Showing papers by "Boston College published in 2013"
TL;DR: In this paper, the same data used for the MRA is used to conduct a fuzzy-set qualitative comparative analysis (fsQCA) for accounting, consumer research, finance, management, and marketing.
1,249 citations
TL;DR: The view of metastatic cancer cells as a macrophage metabolic disease can provide novel insight for therapeutic management and explain the long-standing "seed and soil" hypothesis and the absence of metastasis in plant cancers.
Abstract: Metastasis involves the spread of cancer cells from the primary tumor to surrounding tissues and to distant organs and is the primary cause of cancer morbidity and mortality. In order to complete the metastatic cascade, cancer cells must detach from the primary tumor, intravasate into the circulatory and lymphatic systems, evade immune attack, extravasate at distant capillary beds, and invade and proliferate in distant organs. Currently, several hypotheses have been advanced to explain the origin of cancer metastasis. These involve an epithelial mesenchymal transition, an accumulation of mutations in stem cells, a macrophage facilitation process, and a macrophage origin involving either transformation or fusion hybridization with neoplastic cells. Many of the properties of metastatic cancer cells are also seen in normal macrophages. A macrophage origin of metastasis can also explain the long-standing "seed and soil" hypothesis and the absence of metastasis in plant cancers. The view of metastasis as a macrophage metabolic disease can provide novel insight for therapeutic management.
808 citations
TL;DR: This paper examined corporate financial and investment decisions made by female executives compared with male executives and found that female executives place wider bounds on earnings estimates and are more likely to exercise stock options early.
772 citations
TL;DR: This work theorizes four affordances of social media representing different ways to engage in this publicly visible knowledge conversations: metavoicing, triggered attending, network-informed associating, and generative role-taking, and mechanisms that affect how people engage in the knowledge conversation.
Abstract: The use of social media creates the opportunity to turn organization-wide knowledge sharing in the workplace from an intermittent, centralized knowledge management process to a continuous online knowledge conversation of strangers, unexpected interpretations and re-uses, and dynamic emergence. We theorize four affordances of social media representing different ways to engage in this publicly visible knowledge conversations: metavoicing, triggered attending, network-informed associating, and generative role-taking. We further theorize mechanisms that affect how people engage in the knowledge conversation, finding that some mechanisms, when activated, will have positive effects on moving the knowledge conversation forward, but others will have adverse consequences not intended by the organization. These emergent tensions become the basis for the implications we draw.
638 citations
TL;DR: This work studied the thermoelectric properties of nanostructured SnTe with different dopants, and found indium-doped SnTe showed extraordinarily large Seebeck coefficients that cannot be explained properly by the conventional two-valence band model.
Abstract: From an environmental perspective, lead-free SnTe would be preferable for solid-state waste heat recovery if its thermoelectric figure-of-merit could be brought close to that of the lead-containing chalcogenides. In this work, we studied the thermoelectric properties of nanostructured SnTe with different dopants, and found indium-doped SnTe showed extraordinarily large Seebeck coefficients that cannot be explained properly by the conventional two-valence band model. We attributed this enhancement of Seebeck coefficients to resonant levels created by the indium impurities inside the valence band, supported by the first-principles simulations. This, together with the lower thermal conductivity resulting from the decreased grain size by ball milling and hot pressing, improved both the peak and average nondimensional figure-of-merit (ZT) significantly. A peak ZT of ∼1.1 was obtained in 0.25 atom % In-doped SnTe at about 873 K.
614 citations
TL;DR: In this paper, topological insulators are shown to be protected not only by time-reversal symmetry, but also by crystal lattice symmetry by accounting for the crystalline symmetries.
Abstract: Topological insulators are now shown to be protected not only by time-reversal symmetry, but also by crystal lattice symmetry. By accounting for the crystalline symmetries, additional topological insulators can be predicted.
499 citations
TL;DR: The results show that fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications.
