菰属系统与演化研究——花粉形态

本文首次报道了菰属Zizania L. 及其有关属，共7属，13种，3变种，1变型的花粉形 态。通过光学显微镜和扫描电镜，对其花粉的形状、外壁的层次及纹饰等进行了观察。经过研 究，笔者认为：  菰属应置于禾本科稻族内；菰属在稻族内的演化及菰属内的种间演化均存在 平行演化的现象；菰属在全世界有4种2亚种。这些结论大都吻合笔者对其它形态特征的研 究结果。     

重金属复合胁迫对酢酱草抗氧化酶系统的影响

采用盆栽法考察不同质量浓度的Cd、Zn、Cu、Pb、As 5种重金属复合胁迫对酢酱草抗氧化酶活性的影响。结果显示随着重金属处理浓度梯度的增加,酢酱草过氧化物酶(POD)活性、抗坏血酸过氧化物酶(APX)活性、脯氨酸(PRO)含量及谷胱甘肽(GSH)含量先升高后降低;而超氧化物歧化酶(SOD)活性和过氧化氢酶(CAT)酶活性逐渐下降。结果表明酢酱草在重金属复合胁迫下能防御性的增加POD酶活性、SOD酶活性、PRO含量及GSH含量以减少逆环境的伤害,而重金属复合胁迫浓度过高则会导致酢酱草抗氧化酶系统受到明显损害,生长受到很大程度的抑制。     

Market size and innovation: The intermediary role of technology licensing

Previous literature finds that larger downstream markets fuel the innovation of new technologies by incentivizing firms to spend more on R&D. Our evidence shows that larger markets also increase the extent of licensing-based cooperation between upstream innovators and downstream commercializers. This cooperation is valuable because it pools firms’ complementary capabilities. Thus, downstream market expansions could positively impact innovative outcomes even holding R&D expenditures constant. Evidence is drawn from the drug candidate licensing market, exploiting the quasi-experimental variation introduced by the enactment of the Medicare Part D program in 2003. A model for the determination of equilibrium commercialization strategies in Markets for Technology rationalizes our finding. In this framework, cooperation gains are proportional to market size but transaction costs are not. Thus, larger downstream markets foster cooperation by reducing the relative importance of the latter. To better match the empirical context, the model extends the canonical “one technology–one application” framework of related work, to the more general case of “composite technologies,” which may have more than one end-user application.     

Geographical clustering and firm growth: Differential growth performance among clustered firms

This paper investigates the effect of being located in a cluster on firm growth. In particular, it focuses on the differential growth effect of being located in a cluster, or a growth divide among clustered firms, based on the idea that, contrary to the conventional wisdom, advantages of geographical clustering are not randomly or equally available to clustered firms. Due to the intense competition among clustered firms for resources such as creative talent, firms who are more attractive to the resources are more likely to entice better resources and hence achieve higher growth. Our empirical analysis of firms in nine industries across six countries shows that being located in a cluster per se does not have a positive effect on firm growth and that domestic technological leaders with a sufficient technological distance to the global technological frontier show differentially higher growth due both to the attractiveness to promising resources and to the opportunity for incoming knowledge spillovers from global technological leaders.     

The persistence of entrepreneurship and innovative immigrants

Ethnicity and immigration status may play a role in entrepreneurship and innovation, yet the impact of university entrepreneurship education on this relationship is under-explored. This paper examines the persistence and differences in entrepreneurship by ethnicity and nationality. We find that among Stanford alumni, Asian Americans have a higher rate of entrepreneurship than white Americans. However, non-American Asians have a substantially lower, about 12% points lower, start-up rate than Asian Americans. Such discrepancy not only holds for entrepreneurial choice but also for investing as an angel investor or venture capitalist, or utilizing Stanford networks to find funding sources or partners. Participation in Stanford University’s entrepreneurship program as a student does little to reduce this gap. The low level of parental entrepreneurship and the high degree of intergenerational correlation in entrepreneurship likely result in the lower level of entrepreneurship and participation in university entrepreneurship programs among Asians relative to their Asian American counterparts. Our findings highlight the value of immigration in terms of breaking the persistence in entrepreneurship among certain ethnic groups and promoting potential high-growth entrepreneurship in the United States. In addition, our findings may have important implications for programs to incorporate immigrant entrepreneurs within their home countries to promote entrepreneurship and help break the persistence of entrepreneurship across generations.     

It's never too late: Funding dynamics and self pledges in reward-based crowdfunding

Crowdfunding recently emerged as an alternative funding channel for entrepreneurs. We use pledge-level data from Startnext, the biggest German platform, to gain insights on funding dynamics and pledgers’ motivations. We find that the majority of projects that eventually succeed are not on a successful track at 75% of their funding period. These late successes are boosted by information cascades during the final 25% of the funding duration. We conclude – in contrast with earlier literature – that project success is only partially path-dependent. While early pledges do anticipate project success, a lack of them does not necessarily mean that projects will fail. Interviews and questionnaire responses indicate that projects’ communication efforts play a role in making severely under track projects succeed eventually. Moreover, our dataset uniquely allows us to quantify the extent of self funding. Self pledges account for about 10% of all initial pledges and 9% of all pledges that secure funding. Nonetheless, the late surges at severely under track projects are mostly driven by external funders. Furthermore, we find no evidence of subsequent herding triggered by self pledges.     

Functional centrality and innovation intensity: Employee-level analysis of the Telenor group

Recent research on employee-level innovation focuses on scientists’ ability to source advanced knowledge and use it to create new ideas and innovation within a firm. The present paper introduces a new dimension to this literature: functional departments. We argue that functional centrality, namely the extent to which a functional department is central in the intra-organizational network, affects employees’ innovation intensity. We make use of a rich novel dataset at the employee-level for the Telenor Group, based on a large-scale survey among nearly 16,000 employees in all business units and functions of the company. The empirical results point out that employees’ innovation intensity is higher in departments that are centrally positioned in the company’s internal network. Task characteristics such as quality orientation, entrepreneurial attitude and result pressure moderate the relationship between centrality and innovation.     

丘陵山区覆膜旱作稻田土壤硝态氮和铵态氮动态变化规律探讨

采用田间长期定位试验对丘陵山区连续4年覆膜旱作、裸地旱作和常规水作条件下稻田土壤硝态氮和铵态氮的动态变化规律作了研究。结果表明,覆膜旱作稻田土壤的铵态氮和硝态氮显著高于常规水作。土壤NO^- 3-N占无机氮的81．16％～90．46％,是土壤铵态氮的4．32-9．49倍。因此,丘陵山区覆膜旱作稻田土壤矿质氮主要以硝态氮为主。     

铜对不同水稻品种种子萌发及根尖分生细胞钙分布的影响

以16个水稻品种为材料,测定了铜对水稻种子萌发相关指标,并观察了根尖有丝分裂及分生区Ca分布的影响。结果表明：（1）0．1mM和0．2mMCuSO4溶液处理对水稻根长的抑制作用大于对芽长的抑制,且对不同品种根长的抑制作用存在明显差异;（2）随着铜处理浓度（25、50、75、100μM）的升高,根尖细胞有丝分裂指数及相对有丝分裂指数皆呈下降趋势;（3）t常生长条件下,水稻根尖分生区细胞中的Ca主要分布在液泡和细胞间隙中,而细胞质、细胞核中分布很少;50μM铜处理下,根尖分生区细胞液泡和胞间的Ca沉淀颗粒明显减少,而胞质及核基质中的Ca沉淀颗粒增多。铜胁迫造成根尖细胞中原有Ca分布的变化可能是引起细胞功能的紊乱,进而影响根系生长的原因之一。