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This study was performed to determine the effect of human umbilical cord mesenchymal stem cells (hucMSCs) treatment on pulmonary fibrosis and investigate the circFOXP1-mediated autophagic mechanism of hucMSCs treatment. Pulmonary fibrosis models were established by spraying bleomycin in mice and TGF-ß1 treatment of MRC-5 cells. Results showed that hucMSCs were retained in lung and hucMSCs treatment alleviated pulmonary fibrosis. Morphological staining indicated that hucMSCs-treated mice had thinner alveolar walls, effectively improved alveolar structure, significantly reduced alveolar inflammation, and decreased collagen deposition than control mice. Fibrotic proteins, including vimentin, a-SMA, collagens I and III, and the differentiation-related protein S100 calcium-binding protein A4 was reduced considerably in the hucMSCs-treated group. The mechanistic study revealed that the inhibition of hucMSCs treatment on pulmonary fibrogenesis depended on downregulating circFOXP1, in which hucMSCs treatment promoted circFOXP1-mediated autophagy process via blocking the nuclear human antigen R (HuR) translocation and promoting the HuR degradation, leading to a marked decrease in autophagy negative regulators EZH2, STAT1, and FOXK1. In conclusion, hucMSCs treatment significantly improved pulmonary fibrosis by downregulating the circFOXP1-HuR-EZH2/STAT1/FOXK1 autophagic axis. hucMSCs can act as an effective treatment for pulmonary fibrosis.Graphical Abstract

In order to extract polyester (PET) and microcrystalline cellulose (MCC) from waste polyester-cotton blended fabrics (WPBFs), a deep eutectic solvent (DES) synthesized from choline chloride (ChCl) and p-toluenesulfonic acid (TsOH) was developed as the treatment solvent. The orthogonal experiment method was designed to explore the optimal conditions for the separation process (75 vol.% DES, 110 °C, 10 min). The PET component was easily separated after the degradation of the cotton component from WPBFs. Recycled and untreated products were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), and tensile tests. The results showed that the yields of recycled PET (R-PET) and MCC were 99.20, and 69.46%, respectively. Furthermore, glucose was also obtained with a yield of 38.91%. In particular, there was no significant deterioration in the properties of R-PET. MCC was obtained with crystallinity of 86.46%, which can be applied as the raw material of MCC in various industries. Moreover, the lifetime of the recyclable DES (ChCl/TsOH) showed that its treatment efficiency can still meet the requirement after the fifth recycling.

The smaller size fraction of plastics may be more substantially existing and detrimental than larger-sized particles. However, reports on nanoplastics (NPs), especially their airborne occurrences and potential health hazards to the respiratory system, are scarce. Previous studies limit the understanding of their real respiratory effects, since sphere-type polystyrene (PS) nanoparticles differ from NPs occurring in nature with respect to their physicochemical properties. Here, we employ a mechanical breakdown method, producing NPs directly from bulk plastic, preserving NP properties in nature. We report that among four relatively high abundance NP materials PS, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polyethylene (PE) with a size of 100 nm, PVC induced slightly more severe lung toxicity profiles compared to the other plastics. The lung cytotoxicity of NPs is higher than that of commercial PS NPs and comparable to natural particles silicon dioxide (SiO2) and anatase titanium dioxide (TiO2). Mechanistically, BH3-interacting domain death agonist (Bid) transactivation-mediated mitochondrial dysfunction and nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy or ferroptosis are likely common mechanisms of NPs regardless of their chemical composition. This study provides relatively comprehensive data for evaluating the risk of atmospheric NPs to lung health.

