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Search Results: 1 - 10 of 3819 matches for " Tim Daskalchuk "
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The Drosophila foraging Gene Mediates Adult Plasticity and Gene–Environment Interactions in Behaviour, Metabolites, and Gene Expression in Response to Food Deprivation
Clement F. Kent,Tim Daskalchuk,Lisa Cook,Marla B. Sokolowski ,Ralph J. Greenspan
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000609
Abstract: Nutrition is known to interact with genotype in human metabolic syndromes, obesity, and diabetes, and also in Drosophila metabolism. Plasticity in metabolic responses, such as changes in body fat or blood sugar in response to changes in dietary alterations, may also be affected by genotype. Here we show that variants of the foraging (for) gene in Drosophila melanogaster affect the response to food deprivation in a large suite of adult phenotypes by measuring gene by environment interactions (GEI) in a suite of food-related traits. for affects body fat, carbohydrates, food-leaving behavior, metabolite, and gene expression levels in response to food deprivation. This results in broad patterns of metabolic, genomic, and behavioral gene by environment interactions (GEI), in part by interaction with the insulin signaling pathway. Our results show that a single gene that varies in nature can have far reaching effects on behavior and metabolism by acting through multiple other genes and pathways.
An Activated Form of UFO Alters Leaf Development and Produces Ectopic Floral and Inflorescence Meristems
Eddy Risseeuw, Prakash Venglat, Daoquan Xiang, Kristina Komendant, Tim Daskalchuk, Vivijan Babic, William Crosby, Raju Datla
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0083807
Abstract: Plants are unique in their ability to continuously produce new meristems and organ primordia. In Arabidopsis, the transcription factor LEAFY (LFY) functions as a master regulator of a gene network that is important for floral meristem and organ specification. UNUSUAL FLORAL ORGANS (UFO) is a co-activator of LEAFY and is required for proper activation of APETALA3 in the floral meristem during the specification of stamens and petals. The ufo mutants display defects in other parts of the flower and the inflorescence, suggestive of additional roles. Here we show that the normal determinacy of the developing Arabidopsis leaves is affected by the expression of a gain-of-function UFO fusion protein with the VP16 transcriptional activator domain. In these lines, the rosette and cauline leaf primordia exhibit reiterated serration, and upon flowering produce ectopic meristems that develop into flowers, bract leaves and inflorescences. These striking phenotypes reveal that developing leaves maintain the competency to initiate flower and inflorescence programs. Furthermore, the gain-of-function phenotypes are dependent on LFY and the SEPALLATA (SEP) MADS-box transcription factors, indicative of their functional interactions with UFO. The findings of this study also suggest that UFO promotes the establishment of the lateral meristems and primordia in the peripheral zone of the apical and floral meristems by enhancing the activity of LFY. These novel phenotypes along with the mutant phenotypes of UFO orthologs in other plant species suggest a broader function for UFO in plants.
A Study on Configuration and Integration of Sub-Systems to System-of-Systems with Rule Verification  [PDF]
Tim Warnecke
Engineering (ENG) , 2015, DOI: 10.4236/eng.2015.710056
Abstract: Increasing complexity of today’s software systems is one of the major challenges software engineers have to face. This is aggravated by the fact that formerly isolated systems have to be interconnected to more complex systems, called System-of-Systems (SoS). Those systems are in charge to provide more functionality to the user than all of their independent sub-systems could do. Reducing the complexity of such systems is one goal of the software engineering paradigm called component-based software engineering (CBSE). CBSE enables the developers to treat individual sub-systems as components which interact via interfaces with a simulated environment. Thus those components can be developed and implemented independently from other components. After the implementation a system integrator is able to interconnect the components to a SoS. Despite this much-used approach it is possible to show that constraints, which are valid in an isolated sub-system, are broken after this system is integrated into a SoS. To emphasize this issue we developed a technique based on interconnected timed automata for modelling sub-systems and System-of-Systems in the model checking tool UPPAAL. The presented modelling technique allows it to verify the correctness of single sub-systems as well as the resulting SoS. Additionally we developed a tool which abstracts the complicated timed automata to an easy to read component based language with the goal to help system integrators building and verifying complex SoS.
