title: Milk Spectroscopy

authors: Russell, Andrew

subjects: Milk

abstract: This thesis examines the capability of two different MicroNIR spectrometers to measure the composition of raw milk for an online milk sensor.

On-farm milk testing is an important tool in a developed dairy market. It is used by farmers to determine milk quality, nutrition and individual animal performance. The price farmers receive for milk is based on the fat and protein content. Currently milk composition is monitored on average three times a season, which leads to late diagnosis of poor performance. Daily monitoring of milk composition allows farmers better farm management and optimisation of the processes and feed to achieve success. The International Committee for Animal Recording (ICAR) sets standards for sensors which give farmers confidence in the data they receive. Two low cost spectrometers were assessed to see if they meet the ICAR fat and protein regulations for an online sensor.

The spectrometers covered two spectral regions in the NIR range and were both developed by JDS Uniphase Corporation (JDSU, California, USA). The MicroNIR1700 spectrometer analyses the 870 – 1660 nm region, and the MicroNIR2200 spectrometer covers the 1130 – 2150 nm region. An initial laboratory trial with the unmodified spectrometers did not meet ICAR precision limits for milk analysis. The high prediction errors were caused by insufficient signal, aged milk samples being reheated and excessive dark current.

To improve the signal to noise ratio of the spectrum the lamp voltage was increased. This increased the received signal to the spectrometers but also increased the temperature of the spectrometers. The increase in temperature caused the dark current to excessively increase. To reduce the operating temperature of the spectrometers a thermoelectric cooler was used to cool the spectrometers to 20°C.

The modified spectrometers with increased light and thermoelectric cooler were tested on three different farms to establish if the modifications done can meet ICAR fat and protein precision limits. A total of 590 milk samples were collected across three different farms. Calibration models were tested on each individual farm and across all three farms to assess the capability of calibration models to be transferred across the different farms.

Off-line and on-farm, the modified MicroNIR spectrometers achieved ICAR fat and protein precision limits for an online sensor. For the pooled data set the MicroNIR1700 spectrometer predicted fat and protein with a root mean square error of 0.061 and 0.151 respectively. The MicroNIR2200 predicted fat and protein with a RMSE of 0.061 and 0.138. The independent calibration models could be transferred across farms with only a slight increase in prediction error but still within the ICAR tolerances for an online milk sensor

It is concluded the original MicroNIR spectrometers could not predict fat and protein to ICAR precision limits for an online sensor. To achieve ICAR accuracy with the MicroNIR spectrometers the light output needed to be increased and cooling was required to reduce the operating temperature.

This work shows that there is definite potential for low cost spectrometers to be used for the determination of milk properties.

text: Milk Spectroscopy This thesis examines the capability of two different MicroNIR spectrometers to measure the composition of raw milk for an online milk sensor.

On-farm milk testing is an important tool in a developed dairy market. It is used by farmers to determine milk quality, nutrition and individual animal performance. The price farmers receive for milk is based on the fat and protein content. Currently milk composition is monitored on average three times a season, which leads to late diagnosis of poor performance. Daily monitoring of milk composition allows farmers better farm management and optimisation of the processes and feed to achieve success. The International Committee for Animal Recording (ICAR) sets standards for sensors which give farmers confidence in the data they receive. Two low cost spectrometers were assessed to see if they meet the ICAR fat and protein regulations for an online sensor.

The spectrometers covered two spectral regions in the NIR range and were both developed by JDS Uniphase Corporation (JDSU, California, USA). The MicroNIR1700 spectrometer analyses the 870 – 1660 nm region, and the MicroNIR2200 spectrometer covers the 1130 – 2150 nm region. An initial laboratory trial with the unmodified spectrometers did not meet ICAR precision limits for milk analysis. The high prediction errors were caused by insufficient signal, aged milk samples being reheated and excessive dark current.

To improve the signal to noise ratio of the spectrum the lamp voltage was increased. This increased the received signal to the spectrometers but also increased the temperature of the spectrometers. The increase in temperature caused the dark current to excessively increase. To reduce the operating temperature of the spectrometers a thermoelectric cooler was used to cool the spectrometers to 20°C.

The modified spectrometers with increased light and thermoelectric cooler were tested on three different farms to establish if the modifications done can meet ICAR fat and protein precision limits. A total of 590 milk samples were collected across three different farms. Calibration models were tested on each individual farm and across all three farms to assess the capability of calibration models to be transferred across the different farms.

Off-line and on-farm, the modified MicroNIR spectrometers achieved ICAR fat and protein precision limits for an online sensor. For the pooled data set the MicroNIR1700 spectrometer predicted fat and protein with a root mean square error of 0.061 and 0.151 respectively. The MicroNIR2200 predicted fat and protein with a RMSE of 0.061 and 0.138. The independent calibration models could be transferred across farms with only a slight increase in prediction error but still within the ICAR tolerances for an online milk sensor

It is concluded the original MicroNIR spectrometers could not predict fat and protein to ICAR precision limits for an online sensor. To achieve ICAR accuracy with the MicroNIR spectrometers the light output needed to be increased and cooling was required to reduce the operating temperature.

