Comparative d2/d3 LSU–rDNA sequence study of some Iranian Pratylenchus loosi populations

The D2/D3 LSU rDNA expansion segment of 13 isolates attaching tea shrubs roots in tea gardens that verified by morphological and morphometrical studies as Pratylenchus loosi Loof, 1960 from Guilanprovince, North of Iran, were amplified and sequenced. Amplification of the D2/D3 LSU rDNA expansion segments yielded one fragment at over all sequenced isolates as 787 bp in size. The DNA sequenceswere aligned using Clustral X1.81 together and with three sequences of similar region of P. loosi isolates available in Genbank database (Isolate T from Serilanka and Isolates N1 and N2 from Florida, USA). Also the genetic distance between sequences data were calculated through four methods as following; Uncorrected distance (UC), Jukes-Cantor (JC) Kimura distance (K) and Jin-Neigamma distance (JNG).For generating phyllogenetic trees both Neighbor-joining (NJ) and Unweighted Pair Group Method with Arithmetic Mean (UPGMA) were used. The results indicated that very short genetic distance exist among the Iranian isolates and between the Iranian isolates and isolate T from Serilanka whereas the Iranian isolates and isolate T were genetically distinct from isolates N1 and N2. The phyllogenetic analyses revealed relationship not only among Iranian isolates but also between Iranian isolates and isolate T

Analytical approximations to the core radius and energy of magnetic vortex in thin ferromagnetic disks

The energy of magnetic vortex core and its equilibrium radius in thin circular cylinder were first presented by N.A. Usov and S.E. Peschany in 1994. Yet, the magnetostatic function, entering the energy expression, is hard to evaluate and approximate. In this communication precise and explicit analytical approximations to this function (as well as equilibrium vortex core radius and energy) are derived in terms of elementary functions. Also, several simplifying approximations to the magnetic Hamiltonian and their impact on theoretical stability of magnetic vortex state are discussed.Comment: 5 pages, 1 figur

Thermodynamically self-consistent non-stochastic micromagnetic model for the ferromagnetic state

In this work, a self-consistent thermodynamic approach to micromagnetism is presented. The magnetic degrees of freedom are modeled using the Landau-Lifshitz-Baryakhtar theory, that separates the different contributions to the magnetic damping, and thereby allows them to be coupled to the electron and phonon systems in a self-consistent way. We show that this model can quantitatively reproduce ultrafast magnetization dynamics in Nickel.Comment: 5 pages, 3 figure

Taxonomic study of entomopathogenic nematodes (Nematoda : Steinernematidae, Heterorhabditidae) from Benin

A study on the biodiversity of entomopathogenic nematodes was conducted during 2010 and 2011 in South Benin. Soil samples from eight sites production of annual and perennial crops were analysed. We obtained 13.21 % of positive soil samples out of 280. We here report on the identification of six of these isolates. Molecular, morphometrical and morphological observations classified the isolates within the genus Heterorhabditis ; one isolate was conspecific with H. indica and two other isolates with H. sonorensis. More information is needed for effective identification of the remaining three isolates. Phylogenic analysis based on sequences of ITS regions of rDNA grouped our isolates with H. sonorensis and H. taysearae with bootstrap support values of 94 and 99 % in Maximum Parsimony and Neighbour Joining trees, respectively. Morphological characters of the infective juveniles and males did not correspond to those of H. taysearae, but were close to H. sonorensis. In contrast, the female of the H. sonorensis populations did show some minor differences with the originally described one. No progeny was obtained from the crossbreeding of Beninese isolates and H. taysearae. Crossing with an isolate of H. sonorensis would have been more conclusive, but no isolates were available even for specimen’s morphological comparison.Keywords : Survey, identification, Molecular, cross-hybridization, Heterorhabditis.Etude taxonomique desnematodes entomopathogenes (Nematoda : Steinernematidae, Heterorhabditidae) du BeninUne étude diagnostique réalisée sur les nématodes entomopathogènes (NEP) en 2010 et 2011 dans le Sud- Bénin sur huit sites de production de cultures annuelles et pérennes a conduit à 13,21 % d’échantillons de sols positifs sur 280. Le présent travail a porté sur l’identification de six des isolats de NEP extraits. Les études moléculaires, morphologiques, morphométriques et d’hybridation effectuées utilisant les stades développementaux des nématodes ont révélé un isolat d’H. indica, deux d’H. sonorensis. Pour les autres isolats, des informations complémentaires sont nécessaires pour une identification complète. Le séquençage et l’analyse phylogénétique de la région interspécifique de l’ADN ribosomal ont groupé nos isolats avec H. sonorensis et H. Taysearae dans les arbres de parcimonie maximale et de Neighbour Joining avec les supports respectifs 94 et 99 %. Les caractères morphologiques des juvéniles infectieux et des mâles ne correspondent pas à ceux de la première description d’H. taysearae, mais sont proches d’H. sonorensis. Cependant, certaines femelles avec bouchon copulatoire ne correspondent pas à H. sonorensis. Nos isolats n’ont pas été féconds avec H. taysearae. Un croisement avec H. sonorensis population type serait plus concluant, mais il n’y avait aucun isolat disponible dans la base de gènes.Mots-clés : Etude, identification, moléculaire, hybridation-croisée, Heterorhabditis

