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Nonlinear dielectric metasurfaces provide a promising approach to control and manipulate frequency conversion optical processes at the nanoscale, thus facilitating both advances in fundamental research and the development of new practical applications in photonics, lasing, and sensing. Here, we employ symmetry-broken metasurfaces made of centrosymmetric amorphous silicon for resonantly enhanced second- and third-order nonlinear optical response. Exploiting the rich physics of optical quasi-bound states in the continuum and guided mode resonances, we comprehensively study through rigorous numerical calculations the relative contribution of surface and bulk effects to second-harmonic generation (SHG) and the bulk contribution to third-harmonic generation (THG) from the meta-atoms. Next, we experimentally achieve optical resonances with high quality factors, which greatly boosts light-matter interaction, resulting in about 550 times SHG enhancement and nearly 5000-fold increase of THG. A good agreement between theoretical predictions and experimental measurements is observed. To gain deeper insights into the physics of the investigated nonlinear optical processes, we further numerically study the relation between nonlinear emission and the structural asymmetry of the metasurface and reveal that the generated harmonic signals arising from linear sharp resonances are highly dependent on the asymmetry of the meta-atoms. Our work suggests a fruitful strategy to enhance the harmonic generation and effectively control different orders of harmonics in all-dielectric metasurfaces, enabling the development of efficient active photonic nanodevices.

Abstract Due to its unique intensity distribution, self-acceleration, and beam self-healing properties, Airy beam holds great potential for optical wireless communications in challenging channels, such as underwater environments. As a vital part of 6G wireless network, the Internet of Underwater Things requires high-stability, low-latency, and high-capacity underwater wireless optical communication (UWOC). Currently, the primary challenge of UWOC lies in the prevalent time-varying and complex channel characteristics. Conventional blue Gaussian beam-based systems face difficulties in underwater randomly perturbed links. In this work, we report a full-color circular auto-focusing Airy beams metasurface transmitter for reliable, large-capacity and long-distance UWOC links. The metasurface is designed to exhibits high polarization conversion efficiency over a wide band (440-640 nm), enabling an increased data transmission rate of 91% and reliable 4 K video transmission in wavelength division multiplexing (WDM) based UWOC data link. The successful application of this metasurface in challenging UWOC links establishes a foundation for underwater interconnection scenarios in 6G communication.

The orexin system regulates a variety of physiological functions, including the sleep-wake cycle, addiction, foraging behavior, stress and cognitive functioning. Orexin levels in central and peripheral are related to the pathogenesis of many diseases, most notably the narcolepsy, eating disorders, stress-related psychiatric disorders, and neurodegenerative diseases. Recently, it has been reported that the orexin system is distinctly sexually dimorphic, and is strongly associated with neuropsychiatric disorders. In this review, we analyzed advancements in the sex differences in the orexin system and their connection to psychoneurological conditions. Considering the scarcity of research in this domain, more research is imperative to reveal the underlying mechanisms.

Study region: The Ailaoshan National Nature Reserve forest is a mountainous water catchment area for the Lancang River basin and a subtropical ecological conservation area in southwest China. Study focus: The study aimed to understand how water fluxes in a subtropical forest responds to extreme weather disturbances and their recoveries in the post-damage years. We used eddy covariance data (2010–2019) to investigate the evapotranspiration (ET), transpiration (T), evaporation (E), and canopy conductance (Gc) before and after an extreme snow event in 2015. New Hydrological Insights: In the snow damage year, the leaf area index (LAI) decreased by 49 % compared to the pre-damage levels. The severe vegetation damage caused a significant decrease in ET, T, E, and Gc by 35 %, 36 %, 23 %, and 33 %, respectively, compared to the pre-damage levels. T returned to its pre-damage level in 2016, one year after the snow damage. In contrast, LAI, ET, E and Gc recovered to their pre-damage levels in 2018, four years after the initial damage. Reduced ET caused a strong positive RFET, which diminished forest evaporative cooling and resilience. Our results suggest that the delayed E recovery enables water reserves in the ecosystems to be used through T to support rapid understory vegetation growth. This mechanism plays critical in bolstering ecosystem resilience as it facilitates swift recovery following disturbances in subtropical forests.