Variations in surface air temperature on the eastern Tibetan Plateau (TP‐SAT) during boreal summer, related to Barents‐Kara spring sea ice and summer Arctic Oscillation (AO), are investigated using observations and ERA‐5 reanalysis data during 1979–2018. Results show that the primary mode of summer eastern TP‐SAT (SAT_EOF1) is characterized by the consistent warming pattern with larger values over the northeastern TP, which is linked with the anticyclonic circulation located in the northeastern flank of the TP. This anticyclone enhances westward water vapor transport, warm temperature advection, and causes descending over the eastern TP, Descending further results in deceased middle level cloud cover and increased solar radiation, accordingly, favoring the eastern TP warming. Further statistical analysis reveals a robust connection between Barents‐Kara spring sea ice, summer AO and SAT_EOF1. Moreover, anticyclonic anomaly located in the northeastern region of the TP acts as an important driver of this consistent warming pattern over the eastern TP, which is modulated by two individual Rossby wave trains from the northwestern Russia and northwestern Atlantic. The spring sea ice in Barents‐Kara could cause decreased precipitation and reduced soil moisture in northwestern Russia during following summer, which further induces the Eurasian‐like teleconnection and affects the anticyclonic anomaly situated in the northeastern flank of the TP, thereby favoring eastern TP warming. In addition, from northwestern Atlantic to northeastern region of the TP, the Rossby wave train is mainly affected by summer AO, with positive AO causing anticyclonic anomaly over northeast of the TP, thus contributing to the TP warming. Tibetan Plateau (TP) is a region that is easily affected by the global warming. Numerous studies have extensively documented a remarkable warming trend in the TP during boreal summer, particularly noticeable since the late 1990s. Despite these valuable observations, its mechanisms are not yet clear. In this study, we found that the anticyclonic anomaly over the northeast of TP is a crucial system affecting eastern TP warming in boreal summer. This anticyclonic anomaly leads to the strengthened westward water vapor transport and causes descending over the eastern TP. Descending, in turn, results in the reduction of middle level cloud cover and increased solar radiation. Further analysis indicated that this anomalous anticyclone is mainly modulated by two individual wave trains from the northwestern Russia and northwestern Atlantic, respectively. From northwestern Atlantic to northeastern flank of the TP, the wave train is mainly affected by the summer AO, and another is mainly driven by the spring Barents‐Kara sea ice. Those two factors account for about 36% of the summer eastern TP warming. Anticyclonic anomaly located in the northeastern flank of the TP favors the eastern TP warmingSpring Barents‐Kara sea ice could affect this anticyclone through its influences on summer soil moisture over northwestern RussiaThis anticyclone is also modulated by the wave train from northwestern Atlantic, which is mainly affected by Arctic Oscillation Anticyclonic anomaly located in the northeastern flank of the TP favors the eastern TP warming Spring Barents‐Kara sea ice could affect this anticyclone through its influences on summer soil moisture over northwestern Russia This anticyclone is also modulated by the wave train from northwestern Atlantic, which is mainly affected by Arctic Oscillation

A series of acridines were designed and synthesized for the development of effective inhibitors for mild steel corrosion in 1 M HCl solution, in which the halogen-substituted acridines showed better inhibitive performance than the nonhalogen-substituted acridines. The corrosion protection properties of the halogen-substituted acridines, including 2-chloro-9-phenylacridine (CPA), 2-chloro-9-(2-fluorophenyl)acridine (CFPA), and 2-bromo-9-(2-fluorophenyl)acridine (BFPA), were further investigated using weight loss test and electrochemical techniques. The results indicated the halogen-substituted acridines have excellent inhibitiion performance, and these acridines act as mixed-type inhibitors with predominant cathodic effectiveness. Adsorption of acridines on a mild steel surface obeyed the Langmuir adsorption isotherm. The adsorption of the inhibitor molecules on the steel surface was further supported by scanning electron microscopy (SEM), scanning electrochemical microscopy (SECM), and FTIR spectroscopy. The inhibition mechanism of the investigated halogen-substituted acridines was derived using DFT-based quantum chemical calculations for their neutral as well as protonated forms. Both experimental and DFT studies suggested that the inhibition efficiency of three halogen-substituted acridines followed the order of η(BFPA) > η(CFPA) > η(CPA).

