机械工程学报

Lactobacillus plantarum ZDY04 reduces Trimethylamine N-Oxide-induced atherosclerosis by promoting reverse cholesterol transport in ApoE^-/- mice

TANG Jing-hui, QIN Man-man, TANG Le, WEI Hua, QIU Liang, YU Jun

2023, 1(5): 24-34. doi: 10.13381/j.cnki.cjm.00000-00

[Abstract](152) [FullText HTML] (142)

Abstract:
Objective

To observe the effect of Lactobacillus plantarum ZDY04 in Trimethylamine N-Oxide (TMAO)-induced atherosclerosis in mice and its underlying mechanisms.

Methods

Thirty female (six to eight-weeks old) apolipoprotein E-deficient (ApoE^-/-) mice were randomly assigned into three groups as follows: Chow group, Choline+PBS group and Choline+ZDY04 group, and fed with 1.3% high-choline diet to establish atherosclerosis models, then treated with sterile PBS or ZDY04 containing 15% glycerol for 16 weeks. After treatment, serum lipids were measured using cholesterol kit. The serum TMAO and fecal TMA content were determined by using liquid chromatography-tandem mass spectrometry LC-MS. Atherosclerotic lesion formation in whole aorta was detected with Oil red O staining. Hematoxylin-eosin, Oil red O and Masson staining were used to detect the atherosclerotic area, lipid deposition and collagen content in the aortic roots. Immunofluorescent staining of macrophage specific antigen CD68 and smooth muscle a-actin (SMA) were used to examine the lesion composition in the aortic root. The expression of genes related to reverse cholesterol transport and Fmo3 in liver was detected with RT-qPCR and Western blot.

Results

Compared with Choline+PBS group, the atherosclerotic lesions in the whole aortas significantly reduced in Choline+ZDY04 group. ZDY04 treatment significantly decreased atherosclerotic lesion size, lipid deposition and macrophage content, but not the contents of lesion smooth muscle cells or collagen, when compared to Choline+PBS fed mice. The content of cecum TMA and serum TMAO decreased significantly in Choline+ZDY04 group; serum high density lipoprotein-cholesterol significantly increased, but total cholesterol and low density lipoprotein-cholesterol only marginally decreased. ZDY04 significantly increased the mRNA expression of reverse cholesterol transport genes Sr-b1, Abcg5, Cyp7a1 but not Fmo3. Liver CYP7A1 protein level was also increased by ZDY04 compared to controls.

Conclusion

Lactobacillus plantarum ZDY04 can inhibit TMAO induced thermogenesis by promoting reverse transport and decomposition of cholesterol in ApoE^-/- mice.

A Fundamental Surface Theory for Kinetic Analogy of Thin Elastic Shells

XUE Yun, CHEN Liqun

2023, 44(5): 489-498. doi: 10.21656/1000-0887.430222

[Abstract](50)

Abstract:
The generalization of the Kirchhoff kinetic analogy from thin elastic rods to thin elastic shells, namely the generalized Kirchhoff kinetic analogy, needs a corresponding novel expression of the classical surface theory with its fundamental properties described by means of the concept and method of the rigid body dynamics. A rigid orthogonal-axis system and a curvature-twist vector were defined for the non-orthogonal meshing of a surface, and the Euler angles were used to express the attitude of the system and the partial differential geometric equation of the surface. The curvature-twist vector and the Lamé coefficient were applied to depict the 1st and the 2nd basic quadratic forms of the surface, obtain the normal curvature and calculate the principal curvature and the principal direction. The analysis demonstrates the consistency between the new and the classical expressions of the surface theory. The application example of the proposed method shows that, this method can reasonably express the Rodrigues equation, the Weingarten equation, the Gauss equation and the fundamental equations for the surface, and well describe the differential geometry of the surface. This method has the benefits of conciseness and directness, and lays a mathematical foundation for the generalized Kirchhoff kinetic analogy and its further developments.

