Contribution of spray droplet pinning fragmentation to canopy retention     

《Crop Protection》2014

Drop behaviour during impact affects retention. Increasing adhesion is usually seen as an objective when applying crop protection products, while bouncing and shattering are seen as detrimental to spray retention. However, observation of drop impacts on barley (Hordeum vulgare L.) using high speed shadowgraphy shows that bouncing and fragmentation can occur in Cassie–Baxter as well as in Wenzel wetting regimes. In this last regime, a part of the drop may remain stuck on the surface, contributing to retention. Using simultaneous measurements of drop impacts with high speed imaging and of retention with fluorophotometry for spray mixtures on excised barley leaves using a Teejet 11003 nozzle at 0.2 MPa, it was observed that about 50% of the drops that fragmented in the Wenzel state remain on the horizontal leaf. Depending on the spray mixture, these impact outcomes accounted for 28–46% of retention, the higher contribution being correlated with bigger VMD (Volume Median Diameter). This contribution is not negligible and should be considered when modelling spray retention processes.  相似文献   

The Mentor-Mentee Relationship,Addressing Challenges in Veterinary Medicine Together     

《Veterinary Clinics of North America: Small Animal Practice》2021,51(5):1099-1109

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土壤铅污染对蚯蚓体腔细胞溶酶体的毒性效应   总被引：1，自引：0，他引：1  

王秋丽  朱琳  黄碧捷  李燕 《农业环境科学学报》2007,26(5):1874-1878

以蚯蚓溶酶体膜的稳定性作为亚细胞水平的生物标志物,研究土壤铅污染的毒性效应。将赤子爱胜蚓（Eiseniafetida）暴露于不同浓度乙酸铅染毒的人工土壤,染毒浓度为60、120、480、2400mg·kg^-1,测定蚯蚓体腔细胞溶酶体的中性红保留时间（NRRT）。结果表明,染毒6d后,480mg·kg^-1及2400mg·kg^-1剂量组,NRRT显著下降,抑制率分别为63.06%、68.61%;60mg·kg^-1及120mg·kg^-1剂量组,溶酶体膜稳定性变化不大。染毒14d后,各染毒组NRRT显著低于对照组,抑制率分别为49.43%、56.29%、68.57%、77.14%。将赤子爱胜蚓暴露于沈阳市青年公园、劳动公园、友谊宾馆、冶炼厂原址的现场土壤样品中,随着蚯蚓与土壤接触时间的增加,中性红保留时间逐渐降低,14d后各采样点蚯蚓的中性红保留时间关系为冶炼厂原址〈青年公园〈劳动公园〈友谊宾馆,与土壤铅含量的大小变化相吻合,其中冶炼厂原址差异最为显著,NRRT抑制率为92.55%,表明土壤重金属铅污染对土壤生态系统存在潜在的毒害。  相似文献   

Application of cationic polymer prepared from sulfuric acid lignin as a retention aid for usual rosin sizes to neutral papermaking   总被引：3，自引：0，他引：3  

Yasuyuki?MatsushitaEmail author  Ayuko?Iwatsuki  Seiichi?Yasuda 《Journal of Wood Science》2004,50(6):540-544

Cationic polymers that acted as the retention aids for usual rosin sizes in neutral papermaking were prepared from sulfuric acid lignin (SAL), one type of acid lignin. To convert SAL to the cationic polymer (MP-SAL), SAL was phenolated and then treated by the Mannich reaction to introduce the amino groups. In the MP-SAL single system, MP-SAL exhibited high sizing effectiveness in neutral papermaking with the rosin emulsion size. However, MP-SAL showed no sizing effectiveness when soap rosin size was used. MP-SAL showed increased sizing effectiveness as the pK _a of the introduced amino group increased. From this and comparison of the sizing degrees of MP-SAL and polyethylenimine, which possesses a linear structure, it was suggested that the sizing effectiveness was not only affected by the charge density and molecular weight, but also by the basicity of the introduced amino groups and the molecular structure of the retention aid. In the alum–MP-SAL dual system, alum and MP-SAL synergistically enhanced the sizing effectiveness in the rosin emulsion sizing at neutral pH. In turn, this allowed a decrease in the MP-SAL dosage and resulted in a small decrease in brightness.Part of this report was presented at the 48th Lignin Symposium, October 2003, Fukui  相似文献   

Analysis of nutrient flows in integrated intensive aquaculture systems   总被引：12，自引：0，他引：12  

