正弦偏心旋转诱发的豚鼠前庭眼动反射特点

目的:观察豚鼠于不同频率和偏心半径正弦旋转时相对于轴心旋转的前庭眼动反射变化特点,以提取反映前庭耳石器功能的指标,为建立其功能检测方法提供依据。方法:采用频率0.1,0.2,0.3,0.4,0.5,0.6Hz,峰速60°/s的正弦旋转刺激,分别将豚鼠置于轴心,头向外偏心半径330mm,660mm,990mm处诱发其眼震,分析不同刺激条件下的眼震增益变化规律。结果:频率和偏心半径都对眼震的增益有显著影响:同一偏心半径条件下,眼震增益随频率增加而增大;同一频率条件下,眼震增益随偏心半径增加而增大,以在0.3Hz,0.4Hz最为明显,超过此频率范围后增益随半径变化不明显。结论:提取眼震增益的增强率(enhancementratio,ER)可以表达眼震增益随偏心半径增加而增大的增强效应,并作为反映豚鼠前庭耳石器功能的指标,以0.4Hz,半径990mm的正弦旋转模式作为耳石器功能评价的刺激模式较好。     

分数阶legendre函数微分和积分算子矩阵的推导

本文基于Legendre多项式构造了一类新的正交函数,即分数阶Legendre函数,利用分数阶微分和积分的定义推导微分算子矩阵和乘积算子矩阵。     

方向数据密度函数的最近邻估计

设Ｘ为取值于ｄ＋１维空间中单位球面上的单位随机向量,具有概率密度函数ｆ（ｘ）本文讨论密度函数ｆ（ｘ）的估计问题,给出了基于方向数据的最近邻估计,并建立这种最近邻估计的逐点强,弱相合性,一致强相合性及渐近正态性,得到了与欧氏情形（Ｒ＾ｄ）基本一致的结果。     

作物水分供应订正函数的韦伯函数型

从作物水分生产潜力、潜在水分利用效率与水分满足率的关系及特点入手,引入水分供应订正函数的韦伯形式。与目前常见的水分供应订正函数形式相比,本文给出的韦伯形式的水分供应订正函数具有临界水分满足率和“旋回”特征,能较好地解释作物水分生产潜力与水分满足率之间的数量关系,模型的实用性较广。模型中位置参数表示临界水分满足率;尺度参数表示水分满足率的取值范围;形状参数决定水分供应订正函数的“峰度”和“偏斜度”。根据“图解法”可求取水分供应订正函数的相关参数。其参数也具有明确的生物学和物理学意义,参数值本身也较稳定,使模型在应用中可望具有良好的稳定性。     

点格局研究过程中K-函数的累积效应

植物种群空间格局是生态学研究的基本问题之一, 点格局分析已成为植物种群空间格局研究的重要方法之一, 其中, Ripley's K函数是点格局常用分析方法。然而, 由于Ripley's K函数具有累积效应, 这种累积效应可能会导致特定的格局特征。为了探讨Ripley's K函数的累积效应如何影响种群格局研究结果, 以大针茅种群数据为基础, 通过R软件模拟聚集分布、随机分布和均匀分布3种格局类型, 对比使用具有累积效应的Ripley's K函数和不具有累积效应的成对相关函数进行分析。结果表明: 对于聚集分布和均匀分布, Ripley's K函数的累积效应表现在2个方面: 一方面增加了聚集分布(或均匀分布)的尺度, 另一方面能够检测到聚块或负相互作用范围在取样空间的分布差异而表现出不同的格局特征。而对于随机分布, Ripley's K函数没有累积效应。因此, 在种群格局研究过程中, 通过重复取样且Ripley's K 函数与成对相关函数相结合的方法探讨种群格局, 更能揭示空间格局的本质特征。     

