Arraias da família Potamotrygonidae (Chondrichthyes: Myliobatoidei) são elasmobrânquios endêmicos dos sistemas fluviais da região Neotropical. Nestes hospedeiros residem uma diversa fauna parasitária que inclui vários gêneros de cestóideos. Tanto as arraias como seus cestóideos são derivados de ancestrais marinhos. A taxonomia e sistemática do sistema hospedeiro/parasita, no entanto, é pouco conhecida. Neste contexto, este estudo documenta, pela primeira vez a diversidade molecular das linhagens de Potamotrygonocestus empregando a otimização direta do genes 28S rDNA, ITS1 rDNA, Calmodulina e Citocromo Oxidase I. Objetiva-se avaliar o posicionamento filogenético de seus membros dentro de uma análise cladística. Os resultados corroboram a monofilia do gênero Potamotrygonocestus e recuperaram dois clados principais que correspondem a agrupamentos morfologicamente diagnosticados com base na morfologia do gancho. A hipótese filogenética apresentou indícios que P. chaoi e P. marajoara são sinônimos júnior de P. travassosi, e que P. orinoconoensis é uma espécie válida. Adicionalmente, os resultados indicam a existência de 14 novas linhagens que podem ser elevadas ao nível de espécie. Os membros Potamotrygonocestus revelaram ser mais especialistas aos seus hospedeiros do que se acreditava e, em relação à biogeografia, a hipótese filogenética apresentou padrões biogeográficos semelhantes a diversos membros da ictiofauna neotropical. A ampliação da representatividade biogeográfica bem como a inclusão de dados moleculares à sistemática do gênero possibilitou reconhecer padrões de distribuição e de infestação que antes eram desconhecidos. Esse refinamento pode contribuir de forma interessante para os outros gêneros parasitas de potamotrigonídeos / Stingrays of the Potamotrygonidae family (Chondrichthyes: Myliobatoidei) are endemic elasmobranchs of river systems in the Neotropics. In these hosts a reside diverse fauna of parasite which includes many genera of tapeworms (Cestoda). Both stingrays and their cestodes are derived from marine ancestors. However, the taxonomy and systematics of this host/parasite system is poorly known. This study documents, for the first time, the molecular diversity of Potamotrygonocestus lineages by employing the direct optimization of 28S rDNA, ITS1 rDNA, Calmodulin and Cytochrome Oxidase I genes. The goal of this study is to understand the phylogenetic position of its members within a cladistic analysis. The results support the monophyly of the genus Potamotrygonocestus and recovered two main clades morphologically diagnosed based on hook morphology hook. The phylogenetic hypothesis presented supports the contention that P. chaoi and P. marajoara are junior synonyms of P. travassosi, and P. orinoconoensis should be considered a valid specie. Additionally, the results suggest that there are 14 new lineages that can be raised to the level of species. Members of Potamotrygonocestus proved to be more host specific than previously thought and, in relation to its biogeography, the phylogenetic hypothesis presented mirrors similar patterns of area association reported for many members of the Neotropical ichthyofauna. The expansion of biogeographical representativeness and inclusion of the molecular data in systematics of the genus allowed the recognition of distribution and infestation patterns that were previously unknown. This refinement could be interesting for other potamotrigonids genus parasites

Arraias da família Potamotrygonidae (Chondrichthyes: Myliobatoidei) são elasmobrânquios endêmicos dos sistemas fluviais da região Neotropical. Nestes hospedeiros residem uma diversa fauna parasitária que inclui vários gêneros de cestóideos. Tanto as arraias como seus cestóideos são derivados de ancestrais marinhos. A taxonomia e sistemática do sistema hospedeiro/parasita, no entanto, é pouco conhecida. Neste contexto, este estudo documenta, pela primeira vez a diversidade molecular das linhagens de Potamotrygonocestus empregando a otimização direta do genes 28S rDNA, ITS1 rDNA, Calmodulina e Citocromo Oxidase I. Objetiva-se avaliar o posicionamento filogenético de seus membros dentro de uma análise cladística. Os resultados corroboram a monofilia do gênero Potamotrygonocestus e recuperaram dois clados principais que correspondem a agrupamentos morfologicamente diagnosticados com base na morfologia do gancho. A hipótese filogenética apresentou indícios que P. chaoi e P. marajoara são sinônimos júnior de P. travassosi, e que P. orinoconoensis é uma espécie válida. Adicionalmente, os resultados indicam a existência de 14 novas linhagens que podem ser elevadas ao nível de espécie. Os membros Potamotrygonocestus revelaram ser mais especialistas aos seus hospedeiros do que se acreditava e, em relação à biogeografia, a hipótese filogenética apresentou padrões biogeográficos semelhantes a diversos membros da ictiofauna neotropical. A ampliação da representatividade biogeográfica bem como a inclusão de dados moleculares à sistemática do gênero possibilitou reconhecer padrões de distribuição e de infestação que antes eram desconhecidos. Esse refinamento pode contribuir de forma interessante para os outros gêneros parasitas de potamotrigonídeos / Stingrays of the Potamotrygonidae family (Chondrichthyes: Myliobatoidei) are endemic elasmobranchs of river systems in the Neotropics. In these hosts a reside diverse fauna of parasite which includes many genera of tapeworms (Cestoda). Both stingrays and their cestodes are derived from marine ancestors. However, the taxonomy and systematics of this host/parasite system is poorly known. This study documents, for the first time, the molecular diversity of Potamotrygonocestus lineages by employing the direct optimization of 28S rDNA, ITS1 rDNA, Calmodulin and Cytochrome Oxidase I genes. The goal of this study is to understand the phylogenetic position of its members within a cladistic analysis. The results support the monophyly of the genus Potamotrygonocestus and recovered two main clades morphologically diagnosed based on hook morphology hook. The phylogenetic hypothesis presented supports the contention that P. chaoi and P. marajoara are junior synonyms of P. travassosi, and P. orinoconoensis should be considered a valid specie. Additionally, the results suggest that there are 14 new lineages that can be raised to the level of species. Members of Potamotrygonocestus proved to be more host specific than previously thought and, in relation to its biogeography, the phylogenetic hypothesis presented mirrors similar patterns of area association reported for many members of the Neotropical ichthyofauna. The expansion of biogeographical representativeness and inclusion of the molecular data in systematics of the genus allowed the recognition of distribution and infestation patterns that were previously unknown. This refinement could be interesting for other potamotrigonids genus parasites

