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1.
Physical aging in amorphous poly(ethylene furanoate): Enthalpic recovery,density, and oxygen transport considerations
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Steven K. Burgess Christopher R. Mubarak Robert M. Kriegel William J. Koros 《Journal of Polymer Science.Polymer Physics》2015,53(6):389-399
The current work utilizes three separate techniques to study the physical aging process in amorphous poly(ethylene furanoate) (PEF), which is a recently introduced engineering thermoplastic with enhanced properties compared to petroleum‐sourced poly(ethylene terephthalate). Differential scanning calorimetry aging experiments were conducted at multiple aging temperatures and times, and the resultant enthalpic recovery values compared to the theoretical maximum enthalpy loss evaluated from calculations involving extrapolation of the equilibrium liquid line. Density measurements reveal densification of the matrix for the aged versus unaged samples, and provide an estimate for the reduction in free volume for the aged samples. Complementary oxygen permeation and pressure‐decay sorption experiments provide independent verification of the free volume reduction mechanism for physical aging in glassy polymers. The current work provides the first detailed aging study for PEF. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 389–399 相似文献
2.
Highly sensitive catalytic determination of molybdenum 总被引:1,自引:0,他引:1
A novel, highly sensitive, selective, and simple kinetic method was developed for the determination of Mo(VI) based on its catalytic effect on the oxidation of 1-amino-2-naphthol-4-sulfonic acid (ANSA) with H2O2. The reaction was followed spectrophotometrically by tracing the oxidized product at 465 nm after 30 min of mixing the reagents. The optimum reaction conditions were: 10 mmol l−1 ANSA, 50 mmol l−1 H2O2, 100 mmol l−1 acetate buffer of pH 5.0 ± 0.05 and at 40 °C. Addition of 200 μg ml−1 diethylenetriaminepentaacetic acid (DTPA) conferred high selectivity for the proposed method. Following the recommended procedure, Mo(VI) could be determined with a linear calibration graph up to 2.5 ng ml−1 and a detection limit, based on the 3Sb-criterion, of 0.027 ng ml−1. The unique sensitivity and selectivity of the implemented method allowed its direct application to the determination of Mo(VI) in natural and industrial waste water. The method was validated by comparison with the standard ETAAS method. Moreover, published catalytic-spectrophotometric methods for the determination of molybdenum were reviewed. 相似文献
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Mubarak AT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(6):1163-1170
Synthesis and characterization of several new coordination compounds of dioxouranium(VI) heterochelates with bidentate hydrazono compounds derived from 1-phenyl-3-methyl-5-pyrazolone are described. The ligands and uranayl complexes have been characterized by various physico-chemical techniques. The bond lengths and the force constant have been calculated from asymmetric stretching frequency of OUO groups. The infrared spectral studies showed a monobasic bidentate behaviour with the oxygen and hydrazo nitrogen donor system. The effect of Hammett's constant on the bond distances and the force constants were also discussed and drawn. Wilson's matrix method, Badger's formula, Jones and El-Sonbati equations were used to determine the stretching and interaction force constant from which the UO bond distances were calculated. The bond distances of these complexes were also investigated. 相似文献
6.
A.A. Mubarak 《Journal of magnetism and magnetic materials》2010,322(7):780-785
We present ab-initio investigation of the electronic and magnetic structure of TM(0 0 1) surfaces and TM/Cu(0 0 1) systems (TM=Fe, Co, Ni, Cu) with and without hydrogen adsorbed layer. The adsorption energy of hydrogen atom is found to be energetically more stable above the surface layer of Ni(0 0 1) surface than other TM(0 0 1) surfaces. The adsorption energies of hydrogen on TM/Cu(0 0 1) systems are larger than those on TM(0 0 1) surfaces. The relaxed geometries show that hydrogen has a strong influence on the interlayer distance. Furthermore, a marked reduction of Fe, Co, and Ni surface magnetic moments to 2.54, 1.41 and 0.25 μB, respectively, is obtained due to the presence of hydrogen. 相似文献
7.
