title: The effects of shadow presence on visual object-recognition

authors: Etheredge, Richard

abstract: Shadows provide valuable cues for many aspects of visual perception. This thesis discusses the definitions of cast and attached shadows, and the different types of shadow borders that exist. Eight experiments investigated whether the presence of shadows affects the speed or accuracy of human object recognition performance. Experiments 1 to 4 investigated the contributions of attached shadows to the recognition of novel objects, using a sequential-matching task modelled on that of Tarr, Kersten, and Biilthoff (1998). Their finding, of faster reaction times associated with the presence of shadows, was not replicated. Reaction times were not affected by the presence or absence of shadows. Across the four experiments, discrimination was either unaffected by shadow presence, or was at its highest when there were no shadows present. In Experiments 5 to 7, the effects of cast shadow presence on object recognition were assessed. Visual cues about the shape of the objects were constrained by manipulating the degree of foreshortening of both the objects, and the shadows cast by the objects. Shadow presence was only of benefit to recognition in highly constrained situations: where the objects were severely foreshortened, while their cast shadows were not. Experiment 8 assessed the affect upon recognition of manipulating shape-from-shading cues independently from shadow-border cues. Shadow presence was only beneficial where shading was negligible. It is suggested that shadow presence may only provide observable benefits to object recognition when other cues to an object's identity, such as bounding contour and shape-from-shading, are minimal. It appears that shadows have the potential to facilitate object recognition, but in most situations their presence will not produce any discriminatory, or reaction time, benefit.

text: The effects of shadow presence on visual object-recognition Shadows provide valuable cues for many aspects of visual perception. This thesis discusses the definitions of cast and attached shadows, and the different types of shadow borders that exist. Eight experiments investigated whether the presence of shadows affects the speed or accuracy of human object recognition performance. Experiments 1 to 4 investigated the contributions of attached shadows to the recognition of novel objects, using a sequential-matching task modelled on that of Tarr, Kersten, and Biilthoff (1998). Their finding, of faster reaction times associated with the presence of shadows, was not replicated. Reaction times were not affected by the presence or absence of shadows. Across the four experiments, discrimination was either unaffected by shadow presence, or was at its highest when there were no shadows present. In Experiments 5 to 7, the effects of cast shadow presence on object recognition were assessed. Visual cues about the shape of the objects were constrained by manipulating the degree of foreshortening of both the objects, and the shadows cast by the objects. Shadow presence was only of benefit to recognition in highly constrained situations: where the objects were severely foreshortened, while their cast shadows were not. Experiment 8 assessed the affect upon recognition of manipulating shape-from-shading cues independently from shadow-border cues. Shadow presence was only beneficial where shading was negligible. It is suggested that shadow presence may only provide observable benefits to object recognition when other cues to an object's identity, such as bounding contour and shape-from-shading, are minimal. It appears that shadows have the potential to facilitate object recognition, but in most situations their presence will not produce any discriminatory, or reaction time, benefit.

year: 2004

title: An investigation of low diastase activity in mānuka honey

authors: Bell, Amber

subjects: Mānuka honey

abstract: Mānuka honey with high non-peroxide antibacterial (NPA) activity is a valuable export product in the multi-million-dollar New Zealand honey export industry, with monofloral mānuka honey accounting for 68% (NZ$290 million) of the total export value (NZ$425 million) for the 2019/20 season. Exported honey must meet strict export regulations. Diastase enzyme (alpha amylase) activity is a quality control indicator of detrimental storage conditions (excessive heat treatment or prolonged storage), decreasing over time. International export requires honey to have high diastase activity (Diastase Number, DN > 8). Medium to high NPA mānuka honeys often fail the diastase test, despite careful storage. It is important to determine the cause of low diastase activity in mānuka honey to prevent revenue loss for New Zealand honey exports. Bioactive compounds in the honey were hypothesised to inhibit alpha-amylase, therefore reducing diastase activity.
A database of fresh mānuka and non-mānuka honeys were analysed for various chemical parameters (including moisture content, mānuka chemical marker compounds, dihydroxyacetone (DHA), methylglyoxal (MGO), 5-hydroxymethylfurfural (HMF) and diastase activity) to determine if any correlations were present with diastase activity. Parameters between and within floral honey types varied largely, however no correlations were observed to diastase activity. 
Storage experiments (20 °C, 161 days; 27 °C, 198 days) of selected database honeys showed the mānuka marker compounds were stable. However, the rates of change observed for DHA, MGO, HMF and diastase activity were reliant on intrinsic honey characteristics (not identified). While time and temperature had significant impact on loss of diastase activity in honey, correlation was observed between changes in diastase activity and DHA, MGO and mānuka marker 3-phenyllactic acid (3-PLA) concentrations.
Additionally, a clover honey matrix was perturbed with single bioactive compounds (DHA (MGO-precursor), MGO, mānuka markers compounds, methyl syringate and tannic acid) to observe the effect on diastase activity over time (185 days) and at 20, 27 and 34 °C. MGO and 3 PLA caused diastase activity to decrease at a significantly faster rate than other compounds. The half-life of diastase at 27 °C for the control sample was 590 days compared to the much shorter half-life of diastase in the MGO (440 days) and 3 PLA (380 days) perturbed samples. The mechanism by which these two compounds decrease diastase activity is unknown, however MGO is a highly reactive molecule and has been reported to inhibit other enzymes. Time and temperature were also significant drivers of diastase activity loss; diastase half-life at 20 °C was more than eight times greater than it was at 34 °C (1340 vs. 160 days). 
The experiments indicate that diastase activity is highly variable between fresh honeys and the rate at which it decreases may be dependent not only on temperature and time honey is stored at, but on intrinsic honey compounds and physico-chemical parameters suggesting that diastase activity regulations may not be suitable for mānuka honey.

