Surpassing the limitation of a coherence length in lidar by digital coherence.

In this manuscript, we propose a digital coherent detection method to surpass the limitation of a coherent length on the detection range of a coherent lidar. This method rapidly reconstructs the laser phase noise utilizing the multi-channel delay self-homodyne and the generalized inverse of the system observation matrix. Subsequently, the reconstructed phase noise is utilized to expunge its perturbation onto the target information in the digital domain, thereby effectively surmounting the coherence length limitation. Through experimentation, the proposed method is verified to produce stable and high-quality interference even when the optical path difference between two beams exceeds 1000 times the coherence length. Additionally, the equivalent laser linewidth is compressed by 105 times.

Correction method for the influence of environmental factors on laser-induced breakdown spectroscopy.

Environmental factors include sample temperature, ambient gas composition, and pressure, which have a significant impact on the accuracy and stability of the analysis results of laser-induced breakdown spectroscopy (LIBS). In this study, a method for simultaneously correcting the influence of several environmental factors is proposed. When the calibration and application environment are different, only one sample is needed to be measured in the application environment to correct the influence of environmental factors, so that the calibration model can obtain good analytical accuracy in this environment. When using one to four samples to correct the influence of environmental factors, the application of the calibration models constructed under solid-state conditions at atmosphere pressure to analyze seven elements in molten alloys in vacuum demonstrated the average root mean square error of prediction (RMSEP) of 0.57%, 0.51%, 0.41%, and 0.30% respectively. The accuracy of using only one sample to correct the influence of environmental factors was much higher than using two samples to establish calibration models in the application environment. This proved the effectiveness of the developed method for reducing the difficulty and cost of calibration in the metallurgical processes.

Laser Beam Pointing Stabilization Control through Disturbance Classification.

In laser systems, beam pointing usually drifts as a consequence of various disturbances, e.g., inherent drift, airflow, transmission medium variation, mechanical vibration, and elastic deformation. In this paper, we develop a laser beam pointing control system with Fast Steering Mirrors (FSMs) and Position Sensitive Devices (PSDs), which is capable of stabilizing both the position and angle of a laser beam. Specifically, using the ABCD matrix, we analyze the kinematic model governing the relationship between the rotation angles of two FSMs and the four degree-of-freedom (DOF) beam vector. Then, we design a Jacobian matrix feedback controller, which can be conveniently calibrated. Since disturbances vary significantly in terms of inconsistent physical characteristics and temporal patterns, great challenges are imposed to control strategies. In order to improve beam pointing control performance under a variety of disturbances, we propose a data-driven disturbance classification method by using a Recurrent Neural Network (RNN). The trained RNN model can classify the disturbance type in real time, and the corresponding type can be subsequently used to select suitable control parameters. This approach can realize the universality of the beam stabilization pointing system under various disturbances. Experiments on beam pointing control under several typical external disturbances are carried out to verify the effectiveness of the proposed control system.

Light-emitting-diode-pumped active Q-switched Nd:YLF laser.

An active Q-switching light-emitting diode (LED)-pumped laser is demonstrated by Nd:YLF crystal with acousto-optic modulation for the first time. The spectrum-band pump characteristic is grasped to describe the essential difference between an LED pump and single-absorption-peak matching of laser-diode pump or no matching of lamp pump. An effective absorption spectrum concept is proposed to characterize the absorption features of the gain material with LED-band pumping. According to this new theory, a flat-top beam profile is designed for pumping Nd:YLF crystal with only a 14 W/cm2 peak power, resulting in 165 µJ output energy at 1047 nm. More importantly, by using the acousto-optic Q-switching technique, this LED-pumped Nd:YLF laser has successfully realized a TEM00 mode output with a pulse energy of 10.6 µJ and a pulse width of 452 ns.

Beam-pointing drift prediction in pulsed lasers by a probabilistic learning approach.

