臭氧果蔬保鲜包装技术及试验   总被引：5，自引：1，他引：5  

高德  谷吉海  董静  徐晓娟 《农业机械学报》2006,37(8):190-193

臭氧果蔬保鲜技术的关键是如何控制和调节包装内氧气和二氧化碳的体积分数,包装材料气透率是调节包装内气体体积分数的主要因素。综合果蔬呼吸和薄膜透气两个相互交叉的动态过程,提出一种新的果蔬包装薄膜透气率的计算方法。在清水蜜桃、油豆角的臭氧保鲜试验中测试了臭氧果蔬保鲜薄膜不同厚度以及不同保鲜时间的腐烂率、好果率、失重率、可溶性固形物含量、还原糖含量、总酸、维生素C含量、叶绿素含量等指标,结果表明,以上果蔬的保鲜期至少延长2周以上。  相似文献   

A comparison of soil- and canopy temperature-based methods for the early detection of water stress in a simulated patch of pasture     

Cecilia Stanghellini  Francesca De Lorenzi 《Irrigation Science》1994,14(3):141-146

This paper evaluates the sensitivity of two different methods of water stress detection in a simulated patch of pasture grown in a greenhouse. The performance of two indices, based respectively on canopy temperature and soil water content values — the latter gauged by means of a time domain reflectometry (TDR) system, was assessed against actual evapotranspiration, measured by a very accurate weighing system. Both methods were able to detect water shortage by the time transpiration was reduced to some 80% of its potential value. The soil-based index, however, relied on the estimate of root water extraction rate, which may not be known. It is concluded that detection of water shortage by means of a canopy temperature-based stress index is to be preferred to measuring soil water deficits by time domain reflectometry, despite the accuracy of the TDR-based soil water content estimate.  相似文献   

内燃机燃烧模型的发展现状   总被引：1，自引：0，他引：1  

史春涛  秦德  唐琦  田晓松 《农业机械学报》2007,38(4):181-186

利用CFD技术对内燃机燃烧过程进行数值模拟已成为内燃机研究的重要工具。选用恰当的燃烧模型对准确预测内燃机燃烧过程具有重要意义。内燃机CFD燃烧模型主要针对自燃、预混燃烧和非预混燃烧3种燃烧模式，其中有些模型可以同时模拟2种模式或3种模式。内燃机新的燃烧系统的不断出现促进了燃烧模型的发展。本文以STAR—CD和FIRE软件为出发点，介绍了内燃机燃烧模型的发展现状。  相似文献   

Modification of irrigation requirement of wheat through mulching and foliar application of transpiration suppressants     

Rajat De  D. V. S. Bhujanga Rao  Y. Yogeswara Rao  L. G. Giri Rao  M. Ikramullah 《Irrigation Science》1983,4(3):215-223

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聚乙酸乙烯酯乳液胶的改性   总被引：6，自引：1，他引：6  

张求慧  吴瑞萱  韦铮  张得荣 《木材工业》2001,15(1):26-27,30

本文介绍了用该改性乳液胶合的贴面胶合板的性能改性聚乙酸乙烯酯共聚乳液胶粘剂的聚合工艺，经过改性的乳液胶具有良好的耐水性，达到并超过日本二类特种合板标准，且生产工艺简单，原料易得，成本与普通乙酸乙烯酯均聚液接近,具有较强的实用性。  相似文献   

Transmission of methicillin resistant Staphylococcus aureus among pigs during transportation from farm to abattoir     

Els M. Broens  Elisabeth A.M. Graat  Peter J. Van Der Wolf  Arjen W. Van De Giessen  Mart C.M. De Jong 《Veterinary journal (London, England : 1997)》2011,189(3):302-305

The prevalence of methicillin resistant Staphylococcus aureus (MRSA) in pigs at abattoirs is higher than in pigs sampled on farms. This study investigated whether MRSA negative pigs can become MRSA positive during transportation from the farm to the abattoir after exposure to other pigs and environmental sources of MRSA. Nasal swabs were collected from four batches of pigs during loading at the farm, on arrival at the abattoir and after stunning. Environmental wipes were taken from lorries after transporting pigs and from lairages after holding pigs. All pigs (n = 117) tested MRSA negative before transportation. On arrival at the abattoir, 12/117 (10.3%) pigs in two batches tested MRSA positive. In lorries that tested positive after transportation, the prevalence of MRSA positive pigs was 21.1%, whereas no MRSA was detected in pigs that had been transported in lorries that tested negative after transportation. At stunning, all batches and 70/117 (59.8%) pigs tested MRSA positive. Pigs can become MRSA positive in the short period of time during transportation from the farm to stunning at the abattoir.  相似文献   

Cytokine expression, glucocorticoid and growth hormone changes after porcine reproductive and respiratory syndrome virus (PRRSV-1) infection in vaccinated and unvaccinated naturally exposed pigs     

Paolo Borghetti  Roberta SaleriLuca Ferrari  Marina MorgantiElena De Angelis  Valentina FranceschiEzio Bottarelli  Paolo Martelli 《Comparative immunology, microbiology and infectious diseases》2011,34(2):143-155

