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.

High-Precision Atom Interferometer-Based Dynamic Gravimeter Measurement by Eliminating the Cross-Coupling Effect.

A dynamic gravimeter with an atomic interferometer (AI) can perform absolute gravity measurements with high precision. AI-based dynamic gravity measurement is a type of joint measurement that uses an AI sensor and a classical accelerometer. The coupling of the two sensors may degrade the measurement precision. In this study, we analyzed the cross-coupling effect and introduced a recovery vector to suppress this effect. We improved the phase noise of the interference fringe by a factor of 1.9 by performing marine gravity measurements using an AI-based gravimeter and optimizing the recovery vector. Marine gravity measurements were performed, and high gravity measurement precision was achieved. The external and inner coincidence accuracies of the gravity measurement were ±0.42 mGal and ±0.46 mGal after optimizing the cross-coupling effect, which was improved by factors of 4.18 and 4.21 compared to the cases without optimization.

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.

Proteomic characteristics of PM2.5-induced differentially expressed proteins in k-ras-silenced HBE cells.

The human bronchial epithelial cells (HBE) and K-ras-silenced HBE cells were treated with fine particulate matter (PM2.5) samples from Taiyuan for 24 h. To screen the proteomic characteristics of PM2.5-induced differentially expressed proteins (DEPs), the Q Exactive mass spectrometer was used. Gene ontology (GO) analysis, Kyoto encyclopedia of genes and genomes (KEGG) analysis, functional prediction, protein-protein interaction (PPI) network analysis, and visualization of differential protein interactions were performed. 251 DEPs in K-ras silenced cells and 535 DEPs in normal HBE cells were identified, respectively. KEGG analysis showed that the differentially expressed proteins of PM2.5-treated cells were related to the biosynthesis of ribosomes, antibiotics, and amino acids. On the other hand, K-ras silenced cells were related to metabolic pathways, RNA transport, and DNA replication. Through the construction of a PPI network, the top 10 hub proteins were screened from the two cell groups, among which MRPL13, RPS20, and EIF1AX were of great significance. Our results indicated that the K-ras gene plays an important role in PM2.5-induced DEPs, and the findings provide a scientific basis for the further study of PM2.5 toxic mechanisms and biomarkers.

Proteomic characteristics of PM2.5 -induced differentially expressed proteins in human renal tubular epithelial cells.

Human renal epithelial (HK-2) cells were treated with PM2.5 (50 µg/mL) from Shenzhen and Taiyuan, proteomics and bioinformatics were used to screen the differentially expressed proteins (DEPs). A total of 577 DEPs were screened after HK-2 cells exposed to Shenzhen PM2.5, of which 426 were up-regulated and 151 were down-regulated. A total of 1250 DEPs were screened in HK-2 cells after exposure to Taiyuan PM2.5, of which 488 were up-regulated and 185 were down-regulated. The top 10 proteins with the highest number of nodes were screened using the interaction network map of DEPs. HK-2 cells exposed to Shenzhen PM2.5 contained CYR61, CTGF, and THBS1 proteins, while HK-2 cells exposed to Taiyuan PM2.5 contained ALB, FN1, and CYR61 proteins. Additionally, PM2.5 components were detected, PM2.5 samples from Shenzhen and Taiyuan induced obvious changes in DEPs expression, the difference in DEPs between the two cities was probably associated with the different PM2.5 components.

Effect of c-fos gene silence on PM2.5-induced miRNA alteration in human bronchial epithelial cells.

Human bronchial epithelial (HBE) cells and c-fos-silenced HBE cells were first exposed to fine particulate matter (PM2.5) and the resulting miRNA sequenced. Thereafter, a weighted gene co-expression network analysis was performed using Cytoscape software to visualize the interactions between identified hub miRNAs and their target genes. Nine differentially expressed miRNAs in hub miRNAs were identified in the different treatment groups, of which miR-25-3p, miR-215-5p, and miR-145-5p were selected for further study. Following qPCR validation, both miR-25-3p and miR-215-5p were found to be significantly up-regulated whilst, miR-145-5p was significantly down-regulated (p < 0.05) in the PM2.5 group. Furthermore, miR-25-3p and miR-145-5p were also significantly down-regulated in the untreated group of c-fos silenced HBE cells. However, miR-215-5p was significantly down-regulated in both the untreated and PM2.5-treated groups of c-fos silenced HBE cells. Subsequent analysis of their target genes also illustrated differential gene expression when comparing the treatment groups of the two cell types. The present data indicated that the c-fos gene has an important effect on the miRNA expression profiles and the related signaling pathways in PM2.5-treated HBE cells. Therefore, each of miR-25-3p, miR-145-5p, and miR-215-5p may potentially provide future research information for additional exploration of a PM2.5-induced carcinogenesis mechanism.

