Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

How to effectively utilize low and medium temperature energy is one of the solutions to alleviate the energy shortage and environmental pollution problems. In the past twenty years, because of its feasibility and reliability, organic Rankine cycle has received widespread attentions and researches. In this paper, it reviews the selections of working fluids and expanders for organic Rankine cycle, including an analysis of the influence of working fluids' category and their thermodynamic and physical properties on the organic Rankine cycle's performance, a summary of pure and mixed working fluids' screening researches for organic Rankine cycle, a comparison of pure and mixture working fluids' applications and a discussion of all types of expansion machines' operating characteristics, which would be beneficial to select the optimal working fluid and suitable expansion machine for an effective organic Rankine cycle system.

A review of working fluid and expander selections for organic Rankine cycle

Ammonia for power

Mesenchymal stem cells (MSCs) are multilineage cells with the ability to self-renew and differentiate into a variety of cell types, which play key roles in tissue healing and regenerative medicine. Bone marrow-derived mesenchymal stem cells (BMSCs) are the most frequently used stem cells in cell therapy and tissue engineering. However, it is prerequisite for BMSCs to mobilize from bone marrow and migrate into injured tissues during the healing process, through peripheral circulation. The migration of BMSCs is regulated by mechanical and chemical factors in this trafficking process. In this paper, we review the effects of several main regulatory factors on BMSC migration and its underlying mechanism; discuss two critical roles of BMSCs—namely, directed differentiation and the paracrine function—in tissue repair; and provide insight into the relationship between BMSC migration and tissue repair, which may provide a better guide for clinical applications in tissue repair through the efficient regulation of BMSC migration.

https://www.mdpi.com/2073-4409/8/8/784/pdf

Mesenchymal Stem Cell Migration and Tissue Repair.

This paper presents a review of the research on the Kalina cycle, including the description of the Kalina cycle, the comparison of the Rankine and Kalina cycle, energy and exergy analysis on the Kalina cycle, different Kalina systems and their different applications. Moreover, different correlations for calculating thermodynamic properties of ammonia–water mixture are screened and discussed. In the end, some technique concerns on ammonia–water mixture, i.e., stability, environmental impacts, safety and corrosion problem etc are also discussed.

A review of research on the Kalina cycle

A combined thermodynamic cycle used for waste heat recovery of internal combustion engine

Performance comparison of two absorption-compression hybrid refrigeration systems using R1234yf/ionic liquid as working pair

Objective Heart ischemia/reperfusion (I/R) injury is a common cause of heart failure. However, there is no effective method to treat the disease presently. The present research was to investigate the effects of transforming growth factor-β1 (TGF-β1) on homing of bone marrow mesenchymal stem cells (MSC) in heart I/R injury. Materials and methods Effects of TGF-β1 on the expression of CXCR4 [Chemokine (C-X-C Motif) Receptor 4] and chemotactic effect to SDF-1 (stromal cell-derived factor 1) in MSCs were investigated by in vitro transmembrane chemotaxis. Anti-TGF-β1 was incubated with I/R injury's heart tissue of mice. In addition, effects of TGF-β1 and anti-CXCR4 treatment using MSCs on the expression of SDF-1/CXCR4 in heart tissue and on I/R injury repair were further explored. Results CXCR4 and TGF-β1 expression were significantly increased after TGF-β1 treatment in MSCs; TGF-β1 treatment increased MSCs cell migration, and anti-CXCR4 and anti-TGF-β1 treatment blocked MSCs/TGF-β1cell migration. Expression of TGF-β1 in the I/R injury's myocardial tissue of mice was increased, and MSCs transplantation could enhance the protein expression of CXCR4 in the I/R injury's myocardial tissue of mice, and the expression of CXCR4 was decreased by the anti-TGF-β1 and the anti-CXCR4 treatment. TGF-β1 induced homing of MSCs in the repair of myocardial injury by regulating expression of CXCR4 on the cell membranes. Blue fluorescence of DAPI-positive MSCs cells of myocardial in the I/R+MSC group was enhanced significantly, which was significantly inhibited by anti-TGF-β1 and anti-CXCR4 antibody, and the inhibitory effect of anti-CXCR4 antibody was more evident than that of anti-TGF-β1 antibody. Conclusions TGF-β1 promotes homing of bone marrow (BM) MSCs in I/R injury's myocardial. The study provided useful data on the role of TGF-β1 in regulating SDF-1/CXCR4 axis-induced MSCs homing.

Effect of TGF-β1/SDF-1/CXCR4 signal on BM-MSCs homing in rat heart of ischemia/perfusion injury.

The thermal conductivity of three-dimensional (3D) strongly coupled complex (dusty) plasmas has been calculated through the improved Evan-Gillan nonequilibrium molecular dynamics (NEMD) algorithm. The extensive NEMD simulations are performed to study the performance of the algorithm and compared the results determined for perturbed heat energy current to the results obtained by equilibrium molecular dynamics (EMD) simulations. The calculations show that the present algorithm gives accurate results with fast convergence and small size effects over a wide range of plasma coupling and screening parameters. The present simulation results are in agreement with part of others NEMD and EMD data in the literature with simulation values generally overpredicting the thermal conductivity by 3%–20%, depending on plasma parameters. It is shown that the homogenous perturbed method can be employed to estimate the thermal conductivity and to understand the fundamental behaviors in 3D complex Yukawa liquids.

Maogang He

Papers

A review of research on the Kalina cycle

A combined thermodynamic cycle used for waste heat recovery of internal combustion engine

Performance comparison of two absorption-compression hybrid refrigeration systems using R1234yf/ionic liquid as working pair

Effect of TGF-β1/SDF-1/CXCR4 signal on BM-MSCs homing in rat heart of ischemia/perfusion injury.

Thermal conductivity calculation of complex (dusty) plasmas