• Journal of the Korean Magnetic Resonance Society
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• v.24 no.1
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• pp.9-15
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• 2020

Nitrogen vacancy center (NV center) in diamond has recently been appeared as a promising candidate for hyperpolarization applications due to its optical pumping property by laser. Optically Detected Magnetic Resonance (ODMR) has been used as a conventional method to obtain the resonance spectrum of NV centers. ODMR, however, has a shortcoming of sensitivity and a limitation of subjects, such that the degree of hyperpolarization can hardly be estimated, and that the spins other than NV centers are invisible. In contrast, Electron Spin Resonance (ESR) spectroscopy is known to proportionally reflect the degree of spin polarization. In this work, we successfully observed the optically-induced hyperpolarization of NV spins in diamond through CW-ESR spectroscopy with an X-band system. All the NV peaks were identified by calculating the eigenvalues of NV spin Hamiltonian. The intensities of NV peaks were enhanced over 240 times after optical pumping. The enhanced peaks corresponding to the transition from |m_s=0> to |m_s=-1> revealed inverted phases, while other peaks remained in-phase. The optically-induced hyperpolarization on NV spins can be a useful polarization source, leading to ¹³C nuclear hyperpolarization in diamond.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.5
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• pp.542-548
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• 2005

A fluidized bed reactor containing porous media has been known to be effective for nitrogen and organic matters removal in wastewater. The porous media which attached microbes plays important roles in simultaneous nitrification/denitrification (SND) due to coexistence of oxic, anaerobic and anoxic zone. For SND reaction, oxygen and organic substrates should be effectively diffused from wastewater into the intra-carrier zone. However, the overgrowth heterotrophic microbes at the surface of porous media may restrict from substrates diffusion. From these viewpoints, the existence and effect of heterotrophic bacteria at surface of porous media might be the key point for nitrogen removal. A porous media-membrane hybrid process was found to have improved nitrogen removal efficiency, due to stimulated denitrification as well as nitrification. Microelectrode studies revealed that although intra-media denitrification rate in a conventional fluidized bed was limited by organic carbon, this limitation was reduced in the hybrid process, resulting in the increased denitrification rate from 0.5 to $4.2\; mgNO_3-N/L/hr$.

• Proceedings of KOSOMES biannual meeting
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• 2006.05a
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• pp.117-120
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• 2006

The objective of this study was to evaluate the relationship between nutrients and phytoplankton; and phytoplankton and organic matter. In order to examine the limiting nutrient for phytoplankton, Redfield ration was used and revealed nitrogen limitation. Nitrogen limitation was greatest with a 4.7 DIN/DIP ratio especially during the summer season. Chl.-a increase by 79% and 97% in spring and summer, respectively, compared to winter. COD was lowest with 0.84mg/l in winter and highest with 1.12mg/l in summer. The interrelationship between nutrients and Chl.-a was high. Relationship coefficient$(r^2)$ between DIN and Chl.-a, and DIP and Chl.-a were 0.93 and 0.89, respectively. This suggests Nutrients might be utilized at the increase of phytoplankton. Also, Relationship coefficient$(r^2)$ between Chl.-a and COD was 0.78. COD production rate was calculated with Regression Equation. The COD production rate was 25% in winter and 40% in summer.

• ALGAE
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• v.17 no.2
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• pp.83-87
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• 2002

Photosynthetic parameters of Scendesmus quadricauda, such as the maximum photosynthetic rate ($P_{max}$), photosynthetic efficiency (α) and the initial saturation intensity of irradiance for photosynthesis ($I_K$) were obtained using photosynthesis-irradiance (P-I) curve in a phosphorus-limited chemostat. S. quadricauda exhibitied no photoinhibition until at 200 μmol·$m^{-2}$ . $P_{max}$ (r=0.963, P=0.002) and $I_K$(r=0.904, P=0.013) showed linear relationships with growth rate. Chlorophyll-α concentration and cell dry weight decreased at higher growth rates, ut chlorophyll-α content per cell dry weight increased. The increase in photosynthetic rates at higher growth rates was due to the increase of $P_{max}$ and $I_K$ which was caused mainly by the increase in the absolute amount of chlorophyll-α rather than the increased photosynthetic efficiency of individual chlorphyll-α. The α did not show a significant relationship with growth rate (r=0.714, P=0.111). The cell quota of carbon (r=0.554, P=0.254) was not correlated with growth rate, but cell quota of nitrogen (r=0.818, P=0.047) and phosphorus (r=0.855, P=0.030) exhibited linear correlations with growth rate.