Hamiltonian Structures and Stability Analysis for Rigid-Liquid Coupled Spacecraft Systems

YI Zhonggui, YUE Baozeng, LIU Feng, LU Tao, DENG Mingle

2023, 44(5): 499-512. doi: 10.21656/1000-0887.430379

[Abstract](58)

Abstract:
For the dynamics problems of rigid-liquid coupling spacecraft systems with liquid propellant, a 3D rigid pendulum model was used to simulate the nonlinear sloshing behavior of the propellant. On this basis, the Hamiltonian structure of the rigid-liquid coupling spacecraft system was studied, the R³ reduction (corresponding to the translation invariance or the bus momentum invariance of the system) and the S_o(3) reduction (corresponding to the rotation invariance or the total angular momentum invariance of the system) of the system were introduced, with the reduced Poisson brackets of the system in reduced space s^*_o(3)×s^*_o(3)×S_o(3) derived. Then, the spin stability characteristics of the rigid-liquid coupled spacecraft system were studied. Firstly, the relative equilibrium of the rigid-liquid coupled spacecraft system was derived under the principle of symmetric criticality. Based on the energy-momentum method and the block diagonalization technology, the spin stability conditions and the Arnold form stability boundaries of the system were derived. Finally, the spin stability domains illustrated in the form of graph were given according to the specific model parameters.

Research on Constraint Following Control of Flexible Joint Manipulators Based on Singular Perturbation

OU Jingsong, LI Rong, YIN Hui, WANG Huajian

2023, 44(5): 513-524. doi: 10.21656/1000-0887.430024

[Abstract](39)

Abstract:
For the control of 2-link flexible joint manipulators, a control method based on the singular perturbation theory and the Udwadia-Kalaba (U-K) method was proposed. The control design was implemented by 2 steps. First, the system order was reduced based on the singular perturbation method and the system was divided into fast and slow sub-systems, to simplify the solution process and overcome the system flexibility. Second, the state feedback constraint following control law for the fast and slow sub-systems was designed with the U-K method, to make the constraint following errors of the fast and slow sub-systems converge to zero, even if the system can't initially satisfy the constraints. The proposed method can deal with holonomic and nonholonomic servo constraints at the same time without the auxiliary variables of the Lagrange multiplier and the pseudo generalized velocity. The method was applied to 2-link flexible joint manipulator systems to solve the flexible oscillation and constraint following problems through simulations on MATLAB, and was compared with the traditional PID control, to verify the effectiveness and superiority.

The SAV Scheme Based on the Barycentric Interpolation Collocation Method for the Allen-Cahn Equation

HUANG Rong, DENG Yangfang, WENG Zhifeng

2023, 44(5): 573-582. doi: 10.21656/1000-0887.430149

[Abstract](33)

Abstract:
The scalar auxiliary variable (SAV) approach combined with the barycentric interpolation collocation method was proposed to solve the 2D Allen-Cahn equation. Two unconditional energy-stable SAV schemes were constructed based on the Crank-Nicolson scheme and the 2nd-order backward difference scheme for discretization in time, respectively, and the barycentric Lagrange interpolation collocation method for discretization in space. Moreover, the approximation properties of the barycentric Lagrange interpolation were presented. Numerical experiments show that, the time-convergence rates of the 2 types of SAV schemes are of the 2nd order, and both schemes satisfy the energy decay law. Compared with the finite difference method in space, the barycentric Lagrange interpolation collocation scheme features exponential convergence.

A New Class of Difference Schemes With Intrinsic Parallelism for the KdV-Burgers Equation

PAN Yueyue, YANG Xiaozhong

2023, 44(5): 583-594. doi: 10.21656/1000-0887.430128

[Abstract](46)

Abstract:
The KdV-Burgers equation as a standard equation for turbulent, has a profound physical background and its fast numerical methods are of great practical application value. A new class of parallel difference schemes were proposed for the KdV-Burgers equation. Based on the alternating segment technology, the mixed alternating segment Crank-Nicolson (MASC-N) difference scheme was constructed with the classic Crank-Nicolson (C-N) scheme, the explicit and implicit schemes. The theoretical analyses indicate that, the MASC-N scheme is uniquely solvable, linearly absolutely stable and 2nd-order convergent. Numerical experiments show that, the MASC-N scheme has higher precision and efficiency than the C-N scheme. Compared with the ASE-I and ASC-N difference schemes, the MASC-N parallel difference scheme has the best performance, and can effectively solve the KdV-Burgers equation.