Abstract: We present an experimental demonstration of electronically tunable metamaterial absorbers in the terahertz regime. By incorporation of active liquid crystal into strategic locations within the metamaterial unit cell, we are able to modify the absorption by 30% at 2.62 THz, as well as tune the resonant absorption over 4% in bandwidth. Numerical full-wave simulations match well to experiments and clarify the underlying mechanism, i.e., a simultaneous tuning of both the electric and magnetic response that allows for the preservation of the resonant absorption. These results show that fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications.
480 citations
TL;DR: This work provides new insight into the nature of thermal transport at a quantitative level and predicts a new ultrahigh κ material of potential interest for passive cooling applications.
Abstract: We have calculated the thermal conductivities (κ) of cubic III-V boron compounds using a predictive first principles approach. Boron arsenide is found to have a remarkable room temperature κ over 2000 W m(-1) K(-1); this is comparable to those in diamond and graphite, which are the highest bulk values known. We trace this behavior in boron arsenide to an interplay of certain basic vibrational properties that lie outside of the conventional guidelines in searching for high κ materials, and to relatively weak phonon-isotope scattering. We also find that cubic boron nitride and boron antimonide will have high κ with isotopic purification. This work provides new insight into the nature of thermal transport at a quantitative level and predicts a new ultrahigh κ material of potential interest for passive cooling applications.
474 citations
TL;DR: Experimental data reveal how the properties of such a large graphene subunit are affected by multiple odd-membered-ring defects.
Abstract: Graphite, the most stable form of elemental carbon, consists of pure carbon sheets stacked upon one another like reams of paper. Individual sheets, known as graphene, prefer planar geometries as a consequence of the hexagonal honeycomb-like arrangements of trigonal carbon atoms that comprise their two-dimensional networks. Defects in the form of non-hexagonal rings in such networks cause distortions away from planarity. Herein we report an extreme example of this phenomenon. A 26-ring C80H30 nanographene that incorporates five seven-membered rings and one five-membered ring embedded in a hexagonal lattice was synthesized by stepwise chemical methods, isolated, purified and fully characterized spectroscopically. Its grossly warped structure was revealed by single-crystal X-ray crystallography. An independent synthetic route to a freely soluble derivative of this new type of 'nanocarbon' is also reported. Experimental data reveal how the properties of such a large graphene subunit are affected by multiple odd-membered-ring defects.
448 citations
TL;DR: The similarities and differences of these related techniques are described and their application to the probing of gene function and higher-order genome organization is discussed.
Abstract: The combination of transposon mutagenesis with next-generation sequencing has emerged as a useful tool for identifying putative gene function in a high-throughput manner. Here, van Opijnen and Camilli describe the four main techniques that are used for this purpose, with a focus on their application for uncovering bacterial gene function. Our knowledge of gene function has increasingly lagged behind gene discovery, hindering our understanding of the genetic basis of microbial phenotypes. Recently, however, massively parallel sequencing has been combined with traditional transposon mutagenesis in techniques referred to as transposon sequencing (Tn-seq), high-throughput insertion tracking by deep sequencing (HITS), insertion sequencing (INSeq) and transposon-directed insertion site sequencing (TraDIS), making it possible to identify putative gene functions in a high-throughput manner. Here, we describe the similarities and differences of these related techniques and discuss their application to the probing of gene function and higher-order genome organization.
442 citations
TL;DR: This paper analyzed how corporate venture capital differs from independent venture capital in nurturing innovation in entrepreneurial firms and found that CVC-backed firms are more innovative, as measured by their patenting outcome, although they are younger, riskier, and less profitable than IVC-based firms.
