R~3中的一类拟齐次向量场的性质

利用三维拟齐次向量场和三维齐次向量场之间的等价关系并借鉴对齐次向量场的研究方法,把齐次向量场的一些结论推广到拟齐次向量场.并运用这些理论分析了具有不同增长率的三种群竞争模型的动力学性质和生物意义,得到增长率最大的种群在此竞争系统中占优,增长率最小的种群在此竞争系统中灭绝的结论.     

关于生态场的几点评述

依据植物生态场的系统研究资料,对生态场的概念、场的特征函数、生态场的图形以及生态场对植物相互作用的解释进行了评述.阐明了生态场的最基本属性是物质性,目前的研究水平尚不能确定生态场是否是有别于一般物理场的特殊形式的场.对生态场的基本特征函数-生态势模型给予了形式与模型参数估测方面的评述,表明两种生态势模型各有一定的特点与优越性.作者强调,生态场更具生态学的方法论意义,应用生态场对植物相互作用形式与过程的分析描述,具有定量化、综合性与直观化特点.生态场的绘图为生态学研究开辟了新的途径,特别是应用生态场理论分析群体植物的动态变化过程(由互利共存到干涉竞争)会有合理的定量解释.     

Evaluation of changes in diatom mobility after exposure to 16-Hz electromagnetic fields

The effect of a 16-Hz electromagnetic field on the mobility of the diatom Amphora coffeaformis was examined on agar plates that contained no added calcium and also on agar plates containing 0.25 or 2.5 mM exogenous Ca2+. Exposure conditions consisted of an ac field of 16 Hz with an amplitude of 20.9 microT parallel to the horizontal component of the dc field (BH = 20.9 microT, where BV = 0). To assess results, the percentage of diatoms that moved a distance greater than their body length was determined. We observed the field-associated increase in diatom motion at 0.25 mM Ca++, which was previously reported in the literature. Although the magnitude of the effect at 16 Hz was significant, the percentage of cells that moved was not sufficiently reproducible to allow examination for frequency dependence.     

关于生态场的几点评述

依据植物生态场的系统研究资料,对生态场的概念、场和特征函数、生态场折图形以及生态场对植物相互作用的解释进行了评述。阐明了生态场的最基本属性是物质性,目前的研究水平尚不能确定生态场是还是有别于一稻物理场的特殊形式在场,对生态场的基本特征函数－生态热模型给予了形式与模型参数体测方面的评述,表明两种生态势模型各有一定的特点与优越性。作者强调,生态场更具生态学的方法论意义,应用生态场对植物相互作用形式与过     

Distribution of sound pressure around a singing cricket: radiation pattern and asymmetry in the sound field

Male field crickets generate calls to attract distant females through tegminal stridulation: the rubbing together of the overlying right wing which bears a file of cuticular teeth against the underlying left wing which carries a sclerotized scraper. During stridulation, specialized areas of membrane on both wings are set into oscillating vibrations to produce acoustic radiation. The location of females is unknown to the calling males and thus increasing effective signal range in all directions will maximize transmission effectiveness. However, producing an omnidirectional sound field of high sound pressure levels may be problematic due to the mechanical asymmetry found in this sound generation system. Mechanical asymmetry occurs by the right wing coming to partially cover the left wing during the closing stroke phase of stridulation. As such, it is hypothesized that the sound field on the left-wing side of the animal will contain lower sound pressure components than on the right-wing side as a result of this coverage. This hypothesis was tested using a novel method to accurately record a high-resolution, three dimensional mapping of sound pressure levels around restrained Gryllus bimaculatus field crickets singing under pharmacological stimulation. The results indicate that a bilateral asymmetry is present across individuals, with greater amplitude components present in the right-wing side of the animal. Individual variation in sound pressure to either the right- or left-wing side is also observed. However, statistically significant differences in bilateral sound field asymmetry as presented here may not affect signalling in the field.     

Possible Mechanism for Synchronized Detection of Weak Magnetic Fields by Nerve Cells

We propose that biological systems may detect static and slowly varying magnetic fields by the modification of the timing of firing of adjacent nerve cells through the local influence of the magnetic field generated by current from one cell's firing on its nearest neighbors. The time delay of an adjacent nerve cell pulse with respect to the initial clock nerve cell pulse could serve as a signal for sensing the magnitude and direction of the magnetic field in a direction perpendicular to the current flows in the cells. It has been shown that changes in static magnetic fields modify concentrations of reactive oxygen species, calcium, pH, the growth rates of fibrosarcoma cells, and membrane potentials. These are linked to changes in membrane potentials that can either inhibit or accelerate the firing rate of pacemaker or clock cells. This mechanism may have applications to animals' use of magnetic fields for navigation or other purposes, possibly in conjunction with other mechanisms. Bioelectromagnetics. © 2020 Bioelectromagnetics Society.     

