吸水膨胀橡胶的研究进展

吸水膨胀橡胶是重要的工程防水材料,其既可以吸水止水,还能膨胀受压止水,而且施工便利,在地下施工、水利工程中起到关键作用。但是由于其内部橡胶基体与高吸水树脂相容性差,常会造成反复吸水后止水效果下降,需要频繁更换产品,甚至带来巨大损失。因此,吸水膨胀橡胶的制备及改性研究受到关注。文中综述了吸水膨胀橡胶的机理、制备方法及相关改性研究,对吸水膨胀橡胶研究中存在的问题进行了分析,提出了今后的研究方向。

The impacts of conservation agriculture on crop yield in China depend on specific practices, crops and cropping regions

For smooth and wide application of conservation agriculture(CA), remaining uncertainties about its impacts on crop yield need to be reduced. Based on previous field experiments in China, a meta-analysis was performed to quantify the actual impacts of CA practices(NT: no/reduced-tillage only, CTSR: conventional tillage with straw retention, NTSR: NT with straw retention) on crop yields as compared to conventional tillage without straw retention(CT).Although CA practices increased crop yield by 4.6% on average, there were large variations in their impacts. For each CA practice, CTSR and NTSR significantly increased crop yield by 4.9%and 6.3%, respectively, compared to CT. However, no significant effect was found for NT. Among ecological areas, significant positive effects of CA practices were found in areas with an annual precipitation below 600 mm. Similar effects were found in areas with annual mean air temperature above 5 °C. For cropping regions, CA increased crop yield by 6.4% and 5.5%compared to CT in Northwest and South China, respectively, whereas no significant effects were found in the North China and Northeast China regions. Among crops, the positive effects of CA practices were significantly higher in maize(7.5%) and rice(4.1%) than in wheat(2.9%). NT likely decreased wheat yield. Our results indicate that there are great differences in the impacts of CA practices on crop yield, owing to regional variation in climate and crop types. CA will most likely increase maize yield but reduce wheat yield. It is strongly recommended to apply CA with crop straw retention in maize cropping areas and seasons with a warm and dry climate pattern.

Effects of culm carbohydrate partitioning on basal stem strength in a high-yielding rice population

Rice culm carbohydrate transport can simultaneously affect grain filling and stem lodging resistance by regulating non-structural carbohydrate(NSC) and structural carbohydrate(SC) contents. However, the relationship between carbohydrate transposition and culm strength is not well documented. Accordingly, a high-yielding hybrid rice cultivar(Y Liangyou 2) was tested under different N fertilization regimes at two locations, Taoyuan(a special high-yield eco-site), Yunnan province and Danyang(a representative eco-site of the middle and lower Yangtze), Jiangsu province, China. Significantly higher grain yield and basal stem strength were found at Taoyuan than Danyang under all N rates throughout the two-year experiment. At heading stage, soluble sugars, starch, cellulose and lignin contents of the basal culm at Taoyuan were significantly 132.0%, 73.7%, 1.2%, and 62.7% higher than those at Danyang, respectively. At 20 days after heading, soluble sugars and starch content at Taoyuan decreased significantly compared to Danyang, but lignin content remained higher. Culm carbohydrate transport to kernels at Taoyuan was significantly greater than that at Danyang, and the proportion of soluble sugars and starch was correspondingly 62.9%lower. However, the proportion of lignin and cellulose was 22.7% higher at Taoyuan than that at Danyang. Soluble sugars and starch partitioning were significantly reduced under an increased nitrogen application rate, but SC partitioning was little affected. There were significant positive correlations between basal culm bending stress and dry weight and cellulose and lignin proportions at both locations under all N rates, suggesting that the higher SC proportion at 20 days after heading was primarily responsible for culm strength.These results suggest that high-yielding rice populations with greater culm strength require both moderate NSC transport and greater SC accumulation.

Response of grain yield to plant density and nitrogen rate in spring maize hybrids released from 1970 to 2010 in Northeast China

