共查询到20条相似文献,搜索用时 15 毫秒
1.
l-hreo-2,3-hexodiulosono-1,4-lactone 2-(p-methoxyphenylhydrazone) (1) was condensed with arylhydrazines to give mixed bishydrazones, whose acetylation gave the corresponding di-O-acetyl derivatives. The hydrazone 1 undergoes elimination of one molecule of water per molecule during, the acetylation, and gives 4-(2-acetoxy- ethylidene)-4-hydroxy-2,3-dioxobutano-1,4-lactone 2-(p-methoxyphenylhydrazone), which reacts with methylhydrazine, via a ring transformation process, to give 1-methyl-3-(L-methylpyrazolin-3-yl)-4,5-pyrazoledione 4-(p-methoxyphenylhydrazone). Alkali rearranged the mixed bishydrazones to 1-aryl-3-(l-threo-glycerol-1-yl)-4,5- pyrazoledione 4-(p-methoxyphenylhydrazones), which gave triacetyl and tribenzoyl derivatives, and, upon periodate oxidation, afforded 1-aryl-3-formyl-4,5- pyrazolediones 4-(p-methoxyphenylhydrazones) that gave the corresponding phenylhydrazones. The n.m.r. and mass spectra of some of these derivatives have been investigated. 相似文献
2.
Bottari B Maccari R Monforte F Ottanà R Vigorita MG Bruno G Nicolò F Rotondo A Rotondo E 《Bioorganic & medicinal chemistry》2001,9(8):2203-2211
The reaction of 2,6-diacetylpyridine (dap) and isonicotinoyl- or benzoylhydrazide leads to bishydrazones H(2)dapin (1a) and H(2)dapb (1b), respectively. The condensation can either take place as a bimolecular kinetic process between the two reactants or as a monomolecular metal-templated synthesis in the presence of nickel(II) ions. In the latter case the reaction products are charged 2,6-diacetylpyridine bis(hydrazone) nickel(II) complexes, which can be easily deprotonated to neutral hydrazonates. Diffractometric analysis of one of these [Ni(dapb)](2) (8b) has shown a binuclear structure with two octahedral nickel(II) ions bridged by two helicoidal dap (bishydrazonates) in a spheroidal structure of C(2V) symmetry. The synthesized complexes 8 are promising as antimycobacterial agents against M. tuberculosis H37Rv. In particular, 8b displays significant activity (MIC=0.025 microg/mL) 10-fold higher than rifampin and equal to isoniazid, while its ligand is ineffective. Compound 8b is also capable of reducing HIV-induced cytopathogenic effect in human T(4 )lymphocytes. 相似文献
3.
Controlled reaction of L-threo-2,3-hexodiulosono-1,4-lactone with substituted phenylhydrazines gave the 2-(monoarylhydrazones) (2), which underwent dehydrative acetylation to 4-(2-acetoxyethylidene)-4-hydroxy-2,3-dioxohutyro-1,4-lactone 2-(2-arylhydrazones) (3). The latter reacted with methylhydrazine to give 1-methyl-3-(1-methylpyrazolin-3-yl)-4,5-pyrazoledione 4-(2-arylhydrazones) (4). Reaction of the monoarythydrazones (2) with phenylhydrazine gave the mixed bishydrazones (5), which were rearranged by alkali and acidification to the pyrazolediones (6). Compounds 6 gave triacetyl (7) and tribenzoyl derivatives (8), and, on periodite oxidation, the aldehydes (9), which afforded the monohydrazones (10). The i.r.. n.m.r.. and mass-spectral data of some of the compounds were investigated. 相似文献
4.
景观空间动态模型研究现状和应重点解决的问题 总被引:12,自引:7,他引:12
分析了景观空间动态模型研究的现状及今后的重点发展方向。论文重点介绍了随机景观模型、邻域规则模型和景观过程模型(包括渗透模型、个体行为模型和空间生态系统模型)3类景观空间模型的发展现状、存在的主要问题以及对这些模型途径进行完善的有关工作,并从确证性分析、有效性分析与敏感性分析等3个方面阐述了模型检验技术的发展现状。最后,总结了未来景观空间动态模型发展中应重点解决的主要问题,即模型算法的优化、尺度转换、模型的复杂化与简化、模型检验与评价,通用模型的建立以及传统模型与社会经济因素衔接问题。 相似文献
5.
