Serous surface papillary borderline ovarian tumors: correlation of sonographic features with clinic pathological findings

Serous surface papillary borderline ovarian tumor (SSPBOT) is a distinct subtype of serous borderline ovarian tumor characterized by solid tissue deposition confined to the ovarian surface. Because SSPBOT is rare, there are few published reports on the ultrasonographic features of this condition. In this retrospective study, we investigated 12 cases of SSPBOT. Ultrasound imaging of SSPBOT showed grossly normal ovaries that were encased partially or wholly by tumor deposits that were confined to the surface, with clear demarcation between normal ovarian tissue and surrounding tumors. Color Doppler imaging demonstrated the 'fireworks sign' in all cases of SSPBOT, corresponding to an intratumoral vascular bundle originating from the ovarian vessels and supplying hierarchical branching blood flow to the surrounding tumor. No patient with ovarian high-grade serous carcinoma showed these morphological and Doppler features. In our series, the fireworks sign appeared to be a characteristic feature of SSPBOT that could facilitate correct identification of this tumor. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Ultrafast laser state active controlling based on anisotropic quasi-1D material

Laser state active controlling is challenging under the influence of inherent loss and other nonlinear effects in ultrafast systems. Seeking an extension of degree of freedom in optical devices based on low-dimensional materials may be a way forward. Herein, the anisotropic quasi-one-dimensional layered material Ta2PdS6 was utilized as a saturable absorber to modulate the nonlinear parameters effectively in an ultrafast system by polarization-dependent absorption. The polarization-sensitive nonlinear optical response facilitates the Ta2PdS6-based mode-lock laser to sustain two types of laser states, i.e., conventional soliton and noise-like pulse. The laser state was switchable in the single fiber laser with a mechanism revealed by numerical simulation. Digital coding was further demonstrated in this platform by employing the laser as a codable light source. This work proposed an approach for ultrafast laser state active controlling with low-dimensional material, which offers a new avenue for constructing tunable on-fiber devices.

Phosphorus-doped fiber for flat octave spanning supercontinuum generation

In a fiber supercontinuum (SC) source, the Raman scattering effect plays a significant role in extending the spectrum into a longer wavelength. Here, by using a phosphorus-doped fiber with a broad Raman gain spectrum as the nonlinear medium, we demonstrate flat SC generation spanning from 850 to 2150 nm. Within the wavelength range of 1.1-2.0 µm, the spectral power density fluctuation is less than 7 dB. Compared to a similar SC source based on a germanium-doped fiber with narrower Raman gain spectrum, the wavelength span is 300 nm broader, and the spectral power density fluctuation is 5 dB lower. This work demonstrates the phosphorus-doped fiber's great advantage in spectrally flat SC generation, which is of great significance in many applications such as optical coherence tomography, absorption spectroscopy, and telecommunication.

Influence of wavelength, linewidth, and temperature on second harmonic generation of a superfluorescent fiber source

Low-coherence tunable visible light sources have a wide range of applications in imaging, spectroscopy, medicine, and so on. Second harmonic generation (SHG) based on a superfluorescent fiber source (SFS) can produce high-brightness visible light while retaining most of the characteristics of superfluorescent sources, such as low coherence, low intensity noise and flexible tunability. However, due to the limitations in phase matching conditions, SHG based on SFS is difficult to reach an equilibrium between high efficiency and robustness of phase matching to temperature variation. In this paper, based on a spectral tunable SFS, we provide a comprehensive analysis, both experimental and theoretical, of the impact of wavelength, linewidth, and temperature on the output performance of SHG. Our findings indicate that broader linewidths adversely affect conversion efficiency, yet they enhance the capacity to withstand temperature variations and central wavelength detuning, which is an advantage that traditional SHG methods do not possess. This work may pave the way for utilizing low-coherence visible light in domains and extreme environments where robust output stability becomes imperative.

High power tunable Raman fiber laser at 1.2 μm waveband

Development of a high power fiber laser at special waveband, which is difficult to achieve by conventional rare-earth-doped fibers, is a significant challenge. One of the most common methods for achieving lasing at special wavelength is Raman conversion. Phosphorus-doped fiber (PDF), due to the phosphorus-related large frequency shift Raman peak at 40 THz, is a great choice for large frequency shift Raman conversion. Here, by adopting 150 m large mode area triple-clad PDF as Raman gain medium, and a novel wavelength-selective feedback mechanism to suppress the silica-related Raman emission, we build a high power cladding-pumped Raman fiber laser at 1.2 μm waveband. A Raman signal with power up to 735.8 W at 1252.7 nm is obtained. To the best of our knowledge, this is the highest output power ever reported for fiber lasers at 1.2 μm waveband. Moreover, by tuning the wavelength of the pump source, a tunable Raman output of more than 450 W over a wavelength range of 1240.6-1252.7 nm is demonstrated. This work proves PDF's advantage in high power large frequency shift Raman conversion with a cladding pump scheme, thus providing a good solution for a high power laser source at special waveband.

Monolithic tapered Yb-doped fiber chirped pulse amplifier delivering 126 μJ and 207 MW femtosecond laser with near diffraction-limited beam quality

In this work, a high-energy and high peak power chirped pulse amplification system with near diffraction-limited beam quality based on tapered confined-doped fiber (TCF) is experimentally demonstrated. The TCF has a core numerical aperture of 0.07 with core/cladding diameter of 35/250 µm at the thin end and 56/400 μm at the thick end. With a backward-pumping configuration, a maximum single pulse energy of 177.9 μJ at a repetition rate of 504 kHz is realized, corresponding to an average power of 89.7 W. Through partially compensating for the accumulated nonlinear phase during the amplification process via adjusting the high order dispersion of the stretching chirped fiber Bragg grating, the duration of the amplified pulse is compressed to 401 fs with a pulse energy of 126.3 μJ and a peak power of 207 MW, which to the best of our knowledge represents the highest peak power ever reported from a monolithic ultrafast fiber laser. At the highest energy, the polarization extinction ratio and the M2 factor were respectively measured to be ~ 19 dB and 1.20. In addition, the corresponding intensity noise properties as well as the short- and long-term stability were also examined, verifying a stable operation of the system. It is believed that the demonstrated laser source could find important applications in, for example, advanced manufacturing and photomedicine.

