Saturation response of enhanced vegetation productivity attributes to intricate interactions.

Evidence for the multifaceted responses of terrestrial ecosystems has been shown by the weakening of CO2 fertilization-induced and warming-controlled productivity gains. The intricate relationship between vegetation productivity and various environmental controls still remains elusive spatially. Here several inherent preponderances make China a natural experimental setting to investigate the interaction and relative contributions of five drivers to gross primary productivity for the period from 1982 to 2018 (i.e., elevated atmospheric CO2 concentrations, climate change, nutrient availability, anthropogenic land use change, and soil moisture) by coupling multiple long-term datasets. Despite a strikingly prominent enhancement of vegetation productivity in China, it exhibits similar saturation responses to the aforementioned environmental drivers (elevated CO2 , climatic factors, and soil moisture). The CO2 fertilization-dominated network explains the long-term variations in vegetation productivity in humid regions, but its effect is clearly attenuated or even absent in arid and alpine environments controlled by climate and soil moisture. Divergence in interactions also provides distinct evidence that water availability plays an essential role in limiting the potential effects of climate change and elevated CO2 concentrations on vegetation productivity. Unprecedented industrialization and dramatic surface changes may have breached critical thresholds of terrestrial ecosystems under the diverse natural environment and thus forced a shift from a period dominated by CO2 fertilization to a period with nonlinear interactions. These findings suggest that future benefits in terrestrial ecosystems are likely to be counteracted by uncertainties in the complicated network, implying an increasing reliance on human societies to combat potential risks. Our results therefore highlight the need to account for the intricate interactions globally and thus incorporate them into mitigation and adaptation policies.

Naringenin as a natural immunomodulator against T cell-mediated autoimmune diseases: literature review and network-based pharmacology study.

T cells, especially CD4+ T helper (Th) cells, play a vital role in the pathogenesis of specific autoimmune diseases. Naringenin, a citrus flavonoid, exhibits anti-inflammatory, anti-oxidant, and antitumor properties, which have been verified in animal autoimmune disease models. However, naringenin's possible effects and molecular mechanisms in T cell-mediated autoimmune diseases are unclear. This review summarizes the findings of previous studies and predicts the target of naringenin in T cell-mediated autoimmune disorders such as multiple sclerosis, inflammatory bowel disease, and rheumatoid arthritis through network pharmacology analysis. We performed DAVID enrichment analysis, protein-protein interaction analysis, and molecular docking to predict the positive effect of naringenin on T cell-mediated autoimmune disorders. Sixteen common genes were screened, among which the core genes were PTGS2, ESR1, CAT, CASP3, MAPK1, and AKT1. The possible molecular mechanism relates to HIF-1, estrogen, TNF, and NF-κB signaling pathways. Our findings have significance for future naringenin treatment of T cell-mediated autoimmune diseases.

Development and multicenter performance evaluation of fully automated SARS-CoV-2 IgM and IgG immunoassays.

Objectives: The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread globally. The laboratory diagnosis of SARS-CoV-2 infection has relied on nucleic acid testing; however, it has some limitations, such as low throughput and high rates of false negatives. Tests of higher sensitivity are needed to effectively identify infected patients. Methods: This study has developed fully automated chemiluminescent immunoassays to determine IgM and IgG antibodies to SARS-CoV-2 in human serum. The assay performance has been evaluated at 10 hospitals. Clinical specificity was evaluated by measuring 972 hospitalized patients and 586 donors of a normal population. Clinical sensitivity was assessed on 513 confirmed cases of SARS-CoV-2 by RT-PCR. Results: The assays demonstrated satisfied assay precision with coefficient of variation of less than 4.45%. Inactivation of specimen did not affect assay measurement. SARS-CoV-2 IgM showed clinical specificity of 97.33 and 99.49% for hospitalized patients and the normal population respectively, and SARS-CoV-2 IgG showed clinical specificity of 97.43 and 99.15% respectively. SARS-CoV-2 IgM showed clinical sensitivity of 82.54, 92.93, and 84.62% before 7 days, 7-14 days, and after 14 days respectively, since onset of symptoms, and SARS-CoV-2 IgG showed clinical sensitivity of 80.95, 97.98, and 99.15% respectively at the same time points above. Conclusions: We have developed fully automated immunoassays for detecting SARS-CoV-2 IgM and IgG antibodies in human serum. The assays demonstrated high clinical specificity and sensitivity, and add great value to nucleic acid testing in fighting against the global pandemic of the SARS-CoV-2 infection.

