春小麦施磁肥的增产效应研究

试验结果表明,春小麦每公顷种子拌1500g磁肥,可使春小麦次生根和分蘖增加,防倒伏能力增强,穗数、穗粒数、千粒重均优于对照,公顷产量达3780kg。     

春小麦施磁肥的增产效应研究

试验结果表明,春小麦每公顷种子拌1500g磁肥,可命名春小麦次生根和分蘖增加,防倒伏能力增强,穗数、穗粒数、千粒重均优于对照,公顷产量达3780kg。     

大麦产量构成模型

通过产量构成法构建了适用于不同地区不同品种的大麦产量模拟模型.以南京、昆明、武汉3个地区各试验处理中不同大麦品种最适条件下的产量因素为基础,建立了最适条件下每株穗数相对值、每穗粒数相对值、千粒重相对值与累积光合有效辐射的回归方程,构建了实际条件下的不同大麦品种每株穗数、每穗粒数和千粒重与这三者在最适条件下的潜在值和实际条件下的水肥丰缺因子等变量的函数关系.模型较为全面地考虑了大麦品种生长发育的内外因素,内因主要体现为品种遗传特性（潜在的每株穗数、潜在的每穗粒数、潜在的千粒重和灌浆期因子）,外因包括光合有效辐射和水肥丰缺因子.运用武汉、昆明、扬州3个地区不同品种、不同播期的田间试验资料对模型进行了测试和检验.结果表明,模型对大麦产量构成因子及理论产量的模拟效果较好,模拟值与观测值吻合度高,每株穗数、每穗粒数和千粒重相对误差（RE）绝对值的平均值分别为1.96%、1.88%和1.67%,对这三者及理论产量的模拟值和观测值进行y=x回归分析,相关系数（r）在0.9464～0.9987,相关性显著,说明模型具有较高的预测性和适用性.     

不同土壤类型对北方粳稻穗部性状及产量构成的影响

以北方粳稻品种“长白9”、“东稻4”为试材,研究了水稻土(pH =7.25,ESP=7.60)、苏打盐碱土壤(pH=9.11,ESP=32.80)条件下两品种穗部性状及产量构成的变化规律.结果表明:与水稻土相比,在苏打盐碱土壤条件下,两品种大部分穗部性状有显著变化,枝梗数、枝梗长度、枝梗粒数均显著下降;各产量构成因素也发生显著变化,尤其是穗粒数显著减少(“东稻4”减少30.0％,“长白9”减少30.5％);单株产量与穗部性状相关分析表明,穗粒数较结实率、千粒重对产量的贡献率最大;每穗一次枝梗总粒数的减少主要受每穗一次枝梗数减少的影响,每穗二次枝梗总粒数的减少受每穗二次枝梗数及二次枝梗单枝着粒数减少共同影响;在苏打盐碱土壤条件下,相对一次枝梗来说,二次枝梗粒数更容易受环境影响.     

吉林省主栽水稻品种产量因素的遗传分析和高产育种方向的探讨

利用吉林省主要栽培的9个水稻品种为材料,研究了与单株粒重有关的9个性状的基本遗传参数和遗传通径分析。结果表明：遗传变异系数以单株有效穗和单株粒重最大;株高和结实率最小。穗期、千粒重、穗长的遗传力较大;每穗颖花数、单株穗数、单株粒重遗传力较低。三要素对产量贡献的大小依次为每穗颖花数、千粒重、单株有效穗。在保证足够穗数基础上,大力提高每穗颖花数,适当增加粒重作为吉林省今后高产育种的主攻方向。     

吉林省主栽水稻品种产量因素的遗传分析和高产育种方向的探讨

利用吉林省主要栽培的9个水稻品种为材料,研究了与单株粒重有关的9个性状的基本遗传参数和遗传通径分析。结果表明:遗传变异系数以单株有效穗和单株粒重最大;株高和结实率最小。穗期、千粒重、穗长的遗传力较大;每穗颖花数、单株穗数、单株粒重遗传力较低。三要素对产量贡献的大小依次为每穗颖花数、千粒重、单株有效穗。在保证足够穗数基础上,大力提高每穗颖花数,适当增加粒重作为吉林省今后高产育种的主攻方向。     

水稻穗异常突变体tutou4的鉴定及基因定位

水稻穗异常退化现象在水稻的生长发育过程中经常发生.穗部退化可引起穗长、枝梗数、每穗粒数和结实率下降,影响单株产量.穗退化性状因其遗传基础复杂、受环境和生理因素影响较大,其分子机制及其遗传网络仍知之甚少.tutou4是一个来自于组织培养的稳异常退化突变体,该突变体表现为穗部部分颖花退化,每穗粒数和枝梗数减少,单株产量降低...     

