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Ghim, Young-Sik,Davies, Angela The Optical Society 2012 Applied optics Vol.51 No.12
<P>White-light interferometry uses a white-light source with a short coherent length that provides a narrowly localized interferogram that is used to measure three-dimensional surface profiles with possible large step heights without 2??-ambiguity. Combining coherence and phase information improves the vertical resolution. But, inconsistencies between phase and coherence occur at highly curved surfaces such as spherical and tilted surfaces, and these inconsistencies often cause what are termed ghost steps in the measurement result. In this paper, we describe a modified version of white-light interferometry for eliminating these ghost steps and improving the accuracy of white-light interferometry. Our proposed technique is verified by measuring several test samples.</P>
Dry Deposition of Reactive Nitrogen and Sulfur Compounds in the Greater Seoul Area
Ghim, Young Sung,Kim, Jin Young 한국화학공학회 2002 Korean Journal of Chemical Engineering Vol.19 No.1
While deposition is a removal process of pollutants from the atmosphere, it is an intake process of such pollutants into the ground. It is suggested that surface waters in the Greater Seoul Area, used as a source of drinking water, have been affected by severe air pollution. In this work, the dry deposition of reactive nitrogen and sulfur species was estimated for three typical days in each season for the year of 1997. The CIT (California Institute of Technology) photochemical model incorporated with a gaseous oxidation reaction of SO_2 was used. The study revealed that reactive nitrogen deposition was the largest in summer and sulfur deposition was the largest in winter. Most of the reactive nitrogen was deposited in the form of HNO_3 and NO_2, but HNO_3 deposition is highly dependent on the season according to the extent of photochemical production. On the other hand, the contribution of sulfate to the total deposition of sulfur was minimal partly because of low deposition velocity and of the neglect of possible inflow from the boundaries. Approximately 53% of the reactive nitrogen and 30% of the sulfur emitted in the study area was deposited in the ground in the dry form on an annual basis.
Ghim, Sa-Youl Korean Society of Life Science 2001 Journal of Life Science Vol.11 No.2
The pyrR gene of the pyrimidine biosynthesis (pyr) operon of the thermophile Bacillus caldolyticus, encoding a uracil phosphoribosyltransferase (UPRTase), turned to rely as a pyr operon regulator. It has been proposed that PyrR mediates transcriptional termination-antitermination at three intercistronic regions of the par operon (S.-Y Ghim and J. Neuhard, J. Bacteriol.,176, 3698-3707, 1994). In this research, a plasmid carrying the pyrR region of B. caldolyticus could restore a pyrimidine regulation in a pyrR mutant of B. subtilis. Expression of pyrR was found to increase 6-7 fold during pyrimidine starvation. Additionally, a highly conserved nucleotide sequence which may constitute the binding site for a PyrR protein (PyrR-binding loop) in transcript was staggested. Alternative antiterminator and terminator structures involving three conserved motifs in front of the pyrR, pyrP and pyrB genes, respectively, are proposed to account for the observed regulation pattern.
Synthetic Biology for Biofuels: Building Designer Microbes from the Scratch
Ghim, Cheol-Min,Kim, Tae-Sung,Mitchell, Robert J.,Lee, Sung-Kuk 한국생물공학회 2010 Biotechnology and Bioprocess Engineering Vol.15 No.1
The ultimate goal in the production of biofuels is to produce fuels identical or similar to petroleum-derived transportation fuels more efficiently and in commercial quantities. Synthetic biologists have been engineering microbes to synthesize biofuels, such as butanol and fatty acid- or isoprenoid-based fuels, which are nearly identical to gasoline and diesel. One of the most urgent demands along this direction is to attain a solid framework for characterizing and standardizing the biological parts and devices. It seems quite promising because biotechnologies specially based on miniaturizations have been making a big contribution to this work. Therefore, in this review, recent advances and difficulties in the biofuel field are discussed, along with the advances of synthetic biology, which will make it possible to create designer microorganisms that produce economically viable next generation biofuels, aside from bioethanol, from corn or sugar cane, and biodiesel from plant or animal oils.
3D surface mapping of freeform optics using wavelength scanning lateral shearing interferometry.
Ghim, Young-Sik,Rhee, Hyug-Gyo,Davies, Angela,Yang, Ho-Soon,Lee, Yun-Woo Optical Society of America 2014 Optics express Vol.22 No.5
<P>Freeform optics have emerged as promising components in diverse applications due to the potential for superior optical performance. There are many research fields in the area ranging from fabrication to measurement, with metrology being one of the most challenging tasks. In this paper, we describe a new variant of lateral shearing interferometer with a tunable laser source that enables 3D surface profile measurements of freeform optics with high speed, high vertical resolution, large departure, and large field-of-view. We have verified the proposed technique by comparing our measurement result with that of an existing technique and measuring a representative freeform optic.</P>
Endothelial Deletion of Phospholipase D2 Reduces Hypoxic Response and Pathological Angiogenesis
Ghim, Jaewang,Moon, Jin-Sook,Lee, Chang Sup,Lee, Junyeop,Song, Parkyong,Lee, Areum,Jang, Jin-Hyeok,Kim, Dayea,Yoon, Jong Hyuk,Koh, Young Jun,Chelakkot, Chaithanya,Kang, Byung Jun,Kim, Jung-Min,Kim, Ky American Heart Association, Inc. 2014 Arteriosclerosis, thrombosis, and vascular biology Vol.34 No.8
<P><B>Objective—</B></P><P>Aberrant regulation of the proliferation, survival, and migration of endothelial cells (ECs) is closely related to the abnormal angiogenesis that occurs in hypoxia-induced pathological situations, such as cancer and vascular retinopathy. Hypoxic conditions and the subsequent upregulation of hypoxia-inducible factor-1α and target genes are important for the angiogenic functions of ECs. Phospholipase D2 (PLD2) is a crucial signaling mediator that stimulates the production of the second messenger phosphatidic acid. PLD2 is involved in various cellular functions; however, its specific roles in ECs under hypoxia and in vivo angiogenesis remain unclear. In the present study, we investigated the potential roles of PLD2 in ECs under hypoxia and in hypoxia-induced pathological angiogenesis in vivo.</P><P><B>Approach and Results—</B></P><P><I>Pld2</I> knockout ECs exhibited decreased hypoxia-induced cellular responses in survival, migration, and thus vessel sprouting. Analysis of hypoxia-induced gene expression revealed that PLD2 deficiency disrupted the upregulation of hypoxia-inducible factor-1α target genes, including <I>VEGF</I>, <I>PFKFB3</I>, <I>HMOX-1</I>, and <I>NTRK2</I>. Consistent with this, PLD2 contributed to hypoxia-induced hypoxia-inducible factor-1α expression at the translational level. The roles of PLD2 in hypoxia-induced in vivo pathological angiogenesis were assessed using oxygen-induced retinopathy and tumor implantation models in endothelial-specific <I>Pld2</I> knockout mice. <I>Pld2</I> endothelial-specific knockout retinae showed decreased neovascular tuft formation, despite a larger avascular region. Tumor growth and tumor blood vessel formation were also reduced in <I>Pld2</I> endothelial-specific knockout mice.</P><P><B>Conclusions—</B></P><P>Our findings demonstrate a novel role for endothelial PLD2 in the survival and migration of ECs under hypoxia via the expression of hypoxia-inducible factor-1α and in pathological retinal angiogenesis and tumor angiogenesis in vivo.</P>