基于心理契约机制的农户-龙头企业合作渠道绩效研究——以浙江省农户调研样本为例

从心理契约机制的视角对农户与龙头企业的合作渠道关系深入研究,构建创新理论模型并运用浙江省农户样本调研数据进行实证分析.结果表明,农业龙企与农户的内部心理契约治理机制对农业合作经营渠道绩效有显著作用,通过内部心理默契机制和外部控制机制共同作用,可以有效解决公司与农户合作渠道关系治理失灵问题,最终提高双方的经营效益,促进整个农业走向全面协同、互惠互利的良性循环.     

氯、锌离子对猪精子钙通道和若干酶活调控作用的研究

为了研究了氯离子、锌离子等对猪精子钙通道的调控作用及其机理。将由健康公猪采得的精液经纱布过滤后分为三组,每组6个重复。第一组精液不加任何物质,第二三组精液分别加氯化钠液和硫酸锌液,混匀并静置2.5 h后,观测精子活力和精子、精清中离子含量与酶活。结果表明：（1）在猪精液中分别加适量的氯离子、锌离子,能刺激精清中钙离子向精子中转移,使得精子内钙离子含量显著地(P＜0.05)增加,精清中钙离子有一定程度的(P＞0.05)减少;（2）加锌或加氯离子,精子活力极显著(P＜0.01)地增强;（3）加锌离子组,精子内碱性磷酸酶、碳酸酐酶、腺苷酸环化酶活性极显著地(P＜0.01)提高,cAMP含量极显著地(P＜0.01)增多;精清内碱性磷酸酶、腺苷酸环化酶活性极显著地(P＜0.01)提高,cAMP含量显著地(P＜0.05)增多;（4）加氯离子组,精清内碱性磷酸酶、腺苷酸环化酶活性极显著地(P＜0.01)提高,精清内cAMP含量显著地(P＜0.05)增多;但精子内碳酸酐酶、腺苷酸环化酶活性和cAMP含量都无显著的(P＞0.05)变化。上述结果表明：猪精液加适量锌离子或氯离子,对精子细胞钙通道功能可能都有上调作用,并能提高精液中碱性磷酸酶、腺苷酸环化酶、碳酸酐酶活性,增加精液中cAMP含量,增强精子活力。     

斑点叉尾鮰鱼皮胶原的研究

从斑点叉尾鮰鱼皮中提取酸溶和酶溶胶原并对其进行了部分定性研究。实验中获得的胶原中甘氨酸最为丰富，质量分数超过23％，酸溶胶原的变性温度为32．5℃，比猪皮胶原的变性温度低5℃。SDS—PAGE实验结果表明酸溶胶原至少有2条不同的α链。酸溶胶原和酶溶胶原分别占原料干基的25．8％和38．4％，可以作为猪皮、牛皮胶原的替代品。     

A comparison of new in-pond grading technology to live-car grading for food-sized channel catfish (Ictalurus punctatus)

Grading trials were performed in experimental and commercial catfish ponds to compare an in-pond horizontal floating bar grader to current live-car grading. Three replicate trials were conducted in experimental ponds at three different temperature ranges (warm, >26 °C; cool, 13–26 °C; cold, <13 °C) with catfish size groups stocked in ratios of either 75:25, 50:50, or 25:75 sub-marketable (<0.57 kg) to marketable fish (≥0.57 kg). Commercial pond trials were replicated three times at each temperature range with a fish size range typical of ponds ready to harvest. Stress experienced by fish during harvest and grading was measured by mean serum glucose and cortisol levels. Grading speed was greater (P < 0.05) with the UAPB grader (105–449 kg/min) than the traditional live-car grader (0.5–0.6 kg/min). The UAPB grader decreased (P < 0.05) the proportion of sub-marketable fish during all trials. In contrast, the live car did not reduce the proportion of sub-marketable fish with the experimental methods used in this study during commercial trials or in the 25:75 distributions during warm and cold temperature trials in experimental ponds. The UAPB grader returned an average two to four times (range of 2–52) more sub-marketable fish by weight to the pond than the traditional live car method. Glucose and cortisol levels in fish graded with the two technologies were not significantly different. The UAPB grader sorted fish more accurately, consistently, and quickly than the live car at all temperatures in both experimental and commercial trials.     

Effect of Dietary Lipid Levels on Growth,Feed Conversion,and Muscle Composition of the Walking Catfish,Clarias batrachus

Feeding trials were conducted to determine the feasibility of using spray-dried blood meal (EM) or enzyme-hydrolyzed (EH) and low-ash (LA) poultry products to partially replace fish meal (FM) in diet formulations for palmetto bass. Pelleted diets were formulaled with EM protein replacing 10, 25, or 50% of the FM protein and either EH or LA poultry products replacing approximately 25, 50, or 75% of the FM protein. All diets were formulated to contain 14kJ GE energy/g and 35% crude protein. Fish fed a die1 in which BM replaced 50% of the protein supplied by FM had significantly (P < 0.05) lower weight gain and feed efficiency compared to fish fed the control diet at the end of 6 and 12 weeks. Total body lipid was significantly higher for those fish receiving diets with 10 or 25% BM. However, there were no differences in total body moisture, protein, or ash. When either EH or LA protein rep     

A probabilistic approach to river network detection in digital elevation models

River networks are often derived from digital terrain models and are affected by uncertainty and errors of the corresponding elevation data. The analysis of the spatial distribution of the errors provides information on the confidence level of the derived networks. However indications on the most probable river network as a whole are missing. This study proposes a method to indicate which is the river network maximising the sum of the probability values along the network, given a map reporting the likelihood that a cell belongs to the network itself. The method is considering the inverse of the channel probability map as pseudo-DEM from which drainage networks are derived. A reference network is used to assess the spatial match of the extracted river networks using the Euclidean distance as simple comparison parameter. The network extracted from the inverse of the channel probability map is the closest to the reference. The use of a probabilistic approach to error modelling significantly increases the values of channel probability for extracted river networks and the spatial match with a ground reference dataset.     

