• Applied Science and Convergence Technology
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• 제24권3호
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• pp.67-71
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• 2015

InP/InGaP quantum structures (QSs) were grown on GaAs (001) substrates by a migration-enhanced molecular beam epitaxy method. Temperature-dependent photoluminescence (PL) and emission wavelength-dependent time-resolved PL (TRPL) were performed to investigate the optical properties of InP/InGaP QSs as a function of migration enhanced epitaxy (MEE) growth cycles from 2 to 8. One cycle for the growth of InP QS consists of 2-s In and 2-s P supply with an interruption time of 10 s after each source supply. As the MEE growth cycle increases from 2 to 8, the PL peak is redshifted and exhibited different (larger, comparable, or smaller) bandgap shrinkages with increasing temperature compared to that of bulk InP. The PL decay becomes faster with increasing MEE cycles while the PL decay time increases with increasing emission wavelength. These PL and TRPL results are attributed to the different QS density and size/shape caused by the MEE repetition cycles. Therefore, the size and density of InP QSs can be controlled by changing the MEE growth cycles.

• Neonatal Medicine
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• 제18권2호
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• pp.177-181
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• 2011

Bronchopulmonary dysplasia (BPD) is characterized by arrest of vascular and alveolar development in premature infants. Recent advances in neonatology have increased the survival of immature babies. Consequently, the prevalence of BPD is increasing. Animal studies and autopsy findings of BPD have demonstrated interruption in vascular development and reversal of lung injury through promotion of vasculogenesis. Normal lung development is driven by temporal and spatial specific growth factors and cellto-cell signaling in vascular development. Lung injury through various pathways causes disruption in this complex interactive process and results in aberrant vascular development and subsequent BPD. By understanding the regulation of vascular growth of the lung, it would be possible to find new targets in the treatment and prevention of BPD in premature infants.

• Journal of Microbiology and Biotechnology
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• 제13권3호
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• pp.477-481
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• 2003

The community escape response of Rhodobacter sphaeroides is exerted through the action of CerR and CerI, which code for a LuxR-type regulatory protein and acylhomoserine lactone synthase, respectively. Deletion of chromosomal DNA including cerR and cerI (mutant RI) or insertional interruption of cert (mutant AP3) resulted in two-fold increase in the cellular poly-${\beta}$-hydroxybutyrate (PHB) content In comparison with the wild-type under aerobic growth conditions. The PHB synthase (PhbC) activities of the cer mutants were doubled, and the enzyme expression was regulated at the level of phbC transcription. Thus, CerR, possibly in response to autoinducer (AI), appears to modulate the PHB content of aerobically grown cells by downregulating phbC transcription.

• Applied Science and Convergence Technology
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• 제24권6호
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• pp.254-256
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• 2015

Effect of growth temperature ($T_g$) on the structural and optical properties of $In_{0.5}Ga_{0.5}As$ atomic layer epitaxial (ALE) quantum dots (QDs) is investigated in the range of $T_g=480-510^{\circ}C$. $In_{0.5}Ga_{0.5}As$ ALE QDs consist of 5 periods of short-period superlattices (SPSs) of 1 monolayer-thick InAs and GaAs. Number of coalescent QDs decreases as $T_g$ increases, and they disappear at $T_g=510^{\circ}C$. As $T_g$ increases in the range of $480-495^{\circ}C$, sizes of QDs increase, and densities of QDs decrease due to merge of QDs. On the contrary, although sizes of QDs are maintained at $T_g=495-510^{\circ}C$, densities of QDs decrease. This is attributed to the desorption of material-mainly indium-during the growth interruption. This conjecture is supported by the optical properties of the QDs as a function of $T_g$. As a result, we propose that optimum growth temperature of the QD is $495^{\circ}C$ with less repetition of SPSs than 5.

