Modification of tumor micro-environment to enhance anti-tumor immune response

Wu, Chao-Yi Joy The Johns Hopkins University 2013 해외박사(DDOD)

Increasing attention have been generated to minimized the adverse immune impact of tumor infiltrated myeloid cells to increase the anti-tumor immune response and potentially enhance tumor control. In present study, we've demonstrated that intratumorally administration of a peptide based vaccine in well defined solid tumor combining PADRE peptide and poly I:C leads to an enhanced antitumor effects in treated mice comparing with conventional vaccine route giving subcutaneous (Chapter 2). This challenges the prevailing notion of the tumor as an inherently immune-suppressive site and underscores the dynamic nature of interactions between the tumor and the immune system. Also, we evaluate the phenotype change of macrophages in the peritoneal cavity of disseminated ovarian cancer model after poly I:C treatment. With the help of PEI to increase the uptake of poly I:C by the peritoneal cells, significant improvement was observed in the antitumor effects against murine ovarian tumors. This anti-tumor effect was contributed by the alternative MI activation of peritoneal macrophages when treated and sequentially activate NK cells to clear tumor (Chapter 3). This suggests that the environment of ill-define disseminated tumors can also be changed to significantly benefit tumor control. Last, we focus on how conventional cancer treatments, tumor irradiation impact the tumor microenvironment. In chapter 4, we've show that by combining RT and targeted delivery of antigenic peptide to the tumor, the adjuvant effect generated by RT itself is sufficient to elicit the priming and expansion of antigen-specific CD8+ T cells through the type 1 interferon and toll like receptor 4 dependent pathways and leads to a potent therapeutic antitumor effect. In addition, we demonstrated that CTL-mediated killing of CD11b+ myeloid stromal cells, in the tumor by our approach is important for the control of tumor growth using two different transgenic mouse models. Altogether, we observed a greater tumor control achieved through the suppression of the immunomodulatory effects and the enhancement of favorable immune stimulation due to local RT. In summary, these results demonstrate that the immune-suppressive tumor micro-environment can be reversed by available, commonly practiced, interventions and provide impetus for the development and clinical translation of novel immune-based strategies for cancer therapy. iii.

Characterization and evaluation of PI/PVDF-TrFE composite nanofiber based triboelectric nanogenerators depending on types of electrospinning nozzle systems

오신위 한양대학교 대학원 2020 국내석사

Characterization and evaluation of PI/PVDF-TrFE composite nanofiber based triboelectric nanogenerators depending on types of electrospinning nozzle systems Xinwei Wu Dept. of Mechanical Design The Graduate School Hanyang University Recently, energy problems have become a hot spot of global concern. In order to solve the energy problem, people have developed a variety of energy harvesters, in which triboelectric nanogenerator (TENG) is a portable energy harvester. It has attracted attention because of its high output power, simple, and low-cost structure. In order to improve the performance of TENG, many studies have been performed such as increasing the surface charge density and increasing the contact area. In this study, using designed single-nozzle, conjugated-nozzle and multi-nozzle three electrospinning nozzle systems successfully fabricated different forms of PI/PVDF-TrFE composite nanofibers. These three forms of composite nanofibers were made as the dielectric layer of TENG, and the electrical properties of TENG were measured. Among them, multi-nozzle nanofibers showed the highest open-circuit voltage of 364 V and short-circuit current of 17.2 μA, respectively. The power density of TENG made with multi-nozzle nanofibers is 1.18 W/m2. It was able to stably harvest energy during the tapping experiment of 10,000 cycles and even from palm and foot tapping. The M-TENG could be used for various practical applications such as capacitor charging and LED lighting.

