Simulation of snowmelt erosion using the EROSION 3D model     

Astrid Weigert  Gerald Wenk  Gregor Ollesch  Heiko Fritz 《植物养料与土壤学杂志》2003,166(1):128-130

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Impacts of population growth, economic development, and technical change on global food production and consumption   总被引：3，自引：0，他引：3  

Uwe A. Schneider  Petr HavlíkErwin Schmid  Hugo ValinAline Mosnier  Michael ObersteinerHannes Böttcher  Rastislav SkalskýJuraj Balkovi?  Timm SauerSteffen Fritz 《Agricultural Systems》2011,104(2):204-215

Over the next decades mankind will demand more food from fewer land and water resources. This study quantifies the food production impacts of four alternative development scenarios from the Millennium Ecosystem Assessment and the Special Report on Emission Scenarios. Partially and jointly considered are land and water supply impacts from population growth, and technical change, as well as forest and agricultural commodity demand shifts from population growth and economic development. The income impacts on food demand are computed with dynamic elasticities. Simulations with a global, partial equilibrium model of the agricultural and forest sectors show that per capita food levels increase in all examined development scenarios with minor impacts on food prices. Global agricultural land increases by up to 14% between 2010 and 2030. Deforestation restrictions strongly impact the price of land and water resources but have little consequences for the global level of food production and food prices. While projected income changes have the highest partial impact on per capita food consumption levels, population growth leads to the highest increase in total food production. The impact of technical change is amplified or mitigated by adaptations of land management intensities.  相似文献   

Translating biomolecular recognition into nanomechanics     

Fritz J  Baller MK  Lang HP  Rothuizen H  Vettiger P  Meyer E  Güntherodt H  Gerber C  Gimzewski JK 《Science (New York, N.Y.)》2000,288(5464):316-318

We report the specific transduction, via surface stress changes, of DNA hybridization and receptor-ligand binding into a direct nanomechanical response of microfabricated cantilevers. Cantilevers in an array were functionalized with a selection of biomolecules. The differential deflection of the cantilevers was found to provide a true molecular recognition signal despite large nonspecific responses of individual cantilevers. Hybridization of complementary oligonucleotides shows that a single base mismatch between two 12-mer oligonucleotides is clearly detectable. Similar experiments on protein A-immunoglobulin interactions demonstrate the wide-ranging applicability of nanomechanical transduction to detect biomolecular recognition.  相似文献   

Carbon-13 and oxygen-18 in dinosaur, crocodile, and bird eggshells indicate environmental conditions   总被引：1，自引：0，他引：1  

R E Folinsbee  P Fritz  H R Krouse  A R Robblee 《Science (New York, N.Y.)》1970,168(937):1353-1356

We have gathered, from the nests of dinosaurs, and living and fossil birds, some evidence of the environment in which these creatures lived. However, our isotope determinations suggest it will be impossible to resolve the problem as to whether the dinosaurs were warm-or cold-blooded from the oxygen and carbon isotopes content of their shells.  相似文献   

Ultrafast bond softening in bismuth: mapping a solid's interatomic potential with X-rays     

Fritz DM  Reis DA  Adams B  Akre RA  Arthur J  Blome C  Bucksbaum PH  Cavalieri AL  Engemann S  Fahy S  Falcone RW  Fuoss PH  Gaffney KJ  George MJ  Hajdu J  Hertlein MP  Hillyard PB  Horn-von Hoegen M  Kammler M  Kaspar J  Kienberger R  Krejcik P  Lee SH  Lindenberg AM  McFarland B  Meyer D  Montagne T  Murray ED  Nelson AJ  Nicoul M  Pahl R  Rudati J  Schlarb H  Siddons DP  Sokolowski-Tinten K  Tschentscher T  von der Linde D  Hastings JB 《Science (New York, N.Y.)》2007,315(5812):633-636

Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.  相似文献   

Magnetic resonance spectroscopy identifies neural progenitor cells in the live human brain     

