Study on the Design, Preparation, and Performance Evaluation of Heat-Resistant Interlayer-Polyimide-Resin-Based Neutron-Shielding Materials.

Polymers have an excellent effect in terms of moderating fast neutrons with rich hydrogen and carbon, which plays an indispensable role in shielding devices. As the shielding of neutrons is typically accompanied by the generation of γ-rays, shielding materials are developed from monomers to multi-component composites, multi-layer structures, and even complex structures. In this paper, based on the typical multilayer structure, the integrated design of the shield component structure and the preparation and performance evaluation of the materials is carried out based on the design sample of the heat-resistant lightweight polymer-based interlayer. Through calculation, the component structure of the polymer-based materials and the three-layer thickness of the shield are obtained. The mass fraction of boron carbide accounts for 11% of the polymer-based material. Since the polymer-based material is the weak link of heat resistance of the multilayer shield, in terms of material selection and modification, the B4C/TiO2/polyimide molded plate was prepared by the hot-pressing method, and characterization analysis was conducted for its structure and properties. The results show that the ball milling method can mix the materials well and realize the uniform dispersion of B4C and TiO2 in the polyimide matrices. Boron carbide particles are evenly distributed in the material. Except for Ti, the other elemental content of the selected areas for mapping is in good agreement with the theoretical values of the elemental content of the system. The prepared B4C/TiO2/polyimide molded plate presents excellent thermal properties, and its glass transition temperature and initial thermal decomposition temperature are as high as 363.6 °C and 572.8 °C, respectively. In addition, the molded plate has good toughness performs well in compression resistance, shock resistance, and thermal aging resistance, which allows it to be used for a long time under 300 °C. Finally, the prepared materials are tested experimentally on an americium beryllium neutron source. The experimental results match the simulation results well.

Study on a High-Boron-Content Stainless Steel Composite for Nuclear Radiation.

In this research, a high-boron-content composite material with both neutron and γ rays shielding properties was developed by an optimized design and manufacture. It consists of 304 stainless steel as the matrix and spherical boron carbide (B4C) particles as the functional particles. The content of B4C is 24.68 wt%, and the particles' radius is 1.53 mm. The density of the newly designed material is 5.17 g·cm-3, about 68.02% of that of traditional borated stainless steel containing 1.7 wt% boron, while its neutrons shielding performance is much better. Firstly, focusing on shielding properties and material density, the content and the size of B4C were optimized by the Genetic Algorithm (GA) program combined with the MCNP program. Then, some samples of the material were manufactured by the infiltration casting technique according to the optimized results. The actual density of the samples was 5.21 g cm-3. In addition, the neutron and γ rays shielding performance of the samples and borated stainless steel containing 1.7 wt% boron was tested by using an 241Am-Be neutron source and 60Co and 137Cs γ rays sources, respectively, and the results were compared. It can be concluded that the new designed material could be used as a material for nuclear power plants or spent-fuel storage and transportation containers with high requirements for mobility.

High-speed countercurrent chromatography isolation of flavans from Ixeris chinensis and their identification by NMR spectroscopy.

High-speed countercurrent chromatography, combined with macroporous resin chromatography were applied to the separation and purification of flavans from Ixeris chinensis. Four flavans, namely, 5-methoxy-7,4'-dihydroxyflavan-3-ol (1), 5,7-dimethoxy-4'-hydroxyflavan-3-ol (2), 5,7-dimethoxy-4'-hydroxyflavan (3), and 5,7-dimethoxy-8-methyl-4'-hydroxyflavan (4), were obtained from I. chinensis for the first time. Their chemical structural identification was carried out by spectroscopic methods, including 1D and 2D NMR spectroscopy. Amounts of 13.2 mg of compound 1, 6.4 mg of compound 2, 5.8 mg of compound 3, and 14.5 mg of compound 4 were separated from 120 mg 75% ethanol fraction. The purities of 1-4 were 99.1, 99.2, 97.3, and 98.6 %, respectively.

