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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
291

Contents and forms of potentially toxic elements in reclaimed dumpsite soils after brown coal mining in Northern Bohemia

Vasilkova, Anna January 2015 (has links)
It is an ordinary practice to cover the areas after brown-coal mining with natural topsoil cover (topsoiling). Topsoiling is removal one topsoil from agricultural land, forest or area with vegetation and excavating to another place with poor organic matter content or in our case the brown-coal mining dumpsite. Advantages of topsoiling include higher organic matter and greater available water-holding capacity and nutrient content. Content of potentially toxic elements is very low. Ammonia nitrate (NH4NO3) extraction, BCR sequential analysis and aqua regia determination were applied in this study to prove that the proportion of bioavailable forms of PTE in reclaimed soils is also low. Amounts of potentially toxic elements were compared between different types of reclamation: an agricultural shown higher value for Pb and Cd, forestry has only one contaminant -- Cd. The research shows that toxicity of soil is low and has no dangerous influence for agricultural application.
292

Lignin based adhesives for particleboard production

Özmen, Nilgül January 2000 (has links)
The purpose of this study was to utilise lignin as a partial substitute for phenol in PF resins. To achieve this, initially brown rot lignin was produced by a bioconversion technique. During the course of the study, it became clear that the production of brown rot lignin had a limited success. Since brown rot lignin could not be obtained in sufficient quantity and purity by a bioconversion method, other alternative lignin production methods, as well as commercially available lignin, were chosen; namely production of lignin from black liquor and Alcell® (organosolv) lignin. Before performing production of resin formulations, the lignin sources were characterised in terms of reactivity and physical properties of lignins. Both lignins had a similar reactivity, but organosolv lignin was found to be more pure, with a low ash content. Since isolation of lignin from black liquor in laboratory conditions is more complex and requires more time, it was decided to use organosolv lignin for subsequent production of lignin-based reSIns. The lignin was introduced to the resin in two different ways. The first method was the replacing of a certain percentage of phenol with lignin (as supplied) directly into resins. In the second method, lignin was modified prior to resin manufacture by phenolation. Different degrees of phenol substitution (from 5% to 60%) were tried for the production of lignin-based resins. Bond qualities of lignin-phenol-formaldehyde (LPF) , phenolated-ligninformaldehyde, commercial phenol-formaldehyde (PF _com) and laboratory made phenol-formaldehyde (PF _made) resins were assessed by using an Automatic Bonding Evaluation System (ABES), prior to production of particleboards, in order to eliminate some of the poor quality resins. The effect of press temperature and time on bond strength appeared to be highly significant, as the lignin substitution levels increased. Up to 30% phenol substitution was achieved without sacrificing bond strength. The bond strength values of phenolated-lignin-formaldehyde resins were similar to commercial phenol-formaldehyde and laboratory made phenolformaldehyde resins, but better than the LPF resins. It was apparent that resins containing a high level of lignin substitution gave the poorest bond strength values. From these results, some of the resins were eliminated, prior to particleboard production. In order to evaluate the quality of lignin-based resins, particleboards were produced and mechanical and physical tests performed. Effect of press platen temperature (140°C, 160°C, 180°C) and press cycle time (5 min, 8 min, IS min) on the mechanical properties of particleboard, produced by using lignin-based resins, were investigated. It was found that particleboards bonded with up to 30% lignin content resins gave similar mechanical and physical properties to commercial phenolformaldehyde resin, as long as a sufficient heating regime and time were applied.
293

Exoplanet Meteorology: Characterizing the Atmospheres of Directly Imaged Sub-Stellar Objects

