Electronic Beam Steering Metamaterial Antenna with Dual-Tuned Mode of Liquid Crystal Material.

In this study, a dual-tuned mode of liquid crystal (LC) material was proposed and adopted on reconfigurable metamaterial antennas to expand the fixed-frequency beam-steering range. The novel dual-tuned mode of the LC is composed of double LC layers combined with composite right/left-handed (CRLH) transmission line theory. Through a multi-separated metal layer, the double LC layers can be loaded with controllable bias voltage independently. Therefore, the LC material exhibits four extreme states, among which the permittivity of LC can be varied linearly. On the strength of the dual-tuned mode of LC, a CRLH unit cell is elaborately designed on three-layer substrates with balanced dispersion values under arbitrary LC state. Then five CRLH unit cells are cascaded to form an electronically controlled beam-steering CRLH metamaterial antenna on a downlink Ku satellite communication band with dual-tuned characteristics. The simulated results demonstrate that the metamaterial antenna features' continuous electronic beam-steering capacity from broadside to -35° at 14.4 GHz. Furthermore, the beam-steering properties are implemented in a broad frequency band from 13.8 GHz to 17 GHz, with good impedance matching. The proposed dual-tuned mode can make the regulation of LC material more flexible and enlarge the beam-steering range simultaneously.

[Identifying the Sources of Groudwater NO3--N in Agricultural Region of Qingdao].

To increase crops yields, applying large amounts of fertilizers has become increasingly common in agricultural regions, resulting in NO3--N groundwater pollution. Agricultural non-point pollution is the main source of groundwater NO3--N pollution. To ensure drinking water safety and quality, it is crucial to clarify the sources of NO3--N pollution in agricultural regions. In this study, 35 sampling sites were randomly selected in the Qingdao agricultural area in 2009 and 2019. The spatial distribution of NO3--N concentration was analyzed by the inverse distance weighting method (IDW). The nitrogen and oxygen isotopes were used as a tool to trace sources of NO3--N and the SIAR model was used to quantify contribution proportion of pollution sources. The results showed that the concentration of NO3--N (average) in groundwater in Qingdao has been reduced from 38.49 mg·L-1 in 2009 to 22.37 mg·L-1 in 2019, but it is still higher than the maximum allowable concentration of NO3--N in drinking water set by the World Health Organization (WHO). The NO3--N concentration gradually increased from south to north both in 2009 and 2019. The cross diagram of δ15N-NO3- and δ18O-NO3- show that the main sources of NO3--N in groundwater in Qingdao are chemical fertilizers, soil nitrogen, and manure and sewage. Water isotopes indicate that precipitation was the main source of groundwater in Qingdao. The SIAR model results indicated that the contribution of each source ranked as follows:manure and sewage (47.42%) > soil nitrogen (27.80%) > chemical fertilizer (14.32%) > atmospheric nitrogen depositions (10.43%). From 2009 to 2019, the quality of groundwater in Qingdao has been improved, but NO3--N pollution still cannot be ignored. According to the results, prevention and control should be made to ensure the safety of drinking water and the sustainable development of agriculture.

[Effects of organic and inorganic fertilizers on emission and sources of N2O in vegetable soils.] / æœ‰æœºè‚¥å’Œæ— æœºè‚¥å¯¹èœåœ°åœŸå£¤N2OæŽ’æ”¾åŠå ¶æ¥æºçš„å½±å“.

To clarify the microbial pathway of the N2O production and consumption under different fertilizers and provide theoretical basis for the reduction of N2O emission and rational management of fertilization in vegetable soils, we examined dynamics of N2O flux and isotope signatures under different fertilizer treatments in the vegetable soils of Beijing, by setting up four treatments (organic-acetylene, organic-nonacetylene, inorganic-acetylene, inorganic-nonacetylene) and using the stable isotope technique of natural N2O abundance. The results showed that the cumulative N2O emission from organic-acetylene group, organic-nonacetylene group, inorganic-acetylene group and inorganic-nonacetylene group was (374±37), (283±34), (458±36), (355±41) g·m-2 in cabbage growing season, respectively. N2O fluxes were significantly lower in treatments with organic fertilizer than those with inorganic fertilizer and significantly higher in acetylene group than nonacetylene group. The degree of N2O reduction were similar in both fertilizer treatments, and higher nitrification was found in inorganic fertilizer than organic fertilizer treatments. Acetylene only inhibited partial nitrification and partial N2O reduction at the peak of N2O emission. When the emission was reduced, N2O reduction could be completely suppressed. Therefore, the inorganic fertilizer might trigger nitrification and promote higher N2O emission. The high concentration of N2O could withstand that acetylene to inhibite N2O reduction. Hence, using organic fertilizers instead of some inorganic ones could effectively reduce N2O emission in vegetable soils of Beijing. The N2O concentration threshold should be considered when we identify N2O source by acetylene inhibition method.

