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Charge transport at the molecular scale builds the cornerstone of molecularelectronics (ME), a novel paradigm aiming at the realization of nanoscaleelectronics via tailored molecular functionalities. Biomolecular electronics,lying at the borderline between physics, chemistry and biology, can be con-sidered as a sub-field of ME. In particular, the potential applications of DNAoligomers either as template or as active device element in ME have stronglydrawn the attention of both experimentalist and theoreticians in the past years.While exploiting the self-assembling and self-recognition properties of DNAbased molecular systems is meanwhile a well-established field, the poten-tial of such biomolecules as active devices is much less clear mainly due tothe poorly understood charge conduction mechanisms. One key componentin any theoretical description of charge migration in biomolecular systems,and hence in DNA oligomers, is the inclusion of conformational fluctuationsand their coupling to the transport process. The treatment of such a problemaffords to consider dynamical effects in a non-perturbative way in contrastto, e.g., conventional bulk materials. Here we present an overview of recentwork aiming at combining molecular dynamic simulations and electronicstructure calculations with charge transport in coarse-grained effective model Hamiltonians. This hybrid methodology provides a common theoretical start-ing point to treat charge transfer/transport in strongly structurally fluctuatingmolecular-scale physical systems.

Chemical modification and vertical stacking of two-dimensional materials are promising techniques for new nanoelectronic devices. We present Density Functional Tight Binding (DFTB) calculations of a field-effect device, based on lateral and vertical heterostructures of 2D materials. The device consists of a phosphorene channel protected by graphene sheets, which work as contacts and are divided into the source and drain by local hydrogenation of graphene, which gives insulating graphane. In this device composed of only 3 layers, single sheets of graphene-graphane can work as both leads and oxide gate, while also acting as protective layers for a phosphorene channel. We show how for perfect vdW heterostructures of graphane/phosphorene/graphane and graphene/phosphorene/graphene the Schottky barrier is deeply influenced by normal electric fields, and we characterize electronic transport of such a device. Finally, we characterize phosphorene channel doping and defects, which, at very high densities in the transport direction, enables transport inside the phosphorene bandgap.

Two-dimensional Covalent Organic Frameworks (2D COFs) have attracted considerable interest because of their potential for a broad range of applications. Different combinations of the monomeric units can lead to potentially novel materials with varying physico-chemical properties. In this study, we investigate the electronic properties of various 2D COFs with square lattice topology based on a tight-binding density functional theory approach. We first classify the 2D COFs into different classes according to the degree of π-conjugation. Interestingly, this classification is recovered by using a similarity measure based on specific features of the electronic band-structure of the COFs. Further, we study the effect of aromaticity on the electronic structure of fully-conjugated COFs. Our results show that the conjugation and aromaticity are keys in the electronic band-structure of COFs.

La interrupción de las clases presenciales en las diversas instituciones educativas conllevó a poner en marcha la educación remota que trajo consigo muchos cambios, entre ellas, el modo de evaluar y proporcionar la retroalimentación a los estudiantes, por tal motivo, la presente investigación tuvo como objetivo general analizar cómo se lleva a cabo la retroalimentación de evidencias de los estudiantes en tres escuelas del nivel secundaria de la Educación Básica Regular ubicadas en el departamento de Lima, Perú. Para tal propósito, esta investigación se apoyó en el paradigma hermenéutico interpretativo, bajo el enfoque cualitativo de tipo básico; el instrumento que se usó fue encuestas semiestructuradas las cuales se aplicaron a docentes y estudiantes de tres escuelas diferentes. De ellas, se halló que los docentes realizan la retroalimentación descriptiva y reflexiva de forma constante; y para ello, hacen uso del aplicativo WhatsApp porque permite mandar mensajes en diversos formatos: audio, video y escrito. Además, se identificó que son los docentes quienes mayormente llevan a cabo la retroalimentación y algunas veces los padres ayudan a que los estudiantes manden sus evidencias.