Proteomic characteristics and identification of PM2.5-induced differentially expressed proteins in hepatocytes and c-Myc silenced hepatocytes.

Proteomics and bioinformatics were applied to explore PM2.5-induced differentially expressed proteins (DEPs) in hepatocytes (L02 cells) and c-Myc-silenced hepatocytes. L02 cells and c-Myc-silenced hepatocytes were treated with PM2.5 for 24 h. Fifty-two DEPs were screened in L02 hepatocytes, of which 28 were upregulated and 24 were downregulated. Forty-one DEPs were screened in the c-Myc-silenced hepatocytes, of which 31 were upregulated and 10 were downregulated. GO analysis showed that DEPs in L02 cells were mainly concentrated in the cytosol and were involved in biological processes such as the response to metal ions. DEPs in c-Myc-silenced cells were mainly enriched in the extracellular space and were involved in lipoprotein metabolism. KEGG analysis showed that DEPs in L02 cells were mainly involved in arachidonic acid metabolism and mineral absorption. DEPs in c-Myc-silenced cells were mainly enriched in pathways involving nerve absorption, complement and coagulation cascades, and other pathways. Twenty key proteins, including Metallothionein-2A (MT2A), Metallothionein-1X (MT1X), zinc transporter ZIP10 (SLC39A10) and Serine protease 23 (PRSS23) were screened in two groups through analysis of protein-protein interactions. Based on the identification of the selected DEPs, PRSS23 and SLC39A10 might be the potential biomarker of PM2.5-induced carcinogenesis, which provide the scientific basis for further research into the carcinogenic mechanisms of PM2.5.

Alteration of DNA methylation induced by PM2.5 in human bronchial epithelial cells.

This current study explored the effects of fine particulate matter (PM2.5) on deoxyribonucleic acid methylation in human bronchial epithelial cells. Human bronchial epithelial cells were exposed to PM2.5 for 24 h after which, deoxyribonucleic acid samples were extracted, and the differences between methylation sites were detected using methylation chips. Subsequent gene ontology functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed for the differential methylation sites. Functional epigenetic modules analysis of the overall differential methylation site interactions was also conducted. A total of 127 differential methylation sites in 89 genes were screened in the PM2.5 10 µg/ml group, of which 55 sites demonstrated increased methylation, with methylation levels decreasing in a further 72 sites. Following an exposure of 50 µg/ml PM2.5, a total of 238 differentially methylated sites were screened in 168 genes, of which methylation levels increased in 127 sites, and decreased in 111. KEGG analysis showed that the top 10 enrichment pathways predominantly involve hepatocellular carcinoma pathways and endometrial cancer pathways, whereas functional epigenetic modules analysis screened eight genes (A2M, IL23A, TPIP6, IL27, MYD88, ILE2B, NLRC4, TNF) with the most interactions. Our results indicate that exposure to PM2.5 for 24 h in human bronchial epithelial cells induces marked changes in deoxyribonucleic acid methylation of multiple genes involved in apoptosis and carcinogenesis pathways, these findings can provide a new direction for further study of PM2.5 carcinogenic biomarkers.

A Novel Monitoring Navigation Method for Cold Atom Interference Gyroscope.

The implementation principle of a typical three-pulse cold atom interference gyroscope is introduced in this paper. Based on its configuration and current research status, the problems of cold atom interference gyro are pointed out. The data-rate is insufficient, and it is difficult to achieve high dynamic measurement. Then, based on these two limitations, a novel design of the monitoring navigation system of the cold atom interference gyroscope (CAIG) and an intermediate-grade inertial measurement unit (IMU) was proposed to obtain the long-term position result without GPS signals, such as the Inertial Navigation System (INS) in underwater vehicles. While the CAIG was used as the external gyro, the bias of IMU and the misalignment angle between the CAIG-frame and the IMU-frame are obtained through filtering technique. The simulation test and field test demonstrated the improvements of the long-term positioning accuracy of the INS.

Hybrid wide-band, low-phase-noise scheme for Raman lasers in atom interferometry by integrating an acousto-optic modulator and a feedback loop.

We report a hybrid scheme for phase-coherent Raman lasers with low phase noise in a wide frequency range. In this scheme, a pair of Raman lasers with a frequency difference of 3.04 GHz is generated by the ±1-order diffracted lights of an acousto-optic modulator (1.52 GHz), where a feedback loop is simultaneously applied for suppressing the phase noise. The beat width of the Raman lasers is narrower than 3 Hz. In the low-frequency range, the phase noise of the Raman lasers is suppressed by 35 dB with the feedback. The phase noise is less than -109 dBc/Hz in the high-frequency range. The sensitivity of an atom gyroscope employing the hybrid Raman lasers can be implicitly improved 10 times. Due to the better high-frequency response, the sensitivity is not limited by the durations of Raman pulses. This work is important for improving the performance of atom-interferometer-based measurements.