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1.
The Mediterranean ecosystem of the Carmel Mountain ridge in Israel is subjected to an increasing number of forest fires of various extents and severities due to intense human activities in the region. On 8 April 2005, a low-moderate severity forest fire occurred at the northwestern part of the ridge and burned more than 150 ha of natural vegetation. Soil water repellency (WR) is a property usually modified by the litter and soil organic matter combustion as a consequence of fire, which has implications for the hydrological balance in the affected soils. A field study was conducted with the following objectives: 1) to investigate in situ WR changes at three soil depths as a consequence of the fire, 2) to evaluate the short-term evolution of WR under field conditions, and 3) to study the relationship between pre-fire vegetation type and slope aspect on the persistence of WR in the burned area. Soil WR was measured by the Water Drop Penetration Time (WDPT) test. Measurements were conducted monthly at 31 field sites within the burned area over a period of seven months (April 2005–November 2005), and compared to adjacent unburned areas. Soil WR measurements included more than 3400 WDPT tests at soil surface and at 5 and 10 cm depths. The results indicate that fire induced WR in previously wettable soils exhibited high levels of persistence at the soil surface during the first six weeks after the fire, while at 5 cm depth WR persistence was lower. At 10 cm depth soil was mostly wettable. After six weeks the frequency of WR occurrence diminished at the soil surface and at 5 cm depth. In addition, WR was found to be highly related with the pre-fire vegetation type and with slope aspect. 相似文献
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McClintock WE Bradley ET Vervack RJ Killen RM Sprague AL Izenberg NR Solomon SC 《Science (New York, N.Y.)》2008,321(5885):92-94
During MESSENGER's first Mercury flyby, the Mercury Atmospheric and Surface Composition Spectrometer measured Mercury's exospheric emissions, including those from the antisunward sodium tail, calcium and sodium close to the planet, and hydrogen at high altitudes on the dayside. Spatial variations indicate that multiple source and loss processes generate and maintain the exosphere. Energetic processes connected to the solar wind and magnetospheric interaction with the planet likely played an important role in determining the distributions of exospheric species during the flyby. 相似文献
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The changes in color of sand dunes from white to yellow or red is often interpreted to signify their age or their source materials. In this study we demonstrate the effect seasonal inter-dune freshwater ponds have on the bleaching of the color of sand dunes by iron reduction in the anaerobic conditions they create. By combining spectral measurements of field samples of dune sand together with the analysis of satellite images covering three dune fields in NE Brazil (Lençóis Maranhenses, Jericoacoara and Canoa Quebrada) we demonstrate its existence in the field. In areas where ponds cover 41% of the dune field (as in Lençóis Maranhenses) an almost total bleaching in the color of the sand occurs after which the dunes remain white with no relation to distance from the coastline. In areas with less ponds (e.g. Jericoacoara or Canoa Quebrada) dune whitening is less active, and there are areas where dune rubification occurs. As this process may have occurred in other dune fields during past climate conditions that may have been different from current ones, interpretations of dunes age based on their color should be handled with care. 相似文献
4.
Serena Ciarroni Christopher R. Clarke Haijie Liu Noam Eckshtain-Levi Angelo Mazzaglia Giorgio M. Balestra Boris A. Vinatzer 《Journal of General Plant Pathology》2018,84(3):169-175
Plants and animals independently evolved the ability to recognize flagellin (also called FliC), the building block of the bacterial flagellum, as part of their innate immune response. While animals recognize a relatively large region of FliC, most plants recognize one or two short epitopes of FliC: flg22 and flgII-28. However, since most research in plants has focused on flg22 and flgII-28 and not the actual FliC protein, the importance of any FliC region beyond the two epitopes in plant immunity is poorly understood. Here we report cloning, overexpression, and purification of a Pseudomonas syringae FliC fragment from amino acid 1 to 143, which includes both FliC epitopes and the adjacent alpha helices. Exposing Arabidopsis thaliana leaves to FliC1–143 did not reveal any additional FliC recognition capabilities beyond flg22. However, while the kiwifruit species Actinidia arguta did not respond to either flg22 or flgII-28, treatment of A. arguta leaves with FliC1–143 triggered a significant reactive oxygen response, indicating recognition. This result suggests that in some plant species, recognition of FliC requires regions of FliC beyond the two well-known epitopes and that FliC1–143 represents a useful tool in the study of plant immunity. 相似文献
5.