具有时滞的N种群竞争系统的持久性

本文研究一类具有分离时滞的Ｎ种群积分微分系统的动力性态，通过构造适当的函数得到了该系统持久性的充分条件。     

地统计学方法在长白落叶松人工林凋落物现存量估测中的应用

采用地统计学的变异函数分析方法定量研究了15年生落叶松(Larix olgensis)人工纯林凋落物层重量的空间异质性特征,利用地统计学的克里格内插法结合定积分,对凋落物层的重量进行了估测.结果表明1)不同分解层次的凋落物重量的变异函数曲线理论模型均为球状模型,空间变异主要是由结构性因素引起,且空间自相关程度均属中等以上(空间结构比＞25%).2)非参数统计的成对样本符号检验结果表明,变异函数分析结果基础上的克里格内插法适用于凋落物重量的估计.利用此估计值,拟合其与位置坐标值之间的多元回归关系均为二元十次余弦级数多项式.利用此多项式,通过定积分的方法(积分区间为整块样地的大小),估计出15年生落叶松人工纯林中凋落物层的未分解、半分解、完全分解和腐殖质层的重量分别为4.7753、5.4129、8.0742、10.9269t hm-2.3)采用地统计学的克里格空间插值,结合多元回归和定积分的方法,可以实现落叶松人工林凋落物层重量的准确估计.     

一类非连续数据的GLM模型的应用

分析了因变量取有限个不连续点值的一种情况,给出了因变量Ｙ取值城中任一点值 的概率估计．并运用这种方法,对ＲＫ手术的结果作出了预测．     

绿豆胰蛋白酶抑制剂与猪胰蛋白酶复合物分子在四方和三方两种不同晶体中的取向关系

用Crowther的快速旋转函数研究了绿豆胰蛋白酶抑制剂(MBI)-猪胰蛋白酶(PTRY)复合物的四方晶体和三方晶体中胰蛋白酶分子的取向关系,并得出了它们之间的旋转矩阵。此旋转矩阵能和从胰蛋白酶模型分子为出发点在四方和三方晶体中所求得的胰蛋白酶分子的取向相互印证。此结果将促进绿豆胰蛋白酶抑制剂与胰蛋白酶的复合物立体结构及它们在不同晶形中的差异的研究。     

求解分形介质中分数阶扩散模型的相似方法(英文)

分形介质中输运现象的分数阶扩散方程是一个积分-偏微分方程,含有由分形Hausdorff维数d_f和反常扩散指数d_w确定的参数.对于这类方程的求解问题,给出了尺度变换群的不变子并且导出了关于尺度不变解的积分-常微分方程.最后利用Mellin变换和Fox函数得到尺度不变解.     

The radius of gyration of native and reductively methylated myosin subfragment-1 from neutron scattering.

Reductive methylation of nearly all lysine groups of myosin subfragment-1 (S1) was required for crystallization and solution of its structure at atomic resolution. Possible effects of such methylation on the radius of gyration of chicken skeletal muscle myosin S1 have been investigated by using small-angle neutron scattering. In addition, we have investigated the effect of MgADP.Vi, which is thought to produce an analog of the S1.ADP.Pi state, on the S1 radius of gyration. We find that although methylation of S1, with or without SO42- ion addition, does not significantly alter the structure, addition of ADP plus vanadate does decrease the radius of gyration significantly. The S1 crystal structure predicts a radius of gyration close to that measured here by neutron scattering. These results suggest that the overall shape by crystallography resembles nucleotide-free S1 in solution. In order to estimate the effect of residues missing from the crystal structure, the structure of missing loops was estimated by secondary-structure prediction methods. Calculations using the complete crystal structure show that a simple closure of the nucleotide cleft by a rigid-body torsional rotation of residues (172-180 to 670) around an axis running along the base of the cleft alone does not produce changes as large as seen here and in x-ray scattering results. On the other hand, a rigid body rotation of either the light-chain binding domain (767 to 843 plus light chains) or of a portion of 20-kDa peptide plus this domain (706 to 843 plus light chains) is more readily capable of producing such changes.     

