5,218 research outputs found

    An assessment of the construct validity of environmental strategy measures

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    The natural resource-based view of the company is emerging as a dominant paradigm for understanding the intersection of strategic management and the natural environment. Companies that proactively incorporate a natural environment perspective into their enterprise strategies are said to have sustainable competitive advantages. However, defining and measuring environmental strategy has been challenging, with different approaches yielding inconsistent results. Many studies ignore the empirical difficulties of marrying the theoretical connection between the company's resource base and environmental strategy, and its impact on environmental company performance. In this paper, we apply an inductive approach to derive a measure of environmental strategy theoretically congruent with the natural resource-based-view of the firm. We assess its reliability and, using a multi-trait multi-method matrix, confirm the convergent and discriminant validities of this measure against other measures often used by researchers. We also establish predictive validity of our environmental strategy measure for environmental performance. We discuss the implications of the measure for future research and practice.environmental performance; environmental strategies; inductive study; measures;

    Tensor Decompositions for Signal Processing Applications From Two-way to Multiway Component Analysis

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    The widespread use of multi-sensor technology and the emergence of big datasets has highlighted the limitations of standard flat-view matrix models and the necessity to move towards more versatile data analysis tools. We show that higher-order tensors (i.e., multiway arrays) enable such a fundamental paradigm shift towards models that are essentially polynomial and whose uniqueness, unlike the matrix methods, is guaranteed under verymild and natural conditions. Benefiting fromthe power ofmultilinear algebra as theirmathematical backbone, data analysis techniques using tensor decompositions are shown to have great flexibility in the choice of constraints that match data properties, and to find more general latent components in the data than matrix-based methods. A comprehensive introduction to tensor decompositions is provided from a signal processing perspective, starting from the algebraic foundations, via basic Canonical Polyadic and Tucker models, through to advanced cause-effect and multi-view data analysis schemes. We show that tensor decompositions enable natural generalizations of some commonly used signal processing paradigms, such as canonical correlation and subspace techniques, signal separation, linear regression, feature extraction and classification. We also cover computational aspects, and point out how ideas from compressed sensing and scientific computing may be used for addressing the otherwise unmanageable storage and manipulation problems associated with big datasets. The concepts are supported by illustrative real world case studies illuminating the benefits of the tensor framework, as efficient and promising tools for modern signal processing, data analysis and machine learning applications; these benefits also extend to vector/matrix data through tensorization. Keywords: ICA, NMF, CPD, Tucker decomposition, HOSVD, tensor networks, Tensor Train

    Giant Spin Seebeck Effect through an Interface Organic Semiconductor

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    Interfacing an organic semiconductor C60 with a non-magnetic metallic thin film (Cu or Pt) has created a novel heterostructure that is ferromagnetic at ambient temperature, while its interface with a magnetic metal (Fe or Co) can tune the anisotropic magnetic surface property of the material. Here, we demonstrate that sandwiching C60 in between a magnetic insulator (Y3Fe5O12: YIG) and a non-magnetic, strong spin-orbit metal (Pt) promotes highly efficient spin current transport via the thermally driven spin Seebeck effect (SSE). Experiments and first principles calculations consistently show that the presence of C60 reduces significantly the conductivity mismatch between YIG and Pt and the surface perpendicular magnetic anisotropy of YIG, giving rise to enhanced spin mixing conductance across YIG/C60/Pt interfaces. As a result, a 600% increase in the SSE voltage (VLSSE) has been realized in YIG/C60/Pt relative to YIG/Pt. Temperature-dependent SSE voltage measurements on YIG/C60/Pt with varying C60 layer thicknesses also show an exponential increase in VLSSE at low temperatures below 200 K, resembling the temperature evolution of spin diffusion length of C60. Our study emphasizes the important roles of the magnetic anisotropy and the spin diffusion length of the intermediate layer in the SSE in YIG/C60/Pt structures, providing a new pathway for developing novel spin-caloric materials