基于北方农牧交错带主要作物马铃薯和油葵的叶片气孔导度、净光合速率和气象因子的平行观测数据,对常用气孔导度模型(Jarvis模型、Ball-Berry模型、Leuning模型和Medlyn模型)进行了适用性评价.结果表明:马铃薯的气孔导度与净光合速率呈现较强的线性关系,而油葵气孔导度与净光合速率的线性关系较弱.对于马铃薯气孔导度,Ball-Berry模型模拟效果最佳,Leuning模型和Medlyn模型次之,Jarvis模型模拟效果最差;各模型的模拟值与观测值的均方根误差(RMSE)分别为0.0331、0.0371、0.0456和0.0794 mol·m-2·s-1,归一化均方根误差(NRMSE)分别为26.8%、30.0%、36.9%和64.3%,拟合度(R2)分别为0.96、0.61、0.91和0.88.对于油葵的气孔导度,Jarvis模型模拟效果略好于Ball-Berry模型、Medlyn模型和Leuning模型,其RMSE分别为0.2221、0.2534、0.2547和0.2758 mol·m-2·s-1,NRMSE分别为40.3%、46.0%、46.2%和50.1%,R2分别为0.38、0.22、0.23和0.20.气象因子对气孔导度作用的通径分析表明,北方农牧交错带马铃薯和油葵气孔导度日变化主要受饱和水汽压差影响.模型评价结果表明用于油葵的气孔导度模型需要进一步改进. 相似文献
6.
Dong K. Kim 《In vitro cellular & developmental biology. Animal》1997,33(4):289-293
Summary Doubling time has been widely used to represent the growth pattern of cells. A traditional method for finding the doubling
time is to apply gray-scaled cells, where the logarithmic transformed scale is used. As an alternative statistical method,
the log-linear model was recently proposed, for which actual cell numbers are used instead of the transformed gray-scaled
cells. In this paper, I extend the log-linear model and propose the extended log-linear model. This model is designed for
extra-Poisson variation, where the log-linear model produces the less appropriate estimate of the doubling time. Moreover,
I compare statistical properties of the gray-scaled method, the log-linear model, and the extended log-linear model. For this
purpose, I perform a Monte Carlo simulation study with three data-generating models: the additive error model, the multiplicative
error model, and the overdispersed Poisson model. From the simulation study, I found that the gray-scaled method highly depends
on the normality assumption of the gray-scaled cells; hence, this method is appropriate when the error model is multiplicative
with the log-normally distributed errors. However, it is less efficient for other types of error distributions, especially
when the error model is additive or the errors follow the Poisson distribution. The estimated standard error for the doubling
time is not accurate in this case. The log-linear model was found to be efficient when the errors follow the Poisson distribution
or nearly Poisson distribution. The efficiency of the log-linear model was decreased accordingly as the overdispersion increased,
compared to the extended log-linear model. When the error model is additive or multiplicative with Gamma-distributed errors,
the log-linear model is more efficient than the gray-scaled method. The extended log-linear model performs well overall for
all three data-generating models. The loss of efficiency of the extended log-linear model is observed only when the error
model is multiplicative with log-normally distributed errors, where the gray-scaled method is appropriate. However, the extended
log-linear model is more efficient than the log-linear model in this case. 相似文献
7.
The hydrologic model is the foundation of water resource management and planning. Conceptual model is the essential component of groundwater model. Due to limited understanding of natural hydrogeological conditions, the conceptual model is always constructed incompletely. Therefore, the uncertainty in the model's output is evitable when natural groundwater field is simulated by a single groundwater model. A synthetic groundwater model is built and regarded as the true model, and three alternative conceptual models are constructed by considering incomplete hydrogeological conditions. The outputs (groundwater budget terms from boundary conditions) of these groundwater models are analyzed statistically. The results show that when the conceptual model is closer to the true hydrogeological conditions, the distributions of outputs of the groundwater model are more concentrated on the true outputs. Therefore, the more reliable the structure of the conceptual model is, the more reliable the output of the groundwater model is. Moreover, the uncertainty caused by the conceptual model cannot be compensated by parameter uncertainty. 相似文献
8.
