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This study provided a facile and green method to prepare stable colloid silver nanoparticles in aqueous solution by utilizing the amine-terminated hyperbranched poly(amidoamine) (HPAMAM-NH 2 ) as both stabilizer and reductant. The formation of silver nanoparticles was verified by FTIR, UV-vis, TEM, EDS, and XRD measurements. Monodispersed colloid silver nanoparticles with small particle sizes were obtained, and the average particle size could be effectively controlled from ca. 15 to 4 nm by simply adjusting the molar ratio of N/Ag in feed. The antibacterial activity of the HPAMAM-NH 2 /Ag nanocomposites was also investigated against Gram-positive and Gram-negative bacteria. They were able to efficiently inhibit the growth and multiplication of several bacteria, including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella mobilis, and the bacterial inhibition ratio reached up to 95% at a low silver concentration of 2.7 µg/mL.

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Air pollution fluctuations have been found to strongly depend on the weather dynamics. Here we identify the significant atmospheric processes that affect the local daily variability of air pollution. We develop a multilayered network analysis to detect the interlinks between the 500‐hPa geopotential height and surface air pollution in both China and the United States. We find that Rossby waves significantly affect air pollution fluctuations through the development of cyclone and anticyclone systems and further affect the local stability of the air and the winds. Some of these systems are remote (∼3,000 km) and lead to air pollution 1–2 days later. Thus, the impact of Rossby waves on human life is greater than previously believed. The rapid warming of the Arctic could slow down Rossby waves, thus increasing human health risks. Our method can help to determine the risk assessment of such extreme events and can improve potential predictability.

A novel terminal modification agent to endow hyperbranched polyamidoamine (HPAMAM) with thermo‐/pH‐responsive properties is reported. HPAMAM with terminal vinyl groups is first synthesized and then end‐capped by 1‐adamantylamine (ADA). The resulting hyperbranched polymer (HPAMAM‐ADA) shows interesting thermo‐responsive properties in aqueous solution, which have been investigated by UV‐vis spectroscopy, optical microscopy, and 1H NMR spectroscopy. The lower critical solution temperature can be controlled by adjusting the end‐capping ratio of ADA. In addition, HPAMAM‐ADA exhibits a pH‐dependent water solubility. This pH‐responsive behavior is also studied.magnified image

A crude polysaccharide fraction (DAP-1) was prepared from roots of Dipsacus asperoides by hot water extraction and EtOH precipitation, and tested for anti-complementary activity, mitogenic activity of lymphocytes, and effects on acid phosphatase and phagocytic activities of macrophages. DAP-1 showed not only anti-complementary activity but also a stimulating effect on the mitogenic activity of lymphocytes. DAP-1 also significantly suppressed the phagocytic activity of macrophages.Although DAP-1 directly stimulated the mitogenecity of lymphocytes, it had no effect on lipopolysaccharide-or concanavalin A-induced mitogenic activity of lymphocytes. Periodate oxidation and pronase digestion suggested that the polysaccharide moiety in DAP-1 contributed to the expression of its anticomplementary and mitogenic activities and that the protein moiety in DAP-1 was responsible for its effect on phagocytosis. DAP-1 gave three polysaccharide fractions (DAP-2, 3, and 4) by fractionation using cetyltrimethylammonium bromide. All the fractions had potent anti-complementary activity, but showed different stimulating or suppressive effects on the proliferation of lymphocytes, phagocytosis, or acid phosphatase activity. Three potent anti-complementary polysaccharides (DAP-41-la, DAP-41-lb. and DAP-4lla-1) were purified from DAP-4 by anionexchange chromatography, gel filtration, and HPLC. DAP-4l-la, 1-ib, and ha-i consisted of Ara, Rha, Xyl, Gal, GIc and GIcA in a molar ratio of 1.0:0.7:1.0:18.6:22.2:nil; 1.0:0.1:0.3:19.3 26.8:nil; and 3.7:trace:0.6:26.3:5.5 :1.0; respectively. Among the polysaccharides, only DAP-4lla-1 reacted with /i-glucosylYariv antigen. Methylation analysis indicated that DAP-4l-la mainly comprised 4-linked Gal and 3-, 4-, and 6-linked Glc, whereas DAP-4lla-1 consisted mainly of terminal Araf, 3-linked GIc, and 3,6-branched Gal.