bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of interfacial layers upon the barrier properties of polymer nanocomposites
Authors: Khounlavong Landry , Ganesan Venkat
Published: March 2009

Recent experiments in the context of polymer nanocomposites (PNCs) have observed counter intuitive behavior in which the addition of impenetrable nanofillers into a rigid polymer matrix resulted in the enhancement of the composite membrane’s permeability (and diffusivity) to gas penetrants. Existing theoretical models have rationalized these observations as arising from the presence of interfacial layers around the nanoparticles whose properties differ significantly from the bulk properties of the polymer. Similar influences of interfacial layers have also been noted in the context of other macroscopic properties of nanofiller-polymer mixtures. In this article, we present a numerical approach building upon such earlier theoretical ideas, which: (i) Uses a microscopically based polymer model to determine the penetrant diffusivity characteristics in interfacial layers; (ii) embeds the so-determined interfacial characteristics into a numerical homogenization procedure, which accounts for the overlap of interfacial layers (approximately) and multibody interactions (exactly). The numerical approach is used to elucidate the influence of polymer matrix stiffness, particle sizes and particle volume fractions upon the penetrant diffusivity properties of PNCs.
External electric field effect on the hydrogenic donor impurity in zinc-blende GaN/AlGaN cylindrical quantum dot
Authors: Jiang Liming , Wang Hailong , Wu Huiting , Gong Qian , Feng Songlin
Published: March 2009

The binding energy of a hydrogenic donor impurity in a zinc-blende GaN/AlGaN cylindrical quantum dot (QD) is calculated in the framework of effective-mass envelope-function theory using the plane wave basis. It is shown that the donor binding energy is highly dependent on the impurity position and QD size. The external electric field induces an asymmetrical distribution of the donor binding energy with respect to the center of the QD. The maximum of the donor binding energy is shifted from the center of the QD. The degenerating energy levels for symmetrical positions with respect to the center of QD are also split. The splitting increases with the increase in QD height while the splitting increases up to a maximum and then decreases with the increase in QD radius. In the presence of the external electric field, the donor binding energy is insensitive to dot height when the impurity is located at the left side of the QD with large dot height. In addition, Stark shift dependence on hydrogenic impurity position is calculated.
Calculation of NMR chemical shifts in organic solids: Accounting for motional effects
Authors: Dumez Jean-Nicolas , Pickard Chris J.
Published: March 2009

NMR chemical shifts were calculated from first principles for well defined crystalline organic solids. These density functional theory calculations were carried out within the plane-wave pseudopotential framework, in which truly extended systems are implicitly considered. The influence of motional effects was assessed by averaging over vibrational modes or over snapshots taken from ab initio molecular dynamics simulations. It is observed that the zero-point correction to chemical shifts can be significant, and that thermal effects are particularly noticeable for shielding anisotropies and for a temperature-dependent chemical shift. This study provides insight into the development of highly accurate first principles calculations of chemical shifts in solids, highlighting the role of motional effects on well defined systems.
Experimental correlation of nitroxide recollision spin exchange with free volume and compressibility in alkane and aromatic compounds
Authors: Kurban Mark R.
Published: March 2009

Diffusion of perdeuterated tempone (PDT) in various nonpolar hydrocarbon solvents on both the large and microscopic scales is examined through electron paramagnetic resonance spectroscopy. Spectral line broadening and hyperfine spacing are measured in order to extract both the Heisenberg spin-exchange rate as well as the average recollision times between spin-probe pairs. Probe recollision is responsible for a linear component to the dependence of the line shift on spectral broadening which has been identified in recent years. The present study extends the work of a previous paper by Kurban et al. [J. Chem. Phys. 129, 064501 (2008)], in which it was reported that recollision rates for PDT formed a common curve across n-alkanes when plotted with respect to free volume and to isothermal compressibility. It is now found that such common curves occur within distinct chemical families, in particular, the alkane and aromatic groups. Within each chemical family, the spin probe recollision rate correlates with free volume and compressibility independently of the geometry of the particular solvent. All solvents show significantly enhanced recollisional diffusion over the Stokes–Einstein (SE) prediction at high temperatures. The spin-exchange rate forms a common curve with respect to T/η for all alkanes except cyclohexane and another common curve in all three aromatic compounds. It is reasoned that although all spin-exchange rates are near to the SE prediction, the semblance of hydrodynamic behavior is superficial and arises incidentally from mathematical cancellation of terms in a generalized diffusion coefficient. As a collision pair coexists for a time within a solvation shell, the recollision time places a lower limit on the lifetime of the solvent cage. Although molecular dynamics simulations conducted thus far have yielded cage lifetimes lower than the measured recollision times, this is attributable to the fact that such simulations have mostly examined cage configurations too small to harbor a spin-exchange encounter, and is also likely due to restrictive mathematical definitions of cage lifetimes that are employed in such simulations.
A low band gap, solution processable oligothiophene with a dialkylated diketopyrrolopyrrole chromophore for use in bulk heterojunction solar cells
Authors: Tamayo Arnold Bernarte , Dang Xuan-Dang , Walker Bright , Seo Junghwa , Kent Tyler , Nguyen Thuc-Quyen
Published: March 2009

