bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure loss in channel flow resulting from a sudden change in boundary condition from no-slip to partial-slip
Authors: Ng Chiu-On , Sun Rui
Published: October 2017

A semi-analytical model is presented for pressure-driven flow through a channel, where local pressure loss is incurred at a sudden change in the boundary condition: from no-slip to partial-slip. Assuming low-Reynolds-number incompressible flow and periodic stick–slip wall patterning, the problems for parallel-plate and circular channels are solved using the methods of eigenfunction expansion and point match. The present study aims to examine in detail how the flow will evolve, on passing through the cross section at which the change in the slip condition occurs, from a no-slip parabolic profile to a less sheared profile with a boundary slip. The present problem is germane to, among other applications, flow through a channel bounded by superhydrophobic surfaces, which intrinsically comprise an array of no-slip and partial-slip segments. Results are presented to show that the sudden change in the boundary condition will result in additional resistance to the flow. Near the point on the wall where a slip change occurs is a region of steep pressure gradient and intensive vorticity. The acceleration of near-wall fluid particles in combination with the no-slip boundary condition leads to a very steep velocity gradient at the wall, thereby a sharp increase in the wall shear stress, shortly before the fluid enters the channel with a slippery wall. Results are also presented to show the development of flow in the entrance region in the slippery channel. The additional pressure loss can be represented by a dimensionless loss parameter, which is a pure function of the slip length for channels much longer than the entrance length.
Dynamic large eddy simulation: Stability via realizability
Authors: Mokhtarpoor Reza , Heinz Stefan
Published: October 2017

The concept of dynamic large eddy simulation (LES) is highly attractive: such methods can dynamically adjust to changing flow conditions, which is known to be highly beneficial. For example, this avoids the use of empirical, case dependent approximations (like damping functions). Ideally, dynamic LES should be local in physical space (without involving artificial clipping parameters), and it should be stable for a wide range of simulation time steps, Reynolds numbers, and numerical schemes. These properties are not trivial, but dynamic LES suffers from such problems over decades. We address these questions by performing dynamic LES of periodic hill flow including separation at a high Reynolds number Re = 37 000. For the case considered, the main result of our studies is that it is possible to design LES that has the desired properties. It requires physical consistency: a PDF-realizable and stress-realizable LES model, which requires the inclusion of the turbulent kinetic energy in the LES calculation. LES models that do not honor such physical consistency can become unstable. We do not find support for the previous assumption that long-term correlations of negative dynamic model parameters are responsible for instability. Instead, we concluded that instability is caused by the stable spatial organization of significant unphysical states, which are represented by wall-type gradient streaks of the standard deviation of the dynamic model parameter. The applicability of our realizability stabilization to other dynamic models (including the dynamic Smagorinsky model) is discussed.
Higher order reentrant post modes in cylindrical cavities
Authors: McAllister Ben T. , Shen Yifan , Flower Graeme , Parker Stephen R. , Tobar Michael E.
Published: October 2017

Reentrant cavities are microwave resonant devices employed in a number of different areas of physics. They are appealing due to their simple frequency tuning mechanism, which offers large tuning ranges. Reentrant cavities are, in essence, 3D lumped LC circuits consisting of a conducting central post embedded in a resonant cavity. The lowest order reentrant mode (which transforms from the TM010 mode) has been extensively studied in past publications. In this work, we show the existence of higher order reentrant post modes (which transform from the TM01n mode family). We characterize these new modes in terms of their frequency tuning, filling factors, and quality factors, as well as discuss some possible applications of these modes in fundamental physics tests.
Grain boundary dominated electrical conductivity in ultrananocrystalline diamond
Authors: Wiora Neda , Mertens Michael , Brühne Kai , Fecht Hans-Jörg , Tran Ich C. , Willey Trevor , van Buuren Anthony , Biener Jürgen , Lee Jun-Sik
Published: October 2017

N-type electrically conductive ultrananocrystalline diamond (UNCD) films were deposited using the hot filament chemical vapor deposition technique with a gas mixture of H2, CH4 and NH3. Depending on the deposition temperature and ammonia feed gas concentration, which serves as a nitrogen source, room temperature electrical conductivities in the order of 10−2 to 5 × 101 S/cm and activation energies in the meV range were achieved. In order to understand the origin of the enhanced electrical conductivity and clarify the role of ammonia addition to the process gas, a set of UNCD films was grown by systematically varying the ammonia gas phase concentration. These samples were analyzed with respect to their morphology and electrical properties as well as their carbon and nitrogen bonding environments. Temperature dependent electrical conductivity measurements (300–1200 K) show that the electrical conductivity of the samples increases with temperature. The near edge x-ray absorption fine structure measurements reveal that the electrical conductivity of the UNCD films does not correlate directly with ammonia addition, but depends on the total amount of sp2 bonded carbon in the deposited films.
Computing vibrational energy levels of CH4 with a Smolyak collocation method
Authors: Avila Gustavo , Carrington Tucker
Published: October 2017

