Body composition changes with aging lead to increased adiposity and decreased muscle mass, making the diagnosis of obesity challenging. Conventional anthropometry, including body mass index (BMI), ...while easy to use clinically may misrepresent adiposity. We determined the diagnostic accuracy of BMI using dual-energy X-ray absorptiometry (DEXA) in assessing the degree of obesity in older adults.
The National Health and Nutrition Examination Surveys 1999-2004 were used to identify adults aged ⩾60 years with DEXA measures. They were categorized (yes/no) as having elevated body fat by gender (men: ⩾25%; women ⩾35%) and by BMI ⩾25 and ⩾30 kg m(-)(2). The diagnostic performance of BMI was assessed. Metabolic characteristics were compared in discordant cases of BMI/body fat. Weighting and analyses were performed per NHANES (National Health and Nutrition Examination Survey) guidelines.
We identified 4984 subjects (men: 2453; women: 2531). Mean BMI and % body fat was 28.0 kg m(-2) and 30.8% in men, and 28.5 kg m(-)(2) and 42.1% in women. A BMI ⩾30 kg m(-)(2) had a low sensitivity and moderately high specificity (men: 32.9 and 80.8%, concordance index 0.66; women: 38.5 and 78.5%, concordance 0.69) correctly classifying 41.0 and 45.1% of obese subjects. A BMI ⩾25 kg m(-2) had a moderately high sensitivity and specificity (men: 80.7 and 99.6%, concordance 0.81; women: 76.9 and 98.8%, concordance 0.84) correctly classifying 80.8 and 78.5% of obese subjects. In subjects with BMI <30 kg m(-)(2), body fat was considered elevated in 67.1% and 61.5% of men and women, respectively. For a BMI ⩾30 kg m(-)(2), sensitivity drops from 40.3% to 14.5% and 44.5% to 23.4%, whereas specificity remains elevated (>98%), in men and women, respectively, in those 60-69.9 years to subjects aged ⩾80 years. Correct classification of obesity using a cutoff of 30 kg m(-)(2) drops from 48.1 to 23.9% and 49.0 to 19.6%, in men and women in these two age groups.
Traditional measures poorly identify obesity in the elderly. In older adults, BMI may be a suboptimal marker for adiposity.
The complex influence of salinity and alkalinity on the ameliorative condition of soils is not taken into account while applying modern approaches towards grouping of saline-alkaline soils. On the ...basis of full pressure of soil moisture and the degree of water demand parameters, the grouping of saline-alkaline soils of Ararat plain is carried out. In the result 7 groups of soils having different ameliorative conditions are distinguished.
Context. Fermi Large Area Telescope (Fermi-LAT) has recently detected γ-ray emission from active galactic nuclei (AGN) that do not show clear evidence for optical blazar characteristics or have jets ...pointing away from the observer (nonblazar AGNs). These are interesting γ-ray emitters providing an alternative approach to studying high energy emission processes. Aims. This paper investigates the spectral and temporal properties of γ-ray emission from nonblazar AGNs using the recent Fermi-LAT observational data. Methods. The data collected by Fermi-LAT during 2008–2015, from the observations of 26 nonblazar AGNs, including 11 Fanaroff–Riley Type I (FRI) and ten FRII radio galaxies and steep spectrum radio quasars (SSRQs) and five narrow line seyfert 1s (NLSy1s) are analysed using the new PASS 8 event selection and instrument response function. Possible spectral changes above GeV energies are investigated with a detailed spectral analysis. Light curves generated with normal and adaptive time bins are used to study the γ-ray flux variability. Results. Non-blazar AGNs have a γ-ray photon index in the range of 1.84–2.86 and a flux varying from a few times 10−9 photon cm−2 s−1 to 10−7 photon cm−2 s−1. Over long time periods, the power law provides an adequate description of the γ-ray spectra of almost all sources. Significant curvature is observed in the γ-ray spectra of NGC 1275, NGC 6251, SBS 0846 + 513, and PMN J0948 + 0022 and their spectra are better described by log parabola or by the power law with exponential cut-off models. The