A deterministic bio-economic model was used to estimate the economic values of different traits in Arabic sheep native to the Khuzestan province of Iran. In the studied system, variable costs accounted for about 98.5% of the total costs and among variable costs, feed costs had the highest proportion with 70.7%. Revenue sources included meat, wool, and manure, where meat was the most important one and formed 95.5% of total revenues. Economic value for a trait was estimated as the amount of change in the profit of system as its mean increased by one unit, while the means of other traits were constant. The most important trait in this system was litter size, followed by ewe survival, dressing percentage, and wool weight, respectively. Birth weight had a negative economic value but weight at older ages especially weaning weight and 12-month weight had positive economic values. The sensitivity of economic values of traits was investigated by changing feed and non-feed costs, meat and wool prices by ±10%. Results showed that economic values for dressing percentage and wool weight are not sensitive to change in costs. In addition, changes in marketing and management costs had no effect on the economic value for traits related to body weight in different ages. In general, the economic value for traits which showed sensitivity to the changes of costs, except ewe survival, decreased due to an increase in costs. The economic value for all traits, except birth and wool weight, changed because of a change in meat price. Increasing meat price meant a higher economic importance. Among different factors, meat price fluctuations had the most effect on the economic value of traits. 相似文献
Goal, Scope, and Background The paper describes the integration of the economic input–output life cycle assessment (EIO-LCA) model and the environmental
fate and transport model (CHEMGL) with a risk assessment tool. Utilizing the EIO-LCA, instead of a traditional LCA, enables
a rapid, screening-level analysis of an emerging chemical of concern, decabromodiphenyl ether (DecaBDE). The risk assessment
in this study is evaluated based on the mass of chemical released, estimated concentrations, exposure, and chemical toxicity.
Methods The relative risk from ten economic sectors identified within the EIO-LCA model, 55 chemicals utilized in those sectors and
DecaBDE along with four potential DecaBDE breakdown products, were evaluated for the life cycle stages and exposure pathways.
The relative risk (expressed as toluene equivalents) of the different chemicals, sectors, and life cycle stages were compared
to assess those representing the greatest overall relative risks to humans (via inhalation and ingestion) and fish.
Results The greatest overall risk to human health resulted from the manufacturing and production stages. For fish, the manufacturing
stage represented virtually all of the risk. Of the 56 chemicals evaluated, DecaBDE represented the majority of the total
risk to humans. However, DecaBDE posed the least risk compared to its potential breakdown products.
Discussion The risk to humans from ingestion, which represented the greatest risk, from the production, manufacturing, and consumption
stages can be controlled and reduced through various safety precautions in the workplace. Additionally, the increasing concentration
of DecaBDE in anaerobic compartments represents a threat to humans and fish via the higher risk DecaBDE breakdown products.
Conclusions Overall, the manufacturing and production life cycle stages pose the greatest risk to humans and fish. The sediment compartment
received the highest DecaBDE concentration for the production, manufacturing, and consumption stages. This case study demonstrates
that the integrated EIO-LCA with risk assessment is suitable for screening-level analysis of emerging chemicals due to rapid
life cycle inventory analysis.
Recommendations The production and manufacturing stages allow for greater industry control and government regulation, compared to the consumption
stage, because there are fewer point sources. This integrated life cycle methodology may allow chemical designers to evaluate
each stage and assess areas where risks can be minimized. 相似文献
From a practical point of view, the most efficient strategy for pest control is to combine an array of techniques to control the wide variety of potential pests that may threaten crops in an approach known as integrated pest management (IPM). In this paper, we propose a predator-prey (pest) model of IPM in which pests are impulsively controlled by means of spraying pesticides (the chemical control) and releasing natural predators (the biological control). It is assumed that the biological and chemical control are used with the same periodicity, but not simultaneously. The functional response of the predator is allowed to be predator-dependent, in the form of a Beddington-DeAngelis functional response, rather than to have a perhaps more classical prey-only dependence. The local and global stability of the pest-eradication periodic solution, as well as the permanence of the system, are obtained under integral conditions which are shown to have biological significance. In a certain limiting case, it is shown that a nontrivial periodic solution emerges via a supercritical bifurcation. Finally, our findings are confirmed by means of numerical simulations. 相似文献
Approximately 75% of the cost to load, haul, and deliver a weekly supply of herbaceous biomass from temporary storage locations near the production fields to a bioprocessing plant (50 Mg/h average capacity, 24/7 operation) is truck cost. The management policy that a bioprocessing plant uses to schedule trucks determines the maximum number of trucks required, and thereby, the total cost for the logistic system. Three land use rates corresponding to 50%, 45%, and 40% of existing pastureland within a 3.2-km radius of chosen satellite storage locations were used to establish a production base surrounding the plant location. Total area harvested was 25,500 ha, or about 2.1% of the total land area in the 7-county region studied. Assumed average yield was 8.3 Mg/ha. Two different management policies, one based on travel time (Policy 1) and another based on the assignment of trucks to given sectors of the surrounding production base (Policy 2) were used to develop truck schedules. The logistic system was modeled as a discrete event simulation model, and the schedule was validated.
