Letteratura scientifica selezionata sul tema "Trait decay"
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Articoli di riviste sul tema "Trait decay":
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Hayes, Ryan J., Carlos H. Galeano, Yaguang Luo, Rudie Antonise e Ivan Simko. "Inheritance of Decay of Fresh-cut Lettuce in a Recombinant Inbred Line Population from ‘Salinas 88’ × ‘La Brillante’". Journal of the American Society for Horticultural Science 139, n. 4 (luglio 2014): 388–98. http://dx.doi.org/10.21273/jashs.139.4.388.
Abstract (sommario):
Fresh-cut lettuce (Lactuca sativa) packaged as salad mixes are increasingly popular to consumers but are highly perishable. Cultivars bred with extended shelf life could increase overall production efficiency by reducing the frequency of product replacement in the marketplace. Understanding the inheritance of shelf life is needed to develop efficient breeding strategies for this trait. A population of 95 recombinant inbred lines (RILs) from slow-decaying ‘Salinas 88’ × rapidly decaying ‘La Brillante’ was grown in four field experiments. Cut lettuce was evaluated for decay in modified atmosphere (MA) packages flushed with N2 or air (control). Correlations between field experiments ranged from 0.47 to 0.84 (P < 0.01). Three quantitative trait loci (QTL) for decay of cut lettuce were detected on linkage groups (LGs) 1, 4, and 9 with ‘Salinas 88’ alleles associated with slower decay. The QTL on LG 4 (qSL4) was a major determinant of decay explaining 40% to 74% of the total phenotypic variance of the trait. The greatest effect of this QTL was observed between 29 and 50 days after harvest. QTL × environment interactions contributed less than 14% to the total variation. RILs with the ‘Salinas 88’ allele of qSL4 had slower decay when packaged in air compared with N2, whereas no difference between air and N2 packaging was detected with the ‘La Brillante’ allele. A subset of RILs with either the ‘Salinas 88’ or ‘La Brillante’ allele of qSL4 was grown in two field experiments and evaluated for decay of whole heads. Genetic variation among RILs for whole-head decay was found but could not be attributed to qSL4. Decay of cut lettuce in ‘Salinas 88’ × ‘La Brillante’ is a highly heritable trait conditioned by a few QTL and phenotypic selection is likely to be effective. However, shelf life evaluations are time-consuming, destructive, and require large amounts of field-grown lettuce. Therefore, qSL4 is a good QTL to develop molecular markers for marker-assisted selection. The mechanism of decay controlled by qSL4 is unknown but appears to be specific to cut lettuce and may have allele specific interactions with packaging atmospheric compositions.
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Schwander, Tanja, Bernard J. Crespi, Regine Gries e Gerhard Gries. "Neutral and selection-driven decay of sexual traits in asexual stick insects". Proceedings of the Royal Society B: Biological Sciences 280, n. 1764 (7 agosto 2013): 20130823. http://dx.doi.org/10.1098/rspb.2013.0823.
Abstract (sommario):
Environmental shifts and lifestyle changes may result in formerly adaptive traits becoming non-functional or maladaptive. The subsequent decay of such traits highlights the importance of natural selection for adaptations, yet its causes have rarely been investigated. To study the fate of formerly adaptive traits after lifestyle changes, we evaluated sexual traits in five independently derived asexual lineages, including traits that are specific to males and therefore not exposed to selection. At least four of the asexual lineages retained the capacity to produce males that display normal courtship behaviours and are able to fertilize eggs of females from related sexual species. The maintenance of male traits may stem from pleiotropy, or from these traits only regressing via drift, which may require millions of years to generate phenotypic effects. By contrast, we found parallel decay of sexual traits in females. Asexual females produced altered airborne and contact signals, had modified sperm storage organs, and lost the ability to fertilize their eggs, impeding reversals to sexual reproduction. Female sexual traits were decayed even in recently derived asexuals, suggesting that trait changes following the evolution of asexuality, when they occur, proceed rapidly and are driven by selective processes rather than drift.
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Fois, Mattia, Andrea Bellucci, Marta Malinowska, Morten Greve, Anja Karine Ruud e Torben Asp. "Genome-Wide Association Mapping of Crown and Brown Rust Resistance in Perennial Ryegrass". Genes 13, n. 1 (22 dicembre 2021): 20. http://dx.doi.org/10.3390/genes13010020.
Abstract (sommario):
A population of 239 perennial ryegrass (Lolium perenne L.) genotypes was analyzed to identify marker-trait associations for crown rust (Puccinia coronata f. sp. lolii) and brown rust (Puccinia graminis f. sp. loliina) resistance. Phenotypic data from field trials showed a low correlation (r = 0.17) between the two traits. Genotypes were resequenced, and a total of 14,538,978 SNPs were used to analyze population structure, linkage disequilibrium (LD), and for genome-wide association study. The SNP heritability (h2SNP) was 0.4 and 0.8 for crown and brown rust resistance, respectively. The high-density SNP dataset allowed us to estimate LD decay with the highest possible precision to date for perennial ryegrass. Results showed a low LD extension with a rapid decay of r2 value below 0.2 after 520 bp on average. Additionally, QTL regions for both traits were detected, as well as candidate genes by applying Genome Complex Trait Analysis and Multi-marker Analysis of GenoMic Annotation. Moreover, two significant genes, LpPc6 and LpPl6, were identified for crown and brown rust resistance, respectively, when SNPs were aggregated to the gene level. The two candidate genes encode proteins with phosphatase activity, which putatively can be induced by the host to perceive, amplify and transfer signals to downstream components, thus activating a plant defense response.
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Fernández-Trujillo, Juan Pablo, Javier Obando, Juan Antonio Martínez, Antonio Luis Alarcón, Iban Eduardo, Pere Arús e Antonio José Monforte. "Mapping Fruit Susceptibility to Postharvest Physiological Disorders and Decay Using a Collection of Near-isogenic Lines of Melon". Journal of the American Society for Horticultural Science 132, n. 5 (settembre 2007): 739–48. http://dx.doi.org/10.21273/jashs.132.5.739.
Abstract (sommario):
Melon (Cucumis melo L.) is a perishable fruit that requires refrigeration to extend its shelf life. Postharvest behavior differs substantially among melon varieties due to genetic differences. In this work, we use a collection of near-isogenic lines (NILs) derived from a cross between the Spanish cultivar Piel de Sapo (PS) and an exotic Korean accession ‘Shongwan Charmi’ [SC (PI161375)], each of them with a single introgressed region from SC into the PS background, to detect and map quantitative trait loci (QTLs) involved in postharvest life traits, such as total losses, water-soaking, necrosis of the placental tissue, chilling injury (CI), decay, fruit over-ripening, flesh browning, hollow flesh disorder, and flavor loss during storage. Fruit were examined at harvest and after 35 days at 8 °C. Three QTLs induced desirable quality traits: flv4.1 reduced the loss of fruit flavor after refrigeration, tl8.1 reduced total losses, and fus8.4 reduced the susceptibility to fusarium rot (Fusarium Link). Another 11 QTLs produced a detrimental effect on other quality traits. The NIL population was useful for dissecting complex, difficult-to-measure pre- and postharvest disorder traits of different degrees of development and for investigating flavor loss during storage. Further studies with the QTLs described herein will shed light on the genetic control of melon shelf life and help breeders who are interested in this fruit quality trait.
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Puentes Rodriguez, Y., A. Zubizarreta Gerendiain, A. Pappinen, H. Peltola e P. Pulkkinen. "Differences in wood decay by Heterobasidion parviporum in cloned Norway spruce (Picea abies)". Canadian Journal of Forest Research 39, n. 1 (gennaio 2009): 26–35. http://dx.doi.org/10.1139/x08-159.
Abstract (sommario):
In forest breeding, growth has been used as the main selection trait in Norway spruce (Picea abies L. Karst.), whereas wood properties or resistance to pathogens have been taken as secondary traits. We aimed to investigate, in laboratory conditions, the rate of wood decay caused by Heterobasidion parviporum (Fr.) Niemelä & Korhonen (strains 5 and 7) in 20 Norway spruce clones. We also studied if, on average, growth, wood density, and fibre properties differed in the most and least decayed clones as well as from pith to bark. After 6 months of incubation, strain 7 effected significantly higher wood decay than strain 5 (mean 16.9% and 1.7%, respectively). The difference between the five most decayed and five least decayed clones by strain 7 was also statistically significant (P < 0.05). Moreover, regardless of clone or strain, the wood decay was highest near the pith and lowest near the bark, which is the opposite for wood density and fibre length and width. However, neither wood density nor fibre properties explained, statistically, the differences in average wood decay and decay from pith to bark. On the other hand, we could identify clones that simultaneously provided high wood quantity and relatively high wood density and low decay rate.
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Kampfraath, Andries Augustus, Tjeerd Pieter Dudink, Ken Kraaijeveld, Jacintha Ellers e Zaira Valentina Zizzari. "Male Sexual Trait Decay in Two Asexual Springtail Populations Follows Neutral Mutation Accumulation Theory". Evolutionary Biology 47, n. 4 (20 agosto 2020): 285–92. http://dx.doi.org/10.1007/s11692-020-09511-z.
