Compressive deformation of wood impregnated with low molecular weight phenol formaldehyde (PF) resin II: effects of processing parameters

To obtain high-strength phenol formaldehyde (PF) resin-impregnated compressed wood at low pressing pressure, the effects of resin content, preheating temperature, pressing temperature, and pressing speed on the compressive deformation of oven-dried low molecular weight PF resin-impregnated wood was investigated. With an increase of PF resin content, the Youngs modulus of the cell wall perpendicular to the fiber direction decreases, and collapse-initiating pressure decreases linearly with the Youngs modulus. This indicates that the occurrence of cell wall collapse is strain-dependent. By increasing preheating temperatures, the collapse-initiating pressure increases due to the increment of the Youngs modulus of the cell wall. An increase in pressing temperature results in the thermal softening of the cell wall and causes collapse at a lower pressure. The wood is compressed effectively despite accelerated resin curing. The pressing speed significantly affects the viscoelastic deformation of the cell wall and the wood is well deformed with decreasing pressing speed, although the differences in density and mechanical properties are relatively small after a pressure-holding period of 30min. In all the parameters examined in this study, the Youngs modulus and bending strength increase with increasing density.     

紫云英联合收获物料分离清选机设计与试验

针对紫云英联合收获物料组分构成复杂及其小差异混杂特性,使其在分离清选作业过程中存在高含杂、多损失等问题,提出“先筛分、再气流清”的作业模式,设计了紫云英联合收获物料分离清选机,并对喂料斗出口处料层厚度调节机构、筛分装置、集杂除尘装置等关键部件进行了设计选型与参数计算。基于DEM-CFD耦合数值模拟方法,确定了物料层调节厚度、筛分装置驱振振幅和吸杂管道风量调节手柄挡位等主要影响因素合理的取值范围,运用Minitab进行正交试验设计,以籽粒清洁率和夹带总损失率为响应值,得到影响紫云英联合收获物料分离清选机作业质量的最优因素参数组合：物料层调节厚度为16.8mm、筛分装置驱振振幅为35mm、吸杂管道风量调节手柄在挡位5,此时,籽粒清洁率均值为98.07%,夹带总损失率均值为2.96%,试验结果满足设计要求。     

Chemical cotton stalk destruction for maintenance of host-free periods for the control of overwintering boll weevil in tropical and subtropical climates

In the Lower Rio Grande Valley (LRGV) of Texas, cotton regrows and produces fruit from undestroyed stalks throughout the winter, and in spring weevils from such locations become a serious threat. The success of the boll weevil eradication program, which was reintroduced in the LRGV in 2005, will be dependent on thorough stalk destruction following harvest. However, adverse weather conditions and conservation tillage often impede immediate and complete stalk destruction using typical tool implements, and alternative stalk control methods are needed. This study provides an examination of the efficacy for cotton stalk destruction of different herbicides (thifensulfuron-methyl + tribenuron-methyl, dicamba-diolamine, 2,4-D-dimethylammonium, flumioxazin, 2,4-DB-dimethylammonium and carfentrazone-ethyl) and their rates, spray volumes and application timings on shredded or standing cotton stalks after stripper or picker harvest. None of the tested herbicides, except 2,4-D-dimethylammonium, stopped post-harvest cotton regrowth and fruiting. 2,4-D-dimethylammonium sprayed once (0 or 7 days) after cotton was harvested at 1 lb AE acre(-1) (1.12 kg ha(-1)), in a spray volume of 10 gal water acre(-1) (93.5 L ha(-1)) with 5 mL L(-1) surfactant, was highly effective in stalk destruction (72-90%). The best results were achieved when the herbicide was applied immediately after the cotton was shredded, followed by standing stripper-harvested and standing picker-harvested cotton. 2,4-D-dimethylammonium applied twice, 0 and 14 (or 21) days after cotton harvest, was 100% effective in killing stalks, regardless of whether they were shredded or standing, or whether harvest was by stripper or picker. These findings showed that 2,4-D-dimethylammonium cotton stalk destruction eliminated food and reproductive opportunities for managing overwintering boll weevils [Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae)].     

极早熟机收玉米新玉110号的产量潜力与机收性能分析

【目的】 分析极早熟复播玉米新品种新玉110号的产量潜力和机收性能,为玉米新品种推广提供科学依据。【方法】 以新疆南疆复播极早熟玉米区域试验玉米新品种新玉110号为材料,对照为新玉10号,采用作物品种区域试验统计系统RCT99分析产量、品质等。【结果】 新玉110号复播区试产量522.27 kg/667m²,比对照新玉10号增产12.13%,生产试验552.67 kg/667m²,比对照增产17.01%;生育期87.9 d,比对照早熟2.9 d;籽粒容重768 g/L,粗蛋白含量9.9%,粗淀粉含量74.92%,粗脂肪含量4.6%;抗倒伏,抗玉米瘤黑粉病、丝黑穗病和粗缩病,成熟是苞叶自然张开,脱水快。【结论】 新玉110号产量高,增产潜力大,属极早熟强优势玉米杂交种,品质优良,适应性广,适宜新疆南疆地区复播和北疆冷凉地区春播种植,所需≥10℃有效积温2 200℃,适合机械粒收。     

