The effects of external electric field on the electron transport system of spinach chloroplasts

Since the thylakoid membranes of an active chloroplast are constantly exposed to the electric fields generated by the electron transport system inside the membranes, we have studied the effects of pretreating chloroplasts of spinach ( Spinacia oleracea L.) leaves with an external AC (alternating current) electric field on their electron transport system. It was found that a few minutes electric field pretreatment (333 V cm^-1 across chloroplast samples), especially at low frequency, irreversibly inhibited the activity of photosystem II (PSII), but under certain conditions, stimulated that of photosystem I (PSI). From the measurements of fluorescence from PSII, we ascribe the inhibition to a lesion close to its reaction center P680, leading to increased dissipation of excitation energy to heat. The effect on PSI was investigated by the reduction of its reaction center, P700 by various artificial donors. We suggest that the stimulative effect can be attributed to a positive shift of the surface charge density of thylakoid membranes that brings about an increase in the accessibility of exogenous electronegative donors.     

Effects of low electric current (LEC) treatment on pure bacterial cultures

AIMS: This research focused on the effects of low electric current (LEC) on the cell viability and metabolic activity of Escherichia coli and Bacillus cereus. METHODS AND RESULTS: Different LEC intensities at fixed amperage were applied, employing either graphite or copper electrode pairs, and the effects were determined by conventional cultural methods and bioindicators. On E. coli, the LEC with graphite electrodes at 5 and 10 mA led to no significant variation, but at 20 and 40 mA there was increasing inhibition of both the enzymatic activities and growth, and a reduction in ATP content. On B. cereus, similar experiments at the lower amperages did not have any inhibitor effects, however, the 40 mA current stimulated growth, ATP content and some enzymatic activities. The LEC treatment using copper electrodes caused, already at 5 mA, inhibition of bacterial growth and metabolic and enzymatic activities in both E. coli and B. cereus. CONCLUSIONS: On the basis of the obtained results using different amperages and electrodes, we can conclude that E. coli seem to be more sensitive compared with B. cereus. SIGNIFICANCE AND IMPACT OF THE STUDY: The study increases the knowledge on LEC treatment effects on the pure bacterial cultures.     

三峡库区消落带植被NPP估算——基于机器学习优化CASA模型

三峡库区蓄水后,其生态效应受到广泛关注。消落带植被固碳量作为衡量库区生态系统健康状态的重要指标,对库区碳循环与生态净化具有重要意义。针对消落带不同高程植被接受光照的时间有所差异,且受河流水位变化影响,传统的CASA模型在计算消落带植被固碳量时,存在对植物的光能利用率计算不够精确等问题。以三峡库区香溪河陡坡消落带为研究区域,提出了一种耦合RBFNN模型（Radial Basis Function Neural Network）与CASA模型（Carnegie-Ames-Stanford approach）的新方法（RBF-CASA）。基于RBFNN建立环境影响因子模型,借助高程数据及植被指数等特征计算适合消落带区域的环境影响因子。结合CASA模型中温度和水分胁迫因子,提高植被在像元尺度上的净初级生产力（Net Primary Productivity,NPP）的估算精度,并对反演结果进行验证。模型验证结果显示：RBF-CASA模型估算值与观测值的决定系数（Coefficient of determination, R²）为0.730（P<0.01, n=32）。对比原始CASA模型,平均绝对误差（Mean absolute error, MAE）降低10.991,均方根误差（Root mean square error, RMSE）降低了23.861,相对均方根误差（Relative root mean square error, RRMSE）降低5.10%,平均绝对百分误差（Mean absolute percentage error, MAPE）降低1.12%。使用提出的RBF-CASA模型在库区水位落干期（7-8月份）进行固碳量估算,结果表明：NPP月均值在66.234-134.144g C/m²之间,NPP随着高程的增加呈现起伏变化,其总量在150-155m之间达到峰值,均值在170m以上区域最高。在2021年9月植被NPP均值为35.883g C/m²,2022年9月植被NPP均值为25.964g C/m²,由于降雨量减少、长江水位下降,在2021-2022年间植被恢复情况较差。研究结果可为库区碳循环、生态净化及生态修复等决策提供科学依据。     