Abstract (sommario):
Abstract The transition to asexual reproduction is frequent and widespread across the tree of life and constitutes a major life history change. Without sexual reproduction, selection on sexually selected traits is expected to be weaker or absent, allowing the decay and ultimately loss of sexual traits. In this study, we applied an experimental approach to investigate the decay of reproductive traits under asexuality in two asexual populations of the springtail Folsomia candida. Specifically, we compared several key male sexual traits of a sexual population and two distinct parthenogenetic lines. To allow direct comparisons between sexual and asexual individuals we first determined a suite of life history characteristics in the sexual F. candida population, which performs an indirect transfer of sperm packages (spermatophores).To investigate the decay of male sexual traits under asexuality we measured the size of spermatophores, quantified the amount of sperm DNA material, and tested spermatophore attractiveness to females in all three populations. The amount of sperm DNA material in the sperm droplets and the attractiveness of spermatophores were lower in the asexual lines compared to the sexual population. However, the two asexual lines differed in the extent of decay of these traits. Our results are consistent with predictions from neutral mutation accumulation theory, and thus suggest this to be the main evolutionary process underlying the decay of male traits in F. candida.
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Strauss, S. H., R. Lande e G. Namkoong. "Limitations of molecular-marker-aided selection in forest tree breeding". Canadian Journal of Forest Research 22, n. 7 (1 luglio 1992): 1050–61. http://dx.doi.org/10.1139/x92-140.
Abstract (sommario):
The advances to date with quantitative trait locus identification in agronomic crops, which have mostly been with studies of inter- and intra-specific hybrids, are of little relevance to assessing the potential for marker-aided selection in nonhybrid forest tree populations. Although molecular markers provide great opportunities for dissection of quantitative traits in experimental populations, we expect that their near-term usefulness in most operational tree breeding programs will be limited. In addition to cost, this limitation results from quantitative trait locus–marker associations being limited to specific genetic backgrounds as a result of linkage equilibrium, interactions of quantitative trait locus effects with genetic backgrounds, genotype by environment interaction, and changes of quantitative trait locus allele frequencies among generations. Marker-aided selection within individually mapped full-sib families can substantially aid phenotypic selection, but only where large restrictions of genetic base are tolerated, trait heritabilities are low, markers are able to explain much of the additive variance, selection intensities within families are high compared with that among families, and very large numbers of progeny are examined. Broad use of marker-aided selection in the longer term will require substantial technical advances in a number of areas, including means for precise quantitative trait locus identification; reduction of large-scale mapping and genotyping costs; and changes in breeding and propagation systems. Consideration of trait characteristics suggests that marker-aided selection will be most efficient in direct selection with high-value, low-heritability traits such as height and diameter growth. These traits, however, often show genotype by environment interaction and unfavorable genetic correlations with other desirable traits, and are likely to be controlled by a large number of minor genes rather than relatively few major ones. Traits with the most potential for marker-aided selection in nonhybrid tree populations will therefore be strongly inherited ones for which phenotypic assay is difficult; examples might include wood quality, resistance to biotrophic pathogens, and resistance to air pollutants. Because of the large disequilibrium generated during hybridization and the great phenotypic variance that segregates in F2 and backcross generations, interspecific hybrid programs lend themselves much more readily to marker-aideed selection. Segregation distortion and related meiotic aberrations, however, may substantially hamper precise estimation of quantitative trait locus locations and phenotypic effects. Nonadditive quantitative trait locus effects will likely be greater in hybrid populations than in intraspecific populations. Rapid decay of disequilibrium due to recombination, and allele frequency shifts due to selective breeding and natural selection during early generations after hybridization, are likely to cause instability for quantitative trait locus - marker associations and quantitative trait locus phenotypic effects. Finally, interspecific hybridization of highly heterozygous individuals from species in linkage equilibrium will impede marker-aided selection.
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Poulin, Robert, Boris R. Krasnov, David Mouillot e David W. Thieltges. "The comparative ecology and biogeography of parasites". Philosophical Transactions of the Royal Society B: Biological Sciences 366, n. 1576 (27 agosto 2011): 2379–90. http://dx.doi.org/10.1098/rstb.2011.0048.
Abstract (sommario):
Comparative ecology uses interspecific relationships among traits, while accounting for the phylogenetic non-independence of species, to uncover general evolutionary processes. Applied to biogeographic questions, it can be a powerful tool to explain the spatial distribution of organisms. Here, we review how comparative methods can elucidate biogeographic patterns and processes, using analyses of distributional data on parasites (fleas and helminths) as case studies. Methods exist to detect phylogenetic signals, i.e. the degree of phylogenetic dependence of a given character, and either to control for these signals in statistical analyses of interspecific data, or to measure their contribution to variance. Parasite–host interactions present a special case, as a given trait may be a parasite trait, a host trait or a property of the coevolved association rather than of one participant only. For some analyses, it is therefore necessary to correct simultaneously for both parasite phylogeny and host phylogeny, or to evaluate which has the greatest influence on trait expression. Using comparative approaches, we show that two fundamental properties of parasites, their niche breadth, i.e. host specificity, and the nature of their life cycle, can explain interspecific and latitudinal variation in the sizes of their geographical ranges, or rates of distance decay in the similarity of parasite communities. These findings illustrate the ways in which phylogenetically based comparative methods can contribute to biogeographic research.
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Stork, Sydney, Joseph Jalinsky e Maurine Neiman. "Evidence for stronger discrimination between conspecific and heterospecific mating partners in sexual vs. asexual female freshwater snails". PeerJ 10 (24 novembre 2022): e14470. http://dx.doi.org/10.7717/peerj.14470.
Abstract (sommario):
Once-useful traits that no longer contribute to fitness tend to decay over time. Here, we address whether the expression of mating-related traits that increase the fitness of sexually reproducing individuals but are likely less useful or even costly to asexual counterparts seems to exhibit decay in the latter. Potamopyrgus antipodarum is a New Zealand freshwater snail characterized by repeated transitions from sexual to asexual reproduction. The frequent coexistence of sexual and asexual lineages makes P. antipodarum an excellent model for the study of mating-related trait loss. Under the presumption (inherent in the Biological Species Concept) that failure to discriminate between conspecific and heterospecific mating partners represents a poor mate choice, we used a mating choice assay including sexual and asexual P. antipodarum females and conspecific (presumed better choice) vs. heterospecific (presumed worse choice) males to evaluate the loss of behavioral traits related to sexual reproduction. We found that sexual females engaged in mating behaviors with conspecific mating partners more frequently and for a greater duration than with heterospecific mating partners. By contrast, asexual females mated at similar frequency and duration as sexual females, but did not mate more often or for longer duration with conspecific vs. heterospecific males. While further confirmation will require inclusion of a more diverse array of sexual and asexual lineages, these results are consistent with a scenario where selection acting to maintain effective mate discrimination in asexual P. antipodarum is weak or ineffective relative to sexual females and, thus, where asexual reproduction is associated with the evolutionary decay of mating-related traits in this system.
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Souza, Tancredo, Edjane Oliveira de Lucena, Leonaldo Alves de Andrade, Lucas Jónatan Rodrigues da Silva, Gislaine dos Santos Nascimento e Helena Freitas. "Litter Deposition and Nutrient Cycling of Invaded Environments by Cryptostegia madagascariensis at Tropical Cambisols from Northeastern Brazil". International Journal of Plant Biology 14, n. 1 (20 febbraio 2023): 254–65. http://dx.doi.org/10.3390/ijpb14010021.
Abstract (sommario):
Cryptostegia madagascariensis is an invasive plant species that covers 11% of the Brazilian northeastern territory, but its role on the litter trait in tropical ecosystems remains unclear. Here, we analyzed and compared the litter deposition, litter nutrient content, soil organic matter, and the litter decay rate from invaded and non-invaded environments by C. madagascariensis at a tropical Cambisol. The PCA analysis revealed that litter deposition, litter quality, and soil organic matter were correlated with the invaded environment. We grew plant species in greenhouse conditions to obtain a standard litter material to use in our litter bags in field conditions. We found that litter decay rate was higher in the invaded environment than in the non-invaded one. Our results suggest that C. madagascariensis changes litter traits in tropical ecosystems that in turn create negative plant–soil feedback to the native species by creating a physical barrier on soil surface and to promote its own rhizosphere.
Tesi sul tema "Trait decay":
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Defendini, Hélène. "Bases génétiques et conséquences évolutives de la perte de sexe dans le groupe des pucerons". Electronic Thesis or Diss., Rennes, Agrocampus Ouest, 2023. http://www.theses.fr/2023NSARA094.