γ-ray spectra of PKS 0625-25 and 3C 380 show a possible deviation from a simple power-law shape, indicating a spectral cut-off around the observed photon energy of Ecut = 131.2 ± 88.04 GeV and Ecut = 55.57 ± 50.74 GeV, respectively. Our analysis confirms the previous finding of an unusual spectral turnover in the γ-ray spectrum of Cen A: the photon index changes from Γ = 2.75 ± 0.02 to 2.31 ± 0.1 at 2.35 ± 0.08 GeV. In the Γ−Lγ plane, the luminosity of nonblazar AGNs is spread in the range of (1041–1047) erg s−1, where those with the lowest luminosity are FRI radio galaxies (but typically appear with a harder photon index) and those with the highest luminosity have are SSRQs/NLSY1s (with softer photon indexes). We confirm the previously reported short-timescale flux variability of NGC 1275 and 3C 120. The γ-ray emission from NLSY1s, 1H 0323 + 342, SBS 0846 + 513, and PMN J0948 + 0022 is variable, showing flares in short scales sometimes accompanied by a moderate hardening of their spectra (e.g., for MJD 56146.8 the γ-ray photon index of SBS 0846 + 513 was Γ = 1.73 ± 0.14). Non-blazar AGNs 3C 111, Cen A core, 3C 207, 3C 275.1, 3C 380, 4C + 39.23B, PKS 1502 + 036, and PKS 2004-447 show a long-timescale flux variability in the γ-ray band.
Rapid Gamma-Ray Variability of NGC 1275 Baghmanyan, V.; Gasparyan, S.; Sahakyan, N.
Astrophysical journal/The Astrophysical journal,
10/2017, Letnik:
848, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We report on a detailed analysis of the γ-ray light curve of NGC 1275 using the Fermi Large Area Telescope data accumulated during 2008-2017. Major γ-ray flares were observed in 2015 October and 2016 ...December/2017 January when the source reached a daily peak flux of , achieving a flux of within 3 hr, which corresponds to an apparent isotropic γ-ray luminosity of . The most rapid flare had an e-folding time as short as hr, which had never been previously observed for any radio galaxy in γ-ray band. Also, γ-ray spectral changes were observed during these flares: in the flux versus photon index plane, the spectral evolution follows correspondingly a counterclockwise and a clockwise loop inferred from the light curve generated by an adaptive binning method. On 2016 December 30 and 2017 January 1 the X-ray photon index softened ( ) and the flux increased nearly ∼3 times as compared with the quiet state. The observed hour-scale variability suggests a very compact emission region ( ), implying that the observed emission is most likely produced in the subparsec-scale jet if the entire jet width is responsible for the emission. During the active periods, the γ-ray photon index hardened, shifting the peak of the high-energy spectral component to , making it difficult to explain the observed X-ray and γ-ray data in the standard one-zone synchrotron self-Compton model.
In this paper, we consider the phonons in monolayer graphene and we show the possibility for the spin-triplet superconducting excitations states by discretizing the single-particle excitations near ...Fermi wave vector. The monolayer graphene was supposed to be exposed under the influence of the external gate-potential and the local Coulomb interaction effects have been taken into account at each lattice site position in the monolayer. A sufficiently large temperature domain was found, where the superconducting order parameter is not vanishing. Corresponding to this, at the surprisingly high temperature limit, we obtain a narrow domain of the electron–phonon coupling parameter
λ
eff
, emphasizing the superconducting state. We discuss the localizing role of Hubbard-
U
interaction and the effects external gate potential on the calculated physical parameters in the system. We explain the importance of the chemical potential in the formation of the superconducting state. We show the existence of a large superconducting band-gap in the system even in the case of the absence of the applied electric field potential.
Graphical Abstract
On the Multiwavelength Emission from CTA 102 Gasparyan, S.; Sahakyan, N.; Baghmanyan, V. ...
