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Purpose This paper aims to systematically investigate the effect of the heat treatment process parameters on the microstructure and mechanical properties of the selective laser melting (SLM) AlSi10Mg alloy. Design/methodology/approach The samples with very low porosity were fabricated with optimized processing parameters on a self-developed SLM system. The heat treatment of using the temperature of 170°C∼400°C and the holding time of 0.5∼12 h was studied, and the evolution of the microstructure and mechanical properties of AlSi10Mg alloy under direct aging and annealing was investigated and obtained. Findings After annealing above 300°C for 1 h, the dendrite Si in the sample occurs spheroidization, and the molten pool contour becomes blurred or even disappeared completely, but low-temperature heat treatment does not change the morphology and size of grains significantly. Except for holding at 200°C for 1 h, all other heat treatment processes cause the tensile and yield strengths of SLM AlSi10Mg alloys to decrease and the elongation to increase. When the annealing temperature is higher than 200°C, the higher the temperature and the longer the holding time, the more obvious this effect is. Originality/value The correlation between the mechanical properties and microstructure of SLM AlSi10Mg alloy under different conditions was obtained. According to the characteristics of SLM forming, the direct aging and annealing process are mainly studied, which provided new information for the heat treatment of SLM AlSi10Mg alloy and promoted the engineering application of SLM AlSi10Mg alloy.

Many moons of the Solar System, e.g. the Galilean satellites or Earth’s Moon, are subject to strong tidal deformations. Measurements of the tidal Love number h2 by laser altimeters from orbiting spacecraft may provide crucial constraints on their interior structures and rheology. Using precise observations by laser altimeters estimates for h2 were obtained for the Moon (Mazarico et al. 2014, Thor et al., 2021) and Mercury (Bertone et al., 2021), and are planned for Ganymede (Steinbrügge et al., 2015). Typically, height differences at crossing points of laser profiles, so called crossover points, are used for such measurements (Mazarico et al. 2014, Bertone et al., 2021). However, a new method based on simultaneous inversion of tidal deformations and global topography has recently been demonstrated (Thor et al. 2021) using data from the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter (LRO). Here we propose the refined “self-registration” method, which makes use of an accurate reference digital terrain model (DTM) constructed from the laser profiles themselves. This DTM is obtained by iteratively co-registering random subsets of laser profiles to an intermediate DTM produced by the other profiles. With our method we are not limited to profiles that are actually crossing themselves and can obtain height difference between all available profiles. Moreover, we can overcome the interpolation error at the crossover points as we use the entire profile with all its data points to measure the relative height differences. This method was recently successfully applied to measure the seasonal change of the ice/snow level in polar regions of Mars using Mars Orbiter Laser Altimeter (MOLA) data (Xiao et al., 2021). In order to validate our method and assess its performance we perform a simulation of a tidal signal in the LOLA data with an assumed value for the tidal Love number h2 of the Moon. Thereby the height measurement at the location of the LOLA footprint is derived from a DTM and an artificial tidal signal applied on it. Thereby, we consider viscoelastic effects on the tidal deformation and different tidal frequencies. With the help of these simulations we assess the accuracy of the h2 measurement and check the sensitivity to the measurement of the tidal phase lags. References:Mazarico et al. (2014). Detection of the lunar body tide by the Lunar Orbiter Laser Altimeter. GRL, 41(7), 2282-2288. doi:10.1002/2013GL059085Thor et al. (2021). Determination of the lunar body tide from global laser altimetry data. JoG, 95(1). doi:10.1007/s00190-020-01455-8Bertone et al. (2021). Deriving Mercury Geodetic parameters with Altimetric Crossovers from the Mercury Laser Altimeter (MLA). JGR-Planets, 126(4), e2020JE006683. doi:10.1029/2020JE006683Xiao et al. (2021). Prospects for Mapping Temporal Height Variations of the Seasonal CO2 Snow/Ice Caps at the Martian Poles by Co-registration of MOLA Profiles. Under review in PSS, https://arxiv.org/abs/2109.04899

Understanding biodiversity and biogeographic distribution of soil fauna is an important topic in ecology. While nematode communities have been compared among ecosystems, knowledge remains limited about how environmental factors and nematode distributions are linked at different spatial scales. Here, we employed high-throughput sequencing to compare nematode communities in tropical (Xishuangbanna), subtropical (Ailaoshan), and cold temperate spruce-fir (Lijiang) forest ecosystems with identical spatial sampling. Relationships between nematode communities and environmental factors were analyzed using redundancy analysis (RDA). Our results showed that nematode richness and diversity peaked in Xishuangbanna; however, no significant differences were observed in other two forest ecosystems. Bacterial feeders and Omnivores / Carnivores (Om & Ca) had the lowest relative abundance, but the highest diversity, in Xishuangbanna, with the opposite pattern being detected for fungal and plant feeders. Our data also demonstrated that, for forest ecosystems, climate factors drive nematode communities distributions at the regional scale, while terrain and soil characteristics (including pH and nutrients) drive nematode communities distributions at local scales. This study improves our current understanding of key factors (environmental parameters) responsible for the biogeographical distribution of forest nematode communities at different spatial scales.