Effects of condensed tannins on behavior and performance of a specialist aphid on aspen

Genes involved in plant defences against herbivores and pathogens are often highly polymorphic. This is a putative sign that balancing selection may have operated reciprocally on the hosts and their herbivores. Spatial and temporal variations (for example, in soil nutrients and the plants'' ontogenetic development) may also modulate resistance traits, and thus selection pressures, but have been largely overlooked in theories of plant defences. Important elements of defences in Populus tremula (hereafter aspen) are phenolic compounds, including condensed tannins (CTs). Concentrations of CTs vary considerably with both variations in external factors and time, but they are also believed to provide genotype‐dependent resistance, mainly against chewing herbivores and pathogens. However, evidence of their contributions to resistance is sparse. Detailed studies of co‐evolved plant–herbivore associations could provide valuable insights into these contributions. Therefore, we examined correlations between CT levels in aspen leaves and both the feeding behavior and reproduction of the specialist aspen leaf aphid (Chaitophorus tremulae) in varied conditions. We found that xylem sap intake and probing difficulties were higher on genotypes with high‐CT concentrations. However, aphids engaged in more nonprobing activities on low‐CT genotypes, indicating that CTs were not the only defence traits involved. Thus, high‐CT genotypes were not necessarily more resistant than low‐CT genotypes, but aphid reproduction was generally negatively correlated with local CT accumulation. Genotype‐specific resistance ranking also depended on the experimental conditions. These results support the hypothesis that growth conditions may affect selection pressures mediated by aphids in accordance with balancing selection theory.     

Perinatal exposure to 60-Hz electric fields: Effects on the development of the visual-evoked response in rats

Two independent series of experiments were performed on 114 male Sprague-Dawley derived, albino rat pups, which represented 61 litters in experimental series I and 53 litters in experimental series II. Animals were exposed for 20 h/day from conception to testing (postnatal days 11–20) to a vertical, 65-kV/m, 60-Hz electric field or sham-exposed. Recordings of the visual-evoked response (VER) were obtained using a small silver ball electrode placed epidurally over the visual cortex. Visual stimuli consisted of 10-μS light flashes delivered at 0.2 Hz. Computer-averaged VERs were obtained and power spectral analyses (fast Fourier transform) were performed on the tapered (split cosine-bell window), averaged VERs. The expected age-related changes were clearly evident; however, a detailed analysis of VER component latencies, peak-to-peak amplitude, and power spectra failed to reveal any consistent, statistically significant effect of exposure to 60-Hz electric fields.     

Comparison of electric hand dryers and paper towels for hand hygiene: a critical review of the literature

Numerous studies are published on the benefits of electric hand dryers vs paper towels (PT) for drying hands after washing. Data are conflicting and lacking key variables needed to assess infection risks. We provide a rapid scoping review on hand-drying methods relative to hygiene and health risks. Controlled vocabulary terms and keywords were used to search PubMed (1946–2018) and Embase (1947–2018). Multiple researchers independently screened abstracts for relevance using predetermined criteria and created a quality assessment scoring system for relative study comparisons. Of 293 papers, 23 were included in the final analysis. Five studies did not compare multiple methods; however, 2 generally favoured electric dryers (ED); 7 preferred PT; and 9 had mixed or statistically insignificant results (among these, 3 contained scenarios favourable to ED, 4 had results supporting PT, and the remaining studies had broadly conflicting results). Results were mixed among and within studies and many lacked consistent design or statistical analysis. The breadth of data does not favour one method as being more hygienic. However, some authors extended generalizable recommendations without sufficient scientific evidence. The use of tools in quantitative microbial risk assessment is suggested to evaluate health exposure potentials and risks relative to hand-drying methods. We found no data to support any human health claims associated with hand-drying methods. Inconclusive and conflicting results represent data gaps preventing the advancement of hand-drying policy or practice recommendations.     

