title: Electronic circuitry for shaping current pulses for small scale transcranial magnetic stimulation coils

authors: Raju, Soniya

abstract: Transcranial magnetic stimulation (TMS) uses electromagnetic induction to induce electric currents in brain tissue via a time-varying magnetic field from a coil, stimulating neuronal activity. While extensively studied in humans, small animal TMS coils are less explored, presenting challenges due to the high currents needed and heating issues from coil size and core hysteresis. This research focuses on the development of a new pulse generator tailored for TMS applications, with a specific emphasis on small-scale systems designed for animal studies. A supercapacitor-based design was implemented to serve as the power source, offering a compact, cost-effective solution for generating stable voltage pulses. The pulse generator demonstrated the ability to produce magnetic fields ranging 200 – 400 mT with an input of 1 V, making it a highly efficient tool for small animal TMS coils. In an effort to simplify pulse shaping without using complex circuitry, a mosfet was used as a dynamic element to control current. A triangular gate voltage waveform was introduced. This approach allowed for finer control over critical parameters such as rise time, fall time, and pulse width, which are key to TMS pulse optimization. In order to optimize pulse shape, a Matlab model to predict the behavior of coil current based on varying input gate voltage was developed. This model, which is based on a newly derived equation, align well with experimental data and enables the precise customization of pulse characteristics. It provides a valuable frame work for optimizing new and existing pulse shapes. This research demonstrates the supercapacitor-based pulse generator and its accompanying Matlab model for small-scale TMS applications. The flexibility in pulse generation and the ability to create custom pulse shapes provide a strong foundation for future exploration in TMS research, particularly for animal studies.

text: Electronic circuitry for shaping current pulses for small scale transcranial magnetic stimulation coils Transcranial magnetic stimulation (TMS) uses electromagnetic induction to induce electric currents in brain tissue via a time-varying magnetic field from a coil, stimulating neuronal activity. While extensively studied in humans, small animal TMS coils are less explored, presenting challenges due to the high currents needed and heating issues from coil size and core hysteresis. This research focuses on the development of a new pulse generator tailored for TMS applications, with a specific emphasis on small-scale systems designed for animal studies. A supercapacitor-based design was implemented to serve as the power source, offering a compact, cost-effective solution for generating stable voltage pulses. The pulse generator demonstrated the ability to produce magnetic fields ranging 200 – 400 mT with an input of 1 V, making it a highly efficient tool for small animal TMS coils. In an effort to simplify pulse shaping without using complex circuitry, a mosfet was used as a dynamic element to control current. A triangular gate voltage waveform was introduced. This approach allowed for finer control over critical parameters such as rise time, fall time, and pulse width, which are key to TMS pulse optimization. In order to optimize pulse shape, a Matlab model to predict the behavior of coil current based on varying input gate voltage was developed. This model, which is based on a newly derived equation, align well with experimental data and enables the precise customization of pulse characteristics. It provides a valuable frame work for optimizing new and existing pulse shapes. This research demonstrates the supercapacitor-based pulse generator and its accompanying Matlab model for small-scale TMS applications. The flexibility in pulse generation and the ability to create custom pulse shapes provide a strong foundation for future exploration in TMS research, particularly for animal studies.

year: 2025

title: Alcohol outlet density is related to police events and motor vehicle accidents in Manukau City, New Zealand