Bulk heterojunction solar cells are fabricated from blends of oligothiophene with a dialkylated diketopyrrolopyrrole chromophore:[6,6]-phenyl C71 butyric acid methyl ester. Absorption and photocurrent of the films extend to 800 nm. A power conversion efficiency (PCE) of 3.0% is obtained under simulated 100 mW/cm2 AM1.5 illumination with a 9.2 mA/cm2 short-circuit current density and an open-circuit voltage of 0.75 V. The hole and electron mobilities in the 50:50 blend are fairly balanced, 1.0×10−4 and 4.8×10−4 cm2/V s, respectively. This is the highest PCE reported to date for solar cells using solution processable small molecules.
Strong plasmon absorption in InN thin films
Authors: Dixit A. , Sudakar C. , Thakur J. S. , Padmanabhan K. , Kumar Sanjiv , Naik R. , Naik V. M. , Lawes G.
Published: March 2009

We have fabricated InN thin films using rf magnetron sputtering from an indium (In) metal target. Optical and electrical measurements show that these as-grown films are n-type with carrier concentrations ranging from 1020 to 1021 cm−3. This variation in carrier density is produced by controlling the conditions during the deposition. We used Rutherford backscattering spectrometry to identify possible sources for n-type carriers. We found that in addition to strong direct bandgap optical absorption ranging from 1.4 to 2.0 eV, a large plasmon absorption peak in the infrared region (0.45–0.8 eV) is also observed. This tunable IR absorption suggests that these highly degenerate InN films could be used for a number of applications, including optical filters and infrared devices.
Measurement of apparent temperature in post-detonation fireballs using atomic emission spectroscopy
Authors: Lewis W. K. , Rumchik C. G.
Published: March 2009

The energy release dynamics of explosives are of ongoing interest, but the short timescales involved often limit the measurements that can be made during these processes. We have used atomic emission spectroscopy to measure the temperature of fireballs resulting from detonation of charges of Hexahydro-1,3,5-trinitro-1,3,5-triazine doped with barium nitrate. The time-averaged emission spectra indicate an apparent temperature of ∼3000 K, in good agreement with theoretical predictions. The technique demonstrated herein should be applicable to time-resolved studies, including those on detonation timescales.
Observation of back-surface reflected luminescence in GaAs excited by ultrashort pulses
Authors: Wen X. M. , Smith T. A. , Ghiggino K. P. , Dao L. V. , Hannaford P.
Published: March 2009

Multiple peaks observed in the temporal evolution of the luminescence of GaAs excited by an ultrashort pulse are attributed to the effect of back-surface reflection. The luminescence components originating from the direct emission and the back-surface reflection are well distinguished using up-conversion luminescence. At an appropriately high excitation energy a sharp peak in the luminescence evolution is observed in a self-assembled InGaAs/GaAs quantum dot sample, which is attributed to stimulated emission excited by the back-surface reflection.
Design and evaluation of a nanoscale differential tensile test device for nanofibers
Authors: Edmondson Dennis , Bhattarai Narayan , Jana Soumen , Kim Abraham , Zhang Miqin
Published: March 2009

The development of nanofibers could open new avenues in fundamental research and novel applications. Tensile properties of these nanofibers are a good indicator of their overall mechanical response. However, accurate measurements of tensile properties at the micro- and nanoscales remain a challenge. Here we report a simple but highly efficient differential nanoscale tensile test device constructed from off the shelf state-of-the-art components. The unique feature of this device is that it can measure the applied load and specimen’s deformation in the nanonewton and nanometer scales, respectively. First experimental results on electrospun nanofibers are reported.
Colossal photostructural changes in chalcogenide glasses: Athermal photoinduced polymerization in AsxS100−x bulk glasses revealed by near-bandgap Raman scattering
Authors: Kyriazis F. , Yannopoulos S. N.
Published: March 2009

Near-bandgap Raman scattering was used to induce and study photostructural changes in AsxS100−x bulk glasses (5≤xAs≤40) revealing a new photoinduced polymerization effect. Raman spectra were recorded also in off-resonant conditions allowing for a detailed comparison between the “equilibrium” glass structure and the metastable one induced by illumination. It is shown that in S-rich glasses, structural changes involve the athermal scission of S8 rings and their polymerization to Sn chains. The fraction of bonds involved in this effect is surprisingly high, being one order of magnitude higher than the corresponding fractions reported up to now in photostructural studies in chalcogenide glasses.
Metal mirror assisting light extraction from patterned AlGaInP light-emitting diodes
Authors: Kim Sun-Kyung , Song Hyun Don , Ee Ho-Seok , Choi Hyun Min , Cho Hyun Kyong , Lee Yong-Hee , Park Hong-Gyu
Published: March 2009

We demonstrate light extraction from metal reflector-based AlGaInP photonic crystal (PhC) light-emitting diodes (LEDs). The photons reflected by a high-reflectivity, small-absorption, bottom Ag mirror steadily interact with the PhC, and thus enhanced light extraction is achieved. The square lattice PhC patterns are fabricated on an upper n-doped AlGaInP surface with a depth of 500 nm. An optical power measurement using an integration sphere shows that the extraction efficiency of the PhC LED is ∼1.8 times larger than that of the nonpatterned LED. A three-dimensional finite difference time domain simulation is performed to understand the output enhancement extracted by the PhC and the effect of internal absorption.
Gender, Ethnicity, and Self-Employment: A Multilevel Analysis across US Metropolitan Areas
Authors: Wang Qingfang
Published: March 2009