The objective of this paper was to study the changes of some cytokines and neuroendocrine hormones in vaccinated and unvaccinated pigs that were naturally infected by a PRRSV-1 (porcine reproductive and respiratory syndrome virus) heterologous field strain. We analyzed gene expression of pro-inflammatory (TNF-α, IL-1β, MCP-1, IL-6), pro-immune (IFN-γ) and anti-inflammatory cytokines (IL-10) in PBMC, as well as hormonal (GH and cortisol) levels in blood samples of pigs obtained in a field trial previously reported [Martelli P, Gozio S, Ferrari L, Rosina S, De Angelis E, Quintavalla C, et al. Efficacy of a modified-live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine in pigs naturally exposed to a heterologous European (Italian cluster) field strain: clinical protection and cell-mediated immunity. Vaccine 2009;27:3788-99]. All vaccinated pigs showed an increase in pro-inflammatory and pro-immune cytokine gene expression with respect to controls and a prompt increase in GH that could be consistently associated with pro-inflammatory cytokines in sustaining innate immunity; moreover, the higher levels of cortisol indicates the activation of the hypothalamus-pituitary-adrenal (HPA) axis response. In contrast, unvaccinated pigs showed down-regulation of the cortisol and GH responses, and the pro-inflammatory and pro-immune cytokines remained at a basal or low level, with an increase of TNF-α and IL-6 in association with a higher level of IL-10 in the late phase of natural infection. The associated trends of pro-inflammatory and anti-inflammatory cytokines together with the cortisol level demonstrate that a previous vaccination promotes an early immune responsiveness in pigs and a more efficient control of inflammation in the late phase of infection with a heterologous PRRSV isolate; both events could sustain clinical protection.  相似文献   

Dormouse injuries predispose beech to infection by Neonectria ditissima     

L. Montecchio  L. Scattolin  R. De Battisti 《Forest Pathology》2011,41(2):114-119

After awaking from winter hibernation, the Edible dormouse begins to feed by stripping the bark and the outer part of the xylem from the branches of both broadleaves and conifers. Natural or artificial wounds are essential for the penetration and colonisation of the tissues by the fungal pathogen Neonectria ditissima. This pathogen creates open cankers on beech branches and other broadleaves, which are frequently later infected by wood‐decaying fungi. Because of the high frequencies of both dormouse injuries and branch cankers in a large monospecific beech forest in northern Italy, field and laboratory investigations were conducted to verify whether rodent‐inflicted injuries on beech were a preferred infection point for the pathogen. These studies also examined the susceptibility to infection of the dormouse‐inflicted wounds over time, and the relationships between dormouse damage, Neonectria infection, and wood decay. The results showed a significant direct correlation between the percentage of infections and their proximity to the wounds, indicating that the parasite localises to sites where there are receptive dormouse injuries. In addition, the susceptibility of the wound was found to diminish with increasing age, disappearing in 120–150 days. The association between dormouse injuries, Neonectria cankers and wood decay was also found to cause approximately half of the frequent beech branch breakages during intense weather events.  相似文献   

Satisfaction across urban consumers of smallholder-produced teak (Tectona grandis L.f.) poles in South Benin     

Augustin K.N. Aoudji  Anselme Adégbidi  Jean C. Ganglo  Valentin Agbo  Armand S.I. Yêvidé  Charles De Cannière  Philippe Lebailly 《Forest Policy and Economics》2011,13(8):642-651

The study used the expectancy-disconfirmation framework to investigate the satisfaction among urban consumers of teak pole in South Benin, so as to identify the areas where interventions are needed to secure market opportunity for smallholder forestry. A survey was conducted in five cities; and 223 household-heads were interviewed using systematic sampling, with a random start. Data were collected on socio-demographic characteristics, teak pole consumption forms, behaviour patterns, and motivations. Respondents also rated their expectations and perceptions for a set of nine attributes on a 7 points Likert scale. Hierarchical ascending cluster analysis was performed to identify consumer segments; and satisfaction level was analysed per segment, by determining the gap between expectations and perceptions, for all attributes. Four consumer segments were identified; and sociodemographic profiles differed across those segments. Competitive price was an important purchasing motivation across the identified segments. Consumers were dissatisfied with price, availability, knot frequency, bending, length, hardness, and durability of teak pole. The efforts to meet the consumer expectations should be concentrated on building farmers' capacity in silvicultural management, and ensuring the availability of good planting material. The issue of competitive price might be addressed, through the improvement of the overall efficiency in the value chain.  相似文献   

Estimating diesel degradation rates from N₂, O₂ and CO₂ concentration versus depth data in a loamy sand     

J. Van De  Steene & H. Verplancke 《European Journal of Soil Science》2007,58(1):115-124

The degradation rate of the pollutant is often an important parameter for designing and maintaining an active treatment system or for determining the rate of natural attenuation. A quasi‐steady‐state gas transport model based on Fick’s law with a correction term for advective flux, for estimating diesel degradation rates from N₂, O₂ and CO₂ concentration versus depth data, was evaluated in a laboratory column study. A loamy sand was spiked with diesel fuel at 0, 1000, 5000 and 10 000 mg kg⁻¹ soil (dry weight basis) and incubated for 15 weeks. Soil gas was sampled weekly at 6 selected depths in the columns and analysed for O₂, CO₂ and N₂ concentrations. The agreement between the measured and the modelled concentrations was good for the untreated soil (R²= 0.60) and very good for the soil spiked with 1000 mg kg⁻¹ (R²= 0.96) and 5000 mg kg⁻¹ (R²= 0.97). Oxygen consumption ranged from −0.15 to −2.25 mol O₂ m⁻³ soil day⁻¹ and CO₂ production ranged from 0.20 to 2.07 mol CO₂ m⁻³ soil day⁻¹. A significantly greater mean O₂ consumption (P < 0.001) and CO₂ production (P < 0.005) over time was observed for the soils spiked with diesel compared with the untreated soil, which suggests biodegradation of the diesel substrate. Diesel degradation rates calculated from respiration data were 1.5–2.1 times less than the change in total petroleum hydrocarbon content. The inability of this study to correlate respiration data to actual changes in diesel concentration could be explained by volatilization, long‐term sorption of diesel hydrocarbons to organic matter and incorporation of diesel hydrocarbons into microbial biomass, aspects of which require further investigation.  相似文献