In laser systems, it is well known that beam pointing is shifted due to many un-modeled factors, such as vibrations from the hardware platform and air disturbance. In addition, beam-pointing shift also varies with laser sources as well as time, rendering the modeling of shifting errors difficult. While a few works have addressed the problem of predicting shift dynamics, several challenges still remain. Specifically, a generic approach that can be easily applied to different laser systems is highly desired. In contrast to physical modeling approaches, we aim to predict beam-pointing drift using a well-established probabilistic learning approach, i.e., the Gaussian mixture model. By exploiting sampled datapoints (collected from the laser system) comprising time and corresponding shifting errors, the joint distribution of time and shifting error can be estimated. Subsequently, Gaussian mixture regression is employed to predict the shifting error at any query time. The proposed learning scheme is verified in a pulsed laser system (1064 nm, Nd:YAG, 100 Hz), showing that the drift prediction approach achieves remarkable performances.

High-repetition-rate, high-pulse-energy, and high-beam-quality laser system using an ultraclean closed-type SBS-PCM.

We present a high-repetition-rate, high-pulse-energy, high-beam-quality, and high-average-power laser system using an ultraclean closed-type stimulated-Brillouin-scattering phase-conjugate mirror (SBS-PCM). By controlling microparticles of SBS-PCM down to 40 nm, thermal load capacity of such closed-type SBS-PCM was greatly improved, which presented the best reported cleanliness. The closed-type SBS-PCM, lacking scanning wedge plates, achieved reflectivity as high as 92% and showed no optical breakdown phenomena or obvious thermal effects at a 500 Hz pulse-repetition frequency (PRF). Operation at 550 W output power, approximately 1.1 J pulse energy, and beam quality M2 of approximately 2 represents, to our knowledge, the best reported performance. Thermal phase distortion was compensated, and the maximum-output-power pulse-width compression improved from 30 ns to approximately 10 ns.

Adaptive aberration correction of a 5 J/6.6 ns/200 Hz solid-state Nd:YAG laser.

In this Letter, we present an adaptive aberration correction system to simultaneously compensate for aberrations and reshaping the beams. A low-order aberration corrector is adapted. In this corrector, four lenses are mounted on a motorized rail, whose positions can be obtained using a ray tracing method based on the beam parameters detected by a wavefront sensor. After automatic correction, the PV value of the wavefront is reduced from 26.47 to 1.91 µm, and the beam quality ß is improved from 18.42 to 2.86 times that of the diffraction limit. After further correction with a deformable mirror, the PV value of the wavefront is less than 0.45 µm, and the beam quality is 1.64 times that of the diffraction limit. To the best of our knowledge, this is the highest performance from such a high-power, high-pulse repetition rate Nd:YAG solid-state laser ever built.

Dual-core antiresonant hollow core fibers.

In this work, dual-core antiresonant hollow core fibers (AR-HCFs) are numerically demonstrated, based on our knowledge, for the first time. Two fiber structures are proposed. One is a composite of two single-core nested nodeless AR-HCFs, exhibiting low confinement loss and a circular mode profile in each core. The other has a relatively simple structure, with a whole elliptical outer jacket, presenting a uniform and wide transmission band. The modal couplings of the dual-core AR-HCFs rely on a unique mechanism that transfers power through the air. The core separation and the gap between the two cores influence the modal coupling strength. With proper designs, both of the dual-core fibers can have low phase birefringence and short modal coupling lengths of several centimeters.

Highly efficient and aberration-free off-plane grating spectrometer and monochromator for EUV-soft X-ray applications.