The intraseasonal variation of the Tibetan Plateau summer monsoon (TPSM) during 1979–2011 is investigated. The TPSM shows a dominant quasi‐biweekly oscillation (QBWO) in most summer seasons, and its active/break phases are closely related to more/less precipitation over the Tibetan Plateau. We suggest that the TPSM QBWO is associated with a southeastward propagating nonstationary wave train in the middle and upper troposphere. It shows equivalent barotropic vertical structures over the midlatitudes and a baroclinic structure over the eastern Tibetan Plateau. Wave activity flux analysis indicates that it originates from northern Europe, which is an active center of the summertime Arctic Oscillation (AO). The AO also shows significant QBWO signals and leads TPSM QBWO by about 13 days. Phase composite and wave activity flux analyses of AO QBWO confirmed that the wave train influences TPSM QBWO, suggesting that AO plays an important role in the TPSM on a 10‐ to 20‐day timescale. The intraseasonal variation of the Tibetan Plateau summer monsoon (TPSM) during 1979–2011 is investigated. We suggest that TPSM shows a dominant quasi‐biweekly oscillation (QBWO) in most summer seasons and it is associated with a southeastward propagating nonstationary wave train in the middle and upper troposphere. Wave activity flux analysis indicates that the wave train originates from northern Europe, which is an active center of the summertime Arctic Oscillation (AO). The AO also shows significant QBWO signals and leads TPSM QBWO by about 13 days. Phase composite and wave activity flux analyses of AO QBWO confirmed that the wave train influences TPSM QBWO, suggesting that AO plays an important role in the TPSM on a 10‐ to 20‐day timescale. It is more complicated to understand wave activities of the midlatitudes than along the equator, and at present the related studies are limited. The results of this paper are important to understand the weather and climate of Tibetan Plateau and its linkages to the wave train in the midlatitudes associated with the summer AO. This article provides a basic reference for the study on the intraseasonal oscillation over the midlatitudes and Tibetan Plateau area. The Tibetan Plateau summer monsoon (TPSM) has a dominant quasi‐biweekly oscillation (QBWO) in most summer seasonsThe TPSM QBWO is associated with a southeastward propagating nonstationary wave train originating from northern EuropeNorthern Europe is an active center of the summertime Arctic Oscillation, and the Arctic Oscillation wave train contributes to the TPSM QBWO

The magnitude and spatial pattern of anomalous net biome exchange (NBE) induced by the 2015/16 El Niño over Amazonian rainforests remain uncertain. We here investigated them using multi‐model posterior NBE products in the Orbiting Carbon Observatory‐2 (OCO‐2) version 10 modeling intercomparison project. Results suggest that relative to the annual NBE average in 2017/18, larger anomalous carbon release occurred over the eastern and northern Amazonian rainforests in 2015/16, with a total flux of approximately 0.4 PgC yr−1after assimilating satellite‐observed column CO2concentrations (XCO2) over land. We further find that this anomalous spatial pattern was predominantly determined by soil dryness, while the total positive NBE anomaly was dominated by higher temperature with its contribution of approximately 68～70%. We believe that atmospheric inversions assimilating more satellite‐observed XCO2in future can provide us more comprehensive understanding how Amazonian rainforests cope with the abiotic stresses induced by El Niño events. Interannual variability of carbon flux associated with its drivers over Amazonian rainforests are not fully understood. We here used several groups' newly available posterior CO2flux estimates to comprehensively investigate the net carbon flux anomaly induced by the 2015/16 extreme El Niño. A total net carbon flux anomaly of approximately 0.4 PgC yr−1was estimated, which showed larger carbon release over the eastern and northern Amazonian rainforests. We further suggest that although dry conditions greatly shaped the spatial pattern of the anomalous carbon flux, the total carbon flux anomaly was controlled by the higher temperature, with its contribution of approximately 68∼70%. Net biome exchange (NBE) anomalies over Amazonian rainforests induced by the 2015/16 El Niño were investigated based on multiple atmospheric inversionsThe spatial pattern of NBE anomaly was regulated by soil water with larger anomalies over the eastern and northern Amazonian rainforestsThe total NBE anomaly was estimated at about 0.4 PgC yr−1in 2015/16 relative to the average in 2017/18, dominated by higher temperature Net biome exchange (NBE) anomalies over Amazonian rainforests induced by the 2015/16 El Niño were investigated based on multiple atmospheric inversions The spatial pattern of NBE anomaly was regulated by soil water with larger anomalies over the eastern and northern Amazonian rainforests The total NBE anomaly was estimated at about 0.4 PgC yr−1in 2015/16 relative to the average in 2017/18, dominated by higher temperature

