High-Efficiency Dynamic Terahertz Deflector Utilizing a Mechanically Tunable Metasurface.

Terahertz (THz) wave manipulation, especially the beam deflection, plays an essential role in various applications, such as next-generation communication, space exploration, and high-resolution imaging. Current THz optical components and devices are hampered by their large bulk sizes and passive responses, limiting the development of high-performance, miniaturized THz microsystems. Tunable metasurfaces offer a powerful dynamic optical platform for controlling the propagation of electromagnetic waves. In this article, we presented a mechanically tunable metasurface (MTM), which can achieve terahertz beam deflection and vary the intensity of the anomalous reflected terahertz wave by changing the air gap between the metallic resonator (MR) array with phase discontinuities and Au ground plane. The absence of lossy spacer materials substantially enhances deflection efficiency. The device was fabricated by a combination of the surface and bulk-micromachining processes. The THz beam steering capability was characterized using terahertz time domain spectroscopy. When the air gap is 50 µm, the maximum deflection coefficient reaches 0.60 at 0.61 THz with a deflection angle of ~44.5°, consistent with theoretical predictions. We further established an electrically tunable miniaturized THz device for dynamic beam steering by introducing a micro voice coil motor to control the air gap continuously. It is shown that our designed MTM demonstrates a high modulation depth of deflection coefficient (~ 62.5%) in the target steered angle at the operating frequency. Our results showcase the potential of the proposed MTM as a platform for high-efficiency THz beam manipulation.

Community characteristics of autotrophic CO2-fixing bacteria in karst wetland groundwaters with different nitrogen levels.

Karst wetlands are important in the global carbon and nitrogen cycles as well as in security of water resources. Huixian wetland (Guilin) is the largest natural karst wetland in China. In recent years, groundwater nitrogen pollution has increasingly affected the wetland ecosystem integrity due to anthropogenic activities. In this study, it was hypothesized that autotrophic microbial diversity is impacted with the advent of pollution, adversely affecting autotrophs in the carbon and nitrogen cycles. Autotrophic microbes have important roles in abating groundwater nitrogen pollution. Thus, it is of great significance to study the characteristics of autotrophic bacterial communities and their responses to environmental parameters in nitrogen-polluted karst groundwaters. The abundances of the Calvin-Benson cycle functional genes cbbL and cbbM as well as the autotrophic CO2-fixing bacterial communities were characterized in the karst groundwater samples with different levels of nitrogen pollution. The cbbM gene was generally more abundant than the cbbL gene in the groundwater samples. The cbbL gene abundance was significantly positively correlated with dissolved inorganic nitrogen (DIN) concentration (P < 0.01). In the autotrophic CO2-fixing bacterial communities, Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria of the phylum Proteobacteria were predominant. At the genus level, Rubrivivax and Methylibium were the dominant cbbL gene containing genera, while Halothiobacillus and Endothiovibrio were the dominant genera for the cbbM gene. The abundance of autotrophic CO2-fixing bacterial communities increased but their diversity decreased with the inflow of nitrogen into the karst groundwater system. The community structure of autotrophic CO2-fixing bacteria in the groundwaters was also significantly affected by environmental factors such as the carbonic anhydrase (CA) activity, dissolved inorganic carbon (DIC) concentration, temperature, and oxidation-reduction potential (ORP). Nitrogen inflow significantly changed the characteristics of autotrophic CO2-fixing bacterial communities in the karst groundwaters. Some key genera such as Nitrosospira and Thiobacillus were clearly abundant in the karst groundwaters with high nitrogen levels. Their respective roles in nitrification and denitrification impact nitrogen removal in this ecosystem. The findings in this study provide an important reference for biological abatement of nitrogen pollution in the karst groundwater system.

Contribution of microalgae to carbon sequestration in a natural karst wetland aquatic ecosystem: An in-situ mesocosm study.

Carbonate rock weathering coupled with aquatic photosynthesis in karst areas is an important part in the formation of terrestrial carbon sinks. The capacity of photosynthetic carbon sequestration by aquatic microalgae and carbonic anhydrase (CA) is integral in the estimation of carbon sink potential of karst aquatic ecosystems. To date, carbon sequestration by aquatic microalgae in karst areas has been investigated in laboratory experiments. In the present work, the capacity of carbon sequestration by microalgae and CA under natural karst aquatic conditions and the main environmental factors were investigated in field in-situ mesocosms. The Sizhitan Pond of the Huixian karst wetland in Guilin City, Guangxi Province, China, was selected as a typical karst natural water body for this study. The capacity of photosynthetic carbon sequestration varied with microalgal community composition. The microalgal communities with active extracellular CA showed high capacity of carbon sequestration. The average conversion of inorganic carbon to relatively stable organic carbon by microalgae in the Huixian karst wetland aquatic ecosystem was estimated as 4207.5 t C/a. Approximately 28.7% of the bicarbonate fed by the karst underground river was fixed into organic carbon by microalgal photosynthesis. The major environmental factors affecting the capacity of carbon sequestration by microalgae in the karst wetland aquatic ecosystem were the water CA activity, illumination, temperature, total phosphorus and total nitrogen. This study is the first to address the contribution of aquatic microalgae and CA to carbon sequestration under natural karst aquatic conditions. The findings contribute to establishing groundwork for substantiating the carbon sink potential in global karst ecosystems.

The impacts of infectious complications on outcomes in acute pancreatitis: a retrospective study.

