不同山葡萄品种光响应模型拟合及综合评价

为筛选最适合山葡萄的光合-光响应模型和光能利用效果最佳的山葡萄品种,选取'北冰红"双红'左优红"雪兰红"北国红'和'双丰'6个山葡萄品种,利用直角双曲线模型、非直角双曲线模型、直角双曲线修正模型和指数函数模型4个光响应模型,通过因子分析对最大净光合速率(Pnmax)、表观量子效率(α)、暗呼吸速率(Rdark)、光补...     

割离井公式反求水文地质参数的流量-时间配线法

通过分析初始水位呈水平及抽水过程中井内定水位且上部和下部无流量补给时,均质含水层中割离井渗流模型的井的出水量公式,引进仅与相对井径有关的井流函数,对出水量公式两边取对数,将流量—时间配线法引入割离井法中反求水文地质参数;其步骤与常用泰斯流量—时间配线法的步骤相似;最后用实例验证了该方法的可行性。     

棕壤土水分特征曲线拟合的比较分析

以棕壤土为对象,采用压力膜法测定均质原状土壤样品一系列含水率和对应基质势值,分别用幂函数和Van Genuchten （1980）模型进行拟合,并与实测含水率数据进行比较。结果表明：压力膜法测定土壤水分特征曲线是可行的,所得试验结果合理,可用于土壤水分动态模拟。     

旱稻干物质生产和分配的研究

 为了探讨旱地条件下旱稻品种干物质生产和分配以及籽粒灌浆过程的特点,1986年和1987年在北京农业大学种植5个旱稻品种。用Hunt的生长分析法研究其干物质生产,结果表明旱稻品种的干物质生产和分配与水稻品种不相同。因不同生育阶段群体生长率、净同化率和光合势对旱稻品种总干重的影响不同。籽粒干物质积累过程用Logistic生长曲线拟合,符合度达极显著水平。     

有风险投资与无风险投资组合的研究

本研究通过引入单位风险的概念，并结合有效边界上的单位风险极小点，给出了各种情况下有风险投资和无风险投资的最优组合方案。     

林区公路中线测量计算的微机程序

本文介绍编制的BASIC程序,能承担线路中线测量各种曲线的计算工作,能进行多次快速拟定曲线半径,从而可以选择最合理的半径,能显示线路中线测量各曲线计算需要的数据和曲线里程桩号,并且可以重复显示有关数据,避免了重新输入变量的麻烦。使用该软件进行林区公路中线测量计算,其操作简便,运算速度快,计算精确,工效高。     

Comparative diagnostic test characteristics of oscillometric and Doppler ultrasonographic methods in the detection of systolic hypertension in dogs

Comparison of test characteristics allows a clinician to choose the optimal diagnostic test method for an individual patient. This study assessed the comparative test characteristics of noninvasive (NI) blood pressure measurement methods (oscillometric and Doppler) and used this information to develop optimal cutoff values for diagnosis of systolic hypertension in dogs by these NI methods. Simultaneous NI (oscillometric or Doppler methods) and invasive (arterial puncture [AP]) systolic blood pressure (SBP) measurements were obtained prospectively from normal dogs and dogs suspected of having systemic hypertension based on clinical signs. Oscillometric SBP readings were obtained from the distal hind limb (Osc-L, n = 54) or the proximal tail (T. n = 27). Doppler BP measurements were obtained using a forelimb cuff (n = 57). AP-SBP was categorized as hypertensive if > or = 160 mmHg, and sensitivity (Se). specificity (Sp), and likelihood ratios (LR) were calculated for diagnostic cutoff values ranging from 130 to 220 mmHg. Receiver operator characteristic (ROC) curves were analyzed to determine optimal cutoff values for diagnosis of AP-SBP > or = 160 mmHg. Optimal NI SBP cutoff values considered to reflect AP values > or = 160 mmHg were: Osc-L = 160 mmHg (Se: 65%, Sp: 85%. LR = 4.33: 1), Osc-T = 150 mmHg (Se: 84%, Sp: 75%, LR = 3.36: 1), and Doppler = 160 mmHg (Se: 71%,     