    Effects of shearing on biogas production and microbial community structure during anaerobic digestion with recuperative thickening

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    © 2017 Recuperative thickening can intensify anaerobic digestion to produce more biogas and potentially reduce biosolids odour. This study elucidates the effects of sludge shearing during the thickening process on the microbial community structure and its effect on biogas production. Medium shearing resulted in approximately 15% increase in biogas production. By contrast, excessive or high shearing led to a marked decrease in biogas production, possibly due to sludge disintegration and cell lysis. Microbial analysis using 16S rRNA gene amplicon sequencing showed that medium shearing increased the evenness and diversity of the microbial community in the anaerobic digester, which is consistent with the observed improved biogas production. By contrast, microbial diversity decreased under either excessive shearing or high shearing condition. In good agreement with the observed decrease in biogas production, the abundance of Bacteroidales and Syntrophobaterales (which are responsible for hydrolysis and acetogenesis) decreased due to high shearing during recuperative thickening

    Faxen relations in solids - a generalized approach to particle motion in elasticity and viscoelasticity

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    A movable inclusion in an elastic material oscillates as a rigid body with six degrees of freedom. Displacement/rotation and force/moment tensors which express the motion of the inclusion in terms of the displacement and force at arbitrary exterior points are introduced. Using reciprocity arguments two general identities are derived relating these tensors. Applications of the identities to spherical particles provide several new results, including simple expressions for the force and moment on the particle due to plane wave excitation.Comment: 11 pages, 4 figure

    Detection of lithium in nearby young late-M dwarfs

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    Late M-type dwarfs in the solar neighborhood include a mixture of very low-mass stars and brown dwarfs which is difficult to disentangle due to the lack of constraints on their age such as trigonometric parallax, lithium detection and space velocity. We search for young brown dwarf candidates among a sample of 28 nearby late-M dwarfs with spectral types between M5.0 and M9.0, and we also search for debris disks around three of them. Based on theoretical models, we used the color IJI-J, the JJ-band absolute magnitude and the detection of the Li I 6708 A˚\AA doublet line as a strong constraint to estimate masses and ages of our targets. For the search of debris disks, we observed three targets at submillimeter wavelength of 850 μ\mum. We report here the first clear detections of lithium absorption in four targets and a marginal detection in one target. Our mass estimates indicate that two of them are young brown dwarfs, two are young brown dwarf candidates and one is a young very low-mass star. The closest young field brown dwarf in our sample at only \sim15 pc is an excellent benchmark for further studying physical properties of brown dwarfs in the range 100-150 Myr. We did not detect any debris disks around three late-M dwarfs, and we estimated upper limits to the dust mass of debris disks around them.Comment: 10 pages, 5 figures, accepted for publication in Astronomy and Astrophysic

    Therapies for bleomycin induced lung fibrosis through regulation of TGF-Β1 induced collagen gene expression

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    This review describes normal and abnormal wound healing, the latter characterized by excessive fibrosis and scarring, which for lung can result in morbidity and sometimes mortality. The cells, the extracellular matrix (ECM) proteins, and the growth factors regulating the synthesis, degradation, and deposition of the ECM proteins will be discussed. Therapeutics with particular emphasis given to gene therapies and their effects on specific signaling pathways are described. Bleomycin (BM), a potent antineoplastic antibiotic increases TGF-Β1 transcription, TGF-Β1 gene expression, and TGF-Β protein. Like TGF-Β1, BM acts through the same distal promoter cis -element of the COL1A1 gene causing increased COL1 synthesis and lung fibrosis. Lung fibroblasts exist as subpopulations with one subset predominately responding to fibrogenic stimuli which could be a specific cell therapeutic target for the onset and development of pulmonary fibrosis. J. Cell. Physiol. 211: 585–589, 2007. © 2007 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55994/1/20972_ftp.pd

    A Upf3b-mutant mouse model with behavioral and neurogenesis defects.

