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Kaylor, Nicholas,Xie, Jiahan,Kim, Yong-Su,Pham, Hien N.,Datye, Abhaya K.,Lee, Yong-Kul,Davis, Robert J. Elsevier 2016 Journal of catalysis Vol.344 No.-
<P><B>Abstract</B></P> <P>Silica-supported Pd and PdSn catalysts were prepared by ion exchange or incipient wetness impregnation and characterized with H<SUB>2</SUB> chemisorption, X-ray diffraction, in situ Sn K-edge X-ray absorption near edge structure (XANES), and scanning transmission electron microscopy. The activity of the catalysts was evaluated in the deoxygenation of vapor-phase heptanoic acid at 0.1MPa and 573K. A Pd catalyst synthesized via ion exchange formed nanoparticles of 1.1±0.4nm and was more stable in heptanoic acid conversion compared to a Pd catalyst synthesized via incipient wetness impregnation having nanoparticles of 2.4±0.5nm. The addition of Sn to a Pd catalyst by either co-impregnation of precursors or physical mixing of supported monometallic catalysts improved the overall catalyst stability. Moreover, Sn addition expanded the reaction network from primarily decarbonylation over Pd to include dehydration and decarboxylative ketonization over PdSn. Electron microscopy confirmed the physical migration of Sn during catalytic reaction. In situ XANES analysis during the deoxygenation of a carboxylic acid suggests that partially reduced SnO<SUB>x</SUB> is the active Sn phase associated with Pd nanoparticles under reaction conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Initial decarbonylation rate is inversely correlated to Pd catalyst stability. </LI> <LI> Adding Sn to a Pd/SiO<SUB>2</SUB> catalyst promotes the stable conversion of heptanoic acid. </LI> <LI> Dehydration and decarbonylation are the primary reactions over PdSn/SiO<SUB>2</SUB>. </LI> <LI> Sn migrates to Pd when contacted by vapor-phase heptanoic acid. </LI> <LI> Partially-reduced SnO<SUB>x</SUB> is the promoting species associated with Pd in PdSn catalysts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Twenty-Four Hour pH Study and Manometry in Gastric Esophageal Substitutes in Children
Geeta Kekre,Vishesh Dikshit,Paras Kothari,Ashok Laddha,Abhaya Gupta 대한소아소화기영양학회 2018 Pediatric gastroenterology, hepatology & nutrition Vol.21 No.4
Purpose: Studies on the physiology of the transposed stomach as an esophageal substitute in the form of a gastric pull-up or a gastric tube in children are limited. We conducted a study of motility and the pH of gastric esophageal substitutes using manometry and 24-hour pH measurements in 10 such patients. Methods: Manometry and 24 hour pH studies were performed on 10 children aged 24 to 55 months who had undergone gastric esophageal replacement. Results: Six gastric tubes (4, isoperistaltic; 2, reverse gastric tubes) and 4 gastric pull-ups were studied. Two gastric tubes and 4 gastric pull-ups were transhiatal. Four gastric tubes were retrosternal. The mean of the lowest pH at the midpoint of the substitute was 4.0 (range, 2.8-5.0) and in the stomach remaining below the diaphragm was 3.3 (range, 1.9-4.2). In both types of substitute, the difference between the peak and the nadir pH recorded in the in-tra-thoracic and the sub-diaphragmatic portion of the stomach was statistically significant (p<0.05), with the pH in the portion below the diaphragm being lower. The lowest pH values in the substitute and in the remnant stomach were noted mainly in the evening hours whereas the highest pH was noted mainly in the morning hours. All the cases showed a simultaneous rise in the intra-cavitatory pressure along the substitute while swallowing.Conclusion: The study suggested a normal gastric circadian rhythm in the gastric esophageal substitute. Mass con-tractions occurred in response to swallowing. The substitute may be able to effectively clear contents.
Twenty-Four Hour pH Study and Manometry in Gastric Esophageal Substitutes in Children
Kekre, Geeta,Dikshit, Vishesh,Kothari, Paras,Laddha, Ashok,Gupta, Abhaya The Korean Society of Pediatric Gastroenterology 2018 Pediatric gastroenterology, hepatology & nutrition Vol.21 No.4
Purpose: Studies on the physiology of the transposed stomach as an esophageal substitute in the form of a gastric pull-up or a gastric tube in children are limited. We conducted a study of motility and the pH of gastric esophageal substitutes using manometry and 24-hour pH measurements in 10 such patients. Methods: Manometry and 24 hour pH studies were performed on 10 children aged 24 to 55 months who had undergone gastric esophageal replacement. Results: Six gastric tubes (4, isoperistaltic; 2, reverse gastric tubes) and 4 gastric pull-ups were studied. Two gastric tubes and 4 gastric pull-ups were transhiatal. Four gastric tubes were retrosternal. The mean of the lowest pH at the midpoint of the substitute was 4.0 (range, 2.8-5.0) and in the stomach remaining below the diaphragm was 3.3 (range, 1.9-4.2). In both types of substitute, the difference between the peak and the nadir pH recorded in the intra-thoracic and the sub-diaphragmatic portion of the stomach was statistically significant (p<0.05), with the pH in the portion below the diaphragm being lower. The lowest pH values in the substitute and in the remnant stomach were noted mainly in the evening hours whereas the highest pH was noted mainly in the morning hours. All the cases showed a simultaneous rise in the intra-cavitatory pressure along the substitute while swallowing. Conclusion: The study suggested a normal gastric circadian rhythm in the gastric esophageal substitute. Mass contractions occurred in response to swallowing. The substitute may be able to effectively clear contents.