effect on the visuospatial cognitive performance level by the highly concentrated oxygen administration was due to increase of cerebrum activation and decrease of cerebrum lateralization

Coverage Dependent Adsorption and Electronic Structure of Threonine on Ge (100) Surface

  • Lee, Myeong-Jin;Kim, Gi-Jeong;Lee, Han-Gil
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.212-212
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    • 2012
  • The Coverage dependent attachment of multifunctional groups included in threonine molecules adsorbed to Ge (100)$-2{\times}1$ surface was investigated using core-level photoemission spectroscopy (CLPES) and density functional theory (DFT) calculations. The core-level spectra at a low coverage indicated that the both carboxyl and amine groups participated in the bonding with the Ge (100) surface by "O-H dissociated and N-dative bonded structure". However, at high coverage level, additional adsorption geometry of "O-H dissociation bonded structure" appeared possibly to minimize the steric hindrance between adsorbed molecules. Moreover, the C 1s, N 1s, and O 1s core level spectra confirmed that the carboxyl oxygen is more competitive against the hydroxymethyl oxygen in the adsorption reaction. The adsorption energies calculated using DFT methods suggested that four of six adsorption structures were plausible. These structures were the "O-H dissociated-N dative bonded structure", the "O-H dissociation bonded structure", the "Om-H dissociated-N dative bonded structure", and the "Om-H dissociation bonded structure" (where Om indicates the hydroxymethyl oxygen). These structures are equally likely, according to the adsorption energies alone. Conclusively, we investigate in threonine on Ge (100) surface system that the "O-H dissociated-N dative bonded structure" and the "O-H dissociation bonded structure" are preferred at low coverage and high coverage.

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Effect of NADH-Dependent Enzymes Related to Oxygen Metabolism on Elimination of Oxygen-Stress of Bifidobacteria (NADH요구 산소대사관련 효소가 bifidobacteria의 산소스트레스 제거에 미치는 영향)

  • Ahn, Jun-Bae;Park, Jong-Hyun
    • Korean Journal of Food Science and Technology
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    • v.37 no.6
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    • pp.951-956
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    • 2005
  • Selection of oxygen-tolerant strains and elucidation of their oxygen tolerance mechanism were crucial for effective use of bifidobacteria. Oxygen-tolerant bifidobacteria were able to significantly remove environmental oxygen (oxygen removal activity) as compared to oxygen-sensitive strains. Most oxygen removal activity was inhibited by heat treatment and exposure to extreme pH (2.0) of bifidobacterial cell. NADH oxidase was major enzyme related to oxygen removal activity. Oxygen-tolerant bifidobacteria possessed high NADH peroxidase activity level to detoxify $H_2O_2$ formed from reaction of NADH oxidase. Addition of oxygen to anaerobic culture broth significantly increased activities of HADH oxidase and NADH peroxidase within 1hr and rapid increment of oxygen concentration was prevented. Results showed NADH oxidase and NADH peroxidase of oxygen-tolerant bifidobacteria played important roles in elimination of oxygen and oxygen metabolite $(H_2O_2)$.

Combustion characteristics of coaxial diffusion flame with preheated air temperature and dilution level (예열공기온도와 희석비율에 따른 동축 확산 화염의 연소 특성)

  • Kim, Jin-Sik;Kwark, Ji-Hyun;Jeon, Chung-Hwan;Chang, Young-June
    • 한국연소학회:학술대회논문집
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    • 2001.11a
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    • pp.51-56
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    • 2001
  • An experiment using preheated air in the coaxial diffusion flame burner was carried out in order to decrease NOx emission and improve the thermal efficiency. Preheated air combustion generally produces high NOx emissions but it was known very well to reduce NOx emission by diluting the combustion air with inert gas in preheated air combustion. In our study, $N_2$ gas was used for diluent and propane was utilized for fuel. We set the combustion air temperature on 300K, 500K, 700K, 900K and dilution level from 21% to 10% in terms of oxygen concentration. NOx emission increased along increment of combustion air temperature and decreased along increment of dilution level(lowering of oxygen concentration in combustion air). Flame-off limit with dilution level enhanced, flame length became longer and the location of maximum flame temperature became lower with increasing of combustion air temperature.

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Development of pub Level Dissolved Oxygen Measuring Technology using Clark Cell (Clark Cell을 이용한 ppb단위 용존산소 측정기술개발)

  • 정경열;류길수
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.3
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    • pp.375-381
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    • 2002
  • Measuring of the dissolved oxygen is widely used for the environmental control of natural waters, sewage waste treatment, medical and biochemical studies, soil husbandry, food and drug process control, and prevention of corrosion in boilers. Especially, a power plants need special management for preventing accidents from corrosion, therefore, it is essential to measure the concentration of dissolved oxygen in real-time. In this paper we present a method of measuring dissolved oxygen very accurately up to pub units. This method, called polarograph method, is based on the measures of the electric current generated by the oxidation process in cathode and de-oxidation process in anode, assuming that the amount of the current is proportional to the density of dissolved oxygen.

Microaerophilies of campylobacters and related organisms

  • Han, Yeong-Hwan
    • The Microorganisms and Industry
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    • v.18 no.3
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    • pp.23-33
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    • 1992
  • The general characteristics of campylobacters and related organisms (e.g., species of the genera Helicobacter and Wolinella, Bacteroides ureolyticus, and Bacteroides gracilis) are as follows: slender, non-sporeforming, gram-negative, vibroid bacteria (helical- or spiral- shpaed; except that B. ureolyticus and B. gracilis are straight-rod), 0.2-0.5 .mu.m in width and 0.5 .mu.m in length. (Smibert, 1984; Penner, 1988). The species of genus Campylobacter and related organisms are chemoorganotrophs; however, they neither oxidize nor ferment carbohydrates and instead obtain energy from amino acids, the salts of tricarboxylic acids (TCA) cycle intermediates, the salts of organic acids, or, in some species, H$\_$2/. With regard to their oxygen responses for growth, they all are microaeophilic i.e., they are capable of oxygen-dependent growth (respiring with oxygen as a terminal electron acceptor) but can not grow in the presence of a level of oxygen equivalent to that present in an air atmosphere (21% oxygen). This review will take interests in how these microorganisms response to oxygen for growth and what repiratory types they have.

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EFFECTS OF SPLIT INJECTION AND OXYGEN-ENRICHED AIR ON SOOT EMISSIONS IN A DIESEL ENGINE

  • Nguyen, Khai;Sung, Nak-Won;Lee, Sang-Su
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2965-2970
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    • 2008
  • Effects of split injection and oxygen-enriched air on soot emissions in a DI diesel engine were studied by the KIVA-3V code. When split injection is applied, the second injection of fuel into a cylinder results in two separate stoichiometric zones which increases soot oxidation. As a result, soot emissions are decreased with split injection. When oxygen-enriched air is applied together with split injection, higher concentration of oxygen helps secondary combustion which results in a higher temperature in the cylinder. The increased temperature promotes growth reaction of acetylene with soot but doesn't improve the acetylene formation during the second injection of fuel. As more acetylene is consumed in the growth reaction of acetylene, the net acetylene mass in the cylinder is decreased, which leads to a decrease of soot formation. With an increase of soot oxidation caused by split injection, the soot emissions are decreased significantly. However, to avoid excessive NOx emissions with increased oxygen concentration, the level of oxygen concentration should be lower than 22% in volume.

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