GA_3、ABA和IBA对不同灌溉方式下水稻叶绿素荧光特性及产量构成的影响

为了明确外源激素诱导水稻抗旱性的效果及其生理机制。以中嘉早17为材料,分析外源激素在淹水灌溉、干湿交替灌溉和干旱灌溉方式下叶绿素荧光参数的差异及其对产量与产量构成的影响。结果表明,干旱灌溉显著降低了叶片光系统Ⅱ(PSⅡ)最大光化学量子产量、实际光量子效率、非光化学猝灭值、有效穗数、每穗粒数、结实率,孕穗期比分蘖期更为敏感,表现为相同胁迫时间下最大光化学量子产量、每穗粒数、单株穗数等下降更显著。赤霉素(gibberellin,GA3)处理后降低了PSⅡ最大光化学量子产量、非光化学猝灭和光化学猝灭系数,导致有效穗数减少、千粒重和结实率降低。脱落酸(abscisic acid,ABA)处理能缓解孕穗期干旱胁迫,减轻水稻叶片的光抑制程度,提高叶绿素荧光参数,增强抗旱能力。综合来看,以分蘖期淹水条件下结合IBA处理产量最高,比对照增产7.4%,这可能与淹水条件下吲哚丁酸(indolebutyric acid,IBA)处理能提高光合效率有关。     

不同生育时期水分有限亏缺对冬小麦产量及其构成因素的影响

利用温室盆栽试验研究了施Ｎ与不施Ｎ（施肥）条件下不同生育阶段水分有限亏缺对冬小麦产量及其构成因素的影响。结果表明,在小麦苗期、拔节期、灌浆期进行水分亏缺胁迫处理。对其经济学产量,生物学产量,每盆有效穗数、每穗粒数、千粒重等影响达显著或极显著水平。苗期和灌浆期为水分亏缺不敏感期,拔节期为亏缺敏感期。在施底肥条件下拔节期水分亏缺使每穗粒数、千粒重显著减少,或低于对照水平。从补偿角度看,苗期是生物学产量     

乌桕每株穗数和每穗果数对种子产量的影响初探

本文报道人工栽培乌桕(Sapium sebiferum (L)Roxb.)林在相同的品种、年龄、立地条例、抚有管理等条件下,每株穗数和每穗果数这两个因素在影响株产量的作用,其中以每株穗数对乌桕产量影响较大。     

流域水碳过程耦合模拟——WaSSI-C模型的率定与检验

在复杂的气候变化条件下, 利用水碳耦合模型进行生态水文学研究成为主要的研究手段和途径。该文以杂谷脑河上游流域为例, 在确定生态水文模型WaSSI-C模拟尺度的基础上, 探讨水碳耦合模型在中国西南湿润地区的适用性。杂古脑河上游流域位于岷江上游, 隶属于长江流域。在分析和讨论了模型结构和机理的基础上, 分别对模型蒸散和融雪计算进行了补充改进, 以提高模型的适用性。将1988-1996年作为模型的率定期, 1997-2006年作为模型的验证期, 分别在率定期和验证期利用实测的径流数据和中分辨率成像光谱仪数据的总初级生产力、蒸散(ET)数据, 对模拟结果进行对比验证。并利用决定系数(R²)和Nash-Sutcliffe效率系数(NS)两个指标对模拟效果进行评价。流域总径流率定期和验证期对比验证的R²分别为0.86和0.78; NS分别为0.82和0.67。总生态系统生产力和ET验证期的R²分别为0.89和0.78。可见模型模拟结果的两个评价指标都处于较为理想的区间内, 说明WaSSI-C模型在研究区内具有较好的适用性。并对模型的蒸散计算方法进行了讨论, 在此基础上提出了模型中存在的问题和改进的方向。     