Spatially-distributed orbital angular momentum beam array generation based on greedy algorithms and coherent combining technology.

A novel approach to generate a spatially-distributed orbital angular momentum (OAM) beam array based on coherent combining technology is presented. The arrangement of the multiple fundamental Gaussian beams at the initial plane, as well as the intensity weights and the phase distributions of the array beams, is determined by the reversal of Huygens Fresnel diffraction and the greedy algorithm. This method ensures that a vortex beam array is formed at a specified distance, and the distance can be adjusted by phase modulation. The evolution properties of the synthesized beam array near the receiver plane are studied as well to estimate the robustness of the method. The experimental limitations of this technique are discussed, including the maximum number of beams, the relative separation of each beam and the maximum topological charges. The results illustrate that a spatially-distributed OAM beam array can be effectively generated within a finite distance interval, and the distance is adjustable. This new method enables further applications of a structured optical field, such as optical communication and spatial light structuring.

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.

Associations of polymorphisms in TXNIP and gene-environment interactions with the risk of coronary artery disease in a Chinese Han population.

Single nucleotide polymorphisms (SNPs) in thioredoxin-interacting protein (TXNIP) gene may modulate TXNIP expression, then increase the risk of coronary artery disease (CAD). In a two-stage case-control study with a total of 1818 CAD patients and 1963 controls, we genotyped three SNPs in TXNIP and found that the variant genotypes of SNPs rs7212 [odds ratio (OR) = 1.26, P = 0.001] and rs7211 (OR = 1.23, P = 0.005) were significantly associated with increased CAD risk under a dominant model. In haplotype analyses, compared with the reference haplotype, haplotype 'G-T' had a 1.22-fold increased risk of CAD (P = 0.003). We also observed the cumulative effects of SNPs rs7212 and rs7211 on CAD risk and the severity of coronary atherosclerosis. Moreover, the gene-environment interactions among the variant genotypes of SNP rs7212, smoking habit, alcohol drinking habit and history of type 2 diabetes were associated with a 3.70-fold increased risk of CAD (P < 0.001). Subsequent genotype-phenotype correlation analyses further observed the significant effects of SNP rs7212 on TXNIP mRNA expression, plasma TXNIP and malondialdehyde levels. Taken together, our data suggest that TXNIP SNPs may individually and cumulatively affect CAD risk through a possible mechanism for regulating TXNIP expression and gene-environment interactions.

Gain-switched monolithic fiber laser with ultra-wide tuning range at 2 µm.

We demonstrate a gain-switched thulium-doped fiber laser (TDFL) built in an all-fiber format producing nanosecond pulses with variable wavelength in the 2 µm waveband. The laser features tunable operation in an ultra-wide spectral region of 1765 - 2055 nm (24 THz). The nearly 300 nm tunability doubles the record tuning range of existing gain-switched fiber lasers, and to the best of our knowledge, presents the broadest tuning range that has been reported for a monolithic pulsed rare earth doped fiber laser to date. The TDFL can operate at a repetition rate of 2.5 - 100 kHz with a pulse width as short as ~200 ns. Influences of various system parameters on the laser performance are investigated in detail.

High power broadband all fiber super-fluorescent source with linear polarization and near diffraction-limited beam quality.

