219 research outputs found
Information Length and Localization in One Dimension
The scaling properties of the wave functions in finite samples of the one
dimensional Anderson model are analyzed. The states have been characterized
using a new form of the information or entropic length, and compared with
analytical results obtained by assuming an exponential envelope function. A
perfect agreement is obtained already for systems of -- sites over
a very wide range of disorder parameter . Implications for
higher dimensions are also presented.Comment: 11 pages (+3 Figures upon request), Plain TE
Transitions from the Quantum Hall State to the Anderson Insulator: Fa te of Delocalized States
Transitions between the quantum Hall state and the Anderson insulator are
studied in a two dimensional tight binding model with a uniform magnetic field
and a random potential. By the string (anyon) gauge, the weak magnetic field
regime is explored numerically. The regime is closely related to the continuum
model. The change of the Hall conductance and the trajectoy of the delocalized
states are investigated by the topological arguments and the Thouless number
study.Comment: 10 pages RevTeX, 14 postscript figure
Evaluation of Variability in the Sweet Orange Germplasm through Next Generation Clonal Fingerprinting
The great phenotypic variability characterizing the sweet orange [Citrus sinensis(L.) Osbeck] germplasm arises from spontaneous bud mutations, causing a diversification into major groups (common, Navel and blood oranges). A huge divergence also occurred within each varietal group. The genetic basis of such variability, also including nutritional and qualitative traits (ripening time, colour, fruit shape, acidity, sugars), is currently uncharacterized, and therefore not exploitable. With the aim of describing the somatic mutation events in the sweet orange group a deep-sequencing of 20 Italian and foreign accessions was performed by Illumina platform, allowing the identification of single nucleotide polymorphisms (SNPs), structural variants (SVs) and large deletions, specific to each varietal group or clone-specific. A subset of SNPs used for the design of two 384 SNP - GoldenGate Assays allowed to genotype 225 CREA sweet orange accessions. The developed markers represent the first reliable molecular tools able to unambiguously fingerprint each somatic mutant. Moreover, they might be used to associate mutations with phenotypic traits, and are a powerful tool for traceability. By using the GoldenGate assay, we have been able to fingerprint several blood orange clones starting from DNAs isolated from leaves or juice. These tools will potentially provide the consumer with a guarantee on the quality and origin of juices, avoiding eventual frauds
2D/3D SOIL CONSUMPTION TRACKING IN A MARBLE QUARRY DISTRICT
Abstract. Complex extractive districts, such as the marble quarries in the Apuan Alps (northern Italy), require soil consumption monitoring over the years that could be achieved through high-resolution remotely sensed data. To derive 2D and 3D indicators with appropriate resolution for annual monitoring of high-resolution changes in soil consumption, aerial images, LiDAR acquisitions, satellite data, and Remotely Piloted Aircraft Systems (RPAS) acquisitions were used. In particular, open-access Sentinel-2 multispectral satellite imagery with a spatial resolution of 10 m was used to assess cover changes (2D), and then refined by manual interpretation for 5 years (2016-2021). 3D changes were detected by comparing free aerial LiDAR data from 2009 and 2017, integrated with two stereo models obtained from Pléiades high-resolution satellite images from 2020 and 2022. 3D changes observed over the years by algebraic elevation comparison, performed in QGIS 3.x environment, highlight quarries characterized by intense mining activities (extracted marble blocks, characterized by positive elevation differences) and quarry area management (debris disposal and service infrastructure construction, characterized by negative elevation differences). The combined use of 2D and 3D change indicators can be challenging in order to correctly represent soil consumption over the years. A dual 2D/3D webgis client have been developed for proper representation of 2D/3D spatial indicators of ongoing extraction activities in the Carrara marble basin: high-resolution images have been served as tiled data, while 2D/3D spatial indicators are served as static and/or tiled vector data. Open-Source libraries have used in data processing, serving and representation inside a map interface
Scaling theory of localization: absence of quantum diffusion in two dimensions
Arguments are presented that the T=0 conductance G of a disordered electronic system depends on its length scale L in a universal manner. Asymptotic forms are obtained for the scaling function β(G)=dlnG/dlnL, valid for both G≪Gc≃ e2/ℏ and G≫Gc. In three dimensions, Gc is an unstable fixed point. In two dimensions, there is no true metallic behavior; the conductance crosses over smoothly from logarithmic or slower to exponential decrease with L
Mesoscopic Effects in the Quantum Hall Regime
We report results of a study of (integer) quantum Hall transitions in a
single or multiple Landau levels for non-interacting electrons in disordered
two-dimensional systems, obtained by projecting a tight-binding Hamiltonian to
corresponding magnetic subbands. In finite-size systems, we find that
mesoscopic effects often dominate, leading to apparent non-universal scaling
behaviour in higher Landau levels. This is because localization length, which
grows exponentially with Landau level index, exceeds the system sizes amenable
to numerical study at present. When band mixing between multiple Landau levels
is present, mesoscopic effects cause a crossover from a sequence of quantum
Hall transitions for weak disorder to classical behaviour for strong disorder.
