2,104 research outputs found

    Relatedness and Performance: A Reexamination of the Diversification-Performance Link

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    Empirical studies of firm diversification suggest the existence of a positive relationship between the relatedness of diversification and firm performance. Using evidence from the food manufacturing sector, we find that this relationship is weak at best and that market share appears to be a more powerful predictor of firm performance.Agribusiness, Industrial Organization,

    Restructuring's Effect on Related and Unrelated Diversification Among Top Food Manufacturing Firms in the 1980s

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    Corporate restructuring during the 1980s is argued to have focused on improving firm performance by increasing related and decreasing unrelated diversification. The restructuring patterns of top food manufacturing firms do not support this; instead, much of the restructuring appears to have been driven by the pursuit of stronger market positions. TheAgribusiness, Industrial Organization,

    Nature of vibrational eigenmodes in topologically disordered solids

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    We use a local projectional analysis method to investigate the effect of topological disorder on the vibrational dynamics in a model glass simulated by molecular dynamics. Evidence is presented that the vibrational eigenmodes in the glass are generically related to the corresponding eigenmodes of its crystalline counterpart via disorder-induced level-repelling and hybridization effects. It is argued that the effect of topological disorder in the glass on the dynamical matrix can be simulated by introducing positional disorder in a crystalline counterpart.Comment: 7 pages, 6 figures, PRB, to be publishe

    Detection and characterization of mineralo-organic nanoparticles in human kidneys

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    Ectopic calcification is associated with various human diseases, including atherosclerosis, cancer, chronic kidney disease, and diabetes mellitus. Although mineral nanoparticles have been detected in calcified blood vessels, the nature and role of these particles in the human body remain unclear. Here we show for the first time that human kidney tissues obtained from end-stage chronic kidney disease or renal cancer patients contain round, multilamellar mineral particles of 50 to 1,500 nm, whereas no particles are observed in healthy controls. The mineral particles are found mainly in the extracellular matrix surrounding the convoluted tubules, collecting ducts and loops of Henle as well as within the cytoplasm of tubule-delineating cells, and consist of polycrystalline calcium phosphate similar to the mineral found in bones and ectopic calcifications. The kidney mineral nanoparticles contain several serum proteins that inhibit ectopic calcification in body fluids, including albumin, fetuin-A, and apolipoprotein A1. Since the mineralo-organic nanoparticles are found not only within calcified deposits but also in areas devoid of microscopic calcifications, our observations indicate that the nanoparticles may represent precursors of calcification and renal stones in humans

    Charge disproportionation and the pressure-induced insulator?metal transition in cubic perovskite PbCrO3

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    The perovskite PbCrO3 is an antiferromagnetic insulator. However, the fundamental interactions leading to the insulating state in this single-valent perovskite are unclear. Moreover, the origin of the unprecedented volume drop observed at a modest pressure of P = 1.6 GPa remains an outstanding problem. We report a variety of in situ pressure measurements including electron transport properties, X-ray absorption spectrum, and crystal structure study by X-ray and neutron diffraction. These studies reveal key information leading to the elucidation of the physics behind the insulating state and the pressure-induced transition. We argue that a charge disproportionation 3Cr4+ → 2Cr3+ + Cr6+ in association with the 6s-p hybridization on the Pb2+ is responsible for the insulating ground state of PbCrO3 at ambient pressure and the charge disproportionation phase is suppressed under pressure to give rise to a metallic phase at high pressure. The model is well supported by density function theory plus the correlation energy U (DFT+U) calculations.Fil: Cheng, Jinguang. University Of Texas At Austin; Estados Unidos. Chinese Academy Of Sciences; RepĂșblica de China. University of Tokyo. Institute for Solid State Physics; JapĂłnFil: Kweon, K. E.. University Of Texas At Austin; Estados UnidosFil: Larregola, Sebastian Alberto. University Of Texas At Austin; Estados Unidos. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Centro CientĂ­fico TecnolĂłgico San Luis. Instituto de Investigaciones en TecnologĂ­a QuĂ­mica; ArgentinaFil: Ding, Yang. Argonne National Laboratory; Estados UnidosFil: Shirako, Y.. University Of Texas At Austin; Estados UnidosFil: Marshall, L. G.. University Of Texas At Austin; Estados Unidos. Northeastern University; Estados UnidosFil: Li, Z. Y.. University Of Texas At Austin; Estados UnidosFil: Li, X.. University Of Texas At Austin; Estados UnidosFil: Dos Santos, AntĂłnio M.. Oak Ridge National Laboratory. Quantum Condensed Matter Division; Estados UnidosFil: Suchomel, M. R.. Argonne National Laboratory; Estados UnidosFil: Matsubayashi, K.. University of Tokyo. Institute for Solid State Physics; JapĂłnFil: Uwatoko, Y.. University of Tokyo. Institute for Solid State Physics; JapĂłnFil: Hwang, G. S.. University Of Texas At Austin; Estados UnidosFil: Goodenough, John B.. University Of Texas At Austin; Estados UnidosFil: Zhou, J. S.. University Of Texas At Austin; Estados Unido