Rates of self-employment differ among ethnic groups, between men and women, and by place. Using the 2000 5% Public Use Microdata Samples and hierarchical regression modeling, I examine in this study how metropolitan labor-market characteristics influence the probability of self-employment among non-Hispanic whites, blacks, Hispanics, and Asians in the United States, separately for men and women. The results show that, after controlling for individual-level characteristics, metropolitan labor-market characteristics—including macroeconomic conditions, overall business structure, ethnic composition, and residential segregation—significantly influence self-employment patterns across ethnic and gender groups.
Evaluation and Environmental Governance: The Institutionalisation of Ecological Footprinting
Authors: Collins Andrea , Cowell Richard , Flynn Andrew
Published: March 2009

This paper applies insights from actor-network theory to extend our understanding of the influence of evaluation techniques in decision making. Rather than assuming that evaluation is influential because of the intrinsic methodological veracity of the technique—that is, because it measures ‘the truth’ of our environmental predicament—it is more useful to view the adoption of evaluation tools in terms of their contested translation into decision-making settings. This is demonstrated by the growing use of the ‘ecological footprint’ (EF), which has been presented as a methodologically robust yet intuitive tool for guiding decisions. By following the use of the EF within a UK local government setting (Cardiff Council), one can see that its influence depended only partly on claims to technical credibility; it also depended upon an array of other institutional and personal commitments. The extent to which the EF was translated into policy settings reflected the way in which it had been institutionalised as an ‘obligatory passage point’ (after Latour) in decision-making arrangements, and careful representation of the implications of footprint measures. Overall, the credibility of the EF—as with other evaluation techniques—can be seen as a complex product of internal properties and institutional settings, but also of wider network-building activities which seek to cement the status of footprint calculations.
No correlation between cesarean section rates and perinatal mortality of singleton infants over 2,500 g
Authors: JONSDOTTIR GUDNY , SMARASON ALEXANDER K. , GEIRSSON REYNIR T. , BJARNADOTTIR RAGNHEIDUR I.
Published: March 2009

A rising cesarean section rate has been suggested as of benefit in reducing the already low perinatal death rates seen in developed countries for infants of normal birthweight. Iceland has one of the lowest national corrected and uncorrected perinatal mortality rates. Information was collected through the Icelandic birth registry for all 82,251 deliveries of non‐malformed singletons weighing ≥ 2,500 g at birth, for the 20 years 1987–2006. The mean birthweight‐specific perinatal mortality rate for these pregnancies was 2.0/1,000 per year (range 0.8–4.1/1000) without significant changes over the study period. The cesarean section rate varied between 11.9 and 16.7% and did not correlate with the perinatal mortality rate. Among the nulliparous women, cesarean section rates increased from 13.1 to 17.9% without correlation to the perinatal mortality, which on average was 1.7/1,000. A further benefit from rising cesarean section rates at term in countries with a prior low perinatal mortality is questioned.
Individual attitudes and perceived social norms: Reports on HIV/AIDS‐related stigma among service providers in China
Authors: Li Li , Liang Li‐Jung , Lin Chunqing , Wu Zunyou , Wen Yi
Published: March 2009

This study examined HIV/AIDS‐related stigma among Chinese service providers by comparing their personal attitudes toward people living with HIV/AIDS with their perception of social norms related to people living with HIV/AIDS. We randomly selected three provincial hospitals, four city/prefecture hospitals, 10 county hospitals, 18 township health clinics, and 54 village clinics from Yunnan, China. Doctors and nurses were randomly sampled proportionally to the doctor–nurse ratio of each hospital or clinic. Lab technicians were over‐sampled in order to include an adequate representation in the analysis. A total of 1,101 service providers participated in a voluntary, anonymous survey where demographic characteristics, individual attitude and perceived social norms toward people living with HIV/AIDS, discrimination intent at work, general prejudicial attitude and knowledge on HIV/AIDS were measured. A majority of the sample demonstrated a similarity between their personal views and what they thought most people in society believe. Multiple logistic regressions revealed that participants who were younger or reported personal contact with people living with HIV/AIDS were significantly more likely to report personal attitudes toward the population that were more liberal than their perceived social norms. Holding a more liberal personal attitude toward people living with HIV/AIDS than perceived social norms was significantly and negatively related to the level of discrimination intent at work, perceived discrimination at interpersonal level and the level of general prejudicial attitude toward people living with HIV/AIDS. Results underscored the importance of understanding social norms and personal attitudes in studying HIV‐related stigma and called for the incorporation of existing human capital into future HIV stigma reduction programs.
Which Sectors Drive Regional Economic Development? Changes in Employment in Knowledge-based and Consumption-based Sectors and Regional Economic Performance
Authors: Johnston Andrew
Published: March 2009