Abstract (sommario):
La reproduction sexuée est considérée comme le mode de reproduction ancestral des eucaryotes, mais elle été perdue à plusieurs reprises dans de nombreux taxons. Comprendre les mécanismes par lesquels les lignées asexuées apparaissent et persistent dans le temps reste un défi majeur de la biologie évolutive. Au cours de ma thèse, j'ai étudié les bases génétiques ainsi que les conséquences évolutives de la perte du sexe chez les pucerons, un groupe qui présente un polymorphisme de reproduction. Le mode de reproduction ancestral des pucerons est la parthénogenèse cyclique (CP, une alternance de plusieurs générations parthénogénétiques et d'une génération sexuée), mais la parthénogenèse obligatoire (OP) est fréquemment observée dans ce groupe. Les lignées OP dérivées ne sont pas capables de produire des femelles sexuées bien qu'elles conservent souvent la capacité de produire des mâles. Pour caractériser les régions génomiques impliquées dans la transition de la reproduction CP à OP, nous avons utilisé des approches de scan génomique sur différents taxons de pucerons plus ou moins proches génétiquement et présentant des variations de mode de reproduction. Nous avons montré que la base génétique de la perte du sexe est différente entre les taxons étudiés, sans convergence apparente dans le contenu génique ou les fonctions des gènes. Ainsi, plusieurs régions génomiques indépendantes peuvent être responsables de la perte du sexe chez les pucerons, ce qui suggère qu'il existe de nombreuses voies menant à l'asexualité dans ce groupe. Ensuite, nous avons étudié les conséquences évolutives de la perte du sexe sur les traits et les gènes essentiels à la reproduction sexuée. Comme il est peu probable que les mâles produits par les lignées OP transmettent leurs gènes (les lignées CP étant généralement séparées géographiquement des lignées OP), nous avons testé la prédiction selon laquelle les traits mâles dégénèrent. La production de mâles était en effet réduite dans les lignées OP, supposément en raison de la contre-sélection, mais le succès reproductif des mâles n'était que légèrement inférieur à celui des lignées CP, probablement en raison de la sélection relâchée qui agit lentement ou d’opportunités reproductives sous-estimées. Comme les lignées OP produisent rarement des mâles et ne produisent pas de femelles sexuées, l'expression génétique des femelles parthénogénétiques n'est plus contrainte par celle des autres morphes. Nous avons donc prédit que la disparition du conflit sexuel (qui survient lorsqu'il existe différents optima spécifiques à chaque morphe pour un trait partagé par différents morphes) entraînerait des changements d’expression des gènes. Nous avons donc comparé les profils d'expression génétique des lignées CP et OP pour différents morphes du puceron du pois. Nous avons observé que l'expression des gènes chez les mâles des lignées OP tendait vers l'optimum des femelles parthénogénétiques, comme le prévoyait la théorie. Plus surprenant, les mâles et les femelles parthénogénétiques des lignées OP surexpriment systématiquement des gènes exprimés dans les gonades des morphes sexués. Ces changements dans l'expression des gènes dans les lignées OP peuvent s’expliquer par un relâchement de la sélection ou la reconversion de réseaux de gènes autrement utilisés dans les lignées sexuées. Cette thèse illustre la pertinence de l'utilisation d'espèces aux systèmes de reproduction polymorphes pour comprendre l'histoire évolutive de la perte du sexe et ses conséquencesSexual reproduction is considered the ancestral reproductive mode of eukaryotes, yet it has been lost several times in many taxa. Understanding the mechanisms by which asexual lineages appear and persist over time remains a major challenge of evolutionary biology. During my PhD, I investigated the genetic basis as well as the evolutionary consequences of sex loss in aphids, a group that displays reproductive polymorphism. The ancestral reproductive mode of aphids is cyclical parthenogenesis (CP, an alternation of several parthenogenetic generations and one sexual generation), but obligate parthenogenesis (OP) is frequently observed in this group. Derived OP lineages are not able to produce sexual females though they often retain the ability to produce males. First, to characterize genomic regions involved in the transition from CP to OP reproductive mode, we used genome scan approaches on different aphid taxa that are more or less genetically related and exhibit variation in reproductive mode. We showed that the genetic basis of sex loss is different between the studied taxa, with no apparent convergence in gene content norfunctions. Thus, several independent genomic regions may be responsible for sex loss in aphids, suggesting that there are many paths that lead to asexuality in this group. Second, we studied the evolutionary consequences of the loss of sex on traits and genes essential for sexual reproduction. Since the males produced by OP lineages are unlikely to pass on their genes (because CP lineages are usually separated from OP ones), we tested the prediction that male traits should degenerate. Male production was indeed reduced in OP lineages, supposedly resulting from counter-selection, but male reproductive success was only slightly lower than in CP lineages, presumably due to the slow action of relaxed selection orunderestimation of reproductive opportunities. As OP lineages produce rare males and also do not produce sexual females, the gene expression of parthenogenetic females in these OP lineages is no longer constrained by that of other morphs. We thus predicted that the disappearance of sexual conflict (which arises when there are different morph-specific optima for a trait shared by different morphs) would result in shifts of gene expression. We therefore compared gene expression patterns of CP and OP lineages for different morphs in the pea aphid. We observed that gene expression in males from OP lineages tended towards the parthenogenetic female optimum, as predicted by theory. More surprisingly, males and parthenogenetic females of OP lineages consistently over-expressed genes typically expressed in the gonads of sexual morphs. These changes in gene expression in OP lineages may arise from the relaxation of selection or the repurposing of gene networks otherwise used in sexual lineages. This thesis illustrates the relevance of using species with polymorphic reproductive systems to understand the evolutionary history of sex loss and its consequences
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Minbashi, Niloofar. "Applying Data Analytics to Freight Train Delays in Shunting Yards". Licentiate thesis, KTH, Transportplanering, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284672.
Abstract (sommario):
The European Commission has foreseen a modal share of 30% by 2030 for rail freight transport. To achieve this increase in the modal share, enhanced reliability of rail freight services is required. Optimal functioning of shunting yards is one of the areas that can improve this reliability. Shunting yards are large areas allocated to reassemble freight trains for dispatching to new destinations. Their productivity has a direct impact on the overall performance of a rail freight network. Therefore, analysing and modelling of departure deviations from shunting yards are required to enhance the interactions between shunting yards and the network; this thesis contributes to this gap. Paper I investigates the probability and temporal distribution of departure deviations using a large data set comprising 250,000 departures over seven years from two main shunting yards (Malmö and Hallsberg) in Sweden. The probability distribution of departure deviations is found comparing four main distributions including the exponential, the log-normal, the gamma, and the Weibull according to the maximum likelihood estimates and the results of the Anderson-Darling goodness of fit test. The log-normal and the gamma are shown the best fits for departure deviations: the former on delays, and the latter on early departures. In the temporal delay distribution, the weekly and monthly, but not yearly delayed departures are positively correlated with the network usage. However, for hourly delayed departures, a shunting yard involved with international traffic does not show any correlation between delayed departures and the network usage, whereas a domestic shunting yard shows a significant negative correlation between these two parameters. The findings obtained from this thesis contribute to a better understanding of departure deviations from shunting yards, and can be applied in enhancing the operations and capacity utilization of shunting yards in future models. Papers II and III analyse the relationship between congestion in the arrival yard and departure delays using the same data set as paper I. According to previous research, congestion plays an important role in shunting yard delays. With defining congestion as the number of arriving trains before departure time, paper II analyses this relationship limiting the arrivals and departures between the two shunting yards considering varying time periods before departure,whereas Paper III elaborates the analysis by defining congestion level in a fixed period of time before departure time including all arrivals and departures. Considering the data set used in the analysis, the results show that there is no significant relationship between the congestion in the arrival yard and departure delays of trains. It is possible that congestion may not impact the departure delays of trains, but it may impact the departure delays of wagons due to missed wagon connection or increasing wagon idle time, which can be explored with the availability of wagon connection data. Additionally, future elaboration of congestion definition, covering congestion at the shunting yard level, may lead to further improved analyses.Europeiska kommissionen har förutspått en markansandel på 30% framtill 2030 för järnvägstransporter av gods. För att uppnå denna ökning krävsökad tillförlitlighet hos järnvägstransporttjänster. Rangergodsbangårdars optimalafunktion är ett av de områden som kan förbättra denna tillförlitlighet.Rangergodsbangårdar stora områden som är avsedda för att koppla ihopgodståg för sändning till nya destinationer. Deras produktivitet har en direktinverkan på järnvägsnätets totala prestanda. Därför krävs analys och modelleringav avvikelser från dessa noder för att förbättra interaktionen mellanrangergodsbangårdar och järnvägsnätet. I papper I undersöks sannolikheten och den tidsmässiga fördelningen avavvikelser med hjälp av en stor datamängd som omfattar 250 000 avgångaröver sju år från två rangergodsbangårdar (Malmö och Hallsberg) i Sverige.Sannolikhetsdistributioner av avvikelser jämförs med fyra huvuddistributioner,exponentiell, log-normal, gamma och Weibull enligt de maximalasannolikhetsuppskattningarna och resultaten av Anderson-Darling godhetav passningstest. Log-normal och gamma visar sig passa bäst för avvikelser:den förstnämnda vid förseningar och den senare vid tidiga avgångar. I dentidsmässiga fördröjningsfördelningen är de veckovisa och månatliga men inteårliga försenade avgångarna positivt korrelerade med järnvägsnätets nyttjandegrad.För försenade avgångar per timme visar dock en rangergodsbangårdsom är inblandad i internationell trafik ingen korrelation mellan försenadeavgångar och järnvägsnätets nyttjandegrad, medan en inhemsk rangergodsbangårdvisaren signifikant negativ korrelation mellan dessa två parametrar.Resultaten från denna avhandling bidrar till en bättre förståelse av avvikelserfrån rangergodsbangårdar och kan användas för att förbättra drift och kapacitetsutnyttjandeav rangergodsbangårdar växelplatser i framtida modeller. Papper II och III analyserar förhållandet mellan trängsel i ankomstgårdenoch avgångsförseningar med hjälp av samma datamängd som i papperI. Enligt tidigare analyser spelar trängsel en viktig roll vid förseningar förrangergodsbangårdar. Trängsel definieras som antalet ankommande tåg föreavgångstid och papper II analyserar detta förhållande som begränsar ankomsteroch avgångar mellan de två rangergodsbangårdar med beaktande av olikatidsperioder före avgång, medan papper III utvecklar analysen genom attdefiniera trängselnivån under en fast tidsperiod före avgångstid inklusive allaankomster och avgångar. Med tanke på datamängden som användes i analysenvisar resultaten att det inte finns något signifikant samband mellan trängselni ankomstgården och tågens förseningar. Det är möjligt att trängsel kanskeinte påverkar tågens avgångsfördröjningar, men det kan påverka vagnarnasavgångsfördröjningar på grund av missad vagnanslutning eller öka vagnenstomgångstid, vilket kan undersökas med vid tillgång av vagnanslutningsdata.Dessutom kan framtida vidareutveckling av definitionen av trängsel som påen detaljerad nivå täcker rangergodsbangårdars alla delar, leda till ytterligareförbättrade analyser.
