Enhancement of Mechanical and Antimicrobial Properties of Thermoplastic Poly(lactic acid)/Quaternized Chitosan-Saponite Nanocomposites

Xi Xi,Weijun Zhen,Shengzhen Bian,Wentao Wang 한국고분자학회 2015 폴리머 Vol.39 No.4

Water-soluble N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) was prepared with 2, 3-epoxypropyl trimethyl ammonium chloride grafting to the amino groups of chitosan. Then, chitosan quaternary ammonium intercalated saponite (HTCC-saponite) was synthesized with HTCC and saponite by ultrasonication intercalation. Compared with chitosan, HTCC had a good antibacterial effect. Thermoplastic poly(lactic acid) (PLA)/HTCC-saponite nanocomposites were prepared with HTCC-saponite and PLA by melt intercalation. Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H NMR) showed that HTCC was successfully synthesized by a modified method of two-step reaction. Moreover, X-ray diffraction (XRD) and scanning electron microscope (SEM) also showed that saponite was intercalated or nearly exfoliated by HTCC. It was shown the mechanical properties of PLA/HTCC-saponite nanocomposites attained the optimum when the content of HTCC-saponite was 1 phr. The studies of thermal stability, crystallization and rheological behavior of PLA/HTCC-saponite nanocomposites demonstrated that PLA/HTCC-saponite nanocomposites exhibited high performance compared with PLA.

Synthesis and Characterization of Fluorescent Waterborne Polyurethane Based on 4'-p-N,N-Bis(2-hydroxyethyl)benzyl-3,3':6',2"-Terpyridine

Xixi Han,Can Tao,Zhiqian Xie,Junjie Bao,Yiping Huang,Gewen Xu 한국고분자학회 2017 폴리머 Vol.41 No.3

Cationic waterborne polyurethane fluorescent material based on 4"-p-N,N-bis(2-hydroxyethyl)benzyl-3,3":6",2""-terpyridine (TPPDA-CWPU) was synthesized. The structure was characterized by FTIR and UV-vis spectroscopy. The content of TPPDA in the fluorescent polyurethane was 6.3×10<SUP>-4</SUP> mg/mg and the grafting ratio was 33.87%. The number-averaged and weight-average molecular weights of TPPDA-CWPU were about 16060 and 27131 g·mol<SUP>-1</SUP>, respectively. The maximum absorption wavelength of TPPDA-CWPU was blue shifted ca. 6 nm compared to TPPDA. TPPDACWPU showed different fluorescence properties under different solid content. Compared with 20% solid content, the fluorescence intensity of 1% solid content increased by ten times. The quantum yield of TPPDA-CWPU was 0.3, which was four times higher than that of TPPDA. Moreover, TPPDA-CWPU was sensitive to acidic condition and there was the phenomenon of fluorescence quenching in the case of strong acidic conditions. It is believed that more applications will be possible in the pH-responsive polymer.

Response Inhibition and Emotional Regulation in the Patients with Attention-Deficit/Hyperactivity Disorder and Comorbidity of Disruptive, Impulse-Control, and Conduct Disorders

Xixi Jiang,Yuncheng Zhu,Yiru Fang 대한신경정신의학회 2019 PSYCHIATRY INVESTIGATION Vol.16 No.11

CRYSTAL-FACETS DEPENDENT SOLAR HYDROGEN GENERATION FROM KINETIC GROWTH CONTROLLED CdS NANOPARTICLES

Xixi Wang,Maochang Liu,Zhaohui Zhou,Liejin Guo 한국신재생에너지학회 2015 AFORE Vol.2015 No.11

Biomimetic Prohealing Nanomatrix for Stent and Atherosclerosis Model

Xixi Zhang,Jun Chen,Grant C. Alexander,Patrick TJ. Hwang,Peter G. Anderson,Young-Sup Yoon,Brigitta C. Brott,Ho-Wook Jun(전호욱) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1