text: An investigation of low diastase activity in mānuka honey Mānuka honey with high non-peroxide antibacterial (NPA) activity is a valuable export product in the multi-million-dollar New Zealand honey export industry, with monofloral mānuka honey accounting for 68% (NZ$290 million) of the total export value (NZ$425 million) for the 2019/20 season. Exported honey must meet strict export regulations. Diastase enzyme (alpha amylase) activity is a quality control indicator of detrimental storage conditions (excessive heat treatment or prolonged storage), decreasing over time. International export requires honey to have high diastase activity (Diastase Number, DN > 8). Medium to high NPA mānuka honeys often fail the diastase test, despite careful storage. It is important to determine the cause of low diastase activity in mānuka honey to prevent revenue loss for New Zealand honey exports. Bioactive compounds in the honey were hypothesised to inhibit alpha-amylase, therefore reducing diastase activity.
A database of fresh mānuka and non-mānuka honeys were analysed for various chemical parameters (including moisture content, mānuka chemical marker compounds, dihydroxyacetone (DHA), methylglyoxal (MGO), 5-hydroxymethylfurfural (HMF) and diastase activity) to determine if any correlations were present with diastase activity. Parameters between and within floral honey types varied largely, however no correlations were observed to diastase activity. 
Storage experiments (20 °C, 161 days; 27 °C, 198 days) of selected database honeys showed the mānuka marker compounds were stable. However, the rates of change observed for DHA, MGO, HMF and diastase activity were reliant on intrinsic honey characteristics (not identified). While time and temperature had significant impact on loss of diastase activity in honey, correlation was observed between changes in diastase activity and DHA, MGO and mānuka marker 3-phenyllactic acid (3-PLA) concentrations.
Additionally, a clover honey matrix was perturbed with single bioactive compounds (DHA (MGO-precursor), MGO, mānuka markers compounds, methyl syringate and tannic acid) to observe the effect on diastase activity over time (185 days) and at 20, 27 and 34 °C. MGO and 3 PLA caused diastase activity to decrease at a significantly faster rate than other compounds. The half-life of diastase at 27 °C for the control sample was 590 days compared to the much shorter half-life of diastase in the MGO (440 days) and 3 PLA (380 days) perturbed samples. The mechanism by which these two compounds decrease diastase activity is unknown, however MGO is a highly reactive molecule and has been reported to inhibit other enzymes. Time and temperature were also significant drivers of diastase activity loss; diastase half-life at 20 °C was more than eight times greater than it was at 34 °C (1340 vs. 160 days). 
The experiments indicate that diastase activity is highly variable between fresh honeys and the rate at which it decreases may be dependent not only on temperature and time honey is stored at, but on intrinsic honey compounds and physico-chemical parameters suggesting that diastase activity regulations may not be suitable for mānuka honey.

year: 2022

title: Pūrākau, death, and assisted dying: A Māori framework for understanding end-of-life

authors: Karaka-Clarke, Te Hurinui

subjects: Pūrākau, Assisted Dying, Tikanga Māori, Mōair Cosmology, End of Life: Ethics, Mana Motuhake, Wairua, Whakapapa, Relational Autonomy

abstract: This conceptual article addresses several critical gaps in health literature by exploring the ethical, spiritual, and cultural dimensions of assisted dying through the lens of Tikanga Māori and pūrākau (ancestral narratives).  While existing end-of-life policy frameworks often prioritize Western bioethical principles, this article argues for the inclusion of Kaupapa Māori principles such as whakapapa, wairua, mana motuhake, and tapu/ noa as essential components of culturally resonant care.    Drawing upon foundational narratives including the separation of  Ranginui and Papatūānuku, the creation of Hineahuone, the transformation of Hinetītama into Hinenuitepō, and the fatal attempt of Māui to conquer death, we position pūrākau as dynamic ethical texts that guide decision-making.  This article contributes to Indigenous health discourse by offering a whānau-centred, tikanga-informed critique of the End-of-Life Choice Act 2019 and calls for broader recognition of spiritual and relational dimensions in end-of-life care.   We contend that, when under-taken with whānau engagement, spiritual awareness, and cultural integrity, may be ethically compatible with tikanga Māori

text: Pūrākau, death, and assisted dying: A Māori framework for understanding end-of-life This conceptual article addresses several critical gaps in health literature by exploring the ethical, spiritual, and cultural dimensions of assisted dying through the lens of Tikanga Māori and pūrākau (ancestral narratives).  While existing end-of-life policy frameworks often prioritize Western bioethical principles, this article argues for the inclusion of Kaupapa Māori principles such as whakapapa, wairua, mana motuhake, and tapu/ noa as essential components of culturally resonant care.    Drawing upon foundational narratives including the separation of  Ranginui and Papatūānuku, the creation of Hineahuone, the transformation of Hinetītama into Hinenuitepō, and the fatal attempt of Māui to conquer death, we position pūrākau as dynamic ethical texts that guide decision-making.  This article contributes to Indigenous health discourse by offering a whānau-centred, tikanga-informed critique of the End-of-Life Choice Act 2019 and calls for broader recognition of spiritual and relational dimensions in end-of-life care.   We contend that, when under-taken with whānau engagement, spiritual awareness, and cultural integrity, may be ethically compatible with tikanga Māori

year: 2025-09-24