Abstract: We analyze how corporate venture capital (CVC) differs from independent venture capital (IVC) in nurturing innovation in entrepreneurial firms. We find that CVC-backed firms are more innovative, as measured by their patenting outcome, although they are younger, riskier, and less profitable than IVC-backed firms. Our baseline results continue to hold in a propensity-score-matching analysis of IPO firms and a difference-in-differences analysis of the universe of VC-backed entrepreneurial firms. We present evidence consistent with two possible underlying mechanisms: CVCs’ greater industry knowledge due to the technological fit between their parent firms and entrepreneurial firms and CVCs’ greater tolerance for failure.
TL;DR: Hematite was chosen as a prototypical system for these proof-of-concept demonstrations because it is an earth-abundant material with great promise for high-efficiency, low-cost water splitting and the fundamental reason for the observed limited photovoltage generation by hematite lies in the relatively positive positions of its valenceand conduction-band edges.
Abstract: Sunlight-driven photoelectrochemical (PEC) water splitting offers promise as a method for effective solar-energy harvesting and storage. To transform the reaction into economically competitive technology, we need materials that can absorb sunlight broadly, transfer the energy to excited charges at high efficiencies, and catalyze specific reduction and oxidation reactions. Furthermore, the materials should be inexpensive and stable against photocorrosion. To date, an ideal material that satisfies all of these considerations remains elusive. This challenge can, in principle, be addressed by combining various material components, each purposedesigned to offer desired properties with respect to photovoltage generation, charge transport, and catalytic activity. For example, it has recently been shown that the performance of hematite (a-Fe2O3)-based water splitting can indeed be improved by introducing dedicated charge collectors, buried homoand heterojunctions, and oxygen-evolution catalysts. Hematite was chosen as a prototypical system for these proof-of-concept demonstrations because it is an earth-abundant material with great promise for high-efficiency, low-cost water splitting. To realize the potential of hematite, however, we still need to address a key issue concerning its low photovoltage (Vph, typically 0.4 V), which is unreasonably low given that the bandgap of hematite is 2.0 eV. For successful integration with a small-bandgap photocathode, the photovoltage generated at the photoanode needs to be significantly higher so that a total (combined) photovoltage of 1.61 V (or greater, with a minimum overpotential of 0.38 V) is produced. Herein we show that this issue may be addressed by modifying the hematite surface. When decorated with an amorphous NiFeOx layer (Figure 1), hematite produces photovoltages as high as 0.61 V, which enable the observation of turn-on voltages (Von) as low as 0.62 V (versus the reversible hydrogen electrode, RHE) without the need for a second absorber (unless otherwise noted, all electrochemical potentials reported herein are relative to RHE). When a second absorber, Si, was added, a record-low turn-on voltage of 0.32 V was measured. The basis for our approach is illustrated schematically in Figure 2. The fundamental reason for the observed limited photovoltage generation by hematite lies in the relatively positive positions of its valenceand conduction-band edges. However, even within these limits, the Vph value of 0.6–0.8 V calculated for reported flat-band potentials (Vfb) of 0.4–0.6 V has not been reached.We understand the cause of this discrepancy to be a partial Fermi level pinning effect. That is, owing to the existence of surface states, a nonnegligible potential drop takes place within the Helmholtz layer (hH, Figure 2a). [22] The effect is manifested as a more positive Von value, since a significant portion of the applied potential is used to overcome the overpotential hH (Figure 2c). Appropriate surface modification enables the hH to be minimized or eliminated (Figure 2b) and a less positive Von value to be measured (Figure 2d). The effect of the NiFeOx overlayer was profound: it led to a Von shift from approximately 1.0 V to approximately 0.6 V (Figure 1b). Although the apparent effect of the cathodic Von shift is similar to the effect of reducing the kinetic over[*] C. Du, Dr. X. Yang, Dr. M. T. Mayer, H. Hoyt, J. Xie, Dr. G. McMahon, G. Bischoping, Prof. Dr. D. Wang Department of Chemistry Merkert Chemistry Center, Boston College 2609 Beacon Street, Chestnut Hill, MA, 20467 (USA) E-mail: dunwei.wang@bc.edu Homepage: http://www2.bc.edu/dunwei-wang [] These authors contributed equally to this work.