Astrophysical journal/The Astrophysical journal,
08/2018, Letnik:
863, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We report on broadband observations of CTA 102 (z = 1.037) during the active states in 2016-2017. In the γ-ray band, Fermi-LAT observed several prominent flares that followed a harder-when-brighter ...behavior: the hardest photon index Γ = 1.61 0.10 being unusual for flat-spectrum radio quasars. The peak γ-ray flux above 100 MeV, observed on MJD 57,738.47 within 4.31 minutes, corresponds to an isotropic γ-ray luminosity of , comparable to the highest values observed from blazars so far. The analyses of the Swift UVOT/XRT data show an increase in the UV/optical and X-ray bands that is contemporaneous with the bright γ-ray periods. The X-ray spectrum observed by Swift XRT and NuSTAR during the γ-ray flaring period is characterized by a hard photon index of ∼1.30. The shortest e-folding time was 4.08 1.44 hr, suggesting a very compact emission region cm. We modeled the spectral energy distribution of CTA 102 in several periods (having different properties in UV/optical, X-ray, and γ-ray bands) assuming a compact blob inside and outside the BLR. We found that the high-energy data are better described when the infrared thermal radiation of the dusty torus is considered. In the flaring periods when the correlation between the γ-ray and UV/optical/X-ray bands is lacking, the γ-ray emission can be produced from the interaction of fresh electrons in a different blob, which does not make a dominant contribution at lower energies.
ABSTRACT
The deepest all-sky survey available in the γ-ray band – the last release of the Fermi-LAT catalogue (4FGL-DR3) based on the data accumulated in 12 years contains more than 6600 sources. The ...largest population among the sources is blazar subclass – 3743, 60.1 per cent of which are classified as BL Lacertae objects (BL Lacs) or Flat Spectrum Radio Quasars (FSRQs), while the rest are listed as blazar candidates of uncertain type (BCU) as their firm optical classification is lacking. The goal of this study is to classify BCUs using different machine learning algorithms, which are trained on the spectral and temporal properties of already classified BL Lacs and FSRQs. Artificial Neural Networks, XGBoost, and LightGBM algorithms are employed to construct predictive models for BCU classification. Using 18 input parameters of 2219 BL Lacs and FSRQs, we train (80 per cent of the sample) and test (20 per cent) these algorithms and find that LightGBM model, state-of-the-art classification algorithm based on gradient boosting decision trees, provides the highest performance. Based on our best model, we classify 825 BCUs as BL Lac candidates and 405 as FSRQ candidates, however, 190 remain without a clear prediction, but the percentage of BCUs in 4FGL is reduced to 5.1 per cent. The γ-ray photon index, synchrotron peak frequency, and high-energy peak frequency of a large sample are used to investigate the relationship between FSRQs and BL Lacs (LBLs, IBLs, and HBLs).
ABSTRACT
Blazars research is one of the hot topics of contemporary extragalactic astrophysics. That is because these sources are the most abundant type of extragalactic γ-ray sources and are ...suspected to play a central role in multimessenger astrophysics. We have used Swift$\_$xrtproc, a tool to carry out an accurate spectral and photometric analysis of the Swift-XRT data of all blazars observed by Swift at least 50 times between December 2004 and the end of 2020. We present a database of X-ray spectra, best-fit parameter values, count rates and flux estimations in several energy bands of over 31 000 X-ray observations and single snapshots of 65 blazars. The results of the X-ray analysis have been combined with other multifrequency archival data to assemble the broad-band Spectral Energy Distributions (SEDs) and the long-term light curves of all sources in the sample. Our study shows that large X-ray luminosity variability on different time-scales is present in all objects. Spectral changes are also frequently observed with a ‘harder-when-brighter’ or ‘softer-when-brighter’ behaviour depending on the SED type of the blazars. The peak energy of the synchrotron component (νpeak) in the SED of HBL blazars, estimated from the log-parabolic shape of their X-ray spectra, also exhibits very large changes in the same source, spanning a range of over two orders of magnitude in Mrk421 and Mrk501, the objects with the best data sets in our sample.
