Effects of Catalyst Hydrophobicity on Rates and Selectivities of Alkene Epoxidation

Epoxides are essential for the production of various plastics, fragrances, and pharmaceuticals, but conventional oxidants used for the large-scale synthesis of epoxides produce toxic co-products or over-oxidize to form large amounts of carbon dioxide, a greenhouse gas. Highly disperse titanium metal catalysts activate hydrogen peroxide (a green oxidant) for alkene epoxidation, but there is currently not an understanding of how the hydrophilicity (i.e., the silanol density) of such materials affects how quickly and selectively they catalyze epoxidation. Here, a series of titanium zeolite catalysts with varying silanol density but constant pore size and metal content is synthesized via post-synthetic modification of aluminum zeolite samples. The hydrophilicity of these materials is quantitatively determined, and a combination of kinetic, thermodynamic, and spectroscopic measurements are then used to show that the reactivity of these catalysts depends on their hydrophilicity. In particular, activation enthalpies for 1-octene epoxidation decrease with the density of silanols but are accompanied by a concomitant increase in entropy losses. For liquid-phase 1-octene epoxidation in acetonitrile, reaction barriers decrease by 7.7 kJ mol-1 but entropic losses increase by 22.4 J mol-1 K-1 when the catalyst structure is changed from highly-defective to defect-free, which manifests in turnover rates increasing by a factor of 500. Thus, the competing enthalpic and entropic factors must be balanced by carefully selecting the optimal silanol density for a given set of process conditions (e.g., reaction temperature). Together, these findings provide rational design criteria for the design of catalysts to be used in environmentally-friendly epoxide synthesis.Army Research Office #W911NF-18-1-0100Ope

Effects of Hydrophobicity of Group IV and V Framework-Substituted Zeolite Catalysts on Rates and Selectivities for Olefin Epoxidation

Group IV and V transition metal-substituted zeolites have long been used to catalyze olefin epoxidation, and several studies about how metal identity affects rates for epoxidation exist in the current literature. However, little is known about the effects of different catalytic properties, particularly hydrophobicity, on rates and selectivities for such epoxidations. Limited knowledge of these catalysts prevents hydrogen peroxide-oxidized reactions from replacing less-green methods of epoxide synthesis. Here, kinetic and thermodynamic measurements are used to demonstrate that the activity of group IV (i.e. Ti) and V (i.e. Nb and Ta) catalysts is directly related to the hydrophobicity of the catalyst. In particular, more hydrophobic catalysts give better rates for the desired epoxidation pathway and present smaller enthalpic barriers for epoxidation. Furthermore, a relationship between the Lewis acidity of a metal and its affinity to catalyze epoxidation (and the subsequent determination that Ti *BEA is the most active for epoxidation among this group) has been observed, in agreement with previously published work.NSFOpe

