Search

Objection: The study aimed to explain the effects and mechanisms of long noncoding RNA (lncRNA) MIAT in development of colon cancer. Methods: The adjacent and cancer tissues which were collected from 30 cases colon cancer patients were evaluated pathology by HE staining and lncRNA MIAT expression by ISH assay. In the vitro study, SW620 cells were divided into NC, siRNA-control and siMIAT groups. Measuring cell proliferation, apoptosis, cell cycle, invasion and migration by CCK-8, flow cytometry, transwell and wound healing, and evaluating the relative proteins expressions by WB assay. Results: Compared with adjacent normal tissues, the lncRNA MIAT was significantly up-regulation in colon cancer tissues (P < 0.001). By cell experiment, with lncRNA MIAT knockdown, the cell proliferation was significantly depressed (P < 0.001) via significantly improving cell apoptosis and keeping the cell in the G1 phase (P < 0.001, respectively); the invasion SW620 cell number and wound healing rate were significantly suppressed (P < 0.001, respectively). The relative proteins (CDK2, Cyclin D3 and MMP-9) expressions of siMIAT group were significantly down-regulation compared with those of NC group (P < 0.001, respectively). Conclusion: Our study found that lncRNA MIAT expression is closely associated with colon cancer and may be one of key roles in progression and metastasis in colon cancer.

In the adaptive optics system, the accuracy and robustness of wavefront sensor greatly affect the ability of aberration detection and closed-loop correction. In the condition of the nonuniformity of amplitude distributions or insufficient of beacon light energy, it will cause accuracy decrease of Hartmann wavefront sensing due to the lack of sub-aperture light. Meanwhile, the real-time performance of the wavefront sensing-free adaptive system based on far-field spot inversion cannot meet the practical requirements. The method of the wavefront inversion based on deep learning is to directly obtain aberrations by inputting the far-field light intensity image, which can be used as an effective supplement to the adaptive optical system. Through numerical simulation, this paper proved that the deep residual neural network could directly predict the Zernike coefficient of the wavefront phase through the far-field spot. And experimental demonstrated the corrected residual RMS between input and reconstructed wavefront phase was 0.08 waves, the average computation time was less than 2 ms by GPU acceleration. This method can predict the Zernike coefficient of incident wavefront distortion more accurately, and has a good aberration correction capability, suitable for measuring and correcting the main components of wavefront distortion in traditional adaptive optics method, or providing a good initial wavefront estimation for optimized adaptive optics.

Based on the vehicle front crash finite element analysis, it shows that there is a large acceleration, so it needs further optimization. In order to improve the performance of vehicle collision, eight parts were selected which have large impact for the result, its thickness as design variables to the right of the B-pillar acceleration peak of optimization goal; 17 sample points were selected by Latin hypercube sampling method. Many structure parameters are optimized using sequential quadratic program (SQP) based on the surrogate model. The results show that the improved RSM has high accuracy; the right B-pillar acceleration reduced approximately 22.8%, reached the expected objective and was more conducive to the occupant safety.

The objective of the study is to evaluate the clinical value of ureteroscopic holmium laser lithotripsy for the treatment of nephrolithiasis. Clinical data of 44 patients treated for renal stones with polyscope modular flexible ureter- oscopic holmium laser lithotripsy from May 2014 to April 2015 were retrospectively analysed. Following the operation, F4.7 D-J stents were routinely indwelled for 4 weeks and catheterization for 1-3 days. A plain kidney, ureter, and blad- der (KUB) X-ray was performed on postoperative days too. A total of four success cases were determined following the first treatment. The remaining 40 cases were first placed with double-J stent and the surgery was performed one week later. Stone sizes between 0.8-4.0 cm in diameter were defined. The operation time for the treatment was 80-180 minutes. Patients were discharged within 3-5 days, and the double-J stent was removed within 1-3 months. 39 patients were found to be completely stone-free at approximately three months postoperatively. However, five patients were shown to have 11.1% of residual stones after treatment. No blood transfusion, septic shock, ureteral injury, or other complications were reported. Flexible ureteroscopic holmium laser lithotripsy is safe and effective for the treatment of nephrolithiasis. This approach could be a valuable choice for the treatment of patients with renal stones.

The study of light distribution in orchards is very important for enhancing agricultural production. Nonlinear massive data, amounting to more than 190 MB, were collected over a 6-month period. Information such as the location, illumination, and time was obtained from wireless sensor networks, while that of canopy density and slope aspect was obtained through manual surveys. This paper proposes an improved back propagation (BP) neural network to study sunshine illumination distribution by exploiting these data. The basic BP neural network is divided into Q groups, each of which receives R samples and is trained individually using a gradient descent algorithm. Every grouped neural network records its error at the end of each training round. The new weights and thresholds, selected according to these error values, are employed in the next round of training, and the training process does not terminate until the error is within the desired goal. Finally, to verify the validity of the algorithm according to various criteria, the improved BP neural network is used to study sunshine illumination in an orchard. Our experiments show that the improved BP neural network algorithm performs better than traditional algorithms including the spline interpolation, Kriging, and basic neural network algorithms, and yields an accurate sunshine illumination distribution that can be used to improve agricultural production.