Topic 1 for Stent coating: Cardiovascular disease is the number one cause of death worldwide. Stents are the most commonly implanted devices to effectively treat cardiovascular disease. However, bare metal stent (BMS) remains limited by relatively high rates of in-stent restenosis and the accompanying extracellular matrix deposition. Thus, drug-eluting stents (DES) have been developed to reduce restenosis. Although these efforts were successful, DES has its own set of shortcomings: late stent thrombosis, inflammation and delayed re-endothelialization. To address these issues, we developed a novel prohealing multifunctional stent coating: a nitric oxide (NO)-releasing endothelium-mimicking nanomatrix composed of the biomaterial- Peptide Amphiphile (PA). We evaluated the safety and efficacy of the novel coated stent in the rabbit iliac artery balloon injury model and compared with commercially available BMS and DES. The goal is to demonstrate the advantages of the nanomatrix coating which could enhance re-endothelialization, while reduce restenosis, inflammation, and thrombosis. We hypothesize that the prohealing multifunctional nanomatrix coated stent has several strengths compared with BMS and DES: 1) promoted re-endothelialization; 2) less restenosis than BMS; and 3) less inflammation and thrombosis than DES. Topic 2 for atherosclerosis model: Atherosclerosis is the main cause of cardiovascular disease. To evaluate therapeutics for treating atherosclerosis, in vivo and in vitro atherosclerosis models are developed. However, those atherosclerosis models have their own limitations. In vivo models, like pig and non-human primates, can develop lesions in coronary arteries, however, inducing atherosclerosis in them requires high cholesterol intake, long induction time, gene knock-out, and high expense. Although mouse models are the predominant models used in the labs, however, most of the currently mouse models show different plaque structure and genome from that of human. In vitro models are also used for evaluation due to their low cost; however, most of the those models are not generated following the pathogenesis of human atherosclerosis and are two-dimensional (2D) models which are limited to static culture in tissue culture plate and unable to provide three-dimensional (3D) tissue structures with proper functions. Thus, the main goal of this proposal is to develop an innovative biologically inspired 3D in vitro platform – tissue engineered atherosclerosis model (TEAM), featured with endothelial dysfunction, macrophages, and foam cells, following the pathogenesis of human atherosclerosis with low cost.

최저임금 인상이 중국노동시장에 미치는 영향

부서서 ( Xixi Fu ),오민홍 ( Min Hong Oh ),정남기 ( Namki Chung ) 한국질서경제학회 2018 질서경제저널 Vol.21 No.2

이 연구는 중국 노동시장에서 최저임금이 고용 및 근로시간에 미치는 영향을 분석하였다. 실증분석에 사용된 자료는 중국 사회 조사(CGSS) 2013 데이터에 수록된 20~50세의 고등교육을 받지 못한 노동인구의 월간 최저임금이며, 추정방법은 로지스틱 회귀 분석과 성향 점수 매칭(Propensity Score Matching)이다. 분석결과는 중국 중부지방의 경우 최저임금의 인상이 고용과 노동시간에 미치는 영향은 모두 상당히 부정적으로 나타났다. 산서성의(山西省) 경우 최저 임금이 15% 상승하면 고용은 20% 감소하고 노동시간은 8시간까지 감소하였다. 그리고 중국 서부의 경우에는 표본이 기준을 충족시키지 못하기 때문에 최저임금의 변화가 고용 및 노동시간 미치는 효과를 명확히 언급할 수는 없지만, 산서성과는 달리 긍정적으로 나타났다. 주목해야할 점은 중국의 노동자들은 최저임금의 인상으로 노동시간이 단축되었더라도 중국 노동법에 규정된 노동시간보다 더 많은 시간을 일하고 있다는 것이다. 중국정부는 이러한 현실에 대해 어떠한 형태로든 관심을 기울일 필요가 있는 것으로 사료된다. For a country with huge population such as China, employment never stops being one of the crucial tasks of the government nor a hot issue to the public. This paper investigates one of the most controversial policies which is related to employment, the minimum wage policy, to explore its effects on employment. Even though this issue has been well researched by several Chinese scholars, no consensus has been reached due to the diversities in selections of target groups and regions. Therefore, the paper adopts propensity score matching method to quantitatively investigate the employment effects of minimum wage increase in China based on Chinese General Social Survey (CGSS) 2013 data with the aim to testify the consistency of the findings of previous studies. Through the analyses, statistically significant results were captured in Shanxi and Anhui Provinces. However, since the date of minimum wage adjustment of Anhui fails to meet the selection criteria, only results from Shanxi case are regarded to be qualified. Therefore, the result based on central China shows that minimum wage increase indeed generates statistically significant and negative effects on employment (20% in Shanxi case). Since no western provinces satisfy the selection criteria, the paper is unable to generate valid results of western China, which leaves the employment effect of minimum wage increase in that area to be unclear.

