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The authors have succeeded in isolating an antibiotic, from the cultured filtrate of Asp. oryzae, responsible for, at least, the majority of the active substances against hiochi-bacteria, as pale yellow crystals of m.p. 152~153°C. It has been proved that this antibiotic is identical with hydroxyaspergillic acid. The minimum concentration for complete inhibition in diluted Saké-peptone medium against true hiochi-bacilli, Lactobacillus homohiochii H-42 and Lactobacillus heterohiochii H-l, was 10 γ/ml, and that against hiochi-lactobacilli H-7 and H-34 20 γ/ml.  相似文献   

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Mark Brenner 《Hydrobiologia》1983,103(1):205-210
The long-term impact of Maya culture on a lowland tropical watershed is assessed, using data from a 9.2 m sediment core taken from deep water (28 m) in Lake Quexil. Human population growth, estimated by the 1980 archaeological survey, is associated with a shift in the composition of the sediment to a dominance by inorganic material, the Maya clay formation, beginning ca. 3500 B.P. Increasing settlement densities are correlated with accelerated influxes of phosphorus, carbonates, and siliceous sediment. However, chemical data do not track short-term population fluctuations closely. Because much of the sediment is delivered as colluvium, and not by running water, there is a lag between terrestrial disturbance and impact on the aquatic system. As an indication of this lag, contemporary high sedimentation rates are a residual of Maya activity that virtually ceased some 300–400 years B.P. Comparison of the deep-water core with a shallow-water (7 m) section, based on palynological correlation, reveals only minor differences in proximate chemical composition. Chemical influxes are much higher at the deep-water site, however, as a consequence of sediment focusing in this hyperconical basin. Chemical analyses of soil samples from 21 test pits in the Quexil basin support the principal conclusion that bulk soil movement was the mode of nutrient transfer to the lake, following forest clearance by the Maya.  相似文献   

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Wang  Shichuan  Trilling  Mirko  Sutter  Kathrin  Dittmer  Ulf  Lu  Mengji  Zheng  Xin  Yang  Dongliang  Liu  Jia 《中国病毒学》2020,35(6):673-684
Virologica Sinica - The recent emergence and rapid global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pose an unprecedented medical and socioeconomic crisis, and the...  相似文献   

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Through unexpected circumstances, I went to Lambaréné, in Gabon, to be Dr. Albert Schweitzer's surgeon for 2 months, November and December of 1960.This diary I can honestly say I never thought would become public. The years have passed; I am now 77. I realize that not many of those who served in a medical capacity at his hospital are still alive and not everyone will share his or her experiences.I want to make clear that I was with Dr. Schweitzer only 2 months. I would not want anyone to think that I played a strategic role at the hospital. I did not, but I helped as best I could.Although I have traveled throughout the world and have been a surgeon in many out-of-the-way places, I have not returned to Lambaréné. The reason, I confess, is that I wanted it to remain in my mind as it was. For Dr. Schweitzer and those who served there, his hospital was a way of life. It was a world of its own and, though small, it came into being because of the arching ideals and unflagging dedication of a remarkable man. His example should inspire us to enlarge our personal horizons, not just to recognize the less fortunate but to act without delay on their behalf. For each of us, there is an Ogowe waiting to be crossed.  相似文献   

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The cabbage butterfly, Pieris melete is multivoltine with a pupal summer and winter diapause. Summer and winter diapause are induced principally by relatively long and short daylengths, respectively. The intermediate to relatively short daylengths of autumn permitted some pupae to develop without diapause in the field. A short daylength had a stronger diapause inducing effect than a relatively long one under higher temperatures. The principal sensitive phase for photoperiodic response occurred before the late 3rd larval instar. The critical daylength for wild autumnal populations was between 12h 30min and 12h 40min at an average temperature of 20.5 degrees C. A night interruption by 2h of light averted diapause most effectively when it was placed 10 to 12h after lights-off. High temperatures and long days during summer inhibited the incidence of diapause, suggesting that the occurrence of summer diapause is due to the specific climatic conditions occurring in April and early May, rather than to the high temperatures in summer. This indicates that the butterfly has a cryptic ability to reproduce in summer. High temperatures delayed diapause development, whereas low temperatures enhanced it, indicating that the optimum temperature of diapause development is lower. The diapause regulating mechanisms thus ensure that the species synchronises its development and reproduction with the growth seasons of the host plants and provide the species with a high degree of flexibility in its life cycle.  相似文献   