• Journal of Environmental Science International
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• v.19 no.5
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• pp.607-615
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• 2010

We investigated the temporal variations of heterotrophic dinoflagellates (hereafter HDNF) and photosynthetic dinoflagellates (hereafter PDNF) from 14 June to 4 September 2003 at a single station in Jangmok Bay. We took water samples 47 times from 2 depths (surface and bottom layers) at hide tide. A total of 63 species were encountered and in general the most abundant genera were Prorocentrum and Protoperidinium. The abundance of PDNF and HDNF was in the range of $0.04{\sim}55.8{\times}10^4$ cells/L and in the range of $0.01{\sim}4.35{\times}10^4$ cells/L, respectively. The mean abundance of PDNF was approximately 7 times higher than that of HDNF, and was higher in the surface layer where has enough irradiance for photosynthesis than in the bottom layer. The total dinoflagellate abundance was higher in the NLP (nitrogen limitation period) than in the SLP (silicate limitation period), and the abundance in the hypoxic conditions was similar to that in the normal conditions. The Shannon-Weaver species diversity index were slightly higher in the bottom layer, the SLP and the hypoxic conditions. The PDNF abundance were correlated with temperature, DO, total inorganic nitrogen and phosphate in the whole water column, and the HDNF abundance was significantly correlated with temperature, salinity and DO. This study shows that the dinoflagellate abundance might be affected by abiotic factors such as irradiance, temperature, salinity, DO and the concentrations of inorganic nutrients, and provides baseline information for further studies on plankton dynamics in Jangmok Bay.

• Journal of Microbiology
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• v.41 no.1
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• pp.34-40
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• 2003

Aspergillus nidulans, a homothalic ascomycete, has a complete sexual reproductive cycle as well as an asexual one. Both sexual and asexual development are known to be genetically programmed, but are also strongly affected by environmental factors including nutrients, light, temperature and osmolarity. We have examined these factors to define favored conditions for fruiting body (cleistothecium) formation. In general, fruiting body formation was enhanced where carbon and nitrogen sources were sufficient. Limitation of C-source caused predominant asexual development while inhibiting sexual development. When higher concentrations of glucose were supplied, more cleistothecia were formed. Other carbon sources including lactose, galactose and glycerol made the fungus develop cleistothecia very well, whereas acetate caused asexual sporulation only. Organic nitrogen sources like casein hydrolysate and glycine, and an increase in nitrate or ammonium concentration also enhanced sexual development. In addition to nutrient effects, low levels of aerobic respiration, caused either by platesealing or treatment with various chemicals, favored sexual development. Carbon limitation, light exposure and a high concentration of salts promoted asexual development preferentially, suggesting that stress conditions may drive the cell to develop asexual sporulation while comfortable and wellnourished growth conditions favored sexual development.

• Korean Journal of Environmental Agriculture
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• v.28 no.4
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• pp.371-377
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• 2009

In this study, simultaneous nitrification and denitrification (SND) from synthetic wastewater were performed to evaluate dissolved oxygen(DO) effects on chemical oxygen demand(COD) and nitrogen removal in a single membarne bio-reactor(MBR). DO levels in MBR at Run 1, 2, and 3 were 1.9~2.2, 1.3~1.6, and 0.7~1.0 mg/L, respectively. Experimental results indicated that DO had an important factor to affect COD and total nitrogen(TN) removal. SND were able to be accomplished in the continuous-aeration MBR by controlling ambient DO concentration. It is postulated that, because of the oxygen diffusion limitation, an anoxic micro-zone was formed inside the flocs where the denitrification might occur. From the results of this study, 96% of COD could be removed at DO of 0.7mg/L. At run 2 72.92% of nitrogen was removed by the mechanisms of SND (7.75mg-TN/L in effluent). In this study, SND was successfully occurred in a MBR due to high MLSS that could help to form anoxic zone inside microbial floc at bulk DO concentrations of 1.3~1.6mg/L.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.35-41
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• 2008

