A four coil exposure system (tetracoil) producing a highly uniform magnetic field

We propose a magnetic field exposure system (tetracoil) for in vitro and in vivo experiments, composed of two couples of circular coils satisfying a spherical constraint, whose characteristics are chosen in order to maximize the uniformity region of the magnetic field. Analytical calculations and computer simulations show that our system, as compared to the other most largely used magnetic field exposure systems, represents an optimal compromise in terms of field uniformity, accessibility for biological experiments, and ratio between overall dimension and uniformity region.     

Effect of coexposure to 50 Hz magnetic fields and an aneugen on human lymphocytes,determined by the cytokinesis block micronucleus assay

Interference of 50 Hz extremely low frequency magnetic fields (ELF-MF) with the known aneugen vinblastine (VBL) on micronucleus formation was tested with the in vitro cytokinesis block micronucleus assay in human lymphocyte cultures. Isolated lymphocyte cultures were prepared from 18 individuals. Three groups of quadruplicate cultures from six unrelated individuals were exposed to 50 Hz ELF-MF of background (bkg), 80 and 800 microT, respectively, during the complete incubation period (72 h). Twenty-four hours after culture initiation, one replicate culture from each individual within each ELF-MF group was exposed to 0, 5, 10, or 15 ng/ml VBL. The isolated lymphocyte cultures were scored for the presence of micronuclei, the nuclear division index (NDI), and apoptosis. As expected, increased VBL concentration resulted in an increased micronucleus and apoptosis frequency and in a decreased NDI. In the presence of VBL, there was a systematic tendency for increased micronucleus and apoptosis frequency in the ELF-MF exposed groups compared to the bkg group. In the absence of VBL, we observed no statistically significant effect of ELF-MF on micronucleus induction or apoptosis frequency, but the NDI was significantly higher in the 800 microT group compared to the other groups, suggesting an effect of ELF-MF on cell proliferation. An interaction between ELF-MF and VBL on NDI was observed. This interaction reflected the drastic decrease in NDI due to coexposure to VBL.     

Predicted SAR in Sprague-Dawley rat as a function of permittivity values

Specific absorption rate (SAR) value is dependent on permittivity value. However, variability in the published permittivity values for human and animal tissue and the development of sophisticated 3-dimensional digital anatomical models to predict SAR values has resulted in the need to understand how model parameters (permittivity value) affect the predicted whole body and localized SAR values. In this paper, we establish the partial derivative of whole body SARs and localized SAR values (defined as SAR for individual organs with respect to a change in the permittivity values of all tissue types, as well as for those tissues with the most variable permittivity values. Variations in the published permittivity values may substantially influence whole body and localized SAR values, but only under special conditions. Orientation of the exposed object to the incident electromagnetic wave is one of the most crucial factors. Published 2001 Wiley-Liss, Inc.     

Conjoint control of hippocampal place cell firing by two visual stimuli. Ii. A vector-field theory that predicts modifications of the representation of the environment

Changing the angular separation between two visual stimuli attached to the wall of a recording cylinder causes the firing fields of place cells to move relative to each other, as though the representation of the floor undergoes a topological distortion. The displacement of the firing field center of each cell is a vector whose length is equal to the linear displacement and whose angle indicates the direction that the field center moves in the environment. Based on the observation that neighboring fields move in similar ways, whereas widely separated fields tend to move relative to each other, we develop an empirical vector-field model that accounts for the stated effects of changing the card separation. We then go on to show that the same vector-field equation predicts additional aspects of the experimental results. In one example, we demonstrate that place cell firing fields undergo distortions of shape after the card separation is changed, as though different parts of the same field are affected by the stimulus constellation in the same fashion as fields at different locations. We conclude that the vector-field formalism reflects the organization of the place-cell representation of the environment for the current case, and through suitable modification may be very useful for describing motions of firing patterns induced by a wide variety of stimulus manipulations.     

Visuomotor transformations: early cortical mechanisms of reaching

Recent studies of visually guided reaching in monkeys support the hypothesis that the visuomotor transformations underlying arm movements to spatial targets involve a parallel mechanism that simultaneously engages functionally related frontal and parietal areas linked by reciprocal cortico-cortical connections. The neurons in these areas possess similar combinations of response properties. The multimodal combinatorial properties of these neurons and the gradient architecture of the parieto-frontal network emerge as a potential substrate to link the different sensory and motor signals that arise during reaching behavior into common hybrid reference frames. This convergent combinatorial process is evident at early stages of visual information processing in the occipito-parietal cortex, suggesting the existence of re-entrant motor influences on cortical areas once believed to have only visual functions.     

棉田生态系统氮营养元素循环的研究

在棉田生态系统Ｎ循环中,低,中,高,超高产棉田Ｎ素的输入与输出不平衡,亏盈值（Ｂｋ）分别为－９．８,－１０．６,－１３．５和－１６．２ｋｇ／ｈｍ＾２,平衡值（Ｂ１）为０．９１１３,０．９４３５,０．９４２９．０．９４５８,每种１季棉花,土壤库现存Ｎ减少２‰～６‰,低,中,高,超高产棉田产物Ｎ输出,分别为棉田生态系统总输出Ｎ的５４．４％,４６．５％,４４．９％和４３．４％,其中经济产品（棉子和纤维）     

区域农业综合生产力的AHP-Fuzzy综合评判

根据系统分析原理,在确定区域农业综合生产力系统的层次结构基础上,用层次分析法确定各因素的权重,用模糊多级综合评判法对各区域综合生产力进行综合的评价．具有一定的科学性和实用价格．     

Towards an ecological basis for the conservation of subalpine heath-grassland on the upper ridges of the Vosges

Abstract. The subalpine oligotrophic heath-grasslands, assigned to the Pulsatillo-Vaccinietum and Violo-Nardetum, occurring at the upper ridges in the Vosges at 1100 - 1300 m a.s.l. are of conservational interest because they form natural, mature and stable ecosystems. The Pulsatillo-Vaccinietum is particularly rich in endemic plant species and subspecies due to a local oceanic-subarctic climate and the continuous occurrence of the community throughout the Holocene period, when the association was not affected by changes in the prevailing environmental conditions. After a period of abandonment during and after World War II, agriculture was intensified through mineral fertilization and liming, sometimes mowing, and even ploughing and sowing. Seven pastures were selected to estimate the present plant biodiversity. Losses of biodiversity were assessed on the Kastelberg ridge by diachronic analysis of the vegetation composition and structure over the last 30 years. Species diversity changed in both associations through a decrease in the abundance of oligotrophic, acidophilic species, typical of the mountains of western Europe, and an extension of grassland types of the Violo-Nardetum trifolietosum. Strategies for a return to more natural conditions include the abandonment of fertilization and liming, except locally around farms. Regular mowing is needed in order to decrease the nutrient level of the sites.