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21.
Flow alteration and thermal pollution depress modelled growth rates of an iconic riverine fish,the Murray cod Maccullochella peelii 下载免费PDF全文
Nick S. Whiterod Shaun N. Meredith Paul Humphries Bradford S. Sherman John D. Koehn Robyn J. Watts Brett A. Ingram Tom Ryan 《Ecology of Freshwater Fish》2018,27(3):686-698
The serial discontinuity concept (SDC) proposes that hypolimnetic‐releasing impoundments cause major disruptions to the naturally occurring physical, chemical and biological gradients of rivers but that this impact diminishes with distance downstream. Such a gradient in discharge, flow velocity and temperature regime occurs below a large hypolimnetic‐releasing impoundment, the Hume Dam, on the River Murray in south‐eastern Australia. To examine the effects of this disturbance gradient on a warm‐water large‐bodied freshwater fish, the Murray cod (Maccullochella peelii), a bioenergetics model was developed and calibrated to explore energy expended under differing water velocities and temperature regimes. Model simulations predicted negative growth of juveniles directly downstream of the impoundment, due largely to the energetic costs associated with active and, to a lesser extent, standard metabolism outweighing the achievable energetic gains through food consumption. As flow velocity and temperature regimes became more favourable downstream, so did the simulated growth of the species. It was not until +239 km downstream of the impoundment that the model predicted that flow velocity and temperature regimes were suitable for greater weight gains. The modelled growth responses of juvenile Murray cod are consistent with the predictions of the SDC, emphasising that changes in the bioenergetics of individuals are likely to be reflected in reduced growth rates under the changed flow velocity and temperature regimes imposed by disturbance gradients. This research represents a valuable step in the biological understanding of Murray cod within variable riverine environments and emphasises the urgency required to mitigate impacts associated with hypolimnetic impoundments. 相似文献
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André Fischer Sbrissia Daniel Schmitt Paulo Gonçalves Duchini Sila Carneiro Da Silva 《Journal of Agronomy and Crop Science》2020,206(5):630-639
It is well reported in the scientific literature that pastures can have similar net forage accumulation when managed with contrasting structures. However, we hypothesized that the dynamics of forage accumulation in grazed swards is linked to seasonal-environmental conditions. Marandu palisadegrass (Brachiaria brizantha [Hochst. ex A. Rich.] was used as the forage species model. The experimental treatments were four grazing heights (10, 20, 30 and 40 cm) allocated to experimental units according to a randomized complete block design with four replicates and evaluated throughout four contrasting environmental seasons (summer, autumn, winter–early spring and late spring). Under rainy and warm periods, greater net forage accumulation was observed in pastures maintained taller; on the contrary, during the mild and dry periods, net forage accumulation rate reduced as grazing height increased. Such patterns of responses were related to compensations between tiller population density and tissues flows during summer and late spring and the reduced capacity of taller canopies to compensate lower population with greater growth rates during autumn and winter–early spring. Grazed swards changed their patterns of forage growth as they transitioned from favourable to more abiotic stressful conditions, suggesting that seasonal adjustments in grazing intensities are necessary in order to maximize forage production. 相似文献
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In this article, through the combination of nucleic acid probes and immune chromatography, a simple, sensitive and specific detection system——nucleic acid lateral flow immunoassay (NALFIA) for amplifing foot-and-mouth disease virus (FMDV) 3D RT-PCR products was established.An ultrasensitive nucleic acid biosensor (NAB) based on streptavidin-labeled gold nanoparticles dual labels and lateral flow strip biosensor (LFSB) were used in this system.The biotinylated goat anti-rabbit IgG was marked to the NC membrane as the alleged strip and the anti-digoxin antibody was labeled to the NC membrane to capture the digoxin probe.After assemblying gold-labeled strip and detecting RT-PCR products, the detection limit of NALFIA was 0.3×10-3 to 3×10-3 μg/μL.The NALFIA was compared with agar gel electrophoresis analysis, the results showed that the sensitivity of NALFIA was higher than agar gel electrophoresis.There was an excellent agreement between the two methods.NALFIA was a method with high sensitive, low cost and short time.In conclusion, this method provided a good alternative to detect FMDV. 相似文献
