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21.
22.
Sullivan TJ Moore JA Thomas DR Mallery E Snyder KU Wustenberg M Wustenberg J Mackey SD Moore DL 《Environmental management》2007,40(6):958-965
An experimental study was conducted in Tillamook, Oregon, USA, to quantify the effectiveness of edge-of-field vegetated buffers
for reducing transport of fecal coliform bacteria (FCB) from agricultural fields amended with dairy cow manure. Installation
of vegetated buffers on loamy soils dramatically reduced the bacterial contamination of runoff water from manure-treated pasturelands,
but the size of the vegetated buffer was not an important determinant of bacterial removal efficiency. Only 10% of the runoff
samples collected from treatment cells having vegetated buffers exhibited FCB concentrations >200 colony forming units (cfu)/100
mL (a common water quality standard value), and the median concentration for all cells containing vegetated buffers was only
6 cfu/100 mL. The presence of a vegetated buffer of any size, from 1 to 25 m, generally reduced the median FCB concentration
in runoff by more than 99%. Results for FCB load calculations were similar. Our results suggest that where substantial FCB
contamination of runoff occurs from manure-treated pasturelands, it might be disproportionately associated with specific field
or management conditions, such as the presence of soils that exhibit low water infiltration and generate larger volumes of
runoff or the absence of a vegetated buffer. Buffer size regulations that do not consider such differences might not be efficient
or effective in reducing bacterial contamination of runoff. 相似文献
23.
Sam M. Jones Jelle S. van Zweden Christoph Grüter Cristiano Menezes Denise A. Alves Patrícia Nunes-Silva Tomer Czaczkes Vera L. Imperatriz-Fonseca Francis L. W. Ratnieks 《Behavioral ecology and sociobiology》2012,66(1):1-12
Recent research has shown that entrance guards of the stingless bee Tetragonisca angustula make less errors in distinguishing nestmates from non-nestmates than all other bee species studied to date, but how they
achieve this is unknown. We performed four experiments to investigate nestmate recognition by entrance guards in T. angustula. We first investigated the effect of colony odours on acceptance. Nestmates that acquired odour from non-nestmate workers
were 63% more likely to be rejected while the acceptance rate of non-nestmates treated with nestmate odour increased by only
7%. We further hypothesised that guards standing on the wax entrance tube might use the tube as an odour referent. However,
our findings showed that there was no difference in the acceptance of non-nestmates by guards standing on their own colony’s
entrance tube versus the non-nestmate’s entrance tube. Moreover, treatment of bees with nestmate and non-nestmate resin or
wax had a negative effect on acceptance rates of up to 65%, regardless of the origin of the wax or resin. The role of resin
as a source of recognition cues was further investigated by unidirectionally transferring resin stores between colonies. Acceptance
rates of nestmates declined by 37% for hives that donated resin, contrasting with resin donor hives where acceptance of non-nestmates
increased by 21%. Overall, our results confirm the accuracy of nestmate recognition in T. angustula and reject the hypothesis that this high level of accuracy is due to the use of the wax entrance tubes as a referent for
colony odour. Our findings also suggest that odours directly acquired from resin serve no primary function as nestmate recognition
cues. The lack of consistency among colonies plus the complex results of the third and fourth experiments highlight the need
for further research on the role of nest materials and cuticular profiles in understanding nestmate recognition in T. angustula. 相似文献
24.
25.
A case of confined placental mosaicism (CPM) and maternal uniparental isodisomy 14 identified after placental karyotype revealed trisomy 14 in a newborn with intrauterine growth restriction (IUGR) and minor dysmorphic features is reported. During the second trimester of the pregnancy, multiple marker screening revealed an increased risk for Down syndrome of >1 in 10. The maternal serum human chorionic gonadotrophin (MShCG) was markedly elevated at 4.19 MoM. Amniocentesis revealed a normal 46,XX karyotype. Fetal growth restriction has been associated with elevated MShCG and placental aneuploidy with CPM for chromosomes 2, 7, 9 and 16. The present case of CPM for chromosome 14 was also associated with fetal growth restriction and elevated second trimester MShCG, suggesting a common link. Further studies need to be done to determine if indeed elevation of second trimester MShCG is associated with increased risk of CPM. The present case again demonstrates the need to perform placental karyotype in unexplained fetal growth restriction. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
26.
