scholarly journals Chemical Degradation Pathways in Siloxane Polymers Following Phenyl Excitations

2018 ◽  
Vol 122 (50) ◽  
pp. 12201-12210 ◽  
Author(s):  
Matthew P. Kroonblawd ◽  
Nir Goldman ◽  
James P. Lewicki
2005 ◽  
Vol 16 (5) ◽  
pp. 495-515 ◽  
Author(s):  
M. Qasim ◽  
H. Fredrickson ◽  
P. Honea ◽  
J. Furey ◽  
J. Leszczynski ◽  
...  

2014 ◽  
Vol 936 ◽  
pp. 1556-1559 ◽  
Author(s):  
Rong Wei Liu

This paper is closely related to chemical degradation of PAM. The degradation refers to any process that breaks down the molecular structure of macromolecules. The most important degradation pathways in oil recovery applications are oxidation reduction, ironic ions and divalents. The influences of each factor is discussed, and preventive measures are also put forward. It is beneficial to provide the degradation of the polymer, and it can largely improve the utilization rate of PAM.


2021 ◽  
Vol 42 (1) ◽  
pp. 30-35 ◽  
Author(s):  
Donald P. Tashkin ◽  
Arkady Koltun ◽  
Róisín Wallace

Background: A generic combination of fluticasone propionate and salmeterol xinafoate inhalation powder in a premetered, multidose, nonreusable inhaler was recently approved. Objective: To assess the performance of the generic device. Methods: Findings from three studies with regard to device usability, function, and robustness were reviewed. Results: In a study to assess device function in patients and healthy volunteers, the generic device was successfully used by patients with asthma and chronic obstructive pulmonary disease who were either dry powder inhaler users or dry powder inhaler‐naive, even though they were not trained beyond being provided the instructions for use. In a study to measure inhaled flow rates generated by patients and healthy volunteers, the generic device consistently simulated the delivery of a full dose of drug, even to patients with severe respiratory disease and reduced inspiratory flow rates. Although the generic device had a slightly higher airflow resistance, this study demonstrated that this difference did not result in any clinically meaningful differences in terms of drug delivery. Pressure drop, a key parameter that drives the fluidization and aerosolization of the powder dose, was found to be comparable between the devices. In an open-label study, the generic device met all U.S. Food and Drug Administration specifications for device robustness after 21.5 days of twice-daily dosing via oral inhalation among 111 participants with asthma or chronic obstructive pulmonary disease. All inhalers tested demonstrated conformity with a pharmacopeia with respect to key quality parameters (assay, delivered dose uniformity, aerodynamic size distribution). There was no evidence of chemical degradation of the active ingredients, nor of microbial or water ingress into the powder, as a result of inhaler use.


2013 ◽  
Vol 50 (2) ◽  
pp. 907-918 ◽  
Author(s):  
F. D. Coms ◽  
H. Xu ◽  
T. McCallum ◽  
C. Mittelsteadt
Keyword(s):  

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 502
Author(s):  
Guihua Dong ◽  
Bing Chen ◽  
Bo Liu ◽  
Stanislav R. Stoyanov ◽  
Yiqi Cao ◽  
...  

One of the most commonly produced industrial chemicals worldwide, bisphenol A (BPA), is used as a precursor in plastics, resins, paints, and many other materials. It has been proved that BPA can cause long-term adverse effects on ecosystems and human health due to its toxicity as an endocrine disruptor. In this study, we developed an integrated MnO2/UV/persulfate (PS) process for use in BPA photocatalytic degradation from water and examined the reaction mechanisms, degradation pathways, and toxicity reduction. Comparative tests using MnO2, PS, UV, UV/MnO2, MnO2/PS, and UV/PS processes were conducted under the same conditions to investigate the mechanism of BPA catalytic degradation by the proposed MnO2/UV/PS process. The best performance was observed in the MnO2/UV/PS process in which BPA was completely removed in 30 min with a reduction rate of over 90% for total organic carbon after 2 h. This process also showed a stable removal efficiency with a large variation of pH levels (3.6 to 10.0). Kinetic analysis suggested that 1O2 and SO4•− played more critical roles than •OH for BPA degradation. Infrared spectra showed that UV irradiation could stimulate the generation of –OH groups on the MnO2 photocatalyst surface, facilitating the PS catalytic degradation of BPA in this process. The degradation pathways were further proposed in five steps, and thirteen intermediates were identified by gas chromatography-mass spectrometry. The acute toxicity was analyzed during the treatment, showing a slight increase (by 3.3%) in the first 30 min and then a decrease by four-fold over 2 h. These findings help elucidate the mechanism and pathways of BPA degradation and provide an effective PS catalytic strategy.


Author(s):  
Nurul Hayati Yusof ◽  
Dazylah Darji ◽  
Fatimah Rubaizah Mohd Rasdi ◽  
Krishna Veni Baratha Nesan

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