Showing papers by "Georgia Institute of Technology published in 2003"
TL;DR: In this article, a method was used for preparing gold NRs with aspect ratios ranging from 1.5 to 4.5 for which the surface plasmon absorption maxima are between 600 and 1300 nm.
Abstract: A method is used for preparing gold NRs with aspect ratios ranging from 1.5 to 10 for which the surface plasmon absorption maxima are between 600 and 1300 nm. This method has been adapted from a previously published seed-mediated growth method (Jana et al. Adv. Mater. 2001, 13, 1389). The disadvantages and limitations of the earlier method (i.e., formation of noncylindrical NRs, φ-shaped particles, and formation of a large fraction of spherical particles) have been overcome by use of a hexadecyltrimethylammonium bromide (CTAB)-capped seed instead of a citrate-capped one. In a single-component surfactant system, the silver content of the growth solution was used to grow NRs to a desired length. This results in reproducible formation of NRs with aspect ratios ranging from 1.5 to 4.5. To grow longer NRs with aspect ratios ranging from 4.6 to 10, a binary surfactant mixture composed of benzyldimethylhexadecylammoniumchloride (BDAC) and CTAB was used. NRs are grown in this mixture either by aging or by additio...
4,645 citations
TL;DR: In this article, neighborhood environment characteristics proposed to be relevant to walking/cycling for transport are defined, including population density, connectivity, and land use mix, with evidence suggesting that residents from communities with higher density, greater connectivity and more land-use mix report higher rates of walking and cycling for utilitarian purposes than low-density, poorly connected, and single land use neighborhoods.
Abstract: Research in transportation, urban design, and planning has examined associations between physical environment variables and individuals' walking and cycling for transport. Constructs, methods, and findings from these fields can be applied by physical activity and health researchers to improve understanding of environmental influences on physical activity. In this review, neighborhood environment characteristics proposed to be relevant to walking/cycling for transport are defined, including population density, connectivity, and land use mix. Neighborhood comparison and correlational studies with nonmotorized transport outcomes are considered, with evidence suggesting that residents from communities with higher density, greater connectivity, and more land use mix report higher rates of walking/cycling for utilitarian purposes than low-density, poorly connected, and single land use neighborhoods. Environmental variables appear to add to variance accounted for beyond sociodemographic predictors of walking/cycling for transport. Implications of the transportation literature for physical activity and related research are outlined. Future research directions are detailed for physical activity research to further examine the impact of neighborhood and other physical environment factors on physical activity and the potential interactive effects of psychosocial and environmental variables. The transportation, urban design, and planning literatures provide a valuable starting point for multidisciplinary research on environmental contributions to physical activity levels in the population.
2,218 citations
01 Jul 2003
TL;DR: A new algorithm for image and video texture synthesis where patch regions from a sample image or video are transformed and copied to the output and then stitched together along optimal seams to generate a new (and typically larger) output.
Abstract: In this paper we introduce a new algorithm for image and video texture synthesis. In our approach, patch regions from a sample image or video are transformed and copied to the output and then stitched together along optimal seams to generate a new (and typically larger) output. In contrast to other techniques, the size of the patch is not chosen a-priori, but instead a graph cut technique is used to determine the optimal patch region for any given offset between the input and output texture. Unlike dynamic programming, our graph cut technique for seam optimization is applicable in any dimension. We specifically explore it in 2D and 3D to perform video texture synthesis in addition to regular image synthesis. We present approximative offset search techniques that work well in conjunction with the presented patch size optimization. We show results for synthesizing regular, random, and natural images and videos. We also demonstrate how this method can be used to interactively merge different images to generate new scenes.
1,618 citations
TL;DR: In this article, the authors explore the association between the context of social relationships and individual creativity, and propose the network positions that facilitate and constrain creative work, and describe three moderators.
Abstract: We explore the association between the context of social relationships and individual creativity. We go beyond a one-dimensional treatment of social relationships, highlighting the importance of both static and dynamic social network concepts. We argue that weaker ties are generally but not always beneficial for creativity, propose the network positions that facilitate and constrain creative work, and describe three moderators. A spiraling model is presented, capturing the cyclical relationship between creativity and network position. Collectively, our propositions describe an individual's creative life cycle in terms of network position.
