• Korean Journal of Plant Taxonomy
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• v.49 no.2
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• pp.101-106
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• 2019

A pollen morphological study was conducted using light and scanning electron microscopy involving six species belonging to the subtribe Neoguillauminiinae. Pollen samples from the six species are tricolporate, and the colpi are surrounded by broad margo, with the widest width in the equator, narrower toward the pole, and rounded at the end. Based on the pollen morphology, pollen of the species in the subtribe Neoguillauminiinae were divided into four types: the Neoguillauminia type (T1), the C. collinus type (T2), the C. casuarinoides type (T3) and the C. paucifolius type (T4). The generic divergence between Neoguillauminia and Calycopeplus was supported by the pollen characters of the size, amb and lumina shape. In particular, the traits of rounded shape in the outline of the polar view and circular lumina, which appear only in the pollen grains of N. cleopatra, support the recognition of Neoguillauminia as a monotypic genus. Calycopeplus oligandrus and C. paucifolius had the same reticulate pattern of pollen grains, supporting Forster's hypothesis that these two species are closely related. On the other hand, the close relationship between the morphologically similar C. collinus and C. casuarinoides was not supported by the pollen characters. Within the subtribe there are two equally parsimonious hypotheses regarding the evolution of exine characters. The first consists of two changes of microreticulate through parallel evolution from the primitive reticulate exine, and the second is that the microreticulate pattern is differentiated from the reticulate state and then reversed to reticulate pollen grains.

• Journal of the Korean Mathematical Society
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• v.53 no.5
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• pp.1133-1148
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• 2016

In this paper, we first discuss a representation of solutions to the initial value problem and the initial-boundary value problem for discrete evolution equations $${\sum\limits^l_{n=0}}c_n{\partial}^n_tu(x,t)-{\rho}(x){\Delta}_{\omega}u(x,t)=H(x,t)$$, defined on networks, i.e. on weighted graphs. Secondly, we show that the weight of each link of networks can be uniquely identified by using their Dirichlet data and Neumann data on the boundary, under a monotonicity condition on their weights.

• Macromolecular Research
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• v.9 no.4
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• pp.228-237
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• 2001

The evolution of conformational constraints in bisphenol-A polycarbonate (BAPC) upon quiescent bulk crystallization was quantitatively analyzed from calorimetric study employing a rigid amorphous fraction (RAF) as an indicator of the level of conformational constraints. From the correlation between corrected crystallinity (X$\sub$c/) and total rigid fraction (f$\sub$r/), it was found that, regardless of molar mass distribution and thermal treatment conditions, semicrystalline BAPC always exhibits greater f$\sub$r/ than X$\sub$c/ maintaining a quantitative relationship of f$\sub$r/〓2X$\sub$c/ in the range of 0.0 $\sub$c/< 0.4. This directly indicates the evolution of approximately the same amount of RAF as X$\sub$c/, (i.e., RAF〓X$\sub$c/) upon bulk crystallization of BAPC. It was also found that T$\sub$g/ per se and T$\sub$g/ broadening enhance as RAF increases, and there appears to be a critical level of RAF (>0.2) needed to initiate significant changes in both quantities.

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.39-44
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• 2002

This study was investigated the thermal decomposition characteristics of azo type sponge blowing agent azodicarbonamide(ADCA) using differential scanning calorimeter(DSC). The experimental results showed that the exothermic onset $temperatures(T_{o})$ for ADCA were about $201{\sim}206^{\circ}C$ and evolution heats(Q) were about $144{\sim}150cal/g$. The exothermic onset $temperatures(T_{o})$, exothermic maximum $temperature(T_{m})$ and exothermic final $temperature(T_{f})$ were decreased by decreasing particle size of ADCA and evolution heats(Q) were increased with it. $T_{o}$ and Q for $6.1{\sim}7.2{\mu}m$ ADCA were increased by increasing heating rate at constant sample weight and activation energy was about 37.29kcal/mol. A positive gas pressure was employed in the elucidation of the decomposition behavior of ADCA because it sublimes during linear heating at atmospheric pressure. $T_{o}$ and Q of ADCA tended to increase with a pressure in air or nitrogen. In the case of azo dye, experimental results showed that $T_{o}$ were about $280{\sim}420^{\circ}C$ and Q were about $2{\sim}30cal/g$.

