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Silicon nitride fibers-reinforced silicon nitride matrix (Si3N4f/BN/Si3N4) composites with a BN interphase were fabricated by chemical vapor infiltration (CVI) and precursor infiltration pyrolysis (PIP). It is shown that PIP Si3N4f/BN/Si3N4 composites possessed better mechanical properties and achieved effectively interface debonding and fiber pull-out, whose flexural strength and fracture toughness can achieve 189 ± 17 MPa and 5.6 ± 0.6 MPa·m1/2, about twice and 1.5 times as much as those of CVI Si3N4f/BN/Si3N4 composites, respectively. Combining the micro-nano mechanical and macro-mechanical properties investigations, it is revealed that weakening the interfacial bond and achieving proper modulus matching relationship between fibers and matrix by PIP process could remarkably increase the mechanical properties of the Si3N4f/BN/Si3N4 composites, compared with CVI process.

In this study, three-dimensional silicon nitride fiber-reinforced silicon nitride matrix (3D Si3N4f/BN/Si3N4) composites with a boron nitride (BN) interphase were fabricated through chemical vapor infiltration. Through comparing the changes of microstructure, thermal residual stress, interface bonding state, and interface microstructure evolution of composites before and after heat treatment, the evolution of mechanical and dielectric properties of Si3N4f/BN/Si3N4 composites was analyzed. Flexural strength and fracture toughness of composites acquired the maximum values of 96 ± 5 MPa and 3.8 ± 0.1 MPa·m1/2, respectively, after heat treatment at 800 °C; however, these values were maintained at 83 ± 6 MPa and 3.1 ± 0.2 MPa·m1/2 after heat treatment at 1200 °C, respectively. The relatively low mechanical properties are mainly attributed to the strong interface bonding caused by interfacial diffusion of oxygen and subsequent interfacial reaction and generation of turbostratic BN interphase with relatively high fracture energy. Moreover, the Si3N4f/BN/Si3N4 composites also displayed moderate dielectric constant and dielectric loss fluctuating irregularly around 5.0 and 0.04 before and after heat treatment, respectively. They were mainly determined based on the intrinsic properties of materials system and complex microstructure of composites.

Silicon nitride (Si3N4) hollow microspheres with smaller particle size and narrower distribution can be used to prepare closed-cell ceramics as the pore-forming agent to improve heat insulation performance and wave-transparent performance of porous Si3N4 ceramics. In this work, Si3N4 hollow microspheres with a diameter of about 1 μm and a wall thickness of approximately 150 nm were prepared by using the template method combined with the carbothermal reduction nitridation method. The optimum preparation temperature of the Si3N4 hollow microspheres is 1450 °C. The morphology, microstructure, and phase composition of the prepared Si3N4 hollow microspheres were characterized. The formation mechanism of the Si3N4 hollow microspheres was discussed. The dielectric properties of Si3N4 hollow microspheres were measured using the waveguide method at 8.2-12.4 GHz. The results show that the wave-transparent performance of the Si3N4 hollow microspheres is similar to those of α-Si3N4 particles. It can be used as the pore-forming agent or matrix for preparing lightweight, heat-insulating, wave-transparent, and high-strength porous Si3N4 ceramics.

The chemistry of acetaldehyde (CH3CHO) adsorbed on the anatase TiO2(001)-(1×4) surface has been investigated by temperature-programmed desorption (TPD) method. Our experimental results provide the direct evidence that the perfect lattice sites on the anatase TiO2(001)-(1×4) surface are quite inert for the reaction of CH3CHO, but the reduced defect sites on the surface are active for the thermally driven reductive carbon-carbon coupling reactions of CH3CHO to produce 2-butanone and butene. We propose that the coupling reactions of CH3CHO on the anatase TiO2(001)-(1×4) surface should undergo through the adsorption of paired CH3CHO molecules at the reduced defect sites, since the existing reduced Ti pairs provide the suitable adsorption sites.

When a metal single-atom (SA) catalyst is supported on a semiconducting photocatalyst, the charge transfer of the photoexcited carriers to metal SAs can provide a synergetic activity for the co-catalysts. Here, we report the interfacial electronic coupling of the Au SAs on the TiO2(110) surface using scanning tunneling microscopy/spectroscopy, in combination with first-principles calculations. Distinct energy and spatial distributions of the metal-induced gap states (MIGSs) are experimentally revealed for the Au SAs adsorbed at the terminal Ti sites and the oxygen vacancies. The localized MIGS below the Fermi level provides a dedicated channel for the transfer of a photoexcited hole from the TiO2 substrate to the adsorbed Au SAs. The hole can weaken the Ti-Au bonding and activate the diffusion of Au SAs. Our results shed light on combining the advantages of photocatalysis and metal SA catalysis using a co-catalyst, which is promising to promote chemical reactions at low temperatures.

