Controlled Shock Shells and Intracluster Fusion Reactions in the Explosion of Large Clusters

The ion phase-space dynamics in the Coulomb explosion of very large ($\sim 10^6 - 10^7$ atoms) deuterium clusters can be tailored using two consecutive laser pulses with different intensities and an appropriate time delay. For suitable sets of laser parameters (intensities and delay), large-scale shock shells form during the explosion, thus highly increasing the probability of fusion reactions within the single exploding clusters. In order to analyze the ion dynamics and evaluate the intracluster reaction rate, a one-dimensional theory is used, which approximately accounts for the electron expulsion from the clusters. It is found that, for very large clusters (initial radius $\sim$ 100 nm), and optimal laser parameters, the intracluster fusion yield becomes comparable to the intercluster fusion yield. The validity of the results is confirmed with three-dimensional particle-in-cell simulations.Comment: 25 pages, 11 figures, to appear in Physical Review

Hawksbill (Eretmochelys imbricata) and Green Turtle (Chelonia mydas) Nesting and Beach Selection at Príncipe Island, West Africa

Hawksbills (Eretmochelys imbricata) and green turtles (Chelonia mydas) are the predominant nesting sea turtle species on the beaches of Príncipe Island in the Gulf of Guinea. The extent of nesting has been largely unknown, but such information is essential for management and conservation. Our study is the first island-wide nesting assessment. Results from the survey, conducted from 1 December 2009 to 18 January 2010 (during peak nesting season), show that the potential suitable nesting area (10 km) is scattered around the island’s 50 beaches. Sea turtles nested on 32 of the beaches (hawksbills, 20; green turtles, 28) and used 7.5 km of the suitable nesting habitat (hawksbills, 5.8 km; green turtles, 7.0 km). We estimated that 101 (95% CI = 86–118) clutches were deposited by 17-29 hawksbills and 1088 (95% CI = 999–1245) clutches were deposited by 166-429 green turtles on Príncipe from November 2009 to February 2010 (nesting season). Long-term green turtle nest count data collected from 2007/08 to 2015/16 suggest a positive trend. Analyses of clutch densities in relation to beach characteristics suggested that both species preferred areas where human presence is lower, which coincided with the most sheltered areas. These findings should be used to inform coastal planning and minimize impacts on nesting beaches, as Príncipe is currently targeted for tourism development. Overall, results highlight that Príncipe beaches are very important for the conservation of West African hawksbill and green turtle populations.info:eu-repo/semantics/publishedVersio

Diversidade genética de Dorstenia elata Hook. (Moraceae) em um fragmento de floresta atlântica

Dorstenia é o segundo maior gênero da família Moraceae, contendo espécies endêmicas com qualidades medicinais e interesse farmacêutico. No Brasil, estão distribuídas entre os diversos biomas, inclusive na Floresta Atlântica, e são consideradas hotspot da biodiversidade (elevado nível de biodiversidade, endemismo e alto grau de degradação). Contudo, devido a ação humana, esta floresta vem tendo sua estrutura modificada, causando a redução da densidade entre as espécies, afetando o modo de reprodução, polinização e distribuição do fluxo gênico entre e dentro de populações. Estes fatos podem levar a uma diminuição da diversidade genética. Assim, o objetivo do presente trabalho foi caracterizar a diversidade genética entre e dentro de populações de Dosrtenia elata em um remanescente de Floresta Atlântica no estado do Espírito Santo. Foram coletados três agregados de indivíduos de D. elata no Parque Estadual Mata das Flores (Unidade de Conservação), no município de Castelo. Para a caracterização molecular, foram utilizados 12 primers ISSR (Inter Simple Sequence Repeats), onde os dados obtidos foram analisados e submetidos à analises estatísticas referentes a diversidade entre e dentro de populações. Para análises intrapopulacionais, foi calculada a matriz de distância entre pares de indivíduos, realizada o cálculo da correlação cofenética e gerado um dendrograma de agrupamento das populações, que evidenciaram a formação de dois grupos, o primeiro contendo a população 1 e 2, e o segundo contendo a população 3. Isto pode ter ocorrido em virtude da distância geográfica entre as populações amostradas. Para as análises interpopulacionais, foi realizada a análise de variância molecular, calculado o Índice de Shannon, a heterozigosidade total esperada e o fluxo gênico. De acordo com os resultados obtidos, a maior variabilidade genética foi observada dentro das populações, e o fluxo gênico foi alto tanto entre quanto dentro de populações, indicando que não está havendo perda de diversidade genética devido as barreiras antrópicas ou geográficas, e que o método de dispersão tem grande influência na distribuição da diversidade genética em populações de Dorstenia elata. Palavras-chave