This review is an effort in putting together the latest results about room-temperature magnetoresistive (MR) effects in nanoscale/single-molecule electronic devices consisting of one (few) molecule(s) placed in electrical contact between two nanoscale electrodes. Molecules represent powerful building blocks for developing state-of-the-art MR devices, as they bring long spin relaxation timescales, low cost and high tunability of their electrical and magnetic properties via chemical modifications. The capability to control at room temperature and under bespoke electrodes’ magnetization the MR response of a single-molecule (SM) device has been a longstanding quest. Such SM platforms could serve as fundamental tools to understand what the main mechanistic ingredients of MR effects in a molecular device are, leading to their use as building-blocks for miniaturization in spintronic applications. The work carried out so far in this field has identified two key components directly involved in the MR response of a single(few)-molecule(s) device: (i) The molecule|electrode spinterface, defining the interplay between interfacial electrostatics and spin density, has been proven to play a fundamental role in the interpretation of the observed single-molecule junction's MR effects, which is governed by the electrode material and the electrode-molecule chemistry. (ii) Two aspects of the molecular structure have been demonstrated to be involved in the spin-dependent conduction mechanism: (1) the presence of paramagnetic metal centres in the molecular structure and how their orbitals bearing the unpaired electrons couple with the device electrodes, and (2), the degree of chirality within the molecular wire. This contribution will focus on the above points (i-ii) by making use of specific examples in the literature.

Computerpraktika stellen einen wichtigen Bestandteil vieler Lehrveranstaltungen dar, welche die Grundlagen und Details von computergestützten Methoden vermitteln sollen. In den Materialwissenschaften spielen solche Methoden eine zunehmend wichtige Rolle. Typischerweise setzen die Praktika eine physische Präsenz in den PC Pools voraus, u.a. da eine Vielzahl von verschiedenen Programmen lokal installiert und bereitgestellt werden muss. Um Computerpraktika auch in der Online-Lehre vollumfänglich und weitestgehend unabhängig von den Gegebenheiten der Studierenden einsetzen zu können, wurde im Wintersemester 2020/21 ein virtueller PC Pool auf Basis von virtuellen Maschinen mit Web-basiertem Zugang eingerichtet. Dieser virtuelle PC Pool wurde in verschiedenen Lehrveranstaltungen erfolgreich eingesetzt und kann auch bei hybriden Lehrformaten in verschiedenen Disziplinen verwendet werden.

Background To validate the traditional talk test (TTT) and an alternative talk test (ATT; using a visual analog scale) in overweight/obese (OW-OB) patients and to establish its accuracy in determining the aerobic training zones. Methods We recruited 19 subjects aged 34.9 ± 6.7 years, diagnosed with overweight/obesity (BMI 31.8 ± 5.7). Every subject underwent incremental cycloergometric tests for maximal oxygen consumption, and TTT in a randomized order. At the end of each stage during the TTT, each subject read out loud a 40 words text and then had to identify the comfort to talk in two modalities: TTT which consisted in answering “Yes,” “I don’t know,” or “No” to the question Was talking comfortable?, or ATT through a 1 to 10 numeric perception scale (visual analog scale (VAS)). The magnitude of differences was interpreted in comparison to the smallest worthwhile change and was used to determine agreement. Results There was an agreement between the power output at the VAS 2–3 of ATT and the power output at the ventilatory threshold 1 (VT1) (very likely equivalent; mean difference − 1.3 W, 90% confidence limit (CL) (− 8.2; 5.6), percent chances for higher/similar/lower values of 0.7/99.1/0.2%). Also, there was an agreement between the power output at the VAS 6–7 of ATT and the power output at the ventilatory threshold 2 (VT2) (very likely equivalent; mean difference 11.1 W, 90% CL (2.8; 19.2), percent chances for higher/similar/lower values of 0.0/97.6/2.4%). Conclusions ATT is a tool to determine exercise intensity and to establish aerobic training zones for exercise prescription in OW-OB patients.