Lipophilic Optical Supramolecular Nano Devices in the Aqueous Phase  [PDF]
Heinz Langhals, Tim Pust
Green and Sustainable Chemistry (GSC) , 2011, DOI: 10.4236/gsc.2011.11001
Abstract: Nano micelles of sodium dodecyl sulphate in water were prepared as local lipophilic media for the organisation of interacting chromophores. Such arrangements were controlled by peripheric substituents to operate either as isolated chromophores or as skew oriented pairs where H-type transitions cause hysochromic absorption and J-type transitions bathochromic fluorescence. As a consequence, large Stokes' shift could be obtained.
Aspects of Replayability and Software Engineering: Towards a Methodology of Developing Games  [PDF]
Joseph Krall, Tim Menzies
Journal of Software Engineering and Applications (JSEA) , 2012, DOI: 10.4236/jsea.2012.57052
Abstract: One application of software engineering is the vast and widely popular video game entertainment industry. Success of a video game product depends on how well the player base receives it. Of research towards understanding factors of success behind releasing a video game, we are interested in studying a factor known as Replayability. Towards a software engineering oriented game design methodology, we collect player opinions on Replayability via surveys and provide methods to analyze the data. We believe these results can help game designers to more successfully produce entertaining games with longer lasting appeal by utilizing our software engineering techniques.
Suprafibrillar structures of collagen, evidence for local organization and auxetic behaviour in architectures  [PDF]
Kate Patten, Tim Wess
Journal of Biophysical Chemistry (JBPC) , 2013, DOI: 10.4236/jbpc.2013.43014
Abstract: The suprafibrillar organisation of collagen rich tissues is the keystone to the diversity of resultant structures made from relatively similar materials. The local organisation between fibrils may be essential to suprafibril structures that are critical to functionality such as transparency in cornea, where specific lateral relationships between fibrils dictate optical properties. Here we show that corneal X-ray diffraction combined with mechanical strains to disrupt a specific suprafibrillar relationship between fibrils evidence and a coherent staggered axial relationship between collagen fibrils. The data also shows evidence for auxetic behavior of the collagen fibrils and reveals a 120 nm diffraction feature previously unreported in collagen tissues. The results show that suprafibrillar organisation can be an essential component in tissue architecture that has hitherto been ignored, but now must be considered in mechanical and structural models.
Determinants in Pay-What-You-Want Pricing Decisions—A Cross-Country Study  [PDF]
Tim Dorn, Augustin Suessmair
American Journal of Industrial and Business Management (AJIBM) , 2017, DOI: 10.4236/ajibm.2017.72010
Abstract: Pay-what-you-want (PWYW) pricing has attracted much attention recently. Current research focused on influencing factors and their power across social contexts and countries. This article empirically examines a comprehensive list of 10 empirically tested factors that influence individual price-setting but never have been investigated holistically. Results indicate: (1) some previously assumed influencing factors have stronger moderating effects than do others, and (2) these influences must be interpreted as influential clusters rather than individually, as not all constructs are of significantly differing influence on an individual’s pricing decision. Satisfaction (Cluster 1), price consciousness, and fairness (both Cluster 2) constitute the most crucial moderators, regardless of context. Four country contexts (i.e., Australia, Germany, Poland, United States) revealed further insights about the intercultural perspective of PWYW pricing: Whereas most of the influencing factors/clusters are of comparable importance across the tested countries, loyalty and reputation (Cluster 6) significantly differed in importance depending on country.
Community Perspectives on the Use of Recycled Plastic Posts in Mitigating Livestock Predation in Amboseli Ecosystem, Kenya  [PDF]
David Owino Manoa, Tim Oloo
Natural Resources (NR) , 2016, DOI: 10.4236/nr.2016.75023
Abstract: In the last few decades, the impacts of human activities on ecosystem have rapidly increased resulting to detrimental ecosystem changes. Human-wildlife conflict (HWC) is one of the greatest consequences of human impacts on the environment. Although HWC has been there for decades, its intensity seems to be growing with the spread of human settlements, changes in land use patterns and diminishing suitable natural habitats for wildlife. To mitigate HWC, various strategies have been devised and implemented. This study focused on predator-proof bomas (PPBs) approach that is ongoing in Amboseli ecosystem. The aim was to establish reasons behind the slow adoptions of the recycled plastics poles by owners of PPBs that were constructed using wooden posts between the years 2010 to 2013. Randomly selected 36 PPB homestead owners were interviewed and the physical structures of their PPBs assessed. Results revealed a positive relationship between PPB size and number of poles damaged; and a significant association between the damaged posts and the number of indigenous posts replaced in the three group ranches (X2 = 34.9331, df = 2, p < 0.05). Most of the respondents (89%) cited posts and doors (72%) as the main parts that needed repairs. About 80% of the respondents would recommend the plastic posts for use in constructing new PPBs by other people. Most of the PPB beneficiaries whose PPBs were constructed in 2010-2013 have opted for an “easy” alternative source of posts from the sparsely distrusted trees around their homesteads. It is recommend that an open window period should be tried to entice the wooden post PPBs owners to adopt the recycled plastic posts. This may necessitate upgrading the existing old wooden bomas to a “smart PPBs”. It is suggested that the “smart PPBs” should not only have recycled plastic posts but also “free” energy saving stoves in each household to reduce the level of deforestation.
