车载汽油蒸气回收方法的研究     

韦海燕  何仁 《拖拉机与农用运输车》2008,35(5)

为了减少汽车的加油蒸发排放,分析了加油过程中存在的蒸发污染的问题,通过控制设备的成本、结构等因素的比较,提出了车载汽油蒸气回收的办法。简述了车载汽油蒸气回收装置的类型、特点和工作原理,以动密封式车载汽油蒸气回收装置为例进行粗略的分析。使用车载汽油蒸气回收装置前后汽油车汽油蒸发污染物的排放趋势的预测结果表明,应用车载汽油蒸气回收装置,同时改进在用车上原有的汽油蒸发污染物控制装置,能够减少汽车加油过程中的蒸发污染物,是一种节约汽车能源、防治污染的有效措施。  相似文献   

低温弱光胁迫对辣椒CMS三系幼苗光合特性与叶绿素含量的影响   总被引：9，自引：4，他引：5  

曹克友  魏佑营  吴静  王军伟  魏秉培  邱红 《山东农业科学》2008,(6)

本试验以CMS三系辣椒幼苗为材料,研究了低温弱光胁迫及恢复阶段对辣椒幼苗光合指标和叶绿素含量的影响。结果表明:随着低温弱光胁迫程度和时间的增加,功能叶片Pn、Gs下降,Ci上升,不同处理不同材料间存在较大差异。说明光合作用的降低主要以非气孔限制为主。对照条件下恢复6天后,Pn与Gs未恢复到原来水平,10℃/5℃处理下的辣椒幼苗恢复更为缓慢。低温弱光处理10天后叶绿素a、叶绿素b、叶绿素(a+b)含量及叶绿素(a/b)均降低,叶绿素a下降明显,叶绿素b的变化较小,叶绿素a、b不呈现单一的变化趋势。恢复系的各项指标优于其它材料。  相似文献   

蓝莓组培苗玻璃化及恢复的研究   总被引：5，自引：0，他引：5  

孙阳  魏海蓉  程淑云  刘庆忠  李宪利  刘崇琪 《山东农业科学》2008,(3):61-63

以Sierra、Bluecrop和Reveilla 3个蓝莓品种为试材,以WPM为基本培养基,研究玉米素和培养温度对不同蓝莓品种试管苗玻璃化现象的影响,探索蓝莓试管苗的最佳培养方法。结果表明:玉米素(ZT)浓度和培养温度是导致蓝莓玻璃化的重要因素,当温度在28℃和玉米素浓度在0.3 mg/L条件下,玻璃化程度最重,但品种间的玻璃化程度也有明显差异。随着培养温度的升高或玉米素浓度的增高,品种间玻璃化程度:Reveilla>Sierra>Bluecrop。玻璃化试管苗在调整培养温度及玉米素浓度的条件下,可以不同程度的恢复,培养温度在20~23℃之间变温处理、ZT浓度在0.1 mg/L效果最优;其中Bluecrop恢复时间最短,且效果最好,其次是Sierra,Reveilla最慢。  相似文献   

Fungal but not bacterial soil communities recover after termination of decadal nitrogen additions to boreal forest     

《Soil biology & biochemistry》2014

The rate at which formerly nitrogen loaded forests will return to their natural nitrogen-limited state is of considerable scientific and societal interest. Yet the sensitivity of soil microorganisms to these putative changes is mainly unknown. We report effects on fungal and bacterial communities caused by two decades of chronic nitrogen fertilization and subsequent changes 14 years after termination of nitrogen load. We compare these changes in community composition with those observed in natural nitrogen supply and pH gradients using DNA fingerprinting methods and Sanger sequencing.Soil fungal ITS length-heterogeneity profiles correlated equally well to carbon-to-nitrogen ratios and pH. Sequencing results indicated a clear decrease in the relative abundance of amplicons ascribed to known ectomycorrhizal fungi in both natural and experimental high nitrogen conditions, and a recovery of species in the terminated nitrogen treatment. The dominant sequences in low nitrogen soils were identified as members of Piloderma spp. Terminal restriction fragment length profiles of the bacterial 16S rRNA gene were linked to carbon-to-nitrogen ratios and pH in the natural locations but to soil nitrogen in the nitrogen addition experiment that had low variability in pH. Sequencing revealed the dominance of Acidobacteria and Proteobacteria in all soils but also showed a marked increase in Bacteroidetes in high nitrogen treatment not evident in the natural high nitrogen and high pH environments. Proteobacteria sequences included described strains from high-organic and low-pH systems that are believed be involved in degradation of complex plant material.There were signs of recovery of fungal but not of bacterial communities in the sense that community's in terminated nitrogen addition plots did not differ significantly from those in control plots or from the low nitrogen stands in the natural nitrogen supply gradient. The need of further examination of the seemingly functionally redundant bacterial communities is stressed.  相似文献   

