Buildup and synchronization regimes of a vector pure-quartic soliton molecule in a fiber laser cavity.

Pure-quartic solitons (PQSs) have recently received increasing attention due to their energy-width scaling over the traditional soliton, which has expanded our understanding of soliton dynamics with high-order dispersion in nonlinear systems. Here, we numerically reveal the asynchronization and synchronization processes of the sub-pulse within the vector PQS molecule in a mode-locked fiber laser by solving the coupled Ginzburg-Landau equations. During the establishment of a vector PQS molecule, the repulsion, attraction, and finally stabilization processes have been observed. Specifically, sub-pulse disappearance, regeneration, and finally synchronization with the other pulses are also investigated. Our analysis of the pulse energy, time interval, and relative phase evolution dynamics with the round trip indicates that the asynchronization and synchronization within the vector PQS molecule associate tightly with the gain competition and the cross-phase modulation. Our findings provide insights into the internal mutual dynamics within the vector soliton molecule and offer guidance for the applications of PQS.

Versatile design for temporal shape control of high-power nanosecond pulsed fiber laser amplifier.

This research proposed a novel pulse-shaping design for directly shaping distorted pulses after the amplification. Based on the principle of the design we made a pulse shaper. With this pulse shaper, we successfully manipulate the pulse's leading edge and width to achieve an 'M'-shaped waveform in an amplification system. Comparative experiments were conducted within this system to compare the output with and without the integration of the pulse shaper. The results show a significant suppression of the nonlinear effect upon adding the pulse shaper. This flexible and effective pulse shaper can be easily integrated into a high-power all-fiber system, supplying the capability to realize the desired output waveform and enhance the spectral quality.

High repetition frequency tunability active Q-switched all-fiber laser by multi-gain sub-rings smoothing multipeak pulse and suppressing ASE self-saturation.

This paper provides a method to effectively suppress the severe ASE self-saturation when achieving high repetition frequency tunability with high output power and narrow pulse width in active Q-switched all-fiber lasers. By studying the regularity of the system's multi-stable state, we first ensured that the laser system operated in a steady state. Then output avoids uneven distribution of pulse energy or missing pulses due to period bifurcation state or chaos state. By adding multiple gain sub-rings within the cavity, the sub-ring structure itself indirectly mitigates the ASE self-saturation while smoothing the pulse. The method will avoid the severe power loss caused by traditional smoothing methods by adjusting the AOM rising edge time. It will also avoid lowering the ASE lasing threshold at high repetition frequency. Meanwhile, the intra-cavity backward ASE can be effectively absorbed by inserting the gain fiber in the sub-rings to directly mitigate the ASE self-saturation. The system's continuously adjustable repetition frequency can be as high as over 300 kHz. It ensures that output power above the watt level and a < 0.2 nm narrow bandwidth can be maintained while tuning the repetition frequency. The narrowest smoothing pulse width of 28 ns has been reached.

Association between Peritoneal Glucose Absorption, Lipid Metabolism, and Cardiovascular Disease Risk in Non-Diabetic Patients on Peritoneal Dialysis.

BACKGROUND: Excessive sugar intake increases the energy metabolic burden and the risk of cardiovascular disease (CVD). Patients on peritoneal dialysis (PD) absorb much more glucose than the World Health Organization recommends, but the link to CVD is unclear. OBJECTIVE: To identify the association between peritoneal glucose absorption, lipid metabolism, and CVD. METHODS: We applied generalized additive mixed-effects and mixed-effects Cox proportional hazard models to evaluate the impact of peritoneal glucose absorption on lipid profiles and CVD risk. We performed subgroup analyses by using protein intake (normalized protein nitrogen appearance [nPNA] and normalized protein catabolic rate [nPCR] were used to assess protein intake) and high-sensitivity C-reactive protein (hs-CRP). RESULTS: After multivariable adjustment, peritoneal glucose absorption per 10 g/d increase was associated with an increase in cholesterol of 0.145 (95% confidence interval [CI]: 0.086-0.204) mmol/L. No link with the total risk of CVD was observed; however, protein intake and hs-CRP levels affected the relationship between glucose absorption and CVD risk. Patients with values for nPNA and nPCR < 1.0 g/(kg∙d) were associated with a lower risk of CVD (hazard ratio [HR] 95% CI 0.68 (0.46-0.98)) with glucose absorption per 10 g/d increase. While patients with hs-CRP levels ≥ 3 mg/d or values for nPNA or nPCR ≥ 1.0 g/(kg∙d) were associated with a higher risk of CVD (HR 95% CI 1.32 (1.07-1.63); 1.31 (1.02-1.68)) for glucose absorption per 10 g/d increase. CONCLUSIONS: Our study found a positive correlation between peritoneal glucose absorption and lipid profiles. Increased glucose absorption was associated with a lower risk of CVD in lower protein intake patients, and a higher risk of CVD in higher hs-CRP or protein intake levels in patients on PD.