Broadband tunable Raman fiber laser with monochromatic pump

Raman fiber laser (RFL) has been widely adopted in astronomy, optical sensing, imaging, and communication due to its unique advantages of flexible wavelength and broadband gain spectrum. Conventional RFLs are generally based on silica fiber. Here, we demonstrate that the phosphosilicate fiber has a broader Raman gain spectrum as compared to the common silica fiber, making it a better choice for broadband Raman conversion. By using the phosphosilicate fiber as gain medium, we propose and build a tunable RFL, and compare its operation bandwidth with a silica fiber-based RFL. The silica fiber-based RFL can operate within the Raman shift range of 4.9 THz (9.8-14.7 THz), whereas in the phosphosilicate fiber-based RFL, efficient lasing is achieved over the Raman shift range of 13.7 THz (3.5-17.2 THz). The operation bandwidths of the two RFLs are also calculated theoretically. The simulation results agree well with experimental data, where the operation bandwidth of the phosphosilicate fiber-based RFL is more than twice of that of the silica fiber-based RFL. This work reveals the phosphosilicate fiber's unique advantage in broadband Raman conversion, which has great potential in increasing the reach and capacity of optical communication systems.

Mitigation of TMI in an 8 kW tandem pumped fiber amplifier enabled by inter-mode gain competition mechanism through bending control

In this work, the impact of fiber bending and mode content on transverse mode instability (TMI) is investigated. Based on a modified stimulated thermal Rayleigh scattering (STRS) model considering the gain competition between transverse modes, we theoretically detailed the TMI threshold under various mode content and bending conditions in few-mode fibers. Our theoretical calculations demonstrate that larger bending diameters increase the high order mode (HOM) components in the amplifier, which in turn reduces the frequency-shifted Stokes LP_11o mode due to the inter-mode gain competition mechanism, thus improving the TMI threshold of few-mode amplifiers. The experimental results agree with the simulation. Finally, by optimizing the bending, an 8.38 kW output tandem pumped fiber amplifier is obtained with a beam quality M² of 1.8. Both TMI and stimulated Raman scattering (SRS) are well suppressed at the maximum power. This work provides a comprehensive analysis of the TMI in few-mode amplifiers and offers a practical method to realize high-power high-brightness fiber lasers.

Analytical study on the steady-state thermal blooming effect of high-power ytterbium-doped fiber lasers propagating through the atmosphere

Thermal blooming effect is one of the significant factors affecting the propagation performance of high-power ytterbium-doped fiber lasers (YDFLs) in the atmosphere. In this paper, two 20 kW YDFL systems with typical wavelengths (1070 nm and 1080 nm) are fabricated for propagation comparison experiments, which are used to investigate the thermal blooming effect induced by high-power YDFL propagation through the atmosphere. Under approximately the same laser system parameters (except wavelength) and atmospheric environment, the 1070 nm laser has better propagation characteristics than the 1080 nm laser. Due to the combined effect between the different central wavelengths of the two fiber lasers and the spectral broadening caused by output power scaling, the thermal blooming caused by the different absorptivity of water vapor molecules to the two fiber lasers is the main factor for the variation of the propagation properties. Through theoretical analysis and numerical calculation of factors affecting the thermal blooming effect, and considering the industrial manufacturing difficulty of YDFLs, a reasonable selection of fiber laser parameters can effectively improve atmospheric propagation performance and reduce manufacturing costs.

More than 6 kW near single-mode fiber amplifier based on a bidirectional tandem pumping scheme

We demonstrate the first all-fiber monolithic bidirectional tandem pumping amplifier, to the best of our knowledge, based on a 30/250 µm conventional ytterbium-doped double-clad fiber. By optimizing the bidirectional pumping power distribution, an output power of 6.22 kW is obtained with near single-mode beam quality (M²=1.53), and no transverse mode instability is observed. This work could provide an excellent reference for high-power, higher-brightness fiber lasers.

M2 factor estimation in few-mode fibers based on a shallow neural network

A high-accuracy, high-speed, and low-cost M² factor estimation method for few-mode fibers based on a shallow neural network is presented in this work. Benefiting from the dimensionality reduction technique, which transforms the two-dimension near-field image into a one-dimension vector, a neural network with only two hidden layers can estimate the M² factor directly. In the simulation, the mean estimation error is smaller than 3% even when the mode number increases to 10. The estimation time of 10000 simulation test samples is around 0.16s, which indicates a high potential for real-time applications. The experiment results of 50 samples from the 3-mode fiber have a mean estimation error of 0.86%. The strategies involved in this method can be easily extended to other applications related to laser characterization.

Bidirectional tandem-pumped high-brightness 6 kW level narrow-linewidth confined-doped fiber amplifier exploiting the side-coupled technique

In this work, a bidirectional tandem-pumped high-power narrow-linewidth confined-doped ytterbium fiber amplifier is demonstrated based on side-coupled combiners. Benefiting from the large-mode-area design of the confined-doped fiber, the nonlinear effects, including stimulated Raman (SRS) and stimulated Brillouin scattering (SBS), are effectively suppressed. While the transverse mode instability (TMI) effect is also mitigated through the combination of confined-doped fiber design and the bidirectional tandem pumping scheme. As a result, narrow-linewidth fiber laser with 5.96 kW output power is obtained, the slope efficiency and the 3-dB linewidth of which are ∼81.7% and 0.42 nm, respectively. The beam quality is well maintained during the power scaling process, being around M²= 1.6 before the TMI occurs, and is well kept (M²= 2.0 at 5.96 kW) even after the onset of TMI. No SRS or SBS is observed at the maximum output power, and the signal-to-noise ratio reaches as high as ∼61.4 dB. To the best of our knowledge, this is the record power ever reported in narrow-linewidth fiber lasers. This work could provide a good reference for realizing high-power high-brightness narrow-linewidth fiber lasers.

