P-State Pairing and the Ferromagnetism of ZrZn2     

Enz CP  Matthias BT 《Science (New York, N.Y.)》1978,201(4358):828-829

It is ascertained that, within the range of stability, the transition temperature of the superconducting solutions between Ti and Zr and between Zr and Hf, and the Curie point of the corresponding ferromagnetic solutions between TiZn(2) and ZrZn(2) and between ZrZn(2) and HfZn(2), follow a parallel behavior. From this correlation it is concluded that the weak itinerant ferromagnetism of ZrZn(2) must be due to electron-phonon interaction. Theoretical arguments are advanced to show that the underlying mechanism is hindered p-state pairing, due to a strongly localized repulsive part of the pair-potential that acts as a Hubbard interaction and gives rise to a Stoner instability.  相似文献   

Glutamatergic and dopaminergic neurons mediate anxiogenic and anxiolytic effects of CRHR1     

Refojo D  Schweizer M  Kuehne C  Ehrenberg S  Thoeringer C  Vogl AM  Dedic N  Schumacher M  von Wolff G  Avrabos C  Touma C  Engblom D  Schütz G  Nave KA  Eder M  Wotjak CT  Sillaber I  Holsboer F  Wurst W  Deussing JM 《Science (New York, N.Y.)》2011,333(6051):1903-1907

The corticotropin-releasing hormone receptor 1 (CRHR1) critically controls behavioral adaptation to stress and is causally linked to emotional disorders. Using neurochemical and genetic tools, we determined that CRHR1 is expressed in forebrain glutamatergic and γ-aminobutyric acid-containing (GABAergic) neurons as well as in midbrain dopaminergic neurons. Via specific CRHR1 deletions in glutamatergic, GABAergic, dopaminergic, and serotonergic cells, we found that the lack of CRHR1 in forebrain glutamatergic circuits reduces anxiety and impairs neurotransmission in the amygdala and hippocampus. Selective deletion of CRHR1 in midbrain dopaminergic neurons increases anxiety-like behavior and reduces dopamine release in the prefrontal cortex. These results define a bidirectional model for the role of CRHR1 in anxiety and suggest that an imbalance between CRHR1-controlled anxiogenic glutamatergic and anxiolytic dopaminergic systems might lead to emotional disorders.  相似文献   

Carbon-based supercapacitors produced by activation of graphene     

Zhu Y  Murali S  Stoller MD  Ganesh KJ  Cai W  Ferreira PJ  Pirkle A  Wallace RM  Cychosz KA  Thommes M  Su D  Stach EA  Ruoff RS 《Science (New York, N.Y.)》2011,332(6037):1537-1541

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp(2)-bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.  相似文献   

A global view of gene activity and alternative splicing by deep sequencing of the human transcriptome   总被引：6，自引：0，他引：6  

Sultan M  Schulz MH  Richard H  Magen A  Klingenhoff A  Scherf M  Seifert M  Borodina T  Soldatov A  Parkhomchuk D  Schmidt D  O'Keeffe S  Haas S  Vingron M  Lehrach H  Yaspo ML 《Science (New York, N.Y.)》2008,321(5891):956-960

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Reconstructing the collapse of wetland networks in the Swiss lowlands 1850–2000     

Urs Gimmi  Thibault Lachat  Matthias Bürgi 《Landscape Ecology》2011,26(8):1071-1083