1,571 citations
TL;DR: The data and a literature review suggest that Stroop interference is jointly determined by 2 mechanisms, goal maintenance and competition resolution, and that the dominance of each depends on WM capacity, as well as the task set induced by current and previous contexts.
Abstract: Individual differences in working-memory (WM) capacity predicted performance on the Stroop task in 5 experiments, indicating the importance of executive control and goal maintenance to selective attention. When the Stroop task encouraged goal neglect by including large numbers of congruent trials (RED presented in red), low WM individuals committed more errors than did high WM individuals on the rare incongruent trials (BLUE in red) that required maintaining access to the ?ignore-the-word? goal for accurate responding. In contrast, in tasks with no or few congruent trials, or in high-congruency tasks that followed low-congruency tasks, WM predicted response-time interference. WM was related to latency, not accuracy, in contexts that reinforced the task goal and so minimized the difficulty of actively maintaining it. The data and a literature review suggest that Stroop interference is jointly determined by 2 mechanisms, goal maintenance and competition resolution, and that the dominance of each depends on WM capacity, as well as the task set induced by current and previous contexts.
1,553 citations
TL;DR: In this review, some of the properties of individual and some assembled metallic nanoparticles with a focus on their interaction with cw and pulsed laser light of different energies are discussed.
Abstract: Noble metal particles have long fascinated scientists because of their intense color, which led to their application in stained glass windows as early as the Middle Ages. The recent resurrection of colloidal and cluster chemistry has brought about the strive for new materials that allow a bottoms-up approach of building improved and new devices with nanoparticles or artificial atoms. In this review, we discuss some of the properties of individual and some assembled metallic nanoparticles with a focus on their interaction with cw and pulsed laser light of different energies. The potential application of the plasmon resonance as sensors is discussed.
1,327 citations
TL;DR: Using a sample of 888 bank employees working under 76 branch manages, the authors found that transformational leadership was positively related to both followers' dependence and their empowerment and that personal identification mediated the relationship betweentransformational leadership and followers' dependent on the leader.
Abstract: Followers' identification with the leader and the organizational unit, dependence on the leader, and empowerment by the leader are often attributed to transformational leadership in organizations. However, these hypothesized outcomes have received very little attention in empirical studies. Using a sample of 888 bank employees working under 76 branch manages, the authors tested the relationships between transformational leadership and these outcomes. They found that transformational leadership was positively related to both followers' dependence and their empowerment and that personal identification mediated the relationship between transformational leadership and followers' dependence on the leader, whereas social identification mediated the relationship between transformational leadership and followers' empowerment. The authors discuss the implications of these findings to both theory and practice.
1,287 citations
TL;DR: GoMiner, a program package that organizes lists of 'interesting' genes for biological interpretation in the context of the Gene Ontology, provides quantitative and statistical output files and two useful visualizations.
Abstract: We have developed GoMiner, a program package that organizes lists of 'interesting' genes (for example, under- and overexpressed genes from a microarray experiment) for biological interpretation in the context of the Gene Ontology. GoMiner provides quantitative and statistical output files and two useful visualizations. The first is a tree-like structure analogous to that in the AmiGO browser and the second is a compact, dynamically interactive 'directed acyclic graph'. Genes displayed in GoMiner are linked to major public bioinformatics resources.
1,262 citations
TL;DR: The aim here is to discuss the usability of conducting polymers in both types of electronic applications in light of these two parameters: conductivity and work function.
Abstract: Conducting organic polymers have found two main kinds of application in electronics so far: as materials for construction of various devices and as selective layers in chemical sensors. In either case, interaction with ambient gases is critical. It may compromise the performance of a device based on conducting polymers, whereas it is beneficial in a sensor. Conductivity has been the primary property of interest. Work function--related to conductivity, but in principle a different property--has received only scant attention. Our aim here is to discuss the usability of conducting polymers in both types of electronic applications in light of these two parameters.
1,234 citations
01 Oct 2003
TL;DR: This work presents a system that automatically clusters GPS data taken over an extended period of time into meaningful locations at multiple scales and incorporates these locations into a Markov model that can be consulted for use with a variety of applications in both single-user and collaborative scenarios.