Bharat B. Kashid Anil A. Ghanwat Vijay M. Khedkar Balasaheb B. Dongare Mubarak H. Shaikh Prathmesh P. Deshpande Yogesh B. Wakchaure 《Journal of heterocyclic chemistry》2019,56(3):895-908
A series of novel 2‐substituted benzimidazole and benzoxazole derivatives as a potential antimicrobial and antioxidant agent were synthesized via coupling of N‐methyl‐o‐phenylenediamine or 2‐amino‐phenol with aromatic aldehyde and acid in the presence of polyphosphoric acid as an efficient catalyst as well as solvent by conventional method in short reaction times with excellent yield. The newly synthesized benzimidazole and benzoxazole derivatives were evaluated for antimicrobial and antioxidant activity and exhibited excellent to good activities compared to the standard drugs. Furthermore, the theoretical predictions based on molecular docking against microbial DNA gyrase could provide an insight into the plausible mechanism of action and establish a link between the observed antimicrobial activity and the binding affinity shedding light on specific thermodynamic (bonded and nonbonded) interactions governing the activity. Furthermore, the synthesized compounds were analyzed for absorption, distribution, metabolism, and excretion properties and exhibited potential properties to build up as good oral drug candidates. 相似文献
8.
Yahia Nasser Mabkhot Nahed Ahmed Kaal Seham Alterary Mohammad S. Mubarak Abdulrhman Alsayari Abdullatif Bin Muhsinah 《Journal of heterocyclic chemistry》2019,56(10):2845-2953
Phenacylbromide derivatives constitute a multilateral group of precursors for the synthesis of numerous heterocycles of organic compounds. Briefly, 5‐(2‐bromo‐acetyl)‐substituted‐thiophene derivative has been used as a synthon for synthesis of new thiophene‐containing compounds through the reaction with nucleophilic nitrogen compounds and thioamides. The suggested structures of the newly synthesized thiophene compounds were confirmed and assured with different spectroscopic tools and with CHN elemental analysis. Additionally, the antimicrobial activity of these thiophene compounds was recorded to investigate their potency against various types of bacteria and fungi. Results showed that these compounds exhibit significant inhibitory activity against the growth of tested bacterial and fungal strains and that some derivatives were more potent than the employed reference drugs. 相似文献
9.
Walvekar Rashmi Zairin Danial Aminin Khalid Mohammad Mubarak Nabisab Mujawar TCSM Gupta 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7193-7201
Journal of Thermal Analysis and Calorimetry - This study aims to investigate the thermal conductivity, viscosity and thermal degradation of naphthenic-based mineral oil, palm oil methyl ester... 相似文献
10.
Antioxidant and Anti-Inflammatory Effects of Peganum harmala Extracts: An In Vitro and In Vivo Study
Malik Waseem Abbas Mazhar Hussain Muhammad Qamar Sajed Ali Zahid Shafiq Polrat Wilairatana Mohammad S. Mubarak 《Molecules (Basel, Switzerland)》2021,26(19)
Peganum harmala (P. harmala) belongs to the family Zygophyllaceae, and is utilized in the traditional medicinal systems of Pakistan, China, Morocco, Algeria, and Spain to treat several chronic health disorders. The aim of the present study was to identify the chemical constituents and to evaluate the antioxidant, anti-inflammatory, and toxicity effects of P. harmala extracts both in vitro and in vivo. Sequential crude extracts including 100% dichloromethane, 100% methanol, and 70% aqueous methanol were obtained and their antioxidant and anti-inflammatory effects evaluated both in vitro and in vivo. The anti-inflammatory effect of the extract was investigated using the carrageenan-induced paw edema method in mice, whereas the toxicity of the most active extract was evaluated using an acute and subacute toxicity rat model. In addition, we have used the bioassay-guided approach to obtain potent fractions, using solvent–solvent partitioning and reversed phase high performance liquid chromatography from active crude extracts; identification and quantification of compounds from the active fractions was achieved using electrospray ionization mass spectrometry and high performance liquid chromatography techniques. Results revealed that the 100% methanol extract of P. harmala exhibits significant in vitro antioxidant activity in DPPH assay with an IC50 of 49 µg/mL as compared to the standard quercetin with an IC50 of 25.4 µg/mL. The same extract exhibited 63.0% inhibition against serum albumin denaturation as compared to 97% inhibition by the standard diclofenac sodium in an in vitro anti-inflammatory assay, and in vivo anti-inflammatory against carrageenan-induced paw edema (75.14% inhibition) as compared to 86.1% inhibition caused by the standard indomethacin. Furthermore, this extract was not toxic during a 14 day trial of acute toxicity when given at a dose of 3 g/kg, indicating that the lethal dose (LD50) of P. harmala methanol extract was greater than 3 g/kg. P. harmala methanolic fraction 2 obtained using bioassay-guided fractionation showed the presence of quinic acid, peganine, harmol, harmaline, and harmine, confirmed by electrospray ionization mass spectrometry and quantified using external standards on high performance liquid chromatography. Taken all together, the current investigation further confirms the antioxidant, anti-inflammatory, and safety aspects of P. harmala, which justifies its use in folk medicine. 相似文献