Comparing open-source DEM frameworks for simulations of common bulk processes

Multiple software frameworks based on the Discrete Element Method (DEM) are available for simulating granular materials. All of them employ the same principles of explicit time integration, with each time step consisting of three main steps: contact detection, calculation of interactions, and integration of the equations of motion. However, there exist significant algorithmic differences, such as the choice of contact models, particle and wall shapes, and data analysis methods. Further differences can be observed in the practical implementation, including data structures, architecture, parallelization and domain decomposition techniques, user interaction, and the documentation of resources.This study compares, verifies, and benchmarks nine widely-used software frameworks. Only open-source packages were considered, as these are freely available and their underlying algorithms can be reviewed, edited, and tested. The benchmark consists of three common bulk processes: silo emptying, drum mixing, and particle impact. To keep it simple and comparable, only standard features were used, such as spherical particles and the Hertz-Mindlin model for dry contacts. Scripts for running the benchmarks in each software are provided as a dataset

DATA CENTERS IN THE SCIENTIFIC INFORMATION INFRASTRUCTURE

There is a multiple increase of the volume of scientific data obtained in the course of research each year. Due to this there is a need for continuous improvement, such as data transmission channels and systems for handling and storage of scientific data. For example, data centers show current centers and storage of scientific data and advanced technology in this area, in particular the "cloud" technology. Particular attention is paid to the information infrastructure for data centers storing scientific information

High-efficiency recovery of functional hematopoietic progenitor and stem cells from human cord blood cryopreserved for 15 years

Transplanted cord blood (CB) hematopoietic stem cells (HSC) and progenitor cells (HPC) can treat malignant and nonmalignant disorders. Because long-term cryopreservation is critical for CB banking and transplantation, we assessed the efficiency of recovery of viable HSC/HPC from individual CBs stored frozen for 15 yr. Average recoveries (± 1 SD) of defrosted nucleated cells, colony-forming unit-granulocyte, -macrophage (CFU-GM), burst-forming unit-erythroid (BFU-E), and colony-forming unit-granulocyte, -erythrocyte, -monocyte, and -megakaryocyte (CFU-GEMM) were, respectively, 83 ± 12, 95 ± 16, 84 ± 25, and 85 ± 25 using the same culture conditions as for prefreeze samples. Proliferative capacities of CFU-GM, BFU-E, and CFU-GEMM were intact as colonies generated respectively contained up to 22,500, 182,500, and 292,500 cells. Self-renewal of CFU-GEMM was also retained as replating efficiency of single CFU-GEMM colonies into 2° dishes was >96% and yielded 2° colonies of CFU-GM, BFU-E, and CFU-GEMM. Moreover, CD34(+)CD38(−) cells isolated by FACS after thawing yielded >250-fold ex vivo expansion of HPC. To assess HSC capability, defrosts from single collections were bead-separated into CD34(+) cells and infused into sublethally irradiated nonobese diabetic (NOD)/severe combined immunodeficient (SCID) mice. CD45(+) human cell engraftment with multilineage phenotypes was detected in mice after 11–13 wk; engrafting levels were comparable to that reported with fresh CB. Thus, immature human CB cells with high proliferative, replating, ex vivo expansion and mouse NOD/SCID engrafting ability can be stored frozen for >15 yr, can be efficiently retrieved, and most likely remain effective for clinical transplantation