Abstract: Wearable computers have the potential to act as intelligent agents in everyday life and to assist the user in a variety of tasks, using context to determine how to act. Location is the most common form of context used by these agents to determine the user's task. However, another potential use of location context is the creation of a predictive model of the user's future movements. We present a system that automatically clusters GPS data taken over an extended period of time into meaningful locations at multiple scales. These locations are then incorporated into a Markov model that can be consulted for use with a variety of applications in both single-user and collaborative scenarios.
1,211 citations
TL;DR: In this article, a review of nanostructures of functional oxides, including nanobelts, nanowires, nanosheets, and nanodiskettes, has been presented.
Abstract: Functional oxides are the fundamentals of smart devices. This article reviews novel nanostructures of functional oxides, including nanobelts, nanowires, nanosheets, and nanodiskettes, that have been synthesized in the authors’ laboratory. Among the group of ZnO, SnO2, In2O3, Ga2O3, CdO, and PbO2, which belong to different crystallographic systems and structures, a generic nanobelt structure has been synthesized. The nanobelts are single crystalline and dislocation-free, and their surfaces are atomically flat. The oxides are semiconductors, and have been used for fabrication of nanodevices such as field-effect transistors and gas sensors. Taking SnO2 and SnO as examples, other types of novel nanostructures are illustrated. Their growth, phase transformation, and stability are discussed. The nanobelts and related nanostructures are a unique group that is likely to have important applications in electronic, optical, sensor, and optoelectronic nanodevices.
TL;DR: The Common Land Model (CLM) as mentioned in this paper was developed for community use by a grassroots collaboration of scientists who have an interest in making a general land model available for public use and further development.
Abstract: The Common Land Model (CLM) was developed for community use by a grassroots collaboration of scientists who have an interest in making a general land model available for public use and further development. The major model characteristics include enough unevenly spaced layers to adequately represent soil temperature and soil moisture, and a multilayer parameterization of snow processes; an explicit treatment of the mass of liquid water and ice water and their phase change within the snow and soil system; a runoff parameterization following the TOPMODEL concept; a canopy photo synthesis-conductance model that describes the simultaneous transfer of CO2 and water vapor into and out of vegetation; and a tiled treatment of the subgrid fraction of energy and water balance. CLM has been extensively evaluated in offline mode and coupling runs with the NCAR Community Climate Model (CCM3). The results of two offline runs, presented as examples, are compared with observations and with the simulation of three other la...
TL;DR: In this article, field effect transistors (FETs) based on single SnO2 and ZnO nanobelts of thicknesses between 10 and 30 nm have been fabricated.
Abstract: We have fabricated field-effect transistors (FETs) based on single SnO2 and ZnO nanobelts of thicknesses between 10 and 30 nm. Switching ratios as large as 6 orders of magnitude and conductivities as high as 15 (Ω cm)-1 are observed. Annealing SnO2 nanobelt FETs in an oxygen-deficient atmosphere produces a negative shift in gate threshold voltage, indicating doping by the generation of surface oxygen vacancies. This treatment provides an effective way of tuning the electrical performance of the nanobelt devices. The ability of SnO2 FETs to act as gas sensors is also demonstrated. SnO2 FETs with lengths of about 500 nm or less show an anomalous behavior where the conductance cannot be modulated by the gate. ZnO nanobelt FETs are sensitive to ultraviolet light. Both photogeneration of electron−hole pairs and doping by UV induced surface desorption contribute to the conductivity.
TL;DR: A review of the recent research reveals that WMC and g are indeed highly related, but not identical and WM span tasks involve an executive-control mechanism that is recruited to combat interference and this ability is mediated by portions of the prefrontal cortex.
TL;DR: In this article, the divergence of the surface energy due to intrinsic polarization is controlled by controlling the grasps of the ZnO nanostructures, and the divergence can be further reduced.
Abstract: Growth of (0001) facet-dominated, free-standing, piezoelectric zinc oxide (ZnO) nanostructures is challenged by the divergence of the surface energy due to intrinsic polarization. By controlling gr...
TL;DR: In this article, the authors describe the nature of working memory capacity (WMC), their effects on higher order cognitive tasks, their relationship to attention control and general fluid intelligence, and their neurological substrates.
