Viability of Giardia intestinalis cysts : assessing viability under environmental conditions : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Microbiology at Massey University, Palmerston North, New Zealand

Much work has been put into the detection and monitoring of Giardia, but once found, it is not easy to tell whether the cysts are viable and thus infective. There are fluorescently labelled monoclonal antibody kits which can be used to identify Giardia, but are the Giardia cysts viable? Excystation has been the main method used to determine the viability of cysts. This is quite unreliable as varying excystation conditions seem to be required for different strains of cysts. Using samples of fresh cysts, certain batches consistently measured 80-95% viable, while others resulted in viability measurements of 0-10%. The cysts themselves displayed the normal morphology of viable cysts. The assumption that partially excysted trophozoites as well as completely excysted trophozoites are viable may also lead to over-estimation of viable cyst numbers. Another commonly used method for estimating the viability of Giardia is staining with vital dyes, in particular the combination of fluorescein diacetate (FDA) and propidium iodide (PI). These also gave unexpected results where none of the cysts in a fresh sample stained with FDA, which usually stains viable cysts. An alternative dye, 4',6-diamidino-2-phenylindole (DAPI) was used in the place of FDA. The combination of DAPI and PI showed viabilities of 85.7% for cyst samples. This correlated well with 88% viability using excystation. Using the DAPI/PI combination, the viability of G. intestinalis cysts over time was monitored under different temperature conditions, and in sea water. Temperature was quite significant in the viability of the cysts – cysts stored at 4°C remained viable for 62 days, while those stored at 25°C were non-viable after 5 days. Sea-water had an immediately lethal effect on the G. intestinalis cysts, with all cysts non-viable after 45 minutes. Giardia intestinalis trophozoites can be cultured in the laboratory. By the addition of bile to the growth media, it is possible to transform these into cysts. Over the course of four days in encystation media, a large proportion of the trophozoites in the culture were converted into cysts, 3.5 X 10⁵ cysts/ml from an initial trophozoite concentration of 7.2 X 10⁵ organisms/ml. However, the cysts generated from the strains of G. intestinalis used were completely non-viable, compared with viability rates for fresh in vivo cysts of 80-95%. A population of hamsters was found to be carrying a Giardia which seemed different to recognised species. An analysis was carried out by PCR and sequencing of sections of the ribosomal DNA of this Giardia. Through this it was found to be closely related to Giardia muris, but perhaps not as closely related as to be a species of G. muris, possibly a sub-species. The rDNA analysis used may be very useful in typing other strains and species of Giardia

Standards as a platform for innovation and learning in the global economy: a case study of Chilean salmon farming industry

Conventionally, standards are considered as a governance tool in the production system in a one-directional and hierarchical relationship between foreign trans-national corporations (TNCs) or global buyers on one hand and subsidiaries and producers on the other. They were considered as transmitting necessary specifications of goods (codified knowledge) to the producers. Despite the fact that this process begins with a one-way power relationship and associated flow of knowledge and standards, such one-way flows may become consolidated into two-way interlinkages when power balances themselves reverse with the development of collective capability in catching-up countries. In such a context, standards increasingly act as a catalyst for creating collective interfaces where diverse knowledge from horizontal and vertical relationships (local and global, tacit and codified, and buyer and producer) intercept and converge to promote interactions and learning for those involved. The Chilean salmon farming industry is examined to understand how standards compliance enhanced collective capability.Standards, Industrial standards, Capability, Governance, Fishing industry, Chile, Catching up