중국사회주의 체제하의 인터넷 수용방식

Wu, Jingjing 경북대학교 대학원 2014 국내박사

The Pattern of Internet Acceptance in the Socialism System of China* Jingjing Wu Department of Journalism and Mass Communication Graduate School, Kyungpook National University Daegu, Korea (Supervised by Professor Nam Jeiil) (Abstract) As the main object of study, the process of Internet Acceptance in China from 1994 to 2013, the related laws and regulations enacted by the government of China and the typical social events happened in this period were discussed to analyze the role that the internet played in Chinese socialism, the effect of it on the society and the variation of the related laws and regulations in different stage of internet development, which were compared with that of representative capitalist country. The purpose of this study is to summarize the experience and lessons from the development of internet in China to find the optimum administration of networks which is fit for the present system of China and then promote the mutual development of internet and Chinese society and the progress of democratic society of China. The firsthand information, a large number of research papers and books about the related subject and involved historical material, the secondhand data, various kinds of data sets, annuals, annual reports and white books issued by the government, and some data from the third party were collected to analyze systematically the two main research questions in this paper described as follow by using the method of Literature Research, Data Analysis, Example Analysis and Comparative Analysis. First question is what the acceptance of Chinese internet and the differences of that between socialism and capital is mare. The second question is what the differences of policies of the internet acceptance between socialism and capital is mare. Besides, the collected information was divided into different stage according to the period to analyze the development content of that stage and obta in the results of this thesis. Firstly, the results about question 1 were as follows: With the development of Chinese economy and technology Chinese network and network media have grown up at an explosive speed in the field of popularizing rate and relevance grade, which is similar to that of capitalism countries. In capitalism countries, network is an kind of mainstream media for intensifying the system of democracy, while in the socialism countries as China the progress of internet acceptance was the course of fostering the democratic awareness of citizen and democratic strength and also the development progress of social supervision of Chinese media. The traditional media as the popularsation means of Chinese Communist Party didn’t play any role in the democratic development because of the special system, while the appearance of network offered a field of participant for public voice, which has lighted the infinite and increasing passion of democracy and freedom in China. The results for the question 2 were as follows: All of the countries either the socialism or capitalism are trying their best to seek the balance point between national interest and personal rights of citizen in spite of the difference of social system. The freedom of expression, rights and interests of citizen and standard of network cannot go forward parallelly so that all of countries are doing their best to contain the dysfunction of network while they are also trying to find their own key point under their own social system. In the capitalism countries human rights, privacy and the freedom of expression are the most important factors considered in the administration of network and formation of lows and regulations. However, in the socialism of China the political stability and social safety are considered firstly so that the standard of network is taken the most seriously in that three parties. Because the government of China have to intervene in the standard administration of network to guarantee the political stability which is the most important thing for a single-party system country. Furthermore, China possess the most population in the world, 618 millions till December, 2013 but the degree of education of netizen and the popularizing rate of network are both so low that if complete freedom of expression is implemented, more cyber-violence will happen in China. The appearance and development of network as being a important camp of public voice are extraordinary for Chinese socialism that possess some unsurpassable social function which the traditional media don’t have. Because of its character network has been being the most exoteric mainstream media all over the world although every country have their own feature and principle in the adminstration of network and network media on account of their different social system. The present thesis combined the system of Chinese socialism and the acceptance process of network and network media to carry out a macroscopic study to state the function of network in the development of socialism and the difference of that from capitalism and analyze deeply the cause of this difference and lessons learned from it to provide some theoretical foundation for related subsequent research. Because of the difference of the region and popularizing rate of network every district has their own laws and regulations fit for the local situation which limited our study so that it’s necessary to do some follow-up study in the future about the popularizing rate of network in different regions of China.