Imaging the doping elements is critical for understanding the photocatalytic activity of doped TiO2 thin film. But it is still a challenge to characterize the interactions between the dopants and the TiO2 lattice at the atomic level. Here, we use high angle annular dark-field/annular bright-field scanning transmission electron microscope (HAADF/ABF-STEM) combined with electron energy loss spectroscopy (EELS) to directly image the individual Cr atoms doped in anatase TiO2(001) thin film from [100] direction. The Cr dopants, which are clearly imaged through the atomic-resolution EELS mappings while can not be seen by HADDF/ABF-STEM, occupy both the substitutional sites of Ti atoms and the interstitial sites of TiO2 matrix. Most of them preferentially locate at the substitutional sites of Ti atoms. These results provide the direct evidence for the doping structure of Cr-doped A-TiO2 thin film at the atomic level and also prove the EELS mapping is an excellent technique for characterizing the doped materials.

We report our investigation on the electronic properties of Cr-N codoped rutile TiO2(110) single crystal thin films, homoepitaxially grown by pulsed-laser-deposition method, and characterized using scanning tunneling microscopy and spectroscopy (STM/STS), X-ray/ultraviolet photoemission spectroscopy (XPS/UPS), in combination with first-principles calculations. Our results show that the bandgap reduction of the TiO2(110) surface is mainly contributed by the delocalized states whose position is at 2.0 eV below the Fermi level, introduced by the substitutional codoped Cr-2N pair, which is evidenced by the accordance of the results between the STS spectra and the calculated DOS. The codoped Cr-N pair contributes the gap state at about 0.8 eV below the Fermi level, in consistent with the theoretical calculations. While, the monodoped Cr contributes the states either close to the valence band maximum or the conduction band minimum, which should not contribute to the bandgap reduction too much. Our experimental results joint with theoretical calculations provide an atomic view of the bandgap reduction of the rutile TiO2(110) surface, which indicates that the excess substitutional N atoms should be important to efficiently narrow the bandgap by introducing the Cr-2N pairs.

We here report our investigation on the photocatalytic reactions of methanol on the anatase TiO2(001)-(1×4) surface using scanning tunneling microscopy and temperature-programmed desorption. Our results show that in the reduced surface the Ti-pair defect sites are photoinactive, but in the reoxidized surface the partially oxidized defect sites are photoactive to dissociate methanol and methoxy to formaldehyde. The perfect (1×4) lattice sites are photoactive, even though they are inactive in thermally driven reaction. The photocatalytic reaction of methanol (CD3OH) at the perfect lattice sites is evidenced by the conversion of CD3OH to various other deuterated methanol (CD3OD and CD2HOH) and a small amount of formaldehyde (CD2O) after ultraviolet light irradiation, in contrast with no such conversion reaction in the nonirradiated sample. The production of CD3OD and CD2HOH can be attributed to the reverse reaction between the produced CD2O and the H or D adatoms during or after ultraviolet light irradiation...

We report our investigation using temperature-programmed desorption to detect the activity and the photoactivity of the reduced anatase TiO2(001)-(1 × 4) surface by using CH2O as a probe. We obtain the adsorption energy of 0.55 eV for CH2O on the surface and find that the defect sites in the reduced surface are the only active sites for thermally driven reaction to produce C2H4. We also identify the pathways for photodecomposition of CH2O on the anatase TiO2(001)-(1 × 4) surface, where the C−H bond breaking to form the intermediates of HCOO− should be a key step in the reactions. After the ultraviolet light irradiation, the dissociation of HCOO– produces CO and H2O at elevated temperatures. Accompanied by desorption of H2O, we observe higher production of C2H4 than that in the non-irradiated sample. We interpret our experimental results by attributing the temporary change of the (1 × 4) ridge structure to water desorption, that is, the initially oxygen-rich five-fold coordinated Ti atoms change to four-fo...

Since 1960s, India experiences a series of extreme drought and flood events during the summer months. The Humid Subtropical Climatic Zone (HSTC), which comprises the Indo-Gangetic Plain region of India, is highly vulnerable to the climatic extremities. This region is the home for approximately 40% of total population and yields approximately 50% of total agricultural production of India. We investigate the historical variation in dry/wet conditions and project the future changes in extreme events under two different scenarios of the Coupled Model Inter-comparison Project 5 models. First, the model parameters, that is, precipitation (P) and temperature (T) are bias corrected with respect to observation data and finally six models are selected, which are in right phase with the observation for composite analysis. Next, we calculate the potential evapotranspiration (PET) and the Standardized Potential Evapotranspiration Index to characterize the extreme events. Both P and PET are projected to increase in the HSTC zone; however, both the wet and dry conditions demonstrate a persistent increase in future. In relative terms, P increases faster than PET along the Gangetic Plain region (wet condition) and decreases in the southern and eastern part of the region (dry condition). The mitigating effect (RCP4.5 scenario) of precipitation increase will be overridden by strengthened PET and extreme dry condition project markedly under RCP8.5 scenario. The features are consistent with the increase/ decrease in multimodel mean SPEI, consistent with the spatial pattern of P−PET. The area affected due to wet and dry events will be relatively higher under the RCP4.5 and RCP8.5 scenario, respectively.

