Showing papers by "Georgia Institute of Technology published in 2004"
TL;DR: Sensitive and multicolor fluorescence imaging of cancer cells under in vivo conditions are achieved and a whole-body macro-illumination system with wavelength-resolved spectral imaging is integrated for efficient background removal and precise delineation of weak spectral signatures.
Abstract: We describe the development of multifunctional nanoparticle probes based on semiconductor quantum dots (QDs) for cancer targeting and imaging in living animals. The structural design involves encapsulating luminescent QDs with an ABC triblock copolymer and linking this amphiphilic polymer to tumor-targeting ligands and drug-delivery functionalities. In vivo targeting studies of human prostate cancer growing in nude mice indicate that the QD probes accumulate at tumors both by the enhanced permeability and retention of tumor sites and by antibody binding to cancer-specific cell surface biomarkers. Using both subcutaneous injection of QD-tagged cancer cells and systemic injection of multifunctional QD probes, we have achieved sensitive and multicolor fluorescence imaging of cancer cells under in vivo conditions. We have also integrated a whole-body macro-illumination system with wavelength-resolved spectral imaging for efficient background removal and precise delineation of weak spectral signatures. These results raise new possibilities for ultrasensitive and multiplexed imaging of molecular targets in vivo.
4,634 citations
TL;DR: In this paper, a review of various nanostructures of ZnO grown by the solid-vapour phase technique and their corresponding growth mechanisms is presented. And the application of nanobelts as nanosensors, nanocantilevers, field effect transistors and nanoresonators is demonstrated.
Abstract: Zinc oxide is a unique material that exhibits semiconducting and piezoelectric dual properties. Using a solid–vapour phase thermal sublimation technique, nanocombs, nanorings, nanohelixes/nanosprings, nanobelts, nanowires and nanocages of ZnO have been synthesized under specific growth conditions. These unique nanostructures unambiguously demonstrate that ZnO probably has the richest family of nanostructures among all materials, both in structures and in properties. The nanostructures could have novel applications in optoelectronics, sensors, transducers and biomedical sciences. This article reviews the various nanostructures of ZnO grown by the solid–vapour phase technique and their corresponding growth mechanisms. The application of ZnO nanobelts as nanosensors, nanocantilevers, field effect transistors and nanoresonators is demonstrated.
3,361 citations
TL;DR: In this paper, ultrathin epitaxial graphite films were grown by thermal decomposition on the (0001) surface of 6H−SiC, and characterized by surface science techniques.
Abstract: We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically three graphene sheets, were grown by thermal decomposition on the (0001) surface of 6H−SiC, and characterized by surface science techniques. The low-temperature conductance spans a range of localization regimes according to the structural state (square resistance 1.5 kΩ to 225 kΩ at 4 K, with positive magnetoconductance). Low-resistance samples show characteristics of weak localization in two dimensions, from which we estimate elastic and inelastic mean free paths. At low field, the Hall resistance is linear up to 4.5 T, which is well-explained by n-type carriers of density 1012 cm-2 per graphene sheet. The most highly ordered sample exhibits Shubnikov−de Haas oscillations that correspond to nonlinearities observed in the Hall resistance, indicating a potential new quantum Hall system. We show that the high-mobility films can be patterned via conventional lithographic...
3,315 citations
TL;DR: In this article, the authors reviewed existing knowledge with regard to organic aerosol (OA) of importance for global climate modelling and defined critical gaps needed to reduce the involved uncertainties, and synthesized the information to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosols.
Abstract: The present paper reviews existing knowledge with regard to Organic Aerosol (OA) of importance for global climate modelling and defines critical gaps needed to reduce the involved uncertainties. All pieces required for the representation of OA in a global climate model are sketched out with special attention to Secondary Organic Aerosol (SOA): The emission estimates of primary carbonaceous particles and SOA precursor gases are summarized. The up-to-date understanding of the chemical formation and transformation of condensable organic material is outlined. Knowledge on the hygroscopicity of OA and measurements of optical properties of the organic aerosol constituents are summarized. The mechanisms of interactions of OA with clouds and dry and wet removal processes parameterisations in global models are outlined. This information is synthesized to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosol. The sources of uncertainties at each step of this process are highlighted as areas that require further studies.