生理房室药动学模型

生理药动学模型较ｎ房室模型能更准确地描述药物在体内的处置过程,但在实际应用中由于其计算结果有较大的误差而限制其应用和推广．在生理模型中,某一组织器官中血液分布容积相对于单位时间的血流量来说,如果太大,就去给计算结果带来较大的误差．本文提出的生理房室模型可以减小这种误差,从而更准确地模拟药物在体内的处置过程．文中对一组模拟的生理和生化参数分别求出了生理房室模型和生理模型的数值解．通过两组解的比较,说明生理房室模型可以描述药物在体内处置过程中的细微变化．     

Maintenance requirements: energy supply from simultaneous endogenous respiration and substrate consumption

Abstract A model is presented that describes energy for maintenance purposes (ATP) as being obtained simultaneously from biomass degradation as well as from substrate degradation in excess of growth requirements. The ratio between both catabolic processes was taken to be growth rate dependent. As such, this approach is intermediate between established models; its significant features are negative growth and the absence of substrate consumption at zero substrate concentration, and the attainability of the maximum specific growth rate (the model parameter μ _max) at elevated substrate concentrations. As a simple case, the amounts of ATP obtained from direct substrate catabolism or from the degradation of an equivalent amount of biomass were taken as identical. Also, the maintenance demand in terms of ATP per unit time and biomass was taken to be constant. True growth rate dependency of maintenance can be implemented by relaxing either of these assumptions.     

An EMG-driven model applied for predicting metabolic energy consumption during movement

The relationship between mechanical work and metabolic energy cost during movement is not yet clear. Many studies demonstrated the utility of forward-dynamic musculoskeletal models combined with experimental data to address such question. The aim of this study was to evaluate the applicability of a muscle energy expenditure model at whole body level, using an EMG-driven approach.Four participants performed a 5-min squat exercise on unilateral leg press at two different frequencies and two load levels. Data collected were kinematics, EMG, forces and moments under the foot and gas-exchange data. This same task was simulated using a musculoskeletal model, which took EMG and kinematics as inputs and gave muscle forces and muscle energetics as outputs. Model parameters were taken from literature, but maximal isometric muscle force was optimized in order to match predicted joint moments with measured ones. Energy rates predicted by the model were compared with energy consumption measured by the gas-exchange data.Model results on metabolic energy consumption were close to the values obtained through indirect calorimetry. At the higher frequency level, the model underestimated measured energy consumption. This underestimation can be explained with an increase in energy consumption of the non-muscular mass with movement velocity.In conclusion, results obtained in comparing model predictions with experimental data were promising. More research is needed to evaluate this way of computing mechanical and metabolic work.     

Numerical model (switchable/dual model) of the human head for rigid body and finite elements applications

In this paper, a methodology for the development and validation of a numerical model of the human head using generic procedures is presented. All steps required, starting with the model generation, model validation and applications will be discussed. The proposed model may be considered as a dual one due to its capabilities to switch from deformable to a rigid body according to the application's requirements. The first step is to generate the numerical model of the human head using geometry files or medical images. The required stiffness and damping for the elastic connection used for the rigid body model are identified by performing a natural frequency analysis. The presented applications for model validation are related to impact analysis. The first case is related to Nahum's (Nahum and Smith 1970) experiments pressure data being evaluated and a pressure map generated using the results from discrete elements. For the second case, the relative displacement between the brain and the skull is evaluated according to Hardy's (Hardy WH, Foster CD, Mason, MJ, Yang KH, King A, Tashman S. 2001.Investigation of head injury mechanisms using neutral density technology and high-speed biplanar X-ray. Stapp Car Crash J. 45:337–368, SAE Paper 2001-22-0016) experiments. The main objective is to validate the rigid model as a quick and versatile tool for acquiring the input data for specific brain analyses.     