With the advances in fabrication of materials with feature sizes at the order of nanometers, it has been possible to alter their thermal transport properties dramatically. Miniaturization of device size increases the power density in general, hence faster electronics require better thermal transport, whereas better thermoelectric applications require the opposite. Such diverse needs bring new challenges for material design. Shrinkage of length scales has also changed the experimental and theoretical methods to study thermal transport. Unsurprisingly, novel approaches have emerged to control phonon flow. Besides, ever increasing computational power is another driving force for developing new computational methods. In this review, we discuss three methods developed for computing vibrational thermal transport properties of nano-structured systems, namely Green function, quasi-classical Langevin, and Kubo–Green methods. The Green function methods are explained using both nonequilibrium expressions and the Landauer-type formula. The partitioning scheme, decimation techniques and surface Green functions are reviewed, and a simple model for reservoir Green functions is shown. The expressions for the Kubo–Greenwood method are derived, and Lanczos tridiagonalization, continued fraction and Chebyshev polynomial expansion methods are discussed. Additionally, the quasi-classical Langevin approach, which is useful for incorporating phonon–phonon and other scatterings is summarized., HS acknowledges support from TÜBİTAK (115F445, 117F480) and Bilim Akademisi -the Science Academy, Turkey. SR acknowledges the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706). LMS thanks the Deutscher Akademischer Austauschdienst (DAAD) for financial support. This work has also been partly supported by the German Research Foundation (DFG) within the Cluster of Excellence “Center for Advancing Electronics Dresden”.

Background: to validate the traditional talk test (TTT) and an alternative talk test (ATT; using a visual analog scale) in overweight/obese (OW-OB) patients and to establish its accuracy in determining the aerobic training zones.Methods: We recruited 19 subjects aged 34.9 ± 6.7 years, diagnosed with overweight/obesity (BMI 31.8 ± 5.7). Every subject underwent incremental cycloergometric tests for maximal oxygen consumption, and TTT in a randomized order. At the end of each stage during the TTT each subject read out loud a 40 words text and then had to identify the comfort to talk in two modalities: TTT which consisted in answering “Yes”, “I don’t know” or “No” to the question Was talking comfortable?, or ATT through a 1 to 10 numeric perception scale (visual scale analog: VAS). The magnitude of differences was interpreted in comparison to the smallest worthwhile change and was used to determine agreement.Results: Agreement between the power output at the VAS 2-3 of ATT and the power output at the ventilatory threshold 1 (VT1) (very likely equivalent; mean difference -1.3 Watts (W), 90 % confidence limit (CL) (-8.2; 5.6), % chances for higher/similar/lower values of 0.7/99.1/0.2 %). Also, there was an agreement between the power output at the VAS 6-7 of ATT and the power output at the ventilatory threshold 2 (VT2) (very likely equivalent; mean difference 11.1 W, 90 % CL (2.8; 19.2), % chances for higher/similar/lower values of 0.0/97.6/2.4 %). Conclusions: ATT is a tool to determine exercise intensity and to establish aerobic training zones for exercise prescription in OW-OB patients.

The physical origin of the so-called chirality-induced spin selectivity (CISS) effect has puzzled experimental and theoretical researchers over the past few years. Early experiments were interpreted in terms of unconventional spin-orbit interactions mediated by the helical geometry. However, more recent experimental studies have clearly revealed that electronic exchange interactions also play a key role in the magnetic response of chiral molecules in singlet states. In this investigation, we use spin-polarized closed shell density functional theory calculations to address the influence of exchange contributions to the interaction between helical molecules as well as of helical molecules with magnetized substrates. We show that exchange effects result in differences in the interaction properties with magnetized surfaces, shedding light into the possible origin of two recent important experimental results: enantiomer separation and magnetic exchange force microscopy with AFM tips functionalized with helical peptides.

Achieving efficient and stable ultraviolet emission is a challenging goal in optoelectronic devices. Herein, we investigate the UV luminescence of zinc germanate Zn2GeO4 microwires by means of photoluminescence measurements as a function of temperature and excitation conditions. The emitted UV light is composed of two bands (a broad one and a narrow one) associated with the native defects structure. In addition, with the aid of density functional theory (DFT) calculations, the energy positions of the electronic levels related to native defects in Zn2GeO4 have been calculated. In particular, our results support that zinc interstitials are the responsible for the narrow UV band, which is, in turn, split into two components with different temperature dependence behaviour. The origin of the two components is explained on the basis of the particular location of Zn i in the lattice and agrees with DFT calculations. Furthermore, a kinetic luminescence model is proposed to ascertain the temperature evolution of this UV emission. These results pave the way to exploit defect engineering in achieving functional optoelectronic devices to operate in the UV region.

