Approximate Normal Distribution Research Articles

Analysis and generation of groundwater concentration time series

Abstract Concentration time series are provided by simulated concentrations of a nonreactive solute transported in groundwater, integrated over the transverse direction of a two-dimensional computational domain and recorded at the plume center of mass. The analysis of a statistical ensemble of time series reveals subtle features that are not captured by the first two moments which characterize the approximate Gaussian distribution of the two-dimensional concentration fields. The concentration time series exhibit a complex preasymptotic behavior driven by a nonstationary trend and correlated fluctuations with time-variable amplitude. Time series with almost the same statistics are generated by successively adding to a time-dependent trend a sum of linear regression terms, accounting for correlations between fluctuations around the trend and their increments in time, and terms of an amplitude modulated autoregressive noise of order one with time-varying parameter. The algorithm generalizes mixing models used in probability density function approaches. The well-known interaction by exchange with the mean mixing model is a special case consisting of a linear regression with constant coefficients.

85 The Difference of Professionalism Between Emergency Medicine Residents and Faculty Physicians: Multicenter Cross-Sectional Analysis

Professionalism is one of the critical emergency medicine (EM) physician competencies and professional behavior affects patient satisfaction. Forty-five percent of EM program directors reported that there were two or more residents with unprofessional behavior in their programs per year. Another study reported that role model was the most influential factor. However, there is no evidence to support that there is difference of professionalism between EM residents and EM faculty physicians. Therefore, to investigate difference of professionalism between EM residents and EM faculty physicians may facilitate medical professionalism education. Thus, by using a cross-sectional multicenter survey, we aimed to analyze the responses to common challenges to medical professionalism for EM physicians and to survey the extent of education related to professionalism and satisfaction with it during the time attending medical schools. We conducted a survey of EM residents and EM faculty physicians at several teaching hospitals in Japan, using the Barry questionnaire. The Barry’s questionnaire is one of the assessment of professionalism tools widely used in the US and Japan. The questionnaire instrument contains 6 challenging cases to professionalism: acceptance of gifts; conflict of interest; confidentiality; physician impairment; sexual harassment; and honesty in the documentation. After completing all six scenarios, participants were asked, ‘Have you ever experienced formal educational courses about medical professionalism?’ on yes or no responses. We sent the Barry's questionnaire to 6 hospitals. In addition, we collected data at the Japanese biannual emergency medicine academic meeting. We analyzed the frequency of providing either the best or the second best answers to each scenario as a main outcome measure and compared those frequencies between physicians in EM residents and EM faculty physicians. The Fisher exact test and proportion comparison test with normal distribution approximation were used to analyze data, where appropriate. We collected data from 135 participants (61 EM residents and 74 EM faculty physicians). Capture rate was 87%. The most challenging scenario was the sexual harassment scenario, in which 46.7% provided the best or second best answers, followed by the confidentiality scenario with 71.1%. Table 1 compares the frequencies that the participants provided the best or second best responses between EM resident and EM faculty physician. The frequency of either the best or second best responses to the confidentiality scenario was significantly greater in EM residents than in EM faculty physicians (p= 0.01). There were higher rates of participants who received formal educational courses about medical professionalism in EM residents' group versus in EM faculty physicians' group (23.0% versus 5.4%, p=0.003). EM faculty physicians were unable to provide acceptable response to challenges to professionalism in confidentiality and few had received an education in professionalism during school curricula. The greater teaching of professionalism is needed in medical education for both EM residents and EM faculty physicians in Japan.

Real-time qualitative study of forsterite crystal – Melt lithium distribution by laser-induced breakdown spectroscopy

A factor of lithium distribution between single-crystal forsterite (Cr,Li:Mg2SiO4) and its melt are studied by laser-induced breakdown spectroscopy. Lithium content in the crystalline phase is found to achieve a saturation at relatively low Li concentration in the melt (about 0.02%wt.). An algorithm and software are developed for real-time analysis of the studied spectra of lithium trace amounts at wide variation of the plasma radiation intensity. The analyzed plasma spectra processing method is based on the calculation of lithium emission part in the total emission of the target plasma for each recorded spectrum followed by the error estimation for the series of measurements in the normal distribution approximation.

Testing measurement invariance in longitudinal data with ordered-categorical measures.

