384 research outputs found
Diseases of Asian seabass (or barramundi), Lates calcarifer Bloch
No full textOther than the study by Griffiths (2009) on gill diseases, there has been no comprehensive study and report on the major diseases of Asian seabass (or barramundi) Lates calcarifer Bloch. It is a food fish species of growing importance in Asia and Australia. This study investigates some of the major diseases encountered in the various stages of the culture of L. calcarifer, at the histopathological, ultrastructural and molecular levels. Culture practices can have significant impacts on fish health. Disease outbreaks are influenced by factors involving the host, environment and pathogen. Current knowledge on diseases of L. calcarifer, and these factors which may influence disease outbreaks are discussed in Chapter 1.
This is the first report of an intestinal Eimeria infection in L. calcarifer. The Eimeria infection was associated with severe pathology and significant mortality in the absence of other pathogens. It was detected in diseased L. calcarifer in all five nurseries in Ca Mau, Vietnam. Although these were small scale nurseries which stocked an average of 3000 to 5000 fish at any one time, a mortality rate of up to 30% was reported and is the cause of significant economic losses for these nurseries. Moderate to heavy Eimeria infestation were observed in greater than 80% of diseased fish examined. This high rate of Eimeria infestation is suspected to be linked to the low daily water exchange rates practised in these nurseries. However, the examination of only diseased fish does not allow the determination of prevalence. A systemic iridovirus infection was concurrently observed in some of the fishes but was not consistently present when compared to the Eimeria infection. Molecular analysis showed that the Eimeria of L. calcarifer from Vietnam formed clades with the Eimeria detected in L. calcarifer cultured in Australia, but clustered separately from other known Eimeria species. Although Cryptosporidium was detected in these L. calcarifer tissues, it could not be demonstrated histologically or ultrastructurally, suggesting a low grade infestation or perhaps an environmental contaminant in fish tissues tested. In situ hybridization using labeled PCR products showed that labeled DNA probes generated from 18S PCR products could not be used to distinguish between closely related genera such as Cryptosporidium and Eimeria. Future investigation to determine the origin, transmission and risk factors associated with this Eimeria infestation in L. calcarifer are needed.
‘Scale drop syndrome’ is a novel disease first reported in L. calcarifer in Penang, Malaysia in 1992. Cases with similar gross and clinical presentations were observed in Singapore in 2002, 2006 and 2009. Affected fish have loose scales, which dropped off easily when handled. The disease was initially observed in 100-300g fish, and later in larger fish up to 5kg bodyweight. Cumulative mortalities of 40 to 50% were reported by farms, posing significant economic losses of larger more valuable fish. This investigation forms the first pathological description of ‘scale drop syndrome’ (SDS) in L. calcarifer. To aid recognition of new cases for study, a case definition was developed for ‘scale drop syndrome’ in L. calcarifer as a systemic vasculitis associated with tissue necrosis in all major organs including the skin, with apparent targeting of cells of epithelial origin. Attempts to isolate or detect the causative agent(s) by cell culture, PCR and immunohistochemistry have proven unsuccessful. Further studies to elucidate the definitive aetiology, isolate the causal agent(s) and reproduce the disease will help better understanding and control of SDS.
Although systemic iridoviral disease has been previously reported in many freshwater and marine fish species, this study forms the first report of this disease in L. calcarifer. Systemic iridoviral disease was observed in 5 to 20g L. calcarifer usually 2 to 3 weeks post-transfer into sea cages at two farms. Inclusion bodies suggestive of a systemic iridovirus infection were observed in clinically healthy L. calcarifer from the land-based nursery of one of these two farm; the presence of an iridovirus infection was supported by positive PCR results using Red Sea bream iridovirus (RSIV) primer 1. The presence of inclusions was not accompanied by any tissue necrosis in these clinically healthy fish. This finding suggested that the systemic iridovirus infection occurred before stocking at sea, and did not originate from wild fish or older fish in adjacent sea cages as initially suspected by this farm. Immunohistochemistry on tissues of clinical cases of systemic iridovirus gave positive results using the Red Sea bream iridovirus monoclonal antibody (RSIV M10), although intensity varied between tissues, possibly related to varying exposure of different tissues to fixation chemicals. Inclusion bodies in clinically healthy fish from the same farm did not show positive reaction with RSIV M10. This may be due to a lack of antigenic expression by the viral infected cells at this early stage of infection.
