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We present demonstration of an erbium-doped fiber laser based on the nonlinear amplifying loop mirror mechanism, with a stable phenomenon of flat-top Q-switched mode-locked (FT-QML) dissipative soliton resonance (DSR) pulse, for the first time. In the experiment, we can observe both the flat-top Q-switched envelope and square-wave pulse by the peak power clamping effect inside the cavity. The characteristics of both continuous DSR pulse and flat-top Q-switched mode-locked square-wave are analyzed comprehensively. With the maximum pump power of 363 mW, single pulse energy in the FT-QML envelope can be up to 14 nJ as three times high as the one of continuous DSR. Essentially, the temporal width of the Q-switched mode-locked envelope can reach 4.6 μs with flat-top duration of 3.5 μs. The amplitude fluctuation of the sub-pulse inside the flat-top is stable at about 0.12% by using the formula of RMSE. Therefore, the laser can provide flat-top burst mode pulse sequence, and the pulse width can be controlled by tuning the pump power.

To identify pathogenic variants in two patients with suspected for Mowat-Wilson syndrome (MWS).Genomic DNA was extracted from peripheral blood samples of the patients and his family members, and gene variants were analysis by Trio-whole exome sequences and copy number variation sequencing.Patient 1 was found to carried a de novo heterozygous c.2769CA (p.Y923*) nonsense variant of ZEB2 gene. The variant was not found in his healthy parents and sister. Patient 2 carried a de novo heterozygous frameshift variant of the ZEB2 gene, namely c.315delC (p.A105Afs*3), which has not been previously reported. Both variants were predicted to be pathogenic and can lead to premature occurrence of stop codons.The heterozygous c.2769CA (p.Y923*) and c.315delC (p.A105Afs*3) variants of the ZEB2 gene probably underlay the pathogenesis in the two patients. Gene testing has facilitated confirmation of the diagnosis and genetic counselling.

Photoacoustic computed tomography (PACT) is an emerging hybrid imaging modality which can noninvasively reconstruct high-resolution and high-contrast images in deep tissues. However, due to the presence of acoustic heterogeneities within biological tissues, most existing image reconstruction algorithms based on the assumption of constant speed of sound (SOS) will cause image artifacts and distortions. In this paper, to account for the effects of acoustic heterogeneity in PACT image reconstruction, we introduce ultrasound computed tomography (USCT) to provide detailed SOS distribution of the biological tissues and coupling media. Numerical simulation shows that if the variation of SOS is small enough, image reconstruction algorithm with a constant SOS assumption could produce visually acceptable results; otherwise, significant image artifacts and distortions would appear. While with the aid of USCT, image artifacts induced by acoustic heterogeneity in PACT would be effectively suppressed. Since image artifacts and distortions are common image quality degradation factors in PACT, the proposed technique is expected to expedite the development of high-performance imaging, which is essential for widespread applications of PACT.

We experimentally demonstrate a high signal-to-noise ratio (SNR) partially coherent beam (PCB) source based on wide-spectrum produced by a filtered supercontinuum (SC) which can generate from a segment of highly nonlinear fiber (HNLF) pumped by a picosecond fiber laser. The SNR of PCB source can improve from 12.43 dB to 22.45 dB by filtering out amplified spontaneous emission (ASE) noise of erbium-doped fiber amplifier (EDFA) and using lower power pumped HNLF. We also conduct a 4 Gbit/s transmission experiment using the high SNR PCB source in 1km simulated atmospheric turbulent channel. The characteristics of scintillation indexes (SIs), eye patterns, SNRs and bit error rates (BER) based on CB source and PCB sources after turbulent channel are analyzed. In Δ T = 240 ° C , atmospheric turbulent channel, the SI of the CB link can reduce by 31% by using PCB source. The SNR of PCB source is 8.15 dB higher than the 5.20 dB of the CB source, and the sensitivity of the PCB source has a 2.9 dB improvement compared with the CB source. The PCB source possess high SNR and turbulence resistance, which can improve the performance of free space data transmission.