Comprehensive investigations on the tandem pumping scheme employing the pump fiber laser operating at an extremely short wavelength

In this work, with the aim of improving the nonlinearity threshold in tandem-pumped fiber amplifiers for higher output power, theoretical and experimental work was carried out to enhance the pump absorption and thereby decrease the required length of ytterbium-doped fiber by employing shorter-wavelength fiber lasers as the pump sources. Systematical simulations were first carried out to optimize the cavity parameters of a short-wavelength fiber oscillator at 1007 nm, and subsequently, the performance of the 1007 nm fiber laser in tandem pumping was simulated and compared with that of the 1018 nm fiber laser pumped results. Considerable absorption increment and efficiency improvement could be realized in the 1007 nm fiber laser pumped fiber amplifier relative to the 1018 nm fiber laser pumped one. Furthermore, according to the simulation results, a fiber laser operating at 1007.7 nm with the output power of ∼170 W and a slope efficiency of ∼72.90% was experimentally demonstrated. By applying this fiber laser in tandem pumping a 1080 nm fiber amplifier with different gain fiber lengths, improved performance was acquired in comparison with the 1018.6 nm tandem pumping scheme, the experimental results of which were coherent with the simulation results. This work could provide an effective approach for improving the nonlinearity threshold of tandem-pumped fiber amplifiers and paving the way for higher output power.

High-power tandem-pumped fiber amplifier with beam quality maintenance enabled by the confined-doped fiber

The high absorption confined-doped ytterbium fiber with 40/250 μm core/inner-cladding diameter is proposed and fabricated, where the relative doping ratio of 0.75 is selected according to the simulation analysis. By employing this fiber in a tandem-pumped fiber amplifier, an output power of 6.2 kW with an optical-to-optical efficiency of ∼82.22% is realized. Benefiting from the large-mode-area confined-doped fiber design, the beam quality of the output laser is well maintained during the power scaling process with the beam quality factor of ∼1.7 of the seed laser to ∼ 1.89 at the output power of 5.07 kW, and the signal-to-noise ratio of the output spectrum reaches ∼40 dB under the maximum output power. In the fiber amplifier based on the 40/250 μm fully-doped ytterbium fiber, the beam quality factor constantly degrades with the increasing output power, reaching 2.56 at 2.45 kW. Moreover, the transverse mode instability threshold of the confined-doped fiber amplifier is ∼4.74 kW, which is improved by ∼170% compared with its fully-doped fiber amplifier counterpart.

Seeing the beam cleanup effect in a high-power graded-index-fiber Raman amplifier based on mode decomposition

Due to the beam cleanup effect, brightness enhancement (BE) can be achieved in a Raman fiber amplifier (RFA) based on multimode (MM) graded-index (GRIN) fiber. In this Letter, a novel, to the best of our knowledge, diagnostic tool of mode decomposition (MD) based on a stochastic parallel gradient descent algorithm is demonstrated to observe the beam cleanup effect in a GRIN-fiber-based RFA for the first time, to our knowledge. During output power boosting up to 405 W at 1130 nm, the output beam quality factor M² improves from 3.45 to 2.88, with a BE factor of 10.5. The MD results based on the near-field beam profiles from RFA indicate that the modal weight of the fundamental mode increases from 74.5% to 87%, confirming that the fundamental mode dominates with higher Raman gain. Moreover, the beam quality is found to be limited by the existence of a higher-order (Laguerre-Gaussian) LG₁₀ mode, which is insensitive to the beam cleanup effect. The correlation coefficient reaches over 0.98 for all MD results. Thus, the accuracy of the MD method is high enough to provide further valuable insight into the physics of spatiotemporal beam dynamics in MM GRIN fiber.

Kilowatt level Raman amplifier based on 100 µm core diameter multimode GRIN fiber with M2 = 1.6

In this Letter, we demonstrate a high-power Raman fiber amplifier with excellent beam quality based on graded-index fiber. The Yb-doped fiber laser (YDFL) and bandwidth-tunable amplified spontaneous emission (ASE) source are employed as the pump source to compare the laser performance separately. When the ASE with a bandwidth of 8 nm is employed, a maximum power of 943 W at 1130 nm is achieved, which is twice that pumped by YDFL. The beam quality factor M² at maximum output power is 1.6, with a brightness enhancement (BE) factor of 27. To the best of our knowledge, this is the best beam quality and BE factor based on pure Raman gain with output power of over 100 W.

Over 400 W graded-index fiber Raman laser with brightness enhancement

The power scaling on all-fiberized Raman fiber oscillator with brightness enhancement (BE) based on multimode graded-index (GRIN) fiber is demonstrated. Thanks to beam cleanup of GRIN fiber itself and single-mode selection properties of the fiber Bragg gratings inscribed in the center of GRIN fiber, the efficient BE is realized. For the laser cavity with single OC FBG, continuous-wave power of 334 W with an M² value of 2.8 and BE value of 5.6 were obtained at a wavelength of 1120 nm with an optical-to-optical efficiency of 49.6%. Furthermore, the cavity reflectivity is increased by employing two OC FBGs to scale the output power up to 443 W, while the corresponding M² is 3.5 with BE of 4.2. To our best knowledge, it is the highest power in Raman oscillator based on GRIN fiber.