In Central Europe vast wetland areas have been converted into agricultural land over the past few centuries. Long-term spatially explicit reconstructions of wetland cover changes at regional scale are rare but such information is vital for setting appropriate wetland conservation and restoration goals. In this study wetland cover change over the past 150 years was analyzed for the Canton Zurich (Switzerland) using information from historical and current topographical maps. Mapping instructions changed significantly over time, i.e., wetlands were mapped more conservatively on older maps. Therefore a technique was developed to account for changes in mapping instructions and to reconstruct a series of comparable maps spanning 1850–2000. Wetland cover dramatically decreased from 13,759 ha in 1850 (more than 8% of the total study area) to 1,233 ha in 2000 (less than 1%). Largest loss is observed for the first half of the twentieth century when more than 50% of the total wetland loss occurred. In 1850, almost all wetland patches were connected in two large networks defined by a 500 m buffer around all wetland patches to account for typical dispersal distances of wetland animals. Despite extensive wetland loss, this networks remained largely intact until 1950, but then collapsed into many medium and small networks consisting of only few wetland patches. In addition to the direct loss of wetland habitats increased habitat fragmentation is limiting metapopulation dynamics and hindering genetic exchange between populations. Amphibians and other wetland animals are particularly prone to habitat fragmentation because of their limited migration abilities. This may lead to time-delayed extinction in the future because current species occurrence might rather reflect historical than current wetland cover and habitat configuration. Future restoration efforts should focus on reestablishing connectivity between remaining smaller wetland networks.  相似文献   

A spatially explicit height�Cdiameter model for Scots pine in Estonia     

Matthias Schmidt  Andres Kiviste  Klaus von Gadow 《European Journal of Forest Research》2011,130(2):303-315

This contribution presents an approach to model individual tree height?Cdiameter relationships for Scots pine (Pinus sylvestris) in multi-size and mixed-species stands in Estonia using the Estonian Permanent Forest Research Plot Network. The dataset includes 22,347 trees. The main focus of the study was to use an approach that is spatially explicit allowing for high accuracy prediction from a minimum set of predictor variables that can be easily derived. Consequently, the height?Cdiameter relationship is modeled as a function of only the stand quadratic mean diameter (dg) and the plot geographical coordinates. A specific generalized additive model gam is employed that allows for the integration of a varying coefficient term and 2-dimensional surface estimators representing a spatial trend and a spatially varying coefficient term. The high flexibility of the model is needed due to the very few predictor variables that subsume a variety of potential influential factors. Subsequently, a linear mixed model is used that quantifies the random variation between plots and between measurement occasions within plots, respectively. Hence, our model is based on the theory of structured additive regression models (Fahrmeir et al. 2007) and separates a structured (correlated) spatial effect from an unstructured (uncorrelated) spatial effect. Additionally, the linear mixed model allows for calibration of the model using height measurements as pre-information. Model bias is small, despite the somewhat irregular distribution of experimental areas within the country. The overall model shows some similarity with earlier applications in Finland. However, there are important differences involving the model form, the predictors and the method of parameter estimation.  相似文献   

Produktion von Torfmoosen (Sphagnum sp.) als Torfersatz im Erwerbsgartenbau     

Armin Blievernicht  Stefan Irrgang  Matthias Zander  Christian Ulrichs 《Gesunde Pflanzen》2011,62(3-4):125-131

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Integration of Calneem® oil and parasitoids to control <Emphasis Type="BoldItalic">Cadra cautella</Emphasis> and <Emphasis Type="BoldItalic">Corcyra cephalonica</Emphasis> in stored grain cereals     

Charles Adarkwah  Daniel Obeng-Ofori  Cornel Adler  Carmen Büttner  Christoph Reichmuth  Matthias Schöller 《Phytoparasitica》2011,39(3):223-233