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Viruses were found to be very abundant in the top layer of the sediments of Lac Gilbert, Québec. Viruses were extracted from the sediments using pyrophosphate buffer, and viruses from the diluted extracts were pelleted onto grids and enumerated using transmission electron microscopy. Viral abundance in the sediments ranged from 6.5 × 108 to 1.83 × 1010 ml–1, which is 10- to 1,000-fold greater than the number observed in the water column. This increase corresponds well with the 100- to 1,000-fold increase in bacterial abundance in the sediments. Viral abundance differed significantly among the surface sediment samples taken at different bottom depths and among samples taken at different depths of the water column. Viral abundance also varied significantly between the oxic and anoxic zones of the water column and the sediments. The virus-to-bacteria ratio varied greatly among the different sediment sites but not among depths in the water column. Viral abundance in the water column was related to bacterial abundance and chlorophyll concentration, whereas viruses in the sediments were most abundant in sediments with high organic matter content. Elevated viral abundance and their erratic distribution in the sediments suggest that viruses might play an important role in sediment microbial dynamics. Correspondence to: Roxane Maranger  相似文献   

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The use of wood in construction has had a long history and Chile has a rich cultural heritage of using native woods for building churches and other important structures. In 2000, UNESCO designated a number of the historic churches of Chiloé, built entirely of native woods, as World Heritage Sites. These unique churches were built in the late 1700 s and throughout the 1800 s, and because of their age and exposure to the environment, they have been found to have serious deterioration problems. Efforts are underway to better understand these decay processes and to carryout conservation efforts for the long-term preservation of these important structures. This study characterized the types of degradation taking place and identified the wood decay fungi obtained from eight historic churches in Chiloé, seven of them designated as UNESCO World Heritage sites. Micromorphological observations identified white, brown and soft rot in the structural woods and isolations provided pure cultures of fungi that were identified by sequencing of the internal transcribed region of rDNA. Twenty-nine Basidiomycota and 18 Ascomycota were found. These diverse groups of fungi represent several genera and species not previously reported from Chile and demonstrates a varied microflora is causing decay in these historic buildings.  相似文献   

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Two 16S rRNA gene clone libraries Cores 1U and 2U were constructed using two ice core samples collected from Austre Lovénbreen glacier in Svalbard. The two libraries yielded a total of 262 clones belonging to 59 phylotypes. Sequences fell into 10 major lineages of the domain Bacteria, including Proteobacteria (alpha, beta, gamma and delta subdivisions), Bacteroidetes, Actinobacteria, Firmicutes, Acidobacteria, Deinococcus-Thermus, Chloroflexi, Planctomycetes, Cyanobacteria and candidate division TM7. Among them, Bacteroidetes, Actinobacteria, Alphaproteobacteria and Cyanobacteria were most abundant. UniFrac data showed no significant differences in community composition between the two ice cores. A total of nineteen bacterial strains from the genera Pseudoalteromonas and Psychrobacter were isolated from the ice cores. Phylogenetic and phenotypic analyses revealed a close relationship between the ice core isolates and bacteria in marine environments, indicating a wide distribution of some bacterial phylotypes in both terrestrial and marine ecosystems.  相似文献   

12.
Ophisops elegans, a common lizard with a wide distribution range in Iran, was selected to investigate the influence of environmental factors on its distribution pattern. Based on a distribution model developed with the software Maxent for O. elegans, the most important factors influencing the distribution pattern were found to be high winter precipitation, intermediate levels of Normalized Difference Vegetation Index (NDVI) and intermediate levels of sunshine. It seems that overall plant cover and competition with Mesalina watsonana are the main factors which influence the distribution pattern of O. elegans in the central Iranian Plateau.  相似文献   