熟鸡肉中金黄色葡萄球菌生长预测模型的建立 总被引:2,自引:0,他引:2
【目的】研究不同浓度和不同温度条件下金黄色葡萄球菌接种在熟鸡肉中的生长情况,比较3种常见预测模型拟合的准确性,选择最适合的预测模型建立一级和二级模型,为进一步探讨建立三级模型提供数据基础。【方法】测定浓度为102、103和104 CFU/g的金黄色葡萄球菌接种在15-36°C熟鸡肉中的生长数据,使用Matlab软件分别建立修正的Gompertz、Logistic和Baranyi模型,通过比较残差和拟合度(RSS、AIC、RSE)选择最优模型,并且拟合出生长参数(迟滞期、最大比生长速率和最大细胞密度),在此基础上通过响应面方程建立二级模型。最后对模型的可靠性进行了内部和外部实验验证。【结果】36°C和29°C条件下,修正的Gompertz模型最适合;22°C和15°C条件下,最适合模型按接种浓度依次为修正的Gompertz、Logistic和Baranyi模型,综合考虑,最优模型选择修正的Gompertz模型。通过计算预测标准差(%SEP)、平方根误差(RMSE)、准确性因子(Af)和偏差因子(Bf)对建立的二级模型进行数学检验,检验结果均在可接受范围内。【结论】用修正的Gompertz方程和响应面方程建立的一、二级预测模型可以为建立三级模型提供有效、精确的基础。 相似文献
9.
选取在经济学和社会科学领域广泛应用的零膨胀模型(zero-inflated models)和栅栏模型(Hurdle models)对大兴安岭地区林火发生进行模拟,应用赤池准则(AIC)、似然比检验(LR)和模型残差平方和(SSR)对两类共4个回归模型——零膨胀泊松模型(ZIP)、零膨胀负二项模型(ZINB)、栅栏泊松模型(PH)、栅栏负二项模型(NBH)进行拟合分析,最终选取适合此林火发生特性的预测模型.模型的AIC和SSR值表明,ZINB模型对当地林火数据的拟合度最高.运用LR检验对嵌套模型(ZINB与ZIP,NBH与PH)进行检验,结果显示: ZINB和NBH均优于各自的嵌入模型,说明负二项(NB)模型对数据结构中的过度离散现象可以很好地模拟和解释.根据研究区林火实际发生规律和两类不同模型的应用假设条件判断,零膨胀模型更适合塔河地区的林火特性. 相似文献
10.
根据 SPAC理论建立了一个冬小麦光合和蒸散的耦合模型。冬小麦 CO2 通量包括冠层光合、呼吸和土壤呼吸。冠层光合采用了 Farquhar光合作用生化模型 ,并通过冠层阻力的参数化将光合作用与蒸腾作用耦合起来。用涡度相关方法观测了 CO2通量 ,对模型进行了验证 ,结果显示模型可以较好地模拟 CO2 通量日变化过程。对模型的敏感性分析发现日间 CO2 通量最敏感的参数是初始量子效率。其次 ,CO2 通量对光响应曲线凸度、CO2 补偿点、凋萎点和叶面积指数的变化也有着较强的敏感性 ;夜间 CO2 通量敏感的参数是最适温度下 Rubisco催化能力和暗呼吸参数 相似文献
11.
用光合-蒸散耦合模型模拟冬小麦CO2通量的日变化 总被引:1,自引:0,他引:1
根据SPAC理论建立了一个冬小麦光合和蒸散的耦合模型.冬小麦CO2通量包括冠层光合、呼吸和土壤呼吸.冠层光合采用了Farquhar光合作用生化模型,并通过冠层阻力的参数化将光合作用与蒸腾作用耦合起来.用涡度相关方法观测了CO2通量,对模型进行了验证,结果显示模型可以较好地模拟CO2通量日变化过程.对模型的敏感性分析发现日间CO2通量最敏感的参数是初始量子效率.其次,CO2通量对光响应曲线凸度、CO2补偿点、凋萎点和叶面积指数的变化也有着较强的敏感性;夜间CO2通量敏感的参数是最适温度下Rubisco催化能力和暗呼吸参数. 相似文献
12.
