Ditylenchus africanus sp. n. from South Africa : a morphological and molecular characterization

Une nouvelle espèce de #Ditylenchus parasite de l'arachide en Afrique du Sud est décrite en se fondant sur des caractères morphologiques et sur ceux provenant du polymorphisme des longueurs des fragments de restriction (RFLPs) de l'ADN ribosomal. La nouvelle espèce, #Ditylenchus africanus n. sp., diffère des deux espèces les plus proches, #D. destructor et #D. myceliophagus, par la combinaison de caractères suivante : RFLPs provenant de sept enzymes de restriction situées sur l'espaceur interne transcrit de rADN, stylet de longueur moyenne et relativement peu robuste (en comparaison de celui de #D. destructor$, longueur de la bursa (exprimée en pourcentage de la longueur de la queue) et longueur des spicules. (Résumé d'auteur

Specific probes efficiently distinguish root-knot nematode species using signature sequences in the ribosomal intergenic spacer

Ont été établies des sondes moléculaires - destinées à identifier les espèces de #Meloidogyne - grâce à des différences spécifiques dans l'espaceur intergénique (IGS) de l'ADN ribosomal. Les séquences de nucléotides de l'IGS ont été obtenues en séquençant l'ADN amplifiée par PCR. L'alignement des séquences de l'IGS de #M. chitwoodi et #M. fallax a révélé plusieurs régions contenant des différences localisées. Des amorces PCR ont été synthétisées qui ont donné des produits d'amplification spécifiques lorsqu'utilisées avec des produits d'amorce non spécifiques, ont pu être séparés par leur taille dans un gel d'agarose, procurant ainsi un test fiable et précis ne nécessitant pas de restriction enzymatique. L'amplification de l'ADN d'un nématode juvénile ou d'un oeuf par PCR multiplex a permis d'identifier #M. chitwoodi et #M. fallax et de les séparer de #M. hapla, #M. javanica, #M. arenaria et #M. mayaguensis$. (Résumé d'auteur

Rapide identification of Meloidogyne chitwoodi, M. hapla, and M. fallax using PCR primers to amplify their ribosomal intergenic spacer

Des amorces servant à amplifier la région interne transcrite de l'espaceur (ITS) ont été réorientées de manière divergente pour amplifier par réaction en chaîne par polymérase (PCR) l'espaceur intergénique (IGS) de l'ADNr génomique de #Meloidogyne chitwoodi. La position de l'IGS dans le fragment d'ADN obtenu de 5,5 Kb a bien été identifiée en sous-clonant individuellement des fragments de restriction et en séquençant leurs régions terminales. Des amorces additionnelles ont été construites pour amplifier l'IGS avec un minimum de séquences des gènes 28S et 18S de l'ADNr. Les fragments amplifiés par PCR de l'ADN de #M. chitwoodi, #M. hapla et de #M. fallax ont montré des tailles différentes par électrophorèse sur gel d'agarose. L'identification directe des nématodes à partir de différences de taille des fragments amplifiés est plus efficace que la méthode usuelle d'amplification suivie de digestion à l'aide d'enzymes de restriction. (Résumé d'auteur

Intraspecific rDNA restriction fragment length polymorphism in the Xiphinema americanum group