In this paper, we demonstrate that it is possible to apply collocation to compute vibrational energy levels of a five-atom molecule using an exact kinetic energy operator (with cross terms and coordinate-dependent coefficients). This is made possible by using (1) a pruned basis of products of univariate functions; (2) a Smolyak grid made from nested sequences of grids for each coordinate; (3) a collocation method that obviates the need to solve a generalized eigenvalue problem; (4) an efficient sequential transformation between the (nondirect product) grid and the (nondirect product) basis representations; and (5) hierarchical univariate functions that make it possible to avoid storing large intermediate vectors. The accuracy of the method is confirmed by computing 500 vibrational energy levels of methane.
Impurity and eccentricity effects on the nonlinear optical rectification in a quantum ring under lateral electric fields
Authors: Niculescu E. C. , Stan C. , Bejan D. , Cartoaje C.
Published: October 2017

Within the framework of the effective-mass approximation, the effect of different static perturbations—lateral electric field, impurity donor, and eccentricity distortion—on the nonlinear optical rectification in a GaAs disc-shaped quantum ring has been investigated. For a concentric ring, the influence of the lateral electric field and off-center impurities on the intraband transitions at two values of temperature was studied in detail. We found that the optical response strongly depends on the incident light polarization and donor position within the structure. Compared with the profile at 4 K, the optical rectification spectra exhibit at 77 K additional peaks of reduced magnitude in the low-frequency range. The main transition peaks become smaller, while their positions remain almost unchanged with temperature. For eccentric structures, relevant differences between small and large eccentricity regimes can be observed in the electronic properties. In this case, the energy spectra and the nonlinear optical response are very sensitive to the direction of the applied electric field. The effect can be used to identify the eccentricity of the system.
Dry-transferred CVD graphene for inverted spin valve devices
Authors: Drögeler Marc , Banszerus Luca , Volmer Frank , Taniguchi Takashi , Watanabe Kenji , Beschoten Bernd , Stampfer Christoph
Published: October 2017

Integrating high-mobility graphene grown by chemical vapor deposition (CVD) into spin transport devices is one of the key tasks in graphene spintronics. We use a van der Waals pick-up technique to transfer CVD graphene by hexagonal boron nitride (hBN) from the copper growth substrate onto predefined Co/MgO electrodes to build inverted spin valve devices. Two approaches are presented: (i) a process where the CVD-graphene/hBN stack is first patterned into a bar and then transferred by a second larger hBN crystal onto spin valve electrodes and (ii) a direct transfer of a CVD-graphene/hBN stack. We report record high spin lifetimes in CVD graphene of up to 1.75 ns at room temperature. Overall, the performances of our devices are comparable to devices fabricated from exfoliated graphene also revealing nanosecond spin lifetimes. We expect that our dry transfer methods pave the way towards more advanced device geometries not only for spintronic applications but also for CVD-graphene-based nanoelectronic devices in general where patterning of the CVD graphene is required prior to the assembly of final van der Waals heterostructures.
Defect quasi Fermi level control-based CN reduction in GaN: Evidence for the role of minority carriers
Authors: Reddy Pramod , Kaess Felix , Tweedie James , Kirste Ronny , Mita Seiji , Collazo Ramon , Sitar Zlatko
Published: October 2017

Compensating point defect reduction in wide bandgap semiconductors is possible by above bandgap illumination based defect quasi Fermi level (dQFL) control. The point defect control technique employs excess minority carriers that influence the dQFL of the compensator, increase the corresponding defect formation energy, and consequently are responsible for point defect reduction. Previous studies on various defects in GaN and AlGaN have shown good agreement with the theoretical model, but no direct evidence for the role of minority carriers was provided. In this work, we provide direct evidence for the role of minority carriers in reducing point defects by studying the predicted increase in work done against defect (CN−1) formation with the decrease in the Fermi level (free carrier concentration) in Si doped GaN at a constant illumination intensity. Comparative defect photoluminescence measurements on illuminated and dark regions of GaN show an excellent quantitative agreement with the theory by exhibiting a greater reduction in yellow luminescence attributed to CN−1 at lower doping, thereby providing conclusive evidence for the role of the minority carriers in Fermi level control-based point defect reduction.
Intensity distributions and isolated attosecond pulse generation from molecular high-order harmonic generation in H2+ driven by nonhomogeneous field
Authors: Feng Liqiang , Chu Tianshu
Published: October 2017

