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61.
Migratory songbirds use the geomagnetic field, stars, the Sun, and polarized light patterns to determine their migratory direction. To prevent navigational errors, it is necessary to calibrate all of these compass systems to a common reference. We show that migratory Savannah sparrows use polarized light cues from the region of sky near the horizon to recalibrate the magnetic compass at both sunrise and sunset. We suggest that skylight polarization patterns are used to derive an absolute (i.e., geographic) directional system that provides the primary calibration reference for all of the compasses of migratory songbirds. 相似文献
62.
We observe second-harmonic generation from metamaterials composed of split-ring resonators excited at 1.5-micrometer wavelength. Much larger signals are detected when magnetic-dipole resonances are excited, as compared with purely electric-dipole resonances. The experiments are consistent with calculations based on the magnetic component of the Lorentz force exerted on metal electrons-an intrinsic second-harmonic generation mechanism that plays no role in natural materials. This unusual mechanism becomes relevant in our work as a result of the enhancement and the orientation of the local magnetic fields associated with the magnetic-dipole resonances of the split-ring resonators. 相似文献
63.
Boroffka SA Voorhout G Verbruggen AM Teske E 《American journal of veterinary research》2006,67(10):1743-1749
OBJECTIVE: To assess intra- and interobserver repeatability of ocular biometric measurements obtained by means of high-resolution B-mode ultrasonography in dogs. Animals-6 Beagles without ocular abnormalities. PROCEDURES: B-mode ultrasonography was performed bilaterally with a 10.5-MHz broadband compact linear array transducer. All measurements were made on 2 different occasions by 2 observers. The Bland-Altman method was used to assess agreement between measurements obtained by the 2 observers and between the 2 sets of measurements obtained by each observer. RESULTS: Intra- and interobserver repeatability was highest for larger measurements, such as depth of the eye and depth of the anterior chamber. When repeatability was examined, bias was significantly different from 0 for only a few measurements, but the percentage difference between observations was as high as 180% for some measurements. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that most measurements of intraocular distances and structures obtained by means of high-resolution B-mode ultrasonography have acceptable intra- and interobserver repeatability. However, the percentage difference between observations can be high for smaller measurements. 相似文献
64.
65.
Evolved gas analysis (EGA) in combination with analytical pyrolysis is presented as a new technique for rapid investigations into wooden materials. In a first analytical step, the thermal behaviour of three wood samples was determined by EGA. Based on these results, analytical pyrolysis–gas chromatography/mass spectrometry was carried out to investigate the influence of wood-specific thermal behaviour and the chemical composition on the results. Furthermore, the influence of sample mass and particle size was examined. 相似文献
66.
Andersen SA Petersen HH Ersbøll AK Falk-Rønne J Jacobsen S 《Veterinary journal (London, England : 1997)》2012,191(2):199-202
European and American guidelines for vaccination against tetanus and influenza in horses recommend annual and annual/semi-annual vaccinations, respectively, against the two pathogens. Too-frequent vaccination may, however, have adverse effects, among other things because an inflammatory response is elicited with subsequent alterations in homeostasis. The objective of the study was to compare the acute phase response (APR) in 10 horses following administration of two different types of vaccines, namely, an inactivated Immune Stimulating COMplex (ISCOM) vaccine and a live recombinant vector vaccine. Blood was sampled before and after vaccination to measure levels of serum amyloid A (SAA), fibrinogen, white blood cell counts (WBC) and iron. Vaccination induced a prominent APR with increased WBC, elevated blood levels of SAA and fibrinogen, and decreased serum iron concentrations. The ISCOM vaccine caused significantly (P<0.05) greater SAA, fibrinogen and WBC responses than the vector vaccine. During the APR muscle catabolism and liver and kidney metabolism are altered. Also drug metabolism may change during the APR. The findings of the present study may be relevant for advising horse owners about convalescence after vaccination. 相似文献
67.
Sharifah N. Syed Jaafar Johanna Baron Susanne Siebenhandl‐Ehn Thomas Rosenau Stefan Böhmdorfer Heinrich Grausgruber 《Plant Breeding》2013,132(6):546-552
Due to their antioxidant activity, anthocyanins are of increasing interest for nutritionists, food scientists and plant breeders. Anthocyanins in wheat grains are expressed in either the pericarp or aleurone layer. Previous studies revealed that different anthocyanins are present in wheat varieties carrying genes for either the purple pericarp or the blue aleurone trait. Progeny from crosses between red‐, purple‐ and blue‐grained wheat varieties were selected over several cycles for grain colour by visual scoring. Bulked F5 grains were evaluated for their total anthocyanin content by UV‐VIS spectrophotometry and HPLC‐MS. The results demonstrate that it is possible to increase the anthocyanin content by the combination of the different genetic backgrounds for purple pericarp and blue aleurone, even though the majority of progeny were within the range of the purple‐ and blue‐grained check varieties. Visual scoring for grain colour is efficient, reliable and fast for selection in early breeding generations. Advanced breeding lines with high anthocyanin content can be identified by simple extraction methods and spectrophotometric measurements. 相似文献
68.
Chris Stoate Stephen Jones Felicity Crotty Carol Morris Susanne Seymour 《Soil Use and Management》2019,35(1):150-159
Soil management influences food production, economic performance of farm businesses, and a range of public benefits such as water quality, flood control and aquatic and terrestrial biodiversity. The aim of this paper is to explore the role of participatory research in combining scientific and farmer knowledge of soils to meet these multiple objectives. We use five separate research studies involving communication, consultation and co‐production, carried out in the English East Midlands between 2014 and 2018. We compare the participatory processes for knowledge exchange and their material outcomes and assess them retrospectively against specified criteria for successful application of participatory research. We conclude that, depending on context and scalar fit, multiple approaches to participatory research can be complementary, strengthen engagement and build trust within a farming community, resulting in a greater shared understanding of how to address the soil management objectives of farmers and wider society. 相似文献
69.
Elisabeth Oldenburg Susanne Kramer Stefan Schrader Joachim Weinert 《Soil biology & biochemistry》2008,40(12):3049-3053
When conservation tillage is practised in agriculture, plant residues remain on the soil surface for soil protection purposes. These residues should be widely decomposed within the following vegetation period as microbial plant pathogens surviving on plant litter may endanger the currently cultivated crop. Important soil-borne fungal pathogens that preferably infect small grain cereals belong to the genus Fusarium. These pathogens produce the mycotoxin deoxynivalenol (DON), a cytotoxic agent, in infected cereal organs. This toxin frequently occurs in cereal residues like straw. So far it is unclear if DON degradation is affected by members of the soil food web within decomposing processes in the soil system. For this purpose, a microcosm study was conducted under controlled laboratory conditions to investigate the degradation activity of the earthworm species Lumbricus terrestris when exposed to Fusarium-infected wheat straw being contaminated with DON.Highly Fusarium-infected and DON-contaminated straw seemed to be more attractive to L. terrestris because it was incorporated faster into the soil compared with straw infected and contaminated at low levels. This is supported by a greater body weight gain (exposure time 5 weeks) and smaller body weight loss (exposure time 11 weeks) of L. terrestris, respectively, when highly contaminated straw was offered for different time periods.Furthermore, L. terrestris takes part in the efficient degradation of both Fusarium biomass and DON occurring in straw in close interaction with soil microorganisms. Consequently, earthworm activity contributes to the elimination of potentially infectious plant material from the soil surface. 相似文献
70.
Susanne L?fgren Stina Ekman Ylva Terelius Ronny Fransson-Steen 《Acta veterinaria Scandinavica》2008,50(1):47