The formation and dynamical evolution of young star clusters

Recent observations have revealed a variety of young star clusters, including embedded systems, young massive clusters, and associations. We study the formation and dynamical evolution of these clusters using a combination of simulations and theoretical models. Our simulations start with a turbulent molecular cloud that collapses under its own gravity. The stars are assumed to form in the densest regions in the collapsing cloud after an initial free-fall times of the molecular cloud. The dynamical evolution of these stellar distributions are continued by means of direct $N$-body simulations. The molecular clouds typical for the Milky Way Galaxy tend to form embedded clusters which evolve to resemble open clusters. The associations were initially considerably more clumpy, but lost their irregularity in about a dynamical time scale due to the relaxation process. The densest molecular clouds, which are absent in the Milky Way but are typical in starburst galaxies, form massive young star clusters. They indeed are rare in the Milky Way. Our models indicate a distinct evolutionary path from molecular clouds to open clusters and associations or to massive star clusters. The mass-radius relation for both types of evolutionary tracks excellently matches the observations. According to our calculations the time evolution of the half-mass radius for open clusters and associations follows $r_{\rm h}/{\rm pc}=2.7(t_{\rm age}/{\rm pc})^{2/3}$, whereas for massive star clusters $r_{\rm h}/{\rm pc}=0.34(t_{\rm age}/{\rm Myr})^{2/3}$. Both trends are consistent with the observed age-mass-radius relation for clusters in the Milky Way.Comment: 16 pages, 9 figures, accepted for publication in Ap

THE EFFECT OF SITE CHARACTERISTICS ON RELATIONSHIP QUALITY FACTORS AND E-WORD OF MOUTH IN ONLINE SHOPPING: AN OBSERVATION CONDUCTED IN JAKARTA

THE EFFECT OF SITE CHARACTERISTICS ON RELATIONSHIP QUALITY FACTORS AND E-WORD OF MOUTH IN ONLINE SHOPPING: AN OBSERVATION CONDUCTED IN JAKARTA - Site characteristics, Customer satisfaction, Relationship quality, E-trust, Ecommitment, E-word of mout

Dynamical friction on satellite galaxies

For a rigid model satellite, Chandrasekhar's dynamical friction formula describes the orbital evolution quite accurately, when the Coulomb logarithm is chosen appropriately. However, it is not known if the orbital evolution of a real satellite with the internal degree of freedom can be described by the dynamical friction formula. We performed N-body simulation of the orbital evolution of a self-consistent satellite galaxy within a self-consistent parent galaxy. We found that the orbital decay of the simulated satellite is significantly faster than the estimate from the dynamical friction formula. The main cause of this discrepancy is that the stars stripped out of the satellite are still close to the satellite, and increase the drag force on the satellite through two mechanisms. One is the direct drag force from particles in the trailing tidal arm, a non-axisymmetric force that slows the satellite down. The other is the indirect effect that is caused by the particles remaining close to the satellite after escape. The force from them enhances the wake caused in the parent galaxy by dynamical friction, and this larger wake in turn slows the satellite down more than expected from the contribution of its bound mass. We found these two have comparable effects, and the combined effect can be as large as 20% of the total drag force on the satellite.Comment: 15 pages, 10 figures, submitted to PASJ; v2: 14 pages, 13 figures, accepted by PAS

Uniform Partition in Population Protocol Model Under Weak Fairness

We focus on a uniform partition problem in a population protocol model. The uniform partition problem aims to divide a population into k groups of the same size, where k is a given positive integer. In the case of k=2 (called uniform bipartition), a previous work clarified space complexity under various assumptions: 1) an initialized base station (BS) or no BS, 2) weak or global fairness, 3) designated or arbitrary initial states of agents, and 4) symmetric or asymmetric protocols, except for the setting that agents execute a protocol from arbitrary initial states under weak fairness in the model with an initialized base station. In this paper, we clarify the space complexity for this remaining setting. In this setting, we prove that P states are necessary and sufficient to realize asymmetric protocols, and that P+1 states are necessary and sufficient to realize symmetric protocols, where P is the known upper bound of the number of agents. From these results and the previous work, we have clarified the solvability of the uniform bipartition for each combination of assumptions. Additionally, we newly consider an assumption on a model of a non-initialized BS and clarify solvability and space complexity in the assumption. Moreover, the results in this paper can be applied to the case that k is an arbitrary integer (called uniform k-partition)