Abstract Schizophrenia (SZ) is a complex psychiatric neurodevelopmental disorder with uncertain etiology and pathogenesis. Increasing evidence has recognized the key role of the gut microbiota in SZ. However, few studies have investigated the potential link between oral microbiota and SZ. We studied the tongue coating microbiota and inflammatory profiles of 118 elderly SZ patients and 97 age-matched healthy controls using Illumina MiSeq sequencing and multiplex immunoassays, respectively. Reduced α-diversity, along with a significant difference in β-diversity, were observed in patients with SZ. We have identified SZ-associated oral dysbiosis, characterized by increased Streptococcus and Fusobacterium, as well as decreased Prevotella and Veillonella. These differential genera could potentially serve as biomarkers for SZ, either alone or in combination. Additionally, an elevated Streptococcus/Prevotella ratio could indicate oral dysbiosis. These differential genera formed two distinct clusters: Streptococcus-dominated and Prevotella-dominated, which exhibited different correlations with the altered immunological profiles. Furthermore, we also observed disruptions in the inferred microbiota functions in SZ-associated microbiota, particularly in lipid and amino acid metabolism. Our study provides novel insights into the characteristics of tongue coating microbiota and its associations with immunological disturbances in elderly SZ patients, which offer new targets for the diagnosis and treatment of SZ in the elderly.

Abstract We introduce a new paradigm for generating high-purity vortex beams with metasurfaces. By applying optical neural networks to a system of cascaded phase-only metasurfaces, we demonstrate the efficient generation of high-quality Laguerre-Gaussian (LG) vortex modes. Our approach is based on two metasurfaces where one metasurface redistributes the intensity profile of light in accord with Rayleigh-Sommerfeld diffraction rules, and then the second metasurface matches the required phases for the vortex beams. Consequently, we generate high-purity LG p,l optical modes with record-high Laguerre polynomial orders p = 10 and l = 200, and with the purity in p, l and relative conversion efficiency as 96.71%, 85.47%, and 70.48%, respectively. Our engineered cascaded metasurfaces suppress greatly the backward reflection with a ratio exceeding −17 dB. Such higher-order optical vortices with multiple orthogonal states can revolutionize next-generation optical information processing.

Generation of even-order optical harmonics requires noncentrosymmetric structures being conventionally observed in crystals lacking the center of inversion. In centrosymmetric systems, even-order harmonics may arise, e.g., at surfaces but such effects are usually very weak. Here we observe optical harmonics up to fourth order generated under the normal incidence from centrosymmetric dielectric metasurfaces empowered by resonances. We design silicon metasurfaces supporting optical quasibound states in the continuum and guided-mode resonances, and demonstrate the enhancement of second-harmonic signals by over three orders of magnitude compared to nonresonant thin films. Under the optimal conditions, the brightness of the second harmonic approaches that of the third harmonic, and the fourth-order harmonic becomes detectable.

Soil hydraulic parameters are influenced by various inherent soil properties, such as pore structure and organic matter content, which can vary with changes in the ecosystem. However, identifying the temporal variations of soil hydraulic parameters in a co-evolving soil-vegetation system remains a challenge. This study focused on a tropical forest with significant seasonal variations in vegetation attributes, evaporation, and carbon fluxes over a five-year monitoring period. The particle batch smoother algorithm was integrated with an unsaturated flow model to identify the seasonally varied soil hydraulic parameters through assimilation of in-situ measured soil moisture. As a benchmark, the Generalized Likelihood Uncertainty Estimation method was applied to optimize soil hydraulic parameters without considering temporal variation. The results indicated that the temporally varying soil hydraulic parameters exhibited regular seasonal patterns and outperformed the unvaried soil hydraulic parameters in terms of reducing the errors in modeling of soil moisture and evaporation. Moreover, the seasonal variations in soil hydraulic parameters were closely linked to changes in the litterfall and terrestrial carbon fluxes over time. Specifically, due to the hysteresis of the transformation from litterfall to soil organic matter, the accumulated litterfall in Hot-dry season can replenish the soil organic matter, resulting in an increase in field capacity and saturated hydraulic conductivity in the Hot-rainy season. However, the intense decomposition of soil organic matter under high temperature in Hot-dry season led to a decrease in field capacity and saturated hydraulic conductivity. This study emphasizes the value of the particle batch smoother algorithm in detecting temporal variations in soil hydraulic parameters within a coevolving soil-vegetation system, thereby contributing to a more comprehensive understanding of the intricate dynamics within the ecohydrological system under a changing environment.