January 2017 (has links)
abstract: The field of exoplanet science has matured over the past two decades with over 3500 confirmed exoplanets. However, many fundamental questions regarding the composition, and formation mechanism remain unanswered. Atmospheres are a window into the properties of a planet, and spectroscopic studies can help resolve many of these questions. For the first part of my dissertation, I participated in two studies of the atmospheres of brown dwarfs to search for weather variations. To understand the evolution of weather on brown dwarfs we conducted a multi-epoch study monitoring four cool brown dwarfs to search for photometric variability. These cool brown dwarfs are predicted to have salt and sulfide clouds condensing in their upper atmosphere and we detected one high amplitude variable. Combining observations for all T5 and later brown dwarfs we note a possible correlation between variability and cloud opacity. For the second half of my thesis, I focused on characterizing the atmospheres of directly imaged exoplanets. In the first study Hubble Space Telescope data on HR8799, in wavelengths unobservable from the ground, provide constraints on the presence of clouds in the outer planets. Next, I present research done in collaboration with the Gemini Planet Imager Exoplanet Survey (GPIES) team including an exploration of the instrument contrast against environmental parameters, and an examination of the environment of the planet in the HD 106906 system. By analyzing archival HST data and examining the near-infrared colors of HD 106906b, we conclude that the companion shows weak evidence of a circumplanetary dust disk or cloud. Finally, I measure the properties of the low mass directly imaged planet 51 Eridani b. We combined published J, H spectra with updated LP photometry, new K1, K2 spectra, and MS photometry. The new data confirms that the planet has redder than similar spectral type objects, which might be due to the planet still transitioning from to L-to-T. Model atmospheres indicate a cooler effective temperature best fit by a patchy cloud atmosphere making 51 Eri b an excellent candidate for future variability studies with the James Webb Space Telescope. / Dissertation/Thesis / Doctoral Dissertation Astrophysics 2017
294

De-Escalation in Police-Citizen Encounters: A Mixed Methods Study of a Misunderstood Policing Strategy

January 2017 (has links)
abstract: There is demand for police reform in the United States to reduce use of force and bias, and to improve police-citizen relationships. Many believe de-escalation should be a more central feature of police training and practice. It is suggested that improving officers’ communication and conflict resolution skills will temper police-citizen interactions and reduce police use of force, and that such a change will improve citizen trust in the police. To date, however, de-escalation training has not spread widely across agencies, and de-escalation as a strategy has not been studied. Without an evidence-based understanding of these concepts, de-escalation training will proceed blindly, if at all. Accordingly, this dissertation represents one of the first empirical studies of de-escalation in police work. The author completed this study as an embedded researcher in the Spokane (WA) Police Department, and it proceeds in two parts. Part 1 was exploratory and qualitative, consisting of in-depth interviews (N=8) and a focus group (N=1) with eight highly skilled police de-escalators. These officers were nominated by peers as the best among them at de-escalating difficult encounters with citizens. The results in Part 1 explore officers’ perceptions of de-escalation and offer a definition of de-escalation as well as a description of de-escalation tactics. In Part 2, the author systematically observed the concepts developed in part 1 during 35 ride-alongs with 29 police officers, including the peer nominated officers (N=131 police-citizen encounters). This phase of the research investigated whether characteristics of officers, citizens, and situations are associated with de-escalation use, and de-escalation effectiveness. Implications from these findings are drawn for police practice, theory, and research methods. This dissertation is a launching point for empirical research on de-escalation in police work. / Dissertation/Thesis / Doctoral Dissertation Criminology and Criminal Justice 2017
295

Caracterização morfológica, citogenética e molecular de Mazama gouazoubira () a partir de um topótipo atual / Morphologic, citogenetics and molecular characterization of Mazama gouazoubira (Artiodactyla, Cervidae) from a current topotype