Dynamics and control of the expansion of finite-size plasmas produced in ultraintense laser-matter interactions

The strong influence of the electron dynamics provides the possibility of controlling the expansion of laser-produced plasmas by appropriately shaping the laser pulse. A simple irradiation scheme is proposed to tailor the explosion of large deuterium clusters, inducing the formation of shock structures, capable of driving nuclear fusion reactions. Such a scenario has been thoroughly investigated, resorting to two- and three-dimensional particle-in-cell simulations. Furthermore, the intricate dynamics of ions and electrons during the collisionless expansion of spherical nanoplasmas has been analyzed in detail using a self-consistent ergodic-kinetic model. This study clarifies the transition from hydrodynamic-like to Coulomb-explosion regimes

Tipos nomenclaturais do Herbário IAN: organização, caracterização e divulgação.

Organizadores: Arion Tulio Aranda e Silvana Carvalho Thiengo

Vorton Formation

In this paper we present the first analytic model for vorton formation. We start by deriving the microscopic string equations of motion in Witten's superconducting model, and show that in the relevant chiral limit these coincide with the ones obtained from the supersonic elastic models of Carter and Peter. We then numerically study a number of solutions of these equations of motion and thereby suggest criteria for deciding whether a given superconducting loop configuration can form a vorton. Finally, using a recently developed model for the evolution of currents in superconducting strings we conjecture, by comparison with these criteria, that string networks formed at the GUT phase transition should produce no vortons. On the other hand, a network formed at the electroweak scale can produce vortons accounting for up to 6% of the critical density. Some consequences of our results are discussed.Comment: 41 pages; color figures 3-6 not included, but available from authors. To appear in Phys. Rev.

Human sperm ion channel (dys)function:implications for fertilization

BACKGROUND: Intensive research on sperm ion channels has identified members of several ion channel families in both mouse and human sperm. Gene knock-out studies have unequivocally demonstrated the importance of the calcium and potassium conductances in sperm for fertility. In both species, the calcium current is carried by the highly complex cation channel of sperm (CatSper). In mouse sperm, the potassium current has been conclusively shown to be carried by a channel consisting of the pore forming subunit SLO3 and auxiliary subunit leucine-rich repeat-containing 52 (LRRC52). However, in human sperm it is controversial whether the pore forming subunit of the channel is composed of SLO3 and/or SLO1. Deciphering the role of the proton-specific Hv1 channel is more challenging as it is only expressed in human sperm. However, definitive evidence for a role in, and importance for, human fertility can only be determined through studies using clinical samples.OBJECTIVE AND RATIONALE: This review aims to provide insight into the role of sperm ion channels in human fertilization as evidenced from recent studies of sperm from infertile men. We also summarize the key discoveries from mouse ion channel knock-out models and contrast the properties of mouse and human CatSper and potassium currents. We detail the evidence for, and consequences of, defective ion channels in human sperm and discuss hypotheses to explain how defects arise and why affected sperm have impaired fertilization potential.SEARCH METHODS: Relevant studies were identified using PubMed and were limited to ion channels that have been characterized in mouse and human sperm. Additional notable examples from other species are included as appropriate.OUTCOMES: There are now well-documented fundamental differences between the properties of CatSper and potassium channel currents in mouse and human sperm. However, in both species, sperm lacking either channel cannot fertilize in vivo and CatSper-null sperm also fail to fertilize at IVF. Sperm-lacking potassium currents are capable of fertilizing at IVF, albeit at a much lower rate. However, additional complex and heterogeneous ion channel dysfunction has been reported in sperm from infertile men, the causes of which are unknown. Similarly, the nature of the functional impairment of affected patient sperm remains elusive. There are no reports of studies of Hv1 in human sperm from infertile men.WIDER IMPLICATIONS: Recent studies using sperm from infertile men have given new insight and critical evidence supporting the supposition that calcium and potassium conductances are essential for human fertility. However, it should be highlighted that many fundamental questions remain regarding the nature of molecular and functional defects in sperm with dysfunctional ion channels. The development and application of advanced technologies remains a necessity to progress basic and clinical research in this area, with the aim of providing effective screening methodologies to identify and develop treatments for affected men in order to help prevent failed ART cycles. Conversely, development of drugs that block calcium and/or potassium conductances in sperm is a plausible strategy for producing sperm-specific contraceptives.</p