The objective of this study was to identify the response of grain yield to plant density and nitrogen rate in spring maize hybrids released from 1970 to 2010 and grown extensively in Northeast China.Twenty-one hybrids were grown for 2 years in Northeast China at densities of 30,000,52,500,75,000,and 97,500 plants ha^(-1)and N application levels of 0,150,300,and 450 kg N ha^(-1).Irrespective of density or nitrogen application rate,grain yields both per plant and per unit area were significantly higher for newer than older hybrids.As plant density increased from 30,000 to 97,500 plant ha^(-1),yield per plant of 1970 s,1980 s,1990 s,and 2000 s hybrids decreased by 50%,45%,46%,and 52%,respectively.The response of grain yield per unit area to plant density was curvilinear.The estimated optimum plant densities were about 58,000,49,000,65,000,and 65,000 plants ha^(-1)for hybrids released in the 1970 s,1980s,1990 s,and 2000 s,respectively.The theoretical optimum densities for the hybrids released from the 1970 s to the 2000 s increased by 1750 plants ha^(-1)decade^(-1).Nitrogen fertilization significantly increased grain yields per plant and per unit area for all hybrids.The theoretical optimum N application rates for high yield for hybrids released in the 1970 s and 1980 s were about 280 and 360 kg ha^(-1),and the hybrids from the 1990 s and 2000 s showed highest yield at 330 kg ha^(-1)N.No significant difference in the grain yields of 2000 s hybrids between the N levels of 150 to 450 kg ha^(-1)was found.Significant yield gains per plant and per unit area were found,with average increases of 17.9 g plant^(-1)decade^(-1)and936 kg ha^(-1)decade^(-1)over the period 1970–2010,respectively.Yield gains were attributed mainly to increased yield per plant,contributed by increases in kernel number per ear and1000-kernel weight.The rates of lodging and barren plants of newer hybrids were significantly lower than those of older ones,especially at high plant density.

Organic amendments increase corn yield by enhancing soil resilience to climate change

A 22-year field experiment was conducted in Gongzhuling, Jilin province, China to investigate corn yield response to fertilization practice. Compared to an unfertilized control(CK), all fertilization treatments, including inorganic nitrogen fertilizer only(N), balanced inorganic fertilizers(NPK), NPK plus corn straw(SNPK), and NPK plus farmyard manure(MNPK), resulted in significant increases in corn yield. However, only organic matter amendments sustained increasing yield trends, with annual rates of 0.137 and 0.194 t ha-1for the SPNK and MNPK treatments, respectively(P < 0.05). During the 22 years, the daily mean, maximum and minimum temperatures increased by 0.50, 0.53, and 0.46 °C per decade, whereas precipitation displayed no significant change but showed large seasonal variation. According to a regression analysis, increased air temperature exerted positive effects on corn yields under the SNPK and the MNPK treatments. Under both treatments,soil organic carbon contents and soil nutrient availabilities increased significantly compared to their initial levels in 1990, whereas soil bulk density and total porosity changed slightly under the two treatments, which showed higher soil water storage than other treatments. In contrast, significant increases in soil bulk density and decreases in soil total porosity and soil nutrient availability were observed under the CK, N and NPK treatments. The contributions of soil fertility to corn yield were 28.4%, 37.9%, 38.4%, 39.0%,and 42.9% under CK, N, NPK, SNPK, and MNPK treatments, respectively, whereas climate changes accounted for 27.0%, 14.6%, 12.4%, 11.8%, and 10.8%. These results indicate that, in Northeast China, organic matter amendments can mitigate negative and exploit positive effects of climate change on crop production by enhancing soil quality.

Cropping system innovation for coping with climatic warming in China

China is becoming the largest grain producing and carbon-emitting country in the world,with a steady increase in population and economic development.A review of Chinese experiences in ensuring food self-sufficiency and reducing carbon emission in the agricultural sector can provide a valuable reference for similar countries and regions.According to a comprehensive review of previous publications and recent field observations,China has experienced on average a larger and faster climatic warming trend than the global trend,and there are large uncertainties in precipitation change,which shows a non-significantly increasing trend.Existing evidence shows that the effects of climatic warming on major staple crop production in China could be markedly negative or positive,depending on the specific cropping region,season,and crop.However,historical data analysis and field warming experiments have shown that moderate warming,of less than2.0 °C,could benefit crop production in China overall.During the most recent warming decades,China has made successful adaptations in cropping systems,such as new cultivar breeding,cropping region adjustment,and cropping practice optimization,to exploit the positive rather than to avoid the negative effects of climatic warming on crop growth.All of these successful adaptations have greatly increased crop yield,leading to higher resource use efficiency as well as greatly increased soil organic carbon content with reduced greenhouse gas emissions.Under the warming climate,China has not only achieved great successes in crop production but also realized a large advance in greenhouse gas emission mitigation.Chinese experiences in cropping system innovation for coping with climatic warming demonstrate that food security and climatic warming mitigation can be synergized through policy,knowledge,and technological innovation.With the increasingly critical status of food security and climatic warming,further efforts should be invested in new agricultural policy,knowledge and technology creation,and popularization of climate-smart agriculture,and more financial investments should be made in field infrastructure development to increase cropping system resilience in China.

