title: Statistical analysis of factors affecting the flow characteristics and thermal efficiency of a building integrated thermal (bit) solar collector

authors: Duke, Mike

abstract: Previous research has identified four factors (array geometry, manifold to riser channel ratio, flow direction in manifold, and the mass flow rate) which will influence the distribution of internal fluid flow within a solar thermal collector. In this study, a two level full factorial (2k) experiment was designed in order to statistically rank their impact and also to identify any significant interactions between these factors. The thermal efficiency of the array, calculated by means of a fluid and heat transfer analysis was taken to be the experiment response. During the heat transfer analysis we approximated the fin efficiency of a BIT collector using the finite difference method which considered the heat losses through the structural ribs of the collector. A statistical analysis of the results revealed that all four main effects had a statistical influence on thermal efficiency of the array at 5 per cent significance level. The main effects ranked from highest to lowest in impact were found to be; geometry, manifold to riser fluid channel diameter, mass flow rate, and the direction of flow in the manifolds. Additionally, two secondary interactions were found to have a statistical influence on the experiment response; the array geometry and the direction of flow in the manifold followed by the array geometry and the ratio of manifold to fluid channel diameter. As the geometry of the BIT collector will vary from customer to customer due to its custom nature, these results indicate that the design of a BIT system should consider the effects of flow distribution. Finally, our numerical analysis of the fin efficiency revealed an approximate 5% drop due to additional heat losses through the structural ribs.

text: Statistical analysis of factors affecting the flow characteristics and thermal efficiency of a building integrated thermal (bit) solar collector Previous research has identified four factors (array geometry, manifold to riser channel ratio, flow direction in manifold, and the mass flow rate) which will influence the distribution of internal fluid flow within a solar thermal collector. In this study, a two level full factorial (2k) experiment was designed in order to statistically rank their impact and also to identify any significant interactions between these factors. The thermal efficiency of the array, calculated by means of a fluid and heat transfer analysis was taken to be the experiment response. During the heat transfer analysis we approximated the fin efficiency of a BIT collector using the finite difference method which considered the heat losses through the structural ribs of the collector. A statistical analysis of the results revealed that all four main effects had a statistical influence on thermal efficiency of the array at 5 per cent significance level. The main effects ranked from highest to lowest in impact were found to be; geometry, manifold to riser fluid channel diameter, mass flow rate, and the direction of flow in the manifolds. Additionally, two secondary interactions were found to have a statistical influence on the experiment response; the array geometry and the direction of flow in the manifold followed by the array geometry and the ratio of manifold to fluid channel diameter. As the geometry of the BIT collector will vary from customer to customer due to its custom nature, these results indicate that the design of a BIT system should consider the effects of flow distribution. Finally, our numerical analysis of the fin efficiency revealed an approximate 5% drop due to additional heat losses through the structural ribs.

year: 2014

title: An investigation of the accelerated loss of diastase (α-amylase) activity in mānuka honey

authors: Kaur, Harmanpreet

abstract: New Zealand’s multi-million dollar apiculture industry exports over 10,000 tonnes of honey annually. Each country has import guidelines to ensure honey quality. The diastase activity assay is used to determine whether honey has been exposed to harsh conditions (excess storage time or high temperatures will denature diastase) and reports the activity as diastase number (DN), where DN must be >8 for exports. Unfortunately, mānuka honey (NZ’s high value honey with unique properties) fails the diastase assay more often than other NZ floral honeys. Bioactive compounds [methylglyoxal (MGO), dihydroxyacetone (DHA) and 3-phenyllactic acid (3PLA)] in mānuka honey were predicted to decrease diastase activity by forming modifications on diastase. Hence, the extent, diversity, location and functional impacts of these modifications on diastase were investigated.

Two fresh mānuka honeys, a clover control and clover spiked (MGO, DHA, 3PLA, 3PLA+MGO and 3PLA+DHA) honey samples were stored at 27 °C for ~200 days and periodically tested to observe chemical compositional changes in relation to the loss of diastase activity. The results corroborated previous data; DN decreased in honey over time with increased loss rates observed in mānuka. In the spiked clover samples both DHA and MGO increased rates of diastase activity loss and these rates were enhanced by 3PLA (a proton donor). Enzyme kinetics (enzyme-substrate binding and enzyme rate constants) suggest that denaturation is not the sole mechanism for reduced DN values in honey over time, rather, surface level modifications from bioactive compounds are affecting the affinity of diastase for the substrate.

Diastase was isolated from the honeys (days 0 and ~200) using SDS-PAGE gels and analysed with LC-MS/MS to identify surface modifications on diastase. Results showed evidence of diastase modification over the time trial for all honeys. This occurred in unique locations for both mānuka honeys and MGO and 3PLA+DHA spiked clover honeys. Some of these locations were in proximity to the active site of diastase.

The most abundant honey protein, MRJP1, was used to accurately identify trends in modification changes on proteins over time as a model for the effect occurring on diastase (since similar reactive amino acids are present on both MRJP1 and diastase). All honeys (except the clover control) had an increased number of modifications. The largest increases were observed for the MGO, DHA and 3PLA+MGO spiked honeys. Fewer modifications were detected for the 3PLA+DHA spiked honey despite this having the most pronounced changes in the enzyme kinetic parameters. This is likely because the modification library focused on MGO-induced modifications and did not account for DHA modifications.