This is an article about science and environmental law. More specifically, it is an article about two different versions of science, and how each has affected environmental law and the development of environmental policy. The emergence of science-driven environmental law has significantly affected how humans view and respond to the natural world that makes up the biosphere, which is the thin envelope surrounding the Earth that permits the human species to exist. This Article argues that humans, and law-makers, should embrace a different role for science. Instead of science answering “what is” questions, it should also explain the universal laws of the natural environment, so environmental laws can be consistent with those fundamental natural laws. Only then can environmental policy, and its laws, successfully ensure that the biosphere will continue to be a home for humans. Environmental law was “invented” approximately fifty years ago. In the 1960s, the United States Congress reacted to the growing awareness of human-caused threats to the natural environment by enacting the Water Quality Act of 1965, and then the Natural Environmental Policy Act of 1969. These statutes were just the beginning of an enormous number of environmental laws and regulations, which were put in place to address the widely held perception that human behavior has been adversely affecting the natural environment, and the health and safety of humans living in that environment. Environmental policy has guided these many laws. This policy has been based on various assumptions about how the environment works and how humans behave. Science has provided law-makers with models about how the environment functions and the ways humans make choices about this environment. For much by a classical version of science—utilitarian science. That type of science became essential to the formulation of policy. Science became the critical informational input for environmental decision-making of the lifespan of environmental law, environmental policy has been aided by a classical version of science—utilitarian science. That type of science became essential to the formulation of policy. Science became the critical informational input for environmental decision-making.Utilitarian science is designed to help policymakers reach answers addressing “what is.” Those who make policy supply the “ought” answers. Utilitarian science helps to supply the legal requirements of empirical proof for environmental causation. In addition, environmental statutes call for policymakers to establish regulatory standards as tools for preventing pollution and human-made waste from creating environmental and human harm. Utilitarian science sets these standards. This class of science tells policymakers what is safe for human health and what is not. But classical utilitarian science has several limitations that make it an imperfect fit for environmental law and policy. It often cannot provide the definitive answers to the questions that environmental policymakers ask. This failure to supply answers is due to the many uncertainties that surround environmental science. Moreover, environmental conclusions based on science can easily be attacked in court, and in the political arena, for being based on flawed or inadequate data. Due in part to these shortcomings in utilitarian science, commentators and scholars have increasingly suggested that environmental policymakers should instead consider using a different version of science—explanatory science. Rather than only determining “what is,” in order to inform policymaking, explanatory science provides unifying principles necessary to understand the underlying structure and dynamics of nature and humans. Utilitarian science presumes a separation between science and the value judgments inherent in environmental policy. Explanatory science is more directly linked to policy; it embraces scientific “theories,” such as complexity theory and systems theory, as the best way to bring about successful policy reform. The scientific theories that underlie explanatory science are not separated from policy; they should be integrated into policy, and influence and shape policy. This Article argues that explanatory science should do more than just “influence” environmental policy. The Article advances the proposition that, consistent with the Principle of Universality, science should direct and determine environmental policy. The Principle of Universality is a manifestation of explanatory science which holds that all laws of nature must work the same everywhere,and at every time. The Principle states that it does not matter who conducts the experiment testing nature’s laws, or where or when the test occurs; the results will be the same, regardless of whether the test involves biology, chemistry, physics, or the forces of the universe. From this generally recognized, but underappreciated, principle follows this realization: For environmental policy to succeed, it must conform to the demands of the Principle of Universality. And one of the demands of Universality is this: our laws about nature should be consistent with the laws of nature. This Article makes the case that for environmental laws to succeed, they must reflect and conform to the universal scientific truths of nature. The mantra for policymakers is simple: successful environmental laws, as well as the policies that structure and cabin these laws, should adhere to the fundamental laws of the natural world and our biosphere. What are these universal truths? What laws, or rules, do physical, biological, and chemical systems all follow? Scientists have begun to unravel nature’s secrets, the principles which all natural phenomena obey, and which comprise nature’s master plan. This Article urges that our environmental policies should closely follow the basic workings that nature employs, which resonate throughout all the operating systems of the universe. Part I discusses the two roles that science has played in the development of environmental policy—as a utilitarian tool to provide policymakers with evidence and data, and as an explanatory insight into the unifying principles that describe the behavior of both nature and humans. Part II addresses how utilitarian science has played a critical role in the development of environmental law throughout the twentieth century. Its primary function has been to inform the decision-making of policymakers. Utilitarian science has helped to define a view of how nature works and how humans make choices. These assumptions have become embedded in most of the environmental statutes that now comprise the bulk of environmental law. Part III chronicles how, in the twenty-first century, explanatory science has sought both to alter the relationship between science and policy and to cause us to rethink our previous assumptions about the workings of nature and the behavior of humans. Explanatory science suggests that certain scientific theories, such as complexity theory, chaos theory, and even game theory, should directly influenceenvironmental policy. As a result of explanatory science, new environmental laws have been proposed that better reflect the reality of the natural environment as a nonlinear dynamical complex adaptive system. Environmental laws which embrace this reality opt for adaptive management rules and policies that protect biodiversity and ecosystem services. Similarly, explanatory science has yielded new and counter-intuitive empirical realizations about human behavior. As a result, more twenty-first century laws rely on bottom-up structures that “nudge” people to make better choices about the environment, instead of traditional top-down commands and prohibitions. Part IV proposes a rethinking of environmental law in which science does more than inform decisions (Part II) or influence policy (Part III). Instead, science, particularly explanatory science, should directly determine policy. One central manifestation of explanatory science—the Principle of Universality—should be adopted by environmental policymakers so that environmental laws about nature are consistent with the laws of nature. Part IV identifies the two principal laws of nature, and offers a model of environmental policy which would conform to these universal laws. Environmental policy that satisfies the Principle of Universality stands a better chance of succeeding in establishing an environmental agenda that actually works