Despite increasing as a proportion of economic activity, the role of consumption in regional economic development does not feature highly in associated policies or debates. Instead, the focus is on the promotion of innovative activity and knowledge assets. Using NUTS 3 level data, this paper examines the changing level of employment in consumption-based and knowledge-based sectors in order to assess the contribution of each to regional economic development.
The Revitalization of New England's Small Town Mills: Breathing New Life into Old Places
Authors: Kotval Zenia , Mullin John
Published: March 2009

This paper describes and analyzes the recent experience of communities in the six New England states concerning the revitalization of their 19th century mills and mill yards. It begins with an examination of the importance of these complexes to the economy of New England in the 19th and early 20th centuries and the slow decline of the mills into the present. It then identifies the factors that are now stimulating their revitalization and provides myriad examples of where success has occurred. This is followed by a section on ‘Lessons Learned’ from the experience, and a closing comment concerning future actions.
A CD317/tetherin–RICH2 complex plays a critical role in the organization of the subapical actin cytoskeleton in polarized epithelial cells
Authors: Rollason Ruth , Korolchuk Viktor , Hamilton Clare , Jepson Mark , Banting George
Published: March 2009

CD317/tetherin is a lipid raft–associated integral membrane protein with a novel topology. It has a short N-terminal cytosolic domain, a conventional transmembrane domain, and a C-terminal glycosyl-phosphatidylinositol anchor. We now show that CD317 is expressed at the apical surface of polarized epithelial cells, where it interacts indirectly with the underlying actin cytoskeleton. CD317 is linked to the apical actin network via the proteins RICH2, EBP50, and ezrin. Knocking down expression of either CD317 or RICH2 gives rise to the same phenotype: a loss of the apical actin network with concomitant loss of apical microvilli, an increase in actin bundles at the basal surface, and a reduction in cell height without any loss of tight junctions, transepithelial resistance, or the polarized targeting of apical and basolateral membrane proteins. Thus, CD317 provides a physical link between lipid rafts and the apical actin network in polarized epithelial cells and is crucial for the maintenance of microvilli in such cells.
Influence of cyclin type and dose on mitotic entry and progression in the early Drosophila embryo
Authors: McCleland Mark L. , Farrell Jeffrey A. , O'Farrell Patrick H.
Published: March 2009

Cyclins are key cell cycle regulators, yet few analyses test their role in timing the events that they regulate. We used RNA interference and real-time visualization in embryos to define the events regulated by each of the three mitotic cyclins of Drosophila melanogaster, CycA, CycB, and CycB3. Each individual and pairwise knockdown results in distinct mitotic phenotypes. For example, mitosis without metaphase occurs upon knockdown of CycA and CycB. To separate the role of cyclin levels from the influences of cyclin type, we knocked down two cyclins and reduced the gene dose of the one remaining cyclin. This reduction did not prolong interphase but instead interrupted mitotic progression. Mitotic prophase chromosomes formed, centrosomes divided, and nuclei exited mitosis without executing later events. This prompt but curtailed mitosis shows that accumulation of cyclin function does not directly time mitotic entry in these early embryonic cycles and that cyclin function can be sufficient for some mitotic events although inadequate for others.
Spatiotemporal control of mitosis by the conserved spindle matrix protein Megator
Authors: Lince-Faria Mariana , Maffini Stefano , Orr Bernard , Ding Yun , Florindo Cláudia , Sunkel Claudio E. , Tavares Álvaro , Johansen Jørgen , Johansen Kristen M. , Maiato Helder
Published: March 2009

A putative spindle matrix has been hypothesized to mediate chromosome motion, but its existence and functionality remain controversial. In this report, we show that Megator (Mtor), the Drosophila melanogaster counterpart of the human nuclear pore complex protein translocated promoter region (Tpr), and the spindle assembly checkpoint (SAC) protein Mad2 form a conserved complex that localizes to a nuclear derived spindle matrix in living cells. Fluorescence recovery after photobleaching experiments supports that Mtor is retained around spindle microtubules, where it shows distinct dynamic properties. Mtor/Tpr promotes the recruitment of Mad2 and Mps1 but not Mad1 to unattached kinetochores (KTs), mediating normal mitotic duration and SAC response. At anaphase, Mtor plays a role in spindle elongation, thereby affecting normal chromosome movement. We propose that Mtor/Tpr functions as a spatial regulator of the SAC, which ensures the efficient recruitment of Mad2 to unattached KTs at the onset of mitosis and proper spindle maturation, whereas enrichment of Mad2 in a spindle matrix helps confine the action of a diffusible “wait anaphase” signal to the vicinity of the spindle.
Regulation of Tomato Prf by Pto-like Protein Kinases
Authors: Mucyn Tatiana S. , Wu Ai-Jiuan , Balmuth Alexi L. , Arasteh Julia Maryam , Rathjen John P.
Published: March 2009