Manganas LN  Zhang X  Li Y  Hazel RD  Smith SD  Wagshul ME  Henn F  Benveniste H  Djuric PM  Enikolopov G  Maletic-Savatic M 《Science (New York, N.Y.)》2007,318(5852):980-985

The identification of neural stem and progenitor cells (NPCs) by in vivo brain imaging could have important implications for diagnostic, prognostic, and therapeutic purposes. We describe a metabolic biomarker for the detection and quantification of NPCs in the human brain in vivo. We used proton nuclear magnetic resonance spectroscopy to identify and characterize a biomarker in which NPCs are enriched and demonstrated its use as a reference for monitoring neurogenesis. To detect low concentrations of NPCs in vivo, we developed a signal processing method that enabled the use of magnetic resonance spectroscopy for the analysis of the NPC biomarker in both the rodent brain and the hippocampus of live humans. Our findings thus open the possibility of investigating the role of NPCs and neurogenesis in a wide variety of human brain disorders.  相似文献   

Eruption of the nevado del ruiz volcano, Colombia, on 13 november 1985: tephra fall and lahars     

Naranjo JL  Sigurdsson H  Carey SN  Fritz W 《Science (New York, N.Y.)》1986,233(4767):961-963

A small Plinian eruption of the Nevado del Ruiz volcano in Colombia ejected 3.5 x 10(10) kilograms of mixed dacite and andesite tephra on 13 November 1985, with a maximum column height of 31 kilometers above sea level. Small pyroclastic flows and surges, generated during the initial stage of the eruption, caused surface melting of approximately 10% of the volcano's ice cap, leading to meltwater floods. The erosive floods incorporated soils and loose sediments from the volcano's flanks and developed into lahars, which claimed at least 25,000 lives.  相似文献   

Elephant-induced structural changes in the vegetation and habitat selection by large herbivores in an African savanna     

Marion Valeix  Hervé Fritz  Rodolphe Sabatier  Felix Murindagomo  David Cumming  Patrick Duncan 《Biological conservation》2011,(2):902-912

African elephants can affect the quality of the habitat of other species by breaking or uprooting trees and shrubs in savannas. Their effect on vegetation has been widely studied but less is known about the effects of such vegetation changes on other animals. We studied how changes in the vegetation caused by elephants influence the selection of microhabitats by five African herbivore species (giraffe, kudu, steenbok, impala, and zebra) in Hwange National Park, Zimbabwe. There was no clear significant effect of overall elephant-induced vegetation changes on microhabitat selection except for the small species (steenbok and impala) that used vegetation modified by elephants preferentially. This is consistent with a medium-term browsing facilitation hypothesis. More subtle possible effects were detected for larger browsers (giraffe and kudu). They selected areas with broken and uprooted plants and avoided coppiced areas. All of the browsers selected sites characterized by plants uprooted and broken by elephants, which were associated with a higher visibility, and ultimately a better probability of detecting an approaching predator, suggesting that perceived predation risk plays an important role in microhabitat selection. These results illustrate how elephants can initiate indirect effects that influence microhabitat selection by other herbivores. Understanding the indirect effects of elephants through changes in food availability and predation risk thus needs further investigation. The results of this study do not provide support for the hypothesis that elephant-induced changes in the structure of habitats have caused the declines in the populations of the other herbivores in the study area.  相似文献   

Clinical evaluation of serum alcohol dehydrogenase activity in horses with acute intestinal obstruction     

Naglaa Abdel Megid Gomaa BVSc  MVSc  Gábor Köller Dr rer nat  Gerald Fritz Schusser Dr vet med  DECEIM 《Journal of Veterinary Emergency and Critical Care》2011,21(3):242-252

