C. Albano  C. Parra  G. González 《Macromolecular Symposia》2010,290(1):95-106

Summary: The use of PMMA as dental and osseous cement and also in the fabrication of intraocular lenses has been widely reported. The combination of its excellent properties with those of hydroxyapatite (HA) to form a composite material, can result in very interesting properties as a biomaterial. The key is to obtain a good filler dispersion and interface bonding. Ultrasonic radiation seems to be a very versatile method for the synthesis of these materials, since the use of conventional initiators can be avoided, the filler dispersion improved and the interface interaction can be promoted. In the present work PMMA/HA composite materials were prepared by three different synthesis routes using ultrasonic radiation, in order to study the effect of the synthesis method on the final microstructure. Method I : in situ synthesis of PMMA and HA, under ultrasonic radiation by emulsion polymerization of MMA and HA precursors. Method II : in situ synthesis of HA, (from its precursors) by high frequency ultrasound in commercial PMMA solution Method III : in situ polymerization of MMA under high frequency ultrasonic radiation and adding HA to the solution and Method IV Mixing of hydroxyapatite nanocrystals, in different proportions, in a solution of commercial PMMA, by different periods from 10 min to 7 h, under low frequency (conventional) ultrasonic radiation, to compare the effect of high frequency and conventional ultrasound radiation. The different materials were characterized by FTIR, SEM, TEM, DRX, ¹H NMR and TGA. The results showed that, all the composites prepared by in situ synthesis showed an interaction between HA and PMMA, manifested by a bonding of the phosphate groups with the polar groups of the polymer matrix observed by FTIR. On the other hand, when the synthesis was carried out simultaneously adding HA and PMMA precursors a inhibition of the polymerization reaction of MMA was observed.  相似文献   

    

Hérica A. Magosso  Rita C. S. Luz  Yoshitaka Gushikem 《Electroanalysis》2010,22(2):216-222

The synthesis and properties of the ion exchange polymer 3‐n‐propyl(3‐methylpyridinium)silsesquioxane chloride (SiPy⁺Cl^?) are described. Based on the Langmuir model, the equilibrium constant at the solid‐solution interface for the reaction, SiPy⁺Cl^?+NO ?SiPy⁺NO , was calculated for nitrite adsorption. The value found, β=8.7×10³ L mol^?1, indicates good affinity of the anion for the solid phase. A carbon paste electrode of the material was tested for NO oxidation and a linear response, in the concentration range between 6.3 and 143.6 μmol L^?1, was obtained by amperometry. The analytical applicability of the proposed system was ascertained by the satisfactory results attained in its application to monitoring of nitrite in natural waters.  相似文献   

    

Amr L. Saber 《Electroanalysis》2010,22(24):2997-3002

Simple, selective and accurate sensors were developed for the determination of melatonin and oxomemazine in biological samples (urine) and in pharmaceutical preparations. Potentiometric measurements were based on bismus tetraiodate‐drug ion‐pair as novel electroactive materials incorporating a plasticized PVC membrane with o‐nitrophenyl octyl ether or dioctyl phthalate. Each sensor was conditioned for at least two days in 0.1 M drug solution before use. It exhibited fast and stable Nernstian response for melatonin and oxomemazine over the concentration range of 1.0×10^?6–1.0×10^?2 M and 1.0×10^?5–1.0×10^?2 M, pH range of 3.0–6.5 and 3.5–6.0 for melatonin and oxomemazine sensors, respectively. Results with an average recovery not more than 101 % and a mean standard deviation less than 1.0 % of the nominal were obtained for the four sensors. The sensors showed reasonable selectivity towards investigated drugs in presence of many cations.  相似文献   

  总被引：2，自引：0，他引：2  

《Radiation Physics and Chemistry》2000,57(3-6):331-335

In the Institute of Nuclear Chemistry and Technology research on microbiological decontamination of medicinal herbs by irradiation has been carried out since 1996. It was shown that using ionizing radiation (a dose of 10 kGy) can obtain satisfactory results of microbiological decontamination of these products. The content of essential biologically active substances such as essential oils, flavonoids, glycosides, anthocyans, antra-compounds, poliphenoloacids, triterpene saponins, oleanosides and plants mucus did not change significantly after irradiation. Pharmacological activity of medicinal herbs has been found satisfactory after microbiological decontamination by irradiation.  相似文献   

    

Joong-Ho Kwon  Myung-Woo Byun  Kang-Soo Kim  Il-Jun Kang 《Radiation Physics and Chemistry》2000,57(3-6):309-313

The hygienic, physicochemical, and organoleptic qualities of white ginseng were monitored during 6 months under accelerated conditions (40°C, 90% r.h.) by observing its microbial populations, disinfestation, and some quality attributes following either gamma irradiation at 2.5–10 kGy or commercial phosphine (PH₃) fumigation. In a comparative study, both treatments were found to be effective for disinfecting the stored samples. Phosphine showed no appreciable decontaminating effects on microorganisms contaminated including coliforms, while 5 kGy irradiation was sufficient to control all microorganisms related to the quality of the packed samples. Irradiation at 5 kGy caused negligible changes in physicochemical attributes of the samples, such as ginsenosides, amino acids, fatty acids, and organoleptic properties, whereas phosphine fumigation was found detrimental to sensory flavor (P<0.01). Quality deterioration occurred in the commercially-packed samples was in the following order: the control, 10 kGy-, phosphine-, and 2.5–5 kGy-treated samples. Accordingly, irradiation at <5 kGy was found to be an effective alternative to phosphine fumigation for white ginseng.  相似文献   