• 한국환경과학회지
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• 제1권1호
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• pp.1.1-11
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• 1992

To find heavy metal-specific effects on the photosynthetic apparatus of higher plants, we investigated effects of $CuCl_2$, HgCl_2$ and $ZnCl_2$ on electron transport activity and chlorophyll fluorescence induction kinetics of chloroplasts isolated from barley seedlings. Effects on some related processes such as germination, growth and photosynthetic pigments of the test plants were also studied. Germination and growth rate were inhibited in a concentration-dependent manner by these metals. Mercury was shown to be the most potent inhibitor of germination, growth and biosynthesis of photosynthetic pigments of barley plants. In the inhibition of electron transport activity, quantum yield of PS II, and chlorophyll fluorescence induction kinetics of chloroplasts isolated from barley seedlings, mercury chloride showed more pronounced effects than other two metals. Contrary to the effects of other two metals, mercury chloride increased variable fluorescence significantly and abolished qE in the fluorescence induction kinetics from broken chloroplasts of barley seedlings. This increase in variable fluorescence is due to the inhibition of the electron transport chain after PS ll and the following dark reactions. The inhibition of qE could be attributed to the interruption of pH formation and do-epoxidation of violaxathin to zeaxanthin in thylakoids by mercury. This unique effect of mercury on chlorophyll fluorescence induction pattern could be used as a good indicator for testing the presence and/or the concentration of mercury in the samples contaminated with heavy metals.

• 한국재료학회지
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• 제18권10호
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• pp.535-541
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• 2008

Growth behavior of InGaN/GaN self-assembled quantum dots (QDs) was investigated with respect to different growth parameters in low pressure metalorganic chemical vapor deposition. Locally formed examples of three dimensional InGaN islands were confirmed from the surface observation image with increasing indium source ratio and growth time. The InGaN/GaN QDs were formed in Stranski-Krastanow (SK) growth mode by the continuous supply of metalorganic (MO) sources, whereas they were formed in the Volmer-Weber (V-W) growth mode by the periodic interruption of the MO sources. High density InGaN QDs with $1{\sim}2nm$ height and $40{\sim}50nm$ diameter were formed by the S-K growth mode. Dome shape InGaN dots with $200{\sim}400nm$ diameter were formed by the V-W growth mode. InN content in InGaN QDs was estimated to be reduced with the increase of growth temperature. A strong peak between 420-460 nm (2.96-2.70 eV) was observed for the InGaN QDs grown by S-K growth mode in photoluminescence spectrum together with the GaN buffer layer peak at 362.2 nm (3.41 eV).

• 원예과학기술지
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• 제32권4호
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• pp.434-439
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• 2014

이 연구는 야파 처리 시간대가 살비아 'Salsa'의 영양생장 및 개화에 미치는 영향을 조사하고, 저광도 야파 처리가 광합성을 증가시킬 수 있는지 알아보고자 수행되었다. 살비아는 9시간의 단일조건 또는 9시간 일장에 $3-5{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$의 광도의 야파를 추가한 조건의 식물 생육상에서 재배되었고, 야파 처리는 18시-22시(NI18), 22시-02시(NI22), 02시-06시(NI02)의 세 구간으로 나누어 적용되었다. NI18, NI22, NI02 처리구에서 광합성은 야파 처리 시간 동안에 각각 0.33, 0.16, $0.13{\mu}mol{\cdot}CO_2{\cdot}m^{-2}{\cdot}s^{-1}$만큼 증가하였다. 하지만 엽폭, 엽장 등의 영양생장은 단일 조건하의 식물들과 유의성 있는 차이를 나타내지 못하였다. 야파 처리 시 개화까지 걸리는 시간은 9.8일 단축되었고, 17주간 야파 처리 시 꽃의 수는 단일 조건의 36.4개에 비해 NI02 처리구에서 138.7개로 증가하였다. 이러한 결과는 02시부터 06시까지의 야파 처리가 개화를 촉진하는 데에 가장 효과적이라는 것을 보여준다. 그러나 야파 처리 시간 동안에 증가한 광합성량은 살비아의 영양생장 증가에는 효과를 보이지 못하였다. 비록 야파 처리 동안의 미미한 광합성의 증가가 살비아의 영양생장을 증가시키지는 못하였지만, 개화에는 크게 영향을 미쳤다. 단일 조건에서는 44.4%만이 개화하였지만 8주간 야파 처리시 NI18, NI22, NI02 처리구에서는 각각 77.8, 88.9, 100.0% 개화하였다.