Tomato Prf encodes a nucleotide-binding domain shared by Apaf-1, certain R proteins, and CED-4 fused to C-terminal leucine-rich repeats (NBARC-LRR) protein that is required for bacterial immunity to Pseudomonas syringae and sensitivity to the organophosphate fenthion. The signaling pathways involve two highly related protein kinases. Pto kinase mediates direct recognition of the bacterial effector proteins AvrPto or AvrPtoB. Fen kinase is required for fenthion sensitivity and recognition of bacterial effectors related to AvrPtoB. The role of Pto and its association with Prf has been characterized but Fen is poorly described. We show that, similar to Pto, Fen requires N-myristoylation and kinase activity for signaling and interacts with the N-terminal domain of Prf. Thus, the mechanisms of activation of Prf by the respective protein kinases are similar. Prf–Fen interaction is underlined by coregulatory mechanisms in which Prf negatively regulates Fen, most likely by controlling kinase activity. We further characterized negative regulation of Prf by Pto, and show that regulation is mediated by the previously described negative regulatory patch. Remarkably, the effectors released negative regulation of Prf in a manner dependent on Pto kinase activity. The data suggest a model in which Prf associates generally with Pto-like kinases in tightly regulated complexes, which are activated by effector-mediated disruption of negative regulation. Release of negative regulation may be a general feature of activation of NBARC-LRR proteins by cognate effectors.
Higher Copy Numbers of the Potato RB Transgene Correspond to Enhanced Transcript and Late Blight Resistance Levels
Authors: Bradeen James M. , Iorizzo Massimo , Mollov Dimitre S. , Raasch John , Kramer Lara Colton , Millett Benjamin P. , Austin-Phillips Sandra , Jiang Jiming , Carputo Domenico
Published: March 2009

Late blight of potato ranks among the costliest of crop diseases worldwide. Host resistance offers the best means for controlling late blight, but previously deployed single resistance genes have been short-lived in their effectiveness. The foliar blight resistance gene RB, previously cloned from the wild potato Solanum bulbocastanum, has proven effective in greenhouse tests of transgenic cultivated potato. In this study, we examined the effects of the RB transgene on foliar late blight resistance in transgenic cultivated potato under field production conditions. In a two-year replicated trial, the RB transgene, under the control of its endogenous promoter, provided effective disease resistance in various genetic backgrounds, including commercially prominent potato cultivars, without fungicides. RB copy numbers and transcript levels were estimated with transgene-specific assays. Disease resistance was enhanced as copy numbers and transcript levels increased. The RB gene, like many other disease resistance genes, is constitutively transcribed at low levels. Transgenic potato lines with an estimated 15 copies of the RB transgene maintain high RB transcript levels and were ranked among the most resistant of 57 lines tested. We conclude that even in these ultra–high copy number lines, innate RNA silencing mechanisms have not been fully activated. Our findings suggest resistance-gene transcript levels may have to surpass a threshold before triggering RNA silencing. Strategies for the deployment of RB are discussed in light of the current research.
The Arabidopsis Patatin-Like Protein 2 (PLP2) Plays an Essential Role in Cell Death Execution and Differentially Affects Biosynthesis of Oxylipins and Resistance to Pathogens
Authors: Camera Sylvain La , Balagué Claudine , Göbel Cornelia , Geoffroy Pierrette , Legrand Michel , Feussner Ivo , Roby Dominique , Heitz Thierry
Published: March 2009

We previously reported that patatin-like protein 2 (PLP2), a pathogen-induced patatin-like lipid acyl hydrolase, promotes cell death and negatively affects Arabidopsis resistance to the fungus Botrytis cinerea and to the bacteria Pseudomonas syringae. We show here that, on the contrary, PLP2 contributes to resistance to Cucumber mosaic virus, an obligate parasite inducing the hypersensitive response. These contrasted impacts on different pathosystems were also reflected by differential effects on defense gene induction. To examine a possible link between PLP2 lipolytic activity and oxylipin metabolism, gene expression profiling was performed and identified B. cinerea among these pathogens as the strongest inducer of most oxylipin biosynthetic genes. Quantitative oxylipin profiling in wild-type and PLP2-modified, Botrytis-challenged plants established the massive accumulation of oxidized fatty acid derivatives in infected leaves. Several compounds previously described as modulating plant tissue damage and issued from the α-dioxygenase pathway were found to accumulate in a PLP2-dependent manner. Finally, the contribution of PLP2 to genetically controlled cell death was evaluated using PLP2-silenced or -overexpressing plants crossed with the lesion mimic mutant vascular-associated death 1 (vad1). Phenotypic analysis of double-mutant progeny showed that PLP2 expression strongly promotes necrotic symptoms in vad1 leaves. Collectively, our data indicate that PLP2 is an integral component of the plant cell death execution machinery, possibly providing fatty acid precursors for the biosynthesis of specific oxylipins and differentially affecting resistance to pathogens with distinct lifestyles.
A Rapid Method to Quantify Fungicide Sensitivity in the Brown Rot Pathogen Monilinia fructicola
Authors: Cox Kerik D. , Quello Kacie , Deford Ryan J. , Beckerman Janna L.
Published: March 2009