• Journal of Microbiology and Biotechnology
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• v.16 no.8
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• pp.1210-1215
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• 2006

The properties related to the temperature and oxygen stability of the cytoplasmic hydrogenases from the fermentative strict anaerobic bacterium, Clostridium butyricum NCIB 9576 (Cl. butyricum), and purple sulfur phototrophic bacterium, Thiocapsa roseopersicina NCIB 8347 (T. roseopersicina), were compared. The optimum temperatures for the growth of Cl. butyricum and T. roseopersicina were 37$^{\circ}C$ and 25$^{\circ}C$, respectively, whereas those for the H$_2$ evolution of the cytoplasmic hydrogenases prepared from Cl. butyricum (C-H$_2$ase) and T. roseopersicina (T-H$_2$ase) were 45$^{\circ}C$ and 65$^{\circ}C$, respectively. The T-H$_2$ase was more thermostable than the C-H$_2$ase and retained its full activity for 5 h at 50$^{\circ}C$ under anaerobic conditions and 90% of its activity at 60$^{\circ}C$, whereas the C-H$_2$ase lost its activity drastically at 50$^{\circ}C$. The optimum pHs for H$_2$ oxidation of the C-H$_2$ase and T-H$_2$ase were 9.0 and 7.5, respectively. Both enzymes showed a maximum H$_2$ evolution activity at pH 7.0. Under aerobic conditions, 80% of the T-H$_2$ase activity was retained for 10 h at 30$^{\circ}C$, and 50% of the activity remained after 6 days under the same experimental conditions. However, the C-H$_2$ase was labile to oxygen and lost its activity immediately on exposure to air. Therefore, these properties of the T-H$_2$ase are expected to be advantageous for application in in vitro biological H$_2$ production systems.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.3
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• pp.219-228
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• 2005

Fermentative strict anaerobic bacterium, Clostricium butyricum NCIB 9576 (Cl. butyricum) and purple sulfur phototrophic bacterium, Thiocapsa roseopersicina NCIB 8347 (T. roseopersicina) were compared on their temperature and oxygen stabilities of cytoplasmic hydrogenases. Cell growth phase and the specific activities of evolution $H_2ase$ were related for both strains, exhibiting the highest cytoplasmic $H_2ase$ activities during the logarithmic growth phases which were 4 and 18 hrs after the incubation for Cl. butyricum and T. roseopersicina, respectively. The optimum temperatures for the growth of Cl. butyricum and T. roseopersicina were 37$^{\circ}C$ and 27$^{\circ}C$, respectively, while those for $H_2$ evolution of cytoplsmic hydrogenases prepared from Cl. butyricum ($C-H_2ase$) and T. roseopersicina ($T-H_2ase$) were 45$^{\circ}C$ and 65$^{\circ}C$, respectively. $T-H_2ase$ was more thermo-stable than $C-H_2ase$. $T-H_2ase$ retained its full activity for 5 hrs at 50$^{\circ}C$ and retained 90% of its original activity for 5 hrs at 60$^{\circ}C$, however, $C-H_2ase$ lost its activity drastically at 50$^{\circ}C$. The optimum pHs for $H_2$ oxidation of $C-H_2ase$ and $T-H_2ase$ were 9.0 and 7.5 respectively. The both enzymes showed maximum $H_2$ evolution activity at pH 7.0. Under the aerobic condition, 80% of $T-H_2ase$ activity was retained for 10 hrs at 30$^{\circ}C$, and 50% of activity was still remained after 6 days at the same experimental conditions. But the $C-H_2ase$ was labile to oxygen and lost its activity immediately after the exposure to air.

