Assessment of an ultramicroelectrode array (UMEA) sensor for the determination of trace concentrations of heavy metals in water [online]

The main objectives of this book are (i) to investigate the electrochemical behavior and the analytical performance of a novel ultramicroelectrode array (UMEA); (ii) to assess the analytical parameters of square-wave anodic stripping voltammetric measurements (SWASV) using the UMEA; and (iii) to estimate the potential of the UMEA in developing decentralised analytical equipments for the determination of trace concentrations of heavy metals in natural waters. Surface analytical techniques (SEM, ESEM, and AFM) showed that the UMEA chips are of high quality in manufacture. Cyclic voltammetric and chronoamperometric experiments proved that the electrochemical behavior of the UMEA is dominated by the features characteristic for single microelectrodes.Chronocoulometry was found to be the most suitable method in generating the Hg-film of good quality. A new UMEA chip could be plated at least ten times, corresponding to about 500 measurements of trace metals in synthetic aqueous solutions. Using SWASV, detection limits of <0.1 ï¿g/l could be achieved for the metals (Pb, Cd). Precision and accuracy were found to be approx +/-10% of RSD.In natural waters, the results obtained with the UMEA sensor showed a reasonably good agreement with HR-ICP-MS analyses. Different experimental parameters were optimised and investigated. Interferences (e.g., DOC) were significantly reduced through medium exchange and standard addition. Ultrasonic bath proved to be very efficient in resurfacing electrodes in laboratory.The UMEA sensor shows a great potential in developing a portable trace metal analyzer. However, for in situ and on-site measurements, the protection of the UMEA sensor from fouling seems to be inevitable. In order to achieve a pure microelectrode behavior with the UMEA, increasing the ratio of interelectrode distance to electrode diameter is recommended for further developments

Assessment of an ultramicroelectrode array (UMEA) sensor for the determination of trace concentrations of heavy metals in water [online]

The main objectives of this book are (i) to investigate the electrochemical behavior and the analytical performance of a novel ultramicroelectrode array (UMEA); (ii) to assess the analytical parameters of square-wave anodic stripping voltammetric measurements (SWASV) using the UMEA; and (iii) to estimate the potential of the UMEA in developing decentralised analytical equipments for the determination of trace concentrations of heavy metals in natural waters. Surface analytical techniques (SEM, ESEM, and AFM) showed that the UMEA chips are of high quality in manufacture. Cyclic voltammetric and chronoamperometric experiments proved that the electrochemical behavior of the UMEA is dominated by the features characteristic for single microelectrodes. Chronocoulometry was found to be the most suitable method in generating the Hg-film of good quality. A new UMEA chip could be plated at least ten times, corresponding to about 500 measurements of trace metals in synthetic aqueous solutions. Using SWASV, detection limits of <0.1 ï¿g/l could be achieved for the metals (Pb, Cd). Precision and accuracy were found to be approx +/-10% of RSD. In natural waters, the results obtained with the UMEA sensor showed a reasonably good agreement with HR-ICP-MS analyses. Different experimental parameters were optimised and investigated. Interferences (e.g., DOC) were significantly reduced through medium exchange and standard addition. Ultrasonic bath proved to be very efficient in resurfacing electrodes in laboratory. The UMEA sensor shows a great potential in developing a portable trace metal analyzer. However, for in situ and on-site measurements, the protection of the UMEA sensor from fouling seems to be inevitable. In order to achieve a pure microelectrode behavior with the UMEA, increasing the ratio of interelectrode distance to electrode diameter is recommended for further developments

An Efficient Method for Traffic Image Denoising

AbstractIn this paper, a novel method for traffic image denoising based on the low-rank decomposition is proposed. Firstly, the low-rank decomposition is carried out. Under the sparse and low-rank constraints of low-rank decomposition, the foreground images with complanate background and moving vehicles and the background images with similar road scene are obtained. Then the foreground image is segmented into blocks of a certain size. The variance of each block is calculated, among that the minimum is considered the estimate of the noise power. KSVD algorithm is performed for the foreground image denoising. Furthermore, the noisy pixel discrimination algorithm is performed to distinguish the noisy pixels from the noiseless pixels and the eight- neighborhood weight interpolation algorithm is performed to reconstruct the noisy pixels, where the weighted coefficients are inversely proportional to the Euclidean distances between the pixels. And PCA recovery combined with noisy pixel discrimination and eight-neighborhood weight interpolation is adopted for the background image denoising. Finally, our proposed method is conducted based on the traffic videos obtained under the same view and angle. Moreover, our proposed method is compared with several state-of-the-art denoising methods including BM3D, KSVD and PCA recovery. The experiment results illustrate that our proposed method can more effectively remove the noise, preserve the useful information and achieve a better performance in terms of both PSNR index and visual qualities