This behaviour may be of relevance to experimentally observed transitions
between quantum Hall states and the insulating phase at low magnetic fields.Comment: 13 pages, 6 figures, Proceedings of the International Meeting on
Mesoscopic and Disordered Systems, Bangalore December 2000, to appear in
Pramana, February 200
Perturbation Study of the Conductance through an Interacting Region Connected to Multi-Mode Leads
We study the effects of electron correlation on transport through an
interacting region connected to multi-mode leads based on the perturbation
expansion with respect to the inter-electron interaction. At zero temperature
the conductance defined in the Kubo formalism can be written in terms of a
single-particle Green's function at the Fermi energy, and it can be mapped onto
a transmission coefficient of the free quasiparticles described by an effective
Hamiltonian. We apply this formulation to a two-dimensional Hubbard model of
finite size connected to two noninteracting leads. We calculate the conductance
in the electron-hole symmetric case using the order self-energy. The
conductance shows several maximums in the dependence in some parameter
regions of , where () is the hopping matrix element in the
- (-) directions. This is caused by the resonance occurring in some of
the subbands, and is related with the dependence of the eigenvalues of the
effective Hamiltonian.Comment: 17 pages, 12 figures, to be published in J.Phys.Soc.Jpn. 71(2002)No.
Localization Transition in Multilayered Disordered Systems
The Anderson delocalization-localization transition is studied in
multilayered systems with randomly placed interlayer bonds of density and
strength . In the absence of diagonal disorder (W=0), following an
appropriate perturbation expansion, we estimate the mean free paths in the main
directions and verify by scaling of the conductance that the states remain
extended for any finite , despite the interlayer disorder. In the presence
of additional diagonal disorder () we obtain an Anderson transition with
critical disorder and localization length exponent independently of
the direction. The critical conductance distribution varies,
however, for the parallel and the perpendicular directions. The results are
discussed in connection to disordered anisotropic materials.Comment: 10 pages, Revtex file, 8 postscript files, minor change
The random magnetic flux problem in a quantum wire
The random magnetic flux problem on a lattice and in a quasi one-dimensional
(wire) geometry is studied both analytically and numerically. The first two
moments of the conductance are obtained analytically. Numerical simulations for
the average and variance of the conductance agree with the theory. We find that
the center of the band plays a special role. Away from
, transport properties are those of a disordered quantum wire in
the standard unitary symmetry class. At the band center , the
dependence on the wire length of the conductance departs from the standard
unitary symmetry class and is governed by a new universality class, the chiral
unitary symmetry class. The most remarkable property of this new universality
class is the existence of an even-odd effect in the localized regime:
Exponential decay of the average conductance for an even number of channels is
replaced by algebraic decay for an odd number of channels.Comment: 16 pages, RevTeX; 9 figures included; to appear in Physical Review
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