Intensity distributions and isolated attosecond pulse generation from the molecular high-order harmonic generation (MHHG) in H2+ and T2+ driven by the nonhomogeneous field have been theoretically investigated. (i) Generally speaking, the intensities of the harmonics driven by the homogeneous field can be enhanced as the initial vibrational state increases and much more intense harmonics can be obtained from the light nuclei. However, with the introduction of the nonhomogeneous effect, the enhanced ratios of the harmonic yields are decreased as the initial vibrational state increases. Moreover, the intensities of the harmonics from H2+ and T2+ are very sensitive to the nonhomogeneous effect of the laser field. (ii) The contributions of the MHHG from the two-H nuclei present the periodic variation as a function of the laser phase for the case of the symmetric nonhomogeneous field. However, for the case of the positive and the negative asymmetric nonhomogeneous fields, the left-H and the right-H play the dominating role in the MHHG, respectively. Moreover, as the angle between the laser polarization direction and the molecular axis increases, the intensity differences of the harmonics from the two-H nuclei are increased. (iii) By properly adding a half-cycle pulse into the positive asymmetric nonhomogeneous field, a supercontinuum with the bandwidth of 279 eV and an isolated 25 as pulse can be obtained.
Suppressing unsteady flow in arterio-venous fistulae
Authors: Grechy L. , Iori F. , Corbett R. W. , Shurey S. , Gedroyc W. , Duncan N. , Caro C. G. , Vincent P. E.
Published: October 2017

Arterio-Venous Fistulae (AVF) are regarded as the “gold standard” method of vascular access for patients with end-stage renal disease who require haemodialysis. However, a large proportion of AVF do not mature, and hence fail, as a result of various pathologies such as Intimal Hyperplasia (IH). Unphysiological flow patterns, including high-frequency flow unsteadiness, associated with the unnatural and often complex geometries of AVF are believed to be implicated in the development of IH. In the present study, we employ a Mesh Adaptive Direct Search optimisation framework, computational fluid dynamics simulations, and a new cost function to design a novel non-planar AVF configuration that can suppress high-frequency unsteady flow. A prototype device for holding an AVF in the optimal configuration is then fabricated, and proof-of-concept is demonstrated in a porcine model. Results constitute the first use of numerical optimisation to design a device for suppressing potentially pathological high-frequency flow unsteadiness in AVF.
Impacts on ecosystems, corrective restoration practices, and prospects for recovery: nine case studies in the continental United States
Authors: Jones T. A.
Published: October 2017

Ecological restoration in the United States is growing in terms of the number, size, and diversity of projects. Such efforts are intended to ameliorate past environmental damage and to restore functioning ecosystems that deliver desired levels of ecosystem services. In nine current restoration case studies from across the continental United States, this paper details (1) the impacts of the original disturbance and compounding secondary issues that compel restoration, (2) the corrective practices applied to advance restoration goals, and (3) the prospects for recovery of ecosystem services, including those involving associated animal populations. Ecosystem-altering impacts include flood control (Kissimmee River), flood control and navigation (Atchafalaya Basin), damming for irrigation-water storage (Colorado River) and hydroelectric power (Elwha River), logging and fire suppression (longleaf pine forest), plant invasions that decrease fire-return intervals (Great Basin shrublands, Mojave Desert), nutrient and sediment loading of watersheds (Chesapeake Bay, Mississippi River delta), and conversion of natural lands to agriculture (tallgrass prairie). Animal species targeted for recovery include the greater sage-grouse (Great Basin shrublands), the red-cockaded woodpecker (longleaf pine forest), the south-western willow flycatcher (Colorado River and its tributaries), the desert tortoise (Mojave Desert), eight salmonid fish (Elwha River), and the blue crab and eastern oyster (Chesapeake Bay).
Phylogenetic diversity anomaly in angiosperms between eastern Asia and eastern North America
Authors: Qian Hong , Jin Yi , Ricklefs Robert E.
Published: October 2017

Significance

Phylogenetic diversity is a measure of biodiversity that incorporates both the number of species and their evolutionary histories. Comparisons of biodiversity between regions that are currently ecologically similar but support different numbers of species are informed by considering differences in their geographic and evolutionary histories. Here we analyze diversity in numerous floras distributed across eastern Asia and eastern North America, and find that phylogenetic diversity in eastern Asia substantially exceeds that in eastern North America when controlling statistically for climate and species richness. This difference parallels the more complex history and geography of the Asian continent.
Pressure effects on collective density fluctuations in water and protein solutions
Authors: Russo Daniela , Laloni Alessio , Filabozzi Alessandra , Heyden Matthias
Published: October 2017

Significance

This is a combined study, which employs neutron scattering experiments and molecular dynamics simulations to compare high pressure-induced effects on collective properties of protein solutions and bulk water, to observe changes in the HB network structure of protein hydration water upon compression. Our experimental results reflect distinct properties of water at the protein–water interface, while at the same time atomistic molecular dynamics simulations allow us to analyze its pressure-dependent structural changes. This study therefore provides insights that allow establishing measurements of pressure-induced variations in collective dynamics as a probe to characterize biomolecular systems as complex as entire cells.
Insight into the growth pattern and bone fusion of basal birds from an Early Cretaceous enantiornithine bird
Authors: Wang Min , Li Zhiheng , Zhou Zhonghe
Published: October 2017