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We aimed to determine whether the copepod assemblages in lakes and ponds of northern Québec, Canada, were closer in composition to those found in southern Québec, or to those reported from the subarctic and arctic. Six calanoid and five cyclopoid species were identified from 37 ponds and lakes located in the region between 55° N and 59° N. Species diversity was generally low, ranging from 0 to 4 species per lake. Dominant species were Leptodiaptomus minutus and Acanthocyclops vernalis. The species assemblages showed high affinity with those found in forested regions of southern Québec. Exceptions were Leptodiaptomus tyrrelli, previously only recorded west of Hudson Bay, and Hesperodiaptomus arcticus, hitherto recorded north of 58° N. Relationships between the lakes, species, and environmental variables were explored using multivariate analysis. Lakes situated along the coast and on two offshore islands clustered together and were characterised by higher conductivity and pH than those lakes located further inland. Leptodiaptomus tyrrelli was common in these coastal lakes. Canonical correspondence analysis revealed statistically significant relationships between copepod distributions and conductivity, dissolved organic carbon and pH. These three variables accounted for 70% of the variation in the species' distribution.  相似文献   

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San Pedro River's wetlands sustain trophic nets in the fluvial system, due to the high habitat availability, and space and temporal variations. In order to describe the relationship between environmental parameters and ichthyofauna, this study evaluated fish assemblages composition, distribution, abundance, density, biomass, richness species, diversity and equitability in the wetlands. Sampling considered three different sites and climatic seasons (dry, rainy and cold fronts). The physical and chemical parameters considered were dissolved oxygen, temperature, pH, water transparency and the depth. Fishes were caught with a shrimp net, after six minutes towings and were identified afterwards. A total of 1 049 organisms of 25 fish species were caught, two of which were exotic species: Oreochromis niloticus and Parachromis managuense. A total of 23 species were found at site I (with the highest density 0.23 ind./m2), 17 at site II (0.23 ind./m2) and 14 at site III (0.12 ind./m2). The dry season had the highest species number with 21 species, followed by the rainy season with 17 species, and the cold season with five species. Similarly, the highest biomass (8.30 g/m2) was found in dry season, followed by the rainy (2.16 g/m2) and the cold seasons (0.03 g/m2). Considering seasons, highest density was found during the dry (0.436 ind./m2), followed by the rainy (0.213 ind./m2) and the cold (0.023 ind./m2) seasons. The dominant density species during the study period, according to the quadrants graphic of Olmstead-Tukey were: Petenia splendida, Vieja heterospila, Vieja synspila, Dorosoma petenense and Astyanax aeneus. There were significant differences in the species richness among sites. Temperature, depth and transparency showed differences among the seasons. The canonical correspondence analysis indicated that fish distribution was governed by environmental parameters during all seasons. In terms of fish abundance and composition, environmental parameters play an important role showing spatial and temporal differences in the ecosystem, this could be explained with the fact that most of young fishes have a movement behavior to the wetlands, searching refuge and feed during the dry season. Considering the diversity indexes variation, it may be concluded that San Pedro River's wetlands correspond to a system where the ichthyofauna composition fluctuates spatial and seasonally.  相似文献   

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Diverse reproductive strategies shown by ferns and lycophytes allow them to colonize a variety of habitats, particularly after the incidence of natural or anthropogenic disturbances. This study assessed the presence, abundance and reproductive strategies of ferns growing in soils of temperate forests with different levels of disturbance at the Sierra Nevada mountain range in the State of Mexico. Vegetation, soil and environmental variables were recorded in 200 m2 permanent plots located in four forest stands. One-Way ANOVA and Canonical Correspondence Analysis resulted in the recognition of three landscape types defined by the degree of environmental alteration: low, moderate and severe. Also, from five soil samples collected in each stand, germination of ferns and lycophytes was induced. A positive relationship was found between the alteration degree and Cheilanthes abundance. Under a low landscape alteration regime, species richness is restricted to Cheilanthes bonariensis, C. marginata and Pellaea ternifolia subsp. ternifolia. The soil is a reservoir of spores of Cheilanthes and Pellaea ternifolia subsp. ternifolia because their spores can remain viable for different time intervals. Apogamy is the usual reproductive strategy of Cheilanthes species in disturbed ecosystems, although these species also show sexual reproduction in natural ecosystems with adequate water availability. Apogamy may be related to a shorter generation time in comparison with a low disturbed ecosystem. On the other hand, Pellaea ternifolia subsp. ternifolia only has sexual reproduction. Apogamy might be related to a faster generation in comparison with a low disturbed ecosystem.  相似文献   

