17,233 research outputs found
Effective models for charge transport in DNA nanowires
The rapid progress in the field of molecular electronics has led to an
increasing interest on DNA oligomers as possible components of electronic
circuits at the nanoscale. For this, however, an understanding of charge
transfer and transport mechanisms in this molecule is required. Experiments
show that a large number of factors may influence the electronic properties of
DNA. Though full first principle approaches are the ideal tool for a
theoretical characterization of the structural and electronic properties of
DNA, the structural complexity of this molecule make these methods of limited
use. Consequently, model Hamiltonian approaches, which filter out single
factors influencing charge propagation in the double helix are highly valuable.
In this chapter, we give a review of different DNA models which are thought to
capture the influence of some of these factors. We will specifically focus on
static and dynamic disorder.Comment: to appear in "NanoBioTechnology: BioInspired device and materials of
the future". Edited by O. Shoseyov and I. Levy. Humana Press (2006
Modeling molecular conduction in DNA wires: Charge transfer theories and dissipative quantum transport
Measurements of electron transfer rates as well as of charge transport
characteristics in DNA produced a number of seemingly contradictory results,
ranging from insulating behaviour to the suggestion that DNA is an efficient
medium for charge transport. Among other factors, environmental effects appear
to play a crucial role in determining the effectivity of charge propagation
along the double helix. This chapter gives an overview over charge transfer
theories and their implication for addressing the interaction of a molecular
conductor with a dissipative environment. Further, we focus on possible
applications of these approaches for charge transport through DNA-based
molecular wires
The role of contacts in molecular electronics
Molecular electronic devices are the upmost destiny of the miniaturization
trend of electronic components. Although not yet reproducible on large scale,
molecular devices are since recently subject of intense studies both
experimentally and theoretically, which agree in pointing out the extreme
sensitivity of such devices on the nature and quality of the contacts. This
chapter intends to provide a general theoretical framework for modelling
electronic transport at the molecular scale by describing the implementation of
a hybrid method based on Green function theory and density functional
algorithms. In order to show the presence of contact-dependent features in the
molecular conductance, we discuss three archetypal molecular devices, which are
intended to focus on the importance of the different sub-parts of a molecular
two-terminal setup.Comment: 17 pages, 8 figure
Electron transport in carbon nanotube-metal systems: contact effects
Carbon nanotubes (CNT) have a very large application potential in the rapid
developing field of molecular electronics. Infinite single-wall metallic CNTs
have theoretically a conductance of 4e2/h because of the two electronic bands
crossing the Fermi level. For finite size CNTs experiments have shown that
other values are also possible, indicating a very strong influence of the
contacts. We study electron transport in single- and double-wall CNTs contacted
to metallic electrodes within the Landauer formalism combined with Green
function techniques. We show that the symmetry of the contact region may lead
to blocking of a transport channel. In the case of double-wall CNTs with both
inner and outer shells being metallic, non-diagonal self energy contributions
from the electrodes may induce channel mixing, precluding a simple addition of
the individual shell conductances
Charge migration in organic materials: Can propagating charges affect the key physical quantities controlling their motion?
Charge migration is a ubiquitous phenomenon with profound implications
throughout many areas of chemistry, physics, biology and materials science. The
long-term vision of designing functional materials with tailored molecular
scale properties has triggered an increasing quest to identify prototypical
systems where truly molecular conduction pathways play a fundamental role. Such
pathways can be formed due to the molecular organization of various organic
materials and are widely used to discuss electronic properties at the nanometer
scale. Here, we present a computational methodology to study charge propagation
in organic molecular stacks at nano and sub-nanoscales and exploit this
methodology to demonstrate that moving charge carriers strongly affect the
values of the physical quantities controlling their motion. The approach is
also expected to find broad application in the field of charge migration in
soft matter systems.Comment: 18 pages, 6 figures, accepted for publication in the Israel Journal
of Chemistr
Big Data on Decision Making in Energetic Management of Copper Mining
Indexado en: Web of Science; Scopus.It is proposed an analysis of the related variables with the energetic consumption in the process of concentrate of copper; specifically ball mills and SAG. The methodology considers the analysis of great volumes of data, which allows to identify the variables of interest (tonnage, temperature and power) to reach to an improvement plan in the energetic efficiency. The correct processing of the great volumen of data, previous imputation to the null data, not informed and out of range, coming from the milling process of copper, a decision support systems integrated, it allows to obtain clear and on line information for the decision making. As results it is establish that exist correlation between the energetic consumption of the Ball and SAG Mills, regarding the East, West temperature and winding. Nevertheless, it is not observed correlation between the energetic consumption of the Ball Mills and the SAG Mills, regarding to the tonnages of feed of SAG Mill. In consequence, From the experimental design, a similarity of behavior between two groups of different mills was determined in lines process. In addition, it was determined that there is a difference in energy consumption between the mills of the same group. This approach modifies the method presented in [1].(a)http://www.univagora.ro/jour/index.php/ijccc/article/view/2784/106
Spin selective transport through helical molecular systems
Highly spin selective transport of electrons through a helically shaped
electrostatic potential is demonstrated in the frame of a minimal model
approach. The effect is significant even in the case of weak spin-orbit
coupling. Two main factors determine the selectivity, an unconventional Rashba-
like spin-orbit interaction, reflecting the helical symmetry of the system, and
a weakly dispersive electronic band of the helical system. The weak electronic
coupling, associated with the small dispersion, leads to a low mobility of the
charges in the system and allows even weak spin-orbit interactions to be
effective. The results are expected to be generic for chiral molecular systems
displaying low spin-orbit coupling and low conductivity.Comment: 9 pages, 4 figures v2 (misprints corrected, new figures
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