2,863 citations
TL;DR: The results of this study indicate that the second-order IUIPC factor, which consists of three first-order dimensions--namely, collection, control, and awareness--exhibited desirable psychometric properties in the context of online privacy.
Abstract: The lack of consumer confidence in information privacy has been identified as a major problem hampering the growth of e-commerce. Despite the importance of understanding the nature of online consumers' concerns for information privacy, this topic has received little attention in the information systems community. To fill the gap in the literature, this article focuses on three distinct, yet closely related, issues. First, drawing on social contract theory, we offer a theoretical framework on the dimensionality of Internet users' information privacy concerns (IUIPC). Second, we attempt to operationalize the multidimensional notion of IUIPC using a second-order construct, and we develop a scale for it. Third, we propose and test a causal model on the relationship between IUIPC and behavioral intention toward releasing personal information at the request of a marketer. We conducted two separate field surveys and collected data from 742 household respondents in one-on-one, face-to-face interviews. The results of this study indicate that the second-order IUIPC factor, which consists of three first-order dimensions--namely, collection, control, and awareness--exhibited desirable psychometric properties in the context of online privacy. In addition, we found that the causal model centering on IUIPC fits the data satisfactorily and explains a large amount of variance in behavioral intention, suggesting that the proposed model will serve as a useful tool for analyzing online consumers' reactions to various privacy threats on the Internet.
2,597 citations
2,443 citations
TL;DR: In this paper, the authors systematically review and integrate empirical research that has examined the personal and contextual characteristics that enhance or stifle employee creativity in the workplace, and discuss possible determinants of employee creativity that have received little research attention.
2,273 citations
TL;DR: PeerTrust is presented - a reputation-based trust supporting framework, which includes a coherent adaptive trust model for quantifying and comparing the trustworthiness of peers based on a transaction-based feedback system, and a decentralized implementation of such a model over a structured P2P network.
Abstract: Peer-to-peer (P2P) online communities are commonly perceived as an environment offering both opportunities and threats. One way to minimize threats in such communities is to use community-based reputations to help estimate the trustworthiness of peers. We present PeerTrust - a reputation-based trust supporting framework, which includes a coherent adaptive trust model for quantifying and comparing the trustworthiness of peers based on a transaction-based feedback system, and a decentralized implementation of such a model over a structured P2P network. PeerTrust model has two main features. First, we introduce three basic trust parameters and two adaptive factors in computing trustworthiness of peers, namely, feedback a peer receives from other peers, the total number of transactions a peer performs, the credibility of the feedback sources, transaction context factor, and the community context factor. Second, we define a general trust metric to combine these parameters. Other contributions of the paper include strategies used for implementing the trust model in a decentralized P2P environment, evaluation mechanisms to validate the effectiveness and cost of PeerTrust model, and a set of experiments that show the feasibility and benefit of our approach.
1,847 citations
Abstract: We link the exploration–exploitation framework of organizational learning to a technology venture's strategic alliances and argue that the causal relationship between the venture's alliances and its new product development depends on the type of the alliance. In particular, we propose a product development path beginning with exploration alliances predicting products in development, which in turn predict exploitation alliances, and that concludes with exploitation alliances leading to products on the market. Moreover, we argue that this integrated product development path is moderated negatively by firm size. As a technology venture grows, it tends to withdraw from this product development path to discover, develop, and commercialize promising projects through vertical integration. We test our model on a sample of 325 biotechnology firms that entered 2565 alliances over a 25-year period. We find broad support for the hypothesized product development system and the moderating effect of firm size. Copyright © 2004 John Wiley & Sons, Ltd.
1,821 citations
01 Oct 2004
TL;DR: S sensor-actor and actor-actor coordination is explored and research challenges for coordination and communication problems are described.