Abstract: Publisher Summary This chapter describes the nature of working memory capacity (WMC), and addresses the nature of WMC limitations, their effects on higher order cognitive tasks, their relationship to attention control and general fluid intelligence, and their neurological substrates. Much of work explores these issues in the context of individual differences in WMC and the cause of those individual differences. Measures of WMC are highly reliable and highly valid indicators of some construct of clear relevance to feral cognition. Macroanalytic studies have demonstrated that the construct reflected by WMC tasks has a strong relationship with gF above and beyond what these tasks share with simple span tasks. The conflict might also arise from stimulus representations of competing strength. This two-factor model fits with current thinking about the role of two brain structures: the prefrontal cortex as important to the maintenance of information in an active and easily accessible state and the anterior cingulate as important to the detection and resolution of conflict.
TL;DR: The mechanical deformation of proteins and nucleic acids may provide key insights for understanding the changes in cellular structure, response and function under force, and offer new opportunities for the diagnosis and treatment of disease.
Abstract: Living cells can sense mechanical forces and convert them into biological responses. Similarly, biological and biochemical signals are known to influence the abilities of cells to sense, generate and bear mechanical forces. Studies into the mechanics of single cells, subcellular components and biological molecules have rapidly evolved during the past decade with significant implications for biotechnology and human health. This progress has been facilitated by new capabilities for measuring forces and displacements with piconewton and nanometre resolutions, respectively, and by improvements in bio-imaging. Details of mechanical, chemical and biological interactions in cells remain elusive. However, the mechanical deformation of proteins and nucleic acids may provide key insights for understanding the changes in cellular structure, response and function under force, and offer new opportunities for the diagnosis and treatment of disease. This review discusses some basic features of the deformation of single cells and biomolecules, and examines opportunities for further research.
01 Jan 2003
TL;DR: In this article, Monte Carlo sampling methods for solving large scale stochastic programming problems are discussed, where a random sample is generated outside of an optimization procedure, and then the constructed, so-called sample average approximation (SAA), problem is solved by an appropriate deterministic algorithm.
Abstract: In this chapter we discuss Monte Carlo sampling methods for solving large scale stochastic programming problems We concentrate on the “exterior” approach where a random sample is generated outside of an optimization procedure, and then the constructed, so-called sample average approximation (SAA), problem is solved by an appropriate deterministic algorithm We study statistical properties of the obtained SAA estimators The developed statistical inference is incorporated into validation analysis and error estimation We describe some variance reduction techniques which may enhance convergence of sampling based estimates We also discuss difficulties in extending this methodology to multistage stochastic programming Finally, we briefly discuss the SAA method applied to stochastic generalized equations and variational inequalities
TL;DR: A parametric model for an implicit representation of the segmenting curve is derived by applying principal component analysis to a collection of signed distance representations of the training data to minimize an objective function for segmentation.
Abstract: We propose a shape-based approach to curve evolution for the segmentation of medical images containing known object types. In particular, motivated by the work of Leventon, Grimson, and Faugeras (2000), we derive a parametric model for an implicit representation of the segmenting curve by applying principal component analysis to a collection of signed distance representations of the training data. The parameters of this representation are then manipulated to minimize an objective function for segmentation. The resulting algorithm is able to handle multidimensional data, can deal with topological changes of the curve, is robust to noise and initial contour placements, and is computationally efficient. At the same time, it avoids the need for point correspondences during the training phase of the algorithm. We demonstrate this technique by applying it to two medical applications; two-dimensional segmentation of cardiac magnetic resonance imaging (MRI) and three-dimensional segmentation of prostate MRI.
TL;DR: A nonlinear programming algorithm for solving semidefinite programs (SDPs) in standard form that replaces the symmetric, positive semideFinite variable X with a rectangular variable R according to the factorization X=RRT.
Abstract: In this paper, we present a nonlinear programming algorithm for solving semidefinite programs (SDPs) in standard form. The algorithm's distinguishing feature is a change of variables that replaces the symmetric, positive semidefinite variable X of the SDP with a rectangular variable R according to the factorization X=RR
T
. The rank of the factorization, i.e., the number of columns of R, is chosen minimally so as to enhance computational speed while maintaining equivalence with the SDP. Fundamental results concerning the convergence of the algorithm are derived, and encouraging computational results on some large-scale test problems are also presented.
TL;DR: It is shown that increasing force first prolonged and then shortened the lifetimes of P-selectin complexes with P- selectin glycoprotein ligand-1, revealing both catch and slip bond behaviour.
