Effects of Different Seed Stem Sizes on the Changes of Available Elements in Rhizosphere Soil of Fritillaria thunbergii Miq.

[Objectives]This study was conducted to screen suitable seed stems of Fritillaria thunbergii Miq.from different provenances and to provide a theoretical basis for the high-yielding and high-efficiency cultivation of F.thunbergii Miq.introduced to different places.[Methods]F.thunbergii Miq.from four different provenances including Zhejiang,Nantong and Chongqing were introduced and cultivated in Wanzhou of Chongqing.The contents of available Zn,Fe,Mn,Cu,Mo,N,P,K,Ca and Mg in rhizosphere soil of F.thunbergii Miq.during five growing stages were determined after selecting different stem sizes for field cultivation.[Results]Small stems of Pan an and Ningbo provenances(SSG3,121-160/kg)and middle stems of Nantong and Fengjie provenances(SSG2,81-120/kg)showed higher soil availability.[Conclusions]In the process of introduction and cultivation of F.thunbergii Miq.,high yield and high efficiency can be achieved by selecting smaller seed stems of F.thunbergii Miq.

Early therapeutic effect of platelet-rich fibrin combined with allogeneic bone marrow-derived stem cells on rats’ critical-sized mandibular defects

BACKGROUND Critically sized bone defects represent a significant challenge to orthopaedic surgeons worldwide.These defects generally result from severe trauma or resection of a whole large tumour.Autologous bone grafts are the current gold standard for the reconstruction of such defects.However,due to increased patient morbidity and the need for a second operative site,other lines of treatment should be introduced.To find alternative unconventional therapies to manage such defects,bone tissue engineering using a combination of suitable bioactive factors,cells,and biocompatible scaffolds offers a promising new approach for bone regeneration.AIM To evaluate the healing capacity of platelet-rich fibrin(PRF)membranes seeded with allogeneic mesenchymal bone marrow-derived stem cells(BMSCs)on critically sized mandibular defects in a rat model.METHODS Sixty-three Sprague Dawley rats were subjected to bilateral bone defects of critical size in the mandibles created by a 5-mm diameter trephine bur.Rats were allocated to three equal groups of 21 rats each.Group I bone defects were irrigated with normal saline and designed as negative controls.Defects of group II were grafted with PRF membranes and served as positive controls,while defects of group III were grafted with PRF membranes seeded with allogeneic BMSCs.Seven rats from each group were killed at 1,2 and 4 wk.The mandibles were dissected and prepared for routine haematoxylin and eosin(HE)staining,Masson's trichrome staining and CD68 immunohistochemical staining.RESULTS Four weeks postoperatively,the percentage area of newly formed bone was significantly higher in group III(0.88±0.02)than in groups I(0.02±0.00)and II(0.60±0.02).The amount of granulation tissue formation was lower in group III(0.12±0.02)than in groups I(0.20±0.02)and II(0.40±0.02).The number of inflammatory cells was lower in group III(0.29±0.03)than in groups I(4.82±0.08)and II(3.09±0.07).CONCLUSION Bone regenerative quality of critically sized mandibular bone defects in rats was better promoted by PRF membranes seeded with BMSCs than with PRF membranes alone.

Real-time-guided bone regeneration around standardized critical size calvarial defects using bone marrow-derived mesenchymal stem cells and collagen membrane with and without using tricalcium phosphate: an in vivo microcomputed tomographic and histologic e

The aim of the present real time in vivo micro-computed tomography （pCT） and histologic experiment was to assess the efficacy of guided bone regeneration （GBR） around standardized calvarial critical size defects （CSD） using bone marrow-derived mesenchymal stem cells （BMSCs）, and collagen membrane （CM） with and without tricalcium phosphate （TCP） graft material. In the calvaria of nine female Sprague-Dawley rats, full-thickness CSD （diameter 4.6 mm） were created under general anesthesia. Treatment-wise, rats were divided into three groups. In group 1, CSD was covered with a resorbable CM; in group 2, BMSCs were filled in CSD and covered with CM; and in group 3, TCP soaked in BMSCs was placed in CSD and covered with CM. All defects were closed using resorbable sutures. Bone volume and bone mineral density of newly formed bone （NFB） and remaining TCP particles and rate of new bone formation was determined at baseline, 2, 4, 6, and 10 weeks using in vivo pCT. At the lOth week, the rats were killed and calvarial segments were assessed histologically. The results showed that the hardness of NFB was similar to that of the native bone in groups I and 2 as compared to the NFB in group 3. Likewise, values for the modulus of elasticity were also significantly higher in group 3 compared to groups 1 and 2. This suggests that TCP when used in combination with BMSCs and without CM was unable to form bone of significant strength that could possibly provide mechanical ＂lock＂ between the natural bone and NFB. The use of BMSCs as adjuncts to conventional GBR initiated new bone formation as early as 2 weeks of treatment compared to when GBR is attempted without adiunct BMSC therapy.