Abstract Acquiring real-time spectral information in point-of-care diagnosis, internet-of-thing, and other lab-on-chip applications require spectrometers with hetero-integration capability and miniaturized feature. Compared to conventional semiconductors integrated by heteroepitaxy, solution-processable semiconductors provide a much-flexible integration platform due to their solution-processability, and, therefore, more suitable for the multi-material integrated system. However, solution-processable semiconductors are usually incompatible with the micro-fabrication processes. This work proposes a facile and universal platform to fabricate integrated spectrometers with semiconductor substitutability by unprecedently involving the conjugated mode of the bound states in the continuum (conjugated-BIC) photonics. Specifically, exploiting the conjugated-BIC photonics, which remains unexplored in conventional lasing studies, renders the broadband photodiodes with ultra-narrowband detection ability, detection wavelength tunability, and on-chip integration ability while ensuring the device performance. Spectrometers based on these ultra-narrowband photodiode arrays exhibit high spectral resolution and wide/tunable spectral bandwidth. The fabrication processes are compatible with solution-processable semiconductors photodiodes like perovskites and quantum dots, which can be potentially extended to conventional semiconductors. Signals from the spectrometers directly constitute the incident spectra without being computation-intensive, latency-sensitive, and error-intolerant. As an example, the integrated spectrometers based on perovskite photodiodes are capable of realizing narrowband/broadband light reconstruction and in-situ hyperspectral imaging.

Dual-wavelength lasers are gaining importance for photonic applications. In this work the authors demonstrate that by incorporating a lanthanidedoped material into the size-mismatched coupled microcavities, it is possible to achieve laser switch with high uniformity, long-term stability, and an extremely wide spectral range up to 300 nm

Perovskite nanophotonics is a rapidly emerging field that combines research in synthesis of materials with novel properties and in photonics design strategies. Starting from early pioneering works on halide perovskite compounds that showed great potential across optoelectronics and photonics applications, the field is ready to blossom by combining recent advances in synthetic material design, the development of bottom-up or top-down nanostructuring approaches and new concepts in nanohophotonic engineering of light matter interaction at the nanoscale, with a chance of having real impact on current and future technologies. This roadmap is a collective outlook from pioneers in the field of perovskite nanophotonics that encompasses a number of the emerging research areas with the aim of identifying current and future challenges and highlighting the most promising research directions. It will be of interest and serve as a reference to a wide audience of physicists, chemists and engineers with interest in perovskite nanophotonics.

Plants deploy various ecological strategies in response to environmental heterogeneity. In many forest ecosystems, plants have been reported to have notable inter- and intra-specific trait variation, as well as clear phylogenetic signals, indicating that these species possess a degree of phenotypic plasticity to cope with habitat variation in the community. Savanna communities, however, grow in an open canopy structure and exhibit little species diversification, likely as a result of strong environmental stress. In this study, we hypothesized that the phylogenetic signals of savanna species would be weak, the intraspecific trait variation (ITV) would be low, and the contribution of intraspecific variation to total trait variance would be reduced, owing to low species richness, multiple stresses and relatively homogenous community structure. To test these hypotheses, we sampled dominant woody species in a dry-hot savanna in southwestern China, focusing on leaf traits related to adaptability of plants to harsh conditions (year-round intense radiation, low soil fertility and seasonal droughts). We found weak phylogenetic signals in leaf traits and low ITV (at both individual and canopy-layer levels). Intraspecific variation (including leaf-, layer- and individual-scales) contributed little to the total trait variance, whereas interspecific variation and variation in leaf phenology explained substantial variance. Our study suggests that intraspecific trait variation is reduced in savanna community. Furthermore, our findings indicate that classifying species by leaf phenology may help better understand how species coexist under similar habitats with strong stresses.

