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Vertical electrical sounding (VES) and Rayleigh wave exploration are widely used in the exploration of near-surface structure, but both have limitations. This study aims to make full use of the advantages of the two methods, reduce the multiple solutions of single inversion and improve the accuracy of the inversion. Thus, a nonlinear joint inversion method of VES and Rayleigh wave exploration based on improved differential evolution (DE) algorithm was proposed.

Based on the DE algorithm, a new initialization strategy was proposed. Then, taking AK-type with high-velocity interlayer model and HA-type with low-velocity interlayer model near the surface as examples, the inversion results of different methods were compared and analyzed. Then, the proposed method was applied to the field data in Chengde, Hebei Province, China. The stratum structure was accurately depicted and verified by drilling.

The synthetic data and field data results showed that the joint inversion of VES and Rayleigh wave data based on the improved DE algorithm can effectively improve the interpretation accuracy of the single-method inversion and had strong stability and large generalizable ability in near-surface engineering problems.

A joint inversion method of VES and Rayleigh wave data based on improved DE algorithm is proposed, which can improve the accuracy of single-method inversion.

The coronavirus disease 2019 (COVID-19) is an infectious disease that puts strain on health-care systems. Obesity is considered as a risk factor for the severity of infection. Hypotheses also suggested some nutritional supplements may be useful in COVID-19. This paper aims to assess the role of body mass index (BMI) and nutritional supplements on the severity of COVID-19.

This research was conducted on 603 participants (in five groups including: exposure to virus and healthy, COVID-19 positive patients with severity of mild, moderate, severe and death from COVID-19), in age 18 to 65 years. Demographic data and history of nutritional supplements were asked. Anthropometric measurements were measured in a healthy group and in a patient. They were collected by referring to patients' medical records.

The mean of BMI in groups with severity symptoms of moderate (27.57 kg/m²), severe (29.70 kg/m²) and death persons (28.13 kg/m²), was significantly higher than healthy (26.70 kg/m²) and mild symptoms (26.57 kg/m²) groups (p = 0.001). The logistic regression shown, the fourth quartile of BMI was significantly associated with occurrence of COVID19, odds ratios (ORs) and 95% confidence intervals (CI): [OR: 1.81, (95% CI: 1.13– 2.89), p-for trend = 0.55]. There was no significant difference in the percentage of vitamin C, D3, Zinc, Iron and multivitamin supplements intake, between groups, in the past six months (p = 0.11).

This study indicated the role of higher BMI in the occurrence and severity of COVID-19. Researches are not enough to recommend consumption of nutritional supplements for the prevention of COVID-19.

This paper aims to report an insightful portable microfluidic system for rapid and selective sensing of Hg²⁺ in the picomolar (pM) concentration using microcantilever-based piezoresistive sensor. The detection time for various laboratory-based techniques is generally 12–24 h. The majority of modules used in the proposed platform are battery oriented; therefore, they are portable and handy to carry-out on-field investigations.

In this study, the authors have incorporated the benefit of three technologies, i.e. thin-film, nanoparticles (NPs) and micro-electro-mechanical systems, to selectively capture the Hg²⁺ at the pM concentration. The morphology and topography of the proposed sensor are characterized using field emission scanning electron microscopy and verification of the experimental results using energy dispersive X-ray.

The proposed portable microfluidic system is able to perform the detection in 5 min with a limit of detection (LOD) of 0.163 ng (0.81 pM/mL) for Hg²⁺, which perfectly describes its excellent performance over other reported techniques.

A microcantilever-based technology is perfect for on-site detection, and a LOD of 0.163 ng (0.81 pM/mL) is outstanding compared to other techniques, but the fabrication of microcantilever sensor is complex.

Many researchers used NPs for heavy metal ions sensing, but the excess usage and industrialization of NPs are rapidly expanding harmful consequences on the human life and nature. Also, the LOD of the NPs-based method is limited to nanomolar concentration. The suggested microfluidic system used the benefit of thin-film and microcantilever devices to provide advancement over the NPs-based approach and it has a selective sensing in pM concentration.