We investigate the feasibility and demonstrate the merits of using Mars Orbiter Laser Altimeter (MOLA) profiles to retrieve seasonal height variations of CO2 snow/ice cap in Mars' polar areas by applying a co-registration strategy. We present a prototype analysis on the research region of [85.75{\deg}S, 86.25{\deg}S, 300{\deg}E, 330{\deg}E] that is located on the residual south polar cap. Our method comprises the recomputation of MOLA footprint coordinates with an updated Mars Global Surveyor (MGS) ephemeris and a revised Mars rotation model. The reprocessed MOLA dataset at the South Pole of Mars (poleward of 78{\deg}S) is then self-registered to form a coherent reference digital terrain model (DTM). We co-register segments of reprocessed MOLA profiles to the self-registered MOLA reference DTM to obtain the temporal height differences at either footprints or cross-overs. Subsequently, a two-step Regional Pseudo Cross-over Adjustment (RPCA) procedure is proposed and applied to post-correct the aforementioned temporal height differences for a temporal systematic bias and other residual errors. These pseudo cross-overs are formed by profile pairs that do not necessarily intersect, but are connected through the underlaying DTM. Finally, CO2 snow/ice temporal height variation is obtained by median-filtering those post-corrected temporal height differences. The precision of the derived height change time series is ~4.9 cm. The peak-to-peak height variation is estimated to be ~2 m. In addition, a pronounced "pit" (transient height accumulation) of ~0.5 m in magnitude centered at Ls=210{\deg} in southern spring is observed. The proposed method opens the possibility to map the seasonal CO2 snow/ice height variations at the entire North and South polar regions of Mars.

The rapid development of optical fiber application systems puts forward higher requirements for the miniaturization and integration of optical fiber devices. One promising solution is to integrate diffractive optical microstructures on the end faces of optical fibers. However, rapid microfabrication on such tiny and irregular substrates is a challenge. In recent years, Femtosecond laser polymerization technology has become an effective solution to the challenge, which can be flexibly applied for the fabrication of complex 3D microstructures with ultra-high resolution. When the demand for the lithography resolution is not very high, other microfabrication methods with a lower technical threshold may be developed for achieving a balance between fabrication precision, cost and efficiency. In this paper, we report a Digital Micromirror Device (DMD) based lithography method dedicated to the fabrication of functional optical microstructures on the optical fiber end faces. Especially, it’s also applicable to single-mode fibers (SMFs). By the projection via a 40x objective lens, the fabrication resolution of 0.405 μm was achieved within an exposure area of 209.92 μm × 157.44 μm. We evaluated the microfabrication results by the photomicrographs and the optical diffraction modulation effects of the functional optical microstructures. This method provides a new idea for fabricating both hybrid optical fiber devices and SMF devices, and it may be an alternative method for resolving the conflict between the precision, the cost and the efficiency.

Copper/steel bimetal, one of the most popular and typical multi-material components (MMC), processes excellent comprehensive properties with the high strength of steel and the high thermal conductivity of copper alloy. Additive manufacturing (AM) technology is characterized by layer-wise fabrication, and thus is especially suitable for fabricating MMC. However, considering both the great difference in thermophysical properties between copper and steel and the layer-based fabrication character of the AM process, the optimal processing parameters will vary throughout the deposition process. In this paper, we propose an analytical calculation model to predict the layer-dependent processing parameters when fabricating the 07Cr15Ni5 steel on the CuCr substrate at the fixed layer thickness (0.3 mm) and hatching space (0.3 mm). Specifically, the changes in effective thermal conductivity and specific heat capacity with the layer number, as well as the absorption rate and catchment efficiency with the processing parameters are considered. The parameter maps predicted by the model have good agreement with the experimental results. The proposed analytical model provides new guidance to determine the processing windows for novel multi-material components, especially for the multi-materials whose physical properties are significantly different.