Long-term inorganic plus organic fertilization increases yield and yield stability of winter wheat

An understanding of wheat yield and yield stability response to fertilization is important for sustainable wheat production. A 36-year long-term fertilization experiment was employed to evaluate the yield and yield stability of winter wheat. Five fertilization regimes were compared,including(1) CK, no fertilizer;(2) NPK, inorganic fertilizer only;(3) O, organic fertilizer only;(4)NPKO, 50% of NPK plus 50% of O, and(5) HNPKO, 80% of NPK plus 80% of O. The greatest yield increase was recorded in HNPKO, followed by NPKO, with O producing the lowest mean yield increase. Over the 36 years, the rate of wheat yield increase in fertilized plots ranged from95.31 kg ha-1 year-1 in the HNPKO to 138.65 kg ha-1 year-1 in the O. Yield stability analysis using the additive main effects and multiplicative interactions(AMMI) method assigned 62.3%, 26.3%,and 11.4% of sums of squares to fertilization effect, environmental effect, and fertilization ×environment interaction effect, respectively. The combination of inorganic and organic fertilization(NPKO and HNPKO) appeared to produce more stable yields than O or NPK, with lower coefficients of variation and AMMI stability value. However, wheat grown with O seemed to be the most susceptible to climate change and the least productive among the fertilized plots.Significant correlations of grain yield with soil properties and with mean air temperature were observed. These findings suggest that inorganic + organic fertilizer can increase wheat yield and its stability by improvement in soil fertility and reduction in variability to climate change.

Acclimation of CH_(4)emissions from paddy soil to atmospheric CO_(2)enrichment in a growth chamber experiment

Elevated levels of atmospheric CO_(2)(eCO_(2))promote rice growth and increase methane(CH_(4))emissions from rice paddies,because increased input of plant photosynthate to soil stimulates methanogenic archae.However,temporal trends in the effects of eCO_(2)on rice growth and CH_(4)emissions are still unclear.To investigate changes in the effects of eCO_(2)over time,we conducted a two-season pot experiment in a walk-in growth chamber.Positive effects of eCO_(2)on rice leaf photosynthetic rate,biomass,and grain yield were similar between growing seasons.However,the effects of eCO_(2)on CH_(4) emissions decreased over time.Elevated CO_(2)increased CH_(4)emissions by 48%-101%in the first growing season,but only by 28%-30%in the second growing season.We also identified the microbial process underlying the acclimation of CH4 emissions to atmospheric CO_(2)enrichment:eCO_(2)stimulated the abundance of methanotrophs more strongly in soils that had been previously exposed to eCO_(2)than in soils that had not been.These results emphasize the need for long-term eCO_(2)experiments for accurate predictions of terrestrial feedbacks.

Leader-Follower UAV Formation Model Based on R5DOS-Intersection Model

This paper proposes a formation of multiple unmanned aerial vehicles(UAVs)based on the R5DOS(RCC-5 and orientation direction)intersection model.After improving the R5DOS-intersection model,we evenly arranged 16 UAVs in 16 spatial regions.Compared with those of the rectangular formation model and the grid formation model,the communication costs,time costs,and energy costs of the R5DOS model formation were effectively reduced.At the same time,the operation time of UAV formation was significantly enhanced.The leader-follower method can enhance the robustness of the UAV formation and ensure the integrity of communication during UAV formation operation.Finally,we conducted a simulation experiment on the model and found that the R5DOS model formation was stable and could maintain the desired formation.The randomly generated UAVs could quickly fly to the formation path in a short time,establish formation,and carry out operations.When the leader fails,the follower could travel to the original trajectory of the failed leader in a short time,replace the leader,and continue to communicate and improve the robustness of the formation.To sum up,the UAV formation based on the R5DOS model has the advantages of long operation time,strong endurance,low communication cost,and stable formation,which is of great significance for research on UAV formation.