BNC heteronanotubes are promising materials for the design of nanoscale thermoelectric devices. In particular, the structural BN doping pattern can be exploited to control the electrical and thermal transport properties of BNC nanostructures. We here address the thermoelectric transport properties of (6,6)-BNC heteronanotubes with helical and horizontal BN doping patterns. For this, we use a density functional tight-binding method combined with the Green's function technique. Our results show that the electron transmission is reduced and the electronic bandgap increased as a function of the BN concentration for different doping distribution patterns, so that (6,6)-BNC heteronanotubes become semiconducting with a tunable bandgap. The thermal conductance of helical (6,6)-BNC heteronanotubes, which is dominated by phonons, is weakly dependent on BN concentration in the range of 30-80%. Also, the Seebeck coefficient is enhanced by increasing the concentration of helical BN strips. In particular, helical (6,6)-BNC heteronanotubes with a high BN concentration (>20%) display a larger figure of merit compared to other doping distributions and, for a concentration of 50%, reach values up to 2.3 times and 3.4 times the corresponding values of a CNT at 300 K and 800 K, respectively. Our study yields new insights into the parameters tuning the thermoelectric efficiency and thus provides a starting point for designing thermoelectric devices based on BNC nanostructures.

Background: to validate the traditional talk test (TTT) and an alternative talk test (ATT; using a visual analog scale) in overweight/obese (OW-OB) patients and to establish its accuracy in determining the aerobic training zones.Methods: We recruited 19 subjects aged 34.9 ± 6.7 years, diagnosed with overweight/obesity (BMI 31.8 ± 5.7). Every subject underwent incremental cycloergometric tests for maximal oxygen consumption, and TT in a randomized order. At the end of each stage during the TT each subject read out loud a 40 words text and then had to identify the comfort to talk in two modalities: TTT which consisted in answering “Yes”, “I don’t know” or “No” to the question Was talking comfortable?, or ATT through a 1 to 10 numeric perception scale (visual scale analog: VAS). The magnitude of differences was interpreted in comparison to the smallest worthwhile change (SWC) and was used to determine agreement.Results: Agreement between the power output at the VAS 2-3 of ATT and the power output at the ventilatory threshold 1 (very likely equivalent; mean difference -1.3 W, 90 % CL (-8.2; 5.6), % chances for higher/similar/lower values of 0.7/99.1/0.2 %). Also, there was an agreement between the power output at the VAS 6-7 of ATT and the power output at the ventilatory threshold 2 (very likely equivalent; mean difference 11.1 W, 90 % CL (2.8; 19.2), % chances for higher/similar/lower values of 0.0/97.6/2.4 %). Conclusions: ATT is a tool to determine exercise intensity and to establish aerobic training zones for exercise prescription in OW-OB patients.

The calculation of time-dependent charge and energy currents in nanoscale systems is a challenging task. Nevertheless it is crucial for gaining a deep understanding of the relevant processes at the nanoscale. We extend the auxiliary-mode approach for time-dependent charge transport to allow for the calculation of energy currents for arbitrary time dependencies. We apply the approach to two illustrative examples, a single-level system and a benzene ring, demonstrating its usefulness for a wide range of problems beyond simple toy models, such as molecular devices.