Previously, we have proposed and validated the co-registration of local dynamic Mars Orbiter Laser Altimeter (MOLA) profile segments to static Digital Terrain Models (DTMs) as an approach for obtaining seasonal CO2 ice cover height variations on Mars. Building upon this, we introduce a post-correction procedure called “bi-RPCA” to further lower residual errors in the profiles and improve the precision of the height variation measurements. The ultimate goal is to apply this method to MOLA, SHAllow RADar (SHARAD) radar altimetry to generate long-term seasonal height change time series at the Martian poles with high spatial and temporal resolution. 1. Introduction The dynamic growth and retreat of Martian polar CO2 ice/frost caps is one of the most important themes for the Red Planet’s climate [1, 2]. Accurate measurements of seasonal height and volume changes of snow and ice can serve as important constraints for models of Mars climate and the long-term evolution of the southern residual ice cap. Previously, we have proposed and validated the local co-registration between laser profile segments and high static resolution DTMs in obtaining the temporal height variations at local scale [3]. Building upon that, we now propose a post-correction procedure called “bi-RPCA” to further improve the precision of the obtained height variation time series. 2. Data The Mars Orbiter Laser Altimeter (MOLA) Precision Experimental Data Record (PEDR) dataset includes a total of 8505 profiles, acquired in the mapping and extended phases of Mars Global Surveyor (MGS) from February, 1999 to May, 2001, which spanned approximately a full Martian year [1]. The PEDR dataset was processed using a MGS orbit trajectory- and a Mars rotational model by GSFC dating back to 2003. Therefore, we reprocessed the MOLA data, incorporating a refined orbit model from [4] and the IAU2015 Mars rotational model [5] for new MOLA geolocations. To account for the special relativity effect, a pointing aberration correction has also been applied in the reprocessing [6]. 3. Methods 3.1. Self-registration technique To build coherent reference DTMs of the average Martian surface at South Pole [78°S, 87°S] and an annulus centered at 50°S ([44°S, 56°S]), we resort to the self-registration of the reprocessed MOLA profiles [7, 8]. 3.2. Localized co-registration In order to obtain the height change series, the following steps are performed. First, small segments of the MOLA profiles consisting of a few hundred footprints are co-registered to the reference DTM. In this step we use a window, which is moved along the footprints. The obtained height corrections are assigned to the central footprint within the window. Hence, one obtains an individual height correction for every footprint within the MOLA profile and observation epoch. Finally, the CO2 height change time series are obtained by median-binning those temporal height differences with the precision quantified by scaled median absolute deviation. We name this method “F_LC” [3], where “F” stands for footprints and “LC” the local co-registration. 3.3. Post-correction by regional pseudo cross-over adjustment The regional crossover adjustment (RCA) over a relatively small & non-dynamic areas has been extensively used to improve the internal consistency of biased altimetry profiles on Earth [9]. Here, we adopt the DTM-based pseudo cross-overs acquired within 5 Earth days instead of the traditional cross-overs in the process as the regional pseudo cross-over adjustment (RPCA) for post-correction purposes. Pseudo cross-overs are formed by two profile segments that do not necessarily intersect. However, the connection between the profiles is established by a DTM overlapping with both profiles. Hence, the height difference between these (not necessarily crossing) profiles is obtained by the difference of their height corrections with respect to the self-registered DTM. Due to the inclusion of these pseudo cross-overs the number of “cross-overs” is increasing significantly [10]. The height correction is assumed to be constant for each profile segment. “Bi-RPCA” consists of two consecutive RPCA processes. By performing the RCPA at 50°S annulus, where no seasonal effects are expected, we obtain corrections for a systematic temporal bias within the MOLA data [2]. By assuming that the correction for a specific profile does not change from 50°S to the polar area, we apply the same corrections for profiles at the polar regions. The second RPCA step is carried out in the polar region to obtain height corrections to improve the self-consistency of the profiles, and hence the precision of the obtained temporal height variation using "F_LC". 4. Results Figure 1: Temporal height variation for a polar region along 86°S ([85.75°S, 86.25°S, 270°E, 280°E]) by our “F_LC” & bi-RPCA approach in comparison with results for an annulus at 86.5°S [1] and 86°S [2]. An example of the obtained temporal height variation in study region on the residual ice cap using “F_LC” and post-corrected by “bi-RPCA” is shown in Figure 1. The peak-to-peak height variation is ~2.5 m, similar to that of [2]. However, the peak height in MY25 is ~0.5 m higher than that of MY24, indicating annual variations. The off-season accumulation in southern summer and fall resolved in [2] are clearly visible in our result. The precision quantified by scaled median absolute deviation (the yellow shade in Figure 1) is ~4 cm, much improved over the ~50 cm of the “F_LC” result without the “bi-RPCA” post-correction [3]. 5. Summary We propose the “bi-RPCA” post-correction procedure to simultaneously compensate for systematic temporal bias and remove residual errors in the reprocessed MOLA profiles. The obtained height variation time series at the study region is reaching a high precision of ~4 cm. Thus, in future work the combination of “F_LC” & “bi-RPCA” will be applied to the entire polar regions to map the spatial distribution of the varying depth of the seasonal ice caps. Acknowledgements H. Xiao thanks China Scholarship Council (CSC) for financial support of his study in Germany. Part of this research was carried out within the framework of the DLR BigData Querschnittsplattform.We acknowledge the work by the MOLA instrument and science teams. References [1] Smith et al., Science, 2001, 294, 2141-2146. [2] Aharonson et al., JGR Planets, 2004, 109(E5). [3] Xiao et al., EPSC2020, vol.14, No. 181. [4] Konopliv et al., Icarus, 2006, 182, 23-50. [5] Konopliv et al., Icarus, 2016, 274, 253-260. [6] Xiao et al., JoG, 2021, 95(2), 1-23. [7] Stark et al., EPSC2018, Contrib. No. 890. [8] Stark et al., GRL, 2015, 429, 7881-7889. [9] Ewert et al., J. Geodyn., 2012, 59-60, 111-123 [10] Barker et al., Icarus, 2016, 273, 346-355.