A dosimeter for assessment of exposures to ELF fields

There are currently no biological indicators of electromagnetic field exposure to aid investigation of the biological effects of ELF fields, but this hiatus is partly compensated for by the ease with which the external fields can be measured. The subject of this report is a small electronic instrument that can log electric-, magnetic-, and transient-field intensities of individual subjects for a duration of two weeks, thus allowing exposure to be assessed in considerable detail. A preliminary survey conducted with the instrument has shown clear differences in domestic and occupational exposures of specific groups. Simple analytical models can be fitted to the field-exposure data by adjusting a few parameters such as current, intensity, and distance. Such modeling may be increasingly useful as the data base on exposures expands.     

湿地生态水文结构理论与分析

针对水土资源开发利用引发的湿地消退问题,通过研究湿地水分运动与补给规律,分析湿地和径流进退的关系、湿地生境和生物的扩展关系,分析湿地水文连接度下降引起的湿地消退效应.根据湿地水循环原理和湿地生境空间分布规律,建立湿地径流场与生物多样性场的概念,从而提出湿地生态水文结构理论.以维持湿地存在、保障湿地生物多样性为目标,通过湿地径流场与生物多样性场的耦合关系,将湿地划分为中心区和适宜活动区,以维持湿地生态水文结构所需要的水分条件定义为湿地生态需水.湿地生态需水问题的核心为确定湿地生态水文结构,并以湿地中心区和适宜活动区为边界条件,通过地表水地下水转化的水量平衡模型对湿地生态需水量进行分析计算.以维持中心区的水分条件作为最小生态需水;维持适宜活动区的水分条件作为适宜生态需水.湿地生态水文结构更对湿地管理提供生态安全阈值.根据湿地生态水文结构的稳定程度,建立湿地生态安全危机管理机制,进行不同级别的预警管理.     

Behavioral Differences of the Insect Morimus funereus (Coleoptera,Cerambycidae) Exposed to an Extremely Low Frequency Magnetic Field

Changes in the behavior of Morimus funereus individuals were investigated as early manifestations of the contact of a living system with a changed environment primarily established via the nervous system. These experiments were aimed at revealing possible behavioral differences of a laboratory population of cerambycid beetle M. funereus in an “open field” before and after exposure to an extremely low frequency magnetic field (ELF‐MF, 50 Hz, 2 mT). The experimental groups were divided into several activity categories and exposed to ELF‐MF. The results showed that the activity increased in the groups with medium and low motor activity, but decreased in highly active individuals. High individual variability was found in the experimental groups, as well as differences in motor activities between the sexes, both before and after exposure to ELF‐MF. According to preliminary results, we assume the changes of activity in both sexes after exposure to ELF‐MF. The results showed a tendency toward locomotor activity decrease, the affect being more pronounced in females. As opposed to this type of activity, stereotypic activity of males was increased after the exposure, whereas females maintained the expected tendency of decrease. However, we did not obtain statistically significant differences because of a high individual variability and a low total number of individuals in the experiment (N = 28). Only a detailed analysis of the locomotor activity at 1‐min intervals showed some statistically significant differences in behavior between the sexes.     

Effect of magnetic fields on antioxidative defense and fitness-related traits of Baculum extradentatum (insecta, phasmatodea)

This study aimed to determine the effect of magnetic fields on the antioxidative defense and fitness-related traits of Baculum extradentatum. Following exposure to magnetic fields, antioxidative defense (superoxide dismutase (SOD), catalase (CAT) activities, and total glutathione (GSH) content) and fitness-related traits (egg mortality, development dynamics, and mass of nymphs) were monitored in nymphs. The experimental groups were: control (kept out of influence of the magnets), a group exposed to a constant magnetic field (CMF) of 50 mT, and a group exposed to an alternating magnetic field (AMF) of 50 Hz, 6 mT. We found increased SOD and CAT activities in animals exposed to constant and AMFs, whereas GSH activity was not influenced by experimental magnetic fields. No differences were found in egg mortality between control and experimental groups. Significant differences in the time of development between the control and the CMF group were observed, as well as between the CMF and the AMF group. No differences were found in the mass of the nymphs between the three experimental groups. In conclusion, CMF and AMF have the possibility to modulate the antioxidative defense and some of the fitness-related traits in B. extradentatum.     

