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81.
Kreysing M Pusch R Haverkate D Landsberger M Engelmann J Ruiter J Mora-Ferrer C Ulbricht E Grosche J Franze K Streif S Schumacher S Makarov F Kacza J Guck J Wolburg H Bowmaker JK von der Emde G Schuster S Wagner HJ Reichenbach A Francke M 《Science (New York, N.Y.)》2012,336(6089):1700-1703
Despite their diversity, vertebrate retinae are specialized to maximize either photon catch or visual acuity. Here, we describe a functional type that is optimized for neither purpose. In the retina of the elephantnose fish (Gnathonemus petersii), cone photoreceptors are grouped together within reflecting, photonic crystal-lined cups acting as macroreceptors, but rod photoreceptors are positioned behind these reflectors. This unusual arrangement matches rod and cone sensitivity for detecting color-mixed stimuli, whereas the photoreceptor grouping renders the fish insensitive to spatial noise; together, this enables more reliable flight reactions in the fish's dim and turbid habitat as compared with fish lacking this retinal specialization. 相似文献
82.
Growing evidence for declines in bee populations has caused great concern because of the valuable ecosystem services they provide. Neonicotinoid insecticides have been implicated in these declines because they occur at trace levels in the nectar and pollen of crop plants. We exposed colonies of the bumble bee Bombus terrestris in the laboratory to field-realistic levels of the neonicotinoid imidacloprid, then allowed them to develop naturally under field conditions. Treated colonies had a significantly reduced growth rate and suffered an 85% reduction in production of new queens compared with control colonies. Given the scale of use of neonicotinoids, we suggest that they may be having a considerable negative impact on wild bumble bee populations across the developed world. 相似文献
83.
Behrens M Studt F Kasatkin I Kühl S Hävecker M Abild-Pedersen F Zander S Girgsdies F Kurr P Kniep BL Tovar M Fischer RW Nørskov JK Schlögl R 《Science (New York, N.Y.)》2012,336(6083):893-897
One of the main stumbling blocks in developing rational design strategies for heterogeneous catalysis is that the complexity of the catalysts impairs efforts to characterize their active sites. We show how to identify the crucial atomic structure motif for the industrial Cu/ZnO/Al(2)O(3) methanol synthesis catalyst by using a combination of experimental evidence from bulk, surface-sensitive, and imaging methods collected on real high-performance catalytic systems in combination with density functional theory calculations. The active site consists of Cu steps decorated with Zn atoms, all stabilized by a series of well-defined bulk defects and surface species that need to be present jointly for the system to work. 相似文献
84.
85.
Engel F. Hessel Felix GarlippHerman F.A. Van den Weghe Prof Dr Ir 《Journal of Equine Veterinary Science》2009
Among other factors (eg, bedding material, roughage), feed has an important effect on the airborne particle concentration in the stable air, in particular directly in the breathing zone of the horse during feeding. Therefore, this study was designed to analyze and compare the generation of different airborne particle fractions of diverse feed types and feed processing techniques under standardized laboratory conditions. Oats and barley as well as two commercially formulated ready-prepared pellets and two different commercially formulated ready-prepared mixes were analyzed. Oats were subjected to four different forms of processing (whole uncleaned, whole cleaned, rolled uncleaned, rolled cleaned), barley was subjected to steam flaking in addition to the same forms of processing as oats. In total, 13 feeds were analyzed. Airborne particle concentrations were detected online with a gravimetrically measuring analyzer that was equipped successively with different inlets to measure the particle fractions PM 1, PM 2.5, PM 10, and PM 20. The measurements were carried out in a closed chamber (1 × 1 × 1.5 m) including a bowl (diameter = 0.5 m), which simulated the trough. The sample inlet was situated at a height of 1.0 m above the bowl. Rolling oats and barley led to a significantly increased generation of the PM 20 fraction and a significantly decreased generation of the PM 2.5 fraction. The mechanical cleaning of oat and barley brings a clear decrease in dust generation from straights whether they are left whole or are rolled after cleaning. A considerable reduction in dust generation can be achieved if steam-flaked barley or commercially prepared feeds are used. 相似文献
86.
Immunoreactive corticosterone and corticosterone metabolites (ICCM) were quantified in excreta of permanently single housed (n = 10) and permanently pair housed (n = 20) roosters. The pair housed roosters were separated and single housed, and ICCM were quantified in the droppings before and during 15 days after separation. There was no statistically significant difference in ICCM excretion in the droppings between the permanently single or pair housed roosters. After separation, however, the previously pair housed roosters showed a significantly transient elevated excretion of ICCM in droppings the second day after separation indicating that the separation and relocation is associated with an activation of the hypothalamic-pituitary-adrenal axis.The excretion of ICCM in droppings was not correlated to the concentration of ICCM in droppings. It is thus important that excretion of ICCM be expressed as amount excreted per time unit since the total excretion is dependant on both concentration of ICCM and amount of droppings produced. 相似文献
87.