We demonstrate a novel flat-field, dual-optic imaging EUV-soft X-ray spectrometer and monochromator that attains an unprecedented throughput efficiency exceeding 60% by design, along with a superb spectral resolution of λ/Δλ > 200 accomplished without employing variable line spacing gratings. Exploiting the benefits of the conical diffraction geometry, the optical system is globally optimized in multidimensional parameter space to guarantee optimal imaging performance over a broad spectral range while maintaining circular and elliptical polarization states at the first, second, and third diffraction orders. Moreover, our analysis indicates minimal temporal dispersion, with pulse broadening confined within 80 fs tail-to-tail and an FWHM value of 29 fs, which enables ultrafast spectroscopic and pump-probe studies with femtosecond accuracy. Furthermore, the spectrometer can be effortlessly transformed into a monochromator spanning the EUV-soft X-ray spectral region using a single grating with an aberration-free spatial profile. Such capability allows coherent diffractive imaging applications to be conducted with highly monochromatic light in a broad spectral range and extended to the soft X-ray region with minimal photon loss, thus facilitating state-of-the-art imaging of intricate nano- and bio-systems, with a significantly enhanced spatiotemporal resolution, down to the nanometer-femtosecond level.

Heterogeneous Fe-Co dual-atom catalyst outdistances the homogeneous counterpart for peroxymonosulfate-assisted water decontamination: New surface collision oxidation path and diatomic synergy.

Heterogeneous catalysts lag far behind their homogeneous counterparts in activating peroxymonosulfate (PMS) for water decontamination due to the low site intrinsic activity and sluggish mass transfer. The single-atom catalyst can bridge the gap between heterogeneous and homogeneous catalysts, but the difficulty to break scaling relations originating from the site monotony restricts further efficiency upgradation. Herein through modulating the crystallinity of NH2-UIO-66, a porous carbon support with ultrahigh surface area (1721.71 m2 g-1) is obtained to anchor the dual-atom FeCoN6 site, which exhibits superior turnover frequency over single-atom FeN4 and CoN4 sites (13.07 versus 9.97, 9.07 min-1). The as-synthesized composite thus outperforms the homogeneous catalytic system (Fe3++Co2+) for sulfamethoxazole (SMZ) degradation, and the catalyst-dose-normalized kinetic rate constant (99.26 L min-1 g-1) exceeds reported values by 1∼2 orders of magnitude. Moreover, only 20 mg of the catalyst can run a fluidized-bed reactor to realize continuous zero discharge of SMZ in multiple actual waters for up to 8.33 h. Unlike all reported reaction routes, the catalysis on the diatomic site follows a new surface collision oxidation path, i.e. the dispersed catalyst adsorbs PMS to generate surface-activated PMS with high potential, which collides with surrounding SMZ and directly seizes electron from it to induce pollutant oxidation. Theoretical calculation indicates that the enhanced activity of FeCoN6 site stems from the diatomic synergy, leading to stronger PMS adsorption, larger near-Fermi-level density of states and optimal global Gibbs free energy evolution. Overall, this work provides an effective strategy of constructing heterogeneous dual-atom catalyst/PMS process to achieve faster pollution control than homogeneous system, and sheds light on the interatomic synergetic mechanism for PMS activation.

High-average-power and high-beam-quality Innoslab picosecond laser amplifier.

We demonstrated a laser-diode, end-pumped picosecond amplifier. With effective shaping of the seed laser, we achieved 73 W amplified laser output at the pump power of 255 W, and the optical-optical efficiency was about 28%. The beam propagation factors M(2) measured at the output power of 60 W in the horizontal direction and the vertical direction were 1.5 and 1.4, respectively.

An efficient multi-path 3D convolutional neural network for false-positive reduction of pulmonary nodule detection.

PURPOSE: Considering that false-positive and true pulmonary nodules are highly similar in shapes and sizes between lung computed tomography scans, we develop and evaluate a false-positive nodules reduction method applied to the computer-aided diagnosis system. METHODS: To improve the pulmonary nodule diagnosis quality, a 3D convolutional neural networks (CNN) model is constructed to effectively extract spatial information of candidate nodule features through the hierarchical architecture. Furthermore, three paths corresponding to three receptive field sizes are adopted and concatenated in the network model, so that the feature information is fully extracted and fused to actively adapting to the changes in shapes, sizes, and contextual information between pulmonary nodules. In this way, the false-positive reduction is well implemented in pulmonary nodule detection. RESULTS: Multi-path 3D CNN is performed on LUNA16 dataset, which achieves an average competitive performance metric score of 0.881, and excellent sensitivity of 0.952 and 0.962 occurs to 4, 8 FP/Scans. CONCLUSION: By constructing a multi-path 3D CNN to fully extract candidate target features, it accurately identifies pulmonary nodules with different sizes, shapes, and background information. In addition, the proposed general framework is also suitable for similar 3D medical image classification tasks.