We use a nonlinear master equation formalism to account for thermal and disorder effects on spin-dependent electron transport in helical organic molecules coupled to two ideal leads. The inclusion of these two effects has important consequences in understanding the observed length and temperature dependence of spin polarization in experiments, which cannot be accounted for in a purely coherent tunneling model. Our approach considers a tight-binding helical Hamiltonian with disordered onsite energies to describe the resulting electronic states when low-frequency interacting modes break the electron coherence. The high-frequency fluctuating counterpart of these interactions, typical of intramolecular modes, is included by means of temperature-dependent thermally activated transfer probabilities in the master equation, which lead to hopping between localized states. We focus on the spin-dependent conductance and the spin-polarization in the linear regime (low voltage), which are analyzed as a function of the molecular length and the temperature of the system. Our results at room temperature agree well with experiments because our model predicts that the degree of spin-polarization increases for longer molecules. Also, this effect is temperature-dependent because thermal excitation competes with disorder-induced Anderson localization. We conclude that a transport mechanism based on thermally activated hopping in a disordered system can account for the unexpected behavior of the spin polarization.

Phonons play a major role for the performance of nanoscale devices and consequently a detailed understanding of phonon dynamics is required. Using an auxiliary-mode approach, which has successfully been applied for the case of electrons, we develop a new method to numerically describe time-dependent phonon transport. This method allows one to gain insight into the behavior of local vibrations in molecular junctions, which are driven by time-dependent temperature differences between thermal baths. Exemplarily, we apply the method to study the nonequilibrium dynamics of quantum heat transport in an one-dimensional atomic chain as well as in realistic molecular junctions made of polyacetylene and polyethylene chains, in which the vibrational structure of the junction is described at the density functional theory level. We calculate the transient energies and heat currents and compare the latter to the standard Landauer approach in thermal equilibrium. We show that the auxiliary-mode representation is a powerful and versatile tool to study time-dependent thermal transport in nanoscale systems.

The chirality-induced spin selectivity effect has been confirmed experimentally for a large class of organic molecules. Adequately modeling the effect remains a challenging task, with both phenomenological models and first-principles simulations yielding inconclusive results. Building upon a previously presented model by K. Michaeli and R. Naaman [J. Phys. Chem. C 123, 17043 (2019)], we systematically investigate an effective 1-dimensional model derived as the limit of a 3-dimensional quantum system with strong confinement and including spin-orbit coupling. Having a simple analytic structure, such models can be considered a minimal setup for the description of spin-dependent effects. We use adiabatic perturbation theory to provide a mathematically sound approximation procedure applicable to a large class of spin-dependent continuum models. We take advantage of the simplicity of the models by analyzing its structure to gain a better understanding how the occurrence and magnitude of spin polarization effects relate to the model's parameters and geometry. The obtained spin polarization is not strongly dependent on the strength of the spin-orbit interaction, but it rather results from breaking time-reversal invariance upon selection of a given angular momentum of the incoming electrons.

This article belongs to the Special Issue Biomolecular Electronics., The helical distribution of the electronic density in chiral molecules, such as DNA and bacteriorhodopsin, has been suggested to induce a spin–orbit coupling interaction that may lead to the so-called chirality-induced spin selectivity (CISS) effect. Key ingredients for the theoretical modelling are, in this context, the helically shaped potential of the molecule and, concomitantly, a Rashba-like spin–orbit coupling due to the appearance of a magnetic field in the electron reference frame. Symmetries of these models clearly play a crucial role in explaining the observed effect, but a thorough analysis has been largely ignored in the literature. In this work, we present a study of these symmetries and how they can be exploited to enhance chiral-induced spin selectivity in helical molecular systems., This research was funded by the Spanish Ministry of Science, Innovation and Universities, Grant Nos. MAT2016-75955 and MAT2017-82639. R.G. and G.C. acknowledge financial support from the Volkswagen Stiftung (Grant No. 88366). This work was partly supported by the German Research Foundation (DFG) within the Cluster of Excellence “Center for Advancing Electronics Dresden”. M.S. acknowledges financial support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project-id No. 258499086—SFB1170 “ToCoTronics”, the Free State of Bavaria (Elitenetzwerk Bayern IDK “Topologische Isolatoren”) and the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat(EXC 2147, Grant No. 39085490).