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A species list was elaborated for La Sepultura Biosphere Reserve, Chiapas, Mexico. Line transects and direct observations were made. national and international databases were consulted, and animal traces were registered. Animals were captured during the period May 1994 - December 1999. A total of 848 specimen (248 furs and skulls), 32 tracks in plaster, and 9 osseous fragments were collected. A total of 98 species, 70 genera, 29 families, and 10 orders compose the species list. Of these species 87.7% belong to the orders Chiroptera, Rodentia and Carnivora and 21 species were classified according to some kind of legal protection. These data represent a solid and actualized database useful for designing management and conservation plans for this Biosphere Reserve.  相似文献   

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Data from wildlife disease surveillance programs are used to inform implementation of disease control (e.g., vaccination, population reduction) in space and time. We developed an approach to increase detection of raccoon rabies in raccoons (Procyon lotor) and skunks (Mephitis mephitis) of Québec, Canada, and we examined the implications of using this approach for targeted surveillance. First we modeled the probability of a rabid animal relative to environmental characteristics of sampling locations. Rabid animals were more likely to be found in low-lying flat landscapes that had higher proportions of corn-forest edge habitat and hay agriculture, and that were within 20 km of one or more known rabies cases. From the model, we created 2 complementary risk maps to identify areas where rabid animals were most likely to be sampled. One map accounted for habitat and known rabies case locations, and can be used to define an infection zone from which surveillance can be targeted along the periphery to determine if disease is continuing to spread. The other map only accounted for habitat and can be used to locate areas most likely to contain rabid animals when the disease is present. In a further analysis we compared the 2 most successful methods for detecting raccoon rabies in Québec, given the disease was present. Government trapping operations (active surveillance) detected more cases in the short-term, but citizen notification (passive and enhanced) was more effective after 12 trapping days from which the initial rabies case was found. Our approach can benefit wildlife and public health agencies wanting to assess the disease status of regions by targeting surveillance to habitats most likely to contain infected animals and by defining the duration over which sampling methods are effective. © 2011 The Wildlife Society.  相似文献   

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Summary Following the demise of the stromatoporoid-coral reef community in Late Frasnian time, Lower Carboniferous carbonate shelf profiles possessed a ramp geometry, with major organic buildups represented by mud-rich mounds. Microfacies petrography of the exceptionally well-preserved Upper Viséan (Lower Carboniferous) carbonate ramp of the Béchar Basin, Algerian Sahara, may well contribute significantly to our understanding of the paleoecological zonation of Carboniferous non-rimmed platforms, and of the still enigmatic mounds commonly referred to as Waulsortian banks or mounds. Facies are grouped into two broad groups: (a) a mound facies group which comprises sponge wackestone-bafflestone, sponge-fenestellid bafflestone-wackestone, crinoid wackestone-packstone, and bedded flanks of intraclastic wackestone-packstone, all four facies composing the actual mud-rich mounds, and (b) a supramound facies group composed of coral-microbial framestone, crinoid packstone-grainstone, algal-foraminiferal grainstone and oolite grainstone. Calcareous algae are important bathymetric indicators and are used to delineate three bathymetric zones based on light penetration: the aphotic zone, which contains no calcareous algae; the dysphotic zone, where there is little ambient light, and which is characterized by the presence of red algae (Fasciella, Ungdarella, Stacheia, Epistacheoides) and absence of green algae; and the euphotic zone, which receives the full spectrum of sunlight, and is characterized by the occurrence of both green algae (Koninckopora, Kamaenella, Kamaena, Palaeoberesella, Calcisphaera, Anthracoporellopsis, Issinella, Exvotarisella) and red algae. Integration of algal zonation, distribution of the other biota, and recurrence of distinct assemblages, enable recognition of seven depth-related benthic assemblages. Together with the physical properties of the facies, the benthic assemblages were used to define seven bathymetric zones, from upper to lower ramp: (1) algal assemblage (upper ramp); (2) crinoid-ramose bryozoan assemblage (mid-ramp); and (3) productid brachiopod assemblage, (4) colonial rugose coral-microbial encruster assemblage, (5) crinoid-fenestellid assemblage, (6) sponge-fenestellid, and (7) sponge assemblage (lower ramp). The vertical zonation of the mud-rich mounds and associated facies differ from that reported from the classical Upper Tournaisian-Lower Viséan Waulsortian mound-bearing successions.  相似文献   

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