A goal of developmental research is to examine individual changes in constructs over time. The accuracy of the models answering such research questions hinges on the assumption of longitudinal measurement invariance: The repeatedly measured variables need to represent the same construct in the same metric over time. Measurement invariance can be studied through factor models examining the relations between the observed indicators and the latent constructs. In longitudinal research, ordered-categorical indicators such as self- or observer-report Likert scales are commonly used, and these measures often do not approximate continuous normal distributions. The present didactic article extends previous work on measurement invariance to the longitudinal case for ordered-categorical indicators. We address a number of problems that commonly arise in testing measurement invariance with longitudinal data, including model identification and interpretation, sparse data, missing data, and estimation issues. We also develop a procedure and associated R program for gauging the practical significance of the violations of invariance. We illustrate these issues with an empirical example using a subscale from the Mexican American Cultural Values scale. Finally, we provide comparisons of the current capabilities of 3 major latent variable programs (lavaan, Mplus, OpenMx) and computer scripts for addressing longitudinal measurement invariance. (PsycINFO Database Record

Performance improvement of magnetic anomaly detector using Karhunen–Loeve expansion

In this work, the authors improve the magnetic anomaly detector by using Karhunen-Loeve expansion, for expanding the detection distance of visually obscured ferromagnetic object when the target signal is contaminated by coloured noise. In the detector, the orthonormal basis functions are modified by the autocorrelation function of geomagnetic noise, and the anomaly is detected by matched filtering. Compared with the traditional detector, simulation results show that the modified detector has better performance with coloured Gaussian noise; especially, the improvement is more evident when the noise exponent is bigger. The real geomagnetic noise is proved to be coloured and obey approximate Gaussian distribution by the measurements in experiment. Tests with this noise indicate that the proposed detector achieves an incremental detection probability of 0.1 - 0.2 in the case of low signal-to-noise ratio, which makes it more attractive in practice.

SybilVote: Formulas to Quantify the Success Probability of Sybil Attack in Online Social Network Voting

This letter proposes to derive the success probability of Sybil attack in online social networks with the multiple-choice majority voting. The resultant SybilVote formulas produce outputs that are consistent with the Monte Carlo simulation and more accurate than the existing formula based on the multinomial distribution tail estimate. The computational complexity of SybilVote exact formulas is $O({{{({n + S})}^{k}}})$ , where $n$ , $k$ , and $S$ are the number of real users, choices, and Sybil users, respectively. The accurate approximation formula of SybilVote is also presented with $O(k)$ complexity by using a normal distribution approximation available when $n$ and $k$ are large in a large-population user voting condition. Finally, the effects of parameters on the success probability of Sybil attack have been investigated to highlight usefulness of the formulas.

Synergies between an Observed Port and a Logistic Company: Application of the Discounted Cash–Flow Model and the Monte Carlo Simulation

Abstract The paper addresses an analysis of potential synergies in collaboration between an observed Port in the Mediterranean Sea and Central-European logistic railway-services based company. Both companies have established a strategic partnership. The main motive was cooperation in rail transport, with a particular emphasis on potential synergies that would a rail traffic have brought to a port’s business. For the purpose of synergies valuation under uncertain conditions, a Monte Carlo simulation-based framework with integrated discounted cash flow (DCF) model is applied. The possible values of future synergies are calculated via the DCF model by simultaneously changing values of different uncertain financial parameters at each repetition of a Monte Carlo scenario-playing mechanism. In this process, predicted forecasts of future synergetic throughputs are also used for various types of observed cargo. As it turned out, the generated synergies’ values follow the approximate normal distribution. Based on statistical inference and analysis of probability intervals it was discovered that there might indeed exist certain important synergies in the collaboration between both companies. This fact has convinced us into a belief in the correctness of companies′ decision to enter into such kind of strategic cooperation.

Shewhart dispersion charts made easy for mild to moderately autocorrelated normally distributed data

ABSTRACTThe aim is to make it easier for users to implement dispersion monitoring plans when the data are autocorrelated. If the data follow a low-order ARMA model then the same threshold for the monitoring plan is applicable by revising the rational subgroup size. A robust plan for non-normal data is achieved in most cases by first transforming the data to an approximate normal distribution, and then applying the plan for normally distributed data. The dispersion plan is based on the robust regression estimator of the slope coefficient when regressing the ordered rational sub-group values against their “expected” in-control values.