Management of brown rot of stone fruit relies upon the application of effective fungicides that may be compromised by the development of fungicide resistance. We evaluated fungicide resistance in the brown rot pathogen, Monilinia fructicola, using Alamar blue (AB) dye, or resazurin, a chromogenic substrate that can be used as an indicator of respiration, in a 96-well microtiter format. We compared the AB method to traditional mycelial growth assays for resistance screening using 10 isolates of M. fructicola that represented a range of sensitivities to fenbuconazole. Using traditional mycelial growth assays, isolate sensitivity ranged from 17.7 to 115.3% growth on medium amended with fenbuconazole at 0.03 μg/ml relative to that on nonamended medium. Concordant results between both assays were obtained (R2 = 0.9943, P < 0.0001), but the AB method provided results within 24 h, as opposed to the 3- to 5-day period required for mycelial growth assays. We found that sensitive isolates reduced AB less than resistant isolates in the presence of fungicide. Spore density influenced the reduction of AB by M. fructicola; spectrophotometric discrimination of fungicide sensitivity was best achieved at a density of 105 spores/ml.
Epiphytic Populations ofXanthomonas albilineansand Subsequent Sugarcane Stalk Infection Are Linked to Rainfall in Guadeloupe
Authors: Champoiseau P. , Rott P. , Daugrois J.-H.
Published: March 2009

Three separate field trials were established in Guadeloupe under different agronomic and rainfall conditions to study phyllosphere contamination and infection of sugarcane plants by Xanthomonas albilineans, the causal agent of sugarcane leaf scald. Disease-free and leaf scald susceptible cv. B69566 was planted and monitored during three 1-year crop cycles. Presence of leaf scald contaminated sugarcane fields in the proximity of the disease-free trials appeared critical in early contamination of the sugarcane phyllosphere. Later on, particular meteorological events, such as tropical storms, were also important in aerial spread of the pathogen. A positive correlation was found between epiphytic populations of X. albilineans and severity of leaf necrotic symptoms, but occurrence of leaf symptoms was not always related to subsequent stalk infection. However, when the data of the three crop seasons were considered together, a high correlation was found between rainfall and maximum epiphytic populations of X. albilineans, and between rainfall and subsequent stalk infections. Consequently, rainfall is a key factor to be considered in evaluation of risks of leaf scald epidemics, and protocols for propagation of healthy sugarcane material and screening methods for leaf scald resistance may have to be revised in humid tropical locations.
Crown Rust Development and Selection for Virulence in Puccinia coronata f. sp. avenae in an Oat Multiline Cultivar
Authors: Carson M. L.
Published: March 2009

Crown rust, caused by Puccinia coronata f. sp. avenae is the most important disease of cultivated oat in North America. Numerous race-specific (Pc) genes for crown rust have been found in Avena spp. but this type of resistance has not been durable when used in oat cultivars. Increasing diversity for resistance within a crop by the use of multiline cultivars or varietal mixtures has been proposed as a means of achieving durable resistance to highly variable pathogens such as P. coronata f. sp. avenae. Multiline cv. E77 was evaluated over multiple seasons in the University of Minnesota buckthorn nursery in St. Paul. Buckthorn (Rhamnus cathartica, the alternate host of P. coronata) supports a sexually recombining, highly diverse crown rust population in the St. Paul nursery. Crown rust severity on flag leaves was measured multiple times on E77 and its 10 component lines during grain filling. Single-urediniospore isolates taken from crown rust samples during early stages of the epidemic and at the end of the epidemic were tested for virulence on the 10 component lines of E77 in greenhouse seedling tests. Crown rust development was reduced in E77 compared with the weighted mean of the component lines at all stages of the crown rust epidemics. The mean virulence of single-urediniospore isolates tended to increase late in the epidemic on E77. These data suggest that multilines may select for complex virulence or “super races” and any resistance effect may not be durable.
Disease Risk of Potting Media Infested with Phytophthora ramorum Under Nursery Conditions
Authors: Tjosvold S. A. , Chambers D. L. , Fichtner E. J. , Koike S. T. , Mori S. R.
Published: March 2009

Phytophthora ramorum has been found in potting media of containerized plants; however, the role of infested media on disease development under nursery conditions is unknown. This study assesses pathogen survival, sporulation, and infectivity to rhododendron plants in nursery pots with infected leaf litter that were maintained under greenhouse and field conditions. The influence of environmental conditions and irrigation method on disease incidence was also assessed. Infected leaf disks were buried below the soil surface of potted rhododendrons and retrieved at approximately 10-week intervals for up to 66 weeks. Pathogen survival was assessed by either isolation or induction of sporulation in water over three experimental periods. P. ramorum was recovered from infected leaf disks incubated in planted pots for longer than 1 year. Chlamydospores and sporangia formed on hydrated leaf disks but relative production of each spore type varied with the duration of incubation in soil. Root infections were detected after 40 weeks in infested soil. Foliar infections developed on lower leaves but only after spring rain events. Sprinkler irrigation promoted the development of foliar infections; no disease incidence was observed in drip-irrigated plants unless foliage was in direct contact with infested soil. Management implications are discussed.
Species ofFusariumIsolated from River and Sea Water of Southeastern Spain and Pathogenicity on Four Plant Species
Authors: Palmero D. , Iglesias C. , de Cara M. , Lomas T. , Santos M. , Tello J. C.
Published: March 2009

