In high power fiber lasers, the degradation of beam quality caused by Raman effect has attracted more and more attention in recent years, but its physical mechanism is still unclear. We're going to ...differentiate between heat effect and nonlinear effect by duty cycle operation. The evolution of beam quality at different pump duty cycles has been studied based on a quasi-continuous wave (QCW) fiber laser. It is found that even if the Stokes intensity is only -6 dB (energy proportion: 26%) lower than that of the signal light intensity, the beam quality has no obvious change with the duty cycle of 5%; on the contrary, when the duty cycle gradually approaches 100% (CW-pumped scheme), the beam quality distortion changes faster and faster with the increase of Stokes intensity. The experimental results are contrary to core-pumped Raman effect theory IEEE Photon. Technol. Lett.34, 215 (2022)10.1109/LPT.2022.3148999, and further analysis confirms that the heat accumulation in the process of Stokes frequency shift should be responsible for this phenomenon. That is the first time, to the best of our knowledge, for intuitive reveal of the origin of stimulated Raman scattering (SRS)-induced beam quality distortion under transverse mode instability (TMI) threshold in an experiment.
Accurate estimation of the spatial-temporal variation of the maximum gross primary productivity (GPPmax) of vegetation is of great significance for predicting carbon fluxes and vegetation-climate ...feedback. In this study, the GPPmax estimation models were constructed based on driving variables derived from the MODIS enhanced vegetation index (EVI) and land surface temperature (LST) time series data using a stepwise regression analysis. The models were calibrated and validated with the observed GPPmax from 145 FLUXNET sites with 734 site-year data from 2000 to 2014. The GPPmax estimates and the changes in their trends at the global scale were also compared with other GPPmax products from the vegetation photosynthesis model and the eddy covariance-light use efficiency model. The results showed that the GPPmax for both forest and non-forest vegetation types were estimated well, with R2 of 0.47–0.86 and 0.47–0.95 and relative root mean square error of 10.14–35.14% and 11.25–30.02% for calibration and validation data, respectively. Summer EVI and spring EVI and LST played important roles in explaining the variation in GPPmax. The GPPmax estimates from this study and the changes in their trends were highly correlated with GPPmax estimates from the vegetation photosynthesis model, with R2 > 0.70 for most vegetation types. The GPPmax significantly increased in western North America, northern Europe, and eastern China, but decreased in tropical regions. This study concluded that the variation in GPPmax for various vegetation types on a global scale can be accurately estimated based on MODIS EVI and LST time series data, which provides a simple but effective way for large-scale estimation of GPPmax.
•We built GPPmax estimation models from MODIS EVI/LST data using stepwise regression.•GPPmax for both forest and non-forest vegetation were estimated well.•Summer EVI and spring EVI and LST were important in explaining variations in GPPmax.•This method accurately estimated variations in GPPmax for vegetation globally.•Long-term change trends in GPPmax from different products were different.
Model of the relay mirror system with the transmitter composed of sub-telescope array is established. With this model, the new system is theoretically analyzed in the paper. Power coupling ...efficiencies of the 3-sub-telescope array system and the common system are calculated. The results show that power coupling efficiency of the system with new configuration is significantly improved in comparison with the common relay mirror system.
The selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) method probes RNA local structural and dynamic information at single nucleotide resolution. To gain quantitative insights into ...the relationship between nucleotide flexibility, RNA 3D structure, and SHAPE reactivity, we develop a 3D Structure-SHAPE Relationship model (3DSSR) to rebuild SHAPE profiles from 3D structures. The model starts from RNA structures and combines nucleotide interaction strength and conformational propensity, ligand (SHAPE reagent) accessibility, and base-pairing pattern through a composite function to quantify the correlation between SHAPE reactivity and nucleotide conformational stability. The 3DSSR model shows the relationship between SHAPE reactivity and RNA structure and energetics. Comparisons between the 3DSSR-predicted SHAPE profile and the experimental SHAPE data show correlation, suggesting that the extracted analytical function may have captured the key factors that determine the SHAPE reactivity profile. Furthermore, the theory offers an effective method to sieve RNA 3D models and exclude models that are incompatible with experimental SHAPE data.
Nanoparticles are one of the attractive building blocks for nanotechnology and offer new possibilities for novel lasers. The rare earth doped nanoparticle gas laser possesses the great potential in ...high energy laser (HEL) operation because it inherently combines the advantages of commercial broadband diode pumping and gas flow thermal management. By taking Yb
doped nanoparticle gas laser as the main object, a modified model, which considers some main peculiar characteristics of nanoparticles, is set up and analyzed. The model includes special considerations of the scattering influence of nanoparticles, and the modifications of Yb
fluorescence lifetime as well as the cross sections, which distinguishes it from the traditional lasers. Some main influencing factors are simulated and discussed, including the Yb
concentration, gain length and the output coupler etc., and the energy conversion channels of absorbed pump power are analyzed. The results predict a slope efficiency of greater than 60% at reasonable conditions. The modeling provides a new horizon for further study of the scientists and engineers in the field of HEL.
•A novel model is presented to estimate bamboo forest AGB from MODIS data.•EnKF algorithm highly improved the accuracy of MODIS LAI products.•AGB estimated using assimilated LAI was more accurate ...than using MODIS LAI products.•RF model has solved the collinearity and overfitting problem during AGB estimation.