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Sundqvist, Frej. "Developing Markov chain models for train delay evolution in winter climate". Thesis, Umeå universitet, Institutionen för fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-179526.
Abstract (sommario):
The traffic on Swedish railways is increasing and punctuality is of important matter for both passenger and freight trains. The problem of modeling train delay evolution is complex since conflicts between trains can occur and since a delay can have a wide variety of causes. Swedish railways faces in addition harsh winter climate. Studies of railways in Scandinavia have shown that harsh winter climate decreases the punctuality of trains. This thesis work investigates the possibilities of modeling train delay evolution as continuous time Markov processes and which specific modeling choices are preferable. It also further assesses the impact of a harsh winter climate on the delay evolution. The studied segments are Stockholm - Umeå and Luleå - Kiruna. Both over one winter season. It was found that a change in the time schedule, which in a way redefines the delay, allows for a better fit and better prediction capabilities. It reduced the MSE of the prediction by 50 %. As for the weather variables, four variables were included together with their week long moving averages. Low temperatures were found to increase the risk of a delay (Hazard ratio of 1.10) as well as to decrease the chance of recovering from a delay (Hazard ratio of 0.91). No other significant weather impacts were found.
4
Fakhraei, Roudsari Farzad. "Spatial, temporal and size distribution of freight train time delay in Sweden". Thesis, KTH, Trafik och logistik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-59708.
Abstract (sommario):
Delays and cancelled trains are often described as a problem for companies that transport goods by rail. Lack of reliability of freight trains is seen as a disadvantage compared to other modes. To date there has been limited quantitative information in Sweden about the size and the structure of the problem of trains not arriving in time. In this thesis information for two years, 2008 and 2009 is available that enable us to do the analysis of distribution on a spatial, temporal and seize-frequency scale. Since the spatial and frequency-size distributions describe the vulnerability of a transport network it has potentially important policy implications. In the size-frequency scale, we analyzed different distribution to fit with the arrival delay at the final station and we conclude that, it is not possible to find a distribution for the whole range of observations. However, considering the tail of arrival delays we find that it is exponentially distributed. This implies that the tail makes up the biggest part of total delay time. The 20 % largest delays contribute to about 78% of total delay minutes. In the spatial scale, we defined stations which have the highest value of arrival delay in the whole network and ranked them. We found out that more than 50% of the total arrival delay per year occurs in just 7% of stations. With the help of regression analysis we analyze how delays are propagated in the network. We find that delays at the origin increase arrival delay but that some part of the initial delay is gained at arrival, probably due to large slack in the time tables. Finally, in the temporal scale we analyzed arrival delays in different time scales such as monthly, weekly and daily delays. We expected that the reduction of the total number of trains in 2009 would reduce not only total but also the average arrival delay since there would be more free capacity. The data shows however, that the average delay did not decrease as the number of trains decreased due to the economic contraction in 2009, indicating that capacity might not be as crucial for explaining delays as previously expected.
5
Karthikeyan, Arun Kumar, e Praveen Kumar Mani. "Visual and Analytical Support for Real-time Evaluation of Railway Traffic Re-scheduling Alternatives During Disturbances". Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4299.
Abstract (sommario):
Disturbances in the railway network are frequent and to some extent, inevitable. When this happens, the traffic dispatchers need to re-schedule the train traffic and there is a need for decision support in this process. One purpose of such a decision support system would be to visualize the relevant, alternative re-scheduling solutions and benchmark them based on a set of relevant train traffic attributes which quantify the effects of each solution. Currently, there are two research projects financed by the Swedish Transport Administration (i.e. Trafikverket) which focus on developing decision support to assist the Swedish train traffic managers: The STEG project and the EOT project. Within the STEG project, researchers at Uppsala University in co-operation with Trafikverket are developing a graphical user interface (referred to as the STEG graph). Within the EOT project, researchers at Blekinge Institute of Technology (BTH) are developing fast re-scheduling algorithms to propose to the Swedish train traffic dispatchers a set of relevant re-scheduling alternatives when disturbances occur. However, neither the STEG graph nor the EOT algorithms are at this point designed to evaluate, benchmark and visualize the alternative re-scheduling solutions. The main objective of this work is therefore to identify and analyze different train traffic attributes and how to use the selected relevant ones for benchmarking re-scheduling solutions. This involves enhancing an existing visual tool (EOT GUI) and using this extended version (referred to as the EOT GUI+) to demonstrate and evaluate the benchmarking of different re-scheduling solutions based on the selected train traffic attributes. The train traffic attributes found in the literature (foremost research publications and documents by Trafikverket) were collected and analyzed. A subset of the most commonly used attributes found were then selected and their applicability in benchmarking re-scheduling solutions for the Swedish train traffic system was further analyzed. The formulas for calculating each of the attribute values were either found in the literature and possibly modified, or defined within this thesis project. In order to assess the use of the attributes for benchmark solutions, experiments were conducted using the enhanced visual tool EOT GUI+ and a set of sample solutions for three different disturbance scenarios provided by the EOT project. The tool only performs a benchmark of two solutions at a time (i.e. a pair wise benchmark) and computes the attribute values for the chosen attributes. The literature review and attribute analysis resulted in a first set of ten different attributes to use including e.g. total final delay (with a delay threshold value of 1 and 5 minutes respectively), maximum delay, total accumulated delay, total delay cost, number of delayed trains and robustness. The formulas to compute these attribute values were implemented and applied to the sample solutions in the experiments. The first phase of the experiments showed that in one of the disturbance scenarios, some of the attribute values were in conflict and that none of re-scheduling solution was dominating the others. This observation led to that the set of attributes needed to be narrowed down and internally prioritized. Based on the experimental results and the analysis of what the research community and the main stakeholder (i.e. Trafikverket) consider are the most important attributes in this context, the final set of attributes to use includes average final delay, maximum delay of a single train, total number of delayed trains and robustness. The contribution of this thesis is primarily the review and analysis of what attributes to use when performing a benchmark of re-scheduling solutions in real-time train traffic disturbance management. Furthermore, this thesis also contributes by performing an experimental assessment of how the attributes and their formulas could work in a pair-wise, quantitative benchmark for a set of disturbance scenarios and which issues that may occur due to conflicting objectives and attribute values. Concerning the enhancement of the visual tool and the visualization of the re-scheduling solutions, the experimental evaluation and analysis shows that the tool would not fit directly to the needs of the train dispatchers. This work should therefore only be seen as a starting point for the researchers whom are working with the development of decision support systems in this context. Furthermore, several iterative experiments have been conducted to select the appropriate attributes for benchmarking solutions and suggesting the best re-scheduling solution. During the experiments, we have used a limited set of different problem instances (2+2+7) representing three different types of disturbances. The performance of the enhanced visual tool EOT GUI+ and its functionalities should ideally also be analyzed further and improved by experimenting with a larger number of instances, for other parts of the Swedish railway network and in co-operation with the real users, i.e. the dispatchers.
6
Nilsson, Robert, e Kim Henning. "Predictions of train delays using machine learning". Thesis, KTH, Hälsoinformatik och logistik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230224.
Abstract (sommario):
Train delays occur on a daily basis in the commuter rail of Stockholm. This means that the travellers might become delayed themselves for their particular destination. To find the most accurate method for predicting train delays, the machine learning methods decision tree with and without AdaBoost and neural network were compared with different settings. Neural network achieved the best result when used with 3 layers and 22 neurons in each layer. Its delay predictions had an average error of 122 seconds, compared to the actual delay. It might therefore be the best method for predicting train delays. However the study was very limited in time and more train departure data would need to be collected.Tågförseningar inträffar dagligen i Stockholms pendeltågstrafik. Det orsakar att resenärerna själva kan bli försenade till deras destinationer. För att hitta den mest träffsäkra metoden för att förutspå tågförseningar jämfördes maskininlärningsmetoderna beslutsträd, med och utan AdaBoost, och artificiella neuronnät med olika inställningar. Det artificiella neuronnätet gav det bästa resultatet när det användes med 3 lager och 22 neuroner i varje lager. Dess förseningsförutsägelse hade ett genomsnittligt fel på 122 sekunder jämfört med den verkliga förseningen. Det kan därför vara den bästa metoden för att förutspå tågförseningar. Den här studien hade dock väldigt begränsat med tid och mer information om tågavgångar hade behövts samlas in.
7
Granlöf, Markus. "A study of the effects of winterclimate and atmospheric icing onhigh-speed passenger trains". Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-171868.
Abstract (sommario):
Harsh winter climate causes various problems for both the public andprivate sector in Sweden, especially in the northern part and the railway industryis no exception. This master thesis project covers an investigation of the eects ofthe winter climate and a phenomena called atmospheric icing on the performance ofthe train in a region called the Botnia-Atlantica region. The investigation was donewith data over a short period January-February 2017 with simulated weather datafrom the Weather research and forecast model that was compared with the periodOctober - December 2016. The investigation only included high speed trains.The trains have been analysed based on two dierent performance measurements.The cumulative delay which is the increment in delay over a section and the currentdelay which is the current delay compared to the schedule. Cumulative delaysare investigated with survival analysis and the current delay is investigated with aMulti-state Markov model.The results show that the weather could have an eect on the trains performancewhere the survival analysis detected connection between the weather and cumulativedelays. The Markov model also showed a connection between the weather anddelayed trains including that the presence of atmospheric icing had a negative eecton remaining in a state of non-delay.
