1,101 research outputs found
Effects of crp deletion in Salmonella enterica serotype Gallinarum
No full textBackground.
Salmonella enterica serotype Gallinarum (S. Gallinarum) remains an important pathogen of poultry, especially in developing countries. There is a need to develop effective and safe vaccines. In the current study, the effect of crp deletion was investigated with respect to virulence and biochemical properties and the possible use of a deletion mutant as vaccine candidate was preliminarily tested.
Methods.
Mutants were constructed in S. Gallinarum by P22 transduction from Salmonella Typhimurium (S. Typhimurium) with deletion of the crp gene. The effect was characterized by measuring biochemical properties and by testing of invasion in a chicken loop model and by challenge of six-day-old chickens. Further, birds were immunized with the deleted strain and challenged with the wild type isolate.
Results.
The crp deletions caused complete attenuation of S. Gallinarum. This was shown by ileal loop experiments not to be due to significantly reduced invasion. Strains with such deletions may have vaccine potential, since oral inoculatoin with S. Gallinarum Δcrp completely protected against challenge with the same dose of wild type S. Gallinarum ten days post immunization. Interestingly, the mutations did not cause the same biochemical and growth changes to the two biotypes of S. Gallinarum. All biochemical effects but not virulence could be complemented by providing an intact crp-gene from S. Typhimurium on the plasmid pSD110.
Conclusion.
Transduction of a Tn10 disrupted crp gene from S. Typhimurium caused attenuation in S. Gallinarum and mutated strains are possible candidates for live vaccines against fowl typhoid
Effect of oxygen tension on the amino acid utilisation of human embryonic stem cells
No full textBackground/aims: human embryonic stem cells (hESCs) are a potential source of cells for treatment of many degenerative diseases, but in culture have a propensity to spontaneously differentiate, possibly due to suboptimal conditions. Culture at low oxygen tensions improves hESC maintenance and regulates carbohydrate metabolism. Hence, a greater understanding of the nutrient requirements of hESCs will allow production of more appropriate culture media. This study aims to investigate the effect of environmental oxygen tension on the amino acid metabolism of hESCs. Methods: the production or depletion of amino acids by hESCs cultured at 5% or 20% oxygen in the presence or absence of FGF2 was measured by reversephase HPLC. Results: atmospheric oxygen, or removal of FGF2 from hESCs cultured at 5% oxygen, perturbed the uptake or release of individual amino acids and the total amino acid turnover compared to hESCs cultured at 5% oxygen. In particular, serine uptake was reduced at 20% oxygen and by removal of FGF2. Conclusions: highly pluripotent hESCs, cultured at 5% oxygen, demonstrate a greater amino acid turnover than hESCs cultured at 20% oxygen, or without FGF2. These data suggest that amino acid turnover could be used as a measure of the self-renewal capacity of hESC
Logistic regression for simulating damage occurrence on a fruit grading line
No full textMany factors influence the incidence of mechanical damage in fruit handled on a grading line. This makes it difficult to address damage estimation from an analytical point of view. During fruit transfer from one element of a grading line to another, damage occurs as a combined effect of machinery roughness and the intrinsic susceptibility of fruit. This paper describes a method to estimate bruise probability by means of logistic regression, using data yielded by specific laboratory tests. Model accuracy was measured via the statistical significance of its parameters and its classification ability. The prediction model was then linked to a simulation model through which impacts and load levels, similar to those of real grading lines, could be generated. The simulation output sample size was determined to yield reliable estimations. The process makes it possible to derive a suitable line design and the type of fruit that should be handled to maintain bruise levels within European Union (EU) Standards. A real example with peaches was carried out with the aid of the software implementation SIMLIN®, developed by the authors and registered by Madrid Technical University. This kind of tool has been demanded by inter-professional associations and grading lines designers in recent year
Physicians' Non-Uniform Approach to Prescribing Drugs to Older Patients – A Qualitative Study
No full textKærlighed til viden(ssamfund)
No full textThis paper takes its point of departure in the assumption that institutional philosophy is faced with challenges in the contemporary knowledge society of Denmark, partly due to the rise of the notion of knowledge economy. A theoretical framework is set by John Dewey and Jean-Francois Lyotard in order to assess how American pragmatism, as well as the postmodern society in which meta-narratives are rejected, are able to construct a new approach to institutional philosophy. Furthermore, the applied philosophy course at Aalborg University is taken into account as a reflection of how John Deweys pragmatic approach to philosophy can be incorporated. The paper finds that the respective aspects of the knowledge society, pragmatism and applied philosophy play well together in order to establish a new understanding of the value of institutional philosophy.This paper takes its point of departure in the assumption that institutional philosophy is faced with challenges in the contemporary knowledge society of Denmark, partly due to the rise of the notion of knowledge economy. A theoretical framework is set by John Dewey and Jean-Francois Lyotard in order to assess how American pragmatism, as well as the postmodern society in which meta-narratives are rejected, are able to construct a new approach to institutional philosophy. Furthermore, the applied philosophy course at Aalborg University is taken into account as a reflection of how John Deweys pragmatic approach to philosophy can be incorporated. The paper finds that the respective aspects of the knowledge society, pragmatism and applied philosophy play well together in order to establish a new understanding of the value of institutional philosophy