Though broadband achromatic metalens are attractive for biological applications, existing metalenses show limited performance in the biological imaging window. Here, the authors report high-efficiency broadband achromatic metalens featuring record-high aspect ratio titanium dioxide metasurfaces.

Depression in childhood negatively affects the growth and development, school performance, and peer or family relationships of affected children, and may even lead to suicide. Despite this, its etiology and pathophysiology remain largely unknown. Increasing evidence supports that gut microbiota plays a vital role in the development of childhood depression. However, little is known about the underlying mechanisms, as most clinical studies investigating the link between gut microbiota and depression have been undertaken in adult cohorts. In present study, a total of 140 school-aged children (6–12 years) were enrolled, including 92 with depression (male/female: 42/50) and 48 healthy controls (male/female: 22/26) from Lishui, Zhejiang, China. Illumina sequencing of the V3–V4 region of the 16S rRNA gene was used to investigate gut microbiota profiles while Bio-Plex Pro Human Cytokine 27-plex Panel was employed to explore host immune response. We found that, compared with healthy controls, children with depression had greater bacterial richness and altered β-diversity. Pro-inflammatory genera such as Streptococcus were enriched in the depression group, whereas anti-inflammatory genera such as Faecalibacterium were reduced, as determined by linear discriminant analysis effect size. These changes corresponded to altered bacterial functions, especially the production of immunomodulatory metabolites. We also identified the presence of a complex inflammatory condition in children with depression, characterized by increased levels of pro-inflammatory cytokines such as IL-17 and decreased levels of anti-inflammatory cytokines such as IFN-γ. Correlation analysis demonstrated that the differential cytokine abundance was closely linked to changes in gut microbiota of children with depression. In summary, key functional genera, such as Streptococcus and Faecalibacterium, alone or in combination, could serve as novel and powerful non-invasive biomarkers to distinguish between children with depression from healthy ones. This study was the first to demonstrate that, in Chinese children with depression, gut microbiota homeostasis is disrupted, concomitant with the activation of a complex pro-inflammatory response. These findings suggest that gut microbiota might play an important role in the pathogenesis of depression in school-aged children, while key functional bacteria in gut may serve as novel targets for non-invasive diagnosis and patient-tailored early precise intervention in children with depression.

Abstract Optical microcavities play a significant role in the study of classical and quantum chaos. To date, most experimental explorations of their internal wave dynamics have focused on the properties of their inputs and outputs, without directly interrogating the dynamics and the associated mode patterns inside. As a result, this key information is rarely retrieved with certainty, which significantly restricts the verification and understanding of the actual chaotic motion. Here we demonstrate a simple and robust approach to directly and rapidly map the internal mode patterns in chaotic microcavities. By introducing a local index perturbation through a pump laser, we report a spectral response of optical microcavities that is proportional to the internal field distribution. With this technique, chaotic modes with staggered mode spacings can be distinguished. Consequently, a complete chaos assisted tunneling (CAT) and its time-reversed process are experimentally verified in the optical domain with unprecedented certainty.

A special type of laser enables precise and continuous tuning of spatial coherence, suppressing the coherent artifacts (i) of a meta-hologram while maintaining image sharpness, emission spectrum and power (ii).

Abstract The continuous supersymmetry transformation is applied to the silicon waveguides, and the guidance and conversion of any mode in a wide spectral range are successfully realized in experiments. This proves its great potential in optical spatial mode modulation and space division multiplexing in optical communication.