Effect of transplantation of bone marrow stem cells on myocardial infarction size in a rabbit model

BACKGROUND:Intravenous transplantation has been regarded as a most safe method in stem cell therapies.There is evidence showing the homing of bone marrow stem cells(BMSCs) into the injured sites,and thus these cells can be used in the treatment of acute myocardial infarction(Ml).This study aimed to investigate the effect of intravenous and epicardial transplantion of BMSCs on myocardial infarction size in a rabbit model.METHODS:A total of 60 New Zealand rabbits were randomly divided into three groups:control group,epicardium group(group Ⅰ) and ear vein group(group Ⅱ).The BMSCs were collected from the tibial plateau in group Ⅰ and group Ⅱ,cultured and labeled.In the three groups,rabbits underwent thoracotomy and ligation of the middle left anterior descending artery.The elevation of ST segment>0.2 mV lasting for 30 minutes on the lead Ⅱ and Ⅲ of electrocardiogram suggested successful introduction of myocardial infarction.Two weeks after myocardial infarction,rabbits in group Ⅰ were treated with autogenous BMSCs at the infarct region and those in group Ⅱ received intravenous transplantation of BMSCs.In the control group,rabbits were treated with PBS following thoracotomy.Four weeks after myocardial infarction,the heart was collected from all rabbits and the infarct size was calculated.The heart was cut into sections followed by HE staining and calculation of infarct size with an image system.RESULTS:In groups Ⅰ and Ⅱ,the infarct size was significantly reduced after transplantation with BMSCs when compared with the control group(P<0.05).However,there was no significant difference in the infarct size between groups Ⅰ and Ⅱ(P>0.05).CONCLUSION:Transplantation of BMSCs has therapeutic effect on Ml.Moreover,epicardial and intravenous transplantation of BMSCs has comparable therapeutic efficacy on myocardial infarction.

Healing Mechanism and Osteogenic Capacity of Bovine Bone Mineral—Human Amniotic Mesenchymal Stem Celland Autogenous Bone Graft in Critical Size Mandibular Defect

Experiments on maxillofacial bone tissue engineering showed the promising result;however, its healing mechanisms and effectiveness had not been fully understood. The aim of this study is to compare the bone healing mechanism and osteogenic capacity between bovine bone mineral loaded with hAMSC and autogenous bone graft in the reconstruction of critical size mandibular bone defect. Critical size defects were made at the mandible of 45 New Zealand white rabbits reconstructed with BBM-hAMSC, BBM alone, and ABG, respectively. At the end of first, second, and twelfth weeks, five rabbits from each experimental week were sacrificed for histology and immunohistochemistry staining. Expressions of vascular endothelial growth factor (VEGF), bone mor-phogenic proteins-2 (BMP2), Runx2 and the amount of angiogenesis were analyzed in the first and second week groups, while expressions of Runx2, osteocalcin, collagen type-I fibres, trabecular area and bone incorporation were analyzed in the twelfth week groups. The result showed that expressions of VEGF, BMP2 and Runx2 as well as the amount of angiogenesis were higher in ABG compared with BBM-hAMSC group in the first and second weeks of healing. The result of twelfth week of healing showed that expressions of Runx2 and osteocalcin as well as the thickness of collagen type-I fibres were significantly higher in BBM-hAMSC compared to ABG group, while there was no statistically difference in trabecular area and bone incorporation between BBM-hAMSC and ABG group. This study concluded that early healing activities were higher in auto-genous bone graft than in BBM-hAMSC, while osteogenic activities in the late stage of healing were higher in BBM-hAMSC compared to autogenous bone graft. It was also concluded that the osteo-genic capacity of BBM-hAMSC was comparable to autogenous bone graft in the reconstruction of critical size defect in the mandible.