Hundred-watt-level phosphosilicate Raman fiber laser with less than 1% quantum defect

Quantum defect (QD)-induced high thermal load in high-power fiber lasers can largely affect the conversion efficiency, pose a threat to the system security, and even prohibit the further power scaling. In this Letter, we investigate evolutions and influences of the reflectivity of the output coupler, the length of phosphosilicate fiber, and the pump bandwidth, and demonstrate a hundred-watt-level low-QD Raman fiber laser (RFL). The RFL enabled by the boson peak of phosphosilicate fiber achieves a maximum power of 100.9 W with a reduced QD down to 0.97%; the corresponding conversion efficiency reaches 69.8%. This Letter may offer not only an alternative scheme for a high-power, high-efficiency fiber laser, but also great potential on the suppression of thermal-induced effects such as thermal mode instability and the thermal lens effect.

Brightness enhancement in random Raman fiber laser based on a graded-index fiber with high-power multimode pumping

A brightness-enhanced random Raman fiber laser (RRFL) with maximum power of 306 W at 1120 nm is demonstrated. A half-open cavity is built based on a graded-index (GRIN) passive fiber and single high-reflective fiber Bragg grating written in it directly. Due to the beam cleanup effect in the GRIN fiber enhanced in the half-open RRFL cavity, the output beam quality factor M² is improved from 9.15 (pump) to 1.76-2.35 (Stokes) depending on power, while the pump-Stokes brightness enhancement (BE) factor increases proportionally to output power reaching 6.1 at maximum. To the best of our knowledge, this is the highest power GRIN RRFL with BE.

Bugs and drugs: a systems biology approach to characterising the effect of moxidectin on the horse's faecal microbiome

Background

Anthelmintic treatment is a risk factor for intestinal disease in the horse, known as colic. However the mechanisms involved in the onset of disease post anthelmintic treatment are unknown. The interaction between anthelmintic drugs and the gut microbiota may be associated with this observed increase in risk of colic. Little is known about the interaction between gut microbiota and anthelmintics and how treatment may alter microbiome function. The objectives of this study were: To characterise (1) faecal microbiota, (2) feed fermentation kinetics in vitro and (3) metabolic profiles following moxidectin administration to horses with very low (0 epg) adult strongyle burdens. Hypothesis: Moxidectin will not alter (1) faecal microbiota, (2) feed fermentation in vitro, or, (3) host metabolome.

Results

Moxidectin increased the relative abundance of Deferribacter spp. and Spirochaetes spp. observed after 160 h in moxidectin treated horses. Reduced in vitro fibre fermentation was observed 16 h following moxidectin administration in vivo (P = 0.001), along with lower pH in the in vitro fermentations from the moxidectin treated group. Metabolic profiles from urine samples did not differ between the treatment groups. However metabolic profiles from in vitro fermentations differed between moxidectin and control groups 16 h after treatment (R² = 0.69, Q²Y = 0.48), and within the moxidectin group between 16 h and 160 h post moxidectin treatment (R² = 0.79, Q²Y = 0.77). Metabolic profiles from in vitro fermentations and fermentation kinetics both indicated altered carbohydrate metabolism following in vivo treatment with moxidectin.

Conclusions

These data suggest that in horses with low parasite burdens moxidectin had a small but measurable effect on both the community structure and the function of the gut microbiome.

Effects of EGCG on proliferation and apoptosis of gastric cancer SGC7901 cells via down-regulation of HIF-1α and VEGF under a hypoxic state

OBJECTIVE

To investigate the effects of epigallocatechin-3-gallate (EGCG) on proliferation and apoptosis of human gastric cancer SGC7901 cells under a hypoxic state.

MATERIALS AND METHODS

Human gastric cancer SGC7901 cells were sub-cultured, and the cobalt chloride (CoCl2) hypoxia model was established. The blank control group (normoxia group), hypoxia control group (hypoxia group) and hypoxia + different concentrations of EGCG subgroups (20, 40, 60, 80, 100 μg/mL EGCG) were set up. Cell viability was detected via methyl thiazolyl tetrazolium (MTT) assay, apoptosis was detected via flow cytometry, and expressions of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) were detected via reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting.

RESULTS

Relatively low concentrations of EGCG (20-80 μg/mL) presented no significant inhibiting effect on SGC7901 cell growth within a short time (24 h) (p>0.05). The increasing concentration of EGCG inhibited cell proliferation under a hypoxia state (p<0.05). EGCG induced apoptosis in a dose-dependent manner under hypoxia (p<0.05). EGCG could significantly impede expressions of HIF-1α and VEGF proteins (p<0.05), and down-regulate the level of VEGF mRNA (p<0.05), but it showed no significant effect on the HIF-1α mRNA expression (p>0.05).

CONCLUSIONS

EGCG inhibited cell proliferation under hypoxia via the downregulation of HIF-1α and its downstream target gene VEGF levels, providing a theoretical basis for the early diagnosis and treatment of gastric cancer in clinic.

High-power cladding pumped Raman fiber amplifier with a record beam quality

In this Letter, a high-power, high-brightness all-fiberized Raman amplifier based on a cladding-pumping scheme is presented for the first time, to the best of our knowledge. The triple-clad passive fiber is employed as Raman gain fiber in the laser system. The maximum output power is 762.6 W emitting at 1130 nm. To the best of our knowledge, this is the highest power in the fields of cladding-pumped Raman amplifiers. Through a cladding-pumping process, the beam quality parameter ${{\rm M}^2}$M² improves from 6.12 of seed laser to 2.24 at maximum output power of 762.6 W, while the best ${{\rm M}^2}$M² is 1.9 at 267.2 W. It is also the best beam quality of Raman laser with brightness enhancement in any kind of configuration (graded-index fiber or multi-clad fiber, laser or amplifier, all-fiber or free-space configuration) with power of over 100 W.

