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Enrique Iglesia - One of the best experts on this subject based on the ideXlab platform.
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catalytic consequences of spatial constraints and acid site location for monomolecular alkane activation on zeolites
Journal of the American Chemical Society, 2009Co-Authors: Rajamani Gounder, Enrique IglesiaAbstract:The location of Bronsted acid sites within zeolite channels strongly influences reactivity because of the extent to which spatial constraints determine the stability of reactants and of cationic transition states relevant to alkane activation catalysis. Turnover rates for monomolecular cracking and dehydrogenation of propane and n-butane differed among zeolites with varying channel structure (H-MFI, H-FER, H-MOR) and between OH groups within eight-membered ring (8-MR) side pockets and 12-MR main channels in H-MOR. Measured monomolecular alkane activation barriers depended on catalyst and reactant properties, such as deprotonation enthalpies and proton affinities, respectively, consistent with Born−Haber thermochemical cycles that define energy relations in acid catalysis. Monomolecular alkane cracking and dehydrogenation Turnovers occurred with strong preference on acid sites contained within smaller 8-MR pockets in H-MOR, while rates on sites located within 12-MR channels were much lower and often undete...
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the relationship between the electronic and redox properties of dispersed metal oxides and their Turnover rates in oxidative dehydrogenation reactions
Journal of Catalysis, 2002Co-Authors: Kaidong Chen, Alexis T Bell, Enrique IglesiaAbstract:The mechanistic connections among propane oxidative dehydrogenation (ODH) rates, H2 reduction rates, and the electronic transitions responsible for the absorption edge in the electronic spectra of dispersed metal oxides were explored for VOx, MoOx ,W O x, and NbOx samples consisting predominately of two-dimensional oxide domains supported on Al2O3, ZrO2, and MgO. For a given active oxide, propane Turnover rates increased in parallel with the reduction rate of the oxide catalyst using H2, but propane ODH rates differed significantly among different metal oxide samples with similar H2 reduction rates. For all catalysts, ODH Turnover rates increased monotonically as the energy of the absorption edge in the UV‐visible spectrum decreased. These results, taken together with the respective mechanisms for electron transfer during C‐H bond activation and during the ligand-to-metal charge-transfer processes responsible for the UV‐visible edge, suggest that the stability of activated complexes in C‐H bond dissociation steps depends sensitively on the ability of the active oxide domains to transfer electrons from lattice oxygen atoms to metal centers. The electronic transitions responsible for the UV‐visible absorption edge are mechanistically related to the redox cycles involving lattice oxygens responsible for oxidative dehydrogenation Turnovers of alkanes. As a result, the details of near-edge electronic spectra provide useful guidance about intrinsic reaction rates on active oxides typically used for these reactions. c � 2002 Elsevier Science (USA)
Alfred X. Trautwein - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the Iron Environment in Recombinant Human Tyrosine Hydroxylase, Using Mössbauer and EPR-Spectroscopy
Advances in Experimental Medicine and Biology, 1993Co-Authors: Jan Haavik, Marek Lengen, Torgeir Flatmark, Eckhard Bill, Alfred X. TrautweinAbstract:Tyrosine hydroxylase (tyrosine 3-monooxygenase, EC 1.14.16.2, TH) is a tetrahydropterin-dependent enzyme which catalyses the rate-limiting reaction in the biosynthesis of catecholamines1. The enzyme isolated either from bovine adrenals or rat pheochromocytoma cells contains approximately one atom of tightly bound non-heme iron/subunit2,3. However, the ligands to the iron or its catalytic function is not known. An important question has been the redox state of the iron atom, including possible changes in its redox state during the catalytic cycle. Previous studies on the related enzyme phenylalanine hydroxylase have indicated that the iron is in the ferrous state during catalytic Turnover, but that a small fraction of the iron is oxidised to Fe(III) during the reaction4. It has been shown that the tetrahydropterin cofactor can reduce this Fe(III) back to Fe(II), in addition to its function as an electron donor during the catalytic Turnover5.