应用荧光法测定硒含量的实验研究     

锁守丽  王振隆 《黑龙江畜牧兽医》1998,(3):2-4

采用荧光分光光度计法对检测器及样品的精密度和回收率进行了测定。结果表明，本法的平均变异系数为２．０６７％±１．０７３％，生物样本的精密度均大于标准品的精密度，硒的回收率均在８５％以上。  相似文献   

Restoration and Rehabilitation of Arid and Semiarid Mediterranean Ecosystems in North Africa and West Asia: A Review   总被引：4，自引：0，他引：4  

Henry N. Le Houerou 《Arid Land Research and Management》2013,27(1):3-14

Mediterranean-type vegetation and ecosystems have undergone intense processes of degradation for decades, centuries, or millennia under heavy and prolonged pressure from human and livestock populations. An extensive literature on exclosures, afforestation, reafforestation, rehabilitation, and other regeneration operations over several million hectares in Mediterranean bioclimatic areas from the Atlantic Ocean to the Aral Sea, combined with 50 years of personal field experience, allowed us to draw a number of conclusions on the consequences of these efforts, constraints, and limitations: (1) Exclosure usually permits the restoration and biological recovery of vegetation structure, composition, biomass, and productivity in a time span of 3-5 years in steppic ecosystems and 25-30 years in coniferous or sclerophyllic vegeta tion areas. There are exceptions, however, when vegetation is so degraded to the level that it has reached a new metastable equilibrium, characterized, e.g., unpalatable range weeds, perennial dwarf ephemeroids, cryptogams, or soil surface sealing by raindrop splash or other physical or biological factors. (2) Controlled access and rationally managed utilization of the land may achieve similar and sometimes better results than full exclosure. (3) Afforestation and reafforestation are usually successful above the isohyet of 200 mm a-1 precipitation and, occasionally, at a lower annual precipitation, where the species introduced or reintroduced is appropriate and the causes for degradation have been discontinued or seriously mitigated. (4) Rehabilitation operations, including water and/or soil conservation, may quickly achieve spectacular results but at a higher cost and subjected to a number of constraints pertaining to the techniques utilized and adequate subsequent management. (5) The main constraint for success is the discontinuation of situations that have caused degradation. The most difficult to overcome usually are of a socioeconomic and/or sociocultural nature. The speed of biological recovery is commensurate (inter alia) with the rate to which this constraint is overcome. (6) The present land surface concerned with regeneration (restoration + rehabilitation) in this part of the world represents ca. 4 X 10 6 ha, representing some 6% of the actual ''forest and woodland'' in these areas. The National Regeneration Effort (NRE), a novel concept, is evaluated by using the ratio between the Annual Regeneration Expenditure (ARE) and both the Annual National Budget Expenditure (ANBE) and Gross National Product (GNP).  相似文献   

Factors affecting the behavioural responses of whooper swans (Cygnus c. cygnus) to various human activities     

Eileen C. Rees  Jennifer H. Bruce 《Biological conservation》2005,121(3):369-382

The effects of human activity on bird behaviour and distribution have been studied extensively in recent years, but variation in their response to disturbance is still poorly understood. Here, we analyse variation in the behaviour of wintering whooper swans Cygnus c. cygnus, to determine whether their susceptibility to human activity changes with time, location and the type of disturbance involved. Overall, the swans' feeding activity varied within and between years, and in relation to feeding site, but there was less variation in the amount of time spent alert. Disturbance frequency resulting from human activity was lower with increasing flock size and with increased distance to the nearest road or track. Distances that humans could approach before alerting the birds similarly varied with field characteristics (e.g. size and proximity to roads or tracks), and also with the type of disturbance involved. The distance at which >5% of the flock became alert because of human activity decreased with the number of previous disturbance incidents in the day, indicating that swans become less sensitive to disturbance events if daily disturbance frequency is high, but there was no evidence that habituation to disturbance persisted over longer periods. The time taken for the birds to resume undisturbed behaviour varied with the duration of the disturbance event, which in turn depended on the type of disturbance involved, with pedestrians alerting the birds for longer periods than vehicles and aircraft. Recovery rates following disturbance were also associated with field size, flock size and the proportion of the flock alerted. Feeding activity was influenced by a range of variables, including year, season, field location, crop type and the number of days that the flock had used the field (32.9% of variance in the data explained by these variables), with disturbance factors explaining an additional 4.9% of variance in the proportion feeding per hour. Conversely, alert activity was influenced mainly by disturbance events. The range of factors influencing the swans' feeding behaviour, and variability in their response to human activity, has implications for management programmes and for attempts to predict the effects of human activity on the birds at a local and larger scale.  相似文献   