Human neural stem cells promote proliferation of endogenous neural stem cells and enhance angiogenesis in ischemic rat brain

Transplantation of human neural stem cells into the dentate gyrus or ventricle of rodents has been reportedly to enhance neurogenesis. In this study, we examined endogenous stem cell proliferation and angiogenesis in the ischemic rat brain after the transplantation of human neural stem cells. Focal cerebral ischemia in the rat brain was induced by middle cerebral artery occlusion. Human neural stem cells were transplanted into the subventricular zone. The behavioral performance of human neural stem cells-treated ischemic rats was significantly improved and cerebral infarct volumes were reduced compared to those in untreated animals. Numerous transplanted human neural stem cells were alive and preferentially localized to the ipsilateral ischemic hemisphere. Furthermore, 5-bromo-2′-deoxyuridine-labeled endogenous neural stem cells were observed in the subventricular zone and hippocampus, where they differentiated into cells immunoreactive for the neural markers doublecortin, neuronal nuclear antigen Neu N, and astrocyte marker glial fibrillary acidic protein in human neural stem cells-treated rats, but not in the untreated ischemic animals. The number of 5-bromo-2′-deoxyuridine-positive ？ anti-von Willebrand factor-positive proliferating endothelial cells was higher in the ischemic boundary zone of human neural stem cells-treated rats than in controls. Finally, transplantation of human neural stem cells in the brains of rats with focal cerebral ischemia promoted the proliferation of endogenous neural stem cells and their differentiation into mature neural-like cells, and enhanced angiogenesis. This study provides valuable insights into the effect of human neural stem cell transplantation on focal cerebral ischemia, which can be applied to the development of an effective therapy for stroke.

Effects of heme oxygenase-1-modified bone marrow mesenchymal stem cells on microcirculation and energy metabolism following liver transplantation

AIM To investigate the effects of heme oxygenase-1(HO-1)-modified bone marrow mesenchymal stem cells(BMMSCs)on the microcirculation and energy metabolism of hepatic sinusoids following reduced-size liver transplantation(RLT)in a rat model.METHODS BMMSCs were isolated and cultured in vitro using an adherent method,and then transduced with HO-1-bearing recombinant adenovirus to construct HO-1/BMMSCs.A rat acute rejection model following 50%RLT was established using a two-cuff technique.Recipients were divided into three groups based on the treatment received:normal saline(NS),BMMSCs and HO-1/BMMSCs.Liver function was examined at six time points.The levels of endothelin-1(ET-1),endothelial nitric-oxide synthase(e NOS),inducible nitric-oxide synthase(i NOS),nitric oxide(NO),and hyaluronic acid(HA)were detected using an enzyme-linked immunosorbent assay.The portal vein pressure(PVP)was detected by Power Lab ML880.The expressions of ET-1,i NOS,e NOS,and von Willebrand factor(v WF)protein in the transplanted liver were detected using immunohistochemistry and Western blotting.ATPase in the transplanted liver was detected by chemical colorimetry,and the ultrastructural changes were observed under a transmission electron microscope.RESULTS HO-1/BMMSCs could alleviate the pathological changes and rejection activity index of the transplanted liver,and improve the liver function of rats following 50%RLT,with statistically significant differences compared with those of the NS group and BMMSCs group(P<0.05).In term of the microcirculation of hepatic sinusoids:The PVP on POD7 decreased significantly in the HO-1/BMMSCs and BMMSCs groups compared with that of the NS group(P<0.01);HO-1/BMMSCs could inhibit the expressions of ET-1 and i NOS,increase the expressions of e NOS and inhibit amounts of NO production,and maintain the equilibrium of ET-1/NO(P<0.05);and HO-1/BMMSCs increased the expression of v WF in hepatic sinusoidal endothelial cells(SECs),and promoted the degradation of HA,compared with those of the NS group and BMMSCs group(P<0.05).In term of the energy metabolism of the transplanted liver,HO-1/BMMSCs repaired the damaged mitochondria,and improved the activity of mitochondrial aspartate aminotransferase(ASTm)and ATPase,compared with the other two groups(P<0.05).CONCLUSION HO-1/BMMSCs can improve the microcirculation of hepatic sinusoids significantly,and recover the energy metabolism of damaged hepatocytes in rats following RLT,thus protecting the transplanted liver.