Sam StroichJr. 《Conservation biology》1996,10(2):315-315
27.
Sam H. Johnson Alan C. Early Max K. Lowdermilk 《Journal of the American Water Resources Association》1977,13(6):1253-1268
ABSTRACT: Examples are drawn from the Indus Basin to explain why on-farm water management problems restrict the output of agricultural products in many LDC's. Data is presented to illustrate the low level of water management knowledge of both the farmers and the current extension agents. Examples of the level of corruption and its effect on the operating system are illustrated. Several requirements that must be met before a large-scale irrigation scheme will actually increase the welfare of LDC's farmers are presented. 相似文献
28.
Peng LianXiaodan Gao M. Sam Mannan 《Journal of Loss Prevention in the Process Industries》2012,25(1):103-113
Flammable aerosols have created many fire and explosion hazards in the process industry, but the flammability of aerosols has not been fully understood. The minimum ignition energy has been widely used as an indicator for flammability of combustible mixtures, but the amount of experimental data on the minimum ignition energy of aerosols is very limited. In this work, the minimum ignition energy of tetralin aerosols is predicted using an integrated model. The model applies the flame front propagation theory in aerosol systems to the growth of the flame kernel, which was created during the spark discharge in the ignition process. The aerosol minimum ignition energy was defined as the minimum level of energy in the initial flame kernel to maintain the kernel temperature above the minimum ignition temperature of 1073 K specific for tetralin aerosols during the kernel growth. The minimum ignition energy obtained in the model is influenced by the fuel-air equivalence ratio and the size of the aerosol droplets. For tetralin aerosols of 40 μm diameter, Emin decreases significantly from 0.32 mJ to 4.3 × 10 e−3 mJ when the equivalence ratio rises from 0.57 to 1.0. For tetralin aerosols of 0.57 equivalence ratio, Emin increases from as 0.09 mJ to 0.32 mJ when the droplet diameter rises from 10 μm to 60 μm. The trends are in agreement with previous experimental observations. The method used in current work has the potential to prediction of the minimum ignition energy of aerosol. 相似文献
29.
Christian Diaz-Ovalle Richart Vazquez-Roman Raul Lesso-Arroyo M. Sam Mannan 《Journal of Loss Prevention in the Process Industries》2012,25(6):974-981
Curtain mitigation systems are modeled here since they have experimentally shown their efficiency in reducing the concentration of certain toxic gases within dense gas clouds. Air, water and steam are analyzed in a model as the physical barriers to decrease the gas concentration. The model, developed for a steady-state mitigation process, is based on the mass, energy and momentum conservation laws. Concentration estimations during the dispersion before and after the mitigation are performed with a SLAB type model. A sensitivity analysis for each model is given to detect which variables have bigger effects. A release of chlorine is used as an example and the results are calculated in a prototype developed in Visual C++, where the model is solved using the Runge–Kutta 4th order method. The results include the effects of composition, speed, temperature and height of the releasing point as well as a comparison with CFD simulations. The proposed model is simplified and it cannot reproduce eddy effects but it is fast and robust enough. The model provides a set of equations that can be used in numerical problems where explicit derivatives are required, e.g. optimizations procedures. 相似文献
30.
Alba Pineda-Solano Lina Saenz-Noval Subramanya Nayak Simon Waldram Maria Papadaki M. Sam Mannan 《Process Safety and Environmental Protection》2012,90(5):404-410
Alkylpyridine N-oxides are important intermediates in the pharmaceutical and agrochemicals industries. The N-oxides are produced via the homogeneously catalyzed oxidation of the respective alkylpyridines using a 50% excess of hydrogen peroxide. The competitive hydrogen peroxide decomposition produces oxygen in the flammable environment of alkylpyridines and thus forms a key hazard for this reaction. In this work, the N-oxidation was performed under pressure in the temperature range of 110–125 °C with different catalyst concentrations. It was shown that temperature had an undisputable positive effect on the N-oxidation efficiency. The accurate measurement of the pressure rise due to decomposition was difficult. However, only 5% of the added H2O2 decomposed when stoichiometric quantities were employed, even in the temperature of 110 °C. The N-oxidation was very efficient, even when the lowest concentration of catalyst employed in this study was used. 相似文献