• Communications of the Korean Mathematical Society
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• v.9 no.3
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• pp.547-564
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• 1994

Let X be a real Banach space. We consider the existence of solutions of the abstract nonlinear functional evolution equation : $$ (E) \frac{du(t)}{dt} + A(t)u(t) + F(u)(t) \ni h(t), $$ $$ u(s) = x_o \in D(A(s)), 0 \leq s \leq t \leq T, $$ where u : $[s, T] \to x$ is an unknown function, ${A(t) : 0 \leq t \leq T}$ is a given family of nonlinear (possibly multivalued) operators in X, and $F : C([s, t];X) \to L^{\infty}([s, X];X)$ and $h : [s, T] \to X$ are given functions.

• Journal of the Korean institute of surface engineering
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• v.31 no.6
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• pp.345-358
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• 1998

The evolution of surface roughness and morphology in epitaxial Si and $Si_{0.7}Ge{0.3}$ alloys grown by UHV opm-beam sputter deposition onto nominally-singular, [100]-, and [110]-mi-scut Si(001) was investigated by stomic force microscopy and trasmission electron microscopy. The evolution of surface roughness of epitaxial Si films grown at $300^{\circ}C$ is inconsistent with conventional scaling and hyperscaling laws for kineti roughening. Unstable growth leading to the formation of mounds separated by a well-defined length scale is observed on all substrates. Contraty to previous high-temperature growth results, the presence of steps during deposition at $300^{\circ}C$ increases the tendency toward unstable growth resulting in a much earlier development of mound structures and larger surface roughnesses on vicival substrates. Strain-induced surface roughening was found to dominate in $Si_{0.7}Ge{0.3}$ alloys grown on singular Si(001) substrates at $T_S\ge450^{\circ}C$ where the coherent islands are prererentially bounded along <100> directions and eshibt {105} facetting. Increasing the film thickness above critical values for strain relaxation leads to island coalescence and surface smoothening. At very low growth temperatures ($T_s\le 250^{\circ}C$), film surfaces roughen kinetically, due to limited adatom diffusiviry, but at far lower rates than in the higher-temperature strain-induced regime. There is an intermediate growth temperature range, however, over which alloy film surfaces remain extremely smooth even at thicknesses near critical values for strain relaxation.

• Journal of Microbiology and Biotechnology
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• v.32 no.11
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• pp.1471-1478
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• 2022

2'-Fucosyllactose (2'-FL), the most abundant fucosylated oligosaccharide in human milk, has multiple beneficial effects on human health. However, its biosynthesis by metabolically engineered Escherichia coli is often hampered owing to the insolubility and instability of α-1,2-fucosyltransferase (the rate-limiting enzyme). In this study, we aimed to enhance 2'-FL production by increasing the expression of soluble α-1,2-fucosyltransferase from Helicobacter pylori (FucT2). Because structural information regarding FucT2 has not been unveiled, we decided to improve the expression of soluble FucT2 in E. coli via directed evolution using a protein solubility biosensor that links protein solubility to antimicrobial resistance. For such a system to be viable, the activity of kanamycin resistance protein (Kan^R) should be dependent on FucT2 solubility. Kan^R was fused to the C-terminus of mutant libraries of FucT2, which were generated using a combination of error-prone PCR and DNA shuffling. Notably, one round of the directed evolution process, which consisted of mutant library generation and selection based on kanamycin resistance, resulted in a significant increase in the expression level of soluble FucT2. As a result, a batch fermentation with the ΔL M15 pBCGW strain, expressing the FucT2 mutant (F#1-5) isolated from the first round of the directed evolution process, resulted in the production of 0.31 g/l 2'-FL with a yield of 0.22 g 2'-FL/g lactose, showing 1.72- and 1.51-fold increase in the titer and yield, respectively, compared to those of the control strain. The simple and powerful method developed in this study could be applied to enhance the solubility of other unstable enzymes.