Abstract: Wireless sensor and actor networks (WSANs) refer to a group of sensors and actors linked by wireless medium to perform distributed sensing and acting tasks. The realization of wireless sensor and actor networks (WSANs) needs to satisfy the requirements introduced by the coexistence of sensors and actors. In WSANs, sensors gather information about the physical world, while actors take decisions and then perform appropriate actions upon the environment, which allows a user to effectively sense and act from a distance. In order to provide effective sensing and acting, coordination mechanisms are required among sensors and actors. Moreover, to perform right and timely actions, sensor data must be valid at the time of acting. This paper explores sensor-actor and actor-actor coordination and describes research challenges for coordination and communication problems.
1,624 citations
TL;DR: A review of research examining contextual factors that can either foster or hinder employee creativity at individual, job, group, and organizational level is provided in this paper, where the role of leadership and the use of different human resource practices for developing a work context that is supportive of creativity is discussed.
Abstract: This article provides a current review of research examining contextual factors that can either foster or hinder employee creativity at the individual, job, group, and organizational level. Specifically, we examine the role of leadership and the use of different human resource practices for developing a work context that is supportive of creativity. Finally, based on our review, we discuss practical implications for managers, propose areas that need further research attention, and highlight possible new directions for future research.
TL;DR: The findings support a domain-general view of WM capacity, in which executive-attention processes drive the broad predictive utility of WM span measures, and domain-specific storage and rehearsal processes relate more strongly to domain- specific aspects of complex cognition.
Abstract: A latent-variable study examined whether verbal and visuospatial working memory (WM) capacity measures reflect a primarily domain-general construct by testing 236 participants in 3 span tests each of verbal WM, visuospatial WM, verbal short-term memory (STM), and visuospatial STM, as well as in tests of verbal and spatial reasoning and general fluid intelligence (Gf). Confirmatory factor analyses and structural equation models indicated that the WM tasks largely reflected a domain-general factor, whereas STM tasks, based on the same stimuli as the WM tasks, were much more domain specific. The WM construct was a strong predictor of Gf and a weaker predictor of domain-specific reasoning, and the reverse was true for the STM construct. The findings support a domain-general view of WM capacity, in which executive-attention processes drive the broad predictive utility of WM span measures, and domain-specific storage and rehearsal processes relate more strongly to domain-specific aspects of complex cognition.
TL;DR: An effective approach is demonstrated for growing large-area, hexagonally patterned, aligned ZnO nanorods and opens the possibility of creating patterned one-dimensional nanostructures for applications as sensor arrays, piezoelectric antenna arrays, optoelectronic devices, and interconnects.
Abstract: An effective approach is demonstrated for growing large-area, hexagonally patterned, aligned ZnO nanorods. The synthesis uses a catalyst template produced by a self-assembled monolayer of submicron spheres and guided vapor-liquid-solid (VLS) growth on a single crystal alumina substrate. The ZnO nanorods have uniform shape and length, align vertically on the substrate, and are distributed according to the pattern defined by the catalyst template. The nanorods grow along [0001] with side surfaces defined by {2110}. This approach opens the possibility of creating patterned one-dimensional nanostructures for applications as sensor arrays, piezoelectric antenna arrays, optoelectronic devices, and interconnects.
08 Nov 2004
TL;DR: The paper explores various physical layer research challenges in MIMO-OFDM system design, including physical channel measurements and modeling, analog beam forming techniques using adaptive antenna arrays, and signal processing algorithms used to perform time and frequency synchronization, channel estimation, and channel tracking in M IMO- OFDM systems.