The soil chronosequence is a useful method for investigating pedological theories. Soil chemical, physical and mineralogical properties in chronosequences change over time and exhibit systematic and time-dependent trends, which can be used to analyze the rates and directions of pedogenic changes. The potential of soil spectroscopy as an emerging, rapid and cost-effective technique for predicting soil properties has been widely accepted and has motivated the application of spectroscopic techniques to the analysis of soil chronosequence. We present a soil chronosequence derived from 1000-year-old calcareous marine sediments and examine changes in six soil properties over this period. We evaluated the utility of a soil spectroscopic method to detect soil property changes and to predict the pedogenic properties and soil ages of the chronosequence. The results show that some soil pedogenic processes, such as soil organic matter accumulation, CaCO3 leaching and clay migration, can be identified in the millennium chronosequence. Power chronofunctions are formulated for soil organic matter (SOM) and Logarithmic chronofunctions are fitted for clay, CaCO3 and pH. These pedogenic processes are identified in the reflectance intensity and absorption features of soil spectroscopy, and pedogenic properties can be calibrated via soil reflectance spectroscopy. Profile ages can also be predicted via pseudo multi-depth spectra of soil profiles, and soil spectral curves for 0−30 cm generated the best prediction results (RPD = 1.85). We conclude that soil properties, changing due to weathering and soil formation, act as a bridge linking spectroscopy and weathering levels/pedogenic processes. The results imply that applying spectroscopy techniques to chronosequence study and mapping the degree of soil development in certain areas should be possible.

Climate change is having an increasing effect on human society and ecosystems. The United Nations has established 17 sustainable development goals, one of which is to cope with climate change. How to scientifically explore uncertainties and hazards brought about by climate change in the future is crucial. The new Intergovernmental Panel on Climate Change (IPCC) has proposed shared socioeconomic pathways (SSPs) to project climate change scenarios. SSP has been analyzed globally, but how regions and nations respond to the global climate change and mitigation policies is seldom explored, which do not meet the demand for regional environmental assessment and social sustainable development. Therefore, in this paper, we reviewed and discussed how SSPs were applied to regions, and this can be summarized into four main categories: (1) integrated assessment model (IAM) scenario analysis, (2) SSPs-RCPs-SPAs framework scenario analysis, (3) downscaling global impact assessment model, and (4) regional impact assessment model simulation. The study provides alternative ways to project land use, water resource, energy, and ecosystem service in regions, which can carry out related policies and actions to address climate change in advance and help achieve sustainable development.

Understanding the response of vegetation spring phenology to climatic factors in arid regions is crucial for projecting the land-climate interactions of arid ecosystems under climate change. The Xinjiang region, an important part of northern China with complex climatic features, was selected as a case study. We investigated the impact of temperature, precipitation, and solar radiation on the start of the vegetation growing season (SOS) using a long-term series of the normalized difference vegetation index, climate data from 1982 to 2014, and the partial least squares regression (PLS) method. The primary findings were following: (1) the regional scaling of the mean SOS ranged from 95 to 113 day of year (DOY) and showed distinct spatial heterogeneity for different vegetation types. The relative percentage of the area that exhibited advanced SOS (65.80%) was larger than that of the area that exhibited delayed SOS (34.20%), with a regional advancing tendency of 0.19 days per year during the study period. Different vegetation types showed an advancing SOS, which shifted to delaying after 2005. (2) Temperature significantly affected the SOS for various vegetation types. Generally, the warming spring temperatures led to advanced SOS, whereas reduced warming in spring after 2005 reversed the SOS trends. The higher solar radiation occurring from late winter to spring also contributed to the advance in the SOS. Conversely, the increasing precipitation during this period caused a delay in the SOS. These results can provide a useful reference for improving the vegetation phenology models of arid regions.

In this study, we investigate the spatiotemporal characteristics of drought in India and its impact on agriculture during the summer season (April–September). In the analysis, we use Standardized Precipitation Evapotranspiration Index (SPEI) datasets between 1982 and 2012 at the six-monthly timescale. Based on the criterion SPEI < −1, we obtain a map of the number of occurrences of drought and find that the humid subtropical Upper Middle Gangetic Plain (UMGP) region is highly drought-prone, with an occurrence frequency of 40%–45%. This UMGP region contributes at least 18%–20% of India’s annual cereal production. Not only the probability of drought, but the UMGP region has become increasingly drought-prone in recent decades. Moreover, cereal production in the UMGP region has experienced a gradual declining trend from 2000 onwards, which is consistent with the increase in drought-affected areas from 20%–25% to 50%–60%, before and after 2000, respectively. A higher correlation coefficient (−0.69) between the cereal production changes and drought-affected areas confirms that at least 50% of the agricultural (cereal) losses are associated with drought. While analyzing the individual impact of precipitation and surface temperature on SPEI at 6 month timescale [SPEI (6)] we find that, in the UMGP region, surface temperature plays the primary role in the lowering of the SPEI. The linkage is further confirmed by correlation analysis between SPEI (6) and surface temperature, which exhibits strong negative values in the UMGP region. Higher temperatures may have caused more evaporation and drying, which therefore increased the area affected by drought in recent decades.