[Applicability of established drought index in Huang-Huai-Hai region based on actual evapotranspiration.] / åŸºäºŽå®žé™ è’¸æ•£æž„å»ºçš„å¹²æ—±æŒ‡æ•°åœ¨é»„æ·®æµ·åœ°åŒºçš„é€‚ç”¨æ€§.

Based on the modeled products of actual evapotranspiration with NOAH land surface model, the temporal and spatial variations of actual evapotranspiration were analyzed for the Huang-Huai-Hai region in 2002-2010. In the meantime, the agricultural drought index, namely, drought severity index (DSI) was constructed, incorporated with products of MOD17 potential evapotranspiration and MOD13 NDVI. Furthermore, the applicability of established DSI in this region in the whole year of 2002 was investigated based on the Palmer drought severity index (PDSI), the yield reduction rate of winter wheat, and drought severity data. The results showed that the annual average actual evapotranspiration within the survey region increased from the northwest to the southeast, with the maximum of 800-900 mm in the southeast and the minimum less than 300 mm in the northwest. The DSI and PDSI had positive correlation (R2=0.61) and high concordance in change trend. They all got the low point (-0.61 and -1.33) in 2002 and reached the peak (0.81 and 0.92) in 2003. The correlation between DSI and yield reduction rate of winter wheat (R2=0.43) was more significant than that between PDSI and yield reduction rate of winter wheat (R2=0.06). So, the DSI reflected a high spatial resolution of drought pattern and could reflect the region agricultural drought severity and intensity more accurately.

[Variation characteristics and influencing factors of actual evapotranspiration under various vegetation types: A case study in the Huaihe River Basin, China.] / ä¸åŒæ¤è¢«æ¡ä»¶ä¸‹å®žé™ è’¸æ•£çš„å˜åŒ–ç‰¹å¾åŠå ¶å½±å“å› å­­­ä»¥æ·®æ²³æµåŸŸä¸ºä¾‹.

The actual evapotranspiration was modelled utilizing the boreal ecosystem productivity simulator (BEPS) in Huaihe River Basin from 2001 to 2012. In the meantime, the quantitative analyses of the spatial-temporal variations of actual evapotranspiration characteristics and its influencing factors under different vegetation types were conducted. The results showed that annual evapotranspiration gradually decreased from southeast to northwest, tended to increase annually, and the monthly change for the average annual evapotranspiration was double-peak curve. The differences of evapotranspiration among vegetation types showed that the farmland was the largest contributor for the evapotranspiration of Huaihe Basin. The annual actual evapotranspiration of the mixed forest per unit area was the largest, and that of the bare ground per unit area was the smallest. The changed average annual evapotranspiration per unit area for various vegetation types indicated an increased tendency other than the bare ground, with a most significant increase trend for the evergreen broadleaf forest. The thermodynamic factors (such as average temperature) were the dominant factors affecting the actual evapotranspiration in the Huaihe Basin, followed by radiation and moisture factors.

[Observation of ozone dry deposition in the field of winter wheat.] / 冬麦田臭氧干沉降过程的观测.

Ozone is one of the main atmospheric pollutants over surface layer, and its increasing surface ozone concentration and its impact on main crops have become the focus of the public. In order to explore ozone deposition law and environmental factors influencing ozone deposition process, this study used the micrometeorological methods and carried out the experiment under natural conditions. The results showed that during the observational period (the vigorously growing season of wheat), the mean value of ozone flux was -0.35 µg·m-2·s-1(the negative sign indicated that the deposition direction was toward the ground). The mean rate of ozone deposition was 0.55 cm·s-1. The mean value of aerodynamic resistance was 30 s·m-1, the mean value of sub-layer resistance was 257 s·m-1, and that of the canopy layer stomatic resistance was 163 s·m-1. All the test parameters presented distinct diurnal fluctuation. The ozone deposition resistance was influenced by friction velocity, solar radiation velocity, temperature, relative humidity and other factors.

Analgesic effects and structural elucidation of two new flavone C-glycosides from Artemisa sacrorum.