黄河故道区域土地沙漠化程度的景观尺度评价

黄淮海平原土地沙漠化扩展形势十分严峻,然而人们对它的发生、发展和存在潜在威胁的认识却远远落后于西北内陆和内蒙古高原沙漠区,这是防治该区沙漠化扩展、蔓延的最大障碍。黄淮海平原上的沙漠化以黄河故道和滦河下游冲积平原最为显著。作者以黄河故道典型区域山东聊城市为例,对该区的荒漠化程度进行景观尺度的评价。     

Stability of an upland gravel-bed stream, Swinhope Burn, Northern England

Some upland gravel-bed streams often undergo frequent channel change in response to floods and changes in sediment supply. However, in others, where local conditions permit, long-term channel planform stability can be observed. This paper uses evidence from Swinhope Burn in upper Weardale, Northern England, to demonstrate relative channel stability over a 180-year period.Channel planform change is identified using seven historical maps and air photographs dating from 1815 to 1991. The 1.4-km study reach has retained a stable meandering pattern over a period of 180 years, with a temporary but dramatic change to a straight, low sinuosity, partly divided channel, at some point between 1815 and 1856 (identifiable on the 1844 Tithe Map). Channel planform stability, observed over the historic period, is related in part to the low channel gradient upstream of a cross-valley moraine situated at the lower end of the study reach. This moraine has led to partial closure of the valley system and the development of a small upstream floodplain or ‘sedimentation zone’ (average width of 150 m). The resulting low channel gradient (0.012) inhibits coarse bedload transport and encourages overbank sedimentation. Cohesive banks promote lateral channel stability and the wide floodplain reduces potential coupling between the channel and valley-side slope sediment sources.The probable cause of the observed channel planform change is the combination of a succession of four major floods in the River Wear catchment during the 1820s, and episodic inputs of sediment generated by upstream metal mining between 1823 and 1846. Large floods in the past 40 years have produced very little evidence of lasting channel change. However, locally a channel avulsion has been documented following a flood in February 1997. This represents a useful modern analogue for previous mechanisms of channel change.     

Large wood abundance,distribution and mobilization in a third order Coastal mountain range river system,southern Chile

Large wood (LW) abundance, longitudinal distribution and mobilization were studied in the Vuelta de la Zorra channel draining a third order catchment located in the Coastal mountain range of southern Chile. Seventy-five percent of the 586.8 ha study catchment area is covered by evergreen native rainforests, 24% by Eucalyptus nitens plantations and the remaining 1% are different sites were native tree and shrub species are regenerating in areas that were prepared for forest replacement in the late 1980s but finally left unplanted. In a segment, 1557 m in length, surveyed between November 2008 and February 2009, a total of 484 pieces representing 181 m³ of LW were measured. Using bankfull width and length this volume corresponds to 109 m³ ha⁻¹ or 11.6 m³ 100 m⁻¹. LW was distributed along the channel in correlation with bankfull width. The channel segment was re-surveyed in December 2009 and we found that after one winter season 12% of the LW were transported downstream the river channel and 9 new wood elements were recruited. The LW traveled distance and traveled distance/piece diameter ratio decreased with increasing piece length/mean bankfull ratio. These results contribute to understand the complexity of LW abundance, mobilization and recruitment processes, and their effects on channel morphology, sediment routing and ecology in Chilean catchments.     

Changes in nematode abundances and body length in response to management intensive grazing in a low-input temperate pasture

An evaluation of changes in nematode populations in response to management was performed using a field scale experiment along a gradient of land-use intensity in the context of management intensive grazing. Four levels of decreasing intensity were measured over three growing seasons. The treatments included: 1) intensive grazing management where cows were allowed to graze for each grazing cycle, followed by routine clipping and harrowing; 2) semi-intensive grazing where cows were allowed to graze for each grazing cycle, with only one clipping event per year; 3) extensive grazing where cows were allowed to graze during every 2nd grazing cycle and no clipping or harrowing was performed; 4) stockpiling treatment where cows were permitted to graze only during the final grazing cycle, followed by clipping at the end of the season. Most indices (MI, PPI, ∑MI, and ∑MI25) resulted in significant seasonal differences; however, only familial diversity (H′) and the total number of families showed significant season by treatment interaction. Bacterivores comprised most of the nematode population with Cephalobidae being the most common family. Abundance of plant feeders was affected by season and soil moisture, whereas bacterivore abundance was associated with total organic N and soil pH. Nematode body length increased slightly in most families through time, and was associated with season, bulk density, soil moisture, and total N and C. Although omnivore numbers were highest in the extensive and semi-intensive treatments, there was a significant increase in dorylaimid body length observed in the intensive treatment through time. Increases in body length were also observed in Monhysteridae and Cephalobidae in all treatments.