Power scaling of Raman fiber amplifier based on the optimization of temporal and spectral characteristics

We comprehensively study the effects of temporal and spectral optimization on single-mode Raman fiber amplifiers. Amplified spontaneous emission sources and ytterbium-doped fiber lasers are employed as seed or pump lasers for comparison, and passive fibers are utilized as gain media. The influences of various parameters of the laser on 2^nd order Raman threshold and maximum output power are investigated experimentally, including bandwidth, seed power, wavelength separation between pump and seed laser, and temporal stability. With the 190 m passive fiber, the output power increases from 99.5 W to 142.4 W, corresponding to 43.1% improvement through the optimization of seed laser power, pump wavelength and temporal performance of pump source in this amplifier, which has guidance on the establishment of high-power single-mode Raman fiber amplifiers.

Broadband pumping enabled flat-amplitude multi-wavelength random Raman fiber laser

A flat-amplitude multi-wavelength random Raman fiber laser with broad spectral coverage and a high optical signal-to-noise ratio (OSNR) is challenging and of great interest. In this Letter, we theoretically and experimentally proved that broadband pumping can help realize a broader, flat-amplitude multi-wavelength random Raman fiber laser. The influence of pump bandwidth, tunability of the spectral envelope, and channel spacing are investigated. As a result, with a 40 nm pump bandwidth, a spectral coverage of 1116-1125 nm with 19 laser lines and 31 dB OSNR is achieved, and the standard deviation in the peak intensities of the central nine lines is ${\sim}{1}.{1}\;{\rm dBm}$∼1.1dBm. This technique can also be applied to the multi-wavelength Raman (or random Raman) fiber lasers at other wavelengths and provide a reference for multi-wavelength applications in sensing, communication, and optical component testing.

Fast modal analysis for Hermite-Gaussian beams via deep learning

The eigenmodes of Hermite-Gaussian (HG) beams emitting from solid-state lasers make up a complete and orthonormal basis, and they have gained increasing interest in recent years. Here, we demonstrate a deep learning-based mode decomposition (MD) scheme of HG beams for the first time, to the best of our knowledge. We utilize large amounts of simulated samples to train a convolutional neural network (CNN) and then use this trained CNN to perform MD. The results of simulated testing samples have shown that our scheme can achieve an averaged prediction error of 0.013 when six eigenmodes are involved. The scheme takes only about 23 ms to perform MD for one beam pattern, indicating promising real-time MD ability. When larger numbers of eigenmodes are involved, the method can also succeed with slightly larger prediction error. The robustness of the scheme is also investigated by adding noise to the input beam patterns, and the prediction error is smaller than 0.037 for heavily noisy patterns. This method offers a fast, economic, and robust way to acquire both the mode amplitude and phase information through a single-shot intensity image of HG beams, which will be beneficial to the beam shaping, beam quality evaluation, studies of resonator perturbations, and adaptive optics for resonators of solid-state lasers.

2 kW high-efficiency Raman fiber amplifier based on passive fiber with dynamic analysis on beam cleanup and fluctuation

In this paper, we study the power scaling in high power continuous-wave Raman fiber amplifier employing graded-index passive fiber. The maximum output power reaches 2.087 kW at 1130 nm with an optical conversion efficiency of 90.1% (the output signal power versus the depleted pump power). To the best of our knowledge, this is the highest power in the fields of Raman fiber lasers based merely on Stokes radiation. The beam quality parameter M² improves from 15 to 8.9 during the power boosting process, then beam spot distortion appears at high power level. This is the first observation and analysis on erratic dynamic properties of the transverse modes in high power Raman fiber amplifier.

All-fiberized cascaded random Raman fiber laser with high spectral purity based on filtering feedback

Cascaded random Raman fiber lasers (CRRFLs) with simple configuration and high spectral purity have become a great candidate for power scaling over the 1.1 µm-2 µm spectral band. Recently, CRRFLs with high spectral purity over 90% have been proposed by applying a highly temporal-stable pump source or a free-space short-pass filter, at the cost of increased system complexity. In this work, pumped directly by a Yb-doped fiber oscillator at 1080 nm, an all-fiberized and simplified CRRFL with a short-pass optical filter based on bending fiber and a thin-film wavelength division multiplexer is demonstrated. The transmission loss of the filter for 5th Stokes order at 1440 nm is up to 70 dB. Spectral purity over 92% for all the first four Stokes orders is achieved. The highest output power is 15 W for the 4th Stokes order at 1341 nm.

Higher thyroid-stimulating hormone levels in the first trimester are associated with gestational diabetes in a Chinese population

AIM

To evaluate the relationship between maternal thyroid-stimulating hormone levels during the first trimester and gestational diabetes risk.

METHODS

In Tianjin, China, 7258 women underwent a thyroid-stimulating hormone screening test within 12 gestational weeks and then had a glucose challenge test at 24-28 weeks of gestational age. The women with a glucose challenge test ≥7.8 mmol/l underwent a 75 g oral glucose tolerance test. Gestational diabetes was diagnosed following International Association of Diabetes and Pregnancy Study Group criteria. Restricted cubic spline analysis was performed to explore full-range risk associations of thyroid-stimulating hormone levels with gestational diabetes. Logistic regression was performed to obtain odds ratios and 95% confidence intervals.

RESULTS

In all, 594 women (8.2%) had gestational diabetes. Among women with thyroid-stimulating hormone ≤3.2 mIU/l, a positive association between thyroid-stimulating hormone levels and gestational diabetes risk was found (adjusted OR: 1.13, 95% CI: 1.00-1.27). There was no relationship between thyroid-stimulating hormone levels and gestational diabetes risk in univariable and multivariable analyses among women with thyroid-stimulating hormone >3.2 mIU/l. In subgroup analyses, among women with thyroid-stimulating hormone ≤3.2 mIU/l and BMI ≥25 kg/m² , the adjusted odds ratio for thyroid-stimulating hormone levels with gestational diabetes was enhanced to 1.25 (95% CI: 1.02-1.53).

CONCLUSIONS

In pregnant Chinese women, thyroid-stimulating hormone levels even within normal range in the first trimester were positively related to gestational diabetes risk, especially for pre-pregnancy overweight/obese women.