In coherent beam combining of fiber lasers, the combined beam's quality is strongly affected by not only the piston phase differences between each beamlet, but also the tilt-tip errors of each beamlet. In this paper, we first presented a numerical model of tilt-tip control, then performed the numerical simulation to investigate the tilt-tip wavefront control in coherent beam combining using stochastic parallel gradient descent (SPGD) algorithm. It is demonstrated that the tilt-tip errors can be compensated effectively using SPGD algorithm. Results show that the increase in both the mean square error (MSE) of tilt-tip errors and the number of lasers degrade the control effect. It is difficult to compensate the tilt-tip errors when the MSE is larger than 75% of each beamlet's divergence angle. When the iteration rate of the SPGD algorithm is 100 Hz, the simulated control bandwidth is 16.50 Hz with tilt-tip errors' MSE of 5% of the divergence angle, and 1.90 Hz with MSE of 8% of the divergence angle.

Based on the computational fluid dynamics (CFD) software, an emluator for the optics and fluency coupling effects is established by means of the user defined function (UDF). Thermal blooming effects in a special tube with axial pipe flow are modeled. The simulated results indicate that the velocity distribution of the pipe flow is very asymmetric. However, the fluid density distribution is almost not changed without laser beam heating. As laser beam couples with the fluency, the fluid density distribution varies greatly. The heterogeneous fluid density distribution induces the optical path distinction of the double pearl eye form. This phenomenon is also observed in the previous experiments.

One of the most outstanding limitations in the evolution of the power scaling of fiber laser with near diffraction limited beam quality has been the mode instability since it was found in 2010. For a long time, researchers have focused on the dynamic mode instability (DMI) theoretically and experimentally, and it was not until 2016 that a new analytical model called quasi-static mode instability (QSMI) was proposed. Unlike DMI, because of the one-way energy transfer characteristic on a specific time scale, QSMI will show no apparent fluctuations with respect to the time domain traces. In this paper, based on a counter-pump few-mode fiber amplifier schematic system, the output power, beam quality and time traces of the amplifier under changing seed laser power are measured to investigate its mode instability effect. The ytterbium-doped fiber of the amplifier has a core diameter of 25 μm and inner cladding diameter of 400 μm, which can support 4-5 modes to be transmitted in the amplifier. The experimental results reveal that QSMI happens in the few-mode fiber amplifier. Taking 234 W seed power for example, it is found that when the output power reaches 2030 W, the optical-to-optical efficiency begins to fell from 86% to 32%, and at the same time the M2 value has an abrupt degradation from 2.2 to 2.8, which indicates that MI happens. On the other hand, it can be seen from the time traces of the output laser that there exist no rapid fluctuations, and the Fourier analysis shows no sign of DMI characteristic frequency components either. Quoting the definition of drifting ratio σ, when the output power is 2030 W under 234 W seed power, it is only 4%, and thus verifying that it is QSMI instead of DMI. The experiment also indicates that increasing the seed power has an effective influence on enhancing the mode instability power. When the seed power is raised from 86 W to 528 W, the corresponding threshold power is increased from 1560 W to 3090 W. And for 528 W seed power, when the output laser surpasses 3000 W, the optical-to-optical efficiency does not decline as fast as other relatively low seed power. To sum up, the mode instability effect represents a kind of quasi-static property in these large core diameter few-mode fiber amplifiers, which needs further studying.

