Polymers with pendant isocyanate groups. I. Dual synthesis and properties of poly(styrene-co-styryl isocyanate)

The copolymer poly(styrene-co-styryl isocyanate) was synthesized directly by radical initiation from two different monomer pairs: styrene–cinnamoyl azide and styrene–styryl isocyanate. The copolymerization parameters r₁ = 0.93 ± 0.08, r₂ = ?0.7 ± 0.8 for the first monomer pair and r₁ = 7.8 ± 0.6, r₂ = 0 ± 0.3 for the second pair were determined according to the conventional scheme of copolymerization. The intrinsic viscosities and the thermal behavior of the various copolymers were determined. Further, the chemical reactivity of the pendant isocyanate groups toward alcohol and amines was investigated.     

An easy single step route to synthesize open−ended carbon nanotubes

A simple and easy route is described for the synthesis of multiwalled carbon nanotubes (MWCNTs) by pyrolysis of cetyltrimethyl ammonium decatungstate and cetylpyridinium decatungstate in a specially made LET-LOK union cell. The advantages of using a single component precursor is that the organic moiety present in the precursor acts as the source for carbon and in-situ formed tungsten/tungsten carbide acts as a catalyst for the formation of carbon nanotubes. The method produces large quantities of carbon nanotubes with monodisperse, hollow, open ends. The MWCNTs were characterized systematically using SEM, TEM, HRTEM, Raman and XRD analysis. The MWCNTs have average diameters in the range of 15–35 nm and lengths of several hundreds of nanometers.     

Understanding the Antibacterial Mechanism of CuO Nanoparticles: Revealing the Route of Induced Oxidative Stress

To date, there is still a lack of definite knowledge regarding the interaction of CuO nanoparticles with bacteria and the possible permeation of the nanoparticles into bacterial cells. This study was aimed at shedding light on the size‐dependent (from the microscale down to the small nanoscale) antibacterial activity of CuO. The potent antibacterial activity of CuO nanoparticles was found to be due to ROS‐generation by the nanoparticles attached to the bacterial cells, which in turn provoked an enhancement of the intracellular oxidative stress. This paradigm was confirmed by several assays such as lipid peroxidation and reporter strains of oxidative stress. Furthermore, electron microscopy indicated that the small nanoparticles of CuO penetrated the cells. Collectively, the results reported herein may reconcile conflicting concepts in the literature concerning the antibacterial mechanism of CuO nanoparticles, as well as highlight the potential for developing sustainable CuO nanoparticles‐based devices for inhibiting bacterial infections.     

Selective cytotoxic effect of ZnO nanoparticles on glioma cells

In this study we examined the cytotoxic effect of ZnO nanoparticles on various human cancer and normal cells. We found that the ZnO nanoparticles exerted a cytotoxic effect on the human glioma cell lines A172, U87, LNZ308, LN18, and LN229, whereas no cytotoxic effect was observed on normal human astrocytes. Similarly, the ZnO nanoparticles induced cell death in breast and prostate cancer cell lines while no major effect was observed in the respective normal breast and prostate cell lines. Using the fluorescent dye 2,7-dichlorofluorescein diacetate, we found that treatment of the glioma cells with ZnO nanoparticles induced a large increase in the generation of reactive oxygen species (ROS) and treatment of the cells with N-acetyl cysteine decreased the cytotoxic effect of the ZnO nanoparticles. In contrast, a smaller effect on ROS generation was observed in the normal astrocytes. These results suggest that ZnO nanoparticles may be employed as a selective cytotoxic agent for the eradication of cancer cells.     

纳米金属镍的制备与磁性研究

采用微波polyol还原法成功地制备了单分散5～10 nm镍球颗粒,由高分辨率电子显微镜(HRTEM)观察证实, 5 nm镍的颗粒面间距为0.2033 nm,与文献报道的镍的FCC结构(100)面的0.2034 nm比较吻合[JCPDS: 4-850].通过在不同温度下测量零场冷(ZFC)和场冷(FC,1600 kA·m-1)所获样品的磁滞回线,发现纳米镍从铁磁性过渡到超顺磁性的相变温度Tpt=100 K,在Tpt温度以上,磁滞回线都发生偏置.     

The dying Dead Sea: The microbiology of an increasingly extreme environment

The Dead Sea, on the border between Israel and Jordan, currently contains around 348 g salt L^?1. Divalent cations (Mg²⁺, Ca²⁺) dominate over monovalent cations (Na⁺, K⁺), while Cl^? and Br^? are the main anions. The pH of the Sea is about 6. The water balance of the lake is negative, having dropped over 1 m year^?1 over the past decade. The water is supersaturated with Na⁺, with massive quantities of halite precipitating to the bottom of the lake. Biological monitoring since 1980 has indicated that blooms of the unicellular green alga Dunaliella and halophilic Archaea of the family Halobacteriaceae only develop following significant dilution of the upper water layers in the lake after very rainy winters. Such events occurred in 1980, and even more dramatically in 1992, when up to 3.5 × 10⁷ Archaea mL^?1 in the diluted upper 5–10 m of the water column coloured the lake red. Species isolated from the lake include Haloferax volcanii, Haloarcula marismortui, Halorubrum sodomense and Halobaculum gomorrense. Dunaliella was no longer observed in the lake after 1996, with prokaryote numbers remaining low. To characterize the residual microbial community in the lake, biomass was collected in February 2007 for environmental genomic analyses. The results were compared with the metagenome of microbial bloom material collected in 1992. The 16S rRNA archaeal phylotypes recovered from the 2007 sample were diverse, with phylotypes distantly related to the genera Halorhabdus, Haloplanus, Natronomonas and others. Halorhabdus sp. also was recovered in culture. The 1992 bloom sample was very homogeneous, however, with a single cluster remotely related to Halobacterium salinarum. These results illustrate that the microbial communities are dynamic, even in one of the most extreme environments on Earth, and exhibit strong shifts in species composition as conditions for life become increasingly adverse.