• 대한화학회지
• /
• 제16권2호
• /
• pp.84-92
• /
• 1972

A mechanism for the ring formation of nickel phthalocyanine (Ni-Pc) has been proposed based on chemical kinetics. The effect of the catalyst on the rate was examined, and ammonium molybdate has been found to be the most effective. The reaction order of the ring formation was determined to be of the 1st order over all, with only the concentration of urea affecting the rate of the ring formation. All the results including thermodynamic parameters support a conclusion that the rate-determining step seems to be the enolization of the urea-catalyst transition complex, followed by fast decomposition of the tautomeric enolized urea into ammonia and isocyanic acid. These intermediates then reacted with the phthalic anhydride to form imino and diimino-phthalimide, which condense to form nickel phthalocyanine in the presence of the nickel cation.

• 시멘트 심포지엄
• /
• 1호
• /
• pp.64-68
• /
• 1973

One of the most difficult problems in cement rotary kiln operation must be ring and coating formation. In the Dopol kiln with the capacity of 1,500 t/d($4.4m\phi\times70mL$, meal rings have been accreted on transit zone and end of the kiln and

• 천문학회보
• /
• 제46권1호
• /
• pp.51.2-51.2
• /
• 2021

Nuclear rings are sites of intense star formation at the center of barred spiral galaxies. A straightforward but unanswered question is what controls star formation rate (SFR) in nuclear rings. To understand how the ring SFR is related to mass inflow rate, gas content, and background gravitational field, we run a series of semi-global hydrodynamic simulations of nuclear rings, adopting the TIGRESS framework to handle radiative heating and cooling as well as star formation and supernova feedback. We find: 1) when the mass inflow rate is constant, star formation proceeds in a remarkably steady fashion, without showing any burst-quench behavior suggested in the literature; 2) the steady state SFR has a simple linear relationship with the inflow rate rather than the ring gas mass; 3) the midplane pressure balances the weight of the overlying gas and the SFR surface density is linearly correlated with the midplane pressure, consistent with the self-regulated star formation theory. We suggest that the ring SFR is controlled by the mass inflow rate in the first place, while the gas mass adjusts to the resulting feedback in the course of achieving the vertical dynamical equilibrium.

• Bulletin of the Korean Chemical Society
• /
• 제10권4호
• /
• pp.404-406
• /
• 1989

• Archives of Pharmacal Research
• /
• 제15권3호
• /
• pp.234-238
• /
• 1992

Using cell-free extract of Lysobacter lactamgenus, enzymatic conversion of $\delta$-L-($\alpha$-aminoadiphyl)-L-cysteinyl-D-valine (ACV) the first substrate of $\beta$-lactam biosynthesis, into antibiotic compounds was attempted. In high performance liquid chromatographic (HPLC) analysis, the biosynthetic intermediates for cephalosporin antibiotics including isopenicillin N, deacetoxycephalosporin C, deacetylcephalosporin C and unknown cephem compound were detected in reaction mixtures. It implies that cephabacin compounds from L lactamgenus could be produced by biosynthetic routes through penicillin ring formation and its expansion to cephalosporin ring, likely as cephalosporin C from Cephalosporium or cephamycin C from Streptomyces. Among biosynthetic enzyme in cell-free extract, the ring formation activity (isopenicillin N synthetase activity) was separated in 50-60% of ammonium sulfate fraction, and ring expansion activity (deacetoxycephalosporin C synthetase activity) was found to be in 40-50% fraction. The partially purified isopenicillin N synthetase could convert as much as 90% ACV to isopenicillin N during 6-hour reaction.

• Bulletin of the Korean Chemical Society
• /
• 제26권4호
• /
• pp.619-628
• /
• 2005

We attempted to replace a benzopyran ring of 4-[(N-imidazol-2-ylmethyl)-4-chloroanilino]benzopyran, previously discovered as anti-angiogenic agent with antitumor activity, with pyranopyridines. The [3,2-c]-, [3,2-b]-, [2,3-c]-, and [2,3-b]-pyranopyridines with -(imidazol-2-ylmethyl)aniline moiety at the 4-position, were synthesized respectively, and evaluated for primary anti-angiogenic properties through primary cultured HUVEC tube formation assay. From this study, we found that the pyranopyridine ring, especially [3,2-b]- and [2,3-c]-isomer, can replace the benzopyran ring of the compound 1 and can be optimized through the introduction of substituents both on the pyranopyridine ring and the aniline moiety for the identification of a novel anti-angiogenic agent.

