title: In situ measurement of metal-ligand complex dissociation rates in cave dripwaters

authors: Guo, Xiaoli

abstract: The purpose of this study was to develop a new method for determining the trace metal binding properties of natural organic matter (NOM) in cave dripwaters. The methodology is based on the diffusive gradients in the thin-films (DGT) technique, but differs from DGT by using advective gradients along hydrogel to resolve temporal trends in dissociation. For this reason, it is referred to as advective gradients in thin-films (AGT). 
NOM is a ubiquitous component in natural waters. The complexation capacities of NOM ligands for metal ions in cave waters has a great impact on the transport of trace metals to, and their incorporation in, calcium carbonate cave deposits (speleothems). The relationship between the kinetics of metal-NOM complexes and the concentration of the metal-carbonate solid solution in actively forming cave precipitates, is the major focus in this study. The primary goal of this research is the determination of the mean kinetics of compositionally-unknown metal-NOM complexes in situ with the application of AGT.
The first part of this study was to calibrate the self-assembled AGT device containing a resin gel (for the binding of metal ions). A range of drip rates was tested to establish the relationship between drip rates and flow velocity within the gel with the aim of establishing a calibration function between drip discharge and flow rate within the gel. The second part of this study was to validate the method using metal-ligand complexes of known character. Synthetic solutions containing organic ligands at known concentrations were measured. The experimental data showed acceptable reproducibility, and the modelling results agreed well with the literature. 
After the laboratory-based study of the AGT method, the device was deployed in Aranui Cave, which is a natural cave located in the Waitomo District, New Zealand. Four transition metals were found in both resin gel samples and the water sample. The accumulation behaviour of the metals in the Chelex-100 resin gel demonstrated the capability of the AGT method to measure trace metals bound to unknown NOM ligands in cave dripwaters. The dynamics of the dissociation of metal-NOM complexes can be reflected by the distinct dissociation patterns of the metals.
This newly developed method can semi-qualitatively determine the dissociation rates of labile and partially labile metal-NOM complexes in natural waters. However, further optimisation of the method will be required to improve the precision and accuracy of measurements. In summary, this study provides the basic framework for further research of a new palaeoclimate proxy utilising trace meta-content in speleothems.

text: In situ measurement of metal-ligand complex dissociation rates in cave dripwaters The purpose of this study was to develop a new method for determining the trace metal binding properties of natural organic matter (NOM) in cave dripwaters. The methodology is based on the diffusive gradients in the thin-films (DGT) technique, but differs from DGT by using advective gradients along hydrogel to resolve temporal trends in dissociation. For this reason, it is referred to as advective gradients in thin-films (AGT). 
NOM is a ubiquitous component in natural waters. The complexation capacities of NOM ligands for metal ions in cave waters has a great impact on the transport of trace metals to, and their incorporation in, calcium carbonate cave deposits (speleothems). The relationship between the kinetics of metal-NOM complexes and the concentration of the metal-carbonate solid solution in actively forming cave precipitates, is the major focus in this study. The primary goal of this research is the determination of the mean kinetics of compositionally-unknown metal-NOM complexes in situ with the application of AGT.
The first part of this study was to calibrate the self-assembled AGT device containing a resin gel (for the binding of metal ions). A range of drip rates was tested to establish the relationship between drip rates and flow velocity within the gel with the aim of establishing a calibration function between drip discharge and flow rate within the gel. The second part of this study was to validate the method using metal-ligand complexes of known character. Synthetic solutions containing organic ligands at known concentrations were measured. The experimental data showed acceptable reproducibility, and the modelling results agreed well with the literature. 
After the laboratory-based study of the AGT method, the device was deployed in Aranui Cave, which is a natural cave located in the Waitomo District, New Zealand. Four transition metals were found in both resin gel samples and the water sample. The accumulation behaviour of the metals in the Chelex-100 resin gel demonstrated the capability of the AGT method to measure trace metals bound to unknown NOM ligands in cave dripwaters. The dynamics of the dissociation of metal-NOM complexes can be reflected by the distinct dissociation patterns of the metals.
This newly developed method can semi-qualitatively determine the dissociation rates of labile and partially labile metal-NOM complexes in natural waters. However, further optimisation of the method will be required to improve the precision and accuracy of measurements. In summary, this study provides the basic framework for further research of a new palaeoclimate proxy utilising trace meta-content in speleothems.

year: 2019

title: Analyzing and repairing concept drift adaptation in data stream classification

authors: Halstead, Ben

subjects: computer science

abstract: Data collected over time often exhibit changes in distribution, or concept drift, caused by changes in factors relevant to the classification task, e.g. weather conditions. Incorporating all relevant factors into the model may be able to capture these changes, however, this is usually not practical. Data stream based methods, which instead explicitly detect concept drift, have been shown to retain performance under unknown changing conditions. These methods adapt to concept drift by training a model to classify each distinct data distribution. However, we hypothesize that existing methods do not robustly handle real-world tasks, leading to adaptation errors where context is misidentified. Adaptation errors may cause a system to use a model which does not fit the current data, reducing performance. We propose a novel repair algorithm to identify and correct errors in concept drift adaptation. Evaluation on synthetic data shows that our proposed AiRStream system has higher performance than baseline methods, while is also better at capturing the dynamics of the stream. Evaluation on an air quality inference task shows AiRStream provides increased real-world performance compared to eight baseline methods. A case study shows that AiRStream is able to build a robust model of environmental conditions over this task, allowing the adaptions made to concept drift to be analysed and related to changes in weather. We discovered a strong predictive link between the adaptions made by AiRStream and changes in meteorological conditions.