Influencing Factors of Willingness to Teach among Pre-service English Teachers in Minority Area in China

Xiao,Xixi,Lee,Jiyon 학습자중심교과교육학회 2021 학습자중심교과교육연구 Vol.21 No.23

Objectives The purpose of this study was to explore the influencing factors of willingness to teach among the pre-service English teachers (PETs) in a minority area of China. Methods To achieve this, seven PETs were interviewed, and through qualitative analysis of interview data, in-depth exploration of factors affecting the intention to teach was conducted. Results The results are as follows. Firstly, it was found that the career choice of these participants is the result of the influence of both internal and external factors. Secondly, among internal factors, self-perception is the most important factor which include personal interest and personal abilities, but career dedication is insufficient and needed to be cultivated. Also, sense of achievement was found as an influencing factor. Thirdly, among external factors, opinions of others often plays a very important role and profession restriction is sometimes an influential factor. In addition, other external factors are gender roles and job market. Conclusions Based on the data analysis, we get some enlightenment on how to strengthen the willingness to teach of PETs in minority areas.

Catalytic deoxygenation of vanillin over layered double hydroxide supported Pd catalyst

Chanjuan Liao,Xixi Liu,Yongshen Ren,Daoxin Gong,Zehui Zhang 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.68 No.-

A sustainable method was developed for the upgrade of biomass derived vanillin (a typical model compound of lignin) into the potential liquid biofuels over a layered double hydroxide supported Pd catalyst (abbreviated as CoAl–LDH/Pd). The CoAl–LDH/Pd catalyst showed high catalytic activity towards the hydrodeoxygenation of vanillin into 2-methoxy-4-methylphenol (MMP) under mild conditions in aqueous media. High MMP yield up to 86% was produced at 120 C after 4 h. Kinetic studies revealed that the rate-determining step for the hydrodeoxygenation of vanillin was the hydrogenolysis of vanillyl alcohol. More importantly, the CoAl–LDH/Pd catalyst was highly stable without the loss of activity.

Immunomodulatory effects of Pseudostellaria heterophylla peptide on spleen lymphocytes via a Ca2+/CaN/NFATc1/IFN-γ pathway

Yang, Qian,Cai, Xixi,Huang, Muchen,Jia, Lee,Wang, Shaoyun Royal Society of Chemistry 2019 Food & Function Vol.10 No.6

<P><I>Pseudostellaria heterophylla</I> has been becoming a popular research topic because of its functionally active components. The immunomodulatory activity of <I>P. heterophylla</I> peptide (PPH) derived from protein hydrolysate and the molecular mechanism underlying its immunomodulatory effect were investigated in this study. Immunomodulatory PPH achieved the highest stimulation index of 1.53 at a concentration of 100 μg mL<SUP>−1</SUP> for 48 h in spleen lymphocytes and promoted the secretions of tumor necrosis factor-α, interferon-γ, and interleukin-10. Moreover, PPH could elevate the intracellular Ca<SUP>2+</SUP> concentration, calcineurin activity and nuclear factor of activated T cell (NFAT) c1 mRNA expression. Meanwhile these effects could be diminished by the treatment of verapamil and cyclosporin A, suggesting that PPH may activate spleen lymphocytes <I>via</I> the Ca<SUP>2+</SUP>/CaN/NFATc1/IFN-γ signaling pathway. These findings demonstrate that the <I>P. heterophylla</I> peptide has the potential to be utilized as a nutraceutical supplement to strengthen the immune system in the human body.</P>