Yale University1, Wellcome Trust Sanger Institute2, National Research Council3, University of Michigan4, University of Geneva5, Swiss Institute of Bioinformatics6, NewYork–Presbyterian Hospital7, Cornell University8, Baylor College of Medicine9, Boston College10, Massachusetts Institute of Technology11, Harvard University12, Boston Children's Hospital13, Broad Institute14, Technical University of Denmark15, American Museum of Natural History16, Rutgers University17
TL;DR: In this article, the authors used patterns of polymorphisms in functionally annotated regions in 1092 humans to identify deleterious variants; then, they experimentally validated candidates, finding regions particularly sensitive to mutations and variants that are disruptive because of mechanistic effects on transcription-factor binding.
Abstract: Interpreting variants, especially noncoding ones, in the increasing number of personal genomes is challenging. We used patterns of polymorphisms in functionally annotated regions in 1092 humans to identify deleterious variants; then we experimentally validated candidates. We analyzed both coding and noncoding regions, with the former corroborating the latter. We found regions particularly sensitive to mutations ("ultrasensitive") and variants that are disruptive because of mechanistic effects on transcription-factor binding (that is, "motif-breakers"). We also found variants in regions with higher network centrality tend to be deleterious. Insertions and deletions followed a similar pattern to single-nucleotide variants, with some notable exceptions (e.g., certain deletions and enhancers). On the basis of these patterns, we developed a computational tool (FunSeq), whose application to ~90 cancer genomes reveals nearly a hundred candidate noncoding drivers.
TL;DR: It is shown that on average, there is a weak but consistent V-shaped relation of arousal as a function of valence, but there is large variation at the individual level, so that valence and arousal can in principle show a variety of relations depending on person or circumstances.
Abstract: Affect is basic to many if not all psychological phenomena. This article examines 2 of the most fundamental properties of affective experience--valence and arousal--asking how they are related to each other on a moment to moment basis. Over the past century, 6 distinct types of relations have been suggested or implicitly presupposed in the literature. We critically review the available evidence for each proposal and argue that the evidence does not provide a conclusive answer. Next, we use statistical modeling to verify the different proposals in 8 data sets (with Ns ranging from 80 to 1,417) where participants reported their affective experiences in response to experimental stimuli in laboratory settings or as momentary or remembered in natural settings. We formulate 3 key conclusions about the relation between valence and arousal: (a) on average, there is a weak but consistent V-shaped relation of arousal as a function of valence, but (b) there is large variation at the individual level, so that (c) valence and arousal can in principle show a variety of relations depending on person or circumstances. This casts doubt on the existence of a static, lawful relation between valence and arousal. The meaningfulness of the observed individual differences is supported by their personality and cultural correlates. The malleability and individual differences found in the structure of affect must be taken into account when studying affect and its role in other psychological phenomena.
TL;DR: In this article, a collective model of household behavior was proposed and estimated, which permits identification and estimation of concepts such as "indifference scales" and consumption economies of scale, as well as other related concepts.
Abstract: How much income would a woman living alone require to attain the same standard of living that she would have if she were married? What percentage of a married couple's expenditures are controlled by the husband? How much money does a couple save on consumption goods by living together versus living apart? We propose and estimate a collective model of household behaviour that permits identification and estimation of concepts such as these. We model households in terms of the utility functions of its members, a bargaining or social welfare function, and a consumption technology function. We demonstrate generic non-parametric identification of the model, and hence of a version of adult equivalence scales that we call "indifference scales", as well as consumption economies of scale, the household's resource sharing rule or members' bargaining power, and other related concepts. Copyright 2013, Oxford University Press.
TL;DR: As each individual is a unique metabolic entity, personalization of metabolic therapy as a broad-based cancer treatment strategy will require fine-tuning to match the therapy to an individual’s unique physiology.