The maximum number of trucks needed for the logistic system was 32, 33 and 34 for 50%, 45% and 40% land use rates, respectively. In Policy 1, the maximum number of loads accumulated in the at-plant inventory was 384 truckloads at 50% land use rate (maximum inventory corresponds to about 3 days of plant operation). In Policy 2, the maximum number of loads accumulated in the at-plant inventory was 330 truckloads at 50% land use rate. Total number of loader and unloader operating hours for both the policies was computed, and the loader and unloader utilization rates were 83.5% and 70.8%, respectively. The delivered cost (load, haul, and unload) varied from $14.68 (Policy 1) to $16.14 per Mg (Policy 2) for 15% w.b. moisture content biomass. 相似文献
Abstract 1 The red turpentine beetle, Dendroctonus valens LeConte, is a recent New World introduction to the People's Republic of China. An outbreak of these beetles has infested over 0.5 million hectares of pine forests. 2 Efforts are underway to suppress this outbreak using biological control measures. However, the wide distribution in the native range of D. valens suggests regional variation of the beetle's biology, predators, and parasitoids. Thus, knowledge of the origin of these beetles can help devise precise and effective control measures. 3 A portion of the mitochondrial cytochrome oxidase subunit I gene was sequenced for 218 individuals from 32 populations throughout the native range of D. valens and in China. 4 Haplotype diversity was high. A total of 131 haplotypes were found and Jukes–Cantor corrected nucleotide difference ranged from 0 to 16%. Haplotype diversity ranged from 0.53 to 0.98 and unique haplotypes were found in most populations. 5 Parsimony and statistical parsimony analyses of these haplotypes support the hypothesis that the introduction of D. valens to China was recent and originated from the Pacific North‐west of the U.S.A. 6 In addition, the high haplotype diversity also suggests a large or multiple introductions. However, based on the genetics of the beetle's reproductive behaviour, this diversity may also be explained by a limited number of individuals or introductions. 相似文献
This paper analyzes data on approximately 30,000 women from a survey in Uttar Pradesh in 1995 together with the data from surveys of public and private providers of healthcare and family planning services. A framework was developed for analyzing the effects of quality of services on utilization, and for understanding the gradual evolution of the healthcare infrastructure. The empirical results from logistic regressions for use of female sterilization and IUD showed significant effects of quality of services in government and private hospitals, and of socioeconomic variables such as education, caste, and an index of household possessions. Secondly, models for infant mortality of children born in the preceding 3-year period showed significant effects of socioeconomic variables, quality of healthcare services and birth spacing. Lastly, analysis of data at a more aggregated (Primary Sampling Unit) level indicated differential effects of economic development on the quality of services available in the public and private facilities. 相似文献
This study estimates the economic values of and the dominant contributors to five key ecosystem services of wetlands in Beijing, by using the wetland inventory data in 2014 and economic valuation methods. Results indicate that the 51,434 ha of wetlands in Beijing annually provide 2.07 billion m3 of flood regulation, 944.01 million m3 of water provision, 42,154 tons of chemical oxygen demand (COD) purification, 3.03 PJ of heat absorption, and 9587 ha of habitat. Their economic values are estimated to be 15.89 billion RMB, 1.19 billion RMB, 169 million RMB, 421 million RMB, and 1.08 billion RMB in 2014 (RMB: Chinese currency, US$1 = RMB 6.14), respectively. The total values of five key wetland ecosystem services reach 18.76 billion RMB. In addition, the reservoir and river wetlands in Miyun, Yanqing, Fangshan, Huairou, and Mentougou Districts contribute 78% of key ecosystem services, whereas the urban wetlands in Xicheng, Dongcheng, Haidian, Chaoyang, and Tongzhou Districts more conveniently serve densely local people, hence they should be given particular attentions. In this paper, we develop the valuation methods of wetland ecosystem services, and recommend diversified strategies, regulations, and programs to protect the remaining wetlands in Beijing. This work can also provide a reference for the valuating of wetland ecosystem services for other urban-rural areas. 相似文献
A commercially important coral-reef fish, the spangled emperor Lethrinus nebulosus, settles into seagrass beds at the end of its pelagic larval phase, but the mechanism for locating these beds is unknown. To investigate this mechanism we first used a wide-choice, ex situ setup to examine the ability of captivity-reared naïve L. nebulosus settlers to select their first benthic habitat by reference to chemical cues. Second, we examined the morphology and ultrastructure of the nasal olfactory organ in settling L. nebulosus juveniles. We obtained the first evidence of a tropical seagrass-settling coral reef fish that can use chemical environmental cues in selecting its first benthic habitat at ranges up to at least 2 m. The L. nebulosus settlers exhibited a well developed pair of nasal olfactory organs, positioned in nares on the dorsal side of the head. These organs were elliptical radial rosettes, one in each of the olfactory chambers, and each comprised 12 lamellae, six on each side of a midline raphe, which were totally covered with sensory and non-sensory cilia, except for the margins. This type of cilia distribution is thought to indicate an acute sense of smell. The olfactory epithelium contained mature and immature ciliated receptor neurons bearing three to five cilia, and a second type of receptor neuron bearing six to eight microvilli. 相似文献