Viral nervous necrosis (VNN) is a serious disease of hatchery reared L. calcarifer fry in this study. Mortalities of 50 to 100% were reported in 3wo fry. VNN can be difficult to diagnose in older fry, where it can be associated with few vacuolations or an absence of viral inclusions
‘Pot belly disease’ (PBD) was previously reported in L. calcarifer fry less than 1g, in association with an intracellular coccobacillus infection and mortalities of 80 to 100%. In this study, PBD was observed in 120g L. calcarifer at two sea cage farms, in association with significant granulomatous enteritis. The extent of the granulomatous enteritis is likely to have an effect on affected fish. It was observed concurrently with systemic iridoviral disease at one farm and nocardiosis at another farm. Diagnosis by histopathology and the lack of other confirmatory tests for PBD may result in underdiagnosis of this disease. The epidemiology of PBD needs further study to establish origin and modes of transmission, to facilitate better disease control.
Diseases associated with infections by ubiquitous bacteria such as Vibrio, Tenacibaculum were commonly observed in L. calcarifer post-handling. Tenacibaculosis and vibriosis often occurred concurrently with other diseases such as streptococcosis, systemic iridviral disease or PBD. Streptococcosis can affect fish up to 3kg bodyweight, resulting in significant mortalities greater than 40 to 50%. Like SDS, because streptococcosis can affect up to market size fish, they can cause considerable economic losses. Although vaccines against Streptococcosis are available, conflicting views are held on the efficacy of Streptococcus vaccines by various research groups. Overall, the South-east Asian L. calcarifer farms which practiced vaccination against Streptococcus iniae reported a reduction of mortality, especially in fish greater than 1 to 1.5kg bodyweight.
Nocardiosis has been reported as an emerging disease in marine food fish species caused by acid fast filamentous branching bacterium. Although nocardiosis was observed histopathologically in L. calcarifer at two sea cage farms, the numbers of samples examined were small and no other tests were attempted due to lack of suitable samples. More intensive and extensive study is needed to determine the significance of nocardiosis in L. calcarifer. Chronic granulomatous enteritis was not uncommon in the cases submitted to the Fish Health Laboratory in Perth. Although the peritonitis was associated with heavy bacteria infection, it is unclear if these are secondary invaders. Schipps, Bosmans & Humphreys (2009) reported that Vibrio harveyi and Photobacterium damsela damsela vaccinations appeared to be not efficacious, suggesting that these bacteria were not the primary cause of the disease.
It is well recognized that disease outbreaks in farmed fish are influenced by the interaction between host, the environment and pathogens. While serious diseases are often reported in association with specific aquatic pathogens, not much is known about the risk factors which trigger fish disease outbreaks. Disease outbreaks often occur after stressful events such as net transfers, recent handling or poor water quality. In fact, diseases are often caused by ubiquitous pathogens that are commonly present in the culture environment. Although further research is necessary to gather more information to improve diagnosis and management of specific diseases, general health management strategies can be applied at the various stages in the culture of L. calcarifer to minimize disease outbreaks. This is discussed for L. calcarifer in Chapter 6.
