116 research outputs found
Susceptibilidad de Pinus nigra y Cedrus libani a aislados turcos de Gremmeniella abietina
Gremmeniella abietina causes shoot dieback and stem cankers on conifers throughout Northern hemisphere. The aim of this study was to investigate the virulence of Turkish G. abietina isolates in a field experiment. The lower branches of 15-20-year-old P. nigra and C. libani in a plantation site at 1,050 m a.s.l. in Isparta were inoculated at 1-2-month intervals during September-January. Five isolates obtained from high altitude mountainous forests were used. Each isolate was inoculated into two branches per tree and repeated ten times on both tree species at each inoculation date. The branches were sampled at the end of February, and in August, and lesion lengths in the inner bark measured. The mean lesion length on P. nigra and C libani were 10.6 ± 0.8 and 3.8 ± 0.2 mm in February and 17.6 ± 1.4 and 7.8 ± 0.8 mm in August, respectively. Differences in the mean lesion length between the isolates were small. Nevertheless, there were significant differences between the isolates on P. nigra in November and January inoculations, and on C. libani at all four inoculation times. The mean lesion lengths for all isolates at both sampling dates was the highest (p < 0.01) in December inoculations for both P. nigra (22.0 ± 1.9 February; 32.9 ± 2.9 August) and C. libani (5.6 ± 0.7; 11.3 ± 1.2). There was no difference between the September and January inoculations on P. nigra, despite the almost six-fold difference in incubation period. During the December inoculations, the trees were most likely in winter dormancy, i.e. unable to defend themselves, which would explain the large lesions.La Gremmeniella abietina causa la muerte regresiva de brotes y cancros sobre coníferas en todo el hemisferio norte. El objetivo de este estudio fue investigar la virulencia de aislados turcos de G. abietina en un experimento de campo. Se inocularon las ramas más bajas de P. nigra y C. libani de 15 a 20 años de edad en un sitio de plantación a 1.050 m snm en Isparta a intervalos de 1-2 meses entre septiembre y enero utilizando cinco aislamientos obtenidos de bosques de las zonas montañosas altas. Cada aislado se inoculó en dos ramas por árbol y se repitieron diez veces en las dos especies en cada fecha de inoculación. Se tomaron muestras de las ramas al final del mes de febrero, y en agosto, y se midieron la longitud de la lesión en la corteza interna. La longitud media de la lesión en P. nigra y C. libani fueron 10,6 ± 0,8 y 3,8 ± 0,2 mm en febrero y 17,6 ± 1,4 y 7,8 ± 0,8 mm en agosto, respectivamente. Las diferencias en la longitud de la lesión media entre los aislados eran pequeñas. Sin embargo, hubo diferencias significativas entre los aislamientos de P. nigra en inoculaciones de noviembre y enero, y en C. libani en los cuatro tiempos de inoculación. La longitud media de la lesión para todos los aislamientos en ambas fechas de muestreo fue la más alta (p < 0,01) en las inoculaciones de diciembre tanto para P. nigra (22,0 ± 1,9 de febrero, 32,9 ± 2,9 de agosto) como para C. libani (5,6 ± 0,7; 11,3 ± 1,2). No hubo diferencias entre las de septiembre y enero en P. nigra, a pesar de la diferencia de casi seis veces en el período de incubación. Durante las inoculaciones de diciembre, los árboles estaban probablemente en letargo invernal, es decir, incapaces de defenderse, lo que explicaría las lesiones de gran tamaño
Precision spectroscopy with two correlated atoms
We discuss techniques that allow for long coherence times in laser
spectroscopy experiments with two trapped ions. We show that for this purpose
not only entangled ions prepared in decoherence-free subspaces can be used but
also a pair of ions that are not entangled but subject to the same kind of
phase noise. We apply this technique to a measurement of the electric
quadrupole moment of the 3d D5/2 state of 40Ca+ and to a measurement of the
linewidth of an ultrastable laser exciting a pair of 40Ca+ ions
Distribution and genetic diversity of Dothistroma septosporum in Pinus brutia forests of south-western Turkey
The support of the DIAROD project, funded as EU COST Action FP1102, is gratefully acknowledged. Forest engineers Ali Datumani and Erdal Örtel are thanked for their great help in the field. We are grateful to the anonymous reviewers who helped improve the manuscript. We would like to thank Dr Alkan Unlu for providing the climate data and to Dr Ilker Ercanli for performing the statistical analysis. The study was financially supported by the Forestry Commission, United Kingdom and by the European Regional Development Fund, Project Phytophthora Research Centre Reg. No. CZ.02.1.01/0.0/0.0/15_003/0000453.Peer reviewedPostprin
Diffusion Resonances in Action Space for an Atom Optics Kicked Rotor with Decoherence
We numerically investigate momentum diffusion rates for the pulse kicked
rotor across the quantum to classical transition as the dynamics are made more
macroscopic by increasing the total system action. For initial and late time
rates we observe an enhanced diffusion peak which shifts and scales with
changing kick strength, and we also observe distinctive peaks around quantum
resonances. Our investigations take place in the context of a system of
ultracold atoms which is coupled to its environment via spontaneous emission
decoherence, and the effects should be realisable in ongoing experiments.Comment: 4 Pages, RevTeX 4, 5 Figures. Updated Figures, Minor Changes to text,
Corrected Reference
Testing the stability of fundamental constants with the 199Hg+ single-ion optical clock
Over a two-year duration, we have compared the frequency of the 199Hg+ 5d106s
2S 1/2 (F=0) 5d9 6s2 2D 5/2 (F=2) electric-quadrupole transition at 282 nm
with the frequency of the ground-state hyperfine splitting in neutral 133Cs.