Deep learning enabled superfast and accurate M2 evaluation for fiber beams

We introduce deep learning technique to predict the beam propagation factor M² of the laser beams emitting from few-mode fiber for the first time, to the best of our knowledge. The deep convolutional neural network (CNN) is trained with paired data of simulated near-field beam patterns and their calculated M² value, aiming at learning a fast and accurate mapping from the former to the latter. The trained deep CNN can then be utilized to evaluate M² of the fiber beams from single beam patterns. The results of simulated testing samples have shown that our scheme can achieve an averaged prediction error smaller than 2% even when up to 10 eigenmodes are involved in the fiber. The error becomes slightly larger when heavy noises are added into the input beam patterns but still smaller than 2.5%, which further proves the accuracy and robustness of our method. Furthermore, the M² estimation takes only about 5 ms for a prepared beam pattern with one forward pass, which can be adopted for real-time M² determination with only one supporting Charge-Coupled Device (CCD). The experimental results further prove the feasibility of our scheme. Moreover, the method we proposed can be confidently extended to other kinds of beams provided that adequate training samples are accessible. Deep learning paves the way to superfast and accurate M² evaluation with very low experimental efforts.

Modulation instability induced by intermodal cross-phase modulation in step-index multimode fiber

Based on linear stability analysis, we theoretically investigate the onset condition and gain spectrum of intermodal cross-phase modulation-induced noise-seeded modulation instability taking place in the normal dispersion regime of step-index multimode fiber, specially designed to support four modes (LP₀₁, LP₁₁, LP₂₁, LP₀₂) at 1064 nm. For the case of total power being distributed equally in certain bimodal combinations, the peak sideband frequency scales as the square root of total power, and peak gain increases linearly with total power. For the case of total power being distributed unequally, there exists an optimal power ratio to obtain peak gain, which does not depend on total power significantly. When the mode group velocity mismatch is considered, the range and peak values of gain spectra are notably increased.

All-fiberized transverse mode-switching method based on temperature control

In this paper, an all-fiberized transverse mode-switching method was proposed based on temperature control of few-mode (FM) fiber Bragg gratings (FBGs). Two types of fibers were selected to fabricate the FBG pair in order to match the reflection peaks of the desired mode. The temperature-dependence property of the FM FBGs has been utilized to tune the reflection spectra. Through temperature control, 20 W level output power was obtained when the output laser was switched between the LP₁₁ mode and the LP₀₁ mode in both an all-fiberized ytterbium-doped laser and a Raman laser, which is increased by ∼2 orders of magnitude compared with previous demonstrations (almost less than 100 mW).

Community health perceptions and human environmental exposure to chromium contamination in a small New Jersey City

Following a 1983 chromic acid (hexavalent chromium [CrVI]) spill from a Garfield, NJ electroplating plant, CrVI-contaminated water was found in a local firehouse basement in 1993. An ATSDR public health advisory was issued for the plant site in 2010, and from 2008-2015, fourteen residential properties have required remediation to address CrVI-contaminated dust in the basements. As part of the Community Outreach and Engagement Core of the NYU NIEHS Center, seventytwo Garfield residents aged 18-65 years, participated in a community survey with the goal of identifying concerns related to environmental and community health. Thirty-two percent responded that they 'didn't know' if they were exposed to chemicals or pollutants where they live. This finding suggests a limited awareness of environmental chemical exposures, chromium contamination and/or potential exposure to CrVI. Furthermore, toenail clippings were collected from forty-seven Garfield residents and analyzed for total chromium levels to assess potential long-term exposure. On average, residents living on/inside the contaminated plume area had higher total chromium levels in their toenail clippings than residents living outside the plume area. However, chromium levels for all participants were within the range of historical normal. This study highlights the value of partnerships between environmentally-impacted community's and academic scientists working together to identify potential contaminant exposures and address public health concerns through research and environmental health education.

Learning to decompose the modes in few-mode fibers with deep convolutional neural network

We introduce a deep-learning technique to perform complete mode decomposition for few-mode optical fibers for the first time. Our goal is to learn a fast and accurate mapping from near-field beam patterns to the complete mode coefficients, including both modal amplitudes and phases. We train the convolutional neural network with simulated beam patterns and evaluate the network on both the simulated beam data and the real beam data. In simulated beam data testing, the correlation between the reconstructed and the ideal beam patterns can achieve 0.9993 and 0.995 for 3-mode case and 5-mode case, respectively. While in the real 3-mode beam data testing, the average correlation is 0.9912 and the mode decomposition can be potentially performed at 33 Hz frequency on a graphic processing unit, indicating real-time processing ability. The quantitative evaluations demonstrate the superiority of our deep learning-based approach.

High-beam-quality signal and pump combiner with large-mode-area fiber for high-power fiber laser and amplifier

We investigate a high-beam-quality (6+1)×1 signal and pump combiner with 50 μm core diameter of the output fiber based on the tapered-fused fiber bundle technique for the first time. The influence of taper ratio of the taper bundle for different mode proportions of the output fiber and the transition efficiency of the signal light are analyzed numerically. In the experiment, a signal fiber core diameter matching from 10 to 50 μm in the combiner is achieved. We experimentally demonstrate that the total 1018 nm pump efficiency of the combiner is >98% and the signal light insertion loss is less than 2%, with a beam quality factor M² of 1.59. Also, we have set up an amplifier based on the combiner, whose output laser power can achieve 2340 W with the slope efficiency of 73.76%. The beam quality factor M² of the output laser is 2.83 at the maximum power output, and a high beam quality is maintained when a large-mode-area fiber is employed in the laser system.