Context. Important information on the evolution of a jet can be obtained by comparing the physical state of the plasma at its propagation through the broad-line region (where the jet is most likely ...formed) into the intergalactic medium, where it starts to decelerate significantly. Aims. We compare the constraints on the physical parameters in the innermost (≤pc) and outer (≥kpc) regions of the 3C 120 jet by means of a detailed multiwavelength analysis and theoretical modeling of their broadband spectra. Methods. The data collected by Fermi LAT (γ-ray band), Swift (X-ray and ultraviolet bands), and Chandra (X-ray band) are analyzed together and the spectral energy distributions are modeled using a leptonic synchrotron and inverse Compton model, taking into account the seed photons originating inside and outside the jet. The model parameters are estimated using the Markov chain Monte Carlo method. Results. The γ-ray flux from the inner jet of 3C 120 was characterized by rapid variation from MJD 56 900 to MJD 57 300. Two strong flares were observed on April 24, 2015, when within 19.0 min and 3.15 h the flux was as high as (7.46 ± 1.56) × 10-6 photon cm-2 s-1 and (4.71 ± 0.92) × 10-6 photon cm-2 s-1, respectively, with ≥10σ. During these flares the apparent isotropic γ-ray luminosity was Lγ ≃ (1.20−1.66) × 1046 erg s-1 which is not common for radio galaxies. The broadband emission in the quiet and flaring states can be described as synchrotron self-Compton emission, while inverse Compton scattering of dusty torus photons cannot be excluded for the flaring states. The X-ray emission from the knots can be reproduced by inverse Compton scattering of cosmic microwave background photons only if the jet is highly relativistic (even when δ = 10,Ue/UB is still ≥80). These extreme requirements can be somewhat softened assuming the X-rays are from the synchrotron emission of a second population of very high energy electrons. Conclusions. We found that the jet power estimated at two scales is consistent, suggesting that the jet does not suffer severe dissipation, it simply becomes radiatively inefficient.
The electronic structure of ferromagnetic CePd2P2 Kondo lattice crystallizing in the tetragonal ThCr2Si2-type structure is investigated by means of the Density Functional Theory (DFT) and ...Time-Depedent DFT (TDDFT) methods. The calculated electronic properties from DFT are presented and compared to those of the non-magnetic LaPd2P2 compound. The differences in the FS topologies upon changing magnetic states (paramagnetic → ferromagnetic) is also examined. Including the relativistic effects of without or with spin-orbit coupling, and Hubbard corrections in the calculations, ferromagnetic ground state with an ordered magnetic moment of ∼ 0.8-0.9 μB is corroborated. Meaningful changes in the magnetic moment and electronic properties of CePd2P2 are discussed in terms of effects brought by the Coulomb interaction (U), and the Hund coupling (J). In particular, the reduction in magnetic moment and simultaneously enhancement of DOS at the Fermi energy due to decreasing J are in quantitative concordance with the Kondo lattice characteristic. Furthermore, dynamical model used in TDDFT calculations exhibits that 4 f electrons in CePd2P2 tend to be delocalized. The frequency-temperature behavior of response function allows to estimate the Kondo temperature to amount 19 K.
Upper panel: The imaginary part of frequency dependent response function for Ce 4f5/2 states at several temperatures. The lines are fits to double-Lorentzian function. Lower panel: Full width at half maximum (FWHM) of the peaks in Im Σ (ω).
•First-time reporting of the electronic and magnetic properties of CePd2P2 with the help of DFT and TDDFT methods.•Ferromagnetically ordered ground state mainly dominated by Ce-4f states with reduced magnetic moments compared to those of localized Ce ions.•Finding Kondo lattice characteristic in CePd2P2 with Kondo temperature of T=K19 K.•Magnetic properties are due to strong hybridization between Ce-4f and Pd-4d states and electron-electron correlations (λ=0.648).•Emphasizing the important roles of Hubbard U and Hund's exchange J parameters in determining electronic and magnetic properties of CePd2P2.
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