Laser altimeters are commonly used in planetary research for their high geodetic accuracy. A key procedure in processing of laser altimeter data is the geolocation. In this process, the time-of-flight measurements are converted to coordinates of laser pulse footprints on the surface of the target body. Here, we present a consistent and systematic formulation of three commonly used geolocation models with increasing complexity: static model, spacecraft motion model, pointing aberration model and special relativity model. We show that for small velocities of the spacecraft relative to the target the special relativity model can be reduced to the pointing aberration model without significant loss in the geolocation accuracy. We then discuss the respective accuracies of the proposed models and apply them to time-of-flight measurements from the Mars Orbiter Laser Altimeter (MOLA) onboard the Mars Global Surveyor (MGS) spacecraft and the Mercury Laser Altimeter (MLA) onboard the MErcury Surface, Space ENvironment, GEochemistry and Ranging spacecraft (MESSENGER). While, the archived datasets had not considered the effect of pointing aberration, we demonstrate that a correction due to pointing aberration makes insignificant improvements of 4–5 m laterally and up to ± 3 cm radially for MOLA profiles, these figures enormously increase to up to about 150 m laterally and ± 25 m radially when applied to the MLA orbital profiles.

Abstract We propose the co-registration of local laser profile segments to high resolution Digital Terrain Models (DTMs) as an approach for obtaining seasonal CO2 ice cover height variations on Mars. The co-registration is parameterized in instantaneous MOLA pointing angles involving a rigorous laser altimeter geolocation model. Thereby, the height bias of the MOLA footprint produced by the pointing bias could be compensated through an iterative process. The feasibility and advantages of this method are tested in an example region. The ultimate goal is to apply this method to Mars Orbiter Laser Altimeter (MOLA), SHAllow RADar (SHARAD) radar altimetry and high-resolution stereoscopic DTMs to generate long-term seasonal height change time series at the Martian poles with high spatial and temporal resolution. 1 Introduction The dynamic growth and retreat of polar CO2 frost at the Martian poles has always been one of the focuses of planetary scientists [1, 2, 3]. Accurate measurements of seasonal and long-term elevation and volume changes can serve as important constraints in Mars climate models, help tap into the density evolution of the CO2 snow once combined with gravity measurements, and constrain the degree of stability of the polar deposits. The commonly-used approach to this problem is the cross-over analysis of the laser altimetry profiles, but this method may suffer from significant interpolation errors when spacing between footprints is large, also residual pointing, timing and orbit error may translate into lateral shifts of the laser profiles and further undermine the results. Here, we propose and validate the local co-registration between laser profile segments and high resolution DTMs from stereo pairs as a solution to these limitations. 2 Data 2.1 MOLA records The MOLA Precision Experimental Data Record (PEDR) dataset features a total of 8505 profiles, acquired in the mapping and extended phases of Mars Global Surveyor (MGS) from February, 1999 to May, 2001, which spanned approximately a full Martian year [1]. The PEDR dataset was processed using MGS orbit trajectory model and a Mars rotational model by GSFC dating back to 2003. Therefore, we have incorporated a refined orbit model from [4] and IAU2015 Mars rotational model [5] in the MOLA geolocation reprocessing. Meanwhile, to account for the special relativity effect, the pointing aberration correction has also been taken care of in the reprocessing [6]. 2.2 HRSC DTMs The High Resolution Stereo Camera (HRSC) is a pushbroom camera onboard the European Space Agency (ESA) spacecraft Mars Express. A total of 34 HRSC DTM tiles are adopted which feature a grid size of 50 m and covers the majority of the Martian South Pole [7]. 3 Methods First, the reprocessed MOLA profiles are self-registered to each other to form a coherent reference in the Martian South Pole [8, 9]. Subsequently, individual HRSC DTM tiles have been aligned to the MOLA reference data and mosaiced to a self-consistent reference for the co-registration. The co-registration of the reprocessed MOLA profiles to the aligned HRSC DTM mosaic is setup by compensating for two alignment angles of the boresight and height which incorporates an analytical laser altimeter geolocation model. The benefit is that the height offset induced by bias in pointing can be simultaneously compensated during the iterative co-registration process. The height differences with respect to the DTM mosaic at either footprint, cross-overs, or pseudo cross-overs are assigned as the height corrections from the local co-registration process using segmented profiles centered at these feature points. Here, pseudo cross-overs are DTM-based and formed by two track segments that do not have to actually intersect, substantially increasing the available number of cross-overs [10]. Then, CO2 height change time series are obtained by median-binning those temporal height differences with the uncertainty quantified by scaled median absolute deviation. To get rid of a temporal systematic error, the acquired temporal trend is subtracted from the one at 60°S annulus which features unchanging topography. 4 Results Figure 1: Results using height differences at footprints before the adoption of the local co-registration procedure (“F_LC”, red line, bottom) and comparison to previous literature (lime and aqua lines). Figure 2: Results using height differences at footprints after the adoption of the local co-registration procedure (“F_LC”, red line, bottom) and comparison to previous literature (lime and aqua lines). A test has been carried out at an example region situated right on the residual ice cap where largest peak-to-peak height variation would be expected. The uncertainty of the derived height change time series using height differences at footprints decreased from ~2 m to ~0.5 m after the adoption of the local co-registration procedure, roughly a fourfold enhancement (Figures 1 and 2). The maximum height fluctuation is estimated at ~2.5 m which is similar to that of Aharonson et al. (2004) [2]. The suspicious off-season accumulation pointed out by previous results using MOLA has not been resolved. While a sharp pit-shaped feature of ~1 m depth centered at solar longitude 210° is observed. Similar results have been obtained using height differences at cross-overs and pseudo cross-overs. As a byproduct of the co-registration process, MOLA alignment angles have also been examined to follow some specific temporal patterns. 5 Summary We show the feasibility and merits of the local co-registration strategy in the application of retrieving height changes at either footprints, cross-overs, or pseudo cross-overs. As for the next step, we will put the SHARAD radar altimetry and reflectometry into test [11]. Combined with the MOLA laser altimetry, long-term CO2 height change time series spanning two decades could possibly be retrieved. Apart from height change mapping, the proposed method could also be readily adapted to the tidal Love number measuring, orbit refinement with so called “direct altimetry” [12] and others. Acknowledgements This work was supported by a research grant from Helmholtz Association and German Aerospace Center (DLR). We acknowledge the work by the MOLA and HRSC instrument and science teams. References [1] Smith et al.,Science, 2001, 294, 2141-2146. [2] Aharonson et al., JGRPlanets, 2004, 109(E5). [3] Genova, ActaAstronaut., 2020, 166, 317-329. [4] Konopliv et al., Icarus, 2006, 182, 23-50. [5] Konopliv et al., Icarus, 2016, 274, 253-260. [6] Xiao et al., Submitted to JoG. [7] Putri et al., PSS, 2019, 174, 43-55. [8] Stark et al., EPSC2018, Contrib. No. 890. [9] Stark et al., GRL, 2015, 429, 7881-7889. [10] Barker et al., Icarus, 2016, 273, 346-355. [11] Steinbrügge et al., LPSC2019, LPI Contrib. No. 2132. [12] Goossens et al., Icarus, 2020, 336, 113454.