Ruxolitinib for Glucocorticoid-Refractory Acute Graft-versus-Host Disease

BACKGROUND: Acute graft-versus-host disease (GVHD) remains a major limitation of allogeneic stem-cell transplantation; not all patients have a response to standard glucocorticoid treatment. In a phase 2 trial, ruxolitinib, a selective Janus kinase (JAK1 and JAK2) inhibitor, showed potential efficacy in patients with glucocorticoid-refractory acute GVHD. METHODS: We conducted a multicenter, randomized, open-label, phase 3 trial comparing the efficacy and safety of oral ruxolitinib (10 mg twice daily) with the investigator's choice of therapy from a list of nine commonly used options (control) in patients 12 years of age or older who had glucocorticoid-refractory acute GVHD after allogeneic stem-cell transplantation. The primary end point was overall response (complete response or partial response) at day 28. The key secondary end point was durable overall response at day 56. RESULTS: A total of 309 patients underwent randomization; 154 patients were assigned to the ruxolitinib group and 155 to the control group. Overall response at day 28 was higher in the ruxolitinib group than in the control group (62% [96 patients] vs. 39% [61]; odds ratio, 2.64; 95% confidence interval [CI], 1.65 to 4.22; P<0.001). Durable overall response at day 56 was higher in the ruxolitinib group than in the control group (40% [61 patients] vs. 22% [34]; odds ratio, 2.38; 95% CI, 1.43 to 3.94; P<0.001). The estimated cumulative incidence of loss of response at 6 months was 10% in the ruxolitinib group and 39% in the control group. The median failure-free survival was considerably longer with ruxolitinib than with control (5.0 months vs. 1.0 month; hazard ratio for relapse or progression of hematologic disease, non-relapse-related death, or addition of new systemic therapy for acute GVHD, 0.46; 95% CI, 0.35 to 0.60). The median overall survival was 11.1 months in the ruxolitinib group and 6.5 months in the control group (hazard ratio for death, 0.83; 95% CI, 0.60 to 1.15). The most common adverse events up to day 28 were thrombocytopenia (in 50 of 152 patients [33%] in the ruxolitinib group and 27 of 150 [18%] in the control group), anemia (in 46 [30%] and 42 [28%], respectively), and cytomegalovirus infection (in 39 [26%] and 31 [21%]). CONCLUSIONS: Ruxolitinib therapy led to significant improvements in efficacy outcomes, with a higher incidence of thrombocytopenia, the most frequent toxic effect, than that observed with control therapy

Dígame ‘Docteur’: los viajes culturales de los discursos europeos sobre el crimen y el castigo en las tesis doctorales de la Universidad de Buenos Aires (1827-1860)

Este trabajo se enmarca en la investigación desarrollada para mi tesis de Maestría en Criminología, acerca de las características del saber penal moderno en Argentina, en su etapa de surgimiento. Aquí se identifican y analizan algunos de los aspectos relevantes de ese proceso: el uso de la noción de “ciencia penal”, por parte de los autores, como herramienta para la construcción del nuevo campo experto; y las características de los procesos de importación cultural de ideas provenientes de Europa que aquellos desplegaron. A ese fin, se emplean como material de archivo las tesis doctorales en materia penal del Departamento de Jurisprudencia de la Universidad de Buenos Aires, correspondientes al período 1827-1860. Esos textos son analizados con el marco teórico de la “racionalidad penal moderna”, de Alvaro Pires, para trabajar el primer aspecto; y mediante las categorías planteadas en distintos trabajos por Máximo Sozzo para pensar los procesos de traducción de ideas en materia penal, con relación al segundo

Pharmacokinetics and ocular penetration of grepafloxacin in albino and pigmented rabbits

6 pages, 2 figures, 2 tables.-- PMID: 12356799 [PubMed].The pharmacokinetics of grepafloxacin were determined in albino and pigmented rabbits following a single 10 mg/kg intravenous administration. The penetration of grepafloxacin into various ocular tissues was also determined after continuous intravenous infusion in both types of animal. Grepafloxacin showed a icompartmental model of distribution in both pigmented and albino rabbits with significant differences in the pharmacokinetics between the two types of animal. After continuous intravenous infusion, significantly greater penetration of grepafloxacin was found in the iris, cornea and chorioretina of pigmented rabbits compared with albino rabbits.Peer reviewe

Geometrical optics and video calls: A cool path to Physics, CV and ML in high schools

In this article we discuss an experience developed with high school students during Covid-forced distance learning. Students tried to make actual video calls in perfect Star Wars style using phones and 3D-Holo Pyramids. To achieve some results they were forced to rethink Geometrical Optics, Periodic Phenomena and had to understand some basic tools from Computer Vision (CV) and Machine Learning (ML)

Effects of mono- and multi-valent cations on the inward-rectifying potassium channel in isolated protoplasts from maize roots

none4nomixedBregante M.; Carpaneto A.; Pastorino F.; Gambale F.Bregante, M.; Carpaneto, A.; Pastorino, F.; Gambale, F