text: Analyzing and repairing concept drift adaptation in data stream classification Data collected over time often exhibit changes in distribution, or concept drift, caused by changes in factors relevant to the classification task, e.g. weather conditions. Incorporating all relevant factors into the model may be able to capture these changes, however, this is usually not practical. Data stream based methods, which instead explicitly detect concept drift, have been shown to retain performance under unknown changing conditions. These methods adapt to concept drift by training a model to classify each distinct data distribution. However, we hypothesize that existing methods do not robustly handle real-world tasks, leading to adaptation errors where context is misidentified. Adaptation errors may cause a system to use a model which does not fit the current data, reducing performance. We propose a novel repair algorithm to identify and correct errors in concept drift adaptation. Evaluation on synthetic data shows that our proposed AiRStream system has higher performance than baseline methods, while is also better at capturing the dynamics of the stream. Evaluation on an air quality inference task shows AiRStream provides increased real-world performance compared to eight baseline methods. A case study shows that AiRStream is able to build a robust model of environmental conditions over this task, allowing the adaptions made to concept drift to be analysed and related to changes in weather. We discovered a strong predictive link between the adaptions made by AiRStream and changes in meteorological conditions.

year: 2021

title: Real world initiation of newly funded empagliflozin and dulaglutide under special authority for patients with type 2 diabetes in New Zealand

authors: Chepulis, Lynne Merran

subjects: GLP1RA

abstract: Background: Type 2 diabetes (T2D) is sub-optimally managed for many in Aotearoa New Zealand, and disproportionately affects Māori and Pacific peoples. In February 2021, SGLT2i/GLP1RA agents were funded for use for the first time with prioritisation for Māori, Pacific and those with cardiovascular and/or renal disease or risk (CVRD). This study evaluates the impact of health system factors on initiation of SGLT2i/GLP1RA therapy. 

Methods: Primary care data was collected for patients with T2D aged 18–75 years from four primary care organisations (302 general practices) in the Auckland / Waikato region of New Zealand (Feb 2021 – July 2022). Initiation of SGLT2i/GLP1RA therapy was reviewed by patient (age, gender, ethnicity, CVRD status) and health system variables (funding, provider type, staffing, patient numbers, rurality, after-hours access). Logistic regression was used to estimate the odds ratio of a patient being dispensed SGLT2i/GLP1RA. 

Results: Of 57,743 patients with T2D, 22,331 were eligible for funded SGLT2i/GLP1RA access and 10,272 of those (46.0%) were prescribed. Initiation of therapy was highest in Māori (50.8%) and Pacific (48.8%) patients (vs. 36·2–40·7% of other ethnic groups; P < 0.001), but was comparable in those with and without CVRD (47·1% vs. 48·9%; P = 0.2). Prescribing was highest in practices with higher doctor/patient numbers, low-cost fees, Māori health providers and clinics without after-hours access.

Conclusion: Prioritised access for SGLT2i/GLP1RA appears to be associated with a reduced health equity gap for Māori and Pacific patients with T2D in NZ, but work is required to improve prescribing for patients with CVRD.

text: Real world initiation of newly funded empagliflozin and dulaglutide under special authority for patients with type 2 diabetes in New Zealand Background: Type 2 diabetes (T2D) is sub-optimally managed for many in Aotearoa New Zealand, and disproportionately affects Māori and Pacific peoples. In February 2021, SGLT2i/GLP1RA agents were funded for use for the first time with prioritisation for Māori, Pacific and those with cardiovascular and/or renal disease or risk (CVRD). This study evaluates the impact of health system factors on initiation of SGLT2i/GLP1RA therapy. 

Methods: Primary care data was collected for patients with T2D aged 18–75 years from four primary care organisations (302 general practices) in the Auckland / Waikato region of New Zealand (Feb 2021 – July 2022). Initiation of SGLT2i/GLP1RA therapy was reviewed by patient (age, gender, ethnicity, CVRD status) and health system variables (funding, provider type, staffing, patient numbers, rurality, after-hours access). Logistic regression was used to estimate the odds ratio of a patient being dispensed SGLT2i/GLP1RA. 

Results: Of 57,743 patients with T2D, 22,331 were eligible for funded SGLT2i/GLP1RA access and 10,272 of those (46.0%) were prescribed. Initiation of therapy was highest in Māori (50.8%) and Pacific (48.8%) patients (vs. 36·2–40·7% of other ethnic groups; P < 0.001), but was comparable in those with and without CVRD (47·1% vs. 48·9%; P = 0.2). Prescribing was highest in practices with higher doctor/patient numbers, low-cost fees, Māori health providers and clinics without after-hours access.

Conclusion: Prioritised access for SGLT2i/GLP1RA appears to be associated with a reduced health equity gap for Māori and Pacific patients with T2D in NZ, but work is required to improve prescribing for patients with CVRD.

year: 2025