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排序方式: 共有471条查询结果,搜索用时 15 毫秒
41.
The aim of this study was to reveal how upper level compulsory school students (13 to 16 years old) conceptualize matter. Twenty individually administered interviews were carried out, transcribed word for word and analyzed in accordance with the phenomenographic approach adopted. Six distinctively different conceptions were found. Matter can be understood as (a) homogeneous substance, (b) substance units, (c) substance units with "small atoms," (d) aggregate of particles, (e) particle units, or (f) systems of particles. Differences in focus constitute a variation in the internal structure of each conception. There are also alternative forms of the same conception in some cases. The different conceptions, their varying internal structures, and the alternative forms of conceptions found are logically interrelated in a system, called the "outcome space," which depicts how thinking about matter may vary qualitatively between and within students. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
In this paper we investigate the boundaries of applicability of the theory of the equilibrium states of Runge-Kutta schemes
developed in [1], [2].
Lavoro svolto nell’ambito del Centro interuniversitario di Analisi Numerica e Matematica Computazionale. Classificazione AMS 65L05. 相似文献
Lavoro svolto nell’ambito del Centro interuniversitario di Analisi Numerica e Matematica Computazionale. Classificazione AMS 65L05. 相似文献
43.
Elena Orban Gabriella Di Lena Teresina Nevigato Irene Casini Roberto Caproni Generoso Santaroni Giuliana Giulini 《Food chemistry》2007,101(3):1063-1070
Nutritional quality parameters (proximate and mineral composition, contents of glycogen, fatty acids, cholesterol, plant sterols, fat-soluble vitamins, carotenes) and ecophysiological and commercial quality indicators (Condition Index, percent content of meat and intervalvar fluid) of the striped venus clam, Chamelea gallina, from the central Adriatic coast of Italy were studied at seasonal intervals over a 1-year period. Contents of protein (8.55–10.7 g/100 g), total lipid (0.73–1.59 g/100 g), glycogen (2.25–4.96 g/100 g) and non-protein nitrogen (0.54–0.78 g/100 g) varied significantly during the year, reaching the highest values in winter, in coincidence with a peak of Condition Index. Gas chromatography of total lipids showed high percentages of n − 3 polyunsaturated fatty acids (33.7–41.9% of total fatty acids), in particular eicosapentaenoic (8.16–20.0% of total fatty acids) and docosahexaenoic acids (12.5–20.3% of total fatty acids) and low levels of total n − 6 polyunsaturated fatty acids (3.61–7.87% of total fatty acids). HPLC analysis of the unsaponifiable lipids showed low levels of cholesterol, the dominant sterol (28.3–34.2 mg/ 100 g), and variable amounts of plant sterols (stigmasterol + campesterol, β-sitosterol, fucosterol + brassicasterol), α-tocopherol and carotenes. 相似文献
44.
Sewage sludge can be a suitable, organic-rich substrate to promote vegetation of sulfide-mine tailings, but it may contain contaminants, that, when oxidized, can adversely affect underlying groundwater systems. The geochemical impact of a surface application of 12,000 metric tons of anaerobically-digested sewage sludge on the groundwater quality of a remediated sulfide-tailings impoundment in northern Sweden was evaluated to determine if sludge-borne metals and nitrate were released to the underlying groundwater system. Two years of data from a field-scale groundwater monitoring programme initiated just before the sludge application was compared to groundwater data from 1998 to 2006. Grass was successfully established within 2 years. However, until that occurred, elevated concentrations of sludge-borne metals (Cu, Ni, Pb, Zn) were released to the underlying groundwater. In addition, the release of nitrate likely exacerbated metal concentrations by providing an oxidant for pyrite in the underlying tailings. The release was periodic due to the establishment of the grass, which immobilized metals and nitrate in the sludge. Metals bound as organo-metallic complexes, due to dissolved organic carbon released from the sludge, migrated across the tailings impoundment. Model simulations indicate that the plume will take 6 years to exit the groundwater environment. Though the impacts are relatively short-term, this type of application should be reconsidered in the future. 相似文献
45.
The use of tumble dryers in households is becoming more common. Tumble dryers, however, consume large amounts of electric energy. A statistical model over the tumble dryer is created from a design of experiments. The model will be used to find the best settings for the power supply to the heater, the internal airflow and the external airflow in order to reach a high specific moisture extraction rate (SMER) and a low leakage ratio of water vapour. The aim also involves explaining the trends of the SMER and the leakage ratio based on the physics of the tumble dryer drying process. A statistically significant model, which can be used for improving the SMER and leakage ratio, was established from 19 experiments in a condensing tumble dryer. The results show that a high power supply to the heater, a high internal airflow and a low external airflow give the highest SMER values. This combination of settings also results in the largest leakage ratio values for the dryer. Leakage is most affected by the external airflow. 相似文献
46.