Borges, Carolina Heloisa de Souza [UNESP] 28 August 2017 (has links)
Submitted by Carolina Heloisa de Souza Borges null (carolhsborges@gmail.com) on 2017-09-28T18:45:34Z No. of bitstreams: 1 dissertacao_Carolina_Borges.pdf: 16277523 bytes, checksum: 32a1ce727f92fda87f7269eb6cc433c5 (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-09-29T17:33:47Z (GMT) No. of bitstreams: 1 borges_chs_me_jabo.pdf: 16277523 bytes, checksum: 32a1ce727f92fda87f7269eb6cc433c5 (MD5) / Made available in DSpace on 2017-09-29T17:33:47Z (GMT). No. of bitstreams: 1 borges_chs_me_jabo.pdf: 16277523 bytes, checksum: 32a1ce727f92fda87f7269eb6cc433c5 (MD5) Previous issue date: 2017-08-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O gênero Mazama é circundado de incertezas taxônomicas devido à sua alta diversidade cariotípica inter e intra-específica, origem polifilética e convergência morfológica. O veado-catingueiro é a espécie com a maior distribuição geográfica do gênero, ocorre no Brasil (com exceção da Amazônia), Paraguai, Uruguai, Bolívia e norte da Argentina, e, por causa desta abrangência, aliada ao fato de que apresenta alta variabilidade genética, morfológica e alta frequência de polimorfismos cromossômicos, ainda restam dúvidas sobre sua taxonomia com respeito ao número de subespécies existentes e o possível desdobramento destas em espécies. Por isso, o objetivo deste trabalho foi propor um neótipo para a espécie, através da caracterização de um espécime coletado na localidade tipo (topótipo), e assim auxiliar no esclarecimento da taxonomia de Mazama gouazoubira. O topótipo foi caracterizado por técnicas de morfologia tradicional (medidas cranianas e do pós-crânio, coloração da pelagem, biometria corporal), por análises citogenéticas (banda C, banda G, coloração Ag-RON, coloração convencional Giemsa) e moleculares (análises filogenéticas de genes mitocondriais). Pesquisas feitas em museus internacionais confirmam que o holótipo da espécie não existe, cumprindo requisito necessário para a proposta de neotipificação. O topótipo corroborou com os padrões morfológicos, citogenéticos e moleculares já descritos para o veado-catingueiro e por meio das análises comparativas com outros indivíduos da espécie e outros táxons do gênero, ficou claro que pertence à M. gouazoubira, permitindo a proposta de um neótipo para o táxon. / The genus Mazama is surrounded by taxonomic uncertainties due to its polyphyletic origin, high inter and intra-specific karyotype diversity and morphological convergence. The brown brocket deer is the species with the highest geographic distribution of the group due to its high ecological plasticity and because of this range, ally to the fact that presents high morfological and genetic divergence and high frequency of chromosomal polymorphisms, there are still doubts about the number of subspecies existing and the unfolding of these in species. Therefore, the objective of this work was to propose a neotype for M. gouazoubira through a characterization of a specimen collected in the type locality (topotype), and in this way, help to clarify the taxonomy of Mazama gouazoubira. The topotype was characterized by traditional morphological techniques (cranial measurements, skin color and body biometry), as well as by cytogenetic (C band, G band, Ag-NOR staining, conventional Giemsa staining) and molecular analyzes (phylogenetic analyzes of mitochondrial genes). After an extensive research in scientific collections, the results confirm the holotype does not exists, filling a necessary prerequisit for neotypification. The topotype corroborates the morphological, cytogenetic and molecular patterns already described in the literature for the brown brocket deer and through comparative analysys with other specimens and other taxons of the genus it is clear that the topotype belongs to M. gouazoubira, allowing the proposal of a neotype for the taxon.
296