Species composition, structure and spatial distribution of secondary cold-temperate Picea forest in Guandi Mountain, China

The secondary Picea forest is one of the dominant vegetation types in Guandi Mountain. It's also the representative type of evergreen cold-temperate coniferous forests in subalpine region of north China. A 4 hm2 fixed monitoring Picea forest plot was established in Pangquangou Nature Reserve, Guandi Mountain (GDS plot) to better understand the basic characteristics such as species composition, community structure and its potential ecological process and mechanisms. We analyzed species composition, structure and spatial distribution of sample forest based on the first background survey data in this paper. The results showed that a total of 30 woody plant species existed in the sample area, which belonged to 11 families, 22 genera. The total individual number (including branches) was 26218 (independent individual number was 10266). Floristic composition in the region was defined as north temperate elements. Big differences of individual number, average diameter at breast height (DBH) and basal area among different species caused significant community layering effect, and the dominant species in each layer was obvious. Size-class structure of species showed bimodal skewed normal distribution at the canopy layer, approximate normal distribution at the subtree layer, and 'L' type distribution at the shrub layer. Spatial distribution of the dominant tree species such as Picea wilsonii and Larix principis-rupprechtii showed different pattern features with the changing size class, whether in individual number or in aggregation degree. Compared with the above two species with the same size class, a large number of L. principis-rupprechtii with DBH≥30 cm aggregated in the center of sample plot, but few P. wilsonii individuals with DBH≥30 cm occurred in the plot and had no clustering distribution. Only a few L. principis-rupprechtii with DBH≤10 cm occurred in the plot with a scattering distribution, and a large number of P. wilsonii with DBH≤10 cm aggregated in the center of the plot. There were also many P. wilsonii individuals with DBH≤10 cm distributed in the northwest area of the plot, but Betula albo-sinensis individuals with DBH≤10 cm mostly distributed in the southeast area of the plot. Shrub species such as Cotoneaster acutifolius, Spiraea pubescens and Lonicera szechuanica also showed heterogeneous spatial distribution. Species distribution pattern was affected by habitat conditions, and related to its own development, regeneration traits and ecological habits.

An alternative approach to overcome shortcomings with multiple testing of binary data in ecotoxicology

Binary data such as survival, hatching and mortality are assumed to be best described by a binomial distribution. This article provides a simple and straight forward approach for derivation of a no/lowest observed effect level (NOEL/LOEL) in a one-to-many control versus treatments setup. Practically, NOEL and LOEL values can be derived by means of different procedures, e.g. using Fisher’s exact test in coherence with adjusted p values. However, using adjusted p values heavily decreases statistical power. Alternatively, multiple t tests (e.g. Dunnett test procedure) together with arcsin-square-root transformations can be applied in order to account for variance heterogeneity of binomial data. Arcsin-square-root transformation, however, violates normal distribution because transformed data are constrained, while normal distribution provides data in the range \((-\infty ,\infty )\). Furthermore, results of statistical tests relying on an approximate normal distribution are approximate too. When testing for trends in probabilities of success (probs), the step down Cochran–Armitage trend test (CA) can be applied. The test statistic used is approximately normal. However, if probs approach 0 or 1, normal approximation of the null-distribution is suboptimal. Thus, critical values and p values lack statistical accuracy. We propose applying the closure principle (CP) and Fisher–Freeman–Halton test (FISH). The resulting CPFISH can solve the problems mentioned above. CP is used to overcome \(\alpha\)-inflation while FISH is applied to test for differences in probs between the control and any subset of treatment groups. Its applicability is presented by means of real data sets. Additionally, we performed a simulation study of 81 different setups (differing numbers of control replicates, numbers of treatments etc.), and compared the results of CPFISH to CA allowing us to point out the advantages and disadvantages of the CPFISH.