The 2019 extreme positive Indian Ocean dipole drove climate extremes over Indian Ocean rim countries with unclear carbon‐cycle responses. We investigated its impact on net biome productivity (NBP) and its constituent fluxes, using the Global Carbon Assimilation System (GCASv2) product, process‐based model simulations from TRENDYv9, and satellite‐based gross primary productivity (GPP). By distinguishing two separate regions, the India‐Africa and Asia‐Pacific, GCASv2 indicated enhanced terrestrial carbon uptake of 0.23 ± 0.20 PgC and release of 0.38 ± 0.15 PgC, respectively, during September–December (SOND) 2019. These NBP anomalies had comparable magnitudes to those following the 2015 extreme El Niño which, however, caused the consistent carbon release in both regions. The TRENDYv9 model ensemble confirmed these NBP responses, albeit with smaller magnitudes. These regional NBP anomalies were related to soil moisture variations with a dominant role of GPP. Understanding the impact of IOD provides new insights into mechanisms driving interannual variations in regional carbon cycling. The extreme Indian Ocean Dipole (IOD) can drive climate extremes, such as floods, heatwaves, droughts, and wildfires, over the Indian Ocean rim countries. However, responses of regional terrestrial carbon cycling to IOD remained unclear. We used the net biome productivity (NBP) from an atmospheric inversion and multiple terrestrial biosphere models to demonstrate an enhanced terrestrial carbon uptake and release over the India‐Africa and Asia‐Pacific regions, respectively, during the extreme positive IOD (September–December) in 2019. These IOD‐induced regional NBP anomalies showed comparable magnitudes but different patterns to those following the 2015 extreme El Niño. Along with the more frequent extreme IOD under future greenhouse warming, IOD will be an important mechanism driving interannual variations in regional carbon cycling. The 2019 extreme positive Indian Ocean Dipole caused the enhanced land carbon uptake over India‐Africa and release over Asia‐Pacific during September–DecemberThese regional net biome productivity (NBP) anomalies were closely related to soil moisture variations with a dominant role of gross primary productivityThese Indian Ocean Dipole‐induced regional NBP anomalies showed comparable magnitudes but different patterns to those following the 2015 extreme El Niño The 2019 extreme positive Indian Ocean Dipole caused the enhanced land carbon uptake over India‐Africa and release over Asia‐Pacific during September–December These regional net biome productivity (NBP) anomalies were closely related to soil moisture variations with a dominant role of gross primary productivity These Indian Ocean Dipole‐induced regional NBP anomalies showed comparable magnitudes but different patterns to those following the 2015 extreme El Niño

The ultralong time (a few hours) response properties of magnetic fluid using etched optical fiber are visualized and investigated experimentally. The operating structure is made by injecting magnetic fluid into a capillary tube that contains etched single-mode fiber. An interesting extreme asymmetry is observed, in which the transmitted light intensity after the etched optical fiber cannot reach the final steady value when the external magnetic field is turned on (referred to as the falling process), while it can reach the stable state quickly once the magnetic field is turned off (referred to as the rising process). The relationship between the response times/loss rates of the transmitted light and the strength of the applied magnetic field is obtained. The physical mechanisms of two different processes are discussed qualitatively.