In this manuscript, a high power broadband superfluorescent source (SFS) with linear polarization and near-diffraction-limited beam quality is achieved based on an ytterbium-doped (Yb-doped), all fiberized and polarization-maintained master oscillator power amplifier (MOPA) configuration. The MOPA structure generates a linearly polarized output power of 1427 W with a slope efficiency of 80% and a full width at half maximum (FWHM) of 11 nm, which is power scaled by an order of magnitude compared with the previously reported SFSs with linear polarization. In the experiment, both the polarization extinction ratio (PER) and beam quality (M(2) factor) are degraded little during the power scaling process. At maximal output power, the PER and M(2) factor are measured to be 19.1dB and 1.14, respectively. The root-mean-square (RMS) and peak-vale (PV) values of the power fluctuation at maximal output power are just 0.48% and within 3%, respectively. Further power scaling of the whole system is limited by the available pump sources. To the best of our knowledge, this is the first demonstration of kilowatt level broadband SFS with linear polarization and near-diffraction-limited beam quality.

1.89 kW all-fiberized and polarization-maintained amplifiers with narrow linewidth and near-diffraction-limited beam quality.

In this manuscript, we demonstrate high power, all-fiberized and polarization-maintained amplifiers with narrow linewidth and near-diffraction-limited beam quality by simultaneously suppressing detrimental stimulated Brillouin scattering (SBS) and mode instability (MI) effects. Compared with strictly single frequency amplification, the SBS threshold is scaled up to 12 dB, 15.4 dB, and higher than 18 dB by subsequently using three-stage cascaded phase modulation systems. Output powers of 477 W, 1040 W, and 1890 W are achieved with full widths at half maximums (FWHMs) of within 6 GHz, ~18.5 GHz, and ~45 GHz, respectively. The MI threshold is increased from ~738 W to 1890 W by coiling the active fiber in the main amplifier. Both the polarization extinction ratio (PER) and beam quality (M2 factor) are maintained well during the power scaling process. To the best of our knowledge, this is the first demonstration of all-fiberized amplifiers with narrow linewidth, near linear polarization, and near-diffraction-limited beam quality at 2 kW power-level.

Mitigating transverse mode instability in all-fiber laser oscillator and scaling power up to 2.5 kW employing bidirectional-pump scheme.

Transverse mode instability (TMI) is one of the main limiting factors in kW-level fiber lasers. Unlike fiber amplifiers, TMI in fiber laser oscillators attracts less attention from researchers. In this work, we construct an all-fiber ytterbium-doped laser oscillator and investigate the performance in co-pumping and bidirectional-pumping configurations, respectively. In the co-pumping scheme, TMI occurs at ~1.6kW and restricts further output power scaling. Different from the characteristic of dynamic TMI in fiber amplifiers, quasi-static TMI is observed in the laser oscillator. Details of the temporal characteristic around the TMI threshold are provided. In the bidirectional-pumping scheme, experimental results validate that the TMI is mitigated notably by employing bidirectional-pumping instead of co-pumping. The output laser power is further scaled to 2.5kW with a slope efficiency of 74.5% and good beam quality (M2~1.3). At the maximum power, the FWHM bandwidth of optical spectra is 5.2nm, and the Raman stokes light is ~20dB below the signal.

Short cavity-length random fiber laser with record power and ultrahigh efficiency.

We report the result of achieving a random fiber laser (RFL) with record 200-W-level power output. The highest output power is realized by a simple 120 m long cavity at a working wavelength of 1173 nm while pumping at 1120 nm. The maximum observed optical-to-optical efficiency reaches ∼89%, which is believed to be the highest value ever reported for RFLs. In addition, numerical calculations on different order Raman Stokes wave thresholds based on the theoretical model are carried out for comparison with the experimental data. The presented work effectively advances the power scalability, and the numerical model well describes the lasing thresholds in such short cavity RFLs.

Random distributed feedback fiber laser at 2.1 µm.

