转动参照系中的圆锥摆

讨论了在转动参照系中考虑科里奥利力的作用后，圆锥摆运动的轨迹、半径、速度和周期，并与惯性系中的圆锥摆进行了比较，在转动参照后，若摆锤以惯系中锥摆的初速度和半径开始运动，则其轨迹是椭圆，轨迹以一定的周期顺时针方向转动；若分别以惯性系中的初速度和半径开始作圆周运动，则半径和速度都与惯性系中的不同；在摆锤作逆时针和顺时针方向运动时，以上情况也不相同。     

超重和旋转对小鼠游泳行为的影响及乙酰亮氨酸的作用

通过观测小鼠在超重 (2 g)环境中生存 2周后返回正常 (1g)环境后游泳行为模式的改变和再适应过程及乙酰亮氨酸 (Acetyl_DL_leucine ,AL)对其的影响 ,研究了超重和旋转对前庭功能的影响及AL对前庭代偿的影响 .结果表明 :超重刺激使动物的体重下降但摄食量上升 ,旋转刺激对动物体重和摄食量的影响低于超重刺激 ;正常小鼠入水后 2～3d即达到其最大游泳速度 ;超重刺激明显降低小鼠游泳的平衡能力 ,进入 1g环境 9～10d后可恢复到最大游泳速度 ;旋转刺激对游泳平衡能力的影响低于超重刺激 ,进入 1g环境 5～ 6d后可恢复其最大游泳速度 ;AL抑制超重组小鼠游泳平衡能力的恢复 ,比给药对照组延后 4d ;AL促进旋转组小鼠游泳平衡能力的恢复 ,比给药对照组提前恢复 2d .     

关于刚体绕定点运动几个问题的探讨

本文从一个新的角度讨论了定点运动刚体运动方程的建立,推导了角速度、角加速度及任一点的速度、加速度的计算公式,并且举例说明了各个公式的应用。     

Lusternik-Schnirelmann 定理的推广

本文根据Brouwer映射度的理论和微分拓扑的基本方法推广了Lusternik_Schnirelmann定理     

Orientational anisotropic studies by field rotation technique: near zero-field pulsed EPR experiments of pentacene doped in p-terphenyl

We report a new technique to map the orientational anisotropy of paramagnetic systems without physically changing the crystal orientations in near zero-field (NZF) pulsed EPR experiments. By implementing three sets of orthogonal coils around the sample, we are ble to create a magnetic vector up to 2 mT in any three-dimensional orientation in space. In NZF region, the hyperfine tensor elements are comparable to the electronic Zeeman interaction energy, thus very rich spectral patterns can be obtained by "dialing" in a magnetic field vector without moving the sample. The technique further allows us to examine the site symmetry of organic crystals and powdered solids doped with chromophores which can be photo-excited to the triplet state by laser light. The technique is exemplified in the study of pentacene in p-terphenyl crystals.     

Theoretical Study of Formamide Tautomers—A Discussion of Enol-Keto Isomerizations and Their Corresponding Energies

In order to gain insight into the formamide molecule, seven tautomers and twelve transition states are found after being modeled by the density function theory of Becke's three-parameter hybride (B3LYP) type and ab initio Möller–Plesset second-order perturbation (MP2)-type methods. The isomerization phenomena between enol-keto tautomers and transition states via internal rotation or the proton transfer process are surveyed. A localized analysis is also introduced to ascertain the bond character caused by the delocalization of electrons, which will force the formamide tautomers to become planar. The trans effect in the molecule increases molecular stability.     

Subunit rotation models activation of serotonin 5-HT<Subscript>3AB</Subscript> receptors by agonists

The N-terminal extracellular regions of heterooligomeric 3AB-type human 5-hydroxytryptamine receptors (5-HT3ABR) were modelled based on the crystal structure of snail acetylcholine binding protein AChBP. Stepwise rotation of subunit A by 5 degrees was performed between -10 degrees and 15 degrees to mimic agonist binding and receptor activation. Anticlockwise rotation reduced the size of the binding cavity in interface AB and reorganised the network of hydrogen bonds along the interface. AB subunit dimers with different rotations were applied for docking of ligands with different efficacies: 5-HT, m-chlorophenylbiguanide, SR 57227, quinolinyl piperazine and lerisetron derivatives. All ligands were docked into the dimer with -10 degrees rotation representing ligand-free, open binding cavities similarly, without pharmacological discrimination. Their ammonium ions were in hydrogen bonding distance to the backbone carbonyl of W183. Anticlockwise rotation and contraction of the binding cavity led to distinctive docking interactions of agonists with E129 and cation-pi interactions of their ammonium ions. Side chains of several further amino acids participating in docking (Y143, Y153, Y234 and E236) are in agreement with the effects of point mutations in the binding loops. Our model postulates that 5-HT binds to W183 in a hydrophobic cleft as well as to E236 in a hydrophilic vestibule. Then it elicits anticlockwise rotation to draw in loop C via pi-cation-pi interactions of its ammonium ion with W183 and Y234. Finally, closure of the binding cavity might end in rebinding of 5-HT to E129 in the hydrophilic vestibule.     

Fourier Invariant Partially Approximating Subalgebras of the Irrational Rotation C*-Algebra

For a dense G-set of parameters, the irrational rotation algebrais shown to contain infinitely many C*-subalgebras satisfyingthe following properties. Each subalgebra is isomorphic to adirect sum of two matrix algebras of the same (perfect square)dimension; the Fourier transform maps each summand onto theother; the corresponding unit projection is approximately central;the compressions of the canonical generators of the irrationalrotation algebra are approximately contained in the subalgebra.2000 Mathematics Subject Classification 46L80, 46L40, 46L35.     

A rotation-torsion-vibration treatment with three-dimensional internal coordinate approach and additional FTIR spectral assignments for the CH3-bending fundamentals of methanol

A theoretical model has been developed to account for certain features of both newly observed and previously reported CH₃-bending subbands between 1450 and 1570 cm⁻¹ in the high-resolution Fourier transform infrared spectrum of CH₃OH [Can. J. Phys. 79 (2001) 435]. The features include (i) an apparent inversion of the rotationless E-A torsional splitting with respect to the ground state, i.e., the A state located above the E state, (ii) a pronounced upward slope in the K-reduced torsion-vibration energy pattern for the subband origins, and (iii) unexpected A₁/A₂ inversion of the K=2A and K=3AJ-rotational levels that led to ambiguity in identifying the vibrational mode as or . The model is an effective internal coordinate Hamiltonian constructed in G₆ molecular symmetry with the CH₃-bends coupled to each other and to torsion and including a- and γ-type Coriolis coupling. With this model, 33 out of 36 experimental upper-state K-term values for newly assigned , and ν₁₀ subbands plus previous ν₄ subbands have together been fitted successfully, employing 9 adjustable parameters and 17 fixed parameters to give a standard deviation of 0.14 cm⁻¹. The P_γ Coriolis term appears to be the leading cause of the upward shift in the K-reduced energies. When J-dependence is introduced via a rotational Hamiltonian including b- and c-type Coriolis terms in addition to molecular asymmetry, the observed A₁/A₂ inversion of the K=2A and 3A rotational levels can also be reproduced. Predictions using the fitted K-rotation-torsion-vibration Hamiltonian show an interesting Coriolis-induced crossover and mixing of the ν₅ and ν₁₀ torsion-vibration energy patterns. These predictions played a role in identifying two of the new ν₅ subbands in the crossing region, thereby helping to validate the model.