Schizophrenia (SZ) is a severe neuropsychiatric disorder with largely unknown etiology and pathogenesis. Mounting preclinical and clinical evidence suggests that the gut microbiome is a vital player in SZ. However, the gut microbiota characteristics and its host response in elderly SZ patients are still not well understood. A total of 161 samples was collected, including 90 samples from elderly SZ patients and 71 samples from healthy controls. We explored the gut microbiota profiles targeting the V3–V4 region of the 16S rRNA gene by MiSeq sequencing, and to analyze their associations with host immune response. Our data found that bacterial β-diversity analyses could divide the SZ patients and healthy controls into two different clusters. The Linear discriminant analysis Effect Size (LEfSe) identified the compositional changes in SZ-associated bacteria, including Faecalibacterium, Roseburia, Actinomyces, Butyricicoccus, Prevotella and so on. In addition, the levels of pro-inflammatory cytokines such as IL-1β were greatly increased in SZ patients while the levels of anti-inflammatory cytokines such as IFN-γ were markedly decreased. Correlation analysis suggested that these bacteria contributed to immune disturbances in the host that could be used as non-invasive biomarkers to distinguish the SZ patients from healthy controls. Moreover, several predicted functional modules, including increased lipopolysaccharide biosynthesis, folate biosynthesis, lipoic acid metabolism, and decreased bile acid biosynthesis, fatty acid biosynthesis in SZ-associated microbiota, could be utilized by the bacteria to produce immunomodulatory metabolites. This study, for the first time, demonstrated the structural and functional dysbiosis of the fecal microbiota in Chinese elderly SZ patients, suggesting the potential for using gut key functional bacteria for the early, non-invasive diagnosis of SZ, personalized treatment, and the development of tailor-made probiotics designed for Chinese elderly SZ patients.

Silicon photonic optical phased arrays are promising solutions for solid-state LIDAR. But the nonlinear absorption significantly saturates the optical power in the waveguides at 1.5-μm wavelengths. Besides, the high refractive index contrast of silicon grating exhibits a strong diffraction strength of the antenna, which results in a limited aperture of the device. These ultimately place a limit on the detection accuracy and reach. Here, a shallow etched two-dimensional subwavelength grating structure is proposed to improve the efficiency and aperture of the waveguide antenna. A reduction of diffraction strength is achieved via nanohole structure instead of conventional grating lines. Thus, a millimeter-long optical antenna is demonstrated with a peak efficiency of 71%. The far-field diffracted beam width of 0.035° and vertical field-of-view of 17.5° are achieved within 100 nm wavelengths range from 1.95 μm to 2.05 μm. The operation at 2-μm waveband also guarantees better eye-safety and significantly reduces the nonlinear absorption in silicon waveguide compared with conventional 1.5-μm band.

Here, the authors demonstrate a re-programmable metasurface that can produce arbitrary holographic images for optical encryption. The encrypted information is divided into two matrices and defined to the incident laser to produce arbitrary holographic images.

Integration of III-V semiconductor microlasers into modern Si or Si3N4 based photonic integrated circuits remains a challenge. Here, the authors demonstrate a perovskite vortex microlaser with highly directional outputs and well-controlled topological charges that is highly compatible with most materials.

Here, the authors fabricate a metasurface with high brightness and large gamut structured colors by combining a silicon metasurface with a refractive index matching layer. The experimentally demonstrated gamut is 181.8% of sRGB, 135.6% of Adobe RGB, and 97.2% of Rec.2020.

