title: ‘User-friendly’ primary phosphines and an arsine: synthesis and characterization of new air-stable ligands incorporating the ferrocenyl group

authors: Henderson, William

subjects: chemistry

abstract: Reaction of FcCH₂CH₂P(O)(OH)₂ or FcCH₂P(O)(OH)(OEt) [Fc=Fe(η⁵-C₅H₄)(η⁵-C₅H₅)] with excess CH₂N₂ followed by reduction with Me₃SiCl–LiAlH₄ gives the air-stable primary phosphines FcCH₂CH₂PH₂ and the previously reported analogue FcCH₂PH₂ in high yields. Reduction of 1,1′-Fc′[CH₂P(O)(OEt)₂] [Fc′=Fe(η⁵-C₅H₄)₂] and 1,2-Fc″[CH₂P(O)(OEt)₂] [Fc″=Fe(η⁵-C₅H₅)(η⁵-C₅H₃)] similarly gives the new primary phosphines 1,1′-Fc′(CH₂PH₂)₂ and 1,2-Fc″(CH₂PH₂)₂, respectively. The arsine FcCH₂CH₂AsH₂, which is also air-stable, has been prepared by reduction of the arsonic acid FcCH₂CH₂As(O)(OH)₂ using Zn/HCl. An X-ray structure has been carried out on the arsine, which is only the second structure determination of a free primary arsine. The molybdenum carbonyl complex [1,2-Fc″(CH₂PH₂)₂Mo(CO)₄] was prepared by reaction of the phosphine with [Mo(CO)₄(pip)₂] (pip=piperidine), and characterized by a preliminary X-ray structure determination. However, the same reaction of 1,1′-Fc′(CH₂PH₂)₂with [Mo(CO)₄(pip)₂] gave [1,1′-Fc′(CH₂PH₂)₂Mo(CO)₄] and the dimer [1,1′-Fc′(CH₂PH₂)₂Mo(CO)₄]₂, characterized by electrospray mass spectrometry. 1,1′-Fc′[CH₂PH₂Mo(CO)₅]₂ and 1,2-Fc″[CH₂PH₂Mo(CO)₅]₂ were likewise prepared from the phosphines and excess [Mo(CO)₅(THF)].

text: ‘User-friendly’ primary phosphines and an arsine: synthesis and characterization of new air-stable ligands incorporating the ferrocenyl group Reaction of FcCH₂CH₂P(O)(OH)₂ or FcCH₂P(O)(OH)(OEt) [Fc=Fe(η⁵-C₅H₄)(η⁵-C₅H₅)] with excess CH₂N₂ followed by reduction with Me₃SiCl–LiAlH₄ gives the air-stable primary phosphines FcCH₂CH₂PH₂ and the previously reported analogue FcCH₂PH₂ in high yields. Reduction of 1,1′-Fc′[CH₂P(O)(OEt)₂] [Fc′=Fe(η⁵-C₅H₄)₂] and 1,2-Fc″[CH₂P(O)(OEt)₂] [Fc″=Fe(η⁵-C₅H₅)(η⁵-C₅H₃)] similarly gives the new primary phosphines 1,1′-Fc′(CH₂PH₂)₂ and 1,2-Fc″(CH₂PH₂)₂, respectively. The arsine FcCH₂CH₂AsH₂, which is also air-stable, has been prepared by reduction of the arsonic acid FcCH₂CH₂As(O)(OH)₂ using Zn/HCl. An X-ray structure has been carried out on the arsine, which is only the second structure determination of a free primary arsine. The molybdenum carbonyl complex [1,2-Fc″(CH₂PH₂)₂Mo(CO)₄] was prepared by reaction of the phosphine with [Mo(CO)₄(pip)₂] (pip=piperidine), and characterized by a preliminary X-ray structure determination. However, the same reaction of 1,1′-Fc′(CH₂PH₂)₂with [Mo(CO)₄(pip)₂] gave [1,1′-Fc′(CH₂PH₂)₂Mo(CO)₄] and the dimer [1,1′-Fc′(CH₂PH₂)₂Mo(CO)₄]₂, characterized by electrospray mass spectrometry. 1,1′-Fc′[CH₂PH₂Mo(CO)₅]₂ and 1,2-Fc″[CH₂PH₂Mo(CO)₅]₂ were likewise prepared from the phosphines and excess [Mo(CO)₅(THF)].

year: 2002

title: Methods for eliciting informative prior distributions: A critical review

authors: Falconer, Julia Ruth

subjects: computer science

abstract: Eliciting informative prior distributions for Bayesian inference can often be complex and challenging. Although popular methods rely on asking experts probability-based questions to quantify uncertainty, these methods are not without their drawbacks, and many alternative elicitation methods exist. This paper explores methods for eliciting informative priors categorized by type and briefly discusses their strengths and limitations. Most of the review literature in this field focuses on a particular type of elicitation approach. The primary aim of this work, however, is to provide a more complete yet macro view of the state of the art by highlighting new (and old) approaches in one clear easy-to-read article. Two representative applications are used throughout to explore the suitability, or lack thereof, of the existing methods, one of which highlights a challenge that has not been addressed in the literature yet. We identify some of the gaps in the present work and discuss directions for future research.