Species of Fusarium were isolated from water samples collected from the Andarax River and coastal sea water of the Mediterranean in Granada and Almería provinces of southeastern Spain. In total, 18 water samples were analyzed from the Andarax River, and 10 species of Fusarium were isolated: Fusarium anthophilum, F. acuminatum, F. chlamydosporum, F. culmorum, F. equiseti, F. verticillioides, F. oxysporum, F. proliferatum, F. solani, and F. sambucinum. In addition, five species were isolated from 33 sea water samples from the Mediterranean Sea: F. equiseti, F. verticillioides, F. oxysporum, F. proliferatum, and F. solani. When considering the samples by their origins, 77.8% of the river water samples yielded at least one species of Fusarium, with F. oxysporum comprising 72.2% of the total isolates. In the case of marine water, 45.5% of the samples yielded at least one species of Fusarium, with F. solani comprising 36.3% of the total isolates. The pathogenicity of 41 isolates representing nine of the species collected from river and sea water during the study was evaluated on barley, kohlrabi, melon, and tomato. Inoculation with F. acuminatum, F. chlamydosporum, F. culmorum, F. equiseti, F. verticillioides, F. oxysporum, F. proliferatum F. solani, and F. sambucinum resulted in pre- and post-emergence damping off. Pathogenicity of Fusarium isolates did not seem to be related to the origin of the isolates (sea water or fresh water). However, the presence of pathogenic species of Fusarium in river water flowing to the sea could indicate long-distance dispersal in natural water environments.
Field Evaluation of Biological Control of Fire Blight in the Eastern United States
Authors: Sundin George W. , Werner Nicole A. , Yoder Keith S. , Aldwinckle Herb S.
Published: March 2009

The bacterial antagonists Pseudomonas fluorescens A506, Pantoea agglomerans C9-1, and Pantoea agglomerans E325 and preparations of Bacillus subtilis QST 713 containing bacterial endospores and lipopeptide metabolites were evaluated for efficacy in controlling fire blight in Michigan, New York, and Virginia. When examined individually, the biological control materials were not consistently effective in reducing blossom infection. The average reduction in blossom infection observed in experiments conducted between 2001 and 2007 was variable and ranged from 9.1 to 36.1%, while control with streptomycin was consistent and ranged from 59.0 to 67.3%. Incidence of blossom colonization by the bacterial antagonists was inconsistent, and <60% of stigmata had the antagonists present in 12 of 25 experiments. Consistent control of blossom infection was observed when the biological control materials were integrated into programs with streptomycin, resulting in a reduction of the number of streptomycin applications needed to yield similar levels of control. Our results indicate that the prospects for biological control of fire blight in the eastern United States are currently not high due to the variability in efficacy of existing biological control options.
Comparison of Assessment of Citrus Canker Foliar Symptoms by Experienced and Inexperienced Raters
Authors: Bock C. H. , Parker P. E. , Cook A. Z. , Riley T. , Gottwald T. R.
Published: March 2009

Citrus canker (Xanthomonas citri subsp. citri) is destructive in many citrus production regions in tropical and subtropical parts of the world. Assessment of canker symptoms is required for diverse reasons, including monitoring epidemics, evaluating the efficacy of control strategies, and disease response in breeding material. The objectives were to compare the ability of experienced and inexperienced raters at assessing citrus canker, to identify factors that affect the quality of the assessment, to determine common sources of error, and to discern how error is related to actual disease magnitude. Two-hundred digital leaf images (0 to 37% area infected) were assessed once by 28 raters, five of whom were experienced plant pathologists (PPs), and 23 who had no experience in disease severity assessment (NPPs). True disease (lesion number [LN], % necrotic area [%N], and % chlorotic+necrotic area [%CN]) was measured using image analysis on a leaf-by-leaf basis, and each parameter was estimated by the 28 raters. LN was neither severely over- nor underestimated, while %N was greatly overestimated, with a lesser tendency to overestimate %CN over the true severity range of these two symptom types. A linear relationship existed between estimate of the disease and true disease for all measures of severity. Data were heteroscedastic and error was not constant with increasing true disease. Agreement between rater estimates and true disease was measured with Lin's concordance correlation coefficient (ρc). LN showed greatest agreement (ρc = 0.88 to 0.99), followed by %CN (ρc = 0.80 to 0.95) and %N (ρc = 0.19 to 0.84). Greater lesion number resulted in overestimation of area infected for both %N and %CN. Overestimation was particularly noticeable at low disease severities. There was a linear relationship between log variance and log true disease for LN (r2 = 0.71), %N (r2 = 0.85), and %CN (r2 = 0.88), and raters tended to estimate disease above 10% to the nearest 5 or 10%. GLM analysis showed differences between PP and NPP groups in assessing disease. For LN, precision of assessment for both groups was similar (r2 > 0.92 and 0.94, respectively), but for estimates of %N and %CN, the PPs were more precise (%N and %CN, r2 = 0.61 and 0.73, respectively) compared to NPPs (%N and %CN, r2 = 0.45 and 0.58, respectively). Absolute error for mean LN was low. The absolute error of %N and %CN showed overestimation to approximately 8% area infected. Above 8%, absolute error increased, but comprised both over- and underestimation. For %N and %CN, relative error was almost exclusively positive and dramatic at severity <8% (up to approximately 600%), but at severity >10% it was relatively small. Error in rater estimates of canker severity is ubiquitous. Understanding these sources of error will aid in the development of both appropriate training and relevant rating aids.
First Report of Cherry virus A in Sweet Cherry Trees in China
Authors: Rao W.-L. , Zhang Z.-K. , Li R.
Published: March 2009

