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.     

Wheat straw as substrate for water denitrification

Biological denitrification of drinking water was studied in up-flow laboratory reactors packed with wheat straw which served as the sole carbon source as well as the only physical support for the microorganisms. The highest rates of denitrification (0.053 g N removed l⁻¹ d⁻¹) were observed in fresh reactors during their first week of operation and the efficiency of the process declined thereafter. The addition of fresh wheat straw brought about a temporary improvement of the denitrification performance and a regime of one weekly addition prevented the deterioration of a reactor which was operated for 5 months. The rate of denitrification was affected by the water velocity and decreased at velocities above 0.054 m d⁻¹. Colour and soluble organic carbon associated with fresh straw were removed by adsorption on powdered activated carbon.     

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.     

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.     

NIRS Detection of Moldy Core in Apples

Moldy core of apples is undetectable until the fruit is cut open or bitten into, therefore it can pose serious problems to both producer and consumer. Removal of diseased fruits prior to storage would be most desirable. The objective of this study was to evaluate the ability of VIS-NIR minispectrometers to detect moldy core in apples, on line. An apparatus which is qualified for on-line Near-Infrared Spectroscopy (NIRS) measurements was developed based on an off-the-shelf minispectrometer. Apples, cv. Red Delicious, were collected from several orchards before and during the commercial harvest, and were stored at 0°C pending the tests. The data were analyzed by chemometric procedures, specifically, by partial least squares regression (PLSR), and were classified by means of canonical discriminant analysis. The canonical variables were represented by the latent variables of PLS models based on the spectra. The accuracy of the classification results was high, in light of doubts regarding the moldy fraction threshold of 5%; in such a case the mold covers only the seed carpals of the fruit, where it might remain without really damaging the fruit. Improvements should aim to reduce errors in classifying low-level damage, and also in misclassifying some healthy fruits. The rate of testing (1 s per fruit) is acceptable for quality-control purposes, but should be accelerated for future packing-line implementation.