5,033 research outputs found
General relativistic Poynting-Robertson effect to diagnose wormholes existence: static and spherically symmetric case
We derive the equations of motion of a test particle in the equatorial plane
around a static and spherically symmetric wormhole influenced by a radiation
field including the general relativistic Poynting-Robertson effect. From the
analysis of this dynamical system, we develop a diagnostic to distinguish a
black hole from a wormhole, which can be timely supported by several and
different observational data. This procedure is based on the possibility of
having some wormhole metrics, which smoothly connect to the Schwarzschild
metric in a small transition surface layer very close to the black hole event
horizon. To detect such a metric-change, we analyse the emission proprieties
from the critical hypersurface (stable region where radiation and gravitational
fields balance) together with those from an accretion disk in the Schwarzschild
spacetime toward a distant observer. Indeed, if the observational data are well
fitted within such model, it immediately implies the existence of a black hole;
while in case of strong departures from such description it means that a
wormhole could be present. Finally, we discuss our results and draw the
conclusions.Comment: 17 pages, 11 figures, 1 Table. Paper accepted on April 30, 2020 on
Physical Review
Rough Set Theory for Real Estate Appraisal: An Application to Directional District of Naples
This paper proposes an application of Rough Set Theory (RST) to the real estate field, in order to highlight its operational potentialities for mass appraisal purposes. RST allows one to solve the appraisal of real estate units regardless of the deterministic relationship between characteristics that contribute to the formation of the property market price and the same real estate prices. RST was applied to a real estate sample (office units located in Directional District of Naples) and was also integrated with a functional extension so-called Valued Tolerance Relation (VTR) in order to improve its flexibility. A multiple regression analysis (MRA) was developed on the same real estate sample with the aim to compare RST and MRA results. The case study is followed by a brief discussion on basic theoretical connotations of this methodology
Valuation of real estate investments through Fuzzy Logic
This paper aims to outline the application of Fuzzy Logic in real estate investment. In literature, there is a wide theoretical background on real estate investment decisions, but there has been a lack of empirical support in this regard. For this reason, the paper would fill the gap between theory and practice. The fuzzy logic system is adopted to evaluate the situations of a real estate market with imprecise and vague information. To highlight the applicability of the Possibility Theory, we proceeded to reconsider an example of property investment evaluation through fuzzy logic. The case study concerns the purchase of an office building. The results obtained with Fuzzy Logic have been also compared with those arising from a deterministic approach through the use of crisp numbers
The Partial Visibility Representation Extension Problem
For a graph , a function is called a \emph{bar visibility
representation} of when for each vertex , is a
horizontal line segment (\emph{bar}) and iff there is an
unobstructed, vertical, -wide line of sight between and
. Graphs admitting such representations are well understood (via
simple characterizations) and recognizable in linear time. For a directed graph
, a bar visibility representation of , additionally, puts the bar
strictly below the bar for each directed edge of
. We study a generalization of the recognition problem where a function
defined on a subset of is given and the question is whether
there is a bar visibility representation of with for every . We show that for undirected graphs this problem
together with closely related problems are \NP-complete, but for certain cases
involving directed graphs it is solvable in polynomial time.Comment: Appears in the Proceedings of the 24th International Symposium on
Graph Drawing and Network Visualization (GD 2016
Robust exact differentiators with predefined convergence time
The problem of exactly differentiating a signal with bounded second
derivative is considered. A class of differentiators is proposed, which
converge to the derivative of such a signal within a fixed, i.e., a finite and
uniformly bounded convergence time. A tuning procedure is derived that allows
to assign an arbitrary, predefined upper bound for this convergence time. It is
furthermore shown that this bound can be made arbitrarily tight by appropriate
tuning. The usefulness of the procedure is demonstrated by applying it to the
well-known uniform robust exact differentiator, which the considered class of
differentiators includes as a special case
A study of general practitioners’ awareness of the National Institute for Health and Care Excellence guidelines regarding the use of nonsteroidal anti-inflammatory drugs
Background Non-steroidal anti-inflammatory drugs (NSAIDs) are widely prescribed for their analgesic, anti-pyretic and anti-inflammatory effects. There is no doubt regarding their benefits; however the importance of their side effects including gastrointestinal complications cannot be emphasized enough especially in high risk groups. Objectives This study assessed the awareness of general practitioners (GPs) working within Maltese health centres of the National Institute for Health and Care Excellence (NICE) guidelines on the proper prescription of NSAIDs, especially the co-prescription of gastroprotective agents in high risk groups. Method An online questionnaire based on the NICE guidelines on NSAID Prescribing Issues revised in July 2015 was distributed to doctors working within health centres across Malta. Results Trauma was the most popular reason for NSAID prescription (75%), with the commonest patient age group being that below 45 years of age. Diclofenac was the most popular NSAID choice (55.4%) with COX-2 inhibitors being the preferred choice for 23.2%. Most doctors were aware of factors that need to be considered when initiating NSAIDs, being least aware of liver comorbidities and fertility issues. The majority use licensed gastroprotective agents both in drug choice and in dose. More awareness is required on high risk patient groups especially patients with arthritis and patients on selective serotonin reuptake inhibitors (SSRIs). Conclusion There is room for improvement in awareness on proper NSAID use and gastroprotection especially in identifying high risk groups, drug interactions and choice of gastroprotective agents. The importance of gastroprotection, side effect monitoring, prevention of unnecessary chronic NSAID use and promotion of coxib use over standard NSAIDs needs to be emphasized further especially in high risk groups.peer-reviewe
Analytical results for binary dynamics at the first post-Newtonian order in Einstein-Cartan theory with the Weyssenhoff fluid
The quantum spin effects inside matter can be modeled via the Weyssenhoff
fluid, which permits to unearth a formal analogy between general relativity and
Einstein-Cartan theory at the first post-Newtonian order. In this framework, we
provide some analytical formulas pertaining to the dynamics of binary systems
having the spins aligned perpendicular to the orbital plane. We derive the
expressions of the relative orbit and the coordinate time, which in turn allow
to determine the gravitational waveform, and the energy and angular momentum
fluxes. The potentialities of our results are presented in two astrophysical
applications, where we compute: () the quantum spin contributions to the
energy flux and gravitational waveform during the inspiral phase; () the
macroscopic angular momentum of one of the bodies starting from the
time-averaged energy flux and the knowledge of few timing parameters.Comment: 13 pages, 2 figures, accepted for pubblication on Phys. Rev.
Knuthian Drawings of Series-Parallel Flowcharts
Inspired by a classic paper by Knuth, we revisit the problem of drawing
flowcharts of loop-free algorithms, that is, degree-three series-parallel
digraphs. Our drawing algorithms show that it is possible to produce Knuthian
drawings of degree-three series-parallel digraphs with good aspect ratios and
small numbers of edge bends.Comment: Full versio
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