authors: Cameron, Michael Patrick

subjects: alcohol outlet density

abstract: Objectives: To explore the cross-sectional association between alcohol outlet density and police events in Manukau City, New Zealand.
Methods: Using data for the Census Area Unit (suburb) level, per-capita measures of alcohol outlet density for January 2009 were calculated for off-licence outlets, clubs and bars, and restaurants and cafés. Data on police events and motor vehicle accidents were obtained for the period 1 July 2008 to 30 June 2009, and also converted into per capita measures. A spatial seemingly unrelated regression model was developed, which simultaneously assessed the relationship between densities and all nine categories of police events, and motor vehicle accidents, while controlling for relevant covariates.
Results: All three outlet density measures were significantly associated with a range of police events, but only off-licence density was significantly associated with motor vehicle accidents. An additional off-licence outlet in a given area was associated with 85.4 additional police events and 10.3 additional motor vehicle accidents; an additional club or bar was associated with 34.7 additional police events and 0.5 additional motor vehicle accidents; and an additional restaurant or cafe was associated with 13.2 additional police events and 2.1 additional motor vehicle accidents.
Conclusions: The results do not imply causality. However, they are broadly consistent with availability theory, and imply that local alcohol policy should account for the effects of additional outlets when new licences are granted. While the methodological approach described here is easily transferable to investigate the relationships elsewhere, we suggest some areas for improvement of future studies

text: Alcohol outlet density is related to police events and motor vehicle accidents in Manukau City, New Zealand Objectives: To explore the cross-sectional association between alcohol outlet density and police events in Manukau City, New Zealand.
Methods: Using data for the Census Area Unit (suburb) level, per-capita measures of alcohol outlet density for January 2009 were calculated for off-licence outlets, clubs and bars, and restaurants and cafés. Data on police events and motor vehicle accidents were obtained for the period 1 July 2008 to 30 June 2009, and also converted into per capita measures. A spatial seemingly unrelated regression model was developed, which simultaneously assessed the relationship between densities and all nine categories of police events, and motor vehicle accidents, while controlling for relevant covariates.
Results: All three outlet density measures were significantly associated with a range of police events, but only off-licence density was significantly associated with motor vehicle accidents. An additional off-licence outlet in a given area was associated with 85.4 additional police events and 10.3 additional motor vehicle accidents; an additional club or bar was associated with 34.7 additional police events and 0.5 additional motor vehicle accidents; and an additional restaurant or cafe was associated with 13.2 additional police events and 2.1 additional motor vehicle accidents.
Conclusions: The results do not imply causality. However, they are broadly consistent with availability theory, and imply that local alcohol policy should account for the effects of additional outlets when new licences are granted. While the methodological approach described here is easily transferable to investigate the relationships elsewhere, we suggest some areas for improvement of future studies

year: 2012

title: Ecological Survey of Tauranga Harbour

authors: Ellis, Joanne I.

