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81.
Corneliu Hamciuc Elena Hamciuc Alina Mirela Ipate Mariana Cristea Lidia Okrasa 《应用聚合物科学杂志》2009,113(1):383-391
A series of aromatic copolyethers containing 1,3,4‐oxadiazole rings and fluorene groups was prepared by nucleophilic substitution polymerization technique of 9,9‐bis(4‐hydroxyphenyl)fluorene, 1 , or of different amounts of 1 and an aromatic bisphenol, such as 4,4′‐isopropylidenediphenol or phenolphthalein, with 2,5‐bis(p‐fluorophenyl)‐1,3,4‐oxadiazole. The polymers were easily soluble in polar solvents like N‐methylpyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, and chloroform and can be cast from solutions into thin flexible films. They showed high thermal stability, with decomposition temperature being above 425°C. The polymers exhibited a glass‐transition temperature in the range of 195–295°C, with a reasonable interval between glass‐transition and decomposition temperature. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz and 20°C were in the range of 3.16–3.25. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
82.
Describing Quality and Sensory Attributes of 3 Mango (Mangifera indica L.) Cultivars at 3 Ripeness Stages Based on Firmness 下载免费PDF全文
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Aleksandra Pietrowska Iwona Hoowacz Agnieszka Ulatowska-Jara Mateusz Gu
niczak Anna K. Matczuk Alina Wieliczko Mirela Wolf-Baca Igor Buzalewicz 《International journal of molecular sciences》2022,23(11)
The prevention of biofilm formation is crucial for the limitation of bacterial infections typically associated with postoperative infections, complications in bedridden patients, and a short-term prognosis in affected cancer patients or mechanically ventilated patients. Antimicrobial photodynamic therapy (aPDT) emerges as a promising alternative for the prevention of infections due to the inability of bacteria to become resistant to aPDT inactivation processes. The aim of this study was to demonstrate the use of a functionalized combination of Chlorin e6 and Pheophorbide as a new approach to more effective aPDT by increasing the accumulation of photosensitizers (PSs) within Escherichia coli cells. The accumulation of PSs and changes in the dry mass density of single-cell bacteria before and after aPDT treatment were investigated by digital holotomography (DHT) using the refractive index as an imaging contrast for 3D label-free live bacteria cell imaging. The results confirmed that DHT can be used in complex examination of the cell–photosensitizer interaction and characterization of the efficiency of aPDT. Furthermore, the use of Pheophorbide a as an efflux pomp inhibitor in combination with Chlorin e6 increases photosensitizers accumulation within E. coli and overcomes the limited penetration of Gram-negative cells by anionic and neutral photosensitizers. 相似文献
85.
Uroš Prah Tadej Rojac Magdalena Wencka Mirela Dragomir Andraž Bradeško Andreja Benčan Rachel Sherbondy Geoff Brennecka Zdravko Kutnjak Barbara Malič Hana Uršič 《Journal of the European Ceramic Society》2019,39(14):4122-4130
Designing multicaloric single-phase materials with combined electro- and magnetocaloric effects is still at its initial stage and presents a number of challenges. One of the main challenges encountered so far is to reduce the excessive electrical conductivity, which leads to the appearance of Joule heating that might completely degrade the electrocaloric response. In this work, multicaloric Pb(Fe0.5Nb0.5)O3 material was successfully prepared exhibiting pronounced electrocaloric effect above room temperature and maximum magnetocaloric effect at cryogenic temperature. The conductivity was suppressed by controlling the sintering temperature. The ceramic sintered at 1000 °C exhibits maximum electrocaloric effective cooling of 0.88 °C at 28 °C and maximum magnetocaloric effect of 0.14 °C at ?271 °C. The caloric properties can be further improved by doping Pb(Fe0.5Nb0.5)O3 with manganese. In comparison to the undoped sample, Pb(Fe0.5Nb0.5)O3 doped with 0.5 mol% of manganese exhibits three times higher maxima of electrocaloric effective cooling (2.47 °C at 80 °C) and magnetocaloric temperature change (0.44 °C at ?271 °C). 相似文献
86.