Characterization of Bi4Ge3O12 single crystal by impedance spectroscopy

Bi4Ge3O12 (bismuth germanate - BGO) single crystals were produced by the Czochralski technique and their electrical and dielectric properties were investigated by impedance spectroscopy. The isothermal ac measurements were performed for temperatures from room temperature up to 750 °C, but only the data taken above 500 °C presented a complete semicircle in the complex impedance diagrams. Experimental data were fitted to a parallel RC equivalent circuit, and the electrical conductivity was obtained from the resistivity values. Conductivity values from 5.4 × 10(9) to 4.3 × 10-7 S/cm were found in the temperature range of 500 to 750 °C. This electrical conductivity is thermally activated, following the Arrhenius law with an apparent activation energy of (1.41 ± 0.04) eV. The dielectric properties of BGO single crystal were also studied for the same temperature interval. Permittivity values of 20 ± 2 for frequencies higher than 10³ Hz and a low-frequency dispersion were observed. Both electric and dielectric behavior of BGO are typical of systems in which the conduction mechanism dominates the dielectric response

Efeito da temperatura na multiplicação celular, no desenvolvimento embrionário e na eclosão de juvenis do segundo estádio de Meloidogyne javanica Effect of temperature on embryonic development and in hatching of Meloidogyne javanica

Fatores abióticos influenciam a multiplicação celular, o desenvolvimento embrionário, bem como a sobrevivência e eclosão de juvenis do segundo estádio (J2) de Meloidogyne spp. O efeito relativo à temperatura constante tem sido estudado com várias espécies e populações de Meloidogyne. Entretanto, tem sido pouco pesquisado a flutuação de temperatura, a qual predomina no campo entre o dia e a noite ou durante períodos de predominância de massas polares. Assim, objetivou-se estudar o efeito da flutuação de temperatura em ovos de M. javanica com estádios de desenvolvimento padronizados. Quando foram usados ovos com juvenis já formados, maior percentual de eclosão ocorreu em temperatura fixa de 28 ºC, mas a redução do tempo de exposição a esta temperatura reduziu a eclosão. A exposição dos ovos por 10 horas a 10 ºC, seguido de 14 horas a 28 ºC, proporcionou maior eclosão dos J2 em relação ao mesmo período de exposição mas a 5 ºC seguido de 14 horas a 28 ºC. Já a incubação em temperatura constante de 10 ºC proporcionou menor taxa de eclosão. Ovos no estádio de duas células incubados em temperatura constante de 28 ºC tiveram a multiplicação celular e o desenvolvimento embrionário acelerado em relação às alternadas. Em temperatura constante de 10 ºC ocorreu apenas a multiplicação celular, após a incubação dos ovos por 12 dias. Entretanto, quando incubados por períodos de 10 horas a 10 ºC seguido de 14 horas a 28 ºC ocorreram a formação de juvenis e eclosão de J2, porém significativamente inferior às observadas em temperatura constante de 28 ºC. Em temperaturas de 5 ºC por 10 horas seguida de 28 ºC por 14 horas, não proporcionou eclosão de juvenis no período de 12 dias. Nos ovos ocorreram apenas os estádios pluricelulares, gástrula e "tadpole". Portanto, a temperatura constante de 10 ºC permite apenas a multiplicação celular, e o intervalo de temperatura entre 5 ºC e 10 ºC afeta drasticamente os processos envolvidos no desenvolvimento embrionário de M. javanica.<br>Abiotic factors affect the embryonic development, survival and hatching of second-stage juvenile (J2) of Meloidogyne spp. The effect of constant temperature has been studied with various species and populations of Meloidogyne spp. However, the temperature fluctuation which predominates in the field between day and night or during periods of predominance of polar cold front, has not been well studied. Thus, this work aimed to study the effect of temperature fluctuation on egg of M. javanica with standardized embryo development. When eggs with formed juveniles inside were used, highest percentage of hatching occurred at fixed temperature of 28 ºC. The reduction of the exposure time at 28 ºC reduced hatching. The eggs exposed for 10 hours at 10 ºC and complemented by 14 hours at 28 ºC resulted in greater J2 hatching as compared to 10 hours at 5 ºC complemented by 14 hours at 28 ºC. The incubation at fixed temperature of 10 ºC rendered lowest hatching. When eggs at the two-cell stage were used and incubated at 28 ºC the cell multiplication and embryonic development were speeded up. At constant temperature of 10 ºC for egg incubation during 12 days only cell multiplication occurred. However, when the incubation temperatures varied with period of 10 hours at 10 ºC and complemented by 14 hours at 28 ºC, juveniles were formed inside the eggs and hatched but significantly lower than those at constant temperature of 28 ºC. At alternated temperatures of 10 hours at 5 ºC, complemented by 14 hours at 28 ºC, with the same incubation time, juveniles were not formed. In the eggs occurred only the pluricelular, gastrula and tadpole stages occurred. Therefore, the constant temperature of 10 ºC allows only the cellular multiplication, and the temperature interval of 5 ºC and 10 ºC affect drastically several processes involved in embryo development of M. javanica