We propose the co-registration of laser profiles to high resolution Digital Terrain Models (DTMs) as an approach for retrieving surface elevation changes at the poles of Mars. The edge of this method is validated using reprocessed and simulated Mars Orbiter Laser Altimeter (MOLA) profiles. The ultimate goal is to apply this method to MOLA and HRSC DTMs to generate seasonal and long-term elevation change time series at the Martian poles with high spatial and temporal resolution.

The geochemical data and geochemical proxies of the Niutitang Formation shales in the Yangtze Platform were investigated for deciphering paleodepositional environment and elucidating paleoenvironment conditions responsible for organic carbon accumulation. Ce anomalies, Eu anomalies and Y anomalies of the Niutitang Formation shales is between 0.39 and 0.92, between 0.65 and 1.03, between 0.97 and 1.71, respectively. The REE patterns of the Niutitang Formation shales show enrichment in HREE relative to LREE with negative Ce anomalies, positive Y anomalies and negative Eu anomalies, indicating of a greater influence of seawater compared to hydrothermal fluids. U, V and Mo are enriched in the shales, and Mo/Al exhibits strong covariation with TOC contents, whereas U/Al and V/Al show weak covariation with TOC contents, indicating that H2S associated with hydrothermal vents is present. Compare with upper Niutitang Formation shales, higher V/(V + Ni), Ni/Co and V/Cr ratios in lower Niutitang Formation shales imply that the lower Niutitang Formation shales are deposited in anoxic conditions. Higher Mo/Al and Ni/Al ratios exist in the lower Niutitang Formation shales relative to the upper Niutitang Formation shales, indicating higher primary productivity during deposition of the lower Niutitang Formation shales. Thus, the variations of primary productivity and preservation of organic matter associated with redox conditions of bottom water lead to greater TOC contents in lower Niutitang Formation shales relative to upper Niutitang Formation shales.