RL Read CG Duncan AD Wallace JA Perry FM Duerr 《Journal of the American Veterinary Medical Association》2012,241(6):782-787
Objective-To compare calibration methods for digital radiography in terms of measurement accuracy and interobserver variability. Design-Prospective study. Sample-Digital radiographic images of a 155-mm-long Steinmann pin. Procedures-Measurement of pin length on digital radiographs was determined with a 25.4-mm-diameter calibration ball and commercially available software program via 3 calibration methods (ie, no calibration, autocalibration, and manual calibration). Digital radiographs of the calibration ball and pin were obtained with each placed at various vertical heights from the table (7 heights) and horizontal distances from the center of the beam (4 distances). Measurements of pin length on digital radiographs were made by 4 observers who were blinded to the orientation of the calibration ball and pin. Results-Pin lengths obtained by each calibration method were significantly different from each other and from the true value. Manual calibration was the most accurate. There was no significant interobserver variability in measurements. There was no significant change in measurements when the calibration ball was moved horizontally, but pin length measurements changed significantly when the ball was moved vertically (away from the table) with an approximate magnification error of 1% per centimeter of distance between the calibration ball and pin. Conclusions and Clinical Relevance-For digital radiography, manual calibration is recommended to achieve the most accurate measurements. Ideally, the calibration ball should be placed at the same vertical height as the object to be measured; however, if this cannot be achieved, the magnification error can be expected to be approximately 1% per centimeter of distance. 相似文献
88.
The effects of 3 supplemental Cu concentrations on feedlot performance, mineral absorption, carcass characteristics, and ruminal S metabolism of cattle fed diets containing 60% dried distillers grains with solubles (DDGS) were evaluated in 2 experiments. Experiment 1 was conducted with 84 Angus-cross yearling steers and heifers (initial BW = 238 ± 36 kg), which were blocked by gender and allocated to 12 pens. Supplemental dietary Cu (tribasic copper chloride) treatments were: 1) 0 mg Cu/kg diet DM, 2) 100 mg Cu/kg diet DM, 3) 200 mg Cu/kg diet DM. The remainder of the diet was DDGS (60%), grass hay (10%), pelleted soy hulls (15%), and a vitamin-mineral supplement (15%). Diets were offered ad libitum throughout the finishing phase (168 d). Three cattle from each pen (n = 36) were harvested on d 168 and carcass data and liver samples were collected. Copper supplementation did not affect ADG (P = 0.22). However, the nonsignificant trend for increased ADG and decreased DMI led to a linear increase (P = 0.02) feed efficiency (G:F = 0.167, 0.177, and 0.177 for 0, 100, and 200 mg Cu/kg diet DM, respectively). The apparent absorption of Cu decreased quadratically (P = 0.07) and the apparent absorption of Mn and Zn were decreased linearly (P = 0.03 and P = 0.05, respectively) with increased Cu supplementation. Cattle supplemented with 100 or 200 mg Cu/kg diet DM had greater liver Cu concentrations (P < 0.01) than cattle that were not supplemented with Cu. There were no treatment effects (P > 0.10) on HCW, LM area, USDA yield grade, backfat, or marbling score. Experiment 2 was conducted with 6 ruminally fistulated steers that were fed the same diets as in Exp 1 in a replicated 3 × 3 Latin Square design. Copper supplementation did not affect (P > 0.10) ruminal pH or liquid S(2-) concentrations in steers consuming 60% DDGS diets (total dietary S = 0.55%). From 3 to 9 h after feeding, H(2)S gas concentration was decreased in those cattle supplemented with 100 mg Cu/kg diet. Concentration of H(2)S gas did not differ among cattle supplemented with 0 or 200 mg Cu/kg diet DM on 60% DDGS diets. Supplemental Cu improved feed efficiency in cattle consuming diets containing 60% DDGS; however, effects of Cu on rumen S metabolism were minimal even when supplemented at twice the maximum tolerable limit for beef cattle (NRC, 2000). 相似文献
89.
As a result of the liberalisation of the agricultural market, mountain regions in Central Europe are at great risk of experiencing increasing land abandonment and spontaneous reforestation. Prior to taking measures for landscape maintenance, the ecological and landscape-aesthetic consequences of land abandonment should be analysed. This paper addresses the aesthetic component of such analyses: we investigated whether lay people perceive land abandonment and spontaneous reforestation as a loss or a gain and developed a prototypical technique for rapid aesthetic assessment of reforestation scenarios for vast regions.First, we conducted image experiments to assess the respondents' reactions to increasing levels of reforestation. Based on these experiments we concluded that a medium degree of reforestation is most desirable. Second, we analysed the relationship between scenic beauty and landscape patterns and found that landscape preference values correlate significantly with various quantitative measures of the landscape pattern (e.g., diversity and contagion indices of grey- tone and colour images). Third, we applied a GIS-assisted moving- window technique to transform spatially explicit remote-sensing data (in particular orthophotos) of a test region to spatially explicit data of landscape-pattern indices. Thanks to the significant positive correlation between pattern indices and landscape preference values, the resulting maps can preliminarily be interpreted as beauty-maps of the test-region. 相似文献
90.
Challenging diagnosis--icterus associated with a single perforating duodenal ulcer after long-term nonsteroidal antiinflammatory drug administration in a dog 下载免费PDF全文
Duerr FM Carr AP Bebchuk TN Pople NC 《The Canadian veterinary journal. La revue veterinaire canadienne》2004,45(6):507-510
A dog developed icterus, vomiting, and anorexia 2 wk after orthopedic surgery and treatment with meloxicam for approximately 1 y. Exploratory laparotomy revealed a single perforated duodenal ulcer. The most likely cause of the hyperbilirubinemia was intrahepatic cholestasis resulting from peritonitis associated with the perforation. 相似文献