Protocolos de superovulação em veado-catingueiro (Mazama gouazoubira) /

Zanetti, Eveline dos Santos. January 2009 (has links)
Orientador: José Maurício Barbanti Duarte / Banca: Pietro Sampaio Baruselli / Banca: Marcelo Alcindo de Barros Vaz Guimarães / Banca: Ciro Moraes Barros / Banca: Paulo Henrique Franceschini / Resumo: O conhecimento das técnicas de reprodução assistida nas espécies selvagens pode ser importante para futuros programas de conservação in situ e ex situ. Nosso objetivo foi estabelecer um protocolo de superovulação para o veado-catingueiro (Mazama gouazoubira). Para tanto, foram realizados dois experimentos: (1) No ano de 2007, seis fêmeas da espécie M. gouazoubira receberam um dispositivo intravaginal de progesterona (CIDR®) por 8 dias seguido por uma aplicação i.m. de 0,5mg de BE no momento da inserção (D-8) e de 265μg de cloprostenol (PGF2α) no momento da retirada (D0). Posteriormente foram divididas em três grupos (n=2): no primeiro os animais receberam 600UI de eCG (Tratamento A), no segundo 300UI de eCG (Tratamento B) e no terceiro 250UI de FSH+PVP. (Tratamento C), todos administrados no dia 4 (D-4). O segundo experimento (2) foi desenvolvido no ano de 2009 e utilizou outras seis fêmeas da mesma espécie, divididas em dois grupos (n=3): o primeiro recebeu CIDR® por 8 dias, seguido por uma aplicação i.m. de 0,25mg de BE no D-8, 700UI eCG no D-4 e 265μg PGF2α no D0 (Tratamento D) e o segundo recebeu CIDR® por 7,5 dias seguido por uma aplicação i.m. de 0,25mg de BE no D-7,5; 130mg de FSH em oito doses iguais (iniciando em D-3 e finalizando em D-0,5) e 265μg de PGF2α no D0 (Tratamento E). Em cada experimento os tratamentos foram delineados no esquema "cross-over", com um intervalo de 44 dias após a remoção do CIDR®. Todas as fêmeas receberam uma aplicação i.m. de PGF2α 14 dias após a retirada do CIDR®. Um macho fértil foi utilizado para a detecção do estro e fertilização. A eficácia dos Tratamentos foi avaliada pelo comportamento reprodutivo, contagem de CLs e folículos (maiores que 3mm) e colheita de embriões por laparoscopia, sete dias após a primeira cópula. No Experimento 1, ainda... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Knowledge of assisted reproduction techniques for wild animals is useful for future in situ and ex situ conservation programs. The present study aimed to establish a superovulation protocol for brown brocket deer (Mazama gouazoubira) by evaluating the ovulation rate, the presence of functional corpora lutea (CL), the number of embryos and their development stages after superovulation using different treatments. For this, two experiments were realized: (1) in 2007, six female Mazama gouazoubira received an intravaginal device (CIDR) for 8 days, followed by 0.5mg i.m. injection of OB at the time of insertion (D-8) and 265μg of cloprostenol (PGF2α) at the time of removal (D0). Next, the hinds were divided into 3 groups (n=2): group 1 received an i.m. injection of 600IU eCG (Treatment A), group 2 300IU of eCG (Treatment B) and group 3 250IU of FSH+PVP (Treatment C), all on D4 (D-4). The second Experiment (2) was developed in 2009 and also used six hinds from the same species divided into 2 groups (n=3): the first received CIDR for 8 days, followed by 0.25mg i.m. injection of OB on D-8, 700IU of eCG on D-4 and 265μg of PGF2α on D0 (Treatment D) and the second received CIDR for 7.5 days followed by 0.25mg i.m. injection of OB on D-7.5, 130mg of FSH divided into eight equal doses [beginning on D-3 and ending D-0.5] and 265μg of PGF2α on D0 (Treatment E). In each experiment, the treatments were „crossed over‟ with 44 day intervals after CIDR removal. All the hinds received an i.m. injection of PGF2α 14 days after CIDR® removal. A fertile male was used for estrus detection and fertilization. Treatment efficacy was evaluated by reproductive behavior, observation of CL, unruptured follicles (over 3mm) and embryo collection via laparoscopy 7 days after the first copulation. In Experiment 1, feces were collected... (Complete abstract click electronic access below) / Doutor
297

Reação de genótipos de tangerinas a Alternaria alternata e Elsinoe fawcettii: resistência, suscetibilidade e acúmulo de metabólitos /