Understanding mechanisms of successful colonization by exotic plant species in non-native habitat is critical to meet long-term restoration aims. Overgrowing plants can alter resources, especially soil inorganic nitrogen availability and get benefits from positive feedback. However, comprehensive knowledge on particular mechanisms underlying their successful colonization remains unclear. Here, field examinations and laboratory manipulations were combined to investigate significant impact of overgrowing Ageratina adenophora on soil NO 3 − -N availability and nitrification. Interestingly, we found significant enhancement in soil total N, NO 3 − -N, pH, potential nitrification rates, and ammonia oxidizing bacteria (AOB), while reduced abundance of ammonia oxidizing archaea (AOA) under the influence of A . adenophora . Notably, AOB abundance was positively correlated with both pH and soil potential nitrification rates. AOA abundance was negatively correlated with pH and had no significant correlation with soil nitrification potential. Both AOA and AOB communities significantly differed between populated and non-populated soils. pH was the strongest factor contributing to this community difference. We conclude that A. adenophora stimulates nitrification with the help of AOB rather than AOA under relatively higher soil pH condition.

To combat China’s water crisis tremendous research efforts are undertaken aiming at the improvement of water management in cotton production, which is the major consumer of the scarce water resources in arid Northwestern China. In recent years extensive field experiment based research strongly enhanced the theoretical knowledge of optimal water management in cotton production. However, farmers’ actual irrigation water productivity remains low. To fill the critical void the present study aims at increasing the understanding of Chinese cotton farmers’ actual irrigation water management. The northwestern Chinese Aksu-Tarim Region was selected as a hot-spot of water scarcity in China, where around 60% of total sown crop land are cultivated with cotton. The increasing overuse of scarce surface water resources for irrigation not only leads to severe ecological degradation, but also increases competition among water users triggering the expansion of groundwater exploitation. Based on primary survey data of 228 cotton producing farm households we firstly analyze the production factors determining farmers’ yield and irrigation water productivity (IWP). Apart from soil salinity and unbalanced fertilization, which negatively affect yield and IWP, especially the applied irrigation method (drip vs. flood irrigation) and installation of a groundwater well were identified as major determinants. Secondly, we apply logistic regression to evaluate which household and farm characteristics determine the irrigation method and installation of groundwater well. We find that farm size, crop types and cropping intensity determine the use of drip irrigation. We furthermore find that the installation of well is largely related to marginalization, with farm families of ethnic minorities, remote farms and lower educated families being more likely to install wells. The findings of our study can help policymakers in devising strategies for improving irrigation water productivity, while reducing groundwater degradation in the study region and similar arid production regions in the world.

Heme oxygenase (HO) is the rate-limiting enzyme in heme metabolism. HO-1 exhibits anti-oxidative and anti-inflammatory function via the actions of its metabolite, respectively. A growing body of evidence demonstrates that HO-1 is implicated in the pathogenesis and progression of several types of cancer. However, whether HO-1 takes part in healthy-premalignant-malignant transformation is still undefined. In this study, we took advantage of transgenic mice which over-expressed HO-1 dominant negative mutant (HO-1 G143H) and observed its susceptibility to DEN-induced hepatocarcinogenesis. Our results indicate that HO-1 G143H mutant accelerates the progression of tumorigenesis and tumor growth. The mechanism is closely related to enhancement of ROS production which induce more hepatocytes death and secretion of inflammatory cytokines, proliferation of surviving hepatocytes. Our result provides the direct evidence that HO-1 plays an important protective role in liver carcinogenesis. Alternatively, we suggest the possible explanation on effect of HO-1 promoter polymorphism which involved in tumorigenesis.

In this work, hot compression experiments of 300M steel were performed at 900&ndash, 1150 &deg, C and 0.01&ndash, 10 s&minus, 1. The relation of flow stress and microstructure evolution was analyzed. The intriguing finding was that at a lower strain rate (0.01 s&minus, 1), the flow stress curves were single-peaked, while at a higher strain rate (10 s&minus, 1), no peak occurred. Metallographic observation results revealed the phenomenon was because dynamic recrystallization was more complete at a lower strain rate. In situ compression tests were carried out to compare with the results by ex situ compression tests. Hot working maps representing the influences of strains, strain rates, and temperatures were established. It was found that the power dissipation coefficient was not only related to the recrystallized grain size but was also related to the volume fraction of recrystallized grains. The optimal hot working parameters were suggested. This work provides comprehensive understanding of the hot workability of 300M steel in thermal compression.

An in-depth understanding of the flow behaviors of materials deformed at high temperatures is of paramount significance. However, insufficient research on the nickel-based GH4698 alloy has resulted in inaccurate material flow prediction or even cracking in the practical billet opening of GH4698 large forgings. In this study, hot compressions were performed at 950&ndash, 1150 &deg, C and 0.001&ndash, 3 s&minus, 1. Single-peaked strain-stress curves were obtained under various conditions, owing to dislocation motions in dynamic recrystallizations. The Arrhenius model was formulated to accurately describe the flow stress evolutions and the mean prediction error of the flow stress was 5.90%. Processing maps were constructed at various hot working conditions. It was found that the hot working ability of GH4698 markedly decreased under lower temperatures (950&ndash, 1080 &deg, C) and higher strain rates (0.1&ndash, 1). Optimal thermal processing parameters were suggested. In sum, this study systematically investigated the flow behaviors and hot working ability of GH4698 in isothermal compressions.

