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41.
Khachatryan L Adounkpe J Maskos Z Dellinger B 《Environmental science & technology》2006,40(16):5071-5076
The formation of radicals from the gas-phase pyrolysis of hydroquinone, catechol, and phenol over a temperature range of 400-750 degrees C was studied using the technique of low-temperature matrix isolation electron paramagnetic resonance (LTMI EPR). Cooling the reactor effluent from pyrolysis in a nitrogen carrier gas to 77 K produces a cryogenic matrix that exhibits poorly resolved EPR spectra. However, using carbon dioxide as a carrier gas formed a matrix that, upon annealing by slowly raising the matrix temperature followed by rapid recooling to 77 K, yielded more resolved, identifiable spectra. Annealed spectra of all three samples resulted in the generation of EPR spectra above 700 degrees C with 6 lines, hyperfine splitting constant approximately 6.0 G, and peak to peak width approximately 3 G that was readily assignable, based on comparison to the literature and theoretical calculations, as that of cyclopentadienyl radical. Pyrolysis at temperatures below 700 degrees C generated a carbon dioxide matrix isolation spectrum with a high g-value (>2.0040) that is attributed to oxygen-containing radicals such as semiquinone or phenoxyl. Conclusive identification of anticipated semiquinone, phenoxyl, and hydroxycyclopentadienyl radicals was complicated by the ability of these radicals to exist in carbon-centered and oxygen-centered resonance structures that can give different EPR spectra. 相似文献
42.
Beata Kaczmarek-Szczepaska Justyna Ostrowska Justyna Kozowska Zofia Szota Anna A. Broyna Rita Dreier Russel J. Reiter Andrzej T. Slominski Kerstin Steinbrink Konrad Kleszczyski 《International journal of molecular sciences》2021,22(11)
The development of scaffolds mimicking the extracellular matrix containing bioactive substances has great potential in tissue engineering and wound healing applications. This study investigates melatonin—a methoxyindole present in almost all biological systems. Melatonin is a bioregulator in terms of its potential clinical importance for future therapies of cutaneous diseases. Mammalian skin is not only a prominent melatonin target, but also produces and rapidly metabolizes the multifunctional methoxyindole to biologically active metabolites. In our methodology, chitosan/collagen (CTS/Coll)-contained biomaterials are blended with melatonin at different doses to fabricate biomimetic hybrid scaffolds. We use rat tail tendon- and Salmo salar fish skin-derived collagens to assess biophysical and cellular properties by (i) Fourier transform infrared spectroscopy—attenuated total reflectance (FTIR–ATR), (ii) thermogravimetric analysis (TG), (iii) scanning electron microscope (SEM), and (iv) proliferation ratio of cutaneous cells in vitro. Our results indicate that melatonin itself does not negatively affect biophysical properties of melatonin-immobilized hybrid scaffolds, but it induces a pronounced elevation of cell viability within human epidermal keratinocytes (NHEK), dermal fibroblasts (NHDF), and reference melanoma cells. These results demonstrate that this indoleamine accelerates re-epithelialization. This delivery is a promising technique for additional explorations in future dermatotherapy and protective skin medicine. 相似文献
43.
Alison E. Patteson Katarzyna Pogoda Fitzroy J. Byfield Kalpana Mandal Zofia Ostrowska‐Podhorodecka Elisabeth E. Charrier Peter A. Galie Piotr Deptua Robert Bucki Christopher A. McCulloch Paul A. Janmey 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(50)
The migration of cells through constricting spaces or along fibrous tracks in tissues is important for many biological processes and depends on the mechanical properties of a cytoskeleton made up of three different filaments: F‐actin, microtubules, and intermediate filaments. The signaling pathways and cytoskeletal structures that control cell motility on 2D are often very different from those that control motility in 3D. Previous studies have shown that intermediate filaments can promote actin‐driven protrusions at the cell edge, but have little effect on overall motility of cells on flat surfaces. They are however important for cells to maintain resistance to repeated compressive stresses that are expected to occur in vivo. Using mouse embryonic fibroblasts derived from wild‐type and vimentin‐null mice, it is found that loss of vimentin increases motility in 3D microchannels even though on flat surfaces it has the opposite effect. Atomic force microscopy and traction force microscopy experiments reveal that vimentin enhances perinuclear cell stiffness while maintaining the same level of acto‐myosin contractility in cells. A minimal model in which a perinuclear vimentin cage constricts along with the nucleus during motility through confining spaces, providing mechanical resistance against large strains that could damage the structural integrity of cells, is proposed. 相似文献
44.