The present study was designed to isolate and characterize the analgesic compounds of Artemisa sacrorum Ledeb. The EtOAc crude extracts from the aerial parts of Artemisa sacrorum Ledeb were separated by chromatography and the structures of new compounds were elucidated based on spectral analyses. Analgesic activities of the isolated compounds were assessed in rats with hot plate test and paw pressure assay. Two new flavone C-glycosides, named as Sacroroside A and B (Compounds 1 and 2) were isolated from the EtOAc crude extract of the aerial parts ofArtemisa sacrorum Ledeb. They showed significant analgesic effects. In conclusion, Compounds 1 and 2 are new natural products, which show significant analgesic effects in a dose-dependent manner.

[Study on Chemical Constituents of Panzeria alaschanica].

OBJECTIVE: To study the chemical constituents of the ethyl acetate extract from Panzeria alaschanica. METHODS: The chemical constituents of ethyl acetate extract from Panzeria alaschanica were isolated and purified by silica gel. Their structures were i- dentified by means of spectra. RESULTS: Nine compounds were obtained and identified as 7-Methoxy coumarin (1), Isorhamnetin (2), Caf- feic acid (3), 5-Hydroxy-7,3',4'-trimethoxyflavone (4), 5-Hydroxy-7,4'-dimethoxyflavone (5),Kaempferol (6), Isorhamnetin-3-O-ß-D- glucoside (7) Kaempferol-3-O-ß-D-glucoside (8), and Isorhamnetin-7-O-ß-D-glucuronyl-(1-->6)-O-α-L-rhamnoside (9). CONCLUSION: Compounds 1-4,6,7 and 9 are isolated from this plant for the first time.

[Nitrous oxide flux at the water-air interface of the rivers in Nanjing during summer].

Employing floating static chamber-chromatography method, the N2O diurnal fluxes at the water-air interface of four rivers (Tuanjie River, Jinchuan River, Inner and Outer Qinhuai River) and Jinniu Lake were monitored in Nanjing during summer. The results show that four rivers act as the sources of N2O emission, but Jinniu Lake is characterized by the absorption of N2O. The highest N2O flux from Inner Qinhuai presented at 20:00 because of the changing of hydrodynamic conditions. Both Jinchuan and Tuanjie rivers' minimum N2O fluxes were detected when the content of dissolved oxygen was extremely low. The tendency of N2O from Outer Qinhuai showed a double-peak because of its daytime nitrification and nocturnal denitrification. The flux of N2O from Jinniu Lake had been noted as being generally higher at night than that during light hours due to the effect of wind. For natural rivers, the proper sampling period is from 08:00 to 12:00, but for the river subjected to interference, the sampling period is different.

[An improved method and its application for agricultural drought monitoring based on remote sensing].

From the viewpoint of land surface evapotranspiration, and by using the semi-empirical evapotranspiration model based on the Priestley-Taylor equation and the land surface temperature-vegetation index (LST-VI) triangle algorithm, the current monitoring technology of agricultural drought based on remote sensing was improved, and a simplified Evapotranspiration Stress Index (SESI) was derived. With the application of the MODIS land products from March to November in 2008 and 2009, the triangle algorithm modeling with three different schemes was constructed to calculate the SESI to monitor the agricultural drought in the plain areas of Beijing, Tianjin, and Hebei, in comparison with the Temperature Vegetation Dryness Index (TVDI). The results showed that SESI could effectively simplify the remote sensing drought monitoring method, and there was a good agreement between SESI and surface soil (10 and 20 cm depth) moisture content. Moreover, the performance of SESI was better in spring and autumn than in summer, and the SESI during different periods was more comparable than TVDI. It was feasible to apply the SESI to the continuous monitoring of a large area of agricultural drought.

[Effects of reduced solar radiation on winter wheat flag leaf net photosynthetic rate].