It is of significance to evaluate the equivalent contact heat transfer coefficient (ECHTC) at the sheet-die interface in hot stamping of boron steel (HSBS) for controlling the local cooling rate of the sheet and hence obtaining components with tailored microstructure and properties. Moreover, accurate evaluation of the ECHTC can provide a reliable thermal boundary condition for numerical simulation of the HSBS process. In the study, a simple and effective physical simulation setup for die quenching of boron steel (DQBS) was developed, where the temperatures at measurement points are related only to the ECHTC so as to improve the evaluation accuracy. A FE-based optimization model for inverse evaluating the ECHTC was established. The ECHTCs at the B1500HS sheet-H13 die steel interface were identified under various contact pressures, and it was found that the ECHTC increases exponentially with the pressure increasing. Both the physical simulation of DQBS and the HSBS experiment were performed to verify the ECHTC evaluated, and the maximum relative errors of 9.6 and 19.7 % were observed, respectively, between the predicted and measured temperature histories.

Overuse of nitrogen (N) fertilizer constitutes the major issue of current crop production in China, exerting a substantial effect on global warming through massive emission of greenhouse gas (GHG). Despite the ongoing effort, which includes the promotion of technologically sophisticated N management schemes, farmers' N rates maintain at excessive rates. Therefore the current study tests three simple and easily to apply N fertilizer recommendation strategies, which could be implemented on large scale through the existing agricultural advisory system of China, at comparatively low cost. Building on a detailed crop production dataset of 65 winter wheat (WW) and summer maize (SM) producing farm households of the North China Plain, scenario analysis is applied. The effects of the three N strategies under constant and changing yield levels on product carbon footprint (PCF) and gross margin (GM) are determined for the production condition of every individual farm household. The N fixed rate strategy realized the highest improvement potential in PCF and GM in WW; while the N coefficient strategy performed best in SM. The analysis furthermore revealed that improved N management has a significant positive effect on PCF, but only a marginal and insignificant effect on GM. On the other side, a potential 10% yield loss would have only a marginal effect on PCF, but a detrimental effect on farmers' income. With farmers currently applying excessive N rates as "cheap insurance" against potential N limitation, it will be of vital importance to avoid any yield reductions (caused by N limitation) and respective severe financial losses, when promoting and implementing advanced fertilization strategies. To achieve this, it is furthermore recommended to increase the price of fertilizer, improve the agricultural extensions system, and recognize farmers' fertilizer related decision-making processes as key research areas.

Successional dynamics in terrestrial ecosystems is important for interactions between aboveground and belowground subsystems. In this study, nematode communities in a Hailuogou Glacier Chronosequence from seven stages were investigated to determine whether changes in soil phosphorus (P) and nematode assemblages parallel those observed in aboveground communities, and whether the primary succession in this chronosequence has entered a retrogressive phase after 120 years of succession. The initial 40-year succession, including stages 2, 3 and 4, can be viewed as a build-up phase. Especially at stage 3, vegetation succession from grassland to forest accelerated the accumulation of plant litter and bioavailable P, paralleled with a sharp increase in nematode abundance. The mature phases covering stages 5, 6 and 7 displayed most balanced nematode communities, in which abundance, taxon richness, maturity index and structure index were at highest. However, the last stage 7 appeared to show some retrogressive characteristics, as suggested by the reduced bioavailability of P and a significant decrease in nematode densities, along with the disappearance of some rare genera of nematodes from higher trophic guilds, resulting in decreases in the nematode channel ratio, plant parasite index and enrichment index. Thus, the Hailuogou Glacier Chronosequence may enter its retrogressive phase during the next decade or century. A bacterial-based nematode energy channel dominated the chronosequence during the development; by contrast, a fungivore-based channel was activated at the early and late stages, because fungivores are better adapted to nutrient-poor environments. Our results demonstrated that different nematode guilds have contrasting responses to chronosequence stages, possibly due to their different responses to bottom-up and top-down controls. Furthermore, soil nematode communities could be used as sensitive bioindicators of soil health in glacial-retreat areas. (C) 2015 Elsevier Ltd. All rights reserved.

Power system will occur chaotic oscillation when it is exist periodic load disturbances. As for it, the simplified mathematical model of interconnected two- machine second-order power system is established based on the modelling and analysis of nonlinear system theory, and the dynamic behaviour of chaotic oscillation in power system is analysed. According to the sliding mode control and fuzzy control theory, the fuzzy-based sliding mode control is proposed, it is also analysed and proved theoretically. Simulations results show that the proposed method can suppress the chaotic oscillation in power system effectively. It not only reduce the convergence time, but also reduced the chattering of the system, and has strong robustness.