Observations on the potential of microwaves for weed control

Field tests of a prototype microwave‐based weed killer machine were conducted on Abutilon theophrasti, Panicum miliaceum, lucerne and oilseed rape pure stands. The approach can be considered a thermal weed control method, the microwave radiation causing dielectric heating of plant tissue water that eventually kills the plant. The method could overcome the limitations of other thermal methods, such as fire risk with flaming or the heavy loads required for hot water treatments. Species were effectively controlled by microwave irradiation, but their sensitivity and the evolution of damage symptoms over time differed. Lucerne showed no sigmoidal response and was the least affected by the treatment, while a log‐logistic curve expressed the dose–response relationships of the other species quite well. The estimated microwave dose for a 90% dry weight reduction ranged from 1015 kJ m^?2 in A. theophrasti to 3433 kJ m^?2 in P. miliaceum. Energy cost evaluation indicated that increased efficiency is required for this technique to compete with other thermal methods. Microwave efficiency could be increased by a flux configuration that minimizes soil penetration and maximizes absorption by plants, which, in turn, depends on plant growth form.     

Isolation and Identification of Enterococcus faecalis from Fur-bearing Animals

In order to obtain Enterococcus faecalis from fur animals and evaluate its prebiotic properties,in this study,Enterococcus faecalis was isolated from the feces of healthy adult fur-bearing animals (mink,fox,raccoon dog),identified by morphological observation,biochemical test and 16S rRNA sequence analysis.The growth curve,acid production capacity and antibiotic sensitivity of the Enterococcus faecalis isolates were measured to evaluate their probiotic properties.Some strains were selected to determine their tolerance to temperature,artificial gastric juice and artificial bile salt.The results showed that five strains were Gram-positive,and their biochemical characteristics were basically consistent with the standard strains of Enterococcus faecalis,and they were identified as Enterococcus faecalis by 16S rRNA sequence analysis.The five strains all entered the logarithmic phase at 2 h after culture,and entered the stable phase at 8-10 h,and had weak acid production capacity.The resistance rate of the isolates to tetracycline and levofloxacin was 100%,followed by penicillin (80%),erythromycin (80%),gentamicin (80%) and chloramphenicol (40%).All the isolates were sensitive to ampicillin and vancomycin.Enterococcus faecalis from mink,fox and raccoon dog had strong tolerance to temperature below 60 ℃,artificial gastric juice with pH>3.0 and 0.3%-0.5% concentration of bile salt,but poor tolerance to temperature above 70 ℃,and artificial gastric juice with pH<3.0.In conclusion,five strains of Enterococcus faecalis from fur animals (mink,fox,raccoon dog) were obtained in this study.The isolated strains propagated rapidly,which were suitable for colonization and played a prebiotic role in fur animals' intestines,and had good prebiotic characteristics and stress resistance.They could be used as candidate strains for animal microbiological agents for further study.     

矮化自根砧苹果苗木生长动态及其根系分布特征

【目的】明确矮化自根砧苹果苗木的生长规律及根系空间分布特征,为苗木科学管理提供依据。【方法】以1年生矮化自根砧苹果苗木(富士/M9)为试材,在2013-03-29-2013-10-23,每隔7d对其地上部主干长度进行测量,利用原位取土法每隔30d将根系全部挖出,分析苗木的生长动态和根系空间分布特征。【结果】1年生矮化自根砧苹果苗木主干生长近似"S"型生长曲线,可分为生长渐增期、生长快增期、生长缓增期3个时期,Logistic生长曲线能很好地反映其生长动态。地下部根系在6、9月份出现2个生长高峰,7、8月份根系死亡量较大;在水平方向,吸收根、输导根主要分布在距树干0~30cm处;在垂直方向,吸收根集中分布于0~40cm土层,输导根全部分布于0~30cm土层;根系根长密度在水平方向、垂直方向均呈指数衰减规律;通过建立二维根系密度方程,可知1年生矮化自根砧苹果苗木根系分布符合二维指数分布。【结论】矮化自根砧苹果苗木根系构型呈无主根、侧根集中分布于砧木中下部、水平根分布多而广等特点。