Significance

We report an Early Cretaceous bird from 120 My ago that has a completely fused carpometacarpus and pelvis, pushing back the date for these avian traits by over 40 My. We suggest that this taxon grew more rapidly than other basal birds, but the degree of bone fusion is not causally linked with growth pattern in primitive birds. We hypothesize that the surprisingly high degree of bone fusion in basal birds may have been environmentally induced pertinent to flight or alternatively resultant from genetic modifications. Future developmental studies focusing on the development of bone fusion are needed to test these hypotheses and illustrate how the skeletal system of living birds achieves its modern shape.
Specific cation effects at aqueous solution−vapor interfaces: Surfactant-like behavior of Li
+
revealed by experiments and simulations
Authors: Perrine Kathryn A. , Parry Krista M. , Stern Abraham C. , Van Spyk Marijke H. C. , Makowski Michael J. , Freites J. Alfredo , Winter Bernd , Tobias Douglas J. , Hemminger John C.
Published: October 2017

Significance

Ion adsorption to the interfaces of aqueous salt solutions plays a key role in a wide variety of chemical and biochemical processes. For example, the adsorption of ions to the surface of aqueous aerosol particles in the atmosphere influences their reactivity to gas-phase oxidants. While the so-called chaotropic anions (e.g., I
−
, SCN
−
, and ClO
4
−
) are known to have strong adsorption propensities, inorganic cations are generally regarded as being repelled from aqueous solution−air interfaces. Here we report a concerted experimental and computational study that reveals that Li
+
adsorbs to the interfaces of aqueous lithium halide solutions and, hence, is an exceptional cation.
Bird specimens track 135 years of atmospheric black carbon and environmental policy
Authors: DuBay Shane G. , Fuldner Carl C.
Published: October 2017

Significance

Emission inventories of major climate-forcing agents like black carbon suffer high uncertainty for the early industrial era, thereby limiting their utility for extracting past climate sensitivity to atmospheric pollutants. We identify bird specimens as incidental records of atmospheric black carbon, filling a major historical sampling gap. We find that prevailing emission inventories underestimate black carbon levels in the United States through the first decades of the 20th century, suggesting that black carbon’s contribution to past climate forcing may also be underestimated. This study builds toward a robust, spatially dynamic inventory of atmospheric black carbon, highlighting the value of natural history collections as a resource for addressing present-day environmental challenges.
TREM2 deficiency attenuates neuroinflammation and protects against neurodegeneration in a mouse model of tauopathy
Authors: Leyns Cheryl E. G. , Ulrich Jason D. , Finn Mary B. , Stewart Floy R. , Koscal Lauren J. , Remolina Serrano Javier , Robinson Grace O. , Anderson Elise , Colonna Marco , Holtzman David M.
Published: October 2017

Significance

Alzheimer’s disease (AD) is the most common cause of dementia and is a major public health problem for which there is currently no disease-modifying treatment. There is an urgent need for greater understanding of the molecular mechanisms underlying neurodegeneration in patients to create better therapeutic options. Recently, genetic studies uncovered novel AD risk variants in the microglial receptor, triggering receptor expressed on myeloid cells 2 (TREM2). Previous studies suggested that loss of TREM2 function worsens amyloid-β (Aβ) plaque-related toxicity. In contrast, we observe TREM2 deficiency mitigates neuroinflammation and protects against brain atrophy in the context of tau pathology. These findings indicate dual roles for TREM2 and microglia in the context of amyloid versus tau pathology, which are important to consider for potential treatments targeting TREM2.
Multielectron, multisubstrate molecular catalysis of electrochemical reactions: Formal kinetic analysis in the total catalysis regime
Authors: Costentin Cyrille , Nocera Daniel G. , Brodsky Casey N.
Published: October 2017

Significance

Small-molecule conversions important to contemporary energy science often involve the reaction of two substrates in a multielectron redox process. The design of catalysts to effect such reactions requires knowledge of the reaction mechanism. It was shown over 30 y ago that quantitative kinetics information may be extracted from the cyclic voltammograms of catalysts that promote reactions involving a single electron and a single substrate. Attempts to extend this model to multielectron, multisubstrate reactions have permitted only qualitative kinetics insights to be extracted. The models developed herein allow quantitative kinetics rate constants to be obtained from peak currents and peak potentials of electrocatalytic reactions beyond a single electron and substrate, and accordingly they should be useful for guiding rational catalyst design.
Relation between work function, microstructural and mechanical properties of TiN-films
Authors: Enriquez-Flores C. I. , Cruz-Valeriano E. , Gutierrez-Peralta A. , Gervacio-Arciniega J. J. , Ramírez-Álvarez E. , Leon-Sarabia E. , Moreno-Palmerin J.
Published: October 2017