We demonstrate a random distributed feedback fiber laser at 2.1 µm. A high-power pulsed Tm-doped fiber laser operating at 1.94 µm with a temporal duty ratio of 30% was employed as a pump laser to increase the equivalent incident pump power. A piece of 150 m highly GeO2-doped silica fiber that provides a strong Raman gain and random distributed feedbacks was used to act as the gain medium. The maximum output power reached 0.5 W with the optical efficiency of 9%, which could be further improved by more pump power and optimized fiber length. To the best of our knowledge, this is the first demonstration of random distributed feedback fiber laser at 2 µm band based on Raman gain.

Robust sky light polarization detection with an S-wave plate in a light field camera.

The sky light polarization navigator has many advantages, such as low cost, no decrease in accuracy with continuous operation, etc. However, current celestial polarization measurement methods often suffer from low performance when the sky is covered by clouds, which reduce the accuracy of navigation. In this paper we introduce a new method and structure based on a handheld light field camera and a radial polarizer, composed of an S-wave plate and a linear polarizer, to detect the sky light polarization pattern across a wide field of view in a single snapshot. Each micro-subimage has a special intensity distribution. After extracting the texture feature of these subimages, stable distribution information of the angle of polarization under a cloudy sky can be obtained. Our experimental results match well with the predicted properties of the theory. Because the polarization pattern is obtained through image processing, rather than traditional methods based on mathematical computation, this method is less sensitive to errors of pixel gray value and thus has better anti-interference performance.

All-fiber high-average power nanosecond-pulsed master-oscillator power amplifier at 2 µm with mJ-level pulse energy.

We present a high-power nanosecond-pulsed Tm-doped fiber amplifier at 1.971 µm based on a master-oscillator power amplifier (MOPA) configuration. When the repetition rate is 500 kHz and the pulse width is 63.3 ns, the average power reaches 238 W, the peak power reaches 7.06 kW, and the pulse energy is 0.477 mJ. When the pulse train's repetition rate is 300 kHz with a pulse width of 63.7 ns, the average power reaches 197 W, the peak power reaches 9.73 kW, and the pulse energy is 0.66 mJ. When the pulse train's repetition rate is 200 kHz with a pulse width of 58.2 ns, the average power reaches 150 W, the peak power reaches 12.1 kW, and the pulse energy is 0.749 mJ. The spectral linewidths of the pulse trains are 0.15, 0.14, and 0.10 nm for 500 kHz repetition rate, 300 kHz repetition rate, and 200 kHz repetition rate, respectively. To the best of our knowledge, this is the first demonstration of high-power nanosecond-pulsed MOPA at 2 µm with the maximum average power reaching 238 W, the maximum peak power reaching 12.1 kW, and the maximum pulse energy reaching 0.749 mJ.

Kilowatt-level near-diffraction-limited and linear-polarized Ytterbium-Raman hybrid nonlinear amplifier based on polarization selection loss mechanism.

Ytterbium-Raman cascaded oscillators with linearly polarized output are designed and achieved based on polarization selection loss (PSL) mechanism for the first time. The 1120 nm laser cavity is designed with fully non polarization-maintained (NPM) fiber Bragg gratings (FBGs) and NPM active fiber while the 1080 nm laser cavity is designed based on polarization-maintained (PM) FBGs and PM active fiber. By using PSL mechanism in 1080 nm cavity, even with fully NPM 1120 nm cavity, both linear-polarized 1120 nm and 1080 nm lasers are achieved in the output port of the cascaded oscillators. Based on the new designed cascaded seeds, a high power polarization-maintained Yb-Raman hybrid nonlinear amplifier is established for further power scaling of the 1120 nm laser. In the nonlinear amplifier, only 21-meter-long active fiber and 1.5-meter-long passive fiber is used for power transferring from 1080 nm to 1120 nm. Output power of 1181 W is achieved at central wavelength of 1120 nm with the M(2) factor of <1.2 and polarization-extinction ratio (PER) of 18.2 dB. As far as we known, the output power of this all fiber format is the highest one in 1120 nm with linear polarization. This type of high power Yb-Raman nonlinear amplifier design with linear polarization can be further extended to Yb-Raman amplifying the wavelength range of 1100-1200 nm.