Mirela Samardžić Sanja Petrušić Mateja Hajduković Marija Škobić 《Journal of surfactants and detergents》2019,22(2):339-348
Novel potentiometric sensors for anionic surfactant (AS) determination, with different percentages of tetraoctadecylammonium tetraphenylborate (TODA-TPB) as sensing materials and different electrolytes (sodium chloride, lithium chloride, sodium dodecyl sulfate (NaDS), sodium tetraphenylborate, sodium acetate, and potassium chloride) at varied concentration levels, were developed and compared. The sensor with best response characteristics was further characterized. It had a fast response time (5 s), a low signal drift (2.0 and 2.9 mV h−1 in a detergent solution and NaDS, respectively), a wide pH working range (3–11), and a longer lifetime of 6 months. This novel sensor was characterized with Nernstian response toward NaDS (−58.0 mV decade−1 of activity), a wide working range (1.3 · 10−7–5 · 10−3 M), and a low limit of detection (1.0 · 10−7 M). It proved to be an accurate and reliable sensor for AS determination in multicomponent mixtures of AS and household wastewater using a potentiometric titration method. Nonionic surfactants, which are commonly mixed with AS in commercial products to obtain better properties of products, had an insignificant impact on AS determination. 相似文献
87.
In this paper we present several expert systems that predict the class identity of the modeled compounds, based on a preprocessed spectral database. The expert systems were built using Artificial Neural Networks (ANN) and are designed to predict if an unknown compound has the toxicological activity of amphetamines (stimulant and hallucinogen), or whether it is a nonamphetamine. In attempts to circumvent the laws controlling drugs of abuse, new chemical structures are very frequently introduced on the black market. They are obtained by slightly modifying the controlled molecular structures by adding or changing substituents at various positions on the banned molecules. As a result, no substance similar to those forming a prohibited class may be used nowadays, even if it has not been specifically listed. Therefore, reliable, fast and accessible systems capable of modeling and then identifying similarities at molecular level, are highly needed for epidemiological, clinical, and forensic purposes. In order to obtain the expert systems, we have preprocessed a concatenated spectral database, representing the GC-FTIR (gas chromatography-Fourier transform infrared spectrometry) and GC-MS (gas chromatography-mass spectrometry) spectra of 103 forensic compounds. The database was used as input for a Principal Component Analysis (PCA). The scores of the forensic compounds on the main principal components (PCs) were then used as inputs for the ANN systems. We have built eight PC-ANN systems (principal component analysis coupled with artificial neural network) with a different number of input variables: 15 PCs, 16 PCs, 17 PCs, 18 PCs, 19 PCs, 20 PCs, 21 PCs and 22 PCs. The best expert system was found to be the ANN network built with 18 PCs, which accounts for an explained variance of 77%. This expert system has the best sensitivity (a rate of classification C = 100% and a rate of true positives TP = 100%), as well as a good selectivity (a rate of true negatives TN = 92.77%). A comparative analysis of the validation results of all expert systems is presented, and the input variables with the highest discrimination power are discussed. 相似文献
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Anđela Pustak Mirela Leskovac Iztok Švab Vojko Musil Ivan Šmit 《Polymer-Plastics Technology and Engineering》2015,54(6):647-660
The effects of different silica grades and elastomer content on interfacial properties, morphology and mechanical properties of polypropylene/silica 96/4 composites modified with added 5, 10, 15, and 20% of poly(styrene-b-ethylene-co-butylene-b-styrene) grafted with maleic anhydride (SEBS-g-MA) were investigated. The iPP/silica/SEBS-g-MA composites were designed by adding four silica fillers differing in size (nano- vs. micro-) and in surface properties (hydrophilic vs. hydrophobic) and SEBS-g-MA that was used as a proven effective impact modifier and compatibilizer simultaneously. The morphology of every composite was a spectrum of several morphologies rather than one exclusive morphology. Good concordance between observed and predicted morphology indicated that the morphology of a particular composite was controlled primarily by interfacial properties. Tensile and impact properties were influenced primarily by competitive effects of a stiff filler and tough SEBS-g-MA elastomer. Increased impact strength and strain at break caused by adding SEBS-g-MA indicated a significant overcoming of the elastomeric toughening effect in relation to the filler’s stiffening effect. 相似文献