High peak power, single frequency nanosecond fiber lasers have aroused the intense interest in their applications such as nonlinear frequency generation, LIDAR, and remote sensing. However, self-phase modulation (SPM) will induce a temporally dependent phase shift φNL (L, t)=|Ap (0, t)|2γLeff, where Ap is the amplitude of pump wave, γ is the nonlinear parameter, and Leff is the effective fiber length. The nonlinear phase shift will broaden the spectral linewidth of pulsed laser, which degrades the coherence of the laser and influences the performance of the laser. In order to obtain laser pulses with narrower linewidth, we can phase-modulate the pulsed laser with a value of-φNL(L,t). Thus, the SPM induced the nonlinear phase shift can be eliminated, and the spectra of pulsed laser can remain during the amplification and transmission in the fiber. Stimulated Brillouin scattering (SBS) has very low threshold and should be taken into consideration in narrow linewidth fiber lasers. The SBS threshold, which is dependent on the linewidth of laser, will be changed at the same time when the SPM is pre-compensated for. Because the SPM pre-compensation will change the linewidth of the pulsed laser. According to three coupled amplitude equations, we numerically analyze the influence of SPM pre-compensation on SBS threshold and spectral characteristics. The stimulation results show that in a master oscillator power amplifier structured fiber laser system, when SPM is completely compensated for (φM(t)=φNL(L,t)), the spectrum of the output pulsed laser can be maintained as that of the laser seed, but the SBS threshold usually decreases. When the SPM is compensated for incompletely (φM(t) φNL(L,t)), the spectral linewidth of the output laser cannot be compressed to that of the laser seed, and the SBS threshold in this situation is lower than the SBS threshold obtained when φM(t)=φNL(L,t). When the SPM is overcompensated for (φM(t) > φNL(L, t)), the spectral linewidth of the output laser cannot be compressed to that of the laser seed either, but the the SBS threshold in this situation is higher than the SBS threshold when φM(t)=φNL(L,t). We also build an experimental setup to verify the feasibility of SPM compensation. In our experiment, the linewidth of the pulsed laser is reduced from 1.4 GHz to 120 MHz when SPM is compensated for by phase modulation. The SBS threshold of the system are measured before and after SPM pre-compensation, and correctness of theoretical simulation is experimentally verified. This analysis method can provide the design guidelines for narrow-linewidth pulsed fiber laser systems.

Narrow-linewidth nanosecond pulsed Raman fiber amplifiers possess many applications such as in nonlinear frequency generation, remote sensing and quantum information. By considering nonlinear effects such as stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), self-phase modulation (SPM) and cross-phase modulation (XPM), we build a nonlinear dynamical model of narrow-linewidth nanosecond pulsed Raman fiber amplifier. A numerical simulation model is also built and the simulation is carried out based on the parallelizable bidirectional finite difference time-domain method. The pulse evolution processes in time and spectral domain are simulated. The influences of pump pulse width, fiber length and signal laser power are studied in detail. It is found that SRS peak power threshold is not influenced by pump pulse width, however, pump pulse width will affect SBS threshold and output linewidth. When the pump pulse width is 800 ns, tens of MHz narrow linewidth can be obtained, but the SBS occurs as the increasing of pump energy, which limits the power scaling of the narrow-linewidth laser pulses. When the pump pulse width is 80 ns, the SBS is effectively suppressed and the peak power can be further increased, but the linewidth of output laser is easily broadened to hundreds of MHz. The simulation results also show that lower SRS threshold and higher efficiency can be obtained by using longer passive fiber, however, if shorter passive fiber is used, SPM and XPM can be weakened and narrower linewidth can be obtained. We build an experimental setup to study the influence of fiber length. In our experiment, a polarization-maintained passive fiber with a core diameter of 10 m and core numerical aperture of 0.08 is used as the Raman gain fiber. The signal laser is a 1120 nm single frequency continuous wave fiber laser with an average power of 20 mW, and the pump laser is a 1064 nm pulsed laser with a pulse width of~40 ns and repetition rate of 500 kHz. When the fiber lengths are 100 m and 80 m, the efficiencies of the pulsed Raman amplifier are, respectively, 51.5% and 38.2% at a pump power of 6.8 W. It can also be found that increasing signal power can increase the efficiency of the amplifier, but it will reduce the SBS threshold at the same time. Therefore, in order to balance the different nonlinear effects in the arrow-linewidth nanosecond pulsed Raman fiber amplifier, we should take laser power, linewidth and efficiency into consideration, and choose the suitable system parameters such as pump pulse width, fiber length and signal power. These analyses can serve as design guidelines for narrow-linewidth nanosecond pulsed fiber Raman amplifiers.

To improve the power efficiency of the laser system, it is necessary to transform Gaussian intensity distribution to dark hollow intensity distribution. The phase-only liquid crystal spatial light modulator (LC-SLM) has been used to transform a quasi-Gaussian beam to a dark hollow one. The phase distribution of the shaping system was derived according to the energy conservation law and the constant optical length principle. The influences of input beam waist and shape on shaping effect were discussed based on numerical simulation. The generation of the dark hollow beam has been realized experimentally with the phase-only LC-SLM, and the conversion efficiency was larger than 99%．

Thermal blooming anisoplanatic effect of the circular-symmetric flattened beam is analysed by the method of Gaussian beam expansion. Wave-front distortion of the thermal blooming anisoplanatic effect is expanded by the Zernike polynomials, and the Zernike coefficient and fitting error are obtained. The corrected error of the thermal blooming calculated by the numerical method is consistent with the outcome of the theoretical formula. The numerical simulation results also indicate that the angular anisoplanatic error varies proportionally to the square of the anisoplanatic angle, and the focus anisoplanatic error is in inverse proportion to the 1.71th power of the beacon height, if the caliber size is invariable.