5,797 research outputs found
Two New Species of Leafblight Fungi on Kalmia Latifolia
The evergreen shrub, Kalmia latifolia L., commonly known as mountain laurel, calico bush, or sheep-kill, grows widely on rocky, acid soils in the eastern United States. Whether growing in its natural habit or in cultivation, mountain laurel appears to be equally subject to attack by fungi. The following account characterizes and discusses two of these fungi. One of them has not been described previously and additional observations have been made regarding the developmental morphology of the other one.
Both pathogens are Pyrenomycetes, one a Physalospora and the other a Diaporthe. Each produces a leafblight disease. Tiny brown discolorations on young leaves characterize the early stages of attack by both organisms. These small lesions gradually enlarge and become irregular brown spots that may encompass the major portion of the leaf surface. The invaded tissues are darkest near the margins of the lesions, but a reddish zone lies between the darker border and the surrounding green tissues. Severely attacked leaves are deformed and shed prematurely.
The reproductive structures of the Physalospora occur on the lower surface and begin to develop before the leaves are shed. The pycnidial stromata of the Diaporthe elevate the epidermis and caticle, and consequently produce grayish spots on the leaf surface. Both fungi continue to develop after the leaves have fallen, and since the mycelia extend beyond the margins of the lesions, perithecia ultimately may occupy most of the leaf surface. [excerpt
Non-linear Coulomb blockade microscopy of a correlated one-dimensional quantum dot
We evaluate the chemical potential of a one-dimensional quantum dot, coupled
to an atomic force microscope tip. The dot is described within the Luttinger
liquid framework and the conductance peaks positions as a function of the tip
location are calculated in the linear and non-linear transport regimes for an
arbitrary number of particles. The differences between the chemical potential
oscillations induced by Friedel and Wigner terms are carefully analyzed in the
whole range of interaction strength. It is shown that Friedel oscillations,
differently from the Wigner ones, are sensitive probes to detect excited spin
states and collective spin density waves involved in the transport.Comment: 4 figure
Shot noise in charge and magnetization currents of a quantum ring
The shot noise in a quantum ring, connected to leads, is studied in the
presence of electron interactions in the sequential tunneling regime. Two
qualitatively different noise correlations with distinctly different behaviors
are identified and studied in a large range of parameters. Noise in the total
current is due to the discreteness of the electron charge and can become
super-Poissonian as result of electron interaction. The noise in the
magnetization current is comparatively insensitive to the interaction but can
be greatly enhanced if population inversion of the angular states is assumed.
The characteristic time scales are studied by a Monte-Carlo simulation.Comment: 5 pages, 5 color figure
Crystallization of fractional charges in a strongly interacting quasi-helical quantum dot
The ground-state electron density of a one-dimensional spin-orbit coupled
quantum dot with a Zeeman term and strong electron interaction is studied at
the fractional helical liquid points. We show that at fractional filling
factors (with a non-negative integer) the density
oscillates with peak. For a number of peaks larger than
the number of electrons suggests that a crystal of fractional
quasi-particles with charge (with the electron charge) occurs. The
reported effect is amenable of verification via transport measurements in
charged AFM-coupled dot
Temperature-induced emergence of Wigner correlations in a STM-probed one-dimensional quantum dot
The temperature-induced emergence of Wigner correlations over finite-size
effects in a strongly interacting one-dimensional quantum dot are studied in
the framework of the spin coherent Luttinger liquid. We demonstrate that, for
temperatures comparable with the zero mode spin excitations, Friedel
oscillations are suppressed by the thermal fluctuations of higher spin modes.
On the other hand, the Wigner oscillations, sensitive to the charge mode only,
are stable and become more visible. This behavior is proved to be robust both
in the thermal electron density and in the linear conductance in the presence
of an STM tip. This latter probe is not directly proportional to the electron
density and may confirm the above phenomena with complementary and additional
information
Theory of the STM detection of Wigner molecules in spin incoherent CNTs
The linear conductance of a carbon nanotube quantum dot in the Wigner
molecule regime, coupled to two scanning tunnel microscope tips is inspected.
Considering the high temperature regime, the nanotube quantum dot is described
by means of the spin-incoherent Luttinger liquid picture. The linear
conductance exhibits spatial oscillations induced by the presence of the
correlated, molecular electron state. A power-law scaling of the electron
density and of the conductance as a function of the interaction parameter are
found. They confirm local transport as a sensitive tool to investigate the
Wigner molecule. The double-tip setup allows to explore different transport
regimes with different shapes of the spatial modulation, all bringing
information about the Wigner molecule
AFM probe for the signatures of Wigner correlations in the conductance of a one-dimensional quantum dot
The transport properties of an interacting one-dimensional quantum dot
capacitively coupled to an atomic force microscope probe are investigated. The
dot is described within a Luttinger liquid framework which captures both
Friedel and Wigner oscillations. In the linear regime, we demonstrate that both
the conductance peak position and height oscillate as the tip is scanned along
the dot. A pronounced beating pattern in the conductance maximum is observed,
connected to the oscillations of the electron density. Signatures of the
effects induced by a Wigner molecule are clearly identified and their stability
against the strength of Coulomb interactions are analyzed. While the
oscillations of the peak position due to Wigner get enhanced at strong
interactions, the peak height modulations are suppressed as interactions grow.
Oscillations due to Friedel, on the other hand, are robust against interaction.Comment: 9 figure
Probing Wigner correlations in a suspended carbon nanotube
The influence of the electron-vibron coupling on the transport properties of
a strongly interacting quantum dot built in a suspended carbon nanotube is
analyzed. The latter is probed by a charged AFM tip scanned along the axis of
the CNT which induces oscillations of the chemical potential and of the linear
conductance. These oscillations are due to the competition between finite-size
effects and the formation of a Wigner molecule for strong interactions. Such
oscillations are shown to be suppressed by the electron-vibron coupling. The
suppression is more pronounced in the regime of weak Coulomb interactions,
which ensures that probing Wigner correlations in such a system is in principle
possible
- …