7,347 research outputs found
Oidium longipes, a new powdery mildew fungus on petunia in the USA: A potential threat to ornamental and vegetable solanaceous crops
This is the first North American report of Oidium longipes, an anamorphic powdery mildew species described recently in Europe. It was found on vegetatively propagated petunia grown in a commercial greenhouse in New Jersey, USA, where it caused a rapidly spreading disease. The pathogen might have originated offshore and may have already been distributed in the United States through horticultural trade. During field surveys in Europe, it was found on petunia in Hungary and Austria as well; this is the first report of O. longipes from these two countries. A detailed light microscopy study of American and European specimens of O. longipes, including freshly collected samples and authentic herbarium specimens, revealed that its conidiophore morphology is more variable than illustrated in the original species description or in subsequent works. Microcycle conidiation, a process not yet known to occur in powdery mildews, was repeatedly observed in O. longipes. The rDNA internal transcribed spacer (ITS) sequences were identical in colonies containing different conidiophore types as well as in a total of five specimens collected from petunia in the United States, Austria, Hungary, Germany, and Switzerland. A phylogenetic analysis of the ITS sequences revealed that the closest known relative of O. longipes is O. lycopersici, known to infect tomato only in Australia. Cross-inoculation tests showed that O. longipes from petunia heavily infected tobacco cv. Xanthi, while the tomato and eggplant cultivars tested were moderately susceptible to this pathogen. These results indicate that its spread represents a potential danger to a number of solanaceous crops. Our ad hoc field surveys conducted in 2006 and 2007 did not detect it outside New Jersey in the United States; all the other powdery mildew–infected petunias, collected in New York and Indiana, were infected by Podosphaera xanthii. In Europe, most of the powdery mildew–infected petunias examined in this study were infected by P. xanthii or Golovinomyces orontii. Our multiple inoculation tests revealed that the same petunia plants and even the same leaves can be infected concomitantly by O. longipes, O. neolycopersici, G. orontii, and P. xanthii. Thus, it is at present unclear to what extent O. longipes contributes to the powdery mildew epidemics that develop year after year on solanaceous plants in many parts of the world
Non-monotonic temperature dependent transport in graphene grown by Chemical Vapor Deposition
Temperature-dependent resistivity of graphene grown by chemical vapor
deposition (CVD) is investigated. We observe in low mobility CVD graphene
device a strong insulating behavior at low temperatures and a metallic behavior
at high temperatures manifesting a non-monotonic in the temperature dependent
resistivity.This feature is strongly affected by carrier density modulation. To
understand this anomalous temperature dependence, we introduce thermal
activation of charge carriers in electron-hole puddles induced by randomly
distributed charged impurities. Observed temperature evolution of resistivity
is then understood from the competition among thermal activation of charge
carriers, temperature-dependent screening and phonon scattering effects. Our
results imply that the transport property of transferred CVD-grown graphene is
strongly influenced by the details of the environmentComment: 7 pages, 3 figure
On the question of universality in \RPn and \On Lattice Sigma Models
We argue that there is no essential violation of universality in the
continuum limit of mixed \RPn and \On lattice sigma models in 2 dimensions,
contrary to opposite claims in the literature.Comment: 16 pages (latex) + 3 figures (Postscript), uuencode
Y-System and Deformed Thermodynamic Bethe Ansatz
We introduce a new tool, the Deformed TBA (Deformed Thermodynamic Bethe
Ansatz), to analyze the monodromy problem of the cubic oscillator. The Deformed
TBA is a system of five coupled nonlinear integral equations, which in a
particular case reduces to the Zamolodchikov TBA equation for the 3-state Potts
model. Our method generalizes the Dorey-Tateo analysis of the (monomial) cubic
oscillator. We introduce a Y-system corresponding to the Deformed TBA and give
it an elegant geometric interpretation.Comment: 12 pages. Minor corrections in Section
IoTSan: Fortifying the Safety of IoT Systems
Today's IoT systems include event-driven smart applications (apps) that
interact with sensors and actuators. A problem specific to IoT systems is that
buggy apps, unforeseen bad app interactions, or device/communication failures,
can cause unsafe and dangerous physical states. Detecting flaws that lead to
such states, requires a holistic view of installed apps, component devices,
their configurations, and more importantly, how they interact. In this paper,
we design IoTSan, a novel practical system that uses model checking as a
building block to reveal "interaction-level" flaws by identifying events that
can lead the system to unsafe states. In building IoTSan, we design novel
techniques tailored to IoT systems, to alleviate the state explosion associated
with model checking. IoTSan also automatically translates IoT apps into a
format amenable to model checking. Finally, to understand the root cause of a
detected vulnerability, we design an attribution mechanism to identify
problematic and potentially malicious apps. We evaluate IoTSan on the Samsung
SmartThings platform. From 76 manually configured systems, IoTSan detects 147
vulnerabilities. We also evaluate IoTSan with malicious SmartThings apps from a
previous effort. IoTSan detects the potential safety violations and also
effectively attributes these apps as malicious.Comment: Proc. of the 14th ACM CoNEXT, 201
Frustration of Decoherence in Open Quantum Systems
We study a model of frustration of decoherence in an open quantum system.