Increasing circular RNAs (circRNAs) are involved in the progression of idiopathic pulmonary fibrosis (IPF). However, circRNA biogenesis and circRNA-mediated crosstalk between mechanical stiffness and biochemical signals in IPF remain obscure. In this study, a novel circRNA-ankyrin repeat domain 42 (ANKRD42) from peripheral blood of patients with IPF, which participated in pulmonary fibrosis through the close communication of mechanical stiffness and biochemical signals, was identified. Mechanistic studies revealed that the heterogeneous nuclear ribonucleoprotein L (hnRNP L) activated the circANKRD42 reverse splicing biogenesis. The biogenetic circANKRD42 sponged miR-324-5p to promote the AJUBA expression, which blocked the binding between phosphorylated yes-associated protein 1 (YAP1) and large tumor suppressor kinase 1/2 (LATS1/2), leading to increased YAP1 entering the nucleus. circANKRD42 also sponged miR-136-5p to promote the YAP1 translation. Accumulating YAP1 in nucleus bound to TEAD, which initiated the transcription of genes related to mechanical stiffness. Finally, the therapeutic effect of circANKRD42 was evaluated in mice and the association between circANKRD42 and clinicopathological features was analyzed in IPF patients. Our findings supported that circANKRD42 is a promising biomarker and a potential therapeutic target related to cytoskeleton tension for IPF treatment.

We propose a new design of bulk glass optical current sensor immune to reflection phase shift, in which an annular graded-index magneto-optical glass with a small prism is used as a sensing head, and the inner and outer layers of the glass possess gradient refractive indices, while the center layer is uniform. Our theoretical analyses show that under certain conditions the light beam will no longer reach the interface between the magneto-optical glass and air during the propagation in the sensing head. Therefore the reflection phase shift could be avoided essentially, resulting in dramatic enhancement of the sensitivity. The influences of the geometrical parameters on the beam traces and the effective range of the initial angle are specified by numerical simulations.