Abstract: Orthogonal frequency division multiplexing (OFDM) is a popular method for high data rate wireless transmission. OFDM may be combined with antenna arrays at the transmitter and receiver to increase the diversity gain and/or to enhance the system capacity on time-varying and frequency-selective channels, resulting in a multiple-input multiple-output (MIMO) configuration. The paper explores various physical layer research challenges in MIMO-OFDM system design, including physical channel measurements and modeling, analog beam forming techniques using adaptive antenna arrays, space-time techniques for MIMO-OFDM, error control coding techniques, OFDM preamble and packet design, and signal processing algorithms used to perform time and frequency synchronization, channel estimation, and channel tracking in MIMO-OFDM systems. Finally, the paper considers a software radio implementation of MIMO-OFDM.
TL;DR: Freestanding single-crystal complete nanorings of zinc oxide were formed via a spontaneous self-coiling process during the growth of polar nanobelts, useful for investigating polar surface–induced growth processes, fundamental physics phenomena, and nanoscale devices.
Abstract: On the basis of these observations, LkH 233 is the more evolved of the two systems, with well-defined cavities swept out by bipolar outflow and bisected by a very dark lane. LkH 198 is a less evolved system, which is only in the early stages of developing bipolar cavities and possesses lower extinction in the apparent disk midplane. The observed circumstellar environments are consistent with the rotationally flattened infall envelopes models developed for T Tauri stars, indicating that the process of envelope collapse has similar phases, despite the large disparities in mass and luminosity between these two classes of young stars. This morphological similarity leads us to infer that the conservation and transport of angular momentum is the dominant physical process for both classes of stars. Alternate formation pathways have been suggested for OB stars that invoke new physical mechanisms, such as magnetohydrodynamic turbulence (31 )o r stellar mergers (32). The Herbig Ae stars studied here appear to be below the mass threshhold at which such effects become important.
24 May 2004
TL;DR: This paper describes a mobility-assisted approach which utilizes a set of special mobile nodes called message ferries to provide communication service for nodes in the deployment area and evaluates the performance of MF via extensive ns simulations which confirm it is efficient in both data delivery and energy consumption under a variety of network conditions.
Abstract: Mobile Ad Hoc Networks (MANETs) provide rapidly deployable and self-configuring network capacity required in many critical applications, eg, battlefields, disaster relief and wide area sensing In this paper we study the problem of efficient data delivery in sparse MANETs where network partitions can last for a significant period Previous approaches rely on the use of either long range communication which leads to rapid draining of nodes' limited batteries, or existing node mobility which results in low data delivery rates and large delays In this paper, we describe a Message Ferrying (MF) approach to address the problem MF is a mobility-assisted approach which utilizes a set of special mobile nodes called message ferries (or ferries for short) to provide communication service for nodes in the deployment area The main idea behind the MF approach is to introduce non-randomness in the movement of nodes and exploit such non-randomness to help deliver data We study two variations of MF, depending on whether ferries or nodes initiate proactive movement The MF design exploits mobility to improve data delivery performance and reduce energy consumption in nodes We evaluate the performance of MF via extensive ns simulations which confirm the MF approach is efficient in both data delivery and energy consumption under a variety of network conditions
TL;DR: Zinc oxide (ZnO) is a unique material that exhibits semiconducting, piezoelectric, and pyroelectric multiple properties as discussed by the authors, and it has been shown that ZnO is probably the richest family of nanostructures among all materials.
TL;DR: Microneedles represent a promising technology to deliver therapeutic compounds into the skin for a range of possible applications and the ratio of microneedle fracture force to skin insertion force was found to be optimal for needles with small tip radius and large wall thickness.
TL;DR: The already significant impact this field has made on the administration of various pharmaceuticals is discussed; limitations of the current technology are explored; methods under exploration for overcoming these limitations and the challenges ahead are discussed.
Abstract: The past twenty five years have seen an explosion in the creation and discovery of new medicinal agents. Related innovations in drug delivery systems have not only enabled the successful implementation of many of these novel pharmaceuticals, but have also permitted the development of new medical treatments with existing drugs. The creation of transdermal delivery systems has been one of the most important of these innovations, offering a number of advantages over the oral route. In this article, we discuss the already significant impact this field has made on the administration of various pharmaceuticals; explore limitations of the current technology; and discuss methods under exploration for overcoming these limitations and the challenges ahead.
