Self-calibrated atom-interferometer gyroscope by modulating atomic velocities.

Atom-interferometer gyroscopes have attracted much attention for their long-term stability and extremely low drift. For such high-precision instruments, self-calibration to achieve an absolute rotation measurement is critical. In this work, we propose and demonstrate the self-calibration of an atom-interferometer gyroscope. This calibration is realized by using the detuning of the laser frequency to control the atomic velocity, thus modulating the scale factor of the gyroscope. The modulation determines the order and the initial phase of the interference stripe, thus eliminating the ambiguity caused by the periodicity of the interferometric signal. This self-calibration method is validated through a measurement of the Earth's rotation rate, and a relative uncertainty of 162 ppm is achieved. Long-term stable and self-calibrated atom-interferometer gyroscopes have important applications in the fields of fundamental physics, geophysics, and long-time navigation.

Compact multi-channel radio frequency pulse-sequence generator with fast-switching capability for cold-atom interferometers.

Cold-atom interferometers have matured into a powerful tool for fundamental physics research, and they are currently moving from realizations in the laboratory to applications in the field. A radio frequency (RF) generator is an indispensable component of these devices for controlling lasers and manipulating atoms. In this work, we developed a compact RF generator for fast switching and sweeping the frequencies and amplitudes of atomic-interference pulse sequences. In this generator, multi-channel RF signals are generated using a field-programmable gate array (FPGA) to control eight direct digital synthesizers (DDSs). We further propose and demonstrate a method for pre-loading the parameters of all the RF pulse sequences to the DDS registers before their execution, which eliminates the need for data transfer between the FPGA and DDSs to change RF signals. This sharply decreases the frequency-switching time when the pulse sequences are running. Performance characterization showed that the generated RF signals achieve a 100 ns frequency-switching time and a 40 dB harmonic-rejection ratio. The generated RF pulse sequences were applied to a cold-atom-interferometer gyroscope, and the contrast of atomic interference fringes was found to reach 38%. This compact multi-channel generator with fast frequency/amplitude switching and/or sweeping capability will be beneficial for applications in field-portable atom interferometers.

Proteomics Study on the Differentially Expressed Proteins in c-fos-silenced Cells Exposed to PM 2.5.

OBJECTIVE: To investigate the effect of c-fos gene silencing on differentially expressed proteins (DEPs) in human bronchial epithelial (HBE) cells after exposure to fine particulate matter (PM 2.5). METHODS: HBE cells and c-fos-silenced HBE cells were exposed to 50 µg/mL PM 2.5, LC-MS/MS and tandem mass tag (TMT) labeling methods were combined with bioinformatics methods, and DEPs and interaction networks were identified. RESULTS: In the HBE group, 414 DEPs were screened, of which 227 were up-regulated and 187 down-regulated. In the c-fos silenced HBE group, 480 DEPs were screened, including 240 up-regulated proteins and 240 down-regulated proteins. KEGG annotations showed that DEPs in the HBE group are mainly concentrated in the glycolysis/gluconeogenesis pathway and those in the c-fos silenced group are concentrated mainly in endoplasmic reticulum and the processing of proteins. Additionally, the abnormal expression of GPRC5C, DKK4, and UBE2C was identified in top 15 DEPs. After constructing the protein interaction network, 20 Hub proteins including HNRNPA2B1, HNRNPL, RPS15A, and RPS25 were screened from the HBE group and the c-fos silenced HBE group. CONCLUSION: c-fos gene affected the expression of cancer-related proteins. Our results provided a scientific basis for further study of PM 2.5-induced carcinogenesis mechanism.