Plants in the genus Prunus of the family Rosaceae are important fruit and ornamental trees in China. In June of 2007, sweet cherry (Prunus avium) trees with mottling and mosaic symptoms were observed in a private garden near Kunming, Yunnan Province. Twenty-four samples, six each from sweet cherry, sour cherry (P. cerasus), flowering cherry (P. serrulata), and peach (P. persica) were collected from trees in private and community gardens in the area. The peach and sour and flowering cherry trees did not show any symptoms. Total nucleic acids were extracted using a cetyltrimethylammoniumbromide (CTAB) extraction method, and the extracts were tested for the following eight viruses by reverse transcription (RT)-PCR: American plum line pattern virus, Apple chlorotic leaf spot virus, Cherry green ring mottle virus, Cherry necrotic rusty mottle virus, Cherry virus A (CVA), Little cherry virus 1, Prune dwarf virus, and Prunus necrotic ringspot virus. Only CVA was detected in two symptomatic sweet cherry trees by RT-PCR with forward (5′-GTGGCATTCAACTAGCACCTAT-3′) and reverse (5′-TCAGCTGCCTCAGCTTGGC-3′) primers specific to an 873-bp fragment of the CVA replicase gene (2). The CVA infection of the two trees was confirmed by RT-PCR using primers CVA-7097U and CVA-7383L that amplified a 287-bp fragment from the 3′-untranslated region (UTR) of the virus (1). Amplicons from both amplifications were cloned and sequenced. Analysis of the predicted amino acid sequences of the 873-bp fragments (GenBank Accession Nos. EU862278 and EU862279) showed that they were 98% identical with each other and 97 to 98% with the type isolate of CVA from Germany (GenBank Accession No. NC_003689). The 286-bp sequences of the 3′-UTR (GenBank Accession Nos. FJ608982 and FJ608983) were 93% identical with each other and 93 to 98% with the type isolate. The sequence indicated that the three isolates were very similar and should be considered to be the same strain. CVA is a member of the genus Capillovirus in the family Flexiviridae and has been previously reported in Europe, North America, and Japan. The contribution of CVA to the symptoms observed and its distribution in China remain to be evaluated. To our knowledge, this is the first report of CVA in sweet cherry in China.

References: (1) M. Isogai et al. J. Gen. Plant Pathol. 70:288. (2) W. Jelkmann. J. Gen. Virol. 76:2015, 1995.
First Report of Japanese Apple Rust Caused by Gymnosporangium yamadae on Malus spp. in North America
Authors: Yun H. Y. , Minnis A. M. , Rossman A. Y.
Published: March 2009

Plants in the genus Malus Mill. are grown in temperate regions for fruit crops such as apple and ornamental landscape plants such as flowering crab apple. Gymnosporangium yamadae Miyabe ex G. Yamada, cause of Japanese apple rust, is known to attack economically important species of Malus in Asia. In August 2004 and July 2008, the aecial stage of a rust fungus was observed in Wilmington, DE and nearby in Media, PA on leaves of toringo crab apple (Malus toringo (Siebold) Siebold ex de Vriese), a cultivated plant native to Asia. On the basis of morphological and molecular characteristics, the fungus was identified as G. yamadae. This pathogen has not been previously reported in North America. The identification was confirmed by morphological comparisons with specimens of G. yamadae from Asia and descriptions (1–3) as well as using the D1/D2 domain of 28S rDNA sequence data G. clavariiforme (GenBank Accession No. AR426211), G. clavipes (GenBank Accession No. DQ354545), G. cornutum (GenBank Accession No. AF426210), G. juniperi-virginianae (GenBank Accession Nos. AF522167, AY629316, and DQ354547), G. libocedri (GenBank Accession No. AF522168), G. sabinae (GenBank Accession Nos. AF426209 and AY512845) and G. yamadae (GenBank Accession Nos. FJ559373 and FJ559375). The specimens from North America included aecia of G. yamadae that are foliicolous, hypophyllous, roestelioid, and 4 to 7 mm high. The peridia are yellow-brown to brown and cornute to tubular with a closed brown tip at the apex and lacerate sides; the peridial remains often form a reticulate pattern. The peridial cells are long-narrow rhomboid, 83 to 120 μm long with smooth outer walls and verrucose to echinulate inner and side walls. The aeciospores are globose, 18 to 28 × 19 to 29 μm, with a slightly coronate surface and brown-yellow walls 2 to 3 μm thick. The telia known on Juniperus spp. were not observed. The specimens were deposited in the U.S. National Fungus Collections (BPI 878846, BPI 878847, BPI 878848, and BPI 878849). The 28S rDNA sequence of G. yamadae from BPI 878849 was deposited in GenBank as Accession No. FJ455091. Aecia of G. juniperi-virginianae, cause of cedar apple rust, differ from G. yamadae in having recurved peridial walls at maturity.

References: (1) F. D. Kern. A Revised Taxonomic Account of Gymnosporangium. Pennsylvania State University Press, University Park, PA, 1973. (2) S. K. Lee and M. Kakishima. Mycoscience 40:109, 1999. (3) S. K. Lee and M. Kakishima. Mycoscience 40:121. 1999.