TL;DR: An integrative definition is proposed that suggests that all teams may be defined in terms of their extent of virtualness, and avenues for future research are suggested, including methodological and theoretical considerations that are important to advancing understanding of virtual teams.
TL;DR: A memory polynomial model for the predistorter is proposed and implemented using an indirect learning architecture and linearization performance is demonstrated on a three-carrier WCDMA signal.
Abstract: Power amplifiers (PAs) are inherently nonlinear devices and are used in virtually all communications systems. Digital baseband predistortion is a highly cost-effective way to linearize PAs, but most existing architectures assume that the PA has a memoryless nonlinearity. For wider bandwidth applications such as wideband code-division multiple access (WCDMA) or wideband orthogonal frequency-division multiplexing (W-OFDM), PA memory effects can no longer be ignored, and memoryless predistortion has limited effectiveness. In this paper, instead of focusing on a particular PA model and building a corresponding predistorter, we focus directly on the predistorter structure. In particular, we propose a memory polynomial model for the predistorter and implement it using an indirect learning architecture. Linearization performance is demonstrated on a three-carrier WCDMA signal.
TL;DR: In this paper, the activation energies and the average rate constants were determined in the 298 K−318 K temperature range for the early stages of the nanocatalytic reaction between hexacyanoferrate (III) and thiosulfate ions using 4.8 ± 0.1 nm tetrahedral, 7.1 µm cubic, and 4.9 µm near spherical nanocrystals.
Abstract: The activation energies and the average rate constants are determined in the 298 K−318 K temperature range for the early stages of the nanocatalytic reaction between hexacyanoferrate (III) and thiosulfate ions using 4.8 ± 0.1 nm tetrahedral, 7.1 ± 0.2 nm cubic, and 4.9 ± 0.1 nm “near spherical” nanocrystals. These kinetic parameters are found to correlate with the calculated fraction of surface atoms located on the corners and edges in each size and shape.
TL;DR: In this paper, the authors describe a framework for understanding how age-related changes in adult development affect work motivation, and, building on recent life-span theories and research on cognitive abilities, personality, affect, vocational interests, values, and self-concept, identify four intraindividual change trajectories (loss, gain, reorganization, and exchange).
Abstract: We describe a framework for understanding how age-related changes in adult development affect work motivation, and, building on recent life-span theories and research on cognitive abilities, personality, affect, vocational interests, values, and self-concept, identify four intraindividual change trajectories (loss, gain, reorganization, and exchange). We discuss implications of the integrative framework for the use and effectiveness of different motivational strategies with midlife and older workers in a variety of jobs, as well as abiding issues and future research directions.
TL;DR: It is shown that under ambient conditions in water fullerenes can generate superoxide anions and postulate that these oxygen radicals are responsible for membrane damage and subsequent cell death, and both a strategy for enhancing the toxicity of fullerene for certain applications such as cancer therapeutics or bactericides, as well as a remediation for the possible unwarranted biological effects of pristine fullererenes.
Abstract: We show that the cytotoxicity of water-soluble fullerene species is a sensitive function of surface derivatization; in two different human cell lines, the lethal dose of fullerene changed over 7 orders of magnitude with relatively minor alterations in fullerene structure. In particular, an aggregated form of C 60, the least derivatized of the four materials, was substantially more toxic than highly soluble derivatives such as C3, Na+ 2-3[C60O7-9(OH)12-15] (2-3)- , and C60(OH)24. Oxidative damage to the cell membranes was observed in all cases where fullerene exposure led to cell death. We show that under ambient conditions in water fullerenes can generate superoxide anions and postulate that these oxygen radicals are responsible for membrane damage and subsequent cell death. This work demonstrates both a strategy for enhancing the toxicity of fullerenes for certain applications such as cancer therapeutics or bactericides, as well as a remediation for the possible unwarranted biological effects of pristine fullerenes.
