High-Resolution Studies of Tropolone in the S 0 and S 1 Electronic States: Isotope Driven Dynamics in the Zero-Point Energy Levels

Rotationally resolved microwave (MW) and ultraviolet (UV) spectra of jet-cooled tropolone have been obtained in S0 and S1 electronic states using Fourier-transform microwave and UV-laser/molecular-beam spectrometers. In the ground electronic state, the MW spectra of all heavy-atom isotopomers including one O18 and four C13 isotopomers were observed in natural abundance. The OD isotopomer was obtained from isotopically enriched samples. The two lowest tunneling states of each isotopomer except O18 have been assigned. The observed inversion splitting for the OD isotopomer is 1523.227(5) MHz. For the asymmetric C13 structures, the magnitudes of tunneling-rotation interactions are found to diminish with decreasing distance between the heavy atom and the tunneling proton. In the limit of closest approach, the 0+ state of O18 was well fitted to an asymmetric rotor Hamiltonian, reflecting significant changes in the tautomerization dynamics. Comparisons of the substituted atom coordinates with theoretical predictions at the MP2/aug-cc-pVTZ level of theory suggest the localized 0+ and 0− wave functions of the heavier isotopes favor the C–OH and C=O forms of tropolone, respectively. The only exception occurs for the C13-OH and C13=O structures which correlate to the 0− and 0+ states, respectively. These preferences reflect kinetic isotope effects as quantitatively verified by the calculated zero-point energy differences between members of the asymmetric atom pairs. From rotationally resolved data of the 0+←0+ and 0−←0− bands in S1, line-shape fits have yielded Lorentzian linewidths that differ by 12.2(16) MHz over the 19.88(4)cm−1 interval in S1. The fluorescence decay rates together with previously reported quantum yield data give nonradiative decay rates of 7.7(5)×108 and 8.5(5)×108s−1 for the 0+ and 0− levels of the S1 state of tropolone

Analysis of Autoinduction, Inhibition, and Autoinhibition in a Rh-Catalyzed C-C Cleavage:Mechanism of Decyanative Aryl Silylation

The mechanism the Chatani–Tobisu rhodium-catalyzed decyanative silylation of aryl nitriles by hexamethyldisilane (Me₃Si-SiMe₃) has been investigated by in situ NMR spectroscopy. The production of Ar-SiMe₃ evolves in three distinct phases: slow catalyst induction is followed by a period of rapidly accelerating turnover and then, after approximately three catalyst turnovers, the onset of progressive inhibition. The processes giving rise to these phenomena have been elucidated by isotopic labeling (¹³C/¹⁵N) and kinetic analysis, and it is shown that, in addition to facilitating catalyst turnover to generate Ar-SiMe₃, the reactants serve other roles. Me₃Si-SiMe₃ functions as a slow exogenous precatalyst activator and as a moderately powerful catalyst inhibitor. In contrast, ArCN acts as a precatalyst inhibitor. Moreover, the coproduct from the reaction (trimethylsilyl cyanide, Me₃SiCN) acts as a powerful endogenous precatalyst activator and catalyst inhibitor, together giving rise to sigmoidal temporal concentration profiles for [Ar-SiMe₃]. Kinetic studies of the reaction during the phase of progressive inhibition suggest that, for a given initial catalyst concentration, the maximum rate of turnover is achieved when the concentrations of [Me₃Si-SiMe₃] and [ArCN] partition the Rh equally between two major resting states, one on-cycle, the other off-cycle. The off-cycle resting-state was identified as a Rh­(III) complex: (Me₃Si)₃Rh­(CN-SiMe₃)₃, as confirmed by independent synthesis and isotopic labeling (¹³C/¹⁵N); the on-cycle resting state has been tentatively assigned as (Me₃Si-NC)₃RhAr. Overall, the results indicate that the catalytic process can, in principle, be made much more efficient by engendering a pathway or process for Me₃SiCN sequestration

SISTEMAS DE PROPAGAÇÃO E CULTIVO DA CORTIÇA LISA NO ALTO VALE DO ITAJAÍ

A cortiça-lisa (Rollinia rugulosa) da família Annonaceae é uma das árvores nativas do Brasilque tem grande importância ecológica e potencial de exploração comercial. Atualmente,grande parte da população não tem o conhecimento sobre a existência dessa planta. Sãonecessárias pesquisas que contemplem a propagação eficiente dessa espécie devido ao fatodela estar sendo extinta do nosso ecossistema, apesar de seu potencial de produção econsumo. Além disso, constamos a pouca literatura existente com assuntos relacionados acultura. Com este trabalho pretendemos conhecer métodos mais adequados de produção demudas e verificar a qualidade dos frutos obtidos em acessos da região, identificando plantaspara propagação.O experimento foi conduzido no Instituto Federal Catarinense-Campus Riodo Sul, sendo a produção de mudas no setor de fruticultura e silvicultura e análise dequalidade de frutos no Laboratório de Pós-colheita do IFC, com a espécie de cortiça-lisaRollinia rugulosa. Forão coletadas frutos de acessos de plantas do IFC e região do Alto Vale,a partir de informações e dados coletados de proprietários da região. As sementes foramretiradas dos frutos, lavadas e postas a secar a sombra por um dia. Após este processo, foramavaliados periodicamente a germinação das sementes e o crescimento das plantas.Foramavaliadas quantidade (a campo) e qualidade de frutos quanto a massa, rendimento de polpa,SST (ºbrix), acidez titulável (%), firmeza da polpa e acidez. As sementes obtidas de frutoscoletados foram semeadas e estão sendo avaliados a germinação e crescimento inicial dasmudas, cujos dados completos ainda não estão a disposição.Houve grande variabilidade dedados obtidos nas diferentes localidades (Tabela 1), indicando materiais promissores parautilização comercial, com elevado Brix em torno de 16 0 B e baixa acidez(6 %) em Taió eItuporanga principalmente. Além destes há outros fatores ainda a serem considerados,principalmente após a realização de análise estatística

Exploring the feasibility of a 6-week electric-bike intervention with behavioural support in Australia.