<div>In recent decades the revolutionary possibilities of low-thrust electric propulsion have been demonstrated by the success of missions such as Dawn and Hayabusa 1 and 2. The efficiency of low-thrust engines reduces the propellant mass required to achieve mission objectives and this benefit is frequently worth the additional time of flight incurred, particularly for robotic spacecraft. However, low-thrust trajectory design poses a challenging optimal control problem. At each instant in time, spacecraft control parameters that minimize an objective, typically propellant consumption or time of flight, must be determined. The characteristics of low-thrust optimal solutions are often unintuitive, making it difficult to develop an <i>a priori</i> estimate for the state and control history of a spacecraft that can be used to initialize an optimization algorithm. This investigation seeks to develop a low-thrust trajectory design framework to address this challenge by combining the existing techniques of orbit chaining and direct collocation. Together, these two methods offer a novel approach for low-thrust trajectory design that is intuitive, flexible, and robust.</div><div><br></div><div>This investigation presents a framework for the construction of orbit chains and the convergence of these initial guesses to optimal low-thrust solutions via direct collocation. The general procedure is first demonstrated with simple trajectory design problems which show how dynamical structures, such as periodic orbits and invariant manifolds, are employed to assemble orbits chains. Following this, two practical mission design problems demonstrate the applicability of this framework to real world scenarios. An orbit chain and direct collocation approach is utilized to develop low-thrust transfers for the planned Gateway spacecraft between a variety of lunar and libration point orbits (LPOs). Additionally, the proposed framework is applied to create a systematic method for the construction of transfers for the Lunar IceCube spacecraft from deployment to insertion upon its destination orbit near the Moon. Three and four-body dynamical models are leveraged for preliminary trajectory design in the first and second mission design applications, respectively, before transfers are transitioned to an ephemeris model for validation. Together, these realistic sample applications, along with the early examples, demonstrate that orbit chaining and direct collocation constitute an intuitive, flexible, and robust framework for low-thrust trajectory design. </div>

Ephemeroptera (mayflies) is a monophyletic group of semi-aquatic pterygote insects, comprising 3083 species, 376 genera, and 37 described families and are present on all continents, excluding Antarctica, being associated with freshwater and brackish water habitats. The order is unique among pterygote insects in possessing functional wings at the penultimate molt (subimago stage), prior to the full development of genitalia; in all other insects the presence of functional wings occurs only after the final molt. The purpose of this dissertation is to use molecular and morphological data, in order to investigate the position of the order Ephemeroptera among other insect orders, the higher-level relationships among the major lineages of mayflies, and a detailed analysis of the family Ephemerellidae. Ephemeroptera has been considered by many to be sister to Odonata + Neoptera although alternate hypotheses have been suggested. Data from three molecular loci ambiguously resolve basal pterygote relationships, however, total evidence analysis (combined molecular and morphological data) strongly supports the position of mayflies as sister to all other extant pterygotes. These results and methodologies were recently criticized, and, therefore, the response to the author is included following the manuscript. The phylogenetic relationships among mayfly families is debatable and in some groups unknown. Prior studies have produced phylogenies based on morphological characters mixed with intuition. The first molecular phylogeny for the Order Ephemeroptera is presented. The analyses include 31 of the 37 families, representing ~24% of the genera. The suborders Furcatergalia and Carapacea are supported as monophyletic while Setisura and Pisciforma are not supported as monophyletic. The evolution of the wings, mandibular tusks, burrowing lifestyle, and fishlike body are investigated. Topological sensitivity analysis is used as a tool to examine patterns concerning the stability of relationships across a parameter landscape, providing additional information that may not have been acquired otherwise. The Pannote family Ephemerellidae is comprised of 16 genera and over 300 species and is distinguished from other mayfly families by the absence of the second pair of abdominal gills. The position of Ephemerellidae relative to other closely related pannote mayflies is unclear as are the relationships of the genera within the family. The combined molecular and morphological analyses resulted in a monophyletic Ephemerellidae as sister to the other ephemerelloid families. The subfamily Ephemerellidae was supported as monophyletic, while Timpanoginae had conflicting results.

No description available.