茎段和穴盘大小对北方叶用甘薯越冬育苗的影响

为探索北方叶用甘薯越冬穴盘育苗,设置4个茎段大小(4、6、8、10 cm,用D1、D2、D3、D4表示)和5种穴盘规格(32、50、72、105、128孔),搭配14个处理,研究不同搭配对种苗成活率、幼苗长势(茎粗、株高等)和鲜重等指标的影响。结果表明:相同穴盘下,随着茎段增长,幼苗的成活率、叶片数、基部茎粗和株高呈现增加的趋势,进而地上部鲜重和整株鲜重也随之增加,以D4处理最高。相同茎段下,随着穴盘孔数增加,幼苗的叶片数、基部茎粗、株高、地上部鲜重和全株鲜重减少,源于穴盘对地下部的影响,以32孔处理最高。不同茎段和穴盘搭配下,D4-32处理的生长情况最好,3月中旬,对于地上部鲜重而言,D2-72处理(9.79 g)可达到与D4-32处理相同的效果(两者间无显著性差异),其叶片数、基部茎粗和株高等指标满足移栽水平;对于整株鲜重而言,D2-105处理(10.21 g)可达到与D4-32处理相同的效果,且可节省228.1%的育苗面积,参考其重量,1月中旬,D3-72处理下的地上部和整株鲜重接近上述两个处理的水平,可节省125.0%的育苗面积。综合秧苗生长情况与经济效益,3月中旬移栽时,推荐D2-105,即含2个腋芽茎段与105孔穴盘的搭配,如有生产条件在1月中旬移栽,推荐D3-72,即含3个腋芽茎段与72孔穴盘的搭配。

Construction of hepatocyte growth factor gene recombinant adenovirus vector and its expression in rat bone marrow mesenchymal stem cells

Objective：To construct the adenoviral expression vector system containing human hepatocyte growth factor （hHGF） cDNA, and to further study the transduction efficiency and the expression of HGF in mesenchymal stem cells （MSCs）. Methods：The HGF cDNA was amplificated from the expression plasmid pCMV-HGF, and was subcloned into the adenovirus shuttle plasmid pDC316-IRESEGFP vector containing a green fluorescence protein （GFP） reporter gene. Virus Ad-HGF was produced by homologous recombination in HEK293 package cells. Bone marrow derived MSCs were harvested and cultured, and then were transduced with Ad-HGF. The efficiency of Ad-HGF transduction was assessed by FACS analysis using GFP gene expression. And HGF/MSCs were generated. The HGF concentrations in supernatants of HGF/MSCs were determined by ELISA using anti-human HGF monoclonal antibody. Results： The recombinant, named pDC316-HGF-IRES-eGFP, was digested with restriction enzyme, and the DNA sequencing of HGF was identical to the report in Genebank and did not reveal any mutation. GFP expression could be observed on the second day after packing of the linearized pAd-HGF in HEK293 cells and 7.15 × 10^10pfu/ml titer of Ad-HGF was obtained. Forty-eight hours after transduction, 96.89% of HGF/MSCs were GFP positive. Peak concentration levels of hHGF（103ng/mL） in the cultured supernatants were detected on day 2 post-transduction, and the adenovirus-mediated expression of HGF by MSCs was maintained for at least 2 weeks in vivo. Conclusion：Our data demonstrated that the adenovirus expression＇vector system pDC316-HGF-IRES-EGFP has been constructed successfully, and their effective expressions also have been obtained in MSCs. This will provide material basis for the next study on liver regeneration after small-for-size liver transplantation.

水培茎杆规格对刺龙牙产量和营养品质的影响

为筛选出适宜刺龙牙反季节生产的水培茎杆规格,在温室内对不同长度和粗度的茎杆进行水培,研究其对顶芽萌发率、产量及营养物质(可溶性蛋白质、维生素C等)的影响。结果表明:随着水培茎杆长度和粗度的增加,顶芽萌发率和产量逐渐增加,营养成分含量逐渐提高,水培茎杆粗20 mm以上、长50 cm以上的顶芽均萌发,其中茎杆粗度达到15 mm以上、长60 cm以上时,顶芽产量均超过20 g;水培茎杆规格对顶芽多糖、可溶性糖、可溶性蛋白质和维生素C等营养成分含量的影响显著,各营养成分含量随水培茎杆粗度和长度的增加逐渐增加。结合刺龙牙整形修剪技术,建议在实际生产中水培茎杆规格以粗度(20±0.2)mm、长度50~60 cm为宜。