There is increasing interest in the study of chiral degrees of freedom occurring in matter and in electromagnetic fields. Opportunities in quantum sciences will likely exploit two main areas that are the focus of this Review: (1) recent observations of the chiral-induced spin selectivity (CISS) effect in chiral molecules and engineered nanomaterials and (2) rapidly evolving nanophotonic strategies designed to amplify chiral light-matter interactions. On the one hand, the CISS effect underpins the observation that charge transport through nanoscopic chiral structures favors a particular electronic spin orientation, resulting in large room-temperature spin polarizations. Observations of the CISS effect suggest opportunities for spin control and for the design and fabrication of room-temperature quantum devices from the bottom up, with atomic-scale precision and molecular modularity. On the other hand, chiral-optical effects that depend on both spin- and orbital-angular momentum of photons could offer key advantages in all-optical and quantum information technologies. In particular, amplification of these chiral light-matter interactions using rationally designed plasmonic and dielectric nanomaterials provide approaches to manipulate light intensity, polarization, and phase in confined nanoscale geometries. Any technology that relies on optimal charge transport, or optical control and readout, including quantum devices for logic, sensing, and storage, may benefit from chiral quantum properties. These properties can be theoretically and experimentally investigated from a quantum information perspective, which has not yet been fully developed. There are uncharted implications for the quantum sciences once chiral couplings can be engineered to control the storage, transduction, and manipulation of quantum information. This forward-looking Review provides a survey of the experimental and theoretical fundamentals of chiral-influenced quantum effects and presents a vision for their possible future roles in enabling room-temperature quantum technologies., ACS Nano, 16 (4), ISSN:1936-0851, ISSN:1936-086X

The miniaturization of gears towards the nanoscale is a formidable task posing a variety of challenges to current fabrication technologies. In context, the understanding, via computer simulations, of the mechanisms mediating the transfer of rotational motion between nanoscale gears can be of great help to guide the experimental designs. Based on atomistic molecular dynamics simulations in combination with a nearly rigid-body approximation, we study the transmission of rotational motion between molecule gears and solid-state gears, respectively. For the molecule gears under continuous driving, we identify different regimes of rotational motion depending on the magnitude of the external torque. In contrast, the solid-state gears behave like ideal gears with nearly perfect transmission. Furthermore, we simulate the manipulation of the gears by a scanning-probe tip and we find that the mechanical transmission strongly depends on the center of mass distance between gears. A new regime of transmission is found for the solid-state gears.

The manipulation and coupling of molecule gears is the first step toward realizing molecular-scale mechanical machines. Here, we theoretically investigate the behavior of such gears using molecular-dynamics simulations. Within a nearly rigid-body approximation, we reduce the dynamics of the gears to the rotational motion around the orientation vector. This allows us to study their behavior based on a few collective variables. Specifically, for a single hexa(4-tert-butylphenyl)benzene molecule, we show that the rotational-angle dynamics correspond to those of a Brownian rotor. For two such coupled gears, we extract the effective interaction potential and find that it is strongly dependent on the center-of-mass distance. Finally, we study the collective motion of a train of gears. We demonstrate the existence of three different regimes, depending on the magnitude of the driving torque of the first gear: underdriving, driving, and overdriving, which correspond, respectively, to no collective rotation, collective rotation, and only single-gear rotation. This behavior can be understood in terms of a simplified interaction potential.

The molecular quantum cellular automata paradigm (m-QCA) offers a promising alternative framework to current CMOS implementations. A crucial aspect for implementing this technology concerns the construction of a device which effectively controls intramolecular charge-transfer processes. Tentative experimental implementations have been developed in which a voltage drop is created generating the forces that drive a molecule into a logic state. However, important factors such as the electric field profile, its possible time-dependency and the influence of temperature in the overall success of charge-transfer are relevant issues to be considered in the design of a reliable device. In this work, we theoretically study the role played by these processes in the overall intramolecular charge-transfer process. We have used a Landau–Zener (LZ) model, where different time-dependent electric field profiles have been simulated. The results have been further corroborated employing density functional tight-binding method. The role played by the nuclear motions in the electron-transfer process has been investigated beyond the Born-Oppenheimer approximation by computing the effect of the external electric field in the behavior of the potential energy surface. Hence, we demonstrate that the intramolecular charge-transfer process is a direct consequence of the coherent LZ nonadiabatic tunneling and the hybridization of the diabatic vibronic states which effectively reduces the trapping of the itinerant electron at the donor group.