Assessment of exposure to intermediate frequency electric fields and contact currents from a plasma ball

While electric fields at intermediate frequencies are not widely utilized for industrial technologies, surprisingly, certain toys emit the highest electric fields found in our living environment. These toys, plasma balls, are devices that use high voltage to create ionized light discharges. In this study, we assessed exposure to electric fields and contact/induced current from a recreational plasma ball device. The electric field strength was measured as a function of distance from the device, and the contact/induced current was measured with a current clamp in different exposure situations with point or grasping contact. The characteristic spectra of the electric field and contact current were measured, and both the multiple frequency rule and weighting of the spectra were applied according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) 1998 and 2010 guidelines. The results indicate that the recommended reference levels for the general public are exceeded at distances <1.2 m, and that the contact currents in the hand may be twice higher than recommended by the general public guidelines.     

Investigating short-term exposure to electromagnetic fields on reproductive capacity of invertebrates in the field situation

Organisms are exposed to electromagnetic fields from the introduction of wireless networks that send information all over the world. In this study we examined the impact of exposure to the fields from mobile phone base stations (GSM 900?MHz) on the reproductive capacity of small, virgin, invertebrates. A field experiment was performed exposing four different invertebrate species at different distances from a radiofrequency electromagnetic fields (RF EMF) transmitter for a 48-h period. The control groups were isolated from EMF exposure by use of Faraday cages. The response variables as measured in the laboratory were fecundity and number of offspring. Results showed that distance was not an adequate proxy to explain dose-response regressions. No significant impact of the exposure matrices, measures of central tendency and temporal variability of EMF, on reproductive endpoints was found. Finding no impact on reproductive capacity does not fully exclude the existence of EMF impact, since mechanistically models hypothesizing non-thermal-induced biological effects from RF exposure are still to be developed. The exposure to RF EMF is ubiquitous and is still increasing rapidly over large areas. We plea for more attention toward the possible impacts of EMF on biodiversity.     

Exposure assessment of electromagnetic fields near electrosurgical units

Electrosurgical units (ESU) are widely used in medical health services. By applying sinusoidal or pulsed voltage in the frequency range of 0.3–5 MHz to the electrode tip, the desired mixture of coagulation and cutting are achieved. Due to the high voltage and current in the cable, strong electromagnetic fields appear near the ESU. The surgeon and others inside the operating room such as nurses, anesthesiologists, etc., will be highly exposed to these fields. The stray fields surrounding the ESU have previously been measured, but now a deeper analysis has been made of the curve shape of the field and the implication of this when assessing exposure from a commonly used ESU in accordance with the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) guidelines. The result showed that for some of the modes, especially those using high‐pulsed voltage with only a few sinusoidal periods, the E‐field close to the cable could reach linear spatially averaged values of 20 kV/m compared to the 2.1 kV/m stated in ICNIRP guidelines. Assessing the E‐ and B‐field from ESU is not straightforward since in this frequency range, both induced current density and specific absorption rate are restricted by the ICNIRP guidelines. Nevertheless, work needs to be done to reduce the stray fields from ESU. Bioelectromagnetics 31:513–518, 2010. © 2010 Wiley‐Liss, Inc.     

不同水稻土甲烷氧化菌和产甲烷菌数量与甲烷排放量之间相关性的研究

对不施用任何肥料的浙江黄松土（发育于河流沉积物母质的水稻田土）、老黄筋泥田土（发育于第四纪红壤母质的水稻田土）、青紫泥田土（发育于滨海盐土母质的象山青紫泥水稻土）中甲烷氧化菌、产甲烷菌种群数量及甲烷排放量之间关系作了研究。结果表明,甲烷氧化菌种群数量范围在10^6-10^8cfu/g干土之间,其变化在2个数量级范围内,产甲烷细菌种群数量变化较大,其范围在10^3-10^7cfu/g干土之间,水稻田土壤的甲烷排放量受到甲烷氧化菌、产甲烷菌种群数量及其活性及土壤理化性状的影响,提出了当水稻田土壤的甲烷氧化菌种群数量在10^cfu/g干土、产甲烷菌种群数量在10^5cfu/g干土时,水稻田土壤几乎没有多余的CH4气体排放这一甲烷形成与甲烷氧化两类群微生物之间的数量关系。甲烷排量也与土壤砂粒（＜0．02mm的砂数）含量呈正相关性,土壤砂粒含量越高,其甲烷排放量亦高。     

Spatial gradient effects of 120 mT static magnetic field on endothelial tubular formation in vitro