Study Region: Lancang River Basin (upper reaches of the Mekong River basin within China). Study Focus: Complex terranes and diverse climates are a bottleneck for understanding the hydrology of rivers originating from the Tibetan Plateau. This study deals with the impact of climate change on water storage in the Lancang River Basin, which is governed by the South Asian monsoon system. We evaluated the spatiotemporal distribution of multi-source precipitation, evapotranspiration, and terrestrial water storage (TWS) to understand the hydrological system in the region. We provide evidence of climate change impacts on TWS and basin discharge over an upstream region of the transboundary river system. New Hydrological Insights for the Region: The Five Gravity Recovery and Climate Experiment (GRACE) products and Global Land Data Assimilation System (GLDAS) TWS display analogous seasonal distribution, even though the amounts differ between them. The GRACE and GLDAS TWS exhibited a significant negative trend in the basin from 2002 to 2016. However, the Center for Space Research (CSR-M) at the University of Texas and the Jet Propulsion Laboratory (JPL-M) mascon solutions concede more severe and much wider TWS reduction than the three spherical harmonic (SH) solutions. In addition, a downward trend was observed for basin discharge over 15 years as a response to climate change (decreased precipitation and increased evapotranspiration). Furthermore, we identified a 2-month time lag between precipitation and TWS, which could be a response to climatic factors along with aquifer properties in a karst dominated region.

On-chip mode-division multiplexing has many challenges including crosstalk, losses, and footprint. Here the authors use a nanohole metastructure to create multiplexed bends and crossings for photonic data communications circuit routing with high density that combats these challenges.

Lead halide perovskites attract high interest as semiconductor materials but their exceptional nonlinear properties have not been fully exploited. Here Fan et al. demonstrate third-order harmonic generation and 60-fold enhanced three-photon luminescence, enabling optical encoding applications.

Lead halide perovskite lasers have great potential as microscale organic light sources, but dynamic tuning has yet to be achieved. Here, Zhang, Fan et al. investigate how nonlinear modal interactions enable ultrafast mode switching with crossgain saturation.

We demonstrate the absorption-based fiber humidity sensors working near 1950 nm wavelength which is a strong water absorption peak. No additional coating of humidity-sensitive material is needed for the proposed relative humidity (RH) fiber sensors. Two sensor structures including a taper fiber and a microfiber knot resonator are fabricated. For the taper fiber sensor, upto 0.18 mW/% RH sensitivity has been achieved via direct power measurement. For the fiber knot sensor, the RH variations induce both extinction ratio change and wavelength shift. The optical spectra of the fiber knot resonator under different RH are measured, and the extinction ratio and wavelength shift sensitivity are measured to be 0.034 dB/% RH and 10 pm/% RH, respectively. The response time for the tapered fiber is 1.13 s for RH increasing from 28.6% to 53.4% and 2.27 s for the reverse operation. The microfiber knot sensor can respond in 0.8 and 1.55 s accordingly. The sensor performance for the two structures is also investigated under different temperatures from 25 °C to 45 °C and the results indicate negligible impact from the temperature variations. We believe the simple fabrication and low cost of the sensor will make it potential and practical for the RH measurement.

Due to their single-crystalline structures, comparatively large aspect ratios, tight optical confinement and smooth surfaces, nanowires have increasingly attracted research interests for both fundamental studies and technological applications in on-chip photonic devices. This class of nanostructures typically have cross-sections of 2~200 nm and lengths upwards of several micrometers, allowing for the bridging of the nanoscopic and macroscopic world. In particular, the lasing behaviors can be established from a nanowire resonator with positive feedback via end-facet reflection, making the nanowire a promising candidate in the next generation of optoelectronics. Consequently, versatile nanowire-based devices ranging from nanoscale coherent lasers, optical sensors, waveguides, optical switching, and photonic networks have been proposed and experimentally demonstrated in the past decade. In this article, significant progresses in the nanowire fabrication, lasers, circuits, and devices are reviewed. First, we focus on the achievements of nanowire synthesis and introduce the basics of nanowire optics. Following the cavity configurations and mode categories, then the different light sources consisting of nanowires are presented. Next, we review the recent progress and current status of functional nanowire devices. Finally, we offer our perspective of nanowires regarding their challenges and future opportunities in photonic circuits.