Observations of types of disease agents may be influenced by site conditions or the types of tests or materials examined. For example, some parasites may be more prevalent in certain sites where intermediate hosts abound, or loosely attached ectoparasites may be lost unless wet mount microscopic examinations of fresh tissues were carried out. The study of emerging diseases such as scale drop syndrome (SDS) or pot belly disease (PBD) in L. calcarifer has been hampered by lack of confirmatory diagnostic tools and inadequate knowledge on critical epidemiological factors such as mode of transmission or potential reservoirs. While ideally identification and isolation of the causal agent will help fulfil Koch’s postulates, it may be possible to improve the understanding of disease via cohabitation or infectivity trials using tissue homogenates from diseased fish when pure isolates are not available. There is a need to conduct research to not only establish a definitive aetiology, but also to identify risk factors to facilitate successful disease control. The successful management of disease in aquaculture does not lie in any one strategy but an integrated management of all risks encountered during the culture cycle against disease occurrence or incursions
A Randomised Control Trial and Comparative Analysis of Multi-Dimensional Learning Tools in Anatomy
No full textResearch was funded by the Cakmak Lab and the University of Otago, Otago Medical School. Author notes: These authors contributed equally: Ben Kei Daniel and Mustafa Asil. Contributions: Conception and Design of Study: Y.C. and C.W.; Design of materials: Y.C. and C.W.; Randomization of participants: P.K.; Acquisition of data: C.W.; Data analysis and interpretation: Y.C., M.A., B.D. and C.W.; Drafting of manuscript and/or critical revision: C.W., Y.C., M.A., B.D. and P.K.; All authors read and approved the final manuscript.Peer reviewe
Economists, institutions, and trade restrictions : a review article
No full textA review article on the work of"practitioners of contemporary economic analysis of trade restrictions", this report focuses on three questions : a) are there holes in the case of free trade? B) Why are trade restrictions imposed, and c) how do US policy actions and those of other nations interact ? On the first question, though difficult to identify when there is profit to be captured by trade intervention and to design an appropriate trade intervention policy, capturing a strategic sector and economic rents is important to equity holders without necessarily being of much significance to the economy as a whole. Further, on trade restrictions, these are often aimed at non economic objectives, since economic sanctions tend to be used only when other instruments fail. As for the interaction of US policy actions versus other nations, they are a manifestation of protectionist legislation in the US Congress and perhaps indictments against GATT as wrong headed.TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies,Economic Theory&Research,Rules of Origin,Trade Policy
Modelling of diabetes knowledge, attitudes, self-management, and quality of life: a cross-sectional study with an Australian sample.
No full textBackground: Quality of life (QoL) is an important aspect of wellbeing for people with chronic conditions like type 2 diabetes, making it a noteworthy outcome. Knowledge about diabetes, attitudes, and self-management of diabetes are key factors that might directly or indirectly impact QoL. However, little is known about the inter-relationships between diabetes knowledge, attitudes, self-management and QoL among people with type 2 diabetes mellitus (T2DM). The aim of this study was to examine a model describing the relationship between diabetes knowledge, attitudes, self-management, and QoL of people with T2DM that is based on previous research linking pairs of these variables.
Methods: A cross-sectional study design was employed in this research. A total of 291 participants, 192 males and 99 females, with T2DM, whose mean age was 55.8 (standard deviation = 11.09) completed questionnaires measuring diabetes knowledge (Diabetes Knowledge Scale), attitudes (Diabetes Integration Scale -19), self-management (Summary of Diabetes Self-care Activities Scale), including the aspects of diet, exercise, blood glucose testing, and foot care, and QoL (Diabetes Quality of Life Scale), comprising the aspects of satisfaction and impact on QoL respectively. To examine the model we proposed relating these variables, data were analysed using the path analysis.
Results: In the final model, diabetes knowledge was a significant predictor for attitudes and self-management in
terms of blood glucose testing. Attitudes was a significant predictor for self-management in terms of diet. In addition,
self-management in terms of blood glucose testing was a significant predictor of impact of QoL, and self-management
in terms of diet was a significant predictor of satisfaction and impact of QoL. Self-management in terms of exercise was
a significant predictor of satisfaction in QoL. The final model reflected a good fit (χ2 (14) = 22.52, p = 0.069; CFI = 0.983; GFI = 0.983; RMSEA = 0.046).
