Search

The precipitation characteristics in Hangzhou of Zhejiang Province, China under the background of global climate change are analyzed using the meteorological observation data obtained from the Hangzhou base station in this study. We investigate the climate characteristics of precipitation in Hangzhou from several aspects, such as centennial trend, seasonal change, periodicity and the variation of extreme precipitation. Our results show a linear decreasing trend and obvious interdecadal characteristics in the precipitation of Hangzhou on a centennial timescale. Significantly increased amplitude of precipitation fluctuation was observed since the beginning of the 21st century. For the interdecadal variation of seasonal precipitation on a centennial timescale, precipitation in autumn showed a decreasing trend of 8.1 mm/10a, whereas the trends for the other three seasons were statistically insignificant. The precipitation in Hangzhou showed a decreasing trend in spring and an increasing trend in winter over the past 30 years. Our analyses reveal distinct precipitation cycles, including a quasi-30-year cycle since the 1960s and a quasi-10-year cycle since the 1980s. However, the periodicity has weakened in the past 10 years. In addition, the occurrence of torrential rain has increased rapidly in the past 10 years. Furthermore, influenced by global climate change and regional processes, the variation of extreme precipitation in Hangzhou has changed, which shows strong correlations with the overall trend of annual precipitation. The annual maximum daily precipitation in Hangzhou was mainly in the range of 0–40 mm from 1951 to 1980 and in the range of 40–80 mm from 1981 to 2010 with the maximum daily precipitation occurrence rate of 4.7 times/10a and 6.3 times/10a, respectively. This study emphasizes the risk of urban waterlogging caused by short-term heavy rainfall and provides useful reference to the assessment of extreme meteorological and hydrological disaster risk in Hangzhou.

The oceanic absorption of atmospheric CO _2 acidifies seawater, which accelerates CaCO _3 dissolution of calcifying organisms, a process termed dissolution effect. Promoted CaCO _3 dissolution increases seawater ALK (alkalinity), enhancing ocean carbon sink and mitigating ocean acidification. We incorporate different parameterizations of the link between CaCO _3 dissolution and ocean acidification into an Earth System Model, to quantify the feedback of the dissolution effect on the global carbon cycle. Under SRES A2 CO _2 emission scenario and its extension with emissions of 5,000 PgC in ∼400 years, in the absence of the dissolution effect, accumulated ocean CO _2 uptake between year 1800 and 3500 is 2,041 PgC. The consideration of the dissolution effect increases ocean carbon sink by 195–858 PgC (10%–42%), and mitigates the decrease in surface pH by 0.04–0.17 (a decrease of 10%–48% in [H ^+ ] (hydrogen ion concentration)), depending on the prescribed parameterization scheme. In the epipelagic zone, relative to the Arc-Atlantic Ocean, the Pacific-Indian Ocean experiences greater acidification, leading to greater dissolution effects and the resultant stronger feedbacks on ocean carbon sink and acidification in the Pacific-Indian Ocean. Noteworthy, the feedback of dissolution effect on ocean carbon sink can be comparable with or stronger than the feedback from CO _2 -induced radiative warming. Our study highlights the potentially critical role played by CaCO _3 dissolution effect in the ocean carbon sink, global carbon cycle and climate system.

A facile and productive method has been developed to synthesize uniform LaF3 nanocrystals with controllable shapes, including polyhedrons, nanorods and nanoplates. By tuning the amount of NaOH and ligands (oleic acid and octadecylamine), we can finely tailor the shapes and sizes of LaF3 nanocrystals. Three prepared LaF3 nanostructures were well characterized, followed by a series of control experiments to propose a mechanism for the shape control. Based on the success in materials synthesis, controlled patterning of LaF3 nanoplates on substrates has also been achieved. After Yb/Er or Yb/Tm was co-doped in these LaF3 nanostructures, they could serve as nanoparticulate host matrices to give strong upconversion luminescence, showing great potential in biomedical applications considering their small sizes and well-defined shapes. [ABSTRACT FROM AUTHOR]

One-pot hydrothermal process has been developed to synthesize uniform Te@phenol formaldehyde resin core-shell nanowires with unique fluorescent properties. A synergistic soft-hard template mechanism has been proposed to explain the formation of the core-shell nanowires. The Te@phenol formaldehyde resin core-shell nanowires display unique fluorescent properties, which give strong luminescent emission in the blue-violet and green regions with excitation wavelengths of 270 nm and 402 nm, respectively. [ABSTRACT FROM AUTHOR]

Surface modification of lanthanide-doped upconversion nanocrystals is crucial to make them useful for various biological applications. Unfortunately, the current methods available to achieve a desirable surface exhibiting both high luminescence and good biocompatibility are limited. In this work, we present a facile microemulsion route to coat carbonized glucose on hydrophobic NaYF4 nanocrystals. Owing to the particular structure of the carbonized shell, glucose coating on these UCNs is not only able to preserve strong fluorescence from the core nanocrystals, but it also confers good water solubility and bears various functional groups for conjugating to biomolecules. Compared to 10 nm silica-coated UCNs, these glucose-coated nanocrystals possess better cell biocompatibility, and can be rapidly internalized into cells. Such unique features of glucose-coated UCNs may find promising applications in imaging, diagnosis and therapeutic purposes. Besides, this facile surface-modification route has the potential to be extended to a broad range of other hydrophobic nanocrystals. [ABSTRACT FROM AUTHOR]

Hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals are the best IR-to-visible upconverting materials to date, but user-friendly methods for making pure hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with upconversion fluorescence are still lacking. Most of the methods reported so far require excess fluoride reactants in a high-temperature reaction which are very unfriendly to users and raise safety concerns. In this work, an efficient and user-friendly method was developed for the synthesis of uniform hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with upconversion fluorescence, by forming small solid-state crystal nuclei and further growth and ripening of the nuclei. NaYF4:Yb, Er/Tm nanoplates, nanospheres and nanoellipses were also selectively produced by varying the concentration of the surfactant. All the nanocrystals showed strong upconversion fluorescence, and fluorescence from the nanoplates was observed even when the laser power density was reduced to about 50 mW cm[?]2. These nanocrystals have great potential for use in biology and medicine as fluorescent labels or imaging probes. [ABSTRACT FROM AUTHOR]

Compared to conventional down-conversion fluorescent materials, NIR-to-visible up-conversion fluorescent materials which emit visible light upon near-infrared (NIR) excitation are better suited for biodetection/bioimaging due to their advantages such as minimum photo-damage to living organisms, weak background fluorescence, low signal-to-noise ratio and high detection sensitivity. Uniform hexagonal NaYF4 (b-NaYF4) nanocrystals with up-conversion fluorescence were synthesized. Monodisperse polystyrene nanospheres with an average size of 400 nm in diameter, tagged with different color b-NaYF4 nanocrystals, were prepared using a miniemulsion polymerization method. More than 20 b-NaYF4 nanocrystals were encapsulated in a single polystyrene nanosphere. The nanospheres emit multicolor NIR-to-visible up-conversion fluorescence upon excitation at a wavelength of 980 nm. The nanospheres could be used for a variety of biological applications which require high-sensitivity detection of biomolecules. [ABSTRACT FROM AUTHOR]