播量与秧龄对优质常规水稻黄华占机械育秧秧苗素质的影响

以优质水稻品种黄花占机械育苗为研究对象,探讨在陕西汉中4月20日左右播种育时播量与秧龄对秧苗素质的影响。结果表明：在陕西汉中地区,4月20日左右播种,黄花占机械育秧秧龄在25 d左右,每平方厘米播1.8~2.4粒稻种较为适宜,秧苗素质利于机械插秧,此时,苗高12~14 cm,茎基宽2.4~3.1 mm,成苗率在80%左右。     

玉米不同时间收获与含水率变化

根据田间玉米籽粒含水率来确定最佳机械粒收的时间,能为定边区域春玉米机械粒收技术的推广应用提供依据。通过不同时间收获取样,进行称重、脱粒和测定,了解当地主栽玉米品种的籽粒含水率变化。定边区域春玉米成熟后,经过田间站杆脱水时期,籽粒含水率可以控制在17%~22%之间。每年十月中下旬收获,可保证玉米机械粒收质量。     

不同采毛方式对长毛兔血清蛋白及含氮代谢物水平的影响

文章分析了3种方式（剪毛、直接拔毛和药物拔毛）对皖系长毛兔采毛前、采毛后0、4、8、24、48 h血清蛋白及含氮代谢物变化规律的影响.结果发现：3种采毛方式均显著上调血清总蛋白和肌酐水平,而血清白蛋白仅受药物拔毛影响而显著上调;药物拔毛显著上调血清总胆红素和直接胆红素水平,同时直接胆红素还受其他两种采毛方式影响而显著下调;两种拔毛方式（直接拔毛和药物拔毛）显著上调血清尿素和尿酸水平,但剪毛对这两个指标没有影响.长毛兔在采毛后48 h内,多数血清指标可恢复到采毛前水平,或呈恢复趋势;该研究筛选获得采毛应激指标血清总蛋白和肌酐,拔毛应激指标尿素和尿酸,同时发现肌酐、白蛋白和胆红素受地塞米松的显著影响.该研究结果可为初步揭示不同采毛方式应激生化机制提供参考.     

鹿茸Ca^2＋含量与塔里木马鹿收茸期的关系研究

为了确定不同年龄段塔里木马鹿鹿茸的最佳收茸时间,保证鹿茸的药用价值,试验选取老、中、青3个年龄段的塔里木马鹿各6头,采用火焰原子吸收分光光度法,分别测定不同生茸时期鹿茸中Ca2＋的含量。结果表明：青年组至6月17日鹿茸上段Ca2＋含量增加显著,确定其最佳收茸时间以6月17日为宜;中年、老年组的最佳收茸时期在6月3日左右,三者存在时间差异。     

Effects of mechanical stress in under-sized clams, Tapes philippinarum: a laboratory approach

The present study is a first attempt at evaluating the effects of repeated disturbance, such as that caused by mechanical fishing systems, on the target species, Tapes philippinarum, intensively exploited in the Lagoon of Venice (North-East Italy). In particular, in free-access fishing grounds, detrimental effects of dredging may be suffered by under-sized clams, which are disturbed by fishing tools many times throughout their lives before they are collected. Similar mechanical stress conditions are experienced by T. philippinarum in licensed areas, where they are farmed in aquaculture conditions and undergo the harmful impact of hydraulic dredging. To evaluate the effects of short-term mechanical stress, under-sized clams were subjected to experimental shaking in the laboratory, and detrimental effects on their well-being were investigated by applying the biomarker approach. Changes in physiological, biochemical and behavioural responses were evaluated by determining scope for growth, adenylate energy charge, survival in air time, reburrowing time, and shell damage level. Responses highlighted general worsening in clam condition as mechanical stress increased. Among the various measurements, survival in air and reburrowing time appeared particularly suitable as indices, their responsiveness and applicability suggesting their use in assessing mechanical stress due to dredging in field conditions.     

化学感觉和机械感觉与鱼类摄食行为关系的研究进展

鱼类的摄食行为是多种感觉器官共同作用的结果。然而,不同生态习性的鱼类在摄食行为中起主导作用的感觉器官是不同的。对于底层活动、夜间活动、深水活动的鱼类,由于生存环境光线较弱,非视觉器官,如化学感觉器官、电觉器官和侧线机械感觉器官等在摄食行为中具有更为重要的作用。根据近年来国内外的研究成果,本文综述了化学感觉和机械感觉与鱼类摄食行为关系的研究进展。重点阐述了嗅觉化学感觉和侧线机械感觉在鱼类捕食行为中的作用。