La presente investigacion tiene el objetivo de evaluar la eficiencia de la biorremediacion mediante la aplicacion de los microorganismos eficaces (EM) en cuatro tipos de usos de suelo contaminados con Diesel B5, de origen agricola, costero, urbano y ribereno. La metodologia utilizada consistio, primero en activar los Microorganismo EM durante nueve dias para luego aplicarlo al suelo contaminado. Se aplico por aspersion un litro por semana de Microorganismos EM activados sobre el area afectada durante 28 dias en los cuatro tipos de usos de suelo. Los resultados permitieron determinar la eficiencia de la biorremediacion en los cuatro tipos de usos de suelo; obteniendo para el suelo de uso urbano una eficiencia del 41.60 % con una disminucion de 51 221 mg/kg a 29 911 mg/kg de HTP; para el suelo de uso agricola, una eficiencia de biorremediacion del 40.06 % con una disminucion de 35 674 mg/kg a 21 383 mg/kg de HTP; para el suelo de uso ribereno una eficiencia de 35.05 % con una disminucion de 7 604 mg/kg a 4 939 mg/kg de HTP y finalmente el suelo de uso costero una eficiencia de 15.29 % con una disminucion de 12 973 mg/kg a 10 989 mg/kg de HTP. Asimismo, se determino los coeficientes de correlacion entre el porcentaje de materia organica (M.O) y la densidad aparente (D.A) del suelo con los resulta- dos de la eficiencia de biorremediacion, obteniendo un valor de 0.9984 y 0.9496, respectivamente; observando una relacion directa e indirecta entre las variables.

Recent progress in nanostructuring of materials opens up possibilities to achieve more efficient thermoelectric devices. Nanofilms, nanowires, and nanorings may show increased phonon scattering while keeping good electron transport, two of the basic ingredients for designing more efficient thermoelectric systems. Here we argue that graphene nanorings attached to two leads meet these two requirements. Using a density-functional parametrized tight-binding method combined with Green's function technique, we show that the lattice thermal conductance is largely reduced as compared to that of graphene nanoribbons. At the same time, numerical calculations based on the quantum transmission boundary method, combined with an effective transfer matrix method, predict that the electric properties are not considerably deteriorated, leading to an overall remarkable thermoelectric efficiency. We conclude that graphene nanorings can be regarded as promising candidates for nanoscale thermoelectric devices.

Experiments on electron transport through helical molecules have demonstrated the appearance of high spin selectivity, in spite of the rather weak spin-orbit coupling in organic compounds. Theoretical models usually rely on different mechanisms to explain these experiments, such as large spin-orbit coupling, quantum dephasing, the role of metallic contacts, or the interplay between a helicity-induced spin-orbit coupling and a strong dipole electric field. In this work we consider the coherent electron dynamics in the electric field created by the helical arrangement of dipoles of the molecule backbone, giving rise to an effective spin-orbit coupling. We calculate the spin projection onto the helical axis as a figure of merit for the assessment of the spin dynamics in a very long helical molecule. We prove that the spin projection reaches a steady state regime after a short transient. We compare its asymptotic value for different initial conditions, aiming to better understand the origin of the spin selectivity found in experiments.

A self-assembled two-dimensional (2D) film of tetra-phenyl-porphyrin-4-ferrocene molecules on Au(111) is studied by STM for the presence of intra- and intermolecular correlations in the configurations of the four-pendant ferrocenyl moieties. A statistical analysis of STS images exploits the Pearson's linear correlation coefficient derived from changes in the molecular electron density across lateral positions in the molecular network as a measure of the intra- and intermolecular coupling and/or conjugation between adjacent equivalent molecular components. Density functional theory (DFT) calculation shows that these electron density changes can be assigned to conformational changes of the ferrocenyl units of the molecules. The methodology presented here can be extended to measure correlations in other 2D systems.