1,721,099 research outputs found
Leading gravitational corrections and a unified universe
No full textLeading order gravitational corrections to the Einstein-Hilbert action can lead to a consistent picture of the universe by unifying the epochs of inflation and dark energy in a single framework. While the leading local correction induces an inflationary phase in the early universe, the leading nonlocal term leads to an accelerated expansion of the universe at the present epoch. We argue that both the leading UV and IR terms can be obtained within the framework of a covariant effective field theory of gravity. The perturbative gravitational corrections therefore provide a fundamental basis for understanding a possible connection between the two epochs.</p
On the covariant formalism of the effective field theory of gravity and leading order corrections
No full textWe construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime.</p
On the covariant formalism of the effective field theory of gravity and its cosmological implications
Get PDFFollowing our previous work wherein the leading order effective action was computed in the covariant effective field theory of gravity, here we specialize the effective action to the FRW spacetime and obtain the effective Friedmann equations. In particular, we focus our attention on studying the cosmological implications of the non-local terms when each of them is combined with the Einstein-Hilbert action. We obtain both analytical and iterative solutions to the effective background equations in all the cases and also briefly comment on the consistency between the iterative and numerical solutions whenever possible. We find that among all the non-local terms, the imprints induced by R1/2R are very significant. Interpreting these corrections as an effective dark energy component characterized by an equation of state parameter, we find that the R1/2R correction can indeed lead to an accelerated expansion of the universe at the present epoch even in the absence of a cosmological constant. We briefly discuss some phenomenological consequences of our results.</p
Solid stress generated by spheroid growth estimated using a linear poroelastisity model
No full textThe unchecked growth of a solid tumor produces solid stress, causing deformation of the surrounding tissue. This stress can result in clinical complications, especially in confined environments such as the brain, and may also be responsible for pathophysiological anomalies such as the collapse of blood and lymphatic vessels. High stress levels may also inhibit further cell division within tumors. Unfortunately, little is known about the dynamics of stress accumulation in tumors or its effects on cell biology. We present a mathematical model for tumor growth in a confined, elastic environment such as living tissue. The model, developed from theories of thermal expansion using the current configuration of the material element, allows the stresses within the growing tumor and the surrounding medium to be calculated. The experimental observation that confining environments limit the growth of tumor spheroids to less than the limit imposed by nutrient diffusion is incorporated into the model using a stress dependent rate for tumor growth. The model is validated against experiments for MU89 tumor spheroid growth in Type VII agarose gel. Using the mathematical model and the experimental evidence we show that the tumor cell size is reduced by solid stress inside the tumor spheroid. This leads to the interesting possibility that cell size could be a direct indicator of solid stress level inside the tumors in clinical setting
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Improving effectiveness of preventive maintenance in a captive power plant
No full textAny failure in the functioning of the critical equipment in a captive power plant (CPP) can reduce the plant load factor or stop the plant altogether incurring heavy production loses in the parent heavy industry. To provide uninterrupted power supply the rotating machines as well as other stationary equipment of the power generating units should be operated with maximum efficiency and reliability. This can be ensured by the periodic maintenance system commonly known as preventive maintenance (PM). In this paper we address the issue of how preventive maintenance program can be implemented more effectively. We conceptualize our explanatory framework and the data for suggesting solution are derived from expert and executive managers through personal interview method in a large steel plant in India. Our analysis suggests that by addressing the issues related to the ineffective planning failure to execute the preventive maintenance job on schedule time and a lack of cost plus approach could improve the effectiveness of a preventive maintenance system
A Study on processes of meeting production targers in cold rolling mills in a steel organization
No full textThe steel manufacturing industry in India is facing the challenges with the MNC's due to increasing in globalization and intense competition and customer satisfaction. These challenges require the organization to make continuous improvement by adopting the process improvement to face this competition. As Indian steel industries works on the old method of the operation where all department like marketing operation and planning department are not working together and hence the problem arrived in not achieving the production targets and customer satisfaction. (Caruana G.,Einav L.,20018) in this paper we show the current system or process used in Indian steel organization and problems in current process. On the basis of the literature revies and by doing the expert interviews in different size of the steel organization we proposed a model of manufacturing integration of steel organization. By doing gap analysis between the current method and proposed method we conclude the variable like marketing, material planning, supportive departments and man power training highly affects the production target
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