The compatibility and protectant potential of Calneem® oil derived from the neem tree Azadirachta indica and two parasitoids, Habrobracon hebetor and Venturia canescens, for the control of the rice moth Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) and the tropical warehouse moth Cadra cautella Walker (Lepidoptera: Pyralidae) in stored rice and wheat, were evaluated in the laboratory. Calneem® oil (= neem oil) is a biopesticide produced, registered and marketed in Ghana by AQUA AGRIC Community Projects (AACP/Caldor Ghana Ltd., Tema). It contains 0.3% azadirachtin as its major active ingredient. The oil was emulsified with water using 0.07% soap. Fourth instar moth larvae were held in grain treated with neem oil only, grain treated with one of the parasitoids only, grain treated with a combination of neem and one of the parasitoids, and a control with untreated grain. Neem oil was applied at concentrations from 5,000 to 30,000 ppm. All samples were kept in growth cabinets maintained at 25°C and 65–70% r.h. Adult emergence was recorded after 4 weeks. Parasitoid or neem treatments alone reduced the emergence of C. cephalonica and C. cautella. In general, parasitoid releases were as effective as a combination of neem oil and parasitoids. At the lowest dose, 5,000 ppm, the combination of neem and parasitoid was more effective than the neem alone. The number of adults of H. hebetor and V. canescens that emerged in rice containing either parasitoids alone or in combination with neem oil was similar. This indicates minimal or no adverse effect of neem oil on the two parasitoids. It is thus possible to incorporate neem oil in a well-designed pest management program with parasitoids.  相似文献   

A rapid and simple method for determining fungicide resistance in Botrytis     

Weber  Roland W. S.  Hahn  Matthias 《植物病害和植物保护杂志》2011,118(1):17-25

A simple test based on the germination of conidia of Botrytis on agar media augmented with various fungicides has been developed. Average concentrations causing a 50% reduction of germ-tube growth (EC₅₀) of highly sensitive isolates were determined on 1% malt extract agar (thiophanate-methyl 0.090 ppm; iprodione 0.566 ppm; fludioxonil 0.026 ppm; fenhexamid 0.144 ppm), 1% malt extract agar with 100 ppm salicyl hydroxamic acid (QoI fungicides, viz. trifloxystrobin 0.009 ppm; pyraclostrobin 0.013 ppm; azoxystrobin 0.087 ppm), 0.5% yeast extract agar (boscalid 0.069 ppm) and 0.5% sucrose agar (cyprodinil 0.053 ppm). In order to detect different levels of resistance against these various fungicides, two discriminatory concentrations were identified for each compound. A routine assay method was developed in which drops of a conidial suspension harvested directly from diseased plant material or sporulating cultures were incubated on each of 20 different agar media. Because of a very short time-span of 24–48 h between sample collection and evaluation of results, field-specific information on the occurrence, frequency and types of resistance of Botrytis against common botryticides in soft-fruit production may be generated prior to the main fungicide spray season at blossom time.

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Microbiota accompanying different arbuscular mycorrhizal fungal isolates influence soil aggregation     

Matthias C. Rillig  Emily R. Lutgen  Philip W. Ramsey  John N. Klironomos  James E. Gannon 《Pedobiologia》2005,49(3):43

Arbuscular mycorrhizal fungi (AMF) are key components of ecosystems through their influence on plant communities and ecosystem processes. A major source of information regarding the importance of AMF species richness on process rates are mesocosm experiments using different levels of diversity of AMF as provided by single-species cultures of AMF. Since AMF inocula are generally made available in the form of non-sterile pot culture material, it is possible that AMF symbiosis-associated microbiota are at least partially responsible for some effects hitherto directly attributed to the AMF mycelium. Here, we provide evidence that microbiota associated with single-species cultures of AMF (after long-term pot culture enrichment of 7–8 years) can strongly affect the ecosystem process of soil aggregation. This effect occurred in an AMF isolate specific manner, but in the absence of live and active AMF mycelium. We additionally documented large differences in microbiota communities associated with the different AMF inocula (using PLFA analyses), suggesting that these differences were at least partly responsible for the observed changes in soil aggregation. This result points to AMF–microbiota interactions as a largely unexplored mechanism underlying soil aggregation (and potentially other ecosystem processes). We suggest that a reinterpretation of previous experiments using greenhouse-derived AMF cultures may be necessary, and the need to consider AMF symbiosis-associated microbiota in mechanistic studies of AMF and mycorrhizae in general is emphasized.  相似文献