530 research outputs found
Making Small Claims Courts Work in Montana: Recommendations for Legislative and Judicial Action
Making Small Claims Courts Wor
The Stereochemistry of the SN2' Reaction
In an attempt to determine the preferred stereochemistry of the SN2' reaction of cyclohex-2-en-l-yl systems, it was desired to study the reactions of the cis and trans 6-alkyl cyclohex-2-en-l-yl 2,6-dichlorobenzoates (81, 82, 83; 39, 40, 41) with piperidine. Problems encountered in the preparation of these superficially simple compounds forced the curtailment of this exercise, however, and only the trans 6-isopropyl ester (40) was successfully obtained in a pure state. Attempt were made to find other 6-alkyl cyclohex-2-en-l-yl derivatives which would be suitable substrates for reaction with piperidine These were found in the cis and trans 3,5-dinitrobenzoates (84, 85), and the cis p-nitrobenzoate (87). Analysis of the reactions of these compounds with piperidine was complex - the esters reacted by substitution (SN2, SN2' ) and aminolysis, and were subject to isomerisation, by epimerisation and allylic rearrangement, during the course of reaction. However, it did eventually prove possible to establish that the SN2' reaction, when involved, proceeded only in syn fashion, regardless of the initial configuration of the substrate. The configuration of the SN2' products (229, 43) was confirmed by their comparison, after hydrosnation, with authentically prepared N-(4-alkyl cyclohexyl) piperidines (195, 196). The complexity of the reacting system precluded full kinetic analysis, but it was possible to determine approximate initial rates for the syn SN2 reactions of the cis and trans 3,5-dinitrobenzoates (84, 85) with piperidine. The implications of these findings are discussed
Multi-stage Ensemble-learning-based Model Fusion for Surface Ozone Simulations: A Focus on CMIP6 Models
Accurately simulating the geographical distribution and temporal variability of global surface ozone has long been one of the principal components of chemistry-climate modelling. However, the simulation outcomes have been reported to vary significantly as a result of the complex mixture of uncertain factors that control the tropospheric ozone budget. Settling the cross-model discrepancies to achieve higher accuracy predictions of surface ozone is thus a task of priority, and methods that overcome structural biases in models going beyond naïve averaging of model simulations are urgently required. Building on the Coupled Model Intercomparison Project Phase 6 (CMIP6), we have transplanted a conventional ensemble learning approach, and also constructed an innovative 2-stage enhanced space-time Bayesian neural network to fuse an ensemble of 57 simulations together with a prescribed ozone dataset, both of which have realised outstanding performances (R2 > 0.95, RMSE < 2.12 ppbv). The conventional ensemble learning approach is computationally cheaper and results in higher overall performance, but at the expense of oceanic ozone being overestimated and the learning process being uninterpretable. The Bayesian approach performs better in spatial generalisation and enables perceivable interpretability, but induces heavier computational burdens. Both of these multi-stage machine learning-based approaches provide frameworks for improving the fidelity of composition-climate model outputs for uses in future impact studies
The role of Oklahoma area vocational-technical schools and community/junior colleges in offering vocational education services as perceived by selected groups.
Positron detection in silica monoliths for miniaturised quality control of PET radiotracers
We demonstrate the use of the miniaturised Medipix positron sensor for detection of the clinical PET radiotracer, [⁶⁸Ga]gallium-citrate, on a silica-based monolith, towards microfluidic quality control. The system achieved a far superior signal-to-noise ratio compared to conventional sodium iodide-based radio-HPLC detection and allowed real-time visualisation of positrons in the monolith
Combining Binary Decision Diagrams and Backtracking Search for Scalable Backtrack-Free Interactive Product Configuration
The impact of the formation of HO2-H2O adducts following reaction between H2O and HO2 and subsequent reaction of this adduct on HOx, H2O2 and O3 as a function of relative humidity in the marine boundary layer has been investigated using a zero-dimensional box model. The results of simulations with different product yields for the reaction of HO2-H2O with HO2 were compared with base case data derived from current recommendations for tropospheric modelling. It is suggested that inclusion of reactions of the HO2-H2O adduct may provide a significant sink for HO2 which has so far not been considered in models of tropospheric chemistry and depending on reaction products may have a significant impact on H2O2 and O3
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