Conclusions: Diabetes knowledge, attitudes, and self-management are important factors that can impact the QoL
among people with type 2 diabetes
(Post) Socialism Country's Political Choice of the Economic Reform: Hungary, PRC and Poland
No full text本文主要想回答一個問題：對於正在脫離社會主義經濟體制的轉型國家而言，究竟會選擇什麼樣的策略來進行經濟改革？為什麼？過去一般以正當性變項來對此進行解釋。筆者除反駁此項論述外，並提出一個假設命題：經政初始階段，執政者與舊政權的政經網絡關係決定經改策略的選擇，如果執政者繼承前政權的政經網絡，將偏向採取漸進改革，而如果執政者的政經網絡與舊政權越不同，則越有可能採取震盪療法。並以匈牙利、中國大陸與波蘭為例來驗證此假說。The article is mainly to answer a question: To those (Post) Socialism Countries, which Transition from Socialism, What kind of strategy they will choose to push economic reform? Why? In the past, most scholars thought communism government didn't dare to take actions of the shock therapy and privatize because communism government wanted to maintain the legitimacy of ideology. While a new authority that has the legitimacy of democracy would take steps of the shock therapy. This paper doesn't agree with this discourse, and adduces a hypothetic: In the beginning of the economic reform, the strategy of economic reform opportunity decides on new authorities and the past governor's relationship. If the new authorities follow former relationship, they will take actions of the gradualism. On the contrary, the more different relationship of the new authorities has, the more chances they will take actions of the shock therapy. Then the author will take Hungary, PRC and Poland for example to prove this hypothetic. In order to answer above questions, this paper will divide the article into six parts: the first part is preface to declare the author's question and viewpoint; the second part is to discuss the shock therapy and gradualism, then review correlative articles to lead the writer's hypothetic; the third part will take Hungary for instance to controvert the legitimacy discourse and review the author's hypothetic; the fourth and the fifth part will take PRC and Poland for instance to review the author's hypothetic; the sixth part is the conclusion
Semi-analytical approaches for the prediction of the noise produced by ducted wind turbines
No full textThe integration of wind turbines into urban environments is a challenging task due to the reduced wind speed and high turbulence levels caused by the surface resistance, as well as limited spacing. If a specific building arrangement is explored, an improve ment in wind speed can be obtained. This would be especially beneficial for tall build ings where a wind turbine can be placed on the roof, side, or through a duct. However, the main problem associated with the integration of wind turbines is the acoustic an noyance. Therefore, the focus of this thesis is twofold. First, a robust, accurate, and low computational cost numerical methodology is proposed to predict the trailing edge noise for a ducted wind turbine. Second, a measurement device is developed to acquire noise emitted by a rotating machine where the duct surface cannot be altered. An inves tigation of the incoming flow on the noise emitted by a building-integrated wind turbine is conducted by different aerodynamic roughness lengths…Wind Energ
Processing Risk In Asset Management: Exploring The Boundaries Of Risk Based Optimization Under Uncertainty For An Energy Infrastructure Asset Manager
No full textIn the liberalized energy market Distribution Network Operators (DNOs) are confronted with income reductions by the regulator. The common response to this challenge is the implementation of asset management, which can be regarded as systematically applying Cost Benefit Analysis (CBA) to the risks in the networks. In short, this is Risk Based Optimization (RBO). However, application of RBO is mostly limited to interventions on individual assets like upgrades, replacements and maintenance. Whether RBO is feasible for higher levels of aggregation like the portfolio of interventions or even the whole system was not clear. The unavoidable subjectivity and uncertainty associated with risk decision making could threaten the acceptance of decision outcomes. The experiments conducted in this research reveal that there are no fundamental barriers to risk based optimization of the whole system. Embracing uncertainty and subjectivity allows for relatively simple tools, as the tools do not need to be more accurate than our knowledge of the future. The condition for this to work is that the rational RBO decisions are embedded in a well-designed sociotechnical process. A systematic implementation of RBO on all levels (individual assets, portfolios of interventions and the whole system) results in a reduction of the total costs of the system (expenditure plus residual risk) of about 20%.Engineering Systems and Services, Section Energy & IndustryTechnology, Policy and Managemen