张广才岭温带次生针阔混交林物种组成和群落结构特征

PDF HTML阅读 XML下载 导出引用 引用提醒 张广才岭温带次生针阔混交林物种组成和群落结构特征 DOI: 10.5846/stxb201603050389 作者: 作者单位: 北华大学,北华大学,北京林业大学,北华大学,西南林业大学,北华大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家"十二五"科技支撑项目（2012BAC01B03）；林业公益性科研行业专项"典型森林生态系统样带监测"（200904022） The composition and community structure of coniferous and broadleaved mixed forest species in the Zhangguangcai Mountains, China Author: Affiliation: Beihua University,Beihua University,Beijing Forestry University,Beihua University,Southwest Forestry University,Beihua University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了研究温带次生针阔混交林的树种组成和群落结构特征，于2010年在吉林省蛟河林业实验区管理局建立了面积为21.84 hm2（420 m×520 m）的固定样地。从物种组成、种-面积曲线、植物区系特征、径级分布结构和空间分布格局等方面分析了该地区针阔混交林物种组成和群落结构特征。研究结果表明该样地共有DBH≥1.0 cm的木本植物活立木个体25，908株，隶属于18科27属45种，植株密度为1186株/hm2。植物区系以北温带分布属为主体，共有37属，占总数的82.22%，属长白山植物区系。样地内稀有种18种，偶见种14种。通过对该样地物种多样性计算得出，该样地Margalef多样性指数R、 Shannon-Wienner指数H'、Simpson多样性指数D和物种均匀度Pielou指数Jsw分别为4.31、2.48、0.89和0.65。样地中所有个体的径级分布（以2cm等级排列） 呈偏倒"J"形， 整体更新良好，表现出群落稳定与生长状况良好的趋势。群落中重要值 > 3的9个物种的径级结构表现出一定的差异：胡桃楸、水曲柳呈近似正态分布，表现为中径木个体数量多，而小径木和大径木个体数量少的特点；春榆、大果榆、色木槭、白牛槭、裂叶榆等物种呈倒"J"型或偏倒"J"型，更新良好；而红松由于受到了严重的人为干扰，天然更新不良，径级结构呈现不规律型。通过g（r）双变量函数分析9个优势树种空间分布格局可知，9个优势树种均表现出聚集分布，聚集强度随着尺度的增大而降低。在r<20 m的小尺度上物种聚集强度随尺度增大急剧降低，当尺度超过20 m后聚集强度趋于稳定。 Abstract:Community composition and structure are the foundation of ecological system function and process research. Through a comprehensive understanding of community composition and structure, important information was obtained for further study of species diversity, species coexistence laws, and formation mechanisms. To study species composition and community structure of a coniferous and broadleaved mixed forest, a 21.84 hm2 (420 m × 520 m) permanent forest plot was established at the Jiaohe Forestry Experimental in Jilin Province in July 2010. We measured parameters for each woody plant with diameter at breast height (DBH) ≥ 1.0 cm. These parameters included the number of individuals and species, DBH, tree height, height under the first living branch, crown width, tree growth condition, and others. Structure characteristics of the community in this plot were analyzed based on the species composition, species-area relationships, floristic features, diameter class distribution structure, and spatial distribution patterns. A total of 25,908 living individuals were documented, belonging to 45 species, 27 genera, and 18 families, with a stem density of 1,186 individual/hm2. At the genus level, the North Temperate distribution type was the main vegetation type, which has 37 genera, accounting for 82.22% of all genera. There were 18 and 14 species of rare (≤ 1 individual/hm2) and accidental species (1-10 individual/hm2), respectively, in the plot. The Margalef diversity index R, Shannon-Wiener index H', Simpson diversity index D, and Pielou evenness index Jsw were 4.31, 2.48, 0.89, and 0.65, according to the equations (2)-(5), respectively. The diameter class distribution of all individuals (2cm class) followed a partial reverse "J" shape, which indicated that the natural regeneration understory was good and the forest community exhibited a steady growth trend in this plot. The diameter class distribution of nine species with importance values >3 exhibited some differences: J. mandshurica and F. mandschurica had an approximate normal distribution; U. davidiana var. japonica, U. macrocarpa, A. mono, A. mandshuricum, and U. laciniata exhibited an inverted "J" shape or partial inverted "J" shape, which suggested regeneration was good; P. koraiensis exhibited an irregular pattern because of severe human disturbance and poor natural regeneration. The Paired-correlation g(r) function results indicated that the nine primary tree species had aggregated distributions, and the aggregation intensity decreased with increasing distance. The aggregation intensity decreased dramatically when distance (r) was <20 m, but the trend became steady when distance was > 20 m. 参考文献 相似文献 引证文献

The Monte Carlo study of techniques for determining bremsstrahlung focal spots

The Monte Carlo statistical modeling has been used to study the techniques for determining the size of bremsstrahlung focal spots in the approximation of a normal distribution of bremsstrahlung quanta over the target surface.