This work shows that there is definite potential for low cost spectrometers to be used for the determination of milk properties.

year: 2013

title: Validating the depression anxiety stress scales (DASS-21) across Germany, Ghana, India, and New Zealand using Rasch methodology

authors: Adu, P

subjects: Anxiety

abstract: Psychological distress is widespread globally, affects both mental and physical health, and has been significantly exacerbated by the COVID-19 pandemic. Reliable and valid instruments to assess psychological distress are needed so that interventions to address this condition can be directed and evaluated. We evaluated the psychometric statistics of the Depression Anxiety Stress Scales (DASS-21) using the Rasch method and a population survey sample dataset from four nations. To meet the requirements of the Rasch model, we randomly selected 500 participants (at least 110 from each country) from a total sample of 1822 individuals from Germany (n = 475), Ghana (n = 523), India (n = 411), and New Zealand (n = 413). Minor testlet modifications were necessary to achieve a satisfactory model fit for the depression (χ2 (30) = 40.32, p = 0.099), anxiety (χ2 (32) = 31.22, p = 0.510), and stress (χ2 (20) = 29.64, p = 0.076) subscales, and the full-scale (χ2 (18) = 23.93, p = 0.16). The scales were strictly unidimensional with acceptable reliability reflected by Person Separation Index (PSI) values of 0.86 for depression, 0.74 for anxiety, 0.82 for stress, and 0.87 for the total scale. The scales’ items showed invariance across the countries and sociodemographic factors. The scales also demonstrated convergent, structural, and external validities. The study supported the reliability and validity of the DASS-21 for assessing psychological distress in four countries. Rasch model algorithms developed in this study enable conversion of the ordinal DASS-21 scale and its subscale scores to interval-level scores, which increases the precision of measurement. Future studies should apply Rasch methodology to the DASS-21 in various cultural contexts, incorporating subgroup analyses.

text: Validating the depression anxiety stress scales (DASS-21) across Germany, Ghana, India, and New Zealand using Rasch methodology Psychological distress is widespread globally, affects both mental and physical health, and has been significantly exacerbated by the COVID-19 pandemic. Reliable and valid instruments to assess psychological distress are needed so that interventions to address this condition can be directed and evaluated. We evaluated the psychometric statistics of the Depression Anxiety Stress Scales (DASS-21) using the Rasch method and a population survey sample dataset from four nations. To meet the requirements of the Rasch model, we randomly selected 500 participants (at least 110 from each country) from a total sample of 1822 individuals from Germany (n = 475), Ghana (n = 523), India (n = 411), and New Zealand (n = 413). Minor testlet modifications were necessary to achieve a satisfactory model fit for the depression (χ2 (30) = 40.32, p = 0.099), anxiety (χ2 (32) = 31.22, p = 0.510), and stress (χ2 (20) = 29.64, p = 0.076) subscales, and the full-scale (χ2 (18) = 23.93, p = 0.16). The scales were strictly unidimensional with acceptable reliability reflected by Person Separation Index (PSI) values of 0.86 for depression, 0.74 for anxiety, 0.82 for stress, and 0.87 for the total scale. The scales’ items showed invariance across the countries and sociodemographic factors. The scales also demonstrated convergent, structural, and external validities. The study supported the reliability and validity of the DASS-21 for assessing psychological distress in four countries. Rasch model algorithms developed in this study enable conversion of the ordinal DASS-21 scale and its subscale scores to interval-level scores, which increases the precision of measurement. Future studies should apply Rasch methodology to the DASS-21 in various cultural contexts, incorporating subgroup analyses.

year: 2025

title: Through the eyes of whānau: Destruction of cultural identity through education

authors: Ngaamo, Raewyn Brenda

subjects: Māori

abstract: This thesis examines how the schooling experiences of a dual cultural heritage whānau influenced the development of their identity, their language and culture across three generations. Koro, Tuakana, Teina and Moko share their experiences with us and through these stories reveal how they were forced through the colonising beliefs and practices of schooling to reshape themselves in a bid to belong. The compromise and abuse of cultural identity in wider society, replicated and validated in schooling, created a vicious and dehumanising experience for each of them. School was a major site of assimilation for this whānau. They experienced racism, rejection, low expectations and cultural disconnection across the three generations. They suffered particularly as dual heritage children who experienced rejection and racial micro aggressions from both Pākehā and Māori alike. Instead of education being a means to realise their potential and to achieve success it was actually the vehicle for the destruction of their cultural identity.

text: Through the eyes of whānau: Destruction of cultural identity through education This thesis examines how the schooling experiences of a dual cultural heritage whānau influenced the development of their identity, their language and culture across three generations. Koro, Tuakana, Teina and Moko share their experiences with us and through these stories reveal how they were forced through the colonising beliefs and practices of schooling to reshape themselves in a bid to belong. The compromise and abuse of cultural identity in wider society, replicated and validated in schooling, created a vicious and dehumanising experience for each of them. School was a major site of assimilation for this whānau. They experienced racism, rejection, low expectations and cultural disconnection across the three generations. They suffered particularly as dual heritage children who experienced rejection and racial micro aggressions from both Pākehā and Māori alike. Instead of education being a means to realise their potential and to achieve success it was actually the vehicle for the destruction of their cultural identity.

year: 2019