Molecular replacement studies on crystal structure of DesBl-B2 Despentapeptide (B26-B30) insulin

Using the crystal structure of Despentapeptide (B26-B30) insulin (DPI) as the search model, the crystal structure of DesBl-B2 Despentapeptide (B26-B30) insulin (DesBl-2 DPI) has been studied by the molecular replacement method. There is one DesBl-2 DPI molecule in each crystallographic asymmetric unit. The cross rotation function search and the translation function search show apparent peaks and thus determine the orientation and position of DesBl-2 DPI molecule in the cell respectively. The subsequent three-dimensional structural rebuilding and refine-ment of DesBl-2 DPI molecule confirm the results by molecular replacement method.     

Molecular replacement studies on crystal structure of DesB1-B2 Despentapeptide (B26-B30) insulin

Using the crystal structure of Despentapeptide (B26-B30) insulin (DPI as the search model, the crystal structure of DesB1-B2 Despentapeptide (B26-B30) insulin (DesB1-2 DPI) has been studied by the molecular replacement method. There is one DesB1-2 DPI molecule in each crystallographic asymmetric unit. The cross rotation function search and the translation function search show apparent peaks and thus determine the orientation and position of DesB1-2 DPI molecule in the cell respectively. The subsequent three-dimensional structural rebuilding and refinement of DesB1-2 DPI molecule confirm the results by molecular replacement method.     

Crystal structure and solid state 13C NMR analysis of nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-gluco- and D-galactopyranosides

The X-ray diffraction analysis of o-nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside (1), m-nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside, p-nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside and o-nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside was performed. It was found that except in the case of 1, all other crystals have one molecule in the independent part of the crystal unit cell. The results support the opinion that the nitro group does not conjugate effectively with the phenyl ring. In the 13C CP MAS spectrum of 1 the signals are split, confirming the presence of two independent molecules. Similarly, the 13C CP MAS NMR spectrum of p-nitrophenyl-2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside indicated the presence of two non-equivalent molecules in the crystal unit. One of these molecules has more conformational freedom enabling rotation of the phenyl ring.     

Crystallization and characterization of two crystal forms of the B800-850 light-harvesting complex from Rhodopseudomonas acidophila strain 10050

Two different crystal forms of the B800-850-antenna complex from Rhodopseudomonas acidophila strain 10050 have been grown. This complex is an integral membrane protein and is isolated as an oligomeric assembly with a molecular weight of approximately 84 kDa. This assembly contains six alpha/beta apoprotein pairs, 18 molecules of bacteriochlorophyll a and nine molecules of carotenoid. The first crystal form has dimensions unit cell a = b = 75.8 A, c = 97.5 A with the space group P4 and diffracts to a resolution of 12.0 A. The second crystal form is rhombohedral with dimensions unit cell a = 121.1 A, alpha = 60 degrees, space group R32 and diffracts to a resolution of 3.5 A. Native data have been processes in both cases, to an Rmerge value of 9.0 to 11.0%. The X-ray data suggest that the asymmetric unit, in both crystal forms, contains one 84 kDa antenna complex.     

The effect of scatter correction and radius of rotation on semiquantitative measurements in SPECT 123I-FP-CIT imaging. A phantom study