TL;DR: Highly fluorescent, water-soluble, few-atom Au quantum dots have been created that behave as multielectron artificial atoms with discrete, size-tunable electronic transitions throughout the visible and near IR.
Abstract: Highly fluorescent, water-soluble, few-atom Au quantum dots have been created that behave as multielectron artificial atoms with discrete, size-tunable electronic transitions throughout the visible and near IR. Correlation of nanodot sizes with emission energies fits the simple relation, ${E}_{\mathrm{F}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{i}}/{N}^{1/3}$, predicted by the jellium model. Providing the ``missing link'' between atomic and nanoparticle behavior in noble metals, these emissive, water-soluble Au nanoclusters open new opportunities for biological labels, energy transfer pairs, and light emitting sources in nanoscale optoelectronics.
TL;DR: Fluorescence, absorption, mass, and NMR spectra all indicate that multiple species are present, but that their creation is both nucleotide- and time-dependent, and that the nanoclusters are associated with the chiral ss-DNA template.
Abstract: The high affinity of Ag+ for DNA bases has enabled creation of short oligonucleotide-encapsulated Ag nanoclusters without formation of large nanoparticles. Time-dependent formation of cluster sizes ranging from Ag1 to Ag4/oligonucleotide were observed with strong, characteristic electronic transitions between 400 and 600 nm. The slow nanocluster formation kinetics enables observation of specific aqueous nanocluster absorptions that evolve over a period of 12 h. Induced circular dichroism bands confirm that the nanoclusters are associated with the chiral ss-DNA template. Fluorescence, absorption, mass, and NMR spectra all indicate that multiple species are present, but that their creation is both nucleotide- and time-dependent.
TL;DR: Some benefits and challenges of conducting psychological research via the Internet are described and recommendations to both researchers and institutional review boards for dealing with them are offered.
Abstract: As the Internet has changed communication, commerce, and the distribution of information, so too it is changing psychological research. Psychologists can observe new or rare phenomena online and can do research on traditional psychological topics more efficiently, enabling them to expand the scale and scope of their research. Yet these opportunities entail risk both to research quality and to human subjects. Internet research is inherently no more risky than traditional observational, survey, or experimental methods. Yet the risks and safeguards against them will differ from those characterizing traditional research and will themselves change over time. This article describes some benefits and challenges of conducting psychological research via the Internet and offers recommendations to both researchers and institutional review boards for dealing with them. ((c) 2004 APA, all rights reserved)
TL;DR: The changes of some interesting properties in different colloidal semiconductor nanoparticles, such as the electronic relaxation rates as spherical nanoparticles change to nanorods, and the changes in the structure or size of very small nanoparticles upon adsorbing strongly bound molecules are described.
Abstract: As the size of material becomes equal to or falls below the nanometer length scale that characterizes the motion of its electrons and thus its properties, the latter become sensitive not only to the size but also to the shape and composition of the particles. In this Account, we describe the changes of some interesting properties in different colloidal semiconductor nanoparticles, such as the electronic relaxation rates as spherical nanoparticles change to nanorods, and the changes in the structure or size of very small nanoparticles upon adsorbing strongly bound molecules. We have also determined and explained the difference in the interfacial crossing rates of electrons and holes in a composite nanostructure.
TL;DR: This paper found that most researchers are not particularly cosmopolitan in their selection of collaborators, they tend to work with the people in their own work group and more cosmopolitan collaborators tend to have large grants.
TL;DR: Individual differences in the capacity to control attention as a major contributor to differences in working memory capacity (WMC) are examined.
Abstract: Dual-process theories of the mind are ubiquitous in psychology. A central principle of these theories is that behavior is determined by the interplay of automatic and controlled processing. In this article, the authors examine individual differences in the capacity to control attention as a major contributor to differences in working memory capacity (WMC). The authors discuss the enormous implications of this individual difference for a host of dual-process theories in social, personality, cognitive, and clinical psychology. In addition, the authors propose several new areas of investigation that derive directly from applying the concept of WMC to dual-process theories of the mind.