Model study of the impact of orbital choice on the accuracy of coupled-cluster energies. I. Single-reference-state formulation

Abstract. Atmospheric chemistry and transport of mercury play a key role in the global mercury cycle. However, there are still considerable knowledge gaps concerning the fate of mercury in the atmosphere. This is the second part of a model inter-comparison study investigating the impact of atmospheric chemistry and emissions on mercury in the atmosphere. While the first study focused on ground based observations of mercury concentration and deposition, here we investigate the vertical distribution and speciation of mercury from the planetary boundary layer to the lower stratosphere. So far, there have been few model studies investigating the vertical distribution of mercury, mostly focusing on single aircraft campaigns. Here, we present a first comprehensive analysis based on various aircraft observations in Europe, North America, and on inter-continental flights. The investigated models proved to be able to reproduce the distribution of total and elemental mercury concentrations in the troposphere including inter-hemispheric trends. One key aspect of the study is the investigation of mercury oxidation in the troposphere. We found that different chemistry schemes were better at reproducing observed oxidized mercury (RM) patterns depending on altitude. High RM concentrations in the upper troposphere could be reproduced with oxidation by bromine while elevated concentrations in the lower troposphere were better reproduced by OH and ozone chemistry. However, the results were not always conclusive as the physical and chemical parametrizations in the chemistry transport models also proved to have a substantial impact on model results.

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A Coupled Cluster Approach to the Electron Correlation Problem Using a Correlated Reference State

Recent Progress in Many-Body Theories ◽

10.1007/978-1-4615-1937-9_12 ◽

1995 ◽

pp. 127-133 ◽

Cited By ~ 27

Author(s):

D. Mukherjee

Keyword(s):

Electron Correlation ◽

Reference State ◽

Coupled Cluster ◽

Cluster Approach ◽

Correlation Problem

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Metal and Ligand Effects on Coordinated Methane pKa. Direct Correlation with the Methane Activation Barrier

10.26434/chemrxiv.12323726 ◽

2020 ◽

Author(s):

Amy Guan ◽

Ivy Liang ◽

Christopher Zhou ◽

Thomas Cundari

Keyword(s):

Free Energy ◽

Direct Relationship ◽

Activation Barrier ◽

Methane Activation ◽

Coupled Cluster ◽

Activation Barriers ◽

Ligand Effects ◽

3D Metals ◽

Cluster Methods ◽

The Impact

DFT and coupled cluster methods were used to investigate the impact of 3d metals and ligands upon the acidity and activation of coordinated methane C–H bonds. A strong, direct relationship was established between the pKa of coordinated methane and the subsequent free energy barriers to H3C–H activation. The few outliers to this relationship indicated other factors– such as thermodynamic stability of the product and ligand-metal coordination type – also impacted the methane activation barrier (dG‡). High variations in the activation barriers and pKa values were found with a range of 34.8 kcal/mol for the former and 28.6 pKa units for the latter. Clear trends among specific metals and ligands were also derived; specific metals, such as CoI, as well as Lewis and p-acids consistently yielded higher acidity for the ligated methane and hence lower dG‡.

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A model study on the impact of metal ions on pre-vulcanization of concentrated natural rubber latex and dipped-products

Progress in Rubber Plastics and Recycling Technology ◽

10.1177/14777606211062909 ◽

2021 ◽

pp. 147776062110629

Author(s):

Porntip Rojruthai ◽

Narueporn Payungwong ◽

Jitladda T Sakdapipanich

Keyword(s):

Natural Rubber ◽

Metal Ions ◽

Colloidal Stability ◽

Mechanical Stability ◽

Testing Machine ◽

Natural Rubber Latex ◽

Tensile Testing Machine ◽

Model Study ◽

Stability Time ◽

The Impact

A model study on the influence of some heavy metal ions on the stability and vulcanization efficiency of uncompounded and compounded high-ammonia natural rubber (HANR) latex was carried out by an exogenous addition and then determined by Brookfield viscometer, mechanical stability time (MST) tester, and tensile testing machine. The case of pre-vulcanized HANR latex with different aging times was determined by the change in the volatile fatty acid (VFA) number, MST, and viscosity. The compounded HANR latex was coagulated by adding Mn2+and Mg2+ while it was unaltered by adding Zn2+, Fe2+, and Cu2+ ions, leading to their colloidal stability. Therefore, these metal ions were chosen further to study the pre-vulcanization of compounded HANR latex. The presence of Zn2+, Fe2+, and Cu2+ in the latex is responsible for the delay in the vulcanization process and changes the appearance of compounded latex. Before compounding, the addition of such metal ions led to the reduction in tensile strength of the obtained gloves. At the same time, there was no effect on the tensile properties of the gloves made from the compounded HANR latex containing the metal ions.