An Alternating Direction Multiplier Method for 4th-Order Variational Inequalities With Curvature Obstacle

ZHANG Linsen, CHENG Lan, ZHANG Shougui

2023, 44(5): 595-604. doi: 10.21656/1000-0887.430243

[Abstract](21)

Abstract:
A self-adaptive alternating direction method of multipliers was proposed for the approximation solution of variational inequalities with biharmonic operators and curvature obstacle. An augmented Lagrange functional was introduced with an auxiliary variable to express the curvature function, and a constrained minimization problem equivalent to a saddle-point one was deduced. Then the alternating direction method of multipliers was applied to solve the saddle-point problem. By means of the balance principle and iterative functions, a self-adaptive rule was obtained to adjust the penalty parameter automatically, and improve the computation efficiency. The convergence of this method was proved and the penalty parameter approximation was given in detail with the iterative functions. The numerical results illustrate the effectiveness of the proposed method.

Preset-Time Consensus of Heterogeneous Fractional-Order Nonlinear Multi-Agent Systems

GONG Ping

2023, 44(5): 605-618. doi: 10.21656/1000-0887.430223

[Abstract](35)

Abstract:
The preset-time consensus problem of a class of heterogeneous fractional-order nonlinear multi-agent systems was studied. A type of time-varying function-based preset-time fractional integral controllers were designed, to convert the fractional-order nonlinear multi-agent system into a 1st-order nonlinear multi-agent system. Then, by means of the integer-order Lyapunov function method combined with the preset-time control technology, the accurate bipartite consensus control of multi-agent systems with the connected undirected graph and the directed graph containing spanning trees was realized, respectively. The preset time can be preset with the time-varying function, independent of system initial values and parameters. An example verifies the effectiveness of the theoretical results.

Analyses on water use characteristics of Salix psammophila based on sap flow and leaf water potential

Yang Ruizhi, Ma Jingyong, Liang Chunxuan, Tian Yun, Jia Xin, Zha Tianshan

2023, 41(5): 87-94. doi: 10.13332/j.1000-1522.20180241

[Abstract](272) [FullText HTML] (128)

Abstract:
Objective In arid and semi-arid areas, water transfer process of plants is regulated by a set of effective mechanisms. Understanding the mechanisms of responses of xerophytic plants to soil drought is important for predicting the structure and functioning of dryland ecosystems under changing climate. Method The stem sap flow of Salix psammophila was monitored continuously using five heat balance sensor, and the leaf water potential of the plant was measured at predawn and midday in nineteen sunny days during 1 May to 10 October, 2017. The photosynthetic active radiation above canopy, air temperature, air relative humidity, and soil moisture content were monitored simultaneously. Result The results were that the sap flux density and soil water potential were highly correlated in short term (May to June, July to September). The sap flux density and the water potential drop (Ψ_L−Ψ_S) were positively correlated during the growing season. Leaf transpiration rate increased with leaf water potential and vapor pressure deficit (VPD), respectively, saturating at −3.7 MPa and 1.9 kPa, leaf conductance for water vapour increased positively with VPD, saturating at 0.9 kPa, then decreasing with these variables when greater than their respective threshold. The vulnerability curve was “r” shape for Salix psammophila. The water potential, at which 50% of hydraulic conductivity was lost as a result of xylem embolism (P₅₀), was 0.72 MPa. The whole-branch hydraulic conductance per unit basal sapwood cross-sectional area (K_s) increased with soil water potential (Ψ_S) and leaf conductance (g_L). The correlation between g_L and Ψ_S was low because of the influence of VPD on g_L. The relative sensitivity of stomata and plant hydraulic conductance to declining soil water potentials (ϭ) was 1.035. Conclusion The results show that as water stress develops, Salix psammophila controls the water loss by reducing the K_s and certain level of xylem embolism does not induce the closure of the stomata. This mechanisms may be advantageous in terms of maximizing transpiration and assimilation rates. It has obvious theoretical significance to understand the water use characteristics of plants in arid areas, and lays a foundation for further study on the mechanism of the compensation for hydraulic limitation of Salix psammophila.

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