Towards Public Integrity Audition for Cloud-IoT Data Based on Blockchain

With the rapidly developing of Internet of Things (IoT), the volume ofdata generated by IoT systems is increasing quickly. To release the pressure ofdata management and storage, more and more enterprises and individuals preferto integrate cloud service with IoT systems, in which the IoT data can be outsourced to cloud server. Since cloud service provider (CSP) is not fully trusted,a variety of methods have been proposed to deal with the problem of data integritychecking. In traditional data integrity audition schemes, the task of data auditing isusually performed by Third Party Auditor (TPA) which is assumed to be trustful.However, in real-life TPA is not trusted as people thought. Therefore, theseschemes suffer from the underlying problem of single-point failure. Moreover,most of the traditional schemes are designed by RSA or bilinear map techniqueswhich consume heavy computation and communication cost. To overcome theseshortcomings, we propose a novel data integrity checking scheme for cloud-IoTdata based on blockchain technique and homomorphic hash. In our scheme, thetags of all data blocks are computed by a homomorphic hash function and storedin blockchain. Moreover, each step within the process of data integrity checking issigned by the performer, and the signatures are stored in blockchain through smartcontracts. As a result, each behavior for data integrity checking in our scheme canbe traced and audited which improves the security of the scheme greatly. Furthermore, batch-audition for multiple data challenges is also supported in our scheme.We formalize the system model of our scheme and give the concrete construction.Detailed performance analyses demonstrate that our proposed scheme is efficientand practical without the trust-assumption of TPA.

Source attributions of heavy metals in rice plant along highway in Eastern China

Air and soil pollution from traffic has been considered as a critical issue to crop production and food safety, however, few efforts have been paid on distinguish the source origin of traffic-related contaminants in rice plant along highway. Therefore, we investigated metals （Pb, Cd, Cr, Zn and Cu） concentrations and stable Pb isotope ratios in rice plants exposed and unexposed to highway traffic pollution in Eastern China in 2008. Significant differences in metals concentrations between the exposed and unexposed plants existed in leaf for Pb, Cd and Zn, in stem only for Zn, and in grain for Pb and Cd. About 46% of Pb and 41% of Cd in the grain were attributed to the foliar uptake from atmosphere, and there were no obvious contribution of atmosphere to the accumulations of Cr, Zn and Cu in grain. Except for Zn, all of the heavy metals in stem were attributed to the root uptake from soil, although significant accumulations of Pb and Cd from atmosphere existed in leaf. This indicated that different processes existed in the subsequent translocation of foliar-absorbed heavy metals between rice organs. The distinct separation of stable Pb isotope ratios among rice grain, leaf, stem, soil and vehicle exhaust further provided evidences on the different pathways of heavy metal accumulation in rice plant. These results suggested that further more attentions should be paid to the atmospheric deposition of heavy metals from traffic emission when plan crop layout for food safety along highway.

Elevated CO_2 facilitates C and N accumulation in a rice paddy ecosystem

Elevated CO2 can stimulate wetland carbon （C） and nitrogen （N） exports through gaseous and dissolved pathways, however, the consequent influences on the C and N pools are still not fully known. Therefore, we set up a free-air CO2 enrichment experiment in a paddy field in Eastern China. After five year fumigation, we studied C and N in the plant-water-soil system. The results showed： （1） elevated CO2 stimulated rice aboveground biomass and N accumulations by 19.1% and 12.5%, respectively. （2） Elevated CO2 significantly increased paddy soil TOC and TN contents by 12.5% and 15.5%, respectively in the 0-15 crn layer, and 22.7% and 26.0% in the 15-30 cm soil layer. （3） Averaged across the rice growing period, elevated CO2 greatly increased TOC and TN contents in the surface water by 7.6% and 11.4%, respectively. （4） The TOC/TN ratio and natural 5ISN value in the surface soil showed a decreasing trend under elevated CO2. The above results indicate that elevated CO2 can benefit C and N accumulation in paddy fields. Given the similarity between the paddies and natural wetlands, our results also suggest a great potential for long-term C and N accumulation in natural wetlands under future climate patterns.

PGC-1α overexpression promotes mitochondrial biogenesis to protect auditory cells against cisplatin-induced cytotoxicity

Cisplatin(CDDP)-induced ototoxicity is one of the common adverse effects of cisplatin chemotherapy.Thus far,effective approaches for attenuating hearing loss are unavailable in clinical practice.Mitochondrial biogenesis acts as a master element of mitochondrial health and is necessary for mitochondrial quality control.The current study examined whether mitochondrial biogenesis is involved in CDDP-induced ototoxicity.Herein,we showed that CDDP damaged mitochondrial function and caused death of House Ear Institute-Organ of Corti 1(HEI-OC1)cells by impairing mitochondrial biogenesis.Moreover,overexpression of peroxisome proliferatoractivated receptor-g coactivator-1a,a key factor in mitochondrial biogenesis,promoted mitochondrial biogenesis in HEI-OC1 cells and protected them against CDDP-induced cytotoxicity.These findings suggest that mitochondrial biogenesis is involved in the pathology of CDDP cytotoxicity of HEI-OC1 cells,and activation of peroxisome proliferator-activated receptor-g coactivator-1a can be considered a potential therapeutic strategy to attenuate CDDP-mediated ototoxicity.