    

Anna Lucia C. H. Villavicencio  Jorge Mancini-Filho  Henry Delince 《Radiation Physics and Chemistry》2000,57(3-6):295-298

Based on the enormous potential for food irradiation in Brazil, and to ensure free consumer choice, there is a need to find a convenient and rapid method for detection of irradiated food. Since treatment with ionising radiation causes DNA fragmentation, the analysis of DNA damage might be promising. In this paper, the DNA Comet Assay was used to identify exotic meat (boar, jacaré and capybara), irradiated with ⁶⁰Co gamma rays. The applied radiation doses were 0, 1.5, 3.0 and 4.5 kGy. Analysis of the DNA migration enabled a rapid identification of the radiation treatment.  相似文献   

    

Ingrid Nine de Bruyn   《Radiation Physics and Chemistry》2000,57(3-6):223-225

During the 1950s to the end of the 1970s the United States Army developed the basic methodology to produce shelf-stable irradiated meat, seafood and poultry products. These products are normally packed without gravy, sauce or brine, as liquid is not required to sterilize the product as in the canning process. This leads to the distinctive “dried cooked” taste normally associated with roasts opposed to the casserole taste usually associated with tinned meats. The Biogam group at the Atomic Energy Corporation of South Africa is currently producing shelf-stable irradiated meats on a commercial basis. The meats are cooked, chilled, portioned, vacuum packed and irradiated to the required minimum dose of 45 kGy at a temperature of between −20 and −40°C to ensure absolute sterility even under tropical conditions. The product is packaged in a high quality four layer laminate pouch and will therefore not rust or burst even under adverse weather conditions and can be guaranteed for more than two years as long as the integrity of the packaging is maintained. Safari operators in remote parts of Africa, mountaineers, yachtsmen, canoeists and geological survey teams currently use shelf-stable irradiated meat products produced in South Africa.  相似文献   

    

Anna Lucia C. H. Villavicencio  Jorge Mancini-Filho  Henry Delinc  e  Ralf Greiner 《Radiation Physics and Chemistry》2000,57(3-6):289-293

The Brazilian bean varieties Phaseolus vulgaris L. var. Carioca and Vigna unguiculata (L.) Walp var. Macaçar were irradiated with doses of 0.5, 1.0, 2.5, 5.0 and 10 kGy and subsequently stored at ambient temperature for 6 months. The anti-nutrients phenolic compounds, tannins and phytate were determined to be 0.48 mg g⁻¹ dry basis, 1.8 mg g⁻¹ dry basis and 13.5 μmol g⁻¹ dry basis in the raw non-irradiated Carioca beans and 0.30 mg g⁻¹ dry basis, 0.42 mg g⁻¹ dry basis and 7.5 μmol g⁻¹ dry basis in the raw non-irradiated Macaçar beans. After soaking and cooking a higher content of phenolic compounds and a lower phytate content was observed in both bean varieties. Tannin content was not affected by soaking and cooking of Carioca beans, but higher after soaking and cooking of Macaçar beans. Using radiation doses relevant for food did not effect the content of the anti-nutrients under investigation in both bean varieties.  相似文献   

    

A von Bohlen  R. Klockenk  mper  S. Garbe  G. Gaul  A. Kn  chel  F. Lechtenberg  L. Palmetshofer 《Spectrochimica Acta Part B: Atomic Spectroscopy》1995,50(14):1769-1777

A synchrotron microprobe has been used to characterize ion implantations of nickel and cobalt in silicon (100) or (111) wafers. The synchrotron radiation is collimated by means of a rigid cylindrical glass capillary of 110 mm length, 5 mm outer and 30 μm or 10 μm inner diameter. The beam is pointed at the wafer sample and the emitted radiation of X-rays is detected by an energy dispersive spectrometer. Line scans are recorded step by step over the implantation areas and across their borders. The sharpness of the borders is characterized at a lateral resolution of 13 μm and the edge lengths ranging from 0.6 to 8 mm are determined with an accuracy better than ± 20 μm. The signal intensity and implantation dose of cobalt ranging from 1 × 10¹⁵ to 1 × 10¹⁷ ions cm⁻² show a linear relationship as is to be expected for the micrometre thin implanted layers.  相似文献   

    

Erandimala U. Kulawardana  Douglas C. Neckers 《Journal of polymer science. Part A, Polymer chemistry》2010,48(1):55-62

A photoresponsive oil sorber (POS) with a hydrophobic, photoresponsive core and shell has been synthesized via suspension polymerization. Lauryl acrylate, isodecyl acrylate, and tert‐butylstyrene were used as monomers, 4‐(methacrylamino)azobenzene (Azo‐M) used as photoresponsive monomer, and bis(methacryloylamino)azobenzene (Azo‐CL‐M) used as photoresponsive surface crosslinker. The POS prefers nonpolar solvents. It absorbed 15 times its dry weight in toluene, 19 times its dry weight in chloroform, and 16 times its dry weight in dichloromethane. Rapid and photoresponsive desorption of solvent (86% of solvent expulsed in 30 min) was characteristic. POS is an excellent gasoline absorber rapidly increasing its body weight in its presence. The new POS is less dense than water, and can potentially be used for cleaning oil spills on water. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 55–62, 2010  相似文献