title: Testing for bubbles in time series data using long historical series

authors: Hu, Yang

subjects: thesis with publication

abstract: The concept of asset price bubble has drawn a large amount of academic attention. A bubble is commonly defined as where the asset price is not justified by expectations of the fundamentals. The empirical characteristics of a bubble are widely regarded as a dramatic rise in asset prices in the early periods along with a sudden collapse, which have been observed in a wide range of financial markets including commodity, real estate and stock.
This thesis attempts to examine several well-noticed bubble episodes in history, for example, the Mississippi Bubble in 1719, the South Sea Bubble in 1719-20, Japan’s asset price bubble during the 1980s and the more recent US real estate bubble in the early 2000s. One of the greatest contribution of this thesis is that it has provided econometric-based evidence to support the existence of these famous episodes for the first time using recently developed econometric tests. The origination and collapse dates for these identified episodes are coincided with the traditional view of famous bubbles.
This thesis not only tests for the existence of bubbles but also seeks to provide some empirical evidence to support the existence of bubble spillovers/contagion using the most-documented bubble episodes. The first example considered in this thesis is whether financial bubbles/crises spill-over to housing markets in Amsterdam, Norway and France. The second example is considered for a number of British financial organisations during the South Sea episode in 1719-20 (e.g., the South Sea Company, the Bank of England, East India Company, London Assurance, Million Bank, the Royal African Company and the Royal Exchange Assurance). The South Sea Bubble seems to migrate to other organisations as the British share market was speculative for that period. The timings of some identified episodes can be viewed as possible evidence of spillovers or contagion for this important period in England. The third example looks at the Japan’s real estate and stock markets during the 1980-90s. Based on econometric tools, the findings indicate signs of bubble migration from Japan’s stock market to its real estate market for the first time. Even if this phenomenon has been observed in the literature, none of existing studies provide any solid evidences to support this claim.
This thesis investigates the long-run equilibrium relationship between house prices and economic fundamentals in the US based on quantile cointegration approaches for the first time. The presence of cointegration between house prices and fundamentals would imply convergence to a stable equilibrium relationship, suggesting a temporary run-up or drop in house prices would eventually come back to the equilibrium. By making use of quantile autoregressive distributed lag model (QARDL), this research explores the cointegration relationship across the whole
conditional distribution.

text: Testing for bubbles in time series data using long historical series The concept of asset price bubble has drawn a large amount of academic attention. A bubble is commonly defined as where the asset price is not justified by expectations of the fundamentals. The empirical characteristics of a bubble are widely regarded as a dramatic rise in asset prices in the early periods along with a sudden collapse, which have been observed in a wide range of financial markets including commodity, real estate and stock.
This thesis attempts to examine several well-noticed bubble episodes in history, for example, the Mississippi Bubble in 1719, the South Sea Bubble in 1719-20, Japan’s asset price bubble during the 1980s and the more recent US real estate bubble in the early 2000s. One of the greatest contribution of this thesis is that it has provided econometric-based evidence to support the existence of these famous episodes for the first time using recently developed econometric tests. The origination and collapse dates for these identified episodes are coincided with the traditional view of famous bubbles.
This thesis not only tests for the existence of bubbles but also seeks to provide some empirical evidence to support the existence of bubble spillovers/contagion using the most-documented bubble episodes. The first example considered in this thesis is whether financial bubbles/crises spill-over to housing markets in Amsterdam, Norway and France. The second example is considered for a number of British financial organisations during the South Sea episode in 1719-20 (e.g., the South Sea Company, the Bank of England, East India Company, London Assurance, Million Bank, the Royal African Company and the Royal Exchange Assurance). The South Sea Bubble seems to migrate to other organisations as the British share market was speculative for that period. The timings of some identified episodes can be viewed as possible evidence of spillovers or contagion for this important period in England. The third example looks at the Japan’s real estate and stock markets during the 1980-90s. Based on econometric tools, the findings indicate signs of bubble migration from Japan’s stock market to its real estate market for the first time. Even if this phenomenon has been observed in the literature, none of existing studies provide any solid evidences to support this claim.
This thesis investigates the long-run equilibrium relationship between house prices and economic fundamentals in the US based on quantile cointegration approaches for the first time. The presence of cointegration between house prices and fundamentals would imply convergence to a stable equilibrium relationship, suggesting a temporary run-up or drop in house prices would eventually come back to the equilibrium. By making use of quantile autoregressive distributed lag model (QARDL), this research explores the cointegration relationship across the whole
conditional distribution.