Lauw Tjun Tjun - One of the best experts on this subject based on the ideXlab platform.
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pengaruh cash Turnover receivable Turnover dan inventory Turnover terhadap return on asset perusahaan sektor makanan dan minuman yang terdaftar di bursa efek indonesia periode 2013 2015
Jurnal Akuntansi Maranatha, 2018Co-Authors: Linda Vania Wijaya, Lauw Tjun TjunAbstract:Modal kerja adalah jumlah keseluruhan aktiva lancar yang dimiliki oleh perusahaan seperti kas, surat berharga, piutang, dan persediaan barang yang selalu berputar dengan maksud untuk menghasilkan pendapatan. Penelitian ini bertujuan untuk menguji dan menganalisis (1) pengaruh Cash Turnover, Receivable Turnover, dan Inventory Turnover terhadap Return On Asset, (2) pengaruh Cash Turnover terhadap Return On Asset, (3) pengaruh Receivable Turnover terhadap Return On Asset, dan (4) pengaruh Inventory Turnover terhadap Return On Asset pada perusahaan sektor makanan dan minuman yang terdaftar di Bursa Efek Indonesia periode 2013-2015. Sampel yang diambil dalam penelitian ini menggunakan metode purposive sampling. Data dikumpulkan dengan pencatatan dokumen, kemudian dianalisis menggunakan analisis regresi linear berganda, Uji F, dan Uji T. Hasil penelitian ini menemukan bahwa secara simultan Cash Turnover, Receivable Turnover, dan Inventory Turnover berpengaruh terhadap Return On Asset. Sementara secara parsial, ditemukan bahwa hanya Cash Turnover dan Inventory Turnover yang berpengaruh terhadap Return On Asset.
Nicholas G. Castle - One of the best experts on this subject based on the ideXlab platform.
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Turnover Begets Turnover
The Gerontologist, 2005Co-Authors: Nicholas G. CastleAbstract:Purpose: This study examined the association between Turnover of caregivers and Turnover of nursing home top management. The top managers examined were administrators and directors of nursing, and the caregivers examined were registered nurses, licensed practical nurses, and nurse aides. Design and Methods: The data came from a survey of 419 nursing facilities and the Online Survey, Certification, and Reporting system. Multinomial logistic regression analyses were used to examine the association between Turnover of nursing home top management and Turnover of caregivers. Results: A 10% increase in top management Turnover is associated (p , .05) with a 21% increase in the odds that a facility will have a high Turnover rate of nurse aides and is associated (p , .05) with an 8% decrease in the odds that a facility will have a low Turnover rate of nurse aides. A 10% increase in top management Turnover is associated (p , .1) with a 30% increase in the odds that a facility will have a high Turnover rate for registered and licensed practical nurses. Implications: This study provides preliminary evidence that the Turnover of top managers may have an important influence on caregiver Turnover in nursing homes.
Jan Haavik - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the Iron Environment in Recombinant Human Tyrosine Hydroxylase, Using Mössbauer and EPR-Spectroscopy
Advances in Experimental Medicine and Biology, 1993Co-Authors: Jan Haavik, Marek Lengen, Torgeir Flatmark, Eckhard Bill, Alfred X. TrautweinAbstract:Tyrosine hydroxylase (tyrosine 3-monooxygenase, EC 1.14.16.2, TH) is a tetrahydropterin-dependent enzyme which catalyses the rate-limiting reaction in the biosynthesis of catecholamines1. The enzyme isolated either from bovine adrenals or rat pheochromocytoma cells contains approximately one atom of tightly bound non-heme iron/subunit2,3. However, the ligands to the iron or its catalytic function is not known. An important question has been the redox state of the iron atom, including possible changes in its redox state during the catalytic cycle. Previous studies on the related enzyme phenylalanine hydroxylase have indicated that the iron is in the ferrous state during catalytic Turnover, but that a small fraction of the iron is oxidised to Fe(III) during the reaction4. It has been shown that the tetrahydropterin cofactor can reduce this Fe(III) back to Fe(II), in addition to its function as an electron donor during the catalytic Turnover5.