Dynamic characteristics of stimulated Raman scattering in high power fiber amplifiers in the presence of mode instabilities

Impact of mode instability on dynamic characteristics of stimulated Raman scattering in high power fiber amplifiers has been studied for the first time, which reveals another characterization of mode instability from the aspect of optical spectrum. It shows that, after the onset of mode instability, the measured light spectrums, especially the Raman light spectrums, are different from those without mode instability, which become burr-like. As mode instability evolves into different stages, the intensity of stimulated Raman scattering effects as laser power increasing also behaves differently. During the transition region, the stimulated Raman scattering effect becomes stronger as the lasing power increases until the mode instability evolves into chaotic regions, where the stimulated Raman scattering effect weakens. The effect of stimulated Raman scattering on mode instability has also been studied. Due to that the stimulated Raman scattering effect is weak and that the fraction of Raman light is only a few percent, the stimulated-Raman-scattering-induced mode instability has not been observed in the experiment, and the observed mode instability is induced by ytterbium ion gain of signal laser. It also revealed that the stimulated Raman scattering has negligible influence on the mode instability induced by ytterbium ion gain.

Power scalability of linearly polarized random fiber laser through polarization-rotation-based Raman gain manipulation

Random fiber laser based on Raman gain and random distributed feedback has drawn great attention in recent years. One of the most widely-studied fields is to improve the optical efficiency and the output power. However, the power scaling of a random fiber laser is instinctively restricted by the high order Stokes generation. In this manuscript, we propose a simple yet effective method, which employs a homemade all-fiber Lyot filter to manipulate the polarization dependent Raman gain, thus increasing the threshold of the 2nd-order Stokes wave and enhancing the maximum output power of the linearly polarized random fiber laser. Through reliable theoretical analysis, we optimize the design of the wavelength dependent Lyot filter. Moreover, the performance of the filter and the power scaling capability of the linearly polarized random fiber laser are investigated in detail. A proof-of-principle experiment is carried out by inserting the homemade Lyot filter into a half-opened random fiber laser. The experimental results indicate that the 2nd-order Stokes wave can be effectively suppressed, and the maximum output power of the 1st-order Stokes wave is significantly increased with a range of ~50% (from 43.6 to 63.2 W).

Tapered-fiber-enabled high-power, high-spectral-purity random fiber lasing

Random distributed feedback Raman fiber laser is a new kind of light source that can be applied to generate a high-power laser. In this Letter, we report on a high-power, high-spectral-purity random Raman fiber laser based on tapered fiber, in which the four-wave mixing (FWM) effect has been sufficiently suppressed. By choosing an appropriate tapered fiber length, we achieve a maximum random laser output of 491 W, and the spectral purity can reach to as high as 94%. We carefully compare the influence of different tapered fiber lengths and splicing patterns on the FWM effect by the cutting-back method and lateral-offset splicing. The results show that the transverse modes dispersion is responsible for the appearance of FWM by compensating the phase mismatch. It is believed that a kilowatt-level random laser can be obtained by further optimizing the parameters of tapered fiber.

Incoherent beam combining of fiber lasers by an all-fiber 7 × 1 signal combiner at a power level of 14 kW

We demonstrate an all-fiber 7 × 1 signal combiner with an output core diameter of 50 μm for high power incoherent beam combining of seven self-made Yb-doped single-mode fiber lasers around a wavelength of 1080 nm and output power of 2 kW. 14.1 kW combined output power is achieved with a total transmission efficiency of higher than 98.5% and a beam quality of M² = 5.37, which is close to the theoretical results based on finite-difference beam propagation technique. To the best of our knowledge, this is the highest output power ever reported for all-fiber structure beam combining generation, which indicates the feasibility and potential of >10 kW high brightness incoherent beam combining based on an all-fiber signal combiner.

Development and Validation of a Natural Language Processing Tool to Identify Patients Treated for Pneumonia across VA Emergency Departments

BACKGROUND

Identifying pneumonia using diagnosis codes alone may be insufficient for research on clinical decision making. Natural language processing (NLP) may enable the inclusion of cases missed by diagnosis codes.

OBJECTIVES

This article (1) develops a NLP tool that identifies the clinical assertion of pneumonia from physician emergency department (ED) notes, and (2) compares classification methods using diagnosis codes versus NLP against a gold standard of manual chart review to identify patients initially treated for pneumonia.

METHODS

Among a national population of ED visits occurring between 2006 and 2012 across the Veterans Affairs health system, we extracted 811 physician documents containing search terms for pneumonia for training, and 100 random documents for validation. Two reviewers annotated span- and document-level classifications of the clinical assertion of pneumonia. An NLP tool using a support vector machine was trained on the enriched documents. We extracted diagnosis codes assigned in the ED and upon hospital discharge and calculated performance characteristics for diagnosis codes, NLP, and NLP plus diagnosis codes against manual review in training and validation sets.

RESULTS

Among the training documents, 51% contained clinical assertions of pneumonia; in the validation set, 9% were classified with pneumonia, of which 100% contained pneumonia search terms. After enriching with search terms, the NLP system alone demonstrated a recall/sensitivity of 0.72 (training) and 0.55 (validation), and a precision/positive predictive value (PPV) of 0.89 (training) and 0.71 (validation). ED-assigned diagnostic codes demonstrated lower recall/sensitivity (0.48 and 0.44) but higher precision/PPV (0.95 in training, 1.0 in validation); the NLP system identified more "possible-treated" cases than diagnostic coding. An approach combining NLP and ED-assigned diagnostic coding classification achieved the best performance (sensitivity 0.89 and PPV 0.80).

CONCLUSION

System-wide application of NLP to clinical text can increase capture of initial diagnostic hypotheses, an important inclusion when studying diagnosis and clinical decision-making under uncertainty.