A study of titanium nitride (TiN) films microstructural and mechanical properties at nanoscale using resonance tracking acoustic force atomic microscopy is presented. Also for this study, the work function ( Φe) measured for Kelvin Probe Force Microscopy of TiN films deposited by pulsed dc magnetron sputtering is analysed. The films were deposited on Si and glass substrates using a gas mixture ratio Ar–N2 10 and 12% of N2 and power density from 7.4 to 10.8 W cm−2 using the Pulsed DC Magnetron Sputtering. Mechanical properties at nanoscale are measured and a relation between microstructure and nanoscale elastic domains is seen. It was found that the hardness increases when the Φe increases. This directly proportional relationship between hardness and work function, for the first time observed and reported in this contribution, is more accurate and shows a stronger dependence than the relation between hardness and microstructural properties independently.
Association between Binge Drug use and Suicide Attempt among People who Inject Drugs
Authors: Fournier Charles , Ghabrash Maykel Farag , Artenie Adelina , Roy Elise , Zang Geng , Bruneau Julie , Jutras-Aswad Didier
Published: October 2017

Background: People who inject drugs (PWID) have an elevated risk of suicide attempt. Although different substances are associated with suicide attempt, the overall risk posed by binge behavior, a high-risk pattern of drug use, remains unclear. The objective of this study is to assess the association between binge drug use and suicide attempt in a prospective cohort of PWID in Montreal, Canada. Methods: Participants answered a biannual interviewer-administered questionnaire compiling information on sociodemographics, pattern of substance use (cocaine, amphetamine, opioids, sedative-hypnotics, alcohol, and cannabis), and psychosocial stressors and related markers. The relationship between suicide attempt and binge behavior was modeled using generalized estimating equations (GEEs), controlling for type and pattern of substance use, sociodemographic characteristics, and significant mental health markers. Results: Among 1240 participants (mean age ± SD: 38.2 ± 9.8) at baseline, 222 (17.9%) reported binge during the past 6–months. PWID reporting binge were significantly younger ( P < .001), less educated ( P = .012), less likely male ( P = .047), and had shorter history of injection ( P < .001). In addition, they were younger at first injection ( P = .014), reported higher rates of prostitution and psychological disorders ( P = .003), and were more likely to use other drugs except cannabis and alcohol. Binge was independently associated with attempted suicide in the GEE multivariate model (adjusted odds ratio [aOR 95% CI] = 1.91 [1.38–2.65], P < .001). Conclusions: Among PWID at high risk of suicide attempt, those who binge represent a particularly vulnerable subgroup. Although the exact mechanisms underlying this finding remain unresolved, several hypothesis pertaining to the neurobiological and psychosocial consequences of binge, as well as common personality traits, warrant further investigations.
Audiologist perceptions of diagnosis and management of children with non-organic hearing loss (NOHL)
Authors: Stiles Derek J.
Published: October 2017

Purpose:

About 7% of children between 6 and 17 years of age suffer from non-organic hearing loss (NOHL), yet little is known about how audiologists diagnose and manage this population. Audiologist appraisal of various approaches of evaluating children with NOHL was surveyed in order to determine which approaches are used most frequently and are perceived as most effective.

Method:

A web-based survey was distributed to audiologists working in pediatric centers and by word of mouth. Of 72 respondents, 61 submitted a complete survey. Analysis of the responses was performed to determine what term audiologists use when describing this population, which approaches are perceived as most effective and used most frequently, and what is the perceived role of the audiologist in managing this population.

Results:

As a whole, results were heterogeneous. The most used term to describe this presentation was ‘functional’ by 38% of respondents. The most effective approaches were restricted range, conditioned play, and reinstruction. The least effective approaches were behavioral observation, ear pointing, and counting beeps. Respondents primarily described the role of the audiologist as one of referral source back to the medical home or specialist.

Conclusion:

Overall responses to the survey were heterogeneous. This area may benefit from a practice statement that provides guidance on evaluating this population as well as further research on actual effectiveness of the test approaches (versus perceived).
Microtubule stabilization drives 3D centrosome migration to initiate primary ciliogenesis
Authors: Pitaval Amandine , Senger Fabrice , Letort Gaëlle , Gidrol Xavier , Guyon Laurent , Sillibourne James , Théry Manuel
Published: October 2017

Primary cilia are sensory organelles located at the cell surface. Their assembly is primed by centrosome migration to the apical surface, yet surprisingly little is known about this initiating step. To gain insight into the mechanisms driving centrosome migration, we exploited the reproducibility of cell architecture on adhesive micropatterns to investigate the cytoskeletal remodeling supporting it. Microtubule network densification and bundling, with the transient formation of an array of cold-stable microtubules, and actin cytoskeleton asymmetrical contraction participate in concert to drive apical centrosome migration. The distal appendage protein Cep164 appears to be a key actor involved in the cytoskeleton remodeling and centrosome migration, whereas intraflagellar transport 88’s role seems to be restricted to axoneme elongation. Together, our data elucidate the hitherto unexplored mechanism of centrosome migration and show that it is driven by the increase and clustering of mechanical forces to push the centrosome toward the cell apical pole.
The search environment is not (always) benign: reassessing the risks of organizational search
Authors: MacAulay Samuel C , Steen John , Kastelle Tim
Published: October 2017

