We investigate the ultrafast terahertz response of electrostatically gated graphene upon optical excitation. We observe that the photoinduced terahertz absorption increases in charge neutral graphene ...but decreases in highly doped graphene. We show that this transition from semiconductor-like to metal-like response is unique for zero bandgap materials such as graphene. In charge neutral graphene photoexcited hot carriers effectively increase electron and hole densities and increase the conductivity. In highly doped graphene, however, photoexcitation does not change net conducting carrier concentration. Instead, it mainly increases electron scattering rate and reduce the conductivity.
We demonstrate efficient terahertz (THz) modulation by coupling graphene strongly with a broadband THz metasurface device. This THz metasurface, made of periodic gold slit arrays, shows near unity ...broadband transmission, which arises from coherent radiation of the enhanced local-field in the slits. Utilizing graphene as an active load with tunable conductivity, we can significantly modify the local-field enhancement and strongly modulate the THz wave transmission. This hybrid device also provides a new platform for future nonlinear THz spectroscopy study of graphene.
To date, 5 different human dental stem/progenitor cells have been isolated and characterized: dental pulp stem cells (DPSCs), stem cells from exfoliated deciduous teeth (SHED), periodontal ligament ...stem cells (PDLSCs), stem cells from apical papilla (SCAP), and dental follicle progenitor cells (DFPCs). These postnatal populations have mesenchymal-stem-cell-like (MSC) qualities, including the capacity for self-renewal and multilineage differentiation potential. MSCs derived from bone marrow (BMMSCs) are capable of giving rise to various lineages of cells, such as osteogenic, chondrogenic, adipogenic, myogenic, and neurogenic cells. The dental-tissue-derived stem cells are isolated from specialized tissue with potent capacities to differentiate into odontogenic cells. However, they also have the ability to give rise to other cell lineages similar to, but different in potency from, that of BMMSCs. This article will review the isolation and characterization of the properties of different dental MSC-like populations in comparison with those of other MSCs, such as BMMSCs. Important issues in stem cell biology, such as stem cell niche, homing, and immunoregulation, will also be discussed.
Ingroup vigilance in collectivistic cultures Liu, Shi S.; Morris, Michael W.; Talhelm, Thomas ...
Proceedings of the National Academy of Sciences - PNAS,
07/2019, Volume:
116, Issue:
29
Journal Article
Peer reviewed
Open access
Collectivistic cultures have been characterized as having harmonious, cooperative ingroup relationships. However, we find evidence that people in collectivistic cultures are more vigilant toward ...ingroup members, mindful of their possible unethical intentions. Study 1 found that Chinese participants were more vigilant than Americans in within-group competitions, anticipating more unethical behaviors from their peers. Study 2 replicated this finding by comparing areas within China, finding that people from China’s collectivistic rice-farming regions exhibit greater ingroup vigilance than people from the less collectivistic wheat-farming regions. The rice/wheat difference was mediated by greater perceived within-group competition. Study 3 found that Chinese participants were more likely than Americans to interpret a peer’s friendly behavior as sabotage in disguise. We also manipulated within-group competition and found that it increased ingroup vigilance in both cultures. Finally, study 3 identified two boundary conditions where cultural differences in ingroup vigilance decrease: an unambiguously competitive win–lose situation where Americans also exhibit vigilance, and an unambiguously cooperative win–win situation where Chinese participants relax their vigilance. This research contributes to a more balanced view of collectivism, revealing its interpersonal tensions in the forms of within-group competition and ingroup vigilance.
To date, 5 different human dental stem/progenitor cells have been isolated and characterized: dental pulp stem cells (DPSCs), stem cells from exfoliated deciduous teeth (SHED), periodontal ligament ...stem cells (PDLSCs), stem cells from apical papilla (SCAP), and dental follicle progenitor cells (DFPCs). These post-natal populations have mesenchymal-stem-cell-like (MSC) qualities, including the capacity for self-renewal and multilineage differentiation potential. MSCs derived from bone marrow (BMMSCs) are capable of giving rise to various lineages of cells, such as osteogenic, chondrogenic, adipogenic, myogenic, and neurogenic cells. The dental-tissue-derived stem cells are isolated from specialized tissue with potent capacities to differentiate into odontogenic cells. However, they also have the ability to give rise to other cell lineages similar to, but different in potency from, that of BMMSCs. This article will review the isolation and characterization of the properties of different dental MSC-like populations in comparison with those of other MSCs, such as BMMSCs. Important issues in stem cell biology, such as stem cell niche, homing, and immunoregulation, will also be discussed. PUBLICATION ABSTRACT
We achieve direct electrical readout of the wavelength and polarization dependence of the plasmon resonance in individual gold nanogap antennas by positioning a graphene nanoconstriction within the ...gap as a localized photodetector. The polarization sensitivities can be as large as 99%, while the plasmon-induced photocurrent enhancement is 2−100. The plasmon peak frequency, polarization sensitivity, and photocurrent enhancement all vary between devices, indicating the degree to which the plasmon resonance is sensitive to nanometer-scale irregularities.
Healthy aging is a complex biological process with progressive accumulation of senescent cells characterized by stable cell cycle arrest, resulting in impaired homeostasis, regenerative potential, ...and gradual functional decline in multiple tissues and organs, whereby the aberrant activation of mammalian target of rapamycin (mTOR) signaling networks plays a central role. Herein, we explored the effects of extracellular vesicles (EVs) released by gingiva-derived mesenchymal stem cells (GMSC-EVs) on oxidative stress–induced cellular senescence in human endothelial cells and skin fibroblasts and their antiaging potentials. Our results showed that GMSC-EVs robustly abrogated oxidative stress–induced upregulation in the expression of cellular senescence-related genes, such as β-galactosidase, p21, p53, and γH2AX, and mTOR/pS6 signaling pathway, in human umbilical vein endothelial cells (HUVECs) and skin fibroblasts. Meanwhile, GMSC-EVs restored oxidative stress–induced impairment in proliferation and tube formation by HUVECs. Systemic administration of GMSC-EVs attenuated aging-associated elevation in the expression levels of p21, mTOR/pS6, interleukin 6, and tumor necrosis factor α in skin and heart tissues of aged mice. These findings suggest that GMSC-EVs could be a potential alternative source of cell-free product for attenuation of aging-related skin and vascular dysfunctions due to their potent inhibitory effects on oxidative stress–induced cellular senescence in endothelial cells and skin fibroblasts.
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