text: Methods for eliciting informative prior distributions: A critical review Eliciting informative prior distributions for Bayesian inference can often be complex and challenging. Although popular methods rely on asking experts probability-based questions to quantify uncertainty, these methods are not without their drawbacks, and many alternative elicitation methods exist. This paper explores methods for eliciting informative priors categorized by type and briefly discusses their strengths and limitations. Most of the review literature in this field focuses on a particular type of elicitation approach. The primary aim of this work, however, is to provide a more complete yet macro view of the state of the art by highlighting new (and old) approaches in one clear easy-to-read article. Two representative applications are used throughout to explore the suitability, or lack thereof, of the existing methods, one of which highlights a challenge that has not been addressed in the literature yet. We identify some of the gaps in the present work and discuss directions for future research.

year: 2022

title: Monitoring and hydrodynamic modelling of groundwater inflows into Lake Rotokakahi, New Zealand

authors: Noakes, Katie

subjects: Groundwater

abstract: Lake Rotokakahi is located 10 km south of Rotorua and is of immense cultural importance to the local iwi. The lake also has significant historical and recreational values, which prompted iwi to make the lake private in 1996. Lake Rotokakahi is one of several Rotorua/ Te Arawa lakes. Several of these lakes have become eutrophic and some have declining water quality. This study was prompted by declining water quality of Lake Rotokakahi and the need to identify potential sources of nutrients to the lake, particularly groundwater inflows.

The interaction between groundwater and surface water has a major influence on the trophic status of lakes, particularly those that are predominantly or solely groundwater fed systems. Lake Rotokakahi has one small spring-fed surface water inflow and one outflow, the Te Wairoa stream. Thus the lake is predominantly groundwater fed. The main objective of this thesis was to quantify the contribution of groundwater and surface water to Lake Rotokakahi and to examine interactions of the groundwater system with the lake, in order to provide a basis to improve lake management practices. Multiple monitoring sites were established around the perimeter of the lake to determine the spatial and temporal variation of groundwater inputs, as well as the groundwater nutrient dynamics. A three-dimensional hydrodynamic lake model was set up and simulations were used to examine how groundwater and surface water inflows were dispersed within the lake upon entry.

Monitoring of the shallow groundwater system took place from 1 January to 1 July 2016. Three separate storm events were monitored at high frequency within this monitoring period. The monitoring results showed the groundwater system varied significantly both spatially and temporally and also contributed a high proportion of the total nutrient load to the lake. Groundwater discharge and nutrient concentrations generally increased in association with or immediately following high rainfall events.
 
The three-dimensional model ELCOM was set up using hydrological data for the catchment, meteorological data from a nearby station and bathymetry of the lake. Simulations were based upon different methods of calculating groundwater inflows. Simulation 1 was based upon the common water balance equation method. Simulation 2 used constant groundwater inflow and outflow volumes as determined by a groundwater flow model, MODFLOW, which had been applied to the catchment by White et al., (2015). Simulation 3 combined MODLFOW values and measured groundwater levels to create a varying inflow volume based on water level. The three simulations accurately captured surface and bottom temperatures and had varying lake water levels. Only simulation 3 accurately captured the presence of the groundwater spring near the lake shore and was concluded the more accurate method of groundwater inflow calculation.

text: Monitoring and hydrodynamic modelling of groundwater inflows into Lake Rotokakahi, New Zealand Lake Rotokakahi is located 10 km south of Rotorua and is of immense cultural importance to the local iwi. The lake also has significant historical and recreational values, which prompted iwi to make the lake private in 1996. Lake Rotokakahi is one of several Rotorua/ Te Arawa lakes. Several of these lakes have become eutrophic and some have declining water quality. This study was prompted by declining water quality of Lake Rotokakahi and the need to identify potential sources of nutrients to the lake, particularly groundwater inflows.

The interaction between groundwater and surface water has a major influence on the trophic status of lakes, particularly those that are predominantly or solely groundwater fed systems. Lake Rotokakahi has one small spring-fed surface water inflow and one outflow, the Te Wairoa stream. Thus the lake is predominantly groundwater fed. The main objective of this thesis was to quantify the contribution of groundwater and surface water to Lake Rotokakahi and to examine interactions of the groundwater system with the lake, in order to provide a basis to improve lake management practices. Multiple monitoring sites were established around the perimeter of the lake to determine the spatial and temporal variation of groundwater inputs, as well as the groundwater nutrient dynamics. A three-dimensional hydrodynamic lake model was set up and simulations were used to examine how groundwater and surface water inflows were dispersed within the lake upon entry.

Monitoring of the shallow groundwater system took place from 1 January to 1 July 2016. Three separate storm events were monitored at high frequency within this monitoring period. The monitoring results showed the groundwater system varied significantly both spatially and temporally and also contributed a high proportion of the total nutrient load to the lake. Groundwater discharge and nutrient concentrations generally increased in association with or immediately following high rainfall events.
 
The three-dimensional model ELCOM was set up using hydrological data for the catchment, meteorological data from a nearby station and bathymetry of the lake. Simulations were based upon different methods of calculating groundwater inflows. Simulation 1 was based upon the common water balance equation method. Simulation 2 used constant groundwater inflow and outflow volumes as determined by a groundwater flow model, MODFLOW, which had been applied to the catchment by White et al., (2015). Simulation 3 combined MODLFOW values and measured groundwater levels to create a varying inflow volume based on water level. The three simulations accurately captured surface and bottom temperatures and had varying lake water levels. Only simulation 3 accurately captured the presence of the groundwater spring near the lake shore and was concluded the more accurate method of groundwater inflow calculation.

year: 2016