In summary, MGO modifications on proteins in honey were observed. DHA modifications and the role of 3PLA as a proton donor were deduced from the enzyme kinetic parameters. While time and temperature denature diastase, surface modifications on diastase may be contributing to the accelerated loss of diastase activity observed for mānuka honey. This necessitates the reassessment of diastase activity as a test for honey quality, especially in the context of complex honey matrices (such as mānuka honey).

text: An investigation of the accelerated loss of diastase (α-amylase) activity in mānuka honey New Zealand’s multi-million dollar apiculture industry exports over 10,000 tonnes of honey annually. Each country has import guidelines to ensure honey quality. The diastase activity assay is used to determine whether honey has been exposed to harsh conditions (excess storage time or high temperatures will denature diastase) and reports the activity as diastase number (DN), where DN must be >8 for exports. Unfortunately, mānuka honey (NZ’s high value honey with unique properties) fails the diastase assay more often than other NZ floral honeys. Bioactive compounds [methylglyoxal (MGO), dihydroxyacetone (DHA) and 3-phenyllactic acid (3PLA)] in mānuka honey were predicted to decrease diastase activity by forming modifications on diastase. Hence, the extent, diversity, location and functional impacts of these modifications on diastase were investigated.

Two fresh mānuka honeys, a clover control and clover spiked (MGO, DHA, 3PLA, 3PLA+MGO and 3PLA+DHA) honey samples were stored at 27 °C for ~200 days and periodically tested to observe chemical compositional changes in relation to the loss of diastase activity. The results corroborated previous data; DN decreased in honey over time with increased loss rates observed in mānuka. In the spiked clover samples both DHA and MGO increased rates of diastase activity loss and these rates were enhanced by 3PLA (a proton donor). Enzyme kinetics (enzyme-substrate binding and enzyme rate constants) suggest that denaturation is not the sole mechanism for reduced DN values in honey over time, rather, surface level modifications from bioactive compounds are affecting the affinity of diastase for the substrate.

Diastase was isolated from the honeys (days 0 and ~200) using SDS-PAGE gels and analysed with LC-MS/MS to identify surface modifications on diastase. Results showed evidence of diastase modification over the time trial for all honeys. This occurred in unique locations for both mānuka honeys and MGO and 3PLA+DHA spiked clover honeys. Some of these locations were in proximity to the active site of diastase.

The most abundant honey protein, MRJP1, was used to accurately identify trends in modification changes on proteins over time as a model for the effect occurring on diastase (since similar reactive amino acids are present on both MRJP1 and diastase). All honeys (except the clover control) had an increased number of modifications. The largest increases were observed for the MGO, DHA and 3PLA+MGO spiked honeys. Fewer modifications were detected for the 3PLA+DHA spiked honey despite this having the most pronounced changes in the enzyme kinetic parameters. This is likely because the modification library focused on MGO-induced modifications and did not account for DHA modifications.

In summary, MGO modifications on proteins in honey were observed. DHA modifications and the role of 3PLA as a proton donor were deduced from the enzyme kinetic parameters. While time and temperature denature diastase, surface modifications on diastase may be contributing to the accelerated loss of diastase activity observed for mānuka honey. This necessitates the reassessment of diastase activity as a test for honey quality, especially in the context of complex honey matrices (such as mānuka honey).

year: 2025

title: Sweet as – the [ADJ + as] intensifier construction in Māori English/ Aotearoa English.

authors: Calude, Andreea S.

abstract: We introduce the Waikato Māori English Conversation (MEC) corpus, which consists of 43 dyadic conversations between 49 young adults who self-recorded informal conversations with close friends, in their own homes, with no topic of conversation specified (83 hours of dialogue; nearly 800,000 words). The resulting materials are colloquial and unstructured, capturing a wider range of pragmatic and stylistic modes than is possible in a standard sociolinguistic interview. Here, we report on one such feature, the [ADJ + as] construction, for example: ‘sorry some of the questions are like awkward as’ and ‘that caused a big as drama eh’. This intensifier construction has been identified as a distinctive New Zealand English (NZE) innovation, yet little has been written about this it. However, the Waikato MEC corpus presents the opportunity to analyse the construction in a more systematic manner and to fill existing gaps in analyses of Māori English grammar.

text: Sweet as – the [ADJ + as] intensifier construction in Māori English/ Aotearoa English. We introduce the Waikato Māori English Conversation (MEC) corpus, which consists of 43 dyadic conversations between 49 young adults who self-recorded informal conversations with close friends, in their own homes, with no topic of conversation specified (83 hours of dialogue; nearly 800,000 words). The resulting materials are colloquial and unstructured, capturing a wider range of pragmatic and stylistic modes than is possible in a standard sociolinguistic interview. Here, we report on one such feature, the [ADJ + as] construction, for example: ‘sorry some of the questions are like awkward as’ and ‘that caused a big as drama eh’. This intensifier construction has been identified as a distinctive New Zealand English (NZE) innovation, yet little has been written about this it. However, the Waikato MEC corpus presents the opportunity to analyse the construction in a more systematic manner and to fill existing gaps in analyses of Māori English grammar.

year: 2025