abstract: This report summarises the results of biological and physical data collected from a broad scale intertidal survey of Tauranga Harbour conducted between December 2011 and February 2012. The survey was designed to understand more fully the role of various anthropogenic stressors on the ecology of the harbour. The research was conducted as part of the Manaaki Taha Moana (MTM) programme. The wider research project aims to restore and enhance coastal ecosystems and their services of importance to iwi/hapū, by working with iwi to improve knowledge of these ecosystems and the degradation processes that affect them.
In this report we assess the health of macrofaunal benthic communities (bottom-dwelling animals) as well as trends in sediments, nutrients and contaminants. The results indicate that the sites identified as most impacted were generally located in the upper reaches of estuaries in some of the locations least exposed to wind, waves and currents. In addition, the biological community composition characterising sites with different sediment textures, nutrient and contaminant loadings were found to vary. Sediments within Tauranga Harbour were predominantly sandy with the percentage of mud within a similar range as measured for other New Zealand estuaries. The exceptions included Te Puna Estuary and Apata Estuary, which experience higher rates of sedimentation.
Heavy metal contamination in sediments is often highly correlated with the percentage of mud content due to the adherence of chemicals to fine sediments and/or organic content. It is, therefore, not surprising that heavy metal concentrations were also highest in the depositional inner areas of the harbour, such as Te Puna Estuary. The heavy metal contaminant levels within Tauranga were well below relevant guideline thresholds and lower than concentrations measured in many other estuaries in New Zealand and overseas. Although the three metals recorded were found to be highly correlated, zinc levels tended to be closer to guideline thresholds for possible biological effects.
Sediment nutrient concentrations in the harbour tended to decline with distance from the inner harbour and associated rivers. Te Puna Estuary showed comparatively high nitrogen and phosphorus loadings. Comparison of sediment nutrient concentrations with other New Zealand estuaries indicates that the Tauranga Harbour sits within a range typical for slightly to moderately enriched estuaries. Although total phosphorus was low compared with other estuaries, total N:P ratios suggest Tauranga Harbour is still limited by nitrogen.
We developed a BHM using statistical ordination techniques to identify key stressors affecting the ‘health’ of macrofaunal communities. Sediments, nutrients and heavy metals were identified as key ‘stressors’, i.e. variables affecting the ecology of the harbour. Therefore, three multivariate models were developed based on the variability in community composition using canonical analysis of principal coordinates (CAP). The ecological assemblages generally reflected gradients of stress or pollution very well. However, the CAP models for sedimentation and contamination performed best. In general, the multivariate models were found to be more sensitive to changing ecological health than simple univariate measures (abundance, species diversity, evenness and Shannon-Wiener diversity). This finding has also been reported in the literature where univariate measures based on abundance and diversity were only able to detect significant differences between the most and least disturbed sites, but were not able to differentiate between smaller relative changes in ecological health. Hence univariate measures were less sensitive to smaller degradative changes in community composition. For Tauranga Harbour, ordination models based on community composition appear to be a more sensitive measure of ‘health’ along an ecological gradient and should enable long term degradative change from multiple disturbances to be assessed. This BHM approach can be used as a management or monitoring tool where sites are repeatedly sampled over time and tracked to determine whether the communities are moving towards a more healthy or unhealthy state.
The key species at ‘healthy’ and ‘impacted’ sites as determined from the CAP models were also identified. Species at ‘impacted’ sites can be considered to be tolerant to the stressor (i.e. sediment, nutrients or contaminants), while species with high abundances at only ‘healthy’ sites are sensitive to increasing stressors. We developed species response models for 20 taxa. Although the type of response differed by taxa and stressor, variation in the abundance of most of the taxa modelled was most likely to be better predicted by sedimentation. Unimodal responses were almost always observed in response to nutrients, while declines or skewed unimodal responses were most often observed in response to sedimentation and metals.
The results from this study are consistent with models of macrofaunal species occurrence with respect to sediment mud content developed across a range of New Zealand estuaries by Thrush et al. (2003). Within this report we extend this analysis by also developing models of macrofaunal species occurrence with respect to nutrient and contaminants loadings. Ultimately such statistical models provide a tool to forecast the distribution and abundance of species associated with habitat changes in sediments, nutrients and metals.
In conclusion, Tauranga Harbour is a predominantly sandy harbour with slight to moderate enrichment and low levels of heavy metal contaminants. Sites identified as most impacted by elevated sediments, heavy metal contaminants and nutrients were generally located in the upper reaches of estuaries in some of the least exposed locations. To some extent, this reflects the natural progression of an estuary from land to sea; however, the rates of accumulation of sediments and nutrients have been accelerated as a result of anthropogenic land-based activities. Sediments and contaminants were found to explain the largest variance in benthic communities. Species response models suggest that taxa were either sensitive to elevated sediments, nutrients loading or contamination at all levels, or sensitive to these stressors beyond a critical point.