A Novel High-Precision Railway Obstacle Detection Algorithm Based on 3D LiDAR.

This article presents a high-precision obstacle detection algorithm using 3D mechanical LiDAR to meet railway safety requirements. To address the potential errors in the point cloud, we propose a calibration method based on projection and a novel rail extraction algorithm that effectively handles terrain variations and preserves the point cloud characteristics of the track area. We address the limitations of the traditional process involving fixed Euclidean thresholds by proposing a modulation function based on directional density variations to adjust the threshold dynamically. Finally, using PCA and local-ICP, we conduct feature analysis and classification of the clustered data to obtain the obstacle clusters. We conducted continuous experiments on the testing site, and the results showed that our system and algorithm achieved an STDR (stable detection rate) of over 95% for obstacles with a size of 15 cm × 15 cm × 15 cm in the range of ±25 m; at the same time, for obstacles of 10 cm × 10 cm × 10 cm, an STDR of over 80% was achieved within a range of ±20 m. This research provides a possible solution and approach for railway security via obstacle detection.

Cavity-birefringence-dependent vector pure-quartic soliton fiber laser.

Pure-quartic soliton (PQS) fiber lasers provide a promising avenue for exploring novel soliton interaction dynamics and generating high-energy pulses. Here, we present the numerical observation of vector PQSs generation and the evolution dynamics in a mode-locked fiber laser, using the coupled Ginzburg-Landau equations. We investigate the buildup dynamics of vector PQSs in a mode-locked laser with birefringent fibers, passing through three stages: energy amplification, energy pulsation owing to the cross-phase modulation (XPM) effect, and finally stabilization. Depending on the strength of the cavity-birefringence, the evolution of PQSs in non-polarization-maintaining fibers reveals that both the elliptical-polarization vector PQSs and near-linear-polarization vector PQSs can be formed by the energy conservation and balance between the two orthogonal directions. Additionally, we observe the transition process from vector PQSs to scalar PQSs with higher cavity-birefringence, resulting from the failure compensation of the walk-off via the soliton trapping effect between the two orthogonal components. These results provide valuable insights into the ultrafast transient process of vector solitons and enhance the understanding of PQS generation in fiber lasers.

Demonstration of a 700 W × 2 ports single-stage all-fiber nanosecond amplifier seeded by a multi-cavity passively Q-switched laser.

We demonstrate a single-stage all-fiber nanosecond amplifier with a total average power of greater than 1.4 kW by employing what we believe to be a novel multi-cavity passively Q-switched fiber laser as the seed laser. The multi-cavity seed laser adopts a piece of Yb-doped fiber (YDF) as saturable absorber (SA), and it includes two external cavities resonating at 1030 nm and an internal cavity working at 1064 nm, respectively. Using such a scheme, a stable dual-channel laser output with a total average power of >35 W, a pulse width of 45 ns, and an optical conversion efficiency of 72% operating at 1064 nm is achieved. By power scaling the multi-cavity seed laser, a dual-channel single-stage nanosecond amplifier is obtained with a single-port average power of exceeding 700 W and a pulse energy of about 7.3 mJ. To the best of our knowledge, this work is the highest average power and optical conversion efficiency for passively Q-switched all-fiber laser employing SA fiber, and the highest average power for a single-stage all-fiber nanosecond amplifier.

Controllable multi-stable-state operation in an AOM actively Q-switched all-fiber laser system.