DFT modelling of a diphosphane - N-heterocyclic carbene-Rh(i) pincer complex rearrangement: a computational evaluation of the electronic effects in C-P bond activation

DFT calculations confirmed that the rearrangement of a PCP-Rh-H pincer to a CCP-Rh-phosphane pincer occured by C-P oxidative addition (ΔG^‡ = 29.5 kcal mol^-1, rate-determining step), followed by P-H reductive elimination (ΔG^‡ = 4.8 kcal mol^-1). The oxidative addition proceeded via a 3-centered transition state and is accelerated by electron-withdrawing substituents p- to the reacting C-P bond, resulting in a reaction constant (ρ) of 2.12 for ΔG^‡ and 2.76 for ΔH^‡ in a Hammett-type linear free energy relationship. AIM wavefunction analyses indicated a decrease in the negative charge on the carbon bonded to Rh with a concomitant increase in the positive charge on the latter. The electronic density at the Rh-P bond critical point and the atomic charge on Rh correlate well with the Hammett constants (σ) of the p-substituents. The replacement of the Rh-bound hydride with other anions (CH₃, Ph, t-Bu, OH, F, Cl, and CN) results in a decrease in the OA barrier only for CH₃, which is in accordance with the experimental results. The reductive elimination occurs via a 3-centered (Rh, H, P) transition state, which adopts a conformation wherein the steric clash between the i-Pr groups is minimized, followed by recomplexation of Rh and the newly formed (i-Pr)₂PH by a conformational twist around the Rh-P axis.

Thermally induced mode loss evolution in the coiled ytterbium doped large mode area fiber

We propose a model to calculate the thermally induced mode loss evolution in the coiled ytterbium doped large mode area (LMA) fiber. The mode loss evolution in the coiled conventional step index LMA 20/400 fiber is investigated. Meanwhile, a model of fiber amplifier considering thermally induced mode loss evolution is established. The higher order mode (HOM) suppression between a co-pumping scheme and counter-pumping scheme under the heat load are compared. The simulation shows that the HOM loss decreases quasi-exponentially with the heat load and the bending radius of the ytterbium doped fiber (YDF) should be optimized according to the heat load to achieve effectively single mode operation. Besides, the counter-pumping fiber amplifier shows much better HOM suppression than the co-pumping fiber amplifier. The results in this paper will provide guidance in the design of novel ytterbium doped LMA fiber and the optimization of the high power single mode fiber amplifier.

Multimode fiber modal decomposition based on hybrid genetic global optimization algorithm

Numerical modal decomposition (MD) is an effective approach to reveal modal characteristics in high power fiber lasers. The main challenge is to find a suitable multi-dimensional optimization algorithm to reveal exact superposition of eigenmodes, especially for multimode fiber. A novel hybrid genetic global optimization algorithm, named GA-SPGD, which combines the advantages of genetic algorithm (GA) and stochastic parallel gradient descent (SPGD) algorithm, is firstly proposed to reduce local minima possibilities caused by sensitivity to initial values. Firstly, GA is applied to search the rough global optimization position based on near- and far-field intensity distribution with high accuracy. Upon those initial values, SPGD algorithm is afterwards used to find the exact optimization values based on near-field intensity distribution with fast convergence speed. Numerical simulations validate the feasibility and reliability.

Mode instability dynamics in high-power low-numerical-aperture step-index fiber amplifier

The study on mode instability (MI) in the large-mode-area fiber is generating great interest regarding the high-power applications of fiber lasers. To the best of our knowledge, we have investigated for the first time the dynamics of the output beam from a kilowatt-level all-fiber amplifier based on the low-numerical-aperture (<0.04) step-index (SI) fiber before and after the onset of the MI, including the temporal dynamics and mode evolution. The temporal power fluctuations indicate three evolution stages apart from the onset threshold of the MI, defined as stable, transition, and chaotic regions. In addition, the mode decomposition technique is utilized to accurately observe and investigate the mode evolution and relevant modal content corresponding to the transition and chaotic regions in the SI fiber laser for the first time. According to the mode decomposition results, the reduction of the extracted power can be explained by the high bending loss of the high-order mode excited in the MI process. Finally, the difference of MI dynamics between the fiber lasers based on the SI fiber and rod-type photonic crystal fiber is discussed.

High-power, cladding-pumped all-fiber laser with selective transverse mode generation property

We demonstrate, to the best of our knowledge, the first cladding-pumped all-fiber oscillator configuration with selective transverse mode generation based on a mode-selective fiber Bragg grating pair. Operating in the second-order (LP₁₁) mode, maximum output power of 4.2 W is obtained with slope efficiency of about 38%. This is the highest reported output power of single higher-order transverse mode generation in an all-fiber configuration. The intensity distribution profile and spectral evolution have also been investigated in this paper. Our work suggests the potential of realizing higher power with selective transverse mode operation based on a mode-selective fiber Bragg grating pair.

Hypertensive disorders of pregnancy in women with gestational diabetes mellitus on overweight status of their children

Hypertensive disorders of pregnancy (HDP) as a group of medical complications in pregnancy are believed to be associated with an increased risk of poor fetal growth, but the influence on offspring’s body composition is not clear. The aim of the present study was to evaluate the association between maternal hypertensive disorders of pregnancy and overweight status in the offspring of mothers with gestational diabetes mellitus (GDM).

A cross-sectional study among 1263 GDM mother-child pairs was performed in Tianjin, China. General linear models and logistic regression models were used to assess the associations of maternal hypertension in pregnancy with anthropometry and overweight status in the offspring from birth to 1–5 years old.

Offspring of GDM mothers who were diagnosed with hypertensive disorders during pregnancy had higher mean values of Z scores for birth weight for gestational age and birth weight for length, and higher mean values of Z scores for weight for age, weight for length/height, and body mass index for age at 1–5 years old than those of GDM mothers with normal blood pressure during pregnancy. Maternal hypertensive disorders of pregnancy were associated with increased risks of large for gestational age (OR 1.74, 95%CI 1.08–2.79) and macrosomia (OR 2.02, 95%CI 1.23–3.31) at birth and childhood overweight/obesity at 1–5 years old age (OR 1.88, 95%CI 1.16–3.04).

For offspring of mothers with GDM, maternal hypertension during pregnancy was a risk factor for macrosomia at birth and childhood overweight and obesity, and controlling the maternal hypertension may be more important for preventing large for gestational age babies and childhood obesity.