활성탄의 후처리에 의하여 제조된 전기이중층 커패시터용 전극재의 전기 화학적 특성

WU JINGYU 명지대학교 일반대학원 2008 국내석사

Electrochemical Performance of Activated Carbon Electrode Materials with Post Treatment for EDLC Jingyu Wu Dept.of Chemical Engineering Graduate School Myongi University Two types of commercial activated carbons of coconut shell based and coal char based were applied for EDLC electrode by removing impurities with chemical treatments, and controlling pore size distribution and content of surface functional group with heat treatment. The electrochemical properties were evaluated with coin cell using these activated carbons as electrode. The porosity and surface area of the electrode materials were analyzed by nitrogen adsorption at 77K, and the surface functional groups were studied by Boehm and TPD method. The effects of the pore structure and surface functional groups on the electrochemical performance of the activated carbon electrodes were investigated. The initial gravimetric capacitance of the commercial activated carbon electrodes with coconut shell based and coal char based were 66 and 70 F/g respectively, and after 100 cycles the values were decreased to 54 and 66 F/g respectively showing 82% and 94% of charge-discharge efficiency. Their initial volumetric capacitances were 39 and 36 F/cc, and after 100 cycles, the values were turned out to be 32 and 34 F/cc. The properties of CV graph with the commercial activated carbon electrodes showed the serious polarization as the result of additional reaction between electrolyte and impurities of the electrode materials. So, it was concluded that the commercial activated carbons were not suitable as the EDLC electrode materials. In order to remove the impurities, the commercial activated carbons were chemical treated with various acids. The initial gravimetric capacitances of coconut shell and coal char based activated carbon electrodes which were acid treated by aqua regia were 75 and 79 F/g, and after 100 cycles the values were turned out to be 63 F/g and 71 F/g, showing the highest capacitance among the various acid treatments. The commercial activated carbons were heat treated after nitric acid treatment to control the surface functional groups and were used as electrode to evaluate the electrochemical properties. The initial gravimetric and volumetric capacitances of coconut shell based activated carbon electrodes which were acid treated by HNO3 and then heat treated at 800℃ were 90 and 42 F/cc respectively with 94% of charge-discharge efficiency, showing much improved capacitance. The commercial activated carbons were alkali treated to remove the impurities, which were not soluble in acid solution. The commercial activated carbon treated by NaOH showed a little bit improved gravimetric capacitance but the volumetric capacitance was similar to the raw materials of commercial activated carbon electrode. The removal of impurities from the electrode materials was more efficient with acid treatment than with alkali treatment, showing higher capacitance. In order to remove impurities more efficiently the commercial activated carbons were alkali and acid treatment, and then were heat treated to control the surface functional groups. The surface functional groups decreased with the increased heat temperature and the specific capacitance increased with the decreased surface functional groups. The initial volumetric capacitance of coconut shell based activated carbon electrode which was alkali and nitric acid treated, and then heat treated at 800℃ was 44 F/cc. After 100th cycles the value turned out to be 42 F/cc, showing 95% of charge-discharge efficiency. Such a good electrochemical performance can be possibly applied to the medium capacitance of EDLC. 국문요약 Coconut shell 및 coal char 계 상용활성탄을 전기이중층 커패시터의 전극재로 적용하기 위하여 화학적 처리에 의하여 전극재의 불순물 성분을 제거하였으며 열처리에 의하여 표면 관능기를 제어하고자 하였다. 제조된 활성탄을 전극재로 사용하여 coin cell형태의 전기이중층 커패시터를 제작하여 전기화학적 특성을 평가하였다. 질소등온흡착에 의하여 비표면적과 세공특성을 분석하였고 Boehm 법 및 TPD 방법에 의하여 전극재의 표면의 산성관능기의 종류와 양을 측정하여 전극재의 물리화학적 특성과의 상관관계를 조사하였다. Coconut shell 및 coal char 계 활성탄을 별도의 처리 없이 전기이중층 커패시터의 전극재로 사용하였을 때 초기무게용량은 각각 66과 70 F/g, 100사이클 후의 용량은 54와 66 F/g으로 각각 82%와 94%의 효율을 나타내었고, 초기부피용량은 각각 39와 36 F/cc, 100사이클 이후 32와 34 F/cc로 감소되었다. CV 특성도 사이클 진행에 따라 불순물과 전해질의 부반응에 의한 분극현상이 크게 발생하여 미처리한 상용활성탄은 전극재로서의 사용에 적합하지 않다는 것을 알 수 있었다. 원료의 불순물을 제거하여 전해질과의 전기화학적 부반응을 감소시키기 위하여 상용활성탄을 여러 가지 산에 의하여 화학적으로 처리하였다. 산 처리를 한 활성탄의 무게용량은 원료에 비하여 높은 용량을 나타내어 왕수 처리를 한 coconut shell 및 coal char계 활성탄을 전극 물질로 사용했을 때 초기무게용량은 각각 75와 79 F/g을 나타냈으며 100사이클 후에 63과 71 F/g을 보임으로서 가장 높은 용량을 나타내었다. 열처리에 의하여 산 처리된 활성탄의 관능기를 제어하고 이를 전극재로 사용하여 전기화학적 특성을 평가하였다. 질산 처리된 coconut shell 및 coal char계 활성탄은 열처리 이후 용량이 모두 증가되었으며, 사이클 특성도 우수하였다. 질산 처리 된 coconut shell 계 활성탄을 800℃에서 열처리하여 전극재로 사용한 경우 초기 무게용량은 90 F/g, 100사이클 충•방전 반복 후 무게용량은 85 F/g으로 가장 높은 용량을 나타냈으며, 94%의 충•방전 효율을 나타내었다. 화학적 처리 및 열처리에 의하여 용량에 기여 가능한 크기의 micropore가 증가함에 따라 무게용량과 부피용량이 모두 증가하였으며 mesopore 와 macropore가 증가함에 따라 무게용량과 부피용량이 모두 감소하였다. 활성탄을 알칼리에 용해 가능한 불순물을 제거하기 위하여 여러 가지 알칼리 용액으로 처리하여 전극재로서의 특성을 평가한 결과 수산화나트륨용액으로 처리한 활성탄이 상대적으로 높은 용량을 나타내었으며 원료에 비하여 무게용량은 다소 증가되었으나 부피용량은 원료와 비슷하였다. 알칼리 처리에 의한 전극재의 불순물 제거효율은 산 처리에 의하여 제조된 전극재에 비하여 상대적으로 낮으므로 산 처리에 의하여 제조된 전극재의 용량의 향상효과가 더 높은 것을 알 수 있었다. 불순물을 보다 효과적으로 제거하기 위하여 활성탄을 알칼리와 산으로 차례로 처리하였으며 관능기 제어를 위하여 열처리를 하여 전극물질로 사용하였다. Boehm 법과 TPD 방법을 이용하여 분석한 결과 열처리에 따라 관능기의 양이 감소하는 것을 확인할 수 있었다. 이에 따라 무게용량과 부피용량이 모두 원료에 비하여 증가되었으며 사이클 특성도 우수하여 coconut shell 계 활성탄을 알칼리 및 질산 처리 후 800℃에서 열처리한 전극재의 경우 초기 부피용량 44 F/cc, 100사이클 후 42 F/cc로서 실용화 가능한 수준의 높은 부피용량 및 95% 이상의 높은 충•방전효율을 나타내었다.