year: 2019

title: Bioactive properties of proline-rich peptides derived from dairy milk and colostrum

authors: Tock, Adriënne

abstract: Dipeptidyl peptidase 4 (DPP4) is a serine exopeptidase that cleaves dipeptides from the N-terminus, preferably when proline occupies the penultimate position. This enzyme plays a key role in maintaining glucose homeostasis by degrading insulin secreting incretins, such as gastric inhibitory peptide and glucagon-like peptide 1, thereby reducing insulin secretion. Consequently, inhibiting DPP4 activity has become a major strategy for mitigating the effects of Type 2 diabetes mellitus. A functional food approach involves inhibiting this enzyme with DPP4-inhibiting peptides that are generated from dairy products. Milk and colostrum are associated with various health benefits, largely due to the presence of many bioactive peptides. A significant portion of these are proline-rich peptides (PRPs), some of which exhibit DPP4 inhibitory properties. While many DPP4-inhibitory dairy peptides have been identified or predicted through ‘in silico’ analysis, the variations across different species and between milk and colostrum have yet to be explored.   

This research identified new PRPs in cow, goat, sheep, and deer milk and colostrum and demonstrated that some of these peptides have DPP4-inhibitory activity. Peptide identification and characterisation were performed using liquid chromatography tandem mass spectrometry, a new resin-based DPP4-binding procedure, and in vitro DPP4 inhibition assays. PRPs represented 20-30% of the identified peptides within each sample, with sheep colostrum reaching 35%. Peptides from deer had the lowest alignment with the Cervidae proteome, likely due to database incompleteness. Exact peptide sequence overlap among all samples was minimal. Peptides were chosen for DPP4 inhibition assays based on the resin pull-down assay results, presence of proline in the penultimate position, abundance, length, and origin. Out of the 21 selected peptides, 14 showed over 50% inhibition at 250 µM. Interestingly, these peptides revealed that greater proline content did not reliably predict DPP4 inhibition, which is contradictory to reports in the literature. The top six DPP4-inhibiting peptides were selected for IC50 determination, with values ranging from 46.7 to 103.2 µM. Even though these peptides were all less potent than the reference peptide inhibitor Diprotin A (IC50 of 2.69 ± 1.09 µM, n = 6), they all showed high abundance of at least 105. Additionally, most peptides represented novel sequences that were not previously reported in the literature as DPP4-inhibiting peptides. Pooled peptide fractions from each sample did not show inhibition at the tested concentration, although permeate from a dairy plant showed 34.41% ± 8.27 (n = 3) DPP4 inhibition at only 1.5% w/w of the permeate concentration. AlphaFold 3 predictions revealed that these peptides and Diprotin A docked at similar positions within the DPP4 active site. These findings provide the basis for future studies on interspecies differences, application of novel binding assays to find DPP4 inhibitors, and further exploration of dairy peptides as potential DPP4 inhibitors.

text: Bioactive properties of proline-rich peptides derived from dairy milk and colostrum Dipeptidyl peptidase 4 (DPP4) is a serine exopeptidase that cleaves dipeptides from the N-terminus, preferably when proline occupies the penultimate position. This enzyme plays a key role in maintaining glucose homeostasis by degrading insulin secreting incretins, such as gastric inhibitory peptide and glucagon-like peptide 1, thereby reducing insulin secretion. Consequently, inhibiting DPP4 activity has become a major strategy for mitigating the effects of Type 2 diabetes mellitus. A functional food approach involves inhibiting this enzyme with DPP4-inhibiting peptides that are generated from dairy products. Milk and colostrum are associated with various health benefits, largely due to the presence of many bioactive peptides. A significant portion of these are proline-rich peptides (PRPs), some of which exhibit DPP4 inhibitory properties. While many DPP4-inhibitory dairy peptides have been identified or predicted through ‘in silico’ analysis, the variations across different species and between milk and colostrum have yet to be explored.   