We report our investigation on the intrinsic chemical activity of the anatase TiO2(001)-(1 × 4) reconstructed surface, using epitaxially grown anatase TiO2(001) thin films and using methanol molecules as a probe, characterized by combining scanning tunneling microscopy and temperature-programmed desorption. Our results provide direct evidence that the perfect (1 × 4) lattice sites of the surface are intrinsically quite inert for the reaction of methanol. We obtain that the activation energy for desorption of molecular methanol is about 0.55–0.64 eV, which is in good agreement with our first-principle calculations based on the structural model with 5-fold coordinated Ti atoms at the ridges of (1 × 4) reconstruction. We find that two types of defect sites, that is, reduced Ti pairs and partially oxidized Ti pairs, are responsible for the chemical activity of the surface, evidenced by the desorption of water due to the dehydrogenation of methanol at the defect sites. The methoxy left at the reduced Ti-pair s...

Over the last 30 years, China has industrialized more rapidly than any other society in history and become the world's largest emitter of CO2. This has demonstrated unprecedented ability to change the socioeconomic landscape, produced great wealth, and led to some catastrophic environmental damage. This is the background that has motivated several authors to postulate that China would initiate geoengineering using solar radiation management. But will China be the first to pioneer climate engineering? The answer, we argue here, is likely to be “no!” We reach this conclusion from an analysis of the historic philosophical tradition that informs the Chinese world view, China's experience of mega-engineering projects both ancient and modern, and the policies implemented over the last 60 years. The debate on geoengineering has to-date been almost exclusively Euro-American, but China has mega-engineering experience, huge resources, and a radically different world-view that needs to be acknowledged. Furthermore we contend that these experiences can be useful internationally in helping to frame the debate on climate mitigation from the perspective of the earth as shared, multiuse and finite.

We investigate the dynamic processes of formaldehyde (HCHO) molecules on 5-fold-coordinated titanium (Ti5c) sites of rutile TiO2(110) surface using scanning tunneling microscopy (STM) together with density functional theory simulations. Our results show that the adsorbed HCHO molecules at Ti5c sites are present as two types of protrusions, either centered at Ti5c rows or centered at bridging oxygen (Ob) rows in the STM images, corresponding to the monodentate adsorption configuration through a O–Ti5c bond and to the bidentate adsorption configuration through both O–Ti5c and C–Ob bonds, respectively, which can be well supported by the simulated images. It is also observed that the monodentate adsorption tends to spontaneously switch to bidentate adsorption. Our results confirm the existence of the energetically more favored bidentate adsorption for HCHO at Ti5c sites. We obtain that the energy barriers are approximately 0.28 and 0.75 eV for the adsorbed HCHO molecules switching from monodentate adsorption ...

Understanding the physics of surface plasmons and related phenomena requires knowledge of the spatial, temporal, and spectral distributions of the total electromagnetic field excited within nanostructures and their interfaces, which reflects the electromagnetic mode excitation, confinement, propagation, and damping. We present a microscopic and spectroscopic study of the plasmonic response in single-crystalline Ag wires grown in situ on Si(001) substrates. Excitation of the plasmonic modes with broadly tunable (UV–IR) femtosecond laser pulses excites ultrafast multiphoton photoemission, whose spatial distribution is imaged with an aberration-corrected photoemission electron microscope, thereby providing a time-integrated map of the locally enhanced electromagnetic fields. We show by tuning the wavelength, polarization, and k-vector of the incident laser light that for a few micrometers long wires we can selectively excite either the propagating surface plasmon polariton modes or high-order multipolar reso...

We report our investigation of the reversible reaction of methanol and the migration of hydrogen adatom (Had) on TiO2(110)-(1 × 1) surface at various temperatures and methanol coverages using scanning tunneling microscopy joint with density functional theory (DFT) calculations. At a relatively low coverage measured at room temperature, the methanol species adsorbed at the oxygen vacancy (OV) sites are immobile and appear only as a dissociative form, and the observed Had migration events are very few. However, when the OV sites are fully filled by methanol in the methanol-overdosed sample, the methanol species at the OV sites keep immobile but frequently switch between molecular and dissociative forms, accompanied by dramatically enhanced Had migration. Meanwhile, an established equilibrium shows a concentration ratio of 1:3 between the molecular and dissociative methanol. At 235 K, we directly visualized and confirmed that the reversible reactions of methanol and the enhanced Had migration are mediated by...