A Sub-1V, Micropower Bandgap Reference
No full textBandgap references are used in many ICs to produce ‘stable’ and ‘temperature-independent’ voltage. This thesis describes a sub-1V bandgap reference in 40 nm and 0.16 µm CMOS technologies that is functional from -40 oC to 125 oC. Traditionally, BJT based references are commonly used, but produce an output voltage of 1.2 V and are not suitable for supply voltages below 1 V. Previously area-intensive solutions that were based on resistive sub-divisions were used to realize sub-1V references. In this work, a compact and low power ‘bandgap’ reference was implemented in standard CMOS technology using a device known as a Dynamic Threshold MOSFET (DTMOST). 20 chips have been taped out in NXP 0.16 µm CMOS technology (C14) and packaged in Ceramic DIL packages. A 3 ? spread of 1.25 % is observed. The chips work down to a supply of 0.9 V and occupy 0.05 mm2. Also, a prototype has been designed in a 40 nm CMOS process and post-layout simulations have been performed. The chip works down to a supply of 0.8 V and occupies 0.05 mm2. Simulated 3? spread is 3.7 %. The total current consumption for the chips in both technologies is less than 4 µA in the worst case corners.Electronic InstrumentationElectrical Engineering (Microelectronics)Electrical Engineering, Mathematics and Computer Scienc
Responsive Suburbia: Dwelling and working in IJBurg
No full textA housing project comprised of 72 units is located in IJ Burg— a new suburb east from the center of Amsterdam. More specifically, the project sits on a man-made island called Steigereiland North, on a ‘left-over’ green strip of land. Two types of dwellings (A and B) are disseminated around the site forming various permeable blocks of living and working units. These apartments consist of free-standing, row, and semi-detached typologies, depending on their arrangement and orientation. The capacity of these units to grow and change over time is a key feature of this project. The project has an additional activity strip between the waterside and the housing fabric border which will aid to serve as a lively catalyst for the neighbourhood. This ‘mat’ consists of landscaping and supplementary functions such as: tennis courts, a soccer field, playgrounds, picnic zones, pergolas, a climbing wall, a dance studio, and storage facilities. The newly-added layer of economical, community-driven activities reinvigorates IJ Burg. Introducing light production as well as the creative and working classes into the urban fabric will also result in an extrovert and well-functioning community.At Home in the City, AmsterdamArchitecture and DwellingArchitectur
When Do JONSWAP Spectra Lead to Soliton Gases in Deep Water Conditions?
No full textWhen a large number of solitons dominates the dynamics of a system, scientists describe this collective behaviour of solitons as a soliton gas. Soliton gases are currently the subject of intense practical and theoretical investigations. The existence of soliton gases has been confirmed in experiments, but is not clear what kind of sea states might lead to soliton gases. Therefore, in order to determine the wave parameters for sea states that lead to soliton gases, large numbers of surface wave elevations are generated by the well-known JOSNWAP model in this paper. Here, we only discuss soliton gases in deep water governed by the nonlinear Schrödinger (NLS) equation. The nonlinear Fourier transform (NFT) with vanishing boundary conditions is applied to the simulated ocean surface waves. The resulting nonlinear Fourier spectrum is used to calculate the energy of radiation waves and solitons. We investigate which JONSWAP parameters result in sea states that can be characterized as soliton gases, and find that a large Phillip’s parameter α, a large peak enhancement parameter γ and a short peak period TP are important factors for soliton gas conditions. The results allow researchers to estimate how likely soliton gases are in deep waters. Furthermore, we find that the appearance of rogue waves is slightly increased in highly nonlinear sea states with soliton gas-like conditions.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Michel VerhaegenTeam Sander Wahl
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