Enzymatically degradable versatile hydrogel platform for cell sheet engineering

The structural organization of cells and their associated extracellular matrix (ECM) is critical to overall tissue function. Recapitulating the complex, highly organized structure of a target tissue is a key to achieve the unique functional characteristics of native tissue. However, achieving this goal requires a system in which substrate physicochemical properties such as modulus, topology and surface chemistry can be modulated. Here, we developed a cell sheet-based harvest & transfer system that can rapidly produce patterned 2D cell sheets in any physiologically relevant size and shape for various cell types. We further show that these cell sheets can be stacked one on top of the other with high cell viability while preserving the patterns, and that they remain sufficiently intact in vivo to allow neovascularization. We can thus use this system to mimic both the 2D and 3D structure of native tissue structure. A further advantage of our system is its substrate modulus tuning capability, which allows us to provide an optimal biomechanical environment for the differentiation and phenotypic stabilization of specific cell types. Because hydrogels theoretically have no limit in 2D shape and size, this system is scalable for producing quality controlled multiple cell sheets in a short period of time. Our model should also aid in understanding the mechanisms that underlie cell-cell and cell-ECM communication in 3D environments, which will be imperative to improving engineered tissue design. We thus ultimately envision that our system could allow the rapid fabrication of functionalized three dimensional thick tissues from multiple stacks of cell sheets derived from autologous cells, which would be an important step forward in both tissue modeling and regenerative medicine in general. Finally, this system can also potentially serve as a powerful model to study in vivo tissue formation and growth as well as cancer cell behavior

Origin of micron-scale propagation lengths of heat-carrying acoustic excitations in amorphous silicon

The heat-carrying acoustic excitations of amorphous silicon are of interest because their mean free paths may approach micron scales at room temperature. Despite extensive investigation, the origin of the weak acoustic damping in the heat-carrying frequencies remains a topic of debate. Here, we report measurements of the frequency-dependent mean free path in amorphous silicon thin films from ∼0.1−3 THz and over temperatures from 60 - 315 K using picosecond acoustics and transient grating spectroscopy. The mean free paths are independent of temperature and exhibit a Rayleigh scattering trend from ∼0.3−3 THz, below which the trend is characteristic of damping from density fluctuations or two-level systems. The observed trend is inconsistent with the predictions of numerical studies based on normal mode analysis but agrees with diverse measurements on other glasses. The micron-scale MFPs in amorphous Si arise from the absence of Akhiezer and two-level system damping in the sub-THz frequencies, leading to heat-carrying acoustic excitations with room-temperature damping comparable to that of other glasses at cryogenic temperatures

Origin of micron-scale propagation lengths of heat-carrying acoustic excitations in amorphous silicon

The heat-carrying acoustic excitations of amorphous silicon are of interest because their mean free paths may approach micron scales at room temperature. Despite extensive investigation, the origin of the weak acoustic damping in the heat-carrying frequencies remains a topic of debate. Here, we report measurements of the frequency-dependent mean free path in amorphous silicon thin films from ∼0.1−3 THz and over temperatures from 60 - 315 K using picosecond acoustics and transient grating spectroscopy. The mean free paths are independent of temperature and exhibit a Rayleigh scattering trend from ∼0.3−3 THz, below which the trend is characteristic of damping from density fluctuations or two-level systems. The observed trend is inconsistent with the predictions of numerical studies based on normal mode analysis but agrees with diverse measurements on other glasses. The micron-scale MFPs in amorphous Si arise from the absence of Akhiezer and two-level system damping in the sub-THz frequencies, leading to heat-carrying acoustic excitations with room-temperature damping comparable to that of other glasses at cryogenic temperatures

A new record of the genus Froggattiella Leonardi (Hemiptera, Coccomorpha, Diaspididae) in South Korea

The genus Froggattiella Leonardi, 1900 belongs to the family Diaspididae, and five species of Froggattiella have been recorded worldwide. In this study, Froggattiella penicillata (Green, 1905), which attacks bamboos, is newly recorded in South Korea. The colonies of F. penicillata were collected on a bamboo forest located in Gajwa-dong, Jinju-si, Gyeongsangnam-do, South Korea (35.1599, 128.1029). Description of the adult female, host plant, adult female illustrations, and global distribution of this species are provided.Froggattiella penicillata (Green, 1905) is reported for the first time in South Korea. This species occurrs under sheathing bases of the leaves and is observed attached on the stem and not on the leaf