O. Schneider  V. Sereti  E.H. Eding  J.A.J. Verreth 《Aquacultural Engineering》2005,32(3-4):379-401

This paper analyses nutrient conversions, which are taking place in integrated intensive aquaculture systems. In these systems fish is cultured next to other organisms, which are converting otherwise discharged nutrients into valuable products. These conversions are analyzed based on nitrogen and phosphorous balances using a mass balance approach. The analytical concept of this review comprises a hypothetical system design with five modules: (1) the conversion of feed nutrients into fish biomass, the “Fish-Biomass-Converter”; (2) the separation of solid and dissolved fish waste/nutrients; the “Fish-Waste-Processor”; (3) the conversion of dissolved fish waste/nutrients, the “Phototrophic-herbivore-Converter”; (4 and 5) the conversion of solid fish waste, the “Bacterial-Waste-Converter”, or the “Detrivorous-Converter”. In the reviewed examples, fish culture alone retains 20–50% feed nitrogen (N) and 15–65% feed phosphorous (P). The combination of fish culture with phototrophic conversion increases nutrient retention of feed N by 15–50% and feed P by up to 53%. If in addition herbivore consumption is included, nutrient retention decreases by 60–85% feed N and 50–90% feed P. This is according to the general observation of nutrient losses from one trophic level to the next. The conversion of nutrients into bacteria and detrivorous worm biomass contributes only in smaller margins (e.g. 7% feed N and 6% feed P and 0.06% feed N 0.03 × 10⁻³% feed P, respectively). All integrated modules have their specific limitations, which are related to uptake kinetics, nutrient preference, unwanted conversion processes and abiotic factors.  相似文献   

奶牛子宫内压描记试验及胎衣不下与产后子宫活动性关系的初探   总被引：1，自引：1，他引：0  

龚金贵  陈兆英 《畜牧兽医学报》1990,21(4):347-353

本实验在国内首次建立了描记奶牛子宫内压的体内微型压力传感器法,为对子宫进行生理、病理及药理学研究提供了一个实用手段。 本实验利用压力传感器法描记了16头母牛产后4小时和24小时的子宫内压并同时测定了血浆17β-雌二醇和孕酮的水平,其中胎衣正常排出7头(NRFM),胎衣不下9头(RFM)。结果如下:产后4小时NRFM和RFM牛子宫活动单位(平均收缩压×10分钟收缩次数)分别为183.19±19.15和37.12±16.79(P<0.01);产后24小时子宫活动单位NRFM牛为32.75±4.5,RFM牛为31.65±6.33(P>0.05),此时静注30单位催产素后子宫活动单位分别增加17.4和5.5倍(P<0.01)。NRFM牛产后4和24小时血浆17β-雌二醇水平为99.96±42.69和27.16±10.92pg/ml,RFM牛为188.06±63.85和106.93±72.28pg/ml(P<0.01);产后4和24小时血浆孕酮水平NRFM牛为2.0802±0.4072和1.9815±0.4312ng/ml,RFM牛分别为1.9635±0.6208和1.8734±0.6017ng/ml(P>0.05)。  相似文献   

Retention behavior of size and aluminum components on handsheets in rosin-ester size/alum systems   总被引：1，自引：0，他引：1  

Ken-ich Ito  Akira Isogai  Fumihiko Onabe 《Journal of Wood Science》1999,45(1):46-52

Anionic emulsion sizes consisting of rosin triglyceride esters and partly fortified rosin acids (i.e., rosin-ester sizes), have recently been used as internal sizes for alkaline papermaking. In this study, handsheets were prepared from pulp suspensions with alum and a rosin-ester size under various conditions, and sizing degree and size and aluminum contents of the handsheets were determined. Aluminum compounds originating from alum added to the pulp suspensions behave as retention aids of the rosin-ester size even in alkaline papermaking under limited conditions. Carboxyl groups in pulp are the primary retention sites of aluminum compounds in pulp suspensions. They form cationic sites on pulp fibers, and thus the anionic size emulsion particles are adsorbed on pulp fibers by electrostatic interactions. However, the cationic charges of aluminum compounds on pulp fibers decrease and finally disappear completely with the lapse of time after the alum addition by forming ionic bonds between the cationic sites and OH^– ions. Thus, pH values of the pulp suspensions and timing of the size addition strongly influence the retention values of the rosin-ester size and the resultant sizing features.This research was presented in part at the 1995 autumn meetings of the Society of Fiber Science and Technology Japan in Hamamatsu, October 1995  相似文献   

Improving the efficiency of wild Pecten maximus spat collection: potential effects of spat bag design and of species temporarily settling in spat bags     

Deborah Cashmore  Mark McG. Learmouth  John T. MacMillan 《Aquaculture (Amsterdam, Netherlands)》1998,160(3-4):273-282