Establishing reference intervals of the routine laboratory tests for hepatorenal function in Shanghai by biochemistry

Objective To establish reference intervals of nine laboratory projects for hepatorenal function and verify its reliability by indirect method. Methods ALL test results were extracted from physical examinations that were stored in the laboratory information system of Zhongshan Hospital during 2012 to 2014. Using Skewness-Kurtosis test to detect the normality of data, if not the original data were transformed through BOX-COX transformation to obtain an approximatenormal distribution. Outliers were identified and omitted by Turkey method. The indirect reference intervals were taken by applying Hoffmann method. The reference change value (RCV) was selected to inspect the statistical significance between the calculated and published reference intervals. Results Among those nine laboratory projects, thedifferences betweenthereference intervalsfor ALT, AST, AKP, GGT, TP, BUNwerelessthan their RCV( 26.65%, 9.92%) , and there was a significant difference between the calculated reference intervals and the current reference interval in the laboratory for the lower limit of the UA of male(>26.65%). Conclusion This research further proved the reliability of indirect reference intervals and this technique deserved to be promoted and applied by other clinical laboratories.(Chin J Lab Med, 2016, 39: 906-910) Key words: Liver function tests; Kidney function tests; Reference values

Quantifying the risk of nosocomial infection within Ebola Holding Units: a retrospective cohort study of negative patients discharged from five Ebola Holding Units in Western Area, Sierra Leone.

A central pillar in the response to the 2014 Ebola virus disease (EVD) epidemic in Sierra Leone was the role of Ebola Holding Units (EHUs). These units isolated patients meeting a suspect case definition, tested them for EVD, initiated appropriate early treatment and discharged negative patients to onward inpatient care or home. Positive patients were referred to Ebola Treatment Centres. We aimed to estimate the risk of nosocomial transmission within these EHUs. We followed up a cohort of 543 patients discharged with a negative EVD test from five EHUs in the Western Area, Sierra Leone, and examined all line-listed subsequent EVD tests from any facility in the Western Area to see whether the patient was retested within 30 days, matching by name, age and address. We defined possible readmissions as having the same name and age but uncertain address, and confirmed readmissions where name, age and address matched. We found a positive readmission rate of 3.3% (18 cases), which included 1.5% confirmed readmissions (8 cases) and 1.8% possible readmissions (10 cases). This is lower than rates previously reported. We cannot ascertain whether EVD was acquired within the EHUs or from re-exposure in the community. No demographic or clinical variables were identified as risk factors for positive readmission, likely due to our small sample size. These findings support the EHU model as a safe method for isolation of suspect EVD patients and their role in limiting the spread of EVD.

On Stabilizing the Variance of Dynamic Functional Brain Connectivity Time Series.

Assessment of dynamic functional brain connectivity based on functional magnetic resonance imaging (fMRI) data is an increasingly popular strategy to investigate temporal dynamics of the brain's large-scale network architecture. Current practice when deriving connectivity estimates over time is to use the Fisher transformation, which aims to stabilize the variance of correlation values that fluctuate around varying true correlation values. It is, however, unclear how well the stabilization of signal variance performed by the Fisher transformation works for each connectivity time series, when the true correlation is assumed to be fluctuating. This is of importance because many subsequent analyses either assume or perform better when the time series have stable variance or adheres to an approximate Gaussian distribution. In this article, using simulations and analysis of resting-state fMRI data, we analyze the effect of applying different variance stabilization strategies on connectivity time series. We focus our investigation on the Fisher transformation, the Box–Cox (BC) transformation and an approach that combines both transformations. Our results show that, if the intention of stabilizing the variance is to use metrics on the time series, where stable variance or a Gaussian distribution is desired (e.g., clustering), the Fisher transformation is not optimal and may even skew connectivity time series away from being Gaussian. Furthermore, we show that the suboptimal performance of the Fisher transformation can be substantially improved by including an additional BC transformation after the dynamic functional connectivity time series has been Fisher transformed.

Measuring and estimating the interaction between exposures on a dichotomous outcome for observational studies

ABSTRACTIn observational studies for the interaction between exposures on a dichotomous outcome of a certain population, usually one parameter of a regression model is used to describe the interaction, leading to one measure of the interaction. In this article we use the conditional risk of an outcome given exposures and covariates to describe the interaction and obtain five different measures of the interaction, that is, difference between the marginal risk differences, ratio of the marginal risk ratios, ratio of the marginal odds ratios, ratio of the conditional risk ratios, and ratio of the conditional odds ratios. These measures reflect different aspects of the interaction. By using only one regression model for the conditional risk, we obtain the maximum-likelihood (ML)-based point and interval estimates of these measures, which are most efficient due to the nature of ML. We use the ML estimates of the model parameters to obtain the ML estimates of these measures. We use the approximate normal distribution of the ML estimates of the model parameters to obtain approximate non-normal distributions of the ML estimates of these measures and then confidence intervals of these measures. The method can be easily implemented and is presented via a medical example.