Background: Physical inactivity increases the risk of non-communicable disease development and healthcare-associated burden. Research suggests electric bikes (e-bikes) can support individuals in meeting recommended physical activity (PA) guidelines. This study assessed the feasibility of an e-bike plus a tailored behavioural support intervention for physically inactive overweight or obese adults. Methods: This non-randomized single-group pre-post study saw participants provided with an e-bike free of charge for six weeks. Feasibility was assessed across five domains: 1) feasibility of recruitment, 2) participant retention, 3) intervention adherence, 4) acceptability of questionnaires and lab-based outcome measures and 5) intervention acceptability. Participants completed self-reported measures of PA and self-efficacy for exercise. Lab-based measurements were completed pre-and post-intervention, this included blood pressure, body composition [anthropometrics and dual-energy X-ray absorptiometry (DEXA)], venous blood glucose, insulin, cholesterol, triglycerides, and cardiorespiratory fitness. Results: Our recruitment strategy saw a total of eight participants (three males and five females) complete the intervention (88.9% retention rate). Participants utilised the e-bike for the intervention duration and rode a mean distance of 299.8 km (SD ± 172.2) over the 6-week intervention period. Participants completed all outcomes with minimal data points missing. Participants’ moderate PA levels and self-efficacy for exercise increased post intervention. Lab-based measures showed a downward trend in body fat percentage, fasting blood glucose and brachial diastolic blood pressure. Conclusion: The recruitment strategy, retention, adherence and acceptability of this study support future research. E-bikes are an acceptable way to help people who are physically inactive increase their PA levels. Furthermore, sustained use may contribute to health benefits and improve overall self-efficacy for exercise

Impaired postprandial skeletal muscle vascular responses to a mixed meal challenge in normoglycaemic people with a parent with type 2 diabetes

Aims/hypothesis: Microvascular blood flow (MBF) increases in skeletal muscle postprandially to aid in glucose delivery and uptake in muscle. This vascular action is impaired in individuals who are obese or have type 2 diabetes. Whether MBF is impaired in normoglycaemic people at risk of type 2 diabetes is unknown. We aimed to determine whether apparently healthy people at risk of type 2 diabetes display impaired skeletal muscle microvascular responses to a mixed-nutrient meal. Methods: In this cross-sectional study, participants with no family history of type 2 diabetes (FH-) for two generations (n = 18), participants with a positive family history of type 2 diabetes (FH+; i.e. a parent with type 2 diabetes; n = 16) and those with type 2 diabetes (n = 12) underwent a mixed meal challenge (MMC). Metabolic responses (blood glucose, plasma insulin and indirect calorimetry) were measured before and during the MMC. Skeletal muscle large artery haemodynamics (2D and Doppler ultrasound, and Mobil-O-graph) and microvascular responses (contrast-enhanced ultrasound) were measured at baseline and 1 h post MMC. Results: Despite normal blood glucose concentrations, FH+ individuals displayed impaired metabolic flexibility (reduced ability to switch from fat to carbohydrate oxidation vs FH-; p \u3c 0.05) during the MMC. The MMC increased forearm muscle microvascular blood volume in both the FH- (1.3-fold, p \u3c 0.01) and FH+ (1.3-fold, p \u3c 0.05) groups but not in participants with type 2 diabetes. However, the MMC increased MBF (1.9-fold, p \u3c 0.01), brachial artery diameter (1.1-fold, p \u3c 0.01) and brachial artery blood flow (1.7-fold, p \u3c 0.001) and reduced vascular resistance (0.7-fold, p \u3c 0.001) only in FH- participants, with these changes being absent in FH+ and type 2 diabetes. Participants with type 2 diabetes displayed significantly higher vascular stiffness (p \u3c 0.001) compared with those in the FH- and FH+ groups; however, vascular stiffness did not change during the MMC in any participant group. Conclusions/interpretation: Normoglycaemic FH+ participants display impaired postprandial skeletal muscle macro- and microvascular responses, suggesting that poor vascular responses to a meal may contribute to their increased risk of type 2 diabetes. We conclude that vascular insulin resistance may be an early precursor to type 2 diabetes in humans, which can be revealed using an MMC

Complex and sustained quantum beating patterns in a classic IVR system: the 3¹5¹ Level in S₁ p-difluorobenzene

Using picosecond time-resolved photoelectron imaging we have studied the intramolecular vibrational energy redistribution (IVR) dynamics that occur following the excitation of the 3151 level which lies 2068 cm-1 above the S1 origin in p difluorobenzene. Our technique, which has superior time resolution to that of earlier studies but retains sufficient energy resolution to identify the behavior of individual vibrational states, enables us to determine six distinct beating periods in photoelectron intensity, only one of which has been observed previously. Analysis shows that the IVR dynamics are restricted among only a handful of vibrational levels, despite the relatively high excitation energy. This is deduced to be a consequence of the high symmetry and rigid structure of p-difluorobenzene