This paper presents a comprehensive experimental study of multi-stable-state output characteristics in an all-fiber laser with an acoustic-optical modulator (AOM) as the Q-switcher. For the first time, in this structure, the partitioning of the pulsed output characteristics is explored, dividing the operating status of the laser system into four zones. The output characteristics, the application prospects, and the parameter setting rules for working in stable zones are presented. In the second stable zone, a peak power of 4.68 kW with 24 ns was obtained at 10 kHz. This is the narrowest pulse duration achieved with an AOM actively Q-switched all-fiber linear structure. The pulse narrowing is attributed to the rapid release of signal power and pulse tail truncated by AOM shutdown.

CRISPR-Cas13a-powered electrochemical biosensor for the detection of the L452R mutation in clinical samples of SARS-CoV-2 variants.

Since the end of 2019, a highly contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has deprived numerous lives worldwide, called COVID-19. Up to date, omicron is the latest variant of concern, and BA.5 is replacing the BA.2 variant to become the main subtype rampaging worldwide. These subtypes harbor an L452R mutation, which increases their transmissibility among vaccinated people. Current methods for identifying SARS-CoV-2 variants are mainly based on polymerase chain reaction (PCR) followed by gene sequencing, making time-consuming processes and expensive instrumentation indispensable. In this study, we developed a rapid and ultrasensitive electrochemical biosensor to achieve the goals of high sensitivity, the ability of distinguishing the variants, and the direct detection of RNAs from viruses simultaneously. We used electrodes made of MXene-AuNP (gold nanoparticle) composites for improved sensitivity and the CRISPR/Cas13a system for high specificity in detecting the single-base L452R mutation in RNAs and clinical samples. Our biosensor will be an excellent supplement to the RT-qPCR method enabling the early diagnosis and quick distinguishment of SARS-CoV-2 Omicron BA.5 and BA.2 variants and more potential variants that might arise in the future.

Sum-frequency generation of 133 mJ, 270 ps laser pulses at 266†nm in LBO crystals.

We demonstrate the generation of high-energy (133 mJ) and sub-nanosecond (∼270 ps) deep ultraviolet (DUV) pulses at 266 nm by sum-frequency mixing in LiB3O5 (LBO) crystals. The highest 133 mJ pulse energy ever reported corresponds to a peak power of 0.49 GW and an energy conversion efficiency of 13.3% from the infrared at 1064 nm to DUV at 266 nm. This is the highest output energy ever reported for the DUV sub-nanosecond pulses to the best of our knowledge. Higher energy efficiency of 25.7% can be achieved from 1064 nm to 266 nm when the fundamental energy was reduced to 346 mJ. Furthermore, the DUV generations using LBO and typical ß-BaB2O4 (BBO) crystals were compared regarding the energy efficiency, and the effects of the nonlinear absorption are discussed.

Inulin-type prebiotics reduce serum uric acid levels via gut microbiota modulation: a randomized, controlled crossover trial in peritoneal dialysis patients.

PURPOSE: Increased levels of uric acid (UA), which is mainly excreted through the kidneys, are independently associated with higher mortality in end-stage renal disease (ESRD) patients. The uricolysis of gut microbiota plays an important role in extrarenal excretion of UA. This study aimed to examine the effect of inulin-type prebiotics (a type of fermentable dietary fiber) on intestinal microbiota modulation and serum UA levels in ESRD patients. METHODS: Continuous ambulatory peritoneal dialysis (CAPD) patients were recruited to a randomized, double-blind, placebo-controlled crossover trial of 12-week inulin-type prebiotics. Participants were visited before and after treatment with prebiotics or placebo. Serum UA levels, dietary purine intake, serum xanthine oxidase (XO) activity, daily "renal excretion" of UA, and fecal UA degradation capability were measured at each visit. Fecal metagenomic analysis was conducted to assess microbial composition and function. RESULTS: Sixteen participants (mean age = 37 y; 10 men and 6 women) completed the trial, and 64 specimens were analyzed. The average concentration of serum UA decreased by approximately 10% in the prebiotic intervention group in comparison to the placebo group (p = 0.047) without an increase in daily "renal excretion" of UA via urine and dialysate. There were no significant changes in purine intake or activity of XO. Notably, enhanced fecal UA degradation was observed after prebiotic intervention (p = 0.041), and the ratio of Firmicutes/Bacteroidetes, which was positively associated with fecal UA degradation, increased in the prebiotic period (p = 0.032). Furthermore, prebiotics enriched purine-degrading species in the gut microbiota, including unclassified_o_Clostridiales, Clostridium sp. CAG:7, Clostridium sp. FS41, Clostridium citroniae, Anaerostipes caccae, and Clostridium botulinum. CONCLUSIONS: Inulin-type prebiotics is a promising therapeutic candidate to reduce serum UA levels in renal failure patients, and this urate-lowering effect could possibly be attributed to intestinal microbial degradation of UA. TRIAL REGISTRY: This study was registered at the Chinese Clinical Trials Registry ( http://www.chictr.org.cn/ ), registration ID: ChiCTR-INR-17013739, registration date: 6th Dec 2017.