Taking winter wheat Triticum aestivum L. (cv. Yangmai 13) as test material, a field experiment was conducted in Nanjing City to study the effects of simulated reduced solar radiation on the diurnal variation of winter wheat flag leaf photosynthetic rate and the main affecting factors. Five treatments were installed, i. e., 15% (T15), 20% (T20) , 40% (T40), 60% (T60), and 100% (CK) of total incident solar radiation. Reduced solar irradiance increased the chlorophyll and lutein contents significantly, but decreased the net photosynthetic rate (Pn). Under different solar irradiance, the diurnal variation of Pn had greater difference, and the daily maximum Pn was in the order of CK > T60 > T40 > T 20 > T15. In CK, the Pn exhibited a double peak diurnal curve; while in the other four treatments, the Pn showed a single peak curve, and the peak was lagged behind that of CK. Correlation analysis showed that reduced solar irradiance was the main factor affecting the diurnal variation of Pn, but the physiological parameters also played important roles in determining the diurnal variation of Pn. In treatments T60 and T40, the photosynthesis active radiation (PAR), leaf temperature (T1) , stomatal conductance (Gs) , and transpiration rate (Tr) were significantly positively correlated with Pn, suggesting their positive effects on Pn. The intercellular CO2 concentration (Ci) and stomatal limitation (Ls) had significant negative correlations with Pn in treatments T60 and T40 but significant positive correlations with Pn in treatments T20 and T15, implying that the Ci and Ls had negative (or positive) effects on Pn when the solar irradiance was higher (or lower) than 40% of incident solar irradiance.

[Combination effects of enhanced UV-B radiation and O3 stress on photosynthetic characteristics of winter wheat].

Experiments were conducted under open-top-chambers conditions to assess the photosynthetic responses of wheat plants (Triticum aestivum L., YangMail6) to supplemental UV-B radiation (10%-10.9% higher then control group, T1) and enhanced ozone [(100 +/- 9) nmol x mol(-1), T2], separately and in combination (combination treatment, T3), making use of LCpro + Portable Photosynthesis System and DIVING-PAM Fluorometer to determine gas exchange and chlorophyll fluorescence parameters. Results indicated that P(n), G(s), T(r), P(m) and I(k) of T1, T2 and T3 treatments decreased significantly compared to CK (control group, natural air and UV-B radiant intensity condition), while there were no differences between T3 and T1 or T2 or both in major growth stages. UV-B fiercely inhibited the stomatal conductance and transpiration of plants, while T1 stimulated stomata opening and transpiration in jointing stage. Dark respiration (R(d)) of T1 was increased, while no significance difference was found between T2 and CK or T3 and CK in most stages. T1 and T2 reduced F(v)/F(m) value only in booting stage, while T3 was significant lower than CK except jointing stage. qP value declined significantly in treatments of T1, T2 and T3 as Compared to CK, with decreasing amplitude occurring in the order T3 > T1 > T2. NPQ, Y (NPQ), Y (NO) value of T1, T2 and T3 treatments increased significantly compared to CK, with maximum increasing amplitude occurring in the order T3 > T1 > T2, of which NPQ of T1 and T2 turned to decrease since filling stage, and T3 turned to decrease since flowering stage to a greater degree than T1 and T2. T1, T2 and T3 also caused significance reduction in Y (II), with reducing amplitude occurring in the order T3 > T1 > T2. Obviously, supplemental UV-B radiation and enhanced ozone caused a significant decrease in gas exchange capacity, maximum photochemical capacity and photosynthetic activity of winter wheat, and the photoprotective mechanism was damage, leading to greater proportion of excitation energy dissipated in the form of non-regulated heat and fluorescence. The photosystems of winter wheat were damaged by both excess energy and UV-B or excess energy and O3, or excess energy, UV-B and O3 together. UV-B and O3 in combination enhanced the negative effects on photo-protective mechanisms and excitation energy distribution in PS II compared to UV-B or O3 alone, while the interactive effects were less than addition.

[Effects of ozone stress upon winter wheat photosynthesis, lipid peroxidation and antioxidant systems].