8
Chin, Elizabeth D. "Symptom Experience and Treatment Delay during Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Dissertation". eScholarship@UMMS, 2012. https://escholarship.umassmed.edu/gsn_diss/30.
Abstract (sommario):
Chronic obstructive pulmonary disease (COPD) is a major health problem in the United States. Acute exacerbations of COPD are primarily responsible for the physical, psychological and economic burden of this disease. Early identification and treatment of exacerbations is important to improve patient and healthcare outcomes. Little is known about how patients with COPD recognize an impending exacerbation and subsequently decide to seek treatment. The purpose of this qualitative descriptive study was to explore and describe symptom recognition and treatment delay in individuals experiencing an acute exacerbation of chronic obstructive pulmonary disease (COPD). Leventhal’s Common Sense Model of illness representation undergirded this study. Using semi-structured interviews, adults hospitalized with an acute exacerbation of COPD were asked to describe their symptom experience and self care behaviors, including treatment seeking, in the days to weeks prior to hospitalization. Data analysis revealed one main theme: Recognizing, responding and reacting to change, and six subthemes: Something’s coming, Here we go again, Seeking urgent treatment, Riding it out, Not in charge anymore and My last day that richly described the COPD exacerbation experience. The study revealed that patients experience an illness prodrome prior to exacerbation and have a recurrent exacerbation symptom pattern that was self-recognized. Treatment seeking was most influenced by the speed and acuity of exacerbation onset, severity of breathlessness, fears of death, nature of patient-provider relationship and the perception of stigmatization during prior healthcare encounters. These findings are important for the development of interventions to improve patient recognition and management of COPD exacerbations in the future.
9
Newhall, William George. "Wideband Propagation Measurement Results, Simulation Models, and Processing Techniques for a Sliding Correlator Measurement System". Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/35678.
Abstract (sommario):
Radio wave propagation measurements provide a way to accurately and reliably characterize environments to assist in the development and optimization of wireless communication systems. As digital radio systems occupy wider bandwidths and use multipath signal combining to enhance quality of service, knowledge of time dispersion and the multipath structure of radio channels become increasingly important. The wideband measurement system presented herein provides a practical means to precisely measure the delays and strengths of individual multipath components which arrive at a radio receiver.
Presented in this Thesis are fundamental theory, practical implementation, and simulation models for a sliding correlator measurement system. The sliding correlator technique is explained in detail and large-scale measurement survey is presented. Techniques for statistically quantifying the characteristics of propagation using the sliding correlator measurements are presented and compared. The development of simulations of the sliding correlator system is described, and simulation results are used to test conventional and newly developed post-processing algorithms.
This Thesis presents a practical view of the sliding correlator measurement system, but its foundations are rooted in the theoretical results which are explained and derived herein. Propagation researchers and students in the wireless communication field may find this work and the cited references useful for continued study of wideband propagation measurements or for application of the sliding correlator system as a wideband measurement solution.
Master of Science
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Oharek, Aleš. "Zvyšování bezpečnosti a výkonnosti navigace dopravních letadel po trati letu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228554.
Abstract (sommario):
Thesis presents description of the air traffic safety, efficiency, capacity and preferences of navigation equipment. Those aspect are further used to suggestion of future advancement airspace, which occur during almost all phases of the flight.
Libri sul tema "Trait decay":
1
Guides, Hse. State of Decay 2 PS4, Skills, Traits, Gameplay, Multiplayer, Mods, Achievements, Armory, Weapons, Skills, Game Guide Unofficial. Hiddenstuff Entertainment LLC., 2018.
2
Rammah, Mayyasa, Francesca Rochais e Robert G. Kelly. Incorporation of myocardial progenitors at the arterial pole of the heart. A cura di José Maria Pérez-Pomares, Robert G. Kelly, Maurice van den Hoff, José Luis de la Pompa, David Sedmera, Cristina Basso e Deborah Henderson. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198757269.003.0007.
Abstract (sommario):
The arterial pole of the heart is a hotspot for life-threatening forms of congenital heart defects (CHDs). It is formed by progressive addition of myocardium from epithelial progenitor cells in the second heart field (SHF). SHF cells contribute successively to the right ventricle and proximal and distal outflow tract myocardial walls which, after neural crest influx and cardiac septation, give rise to myocardium at the base of the aorta and pulmonary trunk. SHF cells are characterized by continued proliferation and differentiation delay controlled by an array of transcriptional regulators and signalling pathways which define the SHF progenitor cell niche in pharyngeal mesoderm. Failure of normal SHF deployment leads to a shortened outflow tract and failure of ventriculo-arterial alignment, resulting in a spectrum of conotruncal CHD. We discuss the origins of the SHF in cardiopharyngeal mesoderm and focus on the mechanisms driving SHF deployment, summarizing current understanding of critical signalling pathways and transcription factors.
3
Milcu, Marius, Adrian Brate e Alin Sumedrea. Noi directii si perspective ale cercetarii stiintifice in contexte atipice. Editura Universitara, 2020. http://dx.doi.org/10.5682/9786062812171.
Abstract (sommario):
Traim, se pare, o viata mult mai complicata decat ne inchipuiam, cu doar putina vreme in urma. O viata in care certitudinile s-au imputinat dramatic, in care ne indreptam spre orizonturi necunoscute, incerte, nu tocmai aducatoare de liniste. Profesii care pareau definitiv consacrate s-au diluat si tind sa dispara, domenii intregi de activitate s-au bulversat si au devenit extrem de confuze, comunitatile in care traim se disperseaza, zi dupa zi, astfel incat lumea noastra, asa cum o stiam de multa vreme, a fost inlocuita, rapid si brutal, de o realitate in care ne miscam cu mare greutate si care ne solicita, pentru a supravietui, resursele cele mai bune de care dispunem. Vor fi, capacitatile noastre adaptative, suficient de puternice? Flexibilitatea noastra (mentala si comportamentala) ne va permite trecerea facila spre noua realitate post pandemica? Cum anume va arata, aceasta din urma? Care va fi locul nostru in lumea de maine? Iata doar cateva intrebari carora, pe alocuri, eforturile autorilor incearca sa le ofere raspunsuri.
4
Lambert, Heather. Urinary tract infection in infancy and childhood. A cura di Neil Sheerin. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199592548.003.0180_update_001.
Abstract (sommario):
Urinary tract infection (UTI) in childhood is a common problem, which is frequently dismissed as trivial because most children with UTI have a good outcome. However, UTI is an important cause of acute illness in children and causes a considerable burden of ill health on children and families. In addition, UTI may be a marker of an underlying urinary tract abnormality. UTI in a few may cause significant long-term morbidity, renal scarring, hypertension, and renal impairment that may not present until adult life. Predicting which children will go on to have long-term sequelae remains a challenge.The risk of renal scarring is greatest in infants, the very group in whom diagnosis is often overlooked or delayed because clinical features are non-specific. Delay in treatment is associated with an increased risk of scarring in susceptible children. Thus accurate and rapid diagnosis of UTI is essential and requires a very high index of suspicion particularly in the youngest.The role of vesicoureteric reflux in acquired scarring is not fully understood though there is clearly an association, possibly because it is a risk factor for acute pyelonephritis. Scarring when it occurs is in the areas affected by acute pyelonephritis. Higher grades of reflux are associated with a worse outcome.Management and investigation of children with UTI consumes considerable healthcare resources. Limited understanding of the natural history and basic pathophysiology, variations in strategy with time and setting, and lack of evidence on long-term outcomes have resulted in considerable uncertainty. Some propose a minimal approach doing little investigation unless there is clear evidence for it; others favour an approach of continuation of current practice based on clinical experience until further evidence evolves. Some of the themes behind these controversies are explored.
5
Walsh, Bruce, e Michael Lynch. Short-term Changes in the Variance: 1. Changes in the Additive Variance. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198830870.003.0016.
Abstract (sommario):
Selection changes the additive-genetic variance (and hence the response in the mean) by both changing allele frequencies and by generating correlations among alleles at different loci (linkage disequilibrium). Such selection-induced correlations can be generated even between unlinked loci, and (generally) are negative, such that alleles increasing trait values tend to become increasingly negative correlated under direction or stabilizing selection, and positively correlated under disruptive selection. Such changes in the additive-genetic variance from disequilibrium is called the Bulmer effects. For a large number of loci, the amount of change can be predicted from the Bulmer equation, the analog of the breeder's equation, but now for the change in the variance. Upon cessation of selection, any disequilibrium decays away, and the variances revert back to their additive-genic variances (the additive variance in the absence of disequilibrium). Assortative mating also generates such disequilibrium.
6
Pascu, Emilia. Marfuri alimentare si securitatea consumatorului de alimente, editia a II-a. Editura Universitara, 2022. http://dx.doi.org/10.5682/9786062814519.
Abstract (sommario):
ntr-o lume in care produse neconforme ameninta permanent si intr-o societate in care nivelul de trai determina deseori o alimentatie necorespunzatoare, autoarea, in calitate de titlular al cursului de Marfuri alimentare si securitatea consumatorului, predat la Facultatea de Management Turistic si Comercial din cadrul Universitatii Crestine Dimitrie Cantemir Bucuresti, al carei decan este din 2015, atrage atentia asupra celor mai importante aspecte privind produsele alimentare si compozitia acestora. Autoarea, care detine titlul de doctor in economie cu o teza despre produsele contrafacute si securitatea consumatorilor, ofera un instrument utile celor preocupati de calitatea produselor alimentare, atat in scop personal, dar si in calitate de personal angajat in domenii in care alimentele detin un rol important.