We report on improvements of mode-locked soliton pulse energy and peak power in a thulium-doped fiber laser. At the pump power of 370 mW, conventional soliton can be first generated using nonlinear polarization rotation technology. By increasing the pump power to 550 mW and appropriately adjusting cavity polarization state, the conventional soliton pulse can be converted into the Gaussian pulse. Due to dispersion management, excess accumulation of nonlinear phase shifts in the cavity can be avoided. In this case, the pulse energy and peak power can be increased from 77 pJ to 1.38 nJ and from 106.9 W to 2.67 kW, respectively. These improvements indicate that the Gaussian pulse operation can effectively enhance the pulse energy and peak power of the thulium-doped fiber laser.

We report on the experimental observations of stable single soliton and soliton molecules in an anomalous-dispersion thulium-doped passively mode-locked fiber laser by using the nonlinear polarization rotation technology. The stable single soliton operation can convert to the soliton pair operation by cautiously adjusting the PCs, at the pump power of 350 mW. It is experimentally demonstrated that the formation of stationary soliton pairs is related to the interaction between solitons and dispersive waves. By appropriately adjusting the cavity parameters, more complex soliton molecules composed of three, four, and five bound solitons can be observed. Meanwhile, we experimentally analyze complex nonlinear dynamics of soliton molecules around 2- ${\mu }\text{m}$ .

Image formation in photoacoustic tomography (PAT) is generally based on the assumption that biological tissues are acoustically homogeneous. However, this does not hold, especially when strongly heterogeneous tissues, such as bones and air cavities, are present. Tissue heterogeneity can cause acoustic reflection, refraction, and scattering at interfaces, which may create distortions and artifacts in final images. To mitigate this problem, we propose an adaptive photoacoustic (PA) image reconstruction method based on prior structural information of an acoustically heterogeneous region extracted from ultrasound images. The method works in three steps: acoustic heterogeneity identification via ultrasound imaging; acoustically heterogeneous region segmentation; and adaptive time-domain raw data truncation and image reconstruction. The data truncation is based on a variable cutoff time, which can be adaptively determined according to the relative position of a transducer and an acoustically heterogeneous region. Numerical and in vivo experimental imaging results of human fingers demonstrate that the proposed ultrasound-guided adaptive image reconstruction method can effectively suppress acoustic heterogeneity-induced artifacts and substantially improve image quality. This work provides a practical way to mitigate the influence of acoustic heterogeneity in PAT.

The dissipative soliton resonance (DSR) pulses are demonstrated experimentally in an all polarization-maintaining (PM) thulium-doped mode-locked fiber laser. The mode-locked operation is achieved using of the nonlinear amplifying loop mirror mechanism (NALM). Each loop of the apparatus includes an independently controlled amplifier and a section of gain fiber. The experiment is carried out at a central wavelength of 1969.8 nm and 3.5 ns as the maximum output pulse width. The time domain and spectrum characteristics of output pulse are analyzed with different positions of PM-1950 fiber in the NALM loop. In addition, the DSR pulse properties are experimentally verified by changing the length of the PM-1950 fiber spliced into the NALM loop. We have achieved environmentally stable mode-locked pulses at 3, 2.1, and 1.62 MHz corresponding to the maximum pulse energies of 6.8, 20, and 29.1 nJ. The output pulse is stable and robust at different ambient temperatures.

We report on the switchable generation of a dissipative soliton (DS) pulse and a noise-like pulse (NLP) in an all-fiberized Tm-doped fiber laser in the normal-dispersion region. Mode-locking operation is achieved through a nonlinear polarization rotation component, and the cavity dispersion is compensated using ultra-high numerical aperture (UHNA4) fiber that is easy to integrate and low in cost. At a pump threshold of 510 mW, DS operation can first be achieved without additional filter. The 3 dB spectrum bandwidth of the DS pulse is greater than 50 nm, and the duration of the de-chirped pulse is 193 fs. By increasing the pump power to 880 mW, the mode-locking state can evolve into NLP operation with proper cavity polarization state. The 3 dB spectrum bandwidth and duration of de-chirped coherence spike are 105.6 nm and 121 fs, respectively. Meanwhile, ultra-broadband NLP (over 150 nm considering 3 dB spectrum width) can also be observed with the appropriate cavity parameters. All the proposed pulse patterns present good capacity for achieving narrow pulse width and withstanding high pulse energy.