The Accumulation of Gut Microbiome-derived Indoxyl Sulfate and P-Cresyl Sulfate in Patients With End-stage Renal Disease.

OBJECTIVES: Indoxyl sulfate (IS) and p-cresyl sulfate (pCS) are two important gut microbiota-generated protein-bound uremic toxins. The present study aims to explore the alterations of serum IS and pCS concentrations, their production, and daily removal in end-stage renal disease (ESRD). METHODS: A case-controlled study was conducted based on 11 patients with ESRD and 11 healthy volunteers. The metabolic processes for IS and pCS were compared in these two groups, including gut microbiome, fecal indole and p-cresol, indole-producing bacteria and p-cresol-producing bacteria, serum total IS and pCS concentrations, and their daily removal by urine and spent dialyzate. RESULTS: Compared with healthy controls, patients with ESRD exhibited higher relative abundance of the indole-producing bacteria Escherichia coli (P < .001) and Bacteroides fragilis (P = .010) and p-cresol-producing bacteria Bacteroides fragilis (P = .010) and Bacteroides caccae (P = .047). The predicted functional profiles of gut microbiome based on 16S rRNA gene PhyloChip analysis showed that the microbial tryptophan metabolism pathway (map00380, P = .0006) was significantly enriched in patients with ESRD. However, the fecal precursors indole (P = .332) and p-cresol concentrations (P = .699) were comparable between the two groups. The serum IS (P < .001) and pCS (P < .001) concentrations were far higher in patients with ESRD than those in healthy controls, whereas the daily total removal by urine and dialyzate was much lower for the former than that for the latter (P = .019 for IS, P = .016 for pCS). CONCLUSIONS: The present study showed serious IS and pCS accumulation in patients with ESRD, with significant expansion of indole-producing bacteria and p-cresol-producing bacteria, upregulation of the bacterial tryptophan metabolism pathway, and greatly increased serum IS and pCS concentrations, whereas significant decline of daily IS and pCS removal.

Increased risk of modality failure with higher serum uric acid level in continuous ambulatory peritoneal dialysis patients: a prospective cohort study.

BACKGROUND: Peritoneal dialysis (PD) is one of the most important kidney replacement therapies for patients with end-stage kidney disease (ESKD). PD technique failure can lead to an escalated cost and increased infectious and cardiovascular risk, up and including to death. The accumulation of uric acid (UA) was associated with adverse outcomes in ESKD patients. However, the relationship between serum UA and technique failure is little explored. METHODS: Here, a total of 266 continuous ambulatory peritoneal dialysis (CAPD) patients (age, 41.8 ± 12.6 years; 125 males) were enrolled and followed up for 31.7 months. Serum UA levels were examined at baseline and each visit. Subjects were divided into three groups according to their baseline serum UA concentrations. Multivariable Cox regression models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) of PD technique failure. RESULTS: The level of serum UA increased gradually as time prolonged. During the follow-up period, 77 (28.9%) patients occurred PD technique failure, of which 56 (21.1%) transferred to hemodialysis (HD) and 21 (7.9%) died. Compared to the lowest UA tertile, after adjusting for potential confounders, HRs of technique failure in tertile 2 and tertile 3 were 1.82 (95% CI: 0.95-3.49) and 2.03 (95% CI: 1.05-3.92), respectively, and p for trend was 0.043. Adjusted HRs of all-cause technique failure, transferring to HD and mortality with each 1 mg/dL increase in serum UA were 1.20 (95% CI: 1.03-1.40, p = 0.019), 1.22 (95% CI: 1.01-1.48, p = 0.039), and 1.25 (95% CI: 0.94-1.67, p = 0.128), respectively. CONCLUSION: Higher serum UA level predicted higher risk of technique failure in CAPD patients.