One-Step Synthesis of Thermoplastic Phenylsilsesquioxane Polymer and Its Copolymers with Diphenylsiloxanes 总被引:2,自引:0,他引:2
Elbieta Leniak Zofia M. Michalska Julian Chojnowski 《Journal of Inorganic and Organometallic Polymers》1998,8(1):1-21
The preparation of reversibly softening polymers and copolymers of phenylsilsesquioxane in a one-step synthesis has been studied. The synthetic methods are based on hydrolytic polycondensation of PhSiCl3 or copolycondensation of PhSiCl3 with Ph2SiCl2 using moistened or hydrated salts: (1) moistened Na2CO3, K2CO3, (2) Na2B4O7·10H2O, (3) Na3PO4·12H2O. Syntheses (1) and (2) gave products as reversibly softening and soluble materials, whereas synthesis (3) produced partially cross-linked resins from which a soluble material might be extracted. Polycondensation using borax gave polymers and copolymers with incorporated boron atoms. The polysilsesquioxanes were characterized by size exclusion chromatography (SEC), 1H and 29Si NMR, IR spectroscopy, and elemental analysis. Thermal properties were studied by DSC and thermogravimetry. 相似文献
45.
The aim of this study was to compare the main antioxidant compounds content and the antioxidant activity of white grapefruit and his new hybrid (Jaffa Sweeties). Total phenols were measured colorimetrically using the Folin-Ciocalteu reagent, phenolic acids—by HPLC, anthocyanins and flavonoids—spectrophotometrically. The antioxidant activity of these fruits was determined by total antioxidant activity (TAA) and nitric oxide (NO) methods. Trans-hydroxycinnamic acids (caffeic, p-coumaric, ferulic, and sinapic) were more abundant in white grapefruit than in his hybrid. However, on a fresh weight basis, grapefruit's hybrid has a higher total phenol content as well as a higher antioxidant capacity in comparison with white grapefruit. A linear relationship existed between TAA and anthocyanins (R2=0.8068), TAA and flavonoids (R2=0.9320) and TAA and total phenols (R2=0.9446). Our findings indicate the following: (1) Both studied fruits contain a high concentration of natural antioxidants that have not only a high antioxidant activity, but also a good antioxidant quality. (2) The total phenol content and the antioxidant potential are significantly higher in the grapefruit hybrids than in white grapefruits. 相似文献
46.
Zofia Kalicka 《国际钢铁研究》1991,62(4):157-163
The growth model for nuclei of oxide inclusions growing during the process of steel deoxidation is proposed. The evolution of the inclusion composition has been analysed by solving the continuity equation for the probability-density function f(x,t) (where x is the oxide mole fraction). The calculations were carried out for model parameters and for steel deoxidation by aluminium or silicon-manganese. The result obtained cannot be verified due to the lack of any functional dependence relating chemical composition to inclusion radius. 相似文献
47.
The aim of the work was to evaluate the amino acid composition of fresh spinach and spinach products prepared for consumption. The investigation included fresh and cooked spinach and two kinds of frozen product: one obtained using the traditional method (blanching-freezing-refrigerated storage) and then cooked; and the other, of the ready-to-eat type, obtained using the modified method (cooking-freezing-refrigerated storage) and then prepared for consumption in a microwave oven. In 100 g of edible parts of the as-eaten products, the content of amino acids exceeded that in the raw material from which they were obtained, except for sulphur amino acids and tyrosine. In the as-eaten products, the content of amino acids in protein calculated in 16 g N was similar to that in the raw material, except for lower tyrosine and higher arginine content in the traditional frozen product prepared for consumption. Cystine with methionine was the amino acid limiting the quality of protein in the investigated samples, except for the traditional frozen product prepared for consumption, where the Chemical Score (CS) index was 100. 相似文献
48.