Hydrogen peroxide (H2 O2 ) is generated in many metabolic processes. As a signaling molecule, H2 O2 plays important roles in plant growth and development, as well as environmental stress response. In Arabidopsis, there are three catalase genes, CAT1, CAT2, and CAT3. The encoded catalases are predominately peroxisomal proteins and are critical for scavenging H2 O2 . Since CAT1 and CAT3 are linked on chromosome 1, it has been almost impossible to generate cat1/3 and cat1/2/3 mutants by traditional genetic tools. In this study, we constructed cat1/3 double mutants and cat1/2/3 triple mutants by CRISPR/Cas9 to investigate the role of catalases. The cat1/2/3 triple mutants displayed severe redox disturbance and growth defects under physiological conditions compared with wild-type and the cat2/3 double mutants. Transcriptome analysis showed a more profound transcriptional response in the cat1/2/3 triple mutants compared to the cat2/3 mutants. These differentially expressed genes are involved in plant growth regulation as well as abiotic and biotic stress responses. In addition, expression of OXI1 (OXIDATIVE SIGNAL INDUCIBLE 1) and several MAPK cascade genes were changed dramatically in the catalase triple mutant, suggesting that H2 O2 produced in peroxisomes could serve as a peroxisomal retrograde signal.

In order to better evaluate the relationship between reciprocity and time delay of the fiber receiving system in the atmospheric turbulence channel, a time-domain signal generation mathematical model is proposed for the first time. A numerical solution of Johnson SB probability density distribution (PDF) in time-domain is creatively given for evaluating the reciprocity of both communication ends, which relates to the normalized fluctuation variance of the light intensity and the Greenwood frequency. An experiment is then carried out for verifying the time-domain signal generation model and measuring reciprocity. It shows that the excellent fitting accuracy of Johnson SB PDF signal generation model is first experimentally verified. It also indicates that the system reciprocity is improved by 10% after eliminating the system time delay. Meanwhile, the relationship between time delay and reciprocity under different atmospheric environments are analyzed and the relationship between time delay and system reciprocity at different Greenwood frequencies are discussed. This work provides a time parameter reference for the design of adaptive system and free-space optical (FSO) communication system.

We report on the experimental observation of wavelength-switchable stretched pulse and bound-state pulse in a dispersion-managed Tm-doped laser. At a pump power of 572 mW, a stretched pulse with a pulse duration of 389 fs can be first obtained at 1961 nm. By increasing the pump power and appropriately adjusting the cavity polarization state, the mode-locking wavelength can be switched from 1961 nm to 1980 nm caused by the birefringence filtering effect based on nonlinear polarization rotation, and the corresponding pulse duration is 371 fs. Meanwhile, loosely bound states of two pulses and three pules at 1980 nm can be observed with appropriate cavity parameters.

We demonstrate free-space transmission based on a broadband fiber laser at 16 Gbit/s over a simulated atmospheric turbulence channel. The broadband laser pulse is part of a supercontinuum generated by a homemade picosecond laser based on Raman gain soliton compression pumping a segment of highly nonlinear fiber. The scintillation indices, eye patterns, and bit error rates of transmission based on the broadband laser and a narrow-linewidth laser are compared. The results show a 29.5% reduction in the scintillation index and sensitivity of −28.6 dBm at the forward error correction limit, which has a 2.9 dB improvement compared with the narrow-linewidth system. It is feasible to use broadband lasers as carriers combining optical time division multiplexing as a multiplexing method to improve the communication performance under weak atmospheric turbulent conditions.

