177,643 research outputs found
Vorticity in analog gravity
No full textIn the analog gravity framework, the acoustic disturbances in a moving
fluid can be described by an equation of motion identical to a
relativistic scalar massless field propagating in curved space-time.
This description is possible only when the fluid under consideration is
barotropic, inviscid, and irrotational. In this case, the propagation of
the perturbations is governed by an acoustic metric that depends
algebrically on the local speed of sound, density, and the background
flow velocity, the latter assumed to be vorticity-free. In this work we
provide a straightforward extension in order to go beyond the
irrotational constraint. Using a charged-relativistic and
nonrelativistic-Bose- Einstein condensate as a physical system, we show
that in the low-momentum limit and performing the eikonal approximation
we can derive a d'Alembertian equation of motion for the charged phonons
where the emergent acoustic metric depends on flow velocity in the
presence of vorticity
Analogue black holes in relativistic BECs: Mimicking Killing and universal horizons
No full textRelativistic Bose-Einstein condensates (rBECs) have recently become a
well-established system for analogue gravity. Indeed, while such
relativistic systems cannot be yet realized experimentally, they provide
an interesting framework for mimicking metrics for which no analogue is
yet available, thus paving the way for further theoretical and numerical
explorations. In this vein, we here discuss black holes in rBECs and
explore how their features relate to the bulk properties of the system.
We then propose the coupling of external fields to the rBEC as a way to
mimic nonmetric features. In particular, we use a Proca field to
simulate an aether field, as found in Einstein-aether or Ho.
rava-Lifshitz gravity. This allows us to mimic a universal horizon, the
causal barrier relevant for superluminal modes in these modified
gravitational theories
AdS and dS black hole solutions in analogue gravity: The relativistic and nonrelativistic cases
No full textWe show that Schwarzschild black hole solutions in asymptotically
anti-de Sitter (AdS) and de Sitter spaces may, up to a conformal factor,
be reproduced in the framework of analogue gravity. The aforementioned
derivation is performed using relativistic and nonrelativistic
Bose-Einstein condensates. In addition, we demonstrate that the (2 + 1)
planar AdS black hole can be mapped into the nonrelativistic acoustic
metric. Given that AdS black holes are extensively employed in the
gauge/gravity duality, we then comment on the possibility of studying
the AdS/CFT correspondence and gravity/fluid duality from an analogue
gravity perspective
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Aminaftone, a derivative of 4-aminobenzoic acid, downregulates endothelin-1 production in ECV304 Cells : an in vitro study
No full textBackground and objective: Endothelin-1 (ET-1) plays a central role in the pathogenesis of several vascular diseases. Aminaftone is a drug used for the treatment of capillary disorders but which has a mechanism of action that is not fully understood. We investigated whether aminaftone may exert its effect by interfering with the production of ET-1. Methods: Human ECV304 endothelial cells were incubated with interleukin-1β (IL-1β) 100 IU/mL with or without the addition of increasing concentrations of aminaftone (2, 4 or 6 μg/mL). ET-1 concentrations in surnatants were quantified by enzyme immunoassay kit at 3, 6 and 12 hours. Pre-pro-endothelin-1 (PPET-1) gene expressions were also analysed by real-time polymerase chain reaction (RT-PCR) at the same time points. Endothelin-converting enzyme (ECE) activity was also determined. Results: Incubation with IL-1β increased concentrations of ET-1 and PPET-1 relative gene expression. Incubation with aminaftone significantly reduced production of ET-1 in a concentration-dependent manner. A strong direct correlation was found between ET-1 concentrations and PPET-1 relative gene expression, but aminaftone did not influence ECE activity. Conclusion: Aminaftone inhibits ET-1 production in cell cultures by interfering with transcription of the PPET-1 gene. These findings may account for the clinical efficacy of aminaftone in the treatment of capillary disorders and may encourage conduct of further clinical trials
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Liftings for noncomplete probability spaces
No full textThe current state of knowledge concerning liftings for noncomplete probability spaces is discussed. This is a somewhat expanded version of the author's talk given at the 1991 Summer Conference on General Topology and Applications in Honor of Mary Ellen Rudin and Her Work.PT: S; CR: BURKE MR, IN PRESS P AM MATH S BURKE MR, 1991, ISRAEL J MATH, V73, P33 BURKE MR, 1992, ISRAEL J MATH, V79, P289 CARLSON T, THEOREM LIFTING CHRISTENSEN JPR, 1974, TOPOLOGY BOREL STRUC FREMLIN DH, 1989, HDB BOOLEAN ALGEBRAS, P877 INOESCUTULCEA A, 1966, 5TH P BERK S MATH ST, V2 IONESCUTULCEA A, 1967, CONTRIBUTIONS PROB 1, P63 IONESCUTULCEA A, 1969, TOPICS THEORY LIFTIN JECH TJ, 1978, SET THEORY JOHNSON RA, 1980, P AM MATH SOC, V80, P234 JUST W, IN PRESS T AM MATH S KUPKA J, 1983, INDIANA U MATH J, V32, P717 LOSERT V, 1983, LNM, V1080, P95 MAHARAM D, 1958, P AM MATH SOC, V9, P987 SHELAH S, 1983, ISRAEL J MATH, V45, P90 TALAGRAND M, 1982, P AM MATH SOC, V84, P379 VONNEUMANN J, 1931, CRELLES J MATH, V165, P109; NR: 18; TC: 0; J9: ANN N Y ACAD SCI; PG: 4; GA: BZ86BSource type: Electronic(1
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