We propose a new framework of systematic fracture mapping and major calving event prediction for the large ice shelves in Antarctica using multisource satellite data, including optical imagery, SAR imagery, altimetric data, and stereo mapping imagery. The new framework is implemented and applied for a comprehensive study of the fracturing of Ronne-Filchner Ice Shelf (RFIS), the second largest ice shelf in Antarctica, using a long time dataset dating back to 1957. New remote sensing data that have been made available in the past decade, including Landsat 8, WV-2, ZY-3 and others, greatly enhance our abilities to detect new fractures and monitor large rifts in three dimensions. Two large rifts, Rifts 1 and 2, were newly detected and are comparable to the Grand Chasm that caused a major calving event in the region in 1986. Three-dimensional rift models generated from quasi real-time stereo ZY-3 images revealed important topographic information about the large rifts that can be used to improve the reliability of ice shelf modeling and support enhanced analyses of ice shelf stability. Based on the results of the 2D and 3D fracture mapping, the spatial and temporal analyses of the overall fracture changes and large rift evolutions, i.e., the level of fracturing in RFIS, were slightly increased, particularly at the front of the ice sheet. The overall fracture observations do not seem to suggest immediate significant impacts on the stability of the shelf. However, the most active regional fracturing activities occurred at the front of Filchner Ice Shelf (FIS). A potential upcoming major calving event of FIS is estimated to occur in 2051. The stability of the ice shelf, particularly with regard to the developments of Rifts 1 and 2, should be closely monitored.

A finite element model of graphene strip is developed to predict the instability of dynamic fracture, in which the C-C bonds are represented by Timoshenko beam elements, and the constitutive relation of beam is derived from the atomic potential. Crack instability and branching are observed under loading strain rates from similar to 10(-5) fs(-1) to similar to 10(-8) fs(-1). Under low loading rates, the initiated midway crack propagates straight at supersonic velocity, while kinking and oscillation occur beyond a critical crack velocity similar to 10.33 km/s under high rates. The results demonstrate that our equivalent models could provide efficient information for studying the fracture in graphene. (C) 2015 Elsevier Ltd. All rights reserved.

To assess the attainable greenhouse gas (GHG) mitigation potential from crop production in China's most important grain production region, the North China Plain (NCP), single farm environmental and economic performances of 65 winter wheat–summer maize (WW–SM) producing households were determined. The results revealed a huge heterogeneity among farms, with up to five times higher environmental impact of worst compared to best performing farms. Astonishingly no trade-off between productivity and sustainability could be identified in the region, with high-yield farms emitting no different amounts of GHGs per hectare compared to low-yield farms. Building on cluster analysis, with farms grouped according to their economic and environmental performance into ‘poor’, ‘fair' and ‘good’ producers, the regional GHG mitigation potential was estimated. Under the scenario assumption that all grain in the NCP is produced under ‘good’ production conditions, 21% and 7% of GHG could be mitigated in wheat and maize producti...

Sediment core samples from Nashina Lake, Heilongjiang, China were collected using a gravity sampler. The cores were sliced horizontally at 1 cm each to determine the particle size, total concentrations and speciation of Cd, Cr, Cu, Mn, Ni, Pb, and Zn. Total concentrations of heavy metals were extracted using an acid mixture (containing hydro fluoric acid, nitric acid, and sulphuric acid) and analyzed using an inductively coupled plasma spectrometry. A sequential extraction procedure was employed to separate chemical species. Analysis of results indicate that the concentrations of heavy metals in the sediments of Nashina Lake in descending order are Mn, Cr, Zn, Pb, Ni, Cu, and Cd. The ratios of the average concentrations of four heavy metals (e.g.Cr, Cu, Ni, Zn) to their background values were >1; and those of Mn, Cd, and Pb were >1. Moreover, some toxic metals were mainly distributed in bioavailable fractions. For instance, both Cd and Mn were typically found in Acid-extractable species or Fe–Mn oxide species, and thus can be easily remobilized and enter the food chain. Finally, the analysis of geo-accumulation index showed that anthropogenic pollution levels of Cr, Cu, Mn, Ni, Zn were low, but those of Pb and Cd were at the moderate level. As both Pb and Cd are toxic metals, it is highly necessary to prohibit their transformation and accumulation in the sediments.

Because it is a member of the miR-106b~25 cluster, microRNA-25 (miR-25) is known to be dysregulated in human cancers. However, the expression and role of miR-25 in colon cancer remain unclear. In this study, miR-25 was found to be down-regulated in human colon cancer tissues when compared to those in matched, non-neoplastic mucosa tissues. Functional studies revealed that restoration of miR-25 expression inhibited cell proliferation and migration. In contrast, miR-25 inhibition could promote the proliferation and migratory ability of cells. Stable over-expression of miR-25 also suppressed the growth of colon cancer-cell xenografts in vivo. Furthermore, bioinformatic predictions and experimental validation were used to identify Smad7 as a direct target of miR-25. Functional reverse experiments indicated that the antitumor effects of miR-25 were probably mediated by its repression of Smad7. These results suggest that miR-25 may function as a tumor suppressor by targeting Smad7 in colon cancer. Thus, miR-25 may serve as a potential therapeutic agent or target for cancer therapy.