We systematically investigated the photocatalytic reaction of methanol on the TiO2 (110)-(1 × 1) surface under irradiation with ultraviolet (UV) light performed at various conditions, using scanning tunneling microscopy (STM) jointed with temperature-programmed desorption (TPD) techniques. Our STM and TPD results show that the photocatalytic reaction is indeed initiated from the molecular methanol at the 5-fold coordinated Ti sites, as commonly ascribed to the methanol oxidation by the photogenerated holes, reflecting the highly photoactive nature of methanol. The formaldehyde yield from the TPD results is much smaller by a factor of 2/3 than the amount of dissociated methanol from the STM results at 80 K. This observation can be assigned to the reverse reaction during the TPD measurement, and may explain the lower yield of formaldehyde using molecular methanol than using methoxy. From the fractal-like reaction kinetics of methanol, we can associate the coverage-dependence of the spectral dimensions with ...

The ‘4 per mille’ initiative, launched in 2015, highlighted the crucial role of soil organic carbon (SOC) sequestration in food security and climate change adaptation and mitigation. The objectives of this study were to investigate the changes in the SOC stock (SOCs) with depth and time and explore the SOC accumulation process, in a millennium chronosequence derived from marine sediments. Chronofunctions were formulated based on SOCs at different depths to evaluate the effects of sampling depth on chronofunctions and the rates of SOC sequestration. The depth distribution of SOCs showed that SOC accumulation occurred mainly in the top 40 cm, with 69% of the SOC being distributed in the upper 0–40 cm layers. The chronofunctions yielding the best fits changed from linear to power and then to logarithmic, suggesting that sampling depth affected the chronofunction type. The SOCs for the entire profile (0–100 cm) could be estimated from that in the 0–20 cm or 0–50 cm, which can potentially aid the estimation of legacy SOC data. The SOC sequestration rates were found to be high at the beginning of development, gradually slowing down with time. The soil in this area can sequestrate SOC for more than 2000 years, at a rate greater than 0.4%. Spectroscopy and digital soil mapping methods can provide accurate and acceptable SOC data pertaining to agriculture and climate change and could be a potential technology for global SOC monitoring.

The summer surface air temperature (SAT) in the Humid Subtropical Climate Zone in India, exhibits a significant cooling trend (~−3 °C/40 yrs.) in CRU observational data during 1961–2000. Here we investigate the contribution of internal and external factors, which are driving this cooling trend. Using the Community Earth System Model-Large Ensemble (CESM-LE), we analyze the historical climate change in presence of internal climate variability. Most of the model ensemble members could reproduce this amplified cooling (

Despite globalization and the scale of international food trade, access to sufficient food remains a major challenge in Africa. The most effective way to mitigate food insecurity is to increase crop production. To answer the question that whether African countries have the capacity to mitigate food shortages by best cultivating practices observed on current cropland, in this study, we use the local net primary productivity scaling (LNS) method to evaluate the currently attainable potential yield-gap (CAYgap). The CAYgap is initially used to suggest steps towards best regional agricultural practices and provide an indicator of regional divergence of cropland productivity in each homogeneous agro-climatic zone. Results indicate that under current climatic conditions, improving each countries’ productivity to the zonal optimal level, around ~ 90% of all African countries have the capacity to mitigate their current energy shortages independently. Thus, to achieve ending hunger, possible efforts are needed which include (1) clarifying what and how socio-economic and institutional factors cause yield divergence across agro-climatic zones and establishing relevant practical policies; (2) strengthening the resilience of food access to make national food availability favors households and individuals; and (3) establishing systematically monitoring platforms on dynamics of crop yields from pixel to regional and from growth phrase to decadal scales. Furthermore, our study demonstrates the feasibility of applying satellite-derived indicators for the maximum yield achieved method to quantify and map the current cropland yield divergence by LNS method, and this method could be applied on different spatial level from regional to global scale with reasonable homogeneous zone scheme.

The mechanical and dielectric properties of two types of amorphous silicon nitride (Si3N4) fibers prior to and following annealing at 800 &deg, C were studied. The tensile strengths of the Si3N4 fiber bundles were measured using unidirectional tensile experimentation at room temperature, whereas the permittivity values were measured at 8.2&ndash, 12.4 GHz using the waveguide method. The results demonstrated that the tensile strength and dielectric properties of Si3N4 fibers were correlated to the corresponding composition, microstructure, and intrinsic performance of electrical resistance. The Si3N4 fibers with a lower content of amorphous SiNxOy presented an improved thermal stability, a higher tensile strength, a higher conductivity, and a significantly stable wave-transparent property. These were mainly attributed to the highly pure composition and decomposition of less amorphous SiNxOy.