    Long‐term surveillance biopsy: Is it necessary after pediatric heart transplant?

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    Due to limited and conflicting data in pediatric patients, long‐term routine surveillance endomyocardial biopsy (RSB) in pediatric heart transplant (HT) remains controversial. We sought to characterize the rate of positive RSB and determine factors associated with RSB‐detected rejection. Records of patients transplanted at a single institution from 1995 to 2015 with >2 year of post‐HT biopsy data were reviewed for RSB‐detected rejections occurring >2 year post‐HT. We illustrated the trajectory of significant rejections (ISHLT Grade ≄3A/2R) among total RSB performed over time and used multivariable logistic regression to model the association between time and risk of rejection. We estimated Kaplan‐Meier freedom from rejection rates by patient characteristics and used the log‐rank test to assess differences in rejection probabilities. We identified the best‐fitting Cox proportional hazards regression model. In 140 patients, 86% did not have any episodes of significant RSB‐detected rejection >2 year post‐HT. The overall empirical rate of RSB‐detected rejection >2 year post‐HT was 2.9/100 patient‐years. The percentage of rejection among 815 RSB was 2.6% and remained stable over time. Years since transplant remained unassociated with rejection risk after adjusting for patient characteristics (OR = 0.98; 95% CI 0.78‐1.23; P = 0.86). Older age at HT was the only factor that remained significantly associated with risk of RSB‐detected rejection under multivariable Cox analysis (P = 0.008). Most pediatric patients did not have RSB‐detected rejection beyond 2 years post‐HT, and the majority of those who did were older at time of HT. Indiscriminate long‐term RSB in pediatric heart transplant should be reconsidered given the low rate of detected rejection.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147767/1/petr13330_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147767/2/petr13330.pd

    Anomalous metamagnetism in the low carrier density Kondo lattice YbRh3Si7

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    We report complex metamagnetic transitions in single crystals of the new low carrier Kondo antiferromagnet YbRh3Si7. Electrical transport, magnetization, and specific heat measurements reveal antiferromagnetic order at T_N = 7.5 K. Neutron diffraction measurements show that the magnetic ground state of YbRh3Si7 is a collinear antiferromagnet where the moments are aligned in the ab plane. With such an ordered state, no metamagnetic transitions are expected when a magnetic field is applied along the c axis. It is therefore surprising that high field magnetization, torque, and resistivity measurements with H||c reveal two metamagnetic transitions at mu_0H_1 = 6.7 T and mu_0H_2 = 21 T. When the field is tilted away from the c axis, towards the ab plane, both metamagnetic transitions are shifted to higher fields. The first metamagnetic transition leads to an abrupt increase in the electrical resistivity, while the second transition is accompanied by a dramatic reduction in the electrical resistivity. Thus, the magnetic and electronic degrees of freedom in YbRh3Si7 are strongly coupled. We discuss the origin of the anomalous metamagnetism and conclude that it is related to competition between crystal electric field anisotropy and anisotropic exchange interactions.Comment: 23 pages and 4 figures in the main text. 7 pages and 5 figures in the supplementary materia
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