Ongoing climate changes reportedly affect the potential distribution and carbon sequestration potential (CSP) of forest vegetation. The combined effects of increasing temperature and decreasing precipitation on these features of forest vegetation are poorly understood. In this study, classification and regression tree (CART) models were used to predict the potential distribution and estimate the CSP of forest vegetation in Yunnan Province, Southwest China, under different simulation scenarios. The minimum temperature of the coldest month (TMW) was the main factor limiting the suitable habitat of all forest vegetation types except for warm–temperate coniferous (WTC) forests. When the temperature increased by 1 °C and the precipitation decreased by 20%, the potential distribution area of the 7 forest vegetation types decreased by 12.41% overall. The potential distribution of WTC forests was the least sensitive to temperature increases and precipitation decreases. The CSP of vegetation was higher (1187.69 TgC) under the constant temperature and 10% precipitation decrease scenario than the CSP of vegetation under the 2 °C temperature increase and constant precipitation scenario (647.24 TgC). Specifically, the highest CSP (1337.88 TgC) was observed under the 1 °C temperature increase and 10% precipitation decrease scenario, and the lowest (617.91 TgC) occurred under the constant temperature and 20% precipitation decrease scenario. In summary, the forest vegetation in Yunnan Province has a high CSP under climate change, and the combined effect of increased temperature and decreased precipitation can increase the CSP of forest vegetation in Yunnan Province. This finding is important for improving scientific decision making and policy planning.

Evapotranspiration (ET) plays a crucial role in water balance within the global hydrological cycle. Timely assessment of ET products can provide the scientific basis for quantitative analysis of hydrological cycle processes and water resources assessment. In this paper, four high spatial resolution remote sensing ET products—the Moderate-resolution Imaging Spectroradiometer global terrestrial evapotranspiration product (MOD16), the ET product based on Penman–Monteith–Leuning equation version 2 (PML-V2), the ET product based on the Breathing Earth System Simulator (BESS) and the ET product of the Global LAnd Surface Satellite (GLASS)—were firstly assessed using the eddy covariance (EC) of different vegetation types in the Lancang–Mekong River Basin (LMRB). To fully assess the performances of these four products, spatiotemporal inter-comparisons and literature comparisons were also conducted across different climatic zones. The results are summarized as follows: (1) MOD16 does not perform well as compared to the other three products, with its Root Mean Square Error (RMSE) being higher than GLASS, PML-V2 and BESS, which are approximately 0.47 mm/8-day, 0.66 mm/8-day, and 0.90 mm/8-day, respectively; (2) the performance of each product varies across different vegetation types, and even within the same climate zone. PML-V2 performs best in evergreen broadleaf forests, BESS performs best in deciduous broadleaf forests and croplands, and GLASS performs best in shrubs, grasslands and mixed vegetation; (3) each product can well reflect the spatial difference brought by topography, climate and vegetation over the entire basin but all four ET products do not show either a consistent temporal trend or a uniform spatial distribution; (4) ET ranges of these four products over LMRB are consistent with previous literature in evergreen broadleaf forests, deciduous broadleaf forests, needleleaf forests and mixed forests in other regions with the same climate zones, but they show great differences in croplands, grasslands and shrubs. This study will contribute to improving our understanding of these four ET products in the different climatic zones and vegetation types over LMRB.

We demonstrate integrated 1 × 4 power splitters at 2-μm spectral range with arbitrary power-splitting ratios. The devices are based on digital meta-structures that are designed by algorithm. Four devices with split ratios of 1:1:1:1, 2:2:1:1, 2:2:2:1, and 4:3:2:1 are inversely designed to conceptually prove the capability of arbitrary split ratios. Up to four design objectives including both efficiency and power ratios between the four outputs of each device have been jointly optimized. The total transmission efficiencies of all the algorithm-optimized splitters are above 80%, which is predicted by simulations. The power ratios are well consistent with the design targets as well. Then, the devices are fabricated on silicon-on-insulator platform with the device footprint of only 3.6 μm × 3.6 μm. The fabricated splitters are characterized at wavelength range from 1945 to 1975 nm. The total transmission efficiencies of all the splitters are measured to be higher than 70%, and the power ratios agree with the simulation results.