BACKGROUND: The occurrence of infectious complications characterizes the more severe forms of acute pancreatitis (AP) and is associated with high mortality. We investigated the effects of infection at different sites in patients with AP, including those with necrotizing pancreatitis (NP). METHODS: We conducted a retrospective analysis of 285 patients who met the inclusion criteria for AP and were admitted to Tianjin Nankai Hospital between January 2016 and September 2019. According to the source of the culture positivity during hospitalization, patients were divided into four groups: sterile group(n = 148), pancreatic infection group(n = 65), extrapancreatic infection group(n = 22) and combined infection group(n = 50). The source of infection, microbiology, biochemical parameters and prognostic indicators were analyzed. RESULTS: In terms of baseline characteristics, the four groups were similar in age, sex, aetiology, previous pancreatitis and diabetes. Compared with the severity of the disease in the other groups, the APACHE II scores(9.91 ± 4.65, 9.46 ± 5.05, respectively) and organ failure rate (40.9 and 50%, respectively)were higher in the extrapancreatic infection group and the combined infection group (P < 0.05). The frequency of surgical intervention and hospitalization time in patients with NP complicated with extrapancreatic infection was greatly increased (P < 0.05). Regarding the primary outcome, patients in the combined infection group had longer hospital stays (68.28 ± 51.80 vs 55.58 ± 36.24, P < 0.05) and higher mortality (24.0% vs 9.2%, P < 0.05) than patients in the pancreatic infection group. In addition, patients in the extrapancreatic infection group also showed high intensive care utilization (59.1%) and mortality rates (18.2%). Among the 137 AP patients with infection complications, 89 patients exhibited multidrug-resistant (MDR) microorganisms, and the mortality rate of patients with MDR bacterial infection was higher than that of patients with non-MDR bacterial infection (24.7% vs 3.6%, P = 0.001). CONCLUSION: Clinicians should be aware that extrapancreatic infection (EPI) significantly aggravates the main outcome in pancreatic infection patients. Infection with MDR bacteria is also associated with AP mortality.

Comparative study on nitrogen removal and functional genes response between surface flow constructed wetland and floating treatment wetland planted with Iris pseudacorus.

Excessive nitrogen accumulated from wastewater with low C/N ratio is a new threat to water ecosystem. In this study, surface flow constructed wetland (SFCW) and floating treatment wetland (FTW) planted with Iris pseudacorus were set in parallel for nitrogen removal. The nitrogen removal efficiencies and pathways, as well as the abundance and functional diversities of the microbial community, were investigated. The results demonstrated that SFCW generally had better nitrogen removal performance than FTW did over four seasons. The average total nitrogen removal efficiency was 66.0% and 43.8% in SFCW and FTW, respectively. The plant uptake played a vital role in nitrogen reduction, which accounted for 29.3% and 7.7% of the total removed nitrogen in SFCW and FTW, respectively. A combination of high-throughput sequencing and quantitative polymerase chain reaction analysis revealed that the two wetland systems had complete nitrogen cycling, and the narG gene was the dominant nitrogen-transformation functional gene in both systems. More abundant denitrifying genes in SFCW than in FTW were also responsible for higher removal capacity of nitrogen. The results suggest that the planting pattern of wetland vegetation has an important impact on nitrogen removal efficiency by influencing the plant absorption and the development of microbial communities.

Dual-Mode Gas Sensor Composed of a Silicon Nanoribbon Field Effect Transistor and a Bulk Acoustic Wave Resonator: A Case Study in Freons.

In this paper, we develop a novel dual-mode gas sensor system which comprises a silicon nanoribbon field effect transistor (Si-NR FET) and a film bulk acoustic resonator (FBAR). We investigate their sensing characteristics using polar and nonpolar organic compounds, and demonstrate that polarity has a significant effect on the response of the Si-NR FET sensor, and only a minor effect on the FBAR sensor. In this dual-mode system, qualitative discrimination can be achieved by analyzing polarity with the Si-NR FET and quantitative concentration information can be obtained using a polymer-coated FBAR with a detection limit at the ppm level. The complementary performance of the sensing elements provides higher analytical efficiency. Additionally, a dual mixture of two types of freons (CFC-113 and HCFC-141b) is further analyzed with the dual-mode gas sensor. Owing to the small size and complementary metal-oxide semiconductor (CMOS)-compatibility of the system, the dual-mode gas sensor shows potential as a portable integrated sensing system for the analysis of gas mixtures in the future.

[Synthesis of a novel rare earth light conversion agent and study on its compatibility in plastics].

2-octyl-1, 3-diphenol-1, 3-propdione was synthesized by phase transfer catalysis and its Sm complexes were prepared. These compounds were characterized by IR, EA, UV and 1H NMR; Sm complex and its mixture doped with PE and PVC show photoluminescence at 650 nm. There is excellent compatibility between Sm complex and plastics by the addition of long carbon chain. Therefore, Sm complex with long carbon chain is a superior light conversion agent with good compatibility in resins with emission wavelength suitable to the 643 and 660 nm for plants' photosynthesis.

[Study on the effect of alpha-allyl on luminescence properties of rare earth complexes with acetylacetone].

3-Allyl-2,4-pentanedione (APD) was synthesized and its rare earth complexes were prepared. The compounds were characterized by EA, IR and 1H NMR. The sensitization of acetylacetone was changed by allyl, which became a novel ligand of Eu.