March and Simon’s (1958: 50) assumption that search happens within a “benign environment” has become taken-for-granted in organizational studies. The implications of making this assumption are not widely theorized, investigated, or even discussed, and yet, it often appears to have been unwittingly imported into explanations of organizational learning. March and Simon acknowledged that this assumption was not realistic—our work builds on theirs by investigating the origins and consequences of a non-benign search environment. We draw on in-depth qualitative research at a Fortune 500 mining firm to show how perceptions of social risk problematize the assumption of a benign search environment. Causal links are drawn between role equivalence, performance comparisons, and rivalry for social status to explain how social risk is generated and why it can lead actors to view the intraorganizational search environment as non-benign. These perceptions help create what we describe as a “paradox of local equivalence” that leads actors to search for nonlocal solutions. Our causal logic provides a new way of understanding the phenomena of nonlocal search; complements explanations of nonlocal search founded on myopia in organizational learning; and shows how the micro-foundations of existing search models can be adapted to better explain organizational learning. In doing so, this study contributes to recent efforts to improve behavioral explanations of search and learning by bringing the notion of intraorganizational conflict back to center stage in this important area of organizational theory.
Identification of a Hypervirulent Pathotype of Rice yellow mottle virus: A Threat to Genetic Resistance Deployment in West-Central Africa
Authors: Hébrard Eugénie , Pinel-Galzi Agnès , Oludare Aderonke , Poulicard Nils , Aribi Jamel , Fabre Sandrine , Issaka Souley , Mariac Cédric , Dereeper Alexis , Albar Laurence , Silué Drissa , Fargette Denis
Published: October 2017

Rice yellow mottle virus (RYMV) causes high losses to rice production in Africa. Several sources of varietal high resistance are available but the emergence of virulent pathotypes that are able to overcome one or two resistance alleles can sometimes occur. Both resistance spectra and viral adaptability have to be taken into account to develop sustainable rice breeding strategies against RYMV. In this study, we extended previous resistance spectrum analyses by testing the rymv1-4 and rymv1-5 alleles that are carried by the rice accessions Tog5438 and Tog5674, respectively, against isolates that are representative of RYMV genetic and pathogenic diversity. Our study revealed a hypervirulent pathotype, named thereafter pathotype T′, that is able to overcome all known sources of high resistance. This pathotype, which is spatially localized in West-Central Africa, appears to be more abundant than previously suspected. To better understand the adaptive processes of pathotype T′, molecular determinants of resistance breakdown were identified via Sanger sequencing and validated through directed mutagenesis of an infectious clone. These analyses confirmed the key role of convergent nonsynonymous substitutions in the central part of the viral genome-linked protein to overcome RYMV1-mediated resistance. In addition, deep-sequencing analyses revealed that resistance breakdown does not always coincide with fixed mutations. Actually, virulence mutations that are present in a small proportion of the virus population can be sufficient for resistance breakdown. Considering the spatial distribution of RYMV strains in Africa and their ability to overcome the RYMV resistance genes and alleles, we established a resistance-breaking risk map to optimize strategies for the deployment of sustainable and resistant rice lines in Africa.
Adult Plant Leaf Rust Resistance Derived from Toropi Wheat is Conditioned by Lr78 and Three Minor QTL
Authors: Kolmer J. A. , Bernardo A. , Bai G. , Hayden M. J. , Chao S.
Published: October 2017

Leaf rust caused by Puccinia triticina is an important disease of wheat in many regions worldwide. Durable or long-lasting leaf rust resistance has been difficult to achieve because populations of P. triticina are highly variable for virulence to race-specific resistance genes, and respond to selection by resistance genes in released wheat cultivars. The wheat cultivar Toropi, developed and grown in Brazil, was noted to have long-lasting leaf rust resistance that was effective only in adult plants. The objectives of this study were to determine the chromosome location of the leaf rust resistance genes derived from Toropi in two populations of recombinant inbred lines in a partial Thatcher wheat background. In the first population, a single gene with major effects on chromosome 5DS that mapped 2.2 centimorgans distal to IWA6289, strongly reduced leaf rust severity in all 3 years of field plot tests. This gene for adult plant leaf rust resistance was designated as Lr78. In the second population, quantitative trait loci (QTL) with small effects on chromosomes 1BL, 3BS, and 4BS were found. These QTL expressed inconsistently over 4 years of field plot tests. The adult plant leaf rust resistance derived from Toropi involved a complex combination of QTL with large and small effects.
Challenges for Managing Candidatus Liberibacter spp. (Huanglongbing Disease Pathogen): Current Control Measures and Future Directions
Authors: Blaustein Ryan A. , Lorca Graciela L. , Teplitski Max
Published: October 2017

