9 research outputs found
Weak field and slow motion limits in energy-momentum powered gravity
We explore the weak field and slow motion limits, Newtonian and
Post-Newtonian limits, of the energy-momentum powered gravity (EMPG), viz., the
energy-momentum squared gravity (EMSG) of the form
with
and being constants. We have shown that EMPG with and
general relativity (GR) are not distinguishable by local tests, say, the Solar
System tests; as they lead to the same gravitational potential form, PPN
parameters, and geodesics for the test particles. However, within the EMPG
framework, , the mass of an astrophysical object inferred from
astronomical observations such as planetary orbits and deflection of light,
corresponds to the effective mass , being the actual physical mass and
being the modification due to EMPG. Accordingly, while in GR we simply have the
relation , in EMPG we have . Within
the framework of EMPG, if there is information about the values of
pair or from other independent phenomena (from
cosmological observations, structure of the astrophysical object, etc.), then
in principle it is possible to infer not only alone from
astronomical observations, but and separately. For a proper
analysis within EMPG framework, it is necessary to describe the slow motion
condition (also related to the Newtonian limit approximation) by (where and ), whereas this condition leads to in
GR.Comment: 12 pages, no figures and table
Equivalence of matter-type modified gravity theories to general relativity with nonminimal matter interaction
We show that gravity models, such as , and , that modify the introduction of
the material source in the usual Einstein-Hilbert action by adding only
matter-related terms to the matter Lagrangian density are
equivalent to general relativity with nonminimal interactions. Through the
redefinition ,
these models are exactly GR, yet the usual material field and its
accompanying partner, viz., the modification field
interact nonminimally. That is,
, where
is the interaction kernel that governs the rate of energy transfer.
We focus on the particular model, the energy-momentum squared gravity, where
the usual material field brings in an accompanying energy-momentum
squared field , along with a sui generis nonminimal
interaction between them. Compared to usual phenomenological nonminimal
interaction models in the literature, EMSF gives rise to more intricate
interaction kernels having covariant formulation even with simple forms of the
function. We elaborate upon EMSF via some different aspects: a DE component
induced from the interaction of sources such as cold dark matter and
relativistic species with their accompanying EMSFs generating interacting DE-DM
models, mimicking noncanonical scalar field, etc., or a Hoyle-type creation
field generating steady-state universe models extended to fluids other than
dust and a mimicker of modified generalized Chaplygin gas. We also demonstrate
the proper calculation of second metric variation of , as
well as in models that contain scalars like and .Comment: 16 pages, no figures and table
Screening in a new modified gravity model
We study a new model of Energy-Momentum Squared Gravity (EMSG), called
Energy-Momentum Log Gravity (EMLG), constructed by the addition of the term
, envisaged
as a correction, to the Einstein-Hilbert action with cosmological constant
. The choice of this modification is made as a specific way of
including new terms in the right-hand side of the Einstein field equations,
resulting in constant effective inertial mass density and, importantly, leading
to an explicit exact solution of the matter energy density in terms of
redshift. We look for viable cosmologies, in particular, an extension of the
standard CDM model. EMLG provides an effective dynamical dark energy
passing below zero at large redshifts, accommodating a mechanism for screening
in this region, in line with suggestions for alleviating some of the
tensions that arise between observational data sets within the standard
CDM model. We present a detailed theoretical investigation of the
model and then constrain the free parameter , a normalisation of
, using the latest observational data. The data does not rule out the
CDM limit of our model (), but prefers slightly negative
values of the EMLG model parameter (), which leads to
the screening of . We also discuss how EMLG relaxes the persistent
tension that appears in the measurements of within the standard
CDM model.Comment: 17 pages, 11 figures, 1 table; matches the version published in EPJ
cfDNA in exhaled breath condensate (EBC) and contamination by ambient air: toward volatile biopsies
###EgeUn###Exhaled breath is a source of volatile and nonvolatile biomarkers in the body that can be accessed non-invasively and used for monitoring. The collection of lung secretions by conventional methods such as bronchoalveolar lavage, induced sputum collection, and core biopsies is limited by the invasive nature of these methods. Non-invasive collection of exhaled breath condensate (EBC) provides fluid samples that are representative of airway lining fluids. Various volatile and nonvolatile biomarkers can be detected in volatile condensates, such as H2O2, nitric oxide, lipid mediators, cytokines, chemokines, DNA, and microRNAs. Studies have examined cell-freeDNA(cfDNA) in plasma samples from non-small-cell lung cancer patients, offering to new insights and fostering development of the liquid biopsy. However, few studies have examined cfDNA in EBC samples. This study examined whether EBC is an appropriate source of cfDNA using housekeeping-gene-specific primer probes and quantitative real-time polymerase chain reaction in healthy subjects. Ambient (room) air is contaminated with DNA, so caution is needed. Preliminary studies indicated that volatile biopsies are becoming an important diagnostic tool in lung cancer.Department of Scientific Research Projects of Dokuz Eylul University [KB.SAG.049]; Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [216S435, 216S591]Informed consent was obtained from all research subjects. The study was approved by the Ethics Committee of Ege University and was supported by grants from the Department of Scientific Research Projects of Dokuz Eylul University (Project no: 2017.KB.SAG.049) and the Scientific and Technological Research Council of Turkey (Project no: 216S435 and 216S591)
Existence of SARS-CoV-2 RNA on ambient particulate matter samples: A nationwide study in Turkey
Coronavirus disease 2019 (COVID-19) is caused by the SARS-CoV-2 virus and has been affecting the world since the end of 2019. The disease led to significant mortality and morbidity in Turkey, since the first case was reported on March 11th, 2020. Studies suggest a positive association between air pollution and SARS-CoV-2 infection. The aim of the present study was to investigate the role of ambient particulate matters (PM), as potential carriers for SARS-CoV-2. Ambient PM samples in various size ranges were collected from 13 sites including urban and urban-background locations and hospital gardens in 10 cities across Turkey between 13th of May and 14th of June 2020 to investigate the possible presence of SARS-CoV-2 RNA on ambient PM. A total of 203 daily samples (TSP, n = 80; PM2.5, n = 33; PM2.5-10, n = 23: PM10 mu m, n = 19; and 6 size segregated PM, n = 48) were collected using various samplers. The N1 gene and RdRP gene expressions were analyzed for the presence of SARS-CoV-2, as suggested by the Centers for Disease Control and Prevention (CDC). According to real time (RT)-PCR and three-dimensional (3D) digital (d) PCR analysis, dual RdRP and NI gene positivity were detected in 20 (9.8%) samples. Ambient PM-bound SARS-CoV-2 was analyzed quantitatively and the air concentrations of the virus ranged from 0.1 copies/m(3) to 23 copies/m(3). The highest percentages of virus detection on PM samples were from hospital gardens in Tekirdag, Zonguldak, and Istanbul, especially in PM2.5 mode. Findings of this study have suggested that SARS-CoV-2 may be transported by ambient partides, especially at sites close to the infection hot-spots. However. whether this has an impact on the spread of the virus infection remains to be determined. (C) 2021 Elsevier B.V. All rights reserved