Abstract: Emerging evidence indicates that cancer is primarily a metabolic disease involving disturbances in energy production through respiration and fermentation. The genomic instability observed in tumor cells and all other recognized hallmarks of cancer are considered downstream epiphenomena of the initial disturbance of cellular energy metabolism. The disturbances in tumor cell energy metabolism can be linked to abnormalities in the structure and function of the mitochondria. When viewed as a mitochondrial metabolic disease, the evolutionary theory of Lamarck can better explain cancer progression than can the evolutionary theory of Darwin. Cancer growth and progression can be managed following a whole body transition from fermentable metabolites, primarily glucose and glutamine, to respiratory metabolites, primarily ketone bodies. As each individual is a unique metabolic entity, personalization of metabolic therapy as a broad-based cancer treatment strategy will require fine-tuning to match the therapy to an individual’s unique physiology.
Marcel den Hoed1, Mark Eijgelsheim2, Tõnu Esko3, Bianca J. J. M. Brundel4 +264 more•Institutions (85)
TL;DR: A 2-stage meta-analysis of genome-wide association studies in up to 181,171 individuals identified 14 new loci associated with heart rate and confirmed associations with all 7 previously established loci, providing fresh insights into the mechanisms regulating heart rate.
Abstract: Elevated resting heart rate is associated with greater risk of cardiovascular disease and mortality. In a 2-stage meta-analysis of genome-wide association studies in up to 181,171 individuals, we identified 14 new loci associated with heart rate and confirmed associations with all 7 previously established loci. Experimental downregulation of gene expression in Drosophila melanogaster and Danio rerio identified 20 genes at 11 loci that are relevant for heart rate regulation and highlight a role for genes involved in signal transmission, embryonic cardiac development and the pathophysiology of dilated cardiomyopathy, congenital heart failure and/or sudden cardiac death. In addition, genetic susceptibility to increased heart rate is associated with altered cardiac conduction and reduced risk of sick sinus syndrome, and both heart rate-increasing and heart rate-decreasing variants associate with risk of atrial fibrillation. Our findings provide fresh insights into the mechanisms regulating heart rate and identify new therapeutic targets.
TL;DR: The relationship between informal care and work in the United States, both on the intensive and extensive margins, and wage effects are identified, suggest that the opportunity costs to informal care providers are important to consider when making policy recommendations about the design and funding of public long-term care programs.
TL;DR: In this article, an exact numerical solution of the phonon Boltzmann transport equation is implemented, which uses harmonic and anharmonic interatomic force constants determined from density functional theory as inputs.
Abstract: We use a recently developed ab initio approach to calculate the lattice thermal conductivities of compound semiconductors. An exact numerical solution of the phonon Boltzmann transport equation is implemented, which uses harmonic and anharmonic interatomic force constants determined from density functional theory as inputs. We discuss the method for calculating the anharmonic interatomic force constants in some detail, and we describe their role in providing accurate thermal conductivities in a range of systems. This first-principles approach obtains good agreement with experimental results for well-characterized systems (Si, Ge, and GaAs). We determine the intrinsic upper bound to the thermal conductivities of cubic aluminum-V, gallium-V, and indium-V compounds as limited by anharmonic phonon scattering. The effects of phonon-isotope scattering on the thermal conductivities are examined in these materials and compared to available experimental data. We also obtain the lattice thermal conductivities of other technologically important materials, AlN and SiC. For most materials, good agreement with the experimental lattice thermal conductivities for naturally occurring isotopic compositions is found. We show that the overall frequency scale of the acoustic phonons and the size of the gap between acoustic and optic phonons play important roles in determining the lattice thermal conductivity of each system. The first-principles approach used here can provide quantitative predictions of thermal transport in a wide range of systems.