Advanced modulation formats with intensity modulation and direct detection (IM/DD) have shown promise in a short-reach optical communication system like data center interconnect. However, the conventional fiber transmission spectral window is mostly located at 850, 1310, and 1550 nm. Here, we experimentally demonstrated an amplifierless IM/DD link at the 2-μm spectral band. The signal is encoded with pulse amplitude modulation (PAM) and 3-D carrier-less amplitude and phase modulation (3-D-CAP). The encoded signal is transmitted through a 100 m-long solid-core fiber designed for single mode at 2-μm. We achieve a transmission with bit-rate of 40 Gbit/s using PAM-4 and 24 Gbit/s using CAP16. The measured bit error rates of both formats are below the forward error correction (FEC) limit of 3.8 × 10-3. This study is the first demonstration of PAM4 and CAP transmission at 2-μm, and the results show a significant potential of advanced modulation for 2-μm optical communication.

As one of the important factors affecting plant productivity and plant distribution, temperature also affects the physiological and ecological characteristics of plants to a large extent. We report canopy leaf temperature distribution over a 36 m tall primary tropical rain forest and samplings of 28 tree species in SW China by means of two high resolution thermal cameras (P25, Flir systems, Wilsonville, OR, USA). The leaf temperature of dominant tree Species Pometia tomentosa was the highest (31.8 °C), 10.2 °C higher than that of tree species Mezzettipsis creaghii (21.6 °C). The mean leaf to air temperature difference (Tc–Ta) of Pometia tomentosa was the highest (6.4 K), the second highest was Barringtonia pendula (6.1 K), and Mezzettipsis creaghii had the lowest (Tc–Ta) (1.9K). (Tc–Ta) of tree species with smaller leaves and larger stomatal conductance was lowly sensitive to climate factors. Leaf size and stomatal conductance together decided the effect of climate change to (Tc–Ta) of the different tree species. We have shown that the composition of tree species in tropical rain forest areas is important to the climate through our research.

This paper reports the finding of unstable limit cycles and singular attractors in a two-dimensional dynamical system consisting of an inductor and a bistable bi-local active memristor. Inspired by the idea of nested intervals theorem, a new programmable scheme for finding unstable limit cycles is proposed, and its feasibility is verified by numerical simulations. The unstable limit cycles and their evolution laws in the memristor-based dynamic system are found from two subcritical Hopf bifurcation domains, which are subdomains of twin local activity domains of the memristor. Coexisting singular attractors are discovered in the twin local activity domains, apart from the two corresponding subcritical Hopf bifurcation domains. Of particular interest is the coexistence of a singular attractor and a period-2 or period-3 attractor, observed in numerical simulations.

The distribution of forest vegetation and forest carbon sequestration potential are significantly influenced by climate change. In this study, a map of the current distribution of vegetation in Yunnan Province was compiled based on data from remote sensing imagery from the Advanced Land Observing Satellite (ALOS) from 2008 to 2011. A classification and regression tree (CART) model was used to predict the potential distribution of the main forest vegetation types in Yunnan Province and estimate the changes in carbon storage and carbon sequestration potential (CSP) in response to increasing temperature. The results show that the current total forest area in Yunnan Province is 1.86 × 107 ha and that forest covers 48.63% of the area. As the temperature increases, the area of forest distribution first increases and then decreases, and it decreases by 11% when the temperature increases from 1.5 to 2 °C. The mean carbon density of the seven types of forest vegetation in Yunnan Province is 84.69 Mg/ha. The total carbon storage of the current forest vegetation in Yunnan Province is 871.14 TgC, and the CSP is 1100.61 TgC. The largest CSP (1114.82 TgC) occurs when the temperature increases by 0.5 °C. Incremental warming of 2 °C will sharply decrease the forest CSP, especially in those regions with mature coniferous forest vegetation. Semi-humid evergreen broad-leaved forests were highly sensitive to temperature changes, and the CSP of these forests will decrease with increasing temperature. Warm-hot coniferous forests have the greatest CSP in all simulation scenarios except the scenario of a 2 °C temperature increase. These results indicate that temperature increases can influence the CSP in Yunnan Province, and the largest impact emerged in the 2 °C increase scenario.