996 research outputs found
Dynamics of semifluxons in Nb long Josephson 0-pi junctions
We propose, implement and test experimentally long Josephson 0-pi junctions
fabricated using conventional Nb-AlOx-Nb technology. We show that using a pair
of current injectors, one can create an arbitrary discontinuity of the
Josephson phase and in particular a pi-discontinuity, just like in
d-wave/s-wave or in d-wave/d-wave junctions, and study fractional Josephson
vortices which spontaneously appear. Moreover, using such junctions, we can
investigate the \emph{dynamics} of the fractional vortices -- a domain which is
not yet available for natural 0-pi-junctions due to their inherently high
damping. We observe half-integer zero-field steps which appear on the
current-voltage characteristics due to hopping of semifluxons.Comment: Fractional vortices in conventional superconductors ;-
Non-ideal artificial phase discontinuity in long Josephson 0-kappa-junctions
We investigate the creation of an arbitrary -discontinuity of the
Josephson phase in a long Nb-AlO_x-Nb Josephson junction (LJJ) using a pair of
tiny current injectors, and study the formation of fractional vortices formed
at this discontinuity. The current I_inj, flowing from one injector to the
other, creates a phase discontinuity kappa ~ I_inj. The calibration of
injectors is discussed in detail. The small but finite size of injectors leads
to some deviations of the properties of such a 0-kappa-LJJ from the properties
of a LJJ with an ideal kappa-discontinuity. These experimentally observed
deviations in the dependence of the critical current on I_inj$ and magnetic
field can be well reproduced by numerical simulation assuming a finite injector
size. The physical origin of these deviations is discussed.Comment: Submitted to Phys. Rev. B (12 figures). v 2: refs updated, long eqs
fixed v 3: major changes, fractional vortex dynamics exclude
Spectroscopy of a fractional Josephson vortex molecule
In long Josephson junctions with multiple discontinuities of the Josephson
phase, fractional vortex molecules are spontaneously formed. At each
discontinuity point a fractional Josephson vortex carrying a magnetic flux
, Wb being the magnetic flux
quantum, is pinned. Each vortex has an oscillatory eigenmode with a frequency
that depends on and lies inside the plasma gap.
We experimentally investigate the dependence of the eigenfrequencies of a
two-vortex molecule on the distance between the vortices, on their topological
charge and on the bias current applied to the
Josephson junction. We find that with decreasing distance between vortices, a
splitting of the eigenfrequencies occurs, that corresponds to the emergence of
collective oscillatory modes of both vortices. We use a resonant microwave
spectroscopy technique and find good agreement between experimental results and
theoretical predictions.Comment: submitted to Phys. Rev.
The omnivorous Tyrolean Iceman: colon contents (meat, cereals, pollen, moss and whipworm) and stable isotope analyses
The contents of the colon of the Tyrolean Iceman who lived Ga. 5300 years ago include muscle fibres, cereal remains, a diversity of pollen, and most notably that of the hop hornbeam (Ostrya carpinifolia) retaining cellular contents, as well as a moss leaf (Neckera complanata) and eggs of the parasitic whipworm (Trichuris trichiura). Based almost solely on stable isotope analyses and ignoring the work on the colon contents, two recently published papers on the Iceman's diet draw ill- founded conclusions about vegetarianism and even veganism. Neither the pollen nor the moss is likely to have been deliberately consumed as food by the Iceman. All the available evidence concerning the Iceman's broad-based diet is reviewed and the significance of the colon contents for matters other than assessment of food intake is outlined
Evaluating the In vivo Efficacy of Copper-Chitosan Nanocomposition for Treating Vascular Wilt Disease in Date Palm
Date palm, Phoenix dactylifera, as one of the most important fruit crops in Egypt and many other countries, can be affected by many fungal diseases, among which the vascular wilt disease, caused by the fungal pathogen Fusarium oxysporum, is considered the most deteriorating one. This study aims at evaluating the efficiency of Copper-Chitosan Nanopcomposition for treating the vascular wilt disease in date palm. The study relies mainly on beleaguering the disease via the double-role functionality of copper-chitosan nanocomposition, i.e. its potential antifungal effect on the fungal pathogen, besides its capability to enhance the immune responses of the infected plant. In this regard, chitosan nanoparticles were prepared according to the ionic gelation method, whereas copper nanoparticles were prepared according to the chemical reduction method. Physicochemical characterization of both chitosan and copper nanoparticles was performed using dynamic light scattering (DLS), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD). Copper-chitosan nanocomposition could significantly reduce the vascular wilt disease severity; this means that the nanocomposition can be used in the future for developing new nano-fungicides to control such pathogens
Spectroscopy of the fractional vortex eigenfrequency in a long Josephson 0-kappa junction
Fractional Josephson vortices carry a magnetic flux Phi, which is a fraction
of the magnetic flux quantum Phi_0 ~ 2.07x10^{-15} Wb. Their properties are
very different from the properties of the usual integer fluxons. In particular,
fractional vortices are pinned and have an oscillation eigenfrequency which is
expected to be within the Josephson plasma gap. Using microwave spectroscopy,
we investigate the dependence of the eigenfrequency of a fractional Josephson
vortex on its magnetic flux and on the bias current. The experimental
results are in good agreement with the theoretical predictions.Comment: submitted to PR
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