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Bio-based chiral dopants having an isohexide skeleton for cholesteric liquid crystal materials
Shin, Seunghan,Seo, Jae Won,Cho, Jin Ku,Kim, Sangyong,Cha, Jaeryung,Gong, Myoung Seon The Royal Society of Chemistry 2012 Green chemistry Vol.14 No.4
<P>Chiral dopants were synthesized from bio-based epimeric isohexides (glucose-derived isosorbide and mannose-derived isomannide) and their phase transition behaviors and abilities for developing cholesteric liquid crystal (CLC) films were examined with a consideration of the core structure. In spite of lower reactivity of the <I>endo</I> hydroxy group of isomannide caused by the steric hindrance and intermolecular hydrogen bonding, final synthetic yields of chiral dopants bearing an isomannide core (64.5% for IH-2 and 65.0% for IH-4) did not show conspicuous difference compared with chiral dopants bearing isosorbide (68.4% for IH-1 and 74.0% for IH-3). On the other hand, in phase transition behaviors, chiral dopants bearing an isomannide core showed lower crystalline and melting temperatures than IH-1, IH-3 despite of the same substituents. The helical twisting power (HTP) of chiral dopants bearing isosorbide (IH-1 and IH-3) was higher than that of chiral dopants bearing isomannide (IH-2 and IH-4). The calculated HTPs of IH-1 and IH-3 were 26.6 and 42.1 μm<SUP>−1</SUP>, respectively. In the case of IH-3, the helical pitch length of CLC could be adjusted to reflect visible light by controlling its amount and showed best performance in the range 5.0 to 7.0 mol%. In contrast to IH-1 and IH-3, it was found that IH-2 and IH-4 could not induce CLC films that reflect visible light.</P> <P>Graphic Abstract</P><P>Chiral dopants were synthesized from bio-based isohexides and applied to cholesteric liquid crystal materials. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2gc16261j'> </P>
Shin, Woo-Shik,Lee, Dohoon,Lee, Sang Joung,Chun, Gie-Taek,Choi, Si-Sun,Kim, Eung-Soo,Kim, Sangyong Elsevier 2018 Biochemical and biophysical research communication Vol.499 No.2
<P><B>Abstract</B></P> <P>Cis,<I>cis</I>-muconic acid (CCM) is a biochemical material that can be used for the production of various plastics and polymers and is particularly gaining attention as an adipic acid precursor for the synthesis of nylon-6,6. In the current study, the production of CCM was first attempted by introducing a newly developed protocatechuate (PCA) decarboxylase from <I>Corynebacterium glutamicum</I> 13032 to inha103, which completed the biosynthetic pathway therein. To improve CCM productivity, a phosphoenol pyruvate (PEP)-dependent phosphotransferase system (PTS) that consumed the existing glucose was developed, in the form of a strain with a non-PTS that did not consume PEP. To improve glucose uptake, we developed P25 strain, in which <I>iolR</I> (a transcriptional regulator gene) was additionally deleted. Strain P28, a P25 derivative expressing PCA decarboxylase, produced 4.01 g/L of CCM, which was 14% more than that produced by the parental strain. Moreover, strains P29 and P30, with an active pentose phosphate pathway and overexpressing important genes (<I>qsuB</I>) in the metabolic pathway, produced 4.36 and 4.5 g/L of CCM, respectively. Particularly, the yield per glucose in strain P30 was similar to that of the fed-batch culture of <I>Escherichia coli</I>, which has the highest reported yield of 22% (mol/mol). These results are underpinned by the characteristics of the non-PTS with increased PEP availability and a strain with deletion of the <I>iolR</I> gene, which greatly increased glucose uptake.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Engineered <I>C. glutamicum</I> produced CCM, valued for plastic and polymer production. </LI> <LI> The CCM yield from glucose in the optimized strain was about 22% (mol/mol). </LI> <LI> CCM productivity was enhanced by redirecting carbon flux in non-PTS <I>C. glutamicum</I>. </LI> </UL> </P>
경계변수 값의 동적이 변경을 이용한 점층적 클러스터링 알고리즘
신광철(Kwangcheol Shin),한상용(Sangyong Han) 한국정보과학회 2003 정보과학회논문지 : 소프트웨어 및 응용 Vol.30 No.11·12
This study is purported for suggesting a new clustering algorithm that enables incremental categorization of numerous documents. The suggested algorithm adopts the natures of the spherical k-means algorithm, which clusters a mass amount of high-dimensional documents, and the fuzzy ART(adaptive resonance theory) neural network, which performs clustering incrementally. In short, the suggested algorithm is a combination of the spherical k-means vector space model and concept vector and fuzzy ART vigilance parameter. The new algorithm not only supports incremental clustering and automatically sets the appropriate number of clusters, but also solves the current problems of overfitting caused by outlier and noise. Additionally, concerning the objective function value, which measures the cluster’s coherence that is used to evaluate the Quality of product clusters, tests on the CLASSIC3 data set showed that the newly suggested algorithm works better than the spherical k-means by 8.04% in average. 본 논문은 점층적으로 대규모 문서 분류를 힐 수 있는 새로운 클러스터링 알고리즘에 대한 것으로, 고차원의 대규모 문서 집합에 대한 클러스터링을 수행하는 spherical k-means (SKM) 알고리즘과 점층적인 방식으로 클러스터링을 수행하는 퍼지(fuzzy) ART(adaptive resonance theory) 신경망의 특성을 이용하였다. 즉, SKM의 벡터 공간 모델과 개념벡터를 토대로 퍼지 ART의 경계변수의 개념을 결합한 것이다. 제시하는 알고리즘은 점층적 클러스터링의 지원과 함께 최적의 클러스터 수를 자동으로 결정할 뿐 아니라 이상치(outlier)와 노이즈(noise)에 의한 overfitting의 문제도 해결하였다. 또한 생성된 클러스터들의 질을 평가할 수 있는 응집도를 측정하는 목적 함수의 값에 있어서도 CLASSIC3 데이타 집합으로 실험한 결과 기존의 SKM에 비해 평균 8.04%의 향상된 응집도를 나타냈다.