Abstract: Bonds between adhesion molecules are often mechanically stressed. A striking example is the tensile force applied to selectin-ligand bonds, which mediate the tethering and rolling of flowing leukocytes on vascular surfaces(1-3). It has been suggested that
TL;DR: An experimental framework to analyze adhesive mechanisms controlling cell-surface interactions is established and a general strategy of surface-directed control of adsorbed protein activity to manipulate cell function in biomaterial and biotechnological applications is provided.
Abstract: Integrin-mediated cell adhesion to proteins adsorbed onto synthetic surfaces anchors cells and triggers signals that direct cell function. In the case of fibronectin (Fn), adsorption onto substrates of varying properties alters its conformation/structure and its ability to support cell adhesion. In the present study, self-assembled monolayers (SAMs) of alkanethiols on gold were used as model surfaces to investigate the effects of surface chemistry on Fn adsorption, integrin binding, and cell adhesion. SAMs presenting terminal CH(3), OH, COOH, and NH(2) functionalities modulated adsorbed Fn conformation as determined through differences in the binding affinities of monoclonal antibodies raised against the central cell-binding domain (OH > COOH = NH(2) > CH(3)). Binding of alpha(5)beta(1) integrin to adsorbed Fn was controlled by SAM surface chemistry in a manner consistent with antibody binding (OH > COOH = NH(2) > CH(3)), whereas alpha(V) integrin binding followed the trend: COOH >> OH = NH(2) = CH(3), demonstrating alpha(5)beta(1) integrin specificity for Fn adsorbed onto the NH(2) and OH SAMs. Cell adhesion strength to Fn-coated SAMs correlated with alpha(5)beta(1) integrin binding (OH > COOH = NH(2) > CH(3)), and experiments with function-perturbing antibodies demonstrated that this receptor provides the dominant adhesion mechanism in this cell model. This work establishes an experimental framework to analyze adhesive mechanisms controlling cell-surface interactions and provides a general strategy of surface-directed control of adsorbed protein activity to manipulate cell function in biomaterial and biotechnological applications.
TL;DR: This work demonstrates that composition and internal structure are two important parameters that can be used to tune the optical and electronic properties of multicomponent, alloyed quantum dots.
Abstract: Alloyed semiconductor quantum dots (cadmium selenium telluride) with both homogeneous and gradient internal structures have been prepared to achieve continuous tuning of the optical properties without changing the particle size. Our results demonstrate that composition and internal structure are two important parameters that can be used to tune the optical and electronic properties of multicomponent, alloyed quantum dots. A surprising finding is a nonlinear relationship between the composition and the absorption/emission energies, leading to new properties not obtainable from the parent binary systems. With red-shifted light emission up to 850 nm and quantum yields up to 60%, this new class of alloyed quantum dots opens new possibilities in band gap engineering and in developing near-infrared fluorescent probes for in vivo molecular imaging and biomarker detection.
TL;DR: In this article, the shareholders' wealth affects of supply chain glitches are estimated by computing the abnormal stock returns around the date when information about information about glitches is publicly announced, and the results are based on a sample of 519 glitches announcements made during 1989-2000.
TL;DR: The story of the design of Learning by Design (LBD), a project-based inquiry approach to science learning with roots in case-based reasoning and problem-based learning, is told, pointing out the theoretical contributions of both.
Abstract: This article tells the story of the design of Learning by Design(tm) (LBD), a project-based inquiry approach to science learning with roots in case-based reasoning and problem-based learning, pointing out the theoretical contributions of both, classroom issues that arose upon piloting a first attempt, ways we addressed those challenges, lessons learned about promoting learning taking a project-based inquiry approach, and lessons learned about taking a theory-based approach to designing learning environments. LBD uses what we know about cognition to fashion a learning environment appropriate to deeply learning science concepts and skills and their applicability, in parallel with learning cognitive, social, learning, and communication skills. Our goal, in designing LBD, was to lay the foundation in middle school for students to be successful thinkers, learners, and decisionmakers throughout their lives and especially to help them begin to learn the science they need to know to thrive in the modern world. LB...
TL;DR: A review of the recent bandwidth estimation literature focusing on underlying techniques and methodologies as well as open source bandwidth measurement tools is reviewed.