Effects of hypoxia on Achilles tendon repair using adipose tissue-derived mesenchymal stem cells seeded small intestinal submucosa.

BACKGROUND: The study was performed to evaluate the feasibility of utilizing small intestinal submucosa (SIS) scaffolds seeded with adipose-derived mesenchymal stem cells (ADMSCs) for engineered tendon repairing rat Achilles tendon defects and to compare the effects of preconditioning treatments (hypoxic vs. normoxic) on the tendon healing. METHODS: Fifty SD rats were randomized into five groups. Group A received sham operation (blank control). In other groups, the Achilles tendon was resected and filled with the original tendon (Group B, autograft), cell-free SIS (Group C), or SIS seeded with ADMSCs preconditioned under normoxic conditions (Group D) or hypoxic conditions (Group E). Samples were collected 4 weeks after operation and analyzed by histology, immunohistochemistry, and tensile testing. RESULTS: Histologically, compared with Groups C and D, Group E showed a significant improvement in extracellular matrix production and a higher compactness of collagen fibers. Group E also exhibited a significantly higher peak tensile load than Groups D and C. Additionally, Group D had a significantly higher peak load than Group C. Immunohistochemically, Group E exhibited a significantly higher percentage of MKX + cells than Group D. The proportion of ADMSCs simultaneously positive for both MKX and CM-Dil observed from Group E was also greater than that in Group D. CONCLUSIONS: In this animal model, the engineered tendon grafts created by seeding ADMSCs on SIS were superior to cell-free SIS. The hypoxic precondition further improved the expression of tendon-related genes in the seeded cells and increased the rupture load after grafting in the Achilles tendon defects.

Carbonate-enhanced catalytic activity and stability of Co3O4 nanowires for 1O2-driven bisphenol A degradation via peroxymonosulfate activation: Critical roles of electron and proton acceptors.

Transition-metal catalysts (TMCs) for peroxymonosulfate (PMS) activation suffer from low stability (i.e. severe metal leakage and poor reusability) when maintaining high activity in water decontamination. An innovative carbonate (CO32-)-mediated method to synchronously enhance the catalytic activity and stability of TMCs was developed herein. In a model PMS/Co3O4 nanowire system for bisphenol A (BPA) degradation, the first-order kinetic constant and total organic carbon removal ratio were increased by 202.27% and 71.32% upon adding CO32-, respectively. Meanwhile, the cobalt release amount was significantly reduced from 4.90 to 0.03 mg/L, and the number of reuse with high efficiency (>90% of BPA removal within 10 min) was augmented from 1 to 3 times. The CO32- buffered pH decline to repress metal leakage, and promoted Co(III) reduction into Co(II) to avoid the over-oxidation of catalyst. Under the driving of CO32-, the dominated reactive species were switched from •OH/SO4•- to 1O2 accompanying the migration of catalytic center from Co(II) to Co(III). The Co(III) and CO32-/OH- acted as electron and proton acceptors, respectively, to accelerate PMS decomposition into SO5•- and subsequent generation of vast 1O2. This work proposes a green way to construct novel 1O2-based catalytic systems with excellent activity and stability for pollution remediation.

A 33.2 W High Beam Quality Chirped-Pulse Amplification-Based Femtosecond Laser for Industrial Processing.