This research identified new PRPs in cow, goat, sheep, and deer milk and colostrum and demonstrated that some of these peptides have DPP4-inhibitory activity. Peptide identification and characterisation were performed using liquid chromatography tandem mass spectrometry, a new resin-based DPP4-binding procedure, and in vitro DPP4 inhibition assays. PRPs represented 20-30% of the identified peptides within each sample, with sheep colostrum reaching 35%. Peptides from deer had the lowest alignment with the Cervidae proteome, likely due to database incompleteness. Exact peptide sequence overlap among all samples was minimal. Peptides were chosen for DPP4 inhibition assays based on the resin pull-down assay results, presence of proline in the penultimate position, abundance, length, and origin. Out of the 21 selected peptides, 14 showed over 50% inhibition at 250 µM. Interestingly, these peptides revealed that greater proline content did not reliably predict DPP4 inhibition, which is contradictory to reports in the literature. The top six DPP4-inhibiting peptides were selected for IC50 determination, with values ranging from 46.7 to 103.2 µM. Even though these peptides were all less potent than the reference peptide inhibitor Diprotin A (IC50 of 2.69 ± 1.09 µM, n = 6), they all showed high abundance of at least 105. Additionally, most peptides represented novel sequences that were not previously reported in the literature as DPP4-inhibiting peptides. Pooled peptide fractions from each sample did not show inhibition at the tested concentration, although permeate from a dairy plant showed 34.41% ± 8.27 (n = 3) DPP4 inhibition at only 1.5% w/w of the permeate concentration. AlphaFold 3 predictions revealed that these peptides and Diprotin A docked at similar positions within the DPP4 active site. These findings provide the basis for future studies on interspecies differences, application of novel binding assays to find DPP4 inhibitors, and further exploration of dairy peptides as potential DPP4 inhibitors.

year: 2025

title: Akuhata Mokena: Eldest son of Mokena Hou

authors: Hart, Philip

abstract: Akuhata Mokena was recorded as being the first child of Mokena Hou and Rina. By the early 1860s he was living at the northern boundary of the Aroha Block as well as at Puriri, where he dug kauri gum. From 1857 to 1868 he also cultivated close to the southern edge of the future Thames township. Having run cattle on the Aroha block from 1867 onwards, he settled there in 1878, operating the first hotel to be erected at the hot springs. 
In the land court he tried to obtain interests in as many land blocks as possible, and obtained income by selling some of these. After a brief involvement in Te Aroha mining, when he was the only member of his family to delay ceding their land for mining, he returned to live at Puriri. He also invested, very modestly, in mining at Thames and Puriri. 
A rangatira who was steadfastly loyal to the Crownt, when he died without issue his estate became a cause of conflict between Maori and Pakeha perceptions of how it should be shared amongst his wife and his family.

text: Akuhata Mokena: Eldest son of Mokena Hou Akuhata Mokena was recorded as being the first child of Mokena Hou and Rina. By the early 1860s he was living at the northern boundary of the Aroha Block as well as at Puriri, where he dug kauri gum. From 1857 to 1868 he also cultivated close to the southern edge of the future Thames township. Having run cattle on the Aroha block from 1867 onwards, he settled there in 1878, operating the first hotel to be erected at the hot springs. 
In the land court he tried to obtain interests in as many land blocks as possible, and obtained income by selling some of these. After a brief involvement in Te Aroha mining, when he was the only member of his family to delay ceding their land for mining, he returned to live at Puriri. He also invested, very modestly, in mining at Thames and Puriri. 
A rangatira who was steadfastly loyal to the Crownt, when he died without issue his estate became a cause of conflict between Maori and Pakeha perceptions of how it should be shared amongst his wife and his family.

year: 2016