The development of animal husbandry in China is facing enormous pressure from increasing demand of meat consumption, climate change, degrading grassland, and changing national policies. This paper presents the latest findings from an anthropological field investigation interviewing local herders, traders, and local officials from farming–pastoral ecotone in Inner Mongolia and shed lights on how locals have adapted their lives to climate change and the new national husbandry policies of the twenty-first century. Based on the anthropological interviews, we discussed the future opportunities and challenges of animal husbandry development in farming–pastoral ecotone. Results suggested that national ecological conservation policies and meat price have much larger impacts on animal husbandry than climate change, as perceived by locals. Family Fencing Policy, a relatively new policy aiming to avoid overgrazing and restore vegetation, was neither well accepted nor well implemented by the local herders. This is partially explained by the poor fencing technology, insufficient support facilities, as well as the high costs and low-profit margins in the animal husbandry. We conclude by suggesting that pastoralism in Northern China may greatly benefit from the development of rural cooperatives and active participation of locals in policy designing and implementation.

International research has focused more attention on arid and semiarid regions in recent years, as climate change has already had adverse impacts on grasslands and local households in the Mongolian plateau. Based on meteorological data, GIMMS AVHRR NDVI3g data, and livestock records, through statistical analysis, a significantly strong warming trend and a slightly decreasing trend in precipitation were ascertained in this region. Precipitation patterns are shifting, and intensifying, extreme events, such as droughts and dzud (extremely harsh winters characterized by heavy snow and low temperature), are a major threat to vegetation growth and animal husbandry development. Following a comparative analysis approach, we explored how the vegetation and animal husbandry response to climate change and extreme weather differ between Inner Mongolia and Mongolia. We found that vegetation growth generally decreased after the mid-1990s, but began to recover from 2001 over the entire region. The agricultural intensification level is higher in Inner Mongolia than in Mongolia, and residents in Inner Mongolia have a greater awareness of unexpected disasters than those in Mongolia. To deal with these challenges, this region warrants further study on how climate extremes will impact on regional animal husbandry and local social economics on the arid and semiarid regions. This could have implications for the international community, local government, local residents, and future scientific activities in this space.

Superconductivity is mutually exclusive with ferromagnetism, because the ferromagnetic exchange field is often destructive to superconducting pairing correlation. Well-designed chemical and physical methods have been devoted to realize their coexistence only by structural integrity of inherent superconducting and ferromagnetic ingredients. However, such coexistence in freestanding structure with nonsuperconducting and nonferromagnetic components still remains a great challenge up to now. Here, we demonstrate a molecule-confined engineering in two-dimensional organic–inorganic superlattice using a chemical building-block approach, successfully realizing first freestanding coexistence of superconductivity and ferromagnetism originated from electronic interactions of nonsuperconducting and nonferromagnetic building blocks. We unravel totally different electronic behavior of molecules depending on spatial confinement: flatly lying Co(Cp)2 molecules in strongly confined SnSe2 interlayers weaken the coordinatio...

World population has more than doubled during the past 50 years and it possibly will keep increasing up to 7.56 billions by 2020, 8.18 billions by 2030 and 9 billion by 2050 (FAO 2003) as shown in Figure 1. Not only the total amount but also the structure of population changed. In 1950, only 30% of the global population were urban dwellers, while in the recent years, this percentage has exceeded 50%, and more than 95% of the net increase in the global population

Consumption of fossil fuel resources leads to global warming and climate change. Apart from the negative impact of greenhouse gases on the climate, the increasing emission of anthropogenic heat from energy consumption also brings significant impacts on urban ecosystems and the surface energy balance. The objective of this work is to develop a new method of estimating the global anthropogenic heat budget and validate it on the global scale with a high precision and resolution dataset. A statistical algorithm was applied to estimate the annual mean anthropogenic heat (AH-DMSP) from 1992 to 2010 at 1×1 km2 spatial resolution for the entire planet. AH-DMSP was validated for both provincial and city scales, and results indicate that our dataset performs well at both scales. Compared with other global anthropogenic heat datasets, the AH-DMSP has a higher precision and finer spatial distribution. Although there are some limitations, the AH-DMSP could provide reliable, multi-scale anthropogenic heat information, which could be used for further research on regional or global climate change and urban ecosystems.

Electronic heating of cold crystal lattices in nonlinear multiphoton excitation can transiently alter their physical and chemical properties. In metals where free electron densities are high and the relative fraction of photoexcited hot electrons is low, the effects are small, but in semimetals, where the free electron densities are low and the photoexcited densities can overwhelm them, the intense femtosecond laser excitation can induce profound changes. In semimetal graphite and its derivatives, strong optical absorption, weak screening of the Coulomb potential, and high cohesive energy enable extreme hot electron generation and thermalization to be realized under femtosecond laser excitation. We investigate the nonlinear interactions within a hot electron gas in graphite through multiphoton-induced thermionic emission. Unlike the conventional photoelectric effect, within about 25 fs, the memory of the excitation process, where resonant dipole transitions absorb up to eight quanta of light, is erased to produce statistical Boltzmann electron distributions with temperatures exceeding 5000 K; this ultrafast electronic heating causes thermionic emission to occur from the interlayer band of graphite. The nearly instantaneous thermalization of the photoexcited carriers through Coulomb scattering to extreme electronic temperatures characterized by separate electron and hole chemical potentials can enhance hot electron surface femtochemistry, photovoltaic energy conversion, and incandescence, and drive graphite-to-diamond electronic phase transition.