Souza, Marcelo Claro de. January 2009 (has links)
Resumo: Este trabalho teve por objetivos: (i) selecionar genótipos de tangerinas resistentes a infecção por Alternaria alternata, e estabelecer relações entre níveis de severidade da doença entre folhas e frutos, (ii) avaliar a contribuição de metabólitos na resistência de folhas maduras de tangerinas a A. alternata, (iii) selecionar genótipos de tangerina resistentes a infecção por Elsinoe fawcettii. Para tais experimentos foram utilizados 22 genótipos de tangerina pertencentes ao banco de germoplasma da Estação experimental de Citricultura de Bebedouro, Bebedouro-SP. (i) Dentre os materiais genéticos resistentes, foram constatados quatro genótipos de clementinas (Citrus clementina), seis mandarinas, sendo duas pertencentes a C. reticulata, duas a C. tangerina, uma a C. deliciosa e uma a C. nobilis; um tangelo (C. tangerina x C. paradisi); dois híbridos de mandarinas, sendo um resultante do cruzamento entre C. nobilis x C. deliciosa, e o outro de C. clementina x C. reticulata; um híbrido de tangor (C. clementina x C. sinensis) e dois híbridos de satsumas (C. unshiu x C. deliciosa.). Também foi constatado indícios de relação entre severidade de doença em folhas jovens destacadas e incidência natural de doença em frutos. (ii) Ao final dos experimentos, não foi observado influência desses metabólitos na defesa das folhas maduras de tangerina a MMA. (iii) Dente os genótipos avaliados, foram observados 10 materiais genéticos resistentes a verrugose. Dentre estes materiais, observou-se que os genótipos Commune, Caffin, Bruno, Burgess, Peau Lisse, Zanzibar, Beuty of Glen Retreat, Rode King e Encore também se apresentaram resistentes a MMA. Estes materiais são promissores para o cultivo de tangerinas em áreas de ocorrência destas doenças, e poderão contribuir com futuros trabalhos de melhoramento genético para resistência a MMA e verrugose. / Abstract: The aims of this work were: (i) select tangerine genotypes resistant to Alternaria alternata infection and classify relative degrees of disease severity among leaves and fruits, in order to ultimately control the pathogen; (ii) evaluate metabolites contribuition on mature leaves of tangerines to A. alternata; (iii) select tangerine genotypes resistant to Elsinoe fawcettii. For such experiments 22 tangerines genotypes from germoplasm bank at Estação experimental de Citricultura de Bebedouro, Bebedouro-SP were used. (i) Among the resistant genetic materials, four clementines genotypes (Citrus clementina), six mandarines, being two of C. reticulata, two C. tangerina, one C. deliciosa and one C. nobilis; one tangelo (C. tangerina x C. paradisi); two mandarines hybrids, being one resulted between C. nobilis x C. deliciosa crossing, and other at C. clementina x C. reticulata; one tangor hybrid (C. clementina x C. sinensis) and two satsumas hybrids (C. unshiu x C. deliciosa) were found. A consistent relationship was noted among level of susceptibility in leaves (as evaluated following either natural infection or artificial inoculation), severity and susceptibility of fruit, suggesting a new methodology for diagnosis, identification and selection of Citrus spp. varieties resistant to A. alternata. (ii) At the end of experiments, it was not found any relationship between the presence of these metabolites and resistance to MMA on tangerines mature leaves. (iii) Among the genotypes evaluated, 10 genetic materials resistant to scab were observed. Finally, Commune, Caffin, Bruno, Burgess, Peau Lisse, Zanzibar, Beuty of Glen Retreat, Rode King and Encore cultivars, being resistant to A. alternata and also to E. fawcettii, exhibited good agronomic characteristics and, consequently, show a promising economic exploration. / Orientador: Antonio de Goes / Coorientador: Eduardo Sanches Stuchi / Banca: Antonio Baldo Geraldo Martins / Banca: Sérgio Florentino Pascholati / Mestre
298

The Prototypical Young L/T-Transition Dwarf HD 203030B Likely Has Planetary Mass

Miles-Páez, Paulo A., Metchev, Stanimir, Luhman, Kevin L., Marengo, Massimo, Hulsebus, Alan 29 November 2017 (has links)
Upon its discovery in 2006, the young L7.5 companion to the solar analog HD 203030 was found to be approximate to 200 K cooler than older late-L dwarfs, which is quite unusual. HD. 203030B offered the first clear indication that the effective temperature at the L-to-T spectral type transition depends on surface gravity: now a well-known characteristic of low-gravity ultra-cool dwarfs. An initial age analysis of the G8V primary star indicated that the system was 130-400 Myr old, and so the companion would be between 12 and 31 M-Jup. Using moderate-resolution near-infrared spectra of HD. 203030B, we now find features of very low gravity comparable to those of 10-150 Myr old L7-L8 dwarfs. We also obtained more accurate near-infrared and Spitzer/IRAC photometry, and we find a (J - K) MKO color of 2.56 +/- 0.13 mag-comparable to those observed in other young planetary-mass objects-and a luminosity of log (L-bol/L-circle dot) = -4.75 +/- 0.04 dex. We further re-assess the evidence for the young age of the host star, HD 203030, with a more comprehensive analysis of the photometry and updated stellar activity measurements and age calibrations. Summarizing the age diagnostics for both components of the binary, we adopt an age of 100 Myr for HD 203030B and an age range of 30-150 Myr. Using cloudy evolutionary models, the new companion age range and luminosity result in a mass of 11 M-Jup with a range of 8-15 M-Jup, and an effective temperature of 1040 +/- 50 K.
299