A photonic crystal fiber-based chirped pulse amplification delivering 272 fs pulses of 66.4 µJ energy at a repetition rate of 500 kHz is presented, resulting in an average/peak power of 33.2 W/244 MW. A single grating is adopted for the pulse width stretching and compression, which leads to high-compactness and low cost of the system. The output beam is near-diffraction-limited (M2 = 1.1 ± 0.05) with a power stability better than 0.5%. The cutting of alumina ceramic substrate and flexible printed circuit are demonstrated by using the laser system. The results indicate that the laser is competent for industrial applications.

CB1-Antibody Modified Liposomes for Targeted Modulation of Epileptiform Activities Synchronously Detected by Microelectrode Arrays.

Temporal lobe epilepsy (TLE) is a focal, recurrent, and refractory neurological disorder. Therefore, precisely targeted treatments for TLE are greatly needed. We designed anti-CB1 liposomes that can bind to CB1 receptors in the hippocampus to deliver photocaged compounds (ruthenium bipyridine triphenylphosphine γ-aminobutyric acid, RuBi-GABA) in the TLE rats. A 16-channel silicon microelectrode array (MEA) was implanted for simultaneously monitoring electrophysiological signals of neurons. The results showed that anti-CB1 liposomes were larger in size and remained in the hippocampus longer than unmodified liposomes. Following the blue light stimulation, the neural firing rates and the local field potentials of hippocampal neurons were significantly reduced. It is indicated that RuBi-GABA was enriched near hippocampal neurons due to anti-CB1 liposome delivery and photolyzed by optical stimulation, resulting dissociation of GABA to exert inhibitory actions. Furthermore, K-means cluster analysis revealed that the firing rates of interneurons were decreased to a greater extent than those of pyramidal neurons, which may have been a result of the uneven diffusion of RuBi-GABA due to liposomes binding to CB1. In this study, we developed a novel, targeted method to regulate neural electrophysiology in the hippocampus of the TLE rat using antibody-modified nanoliposomes, implantable MEA, and photocaged compounds. This method effectively suppressed hippocampal activities during seizure ictus with high spatiotemporal resolution, which is a crucial exploration of targeted therapy for epilepsy.

Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy.

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves several steps, include drawing samples, cooling, cutting, transport to the laboratory, and analysis. The whole analysis process requires more than 30 minutes, which hinders on-line process control. Laser-induced breakdown spectroscopy is an excellent on-line analysis method that can satisfy the requirements of vacuum induction melting because it is fast and noncontact and does not require sample preparation. The experimental facility uses a lamp-pumped Q-switched laser to ablate melted liquid steel with an output energy of 80 mJ, a frequency of 5 Hz, a FWHM pulse width of 20 ns, and a working wavelength of 1,064 nm. A multi-channel linear charge coupled device (CCD) spectrometer is used to measure the emission spectrum in real time, with a spectral range from 190 to 600 nm and a resolution of 0.06 nm at a wavelength of 200 nm. The protocol includes several steps: standard alloy sample preparation and an ingredient test, smelting of standard samples and determination of the laser breakdown spectrum, and construction of the elements concentration quantitative analysis curve of each element. To realize the concentration analysis of unknown samples, the spectrum of a sample also needs to be measured and disposed with the same process. The composition of all main elements in the melted alloy can be quantitatively analyzed with an internal standard method. The calibration curve shows that the limit of detection of most metal elements ranges from 20-250 ppm. The concentration of elements, such as Ti, Mo, Nb, V, and Cu, can be lower than 100 ppm, and the concentrations of Cr, Al, Co, Fe, Mn, C, and Si range from 100-200 ppm. The R2 of some calibration curves can exceed 0.94.

[Short-term effectiveness of bone cement combined with screws for repairing tibial plateau defect in total knee arthroplasty].

