1,279 research outputs found
S.B. Axtell K1877 Scrapbook 1875-1877
https://digital.kenyon.edu/scrapbooks/1083/thumbnail.jp
Nonuniversal power law scaling in the probability distribution of scientific citations
We develop a model for the distribution of scientific citations. The model
involves a dual mechanism: in the direct mechanism, the author of a new paper
finds an old paper A and cites it. In the indirect mechanism, the author of a
new paper finds an old paper A only via the reference list of a newer
intermediary paper B, which has previously cited A. By comparison to citation
databases, we find that papers having few citations are cited mainly by the
direct mechanism. Papers already having many citations ('classics') are cited
mainly by the indirect mechanism. The indirect mechanism gives a power-law
tail. The 'tipping point' at which a paper becomes a classic is about 21
citations for papers published in the Institute for Scientific Information
(ISI) Web of Science database in 1981, 29 for Physical Review D papers
published from 1975-1994, and 39 for all publications from a list of high
h-index chemists assembled in 2007. The power-law exponent is not universal.
Individuals who are highly cited have a systematically smaller exponent than
individuals who are less cited.Comment: 7 pages, 3 figures, 2 table
A power-law distribution for tenure lengths of sports managers
We show that the tenure lengths for managers of sport teams follow a power law distribution with an exponent between 2 and 3. We develop a simple theoretical model which replicates this result. The model demonstrates that the empirical phenomenon can be understood as the macroscopic outcome of pairwise interactions among managers in a league, threshold effects in managerial performance evaluation, competitive market forces, and luck at the microscopic level
Understanding the relationship between experiencing workplace cyberbullying, employee mental strain and job satisfaction: a dysempowerment approach
Although the literature on traditional workplace bullying is advancing rapidly, currently investigations addressing workplace cyberbullying are sparse. To counter this, we present three connected research studies framed within dysempowerment theory (Kane, K., & Montgomery, K. (1998). A framework for understanding dysempowerment in organizations. Human Resource Management, 37, 263–275.) which examine the relationship between volume and intensity of cyberbullying experience and individual mental strain and job satisfaction; whether the impact is more negative as compared to traditional bullying; and whether state negative affectivity (NA) and interpersonal justice mediate the relationship. Additionally, we also considered the impact of witnessing cyberbullying acts on individual outcomes. A total sample comprised 331 UK university employees across academic, administrative, research, management and technical roles. Overall, significant relationships between cyberbullying exposure and outcomes emerged, with cyberbullying exposure displaying a stronger negative relationship with job satisfaction when compared to offline bullying. Analysis supported an indirect effect between cyberbullying acts and outcomes via NA and between cyberbullying acts and job satisfaction via interpersonal justice. No support for a serial multiple mediation model of experiencing cyberbullying to justice to NA to outcome was found. Further, perceived intensity of cyberbullying acts and witnessing cyberbullying acts did not significantly relate to negative outcomes. Theoretical and practical implications of the research are discussed
Peroxisome proliferator-activated receptor delta limits the expansion of pathogenic Th cells during central nervous system autoimmunity.
Peroxisome proliferator-activated receptors (PPARs; PPAR-alpha, PPAR-delta, and PPAR-gamma) comprise a family of nuclear receptors that sense fatty acid levels and translate this information into altered gene transcription. Previously, it was reported that treatment of mice with a synthetic ligand activator of PPAR-delta, GW0742, ameliorates experimental autoimmune encephalomyelitis (EAE), indicating a possible role for this nuclear receptor in the control of central nervous system (CNS) autoimmune inflammation. We show that mice deficient in PPAR-delta (PPAR-delta(-/-)) develop a severe inflammatory response during EAE characterized by a striking accumulation of IFN-gamma(+)IL-17A(-) and IFN-gamma(+)IL-17A(+) CD4(+) cells in the spinal cord. The preferential expansion of these T helper subsets in the CNS of PPAR-delta(-/-) mice occurred as a result of a constellation of immune system aberrations that included higher CD4(+) cell proliferation, cytokine production, and T-bet expression and enhanced expression of IL-12 family cytokines by myeloid cells. We also show that the effect of PPAR-delta in inhibiting the production of IFN-gamma and IL-12 family cytokines is ligand dependent and is observed in both mouse and human immune cells. Collectively, these findings suggest that PPAR-delta serves as an important molecular brake for the control of autoimmune inflammation
Alternating Spin and Orbital Dimerization in Strong-coupling Two-band Models
We study a one-dimensional Hamiltonian consisting of coupled SU(2) spin and
orbital degrees of freedom. Using the density matrix renormalization group, we
calculate the phase-diagram and the ground state correlation functions for this
model. We find that, in addition to the ferromagnetic and power-law
antiferromagnetic phases for spin and orbital degrees of freedom, this model
has a gapless line extending from the ferromagnetic phase to the Bethe ansatz
solvable SU(4) critical point, and a gapped phase with doubly degenerate ground
states which form alternating spin and orbital singlets. The spin-gap and the
order parameters are evaluated and the relevance to several recently discovered
spin-gap materials is discussed.Comment: 4 pages REVTEX and 4 Postscript figure
Phase diagram and symmetry breaking of SU(4) spin-orbital chain in a generalized external field
The ground state phases of a one-dimensional SU(4) spin-orbital Hamiltonian
in a generalized external field are studied on the basis of Bethe-ansatz
solution. Introducing three Land\'e factors for spin, orbital and their
products in the SU(4) Zeeman term, we discuss systematically the various
symmetry breaking. The magnetization versus external field are obtained by
solving Bethe-ansatz equations numerically. The phase diagrams corresponding to
distinct residual symmetries are given by means of both numerical and
analytical methods.Comment: Revtex4, 16 pages, 7 figure
“An ethnographic seduction”: how qualitative research and Agent-based models can benefit each other
We provide a general analytical framework for empirically informed agent-based simulations. This methodology provides present-day agent-based models with a sound and proper insight as to the behavior of social agents — an insight that statistical data often fall short of providing at least at a micro level and for hidden and sensitive populations. In the other direction, simulations can provide qualitative researchers in sociology, anthropology and other fields with valuable tools for: (a) testing the consistency and pushing the boundaries, of specific theoretical frameworks; (b) replicating and generalizing results; (c) providing a platform for cross-disciplinary validation of results
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