• 한국진공학회지
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• 제22권2호
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• pp.86-91
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• 2013

Arsenic interruption growth (AIG)법을 이용하여 GaAs 기판에 성장한 InAs 양자점(quantum dots, QDs)의 광학적 특성을 PL (photoluminescence)과 time-resolved PL을 이용하여 분석하였다. AIG법은 InAs 양자점 성장 동안 In 공급은 계속 유지하면서 셔텨(shutter)를 이용해서 As 공급과 차단을 조절하는 방법이다. 본 연구에서는 As 공급과 차단을 1초(S1), 2초(S2), 또는 3초(S3) 동안 반복하여 성장한 InAs QDs과 As 차단 없이 성장한 기준시료(S0)를 사용하였다. AIG법으로 성장한 시료들의 PL 세기는 기준시료보다 모두 강하게 나타나고, As 차단 시간에 따라 PL 피크는 적색이동(redshifted) 또는 청색이동 (blueshifted)하여 나타났다. 기준시료 S0의 PL 피크와 비교하였을 때 S1의 PL 피크의 적색이동은 양자점 평균 길이가 S0보다 증가하였기 때문이며, S3의 청색이동은 양자점 평균 길이가 S0보다 감소하였기 때문이다. AIG법으로 성장한 QDs 시료들의 PL 세기의 증가는 cluster의 감소, 양자점 밀도의 증가, 균일도의 향상, 종횡비(aspect ratio) 향상으로 설명된다. 온도에 따른 PL 세기와 PL 피크 에너지, PL 소멸 시간과 발광 파장에 따른 PL 소멸 시간을 측정하였다. As 공급과 차단을 2초로 하였을 때 cluster는 전혀 나타나지 않았고 양자점의 밀도는 증가하였으며 균일도와 종횡비도 향상되었다. 또한 S2는 가장 강한 PL 세기와 가장 긴 소멸 시간을 나타내었다. 이러한 결과는 AIG법을 이용하여 InAs 양자점의 크기, 조밀도, 균일도, 종횡비 등을 조절하여 원하는 파장대의 양자점을 성장할 수 있으며 발광 특성도 향상시킬 수 있음을 확인하였다.

• Clinical and Experimental Pediatrics
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• 제58권7호
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• pp.270-273
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• 2015

Legg-Calve-Perthes (LCP) disease is characterized by idiopathic avascular osteonecrosis of the epiphysis of the femur head. The main factor that plays a role in the etiology of the disease is decreased blood flow to the epiphysis. Many predisposing factors have been suggested in the etiology of LCP disease, and most have varying degrees of effects. Here we present the case of a boy aged 4 years and 10 months with complaints of short stature and a diagnosis of multiple hypophyseal hormone deficiency, in whom LCP disease and difficult birth-related pituitary stalk interruption syndrome were identified by anamnesis. The present case revealed that LCP disease and hypophyseal hormone deficiency could be secondary to difficult birth and that LCP disease could be secondary to insulin-like growth factor 1 deficiency. Additionally, to the best of our knowledge there is no published case on the relation between LCP disease and insulin-like growth factor 1 deficiency. Therefore, we believe that this case is worthy of presentation.

• 생명과학회지
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• 제24권12호
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• pp.1345-1355
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• 2014

약초 추출물을 이용한 혈관신생 억제는 많은 고형종양을 치료하기 위한 효과적인 방안으로 인식되어 왔다. 현재까지 가장 효과적으로 종양을 억제하는 방법은 VEGF-유도성 혈관형성 경로를 목표로 하는 것이다. 본 연구에서는 처음으로 복분자 온수추출물의 혈관형성 억제효과를 in vitro와 ex vivo 실험을 통해서 확인하였다. 복분자 온수추출물은 VEGF-유도성 혈관신생을 억제할 뿐만 아니라 ERK와 p38의 인산화, MMP의 활성화를 억제하였다. 또한, 복분자 온수추출물은 VEGF에 의해서 유도된 VEGFR2 인산화를 억제하였다. 이 결과들은 복분자 온수추출물이 VEGFR2의 인산화를 저해함으로써 혈관신생을 억제하고 이것은 혈관신생과 관련된 질병을 치료하는데 좋은 소재가 될 수 있을 것으로 사료된다.