Analyzing signal attenuation in PFG anomalous diffusion via a modified Gaussian phase distribution approximation based on fractal derivative model

Pulsed field gradient (PFG) has been increasingly employed to study anomalous diffusions in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI). However, the analysis of PFG anomalous diffusion is complicated. In this paper, a fractal derivative model based modified Gaussian phase distribution method is proposed to describe PFG anomalous diffusion. By using the phase distribution obtained from the effective phase shift diffusion method based on fractal derivatives, and employing some of the traditional Gaussian phase distribution approximation techniques, a general signal attenuation expression for free fractional diffusion is derived. This expression describes a stretched exponential function based attenuation, which is distinct from both the exponential attenuation for normal diffusion obtained from conventional Gaussian phase distribution approximation, and the Mittag-Leffler function based attenuation for anomalous diffusion obtained from fractional derivative. The obtained signal attenuation expression can analyze the finite gradient pulse width (FGPW) effect. Additionally, it can generally be applied to all three types of PFG fractional diffusions classified based on time derivative order alpha and space derivative order beta. These three types of fractional diffusions include time-fractional diffusion, space-fractional diffusion, and general fractional diffusion. The results in this paper are consistent with reported results based on effective phase shift diffusion equation method and instantaneous signal attenuation method. This method provides a new, convenient approximation formalism for analyzing PFG anomalous diffusion experiments.

THE IMPACT OF SOCIAL NETWORKS ON THE SOCIAL HEALTH OF ADOLESCENTS AND YOUNG ADULTS IN ARDABIL

The objective of this study is to identify the effects of virtual social networks on the social health of young people. And the question, Do virtual social networks effect the social health of young is addressed. The main hypothesis of this study is: is a relationship between the rate of using virtual social networks and the social health of youth. The theoretical framework of this study is based on the theories of Keyes, Giddens, and Larson regarding social health, and communication skills theories of Schneider, Berkman, Bartle, Giddens, and the network view and social model of Wellman regarding virtual social networks. In this study, which is a field study, 800 young people from Ardabil in 2014-2015 were selected, using the cluster sampling method. Data was gathered using the Keyes social health questionnaire and a questionnaire regarding virtual social networks. The obtained social health of young people followed an approximate normal distribution. There is a statistically significant relation between relating with friends, internet advertisements, social involvement, negative behavioral effects, invading individual privacy, income, and education with young people's social health. In regression analysis, the variables that form the model, determined about 19% of the changes in the variance of social health. The strongest predicting variables were: relating with friends, and internet advertisements. We can conclude that the social health of young people, as a social construct, is effected positively and negatively by virtual social networks.

Molecular Dynamics Simulation on Hydrogen Ion Implantation Process in Smart-Cut Technology

The hydrogen ion implantation process in Smart-Cut technology is investigated in the present paper using molecular dynamics (MD) simulations. This work focuses on the effects of the implantation energy, dose of hydrogen ions and implantation temperature on the distribution of hydrogen ions and defect rate induced by ion implantation. Numerical analysis shows that implanted hydrogen ions follow an approximate Gaussian distribution which mainly depends on the implantation energy and is independent of the hydrogen ion dose and implantation temperature. By introducing a new parameter of defect rate, the influence of the processing parameters on defect rate is also quantitatively examined.

Spatio-temporally resolved measurement of quantal exocytosis from single cells using microelectrode array modified with poly l-lysine and poly dopamine

Abstract The subsecond, temporal, vesicular exocytosis is ubiquitous, but difficult detecting in communication mechanisms of cells. A microelectrode array (MEA), fabricated by MEMS technology, was applied successfully for real-time monitoring of quantal exocytosis from single pheochromocytoma (PC12) cell. The developed MEA was evaluated by dopamine (DA) using electrochemical methods and the results revealed that the sensitivity of DA was improved to 12659.24 μA L mmol −1 cm −2 . The modified MEA was used to detect in vitro vesicular exocytosis of DA from single PC12 cells stimulated by concentrated 100 mmol L −1 K + cell solution. A total of 592 spikes were measured and analyzed by three parameters and the statistical results revealed the population of each parameter was an approximate Gaussian distribution, and on average, 1.31 × 10 6 ± 9.25 × 10 4 oxidizable molecules were released in each quantal exocytosis. In addition, results also indicate that a single PC12 cell probably releases the spikes with T ranging from 25.6 ms to 35.4 ms corresponding to I max ranging from 45.6 pA to 65.2 pA. The devices, including a homemade computer interface and the MEA modified with polymer film, provides a new means for further research on the neural, intercellular, communication mechanism.