Study of the pitch change of carbon coils during their growth

AbstractIn the present paper, carbon coils (CCs) were prepared by CVD. Their morphology, particularly pitch changes of the carbon coils prepared in different conditions were observed. It was found that the carbon source flow plays an important role in carbon coil growth and its morphology evolution. The appropriate atmosphere and flow rate is beneficial to the steady reactivity of catalyst particles. As such each carbon coil can grow well and have an exact growth rate. When the carbon supply is sufficient, the CCs exhibit close spiral and small coil diameter. When carbon supply decreases, small carbon supply leads to large pitch and coil diameter. CCs can be synthesized with different coil pitch under different carbon supply. This may be of great significance for the controllable preparation of carbon coil and its application

MOLECULAR IDENTIFICATION OF HETERODERA SPP., AN OVERVIEW OF FIFTEEN YEARS OF RESEARCH *

SUMMARY During the last 15 years, researchers have collected and characterised more than 40 species of nematodes from the genus Heterodera. The species were identified by sequencing the ITS-rRNA genes and by PCR-RFLP profiles; these tools remain the best available for identifying cyst-forming nematodes. By restricting the ITS amplicons with one or a combination of seven restriction enzymes (AluI, AvaI, Bsh1236I, BsuRI, CfoI, MvaI, and RsaI), researchers can distinguish most of the agriculturally important cyst nematode species from one another and from their sibling species. Species from the Avenae group can be differentiated from one another using the enzymes AluI, CfoI, HinfI, ItaI, PstI, RsaI, TaqI and Tru9I. However, in some cases, it is not possible to use sequences of ITS-rRNA genes and PCR-RFLPs in diagnostic work. In these cases, morphometric characteristics are better for differentiating these species. Intraspecific polymorphism in the ITS sequences can make identification even more difficult; here, more conclusive molecular identification tools are needed to diagnose some species. In the future, end-point PCR and semi-quantitative PCR (SYBR Green I) with species-specific primers (already developed for Heterodera glycines and H. schachtii) will be the likely choices for fast and reliable detection and quantification of cyst nematodes in samples

Chiral symmetry breaking of magnetic vortices by sample roughness

Finite-element micromagnetic simulations are employed to study the chiral symmetry breaking of magnetic vortices, caused by the surface roughness of thin-film magnetic structures. An asymmetry between vortices with different core polarizations has been experimentally observed for square-shaped platelets. E.g., the threshold fields for vortex core switching were found to differ for core up and down. This asymmetry was however not expected for these symmetrically-shaped structures, where both core polarizations should behave symmetrically. Three-dimensional finite element simulations are employed to show that a small surface roughness can break the symmetry between vortex cores pointing up and down. A relatively small sample roughness is found sufficient to reproduce the experimentally observed asymmetries. It arises from the lack of mirror-symmetry of the rough thin-film structures, which causes vortices with different handedness to exhibit asymmetric dynamics

Magnetic vortex oscillator driven by dc spin-polarized current

Transfer of angular momentum from a spin-polarized current to a ferromagnet provides an efficient means to control the dynamics of nanomagnets. A peculiar consequence of this spin-torque, the ability to induce persistent oscillations of a nanomagnet by applying a dc current, has previously been reported only for spatially uniform nanomagnets. Here we demonstrate that a quintessentially nonuniform magnetic structure, a magnetic vortex, isolated within a nanoscale spin valve structure, can be excited into persistent microwave-frequency oscillations by a spin-polarized dc current. Comparison to micromagnetic simulations leads to identification of the oscillations with a precession of the vortex core. The oscillations, which can be obtained in essentially zero magnetic field, exhibit linewidths that can be narrower than 300 kHz, making these highly compact spin-torque vortex oscillator devices potential candidates for microwave signal-processing applications, and a powerful new tool for fundamental studies of vortex dynamics in magnetic nanostructures.Comment: 14 pages, 4 figure