This study investigated the spatial magnetic gradient effects of static magnetic fields (SMF) on endothelial tubular formation by applying the maximum spatial gradient to a target site of culture wells for cell growth. The respective maximum values of magnetic flux density (B(max)), magnetic flux gradient (G(max)) and the magnetic force product of the magnetic flux density and its gradient (a parameter of magnetic force) were 120 mT, 28 mT/mm and 1428 mT(2)/mm. The effects of gradient SMF on tubular formation were compared with those of uniform SMF that has no spatial gradients on the entire bottom area of culture wells. Five experimental groups of 25 samples each were examined: (1) sham exposure (control); (2) peak gradient exposure in the peripheral part; (3) peak gradient exposure in the central part; (4) uniform exposure to 20 mT; (5) uniform exposure to 120 mT. The SMF or sham exposure was carried out for 10 days. Photomicrographs of tubular cells, immunostained with an anti-platelet-endothelial cell adhesion molecule-1 (PECAM-1 [CD31]) antibody as a pan-endothelial marker, were analyzed after the 10-day culture. Gradient SMF in the peripheral or central part was found to significantly promote tubular formation in terms of the area density and length of tubules in each peak gradient/force part of the wells, compared with the sham exposure. In contrast, uniform SMF did not induce any significant change in the tubular formation. These findings suggest that tubule formation can be promoted by applying the peak gradient/force to a target site of culture wells.     

Histophotometric Quantification of the Field Effect and the Extended Field Effect of Tumors

Histophotometric investigations have been made on samples of human skin. Fresh frozen serial sections were fixed and stained for either reactive protein thiols (PSH,) or total reactive protein sulphur (TRPS) using modifications of the DDD-Fast blue B-method. In addition, total protein thiols (PSH,) were stained with the Mercurochromcyanide-method, and proteins were stained using a modified amido-black procedure. Significant differences were found between the different tumours investigated and normal tissue, and also between apparently normal tissue adjacent to the tumours and normal tissue from patients without tumour. To reveal such tumour-related changes of apparently normal tissue, termed the field effect of tumours, a double quotient had to be calculated from the PSH,- and TWS-values determined from both epithelium (epidermis) and connective tissue. In addition, abdominal skin was investigated from patients without tumour and patients with tumours of the female genital tract, liver or breast. With the aid of the double quotient procedure, highly significant differences were found between normal abdominal skin of patients without tumours versus similar samples taken from patients with tumours. The tumour-related changes found with abdominal skin distant from the tumours have been termed the extended field effect of tumours. These general tumour-related changes, independent of the size, state or degree of malignancy of the distant tumour, could be shown to be due to changes in abdominal dermis.     

Effects of 5 s exposures to a 50 microT, 20 Hz magnetic field on skin conductance and ratings of affect and arousal

This study investigated the effect of a weak magnetic field (50 microT, 20 Hz sinusoidal, 5 s duration) on concurrent perceptions of visual stimuli. Subjects were seated between Helmholtz coils and gave post-exposure ratings for the affective content and arousing nature of presented images. They were blind as to the presence or absence of a simultaneously presented field. Skin conductance and arousal ratings did not show significant differences between experimental and control conditions, but the affective content rating did (P = 0.041), with the images viewed under field exposure being rated as having a more positive affect. Such measures might thus be useful as additional indicators of magnetic field detection. A post-hoc analysis of skin conductance profiles showed that 48% of subjects exhibited a lowering of skin conductance during field exposure, 34% exhibited no apparent reaction, and 17% exhibited an increase. Overall ratings given by each of the groups appeared to relate to these physiological profiles.     

RF Exposure During Use of Electrosurgical Units

Electrosurgical units (ESUs) commonly used in operating suites employ radiofrequency (RF) energy for cutting and coagulation, and operate at different frequencies in the range 0.3–5 MHz. Around the electrode and cables, electric and magnetic fields at similar frequencies will be generated, and the surgeon using the ESU will therefore be exposed to these electromagnetic fields. In this study we have measured the levels of RF fields near the lead wires of two electrosurgical units, BARD 3000 operating at a fixed frequency of 0.5 MHz, and ERBE ICC 350 with a frequency range from 0.3 to 1 MHz. Electric fields were measured at distances from 5–30 cm from the lead wire. Measurements were done with the ESU both cutting and coagulating, and power levels ranging from 10–100 W. The magnetic field outside the lead wire was calculated from the measured current through the leads using standard theory. Using those measurements as a base, the calculated local exposure of the surgeon's hand was estimated to exceed 15 kV/m for the electric field and the corresponding value for the magnetic field was 16 µT. These calculations exceed the suggested international reference levels at 0.5 MHz (610 V/m and 4 µT, respectively).