TL;DR: Specific Bifidobacteria and Bacteroides differentially digest specific individual HMOS, with the major fucosylated milk oligosaccharides most strongly stimulating key species of mutualist symbionts.
Abstract: Human milk oligosaccharides (HMOS) are not digested in the proximal intestine. In distal intestine, HMOS collectively modify the microbiota, but the response of individual bacteria to individual components of the HMOS is not well defined. Here, each of 25 major isolates of the human intestinal microbiota was fed individual major fucosylated and sialylated HMOS in anaerobic culture. This allowed for an assessment of the influence of specific HMOS on the growth and metabolic products of individual microbiota bacteria. Most Bifidobacteria spp. and Bacteroides spp. grew, induced α-L-fucosidase activity, and produced abundant lactate or short-chain fatty acids (SCFAs) when fed 2'-fucosyllactose (2'-FL), 3-FL, and lactodifucotetraose (LDFT). Lactobacillus delbrueckii ATCC7830, Enterococcus faecalis ATCC19433, and Streptococcus thermophilus ATCC19258 exhibited slight growth, pH reduction, and lactate production when supplemented with 2'-FL or 3-FL, but not LDFT. Supplementation with 3'-sialyllactose (3'-SL) and 6'-SL promoted moderate growth of Bifidobacterium longum JCM7007, 7009, 7010, 7011, 1272, 11347, ATCC15708, Bacteroides vulgatus ATCC8482, and B. thetaiotaomicron ATCC29148; accordingly, these bacteria exhibited greater neuraminidase activity and produced copious lactate, SCFA, or both. Lactobacillus delbrueckii ATCC7830 also consumed 6'-SL. In contrast, Clostridium spp., L. rhamnosus ATCC53103, E. faecalis ATCC29200, Staphylococcus spp., Enterobacter spp., and Escherichia coli K12 did not consume milk oligosaccharides nor produce appreciable acidic fermentation products. Specific Bifidobacteria and Bacteroides differentially digest specific individual HMOS, with the major fucosylated milk oligosaccharides most strongly stimulating key species of mutualist symbionts. This suggests strategies for treating dysbiosis of the microbiota and associated inflammatory disorders.
TL;DR: Banked stool and urine samples collected prior to disease onset from infants <29 weeks gestational age indicate that early microbial and metabolomic signatures may provide highly predictive biomarkers of NEC.
Abstract: Background: Necrotizing enterocolitis (NEC) is a devastating intestinal disease that afflicts 10% of extremely preterm infants. The contribution of early intestinal colonization to NEC onset is not understood, and predictive biomarkers to guide prevention are lacking. We analyzed banked stool and urine samples collected prior to disease onset from infants 99% versus 99% versus 38% in the other NEC cases and 84% in controls, P = 0.01). NEC preceded by Firmicutes dysbiosis occurred earlier (onset, days 7 to 21) than NEC preceded by Proteobacteria dysbiosis (onset, days 19 to 39). All NEC cases lacked Propionibacterium and were preceded by either Firmicutes (≥98% relative abundance, days 4 to 9) or Proteobacteria (≥90% relative abundance, days 10 to 16) dysbiosis, while only 25% of controls had this phenotype (predictive value 88%, P = 0.001). Analysis of days 4 to 9 urine samples found no metabolites associated with all NEC cases, but alanine was positively associated with NEC cases that were preceded by Firmicutes dysbiosis (P < 0.001) and histidine was inversely associated with NEC cases preceded by Proteobacteria dysbiosis (P = 0.013). A high urinary alanine:histidine ratio was associated with microbial characteristics (P < 0.001) and provided good prediction of overall NEC (predictive value 78%, P =0 .007). Conclusions: Early dysbiosis is strongly involved in the pathobiology of NEC. These striking findings require validation in larger studies but indicate that early microbial and metabolomic signatures may provide highly predictive biomarkers of NEC.