[Effects of soil water condition on N2O emission and its sources in vegetable farmland of North China Plain]. / 不同灌溉量对华北平原菜地N2OæŽ’æ”¾åŠå ¶æ¥æºçš„å½±å“.

To understand the mechanisms of agricultural N2O emission, we investigated the N2O emission dynamics, the N2O isotope signatures, and the site preference value under different soil water conditions in the vegetable farmland of North China, by using the stable isotope technique and the acetylene inhibition method. The results demonstrated that N2O emission was significantly affec-ted by the water condition, and N2O emissions from soil with water-filled pore space (WFPS) of 70% were significantly higher than that with 50% WFPS. N2O emission occurred mostly in the early stage of fertilization, and decreased rapidly in the later stage of fertilization. At 50% WFPS, nitrification was the major process generating N2O during the early fertilization stage, accounting for approximately 90% of the N2O emission. However, the contribution of nitrification decreased sharply, whereas denitrification became the dominant process, accounting for 80% of the N2O emission 7 days after the fertilization. On the other hand, at 70% WFPS, denitrification was the main process releasing N2O during the early fertilization stage, decreasing from 70% to 40% and then gradually increasing to 80% 10 days after the fertilization. Overall, N2O emission was mainly dominated by the denitrification. The effect of different water treatments on soil nitrification and denitrification took place mainly in the early stage of fertilization, and N2O emission was gradually dominated by the denitrification at the later stage. These results suggested we could reduce N2O emission by approp-riately reducing the amount of irrigation in the vegetable farmland of North China.

[A review on development of stable isotope technique in the studies of N2O formation mechanism]. / ç¨³å®šåŒä½ç´ æŠ€æœ¯åœ¨åœŸå£¤N2Oæº¯æºç ”ç©¶ä¸­çš„åº”ç”¨.

As one of three major greenhouse gases, nitrous oxide (N2O) has solicited substantial attention. Stable isotope has been widely used to explore the sources of N2O emissions. Here, we briefly introduced the microbial processes involved in N2O emissions, and the main influencing factors. We further summarized the development of N2O isotope signature of δ15N, δ18O and SP (site preference of 15N in different positions of N2O molecule) in exploring the N2O formation mechanism. The application of these techniques, especially the SP values, is still at the primary stage in China. Therefore, this paper focused on the development of the isotope ratios analysis in partitioning N2O sources from foreign countries, and put forward suggestions on the future research in China.

[In vivo expression of green fluorescent protein gene and immunogenicity of ES312 vaccine both mediated by starburst polyamidoamine dendrimers].

OBJECTIVE: To study the expression of green fluorescent protein gene and immunogenicity of ES312 vaccine both mediated by Starburst polyamidoamine (PAMAM) dendrimers in vivo. METHODS: The complex of green fluorescent protein or ES312 gene with Starburst PAMAM dendrimers were injected intramuscularly in Balb/c mice. The expression level and distribution of green fluorescent protein gene was detected by flow cytometer, Western blot and immunofluorescence assay. The immunogenicity of DNA vaccine was detected by enzyme-linked immunosorbent assay. RESULTS: The expression of green fluorescent protein mediated by Starburst PAMAM dendrimers was found in heart, liver, spleen, lung, kidney, brain and injected muscle from 2 hours to 7 days after the vaccination. The highest expression level of the gene was detected in kidney, as well as in endothelial cells. The antibody response evoked by the DNA vaccine carried by the Starburst PAMAM dendrimers was significantly higher than that of the net DNA vaccination. Vaccination with Starburst PAMAM dendrimers elicited higher expression level of the gene in brain and kidney than with the net gene itself. CONCLUSION: As a novel non-viral DNA carrier with low self-antigenicity, Starburst PAMAM dendrimers have potential to mediate DNA transfer and expression in vivo.