Characterization of Various classes of Einstein's Metrics : Hwang, Seung Wu

Hwang, Seung Wu State Univ. of New York at Stony Brook 1996 해외박사

이 논문은 두 부분으로 구성되어 있다. 첫 부분은 Einstein 다양체에 어떤 써클 action 이 주어졌을때 그러한 메트릭은 유일함을 보인 것이고, 둘째 부분은 긴밀한 리만 다양체에 Einstein 메트릭이 존재함을 보이고자 한 것이다. 첫 번째 부분은 리찌곡률(Ricci curvature)이 영인 임의의 차원의 완비 리만 다양체(complete Riemann manifold)에 어떤 isometric한 S¹action이 있을 경우를 다루고 있다. S¹action으로 인한 submersion의 기저 다양체가, 주어진 다양체의 부분 다양체가 되는 경우를 static이라고 한다. 이 경우 기저 다양체가 스핀(spin)이고 유도되는 메트릭이 점근적으로 평평(flat)해질 때 주어진 리만 다양체가 리만 Schwarzschild메트릭이 됨을 보였다(정리3). 이 사살은 4차원일 경우에는 알려져 있는데 이 논문에서는 임의의 차원에 대해서도 성립함을 보인 것이다 또한 임의의 n개의 조화함수들이 주어지면, (n+3)차원의 리찌곡퓰 영인 리만 다양체를 구성할 수 있음도 보였다. 두 번째 부분은 주어진 긴밀한 리만 다양체(complete Riemann manifold)에 대한 Yamabe 메트릭 공간 상의 스칼라 곡률 범함수 (scalar curvature functional)의 특이점이 Einstein임을 보이고자 하였다. Yamabe 메트릭 공간이란 스칼라 곡률이 상수인 메트릭들의 집합이다. 주어진 특이점 메트릭의 스칼라 곡률이 양이 아닐 경우에는 Einstein 임이 이미 알려져 있다. 그러나 양일 경우에는 알려져 있지 않다. 이 논문에서는 리만 다양체가 3차원이고 스칼라 곡률이 양일 경우를 다루고 있다. 먼저 포텐셜 함수 f의 level집합들의 위상적 구조를 다루었다(정리6). 또한 주어진 특이점 메트릭의 여러 기하학적 구조를 조사한 후, ()가 f의 함수일때 특이점이 Einstein임을 보였다.(정리7).