7
Medforth, Janet, Linda Ball, Angela Walker, Sue Battersby e Sarah Stables. Introduction. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780198754787.003.0001.
Abstract (sommario):
This chapter comprises a midwifery definition and explains the midwife’s role, focusing on the challenges of a changing population demographic with increasing levels of complexity, ill health, and maternal morbidity. Highlights from the latest MBRRACE (2014) report are reflected as is new evidence of the value of midwifery-led care in all settings. Statutory supervision of midwifery in its current model is unique to UK midwifery and there are proposed changes to the regulatory framework pending in 2017. Meanwhile, current supervision arrangements remain in place until regulations are redrafted. Drug administration information is updated and the latest Human Medicines Regulations (2012) are cited along with the list of midwives exemptions. Independent prescribing is included here to indicate how by undertaking further approved training a midwife could be permitted to prescribe medicines promptly and without delay whilst giving care, e.g. prescription of antibiotics for mastitis, infected perineum, or urinary tract infection.
8
Chiracu, Alina. Adanca mea tristete: Depresia. Editura Universitara, 2022. http://dx.doi.org/10.5682/9786062814892.
Abstract (sommario):
Tristetea face parte din noi, asa cum fac parte bucuria sau mirarea. Uneori ne simtim tristi pentru ca viata nu este asa cum ne-am dorit-o, pentru ca lucrurile se intampla altfel decat ne asteptam. Tristetea exista pentru a ne ajuta sa savuram bucuria prin contrast. Este o stare in care ne lasam sa alunecam sau nu. Depresia este sora mai mare a tristetii. Mai mare si mai imperativa. O sora dependenta care se agata de noi ca un parazit si ne consuma energia. Depresia ne doare, apoi ne amorteste si apoi iar ne doare. Depresia produce o bucla, temporala si spatiala, in care ne cuprinde si ne impresoara. Ne inchide ferestrele si usile si orice alta cale de evadare. Dar exista inca in noi germenii sperantei. Pe aceia nu ni-i poate ucide complet. Nu ne poate anula forta de a supravietui. Depresia este o stare... o stare de adanca scufundare... o stare care ne pune la incercare. Este ca o lectie, grea, dureroasa, dar dupa care invatam ca putem sa traim bine, sa fim multumiti cu ceea ce suntem si ca suntem. Depresia este o tristete nebuna si acaparatoare, dar noi, si mai nebuni, ne desfacem de ea si o privim de sus, o lasam sa se indeparteze si sa dispara cu desavarsire. Putem sa facem asta, avem resursele necesare, trebuie doar sa le gasim in noi.
9
Bonekemper III, Edward H. Grant and Lee. Praeger, 2007. http://dx.doi.org/10.5040/9798400658761.
Abstract (sommario):
Grant and Lee: Victorious American and Vanquished Virginianis a comprehensive, multi-theater, war-long comparison of the commanding general skills of Ulysses S. Grant and Robert E. Lee. Unlike most analyses, Bonekemper clarifies the impact both generals had on the outcome of the Civil War - namely, the assistance that Lee provided to Grant by Lee's excessive casualties in Virginia, the consequent drain of Confederate resources from Grant's battlefronts, and Lee's refusal and delay of reinforcements to the combat areas where Grant was operating. The reader will be left astounded by the level of aggression both generals employed to secure victory for their respective causes, demonstrating that Grant was a national general whose tactics were consistent with achieving Union victory, whereas Lee's own priorities constantly undermined the Confederacy's chances of winning the war. Building on the detailed accounts of both generals' major campaigns and battles, this book provides a detailed comparison of the primary military and personal traits of the two generals. That analysis supports the preface discussion and the chapter-by-chapter conclusions that Grant did what the North needed to do to win the war: be aggressive, eliminate enemy armies, and do so with minimal casualties (154,000), while Lee was too offensive for the undermanned Confederacy, suffered intolerable casualties (209,000), and allowed his obsession with the Commonwealth of Virginia to obscure the broader interests of the Confederacy. In addition, readers will find interest in the 18 clean-cut and lucid battle maps as well as a comprehensive set of appendices that describes the casualties incurred by each army, battle by battle.
10
Lameire, Norbert, Raymond Vanholder e Wim Van Biesen. Clinical approach to the patient with acute kidney injury. A cura di Norbert Lameire. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199592548.003.0222_update_001.
Abstract (sommario):
The prognosis of acute kidney injury (AKI) depends on early diagnosis and therapy. A multitude of causes are classified according to their origin as prerenal, intrinsic (intrarenal), and post-renal.Prerenal AKI means a loss of renal function despite intact nephrons, for example, because of volume depletion and/or hypotension.There is a broad spectrum of intrinsic causes of AKI including acute tubular necrosis (ATN), interstitial nephritis, glomerulonephritis, and vasculitis. Evaluation includes careful review of the patient’s history, physical examination, urinalysis, selected urine chemistries, imaging of the urinary tree, and eventual kidney biopsy. The history should focus on the tempo of loss of function (if known), associated systemic diseases, and symptoms related to the urinary tract (especially those that suggest obstruction). In addition, a review of the medications looking for potentially nephrotoxic drugs is essential. The physical examination is directed towards the identification of findings of a systemic disease and a detailed assessment of the patient’s haemodynamic status. This latter goal may require invasive monitoring, especially in the oliguric patient with conflicting clinical findings, where the physical examination has limited accuracy.Excluding urinary tract obstruction is necessary in all cases and may be established easily by renal ultrasound.Distinction between the two most common causes of AKI (prerenal AKI and ATN) is sometimes difficult, especially because the clinical examination is often misleading in the setting of mild volume depletion or overload. Urinary chemistries, like calculation of the fractional excretion of sodium (FENa), may be used to help in this distinction. In contrast to FENa, the fractional excretion of urea has the advantage of being rather independent of diuretic therapy. Response to fluid repletion is still regarded as the gold standard in the differentiation between prerenal and intrinsic AKI. Return of renal function to baseline or resuming of diuresis within 24 to 72 hours is considered to indicate ‘transient, mostly prerenal AKI’, whereas persistent renal failure usually indicates intrinsic disease. Transient AKI may, however, also occur in short-lived ATN. Furthermore, rapid fluid application is contraindicated in a substantial number of patients, such as those with congestive heart failure.‘Muddy brown’ casts and/or tubular epithelial cell casts in the urine sediment are typically seen in patients with ATN. Their presence is an important tool in the distinction between ATN and prerenal AKI, which is characterized by a normal sediment, or by occasional hyaline casts. There is a possible role for new serum and/or urinary biomarkers in the diagnosis and prognosis of the patient with AKI, including the differential diagnosis between pre-renal AKI and ATN. Further studies are needed before their routine determination can be recommended.When a diagnosis cannot be made with reasonable certainty through this evaluation, renal biopsy should be considered; when intrarenal causes such as crescentic glomerulonephritis or vasculitis are suspected, immediate biopsy to avoid delay in the initiation of therapy is mandatory.
Capitoli di libri sul tema "Trait decay":
1
Odum, Amy L., e Ana A. L. Baumann. "Delay discounting: State and trait variable." In Impulsivity: The behavioral and neurological science of discounting., 39–65. Washington: American Psychological Association, 2010. http://dx.doi.org/10.1037/12069-002.
2
Dawale, Nilesh N., e Sunita Nandgave. "Train Delay Prediction Using Machine Learning". In Algorithms for Intelligent Systems, 663–74. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-4626-6_54.
3
McRae, Leanne. "My State Had a Mining Boom and All I Got Was This Lousy Train-Line". In City Imaging: Regeneration, Renewal and Decay, 29–52. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-7235-9_3.
4
Caimi, Gabrio, Dan Burkolter e Thomas Herrmann. "Finding Delay-Tolerant Train Routings through Stations". In Operations Research Proceedings 2004, 136–43. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/3-540-27679-3_17.
5
Chen, Mo, Tong He, Chengcheng Fu, Xiaowen Wang, Pengfei Sun e Qingyuan Wang. "Study on Train Safety Tracking Operation Under Delay". In Lecture Notes in Electrical Engineering, 891–904. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2259-6_79.
6
Liao, Zhiwen, Yong Qin e Mingming Wang. "Research on Train Operation Adjustment After Initial Delay". In Proceedings of the 5th International Conference on Electrical Engineering and Information Technologies for Rail Transportation (EITRT) 2021, 604–15. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-9909-2_61.
7
Zhang, Yong, Wenqing Li, Shaoquan Ni e Xiaowei Liu. "Research on Train Delay Diagnosis in Train Diagram Based on Big Data Technology". In Advances in Smart Vehicular Technology, Transportation, Communication and Applications, 109–16. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-70730-3_14.
8
Fu, Minglei, Yiluan Zhuang, Maolin He e Zichun Le. "Delay Aware Time Slot Allocation Algorithm in Light-Trail Network". In Internet of Things, 41–48. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-32427-7_6.
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Zhang, Yinggui, Zengru Chen, Min An e Aliyu Mani Umar. "Timetabling, Platforming, and Routing Cooperative Adjustment Method Based on Train Delay". In Lecture Notes in Electrical Engineering, 357–67. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-2914-6_34.
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Ma, Hui, Yong Qin, Guoxing Han, Limin Jia e Tao zhu. "Forecast of Train Delay Propagation Based on Max-Plus Algebra Theory". In Proceedings of the 2015 Chinese Intelligent Systems Conference, 661–72. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-48386-2_67.
Atti di convegni sul tema "Trait decay":
1
Davidovich, Luiz. "Entanglement and Decoherence". In Workshop on Entanglement and Quantum Decoherence. Washington, D.C.: Optica Publishing Group, 2008. http://dx.doi.org/10.1364/weqd.2008.ed1.