Contrary to other dissipative ohmic impurity models, such as the Kondo model or
the dissipative two-level system, the impurity model discussed here never
presents overdamped dynamics even for strong coupling to the environment. We
show that this unusual effect has its origins in the quantum mechanical nature
of the coupling between the quantum impurity and the environment. We study the
problem using analytic and numerical renormalization group methods and obtain
expressions for the frequency and temperature dependence of the impurity
susceptibility in different regimes.Comment: 14 pages, 5 figure
The cap-snatching SFTSV endonuclease domain is an antiviral target
Severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne virus with 12%-30% case mortality rates and is related to the Heartland virus (HRTV) identified in the United States. Together, SFTSV and HRTV are emerging segmented, negative-sense RNA viral (sNSV) pathogens with potential global health impact. Here, we characterize the amino-terminal cap-snatching endonuclease domain of SFTSV polymerase (L) and solve a 2.4-Ã… X-ray crystal structure. While the overall structure is similar to those of other cap-snatching sNSV endonucleases, differences near the C terminus of the SFTSV endonuclease suggest divergence in regulation. Influenza virus endonuclease inhibitors, including the US Food and Drug Administration (FDA) approved Baloxavir (BXA), inhibit the endonuclease activity in in vitro enzymatic assays and in cell-based studies. BXA displays potent activity with a half maximal inhibitory concentration (I
Chiral perturbation theory, finite size effects and the three-dimensional model
We study finite size effects of the d=3 model in terms of the chiral
perturbation theory. We calculate by Monte Carlo simulations physical
quantities which are, to order of , uniquely determined only by two
low energy constants. They are the magnetization and the helicity modulus (or
the Goldstone boson decay constant) in infinite volume. We also pay a special
attention to the region of the validity of the two possible expansions in the
theory.Comment: 34 pages ( 9 PS files are included. harvmac and epsf macros are
needed. ), KYUSHU-HET-17, SAGA-HE-6
Anomalies and Hawking radiation from the Reissner-Nordstr\"om black hole with a global monopole
We extend the work by S. Iso, H. Umetsu and F. Wilczek [Phys. Rev. Lett. 96
(2006) 151302] to derive the Hawking flux via gauge and gravitational anomalies
of a most general two-dimensional non-extremal black hole space-time with the
determinant of its diagonal metric differing from the unity () and use it to investigate Hawking radiation from the Reissner-Nordstrom
black hole with a global monopole by requiring the cancellation of anomalies at
the horizon. It is shown that the compensating energy momentum and gauge fluxes
required to cancel gravitational and gauge anomalies at the horizon are
precisely equivalent to the -dimensional thermal fluxes associated with
Hawking radiation emanating from the horizon at the Hawking temperature. These
fluxes are universally determined by the value of anomalies at the horizon.Comment: 18 pages, 0 figure. 1 footnote and 4 new reference adde
Low-Energy Charge-Density Excitations in MgB: Striking Interplay between Single-Particle and Collective Behavior for Large Momenta
A sharp feature in the charge-density excitation spectra of single-crystal
MgB, displaying a remarkable cosine-like, periodic energy dispersion with
momentum transfer () along the -axis, has been observed for the first
time by high-resolution non-resonant inelastic x-ray scattering (NIXS).
Time-dependent density-functional theory calculations show that the physics
underlying the NIXS data is strong coupling between single-particle and
collective degrees of freedom, mediated by large crystal local-field effects.
As a result, the small- collective mode residing in the single-particle
excitation gap of the B bands reappears periodically in higher Brillouin
zones. The NIXS data thus embody a novel signature of the layered electronic
structure of MgB.Comment: 5 pages, 4 figures, submitted to PR
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