• 천문학회보
• /
• 제38권1호
• /
• pp.47.2-47.2
• /
• 2013

We have performed a set of high-resolution simulations of nuclear star-forming ring that results in an inward gas migration from the galactic disk. Our simulations consider gas heating/cooling, star formation, and supernova feedback. The galactic potential was obtained from a snapshot of a 6.3 million particle simulation of a galactic disk at 1 Gyr, which manifests spiral arms and pseudo-bulge. The potential was modeled with a combination of 3-dimensional spherical (for the pseudo-bulge) and 2-dimensional cylindrical (for the disk) multipole expansion technique. With such a potential model, one can easily set up various realistic 3-dimensional potential models by slightly changing the expansion coefficients. We have performed a set of simulations with a few million gas particles covering the central ~6 kpc of the disk for different pseudo-bulge sizes and non-axisymmetry, and we report the dependence of the gas inflow rate, size of the star-forming ring, and star-formation rate in the ring on the size and strength of the non-axisymmetry in the bulge.

• 천문학회보
• /
• 제42권1호
• /
• pp.31.2-31.2
• /
• 2017

The central regions of barred-spiral galaxies contain interesting gaseous structures such as dust lanes and nuclear rings with intense star formation. While our previous studies were useful in understanding the formation of these structures star formation history, they were limited to 2D isothermal galaxies in which the stellar disk and halo are modeled by fixed gravitational potentials. To study the effects of bar growth as well as the vertical dimension, we use the mesh-free hydrodynamic code named GIZMO and run 3D simulations by treating the stellar disk and halo as being live. We find that the new 3D models form the gaseous features similarly to the previous 2D models, although the detailed formation processes are quite different. For example, a ring has a large radius when it first forms and shrinks over time in the previous 2D models. In the 3D live-potential models, however, a ring forms small and grows in size with time. We present the results of the new simulations and discuss them in comparison with the previous 2D results.

• Journal of the Korean Wood Science and Technology
• /
• 제33권4호통권132호
• /
• pp.1-8
• /
• 2005

춘천지역에서 생장하는 주요수종의 생장특성을 규명하기 위해 형성층 분열기 및 형성층의 휴지기를 조사하였다. 소나무와 잣나무는 3월 중순~하순에 형성층 활동이 시작되었다. 5월 하순에서 7월 중순 사이에 형성층 세포의 분열이 활발하였고, 이 때 잣나무의 세포 수가 소나무의 세포 수보다 크게 증가하였다. 환공재인 신갈나무와 아까시나무의 형성층 분열은 3월 중순경에 개시되었으며 동시에 도관 형성이 시작되었다. 산공재인 층층나무와 산벚나무의 형성층은 4월 초에 분열을 개시하였고 도관은 이보다 1~3주일 늦게 형성되는 것으로 관찰되었다. 형성층 활동이 멈추는 시기는 침엽수 11월 초순경, 활엽수 10월 중순경으로 관찰되었다. 따라서 형성층의 활동은 동일한 환경조건에서도 수종간에 차이가 있는 것으로 나타났다.

• 천문학논총
• /
• 제30권2호
• /
• pp.517-519
• /
• 2015

A large-scale neutral hydrogen ($H\small{I}$) ring serendipitously found in the Leo I galaxy group is 200 kpc in diameter with $M_{H\small{I}}{\sim}1.67{\times}10^9M_{\odot}$, unique in size in the Local Universe. It is still under debate where this $H\small{I}$ ring originated - whether it has formed out of the gas remaining after the formation of a galaxy group (primordial origin) or been stripped during galaxy-galaxy interactions (tidal origin). We are investigating the optical and $H\small{I}$ gas properties of the dwarf galaxies located within the gas ring in order to probe its formation mechanism. In this work, we present the photometric properties of the dwarfs inside the ring using the CFHT MegaCam $u^{\ast}$, $g^{\prime}$, $r^{\prime}$ and $i^{\prime}$-band data. We discuss the origin of the gas ring based on the stellar age and metal abundance of dwarf galaxies contained within it.