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为了提高长输管道仿真精度和速率,基于MacCormack格式基本原理和流动方程建立了长输液体管道水力瞬变流动仿真模型。以某管道为例,分别采用该仿真算法和特征线法模拟了阀门关闭和流量增加引起的瞬变流动,并探讨了MacCormack格式中不同边界条件处理方法及Courant常数值对模拟结果的影响。结果表明:MacCormack格式可用于精确仿真长输管道瞬变流动过程,采用特征线法求解预估层边界参数后,其振荡幅度、收敛速度均优于特征线仿真方法;同时,采用特征线法处理MacCormack格式边界条件较线性外插法更易收敛。研究成果可为长输管道瞬变流动仿真提供参考。 相似文献
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How to characterize ‘good’ and ‘greening’ in the EU Common Agricultural Policy (CAP): the case of clay soils in the Netherlands 下载免费PDF全文
The change in the Common Agricultural Policy (CAP) of the European Union from product to producer support, including requirements for ‘good agricultural and environmental conditions’ and ‘greening’, is excellent. However, these requirements are now defined in rather general terms. Questions can be raised about suitable indicators, and there is a recognized need for effective management recommendations to support farmers in achieving the required ‘good’ conditions. These recommendations are bound to be quite different for different soils in different countries. A study of Dutch clay soils was based on a storyline describing current problems and management options for improvement, which were quantified using a soil–water–crop simulation model. Indicators were defined for agricultural conditions and suggestions made for the use of the model in a predictive mode to help farmers improve their soil management. Environmental conditions were judged by current environmental guidelines for water and air. When modelling, implicit assumptions that soils are homogeneous were shown to be unrealistic for these clay soils, requiring development of innovative methods and procedures, presenting a challenge for soil research. 相似文献
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为了探究坎儿井衰减与地下水补排系统响应关系,利用地下水位观测资料和坎儿井流量监测资料,结合鄯善县历次地下水资源调查评价资料和坎儿井统计数据,分析了地下水补给量、排泄量对坎儿井衰减的影响,并建立了最小二乘回归模型,在执行最严格水资源管理制度下对2020年、2030年坎儿井出水量进行了预测。结果表明,坎儿井流量动态与地下水位动态基本同步;北盆地的坎儿井出水量主要受地下水补给量的影响,南盆地主要受地下水开采量的影响。地下水开采量是影响鄯善县坎儿井衰减的关键因素,在最严格水资源管理制度下鄯善县坎儿井出水量将会在2020年恢复至0.83亿m~3,2030年恢复至0.87亿m~3。 相似文献
29.
The objective of this study was to find difference in vascular perfusion of uterine horns or uterine body throughout the estrous cycle and their relation to circulating nitric oxide and leptin concentrations. Five cyclic mares were subjected to transrectal Doppler ultrasonography and blood sampling for 18 days. Area of color and power Doppler modes was measured in pixels. Day (P = .0001) of the estrous cycle and ovulation (P = .0001) influenced uterine blood flow. Uterine body blood flow directed away from the transducer (blue, P = .0001) increased from day −5 until day 0 (day of ovulation), and its power (P = .0001) blood flow increased from day −6 until day 0; then, both decreased until days 12 and 10, respectively. Conversely to the contralateral uterine horn, ipsilateral uterine horn blood flow directed away from the transducer (blue, P = .0001) increased from day −5 until day −1, and its power (P = .0001) blood flow increased from day −6 until day 0; then, both decreased until day 10. Nitric oxide concentrations (P = .0001) attained two major peaks; the first on day −3 and the other persisted from day 2 until day 5. Leptin concentrations increased (P > .001) with a maximum value on day 0 and then decreased until a minimum value on day 9. In conclusion, during the estrous cycle, ipsilateral uterine horn and uterine body blood vessels had similar blood flow. Both leptin and nitric oxide played a role during follicle growth, ovulation, and corpus luteum development and modulated uterine blood flow before and after ovulation. 相似文献
30.
J P Furstenberg 《African Zoology》2013,48(2):165-173
Quantitative determination of nematode populations in soils frequently necessitates the mixing of representative soil samples to form a homogeneous, compound sample from which the nematodes are extracted. A mixing apparatus was developed and standardized with the aid of a spectrophotometric technique by which the dispersion of a dye through the soil during mixing could be determined. It was found that the mixer is most suitable for use on sandy loam soils. Optimal mixing is obtained at a speed of 15 rpm for 2 minutes. Under these conditions mechanical damage to nematodes during mixing is minimal. 相似文献