Objectives – To measure serum alcohol dehydrogenase (ADH) activity in horses with acute intestinal obstruction and to determine the diagnostic and prognostic utility of this analyte. Design – Prospective observational study. Setting – University Veterinary Hospital. Animals – Thirty healthy horses (control group) and 77 horses with acute intestinal obstruction, including 36 horses with nonstrangulating obstruction (23 with left ventral colon impaction and 13 with left dorsal displacement [G1], 22 with small intestinal strangulation [G2], and 19 with colon torsion [G3]). Interventions – Serum ADH activity was assayed spectrophotometerically in all horses. Serum lactate concentration and hepatic enzyme (aspartate aminotransferase, gamma‐glutamyl transferase, glutamate dehydrogenase) activities were measured using an automatic analyzer. Measurements and Main Results – The median [interquartile range] serum ADH activity in healthy horses was 10.5 [8.7 – 11 U/L]. ADH activity was significantly increased (P<0.05) in G1=16.5 [13.8 – 18 U/L], G2=40 [20 – 74.9 U/L], and G3=63.2 [40 – 78 U/L] compared with healthy controls. Aspartate aminotransferase and glutamate dehydrogenase activities were also significantly increased in G3 in comparison with controls. ADH activity was correlated with serum lactate concentration in G1 and G3, respectively (P<0.01, r=0.55 and 0.8). Other liver enzymes did not show any significant correlation with lactate. ADH activity was directly related to the probability of strangulation; odds ratio=1.11. ADH activity >20 U/L had 80.6% specificity and 80.5% sensitivity for discriminating horses with strangulating obstruction. Twelve horses euthanized before surgery were excluded from the outcome analysis. Increasing ADH activity was associated with nonsurvival; odds ratio=1.03. ADH activity <80 U/L had 94.44% specificity and 66.67% sensitivity for survival. Conclusion – Serum ADH activity may be a useful clinical parameter in detecting intestinal strangulation in horses and may provide some prognostic value in horses with acute intestinal obstruction.  相似文献   

Ergebnisse und Probleme beim Nachweis von Teilprozessen apomiktischer Samenbildung bei Gräserbastarden     

Fritz Matzk 《Genetic Resources and Crop Evolution》1986,34(2):159-175

Zusammenfassung Ausgehend von Erkenntnissen über die Evolution der Apomixis wurden verschiedene Wege zur experimentellen Entwicklung neuer apomiktischer Futtergräser beschritten. Bei den Versuchen, über Rekombination Apomixis zu entwickeln, sind 9 Gräserbastarde von insgesamt 4300 F₁-Art- und Gattungsbastarden selektiert worden, für die sich Hinweise auf Apomeiose bzw. Parthenogenese ergeben hatten. Mit den vorliegenden Untersuchungen wird die Art der Samenbildung von F₁ bis F₄ näher analysiert.Bei 3 Bastarden der KombinationFestuca gigantea ×F. arundinacea wurde parthenogenetische Eizellenentwicklung mittels einer neuen Methode zur Stimulation der Embryoentwicklung durch Auxinbehandlung sicher nachgewiesen. Dagegen waren die Hinweise auf Apomeiose durch somatische und meiotische Instabilitäten vorgetäuscht. Fehlinterpretationen und Probleme beim Nachweis von Apomixis und deren Teilprozesse werden diskutiert. Zur Entwicklung und Manipulierbarkeit der Apomixis sind geeignete Nachweismethoden für die einzelnen Teilprozesse apomiktischer Samenbildung von entscheidender Bedeutung.

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Results and problems in proving sub-processes of apomictic seed formation in grass hybrids

Summary Taking into consideration items of knowledge on the evolution of apoximis, different experimental attempts were made to develop new apomictic fodder grasses. From experiments trying to develop apomixis by recombination nine grass hybrids with indications for apomeiosis or parthenogenesis were selected out of 4300 interspecific and intergeneric F₁ hybrids. The present study was undertaken to analyse more fully the mode of seed formation in F₁ to F₄.In three hybridsFestuca gigantea ×F. arundinacea, parthenogenetic development of egg cells could be confirmed using a new method of stimulating the embryo development by treatment with auxin. On the other hand, the indications for apomeiosis proved to be caused by somatic and meiotic instabilities. Misinterpretations as well as problems in detecting apomixis and its sub-processes are discussed. Development and manipulation of apomixis depends decisively on the availability of suitable methods for the proof of the individual sub-processes of apomictic seed formation.

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