ELF magnetic fields in electric and gasoline‐powered vehicles

We conducted a pilot study to assess magnetic field levels in electric compared to gasoline‐powered vehicles, and established a methodology that would provide valid data for further assessments. The sample consisted of 14 vehicles, all manufactured between January 2000 and April 2009; 6 were gasoline‐powered vehicles and 8 were electric vehicles of various types. Of the eight models available, three were represented by a gasoline‐powered vehicle and at least one electric vehicle, enabling intra‐model comparisons. Vehicles were driven over a 16.3 km test route. Each vehicle was equipped with six EMDEX Lite broadband meters with a 40–1,000 Hz bandwidth programmed to sample every 4 s. Standard statistical testing was based on the fact that the autocorrelation statistic damped quickly with time. For seven electric cars, the geometric mean (GM) of all measurements (N = 18,318) was 0.095 µT with a geometric standard deviation (GSD) of 2.66, compared to 0.051 µT (N = 9,301; GSD = 2.11) for four gasoline‐powered cars (P < 0.0001). Using the data from a previous exposure assessment of residential exposure in eight geographic regions in the United States as a basis for comparison (N = 218), the broadband magnetic fields in electric vehicles covered the same range as personal exposure levels recorded in that study. All fields measured in all vehicles were much less than the exposure limits published by the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) and the Institute of Electrical and Electronics Engineers (IEEE). Future studies should include larger sample sizes representative of a greater cross‐section of electric‐type vehicles. Bioelectromagnetics 34:156–161, 2013. © 2012 Wiley Periodicals, Inc.     

Potassium ion influx measurements on cultured Chinese hamster cells exposed to 60-Hertz electromagnetic fields

Potassium ion influx was measured by monitoring ⁴²KCI uptake by Chinese hamster ovary (CHO) cells grown in suspension culture and exposed in the culture medium to 60–Hz electromagnetic fields up to 2.85 V/m. In the presence of the field CHO cells exhibited two components of uptake, the same as previously observed for those grown under normal conditions; both these components of influx were decreased when compared to sham-exposed cells. Although decreases were consistently observed in exposed cells when plotted as log_c of uptake, the differences between the means of the calculated fluxes of exposed and sham-exposed cells were quite small (on the order of 4–7%). When standard deviations were calculated, there was no significant difference between these means; however, when time-paired uptake data were analyzed, the differences were found to be statistically significant. Cells exposed only to the magnetic field exhibited similar small decreases in influx rates when compared to sham-exposed cells, suggesting that the reduction in K⁺ uptake could be attributed to the magnetic field. Additionally, intracellular K⁺ levels were measured over a prolonged exposure period (96 h), and no apparent differences in intracellular K⁺ levels were observed between field-exposed and shamexposed cultures. These results indicate that high-strength electric fields have a small effect on the rate of transport of potassium ions but no effect on long-term maintenance of intracellular K⁺.     

Neuroendocrine parameters in the rat exposed to 60-Hz electric fields

This study was designed to assess the neuroendocrine response of male Long-Evans rats to sustained or intermittent 60-Hz electric fields when exposed for 1 or 3 h at 100 kV/m. No significant differences were noted in corticosterone, prolactin, or thyrotropin levels between exposed and sham-exposed rats. A statistically significant increase (P less than .01) in growth hormone was noted in rats exposed to intermittent electric fields for 3 h. Emphasis was placed on good experimental design and the need to avoid standard laboratory stressors (excessive handling, temperature extremes, transportation, noise, etc.) known to be present in many biomedical studies. The importance of avoiding reactions due to extraneous factors in experiments predicated on investigating physiological function in relation to electric field exposure is discussed.