David Schmidl Niko S. W. Lindlar né Jonasson Annika Menke Dr. Sabine Schneider Prof. Dr. Lena J. Daumann 《Chembiochem : a European journal of chemical biology》2022,23(11):e202100605
The activation of molecular oxygen for the highly selective functionalization and repair of DNA and RNA nucleobases is achieved by α-ketoglutarate (α-KG)/iron-dependent dioxygenases. Of special interest are the human homologues AlkBH of Escherichia coli EcAlkB and ten-eleven translocation (TET) enzymes. These enzymes are involved in demethylation or dealkylation of DNA and RNA, although additional physiological functions are continuously being found. Given their importance, studying enzyme-substrate interactions, turnover and kinetic parameters is pivotal for the understanding of the mode of action of these enzymes. Diverse analytical methods, including X-ray crystallography, UV/Vis absorption, electron paramagnetic resonance (EPR), circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy have been employed to study the changes in the active site and the overall enzyme structure upon substrate, cofactor, and inhibitor addition. Several methods are now available to assess the activity of these enzymes. By discussing limitations and possibilities of these techniques for EcAlkB, AlkBH and TET we aim to give a comprehensive synopsis from a bioinorganic point-of-view, addressing researchers from different disciplines working in the highly interdisciplinary and rapidly evolving field of epigenetic processes and DNA/RNA repair and modification. 相似文献
47.
Alexandra C. Green Lena M. Lidfors Sabrina Lomax Livio Favaro Cameron E.F. Clark 《Journal of dairy science》2021,104(1):826-838
Mammalian vocalizations can encode contextual information in both the spectrographic components of their individual vocal units and in their temporal organization. Here we observed 23 Holstein-Friesian dairy cows immediately after birth during interactions with their calf and when their calf was separated to the other side of a fence line. We investigated whether the vocalizations emitted in these postpartum contexts would vary temporally. We also described the maternal and stress behaviors preceding and following postpartum vocal production using kinematic diagrams and characterized call sequence structure. The kinematic diagrams highlight the disruption of maternal responses caused by calf separation and show that behavioral and vocal patterns varied according to the cows' emotional states and proximity to the calf in both contexts. During calf interactions, cows mainly produced closed-mouth calls simultaneous to licking their calf, whereas an escalation of stress responses was observed during calf separation, with the cows approaching the fence line, becoming alert to the calf, and emitting more mixed and open-mouth calls. Call sequences were similarly structured across contexts, mostly containing repetitions of a single call type, with a mean interval of 0.57 s between calls and a greater cumulative vocalization duration, attributed to an increased number of vocal units per sequence. Overall, calf separation was associated with a greater proportion of calls emitted as a sequence (inverse of single isolated calls), a shorter interval between separate call sequences, and a greater number of vocal units per sequence, compared with calf interactions. These temporal vocal features varied predictably with the high stress expression from cows during calf separation and may represent temporal modulations of emotional expression. Despite the noisy farm soundscape, empirical call type and temporal vocal features were easy to measure; thus, findings could be applied to future cattle studies wishing to analyze vocalizations for on-farm welfare assessments. 相似文献
48.
Kaushik Viswanathan Iyer Max Müller Lena Sophie Tittel Prof. Dr. Marie-Luise Winz 《Chembiochem : a European journal of chemical biology》2023,24(20):e202300611
During translation, messenger RNAs (mRNAs) are decoded by ribosomes which can stall for various reasons. These include chemical damage, codon composition, starvation, or translation inhibition. Trailing ribosomes can collide with stalled ribosomes, potentially leading to dysfunctional or toxic proteins. Such aberrant proteins can form aggregates and favor diseases, especially neurodegeneration. To prevent this, both eukaryotes and bacteria have evolved different pathways to remove faulty nascent peptides, mRNAs and defective ribosomes from the collided complex. In eukaryotes, ubiquitin ligases play central roles in triggering downstream responses and several complexes have been characterized that split affected ribosomes and facilitate degradation of the various components. As collided ribosomes signal translation stress to affected cells, in eukaryotes additional stress response pathways are triggered when collisions are sensed. These pathways inhibit translation and modulate cell survival and immune responses. Here, we summarize the current state of knowledge about rescue and stress response pathways triggered by ribosome collisions. 相似文献
49.
Ethik in der Medizin - 相似文献
50.
Norgauer Philipp Grunewald Laura Priester Lena Heilemann Jens Hein Michael Stahl Karsten 《Forschung im Ingenieurwesen》2020,84(2):141-150
Forschung im Ingenieurwesen - Schneckengetriebe finden sich in verschiedenen Anwendungen als Stell- und Leistungsgetriebe. Aufgrund der Realisierbarkeit einer hohen Übersetzung bei kleinem... 相似文献