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Implementation, mechanisms of impact and key contextual factors involved in outcomes of the Modification of Diet, Exercise and Lifestyle (MODEL) randomised controlled trial in Australian adults: protocol for a mixed-method process evaluation

BMJ Open ◽

10.1136/bmjopen-2019-036395 ◽

2020 ◽

Vol 10 (11) ◽

pp. e036395

Author(s):

Reindolf Anokye ◽

Simone Radavelli-Bagatini ◽

Catherine P Bondonno ◽

Marc Sim ◽

Lauren C Blekkenhorst ◽

...

Keyword(s):

Process Evaluation ◽

Mixed Method ◽

Controlled Trial ◽

Behavioural Change ◽

Implementation Strategies ◽

Pictorial Representation ◽

Model Study ◽

Study Results ◽

Qualitative Component ◽

The Impact

IntroductionThe Modification of Diet, Exercise and Lifestyle (MODEL) study aims to examine the impact of providing visualisation and pictorial representation of advanced structural vascular disease (abdominal aortic calcification), on ‘healthful’ improvements to diet and lifestyle. This paper reports the protocol for the process evaluation for the MODEL study.Methods and analysisThe overall aim of the process evaluation is to understand the processes that took place during participation in the MODEL study trial and which elements were effective or ineffective for influencing ‘healthful’ behavioural change, and possible ways of improvement to inform wider implementation strategies. A mixed-method approach will be employed with the use of structured questionnaires and semistructured in-depth interviews. All 200 participants enrolled in the trial will undertake the quantitative component of the study and maximum variation sampling will be used to select a subsample for the qualitative component. The sample size for the qualitative component will be determined based on analytical saturation. Interviews will be digitally recorded and transcribed verbatim. Qualitative data will be analysed thematically and reported according to the Consolidated Criteria for Reporting Qualitative Research (COREQ) guidelines.Ethics and disseminationThe MODEL study process evaluation has received approval from Edith Cowan University Human Research Ethics Committee (Project Number: 20513 HODGSON). Written informed consent will be obtained from all participants before they are included in the study. The study results will be shared with the individuals and institutions associated with this study as well as academic audiences through peer-reviewed publication and probable presentation at conferences.Trial registration numberACTRN12618001087246.

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Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-6925-2017 ◽

2017 ◽

Vol 17 (11) ◽

pp. 6925-6955 ◽

Cited By ~ 15

Author(s):

Johannes Bieser ◽

Franz Slemr ◽

Jesse Ambrose ◽

Carl Brenninkmeijer ◽

Steve Brooks ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Lower Troposphere ◽

Elemental Mercury ◽

Mercury Species ◽

Substantial Impact ◽

Model Studies ◽

Model Study ◽

High Concentrations ◽

Intercomparison Study ◽

The Impact

Abstract. Atmospheric chemistry and transport of mercury play a key role in the global mercury cycle. However, there are still considerable knowledge gaps concerning the fate of mercury in the atmosphere. This is the second part of a model intercomparison study investigating the impact of atmospheric chemistry and emissions on mercury in the atmosphere. While the first study focused on ground-based observations of mercury concentration and deposition, here we investigate the vertical and interhemispheric distribution and speciation of mercury from the planetary boundary layer to the lower stratosphere. So far, there have been few model studies investigating the vertical distribution of mercury, mostly focusing on single aircraft campaigns. Here, we present a first comprehensive analysis based on various aircraft observations in Europe, North America, and on intercontinental flights. The investigated models proved to be able to reproduce the distribution of total and elemental mercury concentrations in the troposphere including interhemispheric trends. One key aspect of the study is the investigation of mercury oxidation in the troposphere. We found that different chemistry schemes were better at reproducing observed oxidized mercury patterns depending on altitude. High concentrations of oxidized mercury in the upper troposphere could be reproduced with oxidation by bromine while elevated concentrations in the lower troposphere were better reproduced by OH and ozone chemistry. However, the results were not always conclusive as the physical and chemical parameterizations in the chemistry transport models also proved to have a substantial impact on model results.

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