3,153 research outputs found
Electrospun Thymosin Beta-4 Loaded PLGA/PLA Nanofiber/ Microfiber Hybrid Yarns for Tendon Tissue Engineering Application
Microfiber yarns (MY) have been widely employed to construct tendon tissue grafts. However, suboptimal ultrastructure and inappropriate environments for cell interactions limit their clinical application. Herein, we designed a modified electrospinning device to coat poly(lactic-co-glycolic acid) PLGA nanofibers onto polylactic acid (PLA) MY to generate PLGA/PLA hybrid yarns (HY), which had a well-aligned nanofibrous structure, resembling the ultrastructure of native tendon tissues and showed enhanced failure load compared to PLA MY. PLGA/PLA HY significantly improved the growth, proliferation, and tendon-specific gene expressions of human adipose derived mesenchymal stem cells (HADMSC) compared to PLA MY. Moreover, thymosin beta-4 (Tβ4) loaded PLGA/PLA HY presented a sustained drug release manner for 28 days and showed an additive effect on promoting HADMSC migration, proliferation, and tenogenic differentiation. Collectively, the combination of Tβ4 with the nano-topography of PLGA/PLA HY might be an efficient strategy to promote tenogenesis of adult stem cells for tendon tissue engineering
Periodically driven four-dimensional topological insulator with tunable second Chern number
In recent years, Floquet engineering has attracted considerable attention as
a promising approach for tuning topological phase transitions. In this work, we
investigate the effects of high-frequency time-periodic driving in a
four-dimensional (4D) topological insulator, focusing on topological phase
transitions at the off-resonant quasienergy gap. The 4D topological insulator
hosts gapless three-dimensional boundary states characterized by the second
Chern number . We demonstrate that the second Chern number of 4D
topological insulators can be modulated by tuning the amplitude of
time-periodic driving. This includes transitions from a topological phase with
to another topological phase with , or to a
topological phase with an even second Chern number which is absent
in the 4D static system. Finally, the approximation theory in the
high-frequency limit further confirms the numerical conclusions.Comment: 11 pages, 9 figures. arXiv admin note: text overlap with
arXiv:2312.1601
Optical transitions between Landau levels: AA-stacked bilayer graphene
The low-frequency optical excitations of AA-stacked bilayer graphene are
investigated by the tight-binding model. Two groups of asymmetric LLs lead to
two kinds of absorption peaks resulting from only intragroup excitations. Each
absorption peak obeys a single selection rule similar to that of monolayer
graphene. The excitation channel of each peak is changed as the field strength
approaches a critical strength. This alteration of the excitation channel is
strongly related to the setting of the Fermi level. The peculiar optical
properties can be attributed to the characteristics of the LL wave functions of
the two LL groups. A detailed comparison of optical properties between
AA-stacked and AB-stacked bilayer graphenes is also offered. The compared
results demonstrate that the optical properties are strongly dominated by the
stacking symmetry. Furthermore, the presented results may be used to
discriminate AABG from MG, which can be hardly done by STM
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