The Ascomycete Verticillium longisporum Is a Hybrid and a Plant Pathogen with an Expanded Host Range

Hybridization plays a central role in plant evolution, but its overall importance in fungi is unknown. New plant pathogens are thought to arise by hybridization between formerly separated fungal species. Evolution of hybrid plant pathogens from non-pathogenic ancestors in the fungal-like protist Phytophthora has been demonstrated, but in fungi, the most important group of plant pathogens, there are few well-characterized examples of hybrids. We focused our attention on the hybrid and plant pathogen Verticillium longisporum, the causal agent of the Verticillium wilt disease in crucifer crops. In order to address questions related to the evolutionary origin of V. longisporum, we used phylogenetic analyses of seven nuclear loci and a dataset of 203 isolates of V. longisporum, V. dahliae and related species. We confirmed that V. longisporum was diploid, and originated three different times, involving four different lineages and three different parental species. All hybrids shared a common parent, species A1, that hybridized respectively with species D1, V. dahliae lineage D2 and V. dahliae lineage D3, to give rise to three different lineages of V. longisporum. Species A1 and species D1 constituted as yet unknown taxa. Verticillium longisporum likely originated recently, as each V. longisporum lineage was genetically homogenous, and comprised species A1 alleles that were identical across lineages

Effective viscoelastic plastic material modeling for faster and reliable calculations

Finite Element Simulations of highly integrated and large electronics packages with detailed elastic-plastic material modeling of thousands of solder balls are still challenging tasks on today's computation systems. The complex geometry and mesh and the usage of time-consuming creep laws for solder materials make it nearly impossible to calculate different geometries or process parameters. This paper describes a method to reduce the complexity of the mesh in the region of the solder balls and surrounding underfill with one simple block physically described as a viscoelastic material. Therefore a viscoelastic/plastic behavior of a complex unit cell was modeled in a temperature dependent harmonic frequency sweep or relaxation simulation. The reaction of the unit cell was utilized to synthesize the master curve, Prony coefficients and shift function to an effective material model. Finally, an error estimation of the unit cell approach was carried out. The results show that effective material approach can be used to cut down computation time significantly

Toolbox for visco-elastic material modeling of smart lightweight structures

More and more functionalities will soon be integrated into lightweight structures made of fiber reinforced polymers (FRP). This combines very different materials in minimum space. Consequently, thermo-mechanical risks are of vital concern. The complex stress situation requires a systematic and scalable toolbox of methodologies capable of keeping pace with the growing number and diversity in possible failure risks and sites. The paper reports the status of ongoing work on three expansions to an accelerated test methodology that allows determining the lifetime of FRP structures based on three types of tests: visco-elastic dynamic mechanical analysis, constant strain rate and fatigue tests. The expansions attempt to cover in addition i) various levels of moisture content within the polymer, ii) several laminate stack configurations, and iii) different loading situations including the mix of tension, bending, and shear

Electrical properties of (BaTiO3/SrTiO3)15 superlattices grown by MOCVD

Dielectric multilayers of (BaTiO3/SrTiO3)15 were synthesised on various substrates by a Metal Organic Chemical Vapour Deposition (MOCVD) technique using a pulsed liquid injection source. A single precursor solution was used per compound. The X ray diffraction analysis of the satellite diffraction peaks indicated that the superlattices periodicity can be precisely controlled by the number of injections. Sets of samples were prepared with varying interlayer thickness on doped Nb-SrTiO3 substrates (0.5 atom %). Electrical measurements in the range 20 - 500 K and 20 Hz - 100 kHz were performed on the multilayers, using the STO : Nb substrate as a bottom electrode. As the thickness of the bilayer of the (BaTiO3/SrTiO3)15 superlattices increased (hence the total thickness), the dielectric constant increased as well, reaching values of 650 for (BaTiO3 36 u.c / SrTiO3 36 u.c)15

Challenges of viscoelastic characterization of low TG epoxy based adhesives for automotive applications in DMA and relaxation experiments

Microelectronic devices integrate more and more diverse materials in order to miniaturize the packages. Epoxy resins enable smaller electronic devices with promising features [1]. The performance and the reliability of the product are highly dependent on the material behavior of the components and on their interaction under different loading situation

Master curve synthesis by effective viscoelastic plastic material modeling

Finite Element Simulations of highly integrated and large electronics packages with detailed elastic-plastic material modeling of thousands of solder balls are still challenging tasks for today's computation systems. The complex geometry and mesh and the usage of time consuming creep laws for solder materials makes it nearly impossible to calculate different geometries or process parameters. This paper describes a method to reduce the complexity of the mesh in the region of the solder balls and surrounding underfill with one simple block physically described as a viscoelastic material. Therefore a viscoelastic/plastic behavior of a complex unit cell was modeled in a temperature dependent harmonic frequency sweep or relaxation simulation. The reaction of the unit cell was utilized to synthesize the master curve, Prony coefficients and shift function to an effective material model. Finally an error estimation of the unit cell approach was carried out

Hot pressing sintered CuxMo6S8 targets for laser ablation thin films deposition

International audienc

Characterization of adhesives for microelectronic industry in DMA and relaxation experiments for interfacial fracture toughness characterization – difficulties and solution

Electrically conductive adhesives are widely used in semiconductor technology. The focus of this work is set on Isotropic Conductive Adhesives (ICA) with a high amount of electrically conductive filler particles. The aim of this work is the material characterization of highly filled epoxy based die attaches materials by dynamic mechanical analysis (DMA) and relaxation experiments in order to derive elastic and viscoelastic material models in a wide temperature range. The measurement of the epoxy based highly filled die attach material is a challenging topic. We show how to overcome the difficulties in measuring these materials. Critical interface fracture data, which include the Critical (Strain) Energy Release Rate Gc(Ψ) as a function of temperature, humidity or aging, are crucially needed in microelectronic industry for failure modeling, lifetime prediction and design evaluation associated with reliability [1], but they are rarely given in literature. Therefore fast measurement methods are needed [2, 3]. This work shows a measurement method of the critical fracture mechanic properties with the micro Mixed Mode Tester (μMMT) [2] on samples cut from real products and their numerical evaluation using linear elastic fracture mechanics and cohesive zone modeling