Statistical Characterization of Hot Jupiter Atmospheres Using Spitzer's Secondary Eclipses
No full textabstract: The 78 secondary eclipse depths for a sample of 36 transiting hot Jupiters observed at 3.6- and 4.5 μm using the Spitzer Space Telescope is here reported. Eclipse results for 27 of these planets are new and include highly irradiated worlds such as KELT-7b (Kilodegree Extremely Little Telescope), WASP-87b (Wide Angle Search for Planets), WASP-76b, and WASP-64b, and important targets for the James Webb Space Telescope (JWST) such as WASP-62b. WASP-62b is found to have a slightly eccentric orbit (ecosω=0.00614±0.00058), and the eccentricities of HAT-P-13b (Hungarian Automated Telescope Project) and WASP-14b are confirmed. The remainder are individually consistent with circular orbits, but there is statistical evidence for eccentricity increasing with orbital period in this range from 1 to 5 days. Day-side brightness temperatures (Tb) for the planets yield information on albedo and heat redistribution, following Cowan and Agol (2011). Planets having maximum day side temperatures exceeding ∼2200 K are consistent with zero albedo and distribution of stellar irradiance uniformly over the day-side hemisphere. The most intriguing result is a detection of a systematic difference between the emergent spectra of these hot Jupiters as compared to blackbodies. The ratio of observed brightness temperatures, Tb(4.5)/Tb(3.6), increases with equilibrium temperature by 98±26 parts-per-million per Kelvin, over the entire temperature range in the sample (800K to 2500K). No existing model predicts this trend over such a large range of temperature. This may be due to a structural difference in the atmospheric temperature profile between the real planetary atmospheres as compared to models.Dissertation/ThesisMasters Thesis Geological Sciences 201
Peripherally Inserted Central Catheter for Use in Home Parenteral Nutrition:A 4-Year Follow-up Study
No full textPeripherally inserted central catheters (PICCs) are a relatively new device for home parenteral nutrition (HPN). Usually, tunneled central catheters such as the Hickman catheter are used for this purpose. However, severe complications (eg, pneumothorax) have been reported in association with the insertion of the central catheter. In contrast, PICCs may offer some advantages due to the peripheral insertion. There are only few studies on the use of PICCs for HPN. Method: A retrospective study (2008-2012) was performed in our Center for Nutrition and Bowel Disease. Patients receiving parenteral nutrition through PICCs were identified, their files examined, and indication, dwell time, cause of removal, and complications recorded. Results: Fifty-six patients (aged 28-81 years) had a total of 94 lines. Total catheter days were 9859. Mean catheter days per patient were 179.1, and mean dwell time of each line was 104.9 days (longest, 572 days). There were no major complications in relation to the insertion of the catheters. The catheters were removed due to catheter-related sepsis, mechanical reasons, and thrombotic complications in 1.7, 2.1, and 0.2 per 1000 catheter days, respectively. Conclusion: This study demonstrates that PICCs are appropriate for use in HPN for at least 3-4 months (a period that sometimes unexpectedly becomes long term). The complications equal those reported for tunneled central catheters. We conclude that PICCs are a relevant alternative to patients receiving HPN, especially if they cannot handle a central line. At present, the choice of catheter must be determined on an individual basis
The development of magmatism along the Cameroon Volcanic Line: Evidence from teleseismic receiver functions
No full text[1] The Cameroon Volcanic Line (CVL) in West Africa is a chain of Cenozoic volcanism with no clear age progression. The reasons for its existence are unclear, and the nature of its magmatic plumbing system is poorly understood. Specifically, whether or not the CVL crust presently contains melt and/or mafic intrusions, as is often observed at hot spots and rifts elsewhere, is presently unknown. To address this issue, we present a receiver function study of crustal structure using earthquakes recorded by the Cameroon Broadband Seismic Experiment. In regions of the CVL unaffected by Cretaceous extension associated with the breakup of Gondwana (e.g., the Garoua rift), Vp/Vs ratios are markedly low (network average ?1.74) compared to hot spots elsewhere, providing no evidence for either melt or cooled mafic crustal intrusions due to CVL magmatism. The character of P-to-S conversions from beneath the CVL also indicates that lower-crustal intrusions (often termed underplate) are not present beneath the region. Our observations thus corroborate earlier petrological studies that show CVL alkaline magmas fractionate in the mantle, not the crust, prior to eruption. Hypotheses for the formation of the CVL should not include markedly elevated upper-mantle potential temperatures, or large volumes of partial melt, both of which can explain observations at hot spots and rifts worldwide. The protracted, yet sporadic, development of small-volume alkali melts beneath the CVL may instead be explained better by lower melt volume mechanisms such as shear zone reactivation or lithospheric delamination
Disruptive innovation theory in the paper- and packaging industry : Applying Clayton Christensen in a new context