Objective: To summarize the effectiveness of bone cement combined with screws for repairing tibial plateau defect in total knee arthroplasty (TKA). Methods: Between March 2013 and March 2016, 30 patients were treated with TKA and bone cement combined with screws for repairing tibial plateau defect. Of the 30 patients, 8 were male and 22 were female, with an average age of 64.7 years (range, 55-71 years). And 17 cases were involved in left knees and 13 cases in right knees; 22 cases were osteoarthritis and 8 cases were rheumatoid arthritis. The disease duration ranged from 9 to 27 months (mean, 14 months). Knee Society Score (KSS) was 41.63±6.76. Hospital for Special Surgery Knee Score (HSS) was 38.10±7.00. The varus deformity of knee were involved in 19 cases and valgus deformity in 11 cases. According to the Rand classification criteria, tibial plateau defect were rated as type Ⅱb. Results: All incisions healed by first intention, without infection or deep vein thrombosis. All the patients were followed up 27.5 months on average (range, 10-42 months). At last follow-up, HSS score was 90.70±4.18 and KSS score was 93.20±3.75, showing significant differences when compared with preoperative values ( t=-58.014， P=0.000; t=-60.629， P=0.000). Conclusion: It is a simple and safe method to repair tibial plateau defect complicated with varus and valgus deformities with bone cement and srews in TKA.

Development of a new model for acute myocardial infarction in rabbits.

The rabbit left anterior descending coronary artery is not macroscopically apparent; this often leads to failure in creation of an acute myocardial infarction (AMI) model. In order to devise a simple method with good reproducibility and high success rate for use as a rabbit AMI model, a new surgical technique was developed, in which the obtuse marginal (OM) branch of the left circumflex coronary artery was coagulated with an electric knife using a left parasternal approach. Four weeks after OM branch coagulation, an electrocardiogram (ECG), blood biochemistry analysis, echocardiographic measurements and pathologic analysis were performed. The left parasternal approach provided the surgeon clear visualization of the targeted blood vessel to accurately identify the proper site to occlude. The successful development of AMI was confirmed by ST segment elevation on the ECG, by high levels of AMI-related markers in blood samples, by cardiac functional damage reflected on echocardiographic images and by changes in pathological sections. Furthermore, an acceptable success rate and low mortality were achieved. Hence, this surgical technique was suggested to be a highly reliable and reproducible method to induce AMI in rabbits for the assessment of new therapeutic interventions or regenerative approaches.

[HEMOSTASIS EFFECT OF COMPRESSION DRESSING THERAPY AFTER TOTAL HIP ARTHROPLASTY].

OBJECTIVE: To investigate the hemostasis effect of compression dressing therapy after total hip arthroplasty (THA). METHODS: Thirty-four patients undergding unilateral THA between December 2014 and March 2015 were randomly divided into observation group (compression dressing group, n = 17) and control group (ordinary dressing group, n = 17). There was no significant difference in gender, age, height, weight, lesion hips, pathogeny, disease duration, and preoperative hemoglobin between 2 groups (P > 0.05). The total blood loss theoretical value, the postoperative drainage volume, the visible blood loss, the hidden blood loss, the total blood transfusion volume, the number of patients receiving blood transfusion, and the related complications were compared between 2 groups. RESULTS: No significant difference was found in operation time and hospitalization time between 2 groups (t = 0.337, P = 0.738; t = 0.140, P = 0.889). The incisions healed by first intention in all patients. Six cases had incision subcutaneous hematoma in the control group, no incision subcutaneous hematoma occurred in the observation group (χ² = 7.286, P = 0.018). No postoperative complications of wound superficial infection and venous thrombosis occurred in 2 groups. After operation, blood transfusion was given in 1 case of observation group and 7 cases of control group, showing significant difference (χ² = 5.885, P = 0.039), and the total blood transfusion volume was 600 mL and 3 200 mL, respectively. There was no significant difference in preoperative blood volume and intraoperative blood loss between 2 groups (P>0.05), but the total blood loss theoretical value, the postoperative drainage volume, the visible blood loss, and the hidden blood loss in observation group were significantly less than those in control group (P < 0.05). CONCLUSION: The compression dressing should be performed after THA because it can effectively reduce postoperative blood loss and the incidence of wound hematoma.