Corte e aspectos da biologia reprodutiva do escorpião brasileiro Tityus bahiensis (Scorpiones: Buthidae) / Courtship and reproductive biology of the Brazilian scorpion Tityus bahiensis (Scorpiones: Buthidae)

Sabrina Outeda Jorge 28 April 2010 (has links)
Os escorpiões são únicos dentre os artrópodes terrestres em muitos aspectos da biologia reprodutiva. A corte em escorpiões envolve sequências complexas de comportamentos ritualizados; é dividida em três fases: iniciação, dança e transferência de espermatozoides. Cerca de 50 espécies de escorpiões dentre as 1600 atualmente reconhecidas tiveram a corte descrita. Do mesmo modo, são poucos os estudos com tamanho de prole e investimento reprodutivo em escorpiões. Até o momento, a descrição da corte em Tityus bahiensis foi realizada com base em poucas observações incompletas. Os objetivos deste trabalho foram: estudar a corte em T. bahiensis para reconhecer os repertórios comportamentais e padrões de comportamento para espécie, através de um etograma e de um fluxograma; investigar prováveis funções das categorias comportamentais; abordar aspectos da época reprodutiva; e estudar o tamanho de prole, tempo de gestação e investimento reprodutivo. Dezenove cortes, de 202 pareamentos realizados, foram utilizadas para elaboração do etograma e do fluxograma. As sequências de comportamentos foram analisadas com o programa JWacher sup TM/sup e compiladas através de um script em Perl. Para o estudo do tamanho de prole, data de nascimento e período de gestação, foram compilados dados de 76 fêmeas. Desses nascimentos, 12 foram provenientes de cortes observadas em laboratório. A corte em T. bahiensis é complexa e está organizada de modo que a realização de uma fase prepara e condiciona o aparecimento da seguinte. A fase de iniciação tem funções como a procura por parceiros sexuais e o reconhecimento específico, sexual e da predisposição dos parceiros à corte. A fase de dança é dividida em dois módulos. No módulo I, o macho estimula e conduz a fêmea a uma superfície adequada para deposição do espermatóforo, preferencialmente uma casca de árvore (X2=24,314; g.l.=5; p<0,001). O módulo II apresenta comportamentos frequentes e repetitivos, com a função de estimular a fêmea e preparála para a fase seguinte. A fase de transferência de espermatozoides é rápida e estereotipada. Tem a função de inseminar e estimular a fêmea para uma cópula bemsucedida. Durante a cópula, o macho executa cortejo copulatório (tateamento com pernas e roçar com quelíceras). A fase de pós-transferência segue um padrão, mas apresenta poucas categorias, sendo que a maioria tem a provável função de romper o flagelo do espermatóforo inserido no gonóporo do macho; o macho pode consumir o espermatóforo e não ocorre canibalismo sexual. As fêmeas de T. bahiensis são capazes de controlar diferentes fases da corte obrigando os machos a utilizar comportamentos de estímulo, ao invés de coerção, para serem aceitos. A exibição de cortejo copulatório pelos machos é um forte indicativo da existência de seleção críptica feminina em T. bahiensis, sendo uma estratégia reprodutiva para estimular a fêmea a aceitar os espermatozoides do macho durante a aquisição do esperma. Apesar da época reprodutiva compreender o ano todo, os meses de maior atividade sexual são novembro a abril. O tamanho de prole na primeira parição é 2-25 filhotes (n=76). Além disso, T. bahiensis é capaz de produzir 1-4 proles com uma inseminação. O tempo de gestação é 2,5-12,8 meses e, apesar da capacidade de parir o ano todo, a maioria das parições ocorreu nos meses quentes, sobretudo, entre novembro e janeiro (X2=164,912; g.l.=11; p<0,001). Adicionalmente, o tamanho de prole é correlacionado com o tamanho corpóreo materno (rs=0,593; p=0,042; n=12). Assim, fêmeas maiores produzem mais filhotes e, portanto, apresentam maior investimento reprodutivo. / Scorpions are unique among terrestrial arthropods in many reproductive biology traits. Courtship involves a complex series of ritualized behaviors; it is divided into three phases: initiation, Promenade à deux, and sperm transfer. Courtship behavior has been described for about 50 of the 1600 extant scorpion species. Likewise, litter size and reproductive investment in scorpions are poorly known. Previous studies on Tityus bahiensis described courtship based on few and incomplete observations. The aims of this work were to study courtship behavior in T. bahiensis in order to