Jacek Słupski Zofia Lisiewska Piotr Gębczyński Radosława Skoczeń‐Słupska 《International Journal of Food Science & Technology》2011,46(9):1816-1822
The aim of the investigation was to compare oxalate retention in two types of frozen product prepared for consumption after frozen storage: one obtained using the traditional method (blanching‐freezing‐frozen storage‐cooking) and a convenience food involving cooking‐freezing‐frozen storage‐defrosting and heating in microwave oven. The investigation included three species of legume vegetables: immature (wax‐stage maturity) seeds of broad bean and green pea, and French bean. Fresh broad bean seeds contained 53 mg total oxalates in 100 g fresh matter; pea 38 mg; and French bean 88 mg. Soluble oxalates comprised 53, 58 and 72% of total oxalates. The treatments applied resulted in reduction of the level of total and soluble oxalates, and oxalate to calcium ratio (broad bean and French bean); there was no influence on the level of calcium bound as calcium oxalate; true retention of oxalates was lower than apparent retention (green pea and French bean). 相似文献
49.
Structural changes during crystallization of apatite and wollastonite in the eutectic glass of Ca3(PO4)2‐CaSiO3 system 下载免费PDF全文
Marlin Magallanes‐Perdomo Antonio H. De Aza Isabel Sobrados Jesús Sanz Zofia B. Luklinska Pilar Pena 《Journal of the American Ceramic Society》2017,100(9):4288-4304
In this study, a bioactive glass of eutectic composition based on Ca3(PO4)2‐CaSiO3 system was prepared and investigated. It was found that by controlling the nucleation and growth of crystals, a glass‐ceramics free from cracks, containing one or two crystalline phases, and of controlled nano‐ to microscale microstructure can be obtained. Heat treatment of the parent glass produces various calcium phosphates (Ca‐deficient apatite and α‐tricalcium phosphate) and calcium silicates (pseudo‐wollastonite and/or wollastonite‐2M) plus amorphous phases. By combining a number of experimental techniques like 31P and 29Si magic angle spinning nuclear magnetic resonance spectroscopy, scanning and transmission electron microscopy, energy‐dispersive X‐ray spectrometry, and Rietveld analysis of X‐ray diffraction patterns, a crystallization model was derived, capable of explaining the observed structural and microstructural changes. The determination of amorphous or crystalline phases enabled to produce time‐temperature‐transformation plots. The structural role on the behavior of these materials and its impact on their in vitro bioactivity are also discussed. 相似文献
50.
Zofia Lisiewska Anna Korus Waldemar Kmiecik 《European Food Research and Technology》2002,214(3):216-220
The aim of the work was to evaluate the content of vitamin C, beta-carotene, thiamine, and riboflavin in raw and preserved physiologically immature grass pea seeds. The seeds of the cultivar Krab, differing in their morphology, phytometric traits, and specific gravity were divided into four stages of maturity, which corresponded to the following levels of their dry matter content: I - 25.9, II - 30.1, III - 36.4, and IV 40.6 g/100 g. The evaluation was conducted at the stage of the raw material, the material after blanching, frozen seeds after 6-month storage before and after cooking to the consumption consistency, and canned seeds 6 months after production. With the maturity degree of grass pea seeds the content of vitamin C was reduced by 19%, beta-carotene by 29%, riboflavin by 20%, while that of thiamine increased by 97%. The blanching of seeds led to a statistically significant decrease only in the content of vitamin C. Freezing and frozen storage did not significantly affect the level of the analysed components. The cooking of frozen seeds, the preservation of canned products, and their storage significantly reduced the content of all the analysed components in all the samples. No dependence was found between the magnitude of decreases in the investigated compounds and the degree of seed maturity. After cooking frozen seeds prepared from the raw material at the same maturity degree as the canned product contained 32%-51% more vitamin C, 0%-8% more beta-carotene, 40%-97% more thiamine, and 20%-25% more riboflavin, depending on the degree of seed maturity. 相似文献