F. Martínez-Martínez M.A. Lago M.J. Rupérez C. Monserrat 《Computer methods in biomechanics and biomedical engineering》2013,16(7):747-757
In this study, six biomechanical models for simulating lamb liver behaviour are presented. They are validated using similarity coefficients from Medical Image on reconstructed volumes from computerised tomography images. In particular, the Jaccard and Hausdorff coefficients are used. Loads of 20 and 40 g are applied to the livers and their deformation is simulated by means of the finite element method. The models used are a linear elastic model, a neo-Hookean model, a Mooney–Rivlin model, an Ogden model, a linear viscoelastic model and a viscohyperelastic model. The model that provided a behaviour that is closest to reality was the viscohyperelastic model, where the hyperelastic part was modelled with an Ogden model. 相似文献
13.
地表水热通量研究进展 总被引:18,自引:3,他引:18
介绍了当前国内外地表水热通景观测研究的进展及3种不同类型的土壤-植被-大气传输模型(SVAT):单层模型、双层模型和多层模型。遥感手段常用于监测大面积地表水热通量。基于地表能量平衡方程,现已建立了许多遥感模型以估算水热通量(如简化模型、单层模型、附加阻抗模型、作物缺水指数模型和二源阻抗模型等),并对这些模型复杂程度及应用范围进行了分析。 相似文献
14.
A three-pool growth model of an individual Escherichia coli cell is described herein. The model is based on a previously developed chemically structured complex single cell growth model. The reduction in model complexity and the identification of the essential modes of motion, over the time scale of growth, is achieved by temporal decomposition and analysis of hierarchy in relaxation times. The three-pool model faithfully simulates the changes in cell size, cell shape, cell macromolecular composition, DNA initiation and termination periods, and the dependence of cell growth under abiotic glucose limitation. The predictions made by the reduced model compare favorably with both the experimental data and those of the full single cell model (SCM) without any parameter adjustments. The three-pool model has very few significant parameters and has the potential to find immediate practical use in bioreactor design and process control strategies. The model development illustrates the use of modal analysis to yield reduced physiologically realistic dynamic model of complex microbial system such as E. coll. 相似文献
15.
Dr. Sadao Tomizawa 《Biometrical journal. Biometrische Zeitschrift》1987,29(1):45-55
For square contingency tables with ordered categories, Agresti (1983) considered the linear diagonals-parameter symmetry model. An extended model including that model is proposed which has only one more parameter than that model. The model also includes the conditional symmetry model considered by McCullagh (1978). Decompositions for the proposed model and Agresti's model are given. 相似文献
16.
河北省年均降水量插值方法比较 总被引:15,自引:1,他引:14
以河北省及临近区域120个气象观测站点1971~2000年均降水量数据为基础,选择其中的40个作为检验站点,其余站点分别取80、40、20个作为插值站点,采用局部插值、整体插值、多元线性回归、综合模拟等多种插值模型讨论了降水空间插值问题,主要结论如下:插值站点数、模型类型、模型参数都会影响插值精度.局部插值模型相对误差最小值出现在Spline、IDW模型中,其次为Kridging模型,而整体模型Trend、多元线性回归模型误差均较大,但综合了局部插值模型和统计模型的综合模型一定程度上能改善插值精度及误差分布.河北省80和40个站点的最优插值模型为综合模型,20个站点的最优插值模型为IDW2. 相似文献
17.
The objective of this study is to develop a mathematical model for simulating the thermal physiological responses of clothed infants. By modifying and integrating Gagge's two-node model and Stolwijk's multi-node model, and coupled with the model of dynamic couple heat and moisture transfer in functional clothing, a new seven-node thermoregulation model for closed infants was developed. A series of preliminary numerical test were carried out for naked and clothed infant. The prediction of the new model was compared with the published data, the comparison results demonstrate that the model has good potential predictability. 相似文献
18.