recognize behavior repertories and behavior patterns for the species by making an ethogram and fluxogram; investigate probable functions of behavior categories; address aspects of the reproductive season; and study litter size, gestation period, and reproductive investment. Nineteen courtships, out of 202 interactions, were used to make the ethogram and the fluxogram. Behavioral sequences were analyzed with JWacherTM and compiled by a Perl script. For the study of litter size, date of birth, and gestation period, data of 76 females were compiled. Of these, 12 births were obtained from courtship observed in the laboratory. Courtship in T. bahiensis is complex and it is organized in a way that the execution of one phase prepares and regulates the appearance of the next. Initiation phase has functions such as the search for mating partner and species, sexual, and predisposition to court recognition. Promenade à deux phase is divided into two modules. In module I, male stimulates and leads female to a suitable surface for spermatophore deposition, preferentially a bark (X2=24,314; g.l.=5; p<0,001). Module II is characterized by frequent and repetitive behaviors, with the function of stimulating the female and preparing her to the next phase. Sperm transfer phase is rapid and stereotyped. Its function is to inseminate and stimulate the female for a successful mate. During mate, male executes copulatory courtship (feeling and kissing). Post transfer phase has a pattern, but with feel categories; most of them has the probable function of breaking the spermatophore flagellum inserted in the male gonopore; male may consume spermatophore, and there is no mating cannibalism. The females of T. bahiensis are capable of controlling different courtship phases, engaging males to use stimulating behaviors, rather than coercion, to be accepted. The exhibition of copulatory courtship by males strongly indicates the existence of cryptic female choice in T. bahiensis, being a reproductive strategy to stimulate the female to accept male spermatozoids during sperm uptake. Although reproductive season takes place all year long, the months in which reproductive activity is greater are throughout November to April. Litter size at the first parturition is 2-25 offspring (n=76). Moreover, T. bahiensis is capable of producing 1-4 broods with a single insemination. Gestation period is 2,5-12,8 months, and, although the capacity of giving birth throughout the year, most of the parturition occurred in the warm season, specially throughout November to January (X2=164,912; g.l.=11; p<0,001). In addition, litter size is correlated to female body size (rs=0,593; p=0,042; n=12). Thus, larger females produce more offspring and invest more into reproduction.
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Formation of freely floating sub-stellar objects via close encounters

Vorobyov, Eduard I., Steinrueck, Maria E., Elbakyan, Vardan, Guedel, Manuel 13 December 2017 (has links)
Aims. We numerically studied close encounters between a young stellar system hosting a massive, gravitationally fragmenting disk and an intruder diskless star with the aim of determining the evolution of fragments that have formed in the disk prior to the encounter. Methods. Numerical hydrodynamics simulations in the non-inertial frame of reference of the host star were employed to simulate the prograde and retrograde co-planar encounters. The initial configuration of the target system (star plus disk) was obtained via a separate numerical simulation featuring the gravitational collapse of a solar-mass pre-stellar core. Results. We found that close encounters can lead to the ejection of fragments that have formed in the disk of the target prior to collision. In particular, prograde encounters are more efficient in ejecting the fragments than the retrograde encounters. The masses of ejected fragments are in the brown-dwarf mass regime. They also carry away an appreciable amount of gas in their gravitational radius of influence, implying that these objects may possess extended disks or envelopes, as also previously suggested. Close encounters can also lead to the ejection of entire spiral arms, followed by fragmentation and formation of freely-floating objects straddling the planetary mass limit. However, numerical simulations with a higher resolution are needed to confirm this finding.

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