We present the generation and optimization of square-wave noise-like pulses (NLPs) in a mode-locked Tm-doped fiber laser. Mode-locking operation around the 2-μm band is achieved by a nonlinear amplifying loop mirror. To optimize the output performance, the figure-eight cavity is modified by employing a polarization-dependent isolator in a unidirectional loop, and the cavity length is only 17.2 m. First, by employing a cavity with pure anomalous dispersion, a conventional soliton can evolve into a square-wave NLP by properly setting the pump power and polarization controllers. The pulse energy of the fundamental-frequency operation can be varied from 2.29 to 3.4 nJ. Using an ultrahigh-numerical-aperture fiber to reduce the net dispersion to −1.033 ps2, the 3-dB bandwidth of the spectrum is broadened to 14.78 nm, and the duration of the autocorrelation spike is only 421 fs. The maximum single-pulse energy can increase up to 4.97 nJ. Due to dispersion management mechanism, the threshold and output power are also significantly improved.

The practicability of picosecond supercontinuum (SC) is greatly limited by the noise-seeded modulation instability (MI) in SC generation. In this letter, we experimentally demonstrate SC generation in picosecond regime with control of MI process. With partially coherent seeding involved in SC generation, the pulse-to-pulse fluctuation is greatly improved while the coherence of SC valued by interference fringes keep at a low level that similar with non-seeding SC. Taking these features into account, we believe that the SC with partially coherent seeding can be a suitable source for applications requiring high pulse stability with low coherence such as free space optical (FSO) communication and optical coherence tomography (OCT).

Hydrogen peroxide (H

In this paper, by using a computer algebra system, we prove that ternary Loop subdivision scheme can guarantee C 1 regularity at the extraordinary point of the subdivision surface based on the construction and analysis of its subdivision matrix and the characteristic maps. Besides, an interval is given for the sub-dominant eigenvalue of the subdivision matrix, which can guarantee that ternary Loop rules always generate C 1 subdivision surface. Finally, we propose a new edge rule. This can guarantee the C 1 regularity of the subdivision surface. And also comparing with Loop rules, this scheme has simpler form and faster convergence speed around the extraordinary point.

We report on the experimental generation of various self-organized structures of bound states in a near zero-dispersion mode-locked fiber laser. When the pump power is fixed at 492 mW, appropriately adjusting polarization controllers, the switching of the cavity feedback results in the evolution from the single pulse to the dispersion-managed soliton (i.e., stretched-pulse) pair. With the increase of pump power, bound states composed of more than two pulses can also be observed. Our results of the self-organized structures might enlarge the data-carrying capacity of current fiber-optical communication systems and benefit the investigation of nonlinear dynamics of bound states in fiber lasers at 2 μm.

In order to break through the laser communication technology of one point to multipoint, which is the difficult problems for laser communication. The networking solutions of the antenna structure of three concentric spheres are proposed. Being with the advantages of simple structure, small size and light weight, the antenna structure of three concentric spheres can be applied to short-distance space laser communication. The feasibility of the system can be realized from two aspects, the analysis of link and the analysis of the precision index. On this basis, the whole optical system can be determined by the corresponding optical system design. Under the condition of permitting of link energy, the optical system of antenna structure of three concentric spheres with mobile field azimuth angle of 120°and the pitching angle of 20°is completed. The parameters can meet the requirements in the subsystem of the communication receiving optical path, the communication transmitting optical path and the communication tracking optical system. The results indicate that the antenna structure of three concentric spheres can be applied to the laser communication networking under the short-distance space.

This paper proposes an auto-associative Neural Network pattern that has been utilized for sky-screen signal recognition. The AANN mode has been prepared in VC++ platform. Compared to the level signal recognition, the recognition rate can be increased by 3 % using auto-associative neural network with 30 mm caliber projectiles at a frequency of 7,500 rounds/min for 10 s duration in the sky-screen-repeating projectile test, the accuracy and reliability of the system was fully verified.

In this paper, According to measurements data from experiment of laser propagation along 0.9Km distance near ground path and 45m ground altitude, the received scintillation fluctuation data and spot size are recorded and analyzed without consider the scale of turbulence. Under the strong turbulence, the structure constant of refractive index Cn2 is computed using scintillation fluctuation and then using models of Cn2 to predict atmospheric coherence length r0 for horizontal paths, later the spot size was computed. Compared with measured data of spot size, there is a certain deviation with 200μm2 from each other under the conditions of r0 < 0.055m, but the time variation is similar, at last, various errors caused by both theory and experiment are analyzed and discussed.