Carbon transfer via international trade affects the spatial pattern of global carbon emissions by redistributing emissions related to production of goods and services. It has potential impacts on attribution of the responsibility of various countries for climate change and formulation of carbon-reduction policies. However, the effect of carbon transfer on climate change has not been quantified. Here, we present a quantitative estimate of climatic impacts of carbon transfer based on a simple CO2 Impulse Response Function and three Earth System Models. The results suggest that carbon transfer leads to a migration of CO2 by 0.1–3.9 ppm or 3–9% of the rise in the global atmospheric concentrations from developed countries to developing countries during 1990–2005 and potentially reduces the effectiveness of the Kyoto Protocol by up to 5.3%. However, the induced atmospheric CO2 concentration and climate changes (e.g., in temperature, ocean heat content and sea-ice) are very small and lie within observed interannual variability. Given continuous growth of transferred carbon emissions and their proportion in global total carbon emissions, the climatic effect of traded carbon is likely to become more significant in the future, highlighting the need to consider carbon transfer in future climate negotiations.

This paper discussed the analysis of the survey on sustainability of bioenergy conducted in the Philippines, India and China. It acquired general perceptions of the people by asking them (a) specific questions about their level of familiarity with bioenergy; (b) relationship of their work to bioenergy; and (c) their opinion on contribution of various feedstock on the economy and impact of bioenergy production on food security. In addition to these questions, we estimated preference weights of various feedstock based on the conjoint choices on bioenergy’s contribution to social stability, social welfare and ecological balance. The estimates revealed significant trade-offs not only among these three dimensions of sustainability but also the relative importance of energy security, food security and ecosystem capacity to other economic, social and environmental objectives. The types of first generation feedstock that are currently used for biofuel production in the respective countries and those that offer alternative household use are perceived as important to the economy and preferred bioenergy feedstock. Based on the results of the study, the preferred role of bioenergy for sustainable development reflects the social and economic concerns in the respective Asian countries, e.g., energy security in China, food security in India, and ecosystem degradation in the Philippines.

Argonaute proteins (Ago) are core components of the RNA Induced Silencing Complex (RISC) that load and utilize small guide nucleic acids to silence mRNAs or cleave foreign DNAs. Despite the essential role of Ago in gene regulation and defense against virus, the molecular mechanism of guide-strand loading into Ago remains unclear. We explore such a mechanism in the bacterium Thermus thermophilus Ago (TtAgo), via a computational approach combining molecular dynamics, bias-exchange metadynamics, and protein-DNA docking. We show that apo TtAgo adopts multiple closed states that are unable to accommodate guide-DNA. Conformations able to accommodate the guide are beyond the reach of thermal fluctuations from the closed states. These results suggest an induced-fit dominant mechanism for guide-strand loading in TtAgo, drastically different from the two-step mechanism for human Ago 2 (hAgo2) identified in our previous study. Such a difference between TtAgo and hAgo2 is found to mainly originate from the distinct rigidity of their L1-PAZ hinge. Further comparison among known Ago structures from various species indicates that the L1-PAZ hinge may be flexible in general for prokaryotic Ago's but rigid for eukaryotic Ago's.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU; International audience; A realistic simulation of snow cover and its thermal properties are important for accurate modelling of permafrost. We analyse simulated relationships between air and near-surface (20 cm) soil temperatures in the Northern Hemisphere permafrost region during winter, with a particular focus on snow insulation effects in nine land surface models, and compare them with observations from 268 Russian stations. There are large cross-model differences in the simulated differences between near-surface soil and air temperatures (ΔT; 3 to 14 °C), in the sensitivity of soil-to-air temperature (0.13 to 0.96 °C °C−1), and in the relationship between ΔT and snow depth. The observed relationship between ΔT and snow depth can be used as a metric to evaluate the effects of each model's representation of snow insulation, hence guide improvements to the model's conceptual structure and process parameterisations. Models with better performance apply multilayer snow schemes and consider complex snow processes. Some models show poor performance in representing snow insulation due to underestimation of snow depth and/or overestimation of snow conductivity. Generally, models identified as most acceptable with respect to snow insulation simulate reasonable areas of near-surface permafrost (13.19 to 15.77 million km2). However, there is not a simple relationship between the sophistication of the snow insulation in the acceptable models and the simulated area of Northern Hemisphere near-surface permafrost, because several other factors, such as soil depth used in the models, the treatment of soil organic matter content, hydrology and vegetation cover, also affect the simulated permafrost distribution.