Sexual and reproductive health correlates of polysubstance use among female adolescents who sell sex in the southwest of China

Background Substance use and adverse sexual and reproductive health (SRH) outcomes continue to be significant threats to female adolescents' health and wellbeing, particularly to these marginalized subpopulations. Our research aimed to tackle knowledge gaps regarding the prevalence of concurrent substance use including alcohol, tobacco, illicit drug among Chinese adolescent female sex workers (AFSWs), while to assess the correlates between substance use and SRH risks; the needs for comprehensive SRH services were also examined in this study. Methods A cross-sectional study enrolled 310 AFSWs aged 15-19 years by using cluster sampling method in Kunming, China. Descriptive analysis was employed to characterize the participants who were regular-alcohol users, regular-tobacco users, illicit drug users and polysubstance users. Multivariable logistic regression analysis was performed to detect the SRH correlates of regular-alcohol use, regular-tobacco use, illicit drugs and polysubstance use respectively. Results There is a high prevalence of regular-alcohol drinking (83%, 257/310) among AFSWs, with 44% (136/310) smoking cigarettes regularly and 9% using illicit drug (27/310) in the past year. In multivariate analysis, AFSWs who had middle and high school education, had higher monthly income, experienced of sexual and gender based violence (SGBV) and prior abortion, and regular-tobacco smoking were associated with increased odds of regular-alcohol drinking; engaging in unprotected sex while drunk, having STIs symptoms and using illicit drugs were significantly associated with regular-tobacco smoking; while AFSWs who had an illicit drug using- intimate partner, experienced forced sexual initiation, accessed unsafe medical providers for STIs treatment were associate with increased odds of illicit drug use. Moreover, 35% (105/298) AFSWs sought unsafe medical care for STIs treatment, or no treatment at all, among them, majority were using polysubstance (87%; 91/105). Conclusions Our findings reveal combined threats of substance use to AFSWs' SRH and wellbeing in China, this study emphasises that the coordinated efforts are needed to integrate SRH promotion and harm reduction service across sectors, and not only fragmented measures. An effective response should include an agreed framework, indicators and targets supported by political will, solid leadership and policy reform to deal with AFSWs' overlapping vulnerabilities in a systematic way

Farewell to Mutual Information: Variational Distillation for Cross-Modal Person Re-Identification

The Information Bottleneck (IB) provides an information theoretic principle for representation learning, by retaining all information relevant for predicting label while minimizing the redundancy. Though IB principle has been applied to a wide range of applications, its optimization remains a challenging problem which heavily relies on the accurate estimation of mutual information. In this paper, we present a new strategy, Variational Self-Distillation (VSD), which provides a scalable, flexible and analytic solution to essentially fitting the mutual information but without explicitly estimating it. Under rigorously theoretical guarantee, VSD enables the IB to grasp the intrinsic correlation between representation and label for supervised training. Furthermore, by extending VSD to multi-view learning, we introduce two other strategies, Variational Cross-Distillation (VCD) and Variational Mutual-Learning (VML), which significantly improve the robustness of representation to view-changes by eliminating view-specific and task-irrelevant information. To verify our theoretically grounded strategies, we apply our approaches to cross-modal person Re-ID, and conduct extensive experiments, where the superior performance against state-of-the-art methods are demonstrated. Our intriguing findings highlight the need to rethink the way to estimate mutua

Multi-dark-state resonances in cold multi-Zeeman-sublevel atoms

We present our experimental and theoretical studies of multi-dark-state resonances (MDSRs) generated in a unique cold rubidium atomic system with only one coupling laser beam. Such MDSRs are caused by different transition strengths of the strong coupling beam connecting different Zeeman sublevels. Controlling the transparency windows in such electromagnetically induced transparency system can have potential applications in multi-wavelength optical communication and quantum information processing.Comment: 11pages, 4figure