A method for measuring soil water content based on principal component analysis.

Principal component analysis (PCA) has been applied in many aspects. To address the problem of measuring water content in soil, this paper proposes a method to measure soil water content based on the PCA. We used PCA to reduce the dimension of the data and processed the soil amplitude ratio frequency response spectra. First, we designed the measuring device and measured the soil amplitude ratio frequency response data of different water content, then we used the PCA to extract features from the frequency response spectra of different water contents, established a relationship model of soil water content, and finally, we solved the model, the maximum error between the calculation results and the actual water content was no more than 0.85%. Subsequently, we carried out experimental verification, and we measured six kinds of soil with known water content by this method. The experimental results showed that the maximum error did not exceed 1.16%, and the average error was 0.71%. Thus, the proposed method can provide a useful way of measuring soil water content.

[Development of dynamic ECG acquisition and recording system: review and prospect].

Dynamic electrocardiography (DCG) or Holter is the best device to detect arrhythmia and can help early detection of some sudden cardiac death risk factors. The acquisition and recording system of the DCG, however, affects the data quality and the patients' comfort directly. This paper reviews the related latest studies, and discusses the importance of new ECG electrode and wireless dynamic monitoring in DCG monitoring field. Moreover, the existed main problems are summarized and classified and the prospects for the development trend are presented.

The parameter optimization of lasers' energy ratio of the double-pulse laser induced breakdown spectrometry for heavy metal elements in the soil.

Laser-induced breakdown spectroscopy (LIBS) is a rapid, no-sample preparation, remote detection method that has been applied widely in the area of heavy metal detection in the soil. However, the promotion of LIBS is limited by its disadvantages, such as low precision analysis, a high detection limit, and so on. In recent years, many studies have been conducted to improve the LIBS spectral intensity. The double-pulse LIBS (DP-LIBS) is a representative technology in this area. Most of the research work focuses on the analytical methods of DP-LIBS, including the spatial configuration, the inter-pulse time, and the effect of signal enhancement of the DP-LIBS. However, there are few reports about the effect of the energy proportion of the two lasers and the contribution of different laser energies on the signal enhancement, and the inter-pulse time under the conditions of different laser energies. Moreover, DP-LIBS is mostly evaluated by the enhancement factor of the spectral signal, and there are few reports on the quantitative analysis of double-pulse LIBS. This study, which mainly detects Cu, Ni, and Pb in the soil, focuses on the contribution of the signal enhancement by adjusting the energy ratio of the two lasers and the best inter-pulse time under the conditions of different laser energies. Then, quantitative analysis of spectral signals obtained by single-pulse LIBS (SP-LIBS) and DP-LIBS are performed based on the random forest (RF) model. The results demonstrate that DP-LIBS shows better analytical performance than SP-LIBS, the coefficients of determination (R2) of the test have great improvement, the root-mean-squared error (RMSE) is much decreased and the relative error is much improved. Thus, this study shows that DP-LIBS is an effective method for the quantitative analysis of heavy metals in the soil.

A MnO2-[Ru(dpp)3]Cl2 system for colorimetric and fluorimetric dual-readout detection of H2O2.

Two-dimensional (2D) MnO2 nanosheets were synthesized by a template-free and one-step route, and the dye [Ru(dpp)3]Cl2 was linked onto the MnO2 nanosheet surface via electrostatic interaction. The formed MnO2-[Ru(dpp)3]Cl2 hybrid was used for a dual optical detection for H2O2, an important reactive oxygen species (ROS). Upon addition of H2O2, the reaction of MnO2 with H2O2 results in the dissolution of MnO2 nanosheets and simultaneous generation of O2. The fading of the solution and simultaneous fluorescence change of [Ru(dpp)3]Cl2, sensitive to O2, enables colorimetric and fluorimetric dual-mode detection of H2O2. The dual-output assay in a single probe provides a good sensitivity with a detection limit of 0.18 µM H2O2. The dual-signal strategy can efficiently overcome the shortcoming of the single detection mode, and improve the detection accuracy by an additional correction of output signals from each other. Moreover, the successful determination of H2O2 in the serum samples demonstrates the potential applicability of the MnO2-[Ru(dpp)3]Cl2 based probe in biosensing and bioanalysis.