Precipitation, a key determinant of soil moisture variations, plays an important role in regulating terrestrial carbon fluxes on multiple time scales. It is a critical meteorological forcing to drive terrestrial biosphere model (TBM), however, with a large uncertainty itself. We here investigated to what extent precipitation alone can cause uncertainties of model‐simulated carbon flux from terrestrial ecosystems to atmosphere (FTA), based on eight precipitation products and a TBM, VEGAS. We find that the pattern of uncertainties in simulated FTAobviously differs from the pattern of discrepancies in precipitation, owing to divergent water sensitivities of vegetation over different regions. Globally, the uncertainty in FTAcan be up to approximately 40.73% of the uncertainty in TRENDYv6 multi‐model simulated FTAwhich is caused by model structural and parameter uncertainty. A good linear relationship emerges between global area‐averaged land climatological annual precipitation and simulated total FTAwith the slope of −0.0040 PgC yr−1per mm yr−1(p= 0.03; negative for carbon sink), where 70% is explained by the sensitivity over extra‐tropical Northern Hemisphere (NH). For seasonal cycle, compared to nearly constant inter‐precipitation spreads over tropics plus extra‐tropical southern hemisphere (Trop + SH), uncertainties in corresponding simulated FTAshow obvious seasonal differences with the relatively larger uncertainties in March‐April‐May (MAM) and August‐September‐October (ASO). For interannual variability, uncertainties in simulated total FTAare, albeit smaller, nonnegligible, which are 40.61% (global), 38.17% (Trop + SH), and 29.63% (NH) of the TRENDYv6 inter‐model uncertainty, respectively. Therefore, generating better global precipitation product is important for reducing the uncertainty in simulating terrestrial carbon sinks. Precipitation, a key forcing in terrestrial biosphere model (TBM), has a large uncertainty itself. We here used eight land precipitation products to run TBM VEGAS and explored the resulting uncertainties in simulating carbon flux from terrestrial ecosystems to atmosphere (FTA) on climatology, seasonal cycle, and interannual variability. In climatology, the uncertainty in global FTAinduced by different precipitation can be approximately 40.73% of the uncertainty in TRENDYv6 multi‐model simulations induced by model structural and parameter uncertainty. Furthermore, we find a good linear relationship between global area‐averaged land climatological annual precipitation and simulated total FTA, implying more precipitation over land with stronger carbon sinks, especially over extra‐tropical Northern Hemisphere (NH). For seasonal cycle, uncertainties in simulated FTAover tropics plus extra‐tropical southern hemisphere (Trop + SH) show relatively larger values in March‐April‐May and August‐September‐October. For interannual variability, uncertainties in simulated total FTAare up to 40.61% (global), 38.17% (Trop + SH), and 29.63% (NH) of the TRENDYv6 inter‐model uncertainty, respectively. In general, uncertainty in land precipitation data sets can cause considerable uncertainties in simulating FTA, suggesting the importance of generating the better precipitation product for better simulating the terrestrial carbon sinks. Uncertainties in simulating land‐atmosphere carbon fluxes (FTA) on multiple time scales induced by different precipitation are investigatedUncertainties in climatology and interannual variability of global total FTAare about 41% of uncertainties in TRENDYv6 simulationsA good linear relationship emerges between global area‐averaged land climatological annual precipitation and simulated total FTA Uncertainties in simulating land‐atmosphere carbon fluxes (FTA) on multiple time scales induced by different precipitation are investigated Uncertainties in climatology and interannual variability of global total FTAare about 41% of uncertainties in TRENDYv6 simulations A good linear relationship emerges between global area‐averaged land climatological annual precipitation and simulated total FTA

Grid-based digital elevation data with a spatial resolution of 30 s of latitude or longitude, covering the Hanjiang River basin, were matched spatially with a 1 km × 1 km grid of land use – land cover data generated from remotely sensed data. The ratio of impervious area to subcatchment area (denoted IMP), a parameter in the Xin'anjiang model, can then be extracted directly from the land use – land cover data. Soil free water storage capacity (SM), a sensitive parameter in the Xin'anjiang model, can be obtained for the subcatchment by the relation between SM and the ratio of forest land area to subcatchment area. Thus, in the proposed semidistributed hydrological model, the spatial variability of land surface characteristics is taken into consideration. As a result, the physical meanings of model parameters are so clear that they can be extended from gauged catchments to ungauged catchments according to the land surface characteristics over the catchments. The accuracy of flood forecasting is improved as well. A case study of 24 flood events within the Baohe River, the upper tributary of the Hanjiang River, has shown that constructing the relationship between model parameters and land surface characteristics is an effective way to reduce errors in flood forecasting. In concrete terms, if the result computed by the semidistributed algorithm is compared with the result obtained by the lumped subcatchment algorithm, the Nash–Sutcliffe coefficients of 15 flood events increase, and the relative errors of 22 flood peaks decrease markedly. Also, the sensitivity of SM to flood peak discharge is greater than its sensitivity to the Nash–Sutcliffe coefficient. The semidistributed hydrological model is of practical value to flood forecasting and to the quantitative description of land use – land cover change related to the water cycle. We are convinced that this research is also helpful in the operation of a water supply system for the middle route of the large project involving water transfer from southern to northern China.