High power, widely tunable, narrowband superfluorescent source at 2 µm based on a monolithic Tm-doped fiber amplifier.

We present a widely tunable narrowband superfluorescent source near 2 µm employing a monolithic Tm-doped fiber amplifier (TDFA), and the output power exceeds 250 W. A broadband superfluorescent source with a narrowband tunable band pass filter was used as the seed source. The spectra of the seed source can be tuned in a range of ~1930-2030 nm with full width at half maximum (FWHM) of ~1.7 nm. The Tm-doped fiber amplifier scales up the power of the seed source to a level of more than 250 W with a tuning range of ~35 nm (1966-2001 nm) and a FWHM of ~1.5-2.0 nm, and the slope efficiency is about 0.50. The output power is limited by the available pump power, and the tuning range is limited by the amplifier spontaneous emission at other wavelengths. Higher output power can be achieved if launching more pump power into the amplifier, and the tuning range can be further improved by optimizing the parameters of the TDFA. To the best of our knowledge, this is the first demonstration on a widely tunable narrowband superfluorescent source at 2 µm with average output power exceeding 250 W.

105 W ultra-narrowband nanosecond pulsed laser at 2 µm based on monolithic Tm-doped fiber MOPA.

We present a high power ultra-narrowband pulsed fiber amplifier at 2 µm. A single frequency fiber laser was modulated by a phase modulator and an intensity modulator to serve as the ultra-narrowband pulsed seed laser with a bandwidth of 307 MHz. The pulsed seed laser was amplified by a monolithic Tm-doped fiber master oscillator power amplifier (MOPA). The average output power reaches 105 W with a slope efficiency of 0.41. The output pulse train has a repetition rate of 1 MHz and a pulse width of 66 ns. The output power is limited by the onset of stimulated Brillouin scattering. Higher output power can be achieved by further broadening the linewidth or narrowing the pulse width to several nanoseconds. To the best of our knowledge, this is the first demonstration on a monolithic ultra-narrowband nanosecond pulsed MOPA at 2 µm with an average power exceeding 100 W.

Tunable slow light via stimulated Brillouin scattering at 2 µm based on Tm-doped fiber amplifiers.

We present a slow light system based on stimulated Brillouin scattering (SBS) at 2 µm. A single-frequency fiber laser with Tm-doped fiber amplifiers was used to generate the SBS signal laser and the Brillouin pump light at 1.971 µm. The maximum delay time reaches 16 ns for pulses with 43-ns width, and the pulse width is broadened to 56.4 ns. The maximum delay time for 57-ns pulses reaches 33.4 ns, and the pulse width is broadened to 77.6 ns. The relative delays are 0.37 and 0.58 for 43 and 57 ns pulses, respectively. This is the first demonstration, as far as we know, on a slow light system at 2 µm, which may be substantial for future optical communications and LIDAR systems employing laser sources near 2-µm band.

Kilowatt-level fiber amplifier with spectral-broadening-free property, seeded by a random fiber laser.

In this Letter, we demonstrate a kilowatt (kW) level high-power fiber laser amplifier with a clear sign of spectral-broadening-free property. The high-power fiber lasing is realized by employing a master oscillator power-amplifier (MOPA) configuration, seeded by a temporally stable random fiber laser (RFL) that utilizes Raman amplification and random distributed feedback from a long passive fiber. The output power reaches 1.03 kW with a 1070 nm wavelength and an optical-to-optical efficiency of 74.6%. Despite the typical nonlinear spectral broadening in most traditional MOPA systems, the output spectral linewidth is well maintained during the whole high-power amplification process. The suppressed linewidth broadening in the spectral domain during high-power amplification is significant for further power scaling, spectral beam combination, and other applications that require narrow-linewidth high-power lasing.