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21.
Tessa D. Toumbourou Wolfram H. Dressler Anna Sanders Ekawati Liu Trent Brown Ariane Utomo 《Asia Pacific viewpoint》2023,64(2):188-208
In Indonesia, state and non-state actors frame youth attrition from agriculture as a food security concern and propose policy solutions focused on ‘modern’ farming techniques. Using a critical framing analysis of five national Indonesian news media sources from 2010 to 2020, we examine how government, development and private sector actors portray youth in agriculture, and the underlying assumptions that inform related policy and development agendas. Our analysis reveals contrasting portrayals of youth in agriculture. Youth are often depicted as averse to farming, while also being innovative adopters of modern farming techniques, equipment, and digital technologies. We argue that media frames reflect and reinforce the dominant discourses of state and non-state actors, which have a productivist orientation, proposing technical, capital-intensive agricultural solutions to food insecurity and related issues. News media pays comparatively less attention to structural barriers to youth entry and success in agriculture, such as limited access to land and finance and unfavourable terms of trade. 相似文献
22.
Long-term observational data of the phenological network of the German Weather Service (DWD) were used to derive the altitudinal dependence of leaf unfolding (LU), leaf discolouration (LD) and the length of the vegetation period (LD-LU) of common beech (Fagus sylvatica L.) in different regions of Southern Germany. Depending on altitude, the vegetation period starts in Bavaria between the 2nd and 24th May with a delay of around 2 days per 100 m altitude increase (averaged over the last 30 years). In Southern Bavaria, LU starts a few days earlier as well as increases slightly faster into higher altitudes than in the northern regions. This can be explained by a more favourable supply of warmth and radiation in the south. The end of the vegetation period, defined here as the beginning of LD, showed no altitudinal dependence, which reflects an interaction of endogenous and exogenous factors as triggers for LD. In the Bavarian Forest region, altitudinal dependences are strongly influenced by sites which are affected by cold-air tailback (‘Kaltluftstau’) was obtained. Hence, phenological gradients should only be derived and applied above a phenological inversion zone. The calculated vertical gradients for LU can be used together with available observational data to estimate the beginning of the forest vegetation period of beech for different altitudes of Bavaria. 相似文献
23.
Christoph Dittmar Wolfgang Fricke Wolfram Elling 《European Journal of Forest Research》2006,125(3):249-259
Phenological, temperature, and tree-ring data were used in order to identify and quantify the impact of late frosts on common beech (Fagus sylvatica L.) at different altitudes in Southern Germany during the last century. For this intention, dendroecological investigations were made upon trees at the Meteorological Observatory Hohenpeißenberg as well as from seven stands in the Bavarian Forest and 17 stands at the northern fringe of the Alps. From these locations, a considerable number of severe growth minima in the tree-ring series could be related to late frost in the days of or immediately after leaf unfolding. The frequency of frost-related growth minima increases with altitude. In individual years, radial growth can be reduced by more than 90% (stand mean) in relation to the average growth of the ten previous years. Hence, late frosts are considered as important ecological events that strongly affect beech vitality and competitiveness especially at high altitudes. Evidence of significant impacts on radial growth by late frosts distinct before leaf unfolding or with temperatures above ?3°C was not found. Also, increasing frequency and intensity of late frosts during recent decades were not ascertained. Hence, the recently observed decreased vitality of common beech accompanied by growth depressions especially at high altitude sites in Central Europe cannot be explained as a consequence of late frost damage. 相似文献
24.
Yano J Kern J Sauer K Latimer MJ Pushkar Y Biesiadka J Loll B Saenger W Messinger J Zouni A Yachandra VK 《Science (New York, N.Y.)》2006,314(5800):821-825
The oxidation of water to dioxygen is catalyzed within photosystem II (PSII) by a Mn(4)Ca cluster, the structure of which remains elusive. Polarized extended x-ray absorption fine structure (EXAFS) measurements on PSII single crystals constrain the Mn(4)Ca cluster geometry to a set of three similar high-resolution structures. Combining polarized EXAFS and x-ray diffraction data, the cluster was placed within PSII, taking into account the overall trend of the electron density of the metal site and the putative ligands. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 angstrom-resolution x-ray structures or other previously proposed models. 相似文献
25.
Buescher JM Liebermeister W Jules M Uhr M Muntel J Botella E Hessling B Kleijn RJ Le Chat L Lecointe F Mäder U Nicolas P Piersma S Rügheimer F Becher D Bessieres P Bidnenko E Denham EL Dervyn E Devine KM Doherty G Drulhe S Felicori L Fogg MJ Goelzer A Hansen A Harwood CR Hecker M Hubner S Hultschig C Jarmer H Klipp E Leduc A Lewis P Molina F Noirot P Peres S Pigeonneau N Pohl S Rasmussen S Rinn B Schaffer M Schnidder J Schwikowski B Van Dijl JM Veiga P Walsh S Wilkinson AJ Stelling J Aymerich S 《Science (New York, N.Y.)》2012,335(6072):1099-1103
26.
Wolfram Kller 《Pest management science》1987,18(2):129-147
The chemical diversity of fungicides and antimycotics interfering with the C-14 demethylation of fungal sterols indicates a rather high structural flexibility of the sterol binding site at the specific cytochrome P-450 mixed-function oxygenase. The structural flexibility, however, is opposed by a remarkable stereochemical selectivity. A similar, though not identical, stereochemical discrimination is observed with a group of plant growth regulators chemically related to the fungicidal demethylation inhibitors. The relationship between chemical structure and stereochemical requirements is discussed for both biological activities. 相似文献
27.
28.
Effect of diet on cecal pH and feeding behavior of horses. 总被引:5,自引:0,他引:5
29.
30.
Different methods for the evaluation of species of the genus Mesaphorura (Collembola, Tullbergiinae)
Field studies and laboratory investigations based upon cultures, isoenzyme electrophoresis and RAPD-PCR were carried out to get a better understanding of the value of morphospecies within the genus Mesaphorura.Culturing of seven Mesaphorura species under constant as well as variable conditions provided a basis for evaluation of morphological characters, but did not yield any statistically supportable evidence that intraspecific variability reached interspecific delimitations.In enzyme tests, esterases gave the best results. The search for species-specific band patterns is, however, time and material consuming. DNA investigations using RAPD-PCR resulted in band patterns that appeared to be species specific. Nevertheless, these require further investigations.None of the studies carried out gave any conclusive evidence for invalidation of the morphologically defined species of the genus Mesaphorura. 相似文献