TL;DR: In this article, the authors discuss various approaches for electronic, optical, thermal and nonlinear modulation in distinct material systems such as semiconductors, graphene, pho- tonic crystals and metamaterials.
Abstract: We review different techniques for modulation of the electromagnetic properties of terahertz (THz) waves. We discuss various approaches for electronic, optical, thermal and nonlinear modulation in distinct material systems such as semiconductors, graphene, pho- tonic crystals and metamaterials. The modulators are classified and compared with respect to modulation speed, modulation depth and categorized by the physical quantity they control as e.g. amplitude, phase, spectrum, spatial and temporal properties of the THz wave. Based on the review paper, the reader should obtain guidelines for the proper choice of a specific modulation technique in view of the targeted application.
TL;DR: High-resolution scanning tunneling microscopy studies of a TCI, Pb1-xSnxSe, reveal the coexistence of zero-mass Dirac fermions protected by crystal symmetry with massive Diracfermions consistent with crystal symmetry breaking, which paves the way for engineering the Dirac band gap and realizing interaction-driven topological quantum phenomena in TCIs.
Abstract: In topological crystalline insulators (TCIs), topology and crystal symmetry intertwine to create surface states with unique characteristics. The breaking of crystal symmetry in TCIs is predicted to impart mass to the massless Dirac fermions. Here, we report high-resolution scanning tunneling microscopy studies of a TCI, Pb1-xSnxSe, which reveal the coexistence of zero mass Dirac fermions protected by crystal symmetry with massive Dirac fermions consistent with crystal symmetry breaking. In addition, we show two distinct regimes of the Fermi surface topology separated by a Van-Hove singularity at the Lifshitz transition point. Our work paves the way for engineering the Dirac band gap and realizing interaction-driven topological quantum phenomena in TCIs.
TL;DR: This paper explored the origins and trajectory of the Washington Consensus, the ideas associated with the developing countries' move to free markets in the 1980s and 1990s, and argued that the Consensus was a transnational policy paradigm, shaped by both scholarly and political forces.
Abstract: This paper explores the origins and trajectory of the Washington Consensus – the ideas associated with the developing countries’ move to free markets in the 1980s and 1990s. I argue that the Consensus was a transnational policy paradigm, shaped by both scholarly and political forces (Hall, 1993). At the core of the Consensus was the international financial institutions’ practice of conditionality – making loans to governments in exchange for policy reforms. The Consensus was subsequently weakened by its own unintended consequences, by political forces both within Washington and worldwide and by intellectual changes in the field of economics. However, I argue that the Consensus has yet to encounter any serious rivals.
TL;DR: In this paper, the leg efficiency of thermoelectric conversion for segmented elements based on these n-type materials could potentially reach 12.5% with a cold side at 25 °C and a hot side at 500 °C if appropriate p-type legs are paired.
Abstract: Bismuth telluride (Bi2Te3) and its alloys have been widely investigated as thermoelectric materials for cooling applications at around room temperature. We report a systematic study on many compounds in the Bi2Te3–Bi2Se3–Bi2S3 system. All the samples were fabricated by high energy ball milling followed by hot pressing. Among the investigated compounds, Bi2Te2S1 shows a peak ZT ∼0.8 at 300 °C and Bi2Se1S2 ∼0.8 at 500 °C. The results show that these compounds can be used for mid-temperature power generation applications. The leg efficiency of thermoelectric conversion for segmented elements based on these n-type materials could potentially reach 12.5% with a cold side at 25 °C and a hot side at 500 °C if appropriate p-type legs are paired, which could compete well with the state-of-the-art n-type materials within the same temperature range, including lead tellurides, lead selenides, lead sulfides, filled-skutterudites, and half Heuslers.
TL;DR: The results highlight the power of forming homo- or heterojunctions at the nanoscale, which permits us to engineer the band structures of semiconductors to the specific application of water splitting, and take significant steps towards efficient artificial photosynthesis, an energy harvesting technique necessary for the well-being of humanity.