Nutrient Enrichment Bioassays (NEBs) were conducted in the laboratory during June $22{\sim}28$, 2006 in order to determine primary limiting factor on the phytoplankton growth. For the NEBs, the water was sampled using a 10L polyethylene-lined container and dispensed into 2.5L container in the laboratory. The algal growths response in the control (C) and three treatments of phosphorus (P), 2-fold phosphorus (2P), and nitrate nitrogen $(NO_3-N)$ were monitored during 7 days. In the cubitainers which were spiked as P (T1) and 2P (T2) Chl-${\alpha}$ concentrations were decreased during the test period and the final concentrations was low than initial values. However, Chl-${\alpha}$ in the cubitainers which were spiked as $NO_3$(T3) and $P+NO_3$(T4) showed significant increases compared to the initial values, indicating that in the short-term experiments, nitrogen seemed to be a primary limiting nutrient during the periods of NEBs experiment. Long-term ambient nutrient data of TP and TN, and TN:TP mass ratios, however, showed a potential phosphorus limitation on phytoplankton growth and previous other researchers showed a variations of limiting nutrients by nitrogen or phosphorus depending on the seasons sampled and locations. In this study nitrogen as primary limiting nutrient in the NEBs seem to be an seasonal effect rather than the consistent nitrogen limitation.

• Applied Biological Chemistry
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• v.40 no.3
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• pp.232-237
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• 1997

Soybean plants inoculated Bradrhizobium japonicum MN 110 were grown in outdoor perlite pots with nitrogen free nutrient solution containing 1.0 mM-P(control) and 0.05 mM-P(stress) and harvested at 28, 35, 42 and 49 days after transplanting (DAT) to examine the effect of phosphorus deficiency on ureide concentration of and distribution to diffrent plant organ in nitrogen fixing soybean plant during the vegetative growth. Total dry mass of control plants increased 8.9 fold and that of phosphorus deficient plant increased 2.7 fold during the experimental period. Phosphorus deficiency reduced total phosphorus and nitrogen accumulation by 80%,40% respectively, at 28 DAT and 93%, 84%, respectively, at 49 DAT. Nitrogen concentration was reduced by phosphorus deficiency in all tissues with leaf and stem tissues affected to a greater degree than nodule and root tissues at every sampling date. Phosphorus deficiency significantly reduced soluble reduced-N and ureide-N concentration in leaf and stem but did not affect those in root. The proportion of soluble reduced-N in leaf was reduced from 60% to 50% but increased from 10% to 20% in the roots. The proportion of ureide-N in leaf of control plants was higher than that in phosphorus deficient plants, whereas, roots of phosphorus deficient plants contained a higher propotion of ureide-N than those of control plants. These indicated that phosphorus deficiency not only inhibit nitrogen fixation of nodules but also restrict the translocation of fixed nitrogen out of the root system into the xylem.(Received April 4, 1997; accepted May 2, 1997)

• Korean Journal of Ecology and Environment
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• v.42 no.4
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• pp.432-440
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• 2009

During the period of past fifteen years (1992~2006), variations of chlorophyll a in relation with water quality in freshwater reservoirs were investigated. This study compared total nitrogen (TN), total phosphorus (TP), chlorophyll a, Secchi depth (SD) and total suspended solids (TSS) between terrestrial freshwater reservoir and coastal freshwater reservoir systems based on their location. Regression analyses (linear and non-linear regressions) were applied for all study sites to examine relationship and interaction of these factors in the freshwater systems from in-land to coasts. The results demonstrated that chlorophyll a was significantly correlated to total phosphorus ($R^2=0.94$, P<0.0001) and was remarkably related to TSS increase ($R^2=0.63$, P<0.0001) in the selected reservoirs. The TN : TP ratio in the reservoir systems was higher than Redfield ratio (16 : 1) indicating that the reservoirs are potentially experiencing P limitation. Water quality of coastal freshwater reservoir system was more significantly decreased than the reservoirs located in in-land during the past fifteen years. The strict management of nutrient discharge into freshwater systems should implemented in the coastal reservoirs since the freshwater is introduced into coastal estuarine systems.