부산지역 외국인 근로자 고용실태에 관한 연구

오민홍 ( Min Hong Oh ),( Xixi Bu ) 한국질서경제학회 2018 질서경제저널 Vol.21 No.3

본 연구는 2017년 조사된 부산일자리종합실태조사를 바탕으로 부산지역 외국인 근로자 실태와 함께 이들 외국인 근로자를 고용한 기업의 고용성과를 분석하는데 그 목적이 있다. 부산지역 자치구군은 입지 및 경제발전과정에 따라 산업구조가 상이하며, 이에 따라 외국인 고용의 업종별, 지역별 편차가 존재하는 것으로 나타났다. 먼저 외국인 고용 여부 및 공석 여부별로 사업체 유형을 분류하여 이들의 특징을 살펴본 결과 다음과 같은 특징이 나타난다. 첫 째, 외국인 근로자를 고용하고 있는 사업체는 외국인 근로자가 내국인 비정규직에 비해 생산성이 높다고 평가하고 있으며, 이 때문에 내국인 비정규직에 비해 높은 수준의 임금을 제시하고 있다. 둘 째, 외국인 근로자를 고용하고 있는 기업은 그렇지 않은 사업체에 비해 내국인 근로자에 대해서도 보다 높은 임금을 제시하고 있다. 이러한 현상은 외국인 근로자가 내국인 근로자의 보완적 생산요소로 역할하고 있음을 간접적으로 보여준다. 다만 문제는 기업의 이러한 외국인 근로자 고용 관행이 정부가 고용허가제를 도입한 의도와는 다른 것으로 평가된다는 점이다. 한편, 외국인 근로자 고용 결정요인은 업종, 사업체 규모, 노조 유무, 매출액 규모에 따라 다른 것으로 나타났다. 외국인 고용이 가장 활발한 업종은 제조업으로 나타났으며, 제조업체 중 무노조 상태의 매출액이 상대적으로 높은 사업체의 외국인 근로자 고용 사업체 비중은 무려 55.1%에 이르는 것으로 나타났다. 이에 반해 외국인 근로자 고용의 직접요인으로 평가되는 사업체의 공석 여부는 통계적으로 유의미한 결과를 보여주지 않았다. 외국인 고용결정요인 분석결과를 토대로 외국인을 채용한 사업체와 그렇지 않은 사업체 간 매출액 차이를 분석한 결과, 통계적으로 유의미한 차이가 없는 것으로 나타났다. 이 같은 결과는 외국인 고용이 비용절감을 통해 기업의 경영성과를 높일 것이라는 기대는 사실이 아님을 시사한다. 외국인 근로자의 활용이 사업체의 경영성과에 긍정적 기여를 하지 못하는 상황에서 외국인 근로자를 선호하는 경향성을 보다 면밀히 파악하여, 내국인 근로자의 일자리 확보를 위한 방안이 필요하다. The purpose of this paper is to analyses the employment structure of foreign workers in Busan and its impact on performances of firms that hire those foreign workers, using Busan Job Survey. First of all, geographical distribution of foreign workers vary upon the industrial structure by subregion, Si, Gun, and Gu in Busan. Based on the criteria of foreigner employment and establishment type, we devide firms by 4 categories and explore those characteristics with respect to their practice of foreign worker employment. Firms with foreign workers evaluate that foreign workers tend to be more productive over native non-regular workers, thus pay more to the foreigners. Furthermore, firms hiring foreign workers pay higher wages than firms not hiring foreign. These findings support the view that firms with foreign workers are more profitable and the relationship between native and foreign worker would be complementary each other, boosting productivity of the firm. However, these phenomenon seems to out of the intention of the Work Permit System that allows to hire foreign workers only in certain sectors and firms not being able to find native workers in it. The results of logit and decision tree model to find determinants of firms’ hiring foreign workers revealed that industry, firm size, union and sales volume are the most important variables whether a firm hires foreign worker. Firms in manufacturing sector with higher sales volume and no union tend to hire more foreign workers. However, job vacancies does not seem to have statistical association with firms’ decision to hire foreign workers. In the sense that the Work Permit System in Korea only allow firms with vacancies to hire foreign workers, this is a important check point whether the system works properly. Finally, this paper analyzes whether there are variances in firms’ performances by hiring foreign workers. In order to do so, this paper utilized 1-to-1 matching and PSM together. However, there is no statistically significant differences after controlling firms’ characteristics between firms with and without foreign workers. Based on our results, it would be necessary to find an appropriate policy measure for firms to hire more native workers if the practice of firms’ hiring foreign workers dose not related with their job vacancies and sales volume.