Abstract (sommario):
The interaction between entangled multi-particle systems with the environment leads to both local dynamics, associated with single-particle dissipation, diffusion, and decay, and to global dynamics, which may provoke the disappearance of entanglement at a finite time [1-6]. This phenomenon may occur even when single-particle decoherence is asymptotic in time, and constitutes yet another distinct trait of entanglement. It has been recently demonstrated, for two qubits under the action of independent environments, using an all-optical setup [7]. In this talk, some of the peculiarities of the dynamics of two-qubit entangled states undergoing decoherence will be reviewed, new features of the experiment realized at the Federal University of Rio de Janeiro [7] will be described, and the extension of these considerations to multi-particle entangled states will be discussed. Scaling laws for the decay of entanglement and its finite-time extinction in multi-particle systems will be discussed.
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Bao, Jingjing, Ling Xin, Zihan Tang e Xiang Zang. "Solving the Train Delay Problem with the Periodic Train Diagram". In Second International Conference on Transportation Engineering. Reston, VA: American Society of Civil Engineers, 2009. http://dx.doi.org/10.1061/41039(345)61.
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Spanninger, Thomas, Beda Buchel e Francesco Corman. "Probabilistic Predictions of Train Delay Evolution". In 2021 7th International Conference on Models and Technologies for Intelligent Transportation Systems (MT-ITS). IEEE, 2021. http://dx.doi.org/10.1109/mt-its49943.2021.9529333.
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Kurz, Rainer, Sean Garceau, Min Ji e Klaus Brun. "Compressor Speed Decay During Emergency Shutdowns". In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90020.
Abstract (sommario):
Abstract The emergency shutdown of a compressor train is a necessary safety feature. In this event, the power supply (either from a gas turbine or an electric motor) is cut off. The compressor train will continue to spin due to its inertia, but the speed will reduce fast. To avoid damage of the equipment during a shutdown event, compressor surge must to be avoided. In many instances, the dynamic behavior of the compression system is simulated to ensure that the necessary recycle valves are sized, and arranged properly. One of the key problems of dynamic simulation, and a major source of uncertainty in the results, is the correct treatment of the speed decay of the compressor train. The present study provides the background to evaluate the speed decay, and includes data from actual rundown situations. The evaluation shows general trends, that can be used to reduce the simulation uncertainties in dynamic simulations.
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Bradley, Lee C. "Atomic excitation by a pulse train I: two-level atoms". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.tue5.
Abstract (sommario):
An assembly of ground-state two-level atoms with a Maxwellian velocity distribution is considered to be illuminated by a near-resonant train of Gaussian pulses whose pulse separation is of the same order of magnitude as the natural decay time of the upper state by spontaneous emission. The equations of motion of the density matrix, including spontaneous decay, are numerically integrated over the duration of one pulse and are analytically integrated between pulses. In this way, the transition matrix is derived. The time evolution of the system is then followed by successive multiplications of the state vector by the transition matrix. Steady state is attained after a few pulses. Because the pulse train has side bands separated by the pulse repetition frequency, corresponding velocity groups are preferentially excited. The response (defined as the time-average spontaneous emission of the assembly) is found to be a quasi-sinusoidal function of the number of Rabi flops per pulse. Frequency modulation of the pulse train leads to smaller variation in the response and, consequently, to considerably higher response.
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Schlake, Bryan W., Christopher P. L. Barkan e J. Riley Edwards. "Impact of Automated Inspection Technology on Unit Train Performance". In 2010 Joint Rail Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/jrc2010-36258.
Abstract (sommario):
Automated wayside inspection systems have been developed to monitor rolling stock condition and facilitate predictive maintenance strategies. Improving the effectiveness of railcar condition monitoring has the potential for significant cost savings as a result of reduced derailments and in-service failures. This paper presents an economic analysis of the costs associated with train accidents and mainline delay due to defective railcar components. We consider track and equipment damages as well as train delay costs. We use dispatch simulation software to determine the impact of in-service failures on mainline capacity at varying traffic levels. This analysis provides a basis for the comparison of current railcar inspection practices with new integrated practices incorporating automated inspection systems.
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Yang, Jinhua, e Marc Klemenz. "Railway Timetable Optimization Using Non-Proportional Distributed Allowance Arrangement Method". In 2009 Joint Rail Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/jrc2009-63028.
Abstract (sommario):
In order to keep certain level of train punctuality and flexibility of adjustment in practical operation phase, allowance which normally is set proportionally is added to the minimum running and dwell time. This paper develops a new strategy that through changing allowance arrangement to optimize timetable quality by using non-proportional distributed method–curving train path (CTP). With Railsys® as simulation tool, results shows that CTP is quite optimal to decrease delay and delay transfer, to spare more room for train path while the travel time remains constant, and timetable quality is improved to a new balance level.
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Jiang, Xin, Linhan Guo, Sheng Hong e Jian Zhou. "Modelling delay propagation within a train communication network". In 2015 Annual Reliability and Maintainability Symposium (RAMS). IEEE, 2015. http://dx.doi.org/10.1109/rams.2015.7105059.
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Hansen, Ingo A., Rob M. P. Goverde e Dirk J. van der Meer. "Online train delay recognition and running time prediction". In 2010 13th International IEEE Conference on Intelligent Transportation Systems - (ITSC 2010). IEEE, 2010. http://dx.doi.org/10.1109/itsc.2010.5625081.
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Wang, Ren, e Daniel B. Work. "Data Driven Approaches for Passenger Train Delay Estimation". In 2015 IEEE 18th International Conference on Intelligent Transportation Systems - (ITSC 2015). IEEE, 2015. http://dx.doi.org/10.1109/itsc.2015.94.
Rapporti di organizzazioni sul tema "Trait decay":
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Wisniewski, Michael E., Samir Droby, John L. Norelli, Noa Sela e Elena Levin. Genetic and transcriptomic analysis of postharvest decay resistance in Malus sieversii and the characterization of pathogenicity effectors in Penicillium expansum. United States Department of Agriculture, gennaio 2014. http://dx.doi.org/10.32747/2014.7600013.bard.
Abstract (sommario):
Blue mold of apple caused by Penicilliumexpansumis a major postharvest disease. Selection for postharvest disease resistance in breeding programs has been ignored in favor of fruit quality traits such as size, color, taste, etc. The identification of postharvest disease resistance as a heritable trait would represent a significant accomplishment and has not been attempted in apple. Furthermore, insight into the biology of the pathogenicity of P. expansumin apple could provide new approaches to postharvest decay management. Hypothesis: Postharvest resistance of apple to P. expansumcan be mapped to specific genetic loci and significant quantitative-trait-loci (QTLs) can be identified that account for a major portion of the population variance. Susceptibility of apple fruit to P. expansumis dependent on the ability of the pathogen to produce LysM effectors that actively suppress primary and/or secondary resistance mechanisms in the fruit. Objectives: 1) Identify QTL(s) and molecular markers for blue mold resistance in GMAL4593 mapping population (‘Royal Gala’ X MalussieversiiPI613981), 2) Characterize the transcriptome of the host and pathogen (P. expansum) during the infection process 3) Determine the function of LysM genes in pathogenicity of P. expansum. Methods: A phenotypic evaluation of blue mold resistance in the GMAL4593 mapping population, conducted in several different years, will be used for QTL analysis (using MapQTL 6.0) to identify loci associated with blue mold resistance. Molecular markers will be developed for the resistance loci. Transcriptomic analysis by RNA-seq will be used to conduct a time course study of gene expression in resistant and susceptible apple GMAL4593 genotypes in response to P. expansum, as well as fungal responses to both genotypes. Candidate resistance genes identified in the transcriptomic study and or bioinformatic analysis will be positioned in the ‘Golden Delicious’ genome to identify markers that co-locate with the identified QTL(s). A functional analysis of LysM genes on pathogenicity will be conducted by eliminating or reducing the expression of individual effectors by heterologous recombination and silencing technologies. LysMeffector genes will also be expressed in a yeast expression system to study protein function. Expected Results: Identification of postharvest disease resistance QTLs and tightly-linked genetic markers. Increased knowledge of the role of effectors in blue mold pathogenic
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Green, John G., e Francis J. Miller. Examining the Effects of Precision Scheduled Railroading on Intercity Passenger and High-Speed Rail Service. Mineta Transportation Institute, marzo 2022. http://dx.doi.org/10.31979/mti.2022.2016.
Abstract (sommario):
More than just scheduling terminal-to-terminal trips for trains, “Precision Scheduled Railroading” (PSR) creates entire point-to-point trip plans for individual railroad shipments. Since precision execution was first put into practice, the benefits to shipment arrival reliability and to freight railroads’ profitability have been demonstrated by its use in several Class One freight railroads. However, the effects of the PSR operating strategy on passenger railway operations in shared freight/passenger corridors has not been studied in detail. This research examines the effects of PSR railroad operations on passenger railways, including measuring “Host Railroad Minutes of Delay per 10,000 Train-Miles” and “On-Time Performance” of individual passenger railways, both intercity and high-speed.
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Lin, Pei-Sung. Coordinated Pre-Preemption of Traffic Signals to Enhance Railroad Grade Crossing Safety in Urban Areas and Estimation of Train Impacts to Arterial Travel Time Delay. Tampa, FL: University of South Florida, gennaio 2004. http://dx.doi.org/10.5038/cutr-nctr-rr-2014-06.
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Lers, Amnon, Majid R. Foolad e Haya Friedman. genetic basis for postharvest chilling tolerance in tomato fruit. United States Department of Agriculture, gennaio 2014. http://dx.doi.org/10.32747/2014.7600014.bard.