不同尺寸规格的烟梗吸湿特性及梗丝质量的影响

为研究不同尺寸规格烟梗物理及加工特性的差异,采用单因素试验方法,首先研究了直径与长度对不同地区烟梗贮后含水率增量的影响,并对试验结果进行聚类分析,然后对比分析不同直径规格烟梗制得梗丝的成丝效果及物理质量。结果表明:(1)直径对烟梗贮后含水率增量的影响均达到极显著水平,随烟梗直径的增加,烟梗的含水率增量呈逐渐下降的趋势;长度对部分地区烟梗贮后含水率增量的影响均达到极显著水平,当烟梗长度为20~60 mm时,烟梗贮后含水率增量变化不大。根据聚类分析结果并结合实际生产,可将6地区不同直径烟梗分为4组。(2)对照样(直径2~7 mm混合烟梗)梗丝宽度均匀性较低;直径5~7 mm样品梗丝形态较宽,弹性差;直径2~5 mm样品梗丝的丝状效果较明显,形态更接近叶丝,弹性较好。综合来看,不同尺寸规格烟梗吸湿性差异较大,不宜进行混合加工,对烟梗进行尺寸划分,可改善梗丝物理质量。

半夏种茎规格对产量、品质及植株的影响

在喀斯特温和气候区,采取小区试验方法,按半夏[Pinellia ternate(Thunb.)Breit.]种茎直径≥2.0cm、1.5 cm≤种茎直径<2.0 cm、1.0 cm≤种茎直径<1.5 cm、种茎直径<1.0 cm 4种规格种植,以块茎鲜重产量、总生物碱含量与种茎规格大、中、小的关系为考察依据,研究半夏不同规格种茎种植对块茎产量和总生物碱含量的影响。结果显示,随着种茎规格的增大,半夏块茎鲜重产量呈直线上升,以种茎直径≥2.0cm的产量最高,为2.44 kg/m2。净产量以1.5≤种茎直径<2.0 cm的最高,为0.98 kg/m2;总生物碱含量以1.0 cm≤种茎直径<1.5 cm的最高,为0.302 mg/g,二者均呈开口向下的抛物线变化。考虑到兼顾块茎产量和总生物碱含量,半夏种植以种茎直径为1.0～1.5 cm的较好。

烟梗尺寸对浸梗效果的影响

选择不同尺寸的醇化后烟梗在同一条件下进行浸梗试验,计算不同浸梗时间的烟梗含水率;利用回归分析法研究了不同浸梗时间烟梗含水率的变化趋势,不同尺寸烟梗达到特定含水率所需浸梗时间的变化趋势,以及不同尺寸烟梗浸梗后直径、长度和体积变化率的变化趋势。结果表明:(1)在相同浸梗时间下,随着尺寸的增加,烟梗含水率呈逐渐降低的趋势,烟梗在浸梗过程中的含水率变化符合对数曲线;(2)随着体积的增加,烟梗达到特定含水率所需的浸梗时间呈指数函数增加;(3)不同尺寸烟梗浸梗一定时间后,其直径、长度及体积变化率的变化趋势均符合幂函数曲线。根据上述分析结果,在制梗丝工艺过程中,应根据筛分后烟梗的尺寸区间分布设定适宜的浸梗时间。

微波辐射-水蒸气法制备烟杆基颗粒活性炭

研究了以烟杆废弃物为原料,炭化过程中所产生的木焦油为主的复合粘结剂,采用微波辐射-水蒸气法制备颗粒活性炭的可行性。探讨了微波功率、活化时间以及水蒸气质量流量对颗粒活性炭吸附性能和得率的影响。得到了微波辐射-水蒸气法制备颗粒活性炭的最佳工艺:微波功率700 W,活化时间40 m in,水蒸气质量流量1.70 g/m in。此工艺条件制得的颗粒活性炭,碘吸附值1 060.81 mg/g,亚甲基蓝吸附值175 mL/g,得率30.83%。同时,测定了该颗粒活性炭氮吸附,通过BET法计算了活性炭的比表面积,并通过DFT表征了活性炭的孔结构。结果表明:该活性炭为微孔型,BET比表面积为1 109.22 m2/g,总孔容为0.613 1 mL/g。

微波辐射二氧化碳法制备烟秆基颗粒活性炭

研究了以烟秆废弃物为原料,木焦油为主的复合黏结剂,采用微波辐射二氧化碳法制备颗粒活性炭的可行性.系统探索了微波功率,活化时间以及二氧化碳流量对颗粒活性炭吸附性能和产率的影响,得到了微波辐射二氧化碳法制备颗粒活性炭的最佳工艺条件:微波功率700W,活化时间70min,二氧化碳流量0.15L/min.用此工艺条件制得的颗粒活性炭,碘吸附值为960.30mg/g,亚甲基蓝吸附值13mL/0.1g,产率为43.37%.同时,测定了该颗粒活性炭氮气吸附,通过BET法计算了活性炭的比表面积,并通过DFT表征了活性炭的孔径结果.结果表明,该活性炭为微孔型,BET比表面积为986.65m2/g,总孔容为0.5152mL/g.