The Association of Feeding Practices and Sociodemographic Factors on Underweight and Wasting in Children in Ethiopia: A Secondary Analysis of Four Health Surveys from 2000 to 2016.

BACKGROUND: Feeding practices highly influence the nutritional status of children between 6 and 23 months of age in developing countries, including Ethiopia. Therefore, this study was conducted to investigate the association of feeding practices and sociodemographic factors on underweight and wasting of children aged 6-23 months in Ethiopia. METHODS: Data on 8003 children 6-23 months of age from four Ethiopia demographic and health surveys (EDHS) from 2000 to 2016 were analyzed using complex sample crosstabs for multivariate analysis. The association of feeding practices and sociodemographic factors on underweight and wasting was assessed via multiple logistic regression analyses adjusting the covariates. The outcomes were reported based on the adjusted odds ratios (ORs) with 95% confidence interval (CI). RESULTS: Male children, very small at birth size children, diarrhea and fever, and short stature mother were risk factors for underweight and wasting (p < 0.05-0.001). Also, minimum dietary diversity, rich and middle-income families, vitamin A in the previous 6 months and antenatal care visits during pregnancy were protective factors for both underweight and wasting (p < 0.05-0.001). Minimum meal frequency was significantly related to lower odds of wasting (p < 0.001). Higher age of the child was significantly associated with underweight (p < 0.05-0.001); however, it was less likely wasted (p < 0.05-0.01). CONCLUSION: The present study depicted that among infant young children feeding core indicators except breastfed, all the other indicators did not met the required standard; however, sociodemographic factors on four health surveys from 2000 to 2016 were associated with underweight and wasting in children in Ethiopia. LAY SUMMARY: • Over the years the prevalence of underweight in children aged 6-23 months in the country has shown a significant improvement from 40.2% in 2000 to 34.7% in 2005, then further reduced to 28.9% and 20.0% in 2011 and 2016 EDHS, respectively.• In the same manner, the prevalence of wasting in children aged 6-23 months in Ethiopia also observed improvement from 18.9% in 2000 to 16.7% in 2005, then further reduced to 15.4% and 13.9% in 2011 and 2016 EDHS, respectively.• Male children, very small at birth size children, diarrhea and fever (for the last 2 weeks), and short stature mother were risk factors for underweight and wasting.• Minimum dietary diversity, rich and middle-income families, vitamin A in the previous 6 months and antenatal care visits during pregnancy were protective factors for both underweight and wasting.• Minimum meal frequency was significantly related to lower odds of wasting.• Higher age of the children was significantly associated with underweight; however, less likely wasted.

Design of a 10 kW level diode laser optical stack with a line shape beam spot.

We designed and simulated a diode laser with output power of more than 10 kW and a line shape beam spot of approximately ${14 - 58}\;{\rm mm} \times {1.6}\;{\rm mm}$14-58mm×1.6mm (${{\rm 1/e}^2}$1/e2 width). The diode laser was assembled with high fill factor diode laser bars that can be cooled with filtered tap water. The diode laser bar was beam shaped with a tilted cylindrical lens array to twist the slow axis of individual emitters by 90 deg, and then the slow axis was collimated with a single cylindrical lens. From the simulation, 20 laser diode bars with the same wavelength formed a diode laser optical stack with an output power of more than 3.5 kW, a beam spot of ${31}\;{\rm mm} \times {12}\;{\rm mm}$31mm×12mm size, and full divergence angles of around 6 mrad in both the horizontal and vertical directions. Then, three laser diode optical stacks with different wavelengths were wavelength-multiplexed to obtain an output power of more than 10 kW. Finally, the diode laser optical stack was transformed by simple cylindrical lenses to form a line shape spot with a working distance longer than 250 mm. Our diode laser design is much simpler than previous devices with similar output power and can find various applications such as high-speed laser cladding.