Abstract: In order for the future energy needs of humanity to be adequately and sustainably met, alternative energy techniques such as artificial photosynthesis need to be made more efficient and therefore commercially viable. On a grand scale, the energies coming to and leaving from the earth are balanced. With the fast increasing waste heat produced by human activities, the balance may be shifted to threaten the ecosystem in which we reside. To avoid such dire consequences, it is necessary to power human activities using energy derived from the incoming source, which is predominantly solar irradiation. Indeed, most life on the surface of the earth is supported, directly or indirectly, by photosynthesis that harvests solar energy and stores it in chemical bonds for redistribution. Being able to mimic the process and perform it at high efficiencies using low-cost materials has significant implications. Such an understanding is a major intellectual driving force that motivates research by us and many others.From a t...
TL;DR: In this paper, a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed, which offer significant improvements including more detailed spatial resolution and quantification of uncertainty due to both space weather and instrument errors.
Abstract: The radiation belts and plasma in the Earth’s magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper.
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28 Feb 2013TL;DR: In this paper, the authors present a three-step process to select a measure of distinct states and a domain-specific measurement for the Gordian knot of affective states, which they use to untangle the terminological Gordian knots.
Abstract: Prologue 1 Documenting the breadth and depth of the problem 2 Untangling the terminological Gordian knot 3 Should affective states be considered as distinct entities or as positioned along dimensions? 4 Are pleasant and unpleasant states independent or polar opposites? 5 Selecting a measure: a proposed three-step process 6 The old classics: measures of distinct states 7 Dimensional measures 8 Domain-specific measurement: challenges and solutions 9 Problems of domain specificity: examples from exercise Epilogue
TL;DR: In this article, the authors examine two measures of financial reporting quality (financial restatements and discretionary accruals) and two external auditor oversight (audit and non-audit fees) and find that audit committee members who are both accounting and industry experts perform better than those with only accounting expertise.
Abstract: Calls from practice suggest that audit committee members with industry expertise can improve audit committee effectiveness. Nevertheless, regulators and extant literature have focused on the financial expertise of the audit committee. We posit that audit committee industry knowledge is valuable because accounting guidance, estimates, and oversight of the external auditor are often linked to a company’s operations within a particular industry. Taking a holistic view, we examine two measures of financial reporting quality (financial restatements and discretionary accruals) and two measures of external auditor oversight (audit and non-audit fees). As predicted, we find that audit committee members who are both accounting and industry experts perform better than those with only accounting expertise. We also find that in certain instances, supervisory experts who are also industry experts perform better than supervisory experts alone. Overall, these results suggest that industry expertise, when combined with accounting expertise, can improve the effectiveness of the audit committee in monitoring the financial reporting process.
TL;DR: In this paper, correlations between oxidation level and optical properties of secondary organic aerosol (SOA) have been examined, and SOA chemical composition was characterized with a time-of-flight aerosol mass spectrometer.
Abstract: Brown carbon (BrC), which may include secondary organic aerosol (SOA), can be a significant climate-forcing agent via its optical absorption properties. However, the overall contribution of SOA to BrC remains poorly understood. Here, correlations between oxidation level and optical properties of SOA are examined. SOA was generated in a flow reactor in the absence of NOx by OH oxidation of gas-phase precursors used as surrogates for anthropogenic (naphthalene, tricyclo[5.2.1.02,6]decane), biomass burning (guaiacol), and biogenic (α-pinene) emissions. SOA chemical composition was characterized with a time-of-flight aerosol mass spectrometer. SOA mass-specific absorption cross sections (MAC) and refractive indices were calculated from real-time cavity ring-down photoacoustic spectrometry measurements at 405 and 532 nm and from UV–vis spectrometry measurements of methanol extracts of filter-collected particles (300 to 600 nm). At 405 nm, SOA MAC values and imaginary refractive indices increased with increasin...