Abstract: In a packet network, the terms bandwidth and throughput often characterize the amount of data that the network can transfer per unit of time. Bandwidth estimation is of interest to users wishing to optimize end-to-end transport performance, overlay network routing, and peer-to-peer file distribution. Techniques for accurate bandwidth estimation are also important for traffic engineering and capacity planning support. Existing bandwidth estimation tools measure one or more of three related metrics: capacity, available bandwidth, and bulk transfer capacity. Currently available bandwidth estimation tools employ a variety of strategies to measure these metrics. In this survey we review the recent bandwidth estimation literature focusing on underlying techniques and methodologies as well as open source bandwidth measurement tools.
01 Jun 2003
TL;DR: A new reliable transport scheme for WSN, the event-to-sink reliable transport (ESRT) protocol, is presented in this paper, a novel transport solution developed to achieve reliable event detection in WSN with minimum energy expenditure.
Abstract: Wireless sensor networks (WSN) are event based systems that rely on the collective effort of several microsensor nodes. Reliable event detection at the sink is based on collective information provided by source nodes and not on any individual report. Hence, conventional end-to-end reliability definitions and solutions are inapplicable in the WSN regime and would only lead to a waste of scarce sensor resources. However, the absence of reliable transport altogether can seriously impair event detection. Hence, the WSN paradigm necessitates a collective phevent-to-sink reliability notion rather than the traditional end-to-end notion. To the best of our knowledge, reliable transport in WSN has not been studied from this perspective before.In order to address this need, a new reliable transport scheme for WSN, the event-to-sink reliable transport (ESRT) protocol, is presented in this paper. ESRT is a novel transport solution developed to achieve reliable event detection in WSN with minimum energy expenditure. It includes a congestion control component that serves the dual purpose of achieving reliability and conserving energy. Importantly, the algorithms of ESRT mainly run on the sink, with minimal functionality required at resource constrained sensor nodes. ESRT protocol operation is determined by the current network state based on the reliability achieved and congestion condition in the network. If the event-to-sink reliability is lower than required, ESRT adjusts the reporting frequency of source nodes aggressively in order to reach the target reliability level as soon as possible. If the reliability is higher than required, then ESRT reduces the reporting frequency conservatively in order to conserve energy while still maintaining reliability. This self-configuring nature of ESRT makes it robust to random, dynamic topology in WSN. Analytical performance evaluation and simulation results show that ESRT converges to the desired reliability with minimum energy expenditure, starting from any initial network state.
TL;DR: This paper examines the vulnerabilities of wireless networks and argues that it must include intrusion detection in the security architecture for mobile computing environment, and develops a key mechanism in this architecture, anomaly detection for mobile ad-hoc network, through simulation experiments.
Abstract: The rapid proliferation of wireless networks and mobile computing applications has changed the landscape of network security. The traditional way of protecting networks with firewalls and encryption software is no longer sufficient and effective. We need to search for new architecture and mechanisms to protect the wireless networks and mobile computing application. In this paper, we examine the vulnerabilities of wireless networks and argue that we must include intrusion detection in the security architecture for mobile computing environment. We have developed such an architecture and evaluated a key mechanism in this architecture, anomaly detection for mobile ad-hoc network, through simulation experiments.
TL;DR: A single-electron transistor where the electronic levels of a single π-conjugated molecule in several distinct charged states control the transport properties is described, leading to a very significant reduction of the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital.
Abstract: A combination of classical Coulomb charging, electronic level spacings, spin, and vibrational modes determines the single-electron transfer reactions through nanoscale systems connected to external electrodes by tunnelling barriers1. Coulomb charging effects have been shown to dominate such transport in semiconductor quantum dots2, metallic3 and semiconducting4 nanoparticles, carbon nanotubes5,6, and single molecules7,8,9. Recently, transport has been shown to be also influenced by spin—through the Kondo effect—for both nanotubes10 and single molecules8,9, as well as by vibrational fine structure7,11. Here we describe a single-electron transistor where the electronic levels of a single π-conjugated molecule in several distinct charged states control the transport properties. The molecular electronic levels extracted from the single-electron-transistor measurements are strongly perturbed compared to those of the molecule in solution, leading to a very significant reduction of the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. We suggest, and verify by simple model calculations, that this surprising effect could be caused by image charges generated in the source and drain electrodes resulting in a strong localization of the charges on the molecule.