Oren Froy Noam Zilberberg Nor Chejanovsky Jacob Anglister Erwann Loret Boaz Shaanan Dalia Gordon Michael Gurevitz 《Pest management science》2000,56(5):472-474
Continued use of non‐specific chemical insecticides poses potential risks to the environment and to human health resulting from non‐target toxicity and increased insect resistance to these agents. Scorpions produce anti‐insect selective polypeptide toxins that bind to and modulate voltage‐sensitive ion channels in excitable tissues, thus offering alternative, environmentally safer means for insect pest control. Despite this potential, little is known about their structural elements dictating anti‐insect preference, which may be useful for the design of selective insecticides. We used a bacterial system for expression and genetic dissection of two pharmacologically distinct scorpion toxins: alpha and excitatory. By exploiting a multi‐disciplinary approach consisting of mutagenesis, protein chemistry, electrophysiology, binding and toxicity assays, and structural studies, we elucidated the bioactive surface of two anti‐insect toxins, LqhαIT and Bj‐xtrIT. In both polypeptides the bioactive surface is composed of residues surrounding the C‐terminal region. In addition, a direct, immediate approach in using the toxin genes was demonstrated by engineering baculoviruses with cDNAs encoding LqhIT2 (depressant toxin), and LqhIT1 (excitatory toxin) resulting in viral vectors with significantly improved insecticidal efficacy. © 2000 Society of Chemical Industry 相似文献
6.
A design study on the optimal water refreshment rate in recirculating aquaculture systems 总被引：1，自引：1，他引：0
Refreshment (make-up) water is used in recirculating aquaculture systems (RAS) mainly to purge off-flavors, to add alkalinity and sometimes for temperature control. Alternatively, alkalinity may be added by means of a chemical base and heat may be supplied by a heating system. The objective of this study is to show how the optimal (minimizing cost) mix of the three controls: water, base and heat, can be found for given temperatures and water prices.The optimal solution varies over the temperature space and also depends on the price of water. For conditions at Eilat, Israel (on the Red Sea), using supplementary heating to maintain a constant temperature may become prohibitively expensive. If heating is given up, the remaining choice is between the supply of alkalinity via the refreshment water and adding a base. The supply of alkalinity with the water requires 2.0 m3[water]/kg[feed], much more than the minimum refreshment rate required to purge off-flavors, which is thought to be 0.3 m3[water]/kg[feed]. If the price of water is more than 0.03 USD/m3, the use of sodium bicarbonate for alkalinity control is justified. 相似文献
7.
Gelstein S Yeshurun Y Rozenkrantz L Shushan S Frumin I Roth Y Sobel N 《Science (New York, N.Y.)》2011,331(6014):226-230
Emotional tearing is a poorly understood behavior that is considered uniquely human. In mice, tears serve as a chemosignal. We therefore hypothesized that human tears may similarly serve a chemosignaling function. We found that merely sniffing negative-emotion-related odorless tears obtained from women donors induced reductions in sexual appeal attributed by men to pictures of women's faces. Moreover, after sniffing such tears, men experienced reduced self-rated sexual arousal, reduced physiological measures of arousal, and reduced levels of testosterone. Finally, functional magnetic resonance imaging revealed that sniffing women's tears selectively reduced activity in brain substrates of sexual arousal in men. 相似文献
8.
Gwena?l Imfeld Hanna Pieper Noam Shani Pierre Rossi Marcell Nikolausz Ivonne Nijenhuis Heidrun Paschke Holger Weiss Hans H. Richnow 《Water, air, and soil pollution》2011,221(1-4):107-122
The variability of hydrogeochemical conditions can affect groundwater microbial communities and the natural attenuation of organic chemicals in contaminated aquifers. It is suspected that in situ biodegradation in anoxic plumes of chloroethenes depends on the spatial location of the contaminants and the electron donors and acceptors, as well as the patchiness of bacterial populations capable of reductive dechlorination. However, knowledge about the spatial variability of bacterial communities and in situ biodegradation of chloroethenes in aquifers is limited. Here, we show that changes of the bacterial communities, the distribution of putative dechlorinating bacteria and in situ biodegradation at the border of a chloroethenes plume (Bitterfeld, Germany) are related to local hydrogeochemical conditions. Biotic reductive dechlorination occurred along a 50 m vertical gradient, although significant changes of the hydrogeochemistry and contaminant concentrations, bacterial communities and distribution of putative dechlorinating bacteria (Dehalobacter spp., Desulfitobacterium spp., Dehalococcoides spp., and Geobacter spp.) were observed. The occurrence and variability of in situ biodegradation of chloroethenes were revealed by shifts in the isotope compositions of the chloroethenes along the vertical gradient (??13C ranging from ?14.4?? to ?4.4??). Our results indicate that habitat characteristics were compartmentalized along the vertical gradient and in situ biodegradation occurred with specific reaction conditions at discrete depth. The polyphasic approach that combined geochemical and biomolecular methods with compound-specific analysis enabled to characterize the spatial variability of hydrochemistry, bacterial communities and in situ biodegradation of chloroethenes in a heterogeneous aquifer. 相似文献
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10.
Iris Zohar Nadya Teutsch Noam Levin Gail Mackin Henko de Stigter Revital Bookman 《Journal of Soils and Sediments》2017,17(8):2165-2176