We perform a land-surface model intercomparison to investigate how the simulation of permafrost area on the Tibetan Plateau (TP) varies among six modern stand-alone land-surface models (CLM4.5, CoLM, ISBA, JULES, LPJ-GUESS, UVic). We also examine the variability in simulated permafrost area and distribution introduced by five different methods of diagnosing permafrost (from modeled monthly ground temperature, mean annual ground and air temperatures, air and surface frost indexes). There is good agreement (99 to 135 × 104 km2) between the two diagnostic methods based on air temperature which are also consistent with the observation-based estimate of actual permafrost area (101 × 104 km2). However the uncertainty (1 to 128 × 104 km2) using the three methods that require simulation of ground temperature is much greater. Moreover simulated permafrost distribution on the TP is generally only fair to poor for these three methods (diagnosis of permafrost from monthly, and mean annual ground temperature, and surface frost index), while permafrost distribution using air-temperature-based methods is generally good. Model evaluation at field sites highlights specific problems in process simulations likely related to soil texture specification, vegetation types and snow cover. Models are particularly poor at simulating permafrost distribution using the definition that soil temperature remains at or below 0 °C for 24 consecutive months, which requires reliable simulation of both mean annual ground temperatures and seasonal cycle, and hence is relatively demanding. Although models can produce better permafrost maps using mean annual ground temperature and surface frost index, analysis of simulated soil temperature profiles reveals substantial biases. The current generation of land-surface models need to reduce biases in simulated soil temperature profiles before reliable contemporary permafrost maps and predictions of changes in future permafrost distribution can be made for the Tibetan Plateau.

International audience; We analyze simulated sea ice changes in eight different Earth System Models that have conducted experiment G1 of the Geoengineering Model Intercomparison Project (GeoMIP). The simulated response of balancing abrupt quadrupling of CO2 (abrupt4xCO2) with reduced shortwave radiation successfully moderates annually averaged Arctic temperature rise to about 1°C, with modest changes in seasonal sea ice cycle compared with the preindustrial control simulations (piControl). Changes in summer and autumn sea ice extent are spatially correlated with temperature patterns but much less in winter and spring seasons. However, there are changes of ±20% in sea ice concentration in all seasons, and these will induce changes in atmospheric circulation patterns. In summer and autumn, the models consistently simulate less sea ice relative to preindustrial simulations in the Beaufort, Chukchi, East Siberian, and Laptev Seas, and some models show increased sea ice in the Barents/Kara Seas region. Sea ice extent increases in the Greenland Sea, particularly in winter and spring and is to some extent associated with changed sea ice drift. Decreased sea ice cover in winter and spring in the Barents Sea is associated with increased cyclonic activity entering this area under G1. In comparison, the abrupt4xCO2 experiment shows almost total sea ice loss in September and strong correlation with regional temperatures in all seasons consistent with open ocean conditions. The tropospheric circulation displays a Pacific North America pattern-like anomaly with negative phase in G1-piControl and positive phase under abrupt4xCO2-piControl.

Understanding the processes of historical land-use change is crucial to the research of global environmental sustainability. Here we examine and attempt to disentangle the evolutionary interactions between land-use change and its underlying causes through a historical lens. We compiled and synthesized historical land-use change and various biophysical, political, socioeconomic, and technical datasets, from the Qing dynasty to modern China. The analysis reveals a clear transition period between the 1950s and the 1980s. Before the 1950s, cropland expanded while forested land diminished, which was also accompanied by increasing population; after the 1980s land-use change exhibited new characteristics: changes in cropland, and decoupling of forest from population as a result of agricultural intensification and globalization. Chinese political policies also played an important and complex role, especially during the 1950s–1980s transition periods. Overall, climate change plays an indirect but fundamental role in the dynamics of land use via a series of various cascading effects such as shrinking agricultural production proceeding to population collapse and outbreaks of war. The expected continuation of agricultural intensification this century should be able to support increasing domestic demand for richer diets, but may not be compatible with long-term environmental sustainability.

An evaluation of precipitation and evapotranspiration simulated by mesoscale models is carried out within the African Monsoon Multidisciplinary Analysis (AMMA) program. Six models performed simulations of a mesoscale convective system (MCS) observed to cross part of West Africa in August 2005. Initial and boundary conditions are found to significantly control the locations of rainfall at synoptic scales as simulated with either mesoscale or global models. When initialized and forced at their boundaries by the same analysis, all models forecast a westward-moving rainfall structure, as observed by satellite products. However, rainfall is also forecast at other locations where none was observed, and the nighttime northward propagation of rainfall is not well reproduced. There is a wide spread in the rainfall rates across simulations, but also among satellite products. The range of simulated meridional fluctuations of evapotranspiration (E) appears reasonable, but E displays an overly strong zonal symmetry. Offline land surface modeling and surface energy budget considerations show that errors in the simulated E are not simply related to errors in the surface evaporative fraction, and involve the significant impact of cloud cover on the incoming surface shortwave flux. The use of higher horizontal resolution (a few km) enhances the variability of precipitation, evapotranspiration, and precipitable water (PW) at the mesoscale. It also leads to a weakening of the daytime precipitation, less evapotranspiration, and smaller PW amounts. The simulated MCS propagates farther northward and somewhat faster within an overall drier atmosphere. These changes are associated with a strengthening of the links between PW and precipitation.