These measurements show that any fractional time variation of the ratio
nu(Cs)/nu(Hg) between the two frequencies is smaller than +/- 7 10^-15 / yr (1
sigma uncertainty). According to recent atomic structure calculations, this
sets an upper limit to a possible fractional time variation of g(Cs) m_e / m_p
alpha^6.0 at the same level.Comment: 4 pages with 3 figures. RevTeX 4, Submitted to Phys. Rev. Let
Quantum control, quantum information processing, and quantum-limited metrology with trapped ions
We briefly discuss recent experiments on quantum information processing using
trapped ions at NIST. A central theme of this work has been to increase our
capabilities in terms of quantum computing protocols, but we have also applied
the same concepts to improved metrology, particularly in the area of frequency
standards and atomic clocks. Such work may eventually shed light on more
fundamental issues, such as the quantum measurement problem.Comment: Proceedings of the International Conference on Laser Spectroscopy
(ICOLS), 10 pages, 5 figure
Squeezing of Atoms in a Pulsed Optical Lattice
We study the process of squeezing of an ensemble of cold atoms in a pulsed
optical lattice. The problem is treated both classically and
quantum-mechanically under various thermal conditions. We show that a dramatic
compression of the atomic density near the minima of the optical potential can
be achieved with a proper pulsing of the lattice. Several strategies leading to
the enhanced atomic squeezing are suggested, compared and optimized.Comment: Latex, 9 pages, 10 figures, submitted to PR
Characterization of the absolute frequency stability of an individual reference cavity
We demonstrated for the first time the characterization of absolute frequency
stability of three reference cavities by cross beating three laser beams which
are independently locked to these reference cavities. This method shows the
individual feature of each reference cavity, while conventional beatnote
measurement between two cavities can only provide an upper bound. This method
allows for numerous applications such as optimizing the performance of the
reference cavity for optical clockwork.Comment: 3 figures, 9 page
'Designer atoms' for quantum metrology
Entanglement is recognized as a key resource for quantum computation and
quantum cryptography. For quantum metrology, the use of entangled states has
been discussed and demonstrated as a means of improving the signal-to-noise
ratio. In addition, entangled states have been used in experiments for
efficient quantum state detection and for the measurement of scattering
lengths. In quantum information processing, manipulation of individual quantum
bits allows for the tailored design of specific states that are insensitive to
the detrimental influences of an environment. Such 'decoherence-free subspaces'
protect quantum information and yield significantly enhanced coherence times.
Here we use a decoherence-free subspace with specifically designed entangled
states to demonstrate precision spectroscopy of a pair of trapped Ca+ ions; we
obtain the electric quadrupole moment, which is of use for frequency standard
applications. We find that entangled states are not only useful for enhancing
the signal-to-noise ratio in frequency measurements - a suitably designed pair
of atoms also allows clock measurements in the presence of strong technical
noise. Our technique makes explicit use of non-locality as an entanglement
property and provides an approach for 'designed' quantum metrology
Nanofabrication by magnetic focusing of supersonic beams
We present a new method for nanoscale atom lithography. We propose the use of
a supersonic atomic beam, which provides an extremely high-brightness and cold
source of fast atoms. The atoms are to be focused onto a substrate using a thin
magnetic film, into which apertures with widths on the order of 100 nm have
been etched. Focused spot sizes near or below 10 nm, with focal lengths on the
order of 10 microns, are predicted. This scheme is applicable both to precision
patterning of surfaces with metastable atomic beams and to direct deposition of
material.Comment: 4 pages, 3 figure
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