(A) raging China? : impact of changing media on Chinese nationalism and anti-Japan protests

Wu, Hao Graduate School of International Studies, Korea Un 2017 국내석사

In light of the troubled relationship between China and Japan, anti-Japan protests in China seem to serve not only as the fuel to aggravate the bilateral relation, but also an indication of Chinese hostility against Japan. Despite strong evidence of the impact of popular nationalism on China’s foreign policy, there is a lack of discussion on the nature of such sentiment. The growing anti-Japan protests themselves have often be taken as a sign of growing Chinese aggressiveness towards Japan, which in turn generates the perception of China as an emerging threat to regional stability. This paper seeks to explore the impact of media reform and online communities in causing such outburst of emotion by comparing 5 anti-Japan protests from 1980 to 2010: the 1985 Anti-Japan protest; 1996 Baodiao Protest; 2004 Baodiao movement; 2005 Anti-Japan protest; and 2012 Anti-Japan protest. These protests are selected to allow for a comparison between pre-internet era and post-internet era in order to highlight the changes after the introduction of new media and emergence of online communities. The paper will demonstrate that mass media has created the perception of an imminent Japanese threat that constantly calls for citizens to take up collective action against such perceived foreign threat, and this is manifested through protests serving as the symbolic ritual for Chinese to demonstrate their patriotism.

한중 의학 전문용어 대조 연구

WU, YINGQIU 이화여자대학교 대학원 2022 국내석사

본 연구의 일차적 목적은 사전과 자료들에 나타난 한국어와 중국어의 의학 전문용어에 대한 개념을 세우고 그 범위를 설정하는 것이고, 이를 바탕으로 이차적 목적은 의학 전문용어의 형태적 및 의미적 특성을 밝히는 것이다. 우선 Ⅰ장에서는 본 연구의 목적과 필요성, 한중 의학 전문용어의 선행 연구 및 연구의 방법과 논의의 구성에 대해 검토하였다. Ⅱ장에서는 한국어와 중국어 의학 전문용어에 대해 정의하고 그 범위를 정리하면서 본 연구의 구체적인 대상을 제시하였다. 기존의 여러 견해를 통해 볼 수 있듯이, 의학 전문용어의 개념과 범위를 검토하였는데, 한국어와 중국어 의학 전문용어 사이에 차이가 존재하기 때문에 이런 과정을 통해 그 차이를 분석함으로써 개념과 범위를 설정하는 것이 앞으로의 작업을 위해 필수적이라 할 수 있다. Ⅲ장에서는 한국어와 중국어 의학 전문용어의 형태적 특징을 분석하기 위해 먼저 한중 양국의 의학 전문용어를 어종별로 나누어 살펴보았다. 다음으로 단어 형성이라는 측면에서 단일어, 합성어, 파생어로 분류하여 분석하는 것이다. 이 과정 중에서 한국어와 중국어 의학 전문용어 형태적 특성의 공통점과 차이점도 파악할 필요가 있다. Ⅳ장에서 한국어와 중국어 의학 전문용어의 의미적 특성을 비교하기 위한 의미 변화와 의미 관계의 특성을 파악하고자 한다. 의미 변화의 측면에서 한국어와 중국어는 차별 없이 일반 어휘의 의학 전문용어화와 타 분야 전문용어의 의학 전문용어로의 의미 차용으로 나누고 의미 관계를 상하 관계, 동의 관계와 반의 관계로 분류하고 있다. 또 이를 통해 한중 양국 의학 전문용어의 의미적 특성의 공통점과 차이점을 분석하였다. Ⅴ장에서는 본론의 논의를 요약하며 결론적인 연구 결과를 정리하여 남은 문제 및 전망을 제시하였다. The primary purpose of this study is to establish the concept and scope of medical term in Korean and Chinese, which appear in dictionaries and materials, and based on this, the secondary purpose is to reveal the morphological and semantic characteristics of medical term. First of all, Chapter I reviewed the purpose and necessity of this study, the preceding research on Korean-Chinese medical term, the method of research, and the composition of discussions. In Chapter II, Korean and Chinese medical terms were defined and the scope of them was summarized, and this study was specifically targeted. As can be seen from many previous views, the concept and scope of medical term were reviewed, and since there is a difference between Korean and Chinese medical term, it was prepared as an essential part of analyzing the difference through this process. In Chapter III, in order to reveal the morphological characteristics of Korean and Chinese medical terms, the medical terms of Korean and Chinese were first divided and examined by word types. Next, in terms of word formation, it is classified into a single word, a compound word, and a derivative word. In this process, it is also necessary to understand the commonalities and differences between the morphological characteristics of Korean and Chinese medical terms. Chapter IV attempts to understand the semantical characteristics and semantic relationships to compare the semantic characteristics of Korean and Chinese medical terms. In terms of meaning change, Korean and Chinese are divided into terminologization and transdisciplinary borrowing. and the semantic relationship is classified into a hypernym and hyponym relation , a synonym relation , and an antonymous relation. In addition, through this, the commonalities and differences of the semantic characteristics of medical terms between Korea and China were analyzed. Chapter IV summarizes the discussion of the main body, summarizes the conclusive research results, and presents the remaining problems and future prospects.