骨髓间充质干细胞促进大鼠小体积肝移植后肝再生的实验研究

目的探讨骨髓间充质干细胞能否促进大鼠小体积肝移植后移植肝的再生。方法体外分离、培养、鉴定大鼠骨髓间充质干细胞。在30%大鼠部分肝移植的模型基础上,实验分为对照组(30%PLT)和骨髓间充质干细胞干预组(30%PLT+MSC)。比较两组肝移植术后的存活率,分析肝功能的变化,通过免疫组化来观察移植肝标本Cyclin D1和PCNA的表达,并对移植肝组织结构进行电镜观察。结果骨髓间充质干细胞的干预,能够改善小体积肝移植术后肝功能状况,减轻组织学损伤,并能够提高存活率,30%PLT组与30%PLT+MSC组一周存活率分别为16.7%和58.3%。而在Cyclin D1和PCNA的免疫组化表达中,30%PLT组表达明显抑制,30%PLT+MSC组表达上调。结论骨髓间充质干细胞可以存进大鼠小体积肝移植后移植肝的再生,改善肝功能,并提高存活率。

干细胞因子在大鼠下颌骨缺损修复中的表达研究

目的:探讨在SD大鼠下颌骨临界性骨缺损(critical size bone defect,CSD)与自愈性骨缺损修复过程中,各时相点干细胞因子(stem cell factor,SCF)的表达情况。方法:①分别在36只SD大鼠双侧下颌骨的下颌角部制造临界性骨缺损(直径5 mm)和自愈性骨缺损(直径2 mm)模型,实验动物分为6组,在术后第1、3、5、7、14、21天分别处死;②利用免疫组织化学方法检测骨缺损区各时相点SCF的表达情况;③利用Western印迹法检测骨缺损区各时相点SCF存在与否,并进行半定量分析。结果:成功构建了大鼠双侧下颌骨的临界性骨缺损和自愈性骨缺损模型。免疫组织化学结果显示,骨缺损愈合的各时相点SCF均有较高的表达,但SCF在临界性骨缺损组各时相点的表达,均低于自愈性骨缺损组。结论:SCF在骨缺损修复中发挥重要的作用。

腮腺尺寸变化对初治鼻咽癌调强放疗病例脑干、脊髓剂量的影响

目的:分析腮腺尺寸变化对初治鼻咽癌调强放疗病例脑干、脊髓剂量的影响。方法:选择10例初治鼻咽癌病例,采用自适应软件获取病人在第5、10、15、20、25、30次治疗时腮腺尺寸和脑干、脊髓剂量的变化情况。结果:第25次治疗时,10例病例的腮腺尺寸出现明显退缩,腮腺最大横径和前后径最大退缩率均超过30%。治疗期间有4例病例脑干、脊髓剂量变化与腮腺尺寸改变相关,最小、最大变化率出现在第30次治疗时,第2例病人的脊髓-D_(max)、第3例病人的脑干PRVD_(max)分别增加1.6%、5.38%。结论:初治鼻咽癌病例调强放疗期间,腮腺尺寸变化对脑干、脊髓剂量的影响值得重视。

马铃薯脱毒效果与茎尖大小的关系

以鄂马铃薯3号、米拉和川芋4号为材料,研究了不同品种脱毒效果与茎尖大小的关系。试验结果表明,剥离茎尖大小与成活率及成苗率呈显著正相关,与PVX、PVY、PVS等病毒脱除效果呈负相关;而在不同等级大小的茎尖中,PLRV脱除率均达100%。但为保证成活率,同时兼顾脱毒效果,剥离茎尖长度为0.1～0.3mm并带1～2个叶原基的茎尖较好。

水液压节流阀关键技术的设计研究

介绍了水液压数字节流阀阀体的设计和计算过程。通过给定的参数,确定了阀口形式和结构及进水口、出水口、阀芯与阀芯开口度等尺寸。论述了阀门材料的选择和影响节流阀流量特性的因素。