The single and combined effects of external bag size and external bag mesh size upon the collection and retention of wild King Scallop spat (Pecten maximus L.), other scallop species (Aequipecten opercularis) and other animal groups were investigated in a collection area off the west coast of Scotland. Collection was assessed after 5 weeks and at harvest (after 20 weeks). After 5 weeks, 90% of collected animals consisted of scallops (P. maximus and A. opercularis), Mytilus edulis (Mollusca: Bivalvia) and Lacuna vincta (Mollusca: Gastropoda). One-way analysis of variance on count data obtained after 5 weeks showed that the larger bag and mesh size treatments had collected significantly greater numbers of scallop spat when numbers collected were compared to the quantity of material used for each treatment (P<0.05). This was partly attributed to significantly greater numbers of L. vincta crawling juveniles temporarily recruiting in the smaller bag and mesh treatments (P<0.05). Similar trends of spat abundance in treatment bags were observed at harvest, although all treatments had scallop spat retention efficiencies of less than 12%. The importance of the structural design of spat bags for spat collection and the effects of incidentally collected non-predatory species upon the collection of scallop spat are discussed.  相似文献   

颗粒浓度对文蛤、硬壳蛤和菲律宾蛤仔保留效率的影响          下载免费PDF全文

谢彬  林志华  何琳 《渔业科学进展》2022,43(4):190-198

本研究通过在养殖水体中添加底泥或单胞藻调节悬浮颗粒浓度,研究了悬浮物数量浓度和质量浓度变化对文蛤(Meretrix meretrix)、硬壳蛤(Mercenaria mercenaria)和菲律宾蛤仔(Ruditapes philippinarum)保留效率的影响。结果显示,文蛤、硬壳蛤及菲律宾蛤仔的保留效率分别在粒径为8、6和6 μm时达到最大值,分别为51.1%、59.6%和62.6%。随着数量浓度的增加,文蛤在低(4.32× 107 cells/L)、中(5.27×107 cells/L)、高(6.65×107 cells/L) 3个数量浓度下保留效率达到最大值时的最小粒径逐渐增大,分别为9、13和14 μm,保留效率最大值分别降至49.7%、33.4%和26.2%;与文蛤相似,菲律宾蛤仔保留效率达到最大值时的最小粒径也分别增大至9、12和14 μm,但最大保留值无明显变化;硬壳蛤保留效率的最大值保持不变,但达到最大值时的最小粒径略有增大,分别为8、9和10 μm。随质量浓度的增加,文蛤和菲律宾蛤仔在低(5.7 mg/L)、中(11.8 mg/L)、高(23.3 mg/L) 3个质量浓度下的保留效率最大值和达到最大值时的最小粒径均无明显变化;硬壳蛤保留效率最大值显著降低,分别为60.7%、27.6%和25.5%,但保留效率达到最大值时的最小粒径保持不变。研究表明,文蛤和菲律宾蛤仔的保留效率对食物颗粒数量浓度变化更敏感,而硬壳蛤的保留效率受质量浓度变化影响较大。  相似文献   

Low sulfide concentrations affect nitrate transformations in freshwater and saline coastal retention pond sediments     

C.M. Aelion  U. Warttinger 《Soil biology & biochemistry》2009,41(4):735-181

Coastal areas in the southeastern USA are prone to hurricanes and strong storms that may cause salt-water influx to freshwater aquatic sediments. These changes in environmental conditions may impact sediment processes including nitrogen (N) cycling. The relative abilities of sediment microbial communities from two freshwater golf course retention ponds that drain into the adjacent wetlands, and two proximal saline wetland ponds, to remove nitrate (NO₃⁻) were compared to assess whether low concentrations of sulfide changed N-transformation processes. Microcosms were incubated with NO₃-N (300 μg g dw⁻¹) alone, and with NO₃-N and sulfide (H₂S) (100 and 200 μg g dw⁻¹). Nitrous oxide (N₂O), nitrite (NO₂⁻), NO₃⁻, ammonium (NH₄⁺), SO₄²⁻ and acid volatile sulfides were analyzed over time. The acetylene block technique was used to measure denitrification in sediment microcosms with no added H₂S. Denitrification was measured without acetylene (C₂H₂) addition in microcosms with added H₂S. With no added H₂S, denitrification was greater in the freshwater retention ponds than in the wetland ponds. Although low H₂S concentrations generally increased NO₃-N removal rates at all sites, lag periods were increased and denitrification was inhibited by low sulfide in the freshwater sediments, as evidenced by the greater concentrations of N₂O that accumulated compared to those in the wetland sediments. In addition to the inability of the freshwater sediments to convert N₂O to N₂ in the absence of C₂H₂, anomalously high transient NO₂-N concentrations accumulated in the retention pond samples. NH₄-N formation generally decreased due to H₂S addition at the freshwater sites; NH₄-N formation increased initially at the wetland sites, but was greater when no H₂S was added. Storm events that allow influx of SO₄²⁻-containing seawater into freshwater systems may change the dominant N species produced from nitrate reduction. Even low concentrations of sulfide produced incomplete denitrification and decreased formation of NH₄⁺ in these coastal freshwater sediments.  相似文献