Testing the No-Hair Theorem with Sgr A*
Tim Johannsen
Advances in Astronomy , 2012, DOI: 10.1155/2012/486750
Abstract: The no-hair theorem characterizes the fundamental nature of black holes in general relativity. This theorem can be tested observationally by measuring the mass and spin of a black hole as well as its quadrupole moment, which may deviate from the expected Kerr value. Sgr A*, the supermassive black hole at the center of the Milky Way, is a prime candidate for such tests thanks to its large angular size, high brightness, and rich population of nearby stars. In this paper, I discuss a new theoretical framework for a test of the no-hair theorem that is ideal for imaging observations of Sgr A* with very long baseline interferometry (VLBI). The approach is formulated in terms of a Kerr-like spacetime that depends on a free parameter and is regular everywhere outside of the event horizon. Together with the results from astrometric and timing observations, VLBI imaging of Sgr A* may lead to a secure test of the no-hair theorem. 1. Introduction According to the no-hair theorem, black holes are uniquely characterized by their masses and spins and are described by the Kerr metric [1–6]. Mass and spin are the first two multipole moments of the Kerr spacetime, and all higher-order moments can be expressed in terms of these two [7, 8]. The no-hair theorem, then, naturally leads to the expectation that all astrophysical black holes are Kerr black holes. To date, however, a definite proof for the existence of such black holes is still lacking despite a wealth of observational evidence (see discussion in, e.g., [9]). Tests of the no-hair theorem have been suggested using observations in either the gravitational-wave [10–21] or the electromagnetic spectrum [22–31]. Both approaches are based on parametric frameworks that contain one or more free parameters in addition to mass and spin which measure potential deviations from the Kerr metric [18–20, 32–34]. If no deviation is detected, then the compact object is indeed a Kerr black hole. However, since such deviations can have a significant impact on the observed signals, the no-hair theorem may be tested in a twofold manner: if a deviation is measured to be nonzero and if general relativity is assumed, the object cannot be a black hole [18, 35]. Alternatively, if the object is otherwise known to possess an event horizon, it is a black hole, but different from a Kerr black hole. In the latter case, the no-hair theorem would be falsified [22]. Sgr A*, the supermassive black hole at the center of the Milky Way, is a prime target for testing strong-field gravity and the no-hair theorem with electromagnetic observations (see
Biosynthesis of ribose-5-phosphate and erythrose-4-phosphate in archaea: a phylogenetic analysis of archaeal genomes
Tim Soderberg
Archaea , 2005, DOI: 10.1155/2005/314760
Abstract: A phylogenetic analysis of the genes encoding enzymes in the pentose phosphate pathway (PPP), the ribulose monophosphate (RuMP) pathway, and the chorismate pathway of aromatic amino acid biosynthesis, employing data from 13 complete archaeal genomes, provides a potential explanation for the enigmatic phylogenetic patterns of the PPP genes in archaea. Genomic and biochemical evidence suggests that three archaeal species (Methanocaldococcus jannaschii, Thermoplasma acidophilum and Thermoplasma volcanium) produce ribose-5-phosphate via the nonoxidative PPP (NOPPP), whereas nine species apparently lack an NOPPP but may employ a reverse RuMP pathway for pentose synthesis. One species (Halobacterium sp. NRC-1) lacks both the NOPPP and the RuMP pathway but may possess a modified oxidative PPP (OPPP), the details of which are not yet known. The presence of transketolase in several archaeal species that are missing the other two NOPPP genes can be explained by the existence of differing requirements for erythrose-4-phosphate (E4P) among archaea: six species use transketolase to make E4P as a precursor to aromatic amino acids, six species apparently have an alternate biosynthetic pathway and may not require the ability to make E4P, and one species (Pyrococcus horikoshii) probably does not synthesize aromatic amino acids at all.
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