text: Ecological Survey of Tauranga Harbour This report summarises the results of biological and physical data collected from a broad scale intertidal survey of Tauranga Harbour conducted between December 2011 and February 2012. The survey was designed to understand more fully the role of various anthropogenic stressors on the ecology of the harbour. The research was conducted as part of the Manaaki Taha Moana (MTM) programme. The wider research project aims to restore and enhance coastal ecosystems and their services of importance to iwi/hapū, by working with iwi to improve knowledge of these ecosystems and the degradation processes that affect them.
In this report we assess the health of macrofaunal benthic communities (bottom-dwelling animals) as well as trends in sediments, nutrients and contaminants. The results indicate that the sites identified as most impacted were generally located in the upper reaches of estuaries in some of the locations least exposed to wind, waves and currents. In addition, the biological community composition characterising sites with different sediment textures, nutrient and contaminant loadings were found to vary. Sediments within Tauranga Harbour were predominantly sandy with the percentage of mud within a similar range as measured for other New Zealand estuaries. The exceptions included Te Puna Estuary and Apata Estuary, which experience higher rates of sedimentation.
Heavy metal contamination in sediments is often highly correlated with the percentage of mud content due to the adherence of chemicals to fine sediments and/or organic content. It is, therefore, not surprising that heavy metal concentrations were also highest in the depositional inner areas of the harbour, such as Te Puna Estuary. The heavy metal contaminant levels within Tauranga were well below relevant guideline thresholds and lower than concentrations measured in many other estuaries in New Zealand and overseas. Although the three metals recorded were found to be highly correlated, zinc levels tended to be closer to guideline thresholds for possible biological effects.
Sediment nutrient concentrations in the harbour tended to decline with distance from the inner harbour and associated rivers. Te Puna Estuary showed comparatively high nitrogen and phosphorus loadings. Comparison of sediment nutrient concentrations with other New Zealand estuaries indicates that the Tauranga Harbour sits within a range typical for slightly to moderately enriched estuaries. Although total phosphorus was low compared with other estuaries, total N:P ratios suggest Tauranga Harbour is still limited by nitrogen.
We developed a BHM using statistical ordination techniques to identify key stressors affecting the ‘health’ of macrofaunal communities. Sediments, nutrients and heavy metals were identified as key ‘stressors’, i.e. variables affecting the ecology of the harbour. Therefore, three multivariate models were developed based on the variability in community composition using canonical analysis of principal coordinates (CAP). The ecological assemblages generally reflected gradients of stress or pollution very well. However, the CAP models for sedimentation and contamination performed best. In general, the multivariate models were found to be more sensitive to changing ecological health than simple univariate measures (abundance, species diversity, evenness and Shannon-Wiener diversity). This finding has also been reported in the literature where univariate measures based on abundance and diversity were only able to detect significant differences between the most and least disturbed sites, but were not able to differentiate between smaller relative changes in ecological health. Hence univariate measures were less sensitive to smaller degradative changes in community composition. For Tauranga Harbour, ordination models based on community composition appear to be a more sensitive measure of ‘health’ along an ecological gradient and should enable long term degradative change from multiple disturbances to be assessed. This BHM approach can be used as a management or monitoring tool where sites are repeatedly sampled over time and tracked to determine whether the communities are moving towards a more healthy or unhealthy state.
The key species at ‘healthy’ and ‘impacted’ sites as determined from the CAP models were also identified. Species at ‘impacted’ sites can be considered to be tolerant to the stressor (i.e. sediment, nutrients or contaminants), while species with high abundances at only ‘healthy’ sites are sensitive to increasing stressors. We developed species response models for 20 taxa. Although the type of response differed by taxa and stressor, variation in the abundance of most of the taxa modelled was most likely to be better predicted by sedimentation. Unimodal responses were almost always observed in response to nutrients, while declines or skewed unimodal responses were most often observed in response to sedimentation and metals.
The results from this study are consistent with models of macrofaunal species occurrence with respect to sediment mud content developed across a range of New Zealand estuaries by Thrush et al. (2003). Within this report we extend this analysis by also developing models of macrofaunal species occurrence with respect to nutrient and contaminants loadings. Ultimately such statistical models provide a tool to forecast the distribution and abundance of species associated with habitat changes in sediments, nutrients and metals.
In conclusion, Tauranga Harbour is a predominantly sandy harbour with slight to moderate enrichment and low levels of heavy metal contaminants. Sites identified as most impacted by elevated sediments, heavy metal contaminants and nutrients were generally located in the upper reaches of estuaries in some of the least exposed locations. To some extent, this reflects the natural progression of an estuary from land to sea; however, the rates of accumulation of sediments and nutrients have been accelerated as a result of anthropogenic land-based activities. Sediments and contaminants were found to explain the largest variance in benthic communities. Species response models suggest that taxa were either sensitive to elevated sediments, nutrients loading or contamination at all levels, or sensitive to these stressors beyond a critical point.

year: 2017