Beyond demography and delisting: ecological recovery for Yellowstone's grizzly bears and wolves     

Sanjay Pyare  Joel Berger 《Biological conservation》2003,113(1):63-73

This paper addresses the question, when are threatened or endangered species really recovered? The US Endangered Species Act enables the de-listing of species once demographic criteria are met. In the Greater Yellowstone ecosystem, two protected apex carnivores, grizzly bears (Ursus arctos) and wolves (Canis lupus), face removal from federal government protection due to population increases, a point at which they are expected to be integrated components of this ecosystem. We tested the assumption that these two carnivores are playing normative ecological roles in the Yellowstone ecosystem by comparing the extent to which wolves and bears have re-instilled anti-predator responses in a primary prey species, moose (Alces alces), within wolf and bear recovery zones. As a type of control, we contrasted female moose from two areas in Alaska with different predator regimes to those in Wyoming. Populations from mainland Alaska, a region with a relatively intact carnivore assemblage, responded significantly more to odors of both carnivores. In contrast, a basic anti-predator reaction was lacking in Wyoming; and responses to grizzly bear odor only nominally increased after dependent young experienced heightened mortality. Additionally, the level of response among Alaskan moose living under virtual predator-free conditions for 25+ years closely resembled that of conspecifics in Wyoming. That such striking variation in prey responses exists re-enforces critical ecological differences between predator-intact and -defunct systems. Thus, although grizzly bears and wolves in the Yellowstone area will most likely be de-listed within the next few years, whether such action would be ecologically defensible is arguable. At this point in the recovery process, these predators may currently have limited ecological impacts in large portions of this region, at least as gauged by one potentially important prey species, moose. Although our data suggest ecologically incomplete conditions, other indices of carnivore recovery that include responses of other important prey species such as elk (Cervus elaphus), may be more in tune with carnivore activities. We recommend that different types of ecological data available throughout recovery zones be used in consort with demographic criteria to evaluate when endangered carnivores are more fully integrated into their ecosystems. And, in the event of a disparity between these criteria, we also encourage a dialogue focusing on approaches towards bringing ecological conditions in concordance with demographic criteria, irrespective of whether one considers increasing population levels beyond the current target levels required for de-listing,and/or simply, additional time for the recovery process.  相似文献   

Increase of a Caribbean leatherback turtle Dermochelys coriacea nesting population linked to long-term nest protection     

Donna L. Dutton  Milani Chaloupka 《Biological conservation》2005,126(2):186-194

The leatherback turtle Dermochelys coriacea is considered to be at serious risk of global extinction, despite ongoing conservation efforts. Intensive long-term monitoring of a leatherback nesting population on Sandy Point (St. Croix, US Virgin Islands) offers a unique opportunity to quantify basic population parameters and evaluate effectiveness of nesting beach conservation practices. We report a significant increase in the number of females nesting annually from ca. 18-30 in the 1980s to 186 in 2001, with a corresponding increase in annual hatchling production from ca. 2000 to over 49,000. We then analyzed resighting data from 1991 to 2001 with an open robust-design capture-mark-recapture model to estimate annual nester survival and adult abundance for this population. The expected annual survival probability was estimated at ca. 0.893 (95% CI: 0.87-0.92) and the population was estimated to be increasing ca. 13% pa since the early 1990s. Taken together with DNA fingerprinting that identify mother-daughter relations, our findings suggest that the increase in the size of the nesting population since 1991 was probably due to an aggressive program of beach protection and egg relocation initiated more than 20 years ago. Beach protection and egg relocation provide a simple and effective conservation strategy for this Northern Caribbean nesting population as long as adult survival at sea remains relatively high.  相似文献   

桃子冲击力学特性及其与桃子硬度的数学模型   总被引：10，自引：1，他引：10  

王俊  许乃章 《农业机械学报》1994,25(4):58-62

桃子成熟度不同，其冲击力学性质不同。从３ｃｍ高度自由下落至金属平板上，获得桃子恢复系数ｒ、能量吸收百分率Ｅ和冲击力时间特性参数ｆｐ／ｔｐ，它们与桃子硬度Ｈ间均有极显著相关。建立了这三参数与桃子硬度间的数学模型，分别为１／ｒ＝ａ＋ｂ／Ｈ，Ｅ＝ａｅ￣（ｂ／Ｈ）和１／（ｆｐ／ｔｐ）＝ａ＋ｂ／Ｈ。试验还表明利用冲击力时间特性参数作为按硬度（成熟度）分级的参数比另二参数更适宜，从高度３ｃｍ下落后桃子损伤极小。本试验结果为设计水果成熟度快速检测仪和自动分级机提供了科学依据。  相似文献