大连市银杏叶斑病病原菌鉴定

银杏(Ginkgo biloba L.)是常见的城市园林观赏绿化树种,并具有极高的材用、食用和药用价值.近年来,大连市银杏树发生了一种不明病因且较为严重的叶斑病,查明病因、为病害防治提供理论依据迫在眉睫.从病害发生严重区域采集叶斑病病叶样本,采用感病叶片单斑分离法,对分离菌株进行致病性测定、形态学鉴定及分子生物学鉴定等,对大连市银杏树发生的叶斑病进行了病原菌鉴定.结果表明,大连银杏叶斑病致病菌有2种,分别为链格孢属细极链格孢(Alternaria tenuissima)和链格孢(Alternaria alternata).迄今为止,细极链格孢(Alternaria tenuissima)侵染银杏导致其发生叶斑病鲜有报道.     

Magnetic trapping of neutrons

Accurate measurement of the lifetime of the neutron (which is unstable to beta decay) is important for understanding the weak nuclear force and the creation of matter during the Big Bang. Previous measurements of the neutron lifetime have mainly been limited by certain systematic errors; however, these could in principle be avoided by performing measurements on neutrons stored in a magnetic trap. Neutral-particle and charged-particle traps are widely used for studying both composite and elementary particles, because they allow long interaction times and isolation of particles from perturbing environments. Here we report the magnetic trapping of neutrons. The trapping region is filled with superfluid 4He, which is used to load neutrons into the trap and as a scintillator to detect their decay. Neutrons in the trap have a lifetime of 750(+330)(-200) seconds, mainly limited by their beta decay rather than trap losses. Our experiment verifies theoretical predictions regarding the loading process and magnetic trapping of neutrons. Further refinement of this method should lead to improved precision in the neutron lifetime measurement.     

Patterns of asymmetry in body traits and genitalia in two distant populations of a Neotropical scorpion

The ability of a genotype to control the stable development of a phenotype under different environmental conditions may explain the level of developmental instability. An indicator to developmental instability is Fluctuating Asymmetry. Traits under pressures of sexual selection exhibit greater values of asymmetry that others. These traits have more physiological requirements during morphogenesis and a more complex development. The aims of this work are to analyze asymmetry patterns of genitalic and somatic traits in the scorpion Bothriurus bonariensis (Bothriuridae) and to compare these values between central and peripheral populations of its distribution. We observed that types of asymmetry in genitalic traits differed in both populations. Also, traits of the hemispermatophores (two halves that constitute the spermatophore) showed the highest levels of fluctuating asymmetry, particularly in those characteristics with important role for insemination success. This work offers fundamental baseline knowledge for further works focused on asymmetry of genitalia and mating success in scorpions.     

Three new Idiops (Mygalomorphae: Idiopidae) from Argentina and redescription of the male of I. hirsutipedis Mello-Leitão, 1941

Three new Argentinean species of the front-eyed trapdoor spider genus Idiops namely I. minguito sp. nov. from Salta and Jujuy provinces, I. piluso sp. nov. from Córdoba province and I. tolengo sp. nov. from Santiago del Estero province, are described. The male of I. hirsutipedis is redescribed and new distributional data in Argentina are presented for this species and for I. clarus. An identification key for all these species is provided.

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