Huanglongbing (HLB; “citrus greening” disease) has caused significant damages to the global citrus industry as it has become well established in leading citrus-producing regions and continues to spread worldwide. Insecticidal control has been a critical component of HLB disease management, as there is a direct relationship between vector control and Candidatus Liberibacter spp. (i.e., the HLB pathogen) titer in HLB-infected citrus trees. In recent years, there have been substantial efforts to develop practical strategies for specifically managing Ca. Liberibacter spp.; however, a literature review on the outcomes of such attempts is still lacking. This work summarizes the greenhouse and field studies that have documented the effects and implications of chemical-based treatments (i.e., applications of broad-spectrum antibiotics, small molecule compounds) and nonchemical measures (i.e., applications of plant-beneficial compounds, applications of inorganic fertilizers, biological control, thermotherapy) for phytopathogen control. The ongoing challenges associated with mitigating Ca. Liberibacter spp. populations at the field-scale, such as the seasonality of the phytopathogen and associated HLB disease symptoms, limitations for therapeutics to contact the phytopathogen in planta, adverse impacts of broad-spectrum treatments on plant-beneficial microbiota, and potential implications on public and ecosystem health, are also discussed.
Association of Insulin and Cholesterol Levels With Peripheral Nervous System Function in Overweight Adults: A 3-Year Follow-up
Authors: Isojärvi Henri , Keinänen-Kiukaanniemi Sirkka , Kallio Mika , Kaikkonen Kaisu , Jämsä Timo , Korpelainen Juha , Korpelainen Raija
Published: October 2017

Purpose:

The purpose of this prospective 3-year follow-up was to investigate the association of glucose, insulin, and cholesterol levels with peripheral nervous system function in overweight and obese subjects.

Methods:

Forty nondiabetic overweight and obese adults were enrolled, of whom 29 completed the follow-up. Peripheral nervous system function was measured and defined by conduction studies of the peroneal motor nerve and the radial, sural, and medial plantar sensory nerves. Serum insulin and glucose levels were determined with an oral glucose tolerance test, and cholesterol levels were measured. The measurements were performed at baseline and after 3 years.

Results:

The change in serum insulin level at 120 minutes after an oral glucose tolerance test was positively associated with changes in peroneal nerve conduction velocities and F-wave mean, sural nerve conduction and medial plantar nerve conduction velocities. Action potential amplitudes decreased consistently and significantly in all sensory nerves.

Conclusions:

The change in serum insulin level at 120 minutes appears to be positively associated with changes in nerve conduction velocities more than 3 years but not with nerve action potential amplitudes. Significant decreases in the action potential amplitudes of all sensory nerves suggest that such changes might be the earliest detectable sign of damage to the peripheral nervous system in overweight and obese people without type 2 diabetes.
Gum Arabic promotes oxidation and ester hydrolysis
Authors: Vercruysse Koen P. , Tyler Lauren E. , Readus Jade
Published: October 2017

We studied the interactions between gum Arabic and select catecholic compounds like caffeic acid, chlorogenic acid and catechol. We observed that GA is capable of promoting the auto-oxidation of the above-mentioned compounds into darkly colored pigments without the addition of redox-sensitive cations. Gum Arabic appeared to be unique among polysaccharide-based materials as many other types of polysaccharides promote the oxidation of the above-mentioned compounds only in the presence of redox cations like Fe2+or Cu2+. RP-HPLC and SEC chromatographic techniques were employed to monitor the reactions and to observe the formation of high molecular mass, pigmented materials from gum Arabic and all three catecholic compounds. FT-IR spectroscopic analysis revealed that, despite their darkly colored appearances, the gum Arabic/pigment materials synthesized contain mostly gum Arabic and very little pigment. As chlorogenic acid is an ester of caffeic acid, we studied the capacity of gum Arabic to promote ester hydrolysis using acetylsalicylic acid as the model compound. We observed that gum Arabic did promote the hydrolysis of acetylsalicylic acid into salicylic acid. However, in all our experiments involving the pigment formation between gum Arabic and chlorogenic acid, we did not observe any evidence that chlorogenic acid was hydrolyzed leading to the release of caffeic acid during these reactions. In addition, we observed that heat treatment of gum Arabic did not affect its pro-oxidizing capability, but it did negatively affect its capability to hydrolyze salicylic acid. Thus, these two types of chemical reactivity present in the gum Arabic material may be associated with different components of the gum Arabic material.
Droplet-based microfluidic analysis and screening of single plant cells
Authors: Yu Ziyi , Boehm Christian R. , Hibberd Julian M. , Abell Chris , Haseloff Jim , Burgess Steven J. , Reyna-Llorens Ivan
Published: October 2017

Droplet-based microfluidics has been used to facilitate high throughput analysis of individual prokaryote and mammalian cells. However, there is a scarcity of similar workflows applicable to rapid phenotyping of plant systems. We report on-chip encapsulation and analysis of protoplasts isolated from the emergent plant modelMarchantia polymorphaat processing rates of >100,000 protoplasts per hour. We use our microfluidic system to quantify the stochastic properties of a heat-inducible promoter across a population of transgenic protoplasts to demonstrate that it has the potential to assess gene expression activity in response to environmental conditions. We further demonstrate on-chip sorting of droplets containing YFP-expressing protoplasts from wild type cells using dielectrophoresis force. This work opens the door to droplet-based microfluidic analysis of plant cells for applications ranging from high-throughput characterisation of DNA parts to single-cell genomics.
Automatic detection of complex structural genome variation across world populations
Authors: Zhou Bo , Arthur Joseph G. , Guo Hanmin , Hughes Christopher R. , Kim Taeyoung , Huang Yiling , Pattni Reenal , Lee HoJoon , Ji Hanlee P. , Song Giltae , Palejev Dean , Zhu Xiang , Wong Wing H. , Urban Alexander E.
Published: October 2017