Narrow-bandwidth actively Q-switched all-fiber laser by suppressing ASE gain self-saturation.

This paper proposes and demonstrates a novel method to produce the narrow-bandwidth, narrow-pulse-width and high-repetition-rate pulses with actively Q-switched ring-cavity all-fiber lasers. By using a specially designed low-reflectivity cladding power stripper in the cavity, and inserting a length-optimized ytterbium-doped single-cladding fiber self-pumped by the backward amplified spontaneous emission (ASE) from the YDF to improve the amplification of the initial weak ASE feedback by the narrowband filter, the ASE gain self-saturation can be suppressed efficiently, and the lasing pulses can be established quickly within the opening time of Q-switch even operating for very high repetition-rate. With the proposed technique, watt-level Q-switched pulses with bandwidth and pulse width narrowed to 0.15 nm and 9 ns, and repetition rate up to 175 kHz are achieved.

Reducing the pulse repetition rate of picosecond dissipative soliton passively mode-locked fiber laser.

This paper proposes and demonstrates a method to reduce the repetition rate of all- polarization-maintaining (PM) linear-cavity picosecond dissipative soliton passively mode-locked fiber lasers. An optical coupler (OC) is inserted into the cavity to extract pulse energy, and the cavity length is increased using a low-nonlinear coefficient large-mode field fiber at the rear end of the OC, where the propagated pulse has lower energy. This enables the nonlinear phase shift to be within the tolerated value of the single pulse mode-locking even with a considerably increased cavity length; this allows reducing the laser repetition rate considerably without substantially changing the pulse characteristics. Using the proposed method, for a 0.3-nm filter bandwidth, the laser repetition rate is successfully reduced to 1.77 MHz with a nearly Fourier-transform limited pulse duration of 10 ps; it can be further reduced by optimizing the OC split ratio. The proposed method can be applied to reduce the repetition rate for a picosecond dissipative soliton passively mode-locked fiber laser with an arbitrary bandwidth filter.

Passive coherent beam combination of three Nd:YAG lasers using cascaded Michelson-type compound cavities.

A coaxial multibeam passive coherent combination of lasers with improved beam quality is proposed and verified using cascaded Michelson-type cavities, in which 4f optical systems are used to compensate for the beam waist separation between the combined adjacent lasers. A proof-of-concept experiment shows that three 65 W Nd:YAG lasers with an M2 factor of about 5.5 were coherently combined into a 124.4 W single-lobed output improving the M2 factor to 1.36. The central lobe accounted for 76% of the total power, corresponding to a total combined efficiency of 66.7%.

12-W continuous-wave green output from a 200-µm fiber-coupled diode laser based on TO-Can packaged emitters.

A 12-W green laser diode module with fiber-coupled output is developed. The high-power fiber-coupled output of a green diode laser is realized by using the technologies of beam collimation, spatial beam combining, beam shaping, and fiber coupling based on TO-Can packaged emitters. According to the optical fiber parameters, the detailed beam combination method is described and the maximum quantity of a single emitter in beam combination is calculated theoretically. In the experiment, as many as 16 green laser diode emitters with output power of 1 W each were combined and coupled into a fiber with core diameter of 200 µm and a numerical aperture of 0.22. A total of 12.2 W continuous-wave output at the wavelength of 520 nm was achieved with a coupling efficiency of 86.5% and an electro-optical efficiency of 10.6%.

Beam shaping for kilowatt fiber-coupled diode lasers by using one-step beam cutting-rotating of prisms.

The beam quality mismatch of laser diode stacks in both axes limits many direct applications for fiber or solid laser pumping and material processing. In this paper, a one-step cutting-rotating beam shaping system has been designed to homogenize the beam quality of two polarization-multiplexing laser diode stacks. Coupling laser diode stacks consisting of eight bars into a standard fiber with a core diameter of 600 µm and an NA of 0.22 is achieved. The simulative result shows that the system will have an output power over 1056 W. By using the technique, the production of compact and high brightness fiber-coupling diode lasers can be directly used for laser cladding and laser surface hardening processes.