A Predictive Model for the Pd-Catalyzed Site-Selective Oxidation of Diols

A predictive model, shaped as a set of rules, is presented that predicts site-selectivity in the mono-oxidation of diols by palladium-neocuproine catalysis. For this, the factors that govern this site-selectivity within diols and between different diols have been studied both experimentally and with computation. It is shown that an electronegative substituent antiperiplanar to the C-H bond retards hydride abstraction, resulting in a lower reactivity. This explains the selective oxidation of axial hydroxy groups in vicinal cis-diols. Furthermore, DFT calculations and competition experiments show how the reaction rate of different diols is determined by their configuration and conformational freedom. The model has been validated by the oxidation of several complex natural products, including two steroids. From a synthesis perspective, the model predicts whether a natural product comprising multiple hydroxy groups is a suitable substrate for site-selective palladium-catalyzed oxidation.</p

Effect of water table management and elevated CO 2 on radish productivity and on CH 4 and CO 2 fluxes from peatlands converted to agriculture

Anthropogenic activity is affecting the global climate through the release of greenhouse gases (GHGs) e.g. CO2 and CH4. About a third of anthropogenic GHGs are produced from agriculture, including livestock farming and horticulture. A large proportion of the UK's horticultural farming takes place on drained lowland peatlands, which are a source of significant amounts of CO2 into the atmosphere. This study set out to establish whether raising the water table from the currently used − 50 cm to − 30 cm could reduce GHGs emissions from agricultural peatlands, while simultaneously maintaining the current levels of horticultural productivity. A factorial design experiment used agricultural peat soil collected from the Norfolk Fens (among the largest of the UK's lowland peatlands under intensive cultivation) to assess the effects of water table levels, elevated CO2, and agricultural production on GHG fluxes and crop productivity of radish, one of the most economically important fenland crops. The results of this study show that a water table of − 30 cm can increase the productivity of the radish crop while also reducing soil CO2 emissions but without a resultant loss of CH4 to the atmosphere, under both ambient and elevated CO2 concentrations. Elevated CO2 increased dry shoot biomass, but not bulb biomass nor root biomass, suggesting no immediate advantage of future CO2 levels to horticultural farming on peat soils. Overall, increasing the water table could make an important contribution to global warming mitigation while not having a detrimental impact on crop yield

From Atomistic Modeling to Excitation Transfer and Two-Dimensional Spectra of the FMO Light-Harvesting Complex

The experimental observation of long-lived quantum coherences in the Fenna-Matthews-Olson (FMO) light-harvesting complex at low temperatures has challenged general intuition in the field of complex molecular systems and provoked considerable theoretical effort in search of explanations. Here we report on room-temperature calculations of the excited-state dynamics in FMO using a combination of molecular dynamics simulations and electronic structure calculations. Thus we obtain trajectories for the Hamiltonian of this system which contains time-dependent vertical excitation energies of the individual bacteriochlorophyll molecules and their mutual electronic couplings. The distribution of energies and couplings is analyzed together with possible spatial correlations. It is found that in contrast to frequent assumptions the site energy distribution is non-Gaussian. In a subsequent step, averaged wave packet dynamics is used to determine the exciton dynamics in the system. Finally, with the time-dependent Hamiltonian, linear and two-dimensional spectra are determined. The thus-obtained linear absorption line shape agrees well with experimental observation and is largely determined by the non-Gaussian site energy distribution. The two-dimensional spectra are in line with what one would expect by extrapolation of the experimental observations at lower temperatures and indicate almost total loss of long-lived coherences.

Benchmarking recent national practice in rectal cancer treatment with landmark randomized controlled trials

Contains fulltext : 175601.pdf (publisher's version ) (Closed access

Cross-Sectional Study on MRI Restaging After Chemoradiotherapy and Interval to Surgery in Rectal Cancer: Influence on Short- and Long-Term Outcomes

Background. The time interval between CRT and surgery in rectal cancer patients is still the subject of debate. The aim of this study was to first evaluate the nationwide use of restaging magnetic resonance imaging (MRI) and its impact on timing of surgery, and, second, to evaluate the impact of timing of surgery after chemoradiotherapy (CRT) on short- and long-term outcomes.Methods. Patients were selected from a collaborative rectal cancer research project including 71 Dutch centres, and were subdivided into two groups according to time interval from the start of preoperative CRT to surgery (= 14 weeks), and the long-interval group included a higher proportion of cT4 stage and multivisceral resection patients. Pathological complete response rate (n = 34 [15.2%] vs. n = 47 [18.7%], p = 0.305) and CRM involvement (9.7% vs. 15.9%, p = 0.145) did not significantly differ. Thirty-day surgical complications were similar (20.1% vs. 23.1%, p = 0.943), however no significant differences were found for local and distant recurrence rates, disease-free survival, and overall survival.Conclusions. These real-life data, reflecting routine daily practice in The Netherlands, showed substantial variability in the use and timing of restaging MRI after preoperative CRT for rectal cancer, as well as time interval to surgery. Surgery before or after 14 weeks from the start of CRT resulted in similar short- and long-term outcomes.Surgical oncolog