Stress effects of surface increased ozone concentration on winter wheat photosynthesis, lipid peroxidation and antioxidant systems in varied growth stages (jointing stage, booting stage, blooming stage and grain filling stage) were studied, the winter wheat was exposed to open top chambers (OTCs) in an open field conditions to three levels ozone concentrations (CK, 100 nmol x mol(-1), 150 nmol x mol(-1)). The results revealed that within 150 nmol x mol(-1) ozone concentration, as the ozone concentration and time increased,total chlorophyll content,chlorophyll a and b contents of winter wheat leaves were general declined,but compared to CK, the total chlorophyll and chlorophyll a content of T1 treatment groups were a little higher at booting and blooming stage; the conductance of stomatal was affected, the activation of unit leaf area decreased, intercellular CO2 concentration and stomatal limitation value showed a fluctuation change tendency. At the same time, a self-protective mechanism of winter wheat were launched. Concrete expression of SOD activity first increased rapidly and then gradually decreased, the activity of POD showed a decrease firstly and then rapidly increased. From the jointing stage to the blooming stage and from the grain filling stage one to grain filling stage two, the activity of CAT rapidly increased first and then comparatively decreased, but the content of MDA kept steadily rising. The carotenoid content increased first and then decreased, heat dissipation of unit leaf area increased. These results indicate that antioxidant enzymes can not completely eliminate excessive reactive oxygen species in vivo of winter wheat, then lead to accumulation of reactive oxygen species, further exacerbate the lipid peroxidation, that result in the increase of membrane permeability, degradation of chlorophyll, reduction of net photosynthetic rate, imposing on the winter wheat leaves senescence process.

[Effects of long-term ozone exposure on chlorophyll a fluorescence and gas exchange of winter-wheat leaves].

In order to provide basis for evaluating the effects of air pollutant such as O3 on crops yield and food security, the effects of O3 fumigation (ambient air, CK; 100 nL x L(-1), T1; 150 nL x L(-1), T2) on chlorophyll a fluorescence and gas exchange of a field-grown winter-wheat (Triticum aestivum L. Yang Mai 13) in different growing period were conducted via open-top chamber technique in conjunction with Diving-PAM fluorometer and LC pro + photosynthesis system. Results indicated that Fv/Fm caused by T1 was higher than 0.8, while the Pm, qP, (1-qP)/NPQ and Y(NO) were similar to those of CK, the NPQ and Y(NPQ) were increased by 13.5%-29.0% and 13.3%-22.7% respectively due to O3 stress. Under nature light (rapid light curve, RLC) and after dark adaptation (induction curve in steady-state, IC) the Yield of T1 was decreased by 4.6%-7.6% and 11.3%-19.3% respectively, with 8.0%-9.8% and 11.0%-23.1% reductions in Pn, and Gs compared to CK, respectively. In heading stage and blooming stage, the Ls of T, was greater than CK, but in filling stage and mature stage, it became lower compared to CK. The Fv/Fm was slightly lower than 0.8 under T2 treatment, with the Y(NO), (1-qP)/NPQ and c(i) were increased by 37.9%-75.6%, 157.1%-325.8% and 3.4%-18.1% relative to CK. Under RLC and IC condition, the Yield of T2 was respectively decreased by 10.2%-13.6% and 21.4%-29.1%, and the Pn, Ls, qP, Pm, NPQ and Y(NPQ) were decreased by 28.1%-39.9%, 5.2%-21.3%, 15.8%-30.4%, 27.6%-45.6%, 3.3%-52.9% and 5.7%-17.9% in comparison, respectively. Obviously the enhanced O3 causes a significant decrease in the capacity of photosynthesis of winter wheat, and the influence mechanism presents a series of dynamic changes according to growing seasons. The reduction of Fv/Fm under T1 treatment is a response of PS II reaction center to the increase of NPQ, and the decrease in Pn and Yield is a consequence of protective adjustment, by this approach, the antioxidant system and energy dissipation mechanism can thus prevent light damage to the PS II reaction center of winter wheat. Under T2 treatment, the CO2 assimilation and Q(A) re-oxidizing during actinic illumination are restricted, the energy dissipation mechanism was destroyed, and the reduction of photosynthesis was mainly due to damage in photosystem caused by O3 and excess light. The critical loads for O3 of PS II reaction center is between 100 nL x L(-1) and 150 nL x L(-1) close to 100 nL x L(-1). While the Fv/Fm value is not an effective index for assessing O3 influence on winter-wheat. Although the winter-wheat can have certain adapted ability to O3 stress, the growing enhancement of surface O3 is still a great threat to agricultural production in China.