Abstract (sommario):
ABSTRACT Postharvest losses of fresh produce are estimated globally to be around 30%. Reducing these losses is considered a major solution to ensure global food security. Storage at low temperatures is an efficient practice to prolong postharvest performance of crops with minimal negative impact on produce quality or human health and the environment. However, many fresh produce commodities are susceptible to chilling temperatures, and the application of cold storage is limited as it would cause physiological chilling injury (CI) leading to reduced produce quality. Further, the primary CI becomes a preferred site for pathogens leading to decay and massive produce losses. Thus, chilling sensitive crops should be stored at higher minimal temperatures, which curtails their marketing life and in some cases necessitates the use of other storage strategies. Development of new knowledge about the biological basis for chilling tolerance in fruits and vegetables should allow development of both new varieties more tolerant to cold, and more efficient postharvest storage treatments and storage conditions. In order to improve the agricultural performance of modern crop varieties, including tomato, there is great potential in introgression of marker-defined genomic regions from wild species onto the background of elite breeding lines. To exploit this potential for improving tomato fruit chilling tolerance during postharvest storage, we have used in this research a recombinant inbred line (RIL) population derived from a cross between the red-fruited tomato wild species SolanumpimpinellifoliumL. accession LA2093 and an advanced Solanum lycopersicumL. tomato breeding line NCEBR-1, developed in the laboratory of the US co-PI. The original specific objectives were: 1) Screening of RIL population resulting from the cross NCEBR1 X LA2093 for fruit chilling response during postharvest storage and estimation of its heritability; 2) Perform a transcriptopmic and bioinformatics analysis for the two parental lines following exposure to chilling storage. During the course of the project, we learned that we could measure greater differences in chilling responses among specific RILs compared to that observed between the two parental lines, and thus we decided not to perform transcriptomic analysis and instead invest our efforts more on characterization of the RILs. Performing the transcriptomic analysis for several RILs, which significantly differ in their chilling tolerance/sensitivity, at a later stage could result with more significant insights. The RIL population, (172 lines), was used in field experiment in which fruits were examined for chilling sensitivity by determining CI severity. Following the field experiments, including 4 harvest days and CI measurements, two extreme tails of the response distribution, each consisting of 11 RILs exhibiting either high sensitivity or tolerance to chilling stress, were identified and were further examined for chilling response in greenhouse experiments. Across the RILs, we found significant (P < 0.01) correlation between field and greenhouse grown plants in fruit CI. Two groups of 5 RILs, whose fruits exhibited reproducible chilling tolerant/sensitive phenotypes in both field and greenhouse experiments, were selected for further analyses. Numerous genetic, physiological, biochemical and molecular variations were investigated in response to postharvest chilling stress in the selected RILs. We confirmed the differential response of the parental lines of the RIL population to chilling stress, and examined the extent of variation in the RIL population in response to chilling treatment. We determined parameters which would be useful for further characterization of chilling response in the RIL population. These included chlorophyll fluorescence Fv/Fm, water loss, total non-enzymatic potential of antioxidant activity, ascorbate and proline content, and expression of LeCBF1 gene, known to be associated with cold acclimation. These parameters could be used in continuation studies for the identification and genetic mapping of loci contributing to chilling tolerance in this population, and identifying genetic markers associated with chilling tolerance in tomato. Once genetic markers associated with chilling tolerance are identified, the trait could be transferred to different genetic background via marker-assisted selection (MAS) and breeding. The collaborative research established in this program has resulted in new information and insights in this area of research and the collaboration will be continued to obtain further insights into the genetic, molecular biology and physiology of postharvest chilling tolerance in tomato fruit. The US Co-PI, developed the RIL population that was used for screening and measurement of the relevant chilling stress responses and conducted statistical analyses of the data. Because we were not able to grow the RIL population under field conditions in two successive generations, we could not estimate heritability of response to chilling temperatures. However, we plan to continue the research, grow the RIL progeny in the field again, and determine heritability of chilling tolerance in a near future. The IS and US investigators interacted regularly and plan to continue and expand on this study, since combing the expertise of the Co-PI in genetics and breeding with that of the PI in postharvest physiology and molecular biology will have great impact on this line of research, given the significant findings of this one-year feasibility project.
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Schuster, Gadi, e David Stern. Integration of phosphorus and chloroplast mRNA metabolism through regulated ribonucleases. United States Department of Agriculture, agosto 2008. http://dx.doi.org/10.32747/2008.7695859.bard.
Abstract (sommario):
New potential for engineering chloroplasts to express novel traits has stimulated research into relevant techniques and genetic processes, including plastid transformation and gene regulation. This proposal continued our long time BARD-funded collaboration research into mechanisms that influence chloroplast RNA accumulation, and thus gene expression. Previous work on cpRNA catabolism has elucidated a pathway initiated by endonucleolytic cleavage, followed by polyadenylation and exonucleolytic degradation. A major player in this process is the nucleus-encoded exoribonuclease/polymerasepolynucleotidephoshorylase (PNPase). Biochemical characterization of PNPase has revealed a modular structure that controls its RNA synthesis and degradation activities, which in turn are responsive to the phosphate (P) concentration. However, the in vivo roles and regulation of these opposing activities are poorly understood. The objectives of this project were to define how PNPase is controlled by P and nucleotides, using in vitro assays; To make use of both null and site-directed mutations in the PNPgene to study why PNPase appears to be required for photosynthesis; and to analyze plants defective in P sensing for effects on chloroplast gene expression, to address one aspect of how adaptation is integrated throughout the organism. Our new data show that P deprivation reduces cpRNA decay rates in vivo in a PNPasedependent manner, suggesting that PNPase is part of an organismal P limitation response chain that includes the chloroplast. As an essential component of macromolecules, P availability often limits plant growth, and particularly impacts photosynthesis. Although plants have evolved sophisticated scavenging mechanisms these have yet to be exploited, hence P is the most important fertilizer input for crop plants. cpRNA metabolism was found to be regulated by P concentrations through a global sensing pathway in which PNPase is a central player. In addition several additional discoveries were revealed during the course of this research program. The human mitochondria PNPase was explored and a possible role in maintaining mitochondria homeostasis was outlined. As polyadenylation was found to be a common mechanism that is present in almost all organisms, the few examples of organisms that metabolize RNA with no polyadenylation were analyzed and described. Our experiment shaded new insights into how nutrient stress signals affect yield by influencing photosynthesis and other chloroplast processes, suggesting strategies for improving agriculturally-important plants or plants with novel introduced traits. Our studies illuminated the poorly understood linkage of chloroplast gene expression to environmental influences other than light quality and quantity. Finely, our finding significantly advanced the knowledge about polyadenylation of RNA, the evolution of this process and its function in different organisms including bacteria, archaea, chloroplasts, mitochondria and the eukaryotic cell. These new insights into chloroplast gene regulation will ultimately support plant improvement for agriculture
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Raghothama, Kashchandra G., Avner Silber e Avraham Levy. Biotechnology approaches to enhance phosphorus acquisition of tomato plants. United States Department of Agriculture, gennaio 2006. http://dx.doi.org/10.32747/2006.7586546.bard.
Abstract (sommario):
Abstract: Phosphorus is one of the least available macronutrient in the soil. The high affinity phosphate transporters are known to be associated with phosphate acquisition under natural conditions. Due to unique interactions of phosphate with soil particles, up to 80% of the applied phosphates may be fixed forcing the farmers to apply 4 to 5 times the fertilizers necessary for crop production. Efficient uptake and utilization of this essential nutrient is essential for sustainability and profitability of agriculture. Many predictions point to utilization/exhaustion of high quality phosphate rocks within this century. This calls for efforts to improve the ability of plants to acquire and utilize limiting sources of phosphate in the rhizosphere. Two important molecular and biochemical components associated with phosphate efficiency are phosphate transporters and phosphatases. This research project is aimed at defining molecular determinants of phosphate acquisition and utilization in addition to generating phosphate uptake efficient plants. The main objectives of the project were; Creation and analysis of transgenic tomato plants over-expressing phosphatases and transporters Characterization of the recently identified members (LePT3 and LePT4) of the Pi transporter family Generate molecular tools to study genetic responses of plants to Pi deficiency During the project period we have successfully identified and characterized a novel phosphate transporter associated with mycorrhizal symbiosis. The expression of this transporter increases with mycorrhizal symbiosis. A thorough characterization of mutant tomato lacking the expression of this gene revealed the biological significance of LePT3 and another novel gene LePT4. In addition we have isolated and characterized several phosphate starvation induced genes from tomato using a combination of differential and subtractive mRNA hybridization techniques. One of the genes, LePS2 belongs to the family of phospho-protein phosphatase. The functionality of the recombinant protein was determined using synthetic phosphor-peptides. Over expression of this gene in tomato resulted in significant changes in growth, delay in flowering and senescence. It is anticipated that phospho-protein phosphatase may have regulatory role in phosphate deficiency responses of plants. In addition a novel phosphate starvation induced glycerol 3-phosphate permease gene family was also characterized. Two doctoral research students are continuing the characterization and functional analysis of these genes. Over expression of high affinity phosphate transporters in tobacco showed increased phosphate content under hydroponic conditions. There is growing evidence suggesting that high affinity phosphate transporters are crucial for phosphate acquisition even under phosphate sufficiency conditions. This project has helped train several postdoctoral fellows and graduate students. Further analysis of transgenic plants expressing phosphatases and transporters will not only reveal the biological function of the targeted genes but also result in phosphate uptake and utilization efficient plants.