No full textThe paper- and packaging industry has for a long time transitioned from a production-focused industry towards a customer-orientation – today the customers have become fundamental. Managers are searching for ways to create superior innovations in the industry which can compete against the oil-based solution, i.e. plastic. However, they face challenges as they attempt to launch products in the market. One exciting scholar who has researched much about the challenges of incumbent firms is Clayton Christensen and his theory of disruptive innovation. The theory has received much attention throughout the years and provides with a holistic literature framework to analyze the industry. The thesis aims to investigate Clayton Christensen’s disruptive innovation theory in order to problematize it in a new context, the paper- and packaging industry. This will be done by discussing how individuals argue, understand and use the term ‘disruptive innovation’ and also discuss Christensen’s Innovator’s Dilemma in relation to how incumbents tend to manage their innovation projects in the industry. The research used a qualitative research approach implementing one case study. Interviews with incumbent actors in the industry, one producer and two brand-owners, pertaining to an innovation project constituted for the empirical findings. The data analyzed through a theoretical lens of Christensen’s disruptive innovation theory. From an iterative process between theory and empirical findings the thesis has made the following contributions. First, we have problematized Christensen in a new context and identified an industry which is considered an anomaly in Christensen’s theory. The industry is unlikely to be subjected to the Innovator’s Dilemma due to its fundamentals as an industry, e.g. collaborations between actors and listening to customers. Second, our practical contribution is the importance of differentiating between sustaining and disruptive innovation, especially concerning radical and disruptive innovation. If an individual does not have a theoretical understanding of disruptive, it is common to be confused concerning the differences between radical and disruptive innovation. However, learning about the differences creates an opportunity to identify new ways of gaining value
Heat Transfer in Dielectric Elastomers - Simulating thermal breakdown in multilayered dielectric elastomers
No full textDielectric elastomers are an interesting type of electro-mechanical transducers that can operate both as actuators, generators and sensors. They are composed of an elastomer layer sandwiched between two compliant electrodes and may be arranged in various configurations, including multilayered stacks. During operation dielectric elastomers may undergo several types of electrical breakdown, including thermal breakdown. Thermal breakdown occurs when the thermal energy generated within the dielectric elastomer, due to Joule heating, cannot be balanced by the dissipated heat. Thus a thermal runaway occurs. Thermal breakdown is more prone to occur in a multilayered stack of dielectric elastomers, due to the high volume-to-surface-ratio. This thesis is dedicated to modelling the performance of a multilayered cylindrical stack of dielectric elastomers, with the aim of gaining a better understanding of how various geometrical and operational parameters affects thermal breakdown. Initially a simplified analytical electro-thermal model is set up, which accounts for Joule heating within the stack as well as heat transfer. In the analytical model it is assumed that the top and bottom surfaces of the stack are equal to the ambient temperature and that the cylindrical surface is thermally insulated. Subsequently, two increasingly complex 2D axisymmetric models are set up in the commercial finite-element-method software COMSOL Multiphysics®, where natural convection is assumed to occur at all surfaces of the stack. The first model is a pure electro-thermal model which combines the effects of Joule heating and heat transfer, while the second model is an electrothermal and -mechanical model, thus it also includes the electro-mechanical deformation of the stack. The output of all the models is the estimated point of thermal breakdown, determined as the possible amount of layers in the dielectric elastomer stack before thermal breakdown occurs. It is investigated how various geometrical and operational parameters affects the breakdown point, with the overall desire to increase the amount of layers in the stack as well as the applied voltage. For modelling the elasticity of the elastomer material in the electro-thermal and -mechanical model three types of hyperelastic material models are used; Gent, Mooney-Rivlin and Ogden. It is found that using the Gent model yields the most conservative prediction of breakdown point, whereas using the Ogden model resulted in the least restrictive breakdown point. However, generally the difference in breakdown point, when utilising the three different material models, is small. Furthermore, the electrical conductivity of the elastomer material follows an Arrhenius expression with respect to temperature, but it is concluded that utilising the mathematically simpler Frank-Kamenetskii expression as a function of temperature is acceptable, albeit it yields a more conservative prediction of breakdown point. It is observed that having a single entrapped particle with a higher electrical conductivity than the elastomer material, although still in the range of semiconductors, in the dielectric elastomer stack drastically reduces the breakdown point of the entire stack. Furthermore, it is found that a high temperature of the surroundings also influence the breakdown point significantly, due to the limited heat transfer at high ambient temperatures. On the contrary, including an inactive area in the dielectric elastomer stack has little influence on the breakdown point, although it imposes some mechanical restrictions on the active area, yielding a non uniform electric field as well as stretch ratio. This thesis introduces a model for simulating the performance of a multilayered stack of dielectric elastomers, which accounts for both the electro-thermal and electro-mechanical effects. It is able to determine when a thermal breakdown will occur, and what geometrical and operational parameters that affects the point of breakdown. Furthermore, it is set up in the commercial software COMSOL Multiphysics®, thus accessible to all. Consequently, the electro-thermal and -mechanical model put forth in this work is a great tool when designing and optimizing multilayered stacks of dielectric elastomers
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