A Study on the Effect of NPO-donor Relationship Enhancing Strategies on Charity Intention through Social Media in China

WU QIXIANG 우송대학교 대학원 2020 국내박사

Based on the previous research on enhancing donor relationships and to fill the research gap, this thesis intends to conduct an empirical research on how NPO-donor relationship enhancing strategies affect users' charity intention through social media.

China's energy policy process : focusing on chinese government-petroleum SOE interactions and implications

Wu, Shan Graduate School of International Studies, Korea Un 2012 국내석사

This thesis will explore the interactions between the Chinese government and Petroleum State-owned Enterprises in China’s energy policy-making, and implications of Chinese petroleum SOEs’ overseas investment for international peace and security. The main purpose of the thesis is to understand China’s energy policy process and the Chinese government and SOE interactions in the global context. In general, this thesis conducted a qualitative study of China’s energy policy process, and borrowed the statistical power of quantitative study when necessary. Rather than an economic or an international security approach, this thesis refers to the agency cost theory under the Neoinstitutional Economics framework to study the government-SOE interactions. A fragmented bureaucratic politics approach is applied to China’s energy policy process as well. The findings of this thesis are as follows. First, China’s crude oil energy consumption is on the rise whereas domestic crude oil production tends to increase slowly in the short term and decline in the long term, therefore imported oil dependence rate is expected to increase further in the near future. The Chinese government has attached great importance to the energy security issue, and begun to focus on demand management as well as supply expansion. Second, in the reform era, China’s economic decision-making authority has gone through a decentralization process and is tending towards further decentralization. Due to the fragmented bureaucratic feature of Chinese policy process, central government agency on energy policy-making is unlikely to be formed and government oversight is ineffective. The partial SOE reform has transformed Chinese petroleum SOEs into commercial-driven enterprises with political clout, whose rent-seeking behaviors have been conspicuous in China’s domestic fuel shortage over the past five years. Thus, as indicated in the NIE theory, management of interest convergence has been difficult for the Chinese government and the state’s control of petroleum SOEs has not been as tight as many supposed it to be. Third, the Chinese petroleum SOEs’ overseas expansion reflects more of the enterprises’ commercial interests rather than the state’s political intentions.

Determination of trace elements in food samples by slurry sampling-electrothermal vaporization/low-pressure inductively coupled plasma-atomic emission spectrometry

Wu, Jianyong GRADUATE SCHOOL OF CHANGWON NATIONAL UNIVERSITY 2003 국내박사

The matrix effects of low-pressure ICP were investigated by measurements of the ionic to atomic spectral line intensity ratio of a monitor element: Cd, which was introduced with zinc matrix simultaneously by electrothermal vaporization (ETV). The results show that the characteristics of low-pressure ICP change greatly when the matrix amount succeeded a certain value, probably because the pressure is affected by the matrix. Ultrasonic slurry sampling-electrothermal vaporization/low pressure inductively coupled plasma atomic emission spectrometry (USS-ETV/LP-ICP-AES) was applied to the determination of Zn, Mg, Fe and Mn in an egg powder reference material (NIST RM 8415). An improved tantalum filament ETV device was directly coupled with LP-ICP system for highly efficient vaporization of samples. Standard addition method was used to avoid the matrix effect in low-pressure inductively coupled plasma. The influences of pressure in plasma and slurry preparation on signals were reported. The analysis results agreed with the certified values well. The absolute detection limits of Zn, Mg, Fe and Mn estimated from the standard addition curve were 1.9, 11, 50 and 4.5 pg, respectively; the precision (RSD) was better than 6.1% for all the determinations. The fact that the element with relatively high ionization potential achieves a strong ionic signal in relatively low pressure ICP indicates that the ionization process is probably dominated by electronic impact in low pressure ICP.