Tetraazaisoindigos:Serpentine Syntheses and Their Expected and Unexpected Photophysical and Electronic Properties.

Isoindigo, an electron-withdrawing building block for polymeric field-effect transistors, has long been considered to be non-fluorescent. Moreover, using electron-deficient heterocycle to replace the phenyl ring in the isoindigo core for better electron transport behaviour is synthetically challenging. Here we report the syntheses of a series of tetraazaisoindigos, including pyrazinoisoindigo (PyrII), pyrimidoisoindigo (PymII) and their hybrid (PyrPymII), and the investigation on their photophysical and electric properties. Proper flanking groups need to be chosen to stabilize these highly electron-deficient bislactams. Both PyrII and PymII derivatives show lower LUMO energy levels than that of naphthalene bisimide (NDI). Interestingly, PyrII is instinctively unstable and can be easily reduced, while both PymII derivatives are stable. More surprisingly, PymII derivatives are highly fluorescent and their photoluminescence quantum yields are around 40%, 133 times higher than that of reported isoindigo derivatives. UV-vis spectroscopic results and theoretical calculations show that strong intramolecular hydrogen-bond exists in PymII, which prohibits it from non-radiative decay and accounts for its fluorescent behaviour.  PymII deriviatives are n-type semiconductors, while Ph-PyrII and the hybrid show balanced ambipolar charge transport behaviour, all among the best isoindigo derivatives. Our study not only discloses the structure-property relationship of tetraazaisoindigos, but also provides electron-deficient monomers for conjugated polymers.

Synthesis of Fe3O4@Phoslock® composites and the application in adsorption of phosphate from aqueous solution.

Assisted with an organosilane, Fe3O4@Phoslock® composites with different constituents were synthesized to separate phosphate from aqueous solution. The experimental adsorption data of kinetics and isothermal studies by the composites were well fitted by pseudo-second order and Freundlich models, respectively, suggesting the chemical and heterogeneous adsorption process, i.e., ligand exchange and precipitation. After loading of Fe3O4, Phoslock® became magnetic at the expense of the certain decrease of phosphate uptake from 10.4 to 8.1 mg P/g when [P]0 = 1.0 mmol/L and the solid/liquid ratio of 1.0 g/L were applied. However, compared with the original Fe3O4 nanoparticles, Fe3O4@Phoslock® showed more favorable phosphate uptake and stability against pH variation. The inhibitory influence of anionic ions on phosphate adsorption by three composites followed the order: HCO3- > humate > SiO32- > NO3- ≈ Cl- ≈ SO42-, while the facilitating effect of cations followed the order: Ca2+ > Mg2+ > NH4+. The regeneration rate was higher than 50% for all composites after recycled for 5 times by NaOH, and two of the composites successfully removed 75% phosphate from the landfill leachate treated by the Anammox process with the solid/liquid ratio of 5.0 g/L. This suggests that Fe3O4@Phoslock® composites would be a competitive adsorbent for phosphate removal from real wastewater.

Modeling and research of a space-based spacecraft infrared detection system.

When a spacecraft is in orbit, it is almost impossible to check its working condition. Almost all payload would generate waste heat when working, which is usually ejected by a radiator. By observing the radiator, we can catch a glimpse of a spacecraft's inner information. A thorough model of a space-based infrared detection system is analyzed, taking the radiator into account, which, to the best of our knowledge, has seldom been considered. The calculation result shows that infrared radiation reflected by spacecraft is weak compared with the spacecraft's self-radiation in 8-12 µm, and the contrast ratio between the radiator and surrounding area could be the criterion for judging the working condition of a spacecraft. The limit of detection distance is also increased due the higher temperature of the radiator.

Niche modeling predictions of the potential distribution of Marmota himalayana, the host animal of plague in Yushu County of Qinghai.

BACKGROUND: After the earthquake on 14, April 2010 at Yushu in China, a plague epidemic hosted by Himalayan marmot (Marmota himalayana) became a major public health concern during the reconstruction period. A rapid assessment of the distribution of Himalayan marmot in the area was urgent. The aims of this study were to analyze the relationship between environmental factors and the distribution of burrow systems of the marmot and to predict the distribution of marmots. METHODS: Two types of marmot burrows (hibernation and temporary) in Yushu County were investigated from June to September in 2011. The location of every burrow was recorded with a global positioning system receiver. An ecological niche model was used to determine the relationship between the burrow occurrence data and environmental variables, such as land surface temperature (LST) in winter and summer, normalized difference vegetation index (NDVI) in winter and summer, elevation, and soil type. The predictive accuracies of the models were assessed by the area under the curve of the receiving operator curve. RESULTS: The models for hibernation and temporary burrows both performed well. The contribution orders of the variables were LST in winter and soil type, NDVI in winter and elevation for the hibernation burrow model, and LST in summer, NDVI in summer, soil type and elevation in the temporary burrow model. There were non-linear relationships between the probability of burrow presence and LST, NDVI and elevation. LST of 14 and 23 °C, NDVI of 0.22 and 0.60, and 4100 m were inflection points. A substantially higher probability of burrow presence was observed in swamp soil and dark felty soil than in other soil types. The potential area for hibernation burrows was 5696 km(2) (37.7% of Yushu County), and the area for temporary burrows was 7711 km(2) (51.0% of Yushu County). CONCLUSIONS: The results suggested that marmots preferred warm areas with relatively low altitudes and good vegetation conditions in Yushu County. Based on these results, the present research is useful in understanding the niche selection and distribution pattern of marmots in this region.

[Study on an epidemic of human lung plaque in Nangqian county, Qinghai province].

OBJECTIVE: To study an epidemic of human lung plague fulminant from September to October, 2004 in Nangqian county, Qinghai province. METHODS: Cases were diagnosed through data from epidemiological, clinical, bacteriological, serological and autopsy studies. RESULTS: 14 patients were identified, ending up with 6 deaths and 8 cured. The first case was diagnosed as primary pesticemia late progressed to lung plague. 4 cases were transformed from pesticemia out of 13, leaving the 9 cases as primary lung plague. Situation was under complete control through routinely handling the plague focus. CONCLUSION: The first case was bitten by the infected fleas which parasitized the marmota preyed on a dog but later these fleas were brought into the tent by the dog. The others cases were infected through droplets or dust. Programs on monitoring and controling the amount of marmotas and fleas should to be strengthened to prevent the epidemics of plague in the area.