PurposeThe high energy emissions of ¹²³I and the suboptimal radius of rotation affect the semiquantitative measurements performed during ¹²³I-FP-CIT tomographic imaging. An in-house extra low cost striatum phantom with brain and striatum compartments was constructed and was used to study the effects of Triple Energy Window scatter correction (TEW-SC) and radius of rotation on the Specific Binding Ratio (SBR) measurements.Materials and methodsThe phantom compartments were filled with radioactive ¹²³I solutions with varying concentrations, in a series of experiments. Tomographic images were acquired at six different radii of rotation, with and without TEW-SC and the SBRs were calculated using appropriate regions of interest, as in clinical imaging.ResultsSBRs decreased with increasing radius of rotation in both non-SC and TEW-SC images, the decrease being more pronounced in the latter. The application of TEW-SC increases SBR values by 40% on average. A maximum %Recovery of 42.7% of the true SBR value was achieved in the non-SC images, which increased to 64.6% after TEW-SC. Appropriate correction factors (CF) were calculated in order to make the SBR values independent on the radius of rotation, which could be used to correct SBR values obtained from tomographic acquisitions with suboptimal radius of rotation.ConclusionThe use of appropriate CF can provide more consistent SBR values and a more meaningful comparison between SBRs calculated from images acquired at different radii of rotation.     

A method for measuring joint kinematics designed for accurate registration of kinematic data to models constructed from CT data

A method for measuring three-dimensional kinematics that incorporates the direct cross-registration of experimental kinematics with anatomic geometry from Computed Tomography (CT) data has been developed. Plexiglas registration blocks were attached to the bones of interest and the specimen was CT scanned. Computer models of the bone surface were developed from the CT image data. Determination of discrete kinematics was accomplished by digitizing three pre-selected contiguous surfaces of each registration block using a three-dimensional point digitization system. Cross-registration of bone surface models from the CT data was accomplished by identifying the registration block surfaces within the CT images. Kinematics measured during a biomechanical experiment were applied to the computer models of the bone surface. The overall accuracy of the method was shown to be at or below the accuracy of the digitization system used. For this experimental application, the accuracy was better than +/-0.1mm for position and 0.1 degrees for orientation for linkage digitization and better than +/-0.2mm and +/-0.2 degrees for CT digitization. Surface models of the radius and ulna were constructed from CT data, as an example application. Kinematics of the bones were measured for simulated forearm rotation. Screw-displacement axis analysis showed 0.1mm (proximal) translation of the radius (with respect to the ulna) from supination to neutral (85.2 degrees rotation) and 1.4mm (proximal) translation from neutral to pronation (65.3 degrees rotation). The motion of the radius with respect to the ulna was displayed using the surface models. This methodology is a useful tool for the measurement and application of rigid-body kinematics to computer models.     

Analytical study of the effects of some soil and plant parameters on root growth due to absorption of one mobile ion: A free-boundary model

The object of our study is: a model for root growth through a free-boundary problem and the effects resulting from differences in nutrient availability and transport of only one mobile nutrient between the root surface and the rhizosphere produced by an absorption Michaelis-Menten for low and high concentrations. The model equations are solved by two methods: the quasi-stationary method and the balance integral method. The numerical solutions are used to compute radial root growth. Curves of nutrient concentration at the root-soil interface, curve as a function of root radius as well as curves representing root radius as a function of time are plotted. The parameters which are varied are the root absorption power, flux velocity at the root surface, efflux, rhizosphere radius, diffusion coefficient, buffer power, and maximum influx. The two methods show the theoretical results for radial root growth in the range of low and high concentrations. The balance integral method provides more detailed information.     

Dinucleoside monophosphate having a high anti conformation: the crystal structure of 8,2'-S-cycloadenylyl-(3'-5')-8,2'-S-cycloadenosine hydrochloride

The crystal and molecular structure of 8,2'-S-cycloadenylyl-(3'-5')-8,2'-S-cycloadenosine (AspAs) hydrochloride has been determined by X-ray method. The conformation of two independent AspAs molecules found in an asymmetric unit are almost identical to each other. The torsion angles concerning the sugar-phosphate backbone are different from those in crystalline dinucleoside monophosphates so far determined by X-rays. Both AspAs molecules are in the sharp bend conformations, i.e. each rotation around P-O bond (omega', omega) is (g-, t) rather than the preferred (g-, g-) or (g+, g+) conformation. There is no intramolecular base stacking or base-pairing but the intermolecular base stacking was found.