Saturated absorption spectroscopy reveals the narrowest features so far in molecular gas-filled hollow-core photonic crystal fiber. The 48-68 mum core diameter of the kagome-structured fiber used here allows for 8 MHz full-width half-maximum sub-Doppler features, and its wavelength-insensitive transmission is suitable for high-accuracy frequency measurements. A fiber laser is locked to the (12)C2H2 nu(1); + nu(3) P(13) transition inside kagome fiber, and compared with frequency combs based on both a carbon nanotube fiber laser and a Cr:forsterite laser, each of which are referenced to a GPS-disciplined Rb oscillator. The absolute frequency of the measured line center agrees with those measured in power build-up cavities to within 9.3 kHz (1 sigma error), and the fractional frequency instability is less than 1.2 x 10(-11) at 1 s averaging time.
The number of graphene shells on carbon nanotubes (CNTs) can be rationally controlled to yield high-density, vertically aligned single- and double-walled CNTs. This was obtained by thermal chemical vapor
deposition at 700 °C without the use of etching agents such as water, oxygen, or plasma. The key factors for
this success are controlled dissociative adsorption of acetylene (C2H2) molecules and subnanometer thickness
control of the Al/Fe/Mo trilayer films. We propose that an Al concave meniscus confines the actual growth
surface areas of Fe/Mo catalytic nanoparticles and enables the control of the number of graphene shells on
CNTs.
Mechanical stimulation and estrogen have been proven to be two important factors in promoting mesenchymal stem cell activity, which is closely associated with bone formation, mass maintenance and remodeling. However, the superposition effects of mechanical stimulation and estrogen on stem cells remain unknown. It is also unclear if the estrogen receptor (ER) plays only a key role in estrogen signaling or if it is also involved in the mechanotransduction of stem cells. To investigate the role of estrogen and its receptors in the mechanobiological effects in bone mesenchymal stem cells (BMSCs), isolated mesenchymal stem cells from bone marrow were exposed to mechanical pressure under additional estrogen treatment or ER blockade. Cell proliferation was examined using an MTT assay and alkaline phosphatase (ALP) activity was determined by a modified enzyme kinetic method. Alignment of the cytoskeleton was observed by Coomassie brilliant blue staining and F-actin fluorescent staining. Cellular ultrastructure was observed under transmission electron microscope. Expression of ERα was investigated using Western blot analysis. Results indicated that mechanical pressure promoted cell proliferation, ALP activity, ERα expression and F-actin stress fiber formation. Overall, this effect was enhanced by the addition of estrogen and inhibited by ER blockade. We concluded that pressure stimulated proliferation and differentiation capability via F-actin transduction in BMSCs. The effects were enhanced by the addition of estrogen, and the ER plays an important role in regulating mechanobiological effects and the mechanotransduction processes of BMSCs.
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