Direct ink writing (DIW) of geopolymers with desirable patterns, compositions, and properties holds great promise for sustainable concrete, porous adsorbent, and high-temperature ceramic. However, precisely constructing geopolymers by DIW is subject to the low viscosity of geopolymer inks and the limited choice of alkali metal ions. Here, we realize the production of high-quality geopolymer by adding suitable additives, where the modified Na-, K-, and Cs-based geopolymer inks show high yield stresses of 1002Pa, 1590Pa, and 165Pa, respectively. The optimized rheological properties enable DIW of geopolymers with complex patterns, high spatial resolution, and controllable mechanical properties. Furthermore, we reveal the mechanism underlying the fracture behaviors of the 3D-printed geopolymers combining compression tests, theoretical models, and FEM analysis. Our results pave the way for designing high-quality geopolymer-based materials, which are critical for industrial applications and sustainable development.

We experimentally and theoretically study the abrupt polarization transitions of vector autofocusing Airy beams associated with the spin–orbit interactions. It is shown that when the topological charges of the polarization and the attached spiral phase are equal in number, the local polarizations undergo an abrupt transition from linear to circular polarizations at the focal point, and the associated orbital angular momentum partially converts into the spin of photons. The experimental results are theoretically explained from the far-field properties of the beams in terms of Hankel transformations.

Passive infrared gas imaging systems have been utilized in the equipment leak detection and repair in chemical manufacturers and petroleum refineries. The detection performance mainly relates to the sensitivity of infrared detector, optical depth of gas, atmospheric transmission, wind speed, and so on. Based on our knowledge, the spatial concentration distribution of continuously leaking gas plays an important part in leak detection. Several computational model of gas diffusion were proposed by researchers, such as Gaussian model, BM model, Sutton model and FEM3 model. But these models focus on calculating a large scale gas concentration distribution for a great amount of gas leaks above over 100- meter height, and not applicable to assess detection limit of a gas imaging system in short range. In this paper, a wind tunnel experiment is designed. Under different leaking rate and wind speed, concentration in different spatial positions is measured by portable gas detectors. Through analyzing the experimental data, the two parameters y(x) and z(x) that determine the plume dispersion in Gaussian model are adjusted to produce the best curve fit to the gas concentration data. Then a concentration distribution model for small mount gas leakage in short range is established. Various gases, ethylene and methane are used to testify this model.

As to visualize the leaking gas cloud which is not visible to the naked eyes, three categories of techniques have emerged, Backscatter Absorption Gas Imaging, Passive Thermal Imaging, and Imaging Spectrometer. Among these systems, Signal to Noise Ratio (SNR) is generally used to deduce gas leakage detection limit and leads to several performance evaluation parameters, such as Noise-Equivalent Spectral Radiance and Noise-Equivalent Concentration-Path Length. However, in most cases, measuring the SNR accurately is not accessible and usually needs auxiliary instruments. Therefore, we focus on researching a gas leakage detection model according to the general parameter of a thermal imager, Noise Equivalent Temperature Difference (NETD). Firstly, the Gas Equivalent Blackbody Temperature Difference (GEBTD) is obtained by calculating the attenuated radiation of the On-plume path and that of the Off-plume path respectively. A simplified form of GEBTD was derived by our previous paper, assuming that the work range was short and the affection of atmospheric transmission was omitted. But in this paper, more factors are considered to establish a more realistic and accurate detectivity model. The radiation of the gas cloud and the attenuation of the atmosphere are taken into account as well as the size of the leakage spot which inevitably affects the concentration path length. Secondly, the NETD and the GEBTD are compared to determine the detection capability. At last, an experiment is designed to verify the accuracy and reliability of this model on the basis of the gas cloud concentration cone distribution model.

Photo-written waveguides employing binary optical masks are investigated in an iron-doped lithium niobate crystal. Planar and Y-branch waveguides are experimentally demonstrated. The index variations along the propagation direction of the writing beam in the crystal are experimentally measured and theoretically analyzed. The influence of the diffraction from the optical masks, which imposes a limitation for the applications of the waveguide fabrication method, is numerically specified. Additionally, the asymmetry of the index distribution in the waveguide region, which is related to the transport process of the photoexcited charge carriers, is revealed and qualitatively explained.