Complex structural variants (cxSVs), e.g. inversions with flanking deletions or interspersed inverted duplications, are part of human genetic diversity but their characteristics are not well delineated. Because their structures are difficult to resolve, cxSVs have been largely excluded from genome analysis and population-scale association studies. To permit large-scale detection of cxSVs from paired-end whole-genome sequencing, we developed Automated Reconstruction of Complex Variants (ARC-SV) using a novel probabilistic algorithm and a machine learning approach that leverages the new Human Pangenome Reference Consortium diploid assemblies. Using ARC-SV, we resolved, across 4,262 human genomes spanning all continental super-populations, 8,493 cxSVs belonging to 12 subclasses. Some cxSVs with population-specific signatures are shared with Neanderthals. Overall cxSVs are significantly enriched in regions prone to recombination and germlinede novomutations. Many cxSVs mark phenotypic hotspots (each significantly associated with ≥ 20 traits) identified in genome-wide association studies (GWAS), and 46.4% of all significant GWAS-SNPs catalogued to date reside within ±125 kb of at least one cxSV locus. Common SNPs near cxSVs show significant trait heritability enrichment. Genomic regions affected by cxSVs are enriched for bivalent chromatin states. Rare cxSVs are enriched in neural genes and loci undergoing rapid or accelerated evolution and recently evolvedcis-regulatory regions for human corticogenesis. We also identified 41 fixed loci where divergence from our most recent common ancestor is via localized cxSV. Our method and analysis framework allow for the accurate, efficient, and automatic identification of cxSVs for future population-scale studies of human disease and genome biology.
Executive influence on invention and commercialization
Authors: Sharp Barton M. , Iyer Dinesh N. , Brush Thomas H.
Published: October 2017

Purpose

The purpose of this paper is to expand the understanding of the “front end” of innovation by examining the influence of top executives, who allocate the resources and cultivate the culture in which inventions are born, on the innovation process.

Design/methodology/approach

This paper suggests that the effect of executives on innovation can be better understood by explicitly separating innovation into the component processes of invention and commercialization. This allows us to consider how executive characteristics might have a different effect on technology development outcomes than they do on the subsequent transformation of those technologies into new products. The theory is tested on a sample of firms from the biomedical device industry.

Findings

The findings indicate that top management team (TMT) age and tenure have no effect on the type of technologies a firm develops (radical vs incremental) but do significantly affect the efficiency with which new technologies are turned into new products in some contexts. TMT heterogeneity affects both the type of technologies developed in the firm and also their transformation to new products. Interestingly, the effect of executives on commercialization depends on the type of underlying technologies which the firm has developed.

Originality/value

This paper contributes to the literatures on TMTs and innovation by offering a more granular explanation of how executives differentially impact the disaggregated stages of the innovation process, and thus also contributes to knowledge of the long-term innovation performance implications of executive leadership.
Categorization of control measures in food safety management systems
Authors: Politis Yannis , Krokos Fragoulis D. , Papadakis Ioannis
Published: October 2017

Purpose

All food safety management standards require effective control measures of food safety hazards in order to ensure that food is safe at the time of human consumption. Furthermore, ISO 22000:2005 requires a logical approach to be carried out for the selection and categorization of the control measures according to the level of effect on identified food safety hazards. The purpose of this paper is to describe the COntrol MEasures CATegorization (COMECAT) method for the categorization of control measures in food safety management systems (FSMS) in order to assist organizations to prioritize and deploy their efforts and limited resources mainly to control significant hazards.

Design/methodology/approach

A thorough clarification of the characteristics of the different control measures used in FSMS has been achieved based on the definitions and the descriptions given by the different food safety standards such as the ISO 22000, the IFS and the BRC standards. The basic approaches for the determination of control measures found in literature and web pages have been examined and the proposed methodology has been implemented in feta cheese production in order to evaluate its applicability.

Findings

A decision tree model has been proposed as the most suitable approach for the categorization of control measures in FSMS. The implementation of the proposed COMECAT method in feta cheese production revealed its applicability. The method was able to identify the different risk level of food hazards and prioritize and deploy the organization’s efforts and limited resources for their management accordingly.

Originality/value

In the literature, there is a lack of justified methodologies for the categorization of control measures in FSMS. Most of the approaches concern attempts of private companies operating in the food industry or business consultancies and which can be found in their web pages. This paper describes a well-justified model for the categorization of control measures which is easy to implement and which results in more robust decisions.