High-precision LAI (leaf area index) spatiotemporal data obtained from MODIS satellite remote sensing products are important for studying vegetation growth status, biomass carbon reserves, and the spatiotemporal dynamics of carbon cycling. LAI significantly influences biomass accumulation during the growth of bamboo forest in subtropical zones. Therefore, we applied the ensemble Kalman filter (EnKF) data assimilation algorithm to assimilate MODIS LAI products, and used assimilated LAI and the normalized difference vegetation index, enhanced vegetation index, simple ratio index as variables in the random forest model to estimate bamboo forest above ground biomass (AGB) in Zhejiang Province. Assimilated LAI spatiotemporal data using EnKF greatly improve the accuracy of MODIS LAI products, the R2 between assimilated and observed LAI was 0.92, and the RMSE was 0.37. Variations in the assimilated LAI time series were consistent with the seasonal dynamics of bamboo forest growth and had a significant effect on AGB. Moreover, the random forest model had strong predictive capabilities. A comparison of training and testing results produced accuracy (R) values for the random forest model using the assimilated LAI time series of 0.71 and 0.73, respectively. Using the assimilated LAI achieved a more accurate AGB estimate than using MODIS LAI time series products, as the R values were 54.3% and 58.7% higher, and the RMSE values were 19.2% and 19.1% lower for training and testing results, respectively. The calculated spatial distribution of bamboo forest AGB in Zhejiang province was consistent with the observed values. By combining assimilation technology of the MODIS LAI time series with the random forest model to more accurately estimate bamboo forest AGB in Zhejiang province, this study provided a new method for estimating large scale forest AGB based on low-resolution time series data.
A two-dimensional cluster model in which the morphology of clusters depends on power–law magnetic interactions that decay with distance
r as a
r
−
α
law is introduced. The growth algorithm is a ...generalization of diffusion-limited aggregation (DLA) model. The particles with spin degree diffuse on a square lattice and each spin is allowed to flip under a Monte Carlo probability. The simulation shows that, for the antiferromagnetic coupling, the spins of the particles in clusters tend to be oriented alternately. For the ferromagnetic coupling, however, the spin distribution depends on the exponent
α: for large value of
α, domains with different sizes are observed in the clusters; while for small
α, during the earlier stage of the growth process, the clusters exhibit approximately antiferromagnetic structure, then, in subsequent growth of the outer part of the clusters, the spin states of all particles are similar. The magnetization and system energy of the clusters as well as their evolutions with the growth parameters are also studied in detail.
The mechanism for beam quality degradation in recently developed phase locking of high power solid state lasers, which is caused mainly by partially coherent property of element beam and partially ...phase locking of the laser array, is analyzed in detail. Analytical expression for propagation of partially coherent partially phase-locked laser array in turbulent atmosphere is obtained based on extended Huygens–Fresnel principle. The effect of coherence width, phase error and intensity of turbulence on the beam quality in the target-plane is studied in detail. The tolerance on phase error for laser array with different coherence property is analyzed. It is concluded that the laser array with better coherence is more sensitive to turbulence, and phase control can improve beam quality in the receiving plane only in the case when the element beam has good beam quality and propagates in weak turbulence.
Leukemia stem-like KG-1a cells escape the synergistic cytotoxic effect of arsenic trioxide and aclacinomycin: regulated by survivin
Yongbin YE1 , Xiaojun.XU1 , Liu Qifa2
1Department of Hematology, ...Zhongshan Hospital of Sun Yat-sen University & Zhongshan City People Hospital, Zongshan 528403
2Department of Hematology, Nanfang Hospital of Southern Medical University, Guangzhou,510515
Abstract AIM OF STUDY: Arsenic trioxide combined with aclacinomycin has a synergistic cytotoxic effect on leukemia stem cell-like cells KG-1a in our pervious study, however, there are still a part of KG-1a cells escaped the synergistic cytotoxicity, survivin may plays in a key role in this process. In this study, we have studied the interaction and mechanism of survivin in regulating leukemia stem-like KG-1a cell escape the synergistic cytotoxic effect of arsenic trioxide and aclacinomycin. MATERIALS AND METHODS: The anti-proliferation effect was detected by CCK-8 and colony-forming assay, protein-protein chip assay was used to analysis the expression level of survivin before and after combination treatment. The induction of apoptosis and cell cycle arrest in KG-1a cell line were detected by FACS, the expression of related signal pathway protein was detected by western blot. RESULTS: The anti-proliferation of KG-1a cells caused by arsenic trioxide or aclacinomycin showed a time- and dose-independent manner. However, protein-protein chip assay showed that the expression of survivin had a significant increase after the combination treatment (p<0.05), but when survivin was suppressed, the apoptosis rate had a more significant increase than the single drug treatment. Meanwhile, more prominent cell cycle arrest was observed in the combination treatment, further study found that suppression of survivin combined with chemotherapy may activate the related apoptosis pathway protein but suppress the PI3K/AKT signal pathway. CONCLUSION: survivin play an important role in regulating leukemia stem cell escape the synergistic cytotoxic effect of arsenic trioxide and aclacinomycin. The mechanism of regulation process may through activate the related apoptosis pathway protein and supperss the PI3K/AKT signal pathway. This study may provide a further benefit for reversing chemotherapy resistant for acute leukemia
Key words: arsenic trioxide,aclacinomycin, Acute leukemia; survivin; chemotherapy resistant
No relevant conflicts of interest to declare.
PDF