Hubertus V.M. Hamelers Annemiek ter Heijne Nienke Stein René A. RozendalCees J.N. Buisman 《Bioresource technology》2011,102(1):381-387
A kinetic model of the bio-anode was developed based on a simple representation of the underlying biochemical conversions as described by enzyme kinetics, and electron transfer reactions as described by the Butler-Volmer electron transfer kinetics. This Butler-Volmer-Monod model was well able to describe the measured bio-anode polarization curves. The Butler-Volmer-Monod model was compared to the Nernst-Monod model described the experimental data significantly better. The Butler-Volmer-Monod model has the Nernst-Monod model as its full electrochemically reversible limit. Contrary to the Nernst-Monod model, the Butler-Volmer-Monod model predicts zero current at equilibrium potential. Besides, the Butler-Volmer-Monod model predicts that the apparent Monod constant is dependent on anode potential, which was supported by experimental results. 相似文献
19.
Maki Matsuzaki Nobuo Sakai Tatsuya Matsuzaki Yasuyuki Matsushita Kiyoshi Koyano 《Computer methods in biomechanics and biomedical engineering》2017,20(4):393-402
A number of finite element analyses (FEAs) for the dental implant were performed without regard for preload and with all interfaces ‘fixed-bonded’. The purpose of this study was comparing the stress distributions between the conventional FEA model with all contacting interfaces ‘fixed-bonded’ (bonded model) and the model with the interfaces of the components in ‘contact’ with friction simulated as a preloaded implant (contact model). We further verified the accuracy of the result of the FEA using model experiment. In the contact model, the stress was more widely distributed than in the bonded model. From the model study, the preload induced by screw tightening generated strain at the peri-implant bone, even before the application of external force. As a result, the bonded model could not reproduce the mechanical phenomena, whereas the contact model is considered to be appropriate for analysing mechanical problems. 相似文献
20.
森林生物量估算中模型不确定性分析 总被引:3,自引:1,他引:2
单木生物量估算是区域森林生物量估算的基础。量化单木生物量模型中各种不确定性来源,分析各不确定性来源对森林生物量估算的影响,可为提高森林生物量估算精度提供理论依据。基于52株杉木地上部分生物量实测数据,建立杉木单木地上部分生物量一元与二元模型。在两种模型形式下,根据临安市2009年森林资源连续清查数据中杉木实测数据,分析单木生物量模型中所包含的2种不确定性,即模型参数不确定性和模型残差变异引起的不确定性。最后利用误差传播定律计算单木生物量模型总不确定性。结果表明,基于一元生物量模型的临安市杉木生物量估计均值为6.94 Mg/hm~2,由一元模型残差变异引起的生物量不确定性约为11.1%,模型参数误差引起的生物量不确定性约为14.4%,一元生物量模型估算合成不确定性为18.18%。基于二元生物量模型的临安市杉木生物量估计均值为7.71 Mg/hm~2,模型残差变异引起的不确定性约为7.0%,模型参数误差引起的不确定性约为8.53%,二元生物量模型估算合成不确定性为11.03%。研究表明模型参数不确定性随建模样本的增加逐渐降低,当建模样本由30增加到40再增加到52时,一元生物量模型模型参数不确定性分别为20.26%、16.19%、14.4%,二元生物量模型分别为13.09%、9.4%、8.53%。此外,建模样本的增加对残差变异不确定性也有一定影响,当建模样本由30增加到42再增加到48时,一元模型残差变异不确定性分别为15.2%,12.3%和11.7%;二元模型残差变异不确定性分别为13.3%,9.4%和8.3%。在2种不确定性来源中模型参数不确定性对估计结果影响最大,其次为模型残差变异。由于模型残差变异、参数不确定性与建模样本有关,因此可以通过增加建模样本来减小模型参数不确定性。二元生物量模型总的不确定性要低于一元生物量模型。 相似文献