It is well known that the extremely low-frequency electromagnetic field (EMF) can promote the healing of bone fractures, but its mechanism remains poorly understood. The purpose of this study was to examine the response of neonatal rat calvarial bone cells to the rectangular electromagnetic field (REMF), triangular electromagnetic field (TEMF), sinusoidal electromagnetic field (SEMF), and pulsed electromagnetic field (PEMF). The stimulatory effects of EMF were evaluated by the proliferation (methyltetrazolium colorimetric assay), differentiation (alkaline phosphatase (ALP) activity), and mineralization (area of mineralized nodules of the cells). REMF treatment of osteoblasts increased cellular proliferation and decreased ALP activity (p < 0.05). TEMF had an accelerative effect on the cellular mineralized nodules (p < 0.05). SEMF treatment of osteoblasts decreased the cellular proliferation, increased ALP activity, and suppressed mineralized nodules formation (p < 0.05). PEMF promoted the proliferation of osteoblasts, inhibited their differentiation, and increased the mineralized nodules formation (p < 0.05). Moreover, the effects of PEMF on osteoblasts were concerned with the extracellular calcium, P2 receptor on the membrane, and PLC pathway, but the response of osteoblasts on SEMF was only related to PLC pathway. The results suggested that the waveforms of EMF were the crucial parameters to induce the response of osteoblasts.

Following the previous theoretical study on the open lipid membranes with edges by Tu and Ou-Yang [Phys. Rev. E68, 061915 (2003)], we show that the discocyte solution can give us several interesting open vesicles with two edges and the central singularity of this solution can be avoided in the meantime.

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The spectrum of the microchip Nd:YAG laser subjected to external frequency-shifted feedback is experimentally observed to be broadened. On comparison with a frequency-stabilized Nd:YAG laser, it presents multiple side frequencies around its initial central frequency, whose spacing is related to the shifted frequency in laser external cavity. The number of side frequencies, which can reach as high as 16 in the present scheme, as well as the broadening depend on the feedback level. This phenomenon can be potentially used to broaden the laser spectrum to realize multi-frequency generation in lasers.