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    Nonsense-mediated RNA decay (NMD) is a highly conserved and selective RNA degradation pathway that acts on RNAs terminating their reading frames in specific contexts. NMD is regulated in a tissue-specific and developmentally controlled manner, raising the possibility that it influences developmental events. Indeed, loss or depletion of NMD factors have been shown to disrupt developmental events in organisms spanning the phylogenetic scale. In humans, mutations in the NMD factor gene, UPF3B, cause intellectual disability (ID) and are strongly associated with autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD) and schizophrenia (SCZ). Here, we report the generation and characterization of mice harboring a null Upf3b allele. These Upf3b-null mice exhibit deficits in fear-conditioned learning, but not spatial learning. Upf3b-null mice also have a profound defect in prepulse inhibition (PPI), a measure of sensorimotor gating commonly deficient in individuals with SCZ and other brain disorders. Consistent with both their PPI and learning defects, cortical pyramidal neurons from Upf3b-null mice display deficient dendritic spine maturation in vivo. In addition, neural stem cells from Upf3b-null mice have impaired ability to undergo differentiation and require prolonged culture to give rise to functional neurons with electrical activity. RNA sequencing (RNAseq) analysis of the frontal cortex identified UPF3B-regulated RNAs, including direct NMD target transcripts encoding proteins with known functions in neural differentiation, maturation and disease. We suggest Upf3b-null mice serve as a novel model system to decipher cellular and molecular defects underlying ID and neurodevelopmental disorders

    Regulation of Macrophage‐Derived Fibroblast Growth Factor Release by Arachidonate Metabolites

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    The macrophage is a source of many mediators with direct and indirect fibrogenic potential. In this study, release of macrophage‐derived fibroblast growth factor (MDGF) activity by murine peritoneal macrophages is examined with regard to its regulation by arachidonate metabolites. Upon stimulation with 10 μg/ml lipopolysaccharide (LPS), resident peritoneal macrophages from CBA/J mice released MDGF activity into media rapidly, reaching maximal levels in approximately 1 h. Lysates of these stimulated cells also revealed significantly increased cell‐associated MDGF activity, composing 45% of the total assayable activity. This activity, as assayed by radioactive thymidine incorporation by primary cultures of rat lung fibroblasts, was separable from interleukin‐1 (IL‐1) activity by reverse phase high performance liquid chromatography (HPLC). Furthermore, purified murine IL‐1 had no MDGF activity in this assay system. This stimulated MDGF release was enhanced by the cylooxygenase inhibitors indomethacin, Ibuprofen, and aspirin at micromolar concentrations, but inhibited in a dose‐dependent manner by prostaglandin E2 (PGE2). On the other hand, nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor was inhibitory at 0.1 and 0.4 μM but not at 2.5 μM. Zymosan‐stimulated macrophages also markedly increased MDGF release, albeit with a different time course which was characterized by a delay of approximately 7 h before peak levels were attained. Such stimulation, which is known to cause increased lipoxygenase activity, was also inhibited by 0.5 μM NDGA. In contrast, the lipoxygenase pathway products leukotrienes B4 (LTB4) and C4 (LTC4) stimulated MDGF release in a dose‐dependent (10‐10‐10‐8 M) manner, with LTC4 being more potent on a per unit dose basis. Stimulation by LTC4 was inhibited by the putative leukotriene receptor antagonist, FPL55712, while LTD4 and LTE4 did not stimulate MDGF release, thus suggesting the mediation of this effect by specific LTC4 receptors. These data suggest also that products of the cyclooxygenase and lipoxygenase pathways are potentially important both as exogenous (ie, derived from cells other than the macrophage itself) and auto‐ or self‐regulators of macrophage MDGF release. This, in turn, implies that cyclooxygenase products are antifibrogenic and important in maintaining or returning to the quiescent or normal state, whereas the lipoxygenase products are profibrogenic and important in induction of fibrosis or wound‐healing and tissue repair. Any alteration in the balance between these two pathways may result in either a desirable or a harmful outcome.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141690/1/jlb0106.pd
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