物种分布模型在海洋潜在生境预测的应用研究进展

海洋生物的栖息分布与环境要素的关联性一直是海洋生态学研究的热点之一.近年来,物种分布模型被广泛应用于预测海洋物种分布、潜在适宜性生境评价等研究,为保护海洋生物多样性、防治外来物种入侵及制定渔业管理措施等提供了一条有效途径.物种分布模型主要包括生境适宜性指数模型、机理模型和统计模型.本文对物种分布模型的理论基础进行了归纳和总结,回顾了物种分布模型在预测海洋物种潜在地理分布研究中的开发与应用,重点介绍了不同类型统计模型在海洋物种潜在分布预测中的研究实例.比较各种选取变量和模型验证方法,认为赤池信息准则对于选取模型变量具有优势,Kappa系数和受试者操作特征曲线下面积在验证模型精度中应用最广泛.阐述了物种分布模型存在的问题及未来发展趋势,随着海洋生物生理机制研究的进一步深入,机理模型将是今后物种分布模型发展的重点.     

On the mechanistic underpinning of discrete-time population models with complex dynamics

We present a mechanistic underpinning for various discrete-time population models that can produce limit cycles and chaotic dynamics. Specific examples include the discrete-time logistic model and the Hassell model, which for a long time eluded convincing mechanistic interpretations, and also the Ricker- and Beverton-Holt models. We first formulate a continuous-time resource consumption model for the dynamics within a year, and from that we derive a discrete-time model for the between-year dynamics. Without influx of resources from the outside into the system, the resulting between-year dynamics is always overcompensating and hence may produce complex dynamics as well as extinction in finite time. We recover a connection between various standard types of continuous-time models for the resource dynamics within a year on the one hand and various standard types of discrete-time models for the population dynamics between years on the other. The model readily generalizes to several resource and consumer species as well as to more than two trophic levels for the within-year dynamics.     

Conventional and newly developed bioheat transport models in vascularized tissues: A review

Heat transfer in a biological system is a complex process and its analysis is difficult. Heterogeneous vascular architecture, blood flow in the complex network of arteries and veins, varying metabolic heat generation rates and dependence of tissue properties on its physiological condition contribute to this complexity. The understanding of heat transfer in human body is important for better insight of thermoregulatory mechanism and physiological conditions. Its understanding is also important for accurate prediction of thermal transport and temperature distribution during biomedical applications. During the last three decades, many attempts have been made by researchers to model the complex thermal behavior of the human body. These models, viz., blood perfusion, countercurrent, thermal phase-lag, porous-media, perturbation, radiation, etc. have their corresponding strengths and limitations. Along with their biomedical applications, this article reviews various contextual issues associated with these models. After brief discussion of early bioheat models, the newly developed bioheat models are discussed in detail. Dependence of these models on biological properties, viz., thermophysical and optical properties are also discussed.     

On the mechanistic underpinning of discrete-time population models with Allee effect

The Allee effect means reduction in individual fitness at low population densities. There are many discrete-time population models with an Allee effect in the literature, but most of them are phenomenological. Recently, Geritz and Kisdi [2004. On the mechanistic underpinning of discrete-time population models with complex dynamics. J. Theor. Biol. 228, 261-269] presented a mechanistic underpinning of various discrete-time population models without an Allee effect. Their work was based on a continuous-time resource-consumer model for the dynamics within a year, from which they derived a discrete-time model for the between-year dynamics. In this article, we obtain the Allee effect by adding different mate finding mechanisms to the within-year dynamics. Further, by adding cannibalism we obtain a higher variety of models. We thus present a generator of relatively realistic, discrete-time Allee effect models that also covers some currently used phenomenological models driven more by mathematical convenience.     

Computational framework to model and design surgical meshes for hernia repair

Surgical procedures for hernia surgery are usually performed using prosthetic meshes. In spite of all the improvements in these biomaterials, the perfect match between the prosthesis and the implant site has not been achieved. Thus, new designs of surgical meshes are still being developed. Previous to implantation in humans, the validity of the meshes has to be addressed, and to date experimental studies have been the gold standard in testing and validating new implants. Nevertheless, these procedures involve long periods of time and are expensive. Thus, a computational framework for the simulation of prosthesis and surgical procedures may overcome some disadvantages of the experimental methods. The computational framework includes two computational models for designing and validating the behaviour of new meshes, respectively. Firstly, the beam model, which reproduces the exact geometry of the mesh, is set to design the weave and determine the stiffness of the surgical prosthesis. However, this implies a high computational cost whereas the membrane model, defined within the framework of the large deformation hyperelasticity